Aerosol-generating device having means for detecting the presence, absence, or displacement of an aerosol-generating article within a cavity of the device - Patent Application 20070122997

Abstract

The present invention further relates to an aerosol-generating device for heating an aerosol-forming substrate capable of forming an inhalable aerosol when heated. The device comprises a cavity for removably receiving at least a portion of an aerosol-generating article, including the aerosol-forming substrate to be heated. The device further comprises an electric heating arrangement comprising an electronic circuit and a heating element operably coupled to the electronic circuit for heating the aerosol-generating substrate when the aerosol-generating article is received in the cavity. In addition, the device comprises a controller including a temperature sensor configured to output a signal indicative of the temperature or temperature increase of at least one portion of the electronic circuit during operation of the heating arrangement. The controller is configured to detect the presence, absence, or displacement of the article in the cavity in response to the signal indicating that the temperature or temperature increase has exceeded a predetermined temperature threshold or a predetermined temperature increase threshold, respectively. The present invention further relates to an aerosol-generating system comprising such a device, and a method for detecting the presence, absence, or displacement of an aerosol-generating article in a cavity of an aerosol-generating device.

Description

[Technical Field]

[0001] The present disclosure relates to an aerosol generating system comprising an aerosol generating device and means for detecting the presence, absence or displacement of an aerosol-generating article within a cavity of the aerosol generating device. The present disclosure further relates to a method for detecting the presence, absence or displacement of an aerosol-generating article within a cavity of the aerosol generating device. [Background technology]

[0002] Aerosol-generating devices used to generate inhalable aerosols by electrically heating an aerosol-forming substrate are generally known in the prior art. Such devices may comprise a cavity for removably receiving at least a portion of an aerosol-generating article, including the aerosol-forming substrate to be heated. The device further comprises an electrical heating arrangement for heating the substrate when the article is received in the cavity. To ensure proper functioning of the device and to avoid damage, it is important to accurately detect the presence, absence, or displacement of the aerosol-generating article in the cavity, for example, to enable or disable the heating process. This type of detection can be achieved by a sensor means disposed inside the cavity, where the sensor means is exposed to heat, moisture, and, in the case of induction heating devices, high-frequency electromagnetic fields. These conditions make the detection susceptible to harmful interference effects. Additionally, the sensor may be damaged due to mechanical action, particularly during cleaning of the cavity or during insertion or removal of an article into or from the cavity.

[0003] It would therefore be desirable to have an aerosol generating device that includes means for detecting the presence, absence, or displacement of an aerosol-generating article within a cavity of the device, and a corresponding method that has the advantages of prior art solutions, while mitigating that limitation. In particular, it would be desirable to have an electrically heated aerosol generating device and method that provides improved detection of the presence, absence, or displacement of an aerosol-generating article within a cavity of the device. Summary of the Invention

[0004] According to one aspect of the present invention, an aerosol-generating device for heating an aerosol-forming substrate capable of forming an inhalable aerosol when heated is provided. The device comprises a cavity for removably receiving at least a portion of an aerosol-generating article, including the aerosol-forming substrate to be heated. The device further comprises an electric heating arrangement including an electronic circuit and a heating element operably coupled to the electronic circuit for heating the aerosol-generating substrate when the aerosol-generating article is received in the cavity. In addition, the device comprises a controller including a temperature sensor configured to output a signal indicative of the temperature or temperature increase of at least one portion of the electronic circuit during operation of the heating arrangement. The controller is configured to detect the presence, absence, or displacement of the article in the cavity in response to the signal indicating that the temperature or temperature increase has exceeded a predetermined temperature threshold or a predetermined temperature increase threshold, respectively.

[0005] According to the present invention, it has been found that the temperature or temperature increase of the electronic circuitry during operation of the heating arrangement correlates with the proper placement, displacement, or absence of the aerosol-generating article in the cavity. In particular, it has been found that during normal operation, when the aerosol-generating article is properly placed in the cavity, the power provided by the heating arrangement is largely dissipated or emitted into the aerosol-forming substrate of the article. Only a small portion of the power is dissipated within the electronic circuitry of the heating arrangement. Conversely, when the aerosol-generating article is displaced or absent from the cavity, the power provided by the heating arrangement is largely dissipated within the electronic circuitry. This results in the temperature of at least a portion of the electronic circuitry changing in a manner different from that during normal operation when the article is properly placed in the cavity. In particular, when the aerosol-generating article is displaced or absent from the cavity, the temperature of at least a portion of the electronic circuitry may increase to a temperature higher than that which occurs during normal operation. Similarly, if the aerosol-generating article is displaced or absent from the cavity, the temperature of at least one portion of the electronic circuitry may increase more strongly, and in particular more rapidly, than during normal operation when the article is properly received within the cavity.

[0006] Thus, by monitoring the temperature of at least a portion of the electronic circuitry of the heating arrangement for the temperature or temperature rise to exceed a predetermined temperature threshold or a predetermined temperature rise threshold, the control circuit can reliably detect whether an aerosol-generating article is present in the cavity, displaced, or absent from the cavity.

[0007] As a result, if displacement or absence of the article is detected, operation of the heating arrangement can be disabled. Advantageously, this makes it possible to protect the aerosol generating device, and in particular the electronic circuitry of the heating arrangement, from damage. In particular, if a signal indicative of a temperature or temperature rise of at least one portion of the electronic circuitry is higher (or equal to or higher) than a predetermined temperature threshold or a predetermined temperature rise threshold, the controller can detect displacement or absence of the article. Conversely, if a signal indicative of a temperature or temperature rise of at least one portion of the electronic circuitry is lower (or equal to or lower) than a predetermined temperature threshold or a predetermined temperature rise threshold, the controller can detect the presence of an article in the cavity. Thus, the controller can be configured to compare the signal indicative of the temperature or temperature rise of at least one portion of the electronic circuitry with the predetermined temperature threshold or the predetermined temperature rise threshold, respectively.

[0008] The operation of the heating arrangement may include at least one of a calibration operation of the heating arrangement, a preheating operation of the heating arrangement, a heating operation of the heating arrangement, or an article detection operation of the heating arrangement. The calibration operation may include calibrating the heating power to achieve a desired operating temperature for heating the aerosol-forming substrate in the article. The preheating operation may include preheating the aerosol-forming substrate to an operating temperature sufficient to release a volatile compound capable of forming an aerosol from the substrate at the start of a user experience. The heating operation may be heating the aerosol-forming substrate in the article to an operating temperature to release a volatile compound from the substrate, such as to form an aerosol. The article detection operation may particularly include detecting the insertion of an aerosol-generating article into or removal from a cavity by using the heating arrangement to detect a change in at least one characteristic of the heating arrangement due to the presence or absence of the article or a specific portion of the article, such as a susceptor, in the cavity when the aerosol-generating article is inserted into or removed from the cavity.

[0009] As used herein, the term "temperature increase" refers to an increase in temperature of at least a portion of an electronic circuit above the initial temperature of that portion, particularly above the initial temperature of that portion at the start of operation of the heating arrangement. The temperature increase may occur during a calibration operation of the heating arrangement, or during a preheating operation of the heating arrangement, or during a heating operation of the heating arrangement, or during an item detection operation of the heating arrangement. The initial temperature may be assumed but not measured. For example, the initial temperature may be assumed to be room temperature, particularly 20 degrees Celsius.

[0010] In general, the temperature rise may be the difference between the temperature of at least one portion of the electronic circuit at a first time, in particular at the start of operation of the heating arrangement, and the temperature of the at least one portion of the electronic circuit at a subsequent second time or after a predetermined period of time after the first time. For example, the temperature rise may be the difference between the temperature of the at least one portion of the electronic circuit at the start of a calibration operation, or a pre-heating operation, or a heating operation, and the temperature of the at least one portion of the electronic circuit after a predetermined period of time.

[0011] Thus, to provide a signal indicative of a temperature increase, the temperature sensor and controller may be configured to detect the temperature of at least one portion of the electronic circuit at a first time, in particular at the start of operation of the heating arrangement, and at a subsequent second time, or after a predetermined period of time after the first time.

[0012] The predetermined period may be in the range of 0.5 seconds to 4 seconds, in particular 1 second to 3 seconds, for example 2 seconds.

[0013] The temperature rise may be parameterized by the following formula: Δ_T=[T(t2)-T(t1)], where Δ_T is the temperature rise, T(t1) is the initial temperature of at least one portion of the electronic circuit at a first time t1, and T(t2) is the temperature of at least one portion of the electronic circuit at a second time t2 or a predetermined period of time (t=t2-t1) after the first time t1.

[0014] The signal output by the temperature sensor may be an ADC (analog-to-digital converter) value that correlates with temperature such that high temperatures result in low ADC values ​​and low temperatures result in high ADC values. In this case, with respect to the signal output by the temperature sensor, the signal indicative of a temperature increase may be parameterized by the following equation: Δ_S=[S(t1-S(t2)], where Δ_S is the signal indicative of a temperature increase, S(t1) is a signal indicative of an initial temperature of at least one portion of the electronic circuit at a first time t1, and S(t2) is a signal indicative of a temperature of at least one portion of the electronic circuit at a second time t2 or a predetermined period of time (t=t2-t1) after the first time t1. Here, the signal indicative of the temperature at the second time t2 is subtracted from the signal indicative of the temperature at the first time t1 to yield a positive value.

[0015] The predetermined temperature rise threshold may be at least 80 degrees Celsius, particularly at least 100 degrees Celsius, and preferably at least 120 degrees Celsius. Similarly, the predetermined temperature threshold may be in the range of 80 degrees Celsius to 180 degrees Celsius, particularly 100 degrees Celsius to 160 degrees Celsius. These values ​​are selected to exceed any normal fluctuations in the temperature of the electronic circuitry during normal operation of the device to avoid misinterpretation of the temperature sensor signal. These values ​​therefore ensure that false positive detections of the absence or displacement of an item in the cavity are avoided.

[0016] Detection of the presence, absence, or displacement of the aerosol-generating article within the cavity can also take into account that the heating rate of the electronic circuitry is slower when the initial temperature of the electronic circuitry is already high at the start of device operation. This is the case, for example, when a new heating process follows immediately after a previous one. Heating a mass by a constant temperature requires more heat than when the initial temperature at the beginning of the heating process is low, resulting in a slower heating rate.

[0017] Thus, to determine whether the temperature rise has breached a corresponding predetermined temperature threshold, at least one of the temperature rise or the signal indicative of the temperature rise may be rescaled by a predetermined function of the initial temperature of the at least one portion of the electronic circuit at the start of operation of the heating arrangement, which may be a linear, quadratic, or multiplicative inverse (reciprocal) function of the initial temperature of the at least one portion of the electronic circuit at the start of operation of the heating arrangement.

[0018] In particular, the temperature rise may be rescaled according to the following function: Δ_T_scal=[T(t)-T(0)]t[ct(0)-d], where Δ_T_scal is the rescaled temperature rise compared to a predetermined temperature rise threshold, T(0) is the initial temperature of at least one portion of the electronic circuit at the start of operation of the device, T(t) is the temperature of at least one portion of the electronic circuit a predetermined time period t after the start of operation of the device, and coefficients c and d are constants that can be obtained by calibration. The coefficients c and d may generally be based on the thermal configuration of the device, taking into account the mass of the device and the specific arrangement of possible heat sinks and thermal insulating components. That is, the values ​​of coefficients c and d are based on the physical characteristics of the overall system. As can be seen from this example, when the device is hot, the temperature rise is weighted by multiplying it by the initial temperature or by a linear function of the initial temperature.

[0019] If the signal output by the temperature sensor is an ADC (analog-to-digital converter) value that correlates with temperature (see above), such that high temperatures result in low ADC values ​​and low temperatures result in high ADC values, rescaling involves dividing (instead of multiplying) the signal indicative of the temperature increase by the signal indicative of the initial temperature to weight the temperature increase when the device is hot. Thus, in this example, the signal indicative of the temperature increase may be rescaled according to the following function: Δ_S_scal=kn[S(0)-S(t)] / S(0), where Δ_S_scal is the rescaled signal indicative of the temperature increase compared to a predetermined signal value corresponding to a predetermined temperature increase threshold, S(0) is the signal indicative of the initial temperature of at least one portion of the electronic circuit at the start of operation of the device, and S(t) is the signal indicative of the temperature of at least one portion of the electronic circuit a predetermined time t after the start of operation of the device. The coefficient k is a constant that can be obtained by calibration.

[0020] Similarly, the signal indicative of the temperature rise may be compared to a predetermined temperature rise threshold that is a function of the initial temperature of at least one portion of the electronic circuit at the start of operation of the heating arrangement. That is, the predetermined temperature rise threshold may be a function of the initial temperature of at least one portion of the electronic circuit at the start of operation of the heating arrangement. In other words, the temperature rise (or the signal indicative of the temperature rise) may be compared to the predetermined temperature rise threshold rescaled by a predetermined function of the initial temperature of at least one portion of the electronic circuit at the start of operation of the heating arrangement. Thus, the controller may be configured to detect the presence, absence, or displacement of an item in the cavity in response to a signal indicating that the temperature or temperature rise has breached the predetermined temperature rise threshold rescaled by a predetermined function of the initial temperature of at least one portion of the electronic circuit at the start of operation of the heating arrangement.

[0021] For this aspect, the controller may be configured to detect an initial temperature of at least one portion of the electronic circuitry at the start of operation of the device, and rescale the signal indicative of the temperature increase by a predetermined function of the detected initial temperature to compare the rescaled signal indicative of the temperature increase with a predetermined temperature increase threshold. That is, the controller may be configured to detect the presence, absence, or displacement of the item within the cavity in response to the rescaled signal indicating that the temperature or temperature increase has breached the predetermined temperature threshold or the predetermined temperature increase threshold, respectively. The function for rescaling may be the exemplary functions Δ_T_scal or ΔS_scal provided above, respectively.

[0022] The controller may also be configured to detect an initial temperature of the at least one portion of the electronic circuitry at the start of operation of the device and determine the predetermined temperature rise threshold as a function of the detected initial temperature. Similarly, the controller may be configured to detect an initial temperature of the at least one portion of the electronic circuitry at the start of operation of the device and rescale the predetermined temperature rise threshold by a predetermined function of the initial temperature of the at least one portion of the electronic circuitry at the start of operation of the heating arrangement to compare the rescaled predetermined temperature rise threshold to the signal indicative of a temperature rise.

[0023] The temperature sensor may include at least one of a thermocouple, a thermistor, or a semiconductor integrated circuit sensor.

[0024] A thermocouple is an electrical device consisting of two dissimilar conductors forming an electrical junction. Thermocouples produce a temperature-dependent voltage as a result of the thermoelectric effect, which can be interpreted as a measurement of temperature. Thermocouples are advantageous because of their low cost, simplicity, rapid thermal response, wide temperature range, and robustness.

[0025] A thermistor is a type of resistor whose resistance is positively dependent on temperature. Thermistors are of two opposing basic types: NTC (negative temperature coefficient) thermistors, whose resistance decreases with increasing temperature, and PTC (positive temperature coefficient) thermistors, whose resistance increases with increasing temperature. Thus, the temperature sensor may comprise an NTC thermistor or a PTC thermistor. Preferably, the temperature sensor comprises an NTC thermistor.

[0026] Semiconductor integrated circuit sensors offer high linearity in output and do not require linearization or cold junction compensation. They can be fabricated on the same chip and process as any other electronic chip function, which allows them to easily achieve a high level of integration. They offer high output levels and excellent noise immunity. In particular, they are easily interfaced to any other analog or digital circuitry. Their wide operating temperature range and ability to provide many useful output levels, especially in logic, pulse, digital, and analog forms, make them suitable for many types of electronic circuitry.

[0027] The controller may be configured to stop or limit operation of the electric heating arrangement in response to detecting the displacement or absence of the article. In particular, the controller may be configured to limit operation of the electric heating arrangement by reducing the power provided by the heating arrangement. For example, the power may be reduced to 50 percent, 40 percent, 30 percent, 20 percent, or 10 percent of the power during normal operation of the heating arrangement, i.e., when the aerosol generating system is present in the desired position within the cavity. Advantageously, this allows for saving power and protecting the heating arrangement from damage.

[0028] As previously detailed, the controller may be configured to detect the presence of an item at a desired location within the cavity in response to the signal indicating that the temperature or temperature rise has fallen below a predetermined temperature threshold or a predetermined temperature rise threshold, respectively. Further, the controller may be configured to enable heating operation of the electric heating arrangement in response to detecting the presence of an item at a desired location within the cavity.

[0029] Preferably, at least one portion of the electronic circuit is monitored for excessive or elevated temperatures at short intervals, and thus the controller may be configured to monitor the temperature of at least one portion of the electronic circuit at least every 10 seconds, in particular at least every 5 seconds, preferably at least every 2 seconds, more preferably at least every second.

[0030] The electric heating arrangement may be an induction heating arrangement for inductively heating an aerosol-forming substrate within the article. The induction heating arrangement may include an induction source including an induction coil for generating a varying magnetic field, particularly an alternating magnetic field, within the cavity. In particular, the heating element of the induction heating arrangement may include at least one induction coil for generating a varying magnetic field, particularly an alternating magnetic field, within the cavity, or may be an induction coil. The varying magnetic field may be a high-frequency varying magnetic field. The varying magnetic field may be within the range of 500 kHz (kilohertz) to 30 MHz (megahertz), particularly 5 MHz to 15 MHz, and preferably 5 MHz to 10 MHz. The varying magnetic field is used to inductively heat the susceptor due to at least one of eddy currents or hysteresis losses, depending on the electrical and magnetic properties of the susceptor material. In use, the susceptor is in thermal contact or thermal proximity with the aerosol-forming substrate to be heated when the article is received within the cavity of the apparatus. In general, the susceptor may either be part of the aerosol-generating device or part of the aerosol-generating article that includes the heated aerosol-forming substrate.

[0031] The at least one induction coil may be a helical coil or a flat, planar coil, specifically a pancake coil or a curved, planar coil. The at least one induction coil may be held within one of the main bodies or housings of the aerosol generating device. The induction coil may be disposed so as to surround at least a portion of the cavity or at least a portion of the inner surface of the cavity. For example, the induction coil may be a helical coil disposed within a sidewall of the cavity.

[0032] The induction source may comprise an alternating current (AC) generator. The AC generator may be powered by a power supply of the aerosol generating device. The AC generator is operably coupled to at least one induction coil. In particular, the at least one induction coil may be an integral part of the AC generator. The AC generator is configured to generate a high-frequency oscillating current that passes through the at least one induction coil to generate an alternating magnetic field. The AC current may be supplied to the at least one induction coil continuously after activation of the system, or may be supplied intermittently (e.g., with each puff).

[0033] The aforementioned components of the induction source, except for the induction coil (heating element), may form part of an electronic circuit, which may be disposed on a printed circuit board (PCB).

[0034] The inductive source preferably comprises a DC / AC converter connected to a DC power source including an LC network, the LC network comprising a series connection of a capacitor and an inductor. Furthermore, the inductive source may include a matching network for impedance matching. In particular, the inductive source may include a power amplifier, such as a class C power amplifier, a class D power amplifier, or a class E power amplifier.

[0035] The electric heating arrangement may also be a resistive heating arrangement for resistively heating the aerosol-forming substrate within the article. In this configuration, the heating element may include a resistive heating element. The resistive heating element may be, for example, a resistive heating wire, a resistive heating coil, a resistive heating track (particularly a resistive heating track provided with a heating blade), a resistive heating grid, or a resistive heating mesh. During use of the device, the resistive heating element is in thermal contact with or in thermal proximity to the aerosol-forming substrate to be heated.

[0036] The aerosol-generating device may further comprise a controller configured to control the operation of the heating process, preferably in a closed-loop configuration, in particular to control the heating of the aerosol-forming substrate to a predetermined operating temperature. The operating temperature used to heat the aerosol-forming liquid may be in the range of 100°C to 300°C, in particular in the range of 150°C to 250°C, for example 230°C. Generally, the operating temperature may depend on the type of aerosol-forming substrate being heated. For example, the operating temperature of a liquid aerosol-forming substrate may be lower than the operating temperature of a solid aerosol-forming substrate.

[0037] The controller may be the main control unit (MCU) of the aerosol generating device. The controller may comprise 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. In particular, the induction source may be part of the controller.

[0038] The aerosol generating device may include a power source, specifically a DC power source configured to provide a DC supply voltage and a DC supply current to the induction source. The power source is preferably a battery, such as a lithium iron phosphate battery. Alternatively, the power source may be 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 for discontinuous activation of the induction source.

[0039] In the case of an inductively heated aerosol generating device, the aerosol generating device may further comprise a flux concentrator disposed around at least a portion of the induction coil and configured to distort the alternating magnetic field of the at least one induction source towards the cavity. Thus, when an article is received within the cavity, the alternating magnetic field, if present, is distorted towards the inductively heatable liquid conduit. Preferably, the flux concentrator comprises a flux concentrator foil, in particular a multi-layer flux concentrator foil.

[0040] The cavity may include an insertion opening through which the aerosol-generating article may be inserted into the cavity. As used herein, the direction in which the aerosol-generating article is inserted is designated as the insertion direction. Preferably, the insertion direction corresponds to an extension of the length axis, particularly the central axis, of the cavity.

[0041] After insertion into the 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 denoted with the prefix "proximal," respectively. Sections that are disposed further away are denoted with the prefix "distal."

[0042] The cavity may have any suitable cross-section as viewed in a plane perpendicular to the longitudinal axis of the cavity or perpendicular to the direction of insertion of the article. In particular, the cross-section of the cavity may correspond to the shape of the aerosol-generating article to be received therein. Preferably, the cavity has a substantially circular cross-section. Alternatively, the cavity 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.

[0043] The aerosol generating device may include a main body, which preferably includes at least one of a heating arrangement, a controller, a power source, and at least a portion of the cavity. In addition to the main body, the aerosol generating device may further include a mouthpiece, particularly if the aerosol-generating article used with the device does not include a mouthpiece. The mouthpiece may be attached to the main body of the device. The mouthpiece may be configured to close the receiving cavity when the mouthpiece is attached to the main body. If the device does not include a mouthpiece, the aerosol-generating article used with the aerosol generating device may include a mouthpiece, such as a filter plug.

[0044] The aerosol generating device may comprise at least one air outlet, for example an air outlet in the mouthpiece (if present).

[0045] The aerosol-generating device preferably comprises an air path extending from at least one air inlet, through the cavity, and optionally further to an air outlet in the mouthpiece, if present. The aerosol-generating device preferably comprises at least one air inlet in fluid communication with the cavity. As a result, the aerosol-generating system may comprise an air path extending from the at least one air inlet into the cavity, and optionally further through an aerosol-forming substrate within the article and the mouthpiece and into the user's mouth.

[0046] Preferably, the aerosol generating device is a smoke extractor for generating an aerosol that can be directly inhaled by a user through the user's mouth, in particular the aerosol generating device is a handheld aerosol generating device.

[0047] As further noted above, the electronics of the heating arrangement may be disposed on a printed circuit board (PCB), which may also include a controller for detecting the presence, absence, or displacement of an article.

[0048] The temperature sensor may therefore be configured to output a signal indicative of the temperature or temperature rise of at least one portion of the printed circuit board during operation of the heating arrangement, and for this purpose the temperature sensor may be arranged on the printed circuit board.

[0049] Preferably, the heating element of the heating arrangement is not disposed on a printed circuit board. In particular, the electronic circuit and the heating element may be disposed in separate parts of the aerosol generating device. Preferably, the electronic circuit is disposed in a distal part of the aerosol generating device, and the heating element is disposed in a proximal part of the aerosol generating device, particularly in or around the cavity. This allows the electronic circuit to be thermally separated from the heating element. As a result, the detected temperature or detected temperature increase is more sensitive to the effect of the actual item's position on the temperature of the electronic circuit.

[0050] According to a further aspect of the present invention, there is provided an aerosol generation system comprising an aerosol generating device according to the present invention and an aerosol-generating article for use with the device, the aerosol-generating article comprising an aerosol-forming substrate heated by the device.

[0051] As used herein, the term "aerosol-generating system" refers to the combination of an aerosol-generating article as further described herein and an aerosol-generating device according to the present invention as described herein. In the system, the article and device may cooperate to generate an inhalable aerosol.

[0052] As used herein, the term "aerosol-generating article" refers to an article comprising at least one aerosol-forming substrate that, when heated, releases a volatile compound capable of forming an aerosol. The aerosol-generating article is preferably a heated aerosol-generating article, i.e., an aerosol-generating article comprising at least one aerosol-forming substrate that is intended to be heated, rather than combusted, to release a volatile compound capable of forming an aerosol. The aerosol-generating article may be a consumable product, particularly one that is disposed of after a single use. For example, the article may be a cartridge containing a liquid aerosol-forming substrate that is to be heated. As another example, the article may be a rod-shaped article, particularly a tobacco product similar to a conventional cigarette.

[0053] As used herein, the term "aerosol-forming substrate" refers to a substrate formed from or including an aerosol-forming material capable of releasing volatile compounds upon heating to generate an aerosol. The aerosol-forming substrate is intended to be heated, rather than combusted, to release the aerosol-forming volatile compounds. The aerosol-forming substrate may be a solid aerosol-forming substrate, a liquid aerosol-forming substrate, a gel-like aerosol-forming substrate, or any combination thereof. The aerosol-forming substrate may include 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 include a non-tobacco material. The aerosol-forming substrate may further include an aerosol former. Examples of suitable aerosol formers are glycerin and propylene glycol. The aerosol-forming substrate may also include other additives and ingredients, such as nicotine or flavoring agents. 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, which is compressed or molded into a plug.

[0054] If the aerosol-generating device includes an induction heating arrangement, the aerosol-generating system may include at least one susceptor for inductively heating the aerosol-forming substrate. The susceptor may be an integral part of the aerosol-generating article. Thus, the aerosol-generating article may include at least one susceptor positioned in thermal proximity or thermal contact with the aerosol-forming substrate when the article is received in the cavity of the device, such that the susceptor can be inductively heated by the induction heating arrangement during use. It is also possible for the susceptor to be part of the aerosol-generating device. Similarly, in this configuration, the susceptor is disposed within the device such that it is in thermal proximity or thermal contact with the aerosol-forming substrate when the article is received in the cavity of the device.

[0055] 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.

[0056] The substrate element preferably comprises at least one aerosol-forming substrate that is heated. If the aerosol-generating system is based on induction heating, the substrate element may further comprise a susceptor in thermal contact with or in thermal proximity to the aerosol-forming substrate.

[0057] As used herein, the term "susceptor" refers to an element comprising a material capable of being inductively heated in an alternating electromagnetic field, which may be the result of at least one of hysteresis losses or eddy currents induced within the susceptor, depending on the electrical and magnetic properties of the susceptor material.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] All of the aforementioned elements may be sequentially disposed along the longitudinal axis of the article in the order described above, with the first support element preferably disposed at the distal end of the article and the filter element preferably disposed at the proximal end of the article. Each of the aforementioned elements may be substantially cylindrical. Specifically, all elements may have the same outer cross-sectional shape. Additionally, 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.

[0062] Further features and advantages of the aerosol generating system according to the present invention are described with respect to the aerosol generating device and apply equally.

[0063] According to another aspect of the present invention, there is provided a method for detecting the presence, absence, or displacement of an aerosol-generating article within a cavity of an aerosol-generating device, the device comprising: a cavity for removably receiving at least a portion of the article; and an electric heating arrangement including an electronic circuit and a heating element operatively coupled to the electronic circuit for heating an aerosol-forming substrate contained in the article when the article is received within the cavity, the method comprising: - measuring the temperature or temperature rise of at least one part of the electronic circuit during operation of the heating arrangement; - detecting the presence, absence or displacement of an item within the cavity in response to the temperature or temperature rise breaching a predetermined temperature threshold or a predetermined temperature rise threshold, respectively.

[0064] As described above in relation to the aerosol generating device according to the invention, the predetermined temperature threshold may be in the range of 80° C. to 180° C., in particular 100° C. to 160° C. Similarly, the predetermined temperature rise threshold may be at least 80° C., in particular at least 100° C., preferably at least 120° C.

[0065] Also, as described above with respect to the aerosol generating device according to the present invention, the predetermined temperature rise threshold may be a function, in particular a linear or quadratic function, of the initial temperature of at least one portion of the electronic circuit at the start of operation of the device. Thus, the method may include detecting the initial temperature of at least one portion of the electronic circuit at the start of operation of the device and determining the predetermined temperature rise threshold as a function of the detected initial temperature. Similarly, the method may include detecting the initial temperature of at least one portion of the electronic circuit at the start of operation of the device and, in response to the rescaled temperature rise breaching the predetermined temperature rise threshold, rescaling the temperature rise by a predetermined function of the detected initial temperature to detect the presence, absence, or displacement of an item within the cavity.

[0066] To conserve power and protect the heating arrangement from damage, the method may further include shutting down or limiting operation of the electric heating arrangement in response to detecting the displacement or absence of the item.

[0067] Additionally, the method may include detecting the presence of the item at the desired location within the cavity in response to the temperature or temperature rise falling below a predetermined temperature or temperature rise threshold. In doing so, the method may further include enabling operation of the electric heating arrangement in response to detecting the presence of the item at the desired location within the cavity.

[0068] Preferably, at least one portion of the electronic circuit is monitored for excessive temperature or temperature rise at short intervals, so that the temperature or temperature rise of at least one portion of the electronic circuit may be measured at least every 10 seconds, in particular at least every 5 seconds, preferably at least every 2 seconds, more preferably at least every second.

[0069] Further features and advantages of the method according to the invention are explained with respect to the aerosol generating device and the aerosol generating system and apply equally.

[0070] The present invention is defined in the claims. However, the following provides a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of any other example, embodiment, or aspect described herein.

[0071] Example 1: An aerosol generating device for heating an aerosol-forming substrate capable of forming an inhalable aerosol when heated. Example 1A: An aerosol-generating device according to example 1, comprising a cavity for removably receiving at least a portion of an aerosol-generating article, the article comprising an aerosol-forming substrate that is heated. Example 1B: An aerosol generating device according to any one of the preceding embodiments, comprising an electric heating arrangement. Example 1C: The aerosol generating device according to Example 1B, wherein the electrical heating arrangement comprises an electronic circuit. Example 1D: The aerosol generating device according to Example 1B or 1C, wherein the electrical heating arrangement comprises a heating element. Example 1Ea: The aerosol generating device according to Example 1D, wherein the heating element is operably connected to an electronic circuit. Example 1Eb: An aerosol-generating apparatus according to Example 1Ea, wherein the heating element is for heating the aerosol-forming substrate when the aerosol-generating article is received within the cavity. Example 1F: An aerosol generating device according to Example 1Ea or 1Eb, comprising a controller including a temperature sensor configured to output a signal indicative of the temperature or temperature increase of at least one portion of the electronic circuit during operation of the heating arrangement. Example 1G: An aerosol generating device according to Example 1F, wherein the controller is configured to detect the presence, absence, or displacement of an item in response to a signal indicating that the temperature or temperature rise has exceeded a predetermined temperature threshold or a predetermined temperature rise threshold, respectively. Example 1H: An aerosol generating device according to Example 1G, wherein the controller is configured to detect the presence, absence, or displacement of an item within the cavity. Example 2: The aerosol generating apparatus according to any one of Examples 1 to 1H, wherein the predetermined temperature threshold is in the range of 80 degrees Celsius to 180 degrees Celsius, in particular 100 degrees Celsius to 160 degrees Celsius. Example 3: An aerosol generating device according to any one of the preceding embodiments, wherein the predetermined temperature rise threshold is at least 80 degrees Celsius, in particular at least 100 degrees Celsius, preferably at least 120 degrees Celsius. Example 4: An aerosol generating device according to any one of the preceding embodiments, wherein the predetermined temperature rise threshold is a predetermined function of an initial temperature of at least one portion of the electronic circuitry at the start of operation of the device. Example 5: An aerosol generating device according to either Example 3 or Example 4, wherein the controller is configured to detect an initial temperature of at least one portion of the electronic circuit at the start of operation of the device and determine a predetermined temperature rise threshold as a function of the detected initial temperature. Example 6: An aerosol generating device according to any one of the preceding embodiments, wherein the controller is configured to detect an initial temperature of at least one portion of the electronic circuit at the start of operation of the device, and in response to the rescaled signal, rescale the signal indicative of the temperature increase by a predetermined function of the detected initial temperature in order to detect the presence, absence, or displacement of an item in the cavity. Example 7: An aerosol generating device according to any one of the preceding embodiments, wherein the temperature sensor comprises at least one of a thermocouple, a thermistor, or a semiconductor integrated circuit sensor. Example 8: An aerosol generating device according to any one of the preceding embodiments, wherein the electrical heating arrangement is an induction heating arrangement for inductively heating an aerosol-forming substrate within the article. Example 9: 9. An aerosol-generating article according to example 8, wherein the heating element comprises at least one induction coil for generating a varying magnetic field within the cavity. Example 10: An aerosol-generating apparatus according to any one of Examples 1 to 7, wherein the electrical heating arrangement is a resistive heating arrangement for resistively heating an aerosol-forming substrate within the article. Example 11: 11. An aerosol generating device according to claim 10, wherein the heating element comprises a resistive heating element. Example 12: An aerosol generating device according to one of the preceding embodiments, wherein the electronic circuitry and the heating element are arranged in separate parts of the aerosol generating device. Example 13: An aerosol generating device according to any one of the preceding embodiments, wherein the electronic circuitry is arranged in a distal part of the aerosol generating device and the heating element is arranged in a proximal part of the aerosol generating device, in particular in or around the cavity. Example 14: An aerosol generating device according to any one of the preceding embodiments, wherein the controller is configured to stop or limit operation of the electric heating arrangement in response to detecting a displacement or absence of the article. Example 15: An aerosol generating device according to any one of the preceding embodiments, wherein the controller is configured to detect the presence of an item at a desired location within the cavity in response to the signal indicating that the temperature or temperature rise has fallen below a predetermined temperature threshold or a predetermined temperature rise threshold, respectively. Example 16: An aerosol generating device according to example 15, wherein the controller is configured to enable heating operation of the electrical heating arrangement in response to detecting insertion of an item into the cavity. Example 17: An aerosol generating device according to any one of the preceding embodiments, wherein the controller is configured to monitor the temperature of at least one part of the electronic circuit at least every 10 seconds, in particular at least every 5 seconds, preferably at least every 2 seconds, more preferably at least every second. Example 18: An aerosol-generating system comprising an aerosol-generating device according to any one of the preceding embodiments and an aerosol-generating article for use with the device, the aerosol-generating article comprising an aerosol-forming substrate heated by the device. Example 19: 1. A method for detecting the presence, absence, or displacement of an aerosol-generating article within a cavity of an aerosol-generating device, the device comprising: a cavity for removably receiving at least a portion of the article; and an electric heating arrangement including an electronic circuit and a heating element coupled to an operating circuit in the electronic circuit for heating an aerosol-forming substrate contained in the article when the article is received in the cavity, the method comprising: - measuring the temperature or temperature rise of at least one part of the electronic circuit during operation of the heating arrangement; - detecting the presence, absence, or displacement of an item within the cavity in response to the temperature or temperature rise breaching a predetermined temperature threshold or a predetermined temperature rise threshold, respectively. Example 20: 20. The method according to example 19, wherein the predetermined temperature threshold is in the range of 80 degrees Celsius to 180 degrees Celsius, particularly 100 degrees Celsius to 160 degrees Celsius. Example 21: 21. The method according to any one of embodiments 19 or 20, wherein the predetermined temperature rise threshold is at least 80 degrees Celsius, in particular at least 100 degrees Celsius, preferably at least 120 degrees Celsius. Example 22: 22. The method according to any one of Examples 19-21, further comprising: detecting an initial temperature of at least one portion of the electronic circuit at the start of operation of the device; and determining a predetermined temperature rise threshold as a function of the detected initial temperature. Example 23: 23. The method according to any one of Examples 19-22, comprising detecting an initial temperature of at least one portion of the electronic circuit at the initiation of operation of the device, and rescaling the temperature rise by a predetermined function of the detected initial temperature to detect the presence, absence, or displacement of an item within the cavity in response to the rescaled temperature rise breaching a predetermined temperature rise threshold. Example 24: The method according to any one of examples 19-23, further comprising: in response to detecting the displacement or absence of the article, deactivating or limiting operation of the electric heating arrangement. Example 25: The method according to any one of Examples 19-24, further comprising detecting the presence of an item at a desired location within the cavity in response to the temperature or temperature rise falling below a predetermined temperature threshold or temperature rise threshold. Example 26: 26. The method according to example 25, further comprising enabling operation of the electrical heating arrangement in response to detecting the presence of the item at the desired location within the cavity. Example 27: The method according to any one of Examples 19 to 26, wherein the temperature or temperature increase of at least one part of the electronic circuit is measured at least every 10 seconds, in particular at least every 5 seconds, preferably at least every 2 seconds, more preferably at least every second.

[0072] The embodiments will now be further described with reference to the following figures: [Brief explanation of the drawings]

[0073] [Figure 1] 1-2 show a schematic representation of an aerosol generation system according to a first exemplary embodiment of the present invention, including an aerosol generating device and an aerosol-generating article for use with the device. [Figure 2] Same as above. [Figure 3] FIG. 3 shows diagrammatically an induction heating arrangement for the aerosol generating device according to FIGS. [Figure 4] FIG. 4 shows a diagram reflecting the occurrence of a temperature rise indicative of the presence, absence, or displacement of an aerosol-generating article in a system according to FIGS. [Figure 5] FIG. 5 shows a diagram reflecting the temperature profile for the subsequent heating process of the electronic circuit of the heating arrangement of the aerosol generating device according to FIGS. DETAILED DESCRIPTION OF THE INVENTION

[0074] 1 and 2 show schematically a first 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 inductively heating the substrate upon engagement of the article 10 with the device 100.

[0075] The aerosol-generating article 10 has a substantially rod-shaped configuration resembling 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.

[0076] The elongated aerosol-generating device 100 comprises two parts: a proximal part 102 and a distal part 101. Within the proximal part 102, the device 100 comprises a cavity 103 for removably receiving at least a portion of the aerosol-generating article 10. Within the distal part 101, the device 100 comprises a DC power source 150, such as a rechargeable battery, for powering the operation of the device, and a printed circuit board 160 including a main control unit 161 for, among other things, controlling the operation of the device 100. For heating the substrate, the device 100 comprises an electric heating arrangement 110 comprising an electronic circuit 115 and an induction coil 118 for generating an alternating magnetic field, in particular a high-frequency magnetic field, within the cavity 103.

[0077] In this embodiment, the induction coil 118 is a helical coil disposed within the proximal portion 102 of the apparatus so as to circumferentially surround the cylindrical receiving cavity 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 apparatus 100. The alternating magnetic field is used to inductively heat the susceptor 30 in the aerosol-generating article 10 when the article 10 is received 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 electromagnetic 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 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 takes 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 device 100. The airflow continues through a passage formed between the inner surface of the cylindrical cavity 103 and the outer surface of the article 10 toward the distal end of the cavity 103. At the distal end of the cavity 103, the airflow enters the aerosol-generating article 10 through the substrate element 20 and further passes through the 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.

[0078] FIG. 3 shows details of induction heating arrangement 110. According to this embodiment, induction heating arrangement 110 comprises a DC / AC inverter connected to 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 transistor switch 111; and an LC load network 113 including a shunt capacitor C1 and a series connection of capacitor C2 and inductor L2. Inductor L2 corresponds to induction coil 118 shown in FIGS. 1 and 2, which is used to generate an alternating magnetic field in cavity 103. In addition, a choke L1 is provided for supplying a DC supply voltage +V_DC to DC power supply 150. 3, the ohmic resistance R representing the total equivalent resistance or total resistive load 114 when the system is in use, i.e. when an item is inserted into the cavity 103 of the apparatus 100, is the sum of the ohmic resistance of the induction coil 118 marked 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 induction coil 118. 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.

[0079] The electronics 115 of the electric heating arrangement 110 (excluding the induction coil 118 ) are disposed on a printed circuit board 160 together with a main control unit 161 .

[0080] To adequately heat the aerosol-forming substrate via the susceptor 30, the ohmic resistance of the susceptor 30 is selected to be much greater than the ohmic resistance of the components of the induction coil 118 and the electronic circuitry 115. As a result, when the aerosol-generating article 10 is properly received within the cavity of the apparatus, the power provided by the heating arrangement 110 is mostly dissipated within the susceptor 30 and the aerosol-forming substrate 21 within the article 10. Only a small portion of the power is dissipated within the electronic circuitry 115 of the heating arrangement 110. Conversely, when the aerosol-generating article 10 is displaced within or absent from the cavity, either due to the misalignment of the susceptor 30 with the magnetic field of the induction coil 118 or due to the absence of the susceptor 30, only a small amount of power is dissipated within the susceptor 30 (in the case of displacement), or no power is dissipated within the susceptor 30 (in the case of absence), with the majority being dissipated within the electronic circuitry 115. The additional (excessive) power dissipated in the electronic circuitry 115 may cause the temperature of at least a portion of the electronic circuitry 115 to change differently than during normal operation when an item 10 is properly received within the cavity. In particular, the temperature of at least a portion of the electronic circuitry 115 may rise more rapidly and to a higher temperature than is typically experienced during normal operation when the item 10 is properly received within the cavity 103 of the device 100.

[0081] This is shown in Figure 4, which reflects, on the left side, the occurrence of a typical temperature rise Δ_T at a particular portion of the electronic circuit 115 during operation of the heating arrangement 110 when the item 10 is properly received within the cavity 103. In contrast, the right side of Figure 4 reflects the occurrence of an excessive temperature rise at that particular portion of the electronic circuit 115 when the item is displaced within or absent from the cavity 103. Here, the temperature rise Δ_T is defined as Δ_T = [T(t2) - T(t1)], where T(t1) is the initial temperature of at least one portion of the electronic circuit at a first time t1 during operation of the heating arrangement 110, and T(t2) is the temperature of at least one portion of the electronic circuit at a second time t2 or after a predetermined period t (t = t2 - t1) has elapsed after the first time t1. For example, T(t1) may be the initial temperature of at least one portion of the electronic circuit 115 at the start of a calibration operation of the device, and T(t2) is the temperature of at least one portion of the electronic circuit 2 seconds or 5 seconds later.

[0082] The above-described correlation between the presence, absence, or displacement of the aerosol-generating article 10 in the cavity 103 and the temperature or temperature increase of at least a portion of the electronic circuit 115 is advantageously used to detect the presence, absence, or displacement of the article 10 in the cavity 103 of the device 100. To this end, the aerosol-generating device 100 includes a controller 163 that is part of the main control unit 161. As shown in FIGS. 1 and 2 , the controller 163 includes a temperature sensor 165 disposed in thermal contact with a portion of the electronic circuit 115 of the heating arrangement 110 and configured to output a signal indicative of the temperature or temperature increase of the portion. The temperature sensor 165 may be a thermocouple, a thermistor, or a semiconductor integrated circuit sensor. The controller 163 is configured to detect the presence, absence, or displacement of the article 10 in the cavity 103 in response to the signal indicating that the temperature or temperature increase has breached a predetermined temperature threshold or a predetermined temperature increase threshold Δ_T_threshold, respectively.

[0083] 4, the predetermined temperature rise threshold Δ_T_THRESHOLD is preferably selected between a typical temperature rise Delta_T in that portion of the electronic circuit 115 when an item 10 is properly received in the cavity 103 and an excessive temperature rise in that portion when an item is placed in, displaced from, or absent from the cavity 103. In this embodiment, as indicated by the vertical line in the diagram according to FIG. 4, the predetermined temperature threshold Δ_T_THRESHOLD is selected to be approximately 120 degrees Celsius. This allows the controller to reliably distinguish between a normal temperature rise during operation of the heating arrangement 110, which indicates the presence of an item 10 properly positioned in the cavity 103, and an excessive temperature rise, which indicates the absence or displacement of the item 10.

[0084] In this embodiment, the controller 163 in combination with the temperature sensor 165 may be configured to take two subsequent temperature measurements of the electronic circuit 115, determine a signal indicative of a temperature rise by taking the difference between the temperature signals of the subsequent temperature measurements, and finally compare the signal indicative of a temperature rise of at least one portion of the electronic circuit with a predetermined temperature rise threshold. If the signal indicative of a temperature rise is equal to or greater than the predetermined temperature rise threshold, the controller 163 may detect the displacement or absence of an item. Conversely, if the signal indicative of a temperature rise is less than the predetermined temperature rise threshold, the controller 163 may detect the presence of an item in the cavity.

[0085] To conserve power and protect the heating arrangement 110 from damage, the controller 163 may further be configured to stop or limit operation of the heating arrangement 110 if displacement or absence of the item 10 is detected. Similarly, the controller 163 may be configured to enable heating operation of the electric heating arrangement 110 in response to detecting the presence of the item 10 in a desired position within the cavity 103.

[0086] Detection of the presence, absence, or displacement of the aerosol-generating article in the cavity may also take into account a slow heating rate of the electronic circuit 115 if the initial temperature of the electronic circuit 115 is already high at the start of operation of the apparatus, for example, when a new heating process immediately follows a previous heating process. This situation is illustrated in FIG. 5, which schematically shows the temperature T of the electronic circuit 115 of the heating arrangement according to FIGS. 1 and 2 over time t and for two subsequent heating processes H1 and H2. As can be seen in FIG. 5, the first heating process H1 begins at time T(t0_H1) at a temperature T(t0_H1), which is, for example, approximately room temperature. When the article 10 is received in the cavity 103 of the apparatus 100, the temperature T of the electronic circuit 115 rises during the heating operation to a temperature T_H, as indicated by the first plateau of the heating profile according to FIG. 5. When the item 10 is removed from the apparatus 100, the temperature T of the electronic circuit 115 increases further compared to the initial temperature until it reaches a value T(t1_H1) at time T1_H1), i.e., Δ_T_H1=T(t1_H1)-T(t0_H1), which exceeds a predetermined temperature increase threshold indicating the absence of the item. This may be detected by the controller, and in response, the first heating process may be stopped. As a result, the temperature T of the electronic circuit 115 decreases again toward the initial temperature.

[0087] If the user initiates a second heating process H2 during that cooling, the initial temperature T(t0_H2) of the second heating process H2 may be higher than the initial temperature T(t0_H1) of the first heating process H1. Thus, the heating rate of the electronic circuit 115 may be lower during the second heating process H2 than during the first heating process H1 because heating a mass to a constant temperature requires more heat if the mass has a higher initial temperature at the start of the heating process than if the mass has a lower initial temperature. As a result, when the article 10 is removed from the cavity 103 during the second heating process H2, the actual temperature increase Δ_T_H2=T(t1_H2)−T(t0_H2) of the electronic circuit 115 is less than the corresponding actual temperature increase Δ_T_H1=T(t1_H1)−T(t0_H1) of the electronic circuit 115 during the first heating process H1.

[0088] To compensate for this difference, the temperature rise or the signal indicative of the temperature rise may be rescaled by a predetermined function of the initial temperature of the electronic circuitry at the start of each heating operation H1, H2. For example, if the signal output of the temperature sensor 165 shown in FIGS. 1 and 2 is an ADC (analog-to-digital converter) value that correlates with temperature such that a high temperature corresponds to a low ADC value and a low temperature corresponds to a high ADC value (see above), the rescaling may be performed by dividing the signal indicative of the temperature rise by the signal indicative of the initial temperature of each heating operation. For example, the signal indicative of the temperature rise may be rescaled according to the following function: Δ_S_scal=kn[S(t0)-S(t1)] / S(t0), where Δ_S_scal is the rescaled signal indicative of the temperature rise compared to a predetermined signal value corresponding to a predetermined temperature rise threshold, S(t0) is the signal indicative of the initial temperature of the electronic circuitry 115 at the start of each heating operation H1, H2, and S(t1) is the signal indicative of the temperature of the electronic circuitry 115 of each heating operation H1, H2 at a subsequent time t2. The coefficient k is a constant that can be obtained by calibration. In this way, temperature increases are weighted more when the electronic circuit 115 of the device 10 is (still) at a higher level, for example, due to a previous heating process. In particular, the rescaling function can be selected so that the absence of the item is detected for each heating process within approximately the same period or a predetermined time range after its removal, regardless of the actual initial temperature. That is, as shown in FIG. 5, the rescaling function can be selected so that the respective rescaled signals Δ_S_scal indicating the temperature increase after removal of the item for each heating process are approximately the same value after the same period or a predetermined time range, regardless of the actual initial temperature.

[0089] For purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing amounts, quantities, percentages, and the like should be understood in all instances to be modified by the term "about." Also, all ranges include the disclosed maximum and minimum points, and include any intermediate ranges therebetween, which may or may not be specifically recited herein. Accordingly, in this context, the number A is understood as A ± 5 percent. Within this context, the number A may be considered to include a numerical value that is within the typical standard error for the measurement of the property that the number A modifies. In some cases, as used in the appended claims, the number A may deviate by the percentages recited above, provided that the amount by which A deviates does not materially affect the basic and novel characteristics of the claimed invention. Also, all ranges include the disclosed maximum and minimum points, and include any intermediate ranges 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 cavity for removably receiving at least a portion of an aerosol-generating article comprising said aerosol-forming substrate to be heated; an electric heating arrangement comprising an electronic circuit and a heating element operatively connected to said electronic circuit for heating said aerosol-forming substrate when said aerosol-generating article is received within said cavity; - a controller including a temperature sensor configured to output a signal indicative of the temperature or temperature rise of at least one portion of the electronic circuit during operation of the heating arrangement, the controller being configured to detect the presence, absence, or displacement of the item in the cavity in response to the signal indicating that the temperature or the temperature rise has exceeded a predetermined temperature threshold or a predetermined temperature rise threshold, respectively.

2. 2. The aerosol generating device according to claim 1, wherein the predetermined temperature threshold is in the range of 80 degrees Celsius to 180 degrees Celsius, in particular 100 degrees Celsius to 160 degrees Celsius.

3. 3. An aerosol generating device as claimed in claim 1, wherein the predetermined temperature rise threshold is a predetermined function of the initial temperature of at least one part of the electronic circuit at the start of operation of the device.

4. 4. The aerosol generating device of claim 3, wherein the controller is configured to detect the initial temperature of at least one portion of the electronic circuit at the start of operation of the device and to determine the predetermined temperature rise threshold as a function of the detected initial temperature.

5. An aerosol generating device as described in any one of claims 3 or 4, wherein the controller is configured to detect the initial temperature of at least one portion of the electronic circuit at the start of the operation of the device and, in response to the rescaled signal, rescale the signal indicating the temperature increase by a predetermined function of the detected initial temperature in order to detect the presence, absence, or displacement of the item in the cavity.

6. 6. The aerosol generating device according to claim 1, wherein the temperature sensor comprises at least one of a thermocouple, a thermistor, or a semiconductor integrated circuit sensor.

7. 7. The aerosol generating device according to claim 1, wherein the electric heating arrangement is an induction heating arrangement for inductively heating the aerosol-forming substrate within the article.

8. 7. The aerosol generating device according to claim 1, wherein the electrical heating arrangement is a resistive heating arrangement for resistively heating the aerosol-forming substrate within the article.

9. 9. The aerosol generating device according to claim 1, wherein the electronic circuit and the heating element are disposed in a part separate from the aerosol generating device.

10. An aerosol generating device according to any one of claims 1 to 9, wherein the controller is configured to stop or limit operation of the electric heating arrangement in response to detecting displacement or absence of the item.

11. An aerosol generating device as described in any one of claims 1 to 10, wherein the controller is configured to detect the presence of the item at a desired position within the cavity in response to the signal indicating that the temperature or the temperature rise has fallen below the predetermined temperature threshold or the predetermined temperature rise threshold, respectively.

12. 12. The aerosol generating device of claim 11, wherein the controller is configured to enable heating operation of the electric heating arrangement in response to detecting the presence of the item at the desired location within the cavity.

13. An aerosol generating device according to any one of claims 1 to 12, wherein the controller is configured to monitor the temperature of the at least one portion of the electronic circuit at least every 10 seconds, in particular at least every 5 seconds, preferably at least every 2 seconds, more preferably at least every second.

14. An aerosol generation system comprising an aerosol generating device according to any one of claims 1 to 13 and an aerosol-generating article for use with the device, the aerosol-generating article comprising an aerosol-forming substrate that is heated by the device.

15. 1. A method for detecting the presence, absence, or displacement of an aerosol-generating article within a cavity of an aerosol-generating device, the device comprising: a cavity for removably receiving at least a portion of the article; and an electric heating arrangement including an electronic circuit and a heating element operatively connected to the electronic circuit for heating an aerosol-forming substrate contained in the article when the article is received within the cavity, the method comprising: - measuring the temperature or temperature rise of at least one part of said electronic circuit during operation of said heating arrangement; - detecting the presence, absence or displacement of an item within said cavity in response to the temperature or temperature rise breaching a predetermined temperature threshold or a predetermined temperature rise threshold, respectively.

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