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

Abstract

To provide an aerosol-generating device with means for detecting at least one of insertion of an aerosol-generating article into the device or removal of an aerosol-generating article from the device.SOLUTION: The device comprises a cavity for removably receiving at least a portion of an aerosol-generating article, the article comprising an aerosol-forming substrate and an inductively heatable susceptor for heating the substrate. The apparatus further comprises a DC power supply and an inductive heating arrangement. The device further comprises control circuitry configured to generate probe power pulses to intermittently power the inductive heating arrangement and to detect a change in at least one property of the inductive heating arrangement due to the susceptor being present in or absent from the cavity when the aerosol-generating article is inserted into or removed from the cavity.SELECTED DRAWING: Figure 6

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, as well as a method for operating such a device. [Background technology]

[0002] Aerosol-generating devices used to generate inhalable aerosols by heating an aerosol-forming substrate are generally known in the prior art. Such devices typically include 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 include an induction heating arrangement powered by a battery and configured to generate an alternating magnetic field within the cavity during use of the device, for inductively heating a susceptor in thermal proximity or direct physical contact with the substrate. The susceptor may be an integral part of the aerosol-generating article. Such devices may further include means for detecting the insertion or removal of the aerosol-generating article into the receiving cavity to enable or disable the heating process. This type of detection can be achieved by a separate sensor means that continuously monitors the presence or absence of the article in the cavity. However, separate sensor means typically require additional assembly space within the device. Furthermore, continuous operation of the sensor consumes energy and can therefore significantly reduce the operating time of the device.

[0003] It would therefore be desirable to have an aerosol generating device that has the advantages of, but is not limited to, prior art solutions, and in particular, that provides improved means for detecting the insertion or removal of an aerosol-generating article into a receiving cavity of the device. Summary of the Invention

[0004] According to one aspect of the present invention, there is provided an aerosol generating apparatus for heating an aerosol-forming substrate capable of forming an inhalable aerosol when heated, the apparatus comprising: - a recess 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; - a DC power supply; - an induction heating arrangement connected to a DC power source and configured to generate an alternating magnetic field within the cavity when the article is received within the cavity for inductively heating a susceptor of the article in a heating operation; - a control circuit configured to supply power to the heating arrangement from a DC power source to power the induction heating arrangement, and to detect a change in at least one characteristic of the induction heating arrangement due to the presence or absence of the susceptor in the cavity in response to detecting at least one of the insertion of an article into or removal of an article from the cavity when an aerosol-generating article is inserted into or removed from the cavity.

[0005] According to another aspect of the present invention there is provided an aerosol generating apparatus for heating an aerosol-forming substrate capable of forming an inhalable aerosol when heated, the apparatus comprising: - a recess 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; - a DC power supply; - an induction heating arrangement connected to a DC power source and configured to generate an alternating magnetic field within the cavity when the article is received within the cavity for inductively heating a susceptor of the article in a heating operation; - a control circuit configured to generate power pulses to intermittently power the induction heating arrangement, and to detect a change in at least one characteristic of the induction heating arrangement due to the presence or absence of the susceptor in the cavity in response to detecting at least one of the insertion of the article into or removal of the article from the cavity when the aerosol-generating article is inserted into or removed from the cavity.

[0006] According to the present invention, it has been found that the induction heating arrangement can be used not only to heat the substrate, but also to detect at least one of the insertion of an article into the cavity or the removal of an article from the cavity. Thus, the induction heating arrangement can be used for multiple purposes. Advantageously, this makes it possible to avoid additional assembly space for a separate sensor means.

[0007] Furthermore, it has been found that for the purposes of article detection, operating the induction heating arrangement in pulsed mode advantageously reduces power consumption and therefore increases the overall operating time of the device compared to other solutions.

[0008] According to the present invention, the detection of the insertion or removal of an article is based on the fact that the insertion and removal of an article into the cavity alters at least one property of the induction heating arrangement, in particular at least one electric and / or magnetic property, 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 the susceptor can be due to an interaction between the magnetic field of the induction heating arrangement and the susceptor.

[0009] The at least one characteristic of the induction heating arrangement can be any characteristic having an associated parameter that has a different value in the presence of a susceptor compared to the value in the absence of a susceptor, for example, the at least one characteristic can be the current, voltage, resistance, frequency, phase shift, magnetic flux, and inductance of the induction heating arrangement.

[0010] The characteristic is preferably at least one of the equivalent resistance or inductance of the induction heating arrangement. As used herein, the term "equivalent resistance" refers to the real part of the complex impedance, which is defined as the ratio of the AC voltage supplied to the induction heating arrangement to the measured AC current. Therefore, the "equivalent resistance" may also be viewed as the resistive load of the induction heating arrangement. Similarly, as used herein, the term "inductance" refers to the imaginary part of the complex impedance, which is defined as the ratio of the AC voltage supplied to the measured AC current. Inductance generally includes a characteristic of an electrical circuit that is susceptible to external electromagnetic influences.

[0011] The change in at least one characteristic of the induction heating arrangement may be due to the specific magnetic permeability and / or specific electrical resistivity of the susceptor. That is, the susceptor in the aerosol-generating article may include a material having a specific magnetic permeability and / or a specific electrical resistivity. The susceptor preferably includes an electrically conductive material. For example, the susceptor may include a metallic material. The metallic material may be, for example, aluminum, nickel, iron, or an alloy thereof, such as carbon steel or ferritic stainless steel. Aluminum, when measured at room temperature (20°C), has an electrical resistivity of approximately 2.65×10E-08 ohm-meter and a magnetic permeability of approximately 1.256×10E-06 Henry / meter. Similarly, ferritic stainless steel, when measured at room temperature (20°C), has an electrical resistivity of approximately 6.9×10E-07 ohm-meter and a magnetic permeability ranging from 1.26×10E-03 Henry / meter to 2.26×10E-03 Henry / meter.

[0012] 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 the heating operation to allow the heating operation to be restarted; or removal of the aerosol-generating article from the cavity during the heating operation to stop the heating operation. In the first and second cases, the aerosol-generating device is not in a heating operation but in a specific article detection mode, specifically, an article insertion detection mode or an article removal detection mode, respectively. In the third case, the aerosol-generating device is in a heating operation, i.e., a heating mode. Nevertheless, in the heating mode, the control circuitry may be able to detect removal of the aerosol-generating article from the cavity by detecting a change in at least one characteristic of the induction heating arrangement due to the absence of the susceptor from the cavity when the article is removed from the cavity.

[0013] In the first and second cases, i.e., when the device is in the article detection mode, particularly 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 the cavity or the removal of an aerosol-generating article from the cavity. Thus, the power pulses generated for article detection during the article detection mode, particularly the article insertion detection mode and the article removal detection mode, may be referred to as probe power pulses. Thus, the control circuit may be configured to generate probe power pulses.

[0014] 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, particularly during the heating mode, may be referred to 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 detecting a change in at least one characteristic of the induction heating arrangement due to the absence of the susceptor from the cavity when the article is removed from the cavity.

[0015] Generally, the power pulse in the item insertion detection mode and the power pulse in the item removal mode may be identical. The power pulses 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 consecutive power pulses. Similarly, the power pulse in the item insertion / removal detection mode and the power pulse in the heating mode may be identical. The power pulses 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 consecutive power pulses. In particular, the amplitude of the heating power pulse may be greater 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.

[0016] The control circuit may be configured to disable the heating operation of the induction heating arrangement in response to detecting removal of the article from the cavity during a heating operation. Similarly, the control circuit may be configured to disable the heating operation of the induction heating arrangement after a previous heating operation until after detecting 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. That is, it prevents a user from reusing an aerosol-generating article that has already been used in a previous user experience. Otherwise, reheating a used aerosol-generating article could result in an unsatisfactory user experience, as the used aerosol-generating article may not be able to generate aerosol at a level compatible with an unused aerosol-generating article. As a result, user convenience of the device is improved, as reheating a used aerosol-generating article could otherwise result in an unsatisfactory user experience. Furthermore, safety may be improved, as reheating a used aerosol-generating article could result in damage to the heating arrangement.

[0017] When removal of the item is detected, disabling of the heating operation should be stopped. Thus, the control circuit may be configured to enable activation of a heating operation of the induction heating arrangement in response to detecting removal of the item from the cavity during a heating operation and after disabling of the heating operation. Similarly, the control circuit may be configured to enable activation of a heating operation of the induction heating arrangement in response to detecting removal of the item from the cavity after a previous heating operation.

[0018] 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., occur in response to detecting a particular event. Preferably, the control circuit is 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 begins automatically upon insertion of the article into the cavity, without the need for further user input. In particular, the user experience begins immediately, as is known from conventional cigarettes.

[0019] The control circuit may further include a motion sensor for detecting operation of the aerosol generating device. Advantageously, the motion sensor may enable monitoring of the device for motion, and thus, for example, detection of user handling of the device. That is, when the motion sensor detects motion of the aerosol generating device, this means that the user is holding the device and is therefore about to remove an aerosol-generating article from the cavity or insert an aerosol-generating article into the cavity to begin a new user experience. For example, the motion sensor may detect motion of the aerosol generating device when the aerosol generating device is removed from the power charging unit. When no motion is detected, this typically means that the aerosol generating device is in an idle state. This may be the case when the aerosol generating device is placed in the power charging unit or is idle on a table.

[0020] 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, i.e., the motion sensor may be configured to detect at least one of the acceleration, angular orientation, and / or angular velocity of the aerosol generation device, particularly due to handling of the device by a user.

[0021] 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 further configured to initiate generation of a probe power pulse in response to detecting operation of the aerosol generating device. In particular, the control circuitry may be configured to initiate generation of a power pulse only in response to detecting operation of the aerosol generating device. Detection of device operation is thus used to trigger the item detection mode when a user intends to use the device. Advantageously, this allows for power savings and therefore allows for an increase in the overall operating time of the aerosol generating device.

[0022] The control circuitry is preferably configured to initiate generation of a power pulse, particularly a probe power pulse, in response to detecting that the motion of the device reaches or exceeds a predetermined motion threshold. The predetermined motion threshold may be defined by an acceleration value, an angle value, or an angular velocity value. The predetermined acceleration threshold may be in the range of 0.5 g to 1.5 g, particularly 0.7 g to 1.3 g, where g is 9.80665 m / s 2 It means the standard acceleration due to gravity, defined by the standard [m / s2].

[0023] The control circuitry may be configured to stop generating power pulses, particularly probe power pulses, a predetermined time after detecting operation of the device reaching or exceeding a predetermined operational threshold. The control circuitry may further be configured to stop generating power pulses, particularly 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 a lack of operation for a predetermined idle time. Advantageously, this procedure also helps to reduce power consumption and therefore increase the overall operating time of the device.

[0024] To further reduce power consumption, the control circuit may be configured to reduce the number of power pulses, in particular probe power pulses, per time unit, for example by one half or one third in response to detecting that operation of the device does not reach a predetermined operational threshold for a predetermined idle time, or in response to detecting a lack of operation for a predetermined idle time, which may be in the range of 10 to 90 seconds, in particular 15 to 60 seconds, preferably 15 to 40 seconds.

[0025] According to another configuration, the control circuit may be configured to reduce the number of power pulses, particularly probe power pulses, per time unit, by, for example, one-half or one-third in response to detecting that device movement does not reach a predetermined acceleration threshold during a predetermined first idle time, or in response to detecting a lack of movement during the predetermined first idle time, and then to stop generating power pulses, particularly probe power pulses, in response to detecting that device movement does not reach a predetermined acceleration threshold during a predetermined second idle time starting after the first idle time, or in response to detecting a lack of movement during the predetermined second idle time starting after the first idle time. Advantageously, this configuration further reduces power consumption and thus further increases the overall operating time of the device. The first idle time may be in the range of 5 to 60 seconds, particularly 10 to 30 seconds, and preferably 15 to 25 seconds. Similarly, the second idle time may be in the range of 10 to 90 seconds, particularly 15 to 60 seconds, and preferably 15 to 30 seconds.

[0026] Alternatively or additionally to triggering the item detection mode by monitoring the device for operation, the item detection mode may also be triggered by other events. For example, the item detection mode may be triggered by removing the aerosol generating device from a power charging unit used to recharge the device's DC power supply. To that end, the control circuitry may be configured to detect removal of the aerosol generating device from the power charging unit. Furthermore, the control circuitry may be configured to initiate generation of a power pulse, in particular a probe power pulse, in response to detecting removal of the aerosol generating device from the power charging unit. This procedure may be advantageous for automatic initiation of item insertion detection. In particular, this procedure enhances user convenience, as the user does not need to actively initiate the item detection mode upon recharging the aerosol generating device.

[0027] Similarly, the control circuitry may be configured to detect insertion of the aerosol generating device into the power charging unit. Based on this, the control circuitry may be further configured to stop generating power pulses, particularly probe power pulses, in response to detecting insertion of the aerosol generating device into the power charging unit. Again, this procedure avoids unnecessary power consumption and enhances user convenience, as it is not necessary to actively stop the item detection mode before recharging the DC power source.

[0028] The control circuitry may be configured to terminate heating operation of the device under various conditions, in particular, the control circuitry may be configured to terminate heating operation of the device in response to at least one of detecting a predetermined number of puffs, detecting the lapse of a predetermined heating time, or receiving user input.

[0029] Advantageously, any of these conditions may then initiate detection of the removal of an aerosol-generating article from the cavity. Accordingly, the control circuitry may be configured to initiate generation of power pulses, particularly probe power pulses, to detect article removal in response to detecting cessation of heating operation of the device. As noted above, this procedure also enhances user convenience by eliminating the need to actively initiate article detection mode upon completion of a user experience.

[0030] The control circuitry may also be configured to terminate the heating operation of the induction heating arrangement in response to detecting removal of the article from the cavity. Advantageously, this configuration may be used to abort the heating operation, for example, if 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. In this regard, detection of removal of the article from the cavity may be considered as a further condition that triggers termination of the heating operation. Similarly, the heating operation may be terminated only in response to detecting removal of the article from the cavity.

[0031] The control circuit may be configured to verify insertion of an item into or removal of an item from the cavity by generating at least one verification power pulse a predetermined period after first detecting a change in at least one characteristic of the induction heating arrangement, and by redetecting a change in at least one characteristic of the induction heating arrangement.

[0032] 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, the removal of the aerosol-generating article from the cavity after a heating operation to allow the heating operation to be restarted, or the removal of the aerosol-generating article from the cavity during a heating operation to stop the heating operation.

[0033] As previously mentioned, the first two scenarios relate to detecting the insertion of an article into the cavity and the removal of an aerosol-generating article from the cavity during the article detection mode or operation of the aerosol-generating device, particularly the article insertion detection mode and the article removal detection mode, respectively. In contrast, the third scenario relates to detecting the removal of an aerosol-generating article from the cavity during the heating operation or heating mode of the device. In this regard, the switch may also be used to intermittently supply power to the induction heating arrangement to generate power pulses for pulsed heating of the aerosol-forming substrate during the heating mode of the device. Therefore, this mode may be referred to as a pulse heating mode. In this mode, the power pulses may also be used to monitor the device for the removal of the aerosol-generating article from the cavity to stop the heating operation.

[0034] It is also possible to permanently close the switch and continuously apply DC voltage from the DC power supply to the induction heating arrangement during heating operation of the aerosol-generating device. This mode may therefore be referred to as a continuous heating mode. In the continuous heating mode, the control circuit may also be capable of detecting removal of the aerosol-generating article from the cavity by detecting a change in at least one characteristic of the induction heating arrangement due to the absence of the susceptor from the cavity, as in the pulsed mode.

[0035] The change in the characteristic can be observed by measuring a change in a parameter of the induction heating arrangement. The parameter can be measured directly or indirectly. The presence or absence of the susceptor, and therefore the article, in the cavity can be determined by measuring the parameter and observing that the parameter has a different value in the presence of the susceptor compared to the value in the absence of the susceptor. Preferably, the parameter can be a current. Thus, the control circuit can include a measuring device for measuring a current indicative of at least one characteristic of the induction heating arrangement. In particular, the parameter can be a DC current supplied to the induction heating arrangement from a DC power source. Thus, the control circuit can include a measuring device arranged and configured to measure the DC current supplied to the induction heating arrangement from the DC power source. To this end, the measuring device can include a DC current measuring device arranged in a series connection between the DC power source and the induction heating arrangement. For example, the measuring device can include a resistor and a shunt amplifier. Thus, when the aerosol-generating article is inserted into the cavity of the aerosol-generating device, the susceptor becomes present in the cavity, and the equivalent resistance increases due to the increased resistive load. This results in a reduction in 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 can 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 susceptor is removed from the cavity, reducing the equivalent resistance due to a reduced resistive load. 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 can then activate the next heating operation.

[0036] In general, the pulse duration and the time interval between two consecutive power pulses, particularly probe power pulses, used for item detection, particularly for detecting the insertion or removal of an item into or from a cavity, should be selected to balance the effects of energy depletion and user experience performance. The probe pulse duration should be as short as possible while still being long enough to provide a reliable measurement of the current pulse. Similarly, the longer the time interval between two consecutive power pulses, particularly probe power pulses, the less energy depletion there will be. However, the time interval between two consecutive power pulses, particularly probe power pulses, should not be too long, otherwise the user will have to wait a long time to begin their user experience.

[0037] Taking these into consideration, the power pulse, particularly the probe power pulse, may have a pulse duration in the range of 1 microsecond to 500 microseconds, particularly 10 microseconds to 300 microseconds, preferably 15 microseconds to 120 microseconds, and most preferably 30 microseconds to 100 microseconds.

[0038] As used herein, the term "pulse duration" refers to the time interval during which the heating arrangement is powered, in particular during which the aforementioned switch is closed.

[0039] The time interval between two successive power pulses, in particular probe power pulses, may be in the range of 50 ms to 2 seconds, in particular 100 ms to 2 seconds, preferably 500 ms to 1 second.

[0040] 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 one pulse and the start of the next pulse. The polling time may be in the range of 50 ms to 2.5 s, in particular 51 ms to 2.5 ms, more particularly 100 ms to 2 s, and preferably 500 ms to 1 s.

[0041] For article detection, the power pulse, particularly the probe power pulse, is preferably generated for a predetermined period of time. That is, the detection mode may last for a finite, predetermined period of time. If an article insertion or removal is not detected within the predetermined period of time, the detection mode may be stopped, that is, the generation of power pulses may be turned off to conserve power, as described above. Similarly, if an article insertion or removal is detected within the predetermined period of time, the detection mode may be stopped immediately, particularly in response to the detection of the article insertion or removal.

[0042] Further, as noted above, during heating operation, power pulses may be generated for a predetermined number of puffs or for a predetermined heating time, or until an input is received from a switch, particularly a user input. In particular, the heating mode may include pulse width modulation of the heating power pulses to control the heating temperature.

[0043] In general, the detection mode (detection operation) and the heating mode (heating operation) may differ from each other by at least one characteristic of the power pulses, in particular by at least one of the duration or pulse pattern. For example, the detection mode may include a fixed pulse pattern of the power pulses, in particular the probe power pulses. In contrast, the heating mode may include a non-fixed, in particular variable pulse pattern of the power pulses, in particular the heating power pulses, for example in the case of pulse width modulation of the power pulses.

[0044] The induction heating arrangement may be configured to generate a high frequency alternating magnetic field, which as referred to herein may be in the range of 500 kHz (kilohertz) to 30 MHz (megahertz), particularly 5 MHz (megahertz) to 15 MHz (megahertz), preferably 5 MHz (megahertz) to 10 MHz (megahertz).

[0045] 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, a class D power amplifier, or a class E power amplifier. In particular, the DC / AC converter may include a transistor switch, a transistor switch driver circuit, and an LC network. The LC network may include a series connection of a capacitor and an inductor, where the inductor is configured and arranged to generate an alternating magnetic field in the cavity, particularly for inductive heating of 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 supplying a DC supply voltage +V_DC to the DC power source.

[0046] The inductor used to generate an alternating magnetic field within the cavity for inductive heating of the susceptor and for article detection may include at least one induction coil, particularly a single induction coil, or multiple induction coils. The number of induction coils may depend on the size and / or number of susceptors. The induction coil or 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.

[0047] The at least one induction coil can be a helical coil or a flat, planar coil, particularly a pancake coil or a curved, planar coil. The use of a flat spiral coil allows for a compact design that is robust and inexpensive to manufacture. The use of a helical induction coil advantageously allows for the generation of a homogeneous alternating electromagnetic field. As used herein, a "flat spiral coil" generally refers to a planar coil, with the axis of the coil's windings perpendicular to the surface on which the coil lies. A flat spiral induction coil can have any desired shape within the plane of the coil. For example, a flat spiral coil may have a circular shape or a generally elliptical or rectangular shape. However, the term "flat spiral coil" as used herein encompasses both planar coils and flat spiral coils shaped to conform to curved surfaces. For example, the induction coil may be a "curved" planar coil disposed around a preferably cylindrical coil support (e.g., a ferrite core). Furthermore, the flat spiral coil may comprise, for example, two layers of a four-turn flat spiral coil or a single layer of a four-turn flat spiral coil.

[0048] The at least one induction coil may be held within the housing of the heating arrangement or within 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.

[0049] 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.

[0050] The control circuitry may further be configured to control the overall operation of the aerosol generating device, and the control circuitry and at least part of the induction heating arrangement may be integral parts of the overall electrical circuitry of the aerosol generating device.

[0051] 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-to-voltage conversion, an inverting signal amplifier, a single-ended to differential converter, an analog-to-digital converter, and a microcontroller.

[0052] The microprocessor may be configured to at least one of control a switch used to generate power pulses to intermittently power the induction heating arrangement, read a measurement device to measure the current supplied from the DC power source to the induction heating arrangement, and control a transistor switch driver circuit of the induction heating arrangement.

[0053] The control circuit may be the overall controller of the aerosol generating device or may be part of the overall controller of the aerosol generating device.

[0054] The controller and at least part of the induction source, in particular the induction source apart from the inductor, may be arranged on a common printed circuit board, which is particularly advantageous with regard to a compact design of the heating arrangement.

[0055] Preferably, the DC power source includes at least one battery, such as a lithium iron phosphate battery. Alternatively, the power source may include another form of charge storage device, such as a capacitor. The power source may require recharging, i.e., the power source may be rechargeable. The power source may have a capacity that allows for storage of energy sufficient for one or more user experiences. For example, the power source may have a capacity sufficient to allow continuous generation of aerosol for approximately six minutes, or a multiple of six minutes. In another embodiment, the power source may have a capacity sufficient to allow for a predetermined number of puffs, or discontinuous activation of the induction source. The power source may be the overall power source for the aerosol generating device according to the present invention.

[0056] The receiving recess may have an insertion opening through which the aerosol-generating article may be inserted into the receiving recess. As used herein, the direction in which the aerosol-generating article is inserted is designated as the insertion direction. The insertion direction preferably corresponds to the extension of the length axis, particularly the central axis, of the receiving recess.

[0057] After insertion into the receiving cavity, at least a portion of the aerosol-generating article may still extend outward through the insertion opening. Preferably, the outwardly extending portion is provided for interaction with a user, in particular for placement into the user's mouth. Thus, during use of the device, the insertion opening may be proximate to the mouth. Consequently, as used herein, sections that are proximate to the insertion opening or proximate to the user's mouth when the device is in use are each denoted with the prefix "proximal." Sections that are disposed further away are denoted with the prefix "distal."

[0058] In this practice, the receiving cavity may be disposed or located in a proximal portion of the aerosol generating device, and 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.

[0059] Similarly, the receiving recess may be formed as a recess with a distal end portion and a proximal end portion, in particular as an elongated recess. If present, the insertion opening may be disposed at the proximal end of the receiving recess. The receiving recess may have a bottom at the distal end opposite the insertion opening.

[0060] The aerosol-generating device may have an air path extending from at least one air inlet into the receiving cavity. That is, the aerosol-generating device may have at least one air inlet in fluid communication with the receiving cavity. When an aerosol-generating article is inserted into the cavity, the air path may further extend through the aerosol-forming substrate in the article and the mouthpiece of the article into the user's mouth. Preferably, the air inlet is realized at an insertion opening of the receiving cavity used to insert the article into the cavity. Thus, when the article is received in the cavity, air may be drawn into the receiving cavity at the rim of the insertion opening and further through an airflow passage formed between the outer periphery of the aerosol-generating article and at least one or more portions of the inner surface of the receiving cavity.

[0061] In general, the receiving recess may have any suitable shape. In particular, the shape of the receiving recess may correspond to the shape of the aerosol-generating article to be received therein. Preferably, the receiving recess may have a substantially cylindrical shape or a tapered shape, for example a substantially conical or substantially frustoconical shape.

[0062] Similarly, the receiving recess may have any suitable cross-section as viewed in a plane perpendicular to the longitudinal axis of the receiving recess or perpendicular to the direction of insertion of the article. In particular, the cross-section of the receiving recess may correspond to the shape of the aerosol-generating article to be received therein. Preferably, the receiving recess has a substantially circular cross-section. Alternatively, the receiving recess may have a substantially elliptical cross-section, or a substantially oval cross-section, or a substantially square cross-section, or a substantially rectangular cross-section, or a substantially triangular cross-section, or a substantially polygonal cross-section. As used herein, the above-mentioned shapes and cross-sections preferably refer to the shape or cross-section of the receiving recess without taking into account any protrusions on the inner surface of the receiving recess.

[0063] The inductor may be disposed so as to surround at least a portion of the receiving cavity or at least a portion of the inner surface of the receiving cavity. The inductor may be, for example, a helical coil disposed within a sidewall of the receiving cavity. In particular, the inductor may be integrated into a wall defining the receiving cavity. For example, the inductor may be integrated into a sidewall of the receiving cavity so as to surround at least a portion of the interior of the receiving cavity.

[0064] The receiving cavity may include a plurality of protrusions extending into the interior of the receiving cavity. Preferably, the protrusions are spaced apart from one another such that an airflow passage is formed between adjacent protrusions, i.e., by a gap (free space) between adjacent protrusions. Additionally, the plurality of protrusions may be configured to contact at least a portion of the aerosol-generating article to retain the aerosol-generating article in the receiving cavity. The plurality of protrusions may include or be formed as ribs. Preferably, the one or more ribs extend along a length axis, in particular along a central axis of the receiving cavity. The length axis of the receiving cavity preferably corresponds to an insertion direction, and the aerosol-generating article can be inserted into the receiving cavity along this insertion direction.

[0065] 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 item from the cavity, insertion of an item into the cavity, disabling or enabling of heating operation of the induction heating arrangement. Advantageously, such indicator means may enhance ease of use and user convenience.

[0066] The present invention further relates to an aerosol-generating 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 is removably receivable or removably received in a receiving cavity of the device. The article includes at least one aerosol-forming substrate and an inductively heated susceptor for heating the substrate when the article is received in the cavity.

[0067] The aerosol-generating article may be a consumable product, particularly one 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 that may resemble a conventional cigarette.

[0068] The article may comprise one or more of the following elements: a first support element, a base element, a second support element, a cooling element, and a filter element. Preferably, the aerosol-generating article comprises at least a first support element, a second support element, and a base element located between the first and second support elements.

[0069] All of the aforementioned elements may be sequentially arranged along the longitudinal axis of the article in the order described above, with the first support element preferably being arranged at the distal end of the article and the filter element preferably being arranged at the proximal end of the article. Each of the aforementioned elements may be substantially cylindrical. In particular, all elements may have the same outer cross-sectional shape. In addition, the elements may be surrounded by an outer wrapper to hold the elements together and maintain the desired cross-sectional shape of the rod-shaped article. The wrapper is preferably made of paper.

[0070] 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, 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 contain other additives and ingredients, such as nicotine or flavoring substances. In particular, the liquid aerosol-forming substrate may comprise water, a solvent, ethanol, a plant extract, and a natural or artificial flavor. The aerosol-forming substrate may also be a paste-like material, a sachet of porous material containing the aerosol-forming substrate, or 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.

[0071] The substrate element preferably includes at least one aerosol-forming substrate to be heated. The substrate element may further include a susceptor in thermal contact with or in thermal proximity to the aerosol-forming substrate. As used herein, the term "susceptor" refers to an element comprising a material capable of being inductively heated in an alternating electromagnetic field. This 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.

[0072] The susceptor may have various geometric configurations. The susceptor may be one of a particulate susceptor, a susceptor filament, a susceptor mesh, a susceptor wick, a susceptor pin, a susceptor rod, a susceptor blade, a susceptor strip, a susceptor sleeve, a susceptor cup, a cylindrical susceptor, or a planar susceptor. For example, the susceptor may be an elongated susceptor strip having a length ranging from 8 mm to 16 mm, particularly from 10 mm to 14 mm, and preferably from 12 mm. The width of the susceptor strip may be, for example, from 2 mm to 6 mm, particularly from 4 mm to 5 mm. 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).

[0073] The susceptor may be a multi-layer susceptor, e.g., a multi-layer susceptor strip. In particular, the multi-layer susceptor may include a first susceptor material and a second susceptor material. The first susceptor material is preferably optimized for 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 selected to have a Curie temperature corresponding to a predetermined heating temperature of the susceptor assembly. At that Curie temperature, the magnetic properties of the second susceptor change 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 reaches its Curie temperature, and therefore the predetermined heating temperature. The second susceptor material has a Curie temperature below the ignition point of the aerosol-forming substrate, preferably below 500 degrees Celsius. Suitable materials for the second susceptor material may include nickel and certain nickel alloys.

[0074] At least one of the first support element and the second support element may comprise a central air passageway. Preferably, at least one of the first support element and the second support element may comprise a hollow cellulose acetate tube. Alternatively, the first support element may be used to cover and protect the distal forward end of the base element.

[0075] The aerosol cooling element is an element having a large surface area and low draw resistance (e.g., 15 mmWG to 20 mmWG). In use, the aerosol formed by the volatile compounds released from the base element is drawn through the aerosol cooling element before being conveyed to the proximal end of the aerosol-generating article.

[0076] The filter element preferably functions as a mouthpiece or as part of a mouthpiece together with the aerosol cooling element. As used herein, the term "mouthpiece" refers to the portion of the article through which the aerosol exits the aerosol-generating article.

[0077] Further features and advantages of the aerosol generating system and aerosol generating article according to the invention have already been described above in relation to the aerosol generating device of the invention and apply equally.

[0078] The present 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 described above in relation to the aerosol-generating device and aerosol-generating system according to the invention and apply equally.

[0079] The present invention further relates to a method of operating an aerosol-generating device to heat an aerosol-forming substrate capable of forming an inhalable aerosol when heated. The device comprises a DC power source and a cavity for removably receiving at least a portion of an aerosol-generating article, the aerosol-forming substrate and the cavity including an inductively heated susceptor for heating the substrate. The device further comprises an induction heating arrangement connected to the DC power source and configured to generate an alternating magnetic field within the cavity when the article is received in the cavity for inductively heating the susceptor of the article in a heating operation. In particular, the aerosol-generating device may be an aerosol-generating device according to the present invention as described above. The method comprises: - operating the device in an article removal detection mode, - generating power pulses, in particular probe power pulses, for intermittently powering the induction heating arrangement; - operating by, for each power pulse, in response to removing an aerosol-generating article from the cavity of the apparatus, measuring at least one characteristic of the induction heating arrangement affected by the absence of the susceptor from the cavity, and detecting whether a change in the at least one characteristic of the induction heating arrangement has occurred compared to one or more previous power pulses, thereby indicating the removal of an aerosol-generating article into the cavity; - ceasing operation of the apparatus in the article removal detection mode in response to detecting a change in at least one characteristic of the induction heating arrangement.

[0080] The method comprises: - operating the device in an article insertion detection mode, - generating power pulses, in particular probe power pulses, for intermittently powering the induction heating arrangement; - operating by measuring, for each power pulse, in response to inserting an aerosol-generating article into the cavity of the device, at least one property of the induction heating arrangement that is affected by the presence of the susceptor in the cavity, and detecting whether a change in the at least one property of the induction heating arrangement has occurred compared to one or more previous power pulses, thereby indicating the insertion of an aerosol-generating article into the cavity; - ceasing operation of the apparatus in the article insertion detection mode in response to detecting a change in at least one characteristic of the induction heating arrangement; - operating the apparatus in a heating mode by activating the heating operation of the induction heating arrangement to heat the substrate.

[0081] In general, operating the device in the item insertion detection mode and operating the device in the heating mode may occur before, after, or before and after operating the device in the item removal detection mode, i.e., the method may include cycles of operating the device in the item insertion detection mode, operating the device in the heating mode, and operating the device in the item removal detection mode.

[0082] As described above with respect to the aerosol generating device according to the present invention, the power pulse, particularly the probe power pulse, may have a predetermined pulse duration and a predetermined time interval between two successive power pulses, particularly the probe power pulses. The predetermined pulse duration may be in the range of 1 microsecond to 500 microseconds, particularly 10 microseconds to 300 microseconds, preferably 15 microseconds to 120 microseconds, and most preferably 30 microseconds to 100 microseconds. The time interval between two successive power pulses, particularly the probe power pulses, may be in the range of 50 milliseconds to 2 seconds, particularly 100 milliseconds to 2 seconds, preferably 500 milliseconds to 1 second.

[0083] As further described above with respect to the aerosol generating device according to the invention, the at least one characteristic is preferably at least one of the equivalent resistance of the induction heating arrangement, which may be measured via a DC current supplied to the induction heating arrangement from a DC power source.

[0084] Thus, at least one of operating the device in an article removal detection mode or operating the device in an article insertion detection mode includes: - for each pulse, measuring the equivalent resistance of the induction heating arrangement by measuring the DC current supplied to the induction heating arrangement from the DC power source and detecting whether a change in the DC current and hence the equivalent resistance of the induction heating arrangement occurs compared to the previous pulse, thus indicating the removal of an aerosol-generating article from or the insertion of an aerosol-generating article into the cavity, respectively; - operating the device in the item removal detection mode or ceasing to operate the device in the item insertion detection mode, respectively, in response to detecting a change in the DC current and therefore in the equivalent resistance of the induction heating arrangement.

[0085] Preferably, the article removal detection mode may be triggered by cessation of a previous heating operation of the induction heating arrangement.

[0086] To prevent a user from reusing an aerosol-generating article that has already been used in a previous heating operation, operating the device in the heating mode may be disabled while operating the device in the article removal detection mode. Similarly, operating the device in the heating mode may be enabled in response to ceasing operating the device in the article removal detection mode.

[0087] In order to reduce power consumption and therefore also to increase the overall operating time of the device, the method further comprises operating the device in a standby mode after stopping the generation of power pulses, in particular probe power pulses, or before starting the generation of power pulses, in particular probe power pulses, in the item removal detection mode or the item insertion detection mode, respectively, - monitor the device for operation; - in response to detecting movement of the device or movement of the device reaching or exceeding a predetermined acceleration threshold, may further include operating by initiating operation of the device in an item removal detection mode or an item insertion detection mode, respectively.

[0088] The standby mode may be terminated in response to detecting insertion of the device into the charging unit.

[0089] Also, to avoid unnecessary power consumption, the method further comprises: - operating the device in an idle state monitoring mode during at least one of operating the device in an item removal detection mode or operating the device in an item insertion detection mode, - monitor the device for operation; - in response to measuring no activity of the device for a predetermined idle time, by ceasing operation of the device in the item removal detection mode or the item insertion detection mode, respectively.

[0090] For the same reason, according to a further configuration, the method comprises: - operating the device in an idle state monitoring mode during at least one of operating the device in an item removal detection mode or operating the device in an item insertion detection mode, - monitor the device for operation; - may include operating in response to detecting that movement of the device does not reach a predetermined acceleration threshold for a predetermined idle time, or in response to detecting a lack of movement for a predetermined idle time, by reducing the number of power pulses, in particular probe power pulses, per time unit, for example by one half or one third.

[0091] The idle time may be in the range of 10 to 90 seconds, particularly 15 to 60 seconds, and preferably 15 to 40 seconds.

[0092] According to another alternative configuration, the method comprises: - operating the device in an idle state monitoring mode during at least one of operating the device in an item removal detection mode or operating the device in an item insertion detection mode, - Monitor the operation of the equipment, - operating by reducing the number of power pulses, in particular probe power pulses, per time unit, for example by one half or one third in response to detecting that movement of the device does not reach a predetermined acceleration threshold during a predetermined first idle time, or in response to detecting a lack of movement during the predetermined first idle time, and thereafter ceasing generation of power pulses, in particular probe power pulses, in response to detecting that movement 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 a lack of movement during a predetermined second idle time starting after the first idle time.

[0093] The first idle time may be within a range of 5 to 60 seconds, particularly 10 to 30 seconds, and preferably 15 to 25 seconds. Similarly, the second idle time may be within a range of 10 to 90 seconds, particularly 15 to 60 seconds, and preferably 15 to 30 seconds.

[0094] The item detection mode may be triggered by removing the aerosol generating device from the power charging unit. Advantageously, this procedure increases user convenience as the user does not need to actively initiate the item detection mode upon recharging the aerosol generating device.

[0095] According to yet another aspect of the present invention, there is provided an aerosol-generating device for heating an aerosol-forming substrate capable of forming an inhalable aerosol when heated. The device includes a cavity for removably receiving at least a portion of an aerosol-generating article, the article including the aerosol-forming substrate and an inductively heated susceptor for heating the substrate. The device also includes a DC power source and an induction heating arrangement connected to the DC power source and configured to generate an alternating magnetic field within the cavity when the article is received in the cavity to inductively heat the susceptor of the article. The device further includes control circuitry configured to generate power pulses to intermittently power the induction heating arrangement and to detect a change in at least one characteristic of the induction heating arrangement due to the presence of the susceptor when the aerosol-generating article is received in the cavity, thereby enabling detection of the insertion of the article into the cavity.

[0096] According to the present invention, it has been found that the induction heating arrangement can be used not only to heat the substrate, but also to detect the insertion of an aerosol-generating article into the receiving cavity of the device. Thus, the induction heating arrangement can be used for multiple purposes. Advantageously, this makes it possible to avoid additional assembly space for a separate sensor means. Furthermore, it has been recognized that operating the induction heating arrangement in pulsed mode for the purpose of article detection advantageously reduces power consumption and therefore increases the overall operating time of the device compared to other solutions.

[0097] According to the present invention, article insertion detection is based on the fact that insertion of an article into the cavity modifies at least one property of the induction heating arrangement, in particular at least one electrical and / or magnetic property, due to the presence of a susceptor in the vicinity of the induction heating arrangement. The change in the at least one property caused by the presence of the susceptor can be due to an interaction between the magnetic field of the induction heating arrangement and the susceptor.

[0098] The at least one characteristic of the induction heating arrangement can be any characteristic having an associated parameter that has a different value in the presence of a susceptor compared to the value in the absence of a susceptor, for example, the at least one characteristic can be the current, voltage, resistance, frequency, phase shift, magnetic flux, and inductance of the induction heating arrangement.

[0099] The characteristic is preferably at least one of the equivalent resistance or inductance of the induction heating arrangement. As used herein, the term "equivalent resistance" refers to the real part of the complex impedance, defined as the ratio of the supplied AC voltage to the measured AC current. Thus, the "equivalent resistance" may also be viewed as a resistive load of the induction heating arrangement. Similarly, as used herein, the term "inductance" refers to the imaginary part of the complex impedance, defined as the ratio of the supplied AC voltage to the measured AC current. Inductance generally includes a characteristic of an electrical circuit that is susceptible to external electromagnetic influences.

[0100] The change in at least one characteristic of the induction heating arrangement may be due to the specific magnetic permeability and / or specific electrical resistivity of the susceptor. That is, the susceptor in the aerosol-generating article may include a material having a specific magnetic permeability and / or a specific electrical resistivity. The susceptor preferably includes an electrically conductive material. For example, the susceptor may include a metallic material. The metallic material may be, for example, aluminum, nickel, iron, or an alloy thereof, such as carbon steel or ferritic stainless steel. Aluminum, when measured at room temperature (20°C), has an electrical resistivity of approximately 2.65×10E-08 ohm-meter and a magnetic permeability of approximately 1.256×10E-06 Henry / meter. Similarly, ferritic stainless steel, when measured at room temperature (20°C), has an electrical resistivity of approximately 6.9×10E-07 ohm-meter and a magnetic permeability ranging from 1.26×10E-03 Henry / meter to 2.26×10E-03 Henry / meter.

[0101] Preferably, the control circuitry is further configured to (automatically) activate a heating operation of the induction heating arrangement to heat the substrate upon detection of insertion of the article into the cavity. Advantageously, therefore, a user of the device does not need to perform any additional action to initiate the heating process upon insertion of the aerosol-generating article into the cavity of the device. For example, the user of the device does not need to operate a user interface, such as pressing a button. Instead, the user experience begins immediately and irreversibly, as is known from conventional cigarettes.

[0102] To generate power pulses for intermittently powering the induction heating arrangement, 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 this end, the switch may be intermittently opened and closed to intermittently power the induction heating arrangement for article detection, particularly for detecting the insertion of an article into a cavity, i.e., during an article detection mode of the aerosol generating device. In contrast, during a heating mode of the aerosol generating device, the switch may be permanently closed to continuously apply a DC voltage from the DC power source to the induction heating arrangement. This mode may therefore be referred to as a continuous heating mode. Alternatively, 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 referred to as a pulse heating mode.

[0103] A power pulse generated for article detection, particularly for detecting the insertion of an article into a cavity, may be referred to as a probe power pulse. Similarly, a power pulse generated for pulsed heating of an aerosol-forming substrate may be referred to as a heating power pulse.

[0104] The change in the property can be observed by measuring a change in a parameter of the induction heating arrangement. The parameter can be measured directly or indirectly. The presence of the susceptor, and therefore the article, can be determined by measuring the parameter and observing that the parameter has a different value in the presence of the susceptor compared to the value in the absence of the susceptor. Preferably, the parameter can be a current. Thus, the control circuit can include a measuring device for measuring a current indicative of at least one property of the induction heating arrangement. In particular, the parameter can be a DC current supplied to the induction heating arrangement from a DC power source. Thus, the control circuit can include a measuring device arranged and configured to measure the DC current supplied to the induction heating arrangement from the DC power source. That is, the measuring device can include a DC current measuring device arranged in a series connection between the DC power source and the induction heating arrangement. For example, the measuring device can include a resistor and a shunt amplifier. Thus, when the aerosol-generating article is inserted into the cavity of the aerosol-generating device, the presence of the susceptor increases the equivalent resistance 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 then activates the heating operation of the induction heating arrangement to heat the substrate.

[0105] Generally, the pulse duration and the time interval between two successive power pulses, i.e., the time interval between two successive probe power pulses, used for item detection, particularly for detecting the insertion of an item into a cavity, must be selected to balance the effects of energy depletion and user experience performance. The pulse duration must be as short as possible while still being long enough to provide a reliable measurement of the current pulse. Similarly, the longer the time interval between two successive power pulses, the less energy depletion there will be. However, the time interval between two successive power pulses should not be too long, otherwise the user will have to wait a long time to begin their user experience.

[0106] Taking these into consideration, the power pulse used for article detection, i.e., 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, and most preferably 30 microseconds to 100 microseconds. As used herein, the term "pulse duration" refers to the time interval during which power is supplied to the heating arrangement, in particular during which the above-mentioned switch is closed.

[0107] The time interval between two successive power pulses used for item detection, i.e. the time interval between two successive probe pulses, may be in the range of 50 ms to 2 s, in particular 100 ms to 2 s, preferably 500 ms to 1 s.

[0108] For article detection, the probe power pulse is preferably generated for a predetermined period of time. That is, the detection mode may last for a finite, predetermined period of time. If an article insertion is not detected within the predetermined period of time, the detection mode may be stopped, that is, the generation of power pulses may be turned off to conserve power. Similarly, if an article insertion 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.

[0109] The heating power pulses may be generated for a predetermined number of puffs or for a predetermined heating time, or until an input is received from a switch, particularly a user input. In particular, the heating mode may include pulse width modulation of the heating power pulses to control the heating temperature.

[0110] In general, the detection mode and the heating mode may differ from each other by at least one characteristic of the power pulse, in particular by at least one of the duration or pulse pattern. For example, the detection mode may include a fixed pulse pattern of the probe power pulse. In contrast, the heating mode may include a non-fixed, in particular variable, pulse pattern of the heating power pulse, for example in the case of pulse width modulation of the heating power pulse.

[0111] The induction heating arrangement may be configured to generate a high frequency alternating magnetic field, which as referred to herein may be in the range of 500 kHz (kilohertz) to 30 MHz (megahertz), particularly 5 MHz (megahertz) to 15 MHz (megahertz), preferably 5 MHz (megahertz) to 10 MHz (megahertz).

[0112] 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 inverter may include a class C power amplifier, a class D power amplifier, or a class E power amplifier. In particular, the DC / AC converter may include a transistor switch, a transistor switch driver circuit, and an LC network. The LC network may include a series connection of a capacitor and a coil, and the inductor is configured and arranged to generate an alternating magnetic field in the recess for inductively heating the susceptor. 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 supplying a DC supply voltage +V_DC to the DC power source.

[0113] The inductor used to generate an alternating magnetic field within the cavity for inductively heating the susceptor may include at least one induction coil, particularly a single induction coil, or multiple induction coils. The number of induction coils may depend on the size and / or number of susceptors. The induction coil or 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.

[0114] The at least one induction coil can be a helical coil or a flat, planar coil, particularly a pancake coil or a curved, planar coil. The use of a flat spiral coil allows for a compact design that is robust and inexpensive to manufacture. The use of a helical induction coil advantageously allows for the generation of a homogeneous alternating electromagnetic field. As used herein, a "flat spiral coil" generally refers to a planar coil, with the axis of the coil's windings perpendicular to the surface on which the coil lies. A flat spiral induction coil can have any desired shape within the plane of the coil. For example, a flat spiral coil may have a circular shape or a generally elliptical or rectangular shape. However, the term "flat spiral coil" as used herein encompasses both planar coils and flat spiral coils shaped to conform to curved surfaces. For example, the induction coil may be a "curved" planar coil disposed around a preferably cylindrical coil support (e.g., a ferrite core). Furthermore, the flat spiral coil may comprise, for example, two layers of a four-turn flat spiral coil or a single layer of a four-turn flat spiral coil.

[0115] The at least one induction coil may be held within the housing of the heating arrangement or within 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.

[0116] 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.

[0117] The control circuitry may further be configured to detect removal of the aerosol generating device from the power charging unit and to automatically initiate generation of a power pulse upon detecting removal of the aerosol generating device from the power charging unit.

[0118] The control circuitry may further be configured to control the overall operation of the aerosol generating device, and the control circuitry and at least part of the induction heating arrangement may be integral parts of the overall electrical circuitry of the aerosol generating device.

[0119] 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-to-voltage conversion, an inverting signal amplifier, a single-ended to differential converter, an analog-to-digital converter, and a microcontroller.

[0120] The microprocessor may be configured to at least one of control a switch used to generate power pulses to intermittently power the induction heating arrangement, read a measurement device to measure the current supplied from the DC power source to the induction heating arrangement, and control a transistor switch driver circuit of the induction heating arrangement.

[0121] The control circuit may be the overall controller of the aerosol generating device or may be part of the overall controller of the aerosol generating device.

[0122] The controller and at least part of the induction source, in particular the induction source apart from the inductor, may be arranged on a common printed circuit board, which is particularly advantageous with regard to a compact design of the heating arrangement.

[0123] Preferably, the DC power source includes at least one battery, such as a lithium iron phosphate battery. Alternatively, the power source may include another form of charge storage device, such as a capacitor. The power source may require recharging, i.e., the power source may be rechargeable. The power source may have a capacity that allows for storage of energy sufficient for one or more user experiences. For example, the power source may have a capacity sufficient to allow continuous generation of aerosol for approximately six minutes, or a multiple of six minutes. In another embodiment, the power source may have a capacity sufficient to allow for a predetermined number of puffs, or discontinuous activation of the induction source. The power source may be the overall power source for the aerosol generating device according to the present invention.

[0124] The receiving recess may have an insertion opening through which the aerosol-generating article may be inserted into the receiving recess. As used herein, the direction in which the aerosol-generating article is inserted is designated as the insertion direction. The insertion direction preferably corresponds to the extension of the length axis, particularly the central axis, of the receiving recess.

[0125] After insertion into the receiving cavity, at least a portion of the aerosol-generating article may still extend outward through the insertion opening. Preferably, the outwardly extending portion is provided for interaction with a user, in particular for placement into the user's mouth. Thus, during use of the device, the insertion opening may be proximate to the mouth. Consequently, as used herein, sections that are proximate to the insertion opening or proximate to the user's mouth when the device is in use are each denoted with the prefix "proximal." Sections that are disposed further away are denoted with the prefix "distal."

[0126] In this practice, the receiving cavity may be disposed or located in a proximal portion of the aerosol generating device, and 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.

[0127] Similarly, the receiving recess may be formed as a recess with a distal end portion and a proximal end portion, in particular as an elongated recess. If present, the insertion opening may be disposed at the proximal end of the receiving recess. The receiving recess may have a bottom at the distal end opposite the insertion opening.

[0128] The aerosol-generating device may have an air path extending from at least one air inlet into the receiving cavity. That is, the aerosol-generating device may have at least one air inlet in fluid communication with the receiving cavity. When an aerosol-generating article is inserted into the cavity, the air path may further extend through the aerosol-forming substrate in the article and the mouthpiece of the article into the user's mouth. Preferably, the air inlet is realized at an insertion opening of the receiving cavity used to insert the article into the cavity. Thus, when the article is received in the cavity, air may be drawn into the receiving cavity at the rim of the insertion opening and further through an airflow passage formed between the outer periphery of the aerosol-generating article and at least one or more portions of the inner surface of the receiving cavity.

[0129] In general, the receiving recess may have any suitable shape. In particular, the shape of the receiving recess may correspond to the shape of the aerosol-generating article to be received therein. Preferably, the receiving recess may have a substantially cylindrical shape or a tapered shape, for example a substantially conical or substantially frustoconical shape.

[0130] Similarly, the receiving recess may have any suitable cross-section as viewed in a plane perpendicular to the longitudinal axis of the receiving recess or perpendicular to the direction of insertion of the article. In particular, the cross-section of the receiving recess may correspond to the shape of the aerosol-generating article to be received therein. Preferably, the receiving recess has a substantially circular cross-section. Alternatively, the receiving recess may have a substantially elliptical cross-section, or a substantially oval cross-section, or a substantially square cross-section, or a substantially rectangular cross-section, or a substantially triangular cross-section, or a substantially polygonal cross-section. As used herein, the above-mentioned shapes and cross-sections preferably refer to the shape or cross-section of the receiving recess without taking into account any protrusions on the inner surface of the receiving recess.

[0131] The inductor may be disposed so as to surround at least a portion of the receiving cavity or at least a portion of the inner surface of the receiving cavity. The inductor may be, for example, a helical coil disposed within a sidewall of the receiving cavity. In particular, the inductor may be integrated into a wall defining the receiving cavity. For example, the inductor may be integrated into a sidewall of the receiving cavity so as to surround at least a portion of the interior of the receiving cavity.

[0132] The receiving cavity may include a plurality of protrusions extending into the interior of the receiving cavity. Preferably, the protrusions are spaced apart from one another such that an airflow passage is formed between adjacent protrusions, i.e., by a gap (free space) between adjacent protrusions. Additionally, the plurality of protrusions may be configured to contact at least a portion of the aerosol-generating article to retain the aerosol-generating article in the receiving cavity. The plurality of protrusions may include or be formed as ribs. Preferably, the one or more ribs extend along a length axis, in particular along a central axis of the receiving cavity. The length axis of the receiving cavity preferably corresponds to an insertion direction, and the aerosol-generating article can be inserted into the receiving cavity along this insertion direction.

[0133] The present invention further relates to an aerosol-generating 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 is removably receivable or removably received in a receiving cavity of the device. The article includes at least one aerosol-forming substrate and an inductively heated susceptor for heating the substrate when the article is received in the cavity.

[0134] The aerosol-generating article may be a consumable product, particularly one 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 that may resemble a conventional cigarette.

[0135] The article may comprise one or more of the following elements: a first support element, a base element, a second support element, a cooling element, and a filter element. Preferably, the aerosol-generating article comprises at least a first support element, a second support element, and a base element located between the first and second support elements.

[0136] All of the aforementioned elements may be sequentially arranged along the longitudinal axis of the article in the order described above, with the first support element preferably being arranged at the distal end of the article and the filter element preferably being arranged at the proximal end of the article. Each of the aforementioned elements may be substantially cylindrical. In particular, all elements may have the same outer cross-sectional shape. In addition, the elements may be surrounded by an outer wrapper to hold the elements together and maintain the desired cross-sectional shape of the rod-shaped article. The wrapper is preferably made of paper.

[0137] 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. 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, a solvent, ethanol, a plant extract, and a natural or artificial flavor. The aerosol-forming substrate may also be a paste-like material, a sachet of porous material containing the aerosol-forming substrate, or 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.

[0138] The substrate element preferably includes at least one aerosol-forming substrate to be heated. The substrate element may further include a susceptor in thermal contact with or in thermal proximity to the aerosol-forming substrate. As used herein, the term "susceptor" refers to an element comprising a material capable of being inductively heated in an alternating electromagnetic field. This 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.

[0139] The susceptor may have various geometric configurations. The susceptor may be one of a particulate susceptor, a susceptor filament, a susceptor mesh, a susceptor wick, a susceptor pin, a susceptor rod, a susceptor blade, a susceptor strip, a susceptor sleeve, a susceptor cup, a cylindrical susceptor, or a planar susceptor. For example, the susceptor may be an elongated susceptor strip having a length ranging from 8 mm to 16 mm, particularly from 10 mm to 14 mm, and preferably from 12 mm. The width of the susceptor strip may be, for example, from 2 mm to 6 mm, particularly from 4 mm to 5 mm. 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).

[0140] The susceptor may be a multi-layer susceptor, e.g., a multi-layer susceptor strip. In particular, the multi-layer susceptor may include a first susceptor material and a second susceptor material. The first susceptor material is preferably optimized for 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 selected to have a Curie temperature corresponding to a predetermined heating temperature of the susceptor assembly. At that Curie temperature, the magnetic properties of the second susceptor change 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 reaches its Curie temperature, and therefore the predetermined heating temperature. The second susceptor material has a Curie temperature below the ignition point of the aerosol-forming substrate, preferably below 500 degrees Celsius. Suitable materials for the second susceptor material may include nickel and certain nickel alloys.

[0141] The first support element can be used to cover and protect the distal anterior portion. At least one of the first support element and the second support element can include a central air passageway. Preferably, at least one of the first support element and the second support element can comprise a hollow cellulose acetate tube. Alternatively, the first support element can be an end of the base element.

[0142] The aerosol cooling element is an element having a large surface area and low draw resistance (e.g., 15 mmWG to 20 mmWG). In use, the aerosol formed by the volatile compounds released from the base element is drawn through the aerosol cooling element before being conveyed to the proximal end of the aerosol-generating article.

[0143] The filter element preferably functions as a mouthpiece or as part of a mouthpiece together with the aerosol cooling element. As used herein, the term "mouthpiece" refers to the portion of the article through which the aerosol exits the aerosol-generating article.

[0144] Further features and advantages of the aerosol generating system and aerosol generating article according to the invention have already been described above with respect to the aerosol generating device and apply equally.

[0145] The present invention further relates to a method for operating an aerosol generating device according to the present invention and as described herein, the method comprising: - operating the device in an article insertion detection mode, - generating power pulses, in particular probe power pulses, for intermittently powering the induction heating arrangement; - operating by measuring, for each pulse, at least one characteristic of the induction heating arrangement that is affected by the presence of the susceptor as an aerosol-generating article is inserted into the cavity of the device, and detecting whether a change in the at least one characteristic of the induction heating arrangement occurs compared to the previous pulse, thus indicating the insertion of an aerosol-generating article into the cavity; - ceasing operation of the apparatus in the article detection mode upon detecting a change in at least one characteristic of the induction heating arrangement; - operating the apparatus in a heating mode by activating the heating operation of the induction heating arrangement to heat the substrate.

[0146] In the article detection mode, the power pulses can be generated using a switch. The switch can be disposed between the DC power supply of the aerosol generating device and the induction heating arrangement and can be intermittently opened and closed to intermittently power the induction heating arrangement. In contrast, in the heating mode, the switch can be permanently closed to continuously apply a DC voltage from the DC power supply to the induction heating arrangement.

[0147] As described above with respect to the aerosol generating device according to the present invention, the power pulse, particularly the probe power pulse, may have a predetermined pulse duration and a predetermined time interval between two successive power pulses, particularly the probe power pulses. The predetermined pulse duration may be in the range of 1 microsecond to 500 microseconds, particularly 10 microseconds to 300 microseconds, preferably 15 microseconds to 120 microseconds, and most preferably 30 microseconds to 100 microseconds. The time interval between two successive power pulses, particularly the probe power pulses, may be in the range of 50 milliseconds to 2 seconds, particularly 100 milliseconds to 2 seconds, preferably 500 milliseconds to 1 second.

[0148] As further described above in relation to the aerosol generating device according to the invention, the e characteristic is preferably at least one of the equivalent resistance of the induction heating arrangement, which may be measured via a DC current supplied to the induction heating arrangement from a DC power source.

[0149] Therefore, operating the device in article detection mode preferably involves: - for each pulse, measuring the equivalent resistance [resistive load] of the induction heating arrangement by measuring the DC current supplied to the induction heating arrangement from the DC power source and detecting whether a change in the DC current and therefore in the equivalent resistance of the induction heating arrangement occurs compared to the previous pulse, thus indicating the insertion of an aerosol-generating article into the cavity; - ceasing operation of the device in article detection mode upon detecting a change in the DC current and therefore the equivalent resistance of the induction heating arrangement.

[0150] The item detection mode may be triggered by removing the aerosol generating device from the power charging unit.

[0151] Further features and advantages of the method according to the invention have already been described above with respect to the aerosol generating system and apply equally.

[0152] The present invention is defined in the claims. However, the following non-limiting examples are provided in a non-exhaustive manner. Any one or more features of these examples may be combined with any one or more features of any other example, embodiment, or aspect described herein.

[0153] Example 1: 1. An aerosol generating device for heating an aerosol-forming substrate capable of forming an inhalable aerosol when heated, the device comprising: - a recess 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; - a DC power supply; - an induction heating arrangement connected to a DC power source and configured to generate an alternating magnetic field within the cavity when the article is received within the cavity for inductively heating a susceptor of the article in a heating operation; - control circuitry configured to supply power to the induction heating arrangement from a DC power source to power the heating arrangement, and to detect a change in at least one characteristic of the induction heating arrangement due to the presence or absence of a susceptor in the cavity in response to detecting at least one of an insertion of an article into the cavity or a removal of an article from the cavity when an aerosol-generating article is inserted into or removed from the cavity.

[0154] Example 2: 1. An aerosol generating device for heating an aerosol-forming substrate capable of forming an inhalable aerosol when heated, the device comprising: - a recess for removably receiving at least a portion of an aerosol-generating article, the article including an aerosol-forming substrate and an inductively heatable susceptor for heating the substrate; - a DC power supply; - an induction heating arrangement connected to a DC power source and configured to generate an alternating magnetic field within the cavity when the article is received within the cavity for inductively heating a susceptor of the article in a heating operation; - a control circuit configured to generate power pulses to intermittently power the induction heating arrangement, and to detect a change in at least one characteristic of the induction heating arrangement due to the presence or absence of a susceptor in the cavity in response to detecting at least one of the insertion of an article into the cavity or the removal of an article from the cavity when an aerosol-generating article is inserted into or removed from the cavity.

[0155] Example 3: The control circuit is - in response to detecting the removal of an item from the cavity during a heating operation; or - an aerosol generating device according to embodiment Ex2, configured to disable the heating operation of the induction heating arrangement after a previous heating operation or until after detection of removal of the item from the recess.

[0156] Example 4: The control circuit is - in response to detecting the removal of an item from the cavity during a heating operation and after disabling the heating operation; or - An aerosol generating device according to embodiment Ex2 or Ex3, configured to enable activation of a heating operation of the induction heating arrangement in response to detecting removal of an item from the recess after a previous heating operation.

[0157] Example 5: An aerosol generating device according to any one of the preceding embodiments, wherein the control circuit is configured to verify insertion of an item into or removal of an item from the cavity by generating at least one verification power pulse at a predetermined time period after the 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. Example 6: An aerosol-generating article according to Example Ex5, wherein the predetermined period is within the range of 0.5 seconds to 3 seconds.

[0158] Example 7: An aerosol generating device according to any one of the preceding embodiments, wherein the control circuit is configured to initiate heating operation of the induction heating arrangement in response to detecting insertion of an item into the cavity.

[0159] Example 8: An aerosol generating device according to any one of the preceding embodiments, wherein the control circuitry further comprises an operation sensor for detecting operation of the device.

[0160] Example 9: An aerosol-generating article according to example Ex8, wherein the motion sensor includes at least one of an accelerometer or a gyroscope.

[0161] Example 10: An aerosol-generating article according to example Ex8 or Ex9, wherein the control circuit is configured to initiate generation of a power pulse, in particular a probe power pulse, in response to detecting operation of the device.

[0162] Example 11: An aerosol generating device according to any one of embodiments Ex8 to Ex10, wherein the control circuit is configured to initiate generation of a power pulse, in particular a probe power pulse, in response to detecting operation of the device reaching or exceeding a predetermined operating threshold.

[0163] Example 12: An aerosol-generating article according to any one of embodiments Ex8 to Ex11, wherein the control circuit is configured to cease generating power pulses, in particular probe power pulses, in response to detecting that operation of the device does not reach a predetermined operational threshold for a predetermined idle time, or in response to detecting a lack of operation for a predetermined idle time.

[0164] Example 13: An aerosol-generating article according to any one of embodiments Ex8 to Ex11, wherein the control circuit is configured to reduce the number of power pulses, in particular probe power pulses, per time unit in response to detecting that operation of the device does not reach a predetermined operational threshold for a predetermined idle time, or in response to detecting no operation for a predetermined idle time.

[0165] Example 14: An aerosol-generating article according to embodiment Ex12 or Ex13, wherein the idle time is in the range of from 10 seconds to 90 seconds, in particular from 15 seconds to 60 seconds, preferably from 15 seconds to 40 seconds.

[0166] Example 15: An aerosol-generating article according to any one of embodiments Ex8 to Ex11, wherein the control circuit is configured to reduce the number of power pulses, in particular probe power pulses, per time unit in response to detecting that operation of the device does not reach a predetermined operational threshold during a predetermined first idle time, or in response to detecting a lack of operation during the predetermined first idle time, and thereafter stop generating power pulses, in particular probe power pulses, in response to detecting that operation of the device does not reach a predetermined operational threshold during a predetermined second idle time starting after the first idle time, or in response to detecting a lack of operation during a predetermined second idle time starting after the first idle time.

[0167] Example 16: An aerosol-generating article according to example Ex15, in which the first idle time is in the range of from 5 seconds to 60 seconds, in particular from 10 seconds to 30 seconds, preferably from 15 seconds to 25 seconds.

[0168] Example 17: An aerosol-generating article according to embodiment Ex15 or Ex16, wherein the second idle time is in the range of from 10 seconds to 90 seconds, in particular from 15 seconds to 60 seconds, preferably from 15 seconds to 30 seconds.

[0169] Example 18: An aerosol generating device according to any one of the preceding embodiments, wherein the control circuit is configured to detect removal of the aerosol generating device from the power charging unit.

[0170] Example 19: An aerosol-generating article according to example Ex18, wherein the control circuit is configured to initiate generation of a power pulse, in particular a probe power pulse, in response to detecting removal of the aerosol-generating device from the power charging unit.

[0171] Example 20: An aerosol-generating article according to example Ex18, wherein the control circuit is configured to initiate generation of a power pulse, in particular a probe power pulse, in response to detecting removal of the aerosol-generating device from the power charging unit to detect insertion of the article into the recess.

[0172] Example 21: An aerosol generating device according to any one of the preceding embodiments, wherein the control circuit is configured to detect insertion of the aerosol generating device into the power charging unit.

[0173] Example 22: An aerosol-generating article according to embodiment Ex21, wherein the control circuit is configured to stop generating power pulses, in particular probe power pulses, in response to detecting insertion of the aerosol-generating device into the power charging unit.

[0174] Example 23: An aerosol generating device according to any one of the preceding embodiments, wherein the control circuit is configured to stop the heating operation of the device in response to at least one of detecting a predetermined number of puffs, detecting the passage of a predetermined heating time, or receiving user input.

[0175] Example 24: An aerosol-generating article according to any one of the preceding embodiments, wherein the control circuit is configured to initiate generation of a probe power pulse to detect removal of the article in response to cessation of heating operation of the device, in particular in response to detecting cessation of heating operation of the device.

[0176] Example 25: An aerosol generating device according to any one of the preceding embodiments, wherein the control circuit is configured to stop heating operation of the induction heating arrangement in response to detecting removal of the article from the cavity.

[0177] Example 26: An aerosol generating device according to any one of the preceding embodiments, wherein the control circuit comprises a switch constructed and arranged to control the supply of power from the DC power supply to the induction heating arrangement.

[0178] Example 27: An aerosol generating device according to any one of the preceding embodiments, wherein the control circuit comprises a measuring device for measuring a current indicative of at least one characteristic of the induction heating arrangement.

[0179] Example 28: An aerosol generating device according to any one of the preceding embodiments, wherein the power pulse, in particular the probe power pulse, has 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, and most preferably 30 microseconds to 100 microseconds.

[0180] Example 29: An aerosol generating device according to any one of the preceding embodiments, wherein the time interval between two successive power pulses, in particular probe power pulses, is in the range of 50 milliseconds to 2 seconds, in particular 100 milliseconds to 2 seconds, preferably 500 milliseconds to 1 second.

[0181] Example Ex30: An aerosol generating device according to any one of the preceding embodiments, wherein the induction heating arrangement comprises a DC / AC converter connected to a DC power source and including an LC network, the LC network including a series connection of a capacitor and an inductor, the inductor configured and arranged to generate an alternating magnetic field within the recess for induction heating the susceptor.

[0182] Example Ex31: An aerosol generating device according to any one of the preceding embodiments, wherein the at least one characteristic is an equivalent resistance of the induction heating arrangement or an inductance of the induction heating arrangement.

[0183] Example Ex32: An aerosol generating device according to any one of the preceding embodiments, further comprising optical or tactile indication means for indicating detection of at least one of the following: removal of an item from the cavity, insertion of an item into the cavity, or disabling or enabling of the heating operation of the induction heating arrangement.

[0184] Example Ex33: An aerosol generation system comprising an aerosol generating device according to any one of the preceding embodiments and an aerosol-generating article removably receivable within a cavity of the device, the aerosol-generating article including an aerosol-forming substrate and an inductively heated susceptor for heating the substrate.

[0185] Example Ex34: An aerosol-generating article for use in an aerosol-generating system according to example Ex33 or in an aerosol-generating apparatus according to any one of examples Ex1 to Ex32, wherein the aerosol-generating article comprises an aerosol-forming substrate and an inductively heated susceptor for heating the substrate.

[0186] Example Ex35: 1. A method of operating an aerosol-generating device to heat an aerosol-forming substrate capable of forming an inhalable aerosol when heated, the device comprising: a DC power source; a recess for removably receiving at least a portion of an aerosol-generating article including the aerosol-forming substrate and an inductively heated susceptor for heating the substrate; and an induction heating arrangement connected to the DC power source and configured to generate an alternating magnetic field within the recess when the article is received in the recess for inductively heating the susceptor of the article in a heating operation, the method comprising: operating the device in an article removal detection mode; - generating power pulses, in particular probe power pulses, for intermittently powering the induction heating arrangement; - operating by, for each power pulse, in response to removing an aerosol-generating article from the cavity of the apparatus, measuring at least one characteristic of the induction heating arrangement affected by the absence of the susceptor from the cavity, and detecting whether a change in the at least one characteristic of the induction heating arrangement has occurred compared to one or more previous power pulses, thereby indicating the removal of an aerosol-generating article into the cavity; - ceasing operation of the apparatus in the article removal detection mode in response to detecting a change in at least one characteristic of the induction heating arrangement.

[0187] Example Ex36: - operating the device in an article insertion detection mode, - generating power pulses, in particular probe power pulses, for intermittently powering the induction heating arrangement; - operating by measuring, for each power pulse, in response to inserting an aerosol-generating article into the cavity of the device, at least one property of the induction heating arrangement that is affected by the presence of the susceptor in the cavity, and detecting whether a change in the at least one property of the induction heating arrangement has occurred compared to one or more previous power pulses, thereby indicating the insertion of an aerosol-generating article into the cavity; - ceasing operation of the apparatus in the article insertion detection mode in response to detecting a change in at least one characteristic of the induction heating arrangement; - operating the apparatus in a heating mode by activating a heating operation of the induction heating arrangement to heat the substrate.

[0188] Example Ex37: The method according to embodiment Ex36, wherein operating the device in the article detection mode and operating the device in the heating mode occurs at least one of before or after operating the device in the article detection mode.

[0189] Example Ex38: At least one of operating the device in an article removal detection mode or operating the device in an article insertion detection mode comprises: - measuring the equivalent resistance of the induction heating arrangement by measuring the DC current supplied to the induction heating arrangement from the DC power source for each power pulse, and detecting whether a change in the DC current and thus the equivalent resistance of the induction heating arrangement occurs compared to one or more previous pulses, thereby indicating the removal of an aerosol-generating article from the cavity or the insertion of an aerosol-generating article into the cavity, respectively; - operating the device in the item removal detection mode or ceasing to operate the device in the item insertion detection mode, respectively, in response to detecting a change in the DC current and therefore in the equivalent resistance of the induction heating arrangement.

[0190] Example Ex39: The method according to any one of embodiments Ex35 to Ex38, wherein the power pulses, in particular probe power pulses, have a predetermined pulse duration and a predetermined time interval between two successive power pulses, in particular probe power pulses.

[0191] Example Ex40: The method according to embodiment Ex39, wherein the predetermined pulse duration is 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.

[0192] Example Ex41: The method according to any one of embodiments Ex39 or Ex40, wherein the time interval between two successive power pulses, in particular probe power pulses, is in the range of 50 milliseconds to 2 seconds, in particular 100 milliseconds to 2 seconds, preferably 500 milliseconds to 1 second.

[0193] Example Ex42: The method according to any one of embodiments Ex35 to Ex41, further comprising first verifying the insertion of the article into the cavity or the removal of the article from the cavity, respectively, by generating at least one verification power pulse at a predetermined time period after detecting at least one characteristic of the induction heating arrangement and by redetecting a change in the at least one characteristic of the induction heating arrangement.

[0194] Example Ex43: The method according to example Ex42, wherein the predetermined period is in the range of 0.5 seconds to 3 seconds.

[0195] Example Ex44: The method according to any one of embodiments Ex35 to Ex43, wherein the article removal detection mode is triggered by cessation of a previous heating operation of the induction heating arrangement.

[0196] Example Ex45: The method according to any one of embodiments Ex35 to Ex44, wherein operating the device in the heating mode is disabled while operating the device in the article removal detection mode.

[0197] Example Ex46: The method according to any one of embodiments Ex35 to Ex45, wherein operating the device in the heating mode is enabled in response to ceasing operating the device in the article removal detection.

[0198] Example Ex47: operating the device in an idle state monitoring mode during at least one of operating the device in an item removal detection mode or operating the device in an item insertion detection mode, - monitor the device for operation; The method according to any one of embodiments Ex35 to Ex46, further comprising: - in response to measuring no activity of the device for a predetermined idle time, by ceasing to operate the device in the item removal detection mode or the item insertion detection mode, respectively.

[0199] Example Ex48: operating the device in an idle state monitoring mode during at least one of operating the device in an item removal detection mode or operating the device in an item insertion detection mode, - monitor the device for operation; The method according to any one of embodiments Ex35 to Ex46, further comprising operating in response to detecting that operation of the device does not reach a predetermined operation threshold for a predetermined idle time, or in response to detecting a lack of operation for a predetermined idle time, by reducing the number of power pulses, in particular probe power pulses, per time unit.

[0200] Example Ex49: A method according to embodiment Ex47 or Ex48, wherein the idle time is in the range of 10 seconds to 90 seconds, in particular 15 seconds to 60 seconds, preferably 15 seconds to 40 seconds.

[0201] Example Ex50: operating the device in an idle state monitoring mode during at least one of operating the device in an item removal detection mode or operating the device in an item insertion detection mode, - monitor the device for operation; The method according to any one of embodiments Ex35 to Ex46, further comprising: - operating by: - ​​reducing the number of power pulses, in particular probe power pulses, per time unit in response to detecting that movement of the device does not reach a predetermined acceleration threshold during a predetermined first idle time, or in response to detecting a lack of movement during the predetermined idle time, and thereafter ceasing generation of power pulses, in particular probe power pulses, in response to detecting that movement 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 a lack of movement during a predetermined second idle time starting after the first idle time.

[0202] Example Ex51: The method according to embodiment Ex50, wherein the first idle time is in the range of 5 seconds to 60 seconds, in particular 10 seconds to 30 seconds, preferably 15 seconds to 25 seconds.

[0203] Example Ex52: The method according to any one of embodiments Ex50 or Ex51, wherein the second idle time is in the range of 10 seconds to 90 seconds, in particular 15 seconds to 60 seconds, preferably 15 seconds to 30 seconds.

[0204] Example Ex53: operating the device in a standby mode after stopping the generation of power pulses, in particular probe power pulses, or before starting the generation of power pulses, in particular probe power pulses, in the item removal detection mode or the item insertion detection mode, respectively, - monitor the device for operation; The method according to any one of embodiments Ex35 to Ex52, further comprising: - in response to detecting operation of the device or operation of the device reaching or exceeding a predetermined acceleration threshold, operating the device by initiating operation in an item removal detection mode or an item insertion detection mode, respectively.

[0205] Example Ex54: The method according to any one of embodiments Ex35 to Ex53, wherein the item insertion detection mode is triggered by removing the aerosol generating device from the power charging unit.

[0206] Example Ex55: 1. An aerosol generating device for heating an aerosol-forming substrate capable of forming an inhalable aerosol when heated, the device comprising: - a recess for removably receiving at least a portion of an aerosol-generating article, the article including an aerosol-forming substrate and an inductively heatable susceptor for heating the substrate; - a DC power supply; - an induction heating arrangement connected to a DC power source and configured to generate an alternating magnetic field within the cavity when the article is received within the cavity for inductively heating a susceptor of the article; - a control circuit configured to generate power pulses, in particular probe power pulses, to intermittently power the induction heating arrangement and to detect a change in at least one characteristic of the induction heating arrangement due to the presence of the susceptor when an aerosol-generating article is received into the cavity, thus enabling detection of the insertion of the article into the cavity.

[0207] Example Ex56: An aerosol generating device according to embodiment Ex55, wherein the control circuit is further configured to activate heating operation of the induction heating arrangement to heat the substrate upon detecting insertion of an item into the recess.

[0208] Example Ex57: An aerosol generating apparatus according to any one of embodiments Ex55 or Ex56, wherein the control circuit comprises a switch constructed and arranged to control the supply of power from the DC power source to the induction heating arrangement.

[0209] Example Ex58: An aerosol generating device according to any one of embodiments Ex55 to Ex57, wherein the control circuit comprises a measuring device for measuring a current indicative of at least one characteristic of the induction heating arrangement.

[0210] Example Ex59: The aerosol generating apparatus according to any one of embodiments Ex55 to Ex58, wherein the power pulse, in particular the probe power pulse, has 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, and most preferably 30 microseconds to 100 microseconds.

[0211] Example Ex60: An aerosol generating device according to any one of embodiments Ex55 to Ex59, wherein the time interval between two successive power pulses, in particular probe power pulses, is in the range of 50 milliseconds to 2 seconds, in particular 100 milliseconds to 2 seconds, preferably 500 milliseconds to 1 second.

[0212] Example Ex61: An aerosol generating apparatus according to any one of embodiments Ex55 to Ex60, wherein the induction heating arrangement is connected to a DC power source and includes a DC / AC inverter including an LC network, the LC network including a series connection of a capacitor and a coil, and the inductor is configured and arranged to generate an alternating magnetic field in the recess for induction heating the susceptor.

[0213] Example Ex62: An aerosol generating device according to any one of embodiments Ex55 to Ex61, wherein at least one characteristic is an equivalent resistance of the induction heating arrangement or an inductance of the induction heating arrangement.

[0214] Example Ex63: An aerosol-generating system comprising an aerosol-generating device according to any one of embodiments Ex55 to Ex62 and an aerosol-generating article removably receivable in a cavity of the device, the aerosol-generating article including an aerosol-forming substrate and an inductively heated susceptor for heating the substrate.

[0215] Example Ex64: The method is: - operating the device in an article insertion detection mode, - generating power pulses, in particular probe power pulses, for intermittently powering the induction heating arrangement; - operating by measuring, for each pulse, at least one characteristic of the induction heating arrangement that is affected by the presence of the susceptor as an aerosol-generating article is inserted into the cavity of the device, and detecting whether a change in the at least one characteristic of the induction heating arrangement occurs compared to the previous pulse, thus indicating the insertion of an aerosol-generating article into the cavity; - ceasing operation of the apparatus in the article detection mode upon detecting a change in at least one characteristic of the induction heating arrangement; - operating the device in a heating mode by activating a heating operation of the induction heating arrangement to heat the substrate.

[0216] Example Ex65: The step of operating the apparatus in an article detection mode preferably comprises: - measuring the equivalent resistance of the induction heating arrangement by measuring the DC current supplied to the induction heating arrangement from the DC power source for each pulse and detecting whether a change in the DC current and therefore in the equivalent resistance of the induction heating arrangement occurs compared to the previous pulse, thus indicating the insertion of an aerosol-generating article into the cavity; - ceasing operation of the device in the article detection mode upon detecting a change in the DC current and therefore the equivalent resistance of the induction heating arrangement.

[0217] Example Ex66: The method according to any one of embodiments Ex64 or Ex65, wherein the power pulses, in particular the probe power pulses, have a predetermined pulse duration and a predetermined time interval between two successive power pulses.

[0218] Example Ex67: The method according to embodiment Ex66, wherein the predetermined pulse duration is 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.

[0219] Example Ex68: A method according to any one of embodiments Ex66 or Ex67, wherein the time interval between two successive power pulses, in particular probe power pulses, is in the range of 50 milliseconds to 2 seconds, in particular 100 milliseconds to 2 seconds, preferably 500 milliseconds to 1 second.

[0220] Example Ex69: The method according to any one of embodiments Ex64 to Ex68, wherein the item detection mode is triggered by removing the aerosol generating device from the power charging unit.

[0221] The invention will now be further described, by way of example only, with reference to the accompanying drawings in which: [Brief explanation of the drawings]

[0222] [Figure 1] FIG. 1 shows a schematic diagram of 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. [Figure 2] FIG. 2 shows a schematic diagram of 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. [Figure 3] FIG. 3 shows diagrammatically an induction heating arrangement for an aerosol generating device according to FIGS. [Figure 4] FIG. 4 shows in schematic form the operational details of the method according to the invention. [Figure 5] Figure 5 shows a schematic operational detail of the method according to the invention. [Figure 6] FIG. 6 shows diagrammatically different operation modes of the aerosol generating device according to FIG. 1, in particular different operation modes of the method according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0223] 1 and 2 show schematically 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 upon engagement of the article 10 with the device 100.

[0224] As can be particularly seen in FIG. 1 , the aerosol-generating article 10 has a substantially rod-shaped configuration similar to that of a conventional cigarette. In this embodiment, the article 10 comprises four components sequentially arranged in a coaxial array: a substrate element 20 at the distal end of the article 10, a support element 40 having a central air passageway, an aerosol-cooling element 50, and a filter element 60 disposed at the distal end of the article 10 that functions as a mouthpiece. The substrate element 20 includes an aerosol-forming substrate 21 to be heated and a susceptor 30 in direct physical contact with the substrate 21 and used to inductively heat the substrate 21, as described in more detail below. The four elements are substantially cylindrical in shape and have substantially the same diameter. Additionally, the four elements are surrounded by an outer wrapper 70 that holds the four elements together and maintains the desired circular cross-sectional shape of the rod-like article 10. The wrapper 70 is preferably made of paper. Further details of article 10, in particular the four elements, are disclosed, for example, in WO 2015 / 176898 A1.

[0225] The elongated aerosol-generating device 100 essentially has two sections: a proximal section 102 and a distal section 101. Within the proximal section 102, the device 100 comprises a recess 103 for removably receiving at least a portion of the aerosol-generating article 10. Within the distal section 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, within the recess 103. In this embodiment, the induction coil 118 is a helical coil disposed within the proximal section 102 of the device so as to circumferentially surround the cylindrical receiving recess 103. The coil 118 is disposed 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 within the aerosol-generating article 10 when the article 10 is received within the cavity 103. Thus, upon inserting the article 10 into the cavity 103 of the apparatus 100 (see FIG. 2 ) and activating the heating arrangement 110, the alternating magnetic field within 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 heats up to an operating temperature sufficient to vaporize the aerosol-forming substrate 21 surrounding the susceptor 30 within the article 10. In use of the system, when a user draws a puff, i.e., when 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 apparatus 100. The airflow continues through a passage formed between the inner surface of the cylindrical recess 103 and the outer surface of the article 10 toward the distal end of the recess 103. At the distal end of the recess 103, the airflow enters the aerosol-generating article 10 through the substrate element 20 and further passes through the support element 40, the aerosol-cooling element 50, and the filter element 60, before finally exiting the article 10. At the substrate element 20, vaporized material from the aerosol-forming substrate 21 is entrained in the airflow.Thereafter, as it passes through support element 40, cooling element 50 and filter element 60, the airflow containing the vaporized material is cooled to form an aerosol that exits article 10 through filter element 60.

[0226] FIG. 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 the DC power supply 150 shown in FIGS. 1 and 2. The DC / AC inverter includes a class E power amplifier, which includes the following components: a transistor switch 111 including a field-effect transistor (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, and an LC load network 113 including a shunt capacitor C1 and a series connection of a capacitor C2 and an inductor L2. Inductor L2 corresponds to the induction coil 118 shown in FIGS. 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 device 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.

[0227] Further details of the induction heating arrangement 110 according to this embodiment, in particular with regard to its operating principle, are disclosed, for example, in WO 2015 / 177046 A1.

[0228] 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.

[0229] According to the invention, article insertion and / or removal detection is realized via the heating arrangement 110 itself. Advantageously, this makes it possible to avoid additional assembly space for separate sensor means. The basic idea for detecting the insertion and / or removal of an article into and / or from a cavity is to detect a change in at least one property of the induction heating arrangement due to the presence or removal of a susceptor when an aerosol-generating article 10 is received into or removed from the cavity 103.

[0230] In this embodiment, it is the total resistive load 114 of the heating arrangement 110 that is used as a characteristic of the induction heating arrangement that is indicative of the presence or absence of an item 10 in the receiving cavity 103. As explained above, the value of the total equivalent resistance or total resistive load 114 depends on the presence or absence of a susceptor 30 near the induction coil 118. When an item is inserted into the cavity 103 of the apparatus 100, the total equivalent resistance 118 corresponds to the sum of the ohmic resistance of the inductor coil 118 and the ohmic resistance of the susceptor 30, and when no item is received in the cavity 103, it corresponds to the ohmic resistance of the inductor coil 118.

[0231] This change in the equivalent resistance 118 can be detected via the DC current I_DC provided from the DC power supply 150 to the induction heating arrangement 110, i.e., the LC load network 113. To this end, the aerosol-generating device includes a current measuring device 140 arranged in series between the DC power supply 150 and the LC load network 113. Thus, when the aerosol-generating article 10 is inserted into the cavity 103 of the aerosol-generating device 100, the presence of the susceptor 30 increases the equivalent resistance 118 of the heating arrangement due to an increased resistive load 114. This results in a reduction in the DC current supplied to the induction heating arrangement 110. The reduction in DC current I_DC is detected by the current measuring device 140, which can then be used as a trigger signal to activate the heating operation of the induction heating arrangement 110 to heat the substrate 21.

[0232] Conversely, when the aerosol-generating article 10 is removed from the cavity 103, the absence of the susceptor 30 causes a reduction in the equivalent resistance 118 of the heating arrangement due to a reduction in the resistive load 114. This, in turn, causes an increase in the DC current supplied to the induction heating arrangement 110.

[0233] The decrease and increase in DC current (ΔI_DC) can be detected by the current measuring device 140.

[0234] When the aerosol generating device 100 is in an article detection mode (e.g., either the article insertion detection mode or the article removal detection mode), the heating assembly is operated in a pulsed mode rather than a continuous mode to reduce overall power consumption. To this end, the aerosol generating device 100 includes a switch 130 arranged and configured to control the supply of power from the DC power source 150 to the induction heating arrangement 110. In this embodiment, the switch 130 is arranged in 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 induction heating arrangement 130. In contrast, during the heating mode of the aerosol generating device 100, the switch may be permanently closed to continuously apply a DC voltage from the DC power source to the induction heating arrangement 110. Alternatively, 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 referred to as a pulsed heating mode.

[0235] 3, both switch 130 and current measuring device 140 are part of a control circuit that also includes a microprocessor 160. Microprocessor 160 is configured to control switch 130, which is used to generate power pulses to intermittently power induction heating arrangement 110, to read measuring device 140 to measure the current I_DC supplied to induction heating arrangement 110 from the DC power source, and to control transistor switch driver circuit 112 of induction heating arrangement 110. The control circuit may be the overall controller of aerosol generation device 100 or may be part of the overall controller of the aerosol generation device.

[0236] In the item insertion / removal detection mode, the microprocessor 160 initiates activation of the switch 130 by closing it for a predetermined closed time interval, thereby generating a current pulse having a pulse duration T1 corresponding to the closed time interval. The pulse duration T1 may be in the range of 1 microsecond to 500 microseconds, particularly 10 microseconds to 300 microseconds, preferably 15 microseconds to 120 microseconds, and most preferably 30 microseconds to 100 microseconds. At the end of the closed time interval, the microprocessor 160 reopens the switch 130 for a predetermined open time interval, thereby interrupting the passage of current to the heating arrangement. The open time interval corresponds to the time interval between two successive power pulses, which for item detection may be in the range of 50 milliseconds to 2 seconds, particularly 100 milliseconds to 2 seconds, and preferably 500 milliseconds to 1 second. 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. Therefore, the sum of the closed time interval and the open time interval, or the sum of the pulse duration and the time interval between two consecutive power pulses, corresponds to the periodicity of the series of pulses. Generally, the time interval T2 between two consecutive probe power pulses should be selected to balance the impact of energy depletion and the performance of the user experience. The pulse duration T1 should be as short as possible, yet still be sufficient to provide a reliable measurement of the current pulse.

[0237] 4 is a graph showing the evolution of a current pulse I_DC over time t according to an exemplary embodiment of the method of the present invention. According to this embodiment, a series of current 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.

[0238] As long as no aerosol-generating article is inserted, the current measuring device 140 measures a current having a value I_NA for each pulse (where "NA" stands for "no article"). As explained, the measured value I_NA depends on the ohmic load 114, which is equal to 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 increased ohmic load, the current absorbed by the heating assembly decreases. Therefore, the current measuring device 140 measures a current pulse having a value of I_A, which is lower than I_NA (where "A" stands for "article inserted"). The difference ΔI_DC between I_NA and I_A is recorded by the microcontroller 160, which triggers the start of the heating mode.

[0239] The item insertion detection mode may be triggered, for example, by removing the aerosol generating device 100 from the power charging unit, and thus the aerosol generating device may be configured to detect removal of the device from the power charging unit.

[0240] While FIG. 4 shows only the item insertion detection mode, FIG. 5 shows the evolution of the current pulse I_DC 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 evolution of the current pulse I_DC during the item insertion detection mode, see the above description of FIG. 4. The evolution of the current pulse I_DC during the item removal detection mode is reversed. That is, during the item removal detection mode, the current measuring device 140 measures a current having a value of I_A for each pulse as long as an aerosol-generating article is still received in the cavity 103. As soon as the article is removed from the cavity, the ohmic load 114 decreases and the current absorbed by the heating assembly increases. Therefore, the current measuring device 140 measures a current pulse having a value I_NA. The difference ΔI_DC between I_A and I_NA is also recorded by the microcontroller 160, indicating the removal of the article from the cavity.

[0241] Figure 6 shows an exemplary embodiment of a method according to the invention for operating an aerosol generating device, in particular the aerosol generating device 100 according to Figure 1. In particular, Figure 6 shows a schematic flow diagram illustrating different modes of operation of the aerosol generating device according to the invention.

[0242] Typically, a user begins a new user experience by removing the aerosol generating device 100 from the power charging unit used to charge the device's DC power supply 150. This step is indicated by arrow 1150. During charging, indicated by box 1100, the device 100 is either off or in standby mode. Advantageously, removal 1150 of the aerosol generating device 100 from the power charging unit can be used to trigger an article insertion detection mode, indicated by box 1200, for detecting the insertion of an aerosol-generating article into the aerosol generating device cavity. In article insertion detection mode 1200, a series of probe power pulses are generated to intermittently power the induction heating arrangement. Simultaneously, a characteristic of the induction heating arrangement, preferably the total resistive load of the heating arrangement, is measured with each pulse and compared to the previous pulse to detect whether a change in that characteristic has occurred, thus indicating the insertion of an aerosol-generating article into the cavity. In response to detecting such a change, the article insertion detection mode 1200 is stopped, followed by activating a heating operation of the induction heating arrangement, indicated by box 1300, to operate the apparatus in a heating mode to heat the aerosol-forming substrate. Detection of the insertion of an article preferably triggers the initiation of the heating operation 1300, as indicated by arrow 1250. The heating operation may include different heating steps, such as a pre-heating step and a main heating step.

[0243] The heating operation 1300 may be stopped after a predetermined number of puffs or a predetermined heating time. Alternatively, the heating operation 1300 may be stopped manually, for example, by receiving a user input from a switch.

[0244] When the heating operation 1300 is stopped, the apparatus is operated in an article removal detection mode, as indicated by box 1400. The article removal detection mode 1400 is preferably initiated in response to the cessation of the heating operation 1300, and in particular in response to detecting the cessation of the heating operation 1300. As in the article insertion detection mode 1200, in the article removal detection mode 1400, a series of probe power pulses are generated to intermittently power the induction heating arrangement. Simultaneously, a characteristic of the induction heating arrangement, again preferably the total resistive load of the heating arrangement, is measured with each pulse and compared to the previous pulse to detect whether a change in that characteristic has occurred, thus indicating the removal of the aerosol-generating article from the cavity.

[0245] During the item removal detection mode 1400, activation of new heating operations is disabled to prevent the user from reheating an aerosol-generating article that has been depleted from a previous heating operation. As soon as removal of an aerosol-generating article is detected, the item removal detection mode 1400 is stopped and activation of new heating operations is re-enabled, as indicated by arrow 1450, allowing the user to insert a new aerosol-generating article and begin the next heating operation. Thus, the next item insertion detection mode 1200 may be initiated in response to detecting the removal of an aerosol-generating article.

[0246] To reduce power consumption and therefore also increase the overall operating time of the device, the device may operate in a standby mode, indicated by box 1500, after the (next) item insertion detection mode, particularly after the item removal detection mode 1400 has ceased, i.e., in response to detecting the removal of an aerosol-generating article from a previous user experience. In standby mode, the device is monitored for operation using a motion sensor, for example, an accelerometer. In response to detecting device operation or device operation reaching or exceeding a predetermined operational threshold, the (next) item insertion detection mode is initiated, as indicated by arrow 1550 in FIG. 6. Preferably, the device is continuously monitored for operation until device operation or device operation reaches or exceeds a predetermined operational threshold.

[0247] To reduce power consumption, the device may be operated in an idle monitoring mode while at least one of the device is operating in the item removal detection mode or the device is operating in the item insertion detection mode. As in the standby mode, in the idle monitoring mode, the device is monitored for activity using an activity sensor. In response to detecting that activity of the device does not reach a predetermined activity threshold or that there is no activity for a predetermined idle time, operation of the device is in the item removal detection mode or the item insertion detection mode, respectively.

[0248] In another configuration of the idle monitoring mode, detection is not terminated in response to detecting that device operation does not reach a predetermined operation threshold or is absent for a predetermined idle time. Instead, the number of probe power pulses per time unit may be reduced, for example, by a factor of two or three.

[0249] Yet another configuration of idle monitoring mode is:

[0250] According to another alternative configuration, the number of probe power pulses per time unit may first be reduced in response to detecting that device operation does not reach a predetermined operational threshold or is absent for a predetermined first idle time. In Figure 6, this is illustrated by box 1600 for the item removal detection mode and by box 1700 for the item insertion detection mode. Only thereafter may generation of probe power pulses be stopped in response to detecting that device operation does not reach a predetermined operational threshold or is absent for a predetermined second idle time beginning after the first idle time.

[0251] In either of these configurations, when the generation of probe power pulses is stopped due to the device being idle, as shown by arrows 1650 and 1750, the device may switch to standby mode 1500 to monitor the device for activity, and then, in response to detecting appropriate activity, may (again) begin operation in the device's item removal detection mode 1400 or item insertion detection mode 1200, respectively, as shown by arrow 1550.

[0252] The standby mode may be terminated in response to detecting insertion of the device into the charging unit.

[0253] For purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing amounts, quantities, percentages, and the like are to be understood in all instances as modified by the term "about." Also, all ranges include the disclosed maximum and minimum points, including any intermediate ranges therebetween, 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 a numerical value that is within the general standard error for the measurement of the property that it modifies. In some instances, the number A, as used in the appended claims, may deviate by the percentages recited above, as long as the deviation does not materially affect the basic and novel characteristics of the claimed invention. Also, all ranges include the disclosed maximum and minimum points, including any intermediate ranges therebetween, which may or may not be specifically recited herein.

Claims

1. 1. An aerosol generating device for heating an aerosol-forming substrate capable of forming an inhalable aerosol when heated, said device comprising: a recess for removably receiving at least a portion of an aerosol-generating article, said article including said aerosol-forming substrate and an inductively heated susceptor for heating said substrate; a DC power supply; an induction heating arrangement connected to said DC power supply and configured to generate an alternating magnetic field in said cavity when said article is received in said cavity for inductively heating said susceptor of said article in a heating operation; - a control circuit configured to generate power pulses to intermittently power the induction heating arrangement, and to detect a change in at least one characteristic of the induction heating arrangement due to the presence or absence of the susceptor in the cavity in response to detecting at least one of the insertion of an article into the cavity or the removal of an article from the cavity when an aerosol-generating article is inserted into or removed from the cavity.

2. The control circuit in response to detecting the removal of an item from said cavity during a heating operation, or 10. The aerosol generating device of claim 1, configured to disable the heating operation of the induction heating arrangement after a previous heating operation and until after detection of removal of the item from the cavity.

3. The control circuit - in response to detecting the removal of an item from said cavity during a heating operation and after disabling said heating operation, or - An aerosol generating device as described in claim 1 or 2, configured to activate the heating operation of the induction heating arrangement after a previous heating operation and in response to detecting the removal of the item from the recess.

4. An aerosol generating device as described in any one of claims 1 to 3, wherein the control circuit is configured to initiate heating operation of the induction heating arrangement in response to detecting the insertion of the item into the recess.

5. An aerosol generating device according to any one of claims 1 to 4, wherein the control circuit further comprises an operation sensor for detecting operation of the device.

6. 6. The aerosol-generating article of claim 5, wherein the control circuit is configured to initiate generation of a power pulse in response to detecting operation of the device.

7. 7. The aerosol-generating article of claim 5, wherein the control circuit is configured to cease generating power pulses in response to detecting that operation of the device does not reach a predetermined operational threshold for a predetermined idle time, or in response to detecting a lack of operation for a predetermined idle time.

8. An aerosol generating device according to any one of claims 1 to 7, wherein the control circuit is configured to detect the removal of the aerosol generating device from a power charging unit.

9. 9. The aerosol-generating article of claim 8, wherein the control circuit is configured to initiate generation of the power pulse in response to detecting the removal of the aerosol-generating device from the power charging unit.

10. An aerosol generating device according to any one of claims 1 to 9, wherein the control circuitry is configured to detect the insertion of the aerosol generating device into a power charging unit.

11. 11. The aerosol-generating article of claim 10, wherein the control circuit is configured to cease generating the power pulses in response to detecting insertion of the aerosol-generating device into a power charging unit.

12. An aerosol-generating article according to any one of claims 1 to 11, wherein the control circuit is configured to initiate generation of a power pulse to detect the removal of the article in response to detecting cessation of the heating operation of the device.

13. An aerosol generating device as described in any one of claims 1 to 12, wherein the control circuit is configured to stop the heating operation of the induction heating arrangement in response to detecting the removal of the item from the recess.

14. 14. An aerosol generating device according to any one of claims 1 to 13, wherein the control circuit includes a measuring device for measuring a current indicative of at least one characteristic of the induction heating arrangement.

15. 15. An aerosol-generating article for use in an aerosol-generating device according to any one of claims 1 to 14, wherein the aerosol generation is removably receivable in the cavity of the device, the article comprising an aerosol-forming substrate and an inductively heated susceptor for heating the substrate.

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