Aerosol generating device and system with induction heating device and method of operation thereof

Abstract

A method for controlling aerosol generation in an aerosol generating device including an induction heating arrangement. The method includes performing a calibration process to measure one or more calibration values ​​associated with a susceptor inductively coupled to the induction heating arrangement and controlling power provided to the induction heating arrangement to adjust the temperature of the susceptor based on the one or more calibration values. The method further includes performing a preheating process prior to the calibration process. The preheating process may include controlling power provided to the induction heating arrangement to increase the temperature of the susceptor, monitoring a power supply parameter, and interrupting the provision of power to the induction heating arrangement at a first predetermined value of the monitored power supply parameter.

Description

[Technical Field]

[0001] The present disclosure relates to an induction heating device for heating an aerosol-forming substrate. The present disclosure further relates to an aerosol-generating device including such an induction heating device, and to a method for controlling aerosol generation in an aerosol-generating device. [Background technology]

[0002] The aerosol-generating device may include an electrically powered heat source configured to heat the aerosol-forming substrate to generate the aerosol. It is important for the aerosol-generating device to accurately monitor and control the temperature of the electrically powered heat source to ensure optimal generation and delivery of the aerosol to the user. It is particularly important to ensure that the electrically powered heat source heats the aerosol-forming substrate uniformly to provide the user with optimal taste and aroma, and to prevent the generation of undesirable compounds if portions of the aerosol-forming substrate are overheated.

[0003] To provide uniform heat distribution within the heat source and therefore optimal heating of the energy producing substrate by the aerosol generating device, it is desirable to provide temperature monitoring and control of the induction heating device that provides reliable temperature regulation. Summary of the Invention

[0004] According to one embodiment of the present invention, there is provided a method for controlling aerosol generation in an aerosol generating device, the aerosol generating device comprising an induction heating arrangement and a power supply for providing power to the induction heating arrangement. The method includes: performing a calibration process during a first heating stage during user operation of the aerosol generating device to generate an aerosol to measure one or more calibration values ​​associated with a susceptor inductively coupled to the induction heating arrangement, the susceptor being configured to heat an aerosol-forming substrate; and controlling power provided to the induction heating arrangement during a second heating stage during user operation of the aerosol generating device to generate an aerosol such that the temperature of the susceptor is adjusted based on the one or more calibration values. The method further includes performing a preheating process during the first heating stage, the preheating process being performed prior to the calibration process. The preheating process includes the steps of: i) controlling power provided to the induction heating arrangement to increase the temperature of the susceptor; ii) monitoring a power supply parameter, the power supply parameter being based at least in part on current; and iii) interrupting the provision of power to the induction heating arrangement at a first predetermined value of the monitored power supply parameter, the first predetermined value of the monitored power supply parameter being associated with a current value greater than a minimum operating current.

[0005] The preheating process allows heat to diffuse within the aerosol-forming substrate, distributing heat evenly within the susceptor prior to initiating the calibration process, thereby further improving the reliability of the calibration values. Additionally, the preheating process provides sufficient heating to the susceptor to reduce temperature gradients within the aerosol-forming substrate without having to increase the length of time required for preheating. Thus, the preheating process provides improved heating of the aerosol-forming substrate during user operation of the aerosol-generating device to generate aerosol without impacting the user experience.

[0006] The first predetermined value of the monitored power supply parameter may be between 101 percent and 150 percent of the power supply parameter value at minimum current.

[0007] The first predetermined value of the monitored power supply parameter may correspond to a susceptor temperature of 170-270 degrees Celsius, preferably 170-240 degrees Celsius or 240-270 degrees Celsius.

[0008] The monitored power supply parameter may be conductance or resistance.

[0009] The method may further include storing at least a first predetermined value of the monitored power supply parameter in a memory of the aerosol generating device.

[0010] Heating to a predetermined value reduces the time required for the preheating process and ensures that uniform heating of the aerosol-forming substrate is possible.

[0011] Monitoring the power supply parameter may include measuring a plurality of values ​​of the power supply parameter, and interrupting the provision of power to the induction heating arrangement at a first predetermined value of the monitored power supply parameter may include determining that a difference between successive values ​​of the plurality of values ​​is below a threshold difference.

[0012] After discontinuing the provision of power to the induction heating arrangement, the preheating process may further include: iv) controlling the power provided to the induction heating arrangement to increase the temperature of the susceptor at a second predetermined value of the monitored power supply parameter, wherein the second predetermined value of the monitored power supply parameter is associated with a current value less than the minimum operating current; and vi) repeating steps i) through iv) for a predetermined duration of the preheating process.

[0013] This provides a more uniform heat distribution in the susceptor and aerosol-forming substrate during the preheating process.

[0014] The predetermined duration of the heating process may be between 10 and 15 seconds.

[0015] The method may further include shutting down operation of the aerosol generating device if the monitored power supply parameter does not reach a value corresponding to a minimum operating current of the susceptor during a predetermined duration of the preheating process.

[0016] The susceptor is preferably provided within an aerosol-generating article configured to be inserted into an aerosol-generating device. Aerosol-generating articles not configured for use with an aerosol-generating device will not exhibit the same behavior as authentic aerosol-generating articles. Specifically, for aerosol-generating articles not configured for use with an aerosol-generating device, a minimum current / conductance value or a maximum resistance value is not observed for a predetermined duration during the preheating process. This therefore prevents the use of unauthorized aerosol-generating articles.

[0017] The second predetermined value of the power supply parameter may correspond to a susceptor temperature of 110 to 220 degrees Celsius.

[0018] The pre-heating process may be performed in response to detecting a user input. The user input may correspond to user activation of the aerosol-generating device. The aerosol-generating device may comprise a cavity configured to receive an aerosol-generating article, the aerosol-generating article comprising a susceptor, and the pre-heating process is performed in response to detecting the aerosol-generating article.

[0019] Detecting the aerosol-generating article can include detecting a susceptor.

[0020] The one or more calibration values ​​may include a power supply parameter value that corresponds to a minimum operating temperature of the susceptor.

[0021] The one or more calibration values ​​may further include a power supply parameter value corresponding to a maximum operating temperature of the susceptor.

[0022] Controlling the power provided to the induction heating arrangement so that the temperature of the susceptor is regulated based on one or more calibration values ​​may include maintaining the temperature of the susceptor between a minimum operating temperature of the susceptor and a maximum operating temperature of the susceptor.

[0023] According to one aspect, an aerosol generating device is provided, comprising a power supply for providing a DC supply voltage and a DC current, and power electronics connected to the power supply. The power electronics include a DC / AC converter, an inductor connected to the DC / AC converter for generating an alternating magnetic field, and a controller. The inductor is coupleable to a susceptor, and the susceptor is configured to heat an aerosol-forming substrate when energized by alternating current from the DC / AC converter. The controller is configured to perform a calibration process during a first heating stage during user operation of the aerosol generating device to generate an aerosol to measure one or more calibration values ​​associated with the susceptor, and to control power provided to the inductor during a second heating stage during user operation of the aerosol generating device to generate an aerosol so that the temperature of the susceptor is adjusted based on the one or more calibration values. During the first heating stage, the controller is further configured to perform a preheating process, the preheating process being performed prior to the calibration process. The preheating process includes the steps of: i) controlling power provided to an inductor to increase the temperature of the susceptor; ii) monitoring a power supply parameter, the power supply parameter being based at least in part on current; and iii) interrupting the provision of power to the inductor at a first predetermined value of the monitored power supply parameter, the first predetermined value of the monitored power supply parameter being associated with a current value greater than a minimum operating current.

[0024] The first predetermined value of the monitored power supply parameter may be between 101 percent and 150 percent of the power supply parameter value corresponding to the minimum operating current.

[0025] The first predetermined value of the monitored power supply parameter may correspond to a susceptor temperature of 170-270 degrees Celsius, preferably 170-240 degrees Celsius or 240-270 degrees Celsius.

[0026] The monitored power supply parameter may be conductance or resistance.

[0027] The aerosol generating device may further comprise a memory configured to store at least a first predetermined value of the monitored power supply parameter.

[0028] Monitoring the power supply parameter may include measuring multiple values ​​of the power supply parameter, and discontinuing the provision of power to the inductor at a first predetermined value of the monitored power supply parameter may include determining that a difference between successive values ​​of the multiple values ​​is below a threshold difference.

[0029] After interrupting the supply of power to the power supply electronics, the preheating process may further include: iv) controlling the power provided to the inductor to increase the temperature of the susceptor at a second predetermined value of the monitored power supply parameter, wherein the second predetermined value of the monitored power supply parameter corresponds to a susceptor temperature less than the minimum operating current; and vi) repeating steps i) through iv) for a predetermined duration of the preheating process.

[0030] The predetermined duration of the heating process may be between 10 and 15 seconds.

[0031] The controller may be further configured to stop operation of the aerosol generating device if the monitored power supply parameter does not reach a value corresponding to a minimum operating current value for the susceptor during a predetermined duration of the preheating process.

[0032] The second predetermined value of the monitored power supply parameter may correspond to a susceptor temperature between 110 and 220 degrees Celsius.

[0033] The controller may be configured to implement the preheating process in response to detecting a user input.

[0034] The user input may correspond to user activation of the aerosol generating device.

[0035] The aerosol-generating device may include a cavity configured to receive an aerosol-generating article. The aerosol-generating article may comprise a susceptor. The controller may be configured to implement the preheating process in response to detecting the presence of the aerosol-generating article. Detecting the aerosol-generating article may include detecting the susceptor.

[0036] The one or more calibration values ​​may include a power supply parameter value that corresponds to a minimum operating temperature of the susceptor.

[0037] The one or more calibration values ​​may further include a power supply parameter value corresponding to a maximum operating temperature of the susceptor.

[0038] Controlling the power provided to the induction heating arrangement so that the temperature of the susceptor is regulated based on one or more calibration values ​​may include maintaining the temperature of the susceptor between a minimum operating temperature of the susceptor and a maximum operating temperature of the susceptor.

[0039] According to a further aspect, there is provided an aerosol-generating system comprising the aerosol-generating device described above and an aerosol-generating article, the aerosol-generating article comprising an aerosol-generating substrate and a susceptor.

[0040] As used herein, the term "aerosol-generating device" refers to a device that interacts with an aerosol-forming substrate to generate an aerosol. The aerosol-generating device may interact with one or both of an aerosol-generating article including the aerosol-forming substrate and a cartridge including the aerosol-forming substrate. In some examples, the aerosol-generating device may heat the aerosol-forming substrate to facilitate release of volatile compounds from the substrate. An electrically operated aerosol-generating device may include an atomizer, such as an electric heater, for heating the aerosol-forming substrate to form an aerosol.

[0041] As used herein, the term "aerosol-generating system" refers to the combination of an aerosol-generating device with an aerosol-forming substrate. When the aerosol-forming substrate forms part of an aerosol-generating article, the aerosol-generating system refers to the combination of an aerosol-generating device with the aerosol-generating article. In an aerosol-generating system, the aerosol-forming substrate and the aerosol-generating device work together to generate an aerosol.

[0042] The term "aerosol-forming substrate" as used herein refers to a substrate capable of releasing a volatile compound capable of forming an aerosol. The volatile compound may be released by heating or burning the aerosol-forming substrate. As an alternative to heating or burning, in some cases the volatile compound may be released by a chemical reaction or by mechanical stimulation such as ultrasound. The aerosol-forming substrate may be solid or may contain both solid and liquid components. The aerosol-forming substrate may be part of an aerosol-generating article.

[0043] As used herein, the term "aerosol-generating article" refers to an article comprising an aerosol-forming substrate capable of emitting a volatile compound capable of forming an aerosol. The aerosol-generating article may be disposable. An aerosol-generating article comprising an aerosol-forming substrate containing tobacco may be referred to herein as a tobacco stick.

[0044] The aerosol-forming substrate may comprise nicotine. The aerosol-forming substrate may comprise tobacco, for example, the aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavor compounds that are released from the aerosol-forming substrate upon heating. In a preferred embodiment, the aerosol-forming substrate may comprise a homogenized tobacco material, for example, cast leaf tobacco. The aerosol-forming substrate may comprise both solid and liquid components. The aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavor compounds that are released from the substrate upon heating. The aerosol-forming substrate may comprise a non-tobacco material. The aerosol-forming substrate may further comprise an aerosol former. Examples of suitable aerosol formers are glycerin and propylene glycol.

[0045] As used herein, "aerosol cooling element" refers to a component of an aerosol-generating article that is positioned downstream of an aerosol-forming substrate so that, during use, an aerosol formed by 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 produce a low pressure drop. Filters and other mouthpieces that produce a high pressure drop, such as filters formed from bundles of fibers, are not considered to be aerosol cooling elements. Chambers and cavities within an aerosol-generating article are not considered to be aerosol cooling elements.

[0046] As used herein, the term "mouthpiece" means the portion of an aerosol-generating article, aerosol-generating device, or aerosol-generating system that is placed into the user's mouth for direct inhalation of the aerosol.

[0047] As used herein, the term "susceptor" refers to an element comprising a material capable of converting magnetic field energy into heat. When a susceptor is placed in an alternating magnetic field, the susceptor heats up. Heating of the susceptor can be the result of at least one of hysteresis losses and eddy currents induced within the susceptor, depending on the electrical and magnetic properties of the susceptor material.

[0048] As used herein when referring to an aerosol-generating device, the terms "upstream" and "forward," as well as "downstream" and "rearward," are used to describe the relative positions 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 present invention has a proximal end through which aerosol exits the device during use. The proximal end of an 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 an 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 positions with respect to the airflow path of the aerosol-generating device.

[0049] As used herein, when 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 portions of components of the aerosol-generating article with respect to the direction in which air flows through the aerosol-generating article during use. An aerosol-generating article according to the present invention has a proximal end through which aerosol exits the article during use. The proximal end of the aerosol-generating article 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 article may be described as being upstream or downstream of one another based on their relative positions between the proximal end of the aerosol-generating article and the distal end of the aerosol-generating article. The front of a component or portion of a component of an aerosol-generating article is the portion that is closest to the upstream end of the aerosol-generating article. The rear of a component or portion of a component of an aerosol-generating article is the portion that is closest to the downstream end of the aerosol-generating article.

[0050] As used herein, the term "inductively coupled" refers to heating a susceptor when penetrated by an alternating magnetic field. The heating can be caused by the generation of eddy currents in the susceptor. The heating can also be caused by magnetic hysteresis losses.

[0051] As used herein, the term "puffing" refers to the act of a user inhaling an aerosol into the user's body through the user's mouth or nose.

[0052] As used herein, the term "temperature detector" refers to a thermocouple, a negative temperature coefficient resistance temperature sensor, or a positive temperature coefficient resistance temperature sensor. [Example]

[0053] 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 any other example, embodiment, or aspect described herein.

[0054] Example 1: A method for controlling aerosol generation in an aerosol-generating device, the aerosol-generating device comprising an induction heating arrangement and a power supply for providing power to the induction heating arrangement, the method comprising: performing a calibration process to measure one or more calibration values ​​associated with a susceptor inductively coupled to the induction heating arrangement, the susceptor being configured to heat an aerosol-forming substrate, during a first heating stage during user operation of the aerosol-generating device to generate an aerosol; and adjusting a temperature of the susceptor based on the one or more calibration values ​​during a second heating stage during user operation of the aerosol-generating device to generate an aerosol. and controlling power provided to the induction heating arrangement so as to increase the temperature of the susceptor, the method further comprising performing a pre-heating process during the first heating stage, the pre-heating process being performed before the calibration process, the pre-heating process comprising: i) controlling power provided to the induction heating arrangement to increase the temperature of the susceptor; ii) monitoring a power supply parameter, the power supply parameter being based at least in part on current; and iii) discontinuing the provision of power to the induction heating arrangement at a first predetermined value of the monitored power supply parameter, the first predetermined value of the monitored power supply parameter being associated with a current value greater than a minimum operating current. Example 2: 10. The method of claim 1, wherein the first predetermined value of the monitored power supply parameter is between 101 percent and 150 percent of the power supply parameter value at minimum current. Example 3: 3. The method of any one of claims 1 to 2, wherein the first predetermined value of the monitored power supply parameter corresponds to a susceptor temperature of 170 to 270 degrees Celsius. Example 4: 4. The method according to one of embodiments 1 to 3, wherein the monitored power supply parameter is conductance or resistance. Example 5: The method according to any one of Examples 1 to 4, further comprising storing at least a first predetermined value of the monitored power supply parameter in a memory of the aerosol generating device. Example 6: 5. The method of any one of Examples 1 to 4, wherein monitoring the power supply parameter includes measuring a plurality of values ​​of the power supply parameter, and wherein interrupting the provision of power to the induction heating arrangement at a first predetermined value of the monitored power supply parameter includes determining that a difference between successive values ​​of the plurality of values ​​is below a threshold difference. Example 7: The method of any one of Examples 1 to 6, wherein following interrupting the provision of power to the induction heating arrangement, the preheating process further comprises: iv) controlling the power provided to the induction heating arrangement to increase the temperature of the susceptor at a second predetermined value of the monitored power supply parameter, wherein the second predetermined value of the monitored power supply parameter is associated with a current value less than the minimum operating current; and vi) repeating steps i) to iv) for a predetermined duration of the preheating process. Example 8: The method of example 7, wherein the predetermined duration of the heating process is between 10 seconds and 15 seconds. Example 9: 9. The method of example 7 or 8, further comprising: stopping operation of the aerosol generating device if the monitored power supply parameter does not reach a value corresponding to the minimum operating current of the susceptor during the predetermined duration of the preheating process. Example 10: The method of any one of Examples 7-9, wherein the second predetermined value of the power supply parameter corresponds to a susceptor temperature of 110 to 220 degrees Celsius. Example 11: 11. The method of one of Examples 1-10, wherein the preheating process is performed in response to detecting a user input. Example 12: 12. The method of example 11, wherein the user input corresponds to user activation of the aerosol generating device. Example 13: 11. The method of any one of Examples 1 to 10, wherein the aerosol-generating device comprises a cavity configured to receive an aerosol-generating article, the aerosol-generating article comprising a susceptor, and the preheating process is performed in response to detection of the aerosol-generating article. Example 14: 14. The method of example 13, wherein detecting the aerosol-generating article comprises detecting a susceptor. Example 15: 15. The method of one of embodiments 1-14, wherein the one or more calibration values ​​include a power supply parameter value corresponding to a minimum operating temperature of the susceptor. Example 16: 16. The method of example 15, wherein the one or more calibration values ​​further include a power supply parameter value corresponding to a maximum operating temperature of the susceptor. Example 17: 17. The method of example 16, wherein controlling the power provided to the induction heating arrangement such that the temperature of the susceptor is adjusted based on one or more calibration values ​​comprises maintaining the temperature of the susceptor between a minimum operating temperature of the susceptor and a maximum operating temperature of the susceptor. Example 18: an aerosol generating device, the aerosol generating device comprising: a power supply for providing a DC supply voltage and a DC current; power supply electronics connected to the power supply; a DC / AC converter; and an inductor connected to the DC / AC converter for generating an alternating magnetic field when energized by alternating current from the DC / AC converter, the inductor being couplable with a susceptor, the susceptor being configured to heat an aerosol-forming substrate; and a controller, the controller performing a calibration process to measure one or more calibration values ​​associated with the susceptor during a first heating stage during user operation of the aerosol generating device to generate an aerosol; and the controller performing a calibration process to measure one or more calibration values ​​associated with the susceptor during a second heating stage during user operation of the aerosol generating device to generate an aerosol. and a controller that controls the power provided to the inductor so that the temperature of the susceptor is adjusted based on one or more calibration values, wherein during the first heating stage, the controller is further configured to perform a preheating process, which is performed before the calibration process, the preheating process including: i) controlling the power provided to the inductor to increase the temperature of the susceptor; ii) monitoring a power supply parameter, the power supply parameter being based at least in part on current; and iii) interrupting the supply of power to the inductor at a first predetermined value of the monitored power supply parameter, the first predetermined value of the monitored power supply parameter being associated with a current value greater than a minimum operating current. Example 19: 19. The aerosol generating device of Example 18, wherein the first predetermined value of the monitored power supply parameter is between 101 percent and 150 percent of the power supply parameter value corresponding to the minimum operating current. Example 20: 20. The aerosol generating apparatus of claim 18 or 19, wherein the first predetermined value of the monitored power supply parameter corresponds to a susceptor temperature of 170 to 270 degrees Celsius. Example 21: 21. An aerosol generating device according to one of Examples 18 to 20, wherein the monitored power supply parameter is conductance or resistance. Example 22: An aerosol generating device described in one of Examples 18 to 21, further comprising a memory, the memory configured to store at least a first predetermined value of the monitored power supply parameter. Example 23: An aerosol generating device described in one of Examples 18 to 20, wherein monitoring the power supply parameter includes measuring multiple values ​​of the power supply parameter, and interrupting the provision of power to the inductor at a first predetermined value of the monitored power supply parameter includes determining that the difference between consecutive values ​​of the multiple values ​​is below a threshold difference. Example 24: An aerosol generating apparatus as described in one of Examples 18 to 23, wherein after interrupting the supply of power to the power supply electronics, the preheating process further comprises: iv) controlling the power provided to the inductor at a second predetermined value of the monitored power supply parameter to increase the temperature of the susceptor, wherein the second predetermined value of the monitored power supply parameter corresponds to a susceptor temperature that is less than the minimum operating current; and vi) repeating steps i) to iv) for a predetermined duration of the preheating process. Example 25: 25. The aerosol generating device of Example 24, wherein the predetermined duration of the heating process is 10 to 15 seconds. Example 26: 26. The aerosol generating apparatus of Examples 24 and 25, wherein the controller is further configured to stop operation of the aerosol generating apparatus if the monitored power supply parameter during the predetermined duration of the preheating process does not reach a value corresponding to the minimum operating current of the susceptor. Example 27: 27. The aerosol generating apparatus of any one of Examples 24 to 26, wherein the second predetermined value of the monitored power supply parameter corresponds to a susceptor temperature of 110 to 220 degrees Celsius. Example 28: An aerosol generating device described in one of Examples 18 to 27, wherein the controller is configured to perform a preheating process in response to detecting user input. Example 29: 29. The aerosol generating device of Example 28, wherein the user input corresponds to user activation of the aerosol generating device. Example 30: An aerosol generating apparatus described in one of Examples 18 to 27, wherein the aerosol generating apparatus has a cavity configured to receive an aerosol-generating article, the aerosol-generating article has a susceptor, and the controller is configured to perform a preheating process in response to detecting the aerosol-generating article. Example 31: 31. The aerosol generating apparatus of example 30, wherein detecting the aerosol-generating article comprises detecting a susceptor. Example 32: 32. The aerosol generating apparatus according to one of Examples 18 to 31, wherein the one or more calibration values ​​include a power supply parameter value corresponding to a minimum operating temperature of the susceptor. Example 33: 33. The aerosol generating device of embodiment 32, wherein the one or more calibration values ​​further comprise a power supply parameter value corresponding to a maximum operating temperature of the susceptor. Example 34: An aerosol generating apparatus as described in Example 33, wherein controlling the power provided to the induction heating arrangement so that the temperature of the susceptor is adjusted based on one or more calibration values ​​includes maintaining the temperature of the susceptor between a minimum operating temperature of the susceptor and a maximum operating temperature of the susceptor. Example 35: An aerosol-generating system comprising the aerosol-generating device according to any one of Examples 18 to 34 and an aerosol-generating article, wherein the aerosol-generating article comprises an aerosol-generating substrate and a susceptor.

[0055] The embodiments will now be further described with reference to the figures. [Brief explanation of the drawings]

[0056] [Figure 1] FIG. 1 shows a schematic cross-sectional view of an aerosol-generating article. [Figure 2A]FIG. 2A shows a schematic cross-sectional view of an aerosol generating device for use with the aerosol-generating article shown in FIG. [Figure 2B] FIG. 2B shows a schematic cross-sectional view of an aerosol-generating device that engages the aerosol-generating article shown in FIG. [Figure 3] FIG. 3 is a block diagram showing an induction heating device for the aerosol generating device described in relation to FIG. [Figure 4] FIG. 4 is a schematic diagram showing the electronic components of the induction heating device described in connection with FIG. [Figure 5] FIG. 5 is a schematic diagram of an inductor of an LC load network of the induction heating device described in relation to FIG. [Figure 6] FIG. 6 is a graph of DC current versus time showing the remotely detectable change in current that occurs when the susceptor material undergoes a phase transition associated with its Curie point. [Figure 7] FIG. 7 shows the conductance profile of the susceptor during operation of the aerosol generator. [Figure 8] FIG. 8 is a flow chart illustrating a method for controlling aerosol generation in the aerosol generating device of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0057] It will be understood that the figures are for illustrative purposes and are not to scale.

[0058] 1 shows a schematic side cross-sectional view of an aerosol-generating article 100. The aerosol-generating article 100 comprises a rod of aerosol-forming substrate 110 and a downstream section 115 located downstream of the rod of aerosol-forming substrate 110. The aerosol-generating article 100 comprises an upstream section 150 located upstream of the rod of aerosol-forming substrate 110. The aerosol-generating article 100 thus extends from an upstream or distal end 180 to a downstream or oral end 170. In use, air is drawn through the aerosol-generating article 100 by a user from the distal end 180 to the oral end 170.

[0059] The downstream section 115 includes a support element 120 located immediately downstream of the rod of the aerosol-forming substrate 110, and the support element 120 is longitudinally aligned with the rod 110. The upstream end of the support element 120 abuts the downstream end of the rod of the aerosol-forming substrate 110. In addition, the downstream section 115 includes an aerosol-cooling element 130 located immediately downstream of the support element 120, and the aerosol-cooling element 130 is longitudinally aligned with the rod 110 and the support element 120. The upstream end of the aerosol-cooling element 130 abuts the downstream end of the support element 120. In use, volatile material emitted from the aerosol-forming substrate 110 passes along the aerosol-cooling element 130 toward the mouth end 170 of the aerosol-generating article 100. The volatile material may cool within the aerosol-cooling element 130 to form an aerosol that is inhaled by the user.

[0060] The support element 120 includes a first hollow tubular segment 125. The first hollow tubular segment 125 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The first hollow tubular segment 125 defines an interior cavity 145 that extends entirely from an upstream end 165 of the first hollow tubular segment 125 to a downstream end 175 of the first hollow tubular segment 125.

[0061] The aerosol cooling element 130 includes a second hollow tubular segment 135. The second hollow tubular segment 135 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The second hollow tubular segment 135 defines an interior cavity 155 that extends entirely from an upstream end 185 of the second hollow tubular segment 135 to a downstream end 195 of the second hollow tubular segment 135. In addition, a ventilation zone (not shown) is provided at a location along the second hollow tubular segment 135. The ventilation level of the aerosol-generating article 100 is approximately 25 percent.

[0062] The downstream section 115 further includes a mouthpiece 140 positioned immediately downstream of the aerosol cooling element 130. As shown in the drawing in Figure 1, the upstream end of the mouthpiece 140 abuts the downstream end 195 of the aerosol cooling element 130. The mouthpiece 140 is provided in the form of a cylindrical plug of low-density cellulose acetate.

[0063] The aerosol-generating article 100 further comprises an elongated susceptor 160 within the rod of the aerosol-generating substrate 110. More specifically, the susceptor 160 is disposed substantially longitudinally within the aerosol-forming substrate 110, such as generally parallel to the longitudinal axis of the rod 110. As shown in the drawing in Figure 1, the susceptor 160 is positioned at a radially central location within the rod and extends substantially along the longitudinal axis of the rod 110.

[0064] The susceptor 160 extends completely from the upstream end to the downstream end of the rod of the aerosol-forming substrate 110. In fact, the susceptor 160 has substantially the same length as the rod of the aerosol-forming substrate 110. The susceptor 160 is positioned in thermal contact with the aerosol-forming substrate 110, so that when the susceptor 160 is heated, the aerosol-forming substrate 110 is heated by the susceptor 160.

[0065] The upstream section 150 includes an upstream element 190 located immediately upstream of the rod of the aerosol-forming substrate 110, with the upstream element 190 being longitudinally aligned with the rod 110. The downstream end of the upstream element 190 abuts the upstream end of the rod of the aerosol-forming substrate. This advantageously prevents the susceptor 160 from becoming dislodged. This further ensures that consumers cannot accidentally come into contact with the heated susceptor 160 after use. The upstream element 190 is provided in the form of a cylindrical plug of cellulose acetate surrounded by a hard wrapper.

[0066] The susceptor 160 includes at least two different materials. The susceptor 160 includes at least two layers, namely, 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.

[0067] The susceptor 160 may be formed by electroplating at least one patch of a second susceptor material onto a strip of a first susceptor material. The susceptor may be formed by coating a strip of a second susceptor material onto a strip of a first susceptor material.

[0068] The aerosol-generating article 100 shown in Figure 1 is designed to engage with an aerosol-generating device, such as the aerosol-generating device 200 shown in Figure 2A, to generate an aerosol. The aerosol-generating device 200 comprises a housing 210 having a cavity 220 configured to receive the aerosol-generating article 100, and an induction heating device 230 configured to heat the aerosol-generating article 100 to generate an aerosol. Figure 2B shows the aerosol-generating device 200 when the aerosol-generating article 100 is inserted into the cavity 220.

[0069] The induction heating device 230 is shown in block diagram form in Figure 3. The induction heating device 230 comprises a DC power supply 310 and a heating arrangement 320 (also referred to as power electronics). The heating arrangement 320 includes a controller 330, a DC / AC converter 340, a matching network 350, and an inductor 240.

[0070] The DC power supply 310 is configured to provide DC power to the heating arrangement 320. Specifically, the DC power supply 310 provides a DC supply voltage (V DC) and DC current (I DC ) to DC / AC converter 340. Power supply 310 is preferably a battery, such as a lithium-ion battery. Alternatively, power supply 310 may be another form of charge storage device, such as a capacitor. Power supply 310 may require recharging. For example, power supply 310 may have sufficient capacity to allow continuous generation of aerosol for approximately six minutes, or a multiple of six minutes. In another example, power supply 310 may have sufficient capacity to allow a predetermined number of puffs or discontinuous activation of the heating arrangement.

[0071] DC / AC converter 340 is configured to supply inductor 240 with a high frequency alternating current. As used herein, the term "high frequency alternating current" refers to an alternating current having a frequency of about 500 kilohertz to about 30 megahertz. The high frequency alternating current may have a frequency of about 1 megahertz to about 30 megahertz (e.g., about 1 megahertz to about 10 megahertz, or about 5 megahertz to about 8 megahertz).

[0072] 4 shows a schematic representation of the electrical components of induction heating device 230, in particular DC / AC converter 340. DC / AC converter 340 preferably comprises a class E power amplifier. The class E power amplifier comprises a field effect transistor 420, a transistor switch 410 comprising, for example, a metal oxide semiconductor field effect transistor, a transistor switch supply circuit indicated by arrow 430 for supplying a switching signal (gate-source voltage) to field effect transistor 420, and an LC load network 440 comprising a series connection of inductor L2 and shunt capacitor C1 and capacitor C2 corresponding to inductor 240. Furthermore, a DC power supply 310 with choke L1 reduces the DC current I drawn from DC power supply 310 during operation. DC together with the DC supply voltage V DC The ohmic resistance R of inductor L2 is shown to supply Coil and the ohmic resistance R of the susceptor 160 Load, which represents the total ohmic load 450, is shown in more detail in FIG.

[0073] Although DC / AC converter 340 is shown as including a Class E power amplifier, it should be understood that DC / AC converter 340 may use any suitable circuit for converting DC current to AC current. For example, DC / AC converter 340 may include a Class D power amplifier including two transistor switches. As another example, DC / AC converter 340 may include a full-bridge power inverter having four switching transistors acting in pairs.

[0074] 3, inductor 240 may receive AC current from DC / AC converter 340 through matching network 350 for optimal load matching, although matching network 350 is not required. Matching network 350 may comprise a small matching transformer. Matching network 350 may improve power transfer efficiency between DC / AC converter 340 and inductor 240.

[0075] As shown in FIG. 2A , the inductor 240 is positioned adjacent to the distal portion 225 of the cavity 220 of the aerosol-generating device 200. Thus, during operation of the aerosol-generating device 200, a high-frequency alternating current supplied to the inductor 240 causes the inductor 240 to generate a high-frequency alternating magnetic field within the distal portion 225 of the aerosol-generating device 200. The alternating magnetic field preferably has a frequency of 1 to 30 megahertz, preferably 2 to 10 megahertz, e.g., 5 to 7 megahertz. As can be seen from FIG. 2B , when the aerosol-generating article 100 is inserted into the cavity 200, the aerosol-forming substrate 110 of the aerosol-generating article 100 is positioned adjacent to the inductor 240 such that the susceptor 160 of the aerosol-generating article 100 is positioned within this alternating magnetic field. When the alternating magnetic field penetrates the susceptor 160, the alternating magnetic field causes the susceptor 160 to heat up. For example, eddy currents are generated within the susceptor 160, which consequently becomes heated. Further heating is provided by magnetic hysteresis losses within the susceptor 160. The heated susceptor 160 heats the aerosol-forming substrate 110 of the aerosol-generating article 100 to a temperature sufficient to form an aerosol. The aerosol is drawn downstream through the aerosol-generating article 100 and inhaled by the user.

[0076] The controller 330 may be a microcontroller, preferably a programmable microcontroller, that is programmed to regulate the power supply from the DC power supply 310 to the induction heating arrangement 320 to control the temperature of the susceptor 160.

[0077] FIG. 6 shows the DC current I drawn from the power supply 310 over time as the temperature of the susceptor 160 (shown by the dashed line) increases. DC 6 shows the relationship between the change in DC current I and the temperature of the susceptor material. More specifically, solid line 600 in FIG. 6 shows the remotely detectable change in DC current I that occurs when the susceptor material undergoes a phase transition associated with its Curie point. DC is measured at the input side of DC / AC converter 340. For the purposes of this illustration, the voltage V of power supply 310 DC can be assumed to be approximately constant.

[0078] When the susceptor 160 is inductively heated, the apparent resistance of the susceptor 160 increases. This increase in resistance is due to the DC current I drawn from the power supply 310. DC , which at constant voltage decreases as the temperature of the susceptor 160 increases. The high frequency alternating magnetic field provided by the inductor 240 induces eddy currents near the susceptor surface, an effect known as the skin effect. The resistance of the susceptor 160 depends in part on the electrical resistivity of the first susceptor material, the resistivity of the second susceptor material, and in part on the depth of the skin layer of each material available to the induced eddy currents, which resistivity is temperature dependent.

[0079] When the second susceptor material reaches its Curie temperature, it loses its magnetic properties. This increases the skin layer available for eddy currents within the second susceptor material, thereby decreasing the apparent resistance of the susceptor 160. As a result, the detected DC current I DC increases temporarily. Then, as the skin depth of the second susceptor material begins to increase, the resistance begins to decrease, which is seen as a valley (local minimum 610) in FIG.

[0080] As heating continues, the current continues to increase until it reaches a maximum skin depth, which corresponds to the point at which the second susceptor material loses its spontaneous magnetism. This point is called the Curie temperature and is seen in Figure 6 as a hill (local maximum 620). At this point, the second susceptor material undergoes 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 material-specific temperature).

[0081] If the inductor 240 continues to generate an alternating magnetic field after reaching the Curie temperature (i.e., power to the DC / AC converter 340 is not interrupted), the eddy currents generated within the susceptor 160 will flow against the resistance of the susceptor 160, causing continued Joule heating of the susceptor 160, which causes the resistance to increase again (resistance has a polynomial dependence on temperature, and for most metallic susceptor materials can be approximated for our purposes to a third-order polynomial dependence), and the current will begin to decrease again as long as the inductor 240 continues to supply power to the susceptor 160.

[0082] Thus, the second susceptor material undergoes a reversible phase transition when heated over a (known) temperature range between the valleys 610 and hills 620 shown in Figure 6. The first turning point 610 (corresponding to a local minimum in current and a local maximum in resistance) corresponds to the beginning of the phase transition. The second turning point 620 (corresponding to a local maximum in current and a local minimum in resistance) corresponds to the end of the phase transition.

[0083] As can be seen from FIG. 6, the apparent resistance of the susceptor 160, and therefore the onset and termination of the phase transition, is dependent on the DC current I drawn from the power supply 310. DC Alternatively, the apparent resistance of the susceptor 160, and therefore the onset and end of the phase transition, can be detected remotely by monitoring the conductance value (conductance is the DC current I DC DC supply voltage V DC is defined as the ratio of the DC supply voltage V DC DC current I DC At a minimum, the DC current I drawn from the power supply 310 can be remotely detected by monitoring the DC current I DC is monitored by the controller 330. The DC supply voltage V DC is known, but the DC current I drawn from the power supply 310 DC and DC supply voltage V DC Preferably, both the DC current I and the DC current I are monitored. DC , conductance values, and resistance values ​​may be referred to as source parameters.

[0084] As can be seen from FIG. 6, the apparent resistance of the susceptor 160 (and the corresponding current I drawn from the power supply 310) DC ) may vary with the temperature of the susceptor 160 in a strictly monotonic relationship over a particular temperature range of the susceptor 160, such as between the valleys 610 and the hills 620. The strictly monotonic relationship allows for an unambiguous determination of the temperature of the susceptor 160 from a determination of the apparent resistance (R) or apparent conductance (1 / R). This is because each determined value of 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 160 and the apparent resistance over the temperature range in which the second susceptor material undergoes a reversible phase transition allows for the temperature of the susceptor 160, and therefore the temperature of the aerosol-forming substrate 110, to be determined and controlled.

[0085] The controller 330 regulates the supply of power provided to the heating arrangement 320 based on the power supply parameters. In particular, the heating arrangement 320 regulates the supply of power provided to the heating arrangement 320 based on the DC current I DC The heating arrangement may be provided with a current sensor (not shown) for measuring a DC supply voltage V DC Optionally, a voltage sensor (not shown) may be included to measure the DC current I. The current sensor and voltage sensor are located on the input side of the DC / AC converter 340. DC and optionally a DC supply voltage V DC is provided to the controller 330 by a feedback channel to determine the AC power P AC Controlling further supply of.

[0086] The controller 330 may control the temperature of the susceptor 160 by maintaining the measured power supply parameter value at a target value that corresponds to the target operating temperature of the susceptor 160. The controller 330 may maintain the measured power supply parameter at the target value using any suitable control loop, for example, by using a proportional-integral-derivative control loop.

[0087] To take advantage of the strictly monotonic relationship between the apparent resistance (or apparent conductance) of the susceptor 160 and its temperature, during user operation to generate an aerosol, a power supply parameter measured at the input of the DC / AC converter 340 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 620 of the current plot in FIG. 6). The first calibration temperature is a temperature above the susceptor temperature at which the skin depth of the second susceptor material begins to increase, resulting in a temporary drop in resistance (trough 610 of the current plot in FIG. 6). Therefore, the first calibration temperature is a temperature 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 may be determined by calibrating the susceptor 160, as described in more detail below. The first and second calibration values ​​may be stored as calibration values ​​in the memory of the controller 330. Because 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 the difference between the first and second calibration values ​​is small, so that this dependence may be approximated as linear between the first and second calibration values, and such that the first and second calibration values ​​are in the upper part of the operating temperature range. Therefore, to adjust the temperature to the target operating temperature, the power supply parameters are adjusted according to the first and second calibration values ​​through a linear equation.

[0088] For example, if the first and second calibration values ​​are conductance values, the target conductance value corresponding to the target operating temperature may be given as: G Target =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.

[0089] The controller 330 may control the provision of power to the heating arrangement 320 by adjusting the duty cycle of the switching transistor 410 of the DC / AC converter 340. For example, during heating, the DC / AC converter 340 continuously generates an alternating current that heats the susceptor 160 and simultaneously generates a DC current I DC and optionally a DC supply voltage V DC may be measured preferably every 1 millisecond for 100 milliseconds.

[0090] For example, if conductance or current is monitored by the controller 330 to adjust the susceptor temperature, the duty cycle of the switching transistor 410 is reduced when the conductance or current reaches or exceeds a value corresponding to the target operating temperature for adjusting the susceptor temperature. If resistance is monitored by the controller 330 to adjust the susceptor temperature, the duty cycle of the switching transistor 410 is reduced when the resistance reaches or falls below a value corresponding to the target operating temperature. For example, the duty cycle of the switching transistor 410 may be reduced to about 10%. In other words, the switching transistor 410 may be switched into a mode that pulses only every 10 milliseconds for a duration of 1 millisecond. During this 1 millisecond on state (conducting state) of the switching transistor 410, the DC supply voltage V DC and the value of DC current I DC The value of is measured to determine the conductance. If the conductance decreases (or the resistance increases), indicating that the temperature of the susceptor 160 is below the target operating temperature, the gate of transistor 410 is again supplied with a train of pulses at the system's selected drive frequency.

[0091] Power may be supplied to the inductor 240 by the controller 330 in the form of a series of successive pulses of current. In particular, power may be supplied to the inductor 240 in a series of pulses, each separated by a time interval. The series of pulses may include two or more heating pulses and one or more probing pulses between the successive heating pulses. The heating pulses have an intensity such that they heat the susceptor 160. The probing pulses are separate power pulses that do not heat the susceptor 160 but rather have an intensity such that they provide feedback regarding the evolution (decrease) of the power supply parameters and, subsequently, the susceptor temperature. The controller 330 may control the power by controlling the duration of the time interval between successive heating pulses of power supplied to the inductor 240 by the DC power supply. Additionally or alternatively, the controller 330 may control the power by controlling the length (i.e., duration) of each successive heating pulse of power supplied to the inductor 240 by the DC power supply.

[0092] The controller 330 is programmed to perform a calibration process to obtain calibration values ​​in which the power supply parameters are measured at known temperatures of the susceptor 160. The known temperatures of the susceptor may be a first calibration temperature corresponding to the first calibration value and a second calibration temperature corresponding to the second calibration value. The calibration process is performed each time a user operates the aerosol generating device 200. For example, the calibration process is performed prior to user operation of the aerosol generating device 200 to generate an aerosol, during a first heating phase of the aerosol generating device. The calibration process may be repeated during user operation of the aerosol generating device 200 to generate an aerosol.

[0093] 7 is a graph of conductance versus time showing the heating profile of the susceptor 160, including a first heating stage 710 that includes the calibration process 710B described above. The first heating stage 710 is followed by a second heating stage 720 for heating the aerosol-forming substrate to generate an aerosol for inhalation by a user of the aerosol-generating device.

[0094] Although FIG. 7 is shown as a graph of conductance versus time, it should be understood that the controller 330 may be configured to control the heating of the susceptor 160 during the first heating stage 710 and the second heating stage 720 based on the measured resistance or current as described above.

[0095] During the calibration process, the controller 330 controls the DC / AC converter 340 to continuously or continuously supply power to the inductor 240 to heat the susceptor 160. The controller 330 controls the current I drawn by the power supply. DC , and optionally the supply voltage V DC The power supply parameters are monitored by measuring the current. As described above in connection with FIG. 6, as the susceptor 160 heats up, the measured current decreases until a first turning point E (corresponding to 610 in FIG. 6) is reached and the current begins to increase. This first turning point E corresponds to a local minimum conductance or current value (local maximum resistance value). The controller 330 may record the power supply parameters at the first turning point as a first calibration value.

[0096] If the source parameter is conductance or resistance, the source parameter value is the measured current I DC and the measured voltage V DC Alternatively, the current and voltage V may be determined based on known characteristics of the power supply 310. DC may be assumed to be approximately constant. The temperature of the susceptor 160 at the first calibration value is referred to as the first calibration temperature. The first calibration temperature is preferably between 150 degrees Celsius and 350 degrees Celsius. More preferably, when the aerosol-forming substrate 110 includes tobacco, the first calibration temperature is 320 degrees Celsius. The first calibration temperature is at least 50 degrees Celsius lower than the second calibration temperature.

[0097] As the controller 330 continues to control the power provided by the DC / AC converter 340 to the inductor 240, the controller 330 continues to monitor the power supply parameters until a second turning point F (corresponding to 620 in FIG. 6) is reached. The second turning point corresponds to the maximum current (corresponding to the Curie temperature of the second susceptor material) before the measured current begins to decrease. This turning point F corresponds to a local maximum conductance or current value (local minimum resistance value). The controller 330 records the power supply parameter value at the second turning point F as a second calibration value. The temperature of the susceptor 160 at the second calibration value is referred to as the second calibration temperature. Preferably, the second calibration temperature is between 200° C. and 400° C. When the maximum value is detected, the controller 330 controls the DC / AC converter 340 to interrupt the provision of power to the inductor 240, resulting in a decrease in the temperature of the susceptor 160 and a corresponding decrease in the measured current.

[0098] This process of continuously heating the susceptor 160 to obtain first and second calibration values ​​due to the shape of the graph may be repeated at least once during calibration process 710B. After discontinuing the provision of power to the inductor 240, the controller 330 continues to monitor the power supply parameter until a third turning point is observed. The third turning point corresponds to a second minimum conductance or current value (second maximum resistance value). Once the third turning point is detected, the controller 330 controls the DC / AC converter 340 to continuously provide power to the inductor 240 until a fourth turning point of the monitored power supply parameter is observed. The fourth turning point corresponds to a second maximum conductance or current value (second minimum resistance value). The controller 330 stores the power supply parameter value measured at the third turning point as the first calibration value and stores the power supply parameter value measured at the fourth turning point as the second calibration value. Repeated measurements of the turning points corresponding to the minimum and maximum measured current significantly improve subsequent temperature regulation during user operation of the device to generate an aerosol. Preferably, the controller 330 adjusts the power based on the power supply parameter value obtained from the second maximum and second minimum values, which is more reliable because it requires more time for heat to disperse within the aerosol-forming substrate 110 and the susceptor 160.

[0099] The controller 330 is configured to detect turning points by measuring a sequence of power supply parameter values. With reference to Figures 6 and 7, the sequence of measured power supply parameter values ​​forms a curve, with each value being greater or less than the previous value. The controller 330 is configured to measure a calibration value at the point where the curve begins to flatten. In other words, the controller 330 records a calibration value when the difference between successive power supply parameter values ​​is below a predetermined threshold.

[0100] Additionally, during the first heating stage 710, the controller 330 is programmed to perform a preheating process 710A before a calibration process 710B.

[0101] To perform the preheating process 710A, the controller 330 is configured to continuously supply power to the inductor 240 to increase the temperature of the susceptor 160. As described above, the measured current I DC begins to decrease as the temperature of the susceptor 160 increases until it reaches a turning point A, which corresponds to the minimum measured current. At this stage, the controller 330 continues to supply power to the inductor 240, and the measured current ICD begins to increase as the temperature of the susceptor 110 increases. The controller 330 is configured to discontinue providing power to the inductor 240 when the measured power supply parameter reaches a predetermined value B.

[0102] The predetermined power supply parameter value at which controller 330 discontinues providing power to the inductor may be adjusted according to the power supply parameter value measured at turning point A. For example, if the power supply parameter value is conductance, the conductance value at which controller 330 discontinues providing power to inductor 240 may be given by: G B =G A +(x×ΔG) In the formula, x may be 1.01 to 1.5.

[0103] Alternatively, controller 330 may be configured to discontinue providing power to inductor 240 when an inflection point is reached, in other words, just prior to local maximum 620. In this example, controller 330 is configured to determine the difference between successive measured current values. Controller 330 discontinues providing power to inductor 240 when the determined difference between successive measured current values ​​is less than a predetermined threshold difference, where the predetermined threshold difference is a power supply parameter value.

[0104] When the provision of power to inductor 240 is interrupted, susceptor 160 begins to cool and the value of the monitored current begins to decrease until it reaches a local minimum, C. Controller 330 may be configured to provide power to inductor 240 when the measured power parameter value reaches another predetermined power value corresponding to the current minimum at C. Alternatively, controller 330 may be configured to provide power to the inductor when the measured current reaches another predetermined power value corresponding to a predetermined current value, D. Alternatively, controller 330 is configured to wait a predetermined period of time to allow susceptor 160 to cool before continuing heating.

[0105] The predetermined power supply parameter values ​​are predefined and stored in the memory of the aerosol generating device. The predetermined power supply parameter values ​​are determined prior to use of the aerosol generating device to generate an aerosol for inhalation by a user. For example, the predetermined power supply parameter values ​​may be determined during manufacture of the aerosol generating device.

[0106] 7, the heating and cooling of the susceptor 160 is repeated for a predetermined duration of a preheating process 710A. The predetermined duration of the preheating process 710A is preferably 11 seconds. The predetermined combined duration of the preheating process 710A and the subsequent calibration process 710B is preferably 20 seconds.

[0107] The preheating process 710A improves the reliability of the calibration process 710B by allowing heat to diffuse evenly within the susceptor 160 and the aerosol-forming substrate 110 before performing the calibration. More specifically, when energy is provided to the susceptor 160, heating is greatest at the center of the susceptor 160 along the longitudinal axis. In other words, heat generation in the susceptor 160 decreases axially away from the susceptor center. Heat then diffuses along the susceptor 160 into the aerosol-generating substrate 110. Therefore, there is a temperature gradient within the susceptor 160, and as the susceptor 160 heats up, the temperature increase within the susceptor 160 and the aerosol-forming substrate 110 depends on the axial position along the susceptor 160. However, measured changes in the power supply parameters are related to the temperature of the entire susceptor. Over time, at higher temperatures, the temperature gradient decreases due to heat diffusion within the susceptor 160 and in the aerosol-forming substrate 110 .

[0108] Thus, the preheating stage 710A introduces additional energy into the aerosol-generating article, increasing the average temperature of the aerosol-generating article, specifically by heating to a temperature above the temperature of the turning point A and by allowing time for the generated heat to diffuse along the susceptor into the aerosol-forming substrate.

[0109] During calibration process 710B, additional energy is provided to the susceptor for a short period of time to reach hill point F. Heat generation occurs primarily at the center of the susceptor, as before. However, because more heat was provided during preheating stage 710A, the tip of the susceptor is at a higher temperature compared to the temperature that would be achieved if the susceptor were only heated to reach valley point A during stage 710A. Therefore, the temperature gradient to achieve hill point F is lower. Furthermore, to maintain the same average susceptor temperature, the maximum temperature reached at the susceptor center is lower (because the tip temperature is higher). This reduces the risk of overheating an aerosol-forming substrate located near (or in contact with) the susceptor center, since a lower maximum temperature is reached.

[0110] For example, if the aerosol-forming substrate 110 is particularly dry or in similar conditions, calibration may be performed before heat has spread within the aerosol-forming substrate 110, reducing the reliability of the calibration value. If the aerosol-forming substrate 110 is wet, the susceptor 160 will take longer to reach the valley temperature (depending on the moisture content of the substrate 110). Therefore, performing the pre-heating process 710A for a predetermined duration ensures that the entire aerosol-forming substrate 110 has enough time to reach the minimum operating temperature in order to be ready to be continuously powered and reach the first maximum value F, regardless of the physical state of the substrate 110. This allows calibration to be performed as soon as possible, without the risk that the substrate 110 will not reach the valley point by then.

[0111] Furthermore, the aerosol-generating article 100 may be configured so that the current minimum A is always achieved within a predetermined duration of the pre-heating process 710A. If the current minimum A is not reached within the predetermined duration of the pre-heating process 710A, this may indicate that the aerosol-generating article 100, including the aerosol-forming substrate 110, is not suitable for use with the aerosol-generating device 200. For example, the aerosol-generating article 100 may include an aerosol-forming substrate 110 that is different from or of lower quality than the aerosol-forming substrate 110 intended for use with the aerosol-generating device 200. As another example, the aerosol-generating article 100 may not be configured for use with the heating arrangement 320, for example, if the aerosol-generating article 100 and the aerosol-generating device 200 are manufactured by different manufacturers. To this end, the controller 330 may be further configured to generate a control signal to stop operation of the aerosol-generating device 200 if the controller 330 detects that the current minimum A is not reached within the predetermined duration of the pre-heating process.

[0112] The pre-heating process 710A may be performed in response to receiving a user input, for example, user activation of the aerosol generating device 200. Additionally or alternatively, the controller 330 may be configured to detect the presence of the aerosol-generating article 100 in the aerosol generating device 200, and the pre-heating process may be performed in response to detecting the presence of the aerosol-generating article 100 in the cavity 220 of the aerosol generating device 200. The controller 330 may be configured to automatically perform the calibration process 710B in response to detecting the completion of the pre-heating process 710A. The first heating stage 710 may have a duration of 5 to 30 seconds, preferably 10 to 20 seconds.

[0113] During the second heating stage 720, the controller 330 is configured to control the operating temperature of the susceptor 160 for generating the aerosol based on at least the first calibration value measured during the calibration process 710B. The second heating stage 720 may have a duration of up to 340 seconds. The controller 330 may stop heating during the second heating stage 720 before the end of the second heating stage 720 in response to receiving a user input. Furthermore, the controller 330 may be configured to stop supplying power to the induction heating arrangement during the second heating stage 720 before the end of the second heating stage 720 if a temperature above a predetermined temperature is detected to prevent overheating of the aerosol-forming substrate.

[0114] 7 shows that the second heating stage 720 includes multiple conductance steps corresponding to multiple temperature steps from the first operating temperature of the susceptor 160 to the second operating temperature of the susceptor 160. The first operating temperature of the susceptor 160 is the temperature at which the aerosol-forming substrate 110 forms aerosol, resulting in aerosol formation during each temperature step. The first operating temperature of the susceptor is preferably the minimum temperature at which the aerosol-forming substrate forms aerosol in a volume and amount sufficient to provide a satisfactory user experience when inhaled. The second operating temperature of the susceptor is the maximum temperature to which the aerosol-forming substrate is desired to be heated in order for the user to inhale the aerosol.

[0115] The first operating temperature of the susceptor 160 is equal to or greater than a first calibrated temperature of the susceptor 160 corresponding to a first calibrated value (a valley in the current plot shown in FIG. 6). The first operating temperature may be between 150 degrees Celsius and 330 degrees Celsius. The second operating temperature of the susceptor 160 is equal to or less than a second calibrated temperature of the susceptor 160 corresponding to a second calibrated value (a hill in the current plot in FIG. 6) at the Curie temperature of the second susceptor material. The second operating temperature may be between 200 degrees Celsius and 400 degrees Celsius. The difference between the first operating temperature and the second operating temperature is at least 50 degrees Celsius.

[0116] It will be understood that the number of temperature steps illustrated in FIG. 7 is exemplary. The second heating stage 720 may include at least three consecutive temperature steps, preferably two to fourteen temperature steps, and most preferably three to eight temperature steps. Each temperature step may have a predetermined duration. The duration of the first temperature step is preferably longer than the duration of each subsequent temperature step. The duration of each temperature step is preferably greater than 10 seconds, preferably between 30 and 200 seconds, and more preferably between 40 and 160 seconds. The duration of each temperature step may correspond to a predetermined number of user puffs. Preferably, the first temperature step corresponds to four user puffs, and each subsequent temperature step corresponds to one user puff. Alternatively, the controller 330 may be configured to initiate each temperature step in response to receiving a control signal, such as a user input.

[0117] For the duration of each temperature step, the temperature of the susceptor 160 is maintained at the target operating temperature corresponding to the respective temperature step. Thus, during the duration of each temperature step, the controller 330 controls the provision of power to the heating arrangement 320 such that the measured power supply parameter is maintained at a target value corresponding to the target operating temperature of the respective temperature step, the target value being determined with reference to the first and second calibration values ​​as described above.

[0118] Alternatively, the controller 330 may be configured to control the provision of power to the inductor 240 to maintain the temperature of the susceptor 160 at a constant temperature for the duration of the second heating stage 720. The constant temperature may be between 150 and 400 degrees Celsius.

[0119] 8 is a flow diagram of a method 800 for controlling aerosol generation in the aerosol generating device 200. As described above, the controller 330 may be programmed to implement the method 800.

[0120] The method begins at step 810, where the controller 330 detects user operation of the aerosol generating device 200 to generate aerosol. Detecting user operation of the aerosol generating device 200 may include detecting a user input, such as, for example, user activation of the aerosol generating device 200. Additionally or alternatively, detecting user operation of the aerosol generating device 200 may include detecting that an aerosol-generating article 100 is inserted into the aerosol generating device 200.

[0121] In response to detecting user action in step 810, controller 330 performs pre-heating process 710A in step 820. At the end of the predetermined duration of the pre-heating process, controller 330 is configured to perform calibration process 710B (step 830) described above. After completion of calibration process 710B, controller 330 enters a second heating stage in step 840 in which an aerosol is generated.

[0122] 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 disclosed maximum and minimum points, and include any intermediate ranges therein, which may or may not be specifically recited herein. 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. In some cases, as used in the appended claims, the number A may deviate by the percentages recited above, provided that the amount by which A deviates does not materially affect the basic and novel characteristics of the claimed invention. Also, all ranges include the disclosed maximum and minimum points, and include any intermediate ranges therein, which may or may not be specifically recited herein.

Claims

1. 1. A method for controlling aerosol generation in an aerosol generating device, the aerosol generating device comprising an induction heating arrangement and a power supply for providing power to the induction heating arrangement, the method comprising: performing a calibration process during a first heating stage during user operation of the aerosol-generating device to generate an aerosol to measure one or more calibration values ​​associated with a susceptor inductively coupled to the induction heating arrangement, the susceptor being configured to heat an aerosol-forming substrate; and controlling power provided to the induction heating arrangement such that a temperature of the susceptor is adjusted based on the one or more calibration values ​​during a second heating stage during user operation of the aerosol generating device to generate an aerosol; The method further includes performing a preheating process during a first heating stage, the preheating process being performed before the calibration process, the preheating process comprising: i) controlling the power provided to the induction heating arrangement to increase the temperature of the susceptor; ii) monitoring a power supply parameter, said power supply parameter being based at least in part on current; and iii) interrupting the provision of power to the induction heating arrangement at a first predetermined value of a monitored power supply parameter, the first predetermined value of the monitored power supply parameter being associated with a current value greater than a minimum operating current.

2. 10. The method of claim 1, further comprising storing at least the first predetermined value of the monitored power supply parameter in a memory of the aerosol generating device.

3. After interrupting the provision of power to the induction heating arrangement, the preheating process comprises: iv) controlling the power provided to the induction heating arrangement to increase the temperature of the susceptor at a second predetermined value of the monitored power supply parameter, the second predetermined value of the monitored power supply parameter being associated with a current value less than the minimum operating current; and vi) repeating steps i) to iv) for a predetermined duration of the preheating process.

4. The method of claim 3, wherein the predetermined duration of the heating process is between 10 and 15 seconds.

5. 5. The method of claim 3 or 4, further comprising: stopping operation of the aerosol generating device if the monitored power supply parameter does not reach a value corresponding to the minimum operating current of the susceptor during the predetermined duration of the preheating process.

6. The method of any one of claims 1 to 5, wherein the one or more calibration values ​​include a power supply parameter value corresponding to the minimum operating temperature of the susceptor.

7. The method of claim 6 , wherein the one or more calibration values ​​further include a power supply parameter value corresponding to a maximum operating temperature of the susceptor.

8. An aerosol generating device, comprising: a power supply for providing a DC supply voltage and a DC current; and power supply electronics connected to the power source, the power supply electronics comprising: a DC / AC converter; an inductor connected to the DC / AC converter to generate an alternating magnetic field when energized by alternating current from the DC / AC converter, the inductor being couplable to a susceptor, the susceptor configured to heat an aerosol-forming substrate; a controller, performing a calibration process to measure one or more calibration values ​​associated with the susceptor during a first heating stage during user operation of the aerosol generating device to generate an aerosol; and a controller configured to control power provided to the inductor such that a temperature of the susceptor is adjusted based on the one or more calibration values ​​during a second heating stage during user operation of the aerosol generating device to generate an aerosol; The controller is further configured to perform a pre-heating process during the first heating stage, the pre-heating process being performed before the calibration process, the pre-heating process comprising: i) controlling the power provided to the inductor to increase the temperature of the susceptor; ii) monitoring a power supply parameter, said power supply parameter being based at least in part on current; iii) interrupting the supply of power to the inductor at a first predetermined value of the monitored power supply parameter, wherein the first predetermined value of the monitored power supply parameter is associated with a current value greater than a minimum operating current.

9. 9. The aerosol generating device of claim 8, wherein the monitored power supply parameter is conductance or resistance.

10. 10. The aerosol generating device of claim 8 or 9, wherein monitoring the power supply parameter includes measuring multiple values ​​of the power supply parameter, and interrupting the provision of power to the inductor at a first predetermined value of the monitored power supply parameter includes determining that the difference between successive values ​​of the multiple values ​​is below a threshold difference.

11. After interrupting the provision of power to the power electronics, the preheating process iv) controlling the power provided to the inductor to increase the temperature of the susceptor at a second predetermined value of the monitored power supply parameter, the second predetermined value of the monitored power supply parameter corresponding to a susceptor temperature less than the minimum operating current; and vi) repeating steps i) to iv) for a predetermined duration of the pre-heating process.

12. 12. The aerosol generating device of claim 11, wherein the predetermined duration of the heating process is between 10 and 15 seconds.

13. 13. The aerosol generating device of claim 11 or 12, wherein the controller is further configured to stop operation of the aerosol generating device if the monitored power supply parameter does not reach a value corresponding to the minimum operating current of the susceptor during the predetermined duration of the preheating process.

14. 14. The method of claim 8, wherein the aerosol-generating device comprises a cavity configured to receive an aerosol-generating article, the aerosol-generating article comprising the susceptor, and the controller is configured to perform the pre-heating process in response to detecting the aerosol-generating article.

15. 1. An aerosol generating system comprising: An aerosol generating device according to any one of claims 8 to 14, an aerosol-generating system comprising an aerosol-generating article, the aerosol-generating article comprising an aerosol-generating substrate and the susceptor;

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