Heater Management

Abstract

To provide an electrically operated aerosol-generating system comprising means of detecting failures such as dry heating in a heater.SOLUTION: A system comprises: an electric heater comprising at least one heating element for heating an aerosol-forming substrate; a power supply; and electric circuitry (109) connected to the electric heater and to the power supply and comprising a memory. The electric circuitry is configured to: measure an initial electrical resistance (R1) of the electric heater; measure a subsequent electrical resistance of the electric heater after the measurement of the initial electrical resistance; determine a difference (AR) between the initial electrical resistance and the subsequent electrical resistance; determine that a failure is present if the determined difference between the initial electrical resistance and the subsequent electrical resistance is greater than a maximum threshold value (ARmax) or less than a minimum threshold value (ARmin) stored in the memory; and, on the basis of whether the presence of the failure is determined, control power supplied to the electric heater and / or provide an indication if the presence of the failure is determined.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to heater management. Certain disclosed embodiments relate to heater management within an electrically heated aerosol generation system. Aspects of the present invention are directed to an electrically heated aerosol generation system and a method for operating an electrically heated aerosol generation system. Some of the described embodiments relate to a system capable of detecting an abnormal change in the electrical resistance of a heater element, which may indicate a malfunction in the heater element. For example, the malfunction may indicate a depleted level of an aerosol-forming substrate within the system. In some of the described embodiments, this system may be effective for heater elements having different electrical resistances. In other embodiments, the detected characteristics of the electrical resistance may be used to determine or select how the system may be operated. Some aspects and features of the present invention may be applicable to electrically heated smoking systems.

Background Art

[0002] International Patent Publication No. WO 2012 / 085203 discloses an electrically heated smoking system comprising a liquid storage portion for storing a liquid aerosol-forming substrate, an electric heater comprising at least one heating element for heating the liquid aerosol-forming substrate, and an electric circuit configured to determine depletion of the liquid aerosol-forming substrate based on the relationship between the power applied to the heating element and the resulting temperature change of the heating element. In particular, the electric circuit is configured to calculate the rate of temperature rise of the heating element, and a high rate of temperature rise indicates that the wick carrying the liquid aerosol-forming substrate to the heater has dried out. The system compares the rate of temperature rise to a threshold value stored in memory during manufacture. If the rate of temperature rise exceeds the threshold value, the system may stop supplying power to the heater.

[0003] The system of International Patent Publication No. 2012 / 085203 can use the electrical resistance of the heater element to calculate the temperature of the heating element, which has the advantage of not requiring a dedicated temperature sensor. However, the system still requires the storage of a threshold value that depends on the resistance of the heater element, so the system is optimized for heater elements having a specific electrical resistance or range of resistances.

[0004] However, there may be cases where it is desirable to make the system operable with different heaters. Typically, in a system of the type described in International Patent Publication No. 2012 / 085203, the heater is provided in a disposable cartridge together with a metered liquid aerosol-forming substrate. The heater elements in different cartridges may have different electrical resistances. This may be the result of manufacturing tolerances within the same type of cartridge, or because different cartridge designs are available for use in the system to provide different user experiences. The system of International Patent Publication No. 2012 / 085203 is optimized for heaters having a known specific electrical resistance determined during the manufacture of the system used in this system.

[0005] In an electrically heated aerosol generation system and in particular a system operable using different heaters, it would be desirable to have an alternative system for determining that the heater has dried out or other malfunctions in the heater.

[0006] In an electrically heated aerosol generation system having a permanent device part and a part that is a consumable including an aerosol-forming substrate, it would be desirable for the manufacturer of this device to be able to easily determine whether the consumable part is an "authentic product" or a consumable considered to be compatible with the device. This applies to both systems where the heater is a consumable part and systems where the heater is part of a permanent device. SUMMARY OF THE INVENTION

[0007] In a first aspect of the present invention, there is provided an electrically operated aerosol generating system, the electrically operated aerosol generating system comprising: an electric heater comprising at least one heating element for heating an aerosol forming substrate; a power source; an electric circuit connected to the electric heater and the power source and comprising a memory, the electric circuit being configured to: measure an initial electrical resistance of the electric heater; measure a subsequent electrical resistance of the electric heater after measuring the initial electrical resistance; determine a difference between the initial electrical resistance and the subsequent electrical resistance; determine a fault when the determined difference between the initial electrical resistance and the subsequent electrical resistance is greater than a value of a maximum threshold or less than a value of a minimum threshold stored in the memory, and control the power supplied to the electric heater based on whether a fault has been determined, or provide a display if a fault has been determined; an electric circuit.

[0008] One fault in the aerosol generating system or aerosol generating device is that the aerosol forming substrate in the heater is insufficient or depleted. Generally speaking, the less aerosol forming substrate delivered to the heater for vaporization, the higher the temperature of the heating element for a given applied power. For a given power, the evolution of the temperature of the heating element during a heating cycle, or the way in which that evolution changes over a plurality of heating cycles, can be used to detect whether the amount of aerosol forming substrate in the heater is being depleted, and in particular whether the aerosol forming substrate in the heater is insufficient.

[0009] Another problem is the presence of counterfeit, non - compliant or damaged heaters within a system having refillable or disposable heaters. For a given applied power, if the resistance of the heater element rises more rapidly than expected, this may be because the heater is a counterfeit and has different electrical characteristics from an authentic heater, or because the heater has been damaged in some way. In either case, the electrical circuit may be configured to prevent power supply to the heater.

[0010] Another problem is the presence of counterfeit, non - compliant, old or damaged aerosol - forming substrates within a system. For a given applied power, if the resistance of the heater element rises more rapidly than expected, this may be because the aerosol - forming substrate is counterfeit or old and thus has a higher or lower water content than expected. For example, when a solid aerosol - forming substrate is used, if the substrate is very old or not properly stored, it may be dry. If the substrate is drier than expected, less energy is used for vaporization and the heater temperature will rise more rapidly. This results in an unexpected change in the electrical resistance of the heater element.

[0011] By using the difference between the initial and subsequent resistance of the electrical heater, the system does not need to determine the actual temperature of the heating element or have knowledge of the resistance of the heating element at any pre - stored given temperature. This allows different approved heaters to be used within the system without triggering problems and allows for absolute resistance variations due to manufacturing tolerances of heaters of the same type. This also enables the detection of non - compliant heaters.

[0012] The electrical circuit may be configured to measure the electrical resistance of the initial heater element and the electrical resistance of the heater element at a point in time after the initial power delivery from the power source to the electrical heater. The initial electrical resistance may be measured before the heater is first used. If the initial resistance is measured before the heater is first used, the heater element can be assumed to be around room temperature during the measurement. Measuring the initial resistance at or near room temperature can set a narrower band of expected behavior because the expected change in resistance over time may depend on the initial temperature of the heater element.

[0013] The initial resistance may be calculated as the measured initial resistance minus an assumed parasitic resistance contributed by other electrical components and electrical contacts within the system.

[0014] The system may comprise an apparatus and a cartridge removably coupled to the apparatus, with the power source and the electrical circuit within the apparatus, and the electrical heater and the aerosol-forming substrate within the removable cartridge. As used herein, a cartridge being "removably coupled" to an apparatus means that the cartridge and the apparatus can be coupled and separated from each other without significant damage to either the apparatus or the cartridge.

[0015] The electrical circuit may be configured to detect the insertion and removal of the cartridge into and from the apparatus. The electrical circuit may be configured to measure the initial electrical resistance of the heater when the cartridge is first inserted into the apparatus but before significant heating occurs. The electrical circuit may compare the measured initial resistance to a range of acceptable electrical resistances stored in memory. If the initial resistance is outside the range of acceptable resistances, this may be considered a counterfeit, non-compliant, or damaged cartridge. In that case, the electrical circuit may be configured to prevent power supply until the cartridge is removed and replaced with a different cartridge.

[0016] The device may use cartridges with different characteristics. For example, the device may use two different cartridges with heaters of different sizes. The larger heater may be used to deliver more aerosol for users with such personal preferences.

[0017] The cartridge may be refillable or may be configured to be discarded when the aerosol-forming substrate is depleted.

[0018] The aerosol-forming substrate is a substrate having the ability to release a volatile compound capable of forming an aerosol. The volatile compound may be released by heating the aerosol-forming substrate.

[0019] The aerosol-forming substrate may comprise a plant-derived material. The aerosol-forming substrate may comprise tobacco. The aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavor compounds released from the aerosol-forming substrate upon heating. Alternatively, the aerosol-forming substrate may comprise a non-tobacco-containing material. The aerosol-forming substrate may comprise a homogenized plant-derived material. The aerosol-forming substrate may comprise a homogenized tobacco material. The aerosol-forming substrate may comprise at least one aerosol-forming agent. The aerosol-forming agent is 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, and glycerol), esters of polyhydric alcohols (such as glycerol monoacetate, diacetate, or triacetate), and aliphatic esters of monocarboxylic, dicarboxylic, or polycarboxylic acids (such as dimethyl dodecanedioate and dimethyl tetradecanedioate), but are not limited thereto. Preferred aerosol-forming agents are polyhydric alcohols or mixtures thereof (such as triethylene glycol, 1,3-butanediol, and glycerol (most preferred)). The aerosol-forming substrate may comprise other additives and components (such as flavorants).

[0020] The cartridge may contain a liquid aerosol-forming substrate. For the 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 contains volatile tobacco flavor compounds released from the liquid upon heating. 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 preferably further contains an aerosol-forming agent. Examples of suitable aerosol-forming agents are glycerol and propylene glycol.

[0021] The advantage of providing a liquid storage portion is that the liquid within the liquid storage portion is protected from the ambient air. In some embodiments, ambient light may also be prevented from entering the liquid storage portion so as to avoid photoinduced decomposition of the liquid. Further, a high level of hygiene can be maintained.

[0022] The liquid storage portion is preferably arranged to hold liquid for a predetermined number of smoking sessions. If the liquid storage portion is not refillable and the liquid within the liquid storage portion has been used up, the user needs to replace the liquid storage portion. It is necessary to prevent contamination of the user by the liquid during such replacement. Alternatively, the liquid storage portion may be refillable. In that case, the aerosol generating system may be replaced after a certain number of refills of the liquid storage portion.

[0023] Alternatively, the aerosol-forming substrate may be a solid substrate. The aerosol-forming substrate may include a tobacco-containing material that includes volatile tobacco flavor compounds released from the substrate upon heating. Alternatively, the aerosol-forming substrate may include a non-tobacco material. The aerosol-forming substrate may further include an aerosol former. Examples of suitable aerosol formers are glycerin and propylene glycol.

[0024] When the aerosol-forming substrate is a solid aerosol-forming substrate, the solid aerosol-forming substrate comprises one or more of tobacco leaves, tobacco leaves, fragments of tobacco stems, reconstituted tobacco, homogenized tobacco, extruded tobacco, cast leaf tobacco, and expanded tobacco, and may for example comprise one or more of powders, granules, pellets, fragments, spaghetti, shreds, or sheets. The solid aerosol-forming substrate may be in a form not contained in a container, or may be provided in a suitable container or cartridge. Optionally, the solid aerosol-forming substrate may contain additional tobacco or non-tobacco volatile flavor compounds released upon heating of the substrate. The solid aerosol-forming substrate may also contain capsules containing, for example, additional tobacco or non-tobacco volatile flavor compounds, and such capsules may dissolve during heating of the solid aerosol-forming substrate.

[0025] "Homogenized tobacco", as used herein, means a material formed by aggregating particulate tobacco. The homogenized tobacco may be in the form of a sheet. The homogenized tobacco material may have an aerosol former content of more than 5% on a dry mass basis. Alternatively, the homogenized tobacco material may have an aerosol former content between about 5% and about 30% by weight on a dry mass basis. The sheet of homogenized tobacco material may be formed by aggregating particulate tobacco obtained by grinding or otherwise subdividing one or both of tobacco leaf lamina and tobacco leaf stems. As another method, or additionally, the sheet of homogenized tobacco material may include one or more of, for example, tobacco dust, tobacco fines and other particulate tobacco by-products formed during the processing, handling and transportation of tobacco. The sheet of homogenized tobacco material may include one or more native binders (i.e., tobacco endogenous binders), one or more foreign binders (i.e., tobacco exogenous binders), or a combination thereof to assist in the aggregation of particulate tobacco. As another method, or additionally, the sheet of homogenized tobacco material may include other additives including, but not limited to, tobacco and non-tobacco fibers, aerosol formers, humectants, plasticizers, flavorants, fillers, aqueous and non-aqueous solvents and combinations thereof.

[0026] Optionally, the solid aerosol forming substrate may be provided on or embedded in a thermally stable carrier. The carrier may be in the form of a powder, granule, pellet, fragment, spaghetti, chip or sheet. Alternatively, the carrier may be a tubular carrier having a thin layer of solid substrate disposed on its inner surface, or on its outer surface, or on both its inner and outer surfaces. Such tubular carriers may be formed of, for example, paper, or paper-like material, non-woven carbon fiber mat, low mass coarse mesh metal screen, or perforated metal foil or any other thermally stable polymer matrix.

[0027] The solid aerosol-forming substrate may be arranged on the surface of the carrier, for example, in the form of a sheet, foam, gel or slurry. The solid aerosol-forming substrate may be deposited on the entire surface of the carrier or, alternatively, deposited in a pattern to provide non-uniform flavor delivery during use.

[0028] The electrical circuit may be configured to detect the insertion of the aerosol-forming substrate into the device and its removal from the device. The electrical circuit may be configured to measure the initial electrical resistance of the heater when the aerosol-forming substrate is first inserted into the device, but before significant heating occurs. The electrical circuit may compare the measured initial resistance with the range of acceptable electrical resistances stored in the memory. If the initial resistance is outside the range of acceptable resistances, the aerosol-forming substrate may be considered to be a counterfeit, non-compliant or damaged. In that case, the electrical circuit may be configured to prevent power supply until the aerosol-forming substrate is removed and replaced.

[0029] The electric heater may comprise a single heating element. Alternatively, the electric heater may include a plurality of heating elements, for example two, or three, or four, or five, or six, or more heating elements. The heating element(s) may be appropriately arranged to most effectively heat the liquid aerosol-forming substrate.

[0030] At least one electric heating element preferably includes an electrically resistive material. Suitable electrically resistive materials include, 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. Examples of suitable doped ceramics include doped silicon carbide. Examples of suitable metals include titanium, zirconium, tantalum, and platinum group metals. Examples of suitable 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® (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, encapsulated, or coated with a heat insulating material, or vice versa, depending on the required energy transfer kinetics and external physicochemical 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® (registered trademark), all-layer polyimide, or mica foil. Kapton® is a registered trademark of E.I. du Pont de Nemours and Company.

[0031] At least one electric heating element may take any suitable form. For example, at least one electric heating element may take the form of a heating blade. As another method, at least one electric heating element may take the form of a casing or substrate having different conductive parts or an electrically resistive metal tube. The liquid storage part may incorporate a disposable heating element. As another method, one or more heating needles or rods passing through the liquid aerosol forming substrate may also be suitable in some cases. As another method, at least one electric 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 alloy wires or heating plates. Optionally, the heating element may be disposed within or on a rigid carrier material.

[0032] In one embodiment, the heating element includes a mesh, array, or cloth of conductive filaments. The conductive filaments may define gaps between the filaments, and the width of the gaps may be 10 μm to 100 μm.

[0033] The conductive filaments may form a mesh sized 160 to 600 mesh US (±10%) (i.e., 160 to 600 filaments per inch (±10%)). 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. As another method, the conductive filaments consist of an array of filaments arranged parallel to each other.

[0034] The diameter of the conductive filaments can be 10 μm to 100 μm, preferably 8 μm to 50 μm, and 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, 25 mm2 It is preferably the following and preferably allowable to be incorporated into a handheld system. The mesh, array or cloth of the conductive filaments may be, for example, a rectangle with dimensions of 5 mm × 2 mm. The mesh or array of the conductive filaments preferably covers an area of 10% to 50% of the area of the heater assembly. More preferably, the mesh or array of the 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 includes an array of parallel filaments. When the heating element includes a mesh or cloth of filaments, the filaments may be formed individually and woven together.

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

[0038] At least one heating element may heat the liquid aerosol forming substrate by conduction. The heating element may be at least partially in contact with the substrate. Alternatively, the heat from the heating element may be conducted to the substrate by means of a heat conductive element.

[0039] During use, it is preferable that the aerosol forming substrate is in contact with the heating element.

[0040] The electrically operated aerosol generating system preferably further comprises a capillary material for transporting the liquid aerosol forming substrate from the liquid storage portion to the electrical heater element.

[0041] It is preferable to arrange the capillary material so as to be in contact with the liquid in the liquid storage portion. It is preferable to extend the capillary core into the liquid storage portion. In that case, during use, the liquid is moved from the liquid storage portion to the electric heater by capillary action within the capillary core. In one embodiment, the capillary core has a first end and a second end, the first end extends into the liquid storage portion for contact with the liquid therein, and the electric heater is arranged to heat the liquid within the second end. When the heater is activated, the liquid at the second end of the capillary core is vaporized by at least one heating element of the heater to form supersaturated vapor. The supersaturated vapor is mixed with an air stream and carried in the air stream. During the flow, the vapor is condensed to form an aerosol, and the aerosol is carried towards the user's mouth. The liquid aerosol forming substrate has physical properties including viscosity and surface tension that allow the liquid to be carried through the capillary core by capillary action.

[0042] The capillary core may have a fibrous or spongy structure. The capillary core preferably includes a bundle of capillaries. For example, the capillary core may include a plurality of fibers or threads, or other fine tubes. The fibers or threads may generally be aligned in the longitudinal direction of the aerosol generating system. Alternatively, the capillary core may include 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 forms a plurality of small holes or tubes through which the liquid can be transported by capillary action. The capillary core may include any suitable material or combination of materials. Examples of suitable materials are capillary materials, such as sponge or foam materials, ceramic or graphite-based materials in the form of fibers or sintered powders, foamed metals or plastic materials, for example fibrous materials made of spun or extruded fibers (cellulose acetate, polyester, or bonded polyolefins, polyethylene, terylene or polypropylene fibers, nylon fibers or ceramics, etc.). The capillary core may have any suitable capillarity and porosity for use with different liquid physical properties. The liquid has 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.

[0043] The heating element may be in the form of a heating wire or filament that surrounds and optionally supports the capillary core. During normal use when there are many aerosol-forming substrates, the capillary properties of the core, in combination with the properties of the liquid, ensure that the core is always wet within the heating region.

[0044] Alternatively, as described, the heater element may include a mesh formed from a plurality of conductive filaments. The capillary material may extend into the gaps between the filaments. The heater assembly may draw the liquid aerosol-forming substrate into the gaps by capillary action.

[0045] The housing may include two or more different capillary materials. Here, the first capillary material in contact with the heater element has a higher thermal decomposition temperature, and the second capillary material in contact with the first capillary material but not in contact with the heater element has a lower thermal decomposition temperature. The first capillary material effectively serves as a spacer that separates the heater element from the second capillary material so that the second capillary material is not exposed to a temperature above its thermal decomposition temperature. As used herein, "thermal decomposition temperature" means the temperature at which a material begins to decompose and loses mass by generating gaseous by-products. The second capillary material may advantageously occupy a larger volume than the first capillary material and may also hold more aerosol-forming substrate than the first capillary material. The second capillary material may have a better wicking performance than the first capillary material. The second capillary material may be less expensive than the first capillary material or may have a high filling capacity. The second capillary material may be polypropylene.

[0046] The power source may be any suitable power source, such as, for example, a DC voltage source. In one embodiment, the power source is a lithium-ion battery. As another alternative, the power source may be a nickel-metal hydride battery, a nickel-cadmium battery, or a lithium-based battery, such as a lithium cobalt battery, a lithium iron phosphate battery, a lithium titanate battery, or a lithium polymer battery. Alternatively, the power source may be another form of charge storage device, such as a capacitor. The power source may require recharging and may have a capacity that allows sufficient energy storage for one or more aerosol generation experiences. For example, the power source may have a capacity sufficient to allow continuous generation of aerosol for about 6 minutes, or a multiple of 6 minutes, corresponding to the typical time it takes to smoke one conventional cigarette. In another example, the power source may have a capacity sufficient to allow a predetermined number of puffing or discontinuous activation of the heater.

[0047] The aerosol generating system preferably includes a housing. The housing is preferably elongated. The housing may comprise any suitable material or combination of materials. Suitable materials include, for example, metals, alloys, plastics, or composite materials containing one or more of these materials, or thermoplastic resins suitable for food or pharmaceutical applications such as, for example, polypropylene, polyetheretherketone (PEEK), and polyethylene. The material is preferably lightweight and not brittle.

[0048] The electrically heated aerosol generating system is preferably portable. The electrically heated aerosol generating system may be sized to rival conventional cigars or cigarettes. The overall length of the electrically heated aerosol generating system can be approximately 30 mm to approximately 150 mm. The outer diameter of the electrically heated aerosol generating system can be approximately 5 mm to approximately 30 mm.

[0049] The electrical circuit preferably 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. The system may comprise a temperature sensor.

[0050] If a malfunction is detected, the system does not do more than provide an indication to the user that a malfunction has been detected. This may be done by providing a visual, audible, or tactile warning. Alternatively or additionally, when a malfunction is detected, the electrical circuit may automatically limit the power supplied to the heater or otherwise control it.

[0051] There are numerous possible ways to configure an electrical circuit to control the power supplied to an electric heater when a malfunction is detected. If the aerosol-forming substrate delivered to the heating element is insufficient, or if the solid aerosol-forming substrate becomes dry, it may be desirable to reduce or stop the power supply to the heater. This may be both to ensure a consistent and enjoyable experience for the user and to reduce the risk of overheating and the generation of undesirable compounds in the aerosol. The power supply to the heater may be stopped or restricted. The power supply may be stopped or restricted for a short period of time. However, it is preferable that the power supply can be stopped or restricted until the heater or the aerosol-forming substrate is replaced.

[0052] For example, a 6W pulse may initially be supplied to the heater during smoking. If a malfunction is determined during smoking, the power supply for the remaining smoking may be restricted to a 5W pulse. In some embodiments, the electrical circuit may be configured to supply a 6W pulse that is not restricted to the heater during subsequent smoking until a further malfunction is determined. However, in another preferred embodiment, the electrical circuit may be configured to supply a restricted 5W pulse to the heater during subsequent smoking until the heater or the aerosol-forming substrate is replaced.

[0053] The system may include a smoking detector for detecting when the user is smoking with the system. The smoking detector is connected to the electrical circuit, and the electrical circuit is configured to supply power from the power source to the heater element when smoking is detected by the smoking detector, and the electrical circuit is configured to determine whether there is a malfunction between each smoking.

[0054] The smoking detector may be a dedicated smoking detector that directly measures the airflow through the device, such as a microphone-based smoking detector, or may indirectly detect smoking based on, for example, a temperature change within the device or a change in the electrical resistance of the heater element.

[0055] The electrical circuit may be configured to supply a predetermined power to the heater element during a subsequent period Δt1 of detection of an initial smoking or an initial power supply to the heater. Also, the electrical circuit may be configured to determine a change in the electrical resistance of the heater element based on a measurement of the electrical resistance of the heater element during a period t1 between each smoking. The period Δt1 may be selected to be immediately after the detection of an initial smoking or immediately after the first application of power to the heater (the period). This is particularly advantageous when the circuit detects an incompatible or counterfeit heater or aerosol-forming substrate during the first use following the replacement of a disposable cartridge. For example, the typical duration of a smoking may be 3 seconds, and the response time of the smoking detector may be about 100 ms. Then, Δt1 may be selected to be between 100 ms and 500 ms during the smoking period before the heater temperature stabilizes. Alternatively, the period Δt1 may be selected to be a period during which the temperature of the heating element is expected to stabilize.

[0056] The electrical circuit may be configured to prevent the power supply from the power source to the heater element if a malfunction is determined for a predetermined number of sequential or continuous user smokings. The predetermined number of sequential or continuous smokings may be any suitable number. For example, the predetermined number of sequential or continuous smokings may be 1, 2, 3, 4, 5, or 6. It is preferable that the predetermined number of sequential or continuous smokings is 3.

[0057] The electrical circuit may be configured to continuously determine whether there is a malfunction, and when there is a malfunction, limit or prevent the power supply to the heater, and continue to prevent or reduce the power supply to the heater element until the malfunction disappears.

[0058] In liquid and wick-based systems, excessive smoking may cause the wick to dry out because the liquid cannot be replaced quickly enough near the heater. In these situations, it is desirable to limit the power supply to the heater so that the heater does not become too hot and does not generate undesirable aerosol components. As soon as a malfunction is detected, the power to the heater may be stopped until the next user smoking event.

[0059] Similarly, excessive smoking may not cool the heater as expected between puffs, resulting in a gradual, undesirable increase in heater temperature between puffs. This applies to liquid or solid aerosol-forming substrate-based systems. When a malfunction is determined, the electrical circuit may be configured to prevent or limit the power supply for the remaining puffs and continue to limit the power supply to the heater element for subsequent puffs until the malfunction is resolved. If a malfunction is determined for a predetermined number of sequential or continuous user puffs, the electrical circuit may be configured to disable the heater element or prevent or inhibit the power supply from the power source to the heater element permanently or irreversibly. As used herein, the term "disable" means making the heater element inoperable. For example, the electrical circuit may be configured to blow a fuse connected to the heater element if a malfunction is determined for three consecutive puffs.

[0060] The electrical circuit may be configured to prevent power supply to the heater element during a predetermined stop period when there is a malfunction.

[0061] The electrical circuit may be configured to prevent power supply to the heater until a consumable part containing the aerosol-forming substrate or the heater is replaced.

[0062] Alternatively, or in addition, the electrical circuit may be configured to continuously calculate whether the difference between the initial resistance and the subsequent resistance has reached the value of the maximum threshold or the value of the minimum threshold, and to compare the time taken for the difference to reach the threshold value with the stored time value. If the time taken for the difference to reach the threshold value is less than the stored time value, or if the difference does not reach the threshold value within the expected period, it is determined that there is a defect and the power supply to the heater is prevented or reduced. If the threshold value is reached more quickly than expected, this may indicate burnout of the heater element or burnout of the substrate, or it may indicate a non-compliant heater, a counterfeit heater, or a damaged heater. Similarly, if the threshold value is not reached within the expected period, it may indicate a counterfeit or damaged heater or substrate. This may enable a quick determination of a counterfeit, damaged, or non-compliant heater or substrate.

[0063] Finding a defect may indicate not only a dry condition in the heater element but also a heater with electrical characteristics outside the expected characteristic range. This may be because there is a defect in the heater, because substances accumulate on the heater over its product life, or because it is an unauthorized or counterfeit heater. For example, if the manufacturer uses stainless steel heater elements, those heater elements are expected to have an initial electrical resistance at room temperature within a specific range of electrical resistances. Additionally, the difference between the initial electrical resistance of the heater and the subsequent resistance of the heater may be particularly valuable as it is related to the material of the heater element. The electrical circuit may be configured to determine a defect when the difference between the initial electrical resistance of the heater and the subsequent electrical resistance of the heater is outside the expected range of values and to limit or prevent the power supply to the heater based on the result. This may prevent the use of some unauthorized heaters.

[0064] In order to produce different control strategies for different states, multiple different threshold values may be used. For example, in order to set a boundary that requires the replacement of the heater of the substrate before further power is supplied, the highest threshold value and the lowest threshold value may be used. The electrical circuit may be configured to prevent power supply to the heater until the heater or the aerosol-forming substrate is replaced if the difference exceeds the highest threshold value or is less than the lowest threshold value. One or more intermediate threshold values may be used to detect excessive smoking behavior that results in a dry state in the heater. The electrical circuit may be configured to prevent power supply to the heater for a specific period or until the user smokes thereafter if the intermediate threshold value is exceeded but the highest threshold value is not exceeded. The one or more intermediate threshold values can also be used to trigger, for the user, an indication that the aerosol-forming substrate is almost depleted and needs to be replaced soon. The electrical circuit may be configured to provide an indication that can be visual, audible, or tactile if the intermediate threshold value is exceeded but the highest threshold value is not exceeded.

[0065] One process for detecting a counterfeit heater, a damaged heater, or a non - compliant heater is to check the resistance of the heater or the rate of change of the resistance of the heater when the heater is first used or when it is inserted into an apparatus or system. The electrical circuit may be configured to measure the initial resistance of the heater element within a predetermined period after power is supplied to the heater. The predetermined period may be a short period, and may be 50 ms to 200 ms. For a heater with a mesh heating element, the predetermined period may be approximately 100 ms. Preferably, the predetermined period is 50 ms to 150 ms. The electrical circuit may be configured to measure the initial resistance of the heater, may be configured to supply power to the heater to heat the aerosol - forming substrate using much lower power as a separate routine, or may measure the initial resistance of the heater during the very first moment before the heater starts and significant heating occurs. The electrical circuit may be configured to compare the initial resistance of the heater with a range of acceptable values, and if the initial resistance is outside the range of acceptable values, the electrical circuit may be configured to prevent power supply to the electric heater until the heater or the aerosol - forming substrate is replaced, or to provide an indication.

[0066] If the initial resistance is within the range of acceptable values, the electrical circuit may determine that there is an acceptable heater and control the power supplied to the electric heater based on whether there is an acceptable heater, or may be configured to provide an indication if there is no acceptable heater.

[0067] The electrical circuit may be configured to determine that there is an acceptable heater within 1 second after first supplying power to the heater.

[0068] In a second aspect, there is provided a heater assembly for use in an electrically - operated aerosol - generating system, such as the electrically - operated aerosol - generating system of the first aspect or an electrically - operated aerosol - generating device, the heater assembly comprising An electric heater comprising at least one heating element, An electric circuit connected to the electric heater and comprising a memory, Measuring the initial electrical resistance of the electric heater, Measuring the subsequent electrical resistance of the electric heater after measuring the initial electrical resistance, Determining the difference between the initial electrical resistance and the subsequent electrical resistance, Determining when the determined difference between the subsequent electrical resistance and the initial electrical resistance of the electric heater is greater than the value of the maximum threshold stored in the memory or less than the value of the minimum threshold, and, Controlling the power supplied to the electric heater based on whether a defect has been determined, or providing a display if there is a defect, an electric circuit configured to:

[0069] The heater assembly may be configured for use in an aerosol generation system and may be configured to heat an aerosol-forming substrate during use.

[0070] In a third aspect, there is provided an electrically actuated aerosol generator for use in an electrically actuated aerosol generation system, such as the electrically actuated aerosol generation system of the first aspect, the electrically actuated aerosol generator comprising: A power source, An electric circuit connected to the power source and comprising a memory, the electric circuit being: During use, connected to the electric heater of the electrically actuated aerosol generation system, Measuring the initial electrical resistance of the electric heater, Measuring the subsequent electrical resistance of the electric heater after measuring the initial electrical resistance, Determining the difference between the initial electrical resistance and the subsequent electrical resistance, Determining that there is a defect when the determined difference between the initial electrical resistance and the subsequent electrical resistance is greater than the value of the maximum threshold stored in the memory or less than the value of the minimum threshold, and, A circuit configured to control the power supplied to an electric heater based on whether a malfunction has been determined, or to provide a display if a malfunction has been determined.

[0071] In a fourth aspect of the present invention, there is provided an electrical circuit for an electrically operated aerosol generating system, such as the electrically operated aerosol generating system of the first aspect, or an electrically operated aerosol generating device, such as the electrically operated aerosol generating device of the third aspect. In use, the electrical circuit is connected to an electric heater and a power source. The electrical circuit comprises a memory, and measures an initial electrical resistance of the electric heater, measures a subsequent electrical resistance of the electric heater after said measurement of the initial electrical resistance, determines a difference between the initial electrical resistance and the subsequent electrical resistance, determines a malfunction when the determined difference between the initial electrical resistance and the subsequent electrical resistance is greater than a maximum threshold value stored in the memory or less than a minimum threshold value. Further, configured to control the power supplied to the electric heater based on whether a malfunction has been determined, or to provide a display if a malfunction has been determined.

[0072] In use, the electrical circuit may further be connected to a smoking detector for detecting when a user is smoking with the system. The electrical circuit further determines when the electrical circuit is connected to the electric heater, measures an initial resistance of the electric heater within a predetermined period after the electrical circuit is connected to the electric heater, supplies power from the power source to the heating element when smoking is detected by the smoking detector, measures a subsequent resistance of the electric heater within a predetermined period after the power supply from the power source to the electric heater is started, determines a difference between the subsequent resistance and the initial electrical resistance, Compare the difference between the subsequent resistance and the initial resistance with at least one of the value of the maximum threshold and the value of the minimum threshold stored in the memory, Determine that there is a problem when the difference is greater than the value of the maximum threshold or less than the value of the minimum threshold, and When it is determined that there is a problem, limit the power supplied to the electric heater during smoking, or prevent power from being supplied to the electric heater for the remaining smoking based on whether it is determined that there is a problem. It may be configured as follows.

[0073] In some embodiments, the electrical circuit further Stores the determination of the problem in the memory, Based on the stored determination of the problem, determine the number of consecutive determinations of the problem, and It may be configured to invalidate the cartridge when the determined number of consecutive problem determinations is greater than the value of the maximum threshold.

[0074] The electrical circuit can be configured to invalidate the cartridge by any suitable means. For example, the electrical circuit may be configured to blow a fuse connected to the electric heater.

[0075] In a fifth aspect, there is provided a method of controlling the power supply to an electric heater of an electrically operated aerosol generating system, such as the electrically operated aerosol generating system of the first aspect, or an electrically operated aerosol generating device, such as the electrically operated aerosol generating device of the third aspect. This system or method includes at least one heating element for heating an aerosol-forming substrate and a power source for supplying power to the electric heater. This method includes Supplying power to the electric heater, Measuring the initial electrical resistance of the electric heater, Measuring the subsequent electrical resistance of the electric heater after measuring the initial electrical resistance, Determining the difference between the initial electrical resistance and the subsequent electrical resistance, Determining a defect when a determined difference between a subsequent electrical resistance and an initial electrical resistance is greater than a value of a maximum threshold stored in a memory or less than a value of a minimum threshold; including controlling power supplied to the electric heater based on whether a defect has been determined, or providing an indication if a defect has been determined.

[0076] The method may include measuring an electrical resistance of an initial heater element and measuring an electrical resistance of the heater element at a point in time after an initial power delivery from a power source to the electric heater.

[0077] The method may include supplying a constant power to the heater when power is supplied. As another option, variable power may be supplied depending on other operating parameters. In that case, the value of the threshold may depend on the power supplied to the heater.

[0078] The method may include determining an initial electrical resistance before the heater is first used. If the initial resistance is determined before the heater is first used, the heater element can be assumed to be around room temperature. Since the expected change in resistance over time may depend on the initial temperature of the heater element, measuring the initial resistance at or near room temperature can set a narrower band of expected behavior.

[0079] The method may include calculating the initial resistance measured as the initial resistance minus an assumed parasitic resistance introduced by other electrical components and electrical contacts in the system.

[0080] An electrically operated aerosol generating system may comprise a smoking detector for detecting when a user smokes with the system, and the method may include supplying power from a power source to a heater element when smoking is detected by the smoking detector, determining whether there is a malfunction during each smoking, and preventing power supply from the power source to the heater element if there is a malfunction for a predetermined number of consecutive user smokes.

[0081] The method may include preventing power supply from the power source to the heater element if there is a malfunction.

[0082] The method may include continuously determining whether there is a malfunction, preventing power supply to the heater when there is a malfunction, and continuing to prevent power supply to the heater element until the malfunction ceases.

[0083] The method may include preventing power supply to the heater element for a predetermined period of time when there is a malfunction.

[0084] Alternatively, or additionally, the method may include continuously calculating whether a difference exceeds a maximum threshold value or a minimum threshold value, and comparing the time taken to reach the threshold value with a stored time value, and determining a malfunction and controlling power supply to the heater if the time taken to reach the threshold value is less than the stored time value.

[0085] In some embodiments, the electrically operated aerosol generating system may further comprise a removable cartridge and a device configured to removably receive the removable cartridge, the removable cartridge comprising an electric heater and a liquid aerosol forming substrate, the device comprising a power source and an electrical circuit, the electrical circuit being connected to an inhalation detector for detecting when a user is smoking with the system. In these embodiments, the method may further Measuring the initial resistance of the electric heater before smoking is detected by the smoking detector; Supplying power from the power source to the heating element when smoking is detected by the smoking detector; Measuring the subsequent resistance of the electric heater within a predetermined period after the power supply from the power source to the electric heater is started; Determining the difference between the subsequent resistance and the initial electrical resistance; Comparing the difference between the subsequent resistance and the initial resistance with at least one of the value of the maximum threshold value and the value of the minimum threshold value stored in the memory; Determining that there is a defect when the difference is greater than the value of the maximum threshold value or less than the value of the minimum threshold value; Limiting the power supplied to the electric heater during smoking when it is determined that there is a defect, or preventing power from being supplied to the electric heater for the remaining smoking when it is determined that there is a defect.

[0086] In some embodiments, the method further includes: Determining when the electrical circuit is connected to the electric heater; Measuring the initial resistance of the electric heater within a predetermined period after being connected to the electric heater.

[0087] In a sixth aspect of the present invention, there is provided a method for detecting a non - compliant heater or a damaged heater of an electrically - operated aerosol - generating system, such as the electrically - operated aerosol - generating system of the first aspect, or an electrically - operated aerosol - generating device, such as the electrically - operated aerosol - generating device of the third aspect. The system or device includes an electric heater having at least one heating element for heating an aerosol - forming substrate and a power source for supplying power to the electric heater. The method includes: Supplying power to the electric heater; Measuring the initial electrical resistance of the electric heater; Measuring the subsequent electrical resistance of the electric heater after the measurement of the initial electrical resistance; determining a difference between the initial electrical resistance and the subsequent electrical resistance; determining that the heater is non - compliant or damaged when the difference between the initial electrical resistance and the subsequent electrical resistance is greater than a value of a maximum threshold, or less than a value of a minimum threshold, or when the difference reaches a value of a threshold stored in a memory outside a period in which the difference is expected;

[0088] The method may further include preventing power supply to the electrical heater or providing a display until the heater or the aerosol - forming substrate is replaced when it is determined that the heater is non - compliant.

[0089] The method further includes measuring an initial resistance of the heater or a rate of change of the initial resistance of the heater within a predetermined period after power is supplied to the heater, comparing the initial resistance of the heater or the rate of change of the initial resistance of the heater with a range of acceptable values, and preventing power supply to the electrical heater or providing a display when the initial resistance or the rate of change of the initial resistance is outside the range of acceptable values until the heater or the aerosol - forming substrate is replaced.

[0090] The predetermined period may be a short period, and may be from 50 ms to 200 ms. For a heater provided with a mesh heating element, the predetermined period may be approximately 100 ms. Preferably, the predetermined period is from 50 ms to 150 ms.

[0091] Determining the rate of change of the initial resistance during a predetermined period may be achieved by performing a plurality of resistance measurements at different times during the predetermined period and calculating the rate of change of the resistance based on the plurality of resistance measurements.

[0092] The method may further include detecting when the heater or the aerosol - forming substrate is inserted into the system. The method may be performed immediately after it is detected that the heater or the aerosol - forming substrate has been inserted into the system.

[0093] In a seventh aspect of the present invention, when a computer program product is executed on a microprocessor in an electrically operated aerosol generation system, there is provided a computer program product that can be directly loaded into the internal memory of a microprocessor having a software code portion so as to perform the steps of the fifth or sixth aspect. The system includes an electric heater having at least one heating element for heating an aerosol forming substrate, and a power source for supplying power to the electric heater, and the microprocessor is connected to the electric heater and the power source.

[0094] The computer program product may be provided as one of downloadable software or recorded on a computer-readable storage medium.

[0095] According to an eighth aspect of the present invention, there is provided a computer-readable storage medium on which the computer program according to the seventh aspect is stored.

[0096] The features described in connection with one aspect of the invention may be applicable to other aspects of the invention. In particular, the features described in connection with the first aspect may be applicable to the second, third, and fourth aspects of the present invention. The features described in connection with the first, second, third, and fourth aspects of the present invention may also be applicable to the fifth, sixth, and seventh aspects of the present invention.

Brief Description of the Drawings

[0097] The present invention will be further described by way of example only with reference to the accompanying drawings.

Fig. 1-1

Fig. 1-2

Fig. 2

Fig. 3

Fig. 4

Fig. 5

Fig. 6

Fig. 7

Fig. 8

Fig. 9

DETAILED DESCRIPTION OF THE INVENTION

[0098] Figures 1a - 1d are schematic diagrams of an electrically heated aerosol generation system including a cartridge according to an embodiment of the present invention. Figure 1a is a schematic diagram of the aerosol generation device 10 and a separate cartridge 20, which together form an electrically heated aerosol generation system.

[0099] The cartridge 20 includes an aerosol-forming substrate and is configured to be received within a recess 18 in the device. The cartridge 20 should be replaceable by the user when the aerosol-forming substrate provided within the cartridge is depleted. Figure 1a shows the cartridge 20 immediately prior to insertion into the device, and arrow 1 in Figure 1a indicates the insertion direction of the cartridge.

[0100] 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 main body 11 and a mouthpiece portion 12. The main 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 is equipped with a programmable microprocessor. The mouthpiece portion 12 is connected to the main body 11 by a hinged connection 21 and is movable between an open position shown in FIG. 1 and a closed position shown in FIG. 1d. The mouthpiece portion 12 is placed in the open position to allow the insertion and removal of the cartridge 20, and is placed in the closed position when the system is used for aerosol generation. The mouthpiece portion includes a plurality of air inlets 13 and an air outlet 15. During 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.

[0101] 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 electronic circuit 16 and the battery 14 and the corresponding electrical contacts of the cartridge 20.

[0102] FIG. 1b shows the system of FIG. 1a with the cartridge inserted into the recess 18 and the cover 26 removed. In this position, the electrical connector is positioned relative to the electrical contacts on the cartridge.

[0103] FIG. 1c shows the system of FIG. 1b with the cover 26 completely removed and the mouthpiece portion 12 moved to the closed position.

[0104] 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 fastener mechanism. The mouthpiece portion 12 in the closed position keeps the cartridge in electrical contact with the electrical connector 19 so that good electrical connection is maintained during use regardless of the orientation of the system.

[0105] Figure 2 is an exploded view of the cartridge 20. The cartridge 20 includes a generally cylindrical housing 24 sized and shaped 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 and may be made of any suitable material. In this example, the capillary material is formed from polyester.

[0106] The housing has an open end to which the heater assembly 30 is secured. The heater assembly 30 includes a base 34 in which an opening 35 is formed, a pair of electrical contacts 32 secured to the base and separated from each other by a gap 33, and a plurality of conductive heater filaments 36 secured to the electrical contact on the opposite side of the opening across the opening 35.

[0107] The heater assembly 30 is covered by a removable cover 26. The cover includes a liquid-impermeable plastic sheet that is adhered to the heater assembly but can be easily peeled off. Tabs are provided on the sides of the cover so that the user can grasp the cover when peeling it off. Adhesion is described as a way to secure 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.

[0108] 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 the 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 27, 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 a 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 considered herein, and in alternative embodiments, high density polyethylene (HDPE), or polyethylene terephthalate (PET) may be mentioned.

[0109] 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 filaments 36, 37, 38 may contact the capillary material 27, so that the aerosol-forming substrate can be carried directly to the mesh heater. FIG. 3 is a detailed view of the filament 36 of the heater assembly, showing a 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 so that most of the heat generated by the heater assembly enters directly into the aerosol-forming substrate.

[0110] In this way, during 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. With less liquid to vaporize, less energy is taken up by the enthalpy of vaporization, and more of the energy supplied to the heating filament is directed towards raising the temperature of the heating filament. As the heater element thus dries out, the rate of temperature rise of the heater element for a given applied power increases. The heater element may dry out because most of the aerosol-forming substrate within the cartridge has been used up, or because the user smokes very long or very frequently and cannot deliver the liquid to the heater filament as fast as it is vaporized.

[0111] During use, the heater assembly operates by resistive heating. The current passes through the filament 36 based on the control of the control electronics circuit 16 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 connector 19 so that a high temperature is localized in the filaments. In this embodiment, the system is configured to generate heat by providing current to the heater assembly in response to the user's smoking. In another embodiment, the system may be configured to continuously generate heat while the device is in the "on" state. Different materials may be appropriate for the filament depending on the different systems. For example, in a continuous heating system, a Ni-Cr filament is appropriate because it has a relatively low specific heat capacity and is compatible with low current heating. In a system that operates by smoking where heat is generated in short bursts using high current pulses, a stainless steel filament with a high specific heat capacity may be more appropriate.

[0112] The system includes a smoking sensor configured to detect when a user inhales air through the mouthpiece portion. The smoking sensor (not shown) is connected to a control electronic circuit 16, which 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.

[0113] To detect this increase in the rate of temperature change, the electrical circuit 16 is configured to measure the electrical resistance of the heater filament. The heater filament in this embodiment is formed from stainless steel and thus has a positive temperature coefficient of resistance. This means that as the temperature of the heater filament rises, its electrical resistance also rises. In another embodiment, the heater filament may be formed from a material having a negative temperature coefficient of resistance, so that as the temperature of the heater filaments rises, their electrical resistance decreases.

[0114] Figure 4 is a schematic diagram of the change in the resistance of the heater during user smoking. The x-axis is the time after the initial detection of user smoking and the resulting power supply to the heater. The y-axis is the electrical resistance of the heater assembly. It can be seen that the heater assembly has an initial resistance R1 before any heating occurs. R1 is obtained from the parasitic resistance R P resulting from the electrical contacts 32 and the electrical connectors 19 and the contacts between them, and the resistance R0 of the heater filament. When power is applied to the heater during user smoking, the temperature of the heater filament rises and the electrical resistance of the heater filament increases. As shown, at time t1 after a period Δt1 from the power supply from the power source to the heater, the resistance of the heater assembly is R2. Thus, the change in the electrical resistance of the heater assembly from the initial resistance to the resistance at time t1 is ΔR = R2 - R1.

[0115] In this embodiment, even when the heater filament is heated, the parasitic resistance R Pis assumed to be constant. This is because R P is due to non-heated components such as the electrical contact 32 and the electrical connector 19. R P values are assumed to be the same for all cartridges and the values are stored in the memory of the electrical circuit.

[0116] To detect a sudden increase in the temperature of the heater filament, the display of the dry state in the heater filament and the change in the resistance of the heater filament can be monitored. The electrical circuit can be configured to determine the change in resistance by determining the difference between the measured value R1 of the initial electrical resistance of the heater filament before power is supplied to the heater element, i.e., before smoking, and the measured value R2 of the electrical resistance of the heater filament after a predetermined period Δt1 from when power is supplied to the heater filament. Further, the electrical circuit can be configured to determine whether the change in resistance indicates a sudden change in temperature that is unacceptable by comparing the difference ΔR with a value ΔR max of a predetermined maximum threshold.

[0117] Both R2 and R1 are measured values, and ΔR max is stored in the memory. Ideally, the value of R1 is measured before any heating is done, i.e., before the heater is first activated. The initially measured value can be used for all subsequent smoking to avoid any errors caused by residual heat from previous smoking. Therefore, the initially measured electrical resistance before any heating can be called R 1ref .

[0118] R 1ref may be measured only once for each cartridge, the detection system is used to determine when a new cartridge is inserted, or R1 may be measured each time the system switch is turned on. However, the electrical circuit updates the measured value R 1refIt is preferably configured to be measured periodically. The predetermined period is generally 3 minutes, but can be any appropriate time required to return the heater filament from its operating temperature to room temperature. R 1ref The periodic update for R may re-adjust the electrical circuit to compensate for temperature changes at ambient temperature and changes in the state of the heater filament.

[0119] In this embodiment, the software running on the microprocessor in the electrical circuit performs the following comparison to determine a malfunction.

[0120] R2 > R 1ref +ΔR max If so, the heater is in a dry state. (1) Other malfunctions except for the dry burning state of the heater may also be detected in a similar manner. For example, if a cartridge with a heater formed of a material having a different temperature coefficient of resistance is used in the system, the electrical circuit may be configured to detect it and not supply power to it. In this embodiment, the heater filament is formed of stainless steel. A cartridge with a heater formed of Ni-Cr will have a lower temperature coefficient of resistance, which means its resistance will increase more slowly with an increase in temperature. Therefore, the value of the minimum resistance threshold ΔR min may be stored in the memory of the electrical circuit, which corresponds to the lowest temperature rise for the expected period Δt1 for the stainless steel heater element. The electrical circuit may be configured to determine a malfunction corresponding to an unauthorized cartridge present in the system when the change in resistance between R2 and R1ref is less than the value of the minimum threshold ΔR min .

[0121] That is, the system may be configured to compare R2 and R 1ref with the stored high threshold and the stored low threshold to determine a malfunction. R 1refIt may also be compared with a threshold value (or multiple threshold values) to check if it is within the expected range. These may even be multiple high stored threshold values, and different measures may be taken depending on which high threshold is exceeded. For example, if the highest threshold is exceeded, the circuit may prevent further power supply until the heater and / or the substrate are replaced. This may indicate that the substrate has been completely consumed, or that the heater is damaged or non - compliant. A lower threshold may be used to determine when the substrate is almost in a depleted state. If this lower threshold is exceeded but the higher threshold is not, the circuit may simply provide an indication such as lighting an LED, indicating that the substrate needs to be replaced soon.

[0122] R 1ref The difference between R and R2 may be continuously monitored to determine if the heater cools sufficiently between puffs. If the user smokes very frequently such that the difference does not drop below the cooling threshold between puffs, the electrical circuit may prevent or limit the power supply to the heater until the difference drops below the cooling threshold. Alternatively, a comparison may be made between the maximum value of the difference during a puff and the minimum value of the difference thereafter to determine if sufficient cooling has occurred.

[0123] Also, the difference between R1 and R2 may be continuously monitored, and the time it takes to reach the threshold value may be compared with a time threshold. If the difference between R and R2 reaches the threshold much faster or much slower than expected, this may indicate a problem such as a non - compliant heater. The rate of change can also be determined and compared with the threshold. If the difference rises very rapidly or very slowly, this may indicate a problem. These techniques may enable non - compliant heaters to be detected very quickly. 1ref If the difference between R and R2 reaches the threshold much faster or much slower than expected, this may indicate a problem such as a non - compliant heater. The rate of change can also be determined and compared with the threshold. If the difference rises very rapidly or very slowly, this may indicate a problem. These techniques may enable non - compliant heaters to be detected very quickly.

[0124] FIG. 5 is a schematic electrical circuit diagram showing a way to measure the resistance of a heating element. In FIG. 5, a heater 501 is connected to a battery 503 that provides a voltage V2. The heater resistance measured at a particular point in time is R ヒーター . An additional resistor 505 having a known resistance r is inserted in series with the heater 501 and connected to a voltage V1, which is intermediate between ground and voltage V2. A microprocessor 507 can determine both the current through the heater 501 and the voltage across the ends of the heater 501 in order to measure the resistance R ヒーター of the heater 501. Next, the resistance can be determined using the following well-known formula.

[0125]

Equation

Equation

Equation

Equation

[0126] After a malfunction is detected, the electrical circuit can subsequently control the power supply to the heater in several different ways. Alternatively, or additionally, the electrical circuit may simply indicate to the user that a malfunction has been detected. The system may include an LED or a display, or may be equipped with a microphone, and these components may be used to alert the user of the malfunction.

[0127] Figure 6 illustrates a control process for a system actuated by smoking according to the present invention. Figure 6 illustrates four consecutive smoking events, P1, P2, P3, and P4. The first smoking event P1 is a normal smoking event without any abnormal conditions. The three subsequent smoking events P2, P3, and P4 are all abnormal smoking events, with a high threshold ΔR max being exceeded.

[0128] Each smoking event is detected at time t1 when power is supplied to the heater filament. The resistance of the heater filament at time t1 is denoted as R1. The initial resistance R1 of the heater filament for the first smoking event P1 is equal to the initial resistance R 1ref measured before heating begins. The subsequent abnormal smoking events P2, P3, and P4 show an initial resistance R1 at time t1 that exceeds the initial reference resistance R 1ref . This indicates that the heater filament did not have enough time to return to room temperature between smoking events. The resistance of the heater filament is measured at time t2, after a predetermined period Δt1 following the detection of the smoking event. Each smoking event ends at time t3, and the smoking event continues for a total period of Δt puff .

[0129] In the control process of Figure 6, the electrical circuit stops the power supply to the heater until the end of the user's smoking event as soon as it is determined that the high threshold has been exceeded. This occurs at time t his shown at that point. This can be useful to prevent the heater from getting too hot even when the user smokes excessively. Similar to powering off, reaching the threshold may be indicated.

[0130] When new user smoking is detected, power is supplied to the heater again. This is shown at smoking P3 and P4. A single instance exceeding the high threshold can be the result of the user smoking very long, but several consecutive smokes during which the high threshold is exceeded is more likely to be the result of the cartridge running out rather than that. Thus, in this embodiment, when ΔR exceeds a high threshold ΔR for a specific number of consecutive smokes, typically 3 smokes, the cartridge is disabled by blowing a fuse within the cartridge. The cartridge may be disabled in other ways, for example, by cutting off further power supply to the heater filament until the cartridge is replaced or refilled, or until the user performs a reset operation. max When it exceeds, the cartridge is disabled by blowing a fuse within the cartridge. The cartridge may be disabled in other ways, for example, by cutting off further power supply to the heater filament until the cartridge is replaced or refilled, or until the user performs a reset operation.

[0131] In many embodiments, the cartridge is removable from the device. The user may remove the cartridge from the device and discard or refill the cartridge when the liquid aerosol-forming substrate of the cartridge is empty. The user may also remove a cartridge that is partially empty and still contains the liquid aerosol-forming substrate.

[0132] The user may insert a used cartridge into the device. For example, the user may insert a refilled or partially empty cartridge into the device. When the user inserts a cartridge that was recently used into the device, the heater may not have had enough time to cool to room temperature after the previous use. When the heater filament is still hot, the circuit of the device measures the initial resistance R of the heater filament 1refWhen measuring , this can skew the electrical circuit's determination of a fault, which may result in the heater filament being heated to an undesirable temperature.

[0133] Thus, the electrical circuitry may be configured to determine whether the temperature of the heater of the recently inserted cartridge is stable. In other words, the electrical circuitry may be configured to determine whether the heater of the recently inserted cartridge is at a cool temperature, typically room temperature. This is because the electrical circuitry determines the initial resistance R of the heater filament when the heater filament is hot. 1ref This may substantially prevent or inhibit measurement of the

[0134] In many embodiments, the electrical circuitry is configured to determine when a cartridge is received within the device, such that the electrical circuitry is configured to determine when a cartridge is removed from the device and when a cartridge is inserted into the device.

[0135] When the electrical circuit determines that a cartridge has been inserted into the device, it detects the initial resistance R p1 The electrical circuit can also be configured to measure the initial resistance R of the heater filament after a predetermined period of time ΔT2, typically about 1 s to about 2 s. p2 The device may be configured to measure:

[0136] The electrical circuit then relies on the measured initial resistance R p1 and R p2 The difference between p When the temperature of the heater filament is stable, the difference |ΔR p The magnitude of | is small or zero. However, the difference |ΔR p If the magnitude of | is relatively large, this indicates that the temperature of the heater filament is not stable. p If | is relatively large, this indicates that the heater filament is not hot, but is cooling down over a period of time ΔT2. The electrical circuit calculates the difference ΔRp to the value ΔR of the minimum threshold pmin and configured to determine whether the temperature of the heater filament is stable based on the comparison. The electrical circuit is configured such that if the difference |ΔR p | is greater than the value ΔR of the minimum threshold pmin , it can be determined that the temperature of the heater filament is not stable. The electrical circuit can be configured to perform the following comparison: |R p2 -R p1 |>ΔR pmin , then the temperature of the heater is not stable (6), where R p2 and R p1 are both measured values, and ΔR pmin is stored in the memory.

[0137] In some embodiments, it is understood that the electrical circuit can be configured to compare the magnitude of the difference |ΔR p | to the value ΔR of the minimum threshold. The electrical circuit can be configured to determine that the temperature of the heater filament is not stable when the magnitude of the difference |ΔR pmin | is greater than the value ΔR of the minimum threshold p . pmin

[0138] If the electrical circuit determines that the temperature of the heater filament is not stable, the electrical circuit can prevent power from being supplied to the heater filament and may not measure and store the initial resistance R 1ref . The electrical circuit can then periodically or continuously measure the subsequent primary resistance R p2 , determine the difference ΔR p1 to the initial primary resistance R p , and compare the difference ΔR p to the minimum threshold ΔR pmin until the difference is within the expected level of the heater filament at a stable temperature as close to zero as possible.

[0139] ​When the electrical circuit determines that the temperature of the heater filament is stable, the electrical circuit may be configured to determine an initial reference resistance R 1ref and perform the above normal process.

[0140] In some embodiments, after inserting a new cartridge, the electrical circuit periodically measures a single primary resistance R p1 and determines a difference ΔR p1 between the primary resistance R 1ref and a previous reference resistance R p measured and stored for the previous cartridge before the previous cartridge was removed.

[0141] Although the present invention has been described with reference to a cartridge-based system with a mesh heater, the same method of detecting defects can be used in other aerosol generation systems.

[0142] FIG. 7 illustrates an alternative system according to the present invention that also uses a liquid substrate and a capillary material. The electrically heated aerosol generation system 100 of FIG. 7 includes a housing 101 having a mouthpiece end 103 and a body end 105. At the body end, a power source in the form of a battery 107 and an electrical circuit 109 are provided. A smoking detection system 111 that is interlocked with the electrical circuit 109 is also provided. At the mouthpiece end, a liquid storage portion in the form of a cartridge 113 containing a liquid 115, a capillary core 117, and a heater 119 are provided. Note that in FIG. 7, the heater is only schematically shown. One end of the capillary core 117 extends into the cartridge 113 and the other end of the capillary core 117 is surrounded by the heater 119. The heater is connected to the electrical circuit via a connection portion 121 (not shown in FIG. 7) that may pass along the outside of the cartridge 113. The housing 101 also includes an air inlet 123, an air outlet 125 at the mouthpiece end, and an aerosol formation chamber 127.

[0143] During use, the operation is as follows. Liquid 115 is carried by capillary action from the cartridge 113 from one end of the wick 117 extending into the cartridge to the other end of the wick surrounded by the heater 119. When the user draws at the air outlet 125 with the aerosol generating system, ambient air is drawn through the air inlet 123. In the arrangement shown in FIG. 7, the smoking detection system 111 senses smoking and activates the heater 119. The battery 107 supplies electrical energy to the heater 119 to heat the end of the wick 117 surrounded by the heater. The liquid at the end of the wick 117 is vaporized by the heater 119 to produce supersaturated vapor. At the same time, the vaporized liquid is replaced by further liquid moving along the wick 117 by capillary action. The generated supersaturated vapor is mixed with the airflow from the air inlet 123 and carried in the airflow. In the aerosol formation chamber 127, the vapor condenses to form an inhalable aerosol, which is carried towards the air outlet 125 and into the user's mouth.

[0144] In the embodiment shown in FIG. 7, the electrical circuit 109 and the smoking detection system 111 are programmable as shown in the embodiments of FIGS. 1a - 1d.

[0145] The capillary wick is preferably made of various porous or capillary materials and has a known preset capillary phenomenon. By way of example, there are materials based on ceramics or graphite in the form of fibers or sintered powders. Another porous wick can be used to accommodate liquids with different physical properties such as density, viscosity, surface tension and vapor pressure. The wick must be suitable to deliver the required amount of liquid to the heater when there is sufficient liquid in the liquid storage portion.

[0146] The heater comprises at least one heating wire or filament extending around the capillary wick.

[0147] As in the system described with reference to FIGS. 1-3, the capillary material forming the core may dry out near the heater wire when the liquid in the cartridge is used up, or when the user takes very long and deep puffs. As described with reference to the system of FIGS. 1-3, the change in the resistance of the heater wire during the first portion of each puff can be used to determine if there is a problem such as a dry core.

[0148] In a system of the type illustrated in FIG. 7, due to variations in the length of the heater wire surrounding the core, there may be significant variations in heater resistance even between cartridges of the same type. The present invention is particularly advantageous because the electrical circuit does not need to store a maximum heater resistance value as a threshold, and instead an increase in resistance relative to its initially measured resistance is used.

[0149] FIG. 8 illustrates yet another aerosol generating system in which the present invention can be embodied. The embodiment of FIG. 8 is an electrically heated tobacco device in which a tobacco-based solid substrate is heated without combustion to generate an aerosol for inhalation. In FIG. 8, the components of the aerosol generating device 700 are shown in a simplified manner and the scale is not exact. Elements not relevant to the understanding of this embodiment are omitted to simplify FIG. 8.

[0150] The electrically heated aerosol generating device 200 includes a housing 203 and an aerosol forming substrate 210 such as, for example, a cigarette. The aerosol forming substrate 210 is pushed into a recess 205 whose shape is defined by the housing 203 and comes into thermal proximity with the heater 201. The aerosol forming substrate 210 releases various volatile compounds at different temperatures. By controlling the operating temperature of the electrically heated aerosol generating device 200 to be lower than the release temperature of some of the volatile compounds, the release or formation of smoke components can be avoided.

[0151] Inside the housing 203, there is a power supply 207, for example a rechargeable lithium-ion battery. The electrical circuit 209 is connected to the heater 201 and the power supply 207. The electrical circuit 209 controls the power supplied to the heater 201 in order to regulate its temperature. A detector 213 of the aerosol-forming substrate can detect the presence and identity of the aerosol-forming substrate 210 that is thermally close to the heater 201, and communicates the presence of the aerosol-forming substrate 210 to the electrical circuit 209 as a signal. Providing a detector of the substrate is optional. An airflow sensor 211 is provided within the housing and connected to the electrical circuit 209 to detect the airflow velocity through the device.

[0152] In the described embodiment, the heater 201 is an electrically resistive track (s) deposited on a ceramic substrate. The ceramic substrate is in the form of a blade and is inserted into the aerosol-forming substrate 210 during use. The heater forms part of the device and may be used to heat a number of different substrates. However, the heater may be a replaceable component and the electrical resistance of an alternative heater may be different.

[0153] The system of the type described in FIG. 8 may be a continuously heated system, in which the temperature of the heater is maintained at a target temperature while the system is on, or it may be a smoking-activated system in which the temperature of the heater is increased by supplying more power during the period in which smoking is detected.

[0154] In the case of a smoking-activated system, the operation is very similar to that described with reference to the previous embodiments. When the substrate is dry near the heater, the heater resistance rises more rapidly for a given applied power than when the substrate contains an aerosol-forming agent that can vaporize at a still relatively low temperature.

[0155] In the case of a continuously heated system, when the user smokes with the system, initially there is a temperature drop of the heater due to the cooling effect of the airflow passing through the heater. When smoking is first detected, the heater resistance can be measured and recorded as R1, and in a manner similar to that described, when the system returns the heater to the target temperature, the subsequent resistance R2 can be measured after a period Δt1 following the detection of smoking. Next, ΔR can be calculated as described above, and then compared with the threshold value stored as described above to determine whether the substrate is dry near the heater. The substrate may be dry because it is being consumed by use, or because it is old or has been stored improperly, or because it is a counterfeit and has a water content different from that of a genuine aerosol-forming substrate.

[0156] The system of FIG. 8 includes a warning LED 215 that lights up when a malfunction is detected in the electrical circuit 209.

[0157] FIG. 9 is a flowchart illustrating a method for detecting an unauthorized heater, a damaged heater, or a non-compliant heater. In a first step 300, the insertion of a cartridge containing a heater into the device is detected. Next, in step 300 the electrical resistance of the heater R 1ref is measured. This is done after power has been supplied to the heater, for a predetermined period such as 100 ms. In step 320, the measured resistance R1 is compared with the expected resistance or the range of acceptable resistances. The range of acceptable resistances takes into account the manufacturing tolerances as well as the variations between genuine heaters and substrates. If R1 is outside the expected range, the process proceeds to step 330, where a display such as an audible alarm is provided and the supply of power to the heater is prevented because the device is considered to be non-compliant. The process then returns to step 300 and waits for the detection of the insertion of a new cartridge.

[0158] Alternatively, or in addition, in step 300 the initial resistance R 1refTo measure, within a predetermined period after power is supplied to the heater, for example up to 100 ms, the rate of change of the initial resistance may be measured. This may involve performing a plurality of resistance measurements at different times within the predetermined period and then calculating the rate of change of the initial resistance from the plurality of resistance measurements and the plurality of times at which they were made. In the same way, a particular design of the heater can be expected to have an initial resistance within a range of acceptable values, and a particular design of the heater can be expected to have an initial rate of change of resistance within a range of acceptable values of the rate of change of resistance for a given applied power. The calculated initial rate of change of resistance can be compared to the range of acceptable values of the rate of change of resistance, and if the calculated rate of change of resistance is outside the acceptable range, the process proceeds to step 330.

[0159] In step 320, if it is determined that R 1ref is within the expected range of resistance, the process proceeds to step 340. In step 340, power is applied to the heater for a period Δt1, and then the difference ΔR is calculated. Advantageously, Δt1 is chosen to be a short period before significant aerosol generation. In step 350, the value of ΔR is compared to the expected value or range of acceptable values. The range of expected values also takes into account variations in the manufacture of the heater and the substrate assembly in this case. If the value of ΔR is outside the expected range, the heater is considered non - compliant and the process goes to step 330 as described above and then back to step 300. If the value of ΔR is within the expected range, the process proceeds to step 360, where power is supplied to the heater so that aerosol can be generated according to the user's requirements.

[0160] The present invention has been described with reference to three different types of electrically heated aerosol generation systems, but it will be apparent that the present invention is applicable to other electrically heated aerosol generation systems.

[0161] The present invention should also be apparent that it may be implemented within an existing aerosol generation system as a computer program product for execution on a programmable controller. The computer program product may be provided as one of downloadable software or on a computer-readable medium such as a compact disc.

[0162] The above exemplary embodiments illustrate but do not limit. In light of the exemplary embodiments discussed above, other embodiments consistent with the above exemplary embodiments will be apparent to those skilled in the art.

Claims

1. An electrically operated aerosol generation system comprising: a heating element; a power source; and an electrical circuit connected to the heating element and the power source, the electrical circuit being configured to: measure an initial electrical resistance of the heating element before the heating element is heated by power supplied from the power source; measure a subsequent electrical resistance of the heating element after the measurement of the initial electrical resistance and after power supply from the power source to the heating element has been started, and during user smoking in the system; determine a difference between the initial electrical resistance and the subsequent electrical resistance; compare the difference with a cooling threshold; and prevent or limit power supply to the heating element when the difference exceeds the cooling threshold until the difference falls below the cooling threshold. An electrically operated aerosol generation system.

2. The electrically operated aerosol generation system according to claim 1, wherein the electrical circuit is configured to continuously monitor the difference between the initial electrical resistance and the subsequent electrical resistance.

3. An electrically operated aerosol generation system comprising: a heating element; a power source; and an electrical circuit connected to the at least one heating element and the power source, the electrical circuit being configured to: measure an initial electrical resistance of the heating element before the heating element is heated by power supplied from the power source; measure a subsequent electrical resistance of the heating element after the measurement of the initial electrical resistance and after power supply from the power source to the heating element has been started; determine a difference between the initial electrical resistance and the subsequent electrical resistance; continuously monitor the difference between the initial electrical resistance and the subsequent electrical resistance; determine a maximum value of the difference during user smoking in the system; determine a minimum value of the difference between multiple user smokes in the system; compare the maximum value of the difference during smoking with the minimum value of the difference between multiple user smokes; and determine whether sufficient cooling of the at least one heating element occurs between multiple user smokes based on the comparison. An electrically operated aerosol generation system.

4. The electrically operated aerosol generation system according to claim 3, wherein the electrical circuit is further configured to prevent or limit power supply to the at least one heating element until it is determined that sufficient cooling occurs between multiple user smokes.

5. An electrically operated aerosol generating system according to any one of claims 1 to 4, comprising a smoking sensor for detecting when a user is smoking in the system, and optionally, the electrical circuit is connected to the smoking sensor, and the electrical circuit is configured to supply power to the heating element when smoking is detected by the smoking sensor.

6. An electrically operated aerosol generating system according to any one of claims 1 to 5, 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.

7. The electrical circuit is configured to determine when the electrical circuit is connected to the heating element, and further configured to measure an initial electrical resistance of the heating element within a predetermined period after the heating element is connected to the electrical circuit. An electrically operated aerosol generating system according to claim 6.

8. A heating element, and an electrical circuit connected to the heating element and comprising a memory, the electrical circuit being configured to measure an initial electrical resistance of the heating element before the heating element is heated by power supplied from a power source to the heating element, configured to measure a subsequent electrical resistance of the heating element during a user's smoking after the measurement of the initial electrical resistance and after power supply from the power source to the heating element is started, configured to determine a difference between the initial electrical resistance and the subsequent electrical resistance, configured to compare the difference with a cooling threshold value, and configured to prevent or limit power supply to the heating element when the difference exceeds the cooling threshold value until the difference falls below the cooling threshold value. A heater assembly.

9. A heating element, and an electrical circuit connected to the heating element and comprising a memory, the electrical circuit being configured to measure an initial electrical resistance of the heating element before the heating element is heated by power supplied from a power source to the heating element, configured to measure a subsequent electrical resistance of the heating element after the measurement of the initial electrical resistance and after power supply from the power source to the heating element is started, configured to determine a difference between the initial electrical resistance and the subsequent electrical resistance, configured to continuously monitor the difference between the initial electrical resistance and the subsequent electrical resistance, configured to determine a maximum value of the difference during a user's smoking, and configured to determine a minimum value of the difference between multiple user smokes. Compare the maximum value of the difference during smoking with the minimum value of the difference between multiple user smokings, configured to determine, based on the comparison, whether sufficient cooling of the at least one heating element occurs between multiple user smokings, a heater assembly.

10. An electrically operated aerosol generating device for an electrically operated aerosol generating system, a power source, an electric circuit connected to the power source and having a memory, the electric circuit being, during use, connected to a heating element of the electrically operated aerosol generating system, measuring an initial electrical resistance of the heating element before the heating element is heated by the power supplied from the power source to the heating element, after the measurement of the initial electrical resistance and after the power supply from the power source to the heating element is started, measuring a subsequent electrical resistance of the heating element during a user smoking in the system, determining a difference between the initial electrical resistance and the subsequent electrical resistance, comparing the difference with a cooling threshold value, an electrically operated aerosol generating device configured to prevent or limit the power supply to the heating element until the difference falls below the cooling threshold value when the difference exceeds the cooling threshold value.

11. An electrically operated aerosol generating device for an electrically operated aerosol generating system, a power source, an electric circuit connected to the power source and having a memory, the electric circuit being, during use, connected to a heating element of the electrically operated aerosol generating system, measuring an initial electrical resistance of the heating element before the heating element is heated by the power supplied from the power source to the heating element, after the measurement of the initial electrical resistance and after the power supply from the power source to the heating element is started, measuring a subsequent electrical resistance of the heating element, determining a difference between the initial electrical resistance and the subsequent electrical resistance, continuously monitoring the difference between the initial electrical resistance and the subsequent electrical resistance, determining a maximum value of the difference during user smoking, determining a minimum value of the difference between multiple user smokings, comparing the maximum value of the difference during smoking with the minimum value of the difference between multiple user smokings, an electrically operated aerosol generating device configured to determine, based on the comparison, whether sufficient cooling of the at least one heating element occurs between multiple user smokings.

12. An electric circuit for an electrically operated aerosol generating system, which is connected to a heating element and a power source of the electrically operated aerosol generating system during use and comprises a memory, measuring an initial electrical resistance of the heating element before the heating element is heated by the power supplied from the power source to the heating element, measuring a subsequent electrical resistance of the heating element after the measuring of the initial electrical resistance and after the power supply from the power source to the heating element has been started and during user smoking in the system, determining a difference between the initial electrical resistance and the subsequent electrical resistance, comparing the difference with a cooling threshold value, An electric circuit configured to prevent or limit the power supply to the heating element when the difference exceeds the cooling threshold value until the difference falls below the cooling threshold value.

13. An electric circuit for an electrically operated aerosol generating system, which is connected to a heating element and a power source of the electrically operated aerosol generating system during use and comprises a memory, measuring an initial electrical resistance of the heating element before the heating element is heated by the power supplied from the power source to the heating element, measuring a subsequent electrical resistance of the heating element after the measuring of the initial electrical resistance and after the power supply from the power source to the heating element has been started, determining a difference between the initial electrical resistance and the subsequent electrical resistance, continuously monitoring the difference between the initial electrical resistance and the subsequent electrical resistance, determining a maximum value of the difference during user smoking, determining a minimum value of the difference between multiple user smokes, comparing the maximum value of the difference during smoking with the minimum value of the difference between multiple user smokes, An electric circuit configured to determine, based on the comparison, whether sufficient cooling of the at least one heating element occurs between multiple user smokes.

14. A method for controlling the power supply to a heating element in an electrically operated aerosol generating system, the system comprising a heating element and a power source for supplying power to the heating element, the method comprising: measuring an initial electrical resistance of the heating element before the heating element is heated by the power supplied from the power source to the heating element; measuring a subsequent electrical resistance of the heating element after the measuring of the initial electrical resistance and after the power supply from the power source to the heating element has been started and during user smoking in the system; determining a difference between the initial electrical resistance and the subsequent electrical resistance; comparing the difference with a cooling threshold value; when the difference exceeds the cooling threshold value, preventing or restricting the power supply to the heating element until the difference falls below the cooling threshold value. A method comprising the steps of:

15. A method of controlling power supply to a heating element in an electrically operated aerosol generating system, the system comprising a heating element and a power source for supplying power to the heating element, the method comprising: measuring an initial electrical resistance of the heating element before the heating element is heated by the power supplied from the power source to the heating element; measuring a subsequent electrical resistance of the heating element after the measurement of the initial electrical resistance and after the power supply from the power source to the heating element is started; determining a difference between the initial electrical resistance and the subsequent electrical resistance; continuously monitoring the difference between the initial electrical resistance and the subsequent electrical resistance; determining a maximum value of the difference during user smoking in the system; determining a minimum value of the difference between multiple user smokes in the system; comparing the maximum value of the difference during smoking with the minimum value of the difference between multiple user smokes; determining, based on the comparison, whether sufficient cooling of the at least one heating element occurs between multiple user smokes. A method comprising the steps of:

16. A computer program product loadable directly into an internal memory of a microprocessor, the internal memory comprising software code portions for performing the steps of claim 14 or 15 when the product is executed on a microprocessor in an electrically operated aerosol generating system, the system comprising a heating element and a power source for supplying power to the heating element, the microprocessor being connected to the heating element and the power source. A computer program product.

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