Method for detecting heater conditions in aerosol-generating system

Abstract

To provide an electrically heated aerosol-generating system allowing detection of abnormal or undesirable heater conditions therein.SOLUTION: An electrically operated aerosol-generating system includes: a heating element to heat an aerosol-forming substrate proximate to the heating element; a power supply to supply power to the heating element; and electric circuitry in communication with the heating element and the power supply. The electric circuitry includes a memory, and is configured to: regulate the supply of power to the heating element during a plurality of individual heating cycles in response to user inputs; determine a maximum electrical resistance of the heating element during each heating cycle; calculate a rolling average value of the maximum electrical resistance of the heating element for n preceding heating cycles, where n is an integer of greater than 1; compare the electrical resistance of the heating element with the calculated rolling average value; determine an adverse condition when the electrical resistance is greater than the rolling average value by more than a threshold value, the threshold value stored in the memory; and control power supplied to the heating element based on whether there is an adverse condition at the heating element, or provide an indication based on whether there is an adverse condition at the heating element.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] This specification relates to an aerosol generation system that operates by heating. In particular, the present invention relates to the detection of abnormal or undesirable heater states in an electrically heated aerosol generation system.

Background Art

[0002] In some aerosol generation devices, a liquid aerosol generation substrate is delivered from a liquid storage portion to an electrical heating element. As it is heated to the target temperature, the aerosol generation substrate vaporizes to form an aerosol. The liquid substrate is typically delivered to the heating element by a wick. When the amount of the aerosol generation substrate in the wick is depleted, the heating element may overheat and adversely affect the quality of the aerosol.

[0003] WO2012 / 085203 discloses an aerosol generation system that monitors the temperature rise in a heating element, where a rapid increase in the heater temperature indicates drying of the wick.

[0004] WO2016 / 1050922 and WO2018 / 019533 disclose more complex methods for detecting depletion of the aerosol generation substrate in a heating element. WO2016 / 1050922 teaches a system that depends on the ratio, or proportion, of the change in electrical resistance to a predetermined initial electrical resistance. WO2018 / 019533 discloses a system that does not consider the initial heating resistance. Rather, the system measures the absolute increase in electrical resistance during heating and is configured to shut down when the increase in electrical resistance exceeds a predetermined threshold.

[0005] However, all of these techniques for detecting depletion of the aerosol generation substrate still require a substantial increase in heater temperature to detect the resulting change in electrical resistance. Further, some of these methods require detection of the initial heater resistance.

Summary of the Invention

[0006] According to a first aspect of the present invention, there is provided a heating element for heating an aerosol-forming substrate proximal to the heating element, a power source for supplying power to the heating element, and an electrical circuit in communication with the heating element and the power source, the electrical circuit including a memory, configured to adjust the power supply to the heating element during a heating cycle in response to a user input, determine a first derivative value of the electrical resistance of the heating element with respect to time, and determine that there is a malfunction when the first derivative value of the electrical resistance exceeds a threshold value stored in the memory at a predetermined time within the heating cycle or after a predetermined time during the heating cycle, and control the power supplied to the heating element based on whether there is a malfunction in the heating element, or provide a display based on whether there is a malfunction in the heating element, an electrically-operated aerosol generation system comprising:

[0007] The electrical circuit determines malfunctions such as depletion of the aerosol-forming substrate or system malfunction by monitoring the first derivative value of the electrical resistance of the heating element. The electrical circuit may be configured to determine depletion of the liquid aerosol-forming substrate in the heating element. In this context, "depletion" means either that an insufficient amount of aerosol-forming substrate is provided to the heating element or complete depletion of the aerosol-forming substrate (e.g., an empty cartridge). In either case, this can result in a "dry" heating element as opposed to a "wet" heating element soaked in the liquid aerosol-forming substrate. For example, when the cartridge is empty or nearly empty, an insufficient amount of liquid aerosol-forming substrate may be supplied to the heating element. This may mean that the generated aerosol does not have the desired properties, such as the size or chemical composition of the aerosol particles. This can result in a poor experience for the user.

[0008] The electrical circuit can interrupt the power supply upon detection of a malfunction. This is advantageous as when the drying of the heating element is detected, the user can no longer use the aerosol generation system, thereby avoiding the generation of aerosols without the desired characteristics and thus an unpleasant experience for the user. The electrical circuit may be arranged to stop the heating element by disconnecting an electrical fuse between the heating element and the power supply, or by switching off a switch between the heating element and the power supply. Alternative ways to stop the heating element will be apparent to those skilled in the art. In some situations, the electrical circuit may be configured to reduce, but not completely stop, the power supply to the heating element upon detection of a malfunction.

[0009] Alternatively or additionally, the electrical circuit may provide an indication to the user to inform them of the malfunction. The indication can be one or more of an audible indication, a visual indication, a mechanical indication such as vibration, an olfactory indication, or any other indication means known to those skilled in the art. The user can then prepare for the replacement or refilling of the cartridge.

[0010] Generally, the less aerosol-forming substrate delivered to the heater for vaporization, the higher the temperature of the heating element for a given applied power, because the energy used to heat and vaporize the aerosol-forming substrate is instead applied to heating the heating element. Thus, the electrical resistance of the heating element can increase as the aerosol-forming substrate is depleted.

[0011] Therefore, the electrical circuit can determine a malfunction by monitoring the first derivative of the electrical resistance of the heating element with respect to a given power supply. For example, a malfunction can be determined upon detection of a sudden surge in electrical resistance. Advantageously, this can enable rapid detection of a malfunction, as a malfunction can be easily determined even before the heater temperature reaches a predetermined threshold, as disclosed in prior art systems, providing protection against overheating of the heating element.

[0012] Optionally, the predetermined period is a fixed period after the start of the heating cycle period, and the fixed period is stored in the memory. The predetermined period can be a general period for raising the temperature of the heating element from the ambient temperature to the use temperature. The use temperature can be the temperature at which the aerosol-forming substrate vaporizes. That is, the defect determination can be made only when the aerosol-forming substrate begins to vaporize in the heating element. Therefore, the determination may not take into account the temperature rise during heating of the heating element. For example, a rapid and probably inconsistent temperature rise can be expected during such a temperature rise period, but such a temperature rise may not necessarily be due to the lack of the aerosol-forming substrate. As a result, the determination can be made more accurately when it is executed when the heating element reaches the use temperature.

[0013] The time taken for the heating element to reach its use temperature can vary. For example, in a high ambient temperature or subsequent inhalations in a session of a pre-warmed heating element, the predetermined time required to reach the target temperature can be shortened. Optionally, the electrical circuit is configured to calculate a second derivative value of the electrical resistance of the heating element with respect to time, where the predetermined time is when the second derivative value is greater than or equal to a second derivative threshold value. Advantageously, the second derivative value can enable the active determination of a predetermined period between each of the heating cycles. This can provide a more reliable defect determination.

[0014] Optionally, the second derivative threshold value is zero. This advantageously enables the electrical circuit to identify the instant when the heating element reaches its use temperature. This is because a second derivative value of zero indicates that there is no further temperature change in the heating element. Any further rapid change in the heater temperature thereafter can only be due to a defect.

[0015] According to a second aspect of the present invention, a heating element for heating an aerosol-forming substrate proximal to the heating element, a power source for supplying power to the heating element, an electrical circuit in communication with the heating element and the power source, Adjust the power supply to the heating element during the heating cycle in response to user input, Determine a second derivative value of the electrical resistance with respect to time, Determine a defect when the second derivative value is greater than or equal to a second derivative threshold value, An electrically operating aerosol generation system is provided that includes an electrical circuit configured to control the power supplied to the heating element based on whether there is a defect in the heating element or to provide a display based on whether there is a defect in the heating element.

[0016] The second derivative threshold value may be zero. The second derivative threshold value may be a positive value.

[0017] According to a third aspect of the present invention, a heating element for heating an aerosol-forming substrate proximal to the heating element, a power source for supplying power to the heating element, and an electrical circuit in communication with the heating element and the power source, including a memory, adjusting the power supply to the heating element during a plurality of individual heating cycles in response to user input, determining the maximum electrical resistance of the heating element during each heating cycle, calculating a moving average value of the maximum electrical resistance of the heating element over n heating cycles, where n is an integer greater than 1, comparing the calculated moving average value of the electrical resistance of the heating element, determining a defect when the electrical resistance is greater than a threshold value by more than the moving average value, the threshold value being stored in the memory, and an electrical circuit configured to control the power supplied to the heating element based on whether there is a defect in the heating element or to provide a display based on whether there is a defect in the heating element. An electrically operating aerosol generation system is provided that includes the above.

[0018] For a given power supply to the heating element, the maximum temperature in the heating element is limited by the amount of aerosol-forming substrate available. This is due to the latent heat of vaporization of the aerosol-forming substrate. Therefore, the maximum electrical resistance in the heating element may be related to the amount of aerosol-forming substrate available in the heating element. For example, the lack of aerosol-forming substrate can result in a significant increase in the maximum electrical resistance detected over a plurality of consecutive heating cycles. Thus, an empty cartridge can be detected if the maximum electrical resistance between one puff and the next exceeds a threshold value.

[0019] However, the supply of aerosol-forming substrate in the heating element can decrease stepwise over the life of the cartridge. As the aerosol-forming substrate begins to deplete, the maximum resistance of the heating element can also increase gradually over consecutive puffs. Thus, during a malfunction, there may be no substantial difference in the maximum resistance detected between two consecutive puffs. This means that an empty cartridge may not be detected quickly.

[0020] Thus, advantageously, the maximum resistance detected during a puff can be compared to a moving average of the maximum resistances detected over at least two previous puffs. This ensures that any gradual increase in the maximum resistance over a plurality of previous puffs does not prevent the detection of a malfunction.

[0021] Optionally, n is between 2 and 5.

[0022] Optionally, the electrical circuit is configured to control the power or provide an indication of a malfunction if a malfunction is determined over two consecutive heating cycles. This can reduce false positives resulting from detected maximum resistance variations due to other factors.

[0023] Optionally, the electrical circuit is configured to determine a malfunction only after a predetermined start period has elapsed after the start of a heating cycle, and the predetermined start period is stored in a memory.

[0024] Optionally, the electrical circuit is configured to determine whether there is a malfunction during each heating cycle.

[0025] As used herein, the term "electrically operated aerosol generating system" means a system that generates an aerosol from one or more aerosol-forming substrates.

[0026] As used herein, the term "aerosol-forming substrate" means a substrate having the ability to release a volatile compound capable of forming an aerosol. Such volatile compounds may be released by heating the aerosol-forming substrate.

[0027] The aerosol-forming substrate may be housed within a cartridge. The system may comprise a device to which the cartridge is connected in order to heat one or more aerosol-forming substrates. The electric aerosol generating system may include additional components such as a charging unit for recharging an on-board power supply in an electrically operated aerosol generating device. The advantage of providing a cartridge is that the aerosol-forming substrate is protected from the surrounding environment. In some embodiments, ambient light may also be prevented from entering the cartridge so as to avoid photo-induced degradation of the aerosol-forming substrate. Furthermore, a high level of hygiene can be maintained.

[0028] The aerosol-forming substrate may be housed within a refillable liquid reservoir within the aerosol generating device. The aerosol-forming substrate may be housed within a refillable cartridge within the aerosol generating system. The aerosol-forming substrate is preferably housed within a disposable cartridge within the aerosol generating system. The cartridge may be replaced after a single use session or after a plurality of use sessions. This may enable the user to replace the depleted cartridge in a safe and efficient manner.

[0029] The aerosol-forming substrate may be in a liquid phase at room temperature. As used herein, the terms "liquid" and "solid" mean the state of the aerosol-forming substrate at room temperature. The aerosol-forming substrate may be a flowable liquid at room temperature. For a liquid aerosol-forming substrate, certain physical properties of the substrate, such as vapor pressure or viscosity, are selected to be suitable for use in an aerosol-generating system.

[0030] The aerosol-forming substrate may contain plant-derived materials. The aerosol-forming substrate may contain tobacco. The aerosol-forming substrate may contain a tobacco-containing material that contains volatile tobacco flavor compounds released from the aerosol-forming substrate upon heating. Alternatively, the aerosol-forming substrate may contain a non-tobacco-containing material. The aerosol-forming substrate may contain a homogenized plant-derived material. The aerosol-forming substrate may contain a homogenized tobacco material. The aerosol-forming substrate may contain at least one aerosol-forming agent. The aerosol-forming agent can be any suitable known compound or mixture of compounds that facilitates the formation of a dense and stable aerosol during use and is substantially resistant to thermal decomposition at the operating temperature of the system. Suitable aerosol-forming agents are well known in the art and include polyhydric alcohols (such as triethylene glycol, 1,3-butanediol, glycerin, etc.), esters of polyhydric alcohols (such as glycerol monoacetate, diacetate, or triacetate, etc.), and aliphatic esters of monocarboxylic acids, dicarboxylic acids, or polycarboxylic acids (such as dimethyl dodecanedioate, dimethyl tetradecanedioate, etc.), but are not limited thereto. Preferred aerosol-forming agents are polyhydric alcohols or mixtures thereof (such as triethylene glycol, 1,3-butanediol, and glycerin (most preferred), etc.). The aerosol-forming substrate may contain other additives and components (such as flavorants, etc.).

[0031] For a liquid aerosol forming substrate, certain physical properties of the substrate, such as vapor pressure or viscosity, are selected to be appropriate for use in an aerosol generating system. The liquid preferably contains a tobacco-containing material that, when heated, releases volatile tobacco flavor compounds from the liquid. Alternatively or additionally, the liquid may contain a non-tobacco material. The liquid may contain water, ethanol, or other solvents, plant extracts, nicotine solutions, and natural or artificial flavors. The liquid further preferably contains an aerosol former. Examples of suitable aerosol formers are glycerin and propylene glycol.

[0032] As used herein, the term "heating element" means an electrically heated element that is powered by an on-board power source. The electrically heated element may comprise a single heating element. Alternatively, the heating element may comprise a plurality of individual heating elements, such as two, or three, or four, or five, or six, or more heating elements. The heating element(s) may be arranged appropriately to most effectively heat the liquid aerosol forming substrate.

[0033] The heating element may be a resistive heating element. At least one electric heating element preferably includes an electrically resistive material. Suitable electrically resistive materials include, for example, but are not limited to, semiconductors such as doped ceramics, "conductive" ceramics (e.g., molybdenum disilicide, etc.), carbon, graphite, metals, alloys, and composite materials made of ceramic materials and metal materials. Such composite materials may include doped ceramics or undoped ceramics. An example of a suitable doped ceramic is doped silicon carbide. Examples of suitable metals include titanium, zirconium, tantalum, and platinum group metals. Examples of suitable metal alloys include stainless steel, constantan, nickel-containing, cobalt-containing, chromium-containing, aluminum-containing, titanium-containing, zirconium-containing, hafnium-containing, niobium-containing, molybdenum-containing, tantalum-containing, tungsten-containing, tin-containing, gallium-containing, manganese-containing, and iron-containing alloys, as well as nickel, iron, cobalt, stainless steel-based superalloys, Timetal® (a registered trademark), iron-aluminum-based alloys, and iron-manganese-aluminum-based alloys. Timetal® is a registered trademark of Titanium Metals Corporation. In the composite material, the electrically resistive material may optionally be embedded within, encapsulated within, or coated with a thermal insulation material, or vice versa, depending on the required energy transfer kinetics and external physico-chemical properties. The heating element may include a metal foil that is etched and insulated between two layers of inert material. In that case, the inert material may include Kapton® (a registered trademark), all-layer polyimide, or mica foil. Kapton® is a registered trademark of E.I. du Pont de Nemours and Company.

[0034] The resistive heating element can take the form of a mesh, array or cloth of conductive filaments. The conductive filaments may define gaps between the filaments, and the gaps may have a width of 10 μm to 100 μm. The conductive filaments may form a mesh sized 160 to 600 mesh US (±10%) (i.e., 160 to 600 (±10%) filaments per inch). The width of the gaps is preferably 25 μm to 75 μm. The area ratio of the openings of the mesh, which is the ratio of the area of the gaps to the total area of the mesh, is preferably 25 to 56%. The mesh may be formed using different types of weaving or lattice structures. Alternatively, the conductive filaments consist of an array of filaments arranged parallel to each other. The diameter of the conductive filaments can be 10 μm to 100 μm, preferably 8 μm to 50 μm, more preferably 8 μm to 39 μm. The filaments may have a round cross-section or a flat cross-section.

[0035] The area of the mesh, array or cloth of conductive filaments may be small and is preferably 25 mm 2 or less, and it is preferably acceptable for incorporation into a handheld system. The mesh, array or cloth of conductive filaments may be, for example, a rectangle with dimensions of 5 mm × 2 mm. The mesh or array of conductive filaments preferably covers an area of 10% to 50% of the area of the heater assembly. More preferably, the mesh or array of conductive filaments covers an area of 15 to 25% of the area of the heater assembly.

[0036] The filaments may be formed by etching a sheet material (such as foil). This may be particularly advantageous when the heater assembly comprises an array of parallel filaments. When the heating element includes a mesh or cloth of filaments, the filaments may be formed individually or woven together.

[0037] Preferred materials for the conductive filaments are 304, 316, 304L, and 316L stainless steels.

[0038] Instead of a mesh arrangement, at least one electrical heating element may take the form of a resistive heater coil, or a casing or substrate having different conductive or electrically resistive metal tubes. When the cartridge is received within the recess of the aerosol generating device, the heater may be arranged to surround at least a portion of the cartridge. The cartridge may incorporate a disposable heating element. As another alternative, one or more heating needles or rods passing through the liquid aerosol forming substrate may also be appropriate in some cases. As another alternative, at least one electrical heating element may include a flexible sheet of material. Other alternatives include heating wires or filaments, such as Ni-Cr (nickel-chromium), platinum, tungsten, or wires or heating plates made of alloys. Optionally, the heating element may be disposed within or on a rigid carrier material.

[0039] The aerosol forming substrate is delivered proximal to at least one heating element and heated. At least one heating element may heat the aerosol forming substrate by conduction. The heating element may at least partially contact the substrate. Heat from the heating element may be conducted to the substrate by a thermally conductive element. As another alternative, or in addition, at least one heating element may transfer heat to the incoming ambient air drawn through the electrically actuated aerosol generating system during use, which in turn heats the aerosol forming substrate. The ambient air may be heated before passing through the aerosol forming substrate. The ambient air may first be drawn through the substrate and then heated.

[0040] Temperature sensing may be based on measuring at least the electrical resistance of the resistive heater. In other words, the resistive heater can function as a temperature sensor. For example, if at least one heater has appropriate characteristics of a temperature coefficient of resistance, it may be possible to confirm the temperature of the heater by measuring the electrical resistance of the at least one heater. The electrical circuit may be arranged to measure the electrical resistance of the at least one heater by measuring the current flowing through the at least one heater and the voltage across the at least one heater, and determining the electrical resistance of the at least one heater from the measured current and voltage. In this case, the electrical circuit may include a resistor having a known resistance and in series with the at least one heater, and the electrical circuit may be arranged to measure the voltage across the resistor of the known resistance and to measure the current flowing through the at least one heater by determining the current flowing through the at least one heater from the measured voltage and the known resistance. Therefore, there may be no need to include a dedicated temperature sensor that occupies a large space in the aerosol generation system and can be expensive. In this embodiment, it is emphasized that the electrical resistance is used both as a heater and as a sensor.

[0041] The electrically operated aerosol generation system may further comprise a capillary wick for carrying the liquid aerosol forming substrate from the cartridge to the heater. This can reduce the number of moving parts in the aerosol generation device, thus improving reliability and also reducing weight and cost.

[0042] Optionally, the capillary core is arranged to contact the liquid within the cartridge. Optionally, the capillary core extends into the cartridge. In that case, during use, the liquid can be moved from the cartridge to the heating element by capillary action within the capillary core. In one embodiment, the capillary core includes a first end and a second end, the first end extends into the cartridge to contact the liquid therein, and the heating element can be arranged to heat the liquid within the second end. When the heating element is activated, the liquid at the second end of the capillary core can be vaporized by at least one heating element to form supersaturated vapor. The supersaturated vapor can be mixed with an air stream and carried within the air stream. During flow, the vapor is condensed to form an aerosol, and the aerosol can be carried towards the user's mouth. The liquid aerosol forming substrate can have physical properties including viscosity and surface tension such that the liquid is carried through the capillary core by capillary action.

[0043] The capillary core may have a fibrous or spongy structure. The capillary core preferably comprises a bundle of capillaries. For example, the capillary core may comprise a plurality of fibers or threads, or other microtubes. The fibers or threads may generally be aligned in the longitudinal direction of the aerosol generating system. Alternatively, the capillary core may comprise a sponge-like or foam-like material formed in a rod shape. The rod shape may extend along the longitudinal direction of the aerosol generating system. The structure of the core may form a plurality of small holes or tubes through which liquid can be transported by capillary action. The capillary core may comprise any suitable material or combination of materials. Examples of suitable materials are capillary materials, for example, sponge or foam materials, ceramic-based or graphite-based materials in the form of fibers or sintered powders, foamy metals or plastic materials, for example fibrous materials made of spun or extruded fibers (such as cellulose acetate, polyester, or bonded polyolefins, polyethylene, terylene or polypropylene fibers, nylon fibers or ceramics). The capillary core may have any suitable capillary and porosity for use with different liquid physical properties. The liquid may have physical properties including, but not limited to, viscosity, surface tension, density, thermal conductivity, boiling point and vapor pressure that allow it to be transported through the capillary device by capillary action.

[0044] Optionally, at least one heating element may be in the form of a heating wire or filament that surrounds and optionally supports the capillary core. When there are many aerosol-forming substrates during normal use, the capillary properties of the core, in combination with the properties of the liquid, can ensure that the core is always wet in the heating region.

[0045] The capillary core and the heating element, and optionally the cartridge, may be removable from the aerosol generating system as a single component.

[0046] Optionally, the electrically operated aerosol generating system further comprises a mouthpiece through which a user can inhale to draw the aerosol out of the system, wherein the electrical circuit includes a smoking detector for detecting when the user smokes as user input, and the electrical circuit is configured to supply power from a power source to a heating element when smoking is detected by the smoking detector. The smoking detector may form a user input device in the aerosol generating device. That is, the user may not need to press a mechanical button to initiate the heating cycle.

[0047] The mouthpiece may be configured to engage with the housing of the aerosol generating device or the cartridge. Optionally, the mouthpiece is configured to engage with the aerosol generating device, and the combination of the aerosol generating device and the mouthpiece may mimic the shape and dimensions of a combustible smoking article such as a cigarette, cigar, or slim cigar. Advantageously, in such embodiments, the combination of the aerosol generating device and the mouthpiece may mimic the shape and dimensions of a cigarette.

[0048] The mouthpiece may be designed to be discarded when the aerosol forming substrate within the cartridge is depleted.

[0049] The mouthpiece may be designed to be reusable. In embodiments where the mouthpiece is designed to be reusable, the mouthpiece may advantageously be configured to be removably attached to the housing of the cartridge or the aerosol generating device.

[0050] Optionally, the electrical circuit comprises a microprocessor, and more preferably a programmable microprocessor. The system may comprise a data input port or a wireless receiver so that software can be uploaded onto the microprocessor. The electrical circuit may comprise additional electrical components.

[0051] Optionally, cartridges having different characteristics may be used with the device. For example, the device may be provided with two different cartridges having heating elements of different sizes. For example, a heating element having a higher power rating may be used to deliver more aerosol to the user. A cartridge with a high capacity may be used to reduce the frequency of cartridge replacement.

[0052] The aerosol generating device preferably includes a housing. The housing may comprise any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics, or composite materials containing one or more of these materials, or thermoplastic resins suitable for food or pharmaceutical applications, such as polypropylene, polyetheretherketone (PEEK), and polyethylene. The material is preferably light and not brittle.

[0053] The power source may be any suitable power source, for example a direct voltage source such as a battery. The power source may be a lithium ion battery, nickel metal hydride battery, nickel cadmium battery, or a lithium-based battery (e.g., lithium cobalt battery), lithium iron phosphate battery, lithium titanate, or lithium polymer battery.

[0054] Optionally, the power source may include a rechargeable lithium ion battery. The power supply may include another form of charge storage device, such as a capacitor. The power supply may need to be recharged. The power supply may have a capacity that allows for sufficient energy storage for one or more uses of the aerosol generating device. For example, the power supply may have a capacity sufficient to allow for continuous generation of aerosol for about six minutes, or a multiple of six minutes, corresponding to the typical time taken to smoke a conventional cigarette. In another embodiment, the power supply may have a capacity sufficient to allow for a predetermined number of smoking sessions, or discontinuous activation.

[0055] The electrical circuit may be configured to start supplying power from the power supply source to the heater at the start of the heating cycle. The electrical circuit may be configured to end supplying power from the power supply source to the heater at the end of the heating cycle.

[0056] The electrical circuit may be configured to provide continuous power supply from the power supply source to the heater.

[0057] The electrical circuit may be configured to provide intermittent power supply from the power supply source to the heater. The electrical circuit may be configured to provide pulsed power supply from the power supply source to the heater.

[0058] Advantageously, the pulsed power supply to the heater can facilitate the control of the total output from the heater during the period. Advantageously, controlling the total output from the heater during the period can facilitate the control of the temperature.

[0059] The electrical circuit may be configured to vary the power supply from the power supply source to the heater. The electrical circuit may be configured to vary the duty cycle of the pulsed power supply. The electrical circuit may be configured to vary at least one of the pulse width and the period of the duty cycle.

[0060] Optionally, the aerosol generation system is portable. The aerosol generation system may be a smoking system and may have a size comparable to that of a conventional cigar or cigarette. The overall length of the smoking system may be approximately 30 mm to approximately 150 mm. The outer diameter of the smoking system may be approximately 5 mm to approximately 30 mm.

[0061] Optionally, the aerosol generating device comprises a user input device. The user input device may include at least one of a push button, a scroll wheel, a touch button, a touch screen, and a microphone. The user input device may enable a user to control one or more aspects of the operation of the aerosol generating device. The user input device may enable the user to activate, stop, or both, the power supply to the heater.

[0062] According to a fourth aspect of the present invention, there is provided a method of controlling the power supply to a heating element in an electrically operating aerosol generating system, comprising adjusting the power supply to the heating element during a heating cycle period in response to a user input, determining a first derivative value of the electrical resistance of the heating element with respect to time, determining that there is a defect when the first derivative value of the electrical resistance exceeds a threshold value stored in a memory at a predetermined time within the heating cycle period or after a predetermined time during the heating cycle period, and controlling the power supplied to the heating element based on whether there is a defect in the heating element, or providing a display based on whether there is a defect in the heating element.

[0063] According to a fifth aspect of the present invention, there is provided a method of controlling the power supply to a heating element in an electrically operating aerosol generating system, comprising adjusting the power supply to the heating element during a heating cycle period in response to a user input, determining a second derivative value of the electrical resistance with respect to time, determining that there is a defect when the second derivative value is greater than or equal to a second derivative value threshold, and controlling the power supplied to the heating element based on whether there is a defect in the heating element, or providing a display based on whether there is a defect in the heating element.

[0064] According to a sixth aspect of the present invention, in response to a user input, adjusting the power supply to a heating element during a plurality of individual heating cycles, determining the maximum electrical resistance of the heating element during each heating cycle, calculating a moving average value of the maximum electrical resistance of the heating element between n previous heating cycles, where n is an integer greater than 1, comparing the calculated moving average value of the electrical resistance of the heating element, and determining a malfunction when the electrical resistance is greater than a threshold value by more than the moving average value, the threshold value being stored in a memory, and controlling the power supplied to the heating element based on whether there is a malfunction in the heating element, or providing a display based on whether there is a malfunction in the heating element. A method for controlling the power supply to a heating element in an electrically operated aerosol generation system is provided.

[0065] According to a seventh aspect of the present invention, when a computer program product is executed on a programmable electrical circuit within an electrically operated aerosol generation system, a computer program product is provided that can be directly loaded into the internal memory of a microprocessor comprising a software code portion so as to perform the above-described steps. The system comprises a heating element for heating an aerosol-forming substrate and a power source for supplying power to the heating element. The electrical circuit is connected to the electrical heater and the power source, and the electrical circuit is configured to detect the electrical resistance of the heating element.

[0066] To avoid misunderstanding, the above-described features regarding one aspect of the present invention may be applied to other aspects of the present invention. Furthermore, the features described regarding one aspect may be used in combination with the features of another aspect.

[0067] Here, by way of illustration only, embodiments of the present invention will be described with reference to the following accompanying drawings.

Brief Description of the Drawings

[0068]

Figure 1a

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DETAILED DESCRIPTION OF THE INVENTION

[0069] FIGS. 1a to 1d are schematic diagrams of an electrically heated aerosol generation system according to an embodiment of the present invention. The aerosol generation system includes an aerosol generator 10 and a cartridge 20.

[0070] The cartridge 20 houses an aerosol-forming substrate within a cartridge housing 24 and is configured to be received within a recess 18 in the device. The cartridge 20 is a disposable cartridge. The user can replace the cartridge 20 when the aerosol-forming substrate within the cartridge is depleted. The cartridge includes a removable seal 26 to provide a hermetic seal to the cartridge housing 24. This may enable the aerosol-forming substrate housed within the cartridge housing 24 to be shielded from the environment prior to its first use. Figure 1a shows the cartridge 20 immediately prior to insertion into the device, and arrow 1 in Figure 1a indicates the direction of insertion of the cartridge.

[0071] The aerosol generating device 10 is portable and has a size comparable to that of a conventional cigar or cigarette. The device 10 includes a body 11 and a mouthpiece portion 12. The body 11 contains a battery 14 (such as a lithium iron phosphate battery), an electrical circuit 16, and a recess 18. The electrical circuit 16 comprises a programmable microprocessor. The mouthpiece portion 12 is connected to the body 11 by a hinged connection 21 and is movable between an open position shown in Figure 1a and a closed position shown in Figure 1d. The mouthpiece portion 12 is placed in the open position to allow insertion and removal of the cartridge 20 and in the closed position when the system is used for aerosol generation. The mouthpiece portion comprises a plurality of air inlets 13 and an air outlet 15. In use, the user sucks or inhales at the outlet, drawing air from the air inlets 13 through the mouthpiece portion to the outlet 15 and then into the user's mouth or lungs. An internal baffle 17 is provided to force the flow of air passing through the cartridge through the mouthpiece portion 12.

[0072] The recess 18 has a circular cross-section and is sized to receive the housing 24 of the cartridge 20. An electrical connector 19 is provided on the side of the recess 18 to provide an electrical connection between the control electronics circuit 16 and the battery 14 and the corresponding electrical contacts of the cartridge 20.

[0073] Figure 1b shows the system of Figure 1a with the cartridge inserted into the recess 18 and the removable seal 26 removed. At this position, the electrical connector is positioned against the electrical contacts on the cartridge.

[0074] Figure 1c shows the system of Figure 1b with the peelable seal 26 removed and the mouthpiece portion 12 moved to the closed position.

[0075] Figure 1d shows the system of Figure 1c with the mouthpiece portion 12 in the closed position. The mouthpiece portion 12 is held in the closed position by a fastening mechanism. The mouthpiece portion 12 in the closed position keeps the cartridge in electrical contact with the electrical connector 19 so that a good electrical connection is maintained during use regardless of the orientation of the system.

[0076] Figure 2 is an exploded view of the cartridge 20. The cartridge housing 24 has a size and shape selected to be received within the recess 18. The housing includes capillary materials 27, 28 immersed in a liquid aerosol-forming matrix. In this example, the aerosol-forming matrix includes 39 weight percent glycerin, 39 weight percent propylene glycol, 20 weight percent water and flavorant, and 2 weight percent nicotine. The capillary material is a material that actively transports liquid from one end to the other based on a relative difference in liquid concentration. The capillary material can be made from any suitable material. In this example, the capillary material is formed from polyester.

[0077] The cartridge housing 24 has an open end to which the heater assembly 30 is fixed. The heater assembly 30 includes a base 34 in which an opening 35 is formed, a pair of electrical contacts 32 fixed to the base and separated from each other by a gap 33, and a plurality of conductive heater filaments 36 fixed to the electrical contact on the opposite side of the opening across the opening 35.

[0078] The heater assembly 30 is covered by a peelable seal 26. The peelable seal 26 includes a liquid-impermeable plastic sheet that is adhered to the heater assembly 30 but can be easily peeled off. Tabs are provided on the sides of the peelable seal 26 so that the user can grasp the peelable seal 26 when peeling. Adhesion is described as a method of fixing the impermeable plastic sheet to the heater assembly, but it will be apparent to those skilled in the art that other methods well-known to those skilled in the art, including heat sealing or ultrasonic welding, may also be used as long as the cover can be easily removed by the consumer.

[0079] The cartridge of FIG. 2 has two separate capillary materials 27, 28. A disk of the first capillary material 27 is provided to contact the heater elements 36, 32 during use. The larger body of the second capillary material 28 is provided on the opposite side of the first capillary material 27 to the heater assembly. Both the first capillary material and the second capillary material hold a liquid aerosol-forming substrate. The first capillary material 27 that contacts the heater element has a higher thermal decomposition temperature (at least 160° C. or more, for example, about 250° C., etc.) than the second capillary material 28. The first capillary material 27 effectively serves as a spacer that separates the heater elements 36, 32 from the second capillary material 28 so that the second capillary material is not exposed to a temperature above its thermal decomposition temperature. This is to ensure that the thermal gradient across the first capillary material keeps the second capillary material at a temperature below its thermal decomposition temperature. The second capillary material 28 can be selected to have excellent wicking performance to the first capillary material, can hold more liquid per unit volume than the first capillary material, and can be less expensive than the first capillary material. In this example, the first capillary material is a heat-resistant element such as glass fiber or an element containing glass fiber, and the second capillary material is a polymer such as a suitable capillary material. Exemplary suitable capillary materials include those discussed herein, and in alternative embodiments, high-density polyethylene (HDPE), or polyethylene terephthalate (PET) may be mentioned.

[0080] The capillary materials 27, 28 are advantageously directed to carry liquid to the heater assembly 30 within the housing 24. When the cartridge is assembled, the heater filament 36 may contact the capillary material 27, such that the aerosol forming substrate can be carried directly to the mesh heater. Figure 3 is a detailed view of the filament 36 of the heater assembly 30, showing the meniscus 40 of the liquid aerosol forming substrate between the heater filaments 36. It can be seen that the aerosol forming substrate contacts most of the surface of each filament 36 such that most of the heat generated by the heater assembly 30 enters directly into the aerosol forming substrate.

[0081] In this way, in normal operation, the liquid aerosol forming substrate contacts a large portion of the surface of the heater filament 36. However, when most of the liquid substrate within the cartridge has been used, less liquid aerosol forming substrate is delivered to the heater filament 36. With less liquid to vaporize, less energy is taken up by the enthalpy of vaporization, and more of the energy supplied to the heater filament 36 is directed towards raising the temperature of the heater filament. Similarly, the energy required to maintain the target temperature also decreases as the heater filament 36 dries out. The heater filament 36 may dry out because the aerosol forming substrate within the cartridge has been depleted. Alternatively, although less likely, the heater filament 36 may dry out because the user smokes very long or very frequently and is unable to deliver liquid to the heater filament 36 as quickly as it is vaporized.

[0082] During use, the heater assembly 30 operates by resistive heating. The current, based on the control of the control electronics circuit 16, passes through the filament 36 and heats the filament within a desired temperature range. The mesh or array of filaments has a significantly higher electrical resistance than the electrical contacts 32 and the electrical connectors 19 so that the high temperature is localized to the filaments. This minimizes heat loss to other components of the aerosol generating device 10. In this embodiment, the system is configured to generate heat by providing current to the heater assembly 30 in response to the user's smoking.

[0083] The system includes a smoking sensor configured to detect when the user inhales air through the mouthpiece portion. The smoking sensor (not shown) is connected to the control electronics circuit 16, and the control electronics circuit 16 is configured to supply current to the heater assembly 30 only when it is determined that the user is smoking the device. Any suitable airflow sensor, such as a microphone or a pressure sensor, may be used as the smoking sensor.

[0084] To detect an increase in the temperature of the heater filament, the electrical circuit 16 is configured to measure the electrical resistance of the heater filament. The heater filament of this embodiment is formed from stainless steel and thus has a positive temperature coefficient of resistance. Additionally, in such a system that operates by smoking, a stainless steel filament with a relatively high specific heat capacity is ideal because high current pulses are used to generate heat in short bursts.

[0085] As the temperature of the heater filament 36 increases, its electrical resistance also increases. In another embodiment, the heater filament 36 may be formed from a material having a negative temperature coefficient of resistance, so that as the temperature of the heater filaments increases, their electrical resistance decreases.

[0086] Figure 4 is a plot showing the detected change in the resistance of the heater during a plurality of heating cycles each corresponding to user smoking. Each of the heating cycles persists for a period Δt. The x-axis represents time and the y-axis represents the detected electrical resistance in the heater assembly 30. As shown in Figure 4, during a plurality of different heating cycles: 1) the heater filament 36 is immersed in the aerosol-forming substrate, i.e., during the heating cycle 500 under normal operating conditions, 2) an insufficient supply of the aerosol-forming substrate is provided to the heater filament 36, i.e., the liquid substrate is not sufficiently replenished at the heater filament 36, during the heating cycle 502, and 3) the change in electrical resistance is detected during the heating cycle 504 in which the aerosol-forming substrate of the heater filament is depleted.

[0087] The heater assembly 30 has an initial resistance R Ref This initial resistance R Ref is a characteristic property of the heater assembly 30. This indicates the reference resistance of the heater assembly 30 at room temperature. The initial resistance R Ref is a combination of the parasitic resistance R P at room temperature and the resistance R0 of the heater filament. Thus, R0 can be determined from R0 = R Ref - R P The parasitic resistance R P is the resistance resulting from the electrical contacts 32 and the electrical connectors 19 and the contacts therebetween.

[0088] In some cases, the initial resistance R Ref of a new cartridge 20 can be measured at least once before any power is applied. The detection system is used to determine when a new cartridge 20 is inserted. In some cases, R Ref can be measured only once for each cartridge. Alternatively, R Ref can be measured each time the system is switched on. In a preferred embodiment, the electrical circuit measures the value R Refis configured to be measured periodically. The predetermined period may be about 3 minutes, or any suitable time required to return the heater filament 36 from its operating temperature to the ambient temperature. Such periodic updates of R Ref can be used to readjust the electrical circuit to compensate for changes in ambient temperature and changes in the state of the heater filament 36.

[0089] When power is applied to the heater assembly 30 while the user is smoking, the temperature of the heater filament 36 rises from the ambient temperature. As a result, the electrical resistance R of the heater filament 36 increases. However, the parasitic resistance R P is assumed to remain constant. This is because R P is due to non-heated components such as the electrical contacts 32 and the electrical connector 19. Further, the value of R P is assumed to be the same for all cartridges and not affected by changing the cartridge. The parasitic resistance R P value for a particular aerosol generating device 20 is stored in the memory of the electrical circuit.

[0090] The resistance of the heater filament 36 is linearly related to its temperature in the temperature range of interest. Thus, by actively measuring the electrical resistance, the electrical circuit can determine the heater temperature in the heater assembly 30. As shown in FIG. 4, the electrical circuit stops heating when the detected electrical resistance R rises above a maximum heater resistance threshold R Max . The maximum heater resistance threshold R Max corresponds to the maximum allowable temperature. Under normal conditions where sufficient aerosol-forming substrate is supplied to the heater filament 36, the heater resistance may not be able to rise above the maximum heater resistance threshold R Max . Thus, the electrical circuit determines the maximum heater resistance threshold R MaxWhen reaching [a certain state], it is configured to determine that there is an insufficient supply of the aerosol-forming substrate to cool the heater filament 36. This is shown in heating cycles 502 and 504. However, this method requires raising the heater temperature to a high level before a malfunction can be detected. This can cause the generation of undesirable compounds in the generated aerosol.

[0091] Figure 4 not only shows that the heater resistance R increases when the aerosol-forming substrate is depleted, but also shows that the heater resistance R increases rapidly in the latter half of smoking when the aerosol-forming substrate is insufficient. Therefore, in an embodiment according to the present invention, the depletion of the aerosol-forming substrate is determined by monitoring the first derivative dR / dt of the electrical resistance with respect to time. In other words, this embodiment monitors the rate of change of the heater resistance. This is illustrated in Figure 5, which shows the rate of change of the electrical resistance between each of the heating cycles 510, 512, and 514 corresponding to the heating cycles 500, 502, and 504 of Figure 4. Depending on the required accuracy, the sampling period dt for detecting the change in dR ranges from 1 millisecond to 1 second.

[0092] At the start of smoking, the heater assembly 30 is at the ambient temperature. The temperature rises rapidly until the vaporization of the aerosol-forming substrate occurs. This heating period can be referred to as the temperature rise stage. Regardless of the amount of the aerosol-forming substrate available in the heater filament 36, all of the heating cycles 510, 512, and 514 exhibit a similar trend in which the rate of change of the heater resistance gradually decreases throughout the temperature rise stage. Therefore, this method may not be reliable enough to determine the depletion of the substrate if it is based only on the analysis of the rate of change of the electrical resistance detected during the temperature rise period. Therefore, the electrical circuit is configured to determine whether there is a malfunction only after a predetermined period t min has elapsed, for example, after the start of smoking.

[0093] The predetermined period t minAfter this has elapsed, the rate of change of the electrical resistance R detected in the different heating cycles 510, 512 and 514 begins to differ. In heating cycle 510, the rate of temperature rise of the heater filament 36 slowly decreases. As a result, the first derivative value dR / dt of the electrical resistance decreases stepwise during the heating cycle.

[0094] However, if an insufficient supply of aerosol-forming substrate is provided to the heater filament 36, as shown in heating cycles 512 and 514 of FIG. 5, the rate of increase of the electrical resistance rises rapidly towards the end of the heating cycle. This is because the vaporized aerosol-forming substrate is not rapidly replenished at the heater filament 36. Therefore, when the initial aerosol-forming substrate at the heater filament 36 is vaporized and the amount of substrate at the heater filament decreases, the temperature at the heater filament rises rapidly.

[0095] As shown in FIG. 5, the electrical circuit is configured to determine the dry heater filament 36 when the first derivative value dR / dt of the heater resistance rises immediately upon the elapse of a predetermined period or at any time after the elapse of the predetermined period max above the maximum first derivative threshold value dR / dt. In heating cycle 512, the supply of aerosol-forming substrate is insufficient. In the first part of the heating cycle, since the aerosol-forming substrate is sufficient, after a predetermined period t min has elapsed, the first derivative value dR / dt remains below the maximum first derivative threshold value dR / dt max . However, since the aerosol-forming substrate is not replenished sufficiently rapidly, as the heating cycle progresses, the rate of change of the temperature of the heater filament 36 rises again and exceeds the maximum first derivative threshold value dR / dt max . This indicates that the amount of aerosol-forming substrate at the heater filament 36 is insufficient.

[0096] In contrast, for an empty or nearly empty cartridge as illustrated in smoking 514, the amount of the residual aerosol-forming substrate in the heater filament 36 before heating is a very limited amount. Thus, when a predetermined period t min has elapsed, the first derivative value dR / dt already exceeds the maximum first derivative threshold value dR / dt max . As a result, the electrical circuit determines a malfunction immediately after the elapse of the predetermined period t min .

[0097] In this embodiment, the electrical circuit is configured to stop the power supply to the heater assembly 30 upon detecting that the first derivative value dR / dt of the electrical resistance exceeds the maximum first derivative threshold value dR / dt min either immediately upon the elapse of the predetermined period t min or at any time after the elapse of the predetermined period t max . Further, or alternatively, a visual warning such as a blinking LED signal may be given to the user to prompt cartridge replacement. The electrical circuit may not start another heating cycle again until it detects that the cartridge replacement has been performed. This ensures that the user experience is not affected by an insufficient supply of the liquid substrate or its complete depletion in the heater filament 36.

[0098] In another embodiment, the electrical circuit does not immediately stop the power supply when it detects that the first derivative value dR / dt of the electrical resistance has risen beyond the maximum first derivative threshold value dR / dt max . Instead, the electrical circuit continues to supply power for one or more additional smoking sessions and continues to determine a malfunction. The electrical circuit may only confirm such a malfunction when it determines a dry heater filament 36 over two or more consecutive heating cycles. This enables a more reliable determination and ensures that the user does not discard the cartridge unnecessarily.

[0099] The aerosol generation system can be used over different periods of a day or at a plurality of locations having different climatic conditions. Thus, the ambient temperature may change significantly during use. Since the warm-up phase is the time it takes for the heating element to warm up from the ambient temperature, the predetermined period t min also changes as the ambient conditions change. Therefore, the determination of the predetermined period t min can be actively determined based on the second derivative value of the electrical resistance with respect to time. This makes it possible to start defect determination at the earliest opportunity.

[0100] Figure 6 shows the first derivative value dR / dt of the electrical resistance of the heater assembly during heating cycles 520, 522 and 524. Heating cycles 520, 522 and 524 correspond to heating cycles 500, 502 and 504 of Figure 4 respectively. In this case, the electrical circuit determines a defect when it detects that the second derivative value d check R / dt 2 of the electrical resistance with respect to time reaches zero as shown at point t 2 . For example, t check is the point at which no change occurs in the first derivative value dR / dt of the heater resistance. More specifically, this is the point at which the rate of temperature change begins to increase as a result of the aerosol-forming substrate not being replenished quickly enough to replace the vaporized substrate.

[0101] In heating cycle 520 where the heater filament 36 is immersed in the aerosol-forming substrate, the second derivative value d 2 R / dt 2 does not reach zero before the end of smoking. Therefore, the electrical circuit does not need to compare the first derivative value with a threshold value. Thus, this method can minimize the processing power in the electrical circuit.

[0102] In contrast, the second derivative value d 2 R / dt 2 in heating cycle 522 is the maximum first derivative value threshold dR / dt maxReaches zero at a level below. As a result, the electrical circuit monitors the rise of the first differential value dR / dt until it exceeds the maximum first differential value threshold dR / dt max After that, the electrical circuit determines the dry heater assembly 30. For the heating cycle 522, the application of a predetermined period or the second differentiation method d 2 R / dt 2 does not affect the timing of the defect determination.

[0103] On the other hand, the application of the second differentiation method enables earlier determination of the dry heater assembly 39 in heating 524. The heating cycle 524 is performed when the cartridge is empty or almost empty. The electrical circuit can determine such a defect before the elapse of a predetermined period t min as shown in the heating cycle 514 of FIG. 5. Therefore, the determination of the defect based on the second differential value d 2 R / dt 2 of the electrical resistance enables earlier power supply stop when the cartridge is empty or almost empty.

[0104] In another embodiment, the defect can be determined simply by monitoring the second differential value d 2 R / dt 2 of the electrical resistance. As soon as the second differential value has a positive value greater than zero, a defect can be determined. Also in this case, a positive second differential value over two consecutive heating cycles may be required before a defect is determined.

[0105] In a different embodiment, the electrical circuit determines a defect by comparing the maximum electrical resistance R detected over a plurality of consecutive puffings. This is illustrated in FIG. 7 which is a plot of the electrical resistance R in the succession of heating cycles. The heating cycles shown in FIG. 7 include the heating cycles 530a - f performed under normal operating conditions where the heater filament 36 is immersed in the aerosol - forming substrate, and the heating cycle 532 performed under a defect where an insufficient amount of aerosol - forming substrate is provided to the heater filament 36.

[0106] In this embodiment, the electrical circuit detects the maximum electrical resistance R after the elapse of a predetermined period t following the start of the heating cycle. min The maximum electrical resistance R after the elapse of a predetermined period t max is detected. Similar to the embodiment shown in FIG. 5, the predetermined period t min starts at the start of the heating cycle. The maximum electrical resistance R max1~ R max6 is detected in each of the respective heating cycles 530a to 530f. The maximum electrical resistance R max1 -R max6 increases with each successive heating cycle. This can be attributed to two mechanisms. First, while the first puff starts at the heater assembly 30 at ambient temperature, successive puffs can start at the heater assembly 30 at a higher temperature. This is because during successive puffs, the heater assembly 30 may not be cooled down to ambient temperature before the next heating cycle starts. Second, as the aerosol-forming substrate begins to deplete, the flow of the substrate to the heater assembly 30 decelerates with each successive puff.

[0107] Due to such a stepwise and progressive increase in the maximum electrical resistance observed over successive cycles, there may be no substantial difference in the maximum resistance detected between any two successive puffs. This means that in some situations, the start of an empty cartridge may not be detected.

[0108] To address this, the electrical circuit determines a malfunction by comparing the detected maximum electrical resistance R max with the moving average R of the maximum electrical resistances detected in the n previous puffs or heating cycles. max_AV More specifically, the electrical circuit determines a malfunction when the difference (R max -R max_AV ) between the maximum electrical resistance during the heating cycle and the moving average value exceeds a predetermined threshold ΔR max_offset (i.e., R max >(R max_AV +ΔR max_offset ).

[0109] In this example, the moving average Rmax_AV The number n of previous heating cycles for calculating is 4. Therefore, as shown in FIG. 7, for the heating cycle 532, R max_AV is the average value of R max3 , R max4 , R max5 and R max6 . The electric circuit compares the maximum electric resistance R max detected during the heating cycle 532 with the moving average and R max_AV and determines a defect based on the comparison. This is because the maximum resistance R max in this instance exceeds the sum of the moving average and a predetermined threshold value (R max_AV +ΔR max_offset ).

[0110] Since there is no previous heating cycle, during the first heating cycle 530a in a plurality of consecutive heating cycles, there is no moving average R max_AV for comparison. The maximum electric resistance R max1 detected during the first heating cycle 530a then serves as the moving average R max_AV for the second heating cycle 530b. On the other hand, the maximum electric resistances R max1 and R max2 detected respectively between the first heating cycle 530a and the second heating cycle 530b are used to calculate an updated moving average R max_AV (for example, R max_AV =(R max1 +R max2 ) / 2) for the third heating cycle 530c. Similarly, the maximum electric resistances R max1、 R max2、 R max3 detected between the first three heating cycles 530a to 530c are used to calculate an updated moving average R max_AV (for example, R max_AV =(R max1 +R max2 +R max3 ) / 3) for the fourth heating cycle 530d.

[0111] Generally, the moving average R max_AV for the heating cycle P is Rmax_AV =(R max_P-n +R max_P-(n-1) …R max_P-1 ) / n, where P is greater than n.

[0112] By applying a moving average, the electrical circuit can compare the maximum resistance R detected in a heating cycle with an average value representing the number of previous heating cycles. This enables the accumulation of small increases detected in previous heating cycles, and at the same time enables the electrical circuit to more quickly detect the depletion of the aerosol-forming substrate. max Furthermore, when the airflow passes through the heater assembly, it can significantly reduce the measured temperature. Therefore, in all of the above embodiments, the aerosol-generating device further comprises an airflow sensor for detecting the airflow rate during user smoking. The electrical circuit is configured to correct the detected electrical resistance R or adjust one or more stored threshold values based on the detected airflow rate. The correction can be performed either by a mathematical function stored in the device's memory or by referring to a look-up table. This enables any resistance R to be corrected before being used to determine a malfunction. Such correction provides a more accurate determination of malfunctions.

[0113] The methods described in various embodiments may be used in combination with each other or as selectable options within a single system.

[0114] The methods described in various embodiments may be used in combination with each other or as selectable options within a single system.

[0115] 1. An electrically operating aerosol generation system, said heating element for heating an aerosol-forming substrate proximal to the heating element, a power source for supplying power to said heating element, an electrical circuit in communication with said heating element and said power source, said electrical circuit including a memory, adjusting said power supply to said heating element during a plurality of individual heating cycles in response to a user input, Determining the maximum electrical resistance of the heating element during each heating cycle; Calculating a moving average value of the maximum electrical resistance of the heating element during n previous heating cycles, where n is an integer greater than 1; Comparing the electrical resistance of the heating element with the calculated moving average value; Determining a defect when the electrical resistance is greater than a threshold value by more than the moving average value, where the threshold value is stored in the memory; An electrically operating aerosol generation system comprising an electrical circuit configured to control the power supplied to the heating element based on whether there is a defect in the heating element or to provide a display based on whether there is a defect in the heating element. 2. The electrically operating aerosol generation system according to claim 1, wherein n is from 2 to 5. 3. The electrically operating aerosol generation system according to claim 1 or 2, wherein the electrical circuit is configured to control the power or provide a display when a defect is determined over two consecutive heating cycles. 4. The electrically operating aerosol generation system according to any one of claims 1 to 3, wherein the electrical circuit is configured to determine the defect only after a predetermined start period has elapsed after the start of the heating cycle, and the predetermined start period is stored in the memory. 5. The electrically operating aerosol generation system according to any one of claims 1 to 4, further comprising a mouthpiece through which a user can inhale to draw the aerosol out of the system, wherein the electrical circuit includes a smoking detector for detecting when the user smokes as a user input, and the electrical circuit is configured to supply power from the power source to the heating element when smoking is detected by the smoking detector. 6. The electrically operating aerosol generation system according to any one of claims 1 to 5, wherein the electrical circuit is configured to determine whether there is a defect during each heating cycle. 7. The electrically actuated aerosol generation system according to any one of 1 to 6, wherein the electrical circuit is configured to measure the flow rate of the air flow through the system, and the electrical circuit is configured to adjust an electrical resistance measurement value or one or more stored threshold values based on the measured air flow rate. 8. The electrically actuated aerosol generation system according to any one of 1 to 7, wherein the system comprises an apparatus and a removable cartridge, the power supply and the electrical circuit are within the apparatus, the heating element is within the removable cartridge, and the cartridge comprises a liquid aerosol forming substrate. 9. A method for controlling the power supply to a heating element in an electrically actuated aerosol generation system, comprising: adjusting the power supply to the heating element during a plurality of individual heating cycles in response to a user input; determining a maximum electrical resistance of the heating element during each heating cycle; calculating a moving average value of the maximum electrical resistance of the heating element during n previous heating cycles, where n is an integer greater than 1; comparing the electrical resistance of the heating element with the calculated moving average value; determining a malfunction when the electrical resistance is greater than a threshold value by more than the moving average value, the threshold value being stored in a memory; controlling the power supplied to the heating element based on whether a malfunction exists in the heating element, or providing a display based on whether a malfunction exists in the heating element. 10. A computer program product that can be directly loaded into the internal memory of a microprocessor with a software code portion so as to implement the method according to 9 when executed on a programmable electrical circuit within an electrically operated aerosol generation system, wherein the system comprises a heating element for heating an aerosol-forming substrate and a power source for supplying power to the heating element, the electrical circuit being connected to the heating element and the power source, and the electrical circuit being configured to detect the electrical resistance of the heating element.

Claims

Claim 1 An electrically operated aerosol generating system, comprising: a heating element for heating an aerosol forming substrate proximal to the heating element; a power source for supplying power to the heating element; an electrical circuit in communication with the heating element and the power source, the electrical circuit including a memory; adjusting the power supply to the heating element during a plurality of individual heating cycles in response to a user input; determining a maximum electrical resistance of the heating element during each heating cycle; calculating a moving average value of the maximum electrical resistance of the heating element during n immediately preceding heating cycles, where n is an integer greater than 1; comparing the maximum electrical resistance of the heating element with the calculated moving average value; determining a malfunction when a difference between the maximum electrical resistance and the moving average value exceeds a predetermined threshold value, the threshold value being stored in the memory; controlling the power supplied to the heating element based on whether there is a malfunction in the heating element, or providing a display based on whether there is a malfunction in the heating element, and an electrical circuit configured to perform the above. An electrically operated aerosol generating system comprising the electrical circuit. Claim 2 The electrically operated aerosol generating system according to claim 1, wherein n is 2 to 5. Claim 3 The electrically operated aerosol generating system according to claim 1 or claim 2, wherein the electrical circuit is configured to control power or provide a display when a malfunction is determined over two consecutive heating cycles. Claim 4 The electrically operated aerosol generating system according to any one of claims 1 to 3, wherein the electrical circuit is configured to determine the malfunction only after a predetermined start period has elapsed after the start of the heating cycle, and the predetermined start period is stored in the memory. Claim 5 The electrically operated aerosol generating system according to any one of claims 1 to 4, further comprising a mouthpiece through which a user can inhale to draw the aerosol out of the aerosol generating system, the electrical circuit including a smoking detector for detecting when the user smokes with the aerosol generating system as a user input, and the electrical circuit being configured to supply power from the power source to the heating element when smoking is detected by the smoking detector. Claim 6 The electrically actuated aerosol generation system according to any one of claims 1 to 5, wherein the electrical circuit is configured to determine whether there is a defect during each heating cycle.

7. The electrically actuated aerosol generation system according to any one of claims 1 to 6, wherein the electrical circuit is configured to measure the flow rate of the air stream passing through the aerosol generation system, and the electrical circuit is configured to adjust an electrical resistance measurement value or one or more stored threshold values based on the measured air flow rate.

8. The electrically actuated aerosol generation system according to any one of claims 1 to 7, wherein the aerosol generation system comprises a device and a removable cartridge, the power supply and the electrical circuit are within the device, the heating element is within the removable cartridge, and the cartridge comprises a liquid aerosol forming substrate.

9. A method for controlling the power supply to a heating element in an electrically actuated aerosol generation system, comprising: adjusting the power supply to the heating element during a plurality of individual heating cycles in response to a user input; determining a maximum electrical resistance of the heating element during each heating cycle; calculating a moving average value of the maximum electrical resistance of the heating element during n immediately preceding heating cycles, where n is an integer greater than 1; comparing the maximum electrical resistance of the heating element with the calculated moving average value; determining a defect when the difference between the maximum electrical resistance and the moving average value exceeds a predetermined threshold value, the threshold value being stored in a memory; controlling the power supplied to the heating element based on whether there is a defect in the heating element, or providing a display based on whether there is a defect in the heating element.

10. A computer program product that can be directly loaded into the internal memory of a microprocessor with a software code portion to implement the method according to claim 9 when executed on a programmable electrical circuit within an electrically operating aerosol generation system, wherein the aerosol generation system comprises a heating element for heating an aerosol-forming substrate and a power source for supplying power to the heating element, the electrical circuit is connected to the heating element and the power source, and the electrical circuit is configured to detect the electrical resistance of the heating element.

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