Aerosol-generating system with means for determining whether susceptor is supplied with liquid aerosol-forming substrate

Abstract

The present disclosure relates to an aerosol-generating system. The aerosol-generating system includes a liquid reservoir (44) for storing a liquid aerosol-forming substrate (42). The aerosol-generating system comprises a susceptor (16, 18) for receiving a supply of liquid aerosol-forming substrate (42) from the liquid reservoir (44) and heating the liquid aerosol-forming substrate (42) to form an aerosol. The aerosol-generating system comprises an inductor coil (90) configured to generate an alternating magnetic field for heating the susceptors (16, 18). The aerosol-generating system includes a power source (72) configured to supply power to the inductor coil (90). The aerosol-generating system includes control circuitry (70) configured to determine a parameter indicative of a rate of temperature change of the susceptor based on power supplied to the inductor coil. The control circuitry is configured to determine whether the susceptor is supplied with the liquid aerosol-forming substrate based on a comparison between a dry susceptor threshold and a parameter indicative of a rate of temperature change of the susceptor. The present disclosure also relates to an aerosol-generating device (60) for use in an aerosol-generating system and a method of controlling an aerosol-generating system.

Description

[0001] The present disclosure relates to an aerosol generating system. Specifically, the present disclosure relates to an induction heating aerosol generating system for generating aerosol from a liquid aerosol-forming substrate. The present disclosure also relates to an aerosol generating device used in the aerosol generating system. The present disclosure also relates to a method for controlling an aerosol generating system.

[0002] Aerosol generating systems that use induction heating to heat an aerosol-forming substrate so as to generate an aerosol for inhalation by a user are generally known in the prior art. These systems generally include: an aerosol generating device including an induction heating component, and a cartridge including an aerosol-forming substrate, the aerosol-forming substrate being capable of releasing volatile compounds when heated, the volatile compounds cooling to form an inhalable aerosol. The cartridge is configured to be coupled to the aerosol generating device. The induction heating component includes at least one inductor coil, the at least one inductor coil being configured to generate an alternating magnetic field. A susceptor forming part of the cartridge or device is arranged adjacent to the aerosol-forming substrate and within the alternating magnetic field. When the susceptor is penetrated by the alternating magnetic field, the susceptor is heated by at least one of Joule heating and hysteresis losses of eddy currents induced in the susceptor. The heated susceptor heats the aerosol-forming substrate so that the volatile compounds are released from the aerosol-forming substrate, and the volatile compounds cool to form an inhalable aerosol.

[0003] One advantage of an induction heating system is that the electrical components of the system may be isolated from the aerosol-forming substrate and any generated aerosol. Another advantage is that the construction of the cartridge may be simplified as no electrical connections to the aerosol generating device need to be provided.

[0004] Some induction heating aerosol generating systems are configured to be used with a liquid aerosol-forming substrate stored in a liquid reservoir. During use, when the liquid aerosol-forming substrate is heated to generate an aerosol, the amount of the liquid aerosol-forming substrate in the liquid reservoir is reduced. When the liquid reservoir is empty or almost empty, the amount of liquid aerosol-forming substrate supplied to the receptor may not be sufficient to produce a satisfactory aerosol. For example, the properties of the aerosol, such as volume, composition or flavor, may become unsatisfactory. This may result in a poor user experience. Temporary interruptions in the supply of the liquid aerosol-forming substrate to the receptor may also produce unsatisfactory aerosols.

[0005] It is desirable to provide an induction heated aerosol generating system that can determine whether a susceptor is supplied with a liquid aerosol-forming substrate.It is desirable that such an aerosol generating system does not result in a significant increase in the number of electrical components compared to some known prior art systems.

[0006] According to an example of the present disclosure, an aerosol generating system is provided. The aerosol generating system includes a liquid reservoir for storing a liquid aerosol-forming substrate. The aerosol generating system includes a susceptor for receiving a supply of a liquid aerosol-forming substrate from the liquid reservoir and heating the liquid aerosol-forming substrate to form an aerosol. The aerosol generating system includes an inductor coil, which is configured to generate an alternating magnetic field for heating the susceptor. The aerosol generating system includes a power supply, which is configured to supply power to the inductor coil. The aerosol generating system includes a control circuit system, which is configured to determine a parameter indicating the rate of temperature change of the susceptor based on the power supplied to the inductor coil. The control circuit system is configured to determine whether the susceptor is supplied with a liquid aerosol-forming substrate based on a comparison between a dry susceptor threshold and a parameter indicating the rate of temperature change of the susceptor.

[0007] During heating and cooling of the susceptor, the rate of temperature change of the susceptor varies depending on whether the susceptor is supplied with a liquid aerosol-forming substrate or not. This is because when the susceptor is supplied with a liquid aerosol-forming substrate, the susceptor dissipates most of the heat by transferring the heat to the liquid aerosol-forming substrate. However, when the susceptor is not supplied with a liquid aerosol-forming substrate, the susceptor cannot dissipate the heat as quickly.

[0008] During heating of the susceptor, and for the same supply voltage, the rate of increase in temperature of the susceptor is lower when the susceptor is supplied with the liquid aerosol-forming substrate than when the susceptor is not supplied with the liquid aerosol-forming substrate. On the other hand, during cooling of the susceptor, the rate of decrease in temperature of the susceptor is greater when the susceptor is supplied with the liquid aerosol-forming substrate than when the susceptor is not supplied with the liquid aerosol-forming substrate. Advantageously, determining a parameter indicative of the rate of change in temperature of the susceptor allows the control circuitry to determine whether the susceptor is supplied with the liquid aerosol-forming substrate. This means that the control circuitry can perform an action in response to determining whether the susceptor is supplied with the liquid aerosol-forming substrate.

[0009] The control circuitry determines whether the susceptor is supplied with liquid aerosol-forming substrate based on a comparison between the dry susceptor threshold and a parameter indicative of the rate of temperature change of the susceptor. Advantageously, this allows the dry susceptor threshold to be selected to suit a particular susceptor configuration or composition of the liquid aerosol-forming substrate.

[0010] The parameter indicative of the rate of change of temperature of the susceptor is determined based on the power supplied to the inductor coil. Advantageously, this allows the rate of change of temperature of the susceptor to be detected remotely. That is, no physical connection between the control circuitry and the susceptor is required. Another advantage is that no additional electrical components, such as a temperature sensor, need be provided in order to monitor the rate of change of temperature of the susceptor.

[0011] As used herein, the term “based on power” may refer to “based on at least one of a current and a voltage of power.” Similarly, the term “based on an initial power supply” may refer to “based on at least one of a current and a voltage of an initial power supply.”

[0012] As used herein, the term "susceptor" or "susceptor element" means an element that can be heated by the penetration of an alternating magnetic field. The susceptor can generally be heated by at least one of Joule heating and hysteresis losses by inducing eddy currents in the susceptor. Possible materials for the susceptor include graphite, molybdenum, silicon carbide, stainless steel, niobium and aluminum. Advantageously, the susceptor can have a relative permeability between 1 and 40,000. When it is desired that most of the heating be dependent on eddy currents, a lower permeability material can be used, while when a hysteresis effect is desired, a higher permeability material can be used. Preferably, the material has a relative permeability between 500 and 40,000.

[0013] The parameter indicative of the rate of change of temperature of the susceptor may be based on an electrical characteristic of the inductor coil.The parameter indicative of the rate of change of temperature of the susceptor may be based on a quotient of a voltage and a current of power supplied to the inductor coil.

[0014] The parameter indicative of the rate of change of temperature of the susceptor may be the rate of change of the apparent ohmic resistance of the inductor coil. Alternatively, the parameter indicative of the rate of change of temperature of the susceptor may be the rate of change of the apparent conductance of the inductor coil. Advantageously, when the inductor coil and the susceptor are electromagnetically coupled, the rate of change of the apparent resistance of the inductor coil depends on the rate of change of temperature of the susceptor. Furthermore, there may be a finite delay between the change in temperature of the susceptor and the resulting change in the apparent resistance of the inductor coil. This means that the rate of change of the apparent ohmic resistance may accurately indicate the rate of change of temperature of the susceptor with a finite time lag. Since conductance is the mathematical inverse of resistance, the apparent conductance of the inductor coil also depends on the rate of change of temperature of the susceptor.

[0015] As used herein, the term "apparent ohmic resistance" refers to the ohmic resistance "seen" by the inductor coil when the susceptor is electromagnetically coupled to the inductor coil. When the inductor coil and the susceptor are electromagnetically coupled, the apparent ohmic resistance of the inductor coil includes both the ohmic resistance of the inductor coil and the ohmic resistance of the susceptor. In other words, when the inductor coil and the susceptor are electromagnetically coupled, the apparent ohmic resistance of the inductor coil is the equivalent ohmic resistance of the inductor coil and the susceptor. The ohmic resistance of the inductor coil remains relatively constant during inductive heating of the susceptor, while the ohmic resistance of the susceptor varies with the temperature of the susceptor. Therefore, the apparent ohmic resistance of the inductor coil varies with the temperature of the susceptor. Conductance is the mathematical reciprocal of resistance, so the term "apparent conductance" can be understood similarly.

[0016] The parameter indicative of the rate of change of temperature of the susceptor may be based on a first measurement of power supplied to the inductor coil and a second measurement of power supplied to the inductor coil.

[0017] The control circuit system can be configured to determine a first parameter indicative of a temperature of the susceptor based on the first measurement. For example, the first parameter indicative of the temperature of the susceptor can be a first apparent ohmic resistance of the sensor coil. The control circuit system can be configured to determine a second parameter indicative of the temperature of the susceptor based on the second measurement. For example, the second parameter indicative of the temperature of the susceptor can be a second apparent ohmic resistance of the sensor coil.

[0018] The control circuit system may be configured to determine a first parameter indicative of a rate of change of temperature of the susceptor based on the first measurement. For example, the first parameter indicative of a rate of change of temperature of the susceptor may be a first rate of change of an apparent ohmic resistance of the inductor coil. The control circuit system may be configured to determine a second parameter indicative of a rate of change of temperature of the susceptor based on the second measurement. For example, the second parameter indicative of a rate of change of temperature of the susceptor may be a second rate of change of an apparent ohmic resistance of the inductor coil. The parameter indicative of a rate of change of temperature of the susceptor may be an average of the first parameter indicative of a rate of change of temperature of the susceptor and the second parameter indicative of a rate of change of temperature of the susceptor.

[0019] The first measurement and the second measurement may be separated by a time interval. The time interval may be less than 500 milliseconds, less than 400 milliseconds, less than 300 milliseconds, less than 250 milliseconds, less than 200 milliseconds, less than 150 milliseconds, less than 100 milliseconds or less than 50 milliseconds. The time interval may be between 50 milliseconds and 100 milliseconds. Preferably, the time interval is between 50 milliseconds and 200 milliseconds. Advantageously, a short time interval may allow a parameter indicative of the rate of change of temperature of the susceptor to be determined multiple times during use of the aerosol generating system.

[0020] The parameter indicative of a rate of change of temperature of the susceptor may be a parameter indicative of a rate of increase of temperature of the susceptor.

[0021] The control circuit system may be configured to determine a parameter indicative of a rate of change of temperature of the susceptor based on power supplied to the inductor coil during a heating period of the susceptor. During the heating period, the temperature of the susceptor increases from a first temperature to a second temperature. The temperature of the susceptor may not decrease during the heating period. The first temperature may be less than or equal to 100 degrees Celsius. The second temperature may be greater than or equal to 100 degrees Celsius. The first temperature may be between 50 degrees Celsius and 100 degrees Celsius, between 50 degrees Celsius and 90 degrees Celsius, between 50 degrees Celsius and 80 degrees Celsius, between 50 degrees Celsius and 70 degrees Celsius, or between 50 degrees Celsius and 60 degrees Celsius. The second temperature may be between 120 degrees Celsius and 200 degrees Celsius, between 130 degrees Celsius and 200 degrees Celsius, between 140 degrees Celsius and 200 degrees Celsius, or between 150 degrees Celsius and 200 degrees Celsius.

[0022] The parameter indicative of a rate of change of temperature of the susceptor may be a parameter indicative of a rate of decrease of temperature of the susceptor.

[0023] The control circuit system may be configured to determine a parameter indicative of a rate of change of temperature of the susceptor based on power supplied to the inductor coil during a cooling period of the susceptor. During the cooling period, the temperature of the susceptor decreases from a first temperature to a second temperature. The temperature of the susceptor may not increase during the cooling period. The first temperature may be greater than or equal to 100 degrees Celsius. The second temperature may be less than or equal to 100 degrees Celsius. The first temperature may be between 120 degrees Celsius and 200 degrees Celsius, between 130 degrees Celsius and 200 degrees Celsius, between 140 degrees Celsius and 200 degrees Celsius, or between 150 degrees Celsius and 200 degrees Celsius. The second temperature may be between 50 degrees Celsius and 100 degrees Celsius, between 50 degrees Celsius and 90 degrees Celsius, between 50 degrees Celsius and 80 degrees Celsius, between 50 degrees Celsius and 70 degrees Celsius, or between 50 degrees Celsius and 60 degrees Celsius.

[0024] The control circuit system may be configured to determine that the susceptor is supplied with a liquid aerosol-forming substrate when the parameter indicative of the rate of change of temperature of the susceptor is less than a dry susceptor threshold. In other words, the control circuit system may be configured to determine that the susceptor is not supplied with a liquid aerosol-forming substrate when the parameter indicative of the rate of change of temperature of the susceptor is greater than a dry susceptor threshold.

[0025] The dry receptor threshold during cooling may be different than the dry receptor threshold during heating.

[0026] The control circuitry may be configured to determine whether the liquid reservoir is depleted based on whether the susceptor is supplied with liquid aerosol-forming substrate. Advantageously, this may allow the control circuitry to prevent further use of the aerosol generating system until the liquid reservoir has been replenished.

[0027] The control circuit system may be configured to determine that the liquid reservoir is exhausted when the susceptor is not supplied with liquid aerosol-forming substrate for a length of time equal to or greater than a time threshold. In other words, the control circuit system may be configured to determine that the liquid reservoir is exhausted when a parameter indicative of the rate of temperature change of the susceptor is greater than a dry susceptor threshold for a length of time equal to or greater than the time threshold.

[0028] The control circuitry may be configured to determine that the liquid reservoir is exhausted when the control circuitry determines that the susceptor is not supplied with liquid aerosol-forming substrate for greater than or equal to a predetermined number of consecutive times. Each determination that the susceptor is not supplied with liquid aerosol-forming substrate may be based on a separate measurement of power supplied to the inductor coil. The predetermined number of times may be two, three, four, five, six, seven, eight, nine or ten times.

[0029] The control circuit system may be configured to detect an abnormal condition based on whether the susceptor is supplied with a liquid aerosol-forming substrate. The control circuit system may be configured to detect the abnormal condition when the susceptor is not supplied with a liquid aerosol-forming substrate for a length of time that is less than a time threshold. In other words, the control circuit system may be configured to detect an abnormal condition of the aerosol generating system when a parameter indicative of a rate of change of temperature of the susceptor is greater than a dry susceptor threshold for a length of time that is less than the time threshold.

[0030] The control circuitry may be configured to detect an abnormal condition when the control circuitry determines that the susceptor is not supplied with a liquid aerosol-forming substrate for less than or equal to a predetermined number of consecutive times. Each determination that the susceptor is not supplied with a liquid aerosol-forming substrate may be based on a separate measurement of power supplied to the inductor coil. The predetermined number of times may be two, three, four, five, six, seven, eight, nine or ten times.

[0031] Under abnormal conditions, the aerosol generating system may not function as designed. For example, the supply of liquid aerosol-forming substrate to the receptor may be temporarily interrupted. This may be a result of how the aerosol generating system is oriented.

[0032] The control circuitry may comprise an orientation sensor to detect the orientation of the liquid reservoir.The control circuitry may be configured to use the orientation sensor to determine whether the supply of liquid aerosol-forming substrate to the susceptor is temporarily interrupted.

[0033] The time threshold may be at least 10 milliseconds. The time threshold may be at least 50 milliseconds. The time threshold may be between 10 milliseconds and 2000 milliseconds, between 10 milliseconds and 1500 milliseconds, between 10 milliseconds and 1000 milliseconds, or between 50 milliseconds and 1000 milliseconds. The time threshold may be 10 milliseconds, 50 milliseconds, 100 milliseconds, 150 milliseconds, 200 milliseconds, 250 milliseconds, 300 milliseconds, 350 milliseconds, 400 milliseconds, 450 milliseconds, 500 milliseconds, 550 milliseconds, 600 milliseconds, 650 milliseconds, 700 milliseconds, 750 milliseconds, 800 milliseconds, 950 milliseconds, 1000 milliseconds, 1500 milliseconds, or 2000 milliseconds.

[0034] The control circuit system may be configured to determine a fault condition when an abnormal condition is detected at least twice. The control circuit system may be configured to determine a fault condition when an abnormal condition is detected at least three times. The control circuit system may be configured to determine a fault condition when an abnormal condition is detected at least four times. The control circuit system may be configured to determine a fault condition when an abnormal condition is detected at least five times. In a fault condition, the control circuit system may determine that the abnormal condition is caused by a fault in the aerosol generating system. For example, residue may accumulate in the aerosol generating system, which temporarily prevents the liquid aerosol-forming substrate from being supplied to the receptor. In a fault condition, it may be necessary to replace a portion of the system in order to return the system to normal operation.

[0035] The control circuit system may be configured to provide an indication to the user when it is determined that the susceptor is not supplied with liquid aerosol-forming substrate. The control circuit system may be configured to provide an indication to the user when it is determined that the liquid reservoir is exhausted. The control circuit system may be configured to provide an indication to the user when an abnormal condition is detected. The control circuit system may be configured to provide an indication to the user when a fault condition is detected.

[0036] The control circuitry may be configured to provide an audible indication to a user. For example, the aerosol generating system may comprise a speaker. The control circuitry may be configured to operate the speaker to provide an audible indication to a user.

[0037] The control circuit system may be configured to provide a visual indication to a user. For example, the aerosol generating system may include one or more indicator lights. The control circuit system may be configured to operate the one or more indicator lights to provide a visual indication to a user.

[0038] The control circuit system may be configured to provide a tactile indication to the user. For example, the aerosol generating system may include a vibration motor. The control circuit system may be configured to operate the vibration motor to provide a tactile indication to the user.

[0039] The control circuitry may be configured to operate the aerosol generating system in a first mode and a second mode. The first mode is different from the second mode.

[0040] The first mode may be a high power mode. In the high power mode, the control circuit system may be configured to supply power to the inductor coil. The second mode may be a low power mode. In the low power mode, the control circuit system may be configured to prevent power from being supplied to the inductor coil. Alternatively, in the lower power mode, the control circuit system may be configured to supply a lower power voltage to the inductor coil than in the high power mode.

[0041] The control circuitry may be configured to operate the aerosol generating system in a first mode when the susceptor is supplied with a liquid aerosol-forming substrate.The control circuitry may be configured to operate the aerosol generating system in a second mode when the susceptor is not supplied with a liquid aerosol-forming substrate.

[0042] The control circuitry may be configured to operate the aerosol generating system in a first mode when the liquid reservoir is not depleted.The control circuitry may be configured to operate the aerosol generating system in a second mode when the liquid reservoir is depleted.

[0043] The control circuitry may be configured to operate the aerosol generating system in a first mode when no abnormal condition is detected.The control circuitry may be configured to operate the aerosol generating system in a second mode when an abnormal condition is detected.

[0044] The control circuitry may be configured to operate the aerosol generating system in the first mode when no fault condition is detected.The control circuitry may be configured to operate the aerosol generating system in the second mode when a fault condition is detected.

[0045] The aerosol generating system may include an information storage component. The information storage component may be configured to store the dry receptor threshold. The control circuit system may include means for retrieving the dry receptor threshold from the information storage component. The information storage component may be an electronic memory. The electronic memory may be an RFID (radio frequency identification) tag. The information storage component may be a one-dimensional barcode. The information storage component may be a two-dimensional barcode.

[0046] The dry susceptor threshold may be predetermined. The dry susceptor threshold may be stored on the information storage component. The dry susceptor threshold may be stored in the information storage component during manufacture of the aerosol generating system. The dry susceptor threshold may be determined experimentally. For example, the dry susceptor threshold may be determined by supplying power to the sensor coil when the susceptor is not supplied with a liquid aerosol-forming substrate and determining a parameter indicative of the rate of change of temperature of the susceptor, which parameter may then be used as the dry susceptor threshold.

[0047] The control circuitry may be configured to determine the dry susceptor threshold.Advantageously, this may allow the aerosol generating system to be used with liquid aerosol-forming substrate compositions and susceptor configurations for which the dry susceptor threshold has not been pre-programmed.

[0048] The control circuitry may be configured to determine the dry susceptor threshold based on an initial power supply to the inductor coil. The initial power supply may be supplied to the inductor coil when the aerosol generating system is first switched on. The initial power supply may be supplied to the inductor coil when the first puff is taken on the aerosol generating system.

[0049] The control circuitry may be configured to determine a parameter indicative of an initial rate of temperature change of the susceptor based on an initial supply of power to the inductor coil.

[0050] During the initial supply of power to the inductor coil, the susceptor may not be supplied with a liquid aerosol-forming substrate. For example, the aerosol generating system may include a seal configured to prevent the susceptor from being supplied with a liquid aerosol-forming substrate, and the seal may be broken after determining the parameter indicative of the initial rate of change of temperature of the susceptor. The dry susceptor threshold may be a parameter indicative of the initial rate of change of temperature of the susceptor. In other words, the control circuitry stores the value of the parameter indicative of the initial rate of change of temperature of the susceptor and uses the value as the dry susceptor threshold.

[0051] The aerosol generating system may include a wicking element. The wicking element may be in fluid communication with the susceptor. The wicking element may be in fluid communication with the liquid reservoir. The wicking element may be arranged to transport the liquid aerosol-forming substrate from the liquid reservoir to the susceptor. In particular, the wicking element may be arranged to transport the liquid aerosol-forming substrate from the liquid reservoir across the major surface of the susceptor. The susceptor may be fixed to the wicking element. The susceptor may be integral with the wicking element.

[0052] The wicking element may include a capillary material. A capillary material is a material that can transfer a liquid from one end of the material to the other end by means of capillary action. The capillary material may have a fibrous or spongy structure. The capillary material preferably includes a capillary bundle. For example, the capillary material may include a plurality of fibers or threads or other fine-pored tubes. The fibers or threads may be generally aligned to transport the liquid aerosol-forming substrate across the main surface in the susceptor. The capillary material may include a spongy or foamy material. The structure of the capillary material may form a plurality of pores or tubes through which the liquid aerosol-forming substrate may be transported by capillary action. In the case where the susceptor includes a void or pore, the capillary material may extend into the void or pore in the susceptor element. The susceptor may draw the liquid aerosol-forming substrate into the void or pore by capillary action.

[0053] The susceptor may comprise one or more susceptor elements. The susceptor may be arranged substantially outside the liquid reservoir. The or each susceptor element of the susceptor may be arranged substantially outside the liquid reservoir. In particular, preferably, at least a portion of a major surface of the or each susceptor element is not in direct contact with the liquid reservoir. Preferably, at least a portion of two opposing major surfaces of the susceptor are in direct contact with air in an airflow path in the system.

[0054] The susceptor may include a plurality of susceptor elements. The susceptor may include a first susceptor element and a second susceptor element, the second susceptor element being spaced apart from the first susceptor element. The wicking element may be arranged in a space between the first susceptor element and the second susceptor element. The wicking element may include a first wicking layer and a second wicking layer. The spacing element may be positioned between the first wicking layer and the second wicking layer. The spacing element may be fluid permeable and may be configured to allow a liquid aerosol-forming substrate to move through the spacing element between the first wicking layer and the second wicking layer.

[0055] The first susceptor element may be in physical contact with the first side of the first wicking element. The second side of the first wicking element may be in physical contact with the first side of the spacing element. The second side of the spacing element may be in physical contact with the first side of the second wicking element. The second side of the second wicking element may be in physical contact with the second susceptor element.

[0056] The first susceptor element, the second susceptor element, and the wicking element may be substantially planar, and the first susceptor element may be disposed at a first side of the planar wicking element, and the second susceptor element may be disposed at a second side of the planar wicking element opposite the first side.

[0057] The susceptor may be in the form of a mesh. The or each susceptor element may comprise a mesh. The susceptor or susceptor element may comprise an array of filaments forming a mesh. As used herein, the term "mesh" encompasses grids and arrays of filaments with spaces therebetween. The term mesh also includes woven and nonwoven fabrics.

[0058] The filaments may define interstices between the filaments, and the interstices may have a width of between 10 and 100 microns.Preferably, the filaments create capillary action in the interstices such that, in use, source liquid is drawn into the interstices thereby increasing the contact area between the susceptor element and the liquid.

[0059] The filaments may form a mesh having a size between 160 and 600 US mesh (+ / - 10%), i.e. between 160 and 600 filaments per inch (+ / - 10%). The width of the gaps may be between 35 microns and 140 microns, or between 25 microns and 75 microns. For example, the width of the gaps may be 40 microns or 63 microns. The percentage of open area of ​​the mesh (which is the ratio of the area of ​​the gaps to the total area of ​​the mesh) is preferably between 25% and 56%. The mesh may be formed using different types of weaves or mesh structures. Alternatively, the filaments consist of an array of filaments arranged parallel to each other.

[0060] The filaments may be formed by etching a sheet such as foil. This may be particularly advantageous when the heater assembly comprises an array of parallel filaments. If the heating element comprises a mesh or fabric of filaments, the filaments may be formed individually and woven together.

[0061] Preferably, the mesh is sintered. Advantageously, the sintered mesh produces electrical bonding between the filaments extending in different directions. In particular, where the mesh comprises one or more of a woven and a non-woven fabric, it is advantageous to sinter the mesh to produce electrical bonding between overlapping filaments.

[0062] As is well known in the art, a mesh may also be characterized by its ability to retain liquids.

[0063] The diameter of the filaments of the mesh may be between 8 and 100 microns, between 30 and 100 microns, between 8 and 50 microns, or between 8 and 39 microns. The filaments of the mesh may have a diameter of about 50 microns.

[0064] The filaments of the mesh may have any suitable cross-section. For example, the filaments may have a circular cross-section or may have a flat cross-section.

[0065] Advantageously, the mesh susceptor element may have a relative permeability between 1 and 40,000. When it is desired that most of the heating be dependent on eddy currents, a lower permeability material may be used, whereas when a hysteresis effect is desired, a higher permeability material may be used. Preferably, the material has a relative permeability between 500 and 40,000. This may provide efficient heating of the susceptor element.

[0066] The inductor coil may be a spiral coil. The spiral coil may be formed from a wire. The wire may have a circular cross-section. The wire may be made of copper. The spiral coil may have different pitches. The inductor coil may have a circular cross-section when viewed parallel to the longitudinal axis of the aerosol generating device.

[0067] The inductor coil may include a first inductor coil and a second inductor coil. The first inductor coil may be configured to generate an alternating magnetic field for heating the susceptor. The control circuit system may be configured to determine a parameter indicating a rate of temperature change of the susceptor based on power supplied to the second inductor coil.

[0068] The control circuit system may include a microprocessor. The microprocessor may be a programmable microprocessor, a microcontroller, or an application specific integrated chip (ASIC) or other electronic circuit system capable of providing control. The control circuit system may be configured to continuously supply power to the inductor coil after the system is activated, or may be configured to supply power intermittently, such as on a puff-by-puff basis. Power may be supplied to the inductor coil in the form of current pulses, for example, by means of pulse width modulation (PWM). The control circuit system may include a DC / AC inverter, which may include a class D or class E power amplifier. The control circuit system may include other electronic components. For example, in some embodiments, the control circuit system may include any one of a sensor, a switch, and a display element.

[0069] The power source may be a DC power source. The power source may be a battery. The battery may be a lithium-based battery, such as a lithium cobalt, lithium iron phosphate, lithium titanate, or lithium polymer battery. The battery may be a nickel metal hydride battery or a nickel cadmium battery. The power source may be another form of charge storage device, such as a capacitor. The power source may be rechargeable and configured for many charge and discharge cycles. The power source may have a capacity that allows storage of energy sufficient for one or more user experiences of the aerosol generating system; for example, the power source may have sufficient capacity to allow continuous generation of aerosol for a period of about six minutes, corresponding to the typical time spent smoking a conventional cigarette, or for a period of time that is a multiple of six minutes. In another example, the power source may have sufficient capacity to allow a predetermined number of puffs or discrete activations of the atomizer assembly.

[0070] The aerosol generating system may include an aerosol generating device. The aerosol generating device may include a power source. The aerosol generating device may include an inductor coil. The aerosol generating device may include control circuitry.

[0071] The aerosol generating device may include a housing. The housing may be elongated. The housing may include 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 suitable for food or pharmaceutical applications, such as polypropylene, polyetheretherketone (PEEK), and polyethylene. Preferably, the material is lightweight and non-brittle.

[0072] The aerosol generating device housing may define a cavity for receiving the cartridge.The aerosol generating device may comprise one or more air inlets.The one or more air inlets may enable ambient air to be drawn into the cavity.

[0073] The aerosol generating device may have a connecting end configured to connect the aerosol generating device to the cartridge. The connecting end may comprise a cavity for receiving the cartridge.

[0074] The aerosol generating device may have a distal end opposite the connection end. The distal end may include an electrical connector configured to connect the aerosol generating device to an electrical connector of an external power source for charging the power source of the aerosol generating device.

[0075] The aerosol generating device may include a flux concentrator element. The flux concentrator element may have a larger radius than the inductor coil and at least partially surround the inductor coil. The flux concentrator element may be configured to reduce stray power losses from the generated magnetic field. The flux concentrator element may be configured to concentrate the alternating magnetic field generated by the inductor coil within the cavity.

[0076] The aerosol generating system may comprise a cartridge. The cartridge may comprise a liquid reservoir. The cartridge may comprise a susceptor. The cartridge may comprise an information storage component.

[0077] The cartridge may include an outer housing. The outer housing may be formed of a durable material. The outer housing may be formed of a liquid-impermeable material. The outer housing may be formed of a moldable plastic material such as polypropylene (PP) or polyethylene terephthalate (PET). The outer housing may be formed of the same material as the susceptor holder, or may be formed of a different material.

[0078] The aerosol generating system may include a liquid aerosol forming substrate. The aerosol forming substrate may be liquid at room temperature. The aerosol forming substrate may include both liquid and solid components. The liquid aerosol forming substrate may include nicotine. The nicotine-containing liquid aerosol forming substrate may be a nicotine salt substrate. The liquid aerosol forming substrate may include a plant-based material. The liquid aerosol forming substrate may include tobacco. The liquid aerosol forming substrate may include a tobacco-containing material containing volatile tobacco flavor compounds, which are released from the aerosol forming substrate when heated. The liquid aerosol forming substrate may include a homogenized tobacco material. The liquid aerosol forming substrate may include a tobacco-free material. The liquid aerosol forming substrate may include a homogenized plant-based material.

[0079] The liquid aerosol-forming substrate may include one or more aerosol formers. An aerosol former is any suitable known compound or mixture of compounds that promotes the formation of a dense and stable aerosol in use and is substantially resistant to thermal degradation at the operating temperature of the system. Examples of suitable aerosol formers include glycerol and propylene glycol. Suitable aerosol formers are well known in the art and include, but are not limited to: polyols such as triethylene glycol, 1,3-butylene glycol and glycerol; esters of polyols such as mono-, di- or tri-acetates of glycerol; and aliphatic esters of mono-, di- or polycarboxylic acids such as dimethyl dodecanedioate and dimethyl tetradecanedioate. The liquid aerosol-forming substrate may include water, solvents, ethanol, plant extracts and natural or artificial flavoring agents.

[0080] The liquid aerosol-forming substrate may include nicotine and at least one aerosol former. The aerosol former may be glycerol or propylene glycol. The aerosol former may include both glycerol and propylene glycol. The liquid aerosol-forming substrate may have a nicotine concentration of between about 0.5% and about 10%, for example about 2%.

[0081] The cartridge may comprise two parts: a first part and a second part. The second part may be movable relative to the first part. The first part and the second part of the cartridge may be movable relative to each other between a storage configuration and a use configuration. In the storage configuration, the susceptor may be isolated from the aerosol-forming substrate. In the use configuration, the susceptor may be in fluid communication with the aerosol-forming substrate.

[0082] The liquid reservoir may comprise two parts: a first part and a second part. A seal may be provided between the first part and the second part. The seal may be arranged to prevent fluid communication between the first part of the liquid reservoir and the second part of the liquid reservoir. In other words, the seal may fluidly isolate the first part of the liquid reservoir from the second part of the liquid reservoir. In the storage configuration, the liquid aerosol-forming substrate may be retained in the first part of the liquid reservoir. In the storage configuration, the seal may prevent the aerosol-forming substrate from flowing from the first part of the liquid reservoir to the second part of the liquid reservoir.

[0083] According to an example of the present disclosure, an aerosol generating device is provided. The aerosol generating device may be an aerosol generating device as disclosed herein. In particular, the aerosol generating device may include a power supply, an inductor coil and a control circuit system disclosed herein.

[0084] According to an example of the present disclosure, a method for controlling an aerosol generating system is provided, the aerosol generating system comprising a liquid reservoir for storing a liquid aerosol-forming substrate, a susceptor for receiving a supply of the liquid aerosol-forming substrate, and an inductor coil configured to generate an alternating magnetic field for heating the susceptor. The method comprises supplying power to the inductor coil; determining a parameter indicating a rate of temperature change of the susceptor based on the power supplied to the inductor coil; and determining whether the susceptor is supplied with a liquid aerosol-forming substrate based on a comparison between a dry susceptor threshold and the parameter indicating a rate of temperature change of the susceptor.

[0085] The method may further comprise operating the aerosol generating system in a first mode when the susceptor is supplied with the liquid aerosol-forming substrate, and operating the aerosol generating system in a second mode when the susceptor is not supplied with the liquid aerosol-forming substrate.

[0086] It should be understood that any features described herein with respect to one example of the present disclosure may also be applied to other examples of the present disclosure. In particular, features described with respect to an aerosol generating system may also be applied to an aerosol generating device. Moreover, features described with respect to an aerosol generating system may also be applied to a method of controlling an aerosol generating system.

[0087] The invention is defined in the claims. However, a non-exhaustive list of non-limiting examples is provided below. Any one or more features of these examples may be combined with any one or more features of another example, embodiment or aspect described herein.

[0088] Ex1. An aerosol generating system comprising:

[0089] a liquid reservoir for storing a liquid aerosol-forming substrate;

[0090] a susceptor for receiving a supply of liquid aerosol-forming substrate from the liquid reservoir and heating the liquid aerosol-forming substrate to form an aerosol;

[0091] an inductor coil configured to generate an alternating magnetic field for heating the susceptor;

[0092] a power source configured to supply power to the inductor coil;

[0093] control circuitry configured to determine a parameter indicative of a rate of change of temperature of the susceptor based on power supplied to the inductor coil; and

[0094] Wherein the control circuitry is configured to determine whether the susceptor is supplied with the liquid aerosol-forming substrate based on a comparison between a dry susceptor threshold and a parameter indicative of a rate of change of temperature of the susceptor.

[0095] Ex2. An aerosol generating system according to Ex1, wherein the parameter indicative of the rate of change of temperature of the susceptor is based on an electrical characteristic of the inductor coil.

[0096] Ex3. An aerosol generating system according to Ex1 or Ex2, wherein the parameter indicative of the rate of change of temperature of the susceptor is based on the quotient of the voltage and the current of the power supplied to the inductor coil.

[0097] Ex4. An aerosol generating system according to any preceding example, wherein the parameter indicative of the rate of change of temperature of the susceptor is the rate of change of the apparent ohmic resistance of the inductor coil.

[0098] Ex5. An aerosol generating system according to any one of Ex1 to Ex3, wherein the parameter indicative of the rate of change of temperature of the susceptor is the rate of change of the apparent conductance of the inductor coil.

[0099] Ex6. An aerosol generating system according to any preceding example, wherein the parameter indicative of the rate of change of temperature of the susceptor is based on a first measurement of power supplied to the inductor coil and a second measurement of power supplied to the inductor coil.

[0100] Ex7. An aerosol generating system according to Ex6, wherein the control circuit system is configured to determine a first parameter indicative of a temperature of the receptor based on the first measurement.

[0101] Ex8. An aerosol generating system according to Ex6 or Ex7, wherein the control circuit system is configured to determine a second parameter indicative of a temperature of the receptor based on the second measurement value.

[0102] Ex9. An aerosol generating system according to Ex6, wherein the control circuit system is configured to determine a first parameter indicative of a rate of change of temperature of the receptor based on the first measurement value.

[0103] Ex10. An aerosol generating system according to Ex6 or Ex9, wherein the control circuit system is configured to determine a second parameter indicative of a rate of change of temperature of the receptor based on the second measurement value.

[0104] Ex11. An aerosol generating system according to Ex9 or Ex10, wherein the parameter indicating the rate of change of the temperature of the receptor is an average value of a first parameter indicating the rate of change of the temperature of the receptor and a second parameter indicating the rate of change of the temperature of the receptor.

[0105] Ex12. An aerosol generating system according to any one of Ex6 to Ex11, wherein the first measurement value and the second measurement value are separated by a time interval.

[0106] Ex13. An aerosol generating system according to Ex12, wherein the time interval is less than 500 milliseconds, less than 400 milliseconds, less than 300 milliseconds, less than 250 milliseconds, less than 200 milliseconds, less than 150 milliseconds, less than 100 milliseconds or less than 50 milliseconds.

[0107] Ex14. An aerosol generating system according to any preceding example, wherein the control circuit system is configured to determine a parameter indicative of a rate of change of temperature of the susceptor based on power supplied to the inductor coil during a heating period of the susceptor.

[0108] Ex15. An aerosol generating system according to any preceding example, wherein the control circuit system is configured to determine a parameter indicative of a rate of change of temperature of the susceptor based on power supplied to the inductor coil during a cooling period of the susceptor.

[0109] Ex16. An aerosol generating system according to any preceding example, wherein the control circuit system is configured to determine that the susceptor is supplied with a liquid aerosol-forming substrate when a parameter indicative of a rate of change of temperature of the susceptor is less than the dry susceptor threshold.

[0110] Ex17. An aerosol generating system according to any preceding example, wherein the control circuit system is configured to determine that the susceptor is not supplied with liquid aerosol-forming substrate when a parameter indicative of a rate of change of temperature of the susceptor is greater than the dry susceptor threshold.

[0111] Ex18. An aerosol generating system according to any preceding example, wherein the control circuit system is configured to determine whether the liquid reservoir is exhausted based on whether the susceptor is supplied with liquid aerosol-forming substrate.

[0112] Ex19. An aerosol generating system according to any preceding example, wherein the control circuit system is configured to determine that the liquid reservoir is exhausted when the receptor is not supplied with liquid aerosol-forming substrate for a length of time equal to or greater than a time threshold.

[0113] Ex20. An aerosol generating system according to any preceding example, wherein the control circuit system is configured to detect an abnormal condition based on whether the receptor is supplied with a liquid aerosol-forming substrate.

[0114] Ex21. An aerosol generating system according to any preceding example, wherein the control circuit system is configured to detect an abnormal condition when the receptor is not supplied with liquid aerosol-forming substrate for a length of time less than a time threshold.

[0115] Ex22. An aerosol generating system according to Ex19 or Ex21, wherein the time threshold is between 50 milliseconds and 1000 milliseconds.

[0116] Ex23. An aerosol generating system according to any one of Ex20 to Ex22, wherein the control circuit system is configured to determine a fault condition when an abnormal condition is detected at least twice.

[0117] Ex24. An aerosol generating system according to any preceding example, wherein the control circuit system is configured to provide an indication to the user when it is determined that the receptor is not supplied with liquid aerosol-forming substrate.

[0118] Ex25. An aerosol generating system according to any preceding example, wherein the control circuit system is configured to provide an indication to the user when it is determined that the liquid reservoir is depleted.

[0119] Ex26. An aerosol generating system according to any preceding example, wherein the control circuit system is configured to provide an indication to the user when an abnormal condition is detected.

[0120] Ex27. An aerosol generating system according to any preceding example, wherein the control circuit system is configured to provide an indication to the user when a fault condition is detected.

[0121] Ex28. An aerosol generating system according to any one of Ex24 to Ex27, wherein the control circuit system is configured to provide audible instructions to the user.

[0122] Ex29. An aerosol generating system according to any one of Ex24 to Ex27, wherein the control circuit system is configured to provide visual indications to the user.

[0123] Ex30. An aerosol generating system according to any one of Ex24 to Ex27, wherein the control circuit system is configured to provide tactile indication to the user.

[0124] Ex31. An aerosol generating system according to any of the preceding examples, wherein the control circuit system is configured to operate the aerosol generating system in a first mode and a second mode, the first mode being different from the second mode.

[0125] Ex32. An aerosol generating system according to Ex31, wherein the first mode is a high power mode, wherein the control circuit system can be configured to supply power to the inductor coil.

[0126] Ex33. An aerosol generating system according to Ex31 or Ex32, wherein the second mode is a low power mode.

[0127] Ex34. An aerosol generating system according to Ex33, wherein in the lower power mode, the control circuit system can be configured to prevent power from being supplied to the inductor coil.

[0128] Ex35. An aerosol generating system according to Ex33, wherein, in the lower power mode, the control circuit system is configured to supply a lower power voltage to the inductor coil compared to the high power mode.

[0129] Ex36. An aerosol generating system according to Ex31 to Ex35, wherein the control circuit system is configured to operate the aerosol generating system in the first mode when the susceptor is supplied with a liquid aerosol-forming substrate.

[0130] Ex37. An aerosol generating system according to Ex31 to Ex36, wherein the control circuit system is configured to operate the aerosol generating system in the second mode when the receptor is not supplied with liquid aerosol-forming substrate.

[0131] Ex38. An aerosol generating system according to any preceding example, comprising an information storage component configured to store the dry receptor threshold.

[0132] Ex39. An aerosol generating system according to Ex38, wherein the information storage component is an electronic memory.

[0133] Ex40. An aerosol generating system according to Ex38, wherein the information storage component is an RFID (radio frequency identification) tag.

[0134] Ex41. An aerosol generating system according to Ex38, wherein the information storage component is a one-dimensional barcode.

[0135] Ex42. An aerosol generating system according to Ex28, wherein the information storage component is a two-part barcode.

[0136] Ex43. An aerosol generating system according to Ex38 to E42, wherein the dry receptor threshold is predetermined and stored on the information storage component.

[0137] Ex44. An aerosol generating system according to any one of Ex1 to Ex42, wherein the control circuit system is configured to determine the dry receptor threshold.

[0138] Ex45. An aerosol generating system according to Ex44, wherein the control circuit system can be configured to determine the dry receptor threshold based on an initial power supply to the inductor coil.

[0139] Ex46. An aerosol generating system according to Ex45, wherein the initial power supply is supplied to the inductor coil when the aerosol generating system is first switched on.

[0140] Ex47. An aerosol generating system according to Ex45, wherein the initial power supply is supplied to the inductor coil when a first puff is taken on the aerosol generating system.

[0141] Ex48. An aerosol generating system according to any one of Ex45 to Ex47, wherein the control circuit system is configured to determine a parameter indicative of an initial rate of temperature change of the susceptor based on an initial supply of power to the inductor coil.

[0142] Ex49. An aerosol generating system according to any one of Ex45 to Ex48, wherein the susceptor is not supplied with liquid aerosol-forming substrate during initial power supply of the inductor coil.

[0143] Ex50. An aerosol generating system according to Ex49, wherein the dry receptor threshold is a parameter indicating the rate of initial temperature change of the receptor.

[0144] Ex51. An aerosol generating system according to any preceding example, comprising a wicking element arranged to transport the liquid aerosol-forming substrate from the liquid reservoir to the receptor.

[0145] Ex52. An aerosol generating system according to any preceding example, wherein the receptor is arranged substantially outside the liquid reservoir.

[0146] Ex53. An aerosol generating system according to any preceding example, wherein the susceptor comprises a first susceptor element and a second susceptor element, the second susceptor element being spaced apart from the first susceptor element.

[0147] Ex54. An aerosol generating system according to Ex53, wherein the wicking element or the wicking element is arranged in the space between the first susceptor element and the second susceptor element.

[0148] Ex55. An aerosol generating system according to any preceding example, wherein the receptor comprises a mesh.

[0149] Ex56. An aerosol generating system according to any preceding example, wherein the inductor coil is a spiral coil.

[0150] Ex57. An aerosol generating system according to Ex56, wherein the spiral coil is formed by a wire.

[0151] Ex58. An aerosol generating system according to Ex57, wherein the wire has a circular cross-section.

[0152] Ex59. An aerosol generating system according to Ex57 or Ex58, wherein the wire is made of copper.

[0153] Ex60. An aerosol generating system according to any of the preceding examples, wherein the inductor coil comprises a first inductor coil and a second inductor coil, wherein the first inductor coil is configured to generate an alternating magnetic field for heating the receptor, and the control circuit system is configured to determine a parameter indicating a rate of temperature change of the receptor based on power supplied to the second inductor coil.

[0154] Ex61. An aerosol generating system according to any of the preceding examples, wherein the power source is a DC power source.

[0155] Ex62. An aerosol generating system according to any preceding example, comprising an aerosol generating device, wherein the aerosol generating device comprises the power supply, the inductor coil and the control circuit system.

[0156] Ex63. An aerosol generating system according to any preceding example, comprising a cartridge comprising the liquid reservoir and the receptor.

[0157] Ex64. An aerosol generating system according to Ex63, wherein the cartridge comprises the information storage component.

[0158] Ex65. An aerosol generating device for use in an aerosol generating system according to any preceding example, comprising the power supply, the inductor coil and the control circuit system.

[0159] Ex66. A method of controlling an aerosol generating system, the aerosol generating system comprising a liquid reservoir for storing a liquid aerosol-forming substrate, a susceptor for receiving a supply of the liquid aerosol-forming substrate and an inductor coil, the method comprising:

[0160] supplying power to the inductor coil;

[0161] determining a parameter indicative of a rate of change of temperature of the susceptor based on power supplied to the inductor coil; and

[0162] Based on a comparison between a dry susceptor threshold and a parameter indicative of a rate of change of temperature of the susceptor, it is determined whether the susceptor is supplied with the liquid aerosol-forming substrate.

[0163] Ex67. The method according to Ex66 further comprises operating the aerosol generating system in a first mode when the receptor is supplied with the liquid aerosol-forming substrate, and operating the aerosol generating system in a second mode when the receptor is not supplied with the liquid aerosol-forming substrate.

[0164] Several examples will now be further described with reference to the accompanying drawings, in which:

[0165] Figure 1A A schematic diagram showing a cross section of an aerosol generating system according to an example of the present disclosure;

[0166] Figure 1B Shows Figure 1A a schematic diagram of a cross-section of an aerosol generating system of claim 1, wherein the system is in a configuration for use;

[0167] Figure 2A Shows Figure 1A and 1B A schematic diagram of a cross section of a cylinder;

[0168] Figure 2B Shows Figure 2A A schematic diagram of a cross section of a cylinder rotated 90 degrees around the central longitudinal axis of the cylinder;

[0169] Figure 3 A block diagram showing the electronic components of an aerosol generating system;

[0170] Figure 4A and 4B Some components of the control circuit system are shown;

[0171] Figure 5 , 6 and 7 show situations where the supply of liquid aerosol-forming substrate from the liquid reservoir to the receptor may be interrupted;

[0172] Fig. 8A shows a graph illustrating an example of temperature changes of a susceptor when the susceptor is supplied with a liquid aerosol-forming substrate and when the susceptor is not supplied with a liquid aerosol-forming substrate;

[0173] Figure 8B Shows the description and Fig. 8A A graph showing the rate of change of the apparent ohmic resistance of the inductor coil associated with the temperature change shown in;

[0174] Fig. 9Ashows a graph illustrating the temperature change of a susceptor during heating of the susceptor;

[0175] Fig. 9B Shows the description and Fig. 9A A graph showing the rate of change of the apparent ohmic resistance of the inductor coil associated with the temperature change shown in;

[0176] Fig. 10A showing a graph illustrating temperature changes of a susceptor during cooling of the susceptor; and

[0177] Fig. 10B Shows the description and Fig. 10A A graph of the rate of change of the apparent ohmic resistance of the inductor coil associated with a change in temperature is shown in FIG.

[0178] Figure 1A A schematic diagram of an aerosol generating system according to an example of the present disclosure is shown. The aerosol generating system comprises a cartridge 10 and an aerosol generating device 60. The cartridge 10 may be received by the aerosol generating device 60. Figure 1B Shows Figure 1A Schematic diagram of an aerosol generating system of FIG. 1 , in which a cartridge 10 is received by an aerosol generating device 60. The aerosol generating system is portable and has a size comparable to that of a conventional cigar or cigarette.

[0179] The tube 10 has a mouth end and a connection end. The connection end is arranged relative to the mouth end. The outer shell 36 defines a mouth end air outlet 38 at the mouth end of the tube 10. The tube 10 can also include a mouthpiece at the mouth end. As described in more detail below, the connection end is configured to be used to connect the tube 10 to the aerosol generating device 60.

[0180] The outer housing 36 is formed of a moldable plastic material such as polypropylene. The outer width of the outer housing 36 is greater at the mouth end of the barrel 10 than at the connection end. This forms a shoulder 37 between the mouth end and the connection end. This enables the connection end of the barrel 10 to be received in the cavity 64 of the aerosol generating device 60, wherein the shoulder 37 positions the barrel 10 in the correct position in the aerosol generating device 60. This also enables the mouth end of the barrel 10 to remain outside the aerosol generating device 60, wherein the mouth end conforms to the outer shape of the aerosol generating device 60.

[0181] The cartridge 10 further comprises a liquid reservoir 44. The liquid reservoir 44 is used to store the liquid aerosol-forming substrate 42. The liquid reservoir 44 extends from the mouth end of the outer housing 36 to the connection end of the outer housing 36 and comprises an annular space defined by the outer housing 36. The annular space has an internal passage 48 extending between the mouth end air outlet 38 and the open end of the internal passage 26 of the susceptor holder 14.

[0182] The liquid reservoir 44 also includes two channels 45. The two channels 45 are defined between the inner surface of the outer housing 36 and the outer surface of the susceptor holder 14. The two channels 45 extend from the annular space defined by the outer housing 36 at the mouth end of the cartridge 10 to the connection end of the cartridge 10. The two channels 45 extend on opposite sides of the inner passage 26 of the susceptor holder 14.

[0183] The susceptor holder 14 includes a base 30 that partially closes one end of the internal passageway 26. The base 30 includes an air inlet 32 ​​that enables air to be drawn into the internal passageway 26 through the partially closed end.

[0184] An air passage is formed through the cartridge 10 by the internal passage 26 of the susceptor holder 14 and the internal passage 48 of the liquid reservoir 44. The air passage extends from the air inlet 32 ​​in the base 30 of the susceptor holder 14, through the internal passage 26 of the susceptor holder 14, and through the internal passage 48 of the liquid reservoir 44 to the mouth end air outlet 38. The air passage enables air to be drawn from the connection end through the cartridge 10 to the mouth end.

[0185] The cartridge 10 includes a susceptor assembly 12 mounted in a susceptor holder 14. The susceptor assembly 12 and the susceptor holder 14 are located toward the connection end of the cartridge 10. The susceptor assembly 12 is planar and thin, having a thickness dimension that is substantially smaller than the length and width dimensions. The susceptor assembly 12 is shaped in the form of a rectangle.

[0186] The susceptor assembly 12 includes a susceptor including a first susceptor element 16 and a second susceptor element 18. It should be appreciated that in other embodiments, the susceptor may include a single susceptor element.

[0187] The susceptor assembly 12 also includes a wicking element for transporting the liquid aerosol-forming substrate 42 from the liquid reservoir 44 to the susceptor. The wicking element includes a first wicking layer 20 and a second wicking layer 22. The susceptor assembly 12 also includes a spacing element, which is disposed between the first wicking layer 20 and the second wicking layer 22. Figure 1A Not shown.

[0188] Each of the first susceptor element 16, the second susceptor element 18, the first wicking layer 20 and the second wicking layer 22 is generally formed in a rectangular shape. Each susceptor layer has the same length and width dimensions. The width of the susceptor elements 16, 18 is less than the width of the first wicking layer 20 and the second wicking layer 22. Therefore, each of the first wicking layer 20 and the second wicking layer 22 includes an externally exposed portion of the wicking element, which protrudes into the two channels 45 through the openings in the sidewalls of the susceptor holder 14. The first susceptor element 16 and the second susceptor element 18 are substantially the same and include a sintered mesh formed of ferritic stainless steel wire and austenitic stainless steel wire. The first wicking layer 20 and the second wicking layer 22 include a porous body of cotton yarn. The wicking element is configured to supply the liquid aerosol-forming matrix 42 from the externally exposed surfaces of the first wicking layer 20 and the second wicking layer 22 to the first susceptor element 16 and the second susceptor element 18.

[0189] The first susceptor element 16 and the second susceptor element 18 are configured to be heated by the alternating magnetic field penetration for vaporizing the liquid aerosol-forming substrate 42. The wicking element contacts the susceptor holder 14 such that the susceptor holder 14 supports the susceptor assembly 12 in place in the cartridge 10.

[0190] The susceptor assembly 12 is partially disposed within the interior passage 26 of the tubular susceptor holder 14 and extends in a plane parallel to the central longitudinal axis of the susceptor holder 14. The first susceptor element 16 and the second susceptor element 18 are disposed entirely within the interior passage 26 of the susceptor holder 14.

[0191] The aerosol generating device 60 comprises a generally cylindrical housing 62 having a connection end and a distal end opposite the connection end. A cavity 64 for receiving the connection end of the cartridge 10 is located at the connection end of the device 60. An air inlet 65 is provided at the base of the cavity 64 through the outer housing 62 to enable ambient air to be drawn into the cavity 64 at the base.

[0192] The aerosol generating device 60 comprises an induction heating device arranged within a device outer housing 62. The induction heating device comprises an inductor coil 90, a control circuit system 70 and a power source 72. The power source 72 comprises a rechargeable nickel-cadmium battery, which can be recharged via an electrical connector (not shown) at a distal end of the device 60. The control circuit system 70 is connected to the power source 72 and to the inductor coil 90 so that the control circuit system 70 controls the supply of power to the inductor coil 90. The control circuit system 70 is configured to supply an alternating current to the inductor coil 90.

[0193] When the cartridge 10 is received in the cavity 64, the inductor coil 90 is positioned around the susceptor assembly 12, as shown in FIG. Figure 1BThe size and shape of the inductor coil 90 matches the size and shape of the heating area of ​​the susceptor element. The inductor coil 90 is made of copper wire with a circular cross section and is arranged on a coil former element (not shown). The inductor coil 90 is a spiral coil and has a circular cross section when viewed parallel to the longitudinal axis of the aerosol generating device 60.

[0194] The inductor coil 90 is configured such that when the cartridge 10 is received in the cavity 64 , the inductor coil generates an alternating magnetic field in the region of the susceptor assembly 12 when an alternating current is supplied to the inductor coil.

[0195] The induction heating device further comprises a flux concentrator element 91. The flux concentrator element 91 has a larger radius than the inductor coil 90 and thus partially surrounds the inductor coil 90. The flux concentrator element 91 is configured to reduce stray power losses from the generated magnetic field.

[0196] Figure 1B Shows Figure 1A An aerosol generating system of the invention is provided in which a cartridge 10 is received within an aerosol generating device 60. In operation, when a user draws on the mouth end air outlet 38 of the cartridge 10, ambient air is drawn into the base of the cavity 64 through the system air inlet 65 and into the cartridge 10 through the air inlet 32 ​​in the base 30 of the cartridge 10. Ambient air flows from the base 30 through the cartridge 10 to the mouth end air outlet 38, through the air passageway, and over the susceptor assembly 12, and in particular over and across the first susceptor element 16 and the second susceptor element 18.

[0197] When the system is activated, the control circuit system 70 controls the supply of power from the power supply 72 to the inductor coil 90. The control circuit system 70 includes an airflow sensor 63. The airflow sensor 63 is in fluid communication with the passageway of ambient air drawn through the system by the user. The control circuit system 70 supplies power to the inductor coil 90 when the airflow sensor 63 detects that the user is drawing on the cartridge 10.

[0198] When the system is activated, an alternating current is established in the inductor coil 90, which generates an alternating magnetic field in the cavity 64 that penetrates the susceptor assembly 12, causing the susceptor, including the first susceptor element 16 and the second susceptor element 18, to heat up. The liquid aerosol-forming substrate 42 in the two channels 45 is drawn into the susceptor assembly 12 by the wicking element to reach the susceptor. In particular, the liquid aerosol-forming substrate 32 is drawn to the first susceptor element 16 and the second susceptor element 18 through the first wicking layer 20 and the second wicking layer 22, respectively. The liquid aerosol-forming substrate 42 may also be transferred between the first wicking layer 20 and the second wicking layer 22 through the spacing element. The liquid aerosol-forming substrate 42 at the susceptor is heated, and volatile compounds from the heated liquid aerosol-forming substrate are released into the air passage of the cartridge 10, and the volatile compounds cool to form an aerosol. The aerosol is entrained in the air drawn through the air passageway of the cartridge 10 and is drawn out of the cartridge 10 at the mouth end air outlet 38 for inhalation by the user.

[0199] Figure 2A A schematic diagram of the cartridge 10 is shown separated from the aerosol generating device. Figure 2B Shows Figure 2A Schematic diagram of a barrel rotated 90 degrees around the central longitudinal axis of the barrel.

[0200] Figure 2B The layered structure of the susceptor assembly 12 is shown, and a spacing element 24 is depicted positioned between and in contact with the first wicking layer 20 and the second wicking layer 22. The spacing element 24 is fluid permeable and is configured to allow the liquid aerosol-forming substrate 42 to move between the first wicking layer 20 and the second wicking layer 22. The spacing element 24 is generally formed in a rectangular shape and has the same length and width dimensions as the first wicking layer 20 and the second wicking layer 22. The spacing element 24 comprises a porous body of cotton.

[0201] Figure 3 1 shows a block diagram of the electronic components of the aerosol generating system. The aerosol generating device 60 includes a DC power supply 72 (battery), a microcontroller 301, a DC / AC converter or inverter 302, a matching network 303 for adapting to the load, and an inductor coil 90. The cartridge 10 includes a susceptor including a first susceptor element 16 and a second susceptor element 18. The microcontroller 301, the DC / AC converter or inverter 302 and the matching network 303 are all part of the control circuit system 70. The DC supply voltage V drawn from the DC power supply 72 is DC and current I DC This allows the microcontroller 301 to provide a feedback signal based on the DC supply voltage V DC and the current drawn I CDTo determine the apparent ohmic resistance (or apparent conductance) of the inductor coil. This can also allow the microcontroller 301 to control the AC power P AC Another supply to the inductor coil 90.

[0202] It will be appreciated that a matching network 303 may be provided for optimal adaptation to the load, but the matching network 303 is not necessary. The matching network 303 may improve the efficiency of power transfer between the DC / AC converter 302 and the inductor coil 90.

[0203] During operation of the aerosol generating system, the inductor coil 90 generates a high frequency alternating magnetic field which induces eddy currents in the susceptor, causing the susceptor to heat up. As the susceptor heats up, the apparent resistance of the inductor coil increases as the susceptor temperature increases. This increase in the apparent ohmic resistance of the inductor coil is detected by the control circuitry 70 by measuring the current I drawn from the DC power supply 72. DC It is detected that the current decreases at a constant voltage as the temperature and apparent ohmic resistance of the inductor coil increase. Therefore, the temperature change rate of the susceptor can be determined based on the change rate of the apparent ohmic resistance of the inductor coil.

[0204] Figure 4A More components of the control circuit system 70, more specifically more components of the DC / AC converter 302, are shown. Figure 4A As can be seen, the DC / AC converter 302 includes a class E power amplifier including a transistor switch 3020, the transistor switch including a field effect transistor (FET) 3021, such as a metal oxide semiconductor field effect transistor (MOSFET), a transistor switch supply circuit indicated by arrow 3022 for supplying a switching signal (gate-source voltage) to the FET 3021, and an LC load network 3023 including a parallel capacitor C1 and a series connection of a capacitor C2 and an inductor L2 corresponding to the inductor coil 90. In addition, a DC power source 72 including a choke L1 is shown for supplying a DC supply voltage V DC , where during operation the current I is drawn from the DC power supply 72 DC .like Figure 4B As shown in FIG. , the ohmic resistance R represents the total ohmic load, which is the ohmic resistance R of the inductor L2. coil and the ohmic resistance R of the receptor load The total ohmic load is the apparent ohmic resistance of the inductor coil 90. The ohmic resistance R of the inductor L2 coil does not vary significantly during operation of the aerosol generating system. Therefore, changes in the total ohmic load (or apparent ohmic resistance) can be attributed to the ohmic resistance R of the susceptor. load changes.

[0205] Figure 5 , 6 7 and 8 show diagrammatic representations of situations where the supply of liquid aerosol-forming substrate 42 from the liquid reservoir 44 to the susceptor may be insufficient to generate a satisfactory aerosol.

[0206] Figure 5 Shows Figure 1A 10, wherein the liquid reservoir 44 is empty. In this case, there is no liquid aerosol-forming substrate 42 in contact with the first wicking layer 20 or the second wicking layer 22. Therefore, no liquid aerosol-forming substrate 42 is supplied to the first susceptor element 16 or the second susceptor element 18.

[0207] Figure 6 Shows Figure 1A Schematic diagram of a cross section of a cartridge 10 in which the liquid reservoir 44 is almost empty. In this case, only a portion of the first wicking layer 20 and the second wicking layer 22 are in contact with the remaining liquid aerosol-forming substrate 42. This may result in insufficient supply of the liquid aerosol-forming substrate 42 to the first susceptor element 16 and the second susceptor element 18.

[0208] Figure 7 Shows Figure 1A Schematic diagram of a cross section of a cartridge 10 of a cartridge 10, wherein due to the orientation of the cartridge 10, there is no liquid aerosol-forming substrate 42 in contact with the first wicking layer 20 or the second wicking layer 22. This may occur when the liquid reservoir 44 has been partially exhausted and the user holds the aerosol generating system in a certain orientation, such as when inverted. In this case, there is no liquid aerosol-forming substrate 42 supplied to the first susceptor element 16 or the second susceptor element 18. However, the interruption of the supply of the liquid aerosol-forming substrate 42 to the first susceptor element 16 and the second susceptor element 18 may only be temporary. This is because after a short period of time, the user can reorient the aerosol generating system so that the liquid aerosol-forming substrate 42 is in contact with the first wicking layer 20 and the second wicking layer 22.

[0209] It will be appreciated that there are other situations where the supply of the liquid aerosol-forming substrate 42 to the first susceptor element 16 and the second susceptor element 18 may be temporarily interrupted or otherwise insufficient. For example, when a user draws too hard on the mouth end air outlet 38, the liquid aerosol-forming substrate 42 may be aerosolized at a rate greater than the rate at which the liquid aerosol-forming substrate 42 is supplied to the first susceptor element 16 and the second susceptor element 18.

[0210] By monitoring the temperature of the susceptor, and in particular the rate of change of the temperature of the susceptor, it is possible to detect whether the susceptor is supplied with liquid aerosol-forming substrate 42, or is not supplied with liquid aerosol-forming substrate. This allows appropriate action to be taken when it is detected that the susceptor is not supplied with liquid aerosol-forming substrate. The rate of change of the temperature of the susceptor may be monitored indirectly by monitoring the rate of change of the apparent ohmic resistance (or apparent conductance) of the inductor coil 90.

[0211] Fig. 8A Graphs illustrating examples of temperature changes of a susceptor when the susceptor is supplied with a liquid aerosol-forming substrate 42 and when the susceptor is not supplied with a liquid aerosol-forming substrate 42 are shown. Figure 8B Shows the description and Fig. 8A Graph of the rate of change of the apparent ohmic resistance of the inductor coil 90 associated with the temperature change shown in FIG.

[0212] Fig. 8A A first line 801 is depicted which represents the change in temperature of the susceptor when the susceptor is supplied with a liquid aerosol-forming substrate 42. At time t0, the user begins to draw on the aerosol generating system. As a result, the control circuitry 70 begins to supply power to the inductor coil 90 to heat the susceptor from a first temperature at time t0 to an operating temperature T 2 at time t2. O From time t2 to time t3, control circuit system 70 controls the power supply to inductor coil 90 to maintain the temperature of the susceptor at the operating temperature T O The temperature between time t2 and time t3 is Fig. 8A is depicted as constant in , however, this is for illustration purposes. In reality, there will be small changes in the temperature of the susceptor as it cools and is subsequently reheated to maintain the operating temperature T O The user stops drawing on the aerosol generating system at time t3 and therefore the control circuitry 70 stops supplying power to the inductor coil 90 and the susceptor subsequently begins to cool from time t3 to time t4.

[0213] Fig. 8A A second line 802 is depicted which represents the change in temperature of the susceptor when the susceptor is not supplied with liquid aerosol-forming substrate 42. At time t0, the user begins to draw on the aerosol generating system. As a result, the control circuit system 70 begins to supply power to the inductor coil 90 to heat the susceptor. It can be seen that the susceptor heats up more quickly when it is not supplied with liquid aerosol-forming substrate than when it is supplied with liquid aerosol-forming substrate. This is indicated by the temperature of the susceptor increasing from a first temperature at time t0 to an operating temperature T at time t1. Ot2. This is because heat from the susceptor cannot be transferred to the liquid aerosol-forming substrate 42. The user stops taking a puff on the aerosol generating system at time t3, and therefore the control circuitry 70 stops supplying power to the inductor coil 90, and the susceptor subsequently begins to cool from time t3 to time t4. It can be seen that the susceptor cools more slowly when it is not supplied with the liquid aerosol-forming substrate 42 than when it is supplied with the liquid aerosol-forming substrate 42.

[0214] Figure 8B A first line 803 is depicted, which represents Fig. 8A The rate of change of the apparent ohmic resistance of the inductor coil 90 during a temperature change is depicted by the first line 801 in FIG. Figure 8B A second line 804 is also depicted, which represents the Fig. 8A The second line 802 in FIG. 8 depicts the rate of change of the apparent ohmic resistance of the inductor coil 90 during a temperature change. The relationship between the apparent ohmic resistance of the inductor coil and the temperature of the susceptor is depicted as linear. However, it should be understood that there may be other monotonic relationships between the apparent resistance of the inductor coil and the temperature of the susceptor.

[0215] Figure 8B The first line 803 in FIG. 8 shows the heating of the susceptor from the first temperature to the operating temperature T O The rate of change of the apparent resistance of the inductor coil remains relatively constant during this period. During this period, the rate of change of the apparent ohmic resistance is positive. That is, the rate of change of the apparent ohmic resistance increases as the temperature of the susceptor approaches the operating temperature T O From time t2 to time t3, the rate of change of the apparent resistance is about zero. However, as previously described, there will be cooling and heating of the susceptor during this time period. Therefore, the rate of change of the apparent ohmic resistance of the inductor coil will fluctuate between positive, zero, and negative. From time t3 to t4, the rate of change of the apparent ohmic resistance of the inductor coil is negative due to the cooling of the susceptor.

[0216] Figure 8B The second line 804 in FIG. 8 shows that the magnitude of the rate of change of the apparent ohmic resistance of the inductor coil during the period when the susceptor is heated is greater when liquid aerosol-forming substrate is not supplied to the susceptor than when liquid aerosol-forming substrate is supplied to the susceptor. Figure 8BThe second line 804 in FIG. 8 shows that the magnitude of the rate of change of the apparent ohmic resistance of the sensor coil during the period of susceptor cooling is smaller when the liquid aerosol-forming substrate is not supplied to the susceptor than when the liquid aerosol-forming substrate is supplied to the susceptor. Therefore, it may be determined whether the liquid aerosol-forming substrate is supplied to the susceptor by comparing the rate of change of the apparent ohmic resistance of the sensor coil to a dry susceptor threshold. The dry susceptor threshold may be the rate of change of the apparent ohmic resistance of the sensor coil, which indicates that the liquid aerosol-forming substrate is not supplied to the susceptor.

[0217] The DC supply voltage supplied by power supply 72 is kept constant. Thus, the apparent ohmic resistance of the inductor coil 90 can be determined by measuring the current drawn by the inductor coil 90. Ohm's law can then be used to determine the apparent ohmic resistance of the inductor coil. The rate of change of the apparent ohmic resistance can be determined by making a first measurement of the apparent ohmic resistance at a first time and a second measurement of the apparent ohmic resistance at a second time. Preferably, the time interval between the first measurement and the second measurement is small.

[0218] During the period when the susceptor is heated, power is already supplied to the inductor coil 90. Therefore, the current drawn during the heating period can be used to determine the apparent ohmic resistance of the inductor coil. However, at other times, it may be necessary to specifically supply power to the inductor coil to allow the apparent ohmic resistance of the inductor coil to be determined. In this case, power should only be supplied to the inductor coil for a short period of time to avoid any substantial heating of the susceptor.

[0219] Fig. 9A A graph illustrating the temperature change of a susceptor during a heating period of the susceptor is shown. Fig. 9B Shows the description and Fig. 9A A graph of the rate of change of the apparent ohmic resistance of the inductor coil associated with a change in temperature is shown in FIG. Fig. 9A and 9B In the first case, if Figure 5 In the first scenario, the liquid reservoir 44 is depleted of the liquid aerosol-forming substrate 42 and therefore no liquid aerosol-forming substrate 42 is supplied to the susceptor. In the second scenario, the liquid reservoir 44 is not depleted of the liquid aerosol-forming substrate 42, however, the supply of the liquid aerosol-forming substrate 42 to the susceptor is temporarily interrupted, as shown in FIG. Figure 7 Described in.

[0220] Fig. 9A and 9B A first heating phase of the susceptor from t0 to t1 , a second heating phase of the susceptor from t1 to t2 , and a third heating phase of the susceptor from t2 to t3 are shown.

[0221] In both cases, the rate of increase in temperature of the susceptor during the first heating phase, depicted by line 911, indicates that the susceptor is supplied with liquid aerosol-forming substrate 42. This is indicated by the rate of change of the apparent ohmic resistance of the inductor coil, depicted by line 921, being less than the dry susceptor threshold R T Therefore, by comparing the rate of change of the apparent ohmic resistance of the inductor coil with the dry receptor threshold R T By comparison, the control circuitry 70 determines that the susceptor was supplied with liquid aerosol-forming substrate during the first heating phase.

[0222] In both cases, the rate of increase in temperature of the susceptor during the second heating phase, depicted by line 912, indicates that the susceptor is not supplied with liquid aerosol-forming substrate 42. This is indicated by the rate of change of the apparent ohmic resistance of the inductor coil, depicted by line 922, being greater than the dry susceptor threshold R T Therefore, by comparing the rate of change of the apparent resistance of the inductor coil with the dry receptor threshold R T By comparison, the control circuitry 70 determines that the susceptor was not supplied with liquid aerosol-forming substrate during the second heating phase.

[0223] In the first case, the rate of increase in temperature of the susceptor during the third heating phase, depicted by line 913, indicates that the susceptor is not supplied with liquid aerosol-forming substrate 42. This is shown by the rate of change of the apparent ohmic resistance of the inductor coil, depicted by line 923, which remains greater than the dry susceptor threshold R T However, in the second case, during the third heating phase, the rate at which the liquid aerosol-forming substrate 42 is supplied is less than the dry susceptor threshold R . This is indicated by the rate of change of the apparent ohmic resistance of the inductor coil depicted by line 924. T Shown.

[0224] Control circuitry 70 is configured to distinguish between these two situations.

[0225] In the first case, the control circuit system 70 is configured to determine that the liquid reservoir 44 is exhausted when the receptor does not supply the liquid aerosol-forming substrate 42 for a time length equal to or greater than a time threshold. In this case, the time threshold is equal to a time length of 100 milliseconds from t1 to t3. The control circuit system 70 can then be configured to stop the power supply to the inductor coil 90 until the cartridge 10 is replaced or refilled. Additionally or alternatively, the control circuit system 70 can be configured to remind the user that the cartridge 10 needs to be replaced or refilled.

[0226] In a second scenario, the control circuit system 70 is configured to detect a temporary interruption when the susceptor is not supplied with liquid aerosol-forming substrate 42 for a length of time that is less than a time threshold. The control circuit system 70 may consider this to be an abnormal condition. The control circuit system 70 may not take action on the temporary interruption of the supply of liquid aerosol-forming substrate 42 to the susceptor. Alternatively, the control circuit system 70 may be configured to alert the user that the supply of liquid aerosol-forming substrate to the susceptor is temporarily interrupted.

[0227] Fig. 10A A graph illustrating the temperature change of a susceptor during a cooling period of the susceptor is shown. Fig. 10B Shows the description and Fig. 10A The graph shows the rate of change of the apparent ohmic resistance of the inductor coil associated with a change in temperature. Fig. 9A and 9B ,exist Fig. 10A and 10B In the first case, if Figure 5 In the first scenario, the liquid reservoir 44 is depleted of the liquid aerosol-forming substrate 42 and therefore no liquid aerosol-forming substrate is supplied to the susceptor. In the second scenario, the liquid reservoir 44 is not depleted of the liquid aerosol-forming substrate 42, however, the supply of the liquid aerosol-forming substrate 42 to the susceptor is temporarily interrupted, as shown in FIG. Figure 7 Described in.

[0228] Fig. 10A and 10B A first cooling stage of the susceptor from t0 to t1 , a second cooling stage of the susceptor from t1 to t2 , and a third cooling stage of the susceptor from t2 to t3 are shown.

[0229] In both cases, the rate of decrease in temperature of the susceptor during the first cooling phase, depicted by line 1011, indicates that the susceptor is supplied with liquid aerosol-forming substrate 42. This is indicated by the rate of change of the apparent ohmic resistance of the inductor coil, depicted by line 1021, being less than the dry susceptor threshold R T Therefore, by comparing the rate of change of the apparent ohmic resistance of the inductor coil with the dry receptor threshold R T By comparison, the control circuitry 70 determines that the susceptor was supplied with liquid aerosol-forming substrate 42 during the first cooling phase.

[0230] In both cases, the rate of decrease in temperature of the susceptor during the second cooling phase, depicted by line 1012, indicates that the susceptor is not supplied with liquid aerosol-forming substrate 42. This is indicated by the rate of change of the apparent ohmic resistance of the inductor coil, depicted by line 1022, being greater than the dry susceptor threshold R T Therefore, by comparing the rate of change of the apparent resistance of the inductor coil with the dry receptor threshold RT By comparison, the control circuitry 70 determines that the susceptor is not supplied with liquid aerosol-forming substrate during the second cooling period.

[0231] In the first case, the rate of decrease in temperature of the susceptor depicted by line 1013 indicates that the susceptor is not supplied with liquid aerosol-forming substrate 42. This is shown by the rate of change of the apparent ohmic resistance of the inductor coil depicted by line 1023, which remains greater than the dry susceptor threshold R T However, in the second case, the rate of decrease in temperature of the susceptor depicted by line 1014 indicates that the susceptor is supplied with liquid aerosol-forming substrate 42. This is indicated by the rate of change of the apparent ohmic resistance of the inductor coil depicted by line 1024 being less than the dry susceptor threshold R T Shown.

[0232] As about Fig. 9A and 9B As described, control circuitry 70 is configured to distinguish between these two situations by using a time threshold.

[0233] For the purpose of this specification and the appended claims, unless otherwise indicated, all numbers representing amounts, quantities, percentages, etc. should be understood to be modified by the term "about" in all cases. Moreover, all ranges include the disclosed maximum and minimum points, and include any intermediate ranges therein that may or may not be specifically listed herein. Therefore, in this context, the number A is understood to be A±5%A. In this context, the number A can be regarded as including a value within the general standard error for the measurement of the attribute modified by the number A. In certain cases used in the appended claims, the number A may deviate from the percentages listed above, provided that the amount of A deviation does not substantially affect the basic features and novel features of the invention claimed for protection. Moreover, all ranges include the disclosed maximum and minimum points, and include any intermediate ranges therein that may or may not be specifically listed herein.

Claims

1. An aerosol generating system comprising: a liquid reservoir for storing a liquid aerosol-forming substrate; a susceptor for receiving a supply of liquid aerosol-forming substrate from the liquid reservoir and heating the liquid aerosol-forming substrate to form an aerosol; an inductor coil configured to generate an alternating magnetic field for heating the susceptor; a power source configured to supply power to the inductor coil; control circuitry configured to determine a parameter indicative of a rate of change of temperature of the susceptor based on power supplied to the inductor coil; and Wherein the control circuitry is configured to determine whether the susceptor is supplied with the liquid aerosol-forming substrate based on a comparison between a dry susceptor threshold and a parameter indicative of a rate of change of temperature of the susceptor.

2. An aerosol generating system according to claim 1, wherein the parameter indicative of the rate of change of temperature of the susceptor is the rate of change of the apparent ohmic resistance of the inductor coil.

3. An aerosol generating system according to claim 1 or 2, wherein the parameter indicative of the rate of change of temperature of the susceptor is based on a first measurement of power supplied to the inductor coil and a second measurement of power supplied to the inductor coil.

4. An aerosol generating system according to claim 3, wherein the first measurement and the second measurement are separated by a time interval, and wherein the time interval is less than 500 milliseconds.

5. An aerosol generating system according to any preceding claim, wherein the control circuitry is configured to determine a parameter indicative of a rate of change of temperature of the susceptor based on power supplied to the inductor coil during a cooling period of the susceptor.

6. An aerosol generating system according to any preceding claim, wherein the control circuitry is configured to determine that the susceptor is not supplied with liquid aerosol-forming substrate when a parameter indicative of a rate of change of temperature of the susceptor is greater than the dry susceptor threshold.

7. An aerosol generating system according to any preceding claim, wherein the control circuitry is configured to determine whether the liquid reservoir is depleted based on whether the susceptor is supplied with liquid aerosol-forming substrate.

8. An aerosol generating system according to any preceding claim, wherein the control circuitry is configured to determine that the liquid reservoir is exhausted when the receptor has not been supplied with liquid aerosol-forming substrate for a length of time equal to or greater than a time threshold.

9. An aerosol generating system according to any preceding claim, wherein the control circuitry is configured to detect an abnormal condition when the susceptor is not supplied with liquid aerosol-forming substrate for a length of time that is less than a time threshold.

10. An aerosol generating system according to any preceding claim, wherein the control circuit system is configured to operate the aerosol generating system in a first mode and a second mode, the first mode being different from the second mode, wherein the control circuit system is configured to operate the aerosol generating system in the first mode when the receptor is supplied with a liquid aerosol-forming substrate, and wherein the control circuit system is configured to operate the aerosol generating system in the second mode when the receptor is not supplied with a liquid aerosol-forming substrate.

11. An aerosol generating system according to any preceding claim, wherein the control circuitry is configured to determine the dry susceptor threshold based on an initial supply of power to the inductor coil.

12. An aerosol generating system according to claim 11, wherein the susceptor is not supplied with liquid aerosol-forming substrate during initial power supply of the inductor coil.

13. An aerosol generating system according to claim 12, wherein the control circuit system is configured to determine a parameter indicative of an initial rate of change of temperature of the susceptor based on an initial supply of power to the inductor coil, and wherein the dry susceptor threshold is a parameter indicative of an initial rate of change of temperature of the susceptor.

14. An aerosol generating system according to any preceding claim, wherein the susceptor is in the form of a mesh.

15. A method of controlling an aerosol generating system, the aerosol generating system comprising a liquid reservoir for storing a liquid aerosol-forming substrate, a susceptor for receiving a supply of the liquid aerosol-forming substrate and an inductor coil configured to generate an alternating magnetic field for heating the susceptor, the method comprising: supplying power to the inductor coil; determining a parameter indicative of a rate of change of temperature of the susceptor based on power supplied to the inductor coil; as well as Based on a comparison between a dry susceptor threshold and a parameter indicative of a rate of temperature change of the susceptor, it is determined whether the susceptor is supplied with the liquid aerosol-forming substrate.

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