Aerosol generating system having an induction heating arrangement - Patents.com

Abstract

The inductively heated aerosol generating system comprises an inductor and an inductive heating arrangement having a susceptor. The controller is configured to monitor an electrical control parameter, e.g., apparent conductance, during a heating mode of operation, and to maintain the temperature of the susceptor within an operating temperature range by controlling the power supplied to the inductive heating arrangement with reference to a target value of the electrical control parameter. The controller is further configured to determine whether a response of the electrical control parameter to the power supplied to the inductive heating arrangement satisfies a predetermined condition, e.g., increases or decreases in response to the supplied power, and to implement a change in operation if the response does not satisfy the predetermined condition. This may prevent the temperature from significantly deviating from the operating temperature range in the event of an anomaly.

Description

[Technical field]

[0001] The present disclosure relates to an aerosol generation system comprising an induction heating arrangement and a method for controlling the induction heating arrangement, in particular to an aerosol generation system comprising an induction heating arrangement and a method for controlling the induction heating arrangement in an aerosol generation system to maintain a temperature within a predetermined range without overheating. [Background technology]

[0002] An increasing number of aerosol generating systems, such as e-cigarettes and heated tobacco systems, comprise an induction heating arrangement configured to heat an aerosol-forming substrate to generate an aerosol. The induction heating arrangement typically comprises an inductor inductively coupled to a susceptor. The inductor generates an alternating magnetic field that causes heating of the susceptor. Typically, the susceptor is in direct contact with the aerosol-forming substrate, and heat is transferred from the susceptor to the aerosol-forming substrate primarily by conduction. The temperature of the susceptor needs to be controlled to provide optimal aerosol generation, both in terms of the amount of aerosol generated and in terms of its composition.

[0003] In most inductively heated aerosol generating devices, vapor generated by heating of the aerosol-forming substrate is carried away from the susceptor by an airflow. The vapor cools in the airflow to generate the aerosol. In some aerosol generating devices where the aerosol is intended for inhalation, the airflow may be generated by a user puffing on the device. A user puffing on the device causes an intermittent and irregular airflow to pass through the susceptor. This airflow past the susceptor cools it. Therefore, during operation, more power must be provided to the inductor to counter the cooling effect of the airflow to ensure optimal aerosol generation. More power must be provided in response to a detected user puff.

[0004] It is therefore important for such aerosol generating devices to accurately monitor and control the temperature of the susceptor to ensure optimal aerosol generation and delivery to the user, and to accommodate cooling events such as the user taking a puff on the device.

[0005] Induction heating arrangements provide contactless heating of the susceptor. This is beneficial in many situations, especially when the susceptor is provided in a separate component of the system from the inductor. For the same reasons, it is desirable to monitor and control the susceptor temperature without requiring a direct electrical connection to the susceptor and without requiring a separate dedicated temperature sensor. The apparent resistance or apparent conductance of the susceptor in the induction circuit can be monitored to provide an indication of the susceptor temperature. The power supplied to the inductor can then be controlled to provide the desired susceptor temperature.

[0006] However, there are situations where control based solely on the relationship between apparent resistance or apparent conductance and temperature may lead to the risk of the susceptor being heated to an incorrect temperature. In these situations, relying solely on heating to a target value of apparent resistance or apparent conductance does not preclude the possibility of overheating. One such situation may be the relative movement of the susceptor and the alternating magnetic field during aerosol generation. Another such situation may be the temporary presence of a magnetic element that interferes with the alternating magnetic field during aerosol generation.

[0007] It would be desirable to provide an induction heating arrangement and control method that increases reliability that the susceptor will be heated to a predetermined operating temperature range, thereby reducing the likelihood of overheating the susceptor. Summary of the Invention

[0008] According to an embodiment of the present invention, there is provided an inductively heated aerosol generation system. The system comprises an inductive heating arrangement having an inductor and a susceptor. The system comprises a controller configured to monitor an electrical control parameter during a heating mode of operation. The controller is configured to maintain a temperature of the susceptor within an operating temperature range. The temperature of the susceptor is maintained within the operating temperature range by controlling the power supplied to the inductive heating arrangement with reference to a target value of the electrical control parameter. The controller is configured to determine whether a response of the electrical control parameter to the power supplied to the inductive heating arrangement during the heating mode of operation satisfies a predetermined condition.

[0009] For example, an inductively heated aerosol generating system may comprise an inductive heating arrangement having an inductor and a susceptor, and a controller configured to maintain the temperature of the susceptor within an operational temperature range by monitoring an electrical control parameter during an operational heating mode and controlling the power supplied to the inductive heating arrangement with reference to a target value of the electrical control parameter. The controller may be configured to determine whether a response of the electrical control parameter to the power supplied to the inductive heating arrangement during the operational heating mode satisfies a predetermined condition. The controller may be configured to implement a change in operation if the response does not satisfy the predetermined condition. The change in operation may be a modification of the operational heating mode, for example a suspension of the operational heating mode, or an interruption or termination of the operational heating mode. The change in operation may include switching from the operational heating mode to a different operational mode, for example a recovery mode, or a calibration mode. The change in operation may result in a reduction of the power supplied to the inductive heating arrangement, for example the duty cycle may be reduced or the power source may be terminated. The change in operation preferably results in cooling of the susceptor.

[0010] Monitoring of a suitable electrical control parameter, such as apparent resistance or apparent conductance, may allow the temperature of the susceptor to be determined. This may then allow the temperature of the susceptor to be controlled by controlling the power supplied to the induction heating arrangement with reference to the target value of the electrical control parameter. For example, energy may be supplied to the induction heating arrangement, and such energy supply may be reduced or switched off when the value of the electrical control value is equal to a value corresponding to the target temperature of the susceptor. The energy supply may be resumed after a short period of time, and the process may be repeated, thereby maintaining the temperature of the susceptor within a predetermined temperature range. This process may work well until an anomaly changes the relationship between the electrical control parameter and the temperature of the susceptor. In such a situation, supplying energy to the induction heating arrangement with reference to the target value of the electrical control parameter may result in the temperature of the susceptor being outside the desired operating range. In some situations, the susceptor may be overheated, leading to possible overheating of the aerosol-forming substrate. By checking that the response of the electrical control parameters to the power supplied is an expected response, by checking that the response to the power supplied meets predetermined conditions, it can be determined whether there is an anomaly or change in circumstances that may lead to the temperature of the susceptor being outside of a desired operating range. Advantageously, anomalies or changes that may result in overheating of the susceptor may be detected at an early stage, preferably before such overheating is detectable to a user of the system. Particularly advantageously, the controller may be able to take corrective action in the event of any such anomaly or change occurring, which may prevent any overheating from reaching critical levels and may allow the user to continue with the user experience.

[0011] The controller may be configured to maintain the temperature of the susceptor within an operating temperature range by supplying power to the induction heating arrangement, monitoring the electrical control parameter, and modifying the power supplied to the induction heating arrangement when the value of the electrical control parameter equals a target value of the electrical control parameter. The controller may be configured to control the duty cycle of the power supplied to the induction heating arrangement to maintain the value of the electrical control parameter approximately equal to the target value of the electrical control parameter.

[0012] In a preferred example, the controller may be configured to supply a current pulse, e.g., multiple current pulses, to the induction heating arrangement to maintain the temperature of the susceptor within a desired operating temperature range. When the value of the electrical control parameter is equal to the target value of the electrical control parameter during the pulse, the pulse may be terminated. The susceptor may then be allowed to cool slightly during a period when no current is supplied to the induction heating arrangement prior to a subsequent pulse. As a result, the temperature of the susceptor may be maintained near a temperature corresponding to the target temperature of the electrical control parameter.

[0013] If power is supplied to the induction heating arrangement as current pulses, the step of determining whether the response of the electrical control parameters to the supplied power satisfies a predetermined condition may be performed for each current pulse. A change in operation is preferably performed if the predetermined condition is not satisfied for the duration of the pulse. By checking that the predetermined condition is satisfied for each pulse, any anomalies or changes in conditions can be detected quickly, preferably before the temperature of the susceptor deviates significantly from the desired operating temperature range.

[0014] The electrical control parameter is preferably indicative of the temperature of the susceptor. The electrical control parameter may be indicative of a material property of the susceptor that varies as a function of temperature. The electrical control parameter may be a parameter that varies as a function of the temperature of the susceptor. The electrical control parameter is preferably a parameter selected from the list consisting of the electrical resistance of the susceptor, the apparent electrical resistance of the induction heating arrangement, the electrical conductance of the susceptor, the apparent electrical conductance of the induction heating arrangement, the current supplied to the induction heating arrangement, and the power supplied to the induction heating arrangement. Such parameters may be monitored directly or may be determined in real time by monitoring other parameters and applying appropriate calculations.

[0015] In some examples, the controller may be configured to monitor at least one power parameter representative of power supplied to the induction heating arrangement during operation. The at least one power parameter may be used as an electrical control parameter or the at least one power parameter may be used to derive an electrical control parameter. The at least one power parameter may be or may include a current supplied to the induction heating arrangement during operation. The at least one power parameter may be or may include a voltage across the induction heating arrangement during operation.

[0016] As an example, the apparent conductance of an induction heating arrangement may be calculated by the formula σ=I / V, where σ is the apparent conductivity of the induction heating arrangement, I is the current delivered to the induction heating arrangement, and V is the voltage across the induction heating arrangement. Thus, if power is delivered at a constant voltage, the apparent conductance may be determined in real time by monitoring the current and applying the formula. Both the current and voltage may be monitored, and the values ​​of both of these parameters used to calculate the apparent conductance. The apparent resistance is the inverse of the apparent conductance and may be calculated using the formula ρ=V / I, where ρ is the apparent resistance.

[0017] The predetermined condition is a condition that the electrical control parameter must satisfy in response to power supplied to the induction heating arrangement during the heating mode of operation. The predetermined condition may be that the value of the electrical control parameter increases in response to power supplied to the induction heating arrangement during the heating mode of operation, e.g., increases toward a target value of the control parameter in response to power supplied to the induction heating arrangement during the heating mode of operation. The predetermined condition may be that the value of the electrical control parameter does not decrease in response to power supplied to the induction heating arrangement during the heating mode of operation.

[0018] In some examples, power may be supplied to the induction heating arrangement as a plurality of individual current pulses. The predetermined condition may be that the value of the electrical control parameter increases in response to each current pulse supplied to the induction heating arrangement during the heating mode of operation, e.g., increases toward a target value of the control parameter in response to each current pulse supplied to the induction heating arrangement during the heating mode of operation. The predetermined condition may be that the value of the electrical control parameter does not decrease in response to each current pulse supplied to the induction heating arrangement during the heating mode of operation.

[0019] If the predetermined conditions are met, then there is no need to modify the operating heating mode, and if the predetermined conditions are not met, then the system is preferably configured to implement changes, for example to mitigate or prevent any potential overheating of the susceptor.

[0020] The predetermined condition may be that the value of the electrical control parameter decreases in response to power supplied to the induction heating arrangement during the heating mode of operation, e.g. decreases toward a target value of the control parameter in response to power supplied to the induction heating arrangement during the heating mode of operation. The predetermined condition may be that the value of the electrical control parameter cannot increase in response to power supplied to the induction heating arrangement during the heating mode of operation. If power is supplied to the induction heating arrangement as multiple individual current pulses, the predetermined condition may be that the value of the electrical control parameter decreases or cannot increase in response to each current pulse supplied to the induction heating arrangement during the heating mode of operation.

[0021] In some examples, the electrical control parameter may be a parameter selected from the list consisting of the electrical conductance of the susceptor, the apparent electrical conductance of the induction heating arrangement, the current supplied to the induction heating arrangement, and the power supplied to the induction heating arrangement, and the system may be configured such that in response to the power supplied to the induction heating arrangement during a heating mode of operation, the value of the electrical control parameter increases, e.g., in response to the power supplied to the induction heating arrangement during a heating mode of operation, toward a target value of the control parameter. In such a case, the predetermined condition may be an increase in the value of the electrical control parameter in response to the power supplied to the induction heating arrangement, and if the electrical control parameter does not increase in response to the supplied power, it is an indication that there may be an anomaly in the system affecting the heating of the susceptor.

[0022] In some examples, the electrical control parameter may be a parameter selected from the list consisting of an electrical resistance of the susceptor and an apparent electrical resistance of the induction heating arrangement, and the system may be configured to decrease the value of the electrical control parameter in response to power supplied to the induction heating arrangement during the heating mode of operation, e.g., decrease toward a target value of the control parameter in response to power supplied to the induction heating arrangement during the heating mode of operation.

[0023] The induction heating arrangement may be configured to assist in temperature monitoring and temperature control. In some examples, at least a portion of the susceptor may be configured to undergo a reversible phase transition when heated through a predetermined temperature range. The predetermined temperature range is a temperature range that begins below a start temperature of the reversible phase change and ends above a finish temperature of the reversible phase change. The predetermined temperature range may be, for example, between 100°C and 500°C, such as between 200°C and 400°C.

[0024] The controller is preferably configured to identify upper and lower boundary values ​​for the electrical control parameter associated with upper and lower boundaries of the phase transition. Advantageously, a target value for the electrical control parameter may be set to a value between the upper and lower boundary values. The target value may be a predetermined target value, but advantageously the target value may be determined after identifying the upper and lower boundary values ​​for the electrical control parameter.

[0025] An advantageous example may provide an inductively heated aerosol generation system as described above, comprising an inductive heating arrangement having an inductor and a susceptor, and a controller configured to monitor an electrical control parameter, the controller configured to maintain the temperature of the susceptor within a desired operating temperature range during an operational heating mode by controlling the power supplied to the inductive heating arrangement with reference to a target value of the electrical control parameter, wherein at least a portion of the susceptor is configured to undergo a reversible phase transition when heated through a predetermined temperature range, the controller configured to identify upper and lower boundary values ​​of the electrical control parameter associated with upper and lower boundaries of the phase transition, and a target value of the electrical control parameter is set to a value between the upper and lower boundary values, and a response of the electrical control parameter to the power supplied to the inductive heating arrangement during the operational heating phase is monitored to determine, for example, whether the temperature of the susceptor is within the desired operating temperature range.

[0026] The controller is preferably configured to monitor at least one power parameter indicative of the power supplied to the induction heating arrangement during operation and to derive the electrical control parameter using the power parameter.

[0027] In any example, the susceptor is preferably located or positionable within the alternating electromagnetic field generated by the inductor. The susceptor may be a stationary susceptor, such as a stationary part of an aerosol-generating device. The susceptor may be a susceptor located within or as part of the aerosol-generating article.

[0028] If at least a portion of the susceptor undergoes a phase transition, the upper and lower boundary values ​​of the electrical control parameter may be determined by monitoring and / or analyzing the response of the electrical control parameter as the susceptor is heated through a predetermined temperature range. For example, the variation in the value of the electrical control parameter may be recorded as the susceptor is heated through a predetermined temperature range, and the upper and lower boundary values ​​may be determined, for example, by detecting maximum and / or minimum values ​​of the value of the electrical control parameter as the susceptor is heated through the predetermined temperature range.

[0029] As the susceptor is heated through the predetermined temperature range, a phase transition onset and an end point may be identifiable by a change in the value of the electrical control parameter as the susceptor is heated through the predetermined temperature range. Advantageously, a target value for the electrical control parameter may be determined to be between the values ​​of the electrical control parameter at the phase transition onset and the phase transition end points.

[0030] An induction heating arrangement may exhibit a reversal in apparent resistance or apparent conductance while undergoing a phase transition. For example, the apparent resistance of an induction heating system may increase as the temperature of the susceptor increases prior to the onset of the phase transition. The apparent resistance may then decrease with heating through the phase transition and increase again with heating beyond the end of the phase transition. For example, the apparent conductance of an induction heating system may decrease as the temperature of the susceptor increases prior to the onset of the phase transition. The apparent conductance may then increase with heating through the phase transition and decrease again with heating beyond the end of the phase transition.

[0031] Thus, the value of the electrical control parameter may experience maximum and minimum values ​​as the susceptor heats or cools through its phase transition. Advantageously, an operating temperature range may be bounded by the maximum and minimum values ​​of the electrical control parameter. This may allow for a specific response of the electrical control parameter to the power supplied to the induction heating arrangement. That is, when the susceptor is heated within a temperature range in which it undergoes a phase transition, the electrical control parameter may respond differently to the applied power compared to when the temperature of the susceptor is outside the temperature range in which it undergoes a phase transition. The response of the electrical control parameter to the power supplied to the induction heating arrangement may provide an indication of whether the temperature of the susceptor is within a desired operating temperature range.

[0032] Preferably, power is supplied to the induction heating arrangement as a plurality of discrete current pulses, and the response of the electrical control parameter is determined and / or analyzed for each current pulse to determine whether the value of the electrical control parameter increases or decreases during the pulse. For example, the response to the electrical control parameter may be analyzed for each current pulse to determine whether the slope of the electrical control parameter versus time curve increases or decreases over the duration of the pulse.

[0033] In some examples, the electrical control parameter is the apparent conductance of the induction heating system, and the control parameter is analyzed for each current pulse to determine whether the value of the electrical control parameter increases or decreases over the duration of the pulse. The operating temperature range is preferably the temperature range over which the apparent conductance of the induction heating arrangement increases with application of power. Advantageously, the controller may be configured to switch from the heating mode to the recovery mode if it detects that the value of the electrical control parameter decreases over the duration of the pulse, which may indicate that the temperature of the susceptor is outside the operating temperature range.

[0034] The operating temperature range is preferably selected to optimize the generation of aerosol from the aerosol-forming substrate. The operating temperature range may be set by a target operating temperature and the system may be configured to maintain the temperature of the susceptor as close as possible to the target operating temperature. The operating temperature range may be between 100°C and 500°C, for example between 200°C and 400°C. A preferred operating temperature range may be between 300°C and 400°C, for example between 350°C and 390°C. The operating heating mode may have a target operating temperature between 300°C and 400°C, for example between 350°C and 390°C, for example about 350°C, or 360°C, or 370°C, or 380°C.

[0035] In instances where the susceptor exhibits a reversible phase transition when heated through a predetermined temperature range, the phase transition may be a magnetic phase transition or a crystalline phase transition. For example, the phase transition may be a ferromagnetic / paramagnetic phase transition, or a ferrimagnetic / paramagnetic phase transition, or an antiferromagnetic / paramagnetic phase transition. For example, the susceptor, or a portion of the susceptor, may be a material that undergoes a Curie transition within a predetermined temperature range.

[0036] The susceptor may be configured to optimize heating efficiency while still undergoing a reversible phase transition within a predetermined temperature range. Thus, the susceptor may comprise a first material that does not undergo a reversible phase transition during a predetermined temperature range and a second material that does undergo a reversible phase transition during a predetermined temperature range. The first material may comprise more than 50% by volume, preferably more than 60% by volume, or more than 70% by volume, or more than 80% by volume, or more than 90% by volume, or more than 95% by volume of the susceptor. The first material may be an iron-based alloy, such as stainless steel. The second material may be nickel or a nickel-based alloy. The second material may be present as a patch of material disposed on the first material. The second material may be encapsulated by the first material. The second material may be laminated on or encapsulate the first material.

[0037] Advantageously, the target value of the electrical control parameter may be determined to correspond to a susceptor temperature equal to or less than a Curie temperature of a material within the susceptor. The susceptor may include a first susceptor material having a first Curie temperature and a second susceptor material having a second Curie temperature. The second Curie temperature may be lower than the first Curie temperature. The target value of the electrical control parameter may correspond to a susceptor temperature equal to or less than the second Curie temperature.

[0038] The first and second susceptor materials are preferably two separate materials bonded together and thus in intimate physical contact with each other, thereby ensuring that both susceptor materials have the same temperature due to thermal conduction. The two susceptor materials are preferably two layers or strips bonded along one of their major surfaces. The susceptor may further comprise a further third layer of susceptor material. The third layer of susceptor material is preferably made of the first susceptor material. The thickness of the third layer of susceptor material is preferably less than the thickness of the layer of the second susceptor material.

[0039] The target value of the electrical control parameter may correspond to a susceptor temperature that is within a temperature range in which the conductance of the susceptor increases monotonically with increasing temperature. At the lower end of this temperature range, the material within the susceptor may begin to change phase from a ferromagnetic or ferrimagnetic state to a paramagnetic state. At the upper end of this temperature range, the material may complete the phase change from a ferromagnetic or ferrimagnetic state to a paramagnetic state.

[0040] The susceptor may be formed as a single component, for example as an elongated pin, blade, wire, or strip, or as a sheet or mesh. The susceptor may be an elongated susceptor having a length dimension greater than its width or thickness dimension. The susceptor may have a rectangular or circular transverse cross-section. The susceptor may be in the form of a strip of material or a strip of foil.

[0041] The susceptor may have a length of 8 mm to 100 mm, for example 10 mm to 30 mm, for example 12 mm to 20 mm. The susceptor may have a width of 2 mm to 6 mm, for example 3 mm to 5 mm, for example 3.5 mm to 4.5 mm. The susceptor may have a thickness of 0.01 mm to 2 mm, for example 0.05 mm to 1.5 mm, for example 0.1 mm to 1 mm.

[0042] The susceptor may be formed from a plurality of individual components, for example, from a plurality of elongated pins, blades, wires, or strips, from a plurality of sheets or meshes, or from a plurality of particles, for example, the susceptor may be formed from a plurality of particles disposed in thermal contact with or within the aerosol-forming substrate.

[0043] The system preferably comprises a power source, e.g. a DC power source, e.g. a battery located within the aerosol generator. The aerosol generator may further comprise a DC to AC converter, e.g. a DC to AC inverter, for providing AC power to the inductor.

[0044] The inductor may include an inductor coil. The inductor coil may be a helical coil or a flat planar coil, particularly a pancake coil or a curved planar coil. The inductor may be used to generate a varying magnetic field. The varying magnetic field may be a high frequency varying magnetic field. The varying magnetic field may be in the range of 500 kHz (kilohertz) to 30 MHz (megahertz), particularly 5 MHz to 15 MHz, preferably 5 MHz to 10 MHz. The varying magnetic field is used to inductively heat the susceptor due to at least one of eddy currents or hysteresis losses, depending on the electrical and magnetic properties of the susceptor material.

[0045] The induction heating arrangement may include a DC / AC converter and an inductor connected to the DC / AC converter. The susceptor may be inductively coupled to the inductor. Power from a power source may be provided to the inductor via the DC / AC converter as a plurality of current pulses, each pulse separated by a time interval. Controlling the power provided to the induction heating arrangement may include controlling a time interval between each of the plurality of pulses. Controlling the power provided to the induction heating arrangement may include controlling a length of each pulse of the plurality of pulses.

[0046] The system may be configured to measure the DC current drawn from the power supply at the input side of the DC / AC converter. A conductance or resistance value associated with the susceptor may be determined based on the DC supply voltage of the power supply and from the DC current drawn from the power supply. The system may further be configured to measure the DC supply voltage of the power supply at the input side of the DC / AC converter. This is due to the fact that there is a monotonic relationship between the actual conductance of the susceptor (which cannot be determined if the susceptor forms part of the article) and the apparent conductance thus determined (since the susceptor contributes the conductance of the LCR circuit (of the DC / AC converter) to which it is coupled, with most of the load (R) being due to the resistance of the susceptor. The conductance is 1 / R. Thus, when referring to the conductance of a susceptor in this text, reference is made to the apparent conductance when the susceptor forms part of a separate aerosol-generating article.

[0047] The aerosol-generating system described herein preferably comprises an aerosol-generating article and an aerosol generating device configured to receive the aerosol-generating article. The aerosol-generating article preferably comprises an aerosol-forming substrate, and the susceptor is preferably arranged in thermal communication with the aerosol-forming substrate. The aerosol-generating article is preferably a disposable article, for example an article having the form of a conventional cigarette.

[0048] The aerosol generating device preferably comprises an inductor, a controller, and a power supply for supplying power to the controller. The aerosol generating device may further comprise a DC / AC converter for converting a direct current provided by the power supply to an alternating current for supplying the inductor. The current provided to the DC / AC converter may be monitored and may form or be used to derive an electrical control parameter. The aerosol generating device may be configured to inductively heat an aerosol-forming substrate to generate an inhalable aerosol during a session of use.

[0049] The aerosol generating system, or an aerosol generating device for use in the system, may be configured to operate in both a calibration mode and a heating mode, where the calibration mode may be used, for example, to determine a target value for an electrical control parameter, and the heating mode may be used to maintain the temperature of the susceptor at an operating temperature by controlling the power supplied with reference to the target value of the electrical control parameter.

[0050] The calibration mode may include the steps of heating the susceptor through a predetermined temperature range, allowing the susceptor to cool through the predetermined temperature range, identifying upper and lower boundary values ​​for a control parameter associated with upper and lower boundaries of a phase transition of the susceptor, and determining a target value for the control parameter.

[0051] The step of heating the susceptor through the predetermined temperature range may involve supplying power to an induction heating arrangement and monitoring control parameters to identify boundaries of phase transitions undergone by the susceptor as it heats through the predetermined temperature range.

[0052] During the calibration phase, the power supplied to heat the susceptor through the predetermined temperature range may be supplied at a duty cycle of greater than 80%, such as greater than 90%, such as 100%. Allowing the susceptor to cool through the predetermined temperature range may involve supplying power to the induction heating arrangement at a reduced duty cycle and monitoring the control parameters.

[0053] The step of allowing the susceptor to cool through a predetermined temperature range may involve supplying power to the induction heating arrangement as pulses of energy, e.g. pulses of current, e.g. pulses of energy having a duty cycle of less than 10%, e.g. less than 2% or less than 1%, and monitoring the value of the control parameter during each of the pulses.

[0054] The controller may be configured to operate the system in a heating mode that includes supplying a pulse of energy, e.g., a current pulse, to the induction heating arrangement, monitoring a control parameter, and terminating the pulse if the control parameter reaches a target parameter during the pulse.

[0055] The system or apparatus may be configured to switch from the heating mode to the recovery mode when it is determined that the response of the electrical control parameter to the power supplied to the induction heating arrangement during the heating mode does not satisfy a predetermined condition, for example, in one possible configuration, when the value of the electrical control parameter increases in response to the power supplied to the induction heating arrangement during the heating mode, or, for example, when the value of the electrical control parameter does not decrease in response to the power supplied to the induction heating arrangement during the heating mode, or, for example, in another possible configuration, when the value of the electrical control parameter decreases in response to the power supplied to the induction heating arrangement during the heating mode, or, for example, when the value of the electrical control parameter fails to increase in response to the power supplied to the induction heating arrangement during the heating mode.

[0056] The recovery mode may involve allowing the susceptor to cool, for example by reducing or removing power supplied to the induction heating arrangement. The recovery mode may involve recalibration to determine new target values ​​for the control parameters. The heating mode may be resumed after completion of the recovery mode.

[0057] According to an embodiment of the invention, an aerosol generating device may be provided, the aerosol generating device configured for use in the aerosol generating system described herein.

[0058] According to an embodiment of the invention, an aerosol-generating article may be provided, the aerosol-generating article configured for use in the aerosol generation system described herein.

[0059] According to one embodiment of the present invention, a method for controlling an inductively heated aerosol generating system comprising an inductive heating arrangement having an inductor and a susceptor, and a controller, comprises the steps of: (a) monitoring electrical control parameters during a heating mode of operation of the aerosol generating system; (b) maintaining the temperature of the susceptor within an operating temperature range by controlling the power supplied to the induction heating arrangement with reference to the target value of the electrical control parameter; (c) checking whether a response of the electrical control parameters to the power supplied to the induction heating arrangement during the heating mode of operation satisfies predetermined conditions; and (d) implementing a change in operation if the response does not satisfy the predetermined conditions.

[0060] Step (c) may involve checking whether the value of the electrical control parameter increases or decreases in response to power supplied to the induction heating arrangement.

[0061] A method of controlling an inductively heated aerosol generating system, wherein at least a portion of a susceptor is configured to undergo a reversible phase transition when heated through a predetermined temperature range, comprises: monitoring at least one power parameter indicative of power supplied to the induction heating arrangement during operation; deriving an electrical control parameter from the power parameter; heating the susceptor through a predetermined temperature range; identifying upper and lower boundary values ​​for an electrical control parameter associated with upper and lower boundaries of a phase transition; determining a target value for a control parameter, the target value for the control parameter being between an upper boundary value and a lower boundary value; controlling the power supplied to the induction heating arrangement during the operational heating phase with reference to the target value of the electrical control parameter to maintain the temperature of the susceptor within a desired operational temperature range; and monitoring and analyzing the response of the electrical control parameters to the power supplied to the induction heating arrangement during the operational heating phase to determine whether the temperature of the susceptor is within a desired operational temperature range.

[0062] If the response of the electrical control parameters is deemed to be an inadequate response, the method may include initiating a cooling or recovery mode in which power supplied to the induction heating arrangement is reduced or removed.

[0063] The method may be a method of controlling an aerosol generating system as described herein.

[0064] The term "aerosol-generating device" as used herein 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 that includes an aerosol-forming substrate and a cartridge that includes an aerosol-forming substrate.

[0065] The term "aerosol-generating system" as used herein 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 an aerosol-generating article. In an aerosol-generating system, the aerosol-forming substrate and the aerosol-generating device work together to generate an aerosol.

[0066] 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 include both solid and liquid components. The aerosol-forming substrate may be part of an aerosol-generating article.

[0067] The term "aerosol-generating article" as used herein refers to an article that includes 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 that includes an aerosol-forming substrate that includes tobacco may be referred to herein as a tobacco stick.

[0068] The aerosol-forming substrate may comprise nicotine. The aerosol-forming substrate may comprise tobacco, for example a tobacco-containing material containing volatile tobacco flavour compounds that are released from the aerosol-forming substrate upon heating. In a preferred embodiment, the aerosol-forming substrate may comprise 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 flavour 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.

[0069] 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.

[0070] 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 can 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.

[0071] As used herein, the term "inductively coupled" refers to heating a susceptor when penetrated by an alternating magnetic field. The heating may be caused by the generation of eddy currents in the susceptor. The heating may also be caused by magnetic hysteresis losses.

[0072] As used herein, the term "duty cycle" of a current pulse means the ratio of the pulse duration, or pulse width, to the total period over which the current pulse is delivered.

[0073] As used herein, the term "puffing" refers to the act of a user inhaling an aerosol through the user's mouth or nose and into the user's body.

[0074] 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 of the features of other examples, embodiments, or aspects described herein.

[0075] Example I 1. An inductively heated aerosol generation system, comprising: an induction heating arrangement having an inductor and a susceptor; a controller configured to monitor an electrical control parameter during a heating mode of operation and to maintain a temperature of the susceptor within an operating temperature range by controlling power supplied to the induction heating arrangement with reference to a target value of the electrical control parameter; An inductively heated aerosol generating system, wherein the controller is configured to determine whether a response of an electrical control parameter to power supplied to the inductive heating arrangement during a heating mode of operation satisfies a predetermined condition. Example 1 1. An inductively heated aerosol generation system, comprising: an induction heating arrangement having an inductor and a susceptor; a controller configured to monitor an electrical control parameter during a heating mode of operation and to maintain a temperature of the susceptor within an operating temperature range by controlling power supplied to the induction heating arrangement with reference to a target value of the electrical control parameter; An inductively heated aerosol generating system, wherein the controller is configured to determine whether a response of an electrical control parameter to power supplied to the inductive heating arrangement during a heating mode of operation satisfies a predetermined condition, and to implement an operational change if the response does not satisfy the predetermined condition. Example 2 The aerosol generating system of Example 1, wherein the change in operation is a modification of the heating mode of operation. Example 3 2. The aerosol generating system of example 1, wherein the change in operation is termination of a heating mode of operation. Example 4 The aerosol generating system of Example 1 or 2, wherein the change in operation includes switching from a heating mode of operation to a different mode of operation, such as a recovery mode or a calibration mode. Example 5 5. The aerosol generating system of any of Examples 1-4, wherein the change in operation results in cooling of the susceptor. Example 6 An aerosol generation system as described in any of Examples 1 to 5, wherein the change in operation results in a reduction in the power supplied to the induction heating arrangement, for example the duty cycle is reduced or the power supply is terminated. Example 7 An aerosol generation system described in any of Examples i to 6, wherein the controller is configured to maintain the temperature of the susceptor within an operating temperature range by supplying power to the induction heating arrangement, monitoring an electrical control parameter, and modifying the power supplied to the induction heating arrangement when the value of the electrical control parameter is equal to a target value of the electrical control parameter. Example 8 An aerosol generation system described in any of Examples i to 7, wherein the controller is configured to maintain the temperature of the susceptor within an operating temperature range by supplying power to the induction heating arrangement, monitoring the electrical control parameter, and controlling the duty cycle of the power supplied to the induction heating arrangement to maintain the value of the electrical control parameter approximately equal to a target value of the electrical control parameter. Example 9 An aerosol generation system according to any of Examples i-8, wherein the controller is configured to supply current pulses to the induction heating arrangement to maintain the temperature of the susceptor within a desired operating temperature range. Example 10 10. The aerosol generating system of example 9, wherein the pulse is terminated when the value of the electrical control parameter is equal to the target value of the electrical control parameter during the pulse. Example 11 An aerosol generating system as described in Example 9 or 10, wherein a determination is made for each current pulse as to whether the response of the electrical control parameters to the power supplied to the induction heating arrangement during the heating mode of operation satisfies predetermined conditions. Example 12 An aerosol generation system as described in any of Examples 9 to 11, wherein a change in operation is implemented if a predetermined condition is not met for the duration of the pulse. Example 13 An aerosol generating system described in any of Examples i to 12, wherein the electrical control parameter is indicative of the temperature of the susceptor and / or indicative of a material property of the susceptor that varies as a function of temperature, and / or the electrical control parameter is a parameter that varies as a function of the temperature of the susceptor. Example 14 An aerosol generating system described in any of Examples i to 13, wherein the electrical control parameter is a parameter selected from the list consisting of the electrical resistance of the susceptor, the apparent electrical resistance of the induction heating arrangement, the electrical conductance of the susceptor, the apparent electrical conductance of the induction heating arrangement, the current supplied to the induction heating arrangement, and the power supplied to the induction heating arrangement. Example 15 An aerosol generation system described in any of Examples i to 14, wherein the controller is configured to monitor at least one power parameter representative of the power supplied to the induction heating arrangement during operation. Example 16 An aerosol generation system as described in Example 15, wherein at least one power parameter is used as an electrical control parameter or at least one power parameter is used to derive an electrical control parameter. Example 17 17. An aerosol generation system as described in Example 15 or 16, wherein at least one power parameter is or includes a current supplied to the induction heating arrangement during operation. Example 18 An aerosol generation system as described in any of Examples i to 17, wherein at least one power parameter is or includes a voltage across the induction heating arrangement during operation. Example 19 An aerosol generating system described in any of Examples i to 18, wherein the predetermined condition is that the value of the electrical control parameter increases in response to power supplied to the induction heating arrangement during the heating mode of operation, for example, increasing toward a target value of the control parameter in response to power supplied to the induction heating arrangement during the heating mode of operation. Example 20 An aerosol generation system described in any of Examples i to 19, wherein power is supplied to the induction heating arrangement as a plurality of individual current pulses, and the predetermined condition is that during the heating mode of operation, the value of the electrical control parameter increases in response to each current pulse supplied to the induction heating arrangement, e.g., during the heating mode of operation, the value of the electrical control parameter increases toward a target value of the control parameter in response to each current pulse supplied to the induction heating arrangement. Example 21 An aerosol generating system described in any of Examples i to 18, wherein the predetermined condition is that the value of the electrical control parameter decreases in response to power supplied to the induction heating arrangement during the heating mode of operation, for example, decreasing toward a target value of the control parameter in response to power supplied to the induction heating arrangement during the heating mode of operation. Example 22 An aerosol generation system as described in any of Examples i to 18 and 21, wherein power is supplied to the induction heating arrangement as a plurality of individual current pulses, and the predetermined condition is that during the heating mode of operation, the value of the electrical control parameter decreases in response to each current pulse supplied to the induction heating arrangement, e.g., during the heating mode of operation, the value of the electrical control parameter decreases toward a target value of the control parameter in response to each current pulse supplied to the induction heating arrangement. Example 23 An aerosol generation system described in any of Examples i to 20, wherein the electrical control parameter is a parameter selected from the list consisting of the electrical conductance of the susceptor, the apparent electrical conductance of the induction heating arrangement, the current supplied to the induction heating arrangement, and the power supplied to the induction heating arrangement, and the value of the electrical control parameter increases in response to the power supplied to the induction heating arrangement during the heating mode of operation, for example, increasing toward a target value of the control parameter in response to the power supplied to the induction heating arrangement during the heating mode of operation. Example 24 An aerosol generation system described in any of Examples i to 18, 21, and 22, wherein the electrical control parameter is a parameter selected from the list consisting of the electrical resistance of the susceptor and the apparent electrical resistance of the induction heating arrangement, and the value of the electrical control parameter decreases in response to the power supplied to the induction heating arrangement during the heating mode of operation, for example, decreasing toward a target value of the control parameter in response to the power supplied to the induction heating arrangement during the heating mode of operation. Example 25 An aerosol generation system according to any of Examples i-24, wherein at least a portion of the susceptor is configured to undergo a reversible phase transition when heated through a predetermined temperature range. Example 26 An aerosol generation system as described in Example 25, wherein the controller is configured to identify upper and lower boundary values ​​for an electrical control parameter associated with upper and lower boundaries of the phase transition. Example 27 27. An aerosol generating system as described in Example 26, wherein the target value of the electrical control parameter is set to a value between an upper boundary value and a lower boundary value. Example 28 Includes an inductor and a susceptor An induction heating arrangement and configured to monitor electrical control parameters a controller configured to maintain a temperature of the susceptor within a desired operating temperature range during a heating mode of operation by controlling power supplied to the induction heating arrangement with reference to a target value of an electrical control parameter; at least a portion of the susceptor is configured to undergo a reversible phase transition when heated through a predetermined temperature range, and the controller is configured to identify upper and lower boundary values ​​for an electrical control parameter associated with upper and lower boundaries of the phase transition; A target value of the electrical control parameter is set to a value between an upper boundary value and a lower boundary value; An aerosol generating system described in any of Examples i to 27, wherein the response of the electrical control parameter to the power supplied to the induction heating arrangement during the operational heating phase is monitored to determine whether the temperature of the susceptor is within the desired operating temperature range. Example 29 An aerosol generation system as described in Example 28, wherein the controller is configured to monitor at least one power parameter representative of the power supplied to the induction heating arrangement during operation and to derive the electrical control parameter using the power parameter. Example 30 30. The aerosol generation system of any of Examples i-29, wherein the susceptor is located and / or positionable within an alternating electromagnetic field generated by the inductor. Example 31 An aerosol generating system described in any of Examples 26 to 30, wherein the upper and lower boundary values ​​of the electrical control parameter are determined by analyzing the response of the electrical control parameter as the susceptor is heated through a predetermined temperature range, e.g. by analyzing the variation in the value of the electrical control parameter as the susceptor is heated through a predetermined temperature range, e.g. by detecting the maximum and / or minimum values ​​of the value of the electrical control parameter as the susceptor is heated through a predetermined temperature range. Example 32 An aerosol generating system described in any of Examples i to 31, wherein the susceptor is configured to undergo a reversible phase transition when heated through a predetermined temperature range, and the phase transition start point and the phase transition end point are identifiable by a change in the value of an electrical control parameter as the susceptor is heated through the predetermined temperature range. Example 33 A target value of the electrical control parameter is determined to be between the values ​​of the electrical control parameter at the phase transition start point and the phase transition end point; An aerosol generating system as described in Example 32, wherein the response of an electrical control parameter to the power supplied to the induction heating arrangement is referenced or analyzed to identify whether the temperature of the susceptor is within a desired operating temperature range. Example 34 An aerosol generating system as described in any of Examples 25 to 33, wherein the induction heating arrangement exhibits a reversal in apparent resistance while undergoing a phase transition. Example 35 An aerosol generating system as described in any of Examples 25 to 34, wherein the inductive heating arrangement exhibits a reversal in apparent conductance while undergoing a phase transition. Example 36 An aerosol generating system according to any of Examples 25-35, wherein the apparent resistance of the induction heating system increases before the onset of the phase transition, decreases with heating through the phase transition, and increases with heating beyond the end of the phase transition. Example 37 An aerosol generating system according to any of Examples 25-36, wherein the apparent conductance of the induction heating system decreases before the onset of the phase transition, increases with heating through the phase transition, and decreases with heating beyond the end of the phase transition. Example 38 An aerosol generation system described in any of Examples i to 37, wherein the operating temperature range is bounded by maximum and minimum values ​​of the electrical control parameter. Example 39 An aerosol generation system described in any of Examples i to 38, wherein power is supplied to the induction heating arrangement as a plurality of discrete current pulses and the response of the electrical control parameter is analyzed for each current pulse to determine whether the value of the electrical control parameter increases or decreases during the pulse. Example 40 An aerosol generation system described in any of Examples i to 39, wherein power is supplied to the induction heating arrangement as a plurality of discrete current pulses and the response to the electrical control parameter is analyzed for each current pulse to determine whether the slope of the electrical control parameter versus time curve increases or decreases over the duration of the pulse. Example 41 An aerosol generation system as described in Example 39 or 40, wherein the electrical control parameter is the apparent conductance of the induction heating system, and the control parameter is analyzed for each current pulse to determine whether the value of the electrical control parameter increases or decreases over the duration of the pulse. Example 42 An aerosol generation system as described in Example 41, wherein the controller is configured to switch from the heating mode to the recovery mode when it detects that the value of the electrical control parameter decreases over the duration of the pulse. Example 43 An aerosol generating system as described in Example 41 or 42, wherein the controller is configured to allow the susceptor to be cooled when it detects that the value of the electrical control parameter decreases over the duration of the pulse, for example by reducing the duty cycle of the power supplied to the induction heating arrangement. Example 44 An aerosol generating system described in any of Examples i to 43, wherein the susceptor exhibits a reversible phase transition when heated through a predetermined temperature range, the phase transition being a magnetic phase transition or a crystalline phase transition. Example 45 45. The aerosol generating system of Example 44, wherein the phase transition is a ferromagnetic / paramagnetic phase transition, or a ferrimagnetic / paramagnetic phase transition, or an antiferromagnetic / paramagnetic phase transition. Example 46 An aerosol generating system as described in Example 44 or 45, wherein the susceptor comprises a first material that does not undergo a reversible phase transition within a predetermined temperature range and a second material that undergoes a reversible phase transition within a predetermined temperature range. Example 47 An aerosol generating system as described in Example 46, wherein the first material comprises more than 50% by volume, preferably more than 60% by volume, or more than 70% by volume, or more than 80% by volume, or more than 90% by volume, or more than 95% by volume of a susceptor. Example 48 48. The aerosol generation system of Example 46 or 47, wherein the first material is an iron-based alloy, such as stainless steel. Example 49 49. The aerosol generating system of any of Examples 46-48, wherein the second material is nickel or a nickel-based alloy. Example 50 The aerosol generating system of any of Examples i-49, wherein the susceptor is formed as a single component, such as an elongated pin, blade, wire, or strip, or as a sheet or mesh. Example 51 51. The aerosol generation system of any of Examples i-50, wherein the susceptor is an elongated susceptor having a length dimension greater than its width or thickness dimension. Example 52 The aerosol generation system of any of Examples i-51, wherein the susceptor has a rectangular cross-section or a circular cross-section. Example 53 53. The aerosol generating system according to any of Examples i-52, wherein the susceptor has a length of 8 mm to 100 mm, such as 10 mm to 30 mm, for example 12 mm to 20 mm. Example 54 54. The aerosol generating system according to any of Examples i-53, wherein the susceptor has a width of 2 mm to 6 mm, such as 3 mm to 5 mm, for example 3.5 mm to 4.5 mm. Example 55 55. The aerosol generating system according to any of Examples i-54, wherein the susceptor has a thickness of 0.1 mm to 2 mm, such as 0.2 mm to 1.5 mm, for example 0.4 mm to 1 mm. Example 56 The aerosol generating system of Examples i-55, wherein the susceptor is formed from a plurality of individual components, e.g., from a plurality of elongated pins, blades, wires, or strips, from a plurality of sheets or meshes, or from a plurality of particles, e.g., the susceptor may be formed from a plurality of particles disposed in thermal contact with or within the aerosol-forming substrate. Example 57 An aerosol generation system described in any of Examples i to 56, wherein the system comprises a power source, e.g., a DC power source, e.g., a battery located within the aerosol generation device, and the aerosol generation device further comprises a DC to AC converter, e.g., a DC to AC inverter, for supplying AC power to the inductor. Example 58 The aerosol generating system of any one of Examples i to 57, wherein the system comprises an aerosol generating article and an aerosol generating device configured to receive the aerosol generating article. Example 59 59. The aerosol-generating system of Example 58, wherein the aerosol-generating article comprises an aerosol-forming substrate, and the susceptor is disposed in thermal communication with the aerosol-forming substrate. Example 60 60. An aerosol generating system as described in Example 58 or 59, wherein the aerosol generating article is a disposable article. Example 61 61. The aerosol generating system of any one of Examples 58 to 60, wherein the aerosol generating device comprises an inductor, a controller, and a power source for supplying power to the controller. Example 62 An aerosol generation system according to Example 61, wherein the aerosol generating device further comprises a DC / AC converter that converts the direct current supplied by the power source into alternating current for supplying the inductor. Example 63 An aerosol generation system as described in Example 62, wherein at least one power parameter is or includes a current supplied to a DC / AC converter. Example 64 An aerosol generation system according to any of Examples i to 63, comprising an aerosol generation device configured to inductively heat an aerosol-forming substrate to generate an inhalable aerosol during a session of use. Example 65 An aerosol generation system described in any of Examples i to 64, wherein the system is configured to operate in a calibration mode and a heating mode. Example 66 The aerosol generating system described in Example 65, wherein the controller is configured to operate in a calibration mode, including the steps of heating the susceptor through a predetermined temperature range, allowing the susceptor to cool through a predetermined temperature range, identifying upper and lower boundary values ​​for a control parameter associated with upper and lower boundaries of the phase transition, and determining a target value for the control parameter. Example 67 An aerosol generating system as described in Example 66, wherein the step of heating the susceptor through a predetermined temperature range involves supplying power to an induction heating arrangement and monitoring control parameters to identify boundaries of phase transitions undergone by the susceptor as it heats through the predetermined temperature range. Example 68 An aerosol generating system as described in Example 66 or 67, wherein the power supplied to heat the susceptor through the predetermined temperature range is supplied at a duty cycle of more than 80%, such as more than 90%, such as 100%. Example 69 An aerosol generating system described in any of Examples 66 to 68, wherein the step of allowing the susceptor to cool through a predetermined temperature range involves supplying power to the induction heating arrangement at a reduced duty cycle and monitoring control parameters. Example 70 An aerosol generating system described in any of Examples 66 to 69, wherein the step of allowing the susceptor to cool through a predetermined temperature range involves supplying power to the induction heating arrangement as pulses of energy, such as pulses of current, for example pulses of energy having a duty cycle of less than 10%, for example less than 2% or less than 1%, and monitoring the value of the control parameter during each of the pulses. Example 71 An aerosol generating system described in any of Examples 65 to 70, wherein the controller is configured to operate in a heating mode, including the steps of supplying a pulse of energy, e.g., a current pulse, to the induction heating arrangement, monitoring a control parameter, and turning off the pulse if the control parameter reaches a target parameter during the pulse. Example 72 An aerosol generation system as described in any of Examples i to 71, wherein when it is determined that the response of the electrical control parameter to the power supplied to the induction heating arrangement during the heating mode does not satisfy a predetermined condition, for example, in one possible configuration, if the value of the electrical control parameter increases in response to the power supplied to the induction heating arrangement during the heating mode, or, for example, if the value of the electrical control parameter does not decrease in response to the power supplied to the induction heating arrangement during the heating mode, or, for example, in another possible configuration, if the value of the electrical control parameter decreases in response to the power supplied to the induction heating arrangement during the heating mode, or, for example, if the value of the electrical control parameter cannot increase in response to the power supplied to the induction heating arrangement during the heating mode. Example 73 73. The aerosol generating system of Example 72, wherein the recovery mode includes a step of allowing the susceptor to cool, for example by reducing or removing the power supplied to the induction heating arrangement. Example 74 An aerosol generation system as described in Example 72 or 73, wherein the recovery mode includes recalibration to determine a new target value for the control parameter. Example 75 An aerosol generation system described in any of Examples 72 to 74, wherein the heating mode is resumed after completion of the recovery mode. Example 76 An aerosol generating device configured for use in the aerosol generating system defined in any of Examples i to 75. Example 77 An aerosol-generating article configured for use in an aerosol-generating system as defined in any of Examples i-75. Example 78 1. A method of controlling an inductively heated aerosol generation system, the system comprising: an inductive heating arrangement having an inductor and a susceptor; A controller, The method is (a) monitoring electrical control parameters during a heating mode of operation of the aerosol generating system; (b) maintaining the temperature of the susceptor within an operating temperature range by controlling the power supplied to the induction heating arrangement with reference to the target value of the electrical control parameter; (c) checking whether a response of the electrical control parameters to the power supplied to the induction heating arrangement during a heating mode of operation satisfies predetermined conditions; (d) implementing a change in behavior if the response does not satisfy a predetermined condition. Example 79 79. The method of example 78, wherein step (c) involves checking whether the value of the electrical control parameter increases or decreases in response to power supplied to the induction heating arrangement. Example 80 at least a portion of the susceptor is configured to undergo a reversible phase transition when heated through a predetermined temperature range; The method is monitoring at least one power parameter indicative of power supplied to the induction heating arrangement during operation; deriving an electrical control parameter from the power parameter; heating the susceptor through a predetermined temperature range; identifying upper and lower boundary values ​​for an electrical control parameter associated with upper and lower boundaries of a phase transition; determining a target value for a control parameter, the target value for the control parameter being between an upper boundary value and a lower boundary value; controlling the power supplied to the induction heating arrangement during the operational heating phase with reference to the target value of the electrical control parameter to maintain the temperature of the susceptor within a desired operational temperature range; A method for controlling an inductively heated aerosol generating system as described in Example 78 or 79, comprising the steps of monitoring and analyzing the response of electrical control parameters to the power supplied to the inductive heating arrangement during an operational heating phase to determine whether the temperature of the susceptor is within a desired operating temperature range. Example 81 The method of example 78, 79, or 80, comprising the further step of initiating a cooling or recovery mode in which power supplied to the induction heating arrangement is reduced or removed if the response of the electrical control parameters is deemed to be an inappropriate response. Example 82 A method of controlling an aerosol generation system as defined in any of Examples 78 to 81 using an aerosol generation system as defined in any of Examples i to 75.

[0076] The embodiments will now be further described with reference to the following figures: [Brief description of the drawings]

[0077] [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 with the aerosol-generating article shown in FIG. [Diagram 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 relation to FIG. [Diagram 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 illustrating the remotely detectable change in electrical current that occurs as the susceptor material undergoes a phase transition associated with its Curie point. [Figure 7] FIG. 7 is a graph of apparent conductance versus time illustrating the remotely detectable change in current that occurs as the susceptor material undergoes a phase transition associated with its Curie point. [Figure 8] FIG. 8 is a graph showing the shift in the apparent conductance curve as the susceptor moves in position relative to the conductor. [Figure 9] FIG. 9 illustrates the effect that a shift in the apparent conductance curve can have on the temperature control of a system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0078] Figure 1 illustrates an aerosol-generating article 100 for use in an aerosol-generating system. The aerosol-generating article 100 illustrated in Figure 1 comprises a rod of aerosol-generating substrate 12 and a downstream section 14 located downstream of the rod of aerosol-generating substrate 12. The aerosol-generating article 100 further comprises an upstream section 16 located upstream of the rod of aerosol-generating substrate 12. The aerosol-generating article 100 thus extends from an upstream or distal end 18 to a downstream or oral end 20.

[0079] The downstream section 14 comprises a support element 22 located immediately downstream of the rod 12 of the aerosol-generating substrate, the support element 22 being in longitudinal alignment with the rod 12. In the embodiment of Figure 1, the upstream end of the support element 22 abuts the downstream end of the rod 12 of the aerosol-generating substrate. In addition, the downstream section 14 comprises an aerosol cooling element 24 located immediately downstream of the support element 22, the aerosol cooling element 24 being in longitudinal alignment with the rod 12 and the support element 22. In the embodiment of Figure 1, the upstream end of the aerosol cooling element 24 abuts the downstream end of the support element 22.

[0080] The support element 22 and the aerosol cooling element 24 together define an intermediate hollow section 50 of the aerosol-generating article 100. Taken as a whole, the intermediate hollow section 50 does not contribute substantially to the overall RTD of the aerosol-generating article.

[0081] The support element 22 comprises a first hollow tubular segment 26. The first hollow tubular segment 26 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The first hollow tubular segment 26 defines an interior cavity 28 extending entirely from an upstream end 30 of the first hollow tubular segment to a downstream end 32 of the first hollow tubular segment 26. The interior cavity 28 is substantially empty, thereby permitting substantially unrestricted air flow therealong.

[0082] The first hollow tubular segment 26 has a length of about 8 millimeters, an outer diameter of about 7.25 millimeters, and an inner diameter (D FTS ), the peripheral wall thickness of the first hollow tubular segment 26 is therefore approximately 2.67 millimeters.

[0083] The aerosol cooling element 24 includes a second hollow tubular segment 34. The second hollow tubular segment 34 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The second hollow tubular segment 34 defines an interior cavity 36 extending entirely from an upstream end 38 of the second hollow tubular segment to a downstream end 40 of the second hollow tubular segment 34. The interior cavity 36 is substantially empty, thereby permitting substantially unrestricted airflow therealong.

[0084] The second hollow tubular segment 34 has a length of about 8 millimeters, an outer diameter of about 7.25 millimeters, and an inner diameter (D STS ) The peripheral wall thickness of the second hollow tubular segment 34 is therefore approximately 2 millimeters.

[0085] The aerosol-generating article 100 includes a ventilation zone 60 provided at a location along the second hollow tubular segment 34. More specifically, the ventilation zone is provided approximately 2 millimeters from the upstream end of the second hollow tubular segment 34. The ventilation level of the aerosol-generating article 100 is approximately 25 percent.

[0086] 1, the downstream section 14 further comprises a mouthpiece element 42 located downstream of the intermediate hollow section 50. More specifically, the mouthpiece element 42 is positioned immediately downstream of the aerosol cooling element 24. As shown in the drawing of FIG.

[0087] Mouthpiece element 42 is provided in the form of a cylindrical plug of low density cellulose acetate. Mouthpiece element 42 has a length of about 12 millimeters and an outside diameter of about 7.25 millimeters.

[0088] The rod 12 comprises an aerosol-generating substrate of one of the types described above. The rod 12 of aerosol-generating substrate has an outer diameter of about 7.25 millimeters, and a length of about 12 millimeters.

[0089] The aerosol-generating article 100 further comprises an elongated susceptor element 44 within the rod 12 of the aerosol-generating substrate. More specifically, the susceptor element 44 is substantially longitudinally disposed within the aerosol-generating substrate such that the susceptor element 44 is generally parallel to the longitudinal direction of the rod 12. As shown in the drawing of Figure 1, the susceptor element 44 is positioned at a radially central location within the rod and effectively extends along the longitudinal axis of the rod 12.

[0090] The susceptor element 44 extends completely from the upstream end to the downstream end of the rod 12. In practice, the susceptor element 44 has substantially the same length as the rod 12 of the aerosol-generating substrate.

[0091] In the embodiment of Fig. 1, the susceptor element 44 is provided in the form of a strip, having a length of about 12 millimeters, a thickness of about 60 micrometers, and a width of about 4 millimeters. The upstream section 16 comprises an upstream element 46 located immediately upstream of the rod 12 of the aerosol-generating substrate, the upstream element 46 being longitudinally aligned with the rod 12. In the embodiment of Fig. 1, the downstream end of the upstream element 46 abuts the upstream end of the rod 12 of the aerosol-generating substrate. This advantageously prevents the susceptor element 44 from becoming dislodged. Furthermore, this ensures that a consumer cannot accidentally come into contact with the heated susceptor element 44 after use.

[0092] The upstream element 46 is provided in the form of a cylindrical plug of cellulose acetate surrounded by a rigid wrapper. The upstream element 46 has a length of approximately 5 millimeters.

[0093] The susceptor 44 includes at least two different materials. The susceptor 44 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 be a material that undergoes a Curie transition and therefore 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 undergo a Curie transition and 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. The susceptor 44 may be formed by electroplating at least one patch of the second susceptor material onto a strip of the first susceptor material. The susceptor may be formed by coating a strip of the second susceptor material onto a strip of the first susceptor material.

[0094] In use, air is drawn through the aerosol-generating article 100 by a user from the distal end 18 to the oral end 20. The distal end 18 of the aerosol-generating article 100 may also be described as the upstream end of the aerosol-generating article 100, and the oral end 20 of the aerosol-generating article 100 may also be described as the downstream end of the aerosol-generating article 100. Elements of the aerosol-generating article 100 located between the oral end 20 and the distal end 18 may be described as being upstream of the oral end 20, or alternatively downstream of the distal end 18. The aerosol-forming substrate 12 is located at the distal or upstream end 18 of the aerosol-generating article 100.

[0095] The aerosol-generating article 100 shown in Figure 1 is designed to engage with an aerosol-generating device of an aerosol generation system, such as the aerosol-generating device 200 shown in Figure 2A, to generate an aerosol. The aerosol-generating device 200 includes a housing 210 having a cavity 220 configured to receive the aerosol-generating article 100. The aerosol-generating device 200 further includes 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.

[0096] The induction heating device 230 is shown as a block diagram 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 includes a controller 330, a DC / AC converter 340, a matching network 350, and an inductor 240.

[0097] 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 the DC / AC converter 340. The power source 310 is preferably a battery, such as a lithium ion battery. Alternatively, the power source 310 may be another form of charge storage device, such as a capacitor. The power source 310 may require recharging. For example, the power source 310 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 310 may have a capacity sufficient to allow a predetermined number of puffs, or discontinuous activation of the heating arrangement.

[0098] The DC / AC converter 340 is configured to supply a high frequency alternating current to the inductor 240. 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 (such as about 1 megahertz to about 10 megahertz, or about 5 megahertz to about 8 megahertz).

[0099] 4 shows diagrammatically the electrical components of the induction heating device 230, in particular the DC / AC converter 340. The DC / AC converter 340 preferably comprises a class E power amplifier. The class E power amplifier comprises a transistor switch 410 comprising a field effect transistor 420, e.g. 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 the field effect transistor 420, and an LC load network 440 comprising a series connection of a capacitor C2 and an inductor L2, which corresponds to a shunt capacitor C1 and the inductor 240. Furthermore, a DC power supply 310 with a choke L1 is connected to the DC power supply 310 during operation, i.e., a DC current I DC along with the DC supply voltage V DC The ohmic resistance of inductor L2, R coil and the ohmic resistance R of the susceptor 44. load 4. The ohmic resistance R, which represents the total ohmic load 450, is shown in more detail in FIG.

[0100] 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.

[0101] Returning to Figure 3, the inductor 240 may receive the AC current from the DC / AC converter 340 through a matching network 350 for optimal matching to the load, although the matching network 350 is not required. The matching network 350 may comprise a small matching transformer. The matching network 350 may improve the power transfer efficiency between the DC / AC converter 340 and the inductor 240.

[0102] As shown in FIG. 2A, the inductor 240 is located 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 in the distal portion 225 of the aerosol generating device 200. The alternating magnetic field has a frequency preferably between 1 and 30 megahertz, preferably between 2 and 10 megahertz, for example between 5 and 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 12 of the aerosol generating article 100 is located adjacent to the inductor 240 such that the susceptor 44 of the aerosol generating article 100 is located within this alternating magnetic field. When the alternating magnetic field penetrates the susceptor 44, the alternating magnetic field causes the susceptor 44 to heat up. For example, eddy currents are generated within the susceptor 44 which, as a result, is heated. Further heating is provided by magnetic hysteresis losses within the susceptor 44. The heated susceptor 44 heats the aerosol-forming substrate 12 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.

[0103] 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 44. The controller may receive input from a smoke puff sensor 360, as will be described.

[0104] FIG. 6 illustrates the DC current I drawn from the power supply 310 over time as the temperature of the susceptor 44 increases (the temperature is indicated by dashed line 620). DC The relationship between the DC current is shown by line 600. The DC current I drawn from the power supply 310 DC is measured at the input of the DC / AC converter 340. For the purposes of this figure, the voltage V DC may be assumed to be approximately constant. The inductor and susceptor form part of the induction heating arrangement. As the susceptor 44 is inductively heated, the apparent resistance of the induction heating arrangement and the susceptor itself increases, and since conductance is the reciprocal of resistance, the apparent conductance of the induction heating arrangement decreases. The increase in resistance reduces the DC current I drawn from the power supply 310. DC , which at constant voltage decreases as the temperature of the susceptor 44 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 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 layer of each material available for the induced eddy currents, the resistivity being temperature dependent. When the second susceptor material reaches its Curie temperature, it loses its magnetic properties. This causes more skin layer to be available for eddy currents in the second susceptor material, which decreases the apparent resistance of the susceptor 44. As a result, the detected DC current I DCA temporary increase in current occurs. This is seen as a valley 602 (local minimum) in FIG. 6. The current continues to increase until it reaches a maximum skin depth which coincides 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. 6 as a hill 601 (local maximum). 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 44 is at a known temperature (the Curie temperature, which is an intrinsic material specific temperature). If the inductor 240 continues to generate an alternating magnetic field after the Curie temperature is reached (i.e., power to the DC / AC converter 340 is not interrupted), the 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, 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 44.

[0105] Thus, as can be seen from FIG. 6, the apparent resistance of the susceptor 44 (and the corresponding current I drawn from the power supply 310) DC ) may vary with the temperature of the susceptor 44 in a strictly monotonic relationship over a particular temperature range of the susceptor 44. The strictly monotonic relationship allows for an unambiguous determination of the temperature of the susceptor 44 from a determination of the apparent resistance 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 44 and the apparent resistance allows the temperature of the susceptor 44, and therefore the temperature of the aerosol-forming substrate 12, to be determined and controlled. The apparent resistance of the susceptor 44 is determined by at least the DC current I drawn from the DC power supply 310. DC This can be detected remotely by monitoring

[0106] At least the DC current I drawn from the power supply 310 DCis monitored by the controller 330. Preferably, the DC current drawn from the power supply 310, I DC and DC supply voltage V DC The controller 330 adjusts the supply of power provided to the heating arrangement 320 based on the conductance or resistance value. The conductance is proportional to 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 The heating arrangement 320 is defined as a ratio of 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 A voltage sensor (not shown) may optionally be included to measure the DC current I. The current sensor and the 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 by a feedback channel to the controller 330 and represents the AC power P AC Controlling further supply of.

[0107] The controller 330 may control the temperature of the susceptor 44 by maintaining an electrical control parameter, which may be a measured apparent conductance value or a measured apparent resistance value, at a target value that corresponds to a target operating temperature of the susceptor 44. The controller 330 may maintain the measured conductance value or the measured resistance value at the target value using any suitable control loop, for example, by using a proportional-integral-derivative control loop.

[0108] 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 conductance value or resistance value associated with the susceptor and measured at the input side 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 601 of the current plot in FIG. 6). 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). 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 preferably at least 50 degrees Celsius lower than the second calibration temperature. At least the second calibration value may be 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 a memory of the controller 330.

[0109] Since the conductance (resistance) has a polynomial dependence on temperature, the conductance (resistance) behaves 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 conductance is adjusted according to the first and second calibration values ​​via a linear equation. For example, if the first and second calibration values ​​are conductance values, the target conductance value corresponding to the target operating temperature can be given as follows: G Target =G Lower +(x×ΔG) where ΔG is the difference between the first conductance value and the second conductance value, and x is the ratio of ΔG.

[0110] 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 may continuously generate an alternating current that heats the susceptor 44 and simultaneously generate a DC supply voltage V DC and DC current I DC may be measured, preferably every 1 millisecond, for 100 milliseconds. If conductance is monitored by the controller 330, the duty cycle of the switching transistor 410 is reduced when the conductance reaches or exceeds a value corresponding to the target operating temperature. If resistance is monitored by the controller 330, 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 9%. 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 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 44 is below the target operating temperature, then the gate of transistor 410 is again supplied with a train of pulses at the system's selected drive frequency.

[0111] Power may be supplied to the inductor 240 by the controller 330 in the form of a successive series of 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 successive 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 44. The probing pulses are separate power pulses having an intensity such that they do not heat the susceptor 44, but rather obtain feedback on the evolution (decrease) of the conductance or resistance value and then 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 (in other words, the duration) of each of the successive heating pulses of power supplied to the inductor 240 by the DC power supply.

[0112] The controller 330 is programmed to perform a calibration process to obtain calibration values ​​where the conductance is measured at known temperatures of the susceptor 44. 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. Preferably, the calibration process is performed each time the user operates the aerosol generating device 200, e.g., each time the user inserts an aerosol-generating article 100 into the aerosol generating device 200.

[0113] During the calibration process, the controller 330 controls the DC / AC converter 340 to continuously or intermittently supply power to the inductor 240 to heat the susceptor 44. The controller 330 controls the current I drawn by the power supply. DC , and possibly the supply voltage V DCThe conductance or resistance associated with the induction heating arrangement or susceptor 44 is monitored by measuring the current I. As described above in connection with FIG. 6, as the susceptor 44 heats up, the measured current decreases until a first turning point 602 is reached and the current increases. This first turning point or valley 602 corresponds to a local minimum conductance value (local maximum resistance value). The controller 330 may record the local minimum in conductance (or local maximum in resistance) as a first calibration value. The controller may record the value of the conductance or resistance at a predetermined time after the minimum current is reached as the first calibration value. The conductance or resistance is proportional to the measured current I. DC and the measured voltage V DC Alternatively, the supply voltage V DC may be assumed to be approximately constant. The temperature of the susceptor 44 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 12 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.

[0114] As the controller 330 continues to control the power to the inductor 240 provided by the DC / AC converter 340, the measured current increases until a second turning point 601 is reached and a maximum current (corresponding to the Curie temperature of the second susceptor material) is observed before the measured current begins to decrease. This turning point or hill 601 corresponds to a local maximum conductance value (local minimum resistance value). The controller 330 records the local maximum of conductance (or local minimum of resistance) as a second calibration value. The temperature of the susceptor 44 at the second calibration value is referred to as the second calibration temperature. Preferably, the second calibration temperature is between 200 degrees Celsius and 400 degrees Celsius. 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 cooling of the susceptor.

[0115] This calibration process of successively heating the susceptor 44 to obtain first and second calibration values ​​may be repeated at least once to improve the reliability of the calibration.

[0116] To further improve the reliability of the calibration process, the controller 310 may be optionally programmed to perform a pre-heating process prior to the calibration process. For example, if the aerosol-forming substrate 12 is particularly dry or in similar conditions, the calibration may be performed before heat spreads into the aerosol-forming substrate 12, reducing the reliability of the calibration value. If the aerosol-forming substrate 12 is wet, the susceptor 44 will take longer to reach the valley temperature (depending on the moisture content of the substrate 12).

[0117] To perform the preheating process, the controller 330 is configured to continuously supply power to the inductor 240. As described above, the current begins to decrease with increasing temperature of the susceptor 44 and reaches a minimum value. At this stage, the controller 330 is configured to wait a predetermined period of time to allow the susceptor 44 to cool before continuing heating. Thus, the controller 330 controls the DC / AC converter 340 to discontinue providing power to the inductor 240. After the predetermined period of time, the controller 330 controls the DC / AC converter 340 to supply power until a minimum value is reached. At this point, the controller controls the DC / AC converter 340 to again discontinue providing power to the inductor 240. The controller 330 again waits the same predetermined time to allow the susceptor 44 to cool before continuing heating. This heating and cooling of the susceptor 44 is repeated for the predetermined duration of the preheating process. The predetermined duration of the preheating process is preferably 11 seconds. Following the pre-heating process, the calibration process is preferably for a predetermined combined duration of 20 seconds.

[0118] If the aerosol-forming substrate 12 is dry, the first minimum of the pre-heating process is reached within the predetermined time and the interruption of power is repeated until the end of the predetermined time. If the aerosol-forming substrate 12 is wet, the first minimum of the pre-heating process is reached towards the end of the predetermined time. Thus, carrying out the pre-heating process for a predetermined duration ensures that, regardless of the physical state of the substrate 12, the substrate 12 has enough time to reach a minimum temperature in order to be ready to continue applying power to reach the first maximum. This allows for calibration as early as possible without the risk that the substrate 12 has not reached the valley beforehand.

[0119] Furthermore, the aerosol-generating article 100 may be configured such that the minimum value is always reached within a predetermined duration of the pre-heating process. If the minimum value is not reached within a predetermined duration of the pre-heating process, this may indicate that the aerosol-generating article 100, including the aerosol-forming substrate 12, is not suitable for use in the aerosol-generating device 200. For example, the aerosol-generating article 100 may include an aerosol-forming substrate 12 of a different or lower quality than the aerosol-forming substrate 100 intended for use in 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. Thus, the controller 330 may be configured to generate a control signal to stop operation of the aerosol-generating device 200.

[0120] The pre-heating process may be performed in response to receiving a user input, such as, for example, a 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.

[0121] Following the preheat and calibration processes, the controller 330 controls the DC / AC converter 340 to maintain the conductance or resistance associated with the susceptor 44 at a target value. This is referred to as the heating process or heating mode of operation. The target value may change over time, either continuously or in steps, but always remains between the maximum and minimum values ​​determined during the calibration process. A recalibration process may be performed at set time intervals during the heating process to re-establish maximum and minimum values ​​that may drift over the life of the device.

[0122] To maintain the conductance or resistance associated with the susceptor 44 at a target value, the controller 330 varies the duty cycle of the DC / AC converter 340. If the susceptor is cooled by increased airflow past the susceptor, such as during a user puff on the system, the conductance associated with the susceptor decreases. The controller 330 then increases the duty cycle of the current pulse to increase the power provided to the inductor, thereby moving the conductance of the susceptor back toward the target value.

[0123] One or more safety processes may be implemented to prevent overheating of the apparatus or susceptor during operation. One safety process, illustrated diagrammatically with respect to Figures 7, 8 and 9, involves monitoring the response of electrical control parameters to current pulses supplied to the induction heating arrangement, i.e., the response of apparent conductance to supplied current, to check that a predetermined condition is met. The predetermined condition is that the conductance value rises for the duration of each pulse during the heating mode of operation. If this condition is not met, the controller implements a recovery mode in which the susceptor cools and recalibrates to determine an updated target value for conductance.

[0124] FIG. 7 illustrates the response of the calculated apparent conductance of an induction heating arrangement to the continuous application of power, for example in the calibration mode described above. It is noted that the calibration mode is unlikely to result in heating of the susceptor substantially beyond the maximum value indicated by reference numeral 704, as this may result in overheating of the susceptor. Line 705 continues beyond the maximum value 704 in FIG. 7 for illustrative purposes. The article and apparatus are as described above. Supplying current to the inductor increases the temperature of the susceptor. As the temperature of the susceptor increases, its conductance initially decreases 701. The susceptor includes a portion of a material (such as a nickel alloy) that undergoes a phase transition, specifically a Curie transition from a ferromagnetic phase to a paramagnetic phase, at a particular temperature (e.g., within a temperature range of about 300-400° C.). As described above, the onset of this transition is detectable by a local minimum in the conductance 702. As the temperature of the susceptor continues to increase with continued current application, the phase transition progresses and the conductance continues to increase 703. At the Curie temperature of the transitioning susceptor material, the phase transition is complete, detectable by a local maximum in conductance 704. The relationship between conductance and temperature now returns to its original state, with conductance decreasing with increasing temperature 705.

[0125] By operating the calibration mode, the value of the apparent conductance can be matched to the temperature of any particular induction heating arrangement (i.e., formed by a particular inductor / susceptor pair). Since the Curie temperature is therefore known, this temperature can be determined to be equal to the value of the apparent conductance at the maximum 704. The temperature of the susceptor can then be controlled with reference to a target value of the apparent conductance 750 set between the minimum 702 and maximum 704 of the calibrated conductance time curve.

[0126] It is worth noting that the target value of the apparent conductance is set between a minimum value 702 and a maximum value 701. In this region, the apparent conductance increases with increasing temperature. On either side of the phase transition, i.e., before the minimum value 702 or after the maximum value 704, the apparent conductance decreases with temperature. It is also worth noting that while the target value of the apparent conductance 750 is equal to the target operating temperature while the susceptor is undergoing its phase transition (i.e., between the minimum value 702 and the maximum value 704), the s-shape of the curve means that the same value of apparent resistance occurs at lower and higher temperatures.

[0127] During the heating mode for generating an aerosol, current is supplied to the induction heating arrangement as current pulses, and these pulses are controlled with reference to the target value of the apparent conductance as described above. To check that the temperature of the susceptor is correctly controlled, the response of the apparent conductance to the current pulses is determined. If the susceptor is maintained at the correct temperature, the apparent conductance rises in response to the current pulses. This verifies that the temperature of the susceptor is between maximum and minimum values ​​determined by calibration, and that the desired operating temperature is achieved by controlling with reference to the target value of the apparent conductance. If the apparent conductance does not meet this predetermined criterion to rise in response to the current pulses, a fault is assumed and the controller implements a recovery mode in which it cools the susceptor and implements a calibration mode.

[0128] The curves shown in Figure 7 are examples of apparent conductance responses to a calibration mode. Such a mode may be performed when an article is inserted into the device prior to generating an aerosol. Several scenarios may occur that may invalidate the calibration and result in the susceptor temperature being maintained inaccurately.

[0129] For example, an article may be inserted incorrectly into the apparatus when the calibration is performed. Despite this, the apparatus successfully regulates the temperature to the conductance target value 750 determined by the calibration. However, during use, the article may be pushed further into the apparatus, causing the susceptor to move relative to the inductor. This causes the S-curve to shift down from its initial calibrated value 700 to a new position 800, as shown in FIG.

[0130] The problem is that the conductance target 750 is now located above the maximum 804 of the new s-curve 800. As a result, the device attempts to control the current supply with reference to the calibrated target 750, but is unable to reach this target due to the repositioning of the s-curve, where the new maximum 804 is the maximum conductance value that can be reached. The device continues to heat in an attempt to meet the calibrated conductance target 750, but eventually reaches the new maximum 804. After reaching the new maximum 804, the device continues to heat until it actually passes the maximum 804. After the maximum 804, the response of the conductance to temperature is reversed, which means that a power pulse triggers causing a decrease in the apparent conductance.

[0131] The effect can be seen in FIG. 9. After an initial calibration, a target conductance 750 is set between the maximum 704 and minimum 702 of the calibration curve. Initially, during the heating mode, current pulses are supplied to the induction heating arrangement and are controlled with reference to the target conductance value 750. Such controlled pulses are seen in the group of pulses 900 in FIG. 9. The slope of these pulses can be seen to be positive as the conductance increases over the duration of each pulse. After the article moves in the device, the s-curve is displaced as described above. As a result, the first current pulse after this anomalous movement 905 records a lower apparent conductance. If the controller tries to raise the conductance to the target level 750, the conductance increases with the subsequent pulses. However, the new maximum 804 is lower than the target value 750, which means that the current pulses are not controlled. As the temperature of the susceptor increases, the apparent conductance response to the applied power changes and the conductance begins to decrease with each pulse 910. Without a safety mechanism, the temperature may continue to increase as the conductance decreases. However, once the first pulse is detected (e.g., pulse 910) that does not show an increase in conductance over its duration, the controller initiates a recovery mode.

[0132] For the purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing amounts, quantities, percentages, and the like should be understood in all cases to be modified 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. 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 cases as 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.

Claims

1. An induction heating aerosol generation system, comprising: an induction heating arrangement having an inductor and a susceptor; a controller configured to monitor electrical control parameters during an operating heating mode and to control the power supplied to the induction heating arrangement with reference to a target value of the electrical control parameters so as to maintain the temperature of the susceptor within an operating temperature range; the controller being configured to determine whether a response of the electrical control parameters to the power supplied to the induction heating arrangement during the operating heating mode satisfies a predetermined condition, and to effect a change in operation if the response does not satisfy the predetermined condition; an induction heating aerosol generation system in which power is supplied to the induction heating arrangement as a plurality of individual current pulses, and the response of the electrical control parameters is analyzed for each current pulse to determine whether the value of the electrical control parameters rises or falls during the pulse.

2. The aerosol generation system according to claim 1, wherein the controller is configured to supply power to the induction heating arrangement, monitor the electrical control parameters, and correct the power supplied to the induction heating arrangement when the value of the electrical control parameters matches the target value of the electrical control parameters so as to maintain the temperature of the susceptor within the operating temperature range.

3. The aerosol generation system according to any one of claims 1 to 2, wherein the controller is configured to supply current pulses to the induction heating arrangement so as to maintain the temperature of the susceptor within a desired operating temperature range.

4. The aerosol generation system according to claim 3, wherein the determination as to whether the response of the electrical control parameters to the power supplied to the induction heating arrangement during the operating heating mode satisfies a predetermined condition is carried out for each current pulse.

5. The aerosol generation system according to claim 3, wherein a change in operation is effected if the predetermined condition is not satisfied over the duration of the pulse.

6. The aerosol generation system according to any one of claims 1 to 2, wherein the electrical control parameter is a parameter selected from the list consisting of the electrical resistance of the susceptor, the apparent electrical resistance of the induction heating arrangement, the electrical conductance of the susceptor, the apparent electrical conductance of the induction heating arrangement, the current supplied to the induction heating arrangement, and the power supplied to the induction heating arrangement.

7. The aerosol generation system according to any one of claims 1 to 2, wherein the predetermined condition is that during the operation heating mode, in response to the power supplied to the induction heating arrangement, the value of the electrical control parameter increases, for example, during the operation heating mode, in response to the power supplied to the induction heating arrangement, it increases towards the target value of the control parameter.

8. The aerosol generation system according to any one of claims 1 to 2, wherein power is supplied to the induction heating arrangement as a plurality of individual current pulses, and the response to the electrical control parameter is analyzed for each current pulse to determine whether the slope of the electrical control parameter with respect to the time curve increases or decreases over the duration of the pulse.

9. The aerosol generation system according to claim 8, wherein the electrical control parameter is the apparent conductance of the induction heating system, and the control parameter is analyzed for each current pulse to determine whether the value of the electrical control parameter increases or decreases over the duration of the pulse.

10. The aerosol generation system according to claim 9, wherein the controller is configured to switch from the heating mode to the recovery mode when it detects that the value of the electrical control parameter decreases over the duration of the pulse.

11. The aerosol generation system according to claim 9, wherein the controller is configured to enable cooling of the susceptor, for example, by reducing the load cycle of the power supplied to the induction heating arrangement, when it detects that the value of the electrical control parameter decreases over the duration of the pulse.

Images