AEROSOL-GENERATING DEVICE WITH ACOUSTIC SENSOR

[0001]The present invention relates to an aerosol-generating device. The present invention relates to an aerosol-generating system. The present invention relates to a method of controlling an aerosol-generating device.

[0002]It is known to provide an aerosol-generating device for generating an inhalable vapor. Such devices may heat aerosol-forming substrate to a temperature at which one or more components of the aerosol-forming substrate are volatilised without burning the aerosol-forming substrate. The aerosol-forming substrate may be present in solid form or in liquid form. Aerosol-forming substrate may be provided as part of an aerosol-generating article. The aerosol-generating article may have a rod shape for insertion of the aerosol-generating article into a cavity, such as a heating chamber, of the aerosol-generating device. A heating element may be arranged in or around the heating chamber for heating the aerosol-forming substrate once the aerosol-generating article is inserted into the heating chamber of the aerosol-generating device. In addition or alternatively, a cartridge comprising a liquid aerosol-forming substrate may be attached to or inserted into the aerosol-generating device for supplying the liquid aerosol-forming substrate to the device for aerosol generation.

[0003]To ensure optimal conditions during heating of the aerosol-forming substrate, the temperature within the device is usually monitored. Such temperature monitoring usually works via a temperature sensor. However, such a temperature sensor cannot always be easily implemented into the heating chamber, for example, the implementation in a sealed heating chamber can be difficult.

[0004]It would be desirable to provide an aerosol-generating device that provides monitoring of the heating conditions within the aerosol-generating device. It would be desirable to provide an aerosol-generating device that provides real time monitoring of the temperature within the aerosol-generating device. It would be desirable to provide an aerosol-generating device that provides easy monitoring of the temperature within the aerosol-generating device. It would be desirable to provide an aerosol-generating device that provides a reliable monitoring of the temperature within the aerosol-generating device.

[0005]According to an embodiment of the invention there is provided an aerosol-generating device configured to receive an aerosol-forming substrate. The aerosol-generating device may comprise an acoustic sensor, a controller and a heating element. The heating element may be configured to heat the aerosol-forming substrate received in the aerosol-generating device. The acoustic sensor may be configured to detect an acoustic signal generated within the aerosol-generating device upon heating of the aerosol-forming substrate. The controller may be configured to determine a heating condition of the heated aerosol-forming substrate based on the acoustic signal detected by the acoustic sensor.

[0006]According to an embodiment of the invention there is provided an aerosol-generating device configured to receive an aerosol-forming substrate. The aerosol-generating device may comprise an acoustic sensor, a controller and a heating element. The heating element may be configured to heat the aerosol-forming substrate received in the aerosol-generating device. The acoustic sensor may be configured to detect an acoustic signal generated within the aerosol-generating device upon heating of the aerosol-forming substrate. The controller may be configured to determine a temperature of the heated aerosol-forming substrate based on the acoustic signal detected by the acoustic sensor.

[0007]According to an embodiment of the invention there is provided an aerosol-generating device configured to receive an aerosol-forming substrate. The aerosol-generating device comprises an acoustic sensor, a controller and a heating element. The heating element is configured to heat the aerosol-forming substrate received in the aerosol-generating device. The acoustic sensor is configured to detect an acoustic signal generated within the aerosol-generating device upon heating of the aerosol-forming substrate. The controller is configured to determine a temperature of the heated aerosol-forming substrate based on the acoustic signal detected by the acoustic sensor.

[0008]Acoustic signals are well-known from everyday life phenomena. The sound of breaking glass or cracking ice are examples of sounds we may hear from different objects subjected to stress like mechanical load or thermal load. An acoustic signal is a phenomenon of sound and ultrasound wave generation by materials that undergo an irreversible change in their internal structure for example as a result of crack formation or a temperature gradient. Sources generating acoustic signals in different materials are unique: Leaks, friction, knocks, chemical reactions, changes of size of magnetic domains are few examples of sources generating acoustic emission waves. Quantitative and qualitative characteristics of acoustic emission waves, generated by sources of different nature depend directly on material properties and environmental factors. More in particular, it is shown that acoustic emissions are generated during many chemical reactions and that they can easily be detected and monitored via a microphone arranged in close proximity of the chemical reaction container/location. They may be collected as transient signals or continuously recorded as a plot of acoustic power vs. time: power spectral density (or simply power spectrum).

[0009]Heating of the heating element of the aerosol-generating device may generate acoustic signals generated by components of the aerosol-generating device. These acoustic signals may, for example, be generated by vibrations of a component of the aerosol-generating device. These acoustic signals may be detected by the acoustic sensor within the device. By detecting the acoustic signals generated upon heating of the heating element by the acoustic sensor, the heating conditions may be monitored.

[0010]Further, the heating of an aerosol-forming substrate received in an aerosol-generating device may generate characteristic acoustic signals. The acoustic signals may be emitted by the heated aerosol-forming substrate. The aerosol-forming substrate may generate varying acoustic signals in dependence of the temperature exposed to the aerosol-forming substrate. The acoustic signals of the heated aerosol-forming substrate may be generated because its kinetic energy changes with the temperature. The specific magnitude of the acoustic signals may be associated to different phases of an aerosol-forming substrate heating profile. The generated acoustic signals may depend on the kind of heated aerosol-forming substrate. For example, if a solid or liquid aerosol-forming substrate is used. The substrate may also be in a form of a gel. By detecting the acoustic signals generated upon heating of the aerosol-forming substrate by the acoustic sensor, real time monitoring of the temperature within the aerosol-generating device may be provided. By detecting the acoustic signals generated upon heating of the aerosol-forming substrate by the acoustic sensor, easy monitoring of the temperature within the aerosol-generating device may be provided. By detecting the acoustic signals generated upon heating of the aerosol-forming substrate by the acoustic sensor, reliable monitoring of the temperature within the aerosol-generating device may be provided.

[0011]The acoustic signal may be generated by one or both of the heating element and the heated aerosol-forming substrate. The acoustic signal may be generated by the heated heating element. The acoustic signal may be emitted by the heated heating element. The acoustic signal may be generated by heating of the aerosol-forming substrate. The acoustic signal may be emitted by the heated aerosol-forming substrate. The acoustic signal may comprise a plurality of acoustic signals.

[0012]The controller may be configured to analyse the acoustic signal detected by the acoustic sensor. The controller may be configured to perform a spectrum components analysis on the acoustic signal. The spectrum components analysis may highlight the density and the magnitude of the acoustic signal at each phase. The controller may be configured to compare the analysed acoustic data with stored acoustic signals.

[0013]The heating element and the acoustic sensor may be connected to the controller. The heating element and the acoustic sensor may be electrically connected to the controller.

[0014]The aerosol-generating device may comprise a temperature sensor. The temperature sensor may be configured to determine the temperature of the heated aerosol-forming substrate. The controller may be configured to compare the temperature determined by the temperature sensor with the temperature determined based on the detected acoustic signal.

[0015]The controller may be configured to control the heating element based on the acoustic signal detected by the acoustic sensor. The controller may be configured to monitor heating of the heating element. The controller may be a microcontroller.

[0016]The acoustic sensor may comprise at least one microphone, preferably at least one MEMS microphone. A MEMS microphone may operate based on capacitive principle. A MEMS microphone is a micro-scale device that offers significant advantages. A MEMS microphone has a comparably high signal-to-noise ratio (SNR), low power consumption, good sensitivity and strong vibration resistance. In addition, MEMS microphones are small enough to be included in a tightly-integrated electronic product. The acoustic sensor may comprise a plurality of acoustic sensors, preferably microphones, more preferably MEMS microphones. The acoustic sensor may comprise, two, three, four, five, or six microphones, preferably MEMS microphones. The plurality of acoustic sensors may be symmetrically arranged around the aerosol-forming substrate. The plurality of microphones may be identical or may be of different types. Using different types of acoustic sensors and placing the acoustic sensors at different locations may allow to cover a larger dynamic range for detection of the acoustic signal. Using a plurality of acoustic sensors may also improve spatial resolution of the detection.

[0017]The acoustic sensor may be placed in contact with a surface of the aerosol-generating device. The acoustic sensor may be placed in contact with a surface of a housing of the aerosol-generating device. By placing the acoustic sensor in contact with a surface of the aerosol-generating device, acoustic signals transmitted through the material of the respective surface of the aerosol-generating device may be detected.

[0018]The acoustic sensor may also be placed distant from a surface of the aerosol-generating device. For example, the acoustic sensor may be placed hanging in open space within the aerosol-generating device. By placing the acoustic sensor remote from an internal surface of the aerosol-generating device, the acoustic sensor may be mechanically decoupled from the surfaces of the aerosol-generating device. In such configuration, the acoustic sensor may be particularly sensitive to acoustic signals transmitted from the aerosol-forming substrate to the acoustic sensor via the air in the internal volume of the aerosol-generating device.

[0019]The acoustic sensor may be directly connected to an electronic board. This is particularly suitable if the acoustic sensor is a MEMS microphone. A MEMS microphone may be provided integral with electronic circuitry of an electronic board. Such system may allow for sufficient amplification and noise reduction and may therefore be beneficial for a subsequent signal processing.

[0020]The aerosol-forming substrate may comprise one or both of a solid aerosol-forming substrate and a liquid aerosol-forming substrate. During heating the aerosol-forming substrate may undergo a phase transition. The phase transition may emit a characteristic acoustic signal. The acoustic sensor may detect the characteristic acoustic signal emitted during the phase transition of the aerosol-forming substrate. The controller may be configured to detect the phase transition of the aerosol-forming substrate. The controller may be configured to determine the temperature of the aerosol-forming substrate based on the detected phase transition of the aerosol-forming substrate.

[0021]The aerosol-forming substrate may comprise a water-based aerosol-forming substrate. During heating of such an aerosol-forming substrate at about 95° C. cavitation may start to occur which may cause an acoustic signal. This acoustic signal may be detected by the acoustic sensor.

[0022]The aerosol-forming substrate may comprise a sound marker. The sound marker may be configured to generate an acoustic signal at a predetermined temperature. The sound marker may be configured to generate an ad-hoc acoustic signal. The acoustic sensor may be configured to detect the acoustic signal of the sound marker, preferably the ad-hoc signal. The controller may be configured to recognize the acoustic signal generated by the sound marker, preferably the ad-hoc signal. The controller may be configured to determine the temperature of the heated aerosol-forming substrate by the acoustic signal generated by the sound marker, preferably by the ad-hoc signal. The sound marker may be embedded into the solid aerosol-forming substrate. The acoustic signal generated by the sound marker may be used to set a reference point for the control of the heating temperature.

[0023]The sound marker may comprise one or more of a crystal, a polymer and graphite. The sound marker may emit the acoustic signal due to a phase change. The aerosol-forming substrate may comprise one or more sound marker.

[0024]The aerosol-generating device may comprise a heating chamber. The heating chamber may be configured to receive the aerosol-forming substrate. The aerosol-forming substrate may be heated within the heating chamber. The heating chamber may be configured to receive an aerosol-generating article. The heating chamber may be a hollow tubular portion. The heating chamber may be in a form of a cube or a parallelepiped or the like. The heating chamber may comprise a cylindrical wall. The heating chamber may be elongate. The heating chamber may comprise a proximal end and a distal end. The distal end may comprise a bottom wall. The heating chamber may comprise a metal. The heating chamber may comprise stainless steel. The heating chamber may consist of a metal, preferably stainless steel. The heating chamber may be configured to transmit the acoustic signal generated within the heating chamber upon heating of the aerosol-forming substrate to the acoustic sensor.

[0025]The acoustic sensor may be arranged in close proximity to the heating chamber. Alternatively, the acoustic sensor may be arranged in the heating chamber. The acoustic sensor may be arranged in the cylindrical wall of the heating chamber. The acoustic sensor may be arranged in the bottom wall of the heating chamber.

[0026]The heating chamber may comprise a sound transmission element. The heating chamber may be a sound transmission element. The heating chamber may comprise a metal providing sound transmission. The heating chamber may be made of one or more of a metal, glass and plastic. The sound transmission element may be configured to transmit an acoustic signal generated in the heating chamber to the acoustic sensor. The acoustic sensor may be arranged on a wall of the heating chamber comprising a sound transmission element.

[0027]In one embodiment the heating chamber may be a hollow tubular portion comprising a sound transmission element and the acoustic sensor may be positioned outside the heating chamber. The sound transmission element may transmit acoustic signal generated in the heating chamber to the acoustic sensor being outside the heating chamber. Thereby the heating chamber may be more simplified.

[0028]The aerosol-generating device may comprise a liquid storage portion. The microphone may be arranged in close proximity to the liquid storage portion. The liquid storage portion may comprise the liquid aerosol-forming substrate. The liquid storage portion may be configured as a container or a reservoir for storing the liquid aerosol-forming substrate.

[0029]The heating element may be a resistive heating element. The resistive heating element may comprise electrically resistive material. Suitable electrically resistive materials include but are not limited to: semiconductors such as doped ceramics, electrically “conductive” ceramics (such as, for example, molybdenum disilicide), carbon, graphite, metals, metal alloys and composite materials made of a ceramic material and a metallic material. Such composite materials may comprise doped or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbides. Examples of suitable metals include titanium, zirconium, tantalum platinum, gold and silver. Examples of suitable metal alloys include stainless steel, nickel-, cobalt-, chromium-, aluminium-titanium-zirconium-, hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese-, gold- and iron-containing alloys, and super-alloys based on nickel, iron, cobalt, stainless steel, Timetal® and iron-manganese-aluminium based alloys. In composite materials, the electrically resistive material may optionally be embedded in, encapsulated or coated with an insulating material or vice-versa, depending on the kinetics of energy transfer and the external physicochemical properties required.

[0030]The resistive heating element may comprise a mesh. The heating element may alternatively comprise a grid shaped structure, a tubular shape or a coil shape. The heating element may comprise a mesh heater. The mesh heater may comprise a heater body and at least one mesh. The mesh heater may be configured as an electrically resistive metal heater. The at least one mesh may comprise a plurality of electrically conductive filaments configured to form the individual mesh. The filaments may be provided with a woven or non-woven fabric. The electrically conductive filaments may define interstices between the filaments and the interstices may have a width of between 10 μm and 100 μm. Preferably the filaments give rise to capillary action in the interstices, so that in use, substrate to be vaporized is drawn into the interstices, increasing the contact area between the heater and the substrate.

[0031]The electrically conductive filaments may comprise any suitable electrically conductive material. Suitable materials include but are not limited to: semiconductors such as doped ceramics, electrically “conductive” ceramics (such as, for example, molybdenum disilicide), carbon, graphite, metals, metal alloys and composite materials made of a ceramic material and a metallic material. Preferred materials for the electrically conductive filaments are 304, 316, 304L, 316L stainless steel, and graphite. Preferably, stainless steel, nichrome wire, aluminium or tungsten is used.

[0032]The aerosol-generating device may comprise a liquid wicking material. The liquid wicking material may convey liquid aerosol-forming substrate from the liquid storage portion to the heating element, preferably the mesh heater. The liquid wicking material may comprise a capillary material. The capillary material may be in contact with the electrically conductive filaments of the mesh heater. The capillary material may extend into interstices between the filaments. The heater may draw liquid aerosol-forming substrate into the interstices by capillary action.

[0033]The aerosol-generating device may comprise an acoustic sensor in close proximity to the heating element. The acoustic sensor may be configured to detect the acoustic signal emitted by the heated heating element, preferably the heated mesh. The controller may be configured to analyse the acoustic signal emitted by the heated heating element, preferably the heated mesh. The controller may be configured to detect an overheating of the heated heating element, preferably the heated mesh. The mesh heater may generate a different acoustic signal if the mesh is run dry. The controller may be configured to detect such a dry state of the heated mesh. The mesh heater may generate a different acoustic signal when it is overheated. The controller may be configured to detect such an overheated state of the heated mesh heater. The controller may be configured to detect a depletion of a cartridge comprising the mesh heater upon detection of the acoustic signal generated by the heated mesh heater.

[0034]In one embodiment the heating element may comprise a heating blade. The heating blade may comprise one or more of a plurality of resistive tracks on an electrically insulating substrate. The heating blade may be mounted to the bottom wall of the heating chamber. The heating blade may be configured to be inserted into an aerosol-generating article. The heating blade may comprise an acoustic transmission element. The heating blade may be configured to transmit the acoustic signal generated within the heating chamber outside the heating chamber. The acoustic sensor may be arranged distal to the bottom wall. The heating blade may transmit the acoustic signal through the bottom wall of the heating chamber.

[0035]In one embodiment the heating element may comprise one or both of multi-strands and an inductive mesh. Such a heating element may generate a different acoustic signal if the heating element is in a pre-dry state or completely dry. The controller may be configured to detect such a pre-dry or dry state of the heating element.

[0036]Alternatively or additionally, the heating element may be an inductive heating element. The inductive heating element may comprise at least one inductor coil. The inductor coil may be at least partly arranged around the heating chamber of the main body. The inductor coil may be configured to heat susceptor material comprised in an aerosol-generating article received in the heating chamber of the aerosol-generating device. The acoustic sensor may be arranged in close proximity to the inductor coil. Thereby the acoustic sensor may detect an acoustic signal generated by the inductor coil. By detecting an acoustic signal of the inductor coil the inductor coil may be monitored. By monitoring the inductor coil aging may be detected. The acoustic signal generated by the inductor coil may be analysed by the controller. The inductor coil may generate a different acoustic signal when the coil ages. The controller may be configured to detect a change in the acoustic signal generated by the inductive coil. Thereby the controller may be configured to detect a coil aging of the inductive coil. If the controller detects a coil aging, the controller may be configured to provide a signal to the user.

[0037]The aerosol-generating device may comprise a memory unit configured to store the detected acoustic signal. The controller may comprise the memory unit. The memory unit may comprise reference data of acoustic signals for various aerosol-forming substrates. The memory unit may comprise reference data of acoustic signals for various aerosol-generating articles. The controller may be configured to compare the analysed acoustic signals with the reference data stored in the memory unit.

[0038]The aerosol-generating device may comprise a mouthpiece. The mouthpiece may be removable. A proximal end of the aerosol-generating device may comprise the mouthpiece. The user may puff on the mouthpiece. Alternatively, the user may puff on an aerosol-generating article received within the aerosol-forming device. The acoustic sensor may be configured to detect a puff on the mouthpiece of the aerosol-generating device. The acoustic sensor may be configured to detect a puff on an aerosol-generating article received within the aerosol-generating device.

[0039]In one embodiment the heating element may be an inductive heating element and the aerosol-forming substrate may be liquid. The acoustic sensor may be provided in a channel arranged parallel to a puff detection channel.

[0040]The present invention further relates to an aerosol-generating system comprising the device described herein and an aerosol-generating article comprising the aerosol-forming substrate. The aerosol-generating article may be configured to be at least partly received within the aerosol-generating device. The controller may be configured to identify the received aerosol-generating article based on the acoustic signal generated during heating of the aerosol-generating article. The aerosol-generating device may comprise the memory unit storing reference data of various aerosol-generating articles. The aerosol-generating article may comprise at least one sound marker. The aerosol-generating article may comprise solid aerosol-forming substate. The at least one sound marker may be embedded in the solid aerosol-forming substrate. The controller may be configured to identify the received aerosol-generating article based on the acoustic signal generated by the heated sound marker.

[0041]The present invention further relates to an aerosol-generating system comprising the device described herein and a cartridge comprising the aerosol-forming substrate. The cartridge may comprise the liquid storage portion.

[0042]The controller may be capable of identifying an aerosol-generating article, particularly an authorized aerosol-generating article. The controller may be capable of operating differently depending upon an identified type of aerosol-generating article. This may be beneficial if aerosol-generating articles of different types are to be used with a single aerosol-generating device. Exemplarily, the aerosol-generating article of a first type may enable a different user experience in comparison with an aerosol-generating article of a different second type. Having a single aerosol-generating device comprising a controller able to operate in different modes for both of such different aerosol-generating articles may be convenient for user. For instance, this avoids the need for the user to possess a variety of different devices each for use with a particular type of aerosol-generating article.

[0043]The first operational mode may further differ from the second operational mode by a heating profile of a heating element of the aerosol-generating device.

[0044]A heating profile of the heating element may comprise one or more of: a duration of operation of the heating element, a maximum temperature of the heating element, a minimum temperature of the heating element, an average temperature of the heating element and a temperature profile of the heating element. A temperature profile may comprise one or more temperature set points to which the aerosol-forming substrate and/or the heating element is heated. Exemplarily, a larger aerosol volume per puff may be desired in the first operational mode. This may be realized by, for example, one or both of a higher maximum temperature and a higher average temperature of the heating element. In the second operational mode, a lower aerosol volume per puff may be desired. This may be realized by, for example, one or both of a lower maximum temperature and a lower average temperature of the heating element. In a further example, a quicker aerosol delivery may be desired in the first operational mode. This may be realized by, for example, a quicker temperature increase in the temperature profile of the heating element. A slow aerosol delivery may be desired in the second operational mode. This may be realized by, for example, a slower temperature increase in the temperature profile of the heating element.

[0049]Particularly preferred, the first operational mode may have a predetermined maximum number of puffs and a predetermined maximum duration before the end of the first operational mode. The second operational mode may have a predetermined maximum volume of aerosol generated and a predetermined maximum duration before the end of the second operational mode.

[0050]The predetermined maximum number of puffs may be 20. The predetermined maximum number of puffs may be 19. The predetermined maximum number of puffs may be 18. The predetermined maximum number of puffs may be 17. The predetermined maximum number of puffs may be 16. The predetermined maximum number of puffs may be 15. The predetermined maximum number of puffs may be 14. The predetermined maximum number of puffs may be 13. The predetermined maximum number of puffs may be 12. The predetermined maximum number of puffs may be 11. The predetermined maximum number of puffs may be 10. The predetermined maximum number of puffs may be 9. The predetermined maximum number of puffs may be 8.

[0051]The predetermined maximum number of puffs of the first operational mode may be 10 or less. The predetermined maximum number of puffs of the second operational mode may be more than 10.

[0052]The predetermined maximum number of puffs of the first operational mode may be 14 or less. The predetermined maximum number of puffs of the second operational mode may be more than 14.

[0053]The predetermined maximum number of puffs of the first operational mode may be 18 or less. The predetermined maximum number of puffs of the second operational mode may be more than 18.

[0054]The predetermined maximum number of puffs of the second operational mode may be lower than the predetermined maximum number of puffs of the first operational mode.

[0055]The predetermined maximum duration may be below 10 minutes. The predetermined maximum duration may be below 9 minutes. The predetermined maximum duration may be below 8 minutes. The predetermined maximum duration may be below 7 minutes. The predetermined maximum duration may be below 6 minutes. The predetermined maximum duration may be below 5 minutes. The predetermined maximum duration may be below 4 minutes. The predetermined maximum duration may be below 3 minutes.

[0056]The predetermined maximum duration of the first operational mode may be 4 minutes or less. The predetermined maximum number of puffs of the second operational mode may be more than 4 minutes.

[0057]The predetermined maximum duration of the first operational mode may be 6 minutes or less. The predetermined maximum number of puffs of the second operational mode may be more than 6 minutes.

[0058]The predetermined maximum duration of the first operational mode may be 8 minutes or less. The predetermined maximum number of puffs of the second operational mode may be more than 8 minutes.

[0059]The predetermined maximum duration of the second operational mode may be lower than the predetermined maximum duration of the first operational mode.

[0060]The controller may be configured to choose a heating profile of the aerosol-generating device depending upon the acoustic signal detected by the acoustic sensor.

[0061]The controller may be configured to choose a different heating profile for each different type of aerosol-generating article.

[0062]The controller may comprise a memory. The memory may comprise pre-stored reference data. The reference data may comprise reference acoustic signals. Each reference acoustic signal may correspond to an aerosol-generating article having a specific type.

[0063]The controller may be configured to initiate an operational mode, preferably the first operational mode or the second operational mode, depending upon the detected type of aerosol-generating article.

[0064]The controller may be configured to, in dependence on the article type identified, adjust one or more of: an amplitude of a current supplied to a heating element of the aerosol-generating device; a frequency of a current supplied to the heating element; a time period of power supply; a temperature of the heating element; a signal powering the heating element and a maximum number of power pulses to the heating element.

[0065]Increasing or decreasing the amplitude of the current supplied to the heating element may increase or decrease the heating temperature of the heating element. Increasing or decreasing the frequency of the current supplied to the heating element may increase or decrease the heating temperature of the heating element. Increasing or decreasing the time period of power supply to the heating element may increase or decrease the heating duration of the heating element. The signal powering the heating element may enable powering of the heating element or disabled powering of the heating element. The mixture duration of activation of the heating element may be controlled by the signal powering the heating element. The maximum number of power pulses to the heating element may determine the maximum number of puffs. Each power pulse sent to the heating element may correspond to a user puff.

[0066]The present invention further relates to a method of controlling the aerosol-generating device described herein comprising detecting the acoustic signal generated by heating of the aerosol-forming substrate by the acoustic sensor transmitting the detected acoustic signal to the controller and determining a heating condition of the heated aerosol-forming substrate based on the detected acoustic signal by the controller.

[0067]The present invention may further relate to a method of controlling the aerosol-generating device described herein comprising detecting the acoustic signal generated by heating of the aerosol-forming substrate by the acoustic sensor transmitting the detected acoustic signal to the controller and determining the heating condition such as the temperature of the heated aerosol-forming substrate based on the detected acoustic signal by the controller.

[0068]The method may further comprise analysing the acoustic signal by the controller. The method may further comprise controlling the operation of the heating element based on the determined heating condition such as the temperature of the heated aerosol-forming substrate by the controller

[0069]The aerosol-generating device of the method may comprise a memory unit, and the controller may be configured to evaluate the acoustic signal. The controller may be configured to evaluate the acoustic signal based on predefined diagnostic models. The predefined diagnostic models may be developed based on using machine learning technologies. For this purpose, a controller may be trained using a dataset of experimentally recorded acoustic signals. Such signals include desirable and undesirable acoustic signals. A portion of this dataset may be used as a training set to adjust the controller. Once the controller is sufficiently adjusted, the controller settings may be verified and validated by using further portion of the data set. The validation data set is used to further adjust parameters of the controller and to repeat the training until a diagnostic model is obtained which performs well on the validation data set. A final test set may be used to finally evaluate performance of the diagnostic model.

[0070]As used herein, the term ‘proximal’ refers to a user-end, or mouth-end of the aerosol-generating device or system or a part or portion thereof, and the term ‘distal’ refers to the end opposite to the proximal end. When referring to the heating chamber, the term ‘proximal’ refers to the region closest to the open end of the cavity and the term ‘distal’ refers to the region closest to the closed end.

[0071]The term ‘close proximity’ may mean a distance of up to 7 millimetres. The term ‘close proximity’ may mean a distance of up to 5 millimetres. The term ‘close proximity’ may mean a distance of up to 3 millimetres. The term ‘close proximity’ may mean a distance of up to 1 millimetre.

[0072]As used herein, the term ‘aerosol-generating article’ refers to an article comprising an aerosol-forming substrate that is capable of releasing volatile compounds that can form an aerosol. For example, an aerosol-generating article may be an article that generates an aerosol that is directly inhalable by the user drawing or puffing on a mouthpiece at a proximal or user-end of the device. An aerosol-generating article may be disposable. The aerosol-generating article may be insertable into the heating chamber of the aerosol-generating device. The aerosol-generating article may comprise a substrate portion comprising aerosol-forming substate and a mouthpiece portion comprising a filter material.

[0073]As used herein, the term ‘aerosol-forming substrate’ relates to a substrate capable of releasing volatile compounds that can form an aerosol or a vapor. Such volatile compounds may be released by heating the aerosol-forming substrate. The aerosol-forming substrate may be in solid form or may be in liquid form. The terms ‘aerosol’ and ‘vapor’ are used synonymously.

[0074]As used herein, the term ‘aerosol-generating device’ refers to a device that interacts with one or both of an aerosol-generating article and a cartridge to generate an aerosol.

[0075]As used herein, the term ‘aerosol-generating system’ refers to the combination of an aerosol-generating device with one or both of a cartridge and an aerosol-generating article. In the system, the aerosol-generating device and one or both of the aerosol-generating article and the cartridge cooperate to generate a respirable aerosol.

[0076]The aerosol-forming substrate may comprise nicotine. The nicotine-containing aerosol-forming substrate may be a nicotine salt matrix. Alternatively, the substrate may be provided without nicotine or tobacco and without any plant based material.

[0077]The aerosol-forming substrate may comprise plant-based material. The aerosol-forming substrate may comprise tobacco. The aerosol-forming substrate may comprise a tobacco-containing material including volatile tobacco flavour compounds which are released from the aerosol-forming substrate upon heating. Alternatively, the aerosol-forming substrate may comprise a non-tobacco material. The aerosol-forming substrate may comprise homogenised plant-based material. The aerosol-forming substrate may comprise homogenised tobacco material. Homogenised tobacco material may be formed by agglomerating particulate tobacco.

[0078]The aerosol-forming substrate may comprise at least one aerosol-former. An aerosol-former is any suitable known compound or mixture of compounds that, in use, facilitates formation of a dense and stable aerosol and that is substantially resistant to thermal degradation at the temperature of operation of the aerosol-generating system. Suitable aerosol-formers are well known in the art and include, but are not limited to: polyhydric alcohols, such as triethylene glycol, 1,3-butanediol and glycerine; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. Preferred aerosol formers are polyhydric alcohols or mixtures thereof, such as triethylene glycol, 1,3-butanediol. Preferably, the aerosol former is glycerine. Where present, the homogenised tobacco material may have an aerosol-former content of equal to or greater than 5 percent by weight on a dry weight basis, and preferably from 5 percent to 30 percent by weight on a dry weight basis. The aerosol-forming substrate may comprise other additives and ingredients, such as flavourants.

[0079]As used herein, a ‘susceptor’ or ‘susceptor element’ means an element that heats up when subjected to an alternating magnetic field. This may be the result of eddy currents induced in the susceptor element, hysteresis losses, or both eddy currents and hysteresis losses. During use, the susceptor element is located in thermal contact or close thermal proximity with an aerosol-forming substrate received in the aerosol-generating article or cartridge. In this manner, the aerosol-forming substrate is heated by the susceptor such that an aerosol is formed.

[0080]The aerosol-generating device may comprise a housing. The housing may be elongate. The housing may comprise any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics or composite materials containing one or more of those materials, or thermoplastics that are suitable for food or pharmaceutical applications, for example polypropylene, polyetheretherketone (PEEK) and polyethylene. Preferably, the material is light and non-brittle. The housing may include a user interface to activate the aerosol-generating device, for example a button to initiate heating of the aerosol-generating device or a display to indicate a state of the aerosol-generating device or of the aerosol-forming substrate.

[0081]The aerosol-generating device may comprise a power supply. The power supply may require recharging and may have a capacity that enables to store enough energy for one or more usage experiences; for example, the power supply may have sufficient capacity to continuously generate aerosol for a period of around six minutes or for a period of a multiple of six minutes. In another example, the power supply may have sufficient capacity to provide a predetermined number of puffs or discrete activations of the heating element. The aerosol-generating device may comprise a charging port for recharging the power supply.

[0082]The power supply may be a direct current (DC) power supply. In one embodiment, the power supply is a DC power supply having a DC supply voltage in the range of 2.5 Volts to 4.5 Volts and a DC supply current in the range of 1 Amp to 10 Amps (corresponding to a DC power supply in the range of 2.5 Watts to 45 Watts). The aerosol-generating device may advantageously comprise a direct current to alternating current (DC/AC) inverter for converting a DC current supplied by the DC power supply to an alternating current. The DC/AC converter may comprise a Class-D, Class-C or Class-E power amplifier. The AC power output of the DC/AC converter is supplied to the induction coil.

[0083]Below, there is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

[0088]Example Ex 2: The aerosol-generating device according to example Ex 1, wherein the acoustic signal is generated by one or both of the heating element and the heated aerosol-forming substrate.

[0089]Example Ex 3: The aerosol-generating device according to any of the preceding examples, wherein the controller is configured to analyse the acoustic signal detected by the acoustic sensor.

[0090]Example Ex 4: The aerosol-generating device according to any of the preceding examples, wherein the heating element and the acoustic sensor are connected to the controller.

[0091]Example Ex 5: The aerosol-generating device according to any of the preceding examples, comprising a temperature sensor, wherein the temperature sensor is configured to determine the temperature of the heated aerosol-forming substrate, wherein the controller is configured to compare the temperature determined by the temperature sensor with the temperature determined based on the detected acoustic signal.

[0092]Example Ex 6: The aerosol-generating device according to any of the preceding examples, wherein the controller is configured to control the heating element based on the acoustic signal detected by the acoustic sensor.

[0093]Example Ex 7: The aerosol-generating device according to any of the preceding examples, wherein the controller is configured to monitor heating of the heating element.

[0094]Example Ex 8: The aerosol-generating device according to any of the preceding examples, wherein the acoustic sensor comprises at least one microphone, preferably at least one MEMS microphone.

[0095]Example Ex 9: The aerosol-generating device according to any of the preceding examples, wherein the aerosol-forming substrate comprises one or both of a solid aerosol-forming substrate and a liquid aerosol-forming substrate.

[0096]Example Ex 10: The aerosol-generating device according to any of the preceding examples, wherein the aerosol-forming substrate comprises a sound marker, wherein the sound marker is configured to generate an acoustic signal at a predetermined temperature.

[0097]Example Ex 11: The aerosol-generating device according to example Ex 10, wherein the sound marker comprises one or more of a crystal, a polymer and graphite.

[0098]Example Ex 12: The aerosol-generating device according to any of the preceding examples, comprising a heating chamber, wherein the acoustic sensor is arranged in close proximity to the heating chamber, or wherein the acoustic sensor is arranged in the heating chamber.

[0099]Example Ex 13: The aerosol-generating device according to example Ex 12, wherein the heating chamber comprises a sound transmission element, wherein the sound transmission element is configured to transmit an acoustic signal generated in the heating chamber to the acoustic sensor.

[0100]Example Ex 14: The aerosol-generating device according to any of the preceding examples, comprising a liquid storage portion, wherein the acoustic sensor is arranged in close proximity to the liquid storage portion.

[0101]Example Ex 15: The aerosol-generating device according to any of the preceding examples, wherein the heating element is a resistive heating element, preferably a resistive heating element comprising a mesh; or wherein the heating element is an inductive heating element, preferably an inductive heating element comprising at least one inductor coil.

[0102]Example Ex 16: The aerosol-generating device according to any of the preceding examples, wherein the controller is a microcontroller.

[0103]Example Ex 17: The aerosol-generating device according to any of the preceding examples, comprising a memory unit configured to store the detected acoustic signal, preferably wherein the controller comprises the memory unit.

[0104]Example Ex 18: The aerosol-generating device according to any of the preceding examples, wherein the acoustic sensor is configured to detect a puff on a mouthpiece of the aerosol-generating device, or a puff on an aerosol-generating article received within the aerosol-generating device.

[0105]Example Ex 19: An aerosol-generating system comprising the device of any of the preceding examples and an aerosol-generating article comprising the aerosol-forming substrate, wherein the aerosol-generating article is configured to be at least partly received within the aerosol-generating device.

[0106]Example Ex 20: The aerosol-generating system of example Ex 19, wherein the controller is configured to identify the received aerosol-generating article based on the acoustic signal generated during heating of the aerosol-generating article.

[0107]Example Ex 21: An aerosol-generating system comprising the device of any of examples Ex 1 to Ex 18 and a cartridge comprising the aerosol-forming substrate.

[0112]Example Ex 23: The method according to example Ex 22, comprising analysing the acoustic signal by the controller.

[0113]Example Ex 24: The method according to any of example Ex 22 or Ex 23, comprising controlling the operation of the heating element based on the determined temperature of the heated aerosol-forming substrate by the controller

[0114]Example Ex 25: The method according to any of example Ex 22 to Ex 24, wherein the aerosol-generating device comprises a memory unit, and wherein the controller is configured to evaluate the acoustic signal, preferably wherein the controller is configured to evaluate the acoustic signal based on predefined diagnostic model.

[0115]Example Ex 26: The method according to example Ex 25, wherein the predefined diagnostic models are developed based on using machine learning technologies.

[0116]Features described in relation to one embodiment may equally be applied to other embodiments of the invention.

[0117]The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

[0118]FIG. 1A shows a 3D view of an aerosol-generating system comprising an aerosol-generating device and an aerosol-generating article, FIG. 1B shows a cross sectional view of the aerosol-generating device;

[0119]FIG. 2A shows a cross sectional view of an aerosol-generating device, FIG. 2B shows a cross sectional view of an aerosol-generating system comprising the aerosol-generating device and an aerosol-generating article;

[0120]FIG. 3 shows a cross sectional view of an aerosol-generating device;

[0121]FIG. 4 shows a cross sectional view of an aerosol-generating system comprising an aerosol-generating device and a cartridge, and

[0122]FIG. 5 shows two acoustic signals of two different aerosol-generating articles.

[0123]FIG. 1A shows a 3D view of an aerosol-generating system comprising an aerosol-generating device 10 and an aerosol-generating article 12. The aerosol-generating article 12 comprises a substrate portion (not shown) comprising aerosol-forming substrate and a mouthpiece portion 14. FIG. 1B shows a cross sectional view of the aerosol-generating device 10. The aerosol-generating device 10 comprises a housing 16 comprising a cavity 18. The cavity 18 defines a heating chamber into which the aerosol-generating article 12 can be inserted. The heating chamber is confined by a cylindrical wall 20 and a bottom portion 22. The cavity 18 comprises a heating blade 24 mounted to the bottom portion 22.

[0124]The aerosol-generating device 10 comprises distal to the bottom wall 22 an acoustic sensor 26. The acoustic sensor 26 is a microphone, preferably a MEMS microphone. The aerosol-generating device 10 further comprises a controller 28, a power supply 30 and a charging port 32.

[0125]The aerosol-generating article 12 can be inserted into the cavity 18 until the heating blade 24 is fully inserted into the aerosol-generating article 12. The heating blade 24 heats the aerosol-forming substrate in the aerosol-forming article 12 whereby an acoustic signal is generated (not shown). The heating blade 24 comprises a transmission element 34 on a distal end. The transmission element 34 transfers the acoustic signal through the bottom wall 22 to the microphone 26. The detected acoustic signal is then transmitted to the controller 28 via wirings 36. The controller 28 is connected to the battery portion via wirings 38. The heating blade 24 is connected to the controller via wirings as well (not shown). The controller 28 analyses the acoustic signal to determine a temperature of the aerosol-forming substrate. In dependence of the determined temperature of the aerosol-forming substrate the controller controls the heating blade 24.

[0126]FIG. 2A shows a cross sectional view of an inductive aerosol-generating device 40. The aerosol-generating device 40 comprises a cavity 18 for insertion of an aerosol-generating article comprising aerosol-forming substate (not shown). The aerosol-generating device 40 comprises an inductor coil 42 arranged around the cylindrical wall 20 of the heating chamber. In close proximity to the cylindrical wall 20 a microphone 26 is arranged. The microphone 26 is attached to the housing 16. The microphone 26 is arranged in close proximity to the inductor coil 42. The inductor coil 42 and the microphone 26 are connected to the controller 28 (not shown). The controller 28 comprises a memory unit 44. The memory unit 44 is configured to store acoustic signals generated by the heated aerosol-forming substrate or generated by the inductor coil 42. The memory unit 44 comprises reference signals of acoustic signals of aerosol-generating articles.

[0127]Into the cavity 18 an aerosol-generating article comprising susceptor material (not shown) can be inserted. Upon activation of the inductor coil 42, the susceptor material of the aerosol-generating article is heated, whereby the aerosol-forming substrate of the article is heated as well. Upon heating of the aerosol-forming substrate an acoustic signal is generated by the aerosol-forming substrate. The acoustic signal emitted inside the cavity 18 is then transferred via the cylindrical wall 22 of the heating chamber to the microphone 26 where it is detected by the microphone 26. The detected acoustic signal is then transferred from the microphone 26 to the controller 28. The controller 28 analyses the acoustic signal and may also compare the acoustic signal with reference signals stored in the memory unit 44. Based on the analysed acoustic signal, the controller 28 determines the temperature of the heated aerosol-forming substrate. In dependence of the determined temperature of the aerosol-forming substrate the controller 28 controls the inductor coil 42.

[0128]In addition, the microphone 26 may detect an acoustic signal generated by the inductor coil 42. The controller may compare the analysed acoustic signal of the inductor coil 42 with reference signals of acoustic signals stored in the memory unit 44.

[0129]FIG. 2B shows a cross sectional view of an aerosol-generating system comprising the inductive aerosol-generating device 40 and an aerosol-generating article 46. The aerosol-generating article 46 comprises a sound marker 48 and susceptor material (not shown). When the susceptor material of the aerosol-generating article 46 is heated by the induction coil 42, the temperature of the aerosol-forming substrate increases and thus the ambient temperature of the sound marker 48 increases. Upon reaching of a predetermined temperature the sound marker 48 undergoes a phase transition whereby a characteristic acoustic signal is emitted (not shown). This acoustic signal is then detected by the microphone 26. The acoustic signal of the sound marker 48 can be used to identify an aerosol-forming article. Alternatively or additionally, the acoustic signal of the sound marker 48 can be used to set a reference point for the control of the heating temperature.

[0130]FIG. 3 shows a cross sectional view of another aerosol-generating device 50. The aerosol-generating device 50 comprises a cavity 18 comprising a resistive coil 52, a liquid wicking element 54 and a liquid storage portion 56. The liquid wicking element 54 transports liquid aerosol-forming substrate stored within the liquid storage portion 56 to the resistive coil 52 where it is heated to form an aerosol. The aerosol (not shown) is emitted at the mouth end 58. Around the resistive coil 52 microphones 26 and 26′ are positioned. The cavity 18 may comprise a plurality of microphones 26 and 26′. The plurality of microphones may be arranged in a symmetrical manner. Air enters the aerosol-generating device 50 at the air inlet 60. The heater 52 and the microphones 26 and 26′ are connected to the controller 28.

[0131]During use, the resistive coil 52 is powered by the power supply 30 whereby the resistive coil 52 is heated. Upon heating of the resistive coil 52, the liquid aerosol-forming substrate inside the liquid wicking element 54 is vaporised. The vaporisation of the liquid aerosol-forming substrate generates an acoustic signal which is then detected by the microphones 26 and 26′. The detected acoustic signal is transmitted to the controller 28 where it is analysed to determine the temperature of the aerosol-forming substrate.

[0132]FIG. 4 shows a cross sectional view of an aerosol-generating system comprising an aerosol-generating device 60 and a cartridge 62. The cartridge comprises a liquid storage portion 64 comprising liquid aerosol-forming substrate, a mesh heater 66 and a heater mounting 68. The mesh heater 66 is in contact with a liquid wicking material (not shown) which transports the liquid aerosol-forming substrate from the liquid storage portion 64 to the mesh heater 66. The cartridge comprises an electrical connection portion (not shown) being connected to the controller 28. The device further comprises a mouthpiece 70. The mouthpiece 70 can be removable or partially removable, for example via a hinge (not shown). Thereby a depleted cartridge 62 can be removed from the aerosol-generating device 60 and replaced by a fresh cartridge 62.

[0133]The aerosol-generating device 60 comprises a microphone 26 positioned in close proximity to the heater mounting 68 and the mesh heater 66. The microphone is connected to the controller 28 via wirings 72. The heater mounting 68 may be configured to transmit the acoustic signals generated by the heated mesh heater 66 to the microphone 26. The microphone 26 detects the acoustic signal generated by the heated mesh heater 66.

[0134]The mouthpiece 70 may further comprise a microphone 26′. The microphone 26′ detects an acoustic signal generated by the heated aerosol-forming substrate.

[0135]FIG. 5 shows spectra of two acoustic signals 74 and 76 as generated by two different aerosol-generating articles over a period of 20 seconds. The acoustic signals 74 and 76 are generated during a user experience in which the substrate is heated from ambient temperature to about 200° C. The aerosol-generating articles differ in their composition of the aerosol-forming substrate. The x-axis of the spectra gives the time in seconds and the y-axis the recorded amplitude of the detected acoustic signals 74 and 76. It can be seen that the aerosol-generating articles generated different characteristic acoustic signals. The acoustic signal shows an increased oscillation at about 12.5 seconds. This increased oscillation is indicative of increased acoustic signal occurring at or around a temperature of about 120° C. The signals are shifted and therefore characteristic for the respective aerosol-generating article.