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 generating system. Aspects of the present invention are directed to electrically heated aerosol generating systems and methods for operating electrically heated aerosol generating systems. Some described embodiments relate to a system capable of detecting abnormal changes in the electrical resistance of a heater element, which may indicate a malfunction in the heater element. For example, a malfunction may indicate a depleted level of aerosol-forming substrate within the system. In some described embodiments, the system may be effective for heater elements having different electrical resistances. In other embodiments, 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 applied to electrically heated smoking systems. [Background technology]

[0002] International Patent Publication No. 2012 / 085203 discloses an electrically heated smoking system comprising a liquid reservoir for storing a liquid aerosol-forming substrate, an electric heater with at least one heating element for heating the liquid aerosol-forming substrate, and an electrical circuit configured to determine consumption 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 electrical circuit is configured to calculate the rate of temperature rise of the heating element, where 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 with a threshold value stored in memory during manufacture. If the rate of temperature rise exceeds the threshold, the system may stop supplying power to the heater.

[0003] The system of WO 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 that the system is optimized for heater elements with a particular electrical resistance or range of resistances.

[0004] However, it may be desirable to enable the system to operate with different heaters. Typically, in systems of the type described in WO 2012 / 085203, the heater is provided in a disposable cartridge along with a quantity of 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 with the system to provide different user experiences. The WO 2012 / 085203 system is optimized for heaters with known specific electrical resistances that are determined during system manufacture for use in the system.

[0005] In electrically heated aerosol generating systems, and particularly in systems that can operate with different heaters, it would be desirable to have an alternative system for determining when the heater has dried out or other malfunction in the heater.

[0006] In electrically heated aerosol generating systems that have permanent device parts and consumable parts, including an aerosol-forming substrate, it would be desirable for the manufacturer of the device to be able to easily determine whether the consumable parts are "genuine" or consumables that are considered compatible with the device. This applies to both systems in which the heater is a consumable component and systems in which 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 generation system, the electrically operated aerosol generation system comprising: an electric heater comprising at least one heating element for heating the aerosol-forming substrate; Power supply and an electric circuit connected to an electric heater and a power source and having a memory, the electric circuit comprising: Measure the initial electrical resistance of the electric heater, After measuring the initial electrical resistance, measure the electrical resistance of the electric heater thereafter, determining the difference between the initial electrical resistance and the subsequent electrical resistance; determining a fault when the determined difference between the initial electrical resistance and the subsequent electrical resistance is greater than a maximum threshold value or less than a minimum threshold value stored in memory; and and an electrical circuit configured to control power supplied to the electric heater based on whether a malfunction is determined, or to provide an indication if a malfunction is determined.

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

[0009] Another fault is the presence of a counterfeit, incompatible, or damaged heater in a system with replicable or disposable heaters. If the resistance of a heater element rises more quickly than expected for a given applied power, this may be because the heater is counterfeit and has different electrical characteristics than an authentic heater, or it may be because the heater has been damaged in some way. In either case, the electrical circuit may be configured to prevent power from being supplied to the heater.

[0010] Another problem is the presence of a counterfeit, incompatible, old, or damaged aerosol-forming substrate in the system. If the resistance of the heater element increases more quickly than expected for a given applied power, this may indicate that the aerosol-forming substrate is counterfeit or old, and therefore has a higher or lower moisture content than expected. For example, if a solid aerosol-forming substrate is used, the substrate may be very old or dry if it has not been properly stored. If the substrate is drier than expected, less energy is used for vaporization than expected, and the heater temperature will increase more quickly. 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 electric heater, the system does not need to determine the actual temperature of the heating element or have any pre-stored knowledge of the heating element's resistance at a given temperature. This allows for the use of different approved heaters in the system without triggering a fault, and also allows for variations in absolute resistance due to manufacturing tolerances of heaters of the same type. This also allows for the detection of incompatible heaters.

[0012] The electrical circuit may be configured to measure the initial electrical resistance of the heater element and the electrical resistance of the heater element at a time after the initial delivery of power from the power source to the electric 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, it can be assumed that the heater element is at or near room temperature at the time of measurement. Because 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 establish a narrower band of expected behavior.

[0013] The initial resistance may be calculated as the measured initial resistance minus assumed parasitic resistances resulting from other electrical components and electrical contacts in the system.

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

[0015] The electrical circuitry may be configured to detect the insertion and removal of the cartridge into and from the device. The electrical circuitry may be configured to measure the initial electrical resistance of the heater when the cartridge is first inserted into the device, but before any significant heating occurs. The electrical circuitry may compare the measured initial resistance with a range of acceptable electrical resistances stored in memory. If the initial resistance is outside the range of acceptable resistances, it may be considered counterfeit, incompatible, or damaged. In that case, the electrical circuitry may be configured to prevent the delivery of power 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 different sized heaters. A 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 disposed of when depleted of the aerosol-forming substrate.

[0018] An aerosol-forming substrate is a substrate capable of releasing 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 that are 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 former. The aerosol former is any suitable known compound or mixture of compounds that facilitates the formation of a dense, stable aerosol in use and that is substantially resistant to thermal decomposition at the operating temperatures of the system. Suitable aerosol formers are well known in the art and include, but are not limited to, polyhydric alcohols (such as triethylene glycol, 1,3-butanediol, and glycerin), 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). Preferred aerosol formers are polyhydric alcohols or mixtures thereof (such as triethylene glycol, 1,3-butanediol, and glycerin, most preferred). The aerosol-forming substrate may also contain other additives and ingredients, such as flavorings.

[0020] The cartridge may include a liquid aerosol-forming substrate. For liquid aerosol-forming substrates, certain physical properties of the substrate, such as vapor pressure or viscosity, are selected to make it suitable for use in the aerosol generating system. The liquid preferably includes a tobacco-containing material containing volatile tobacco flavor compounds that are released from the liquid when heated. Alternatively or additionally, the liquid may include non-tobacco materials. The liquid may include water, ethanol or other solvents, plant extracts, nicotine solutions, and natural or artificial flavors. Preferably, the liquid further includes an aerosol former. Examples of suitable aerosol formers are glycerin and propylene glycol.

[0021] An advantage of providing a liquid reservoir is that the liquid therein is protected from ambient air. In some embodiments, ambient light is likewise prevented from entering the liquid reservoir, so that light-induced degradation of the liquid can be avoided. Furthermore, a high level of hygiene can be maintained.

[0022] Preferably, the liquid reservoir is arranged to hold liquid for a predetermined number of puffs. If the liquid reservoir is not refillable and the liquid in the liquid reservoir is used up, the user must replace the liquid reservoir. Contamination of the user by the liquid during such replacement must be prevented. Alternatively, the liquid reservoir may be refillable. In that case, the aerosol generation system may be replaced after a certain number of refills of the liquid reservoir.

[0023] Alternatively, the aerosol-forming substrate may be a solid substrate. The aerosol-forming substrate may comprise a tobacco-containing material containing volatile tobacco flavor compounds that are released from the substrate upon heating. Alternatively, the aerosol-forming substrate may comprise a non-tobacco material. The aerosol-forming substrate may further comprise 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 may comprise, for example, one or more of powder, granules, pellets, shreds, spaghetti, strips, or sheets, including one or more of herb leaves, tobacco leaves, tobacco stem fragments, reconstituted tobacco, homogenized tobacco, extruded tobacco, cast leaf tobacco, and expanded tobacco. The solid aerosol-forming substrate may be in loose form or may be provided in a suitable container or cartridge. Optionally, the solid aerosol-forming substrate may comprise additional tobacco or non-tobacco volatile flavor compounds that are released upon heating of the substrate. The solid aerosol-forming substrate may also contain capsules, for example, containing additional tobacco or non-tobacco volatile flavor compounds, which may dissolve during heating of the solid aerosol-forming substrate.

[0025] "Homogenized tobacco," as used herein, refers to a material formed by agglomerating particulate tobacco. The homogenized tobacco may be in the form of a sheet. The homogenized tobacco material may have an aerosol former content of greater than 5% on a dry weight basis. Alternatively, the homogenized tobacco material may have an aerosol former content of between about 5 and about 30 weight percent on a dry weight basis. The homogenized tobacco material sheet may be formed by agglomerating particulate tobacco obtained by grinding or otherwise comminuted one or both of tobacco lamina and tobacco stems. Alternatively, or additionally, the homogenized tobacco material sheet may include one or more of tobacco dust, tobacco fines, and other particulate tobacco by-products formed, for example, during tobacco processing, handling, and transportation. The homogenized tobacco material sheet may include one or more inherent binders (i.e., tobacco intrinsic binders), one or more extrinsic binders (i.e., tobacco extrinsic binders), or a combination thereof to aid in the cohesion of the particulate tobacco, although alternatively or additionally, the homogenized tobacco material sheet may include other additives, including but not limited to tobacco and non-tobacco fibers, aerosol formers, humectants, plasticizers, flavorings, 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 take the form of a powder, granules, pellets, pieces, spaghetti, strips, or sheets, etc. Alternatively, the carrier may be a tubular carrier having a thin layer of the solid substrate disposed on its interior surface, its exterior surface, or both its interior and exterior surfaces. Such a tubular carrier may be formed, for example, of paper or paper-like material, nonwoven carbon fiber mat, low-mass open-mesh metal screen, or perforated metal foil, or any other thermally stable polymeric matrix.

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

[0028] The electrical circuit may be configured to detect the insertion and removal of an aerosol-forming substrate into and 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 any significant heating occurs. The electrical circuit may compare the measured initial resistance with a range of acceptable electrical resistances stored in memory. If the initial resistance is outside the range of acceptable resistances, the aerosol-forming substrate may be considered counterfeit, incompatible, or damaged. In that case, the electrical circuit may be configured to prevent the supply of power 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 multiple heating elements, for example, two, three, four, five, six, or more heating elements. The heating element(s) may be appropriately arranged to most effectively heat the liquid aerosol-forming substrate.

[0030] Preferably, at least one electric heating element comprises 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), carbon, graphite, metals, alloys, and composites made of ceramic and metallic materials. Such composites may include doped 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-, cobalt-, chromium-, aluminum-, titanium-, zirconium-, hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese-, and iron-containing alloys, as well as nickel-, iron-, cobalt-, and stainless steel-based superalloys, Timetal®, iron-aluminum-based alloys, and iron-manganese-aluminum-based alloys. Timetal® is a registered trademark of Titanium Metals Corporation. In composite materials, the electrically resistive material may optionally be embedded, encapsulated, or coated with an insulating material, or vice versa, depending on the required energy transfer kinetics and external physicochemical properties. The heating element may include a metallic, etched foil insulated between two layers of inert material. In this case, the inert material may include Kapton®, an all-layer polyimide, or mica foil. Kapton® is a registered trademark of EI du Pont de Nemours and Company.

[0031] The at least one electric heating element may take any suitable form. For example, the at least one electric heating element may take the form of a heating blade. Alternatively, the at least one electric heating element may take the form of a casing or substrate with different conductive sections or electrically resistive metal tubes. The liquid reservoir may incorporate a disposable heating element. Alternatively, one or more heating needles or rods that penetrate the liquid aerosol-forming substrate may also be suitable. Alternatively, the at least one electric heating element may comprise a flexible sheet of material. Other alternatives include a heating wire or filament, such as a wire or heating plate made of Ni-Cr (nickel-chromium), platinum, tungsten, or an alloy. Optionally, the heating element may be disposed within or on a rigid carrier material.

[0032] In one embodiment, the heating element comprises a mesh, array, or fabric of conductive filaments, which may define interstices between the filaments, and the interstices may have a width between 10 μm and 100 μm.

[0033] The conductive filaments may form a mesh with a size of 160 to 600 mesh US (±10%) (i.e., 160 to 600 filaments per inch (±10%)). The gap width is preferably 25 μm to 75 μm. The open area ratio of the mesh, which is the ratio of the gap area to the total area of ​​the mesh, is preferably 25 to 56%. The mesh may be formed using different types of weave or lattice structures. Alternatively, 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 or flat cross section.

[0035] The area of ​​the mesh, array or fabric of conductive filaments may be small, 25 mm2 Preferably, the conductive filament mesh, array, or fabric is rectangular, for example, measuring 5 mm x 2 mm. Preferably, the conductive filament mesh or array covers an area of ​​10% to 50% of the area of ​​the heater assembly. More preferably, the conductive filament mesh or array covers an area of ​​15% to 25% of the area of ​​the heater assembly.

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

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

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

[0039] In use, the aerosol-forming substrate is preferably in contact with a heating element.

[0040] The electrically operated aerosol generating system preferably further comprises a capillary material for conveying the liquid aerosol-forming substrate from the liquid reservoir to the electric heater element.

[0041] Preferably, a capillary material is positioned to contact the liquid in the liquid storage portion. Preferably, a capillary wick extends into the liquid storage portion. In use, the liquid is then transferred from the liquid storage portion to the electric heater by capillary action within the capillary wick. In one embodiment, the capillary wick has a first end and a second end, the first end extending into the liquid storage portion for contacting the liquid therein, and the electric heater is positioned to heat the liquid in the second end. When the heater is activated, the liquid at the second end of the capillary wick is vaporized by at least one heating element of the heater to form a supersaturated vapor. The supersaturated vapor mixes with and is carried in the airflow. During the flow, the vapor condenses to form an aerosol, which is carried toward the user's mouth. The liquid aerosol-forming substrate has physical properties, including viscosity and surface tension, that allow the liquid to be transported through the capillary wick by capillary action.

[0042] The capillary wick may have a fibrous or spongy structure. Preferably, the capillary wick comprises a bundle of capillaries. For example, the capillary wick may comprise a plurality of fibers or threads, or other fine tubes. The fibers or threads may be generally aligned along the longitudinal axis of the aerosol generation system. Alternatively, the capillary wick may comprise a spongy or foam-like material formed into a rod shape. The rod shape may extend along the longitudinal axis of the aerosol generation system. The wick structure forms a plurality of small holes or tubes through which liquid can be transported by capillary action. The capillary wick may comprise 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 metal or plastic materials, and fibrous materials made from spun or extruded fibers (such as cellulose acetate, polyester, or bonded polyolefin, polyethylene, terylene, or polypropylene fibers, nylon fibers, or ceramics). The capillary wick may have any suitable capillary and porosity for use with different liquid physical properties. Liquids have physical properties, including but not limited to viscosity, surface tension, density, thermal conductivity, boiling point, and vapor pressure, that allow them to be transported through a capillary device by capillary action.

[0043] The heating element may be in the form of a heated wire or filament that surrounds and optionally supports the capillary wick. During normal use, when there is a lot of aerosol-forming substrate, the capillary properties of the wick, combined with the liquid properties, ensure that the wick remains wet within the heated area.

[0044] Alternatively, as described, the heater element may include a mesh formed from a plurality of conductive filaments. A 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, where a first capillary material in contact with the heater element has a higher thermal decomposition temperature and a second capillary material in contact with the first capillary material but not the heater element has a lower thermal decomposition temperature. The first capillary material effectively serves as a spacer separating the heater element from the second capillary material, preventing the second capillary material from being exposed to temperatures above its thermal decomposition temperature. As used herein, "thermal decomposition temperature" refers to the temperature at which a material begins to decompose and lose mass by generating gaseous by-products. The second capillary material may advantageously occupy a larger volume than the first capillary material and may hold more aerosol-forming substrate than the first capillary material. The second capillary material may have better wick performance than the first capillary material. The second capillary material may be less expensive or have a higher filling capacity than the first capillary material. The second capillary material may be polypropylene.

[0046] The power source may be any suitable power source, such as a DC voltage supply. In one embodiment, the power source is a lithium-ion battery. Alternatively, 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 for the storage of sufficient energy for one or more aerosol-generating experiences. For example, the power source may have a capacity sufficient to allow continuous aerosol generation for approximately six minutes, or a multiple of six 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 for a predetermined number of puffs or discontinuous activation of the heater.

[0047] The aerosol generation 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 composites containing one or more of these materials, or thermoplastics suitable for food or pharmaceutical applications, such as polypropylene, polyetheretherketone (PEEK), and polyethylene. Preferably, the material is lightweight and not brittle.

[0048] The electrically heated aerosol generating system is preferably portable. The electrically heated aerosol generating system may be comparable in size to a conventional cigar or cigarette. The overall length of the electrically heated aerosol generating system may be between approximately 30 mm and approximately 150 mm. The outer diameter of the electrically heated aerosol generating system may be between approximately 5 mm and approximately 30 mm.

[0049] Preferably, the electrical circuitry comprises a microprocessor, 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 circuitry may comprise additional electrical components. The system may comprise a temperature sensor.

[0050] If a fault is detected, the system does nothing more than provide an indication to the user that a fault has been detected. This may be done by providing a visual, audible, or tactile warning. Alternatively, or additionally, the electrical circuitry may automatically limit or otherwise control the power supplied to the heater when a fault is detected.

[0051] There are many possible ways in which the electrical circuit can be configured to control the power supplied to the electric heater when a malfunction is detected. If insufficient aerosol-forming substrate is delivered to the heating element, 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 to both ensure a consistent and enjoyable experience for the user and to mitigate the possibility of overheating and the generation of undesirable compounds in the aerosol. The power supply to the heater may be stopped or limited. The power supply may be stopped or limited for a short period of time. However, it is preferred that the power supply be stopped or limited until the heater or aerosol-forming substrate is replaced.

[0052] For example, a 6 W pulse may be delivered to the heater initially during a puff. If a malfunction is determined during the puff, power delivery may be limited to 5 W pulses for the remainder of the puff. In some embodiments, the electrical circuit may be configured to deliver unlimited 6 W pulses to the heater in subsequent puffs until a further malfunction is determined. However, in another preferred embodiment, the electrical circuit may be configured to deliver limited 5 W pulses to the heater in subsequent puffs until the heater or aerosol-forming substrate is replaced.

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

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

[0055] The electrical circuit may be configured to supply a predetermined power to the heater element for a period Δt1 following the detection of an initial puff or the initial application of power to the heater, and the electrical circuit may be configured to determine a change in the heater element's electrical resistance based on measuring the heater element's electrical resistance during the period t1 between each puff. The period Δt1 may be selected to occur immediately after the detection of the initial puff or immediately after the initial application of power to the heater. This is particularly advantageous if the circuit detects an incompatible or counterfeit heater or aerosol-forming substrate during first use following replacement of a disposable cartridge. For example, a typical puff may last 3 seconds, and the puff detector's response time may be approximately 100 ms. Δt1 may then be selected to be 100 ms to 500 ms during the puff before the heater temperature stabilizes. Alternatively, the period Δt1 may be selected to correspond to the period during which the temperature of the heating element is expected to stabilize.

[0056] The electrical circuitry may be configured to prevent power from being supplied from the power source to the heater element if a malfunction is determined after a predetermined number of consecutive or successive user puffs. The predetermined number of consecutive or successive puffs may be any suitable number. For example, the predetermined number of consecutive or successive puffs may be 1, 2, 3, 4, 5, or 6 puffs. Preferably, the predetermined number of consecutive or successive puffs is 3 puffs.

[0057] The electrical circuitry may be configured to continually determine whether a malfunction is present, limit or prevent power supply to the heater when a malfunction is present, and continue to prevent or reduce power supply to the heater element until the malfunction is eliminated.

[0058] In liquid and wick-based systems, excessive puffs can result in the wick drying 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 it does not get too hot and generate undesirable aerosol components. As soon as a malfunction is detected, power to the heater may be shut off until the next user puff.

[0059] Similarly, excessive puffs may not allow the heater to cool as expected between puffs, resulting in a gradual, undesirable increase in heater temperature between puffs. This is true for liquid or solid aerosol-forming substrate-based systems. When a malfunction is determined, the electrical circuit may be configured to prevent or limit power supply for the remaining puffs to slow the undesirable increase in heater temperature between puffs and continue to limit power supply to the heater element for subsequent puffs until the malfunction is eliminated. The electrical circuit may be configured to disable the heater element or permanently or irreversibly prevent or inhibit power supply from the power source to the heater element if a malfunction is determined after a predetermined number of sequential or consecutive user puffs. As used herein, the term "disable" means to render 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 after three consecutive puffs.

[0060] The electrical circuit may be configured to prevent power from being supplied to the heater element for a predetermined shutdown period in the event of a malfunction.

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

[0062] Alternatively, or additionally, the electrical circuitry may be configured to continuously calculate whether the difference between the initial resistance and the subsequent resistance reaches a maximum or minimum threshold value, compare the time it took for the difference to reach the threshold value with a stored time value, and determine that there is a malfunction and prevent or reduce power to the heater if the time it took to reach the threshold value is less than the stored time value, or if the difference does not reach the threshold value within an expected period of time. If the threshold value is reached more quickly than expected, this may indicate a dry-fired heater element or dry-fired substrate, or may indicate an incompatible, counterfeit, or damaged heater. Similarly, if the threshold value is not reached within the expected period of time, this may indicate a counterfeit or damaged heater or substrate. This may allow for quick determination of a counterfeit, damaged, or incompatible heater or substrate.

[0063] Finding a fault may indicate not only a dry condition in the heater element, but also a heater with electrical characteristics outside of an expected range. This may be because the heater is defective, because materials have accumulated on the heater over its lifespan, or because it is an unauthorized or counterfeit heater. For example, if a 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 resistance. Furthermore, the difference between the heater's initial electrical resistance and its subsequent resistance may be expected to be particularly valuable because it is related to the heater element's material. The electrical circuit may be configured to determine a fault when the difference between the heater's initial electrical resistance and its subsequent electrical resistance is outside of an expected range of values ​​and to limit or prevent power to the heater based on the result. This may prevent the use of some unauthorized heaters.

[0064] Different thresholds may be used to generate different control strategies for different conditions. For example, a maximum threshold and a minimum threshold may be used to set a boundary requiring replacement of the heater of the substrate before further power is applied. The electrical circuit may be configured to prevent power from being applied to the heater until the heater or aerosol-forming substrate is replaced if the difference exceeds the maximum threshold or is less than the minimum threshold. One or more intermediate thresholds may be used to detect excessive puffing behavior resulting in a dry condition in the heater. The electrical circuit may be configured to prevent power from being applied to the heater for a specified period of time or until a subsequent user puff if the intermediate threshold is exceeded but not the maximum threshold. One or more intermediate thresholds may also be used to trigger an indication to the user that the aerosol-forming substrate is nearly worn out and will soon need to be replaced. The electrical circuit may be configured to provide an indication, which may be visual, audible, or tactile, if the intermediate threshold is exceeded but not the maximum threshold.

[0065] One process for detecting counterfeit, damaged, or incompatible heaters is to check the heater's resistance or the rate of change of its resistance when the heater is first used or inserted into a device or system. The electrical circuit may be configured to measure the initial resistance of the heater element within a predetermined period of time after power is applied to the heater. The predetermined period may be short, ranging from 50 ms to 200 ms. For heaters with mesh heating elements, the predetermined period may be approximately 100 ms. Preferably, the predetermined period is between 50 ms and 150 ms. The electrical circuit may be configured to measure the initial resistance of the heater, apply power to the heater to heat the aerosol-forming substrate using a much lower power as a separate routine, or measure the initial resistance of the heater for the first short time after the heater is activated before 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 application to the electric heater until the heater or aerosol-forming substrate is replaced or provide an indication.

[0066] If the initial resistance is within an acceptable range of values, the electrical circuitry may be configured to determine that an acceptable heater is present and control the power supplied to the electric heater based on whether an acceptable heater is present, or to provide an indication if an acceptable heater is not present.

[0067] The electrical circuitry may be configured to determine that an acceptable heater is present within one second of first applying power to the heater.

[0068] In a second aspect, there is provided a heater assembly for use in an electrically powered aerosol generating system, such as the electrically powered aerosol generating system of the first aspect or an electrically powered aerosol generator, the heater assembly comprising: an electric heater comprising at least one heating element; An electric circuit connected to an electric heater and having a memory, comprising: Measure the initial electrical resistance of the electric heater, After measuring the initial electrical resistance, measure the electrical resistance of the electric heater thereafter, 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 a maximum threshold value or less than a minimum threshold value stored in memory; and and an electrical circuit configured to control power supplied to the electric heater based on whether a malfunction is determined or to provide an indication if a malfunction exists.

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

[0070] In a third aspect, there is provided an electrically actuated aerosol generating device for use in an electrically actuated aerosol generating system, such as the electrically actuated aerosol generating system of the first aspect, the electrically actuated aerosol generating device comprising: Power supply and 1. An electrical circuit connected to a power source and having a memory, the electrical circuit comprising: In use, the device is connected to an electric heater in an electrically operated aerosol generating system; Measure the initial electrical resistance of the electric heater, After measuring the initial electrical resistance, measure the electrical resistance of the electric heater thereafter, determining the difference between the initial electrical resistance and the subsequent electrical resistance; determining that a fault exists when the determined difference between the initial electrical resistance and the subsequent electrical resistance is greater than a maximum threshold value or less than a minimum threshold value stored in memory; and and an electrical circuit configured to control power supplied to the electric heater based on whether a malfunction is determined, or to provide an indication if a malfunction is determined.

[0071] In a fourth aspect of the present invention there is provided an electrical circuit for an electrically powered aerosol generation system, such as the electrically powered aerosol generation system of the first aspect, or an electrically powered aerosol generation device, such as the electrically powered aerosol generation device of the third aspect, wherein, in use, the electrical circuit is connected to an electric heater and a power source, the electrical circuit comprising a memory, and Measure the initial electrical resistance of the electric heater, measuring a subsequent electrical resistance of the electric heater after said measuring of said initial electrical resistance; determining the difference between the initial electrical resistance and the subsequent electrical resistance; determining a fault when the determined difference between the initial electrical resistance and the subsequent electrical resistance is greater than a maximum threshold value or less than a minimum threshold value stored in memory; and The system is configured to control the power supplied to the electric heater based on whether a malfunction is determined, or to provide an indication if a malfunction is determined.

[0072] In use, the electrical circuitry may further be connected to a smoke detector for detecting when a user is taking a puff on the system, the electrical circuitry further comprising: Determine when the electric circuit is connected to the electric heater; measuring the initial resistance of the electric heater within a predetermined period of time after the electric circuit is connected to the electric heater; supplying power to the heating element from the power source when smoke is detected by the smoke detector; measuring the subsequent resistance of the electric heater within a predetermined period of time after the supply of power from the power source to the electric heater is initiated; Determine the difference between the subsequent resistance and the initial electrical resistance, comparing the difference between the subsequent resistance and the initial resistance to at least one of a maximum threshold value and a minimum threshold value stored in memory; determining that there is a fault if the difference is greater than a maximum threshold value or less than a minimum threshold value; and It may be configured to limit the power supplied to the electric heater during a puff if a malfunction is determined, or to prevent power from being supplied to the electric heater for the remainder of the puff based on whether a malfunction is determined.

[0073] In some embodiments, the electrical circuitry further comprises: Store the failure decision in memory, determining a number of consecutive failure determinations based on the stored failure determinations; and The cartridge may be configured to be disabled if the number of consecutive determined failure determinations is greater than a maximum threshold value.

[0074] The electrical circuit may be configured to disable 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 supply of power to an electric heater in an electrically powered aerosol generating system, such as the electrically powered aerosol generating system of the first aspect, or an electrically powered aerosol generating device, such as the electrically powered aerosol generating device of the third aspect, the system or method comprising at least one heating element for heating an aerosol-forming substrate, and a power supply for supplying power to the electric heater, the method comprising: providing power to an electric heater; measuring the initial electrical resistance of the electric heater; measuring the electrical resistance of the electric heater after the initial electrical resistance measurement; determining the difference between the initial electrical resistance and the subsequent electrical resistance; determining a fault when the determined difference between the subsequent electrical resistance and the initial electrical resistance is greater than a maximum threshold value or less than a minimum threshold value stored in memory; and controlling power supplied to the electric heater based on whether a malfunction has been determined or providing an indication if a malfunction has been determined.

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

[0077] The method may include providing a constant power to the heater when power is applied, or alternatively, providing a variable power depending on other operating parameters, in which case the threshold value may depend on the power applied to the heater.

[0078] The method may include determining an initial electrical resistance before first using the heater. If the initial resistance is determined before first using the heater, the heater element can be assumed to be at about room temperature. Because 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 as the measured initial resistance minus assumed parasitic resistances resulting from other electrical components and electrical contacts in the system.

[0080] The electrically operated aerosol generating system may include a puff detector for detecting when a user takes a puff on the system, and the method may include providing power from the power source to the heater element when a puff is detected by the puff detector, determining whether there is a malfunction between each puff, and preventing the power source from providing power to the heater element if there is a malfunction for a predetermined number of consecutive user puffs.

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

[0082] The method may include continually determining whether a malfunction is present, and when a malfunction is present, preventing power from being supplied to the heater, and continuing to prevent power from being supplied to the heater element until the malfunction is eliminated.

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

[0084] Alternatively, or additionally, the method may include continually calculating whether the 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 may include determining a fault and controlling the supply of power 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 generation 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 electrical circuitry, the electrical circuitry connected to a puff detector for detecting when a user is taking a puff on the system. measuring an initial resistance of the electric heater before smoke puff is detected by the smoke detector; providing power to the heating element from a power source when a puff of smoke is detected by the smoke detector; measuring a subsequent resistance of the electric heater within a predetermined period of time after the supply of power from the power source to the electric heater is initiated; determining the difference between the subsequent resistance and the initial electrical resistance; comparing the difference between the subsequent resistance and the initial resistance to at least one of a maximum threshold value and a minimum threshold value stored in memory; determining that there is a fault if the difference is greater than a maximum threshold value or less than a minimum threshold value; limiting power supplied to the electric heater during the puff if a failure is determined, or preventing power from being supplied to the electric heater for the remainder of the puff if a failure is determined.

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

[0087] In a sixth aspect of the present invention, there is provided a method of detecting an incompatible or damaged heater in an electrically powered aerosol generation system, such as the electrically powered aerosol generation system of the first aspect, or an electrically powered aerosol generation device, such as the electrically powered aerosol generation device of the third aspect, the system or device comprising an electric heater comprising at least one heating element for heating an aerosol-forming substrate, and a power supply for supplying power to the electric heater, the method comprising: providing power to an electric heater; measuring the initial electrical resistance of the electric heater; measuring a subsequent electrical resistance of the electric heater after said measuring of the initial electrical resistance; determining the difference between the initial electrical resistance and the subsequent electrical resistance; determining an incompatible or damaged heater when a difference between the initial electrical resistance and the subsequent electrical resistance is greater than a maximum threshold value or less than a minimum threshold value, or when the difference reaches a threshold value stored in memory outside of an expected period of time.

[0088] If an incompatible heater is determined, the method may include preventing power to the electric heater or providing an indication until the heater or aerosol-forming substrate is replaced.

[0089] The method further includes measuring the initial resistance of the heater or the rate of change of the initial resistance of the heater within a predetermined period of time 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 if the initial resistance or the rate of change of the initial resistance is outside the range of acceptable values, preventing the supply of power to the electric heater until the heater or the aerosol-forming substrate is replaced or providing an indication.

[0090] The predetermined period of time may be short, between 50 ms and 200 ms. For heaters with mesh heating elements, the predetermined period of time may be approximately 100 ms. Preferably, the predetermined period of time is between 50 ms and 150 ms.

[0091] Determining the rate of change of the initial resistance during a predetermined period of time may be accomplished by taking multiple resistance measurements at different times during the predetermined period of time and calculating the rate of change of resistance based on the multiple resistance measurements.

[0092] The method may further comprise detecting when a heater or aerosol-forming substrate is inserted into the system. The method may be carried out immediately after detecting that a heater or aerosol-forming substrate has been inserted into the system.

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

[0094] The computer program product may be provided as a piece 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 having stored thereon a computer program according to the seventh aspect.

[0096] Features described in relation to one aspect of the invention may also be applied to other aspects of the invention. In particular, features described in relation to the first aspect may also be applied to the second, third and fourth aspects of the invention. Features described in relation to the first, second, third and fourth aspects of the invention may also be applied to the fifth, sixth and seventh aspects of the invention. [Brief explanation of the drawings]

[0097] The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1-1] 1a-1d are schematic diagrams of a system according to an embodiment of the present invention. [Figure 1-2] Same as above. [Figure 2] FIG. 2 is an exploded view of a cartridge for use in the system shown in FIGS. 1a-1d. [Figure 3]FIG. 3 is a detailed view of the heater filaments showing the meniscus of the liquid aerosol-forming substrate between the filaments. [Figure 4] FIG. 4 is a schematic diagram of the change in resistance of the heater during a user's puff. [Figure 5] FIG. 5 is an electrical diagram illustrating how the resistance of a heating element may be measured. [Figure 6] FIG. 6 illustrates the subsequent control process upon detection of a fault. [Figure 7] FIG. 7 is a schematic diagram of a first alternative aerosol generation system. [Figure 8] FIG. 8 is a schematic diagram of a second alternative aerosol generation system. [Figure 9] FIG. 9 is a flow chart illustrating a method for detecting unauthorized, damaged, or incompatible heaters. DETAILED DESCRIPTION OF THE INVENTION

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

[0099] The cartridge 20 contains an aerosol-forming substrate and is configured to be received in a recess 18 in the device. The cartridge 20 should be replaceable by the user when the aerosol-forming substrate provided therein is depleted. Figure 1a shows the cartridge 20 just prior to insertion into the device, with arrow 1 in Figure 1a indicating the direction of insertion 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 (e.g., a lithium iron phosphate battery), an electrical circuit 16, and a recess 18. The electrical circuit 16 includes 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 positioned in the open position to allow insertion and removal of a cartridge 20 and in the closed position when the system is used to generate aerosol. The mouthpiece portion includes multiple air inlets 13 and an air outlet 15. During use, a user draws or inhales through the outlets, drawing air from the air inlets 13 through the mouthpiece portion and into the outlet 15, which then enters the user's mouth or lungs. An internal baffle 17 is provided to force air flow through the mouthpiece portion 12 and past the cartridge.

[0101] The cavity 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 cavity 18 to provide electrical connection between the control electronics 16 and battery 14 and corresponding electrical contacts on the cartridge 20.

[0102] Figure 1b shows the system of Figure 1a with the cartridge inserted into the cavity 18 and the cover 26 removed. In this position, the electrical connector rests against the electrical contacts on the cartridge.

[0103] FIG. 1c shows the system of FIG. 1b with cover 26 completely removed and 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 clasp mechanism. The mouthpiece portion 12 in the closed position keeps the cartridge in electrical contact with the electrical connector 19 so that a good electrical connection is maintained during use regardless of the orientation of the system.

[0105] FIG. 2 is an exploded view of cartridge 20. Cartridge 20 includes a generally cylindrical housing 24 having a size and shape selected to be received within cavity 18. The housing includes capillary material 27, 28 immersed in a liquid aerosol-forming substrate. In this example, the aerosol-forming substrate includes 39 weight percent glycerin, 39 weight percent propylene glycol, 20 weight percent water and flavorings, 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 in which a heater assembly 30 is secured. The heater assembly 30 includes a base 34 having an opening 35 formed therein, a pair of electrical contacts 32 secured to the base and separated from one another by a gap 33, and a plurality of conductive heater filaments 36 secured across the opening to the electrical contacts on opposite sides of the opening 35.

[0107] The heater assembly 30 is covered by a removable cover 26. The cover comprises a liquid-impermeable plastic sheet that is adhered to the heater assembly but is easily removable. Tabs are provided on the sides of the cover to allow the user to grasp the cover when removing it. It will be apparent to those skilled in the art that although adhesion is described as a method of securing the impermeable plastic sheet to the heater assembly, other methods familiar to those skilled in the art may also be used, including heat sealing or ultrasonic welding, so long as the cover can be easily removed by the consumer.

[0108] The cartridge of FIG. 2 includes 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. A 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 and second capillary materials hold a liquid aerosol-forming substrate. The first capillary material 27, which contacts the heater elements, has a higher thermal decomposition temperature (at least 160°C or higher, e.g., about 250°C) than the second capillary material 28. The first capillary material 27 effectively acts as a spacer, separating the heater elements 36, 32 from the second capillary material 28, so that the second capillary material is not exposed to temperatures above its thermal decomposition temperature. A thermal gradient across the first capillary material ensures that the second capillary material is exposed to temperatures below its thermal decomposition temperature. The second capillary material 28 can be selected to have superior 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 glass fiber or a glass fiber-containing element, and the second capillary material is a polymer, such as a suitable capillary material. Exemplary suitable capillary materials include those discussed herein and, in alternative embodiments, can include high density polyethylene (HDPE) or polyethylene terephthalate (PET).

[0109] The capillary material 27, 28 is advantageously oriented within the housing 24 to deliver the liquid to the heater assembly 30. 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 delivered directly to the mesh heater. Figure 3 is a detailed view of the filaments 36 of the heater assembly, showing the meniscus 40 of the liquid aerosol-forming substrate between the heater filaments 36. It can be seen that the aerosol-forming substrate contacts most of the surface of each filament, such that most of the heat generated by the heater assembly enters directly into the aerosol-forming substrate.

[0110] Thus, in normal operation, the liquid aerosol-forming substrate contacts a large portion of the surface of the heater filament 36. However, when most of the liquid substrate in the cartridge is 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 heater filament is directed toward raising the temperature of the heater filament. As the heater element dries out, the rate at which the heater element heats up for a given applied power increases. The heater element may dry out because the aerosol-forming substrate in the cartridge is nearly used up, or because the user takes very long or very frequent puffs and is unable to deliver liquid to the heater filament as fast as it can vaporize.

[0111] In use, the heater assembly operates by resistive heating. Under the control of the control electronics 16, an electrical current is passed through the filament 36, heating it to a desired temperature range. The mesh or array of filaments has a significantly higher electrical resistance than the electrical contacts 32 and electrical connector 19, so that the high temperature is localized to the filament. In this example, the system is configured to generate heat by providing an electrical current to the heater assembly in response to a user's puff. In another embodiment, the system may be configured to generate heat continuously while the device is in the "on" state. Different materials for the filament may be appropriate for different systems. For example, in a continuous heating system, a Ni-Cr filament is appropriate because of its relatively low specific heat capacity and compatibility with low-current heating. In a puff-operated system in which 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 puff sensor configured to detect when a user draws air through the mouthpiece portion. The puff sensor (not shown) is connected to the control electronics 16, which is configured to supply current to the heater assembly 30 only when it is determined that the user is puffing on the device. Any suitable airflow sensor, such as a microphone or pressure sensor, may be used as the puff sensor.

[0113] To detect this increase in the rate of temperature change, electrical circuitry 16 is configured to measure the electrical resistance of the heater filaments. The heater filaments in this example are formed from stainless steel and therefore have a positive temperature coefficient of resistance. This means that as the temperature of the heater filaments increases, their electrical resistance also increases. In another embodiment, the heater filaments may be formed from a material with a negative coefficient of resistance, such that as the temperature of the heater filaments increases, their electrical resistance decreases.

[0114] FIG. 4 is a schematic diagram of the change in resistance of the heater during a user's puff. The x-axis is time after detection of the initial user puff 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 a function of the parasitic resistance R resulting from the electrical contacts 32 and electrical connector 19 and the contacts between them. P and the resistance of the heater filament, R0. When power is applied to the heater during a user's puff, the temperature of the heater filament increases, causing the electrical resistance of the heater filament to increase. As shown, at time t1, after a period of time Δt1 from the application of power to the heater from the power source, the resistance of the heater assembly is R2. Therefore, the change in electrical resistance of the heater assembly from its initial resistance to its resistance at time t1 is ΔR=R2-R1.

[0115] In this example, even if the heater filament is heated, the parasitic resistance R Pis assumed to be unchanged. This means that R P This is because the heat generated by the electrical contacts 32 and the electrical connector 19 is not heated. P The value of is assumed to be the same for all cartridges and is stored in the memory of the electronics.

[0116] To detect a sudden increase in the heater filament temperature, an indication of a dry state in the heater filament, a change in the heater filament resistance, may be monitored. The electrical circuit may be configured to determine the change in resistance by determining the difference between a measurement of the heater filament's initial electrical resistance R1 before power is applied to the heater element, i.e., before a puff, and a measurement of the heater filament's electrical resistance R2 after a predetermined time period Δt1 from when power is applied to the heater filament. Further, the electrical circuit may be configured to measure the difference ΔR relative to a predetermined maximum threshold value ΔR max may be configured to determine whether a change in resistance indicates an unacceptably rapid change in temperature by comparing the change in resistance with the

[0117] R2 and R1 are both measured values, and ΔR max is stored in memory. Ideally, the value of R1 is measured before any heating is done, in other words, before the heater is turned on for the first time. The initial measured value can be used for all subsequent puffs to avoid any errors introduced by residual heat from previous puffs. Therefore, the initial measured electrical resistance before any heating is done is R 1ref It can be called.

[0118] R 1ref R may be measured only once for each cartridge, a detection system may be used to determine when a new cartridge is inserted, or R may be measured each time the system is switched on. However, the electrical circuitry may measure an updated measurement R after a predetermined period when no power is supplied to the heater filament. 1refPreferably, the temperature sensor is configured to periodically measure R. The predetermined period is typically 3 minutes, but may be any suitable time required for the heater filament to return to room temperature from its operating temperature. 1ref Periodic updates to may retune the electrical circuitry to compensate for temperature changes in the ambient temperature and changes in the state of the heater filament.

[0119] In this embodiment, software running on a microprocessor in the electrical circuit performs the following comparisons to determine the fault:

[0120] R2>R 1ref +ΔR max If so, there is a dry condition in the heater. (1) Other faults besides a dry-fire heater condition may also be detected in a similar manner. For example, if a cartridge with a heater made of a material with a different temperature coefficient of resistance is used in the system, the electrical circuit may be configured to detect this and not supply power to it. In this example, the heater filament is made of stainless steel. A cartridge with a heater made of Ni-Cr will have a lower temperature coefficient of resistance, meaning that its resistance will increase more slowly with increasing temperature. Therefore, the minimum resistance threshold value ΔR min may be stored in the memory of the electrical circuit, which corresponds to the lowest temperature rise expected for the stainless steel heater element over a period of time Δt1. The electrical circuit then determines the threshold value ΔR at which the change in resistance between R2 and R1ref is smallest. min If the threshold is less than 0.001, the system may be configured to determine a fault corresponding to an unauthorized cartridge being present in the system.

[0121] That is, the system uses R2 and R 1ref may be configured to compare R with a stored high threshold and a stored low threshold. 1refmay also be compared to a threshold(s) to check that it is within an expected range. These may even be multiple high stored thresholds, with different actions 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 substrate are replaced. This may indicate a completely worn-out substrate, or a damaged or incompatible heater. A lower threshold may be used to determine when the substrate is nearly worn out. If this lower threshold is exceeded but not a higher threshold, the circuit may simply provide an indication, such as an illuminating LED, that the substrate will soon need to be replaced.

[0122] R 1ref The difference between R and R2 may be continuously monitored to determine whether the heater cools sufficiently between puffs. If the user puffs so frequently that the difference between puffs does not fall below the cooling threshold, the electrical circuitry may prevent or limit power to the heater until the difference falls below the cooling threshold. Alternatively, a comparison may be made between the maximum difference between puffs and the minimum difference for subsequent puffs to determine whether sufficient cooling is occurring.

[0123] Alternatively, the difference between R1 and R2 may be continuously monitored and the time to reach a threshold value may be compared to a time threshold. 1ref If the difference between R and R2 reaches a threshold much faster, or slower than expected, this may indicate a malfunction such as an incompatible heater. The rate of change can also be determined and compared to a threshold. If the difference rises too quickly or too slowly, this may indicate a malfunction. These techniques may allow an incompatible heater to be detected very quickly.

[0124] Figure 5 is a schematic electrical diagram showing how the resistance of a heating element may be measured. In Figure 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 with known resistance r is inserted in series with the heater 501 and connected to a voltage V1, which is halfway between ground and voltage V2. A microprocessor 507 calculates the resistance R of the heater 501. ヒーター To measure , both the current through heater 501 and the voltage across heater 501 can be determined. The resistance can then be determined using the well-known formula:

[0125]

number

number

number

number

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

[0127] Figure 6 illustrates a control process for a puff-activated system according to the present invention. Figure 6 illustrates four consecutive puffs, P1, P2, P3, and P4. The first puff, P1, is a typical puff with no abnormal conditions. Three subsequent puffs, P2, P3, and P4, are all abnormal puffs and exceed the high threshold ΔR max It exceeds that.

[0128] Each puff is detected at time t1 when power is applied 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 puff P1 is calculated by subtracting the initial resistance R1 from the initial resistance R2 measured before heating begins. 1ref Subsequent abnormal puffs P2, P3 and P4 are equal to the initial reference resistance R 1ref The figure shows the initial resistance R1 at time t1, which exceeds Δt. This indicates that the heater filament did not have enough time to return to room temperature between puffs. Following detection of a puff, the resistance of the heater filament is measured at time t2, a predetermined period Δt1 later. At time t3, each puff ends, and the puffs are measured for a total of Δt. puff It lasts for a period of time.

[0129] In the control process of Figure 6, the electrical circuitry stops powering the heater until the end of the user puff as soon as it determines that the high threshold has been exceeded. This applies to the second puff P2, the third puff P3, and the fourth puff P4. hThis can be useful to prevent the heater from getting too hot, even when the user is taking an excessive puff. Reaching a threshold can be indicated as well as cutting off the power.

[0130] When a new user puff is detected, power is again applied to the heater. This is shown in puffs P3 and P4. While a single instance of exceeding the high threshold may be the result of a very long user puff, exceeding the high threshold over several consecutive puffs is more likely the result of the cartridge being empty. Thus, in this example, ΔR exceeds the high threshold ΔR for a particular number of consecutive puffs, typically three puffs. max If the cartridge exceeds this threshold, the cartridge is disabled by blowing a fuse within the cartridge. The cartridge may also be disabled in other ways, such as by cutting off further power 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. A user may remove the cartridge from the device when the cartridge is empty of liquid aerosol-forming substrate and discard or refill the cartridge. A user may also remove a partially empty cartridge that still contains liquid aerosol-forming substrate.

[0132] A user may insert a used cartridge into the device. For example, a user may insert a refilled or partially empty cartridge into the device. When a user inserts a recently used cartridge into the device, the heater may not have had enough time to cool to room temperature after the previous use. The device circuitry may detect the initial resistance R of the heater filament while the heater filament is still hot. 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 can be configured to determine whether the heater temperature of the recently inserted cartridge is stable. In other words, the electrical circuitry can 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 may substantially prevent or inhibit measurement of

[0134] In many embodiments, the electrical circuitry is configured to determine when the cartridge is received within the device, and thus the electrical circuitry is configured to determine when the cartridge is removed from the device and when the 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 of the heater filament. p1 The electrical circuit may 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 flows through the measured initial resistance R p1 and R p2 The difference ΔR between p When the temperature of the heater filament is stable, the difference |ΔR p The magnitude of | is small or zero, except for 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 over a period of time ΔT2.p The minimum threshold value ΔR pmin and determining whether the temperature of the heater filament is stable based on the comparison. p | is the minimum threshold value ΔR pmin The electrical circuit may be configured to determine that the temperature of the heater filament is not stable if the temperature of the heater filament is greater than |R p2 -R p1 |>ΔR pmin If so, the heater temperature is not stable (6), where R p2 and R p1 are both measured values, and ΔR pmin is stored in memory.

[0137] In some embodiments, the electrical circuitry determines the difference |ΔR p |The magnitude of the minimum threshold value ΔR pmin It will be appreciated that the electrical circuit may be configured to compare the difference |ΔR p The minimum threshold value ΔR pmin The temperature control unit 100 may be configured to determine that the temperature of the heater filament is not stable when the temperature control unit 100 detects that the temperature of the heater filament is not stable.

[0138] If the electrical circuit determines that the temperature of the heater filament is not stable, the electrical circuit prevents power from being supplied to the heater filament and reduces the initial resistance R 1ref There is no need to measure and store the primary resistance R p2 is measured periodically or continuously, and the initial primary resistance R p1 Difference ΔR p Determine the difference ΔR until the difference is as close to zero as possible, within the expected level of the heater filament at a stable temperature. p The minimum threshold ΔR pmin The control unit 100 may be configured to compare the signal with the signal.

[0139] When the electrical circuit determines that the heater filament temperature is stable, it determines that the initial reference resistance R 1ref and may be configured to perform the general process described above.

[0140] In some embodiments, the electrical circuitry operates by switching on a single primary resistor R after inserting a new cartridge. p1 is measured periodically, and the primary resistance R p1 and the previous reference resistance R that was measured and stored for the previous cartridge before it was removed. 1ref The difference ΔR between p The method may be configured to determine:

[0141] Although the present invention has been described with reference to a cartridge-based system with a mesh heater, the same fault detection method can be used with other aerosol generating systems.

[0142] FIG. 7 illustrates an alternative system according to the present invention, also using a liquid substrate and capillary material. The electrically heated aerosol generating system 100 of FIG. 7 comprises a housing 101 having a mouthpiece end 103 and a body end 105. The body end is provided with a power source in the form of a battery 107 and electrical circuitry 109. A puff detection system 111 is also provided in conjunction with the electrical circuitry 109. The mouthpiece end is provided with a liquid reservoir in the form of a cartridge 113 containing a liquid 115, a capillary wick 117, and a heater 119. Note that in FIG. 7, the heater is only shown diagrammatically. One end of the capillary wick 117 extends into the cartridge 113, and the other end of the capillary wick 117 is surrounded by the heater 119. The heater is connected to the electrical circuitry via a connection 121, which may run along the outside of the cartridge 113 (not shown in FIG. 7). The housing 101 also includes an air inlet 123, an air outlet 125 at the mouthpiece end, and an aerosol-forming chamber 127.

[0143] In use, operation is as follows: liquid 115 is transported by capillary action from cartridge 113 from one end of wick 117 extending into the cartridge to the other end of the wick surrounded by heater 119. When a user draws on the aerosol generating system at air outlet 125, ambient air is drawn through air inlet 123. In the arrangement shown in FIG. 7, puff detection system 111 senses a puff and activates heater 119. Battery 107 provides electrical energy to heater 119 to heat the end of wick 117 surrounded by the heater. Liquid at the end of wick 117 is vaporized by heater 119, producing supersaturated vapor. Simultaneously, the vaporized liquid is replaced by additional liquid moving along wick 117 by capillary action. The generated supersaturated vapor mixes with and is carried by the airflow from air inlet 123. Within the aerosol forming 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 Figure 7, the electrical circuitry 109 and puff detection system 111 are programmable as shown in the embodiment of Figures 1a-1d.

[0145] The capillary wick may be made of a variety of porous or capillary materials, preferably with known, pre-set capillary behavior. Examples include ceramic or graphite-based materials in the form of fibers or sintered powders. Different porous wicks 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 reservoir.

[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 Figures 1-3, the capillary material forming the wick may dry out near the heater wire if the liquid in the cartridge is used up or if the user takes a very long, deep puff. As described with reference to the system of Figures 1-3, the change in resistance of the heater wire during the first portion of each puff can be used to determine whether there is a defect such as a dried wick.

[0148] In systems of the type illustrated in Figure 7, there may be considerable variation in heater resistance even between cartridges of the same type due to variations in the length of the heater wire wrapped around the wick. The present invention is particularly advantageous because the electrical circuitry does not need to store a maximum heater resistance value as a threshold; instead, the increase in resistance relative to that initial measured resistance is used.

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

[0150] The electrically heated aerosol generating device 200 comprises a housing 203 and an aerosol-forming substrate 210, such as a cigarette. The aerosol-forming substrate 210 is pressed into a cavity 205 defined by the housing 203, bringing it 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 temperatures of some volatile compounds, the release or formation of smoke components can be avoided.

[0151] Within the housing 203 is a power supply 207, such as a rechargeable lithium-ion battery. An 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 to regulate its temperature. An aerosol-forming substrate detector 213 is capable of detecting the presence and identity of an aerosol-forming substrate 210 in thermal proximity to the heater 201 and signals the presence of the aerosol-forming substrate 210 to the electrical circuit 209. The provision of a substrate detector is optional. An airflow sensor 211 is provided within the housing and connected to the electrical circuit 209 to detect the airflow rate 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 that, in use, is inserted into the aerosol-forming substrate 210. 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 alternative heaters may have different electrical resistances.

[0153] A system of the type illustrated in Figure 8 may be a continuously heated system in which the heater temperature is maintained at a target temperature while the system is on, or it may be a puff-activated system in which the heater temperature is increased by supplying more power during periods when a puff is detected.

[0154] In the case of a smoke-activated system, operation is very similar to that described with reference to the previous embodiment: if the substrate is dry near the heater, the heater resistance will rise more quickly for a given applied power than if the substrate contains an aerosol-forming agent that can still vaporize at a relatively low temperature.

[0155] In the case of a continuously heated system, when a user takes a puff on the system, there will initially be a drop in heater temperature due to the cooling effect of the airflow through the heater. When a puff is first detected, the heater resistance can be measured and recorded as R1, and in a manner similar to that described, a subsequent resistance R2 can be measured a period of time Δt1 after the puff is detected when the system returns the heater to the target temperature. ΔR can then be calculated as described above, and then compared to a stored threshold value as described above to determine whether a substrate is dry near the heater. A substrate may be dry because it has been worn out from use, or because it is old or improperly stored, or because it is counterfeit and has a moisture content different from that of an authentic aerosol-forming substrate.

[0156] The system of Figure 8 includes a warning LED 215 in the electrical circuit 209 that illuminates when a fault is detected.

[0157] 9 is a flow chart illustrating a method for detecting unauthorized, damaged, or incompatible heaters. In a first step 300, the insertion of a cartridge containing a heater into the device is detected. Next, in step 300, the heater R 1ref The electrical resistance of the heater is measured. This occurs a predetermined period, such as 100 ms, after power is applied to the heater. In step 320, the measured resistance R1 is compared to an expected or acceptable range of resistance. The acceptable range of resistance takes into account manufacturing tolerances and variations between original equipment heaters and substrates. If R1 is outside the expected range, the process proceeds to step 330, where an indication, such as an audible alarm, is provided and power is prevented from being applied to the heater because the device is deemed incompatible. The process then returns to step 300 to await detection of the insertion of a new cartridge.

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

[0159] In step 320, R 1ref If it is determined that ΔR 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, after which the difference ΔR is calculated. Advantageously, Δt1 is chosen to be a short period of time before significant aerosol generation. In step 350, the value of ΔR is compared to an expected value or range of acceptable values. The expected range of values ​​again takes into account variations in manufacturing of the heater and substrate assembly. If the value of ΔR is outside the expected range, the heater is deemed incompatible and the process proceeds to step 330 as described above, then returns to step 300. If the value of ΔR is within the expected range, the process proceeds to step 360, where power is applied to the heater so that it can generate aerosols in response to user demand.

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

[0161] It should also be apparent that the present invention may be implemented within existing aerosol generation systems as a computer program product for execution on a programmable controller, which may be provided as a piece of downloadable software or on a computer-readable medium such as a compact disc.

[0162] The above-described exemplary embodiments are illustrative and not limiting. 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.

[0163] 1. An electrically operated aerosol generating system comprising: an electric heater comprising at least one heating element for heating the aerosol-forming substrate; Power supply and an electric circuit connected to the electric heater and the power source, the electric circuit comprising a memory, measuring the initial electrical resistance of the electric heater; measuring a subsequent electrical resistance of the electric heater after said measurement of said initial electrical resistance; determining the difference between the initial electrical resistance and the subsequent electrical resistance; determining a fault when the determined difference between the subsequent electrical resistance and the initial electrical resistance is greater than a maximum threshold value or less than a minimum threshold value stored in the memory; and and an electrical circuit configured to control the power supplied to the electric heater based on whether a malfunction is determined, or to provide an indication if a malfunction is determined. 2. The electrically operated aerosol generating system described in 1, wherein the system comprises a device and a removable cartridge, the power source and the electrical circuit are within the device, and the electric heater is within the removable cartridge, and the cartridge comprises a liquid aerosol-forming substrate. 3. An electrically operated aerosol generation system as described in 1 or 2, further comprising a puff detector for detecting when a user is taking a puff on the system, the puff detector connected to the electrical circuit and configured to supply power to the heating element from the power source when a puff is detected by the puff detector, and the electrical circuit configured to determine whether there is a malfunction between each puff. 4. The system comprises: A removable cartridge, a liquid aerosol-forming substrate; a removable cartridge comprising the electric heater; and a device configured to removably receive the removable cartridge, a puff detector for detecting when a user is puffing on said system; the power source; the electrical circuitry connected to the smoke detector and the power supply and, in use, connected to the electric heater, the electrical circuitry comprising a memory; and measuring the initial electrical resistance of the electric heater before a puff is detected by the smoke detector; providing power to the heating element from the power source when a puff of smoke is detected by the smoke detector; measuring a subsequent resistance of the electric heater within a predetermined period of time after the supply of power from the power source to the electric heater is initiated; determining the difference between the subsequent resistance and the initial electrical resistance; comparing the difference between the subsequent resistance and the initial resistance to at least one of a maximum threshold value and a minimum threshold value stored in the memory; determining that there is a fault if the difference is greater than the maximum threshold value or less than the minimum threshold value; 2. The electrically operated aerosol generation system of claim 1, comprising an apparatus comprising: an electrical circuit configured to limit the power supplied to the electric heater during a puff if a malfunction is determined, or to prevent power from being supplied to the electric heater for the remainder of the puff if a malfunction is determined. 5. The electrical circuit is determining when the electrical circuit is connected to the electric heater; 5. An electrically operated aerosol generation system as described in 2 or 4, further configured to measure the initial resistance of the electric heater within a predetermined period of time after the electric heater is connected to the electric circuit. 6. The electrical circuit is storing the failure determination in the memory; determining a number of consecutive failure determinations based on the stored failure determinations; and An electrically operated aerosol generation system as described in any one of 1 to 5, further configured to disable the cartridge if the number of consecutive malfunction determinations determined is greater than a maximum threshold value. 7. An electric heater comprising at least one heating element; an electric circuit connected to the electric heater and having a memory, measuring the initial electrical resistance of the electric heater; measuring a subsequent electrical resistance of the electric heater after said measurement of said 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 a maximum threshold value or less than a minimum threshold value stored in the memory; and and an electrical circuit configured to control power supplied to the electric heater based on whether a malfunction is determined or to provide an indication if a malfunction exists. 8. The electrically operated aerosol generating device comprises: Power supply and an electrical circuit connected to the power source and comprising a memory, In use, connecting to an electric heater of the electrically operated aerosol generating system; measuring the initial electrical resistance of the electric heater; measuring a subsequent electrical resistance of the electric heater after said measurement of said initial electrical resistance; determining the difference between the initial electrical resistance and the subsequent electrical resistance; determining that there is a fault when the determined difference between the subsequent electrical resistance and the initial electrical resistance is greater than a maximum threshold value or less than a minimum threshold value stored in the memory; and An electrically powered aerosol generating device for an electrically powered aerosol generating system as described in 4 or 5, comprising: an electrical circuit configured to control the power supplied to the electric heater based on whether a malfunction is determined, or to provide an indication if a malfunction is determined. 9. In use, the electrical circuit is connected to an electric heater and a power source of the electrically powered aerosol generating system, the electrical circuit comprising a memory; and measuring the initial electrical resistance of the electric heater; measuring a subsequent electrical resistance of the electric heater after said measurement of said initial electrical resistance; determining the difference between the initial electrical resistance and the subsequent electrical resistance; determining a fault when the determined difference between the subsequent electrical resistance and the initial electrical resistance is greater than a maximum threshold value or less than a minimum threshold value stored in the memory; and An electrical circuit for an electrically operated aerosol generation system described in any one of claims 1 to 6, configured to control the power supplied to the electric heater based on whether a malfunction is determined, or to provide an indication if a malfunction is determined. 10. In use, the electrical circuit is further connected to a puff detector for detecting when a user is puffing on the system, the electrical circuit comprising: determining when the electrical circuit is connected to the electric heater; measuring the initial resistance of the electric heater within a predetermined period of time after the electric circuit is connected to the electric heater; providing power to the heating element from the power source when a puff of smoke is detected by the smoke detector; measuring the subsequent resistance of the electric heater within a predetermined period of time after the supply of power from the power source to the electric heater is initiated; determining the difference between the subsequent resistance and the initial electrical resistance; comparing a difference between the subsequent resistance and the initial resistance to at least one of a maximum threshold value and a minimum threshold value; determining that there is a fault if the difference is greater than the maximum threshold value or less than the minimum threshold value; and 10. The electrical circuit of claim 9, further configured to limit the power supplied to the electric heater during a puff if a malfunction is determined, or to prevent power from being supplied to the electric heater for the remainder of the puff if a malfunction is determined. 11. The electric circuit comprises: storing the failure determination in the memory; determining a number of consecutive failure determinations based on the stored failure determinations; and 11. The electrical circuit of claim 9 or 10, further configured to disable the cartridge if the determined number of consecutive failure determinations is greater than a maximum threshold value. 12. A method for controlling the supply of power to an electric heater in an electrically operated aerosol-generating system, the system comprising 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 comprising: supplying power to the electric heater; measuring the initial resistance of the electric heater; measuring a subsequent electrical resistance of the electric heater after said measuring of said initial electrical resistance; determining the difference between the initial electrical resistance and the subsequent electrical resistance; determining a fault when the determined difference between the subsequent electrical resistance and the initial electrical resistance is greater than a maximum threshold value or less than a minimum threshold value; controlling the power supplied to the electric heater based on whether a malfunction is determined or providing an indication if a malfunction is determined. 13. The electrically operated aerosol generation system further comprises a removable cartridge and a device configured to receive the removable cartridge, the removable cartridge comprising the electric heater and liquid aerosol-forming substrate, the device further comprising the power source, the electrical circuitry, and a puff detector for detecting when a user puffs on the system, and the method further comprises: measuring the initial resistance of the electric heater before a puff is detected by the smoke detector; providing power to the heating element from the power source when a puff is detected by the smoke detector; measuring the subsequent resistance of the electric heater within a predetermined period of time after the supply of power from the power source to the electric heater is initiated; determining the difference between the subsequent electrical resistance and the initial resistance; comparing the difference between the subsequent resistance and the initial resistance to a maximum threshold value or a minimum threshold value; determining that there is a fault if the difference is greater than the maximum threshold value or less than the minimum threshold value; 13. The method of claim 12, comprising limiting power supplied to the electric heater during a puff if a malfunction is determined, or preventing power from being supplied to the electric heater for the remainder of the puff if a malfunction is determined. 14. Determining when the electrical circuit is connected to the electric heater; 14. The method of claim 13, further comprising measuring the initial resistance of the electric heater within a predetermined period of time after it is decided to connect the electric circuit to the electric heater. 15. A computer program product that can be directly loaded into the internal memory of a microprocessor comprising software code portions so as to perform the steps of any of 12 to 14 when the computer program product is executed on a microprocessor in an electrically operated aerosol generating system, the system comprising an electric heater having at least one heating element for heating an aerosol-forming substrate, and a power supply for supplying power to the electric heater, the microprocessor being connected to the electric heater and the power supply.

Claims

1. 1. An aerosol generating system comprising: a body configured to receive an aerosol-forming substrate; a cartridge including a heater, the cartridge configured to couple with the body, the heater configured to heat the aerosol-forming substrate; a power source configured to provide current to the heater; an electrical circuit connected to the heater and the power source, the electrical circuit including a memory, the electrical circuit comprising: Detecting coupling of the cartridge to the body; determining an initial resistance of the heater in response to the detection of the coupling of the cartridge to the body; determining a subsequent resistance of the heater; An aerosol generation system configured to determine the presence of a malfunction based on a change in the resistance of the heater compared to a threshold stored in the memory, the change in the resistance of the heater being based on the determined initial resistance and the subsequent resistance.

2. 10. The aerosol generating system of claim 1, further comprising an aerosol generating device including the body, the power source, and the electrical circuit.

3. 3. The aerosol generation system of claim 2, wherein the cartridge is further configured to be inserted into the aerosol generation device and to house the aerosol-forming substrate.

4. 4. The aerosol generation system of claim 3, wherein the aerosol generation device and the cartridge are configured such that the cartridge is removable from the aerosol generation device after the insertion.

5. 4. The aerosol generating system of claim 3, wherein the cartridge further comprises a capillary material configured to convey the aerosol-forming substrate to the heater.

6. The aerosol generating system of claim 5 , wherein the capillary material comprises a first material and a second material.

7. 7. The aerosol generating system of claim 6, wherein the first material is between the heater and the second material.

8. 7. The aerosol generating system of claim 6, wherein the first material has a higher thermal decomposition temperature than the second material.

9. 7. The aerosol generating system of claim 6, wherein the second material is configured to hold more liquid per unit volume than the first material.

10. 3. The aerosol generation system of claim 2, wherein the aerosol generating device further includes a puff detector configured to detect puffs, the power source configured to supply the current to the heater when the puff is detected by the puff detector, and the electrical circuit configured to determine the presence of the malfunction during the puff.

11. The aerosol generating system of claim 1 , wherein the heater comprises multiple filaments.

12. 12. The aerosol generating system of claim 11, wherein the plurality of filaments are in the form of a mesh.

13. 13. The aerosol generating system of claim 12, wherein the mesh defines interstices configured to exhibit capillary action.

14. 2. The aerosol generating system of claim 1, wherein the change in resistance comprises a difference in resistance between the initial resistance and the subsequent resistance of the heater.

15. 15. The aerosol generation system of claim 14, wherein the electrical circuit is further configured to measure the initial resistance of the heater before the current is supplied and to measure the subsequent resistance of the heater after the current is supplied.

16. 15. The aerosol generation system of claim 14, wherein the electrical circuit is further configured to detect the presence of an electrical connection between the electrical circuit and the heater and measure the initial resistance of the heater after the electrical connection is detected.

17. 10. The aerosol generating system of claim 1, wherein the thresholds include a lower threshold and an upper threshold.

18. 18. The aerosol generating system of claim 17, wherein the electrical circuit is further configured to provide an indication of the malfunction when the change in resistance is greater than the lower threshold and less than the upper threshold.

19. 18. The aerosol generation system of claim 17, wherein the electrical circuit is further configured to reduce or stop the current to the heater when the change in resistance is greater than the upper threshold.

20. 2. The aerosol generating system of claim 1, wherein the electrical circuit is further configured to store the determination of the malfunction in the memory, determine the number of consecutive determinations of the malfunction, and disable the heater based on the number of consecutive determinations of the malfunction.

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