Aerosol generating device with means for detecting at least one of the insertion of an aerosol generating article into the device or the removal of an aerosol generating article from the device - Patent Application 20070123333

Abstract

The present invention relates to an aerosol generating device for heating an aerosol-forming substrate capable of forming an inhalable aerosol when heated. The device comprises a cavity for removably receiving at least a portion of an aerosol-generating article, the article including an aerosol-forming substrate and an inductively heated susceptor for heating the substrate. The device further comprises an induction heating arrangement configured to generate an alternating magnetic field in the cavity for inductively heating the susceptor of the article when the article is received in the cavity. The device also comprises a control circuit configured to generate power pulses for intermittently powering the induction heating arrangement, to determine, during one or more power pulses, a value of at least one characteristic of the induction heating arrangement, the value being dependent on an article having a susceptor present or absent in the cavity, and to detect at least one of an insertion of an article into the cavity or a removal of an article from the cavity based on the determined value and a predefined threshold. The present invention further relates to an aerosol generating system comprising such an apparatus, and to a method for detecting the presence or absence of an aerosol-generating article in a cavity of an aerosol generating device.

Description

[Technical field]

[0001] The present invention relates to an aerosol generating device comprising a cavity and means for detecting the insertion or removal of an aerosol generating article into the cavity. The present invention further relates to an aerosol generating system comprising such a device and to a method for detecting the presence or absence of an aerosol generating article in a cavity of an aerosol generating device. [Background technology]

[0002] Aerosol generating devices used to generate inhalable aerosols by heating an aerosol-forming substrate are generally known from the prior art. Such devices may comprise a cavity for removably receiving at least a portion of an aerosol-generating article including the aerosol-forming substrate to be heated. To heat the substrate, the device may further comprise an induction heating arrangement powered by a battery and configured, when the device is in use, to generate an alternating magnetic field in the cavity for inductively heating a susceptor in thermal proximity or in direct physical contact with the substrate. The susceptor may be an integral part of the aerosol-generating article. Such devices may further comprise means for detecting the presence or absence of an aerosol-generating article in the receiving cavity in order to activate or deactivate the heating process. This type of detection may be achieved by a separate sensor means that continuously monitors the presence or absence of the article in the cavity. However, a separate sensor means generally requires additional assembly space in the device. Furthermore, the continuous operation of the sensor consumes energy and may thus significantly reduce the operating time of the device.

[0003] It would therefore be desirable to have an aerosol generating device that possesses the advantages of the prior art solutions but alleviates their limitations, and in particular, it would be desirable to have an aerosol generating device that provides improved means for detecting the insertion or removal of an aerosol-generating article into the receiving cavity of the device. Summary of the Invention

[0004] According to the present invention, an aerosol generating device is provided for heating an aerosol-forming substrate capable of forming an inhalable aerosol when heated. The device comprises a cavity for removably receiving at least a portion of an aerosol-generating article, the article including an aerosol-forming substrate and an inductively heated susceptor for heating the substrate. The device further comprises an induction heating arrangement configured to generate an alternating magnetic field in the cavity for inductively heating the susceptor of the article when the article is received in the cavity. The device also comprises a control circuit configured to generate power pulses for intermittently powering the induction heating arrangement and to determine a value of at least one characteristic of the induction heating arrangement during one or more power pulses, the value depending on an article having a susceptor present or absent in the cavity. Furthermore, the control circuit is configured to detect at least one of an insertion of an article into the cavity or a removal of an article from the cavity based on the determined value and a predetermined threshold, in particular based on a comparison of the determined value with the predetermined threshold, and more particularly in response to the determined value breaching the predetermined threshold.

[0005] According to the invention, it has been found that the induction heating arrangement can be used not only for heating the substrate, but also for detecting at least one of the insertion or removal of an article into or from the cavity. The induction heating arrangement can thus be used for multiple purposes. Advantageously, this makes it possible to avoid additional assembly space for a separate sensor means.

[0006] Furthermore, for the purposes of article detection, it has been found that operating the induction heating arrangement in a pulsed mode advantageously reduces power consumption and therefore increases the overall operating time of the device compared to other solutions.

[0007] According to the invention, the insertion or removal of the article is based on the fact that the insertion and removal of the article into the cavity causes at least one property of the induction heating arrangement, in particular at least one electric and / or magnetic property, to be modified due to the presence or absence of a susceptor in the vicinity of the induction heating arrangement. The change in the at least one property caused by the presence or absence of a susceptor can be due to an interaction between the magnetic field of the induction heating arrangement and the susceptor. That is, the at least one property of the induction heating arrangement has a different value depending on whether an article with a susceptor is present or absent in the cavity.

[0008] However, instead of detecting a change in at least one characteristic that occurs when an article is inserted into or removed from the cavity, the invention proposes to determine a value of at least one characteristic of the induction heating arrangement and to detect at least one of the insertion of an article into or removal from the cavity on the basis of the determined value and a predefined threshold. In particular, the invention proposes to compare the determined value with a predefined threshold that is chosen so as to make it possible to clearly distinguish between an article present in the cavity and an article not present in the cavity. Advantageously, determining a value of at least one characteristic and comparing the determined value with a predefined threshold that does not derive from an instantaneous measurement makes the detection of the insertion or removal of an aerosol-generating article more reliable. In particular, this procedure avoids undesirable false positive or false negative detections of the insertion or removal of an aerosol-generating article, for example when an article is inserted into and removed from the cavity only gradually or partially.

[0009] As used herein, a / value of at least one characteristic of the induction heating arrangement determined (or to be determined) by the control circuit may refer to the actual value of the at least one characteristic of the induction heating arrangement as (instantaneously) determined by the control circuit. The actual value of the at least one characteristic of the induction heating arrangement determined (instantaneously) by the control circuit may be within 20% of the actual value, or within 15% of the actual value, or within 10% of the actual value, or within 5% of the actual value of the at least one characteristic of the induction heating arrangement that is actually present in the induction heating arrangement.

[0010] The at least one characteristic of the induction heating arrangement can be any characteristic that has a different value depending on whether a susceptor is present or not in the cavity, i.e., a different value when a susceptor is present compared to a value when the susceptor is not present. For example, the at least one characteristic can be a current, a voltage, an electrical resistance, an electrical conductance, a frequency, a phase shift, a magnetic flux, and an inductance of the induction heating arrangement.

[0011] The characteristic is preferably at least one of the electrical (equivalent) resistance, electrical (equivalent) conductance or inductance of the induction heating arrangement. The term "electrical (equivalent) resistance" as used herein refers to the real part of the complex impedance defined as the ratio of the AC voltage supplied to the induction heating arrangement to the measured AC current. Thus, the "equivalent resistance" may also be viewed as a resistive load of the induction heating arrangement. Conversely, the term "electrical (equivalent) conductance" refers to the inverse of the electrical (equivalent) resistance, i.e., the ratio of the measured current to the voltage supplied to the induction heating arrangement. Similarly, the term "inductance" as used herein refers to the imaginary part of the complex impedance defined as the ratio of the supplied voltage to the measured current. Inductance generally includes the characteristic of an electric circuit that is susceptible to external electromagnetic influences.

[0012] The change in at least one characteristic of the induction heating arrangement that leads to the breaching of the predetermined threshold may be due to a specific magnetic permeability and / or a specific electrical resistivity of the susceptor. That is, the susceptor in the aerosol-generating article may comprise a material having a specific magnetic permeability and / or a specific electrical resistivity. The susceptor preferably comprises an electrically conductive material. For example, the susceptor may comprise a metallic material. The metallic material may be, for example, one of aluminum, nickel, iron, or an alloy thereof, for example, carbon steel or ferritic stainless steel. Aluminum has an electrical resistivity of about 2.65×10E-08 ohm-meter and a magnetic permeability of about 1.256×10E-06 henry / meter, measured at room temperature (20° C.). Similarly, ferritic stainless steels have an electrical resistivity of approximately 6.9×10E-07 ohm-meter and a magnetic permeability in the range of 1.26×10E-03 henry / meter to 2.26×10E-03 henry / meter when measured at room temperature (20° C.).

[0013] In general, the predefined threshold value may be a predefined function of a reference value of at least one characteristic of the induction heating arrangement determined (in advance) when no aerosol-generating article comprising a susceptor is present in the cavity. In this case, the reference value defines a clear value of the at least one characteristic, which indicates that no aerosol-generating article is present in the cavity. In contrast, the threshold value defines an upper or lower value, which indicates that an aerosol-generating article is present in the cavity, depending on whether the value of the at least one characteristic determined for one or more power pulses during operation of the device increases or decreases when an aerosol-generating article is inserted into the device. Thus, depending on whether the at least one characteristic of the induction heating arrangement increases or decreases when an aerosol-generating article is inserted into the device, this function must be selected such that the threshold value is higher or lower than the reference value obtained when no article is present in the cavity. Similarly, the predefined threshold value may be a predefined function of a reference value of at least one characteristic of the induction heating arrangement determined (in advance) when an aerosol-generating article comprising a susceptor is present in the cavity. In this case, the reference value defines a clear value of the at least one characteristic that indicates the presence of an aerosol-generating article in the cavity. In contrast, the threshold value defines an upper or lower value, at which the value of the at least one characteristic determined for one or more power pulses during operation of the device indicates the absence of an aerosol-generating article in the cavity, depending on whether the at least one characteristic of the induction heating arrangement increases or decreases when an aerosol-generating article is inserted into the device. Thus, depending on whether the at least one characteristic of the induction heating arrangement increases or decreases when an aerosol-generating article is inserted into the device, this function must be selected such that the threshold value is smaller or larger than the reference value obtained when the article is present in the cavity. In either case, the threshold value lies somewhere between the value of the at least one characteristic measured when the article is present in the cavity (reference value) and the value of the at least one characteristic measured when the article is not present in the cavity.

[0014] The predefined function may be a linear function. That is, the threshold value may be a linear function of the reference value of the at least one characteristic of the induction heating arrangement, determined when the aerosol-generating article comprising a susceptor is not present in the cavity. In particular, the predefined threshold value may correspond to the reference value of the at least one characteristic of the induction heating arrangement, determined (pre-determined) when the aerosol-generating article comprising a susceptor is not present in the cavity, multiplied by a predefined scale factor. Similarly, the threshold value may be a linear function of the reference value of the at least one characteristic of the induction heating arrangement, determined when the aerosol-generating article comprising a susceptor is present in the cavity. Also in this case, the predefined threshold value may correspond to the reference value of the at least one characteristic of the induction heating arrangement, determined (pre-determined) when the aerosol-generating article comprising a susceptor is present in the cavity, multiplied by a predefined scale factor. Depending on whether the at least one characteristic of the induction heating arrangement increases or decreases when the aerosol-generating article comprising a susceptor is inserted into the device, the scale factor may be greater or less than 1.

[0015] If the reference value of the at least one characteristic of the induction heating arrangement is (pre)determined when no aerosol-generating article including a susceptor is present in the cavity, the predetermined scale factor may be in the range of 0.8 to 0.98, in particular 0.9 to 0.95, more particularly 0.92 to 0.94, if the at least one characteristic of the induction heating arrangement decreases when the aerosol-generating article is inserted into the device. Similarly, the predetermined scale factor may be in the range of 1.02 to 1.2, in particular 1.05 to 1.1, more particularly 1.06 to 1.08, if the at least one characteristic of the induction heating arrangement increases when the aerosol-generating article is inserted into the device. By way of example, if the at least one characteristic of the induction heating arrangement is the electrical (equivalent) conductance of the induction heating arrangement, the conductance decreases when the aerosol-generating article is inserted into the device. In this case the scale factor may be, for example, 0.94. The aforementioned scale factors have proven to be suitable for clearly distinguishing between articles not present in the cavity and those present in the cavity.

[0016] If the reference value of the at least one characteristic of the induction heating arrangement is (pre)determined when the aerosol-generating article comprising the susceptor is present in the cavity, the predetermined scale factor may be in the range of 1.02 to 1.2, in particular 1.05 to 1.1, more particularly 1.06 to 1.08, if the at least one characteristic of the induction heating arrangement decreases when the aerosol-generating article is inserted into the device. Similarly, the predetermined scale factor may be in the range of 0.8 to 0.98, in particular 0.9 to 0.95, more particularly 0.92 to 0.94, if the at least one characteristic of the induction heating arrangement increases when the aerosol-generating article is inserted into the device.

[0017] The aforementioned scale factors have proven adequate to clearly distinguish between items not present in the cavity and items present within the cavity.

[0018] The predetermined threshold value may also correspond to a reference value of the at least one characteristic of the induction heating arrangement -predetermined when the aerosol-generating article, including the susceptor, is absent or present in the cavity- plus or minus a predetermined offset value, depending on whether the at least one characteristic of the induction heating arrangement increases or decreases when the aerosol-generating article is inserted into the device. The offset value may be in the range of 2 percent to 20 percent, in particular 5 percent to 10 percent, more particularly 6 percent to 8 percent of the predetermined reference value of the at least one characteristic of the induction heating arrangement. The aforementioned offset value has also proven to be suitable for clearly distinguishing between an article absent from the cavity and an article present in the cavity.

[0019] Preferably, the reference value, and therefore the threshold value, of the at least one characteristic of the induction heating arrangement may be (initially) predetermined and stored in the control circuit during manufacture of the aerosol generating device. For this purpose, the device may be calibrated in the manufacturing state, whether an article is present in the cavity or not, by operating the device such that the control circuit generates one or more pulses for intermittently powering the induction heating arrangement. During the one or more pulses, the control circuit determines a value of the at least one characteristic of the induction heating arrangement, which defines a reference value of the at least one characteristic of the induction heating arrangement for an article not present in the cavity or present in the cavity. This reference value is used to determine the threshold value based on a predetermined function. The predetermined function may be stored in the control circuit. The thus determined threshold value may then be stored in the device to be available later during normal user operation, for comparison with the determined value of the at least one characteristic determined during the one or more power pulses.

[0020] Advantageously, the reference value of the at least one characteristic of the induction heating arrangement may be updated at predetermined regular intervals during the life of the aerosol generating device. This procedure may help to counter drifts (decrease or increase) of the at least one characteristic that may occur during the life of the aerosol generating device due to natural change effects, in particular drifts of the electrical parameters of the heating arrangement. For example, if the electrical conductance of the heating arrangement is used as the at least one characteristic, it has been found that an initial reference value of the conductance obtained in the manufacturing state, for example when no article was present in the cavity, is smaller when redetermined after some time. In some cases, already after several heating cycles, the conductance value obtained when no article is present in the cavity may be even smaller than a threshold value determined on the basis of the initial reference value measured in the manufacturing state and stored in the device. As a result, the control circuit always returns a value of the conductance that is interpreted as indicating the presence, even when no article is present in the cavity. The device will therefore not be able to reliably detect the insertion or removal of an article into the cavity.

[0021] To prevent the possibility of false alarms in article detection, the reference value of at least one characteristic of the induction heating arrangement may be updated every ten times, particularly every fifth time, more particularly every second time, when an aerosol-generating article including a susceptor is not present in the cavity, preferably after every user experience.

[0022] The reference value of at least one characteristic of the induction heating arrangement is preferably updated by redetermining at least one characteristic of the induction heating arrangement during one or more power pulses when an aerosol-generating article including a susceptor is absent from the cavity or is present in the cavity, and by storing the redetermined value in the control circuit as an updated reference value.

[0023] The at least one characteristic may be observed by measuring any parameter of the induction heating arrangement indicative of the at least one characteristic. The parameter may be measured directly or indirectly. Preferably, the parameter may be at least one of a current and a voltage. Thus, the control circuit may include a measurement device for determining at least one of a current and a voltage indicative of the at least one characteristic of the induction heating arrangement. In particular, the parameter may be a DC current supplied to the induction heating arrangement from a DC power source of the apparatus. Thus, the control circuit may include a current measurement device arranged and configured to measure the DC current supplied to the induction heating arrangement from the DC power source. To that end, the measurement device may include a DC current measurement device arranged in a series connection between the DC power source and the induction heating arrangement. For example, the measurement device may include a resistor and a shunt amplifier. Thus, when the aerosol-generating article is inserted into the cavity of the aerosol-generating apparatus, the susceptor is present in the cavity, causing an equivalent resistance to increase or a conductance to decrease due to an increased resistive load. This results in a reduction in the DC current supplied to the induction heating arrangement. The reduction in DC current is detected by a current measuring device in the control circuit, which may then activate a heating operation of the induction heating arrangement to heat the substrate. Similarly, when the aerosol-generating article is removed from the cavity of the aerosol-generating device, the cavity is clear of the susceptor, causing a reduction in the resistive load, resulting in a reduction in the equivalent resistance or an increase in conductance. This results in an increase in DC current supplied to the induction heating arrangement. The increase in DC current is detected by a current measuring device in the control circuit, which may then activate the next heating operation.

[0024] In addition to the current measuring device, the control circuit may include a voltage measuring device arranged and configured to measure a DC voltage supplied by the DC power supply to the induction heating arrangement. The voltage measuring device may be arranged in parallel with a DC power supply of the apparatus to determine the DC voltage supplied by the DC power supply to the induction heating arrangement.

[0025] Furthermore, the control circuit may be configured to determine a value of the electrical conductance of the induction heating arrangement from the ratio of the determined DC current to the determined DC voltage. Similarly, the control circuit may be configured to determine a value of the electrical (equivalent) resistance of the induction heating arrangement from the ratio of the determined DC voltage to the determined DC current. Advantageously, determining the electrical conductance or electrical (equivalent) resistance of the induction heating arrangement from both the determined DC current and the determined DC voltage takes into account drift, in particular the gradual decrease in the power used to drive the heating arrangement. Typically, the power used to drive the heating arrangement is provided by a battery. Thus, the control circuit may appropriately determine the value of the electrical conductance regardless of the actual power provided to the heating arrangement.

[0026] As mentioned above, the aerosol generating device may comprise a power source, in particular a DC power source configured to provide a DC supply voltage and a DC supply current to the induction heating arrangement. The power source is preferably a battery, such as a lithium iron phosphate battery. The power source may be rechargeable. The power source may have a capacity that allows for storage of sufficient energy for one or more user experiences. For example, the power source may have a capacity sufficient to allow continuous generation of aerosol for about six minutes, or a multiple of six minutes. In another embodiment, the power source may have a capacity sufficient to allow a predetermined number of puffs, or discontinuous activation of the induction heating arrangement.

[0027] Generally, the control circuitry may be configured to detect at least one of the following: insertion of an aerosol-generating article into the cavity to initiate a heating operation, removal of the aerosol-generating article from the cavity after a heating operation to allow the heating operation to be initiated again, or removal of the aerosol-generating article from the cavity during a heating operation to stop the heating operation.

[0028] In the first and second cases, the aerosol generating device is not in heating operation but in a specific article detection mode, in particular an article insertion detection mode or an article removal detection mode, respectively. In the third case, the aerosol generating device is in heating operation, i.e. in the heating mode. Nevertheless, in the heating mode, the control circuit may be able to detect the removal of an aerosol-generating article from the cavity by determining a value of at least one characteristic of the induction heating arrangement and comparing it with a predefined threshold, in particular by detecting that the determined value of the at least one characteristic of the induction heating arrangement determined for one or more power pulses has breached the predefined threshold. In the first and second cases, i.e. when the device is in the article detection mode, in particular the article insertion detection mode and the article removal detection mode, the power pulses generated by the control circuit are particularly aimed at detecting the insertion of an aerosol-generating article into or removal of an aerosol-generating article from the cavity. Thus, the power pulses generated for article detection during the article detection mode, in particular in the article insertion detection mode and the article removal detection mode, may be displayed as probe power pulses. Thus, the control circuit may be configured to generate probe power pulses. In the third case, i.e. when the device is in the heating mode, the power pulses generated by the control circuit may be intended to heat the aerosol-forming substrate by pulsed heating. Thus, the power pulses generated during the heating operation, in particular during the heating mode, may be denoted as heating power pulses. Furthermore, during the heating operation, i.e. in the heating mode, the power pulses may also be used to monitor the device for removal of the aerosol-generating article from the cavity in order to stop the heating operation. That is, the power pulses during the heating mode may also be used to detect removal of the aerosol-generating article from the cavity by determining a value of at least one characteristic of the induction heating arrangement and comparing it with a predefined threshold, in particular by detecting that the determined value of at least one characteristic of the induction heating arrangement determined for one or more power pulses has breached a predefined threshold.

[0029] In general, the power pulse in the item insertion detection mode and the power pulse in the item removal mode may be identical. Also, the power pulse in the item insertion detection mode and the item removal detection mode may differ from each other by at least one characteristic, such as the amplitude of the power pulse, the pulse duration, and the time interval between two successive power pulses. Similarly, the power pulse in the item insertion / removal detection mode and the power pulse in the heating mode may be identical. Also, the power pulse in the insertion / removal detection mode and the heating mode, i.e. the probe power pulse and the heating power pulse, may differ from each other by at least one characteristic, such as the amplitude of the power pulse, the pulse duration, and the time interval between two successive power pulses. In particular, the amplitude of the heating power pulse may be larger than the amplitude of the probe power pulse. In addition, the probe power pulse may have a fixed pulse pattern, in particular a fixed periodicity. In contrast, the heating power pulse may have a non-fixed, in particular a variable pulse pattern, for example in the case of pulse width modulation of the heating power.

[0030] The control circuitry may be configured to disable a heating operation of the induction heating arrangement in response to detecting removal of an article from the cavity during a heating operation. Similarly, the control circuitry may be configured to disable a heating operation of the induction heating arrangement after a previous heating operation and until after detection of removal of the article from the cavity. Advantageously, this prevents a user of the device from initiating a new heating operation with a depleted aerosol-generating article. Furthermore, safety may be improved as re-heating a used aerosol-generating article may cause damage to the heating arrangement.

[0031] Disabling of the heating operation should cease when removal of the article is detected. Thus, the control circuitry may be configured to enable activation of a heating operation of the induction heating arrangement in response to detecting removal of the article from the cavity during a heating operation and after disabling of the heating operation. Similarly, the control circuitry may be configured to enable activation of a heating operation of the induction heating arrangement in response to detecting removal of the article from the cavity after a previous heating operation.

[0032] Generally, the heating operation of the induction heating arrangement may be activated manually, i.e. by user input. Alternatively or additionally, activation of the heating operation may be event driven, i.e. occurring in response to detecting a particular event. The control circuitry is preferably configured to initiate the heating operation of the induction heating arrangement in response to detecting the insertion of an article into the cavity. Advantageously, this enhances user convenience, as the heating operation is automatically initiated upon insertion of an article into the cavity without the need for further user input.

[0033] The control circuitry may further include a motion sensor for detecting operation of the aerosol generating device. Advantageously, the motion sensor may make it possible to monitor the device for movement and thus detect, for example, whether a user removes an aerosol generating article from the cavity or inserts an article into the cavity, thus initiating a new user experience. By way of example, the motion sensor may include at least one of an accelerometer or a gyroscope for measuring the angular orientation or angular velocity of the device. That is, the motion sensor may be configured to detect at least one of the acceleration, angular orientation, and / or angular velocity of the aerosol generating device, in particular due to the user's handling of the device. In order to avoid unnecessary pulse generation during idle phases, i.e. periods when the aerosol generating device is not in use, the control circuitry may be configured to initiate generation of probe power pulses only in response to detection of operation of the aerosol generating device. Thus, detection of device movement is used to trigger the article detection mode when a user intends to use the device. Advantageously, this allows to save power and therefore increase the overall operating time of the aerosol generating device. The control circuitry is preferably configured to initiate generation of (probe) power pulses in response to detecting operation of the device reaching or exceeding a predetermined operational threshold. Similarly, the control circuitry may be configured to stop generation of (probe) power pulses a predetermined time after detecting operation of the device reaching or exceeding a predetermined operational threshold. The control circuitry may also be configured to stop generation of (probe) power pulses in response to detecting operation of the device not reaching a predetermined operational threshold for a predetermined idle time, or in response to detecting no operation for a predetermined idle time. Advantageously, this procedure also helps to reduce power consumption and thus increase the overall operational time of the device.

[0034] To further reduce power consumption, the control circuit may be configured to reduce the number of (probe) power pulses per time unit, for example by a factor of two or a factor of three, in response to detecting that the operation of the device does not reach a predetermined operation threshold during a predetermined idle time or in response to detecting the absence of operation during a predetermined idle time. The idle time may be in the range of 10 seconds to 90 seconds, in particular 15 seconds to 60 seconds, preferably 15 seconds to 40 seconds. According to another configuration, the control circuit may be configured to reduce the number of (probe) power pulses per time unit, for example by a factor of two or a factor of three, in response to detecting that the operation of the device does not reach a predetermined acceleration threshold during a predetermined first idle time or in response to detecting the absence of operation during a predetermined first idle time, and then to stop generating power pulses, in particular probe power pulses, in response to detecting that the operation of the device does not reach a predetermined acceleration threshold during a predetermined second idle time starting after the first idle time or in response to detecting the absence of operation during a predetermined second idle time starting after the first idle time. Advantageously, this configuration further reduces power consumption and therefore increases the overall operating time of the device even more. The first idle time may be in the range of 5 seconds to 60 seconds, in particular 10 seconds to 30 seconds, and preferably 15 seconds to 25 seconds. Similarly, the second idle time may be in the range of 10 seconds to 90 seconds, in particular 15 seconds to 60 seconds, and preferably 15 seconds to 30 seconds.

[0035] Alternatively or additionally to triggering the article detection mode by monitoring the device for operation, the article detection mode may also be triggered by other events. For example, the article detection mode may be triggered by removing the aerosol generating device from a power charging unit used to recharge the DC power supply of the device. For this purpose, the control circuit may be configured to detect the removal of the aerosol generating device from the power charging unit and to initiate the generation of a (probe) power pulse in response to detecting the removal of the aerosol generating device from the power charging unit. Similarly, the control circuit may be configured to detect the insertion of the aerosol generating device into the power charging unit and to stop the generation of a (probe) power pulse in response to detecting the insertion of the aerosol generating device into the power charging unit. This procedure avoids unnecessary power consumption and enhances user convenience, since the article detection mode does not have to be actively started or stopped.

[0036] The control circuitry may be configured to cease heating operation of the device according to various conditions, for example in response to at least one of detecting a predetermined number of puffs, detecting the lapse of a predetermined heating time, or receiving a user input. Advantageously, any of these conditions may then trigger detection of removal of the aerosol-generating article from the cavity. Thus, in response to detecting cessation of heating operation of the device, the control circuitry may be configured to initiate generation of a power pulse, in particular a probe power pulse, to detect removal of the article. As mentioned above, this procedure also enhances user convenience.

[0037] The control circuitry may also be configured to terminate heating operation of the induction heating arrangement in response to detecting removal of the article from the cavity. Advantageously, this may be used to discontinue heating operation if, for example, the aerosol-generating article is prematurely removed, for example, before the expiration of a predetermined heating time, or before the expiration of a predetermined number of puffs, or before a user input.

[0038] The control circuit may be configured to verify insertion of an article into or removal of an article from the cavity by generating at least one verification power pulse a predetermined period after a first detection of a change in at least one characteristic of the induction heating arrangement, and by redetecting the change in at least one characteristic of the induction heating arrangement.

[0039] The control circuit may include a switch constructed and arranged to control the supply of power from the DC power source to the induction heating arrangement to generate power pulses for intermittently powering the induction heating arrangement, and to this end, the switch may be intermittently opened and closed to intermittently power the induction heating arrangement to detect at least one of the insertion of an aerosol-generating article into the cavity to initiate a heating operation (article insertion detection mode), the removal of an aerosol-generating article from the cavity after a heating operation to allow the heating operation to be initiated again (article removal detection mode), or the removal of an aerosol-generating article from the cavity during a heating operation to stop the heating operation.

[0040] The switch may also be used to intermittently supply power to the induction heating arrangement during the heating mode of the device to generate power pulses for pulsed heating of the aerosol-forming substrate. This mode may therefore be denoted as a pulsed heating mode. In this mode, the power pulses may also be used to monitor the device for removal of the aerosol-generating article from the cavity to stop the heating operation. It is also possible to permanently close the switch to continuously apply a DC voltage from the DC power source to the induction heating arrangement during the heating operation of the aerosol generating device. This mode may therefore be denoted as a continuous heating mode. In the continuous heating mode, the control circuit may also be able to detect removal of the article from the cavity by determining a value of at least one characteristic of the induction heating arrangement and comparing it to a predefined threshold, in particular by detecting that the determined value of at least one characteristic of the induction heating arrangement has breached the predefined threshold.

[0041] In general, the pulse duration and the time interval between two successive (probe) power pulses should be selected to balance the effects of energy depletion and the performance of the user experience. The (probe) power pulse may have a pulse duration in the range of 1 microsecond to 500 microseconds, in particular 10 microseconds to 300 microseconds, preferably 15 microseconds to 120 microseconds, most preferably 30 microseconds to 100 microseconds. The term "pulse duration" as used herein means the time interval during which the heating arrangement is powered, in particular during which the above-mentioned switch is closed. The time interval between two successive (probe) power pulses may be in the range of 50 milliseconds to 2 seconds, in particular 100 milliseconds to 2 seconds, preferably 500 milliseconds to 1 second. The sum of the pulse duration and the time interval between two successive power pulses may be expressed as the polling time, i.e. the difference in time between the start of a pulse and the start of the next pulse. The polling time may be in the range of 50 ms to 2.5 seconds, in particular 51 ms to 2.5 ms, more particularly 100 ms to 2 seconds, and preferably 500 ms to 1 second.

[0042] For article detection, the (probe) power pulse is preferably generated only for a predetermined period of time. If no article insertion or removal is detected within the predetermined period of time, the generation of the power pulse, i.e., the article detection mode, as described above, may be stopped to conserve power. Similarly, if an article insertion or removal is detected within the predetermined period of time, the detection mode may be stopped immediately, specifically in response to the detection of the article insertion or removal.

[0043] The induction heating arrangement may be configured to generate a high frequency alternating magnetic field, as referred to herein, in the range of 500 kHz to 30 MHz, in particular 5 MHz to 15 MHz, preferably 5 MHz to 10 MHz.

[0044] To generate the alternating magnetic field, the induction heating arrangement may include a DC / AC converter connected to the DC power source. The DC / AC converter may include an LC network. For example, the DC / AC converter may include a class C power amplifier, or a class D power amplifier, or a class E power amplifier. In particular, the DC / AC converter may include a transistor switch and a transistor switch driver circuit and an LC network. The LC network may include a series connection of a capacitor and an inductor, the inductor being configured and arranged to generate an alternating magnetic field in the cavity, in particular for inductive heating the susceptor and for article detection. The LC network may further include a shunt capacitor in parallel with the transistor switch. In addition, the DC / AC converter may include a choke inductor for providing a DC supply voltage +V_DC to the DC power source.

[0045] The inductor used for generating an alternating magnetic field in the cavity for inductive heating of the susceptor and for article detection may include at least one induction coil, in particular a single induction coil or multiple induction coils. The number of induction coils may depend on the size and / or number of the susceptors. The induction coil or multiple induction coils may have a shape that matches the shape of one or more susceptors in the aerosol-generating article. Similarly, the induction coil(s) may have a shape that matches the shape of the housing of the aerosol-generating device. The at least one induction coil may be a helical coil or a flat planar coil, in particular a pancake coil or a curved planar coil. The at least one induction coil may be held in the housing of the heating arrangement or in one of the main body or housing of the aerosol-generating device comprising the heating arrangement. The at least one induction coil may be wound around a preferably cylindrical coil support, for example a ferrite core. The induction heating arrangement may be configured to generate an alternating magnetic field continuously after activation of the system or intermittently, such as after every puff.

[0046] The control circuitry may further be configured to control the overall operation of the aerosol generating device. The control circuitry and at least part of the inductive heating arrangement may be integral parts of the overall electrical circuitry of the aerosol generating device.

[0047] The control circuit may include a microprocessor, such as a programmable microprocessor, a microcontroller, or an application specific integrated circuit chip (ASIC) or other electronic circuit capable of providing control. The control circuit may include at least one of a transimpedance amplifier for current-voltage conversion, an inverting signal amplifier, a single-ended to differential converter, an analog-to-digital converter, and a microcontroller. The microprocessor may be configured to at least one of control a switch used to generate power pulses for intermittently powering the induction heating arrangement, read a measuring device to measure the current supplied from a DC power source to the induction heating arrangement, and control a transistor switch driver circuit of the induction heating arrangement. The control circuit may be an overall controller of the aerosol generating device or may be part of an overall controller of the aerosol generating device. The control circuit and at least a part of the induction heating arrangement (apart from the inductor) may be arranged on a common printed circuit board. This is particularly advantageous with regard to a compact design of the heating arrangement.

[0048] The receiving cavity may comprise an insertion opening through which the aerosol-generating article may be inserted into the receiving cavity. As used herein, the direction in which the aerosol-generating article is inserted is indicated as the insertion direction. The insertion direction preferably corresponds to an extension of the length axis, in particular the central axis, of the receiving cavity. After insertion into the receiving cavity, at least a portion of the aerosol-generating article may still extend outwardly through the insertion opening. The outwardly extending portion is preferably provided for interaction with a user, in particular for being placed into the user's mouth. Thus, during use of the device, the insertion opening may be proximal to the mouth. As a result, as used herein, the section proximal to the insertion opening or proximal to the user's mouth during use of the device, respectively, is indicated with the prefix "proximal". Sections that are disposed further away are indicated with the prefix "distal". With respect to this convention, the receiving cavity may be disposed or located in the proximal part of the aerosol-generating device. The insertion opening may be disposed or located at the proximal end of the aerosol generating device, in particular at the proximal end of the receiving cavity. In general, the receiving cavity may have any suitable shape. In particular, the shape of the receiving cavity may correspond to the shape of the aerosol-generating article to be received therein. Preferably, the receiving cavity may have a substantially cylindrical shape or a tapered shape, for example a substantially conical or substantially frustoconical shape.

[0049] The aerosol generating device may further comprise optical or tactile indicator means for indicating detection of at least one of the following: removal of an article from the cavity, insertion of an article into the cavity, disabling or enabling of the heating operation of the induction heating arrangement. Advantageously, such indicator means may enhance ease of use and user convenience.

[0050] The present invention further relates to an aerosol generation system comprising an aerosol generating device according to the present invention and as described herein. The system further comprises an aerosol-generating article, at least a portion of which may be removably receivable or removably receivable in a receiving cavity of the device. The article comprises at least one aerosol-forming substrate and an inductively heated susceptor for heating the substrate when the article is received in the cavity.

[0051] The aerosol-generating article may be a consumable product, in particular intended for single use. The aerosol-generating article may be a tobacco article. In particular, the article may be a rod-shaped article, preferably a cylindrical rod-shaped article, which may resemble a conventional cigarette. The article is preferably an elongated or rod-shaped article. The elongated or rod-shaped article may have a shape similar to that of a conventional cigarette. The aerosol-generating article, in particular the elongated or rod-shaped article, may have a circular or elliptical or oval or square or rectangular or triangular or polygonal cross-section.

[0052] As an example, the aerosol-generating article may be a rod-shaped article, in particular a cylindrical article comprising one or more of the following elements: a distal front plug element, a base element, a first tube element, a second tube element and a filter element. The base element preferably comprises at least one aerosol-forming substrate to be heated and a susceptor arrangement in thermal contact or in thermal proximity with the aerosol-forming substrate. The base element may have a length of 10 mm to 14 mm, for example 12 mm. The first tube element is distal to the second tube element. Preferably, the first tube element is proximal to the base element and the second tube element is proximal to the first tube element and distal to the filter element, i.e. between the first tube element and the filter element. At least one of the first tube element and the second tube element may comprise a central air passage. The cross section of the central air passage of the second tube element may be larger than the cross section of the central air passage of the first tube element. Preferably, at least one of the first and second tube elements may comprise a hollow cellulose acetate tube. At least one of the first and second tube elements may have a length between 6 mm and 10 mm, for example 8 mm. The filter element preferably functions as a mouthpiece or as part of the mouthpiece together with the second tube element. The term "mouthpiece" as used herein refers to a portion of the article through which the aerosol exits the aerosol-generating article. The filter element may have a length between 10 mm and 14 mm, for example 12 mm. The distal forward plug element may be used to cover and protect the distal forward end of the base element. The distal forward plug element may have a length between 3 mm and 6 mm, for example 5 mm. The distal forward plug element may be made of the same material as the filter element. All the aforementioned elements may be consecutively arranged along the length axis of the article in the above mentioned order, with the distal forward plug element being preferably arranged at the distal end of the article and the filter element being preferably arranged at the proximal end of the article. Each of the aforementioned elements may be substantially cylindrical. Specifically, all of the elements may have the same external cross-sectional shape and / or dimensions.In addition, the elements may be surrounded by one or more outer wrappers, such as to hold the elements together and to maintain the desired cross-sectional shape of the rod-like article. The wrapper is preferably made of paper. The wrapper may further comprise an adhesive that bonds the overlapping free ends of the wrappers to each other. For example, the distal forward plug element, the base element, and the first tube element may be surrounded by a first wrapper, and the second tube element and the filter element may be surrounded by a second wrapper. The second wrapper may also surround at least a portion of the first tube element (after being wrapped by the first wrapper) to connect the distal forward plug element, the base element, and the first tube element surrounded by the first wrapper to the second tube element and the filter element. The second wrapper may comprise perforations around its circumference.

[0053] As used herein, the term "aerosol-forming substrate" refers to a substrate capable of releasing volatile compounds capable of forming an aerosol when heated. The aerosol-forming substrate may be a solid aerosol-forming substrate, or a liquid aerosol-forming substrate, or a gel-like aerosol-forming substrate. The aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavor compounds that are released from the substrate upon heating. Alternatively or additionally, 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. The aerosol-forming substrate may also comprise other additives and ingredients such as nicotine or flavoring substances. In particular, the liquid aerosol-forming substrate may comprise water, solvents, ethanol, plant extracts, and natural or artificial flavors. The aerosol-forming substrate may also be a paste-like material, a sachet of porous material containing the aerosol-forming substrate, or even loose tobacco mixed with, for example, a gelling or adhesive agent, which may include a common aerosol former such as glycerin, and then compressed or shaped into a plug.

[0054] As used herein, the term "susceptor" refers to an element that includes a material capable of being inductively heated in an alternating electromagnetic field, which may be the result of at least one of hysteresis losses or eddy currents induced within the susceptor, depending on the electrical and magnetic properties of the susceptor material.

[0055] The susceptor may include various geometric configurations. The susceptor may be one of a particulate susceptor, or a susceptor filament, or a susceptor mesh, or a susceptor wick, or a susceptor pin, or a susceptor rod, or a susceptor blade, or a susceptor strip, or a susceptor sleeve, or a susceptor cup, or a cylindrical susceptor, or a planar susceptor. For example, the susceptor may be an elongated susceptor strip having a length in the range of 8 mm (millimeter) to 16 mm (millimeter), in particular 10 mm (millimeter) to 14 mm (millimeter), preferably 12 mm (millimeter). The width of the susceptor strip may be, for example, in the range of 2 mm (millimeter) to 6 mm (millimeter), in particular 4 mm (millimeter) to 5 mm (millimeter). The thickness of the susceptor strip is preferably in the range of 0.03 mm (millimeter) to 0.15 mm (millimeter), more preferably 0.05 mm (millimeter) to 0.09 mm (millimeter).

[0056] The susceptor may be a multi-layer susceptor, for example a multi-layer susceptor strip. In particular, the multi-layer susceptor may comprise a first susceptor material and a second susceptor material. The first susceptor material is preferably optimized with respect to heat loss and therefore heating efficiency. For example, the first susceptor material may be aluminum or a ferrous material such as stainless steel. In contrast, the second susceptor material is preferably used as a temperature marker. For this purpose, the second susceptor material is chosen to have a Curie temperature that corresponds to a predetermined heating temperature of the susceptor assembly. At that Curie temperature, the magnetic property of the second susceptor changes from ferromagnetic to paramagnetic, accompanied by a temporary change in its electrical resistance. Therefore, by monitoring the corresponding change in the current absorbed by the induction source, it is possible to detect when the second susceptor material has reached its Curie temperature, and therefore when the predetermined heating temperature has been reached. The second susceptor material has a Curie temperature lower than the ignition point of the aerosol-forming substrate, preferably less than 500 degrees C. Suitable materials for the second susceptor material may include nickel and certain nickel alloys.

[0057] Further features and advantages of the aerosol generating system and aerosol generating article according to the invention have already been mentioned above in relation to the aerosol generating device according to the invention and apply equally.

[0058] The invention further relates to an aerosol-generating article for use in an aerosol-generating system according to the invention or in an aerosol-generating device according to the invention. The aerosol-generating article comprises an aerosol-forming substrate and an inductively heated susceptor for heating the substrate. Further features and advantages of the aerosol-generating article have already been mentioned above with respect to the aerosol-generating device and the aerosol-generating system according to the invention and apply equally.

[0059] The invention further relates to a method for detecting the presence or absence of an aerosol-generating article having an inductively heated susceptor in a cavity of an aerosol generating device, the apparatus comprising a cavity for removably receiving at least a portion of the article, and an induction heating arrangement configured to generate an alternating magnetic field in the cavity for inductively heating the susceptor of the article when the article is received in the cavity. The aerosol generating device is preferably an aerosol generating device according to the invention and as described herein. The method comprises:

[0060] - determining a value of at least one characteristic of the induction heating arrangement during one or more power pulses of the induction heating arrangement, the value being dependent on the article having a susceptor present or absent in the cavity;

[0061] - detecting at least one of an insertion of an object into the cavity or a removal of an object from the cavity based on the determined value and a predetermined threshold, in particular based on a comparison of the determined value with the predetermined threshold, more particularly in response to the determined value breaching the predetermined threshold.

[0062] As described above with respect to the apparatus, the predetermined threshold value is a predetermined function of a reference value of at least one characteristic of the induction heating arrangement, determined beforehand when an aerosol-generating article comprising a susceptor is absent or present in the cavity. In particular, the predetermined threshold value may correspond to a reference value of at least one characteristic of the induction heating arrangement, determined beforehand when an aerosol-generating article comprising a susceptor is absent or present in the cavity, multiplied by a predetermined scale factor. The predetermined scale factor is in the range of 0.8 to 0.98, in particular 0.9 to 0.95, more particularly 0.92 to 0.94, or the predetermined scale factor is in the range of 1.02 to 1.2, in particular 1.05 to 1.1, more particularly 1.06 to 1.08. Similarly, the predetermined threshold value may correspond to a reference value of at least one characteristic of the induction heating arrangement, determined beforehand when an aerosol-generating article comprising a susceptor is absent or present in the cavity, plus or minus a predetermined offset value. The offset value may be within the range of 2 percent to 20 percent, in particular 5 percent to 10 percent, and more particularly 6 percent to 8 percent of a predetermined reference value of at least one characteristic of the induction heating arrangement.

[0063] Preferably, a reference value for at least one characteristic of the induction heating arrangement may be initially predetermined and stored within the aerosol generating device during manufacture of the device.

[0064] Also, as mentioned above with respect to the device, the reference values ​​and thresholds may be subject to drifts in the electrical parameters of the heating arrangement. Thus, the method may further comprise updating the reference value of at least one characteristic of the induction heating arrangement at predetermined regular intervals during the life of the aerosol generating device. In particular, the updating of the reference value of at least one characteristic of the induction heating arrangement may occur every tenth, in particular every fifth, more particularly every second, preferably after every user experience when no aerosol-generating article comprising a susceptor is present in the cavity. Updating the reference value of at least one characteristic of the induction heating arrangement may comprise redetermining at least one characteristic of the induction heating arrangement during one or more power pulses when no aerosol-generating article comprising a susceptor is present in the cavity or when no aerosol-generating article comprising a susceptor is present in the cavity, and storing the redetermined value in the device as an updated reference value.

[0065] Further features and advantages of the method according to the invention have already been mentioned above with reference to the aerosol generating device and the aerosol generating system according to the invention and apply equally.

[0066] The present invention is defined in the claims. However, below is provided a non-exhaustive list of non-limiting examples. Any one or more features of these examples may be combined with any one or more features of other examples, embodiments, or aspects described herein.

[0067] Example 1: 1. An aerosol generating device for heating an aerosol-forming substrate capable of forming an inhalable aerosol when heated, comprising: Example 2: - a cavity for removably receiving at least a portion of an aerosol-generating article, the article including an aerosol-forming substrate and an inductively heated susceptor for heating the substrate; an induction heating arrangement configured to generate an alternating magnetic field in the cavity for inductively heating a susceptor of the article when the article is received in the cavity; - a control circuit configured to generate power pulses for intermittently powering the induction heating arrangement, determine during one or more power pulses a value of at least one characteristic of the induction heating arrangement, the value having different values ​​depending on whether an article having a susceptor is present in the cavity or not, and detect at least one of the insertion of an article into the cavity or the removal of an article from the cavity based on a comparison of the determined value with a predetermined threshold, in particular the determined value with the predetermined threshold. Example 1a: 1. An aerosol generating device for heating an aerosol-forming substrate capable of forming an inhalable aerosol when heated, comprising: - a cavity for removably receiving at least a portion of an aerosol-generating article, the article including an aerosol-forming substrate and an inductively heated susceptor for heating the substrate; an induction heating arrangement configured to generate an alternating magnetic field in the cavity for inductively heating a susceptor of the article when the article is received in the cavity; - a control circuit configured to generate power pulses to intermittently power the induction heating arrangement, determine during one or more power pulses a value of at least one characteristic of the induction heating arrangement, the value varying depending on an article having a susceptor present or absent in the cavity, and detect at least one of the insertion of an article into the cavity or the removal of an article from the cavity in response to the determined value breaching a predetermined threshold. Example 3: An aerosol generating apparatus as described in Example 1 or Example 1a, wherein the predetermined threshold is a predetermined function of a reference value of at least one characteristic of the induction heating arrangement that is determined in advance when an aerosol-generating article including a susceptor is not present in the cavity or is present in the cavity. Example 4: An aerosol generating device as described in any one of Examples 1 or 2, wherein the predetermined threshold value corresponds to a reference value of at least one characteristic of the induction heating arrangement - predetermined to be determined when an aerosol generating article including a susceptor is not present in the cavity or is present in the cavity - multiplied by a predetermined scale factor. Example 5: The aerosol generating apparatus according to Example 3, wherein the predetermined scale factor is in the range of 0.8 to 0.98, particularly 0.9 to 0.95, more particularly 0.92 to 0.94, or the predetermined scale factor is in the range of 1.02 to 1.2, particularly 1.05 to 1.1, more particularly 1.06 to 1.08. Example 6: An aerosol generating device as described in any one of Examples 1, 1a, or 2, wherein the predetermined threshold value corresponds to a reference value of at least one characteristic of the induction heating arrangement - predetermined when an aerosol generating article including a susceptor is not present in the cavity or is present in the cavity - plus or minus a predetermined offset value. Example 7: An aerosol generating apparatus as described in Example 5, wherein the offset value is within the range of 2 percent to 20 percent, particularly 5 percent to 10 percent, and more particularly 6 percent to 8 percent of a predetermined reference value of at least one characteristic of the induction heating arrangement. Example 8: 7. An aerosol generating device according to any one of embodiments 1 to 6, wherein the reference value of at least one characteristic of the induction heating arrangement is determined in advance and stored in the control circuit during manufacture of the aerosol generating device. Example 9: An aerosol generating device according to any one of the preceding embodiments, wherein the reference value of at least one characteristic of the induction heating arrangement is updated at predetermined regular intervals during the life of the aerosol generating device. Example 10: An aerosol generating device as described in Example 8, wherein the reference value of at least one characteristic of the induction heating arrangement is updated every ten times, particularly every five times, more particularly every two times, preferably after each user experience, when an aerosol generating article including a susceptor is not present in the cavity. Example 11: An aerosol generating device as described in either Example 8 or Example 9, wherein a reference value of at least one characteristic of the induction heating arrangement is updated by redetermining at least one characteristic of the induction heating arrangement during one or more power pulses when an aerosol generating article including a susceptor is not present in the cavity or is present in the cavity, and by storing the redetermined value in the control circuit as an updated reference value. Example 12: An aerosol generating apparatus as described in any one of Examples 1 to 10, wherein at least one characteristic of the induction heating arrangement is one of the current, voltage, electrical resistance, electrical conductance, frequency, phase shift, magnetic flux, and inductance of the induction heating arrangement. Example 13: 12. An aerosol generating device according to any one of the preceding embodiments, wherein the control circuitry comprises a measuring device for measuring at least one of a current and a voltage indicative of at least one characteristic of the induction heating arrangement. Example 14: An aerosol generating device as described in any one of Examples 1 to 12, wherein the control circuit comprises a current measuring device for determining the DC current drawn by the induction heating arrangement from the DC power supply of the device, and a voltage measuring device for determining the DC voltage supplied to the induction heating arrangement by the DC power supply, and the control circuit is configured to determine a value of the electrical conductance of the induction heating arrangement from the ratio of the determined DC current to the determined DC voltage. Example 15: An aerosol generating system comprising an aerosol generating device according to any one of Examples 1 to 13, wherein at least a portion of the article is removably receivable or removably received within a receiving cavity of the device, and the article comprises an aerosol-forming substrate and an inductively heated susceptor for heating the substrate when the article is received within the cavity, and an aerosol generating article for use with the device. Example 16: 1. A method for detecting the presence or absence of an aerosol-generating article having an inductively heated susceptor within a cavity of an aerosol generating device, the apparatus comprising: a cavity for removably receiving at least a portion of the article; and an induction heating arrangement configured to generate an alternating magnetic field within the cavity for inductively heating a susceptor of the article when the article is received within the cavity, the method comprising: - determining a value of at least one characteristic of the induction heating arrangement during one or more power pulses of the induction heating arrangement, the value depending on the article having a susceptor present or absent in the cavity; - detecting at least one of an insertion of an object into the cavity or a removal of an object from the cavity based on the determined value and a predetermined threshold, in particular based on a comparison of the determined value with a predetermined threshold. Example 15a: 1. A method for detecting the presence or absence of an aerosol-generating article having an inductively heated susceptor within a cavity of an aerosol generating device, the apparatus comprising: a cavity for removably receiving at least a portion of the article; and an induction heating arrangement configured to generate an alternating magnetic field within the cavity for inductively heating a susceptor of the article when the article is received within the cavity, the method comprising: - determining a value of at least one characteristic of the induction heating arrangement during one or more power pulses of the induction heating arrangement, the value depending on whether the article has a susceptor present in the cavity or not; - detecting at least one of an insertion of an object into the cavity or a removal of an object from the cavity in response to the determined value breaching a predetermined threshold. Example 17: The method of example 15 or example 15a, wherein the predetermined threshold is a predetermined function of a reference value of at least one characteristic of the induction heating arrangement that is determined in advance when the aerosol-generating article including the susceptor is not present in the cavity or is present in the cavity. Example 16a: 17. The method of embodiment 16, further comprising updating the baseline value of at least one characteristic of the induction heating arrangement at predetermined regular intervals during the life of the aerosol generating device. Example 18: The method of Example 16a, wherein updating the reference value of at least one characteristic of the induction heating arrangement occurs every ten times, in particular every fifth time, more particularly every second time, preferably after every user experience, when an aerosol-generating article comprising a susceptor is not present in the cavity. Example 19: The method of example 16a or example 17, wherein updating the reference value of at least one characteristic of the induction heating arrangement includes redetermining at least one characteristic of the induction heating arrangement during one or more power pulses when an aerosol-generating article including a susceptor is not present in the cavity or is present in the cavity, and storing the redetermined value in the apparatus as an updated reference value. Example 20: The method of any of claims 15 to 18, wherein the predetermined threshold value corresponds to a reference value of at least one characteristic of the induction heating arrangement - previously determined when an aerosol-generating article including a susceptor is absent or present in the cavity - multiplied by a predetermined scale factor. Example 21: The method according to example 19, wherein the predetermined scale factor is in the range of 0.8 to 0.98, in particular 0.9 to 0.95, more particularly 0.92 to 0.94, or the predetermined scale factor is in the range of 1.02 to 1.2, in particular 1.05 to 1.1, more particularly 1.06 to 1.08. Example 22: A method according to any of claims 15 to 18, wherein the predetermined threshold value corresponds to a reference value of at least one characteristic of the induction heating arrangement - predetermined when an aerosol-generating article including a susceptor is absent or present in the cavity - plus or minus a predetermined offset value. Example 23: The method according to embodiment 21, wherein the offset value is within the range of 2 percent to 20 percent, in particular 5 percent to 10 percent, more particularly 6 percent to 8 percent of a predetermined reference value of at least one characteristic of the induction heating arrangement. The embodiments will now be further described with reference to the following figures: [Brief description of the drawings]

[0068] [Figure 1] FIG. 1 illustrates generally an exemplary embodiment of an aerosol generation system according to the present invention, including an aerosol generating device and an aerosol generating article for use in the device. [Diagram 2] FIG. 2 illustrates generally an exemplary embodiment of an aerosol generation system according to the present invention, including an aerosol generating device and an aerosol generating article for use in the device. [Diagram 3] FIG. 3 shows diagrammatically an induction heating arrangement for the aerosol generating device according to FIGS. [Figure 4] FIG. 4 illustrates diagrammatically the operational details of the method according to the invention. [Diagram 5] FIG. 5 illustrates diagrammatically the operational details of the method according to the invention. [Figure 6] FIG. 6 shows diagrammatically the drift in conductance of the heating arrangement shown in FIGS. 1 and 2 during its lifetime. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0069] 1 and 2 show diagrammatically an exemplary embodiment of an aerosol-generating system 1 according to the present invention, which is used to generate an inhalable aerosol by heating an aerosol-forming substrate. The system 1 comprises an aerosol-generating article 10 including an aerosol-forming substrate 21 to be heated, and an aerosol-generating device 100 for heating the substrate as the article 10 is engaged with the device 100. As can be particularly seen in FIG. 1, the aerosol-generating article 10 has a substantially rod shape similar to the shape of a conventional cigarette. In this embodiment, the article 10 comprises five elements successively arranged in coaxial alignment: a distal front plug element 50, a base element 20, a first tube element 40, a second tube element 45, and a filter element 60. The distal front plug element 50 is disposed at the distal end of the article 10 and covers and protects the distal front end of the base element 20, while the filter element 60 is disposed at the proximal end of the article 10. Both the distal front plug element 50 and the filter element 60 may be made of the same filter material. The filter element 60 preferably functions as a mouthpiece, preferably together with the second tube element 45, as part of the mouthpiece. The filter element may have a length of 10 mm to 14 mm, for example 12 mm, while the distal front plug element 50 may have a length of 3 mm to 6 mm, for example 5 mm. The base element 20 comprises a heated aerosol-forming substrate 21 and a susceptor arrangement 30 configured and arranged to heat the substrate 21 when exposed to an alternating magnetic field. The susceptor arrangement 30 is fully embedded in the substrate 21 so as to be in direct thermal contact with the substrate 21. The base element 20 may have a length of 10 mm to 14 mm, for example 12 mm. Each of the first tube element 40 and the second tube element 45 is a hollow cellulose acetate tube having a central air passage 41, 46, the cross section of the central air passage 46 of the second tube element 45 being larger than the cross section of the central air passage 41 of the first tube element 40. The first tube element 40 and the second tube element 14 may have a length of between 6 mm and 10 mm, for example 8 mm.

[0070] In use, the aerosol formed by the volatile compounds released from the base element 20 is drawn through the first tube element 40, the second tube element 45, and the filter element 60 toward the proximal end of the article 10. Each of the aforementioned elements 50, 20, 40, 45, 60 may be substantially cylindrical. Specifically, all elements 50, 20, 40, 45, 60 may have the same external cross-sectional shape and dimensions. In addition, the elements may be surrounded by one or more outer wrappers to hold the elements together and to maintain the desired cross-sectional shape of the rod-like article, etc. In this embodiment, the distal forward plug element 50, the base element 20, and the first tube element 40 are surrounded by a first wrapper 71, while the second tube element 45 and the filter element 60 are surrounded by a second wrapper 72. The second wrapper 72 also surrounds at least a portion of the first tube element 40 (after being wrapped by the first wrapper 71) and connects the distal forward plug element 50 (surrounded by the first wrapper 71), the base element 20, and the first tube element 40 to the second tube element 45 and the filter element 60. The first wrapper 71 and the second wrapper 72 are preferably made of paper. In addition, the second wrapper 72 may be provided with perforations around its circumference (not shown). The wrappers 71, 72 may further comprise an adhesive that bonds the overlapping free ends of the wrappers to one another.

[0071] The elongated aerosol-generating device 100 essentially has two parts, a proximal part 102 and a distal part 101. In the proximal part 102, the device 100 comprises a cavity 103 for removably receiving at least a portion of the aerosol-generating article 10. In the distal part 101, the device 100 comprises a power supply 150 and a controller 160 for powering and controlling the operation of the device 100. To heat the substrate, the device 100 comprises an induction heating arrangement 110 including an induction coil 118 for generating an alternating magnetic field, in particular a high-frequency magnetic field, in the cavity 103. In this embodiment, the induction coil 118 is a helical coil arranged in the proximal part 102 of the device so as to circumferentially surround the cylindrical receiving cavity 103. The coil 118 is arranged such that the susceptor 30 of the aerosol-generating article 10 experiences an electromagnetic field when the article 10 is engaged with the device 100. The alternating magnetic field is used to inductively heat the susceptor 30 in the aerosol-generating article 10 when the article 10 is received in the cavity 103. Thus, upon inserting the article 10 into the cavity 103 of the device 100 (see FIG. 2) and activating the heating arrangement 110, the alternating electromagnetic field in the cavity 103 induces eddy currents and / or hysteresis losses in the susceptor 30 depending on the magnetic and electrical properties of the susceptor material. As a result, the susceptor 30 is heated until it reaches an operating temperature sufficient to vaporize the aerosol-forming substrate 21 surrounding the susceptor 30 in the article 10. In use of the system, when a user puffs, i.e., negative pressure is applied to the filter element 60 of the article 10, air is drawn into the cavity 103 at the rim of the article insertion opening 105 of the device 100. The airflow further extends through a passage formed between the inner surface of the cylindrical cavity 103 and the outer surface of the article 10 towards the distal end of the cavity 103. At the distal end of the cavity 103, the airflow enters the aerosol-generating article 10 through the substrate element 20 and further passes through the first tube element 40, the second tube element 45, and the filter element 60, and finally exits the article 10. At the substrate element 20, vaporized material from the aerosol-forming substrate 21 is entrained into the airflow.Thereafter, as it passes through the first tube element 40, the second tube element 45, and the filter element 60, the airflow containing the vaporized material is cooled to form an aerosol that exits the article 10 through the filter element 60.

[0072] Figure 3 shows further details of the induction heating arrangement 110 used to generate the alternating magnetic field in the cavity 103. According to this embodiment, the induction heating arrangement 110 comprises a DC / AC inverter connected to a DC power supply 150 as shown in Figures 1 and 2. The DC / AC inverter comprises a class E power amplifier, which comprises the following components: a transistor switch 111 comprising a field effect transistor T (FET), e.g. a metal oxide semiconductor field effect transistor (MOSFET), a transistor switch supply circuit, indicated by arrow 112, for supplying a switching signal (gate-source voltage) to the transistor switch 111, a shunt capacitor C1 and an LC load network 113 comprising a series connection of a capacitor C2 and an inductor L2. The inductor L2 corresponds to the induction coil 118 as shown in Figures 1 and 2 used to generate the alternating magnetic field in the cavity 103. In addition, a choke L1 is provided for supplying a DC supply voltage +V_DC to the DC power supply 150. 3, the ohmic resistance R representing the total equivalent resistance or total resistive load 114 when the system is in use, i.e. when an item is inserted into the cavity 103 of the apparatus 100, is the sum of the ohmic resistance of the inductor coil 118 marked with L2 and the ohmic resistance of the susceptor. Otherwise, when no item is inserted into the cavity 103, the equivalent resistance or resistive load 114 corresponds only to the ohmic resistance of the inductor coil 118.

[0073] For various purposes, in particular to automatically enable or disable the heating process and / or to prevent a user from reheating a depleted aerosol-generating article, it may be desirable to detect at least one of the insertion and removal of an aerosol-generating article into and from the receiving cavity 103. To this end, the aerosol generating device according to this embodiment may operate in at least one of an article insertion detection mode or an article removal detection mode.

[0074] According to the invention, the detection of the insertion and / or removal of the article 10 in the cavity 103 is realized via the heating arrangement 110. Advantageously, this avoids additional assembly space for separate sensor means. The basic idea is to determine a value of at least one characteristic of the induction heating arrangement 110, the value depending on the presence or absence of the article 10 with the susceptor 30 in the cavity 103, based on the determined value and a predefined threshold value, in particular in response to the determined value breaching the predefined threshold value, to detect at least one of the insertion of the article 10 into the cavity 103 or the removal of the article 10 from the cavity 103. In this embodiment, it is the electrical conductance of the heating arrangement 110 that is used as the characteristic of the induction heating arrangement indicating the presence or absence of the article 10 in the receiving cavity 103. As explained above, the value of the electrical conductance of the heating arrangement 110 is the inverse of the total equivalent resistance or total resistive load 114 of the heating arrangement 110, both of which depend on the presence or absence of the susceptor 30 in the vicinity of the induction coil 118. When an article is inserted into the cavity 103 of the device 100, the total equivalent resistance corresponds to the sum of the ohmic resistance of the inductor coil 118 and the ohmic resistance of the susceptor 30. In contrast, when no article is received in the cavity 103, the equivalent resistance corresponds only to the ohmic resistance of the inductor coil 118. This change in the equivalent resistance is accompanied by a corresponding inverse change in the electrical conductance of the heating arrangement 110. Thus, when an aerosol-generating article 10 is inserted into the cavity 103 of the aerosol-generating device 100, the presence of the susceptor 30 reduces the conductance of the heating arrangement 110 due to an increase in the resistive load 114. Conversely, when the aerosol-generating article 10 is removed from the cavity 103 , the absence of the susceptor 30 causes an increase in the conductance of the heating arrangement 110 due to a reduced resistive load 114 .

[0075] The electrical conductance of the heating arrangement 110 can be detected via the DC voltage V_DC and DC current I_DC provided from the DC power source 150 to the induction heating arrangement 110, i.e. to the LC load network 113. For this purpose, the aerosol generating device 100 comprises a current measuring device 140 connected in series between the DC power source 150 and the LC load network 113 and a voltage measuring device 145 connected in parallel to the DC power source 150. Both the current measuring device 140 and the voltage measuring device 145 are part of a control circuit which may be or may be part of the overall controller of the aerosol generating device 100. The control circuit is configured to determine a value of the electrical conductance of the induction heating arrangement 110 from the ratio between the determined DC current and the determined DC voltage.

[0076] When the aerosol generating device 100 is in an article detection mode (e.g., either an article insertion detection mode or an article removal detection mode), the heating assembly 110 is not operated in a continuous mode, but in a pulsed mode, in order to reduce the overall power consumption. To this end, the aerosol generating device 100 comprises a switch 130 arranged and configured to control the power supply from the DC power source 150 to the inductive heating arrangement 110. In this embodiment, the switch 130 is arranged in a series connection between the DC power source 150 and the LC load network 113. During the article detection mode, the switch is intermittently opened and closed to generate power pulses for intermittently powering the inductive heating arrangement 130. In contrast, during the heating mode of the aerosol generating device 100, the switch 130 may be permanently closed to continuously apply a DC voltage from the DC power source to the inductive heating arrangement 110. Also, the switch may be intermittently opened and closed during the heating mode of the aerosol generating device to generate heating power pulses for pulsed heating of the aerosol-forming substrate. This mode may therefore be denoted as a pulsed heating mode.

[0077] As shown in FIG. 3, the microprocessor 160 of the control circuit is used to control the switch 130 to generate power pulses for intermittently powering the induction heating arrangement 110. The microprocessor 160 is also configured to control the transistor switch driver circuit 112 of the induction heating arrangement 110 and to read the current measuring device 140 and the voltage measuring device 145 to determine a value of the electrical conductance of the induction heating arrangement 110 from the ratio of the determined DC current and the determined DC voltage. In an article insertion / removal detection mode, the microprocessor 160 initiates actuation of the switch 130 by closing the switch 130 for a predetermined closing time interval, thereby generating a power pulse having a pulse duration T1 corresponding to the closing time interval. The pulse duration T1 may be in the range of 1 microsecond to 500 microseconds, in particular 10 microseconds to 300 microseconds, preferably 15 microseconds to 120 microseconds, and most preferably 30 microseconds to 100 microseconds. At the end of the closing time interval, the microprocessor 160 reopens the switch 130 for a predefined opening time interval, thereby interrupting the passage of current to the heating arrangement. The opening time interval corresponds to the time interval between two successive power pulses, which may be in the range of 50 ms to 2 s, in particular 100 ms to 2 s, preferably 500 ms to 1 s for article detection. The opening and closing of the switch 130 may occur at regular time intervals to generate periodic power pulses for periodically powering the induction heating arrangement 110. Thus, the sum of the closing time interval and the opening time interval, or the sum of the pulse duration and the time interval between two successive power pulses, corresponds to the periodicity of the series of pulses. In general, the time interval T2 between two successive probe power pulses should be selected to balance the effects of energy depletion and the performance of the user experience. The pulse duration T1 should be as short as possible to provide a reliable measurement of the conductance.

[0078] FIG. 4 is a graph showing the change in the conductance G determined for a series of power pulses over time t. In this embodiment, the series of power pulses is generated with a pulse duration T1 of 100 microseconds and a time interval T2 between two successive power pulses of 1 second. Of course, these values ​​are only exemplary and may vary. As long as no aerosol-generating article is inserted, the control circuit determines for each pulse a conductance having a value G_NA from the ratio of the determined DC current to the determined DC voltage ("NA" stands for "no article"). As mentioned above, the value of the conductance G_NA is a function of the ohmic load 114 in the absence of an article, i.e. a function that depends essentially only on the ohmic resistance of the inductor L2. In contrast, when the user inserts an aerosol-generating article into the cavity 103, the ohmic load 114 increases because the ohmic load is equal to the ohmic resistance of the inductor L2 and the ohmic resistance of the susceptor 21. Due to the increase in ohmic load, the conductance of the heating arrangement 110 decreases to a value of G_A (where "A" stands for "inserted article") which is lower than G_NA.

[0079] However, instead of detecting a change in the conductance, the invention proposes to compare the determined value G of the conductance with a predefined threshold value chosen to be between values ​​G_NA and G_A, in order to make it possible to clearly distinguish between an article 10 present in the cavity 103 and an article not present in the cavity 103. That is to say, the control circuit is configured to detect the insertion of an article 10 into the cavity 103 or the removal of an article 10 from the cavity 103 in response to the determined value G of the conductance (determined for each power pulse) breaking through a predefined threshold value G_THRESHOLD. Advantageously, determining the value G of the conductance and comparing it with a predefined threshold value G_THRESHOLD that does not originate from an instantaneous measurement makes the article detection more reliable. In particular, this procedure avoids undesirable false positive or false negative detection of the insertion or removal of an aerosol-generating article, for example when an article is inserted into and removed from the cavity only gradually or partially. Once detected, the breaking through of the predefined threshold value G_THRESHOLD may trigger the initiation of a heating mode.

[0080] While FIG. 4 shows only the item insertion detection mode, FIG. 5 shows the change in conductance both during the item insertion detection mode (see the left half of FIG. 5) as well as during the item removal detection mode (see the right half of FIG. 5). For the item insertion detection mode, reference is made to the above description of FIG. 4. The change in conductance during the item removal detection mode is reversed. That is, during the item removal detection mode, the control circuit determines a conductance having a value of G_A for each pulse as long as the aerosol-generating article 10 is still received in the cavity 103. As soon as the article 10 is removed from the cavity 103, the ohmic load 114 is reduced and the conductance of the heating assembly increases. Thus, the control circuit determines a conductance having a value G_NA that exceeds a predefined threshold G_THRESHOLD, thus indicating the removal or absence of the article 10 from the cavity 103.

[0081] In general, the predefined threshold value may be a predefined function of a reference value of a characteristic of the induction heating arrangement, determined (a priori) when no aerosol-generating article is present in the cavity 103. In this embodiment, the threshold value G_THRESHOLD is a linear function of the reference value G_ref of the conductance, determined (a priori) when no article 10 is present in the cavity 103. For example, a threshold value G_THRESHOLD of 6 percent less than the reference value G_ref has been found to be adequate to clearly distinguish between an article 10 present in the cavity 103 and an article not present in the cavity 103. Thus, the linear function describing the dependence of the threshold value G_THRESHOLD from the reference value G_ref in this particular example is: G_THRESHOLD=0.94×G_ref In other words, the threshold value G_THRESHOLD corresponds to the reference value G_ref of the conductance, determined (a priori) when no article 10 is present in the cavity 103, minus an offset of 6 percent of the reference value G_ref.

[0082] The reference value of the conductance G_ref is preferably predetermined during manufacture of the aerosol generating device 100 and stored in the control circuit. Thus, the device 100 may be calibrated in the manufacturing state, for example, without the presence of an article 10 in the cavity 103. Calibration may be achieved by operating the device 100 such that the control circuit generates one or more pulses for intermittently powering the induction heating arrangement 110. During the one or more pulses, the control circuit determines a value of the conductance that defines the reference value G_ref of the conductance of an article not present in the cavity. This reference value G_ref is used to determine the threshold value G_threshold based on a predefined function stored in the control circuit. The threshold value G_threshold thus determined may then be stored in the device so as to be available later during normal user operation for comparison with the value of the conductance.

[0083] Advantageously, the reference value of the conductance G_ref is updated at predetermined regular intervals during the life of the aerosol generating device 10. This procedure can help to counter possible drifts (decrease or increase) of the conductance during the life of the device 10, in particular due to drifts of the electrical parameters of the heating arrangement 110. This drift behavior is exemplarily illustrated in FIG. 6, which shows the measurements G_NA and G_A of the conductance (closed solid lines) in months over time t. As can be seen, both values ​​gradually decrease over time. Only after a few days of operation can the value of the conductance G_NA, in the absence of an article in the cavity, be even smaller than the threshold value G_threshold (dash-dotted line), determined on the basis of an initial reference value G_ref (dashed line) measured in the manufacturing state (as indicated by the arrow 999) and stored in the device. As a result, the control circuit always returns a value of the conductance that is interpreted as indicating the presence, even if the article 10 is not present in the cavity 103. Thus, the device 100 will not be able to reliably detect the insertion or removal of the article 10 in the cavity 103. To compensate for the observed drift behavior, the reference value of the conductance is updated at least every tenth time, preferably after each user experience, by redetermining the value of the conductance during one or more power pulses when the article 10 is not present in the cavity, and by storing the redetermined value in the control circuit as an updated reference value G_ref*. The updated reference value G_ref* essentially corresponds to the value G_NA determined during the item insertion detection mode or the item removal detection mode of the previous user experience cycle. The updated and stored reference value G_ref* may then be used to update the threshold value G_threshold*, which may then be used during the item insertion detection mode or the item removal detection mode of the next user experience cycle to determine whether an aerosol-generating article 10 is present or absent in the cavity 103 of the device 100.

[0084] 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 instances as being 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. Thus, in this context, the number A is understood as A±5%. Within this context, the number A may be considered to include values ​​that are within the general standard error for the measurement of the property that the number A modifies. The number A may, in some instances used in the appended claims, deviate by the percentages recited above, without materially affecting 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 aerosol generating device for heating an aerosol forming substrate having the ability to form an inhalable aerosol when heated, - a cavity for removably receiving at least a portion of an aerosol generating article, said article comprising said aerosol forming substrate and an inductive heating susceptor for heating said substrate, the cavity; - an inductive heating arrangement configured to generate an alternating magnetic field in the cavity for inductively heating the susceptor of the article when the article is received in the cavity; - generating a power pulse for intermittently supplying power to the inductive heating arrangement, determining a value of at least one characteristic of the inductive heating arrangement during one or more power pulses, said value depending on an article having a susceptor present or not present in the cavity, and detecting at least one of insertion of an article into the cavity or removal of an article from the cavity based on the determined value and a predetermined threshold value, a control circuit configured to, an aerosol generating device.

2. The aerosol generating device according to claim 1, wherein the predetermined threshold value is a predetermined function of a reference value of the at least one characteristic of the inductive heating arrangement determined in advance when an aerosol generating article containing a susceptor is not present in the cavity or is present in the cavity.

3. The aerosol generating device according to claim 2, wherein the predetermined threshold value corresponds to the reference value of the at least one characteristic of the inductive heating arrangement determined in advance when an aerosol generating article containing a susceptor is not present in the cavity or is present in the cavity, multiplied by a predetermined scale factor.

4. The aerosol generating device according to claim 3, wherein the predetermined scale factor is in the range of 0.8 to 0.98, particularly 0.9 to 0.95, more specifically 0.92 to 0.94, or the predetermined scale factor is in the range of 1.02 to 1.2, particularly 1.05 to 1.1, more specifically 1.06 to 1.

08.

5. The aerosol generating device according to claim 2, wherein the predetermined threshold value corresponds to the reference value of the at least one characteristic of the inductive heating arrangement determined in advance when an aerosol generating article containing a susceptor is not present in the cavity or is present in the cavity, plus or minus a predetermined offset value.

6. The aerosol generating device according to claim 5, wherein the offset value is in the range of 2% to 20%, particularly 5% to 10%, more specifically 6% to 8% of the predetermined reference value of the at least one characteristic of the induction heating arrangement.

7. The aerosol generating device according to any one of claims 2 to 6, wherein the reference value of the at least one characteristic of the induction heating arrangement is determined in advance during the manufacture of the aerosol generating device and stored in the control circuit.

8. The aerosol generating device according to any one of claims 2 to 6, wherein the reference value of the at least one characteristic of the induction heating arrangement is updated at predetermined regular intervals during the life of the aerosol generating device.

9. The aerosol generating device according to claim 8, wherein the reference value of the at least one characteristic of the induction heating arrangement is preferably updated every time, particularly every five times, more specifically every two times, after a user experience when an aerosol generating article containing a susceptor is not present in the cavity.

10. The aerosol generating device according to claim 8, wherein the reference value of the at least one characteristic of the induction heating arrangement is updated by re-determining the at least one characteristic of the induction heating arrangement during one or more power pulses and storing the re-determined value in the control circuit as the updated reference value.

11. The aerosol generating device according to any one of claims 1 to 6, wherein the threshold value is between the value of the at least one characteristic measured when an article is present in the cavity and the value of the at least one characteristic measured when an article is not present in the cavity.

12. The aerosol generating device according to any one of claims 1 to 6, wherein the at least one characteristic of the induction heating arrangement is one of the current, voltage, electrical resistance, electrical conductance, frequency, phase shift, magnetic flux, and inductance of the induction heating arrangement.

13. The aerosol generating device according to any one of claims 1 to 6, wherein the control circuit includes a measuring device for determining at least one of the current and voltage indicating the at least one characteristic of the induction heating arrangement.

14. The aerosol generator according to any one of claims 1 to 6, wherein the control circuit includes a current measuring device for determining a DC current drawn from a DC power supply of the device by the induction heating arrangement, and a voltage measuring device for determining a DC voltage supplied to the induction heating arrangement by the DC power supply, and the control circuit is configured to determine a value of the electrical conductance of the induction heating arrangement from a ratio of the determined DC current and the determined DC voltage.

15. An aerosol generation system comprising the aerosol generator according to any one of claims 1 to 6 and an aerosol generation article for use with the device, wherein at least a portion of the article is removably receivable within the receiving cavity of the device or is removably received therein, and when the article is received within the cavity, the article comprises an aerosol formation substrate and an inductive susceptor for heating the substrate.

16. A method for detecting whether an aerosol generation article having an inductive susceptor is present within or not within a cavity of an aerosol generator, the device comprising a cavity for removably receiving at least a portion of the article and an induction heating arrangement configured to generate an alternating magnetic field within the cavity for inductively heating the susceptor of the article when the article is received within the cavity, the method comprising: - determining a value of at least one characteristic of the induction heating arrangement during one or more power pulses of the induction heating arrangement, the value being dependent on an article having a susceptor present within or not within the cavity; - detecting at least one of insertion of the article into the cavity or removal of the article from the cavity based on the determined value and a predetermined threshold.

17. The method according to claim 16, wherein the predetermined threshold is a predetermined function of a reference value of the at least one characteristic of the induction heating arrangement determined in advance when an aerosol generation article including a susceptor is not present within or is present within the cavity.

18. - The predetermined threshold value corresponds to the reference value of the at least one characteristic of the induction heating arrangement, which is determined in advance when the aerosol generating article including the susceptor is not present in the cavity or is present in the cavity, multiplied by a predetermined scale factor, and the predetermined scale factor is in the range of 0.8 to 0.98, particularly 0.9 to 0.95, more specifically 0.92 to 0.94, or the predetermined scale factor is in the range of 1.02 to 1.2, particularly 1.05 to 1.1, more specifically 1.06 to 1.

08. Or, - The predetermined threshold value corresponds to the reference value of the at least one characteristic of the induction heating arrangement, which is determined in advance when the aerosol generating article including the susceptor is not present in the cavity or is present in the cavity, plus or minus a predetermined offset value, and the offset value is in the range of 2% to 20%, particularly 5% to 10%, more specifically 6% to 8% of the predetermined reference value of the at least one characteristic of the induction heating arrangement. The method according to claim 17.

19. The method according to any one of claims 17 or 18, wherein the reference value of the at least one characteristic of the induction heating arrangement is updated at predetermined regular intervals during the life of the aerosol generating device.

20. The method according to any one of claims 16 to 18, wherein the threshold value is between the value of the at least one characteristic measured when the article is present in the cavity and the value of the at least one characteristic measured when the article is not present in the cavity.

Images