Detection of adverse heater conditions in electrically heated aerosol generating system

Abstract

To provide detection of a dry heating element or other undesirable condition in an aerosol generating system.SOLUTION: An electrically operated aerosol-generating system comprises: a heating element configured to heat an aerosol-forming substrate; a power supply configured to supply power to the heating element; a temperature sensor configured to sense a temperature at the heating element; and electric circuitry in communication with the heating element, the sensor and the power supply, the electric circuitry comprising a memory. The electric circuitry can: regulate a supply of power to the heating element based on the measured temperature from the temperature sensor; determine an adverse condition when either (i) a rate of change of power supplied to the heating element required to reach or maintain a predetermined temperature or (ii) a reduction in power supplied to the heating element required to reach or maintain a predetermined temperature over successive heating cycles falls outside a predefined range stored in the memory; and control power supplied to the heating element or provide an indication when there is an adverse condition.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to an aerosol generation system. In particular, the present invention relates to the detection of a dried heating element or other undesirable conditions in an aerosol generation system.

Background Art

[0002] In some aerosol generating devices, a liquid aerosol forming substrate is delivered from a liquid storage portion to an electrical heating element. When heated to a target temperature, the aerosol forming substrate vaporizes to form an aerosol. The liquid substrate is typically delivered to the heating element by a wick. When the amount of the aerosol forming substrate in the wick is depleted, the heating element may overheat and adversely affect the quality of the aerosol. This is particularly important in aerosol generation systems configured to generate an aerosol for user inhalation.

[0003] WO2012 / 085203 discloses an aerosol generation system that monitors the temperature rise at the heating element, and a rapid increase in the heater temperature indicates drying of the wick. More specifically, the system compares the rate of temperature rise with a threshold value stored in memory. When the rate of temperature rise exceeds the threshold value, the system stops the power supply to the heating element. The device disclosed in WO2012 / 085203 monitors the heater temperature based on the electrical resistance of the heater, thereby eliminating the need for a dedicated temperature sensor.

[0004] WO2016 / 1050922 and WO2018 / 019533 disclose more complex methods for detecting depletion of an aerosol-forming substrate in a heating element. WO2016 / 1050922 teaches a system that depends on the ratio, or proportion, of the change in electrical resistance to a predetermined initial electrical resistance. The initial electrical resistance takes into account parasitic resistances arising from auxiliary components such as electrical contacts and connections, as well as the electrical resistance of the heating element before heating. This results in a more accurate and responsive detection of substrate depletion. WO2018 / 019533 discloses a system that does not consider the initial heating resistance. Instead, the system measures the absolute increase in electrical resistance during heating and is configured to shut down when the increase in electrical resistance exceeds a predetermined threshold. This enables the same detection mechanism to be applied to a wide range of heating elements and aerosol generation systems in a robust and reliable manner.

[0005] However, all of these techniques for detecting depletion of the aerosol-forming substrate require, or may be slow to, substantially increase the heater temperature to detect the resulting change in electrical resistance. SUMMARY OF THE INVENTION

[0006] According to an aspect of the present invention, there is provided an electrically - operated aerosol - generating system comprising a heating element for heating an aerosol - forming substrate, a power source for supplying power to the heating element, a temperature sensor for sensing the temperature of the heating element, and an electrical circuit in communication with the heating element, the sensor, and the power source, the electrical circuit comprising a memory and being configured to adjust the power supply to the heating element based on the measured temperature from the temperature sensor, and being configured to determine a harmful state when i) the rate of change of the power supplied to the heating element required to achieve or maintain a predetermined temperature, or ii) the decrease in the power supplied to the heating element required to achieve or maintain a predetermined temperature over a continuous heating cycle is outside a predefined range, the predefined range being stored in the memory, and being configured to control the power supplied to the heating element based on whether there is a harmful state, or to provide an indication when there is a harmful state.

[0007] As used herein, the term "electrically - operated aerosol - generating system" means a system that generates an aerosol from one or more aerosol - forming substrates. The aerosol - forming substrate may be contained within a cartridge. The advantage of providing a cartridge is that the aerosol - forming substrate is protected from the surrounding environment. Further, a high level of hygiene can be maintained. The system may comprise an apparatus for heating one or more aerosol - forming substrates. The electric aerosol - generating system may include additional components such as a charging unit for recharging an on - board power source in an electrically - operated aerosol - generating device. The aerosol - generating system may be a system configured to generate an aerosol for user inhalation, such as an inhaler, a personal vaporizer, or an e - cigarette.

[0008] As used herein, the term "aerosol - forming substrate" means a substrate having the ability to release a volatile compound that can form an aerosol. Such volatile compounds may be released by heating the aerosol - forming substrate.

[0009] Advantageously, the electrical circuit can determine harmful states such as depletion of the aerosol-forming substrate or system malfunction by monitoring the power supply to the heating element. The electrical circuit can be configured to determine depletion of the liquid aerosol-forming substrate at the heating element. In this context, "depletion" means either that an insufficient amount of the aerosol-forming substrate is being provided at the heating element or complete depletion of the aerosol-forming substrate. In either case, this can result in a "dry" heating element as opposed to a "wet" heating element soaked in the liquid aerosol-forming substrate. For example, when the cartridge is empty or nearly empty, an insufficient amount of the liquid aerosol-forming substrate can be supplied to the heating element. This can mean that the generated aerosol does not have the desired attributes (such as the size or chemical composition of the aerosol particles). This can result in a poor experience for the user.

[0010] When the electrical circuit detects a harmful state, it can stop the power supply. This is advantageous because when drying of the heating element is detected, the user can no longer use the aerosol generation system. This can avoid the generation of an aerosol that does not have the desired characteristics. Also, and thus, this can avoid a poor experience for the user. The electrical circuit may be arranged to stop the heating element by tripping an electrical fuse between the heating element and the power supply. The electrical circuit may be arranged to stop the heating element by switching off a switch between the heating element and the power supply. Alternative ways to stop the heating element will be apparent to those skilled in the art.

[0011] As another or additional method, the electrical circuit may provide an indication to the user to warn the user of the harmful state. The indication can be one or more of an audible indication, a visual indication, a mechanical indication such as vibration, an olfactory indication, or any other indication means known to those skilled in the art. Then, the user can be prepared to replace or refill the cartridge.

[0012] Advantageously, the electrical circuit can determine a harmful state based on monitoring the power supplied to the heating element. Generally, the lower the amount of aerosol-forming substrate delivered to the heater for vaporization, the higher the temperature of the heating element for a given applied power. Accordingly, the power required by the heating element to maintain or achieve the target temperature can decrease accordingly with depletion of the aerosol-forming substrate. This is because there is less or no aerosol-forming substrate that the heating element may need to heat.

[0013] Accordingly, the electrical circuit determines the harmful state by monitoring the rate of change of the power supply to the heating element required to achieve or maintain a predetermined temperature. For example, a harmful state can be determined when a sudden surge or drop in the power supply is detected while maintaining the target temperature. Advantageously, this method can enable earlier detection of the harmful state, as it can readily determine the harmful state even before the power supply reaches a predetermined threshold, as disclosed in prior art systems. Further, this method does not rely on monitoring an absolute increase in the power supply and, therefore, advantageously enables determination of the harmful state to be more independent of ambient conditions and also enables different substrates.

[0014] As another or additional method, the electrical circuit can determine a harmful state by monitoring a decrease in the power supply required to achieve or maintain a predetermined temperature over a continuous heating cycle, or more specifically, the minimum power supply required. In this context, a "heating cycle" means the period of power supply to the heating element. Typically, each heating cycle corresponds to user smoking. Due to variations between different combinations of heating elements and substrates, the power required to maintain a constant temperature can vary between different aerosol generation systems. Accordingly, by comparing the minimum power supply in a given heating cycle with the power supplied in a previous heating cycle in the same aerosol generation system, the electrical circuit can detect small changes in power consumption. This advantageously enables earlier detection of the harmful state.

[0015] Optionally, the electrical circuit is configured to determine a harmful state only after the temperature of the heating element has risen from the initial temperature to the target temperature. The electrical circuit can be configured to determine a harmful state only after the heating element has been maintained at the target temperature for a predetermined time. More specifically, the power required to raise the temperature of the heating element from the initial temperature to the target temperature can vary particularly depending on the ambient conditions. Therefore, if the determination of the harmful state is based on the power supply during these periods, such determinations can be less reliable. In comparison, a consistent and constant level of power supply can be observed when the heating element is maintained at the target temperature. The power supply can deviate from a certain value only when there is a harmful state, such as depletion of the aerosol-forming substrate in the heating element or malfunction of the aerosol generation system. Therefore, the electrical circuit can determine a harmful state when the temperature of the heating element reaches and is maintained at the target temperature. Preferably, the electrical circuit can determine a harmful state when the detected resistance reaches a predetermined value indicating the target temperature.

[0016] The predefined range may be based on the value of the maximum threshold of the rate of change of the power supply. A harmful state can be determined when the rate of change of the power supply exceeds the maximum threshold value. This advantageously allows for small fluctuations in the power supply when there is no harmful state due to changes in the ambient conditions.

[0017] As another method, the predefined range is based on the minimum threshold of the decrease in the minimum power supplied over consecutive heating cycles. A harmful state can be determined when the decrease in the power supplied to the heating element over consecutive heating cycles increases more than the minimum threshold. This advantageously allows for small decreases in the power supply over consecutive heating cycles before a harmful state is determined.

[0018] As used herein, the term "heating element" means an electrically heated element that is powered by an on-board power source. The electrically heated element may include a single heating element. Alternatively, the heating element may include a plurality of separate heating elements, such as two, or three, or four, or five, or six, or more heating elements. The heating element(s) may be suitably arranged to most effectively heat the liquid aerosol-forming substrate.

[0019] The heating element may be a resistive heating element. At least one electric heating element preferably comprises an electrically resistive material. Suitable electrically resistive materials include, for example, semiconductors such as doped ceramics, "conductive" ceramics (such as molybdenum disilicide), carbon, graphite, metals, metal alloys, composite materials made of ceramic materials or metal materials, but are not limited thereto. Such composite materials may include doped ceramics or undoped ceramics. An example of a suitable doped ceramic is doped silicon carbide. Examples of suitable metals include titanium, zirconium, tantalum, and platinum group metals. Examples of suitable metal alloys include stainless steel, constantan, nickel-containing, cobalt-containing, chromium-containing, aluminum-containing, titanium-containing, zirconium-containing, hafnium-containing, niobium-containing, molybdenum-containing, tantalum-containing, tungsten-containing, tin-containing, gallium-containing, manganese-containing, and iron-containing alloys, as well as nickel, iron, cobalt, stainless steel-based superalloys, Timetal® (registered trademark), iron-aluminum-based alloys, and iron-manganese-aluminum-based alloys. Timetal® is a registered trademark of Titanium Metals Corporation. In the composite material, the electrically resistive material may optionally be embedded in, encapsulated in, or coated with the insulating material, or vice versa, depending on the required energy transfer kinetics and external physico-chemical properties. The heating element may include a metal foil that is etched and insulated between two layers of inert material. In that case, the inert material may include Kapton® (registered trademark), all-layer polyimide, or mica foil. Kapton® is a registered trademark of E.I. du Pont de Nemours and Company.

[0020] The resistive heating element can take the form of a mesh, array, or fiber of conductive filaments. The conductive filaments may define gaps between the filaments, and the gaps may have a width of 10 μm to 100 μm. The conductive filaments may form a mesh sized 160 - 600 mesh US (±10%) (i.e., 160 - 600 (±10%) filaments per inch). The width of the gaps is preferably 75 μm to 25 μm. The area ratio of the openings of the mesh, which is the ratio of the area of the gaps to the total area of the mesh, is preferably 25 - 56%. The mesh may be formed using different types of weaving or lattice structures. Alternatively, the conductive filaments consist of an array of filaments arranged parallel to each other. The conductive filaments can have a diameter of 8 μm to 100 μm, preferably have a diameter of 8 μm to 50 μm, and more preferably have a diameter of 8 μm to 39 μm. The filaments may have a round cross-section or a flat cross-section.

[0021] The area of the mesh, array, or fiber of conductive filaments may be small and is preferably 25 mm 2 or less, enabling it to be incorporated into a handheld system. The mesh, array, or fiber of conductive filaments may be, for example, rectangular with dimensions of 5 mm × 2 mm. The mesh or array of conductive filaments preferably covers an area of 10% - 50% of the area of the heater assembly. More preferably, the mesh or array of conductive filaments covers an area of 15 - 25% of the area of the heater assembly.

[0022] The filaments may be formed by etching a sheet material (such as foil). This can be particularly advantageous when the heater assembly comprises an array of parallel filaments. When the heating element includes a mesh or fiber of filaments, the filaments may be formed individually or woven together.

[0023] Preferred materials for the conductive filaments are 304, 316, 304L, and 316L stainless steel.

[0024] Instead of a mesh arrangement, at least one electrical heating element may take the form of a resistance heater coil, or a casing or substrate having different conductive portions, or an electrically resistive metal tube. When the cartridge is received within the recess of the aerosol generating device, the heater may be arranged to surround at least a portion of the cartridge. The cartridge may incorporate a disposable heating element. As another method, one or more heating needles or rods passing through the liquid aerosol forming substrate may also be appropriate in some cases. As another method, at least one electrical heating element may include a flexible sheet of material. Other alternatives include heating wires or filaments such as Ni-Cr (nickel chromium), platinum, tungsten, or alloy wires or heating plates. Optionally, the heating element may be disposed within or on a rigid carrier material.

[0025] At least one heating element may heat the aerosol forming substrate by conduction. The heating element may be at least partially in contact with the substrate. As another method, heat from the heating element may be conducted to the substrate by means of a heat conductive element.

[0026] At least one heating element may transfer heat to the incoming ambient air drawn through the aerosol generating system during use, which in turn heats the aerosol forming substrate. The ambient air may be heated before passing through the aerosol forming substrate. As another method, the ambient air may first be drawn through the substrate and then heated.

[0027] The resistive heating element can function as a temperature sensor. When at least one heating element has appropriate characteristics of the temperature coefficient of resistance, measuring the electrical resistance of at least one heating element makes it possible to confirm the temperature of the heating element. The electrical circuit can be arranged to measure the electrical resistance of at least one heating element by measuring the current flowing through at least one heating element and the voltage across both ends of at least one heating element, and determining the electrical resistance of at least one heating element from the measured current and voltage. In this case, the electrical circuit may include a resistor having a known resistance and in series with at least one heating element, and this electrical circuit can be arranged to measure the voltage across both ends of the resistor with the known resistance, and measure the current flowing through at least one heating element by determining the current flowing through at least one heating element from the measured voltage and the known resistance. Therefore, it may not be necessary to include a dedicated temperature sensor that occupies valuable space in the aerosol generation system and can be expensive. In this embodiment, it is emphasized that the electrical resistance is used as both the heating element and the sensor.

[0028] The aerosol-forming substrate may be in a liquid phase at room temperature.The terms "liquid" and "solid" as used herein refer to the state of the aerosol-forming substrate at room temperature. The aerosol-forming substrate may be a fluid liquid at room temperature. For a liquid aerosol-forming substrate, certain physical properties of the substrate, such as vapor pressure or viscosity, are selected to be suitable for use in an aerosol generation system.

[0029] The aerosol-forming substrate may contain plant-derived materials. The aerosol-forming substrate may contain tobacco. The aerosol-forming substrate may contain a tobacco-containing material containing volatile tobacco flavor compounds released from the aerosol-forming substrate upon heating. Alternatively, the aerosol-forming substrate may contain a non-tobacco-containing material. The aerosol-forming substrate may contain a homogenized plant-derived material. The aerosol-forming substrate may contain a homogenized tobacco material. The aerosol-forming substrate may contain at least one aerosol-forming agent. The aerosol-forming agent can be any suitable well-known compound or mixture of compounds that facilitates the formation of a high-density stable aerosol during use and is substantially resistant to thermal decomposition at the operating temperature of the system. Suitable aerosol-forming agents are well known in the art and include polyhydric alcohols (such as triethylene glycol, 1,3-butanediol, glycerin, etc.), esters of polyhydric alcohols (such as glycerol monoacetate, diacetate, or triacetate, etc.), and aliphatic esters of monocarboxylic acids, dicarboxylic acids, or polycarboxylic acids (such as dimethyl dodecanedioate, dimethyl tetradecanedioate, etc.), but are not limited thereto. Preferred aerosol-forming agents are polyhydric alcohols or mixtures thereof (such as triethylene glycol, 1,3-butanediol, and glycerin (most preferred), etc.). The aerosol-forming substrate may contain other additives and components (such as flavoring agents, etc.).

[0030] In the case of a liquid aerosol-forming substrate, certain physical properties of the substrate, such as vapor pressure or viscosity, are selected to be suitable for use in an aerosol-generating system. The liquid preferably contains a tobacco-containing material that contains volatile tobacco flavor compounds released from the liquid upon heating. Alternatively, or additionally, the liquid may contain a non-tobacco material. The liquid may contain water, ethanol, or other solvents, plant extracts, nicotine solutions, and natural or artificial flavors. The liquid preferably further contains an aerosol-forming agent. Examples of suitable aerosol-forming agents are glycerin and propylene glycol.

[0031] The aerosol-forming substrate may be contained in a refillable liquid storage part of an aerosol generating device or may be a disposable cartridge in an aerosol generating system. The aerosol-forming substrate is preferably contained in a disposable cartridge in the aerosol generating system. The cartridge may be replaced after a single use session or after a plurality of use sessions. This may enable the user to replace an exhausted cartridge in a safe and efficient manner.

[0032] The liquid aerosol-forming substrate may be delivered from the cartridge to the heating element by a mechanical device such as, for example, a manual pump or an electric pump.

[0033] The electrically-operated aerosol generating system preferably further comprises a capillary wick for transporting the liquid aerosol-forming substrate to the heating element. This can reduce the number of moving parts of the aerosol generating device and thus improve reliability, reduce weight and cost.

[0034] Optionally, the capillary wick is arranged to contact the liquid of the cartridge. Optionally, the capillary wick extends into the cartridge. In that case, during use, the liquid can be moved from the cartridge to the heating element by the capillary action of the capillary wick. In one embodiment, the capillary wick may have a first end and a second end, the first end may extend into the cartridge to contact the liquid in the cartridge, and the heating element may be arranged to heat the liquid in the second end. When the heating element is activated, the liquid at the second end of the capillary wick can be vaporized by at least one heating element to form a supersaturated vapor. The supersaturated vapor can be mixed with an air stream and carried in the air stream. During the flow, the vapor can be condensed to form an aerosol, and the aerosol can be carried towards the user's mouth. The liquid aerosol-forming substrate may have physical properties including viscosity and surface tension that enable the liquid to be carried through the capillary wick by capillary action.

[0035] The capillary core may have a fibrous or spongy structure. The capillary core preferably comprises a bundle of capillaries. For example, the capillary core may comprise a plurality of fibers or threads, or other fine tubes. The fibers or threads may generally be aligned in the longitudinal direction of the aerosol generating system. Alternatively, the capillary core may comprise a sponge-like or foam-like material formed in a rod shape. The rod shape may extend along the longitudinal direction of the aerosol generating system. The structure of the core may form a plurality of small holes or tubes through which liquid can be transported by capillary action. The capillary core may comprise any suitable material or combination of materials. Examples of suitable materials are capillary materials, such as sponge or foam materials, ceramic or graphite-based materials in the form of fibers or sintered powders, foamed metals or plastic materials, such as fibrous materials made of spun or extruded fibers (cellulose acetate, polyester, or combined polyolefins, polyethylene, terylene or polypropylene fibers, nylon fibers or ceramics, etc.). The capillary core may have any suitable capillary and porosity to be used with different liquid physical properties. The liquid may have physical properties including but not limited to viscosity, surface tension, density, thermal conductivity, boiling point and vapor pressure that enable it to be transported through the capillary device by capillary action. The capillary properties of the core combined with the properties of the liquid aerosol forming substrate ensure that the core is always wet in the heating region during normal use when there are many aerosol forming substrates.

[0036] The capillary core and the heating element, and optionally the cartridge, may be removable from the aerosol generating system as a single component.

[0037] The system may comprise an aerosol generating device and a removable cartridge, with a power source and an electrical circuit provided within the device, and the heating element may be provided within the removable cartridge, which cartridge comprises a liquid aerosol forming substrate. The heating element may be configured to connect to the power source and the electrical circuit by means of a suitable connector. The heating element may be a disposable heating element. The heating element may be exchangeable with the removable cartridge.

[0038] Optionally, cartridges having different characteristics can be used with the device. For example, two different cartridges having heating elements of different sizes can be provided for the device. For example, a heating element having a higher power rating can be used to deliver more aerosol. A cartridge having a higher capacity can be used to reduce the frequency of cartridge replacement.

[0039] The aerosol generating device preferably comprises a housing. The housing is preferably elongated. If the aerosol generating device includes a capillary core, the longitudinal axis of the capillary core and the longitudinal axis of the housing can be substantially parallel.

[0040] The housing can comprise any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics, or composite materials containing one or more of these materials, or thermoplastic resins suitable for food or pharmaceutical applications, such as polypropylene, polyetheretherketone (PEEK), and polyethylene. The material is preferably lightweight and not brittle.

[0041] Optionally, the aerosol generating device comprises a user input device. The user input device may comprise at least one of a push button, a scroll wheel, a touch button, a touch screen, and a microphone. The user input device may enable a user to control one or more aspects of the operation of the aerosol generating device. The user input device may enable a user to initiate power supply to the heater, or to stop power supply to the heater, or both.

[0042] Optionally, the electrical circuit comprises a microprocessor, and more preferably comprises a programmable microprocessor. The system may comprise a data input port or a wireless receiver to enable uploading software onto the microprocessor. The electrical circuit may comprise additional electrical components.

[0043] Optionally, the aerosol generating system further comprises a smoking detector for detecting when a user is smoking the system. The smoking detector may communicate with the electrical circuit. The electrical circuit may be configured to supply power from the power source to the heating element when smoking is detected by the smoking detector such that each smoking corresponds to a heating cycle. The electrical circuit may be configured to determine whether there is a harmful condition during each heating cycle. The smoking detector may form the user input device in the aerosol generating device. That is, the user may not need to press a mechanical button to initiate a heating cycle.

[0044] The aerosol generating device may further comprise a mouthpiece. The mouthpiece may be configured to engage with the housing or cartridge of the aerosol generating device. Optionally, the mouthpiece is configured to engage with the aerosol generating device, and the combination of the aerosol generating device and the mouthpiece may mimic the shape and dimensions of a combustible smoking article such as a cigarette, a cigar, or a slender cigar. Advantageously, in such embodiments, the combination of the aerosol generating device and the mouthpiece may mimic the shape and dimensions of a cigarette.

[0045] The power source may be any suitable power source, such as a DC voltage source like a battery. The power source may be a lithium-ion battery, a nickel-metal hydride battery, a nickel-cadmium battery, or a lithium-based battery (e.g., a lithium cobalt battery), a lithium iron phosphate battery, lithium titanate, or a lithium polymer battery.

[0046] Optionally, the power source may include a rechargeable lithium-ion battery. The power supply may include another form of charge storage device such as a capacitor. The power supply may require recharging. The power supply may have a capacity that allows for sufficient energy storage for one or more uses of the aerosol generator. For example, the power supply may have a capacity sufficient to allow for continuous generation of aerosol for about 6 minutes, corresponding to the typical time it takes to smoke one conventional cigarette, and for times that are multiples of 6 minutes. In another embodiment, the power supply may have a capacity sufficient to allow for a predetermined number of smoking sessions or discontinuous activations.

[0047] The electrical circuit may be configured to start supplying power from the power source to the heater at the start of the heating cycle. The electrical circuit may be configured to end supplying power from the power source to the heater at the end of the heating cycle.

[0048] The electrical circuit may be configured to provide continuous supply of power from the power source to the heater.

[0049] The electrical circuit may be configured to provide intermittent supply of power from the power source to the heater. The electrical circuit may be configured to provide pulsed supply of power from the power source to the heater.

[0050] Advantageously, the pulsed supply of power to the heater may facilitate control of the total output from the heater during the period. Advantageously, controlling the total output from the heater during the period may facilitate temperature control.

[0051] The electrical circuit may be configured to vary the supply of power from a power source to the heater. The electrical circuit can be configured to vary the duty cycle of the pulsed power supply. The electrical circuit can be configured to vary at least one of the pulse width and the period of the duty cycle.

[0052] Optionally, the aerosol generating system is portable. The aerosol generating system may be a smoking system and may have a size comparable to that of a conventional cigar or cigarette. The overall length of the smoking system may be approximately 30 mm to approximately 150 mm. The outer diameter of the smoking system may be approximately 5 mm to approximately 30 mm.

[0053] According to a second aspect of the present invention, there is provided a method of controlling the power supply to a heating element in an electrically operated aerosol generating system, the method comprising measuring the temperature of the heating element, adjusting the power supply to the heating element based on the measured temperature, and determining a harmful state when i) the rate of change of the power supplied to the heating element required to achieve or maintain a predetermined temperature, or ii) the decrease in the power supplied to the heating element required to achieve or maintain a predetermined temperature over a continuous heating cycle, is outside a predefined range, the predefined range being stored in a memory, and controlling the power supplied to the heating element based on whether there is a harmful state, or providing an indication when there is a harmful state.

[0054] According to a third aspect of the present invention, there is provided a computer program product directly loadable into an internal memory of a microprocessor, comprising software code portions for performing the steps of the second aspect when the computer program product is executed on the microprocessor in an electrically operated aerosol generating system, the system comprising a heating element for heating an aerosol-forming substrate, a sensor for sensing the temperature of the heating element, and a power source for supplying power to the heating element, the microprocessor being connected to the heating element, the sensor, and the power source.

[0055] To avoid misunderstanding, the above-described features regarding one aspect of the present invention may also be applied to other aspects of the present invention.

[0056] The features described with respect to one aspect may equally apply to other aspects of the present invention.

[0057] Here, by way of example only, embodiments of the present invention will be described with reference to the following accompanying drawings.

Brief Description of the Drawings

[0058]

Fig. 1a

Fig. 1b

Fig. 1c

Fig. 1d

Fig. 2

Fig. 3

Fig. 4

Fig. 5

Fig. 6

Fig. 7

Best Mode for Carrying Out the Invention

[0059] Figures 1a to 1d are schematic views of an electrically heated aerosol generation system according to an embodiment of the present invention. The aerosol generation system comprises an aerosol generator 10 and a cartridge 20.

[0060] The cartridge 20 contains an aerosol-forming substrate in a cartridge housing 24 and is configured to be received within a recess 18 in the device. The cartridge 20 is a disposable cartridge. The user can replace the cartridge 20 when the aerosol-forming substrate in the cartridge is depleted. The cartridge comprises a removable seal 26 for providing a hermetic seal to the cartridge housing 24. This enables the aerosol-forming substrate contained within the cartridge housing 24 to be shielded from the environment prior to its first use. Figure 1a shows the cartridge 20 immediately prior to insertion into the device, and arrow 1 in Figure 1a indicates the direction of insertion of the cartridge.

[0061] The aerosol generating device 10 is portable and has a size comparable to that of a conventional cigar or cigarette. The device 10 comprises a main body 11 and a mouthpiece portion 12. The main body 11 includes a battery 14 (such as a lithium iron phosphate battery), an electrical circuit 16, and a recess 18. The electrical circuit 16 comprises a programmable microprocessor. The mouthpiece portion 12 is connected to the main body 11 by a hinge connection 21 and is movable between an open position shown in Figure 1a and a closed position shown in Figure 1d. The mouthpiece portion 12 is placed in the open position to enable the insertion and removal of the cartridge 20, and is placed in the closed position when the system is used for aerosol generation. The mouthpiece portion comprises a plurality of air inlets 13 and an air outlet 15. In use, the user sucks or smokes at the outlet, drawing air from the air inlets 13 through the mouthpiece portion to the outlet 15 and then into the user's mouth or lungs. An internal baffle 17 is provided to force the flow of air passing through the cartridge through the mouthpiece portion 12.

[0062] The recess 18 has a circular cross-section and is sized to receive the housing 24 of the cartridge 20. An electrical connector 19 is provided on the side of the recess 18 to provide an electrical connection between the control electronic circuit 16, the battery 14, and the corresponding electrical contacts of the cartridge 20.

[0063] Figure 1b shows the system of Figure 1a with the cartridge inserted into the recess 18 and the removable seal 26 removed. In this position, the electrical connector is positioned against the electrical contacts on the cartridge.

[0064] Figure 1c shows the system of Figure 1b with the removable seal 26 removed and the mouthpiece portion 12 moved to the closed position.

[0065] Figure 1d shows the system of Figure 1c with the mouthpiece portion 12 in the closed position. The mouthpiece portion 12 is held in the closed position by a fastening mechanism. The mouthpiece portion 12 in the closed position keeps the cartridge in electrical contact with the electrical connector 19 so that a good electrical connection is maintained during use regardless of the orientation of the system.

[0066] Figure 2 is an exploded view of the cartridge 20. The cartridge housing 24 has a size and shape selected to be received within the recess 18. The housing includes capillary materials 27, 28 immersed in a liquid aerosol-forming substrate. In this example, the aerosol-forming substrate includes 39 weight percent glycerin, 39 weight percent propylene glycol, 20 weight percent water and flavorant, and 2 weight percent nicotine. The capillary material is a material that actively transports liquid from one end to the other based on a relative difference in liquid concentration. The capillary material can be made from any suitable material. In this example, the capillary material is formed from polyester.

[0067] The cartridge housing 24 has an open end to which the heater assembly 30 is fixed. The heater assembly 30 includes a substrate 34 with an opening 35 formed therein, a pair of electrical contacts 32 fixed to the substrate and separated from each other by a gap 33, and a plurality of conductive heater filaments 36 spanning the opening and fixed to the electrical contact on the opposite side of the opening 35.

[0068] The heater assembly 30 is covered by a peelable seal 26. The peelable seal 26 includes a liquid-impermeable plastic sheet that is adhered to the heater assembly 30 but can be easily peeled off. Tabs are provided on the sides of the peelable seal 26 to enable the user to grasp the peelable seal 26 when peeling. Although adhesion is described as a method of fixing the impermeable plastic sheet to the heater assembly, it will be apparent to those skilled in the art that other methods well-known to those skilled in the art, including heat sealing or ultrasonic welding, may also be used as long as the cover can be easily removed by the consumer.

[0069] The cartridge of FIG. 2 has two separate capillary materials 27, 28. Disks of the first capillary material 27 are 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 heater assembly from the first capillary material 27. Both the first capillary material and the second capillary material hold a liquid aerosol-forming substrate. The first capillary material 27 that contacts the heater element has a higher thermal decomposition temperature (at least 160° C. or more, for example, about 250° C., etc.) than the second capillary material 28. The first capillary material 27 effectively serves as a spacer separating the heater elements 36, 32 from the second capillary material 28 so that the second capillary material is not exposed to a temperature above its thermal decomposition temperature. This is to ensure that the thermal gradient across the first capillary material keeps the second capillary material at a temperature below its thermal decomposition temperature. The second capillary material 28 can be selected to have better wicking performance than the first capillary material 27, be able to hold more liquid per unit volume than the first capillary material, and be less expensive than the first capillary material. In this example, the first capillary material is a heat-resistant material (such as glass fiber or a glass fiber-containing material), and the second capillary material is a polymer (such as a suitable wicking material). Exemplary suitable wicking materials include those described herein, and in alternative embodiments, high-density polyethylene (HDPE) or polyethylene terephthalate (PET) may be mentioned.

[0070] The capillary materials 27, 28 are advantageously directed within the housing 24 in order to convey liquid to the heater assembly 30. When the cartridge is assembled, the heater filament 36 may contact the capillary material 27, so that the aerosol-forming substrate can be conveyed directly to the mesh heater. FIG. 3 is a detailed view of the filament 36 of the heater assembly 30, showing a meniscus 40 of the liquid aerosol-forming substrate between the heater filaments 36. It can be seen that the aerosol-forming substrate contacts most of the surface of each filament 36 so that most of the heat generated by the heater assembly 30 directly enters the aerosol-forming substrate.

[0071] 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 has been used, the liquid aerosol-forming substrate delivered to the heater filament 36 is less. With less liquid to vaporize, the energy required for the enthalpy of vaporization is less, and more of the energy supplied to the heater filament 36 is directed to raising the temperature of the heater filament. Similarly, the energy required to maintain the target temperature also decreases as the heater filament 36 dries out. The heater filament 36 may dry out because the aerosol-forming substrate in the cartridge has been depleted. Alternatively, although less likely, the heater filament 36 may dry out because the user smokes for a very long time or very frequently and the liquid cannot be delivered to the heater filament 36 at the same rate at which the liquid is vaporized.

[0072] In use, the heater assembly 30 operates by resistive heating. The current, under the control of the control electronics circuit 16, passes through the filament 36 and heats the filament within a desired temperature range. The mesh or array of filaments has a significantly higher electrical resistance than the electrical contacts 32 and the electrical connector 19 so that the high temperature is confined to the filaments. This minimizes heat loss to other parts of the aerosol generating device 10. In this embodiment, the system is configured to generate heat by providing current to the heater assembly 30 in response to the user's smoking.

[0073] The system includes a smoking sensor configured to detect when the user is drawing air through the mouthpiece portion. The smoking sensor (not shown) is connected to the control electronics circuit 16, which is configured to supply current to the heater assembly 30 only when it is determined that the user is smoking the device. Any suitable airflow sensor may be used as the smoking sensor (such as a microphone or a pressure sensor).

[0074] To detect the increase in temperature, the electrical circuit 16 is configured to measure the electrical resistance of the heater filament. The heater filament 36 in this embodiment is formed from stainless steel and thus has a positive temperature coefficient of resistance. Additionally, in such a system that operates by smoking, a stainless steel filament with a relatively high specific heat capacity is ideal because heat is generated in short bursts using high current pulses.

[0075] As the temperature of the heater filaments 36 increases, their electrical resistance also increases. It will be understood that in other embodiments, the heater filaments 36 may be formed from a material having a negative coefficient of resistance such that their electrical resistance decreases as the temperature of the heater filaments increases.

[0076] Figure 4 is a plot showing the change in the resistance of the heater detected during multiple smoking sessions by the user. Each of the smoking sessions lasts for a smoking time Δt. The x-axis represents time and the y-axis represents the electrical resistance detected in the heater assembly 30. In Figure 4, the change in electrical resistance is detected in three different heating cycles, each corresponding to 1) the heater filament 36 being immersed in the aerosol-forming substrate, for example, during the heating cycle 500 under normal operation, 2) an insufficient supply of the aerosol-forming substrate being provided to the heater filament 36, for example, during the heating cycle 502 where the liquid substrate does not fully replenish the heater filament 36, and 3) the aerosol-forming substrate of the heater filament 36 being depleted during the heating cycle 504 corresponding to user smoking. The electrical circuit can be configured to determine that both the heating cycle 502 and the heating cycle 504 include a harmful condition. Alternatively, the electrical circuit can be configured to determine that only the heating cycle 504 is in a harmful condition.

[0077] The heater assembly 30 has an initial resistance R 基準 Thereof. The said initial resistance R 基準 is an inherent characteristic of the heater assembly 30. This indicates the reference resistance of the heater assembly 30 at room temperature. The initial resistance R 基準 is a combination of the parasitic resistance R P and the resistance R0 of the heater filament at room temperature. Therefore, R0 can be determined from R0 = R 基準 - R P More specifically, the parasitic resistance R P is the resistance resulting from the electrical contacts 32 and the electrical connectors 19 and the contacts therebetween. R0 is the resistance of the heater filament 36 at ambient temperature.

[0078] The initial resistance R 基準 of the new cartridge 20 is measured at least once before heating is applied. The detection system is used to determine when the new cartridge 20 is inserted. In some cases, R 基準 can be measured only once for each cartridge. R 基準It may be measured each time the system switch is turned on. In this embodiment, the electrical circuit is configured to periodically take updated measured values of R after a predetermined time when power is not supplied to the heater filament 36. The predetermined time lasts for 3 minutes each, but any suitable time required for the heater filament 36 to cool and return from its operating temperature to the ambient temperature can be selected. 基準 These periodic updates of R correct the electrical circuit to account for changes in the ambient temperature and the state of the heater filament 36. 基準 As power is applied to the heater assembly 30 during user smoking, the temperature of the heater filament 36 rises from the ambient temperature. This increases the electrical resistance R of the heater filament 36. However, it is assumed that the parasitic resistance R

[0079] remains constant. This is because R P is due to non-heated components such as the electrical contacts 32 and the electrical connector 19. In addition, the value of R P is assumed to be the same for all cartridges and is not affected by changing to a different cartridge. The parasitic resistance R P value of a particular aerosol generating device 20 is stored in the memory of the electrical circuit. P The resistance of the heater filament 36 is linearly correlated with its temperature. Therefore, the temperature of the heater assembly can be adjusted by controlling the resistance R to a target resistance R

[0080] based on a factor K. Here, R T = (R0)·K, or R T = (R T - R 基準 )·K. K may be a predefined value and may be stored in the memory of the electrical circuit. P

[0081] Figure 4 illustrates the change in electrical resistance ΔR across the heater assembly 30 when being heated from the ambient temperature and then when being maintained at the target heater temperature during user smoking. Each of the heating cycles 500, 502, 504 corresponds to user smoking and has a duration of Δt. In the illustrated example, each heating cycle begins with the heater assembly 30 at the ambient temperature and the resistance (R 基準 ) of the heater assembly. However, this may not always be the case because the heater assembly 30 may not be completely cooled in the smoking chamber. Thus, the electrical resistance R in actual use can start at a level higher than R 基準 . However, the temperature of the heater assembly 30 or the corresponding electrical resistance R at the start of the heating cycle is not significant. This is because the electrical circuit is configured to determine a harmful condition when the heater assembly 30 reaches its target temperature.

[0082] The heater assembly 30 during heating cycle 500 is immersed in the liquid aerosol-forming substrate. This indicates a normal operating state. In this example, the temperature of the heater assembly 30 is configured to be adjusted by a factor K of 1.2. At the start of the heating cycle, the electrical circuit supplies electrical energy to the heater assembly 30 while measuring the heater resistance R. This period of heating can be called the heating stage. During the heating stage, the electrical circuit can continue to supply power to the heater assembly 30 until the measured heater resistance R equals R T (in this case 1.2R0).

[0083] R T When it reaches, the electrical circuit can continue to supply power at a reduced level or in an intermittent manner to adjust the heater resistance R to the target heater resistance R T . This results in a constant heater temperature. This temperature maintenance period can be called the maintenance stage. During such a maintenance stage, the heater resistance R is adjusted to remain at a constant value.

[0084] The factor K may be set as a default value during factory shipment. The factor K correlates with the default target temperature of the heater filament 36. Additionally, the user may adjust the factor K from its default value using a user input device such as a mechanical button or a scroll wheel. This enables the user to adjust the target heater temperature according to their preferences.

[0085] When the heater assembly receives a reduced amount of the liquid substrate, the rate of temperature increase (dT / dt) at the heater filament 36 during the heating stage increases. As a result, the rate of increase of resistance dR / dt at the heater filament 36 during this period also increases. Such a situation can occur, for example, when the liquid substrate cannot be fully replenished at the heater filament 36. This is illustrated in the heating cycle 502 of FIG. 4. The heater filament 36 has an insufficient liquid substrate supply. During the heating stage of the heating cycle 502, the rate of increase of the electrical resistance dR / dt is higher than that during the heating cycle 500. As shown in the heating cycle 504 of FIG. 4, when the liquid substrate of the heater filament 36 is completely depleted, the rate of increase of the electrical resistance dR / dt further increases. In some cases, due to the absence of the liquid substrate, the heater temperature rises rapidly and the heater assembly 30 cannot dissipate heat fast enough, increasing the electrical resistance to be higher than R T as shown in the heating cycle 504.

[0086] In one embodiment, the electrical circuit is configured to stop the power supply to the heater assembly when it detects that the rate of increase of the electrical resistance dR / dt exceeds an upper threshold value. For example, such an upper threshold value may be the rate of increase of electrical resistance shown only when the cartridge is empty. Additionally, a visual warning such as a blinking LED signal may be given to the user to prompt cartridge replacement.

[0087] Power supply to the heater assembly 30 can also be used to determine depletion of the aerosol-forming substrate at the heater filament 36. This is illustrated by the heating cycles 510, 512, and 514 shown in FIG. 5, each showing the power supplied during the heating cycles 500, 502, and 504 of FIG. 4. The power supplied is determined based on the change in power (ΔW) within a particular time interval. For example, the power supplied is detected every 100 milliseconds.

[0088] Heating cycle 510 shows the change in power supplied during smoking when the heater filament 36 is immersed in the liquid substrate. It can be seen that the power supply gradually rises to a maximum level during the heating period. This enables the heater assembly 30 to heat up rapidly. In some cases, the power supply may start at the highest level at the start of the heating cycle, which allows for even faster heating.

[0089] Thereafter, the power supply decreases and stabilizes at a lower level during the maintenance phase. The electrical circuit sets a predetermined power supply limit 516 to limit the maximum power supply to the heater assembly 30. The power supply limit 516 forms a passive safety mechanism to prevent overheating. In the illustrated example, the power supply limit 516 is variable and has a higher limit during the heating phase compared to the maintenance phase.

[0090] Heating cycle 512 shows the change in power supply during smoking when an insufficient amount of liquid substrate is being supplied to the heater filament. The power supply during the heating phase of heating cycle 512 is similar to the power supplied when the heater filament 36 is immersed in the liquid substrate, as shown in heating cycle 510. However, if the inflow of the liquid substrate fails to replenish the vaporized substrate at the heater filament 36, the power required to maintain the heater assembly 30 at its target temperature gradually decreases as the user approaches the end of the smoking session.

[0091] The heating cycle 514 shows the change in power supply during smoking when the liquid matrix is depleted by the heater filament. Since the liquid matrix is absent, the power supplied to the heater assembly 30 during the heating stage is significantly lower than that in the heating cycles 510 and 512. Similar to the heating cycle 512, when the liquid matrix is depleted by the heater filament 36, the power required to maintain its target temperature rapidly decreases as the end of user smoking approaches.

[0092] The electrical circuit is configured to detect an insufficient liquid matrix at the heater filament 36 during the maintenance stage based on the decrease in the supplied power. More specifically, when the heater assembly 30 reaches the target resistance indicating the target temperature, the power supply gradually decreases until it reaches a predetermined minimum power threshold (P 最小 ). Thereafter, the electrical circuit determines the level of insufficient liquid matrix at the heater filament 36 as shown in the heating cycle 512, or when the cartridge is empty as shown in the heating cycle 514.

[0093] In contrast, a heater filament immersed in the liquid matrix requires more power than the minimum power threshold (P T ) to maintain its electrical resistance R at the target resistance (R 最小 ). Therefore, power consumption below the predetermined minimum power threshold (P 最小 ) can only be achieved when there is no liquid matrix at the heater filament 36.

[0094] In this embodiment, the electrical circuit is configured to immediately stop the power supply when it detects that the power supply has dropped below the minimum power threshold (P 最小 ).

[0095] As another approach, even if an insufficient liquid substrate at the heater filament 36 is detected, the electrical circuit does not immediately stop the power supply. Instead, the electrical circuit can continue to supply power for one or more additional smoking events. For example, the electrical circuit can continue to supply power for two additional smoking events. This enables the electrical circuit to continue to monitor the power supply during consecutive smoking events to confirm depletion of the substrate at the heater filament 36.

[0096] In another embodiment, depletion of the liquid substrate can be determined by monitoring a decrease in the minimum power supply over consecutive smoking events. More specifically, the electrical circuit can compare the minimum power supply P 最小 recorded during each of the consecutive smoking events. The electrical circuit can then determine a harmful state when the difference between the minimum power supplies (P 最小 ) over consecutive cycles exceeds an offset threshold (ΔP オフセット ). This is illustrated in FIG. 6 and shows the power supply over three consecutive heating cycles corresponding to three consecutive smoking events by a user during 1) a heating cycle 520 in which the heater filament is immersed in an aerosol-forming substrate, which is a normal operating state, 2) a heating cycle 522 in which an insufficient supply of the aerosol-forming substrate is provided to the heater filament, and 3) a heating cycle 524 in which the aerosol-forming substrate is depleted at the heater filament.

[0097] Under normal operating conditions when the heater filament 36 is immersed in a liquid aerosol-forming substrate, the minimum power supply during one smoking event is P 最小1 . If all of the consecutive smoking events within a particular session are performed under normal operation, the minimum power supply P 最小 recorded during each heating cycle will be approximately P 最小1 . That is, under normal operating conditions, the recorded minimum power supply P 最小 from smoking event to smoking event is substantially consistent. The offset of the minimum power supply P 最小 is expected to be very small. In particular, when the heater filament 36 is immersed in a liquid substrate, the offset of the minimum power supply is below a predetermined threshold (ΔPオフセット does not exceed

[0098] However, the amount of the available liquid aerosol-forming substrate in the cartridge decreases with each successive smoking. When the cartridge is nearly empty, the liquid aerosol-forming substrate begins to deplete at the heater filament 36. In this case, the minimum power supply (P 最小 ) recorded during smoking decreases with each successive smoking. For example, P 最小2 represents the minimum power supply recorded during the second heating cycle 522, which is lower than P 最小1 recorded during the preceding heating cycle. In this case, the difference between P 最小2 and P 最小1 exceeds a predetermined ΔP オフセット , so that P 最小2 < (P 最小1 - ΔP<( オフセット ). Accordingly, the electric circuit determines that the supply of the liquid substrate at the heater assembly is insufficient. As a result, the electric circuit immediately stops the power supply to the heater filament 36 and indicates to the user to replace the empty cartridge.

[0099] Alternatively, the electric circuit may continue to monitor the minimum power supply during at least one or more heating cycles. In this case, P 最小3 is recorded during the third heating cycle 524 following the second heating cycle 522. In this case, the difference between P 最小3 and P 最小2 again exceeds a predetermined ΔP オフセット , so that P 最小3 < (P 最小2 - ΔP オフセット ). Since the minimum power supply (P 最小 ) continues to decrease in successive cycles, the electric circuit determines that the liquid substrate is depleted at the heater filament 36. As a result, the electric circuit stops the power supply to the heater assembly 30 and indicates to the user to replace the empty cartridge.

[0100] Alternatively, the electric circuit is the minimum power supply P 最小with that recorded during the first heating cycle 520, i.e., P 最小1 can be configured to be compared. In this case, the electrical circuit compares P 最小3 with P 最小1 . The electrical circuit is configured to compare P 最小3 with P 最小1 . If the difference between P オフセット and P exceeds a predetermined ΔP 最小3 threshold, so that P 最小1 < (P オフセット - ΔP

[0101] As another method, the electrical circuit may compare the minimum power supply with the rolling average P 最小平均 of the minimum power supply over the previous n heating cycles, where n is a positive integer greater than 1. For example, the electrical circuit averages the P 最小 recorded in the last n puffs to generate the rolling average P 最小平均 . If the difference between P 最小 and P 最小平均 exceeds a predetermined ΔP オフセット threshold, so that P 最小 < (P 最小平均 - ΔP オフセット ), the electrical circuit determines that the liquid substrate is depleted at the heater filament 36. This ensures that the comparison is always made against a new cartridge or at least a cartridge in which the liquid aerosol has not been depleted.

[0102] A decrease in the minimum power supply during the maintenance phase is a good indicator indicating insufficient liquid substrate at the heater filament 36. However, until the power supply decreases below the minimum power threshold, the electrical circuit cannot confirm a harmful state. That is, the response to the harmful state may not be issued promptly. In another embodiment, the electrical circuit is configured to determine an insufficient liquid substrate from the first derivative of the power supply with respect to time (dP / dt). This is illustrated in FIG. 7, which shows 1) during the heating cycle 530 in which the heater filament 36, which is in a normal operating state, is immersed in the aerosol-forming substrate, 2) during the heating cycle 532 in which an insufficient supply of the aerosol-forming substrate is provided to the heater filament 36, and 3) during the heating cycle 534 in which the aerosol-forming substrate has dried up at the heater filament, the rate of change of the power supply during three heating cycles corresponding to a user's puff.

[0103] Under normal operation, as shown in heating cycle 530, when the heater filament is immersed in the liquid substrate, dP / dt gradually decreases as the heater assembly 30 heats up. When the electrical resistance reaches and is maintained at the target resistance R T , dP / dt remains at a generally constant level. This is because the amount of substrate vaporization is maintained constant at the target temperature.

[0104] However, as shown in heating cycle 532, if the supply of the liquid substrate is insufficient, dP / dt decreases to maintain the electrical resistance at the target resistance R T . The electrical circuit is configured to determine a harmful state when dP / dt decreases below a predetermined minimum rate-of-change threshold (dP / dt 最小 ). For example, a sudden loss of the liquid substrate supply at the heater filament 36 will cause the power supply to decrease rapidly. This results in a decrease in dP / dt. In severe cases, dP / dt decreases below a predetermined minimum rate-of-change threshold (dP / dt 最小 ).

[0105] In the worst case, as shown in heating cycle 524, when the liquid substrate of the cartridge is completely depleted, dP / dt decreases more rapidly, so the time to reach dP / dt 最小 is shorter. The drier the heater filament 36, the more rapidly the harmful condition can be detected and the power supply can be stopped or reduced more quickly.

[0106] The methods as described in the various embodiments can each be applied to determine a harmful condition. Alternatively, the determination of the harmful condition may be based on a combination of the described plurality of methods. The aerosol generation system can be configured to use different methods to determine harmful conditions in different modes. The described methods may also be used in an internal system diagnostic tool.

[0107] 1. A heating element for heating an aerosol-forming substrate, a power supply for supplying power to the heating element, a temperature sensor for sensing the temperature of the heating element, an electrically operating aerosol generation system comprising the heating element, the sensor and an electrical circuit in communication with the power supply, wherein the electrical circuit comprises a memory and is configured to adjust the power supply to the heating element based on the measured temperature from the temperature sensor, i) the rate of change of the power supplied to the heating element required to achieve or maintain a predetermined temperature, or ii) a decrease in the power supplied to the heating element required to achieve or maintain a predetermined temperature over successive heating cycles, is configured to determine a harmful condition when outside a predefined range, the predefined range being stored in the memory, is configured to control the power supplied to the heating element based on whether there is a harmful condition, or to provide an indication when there is a harmful condition, An electrically operated aerosol generating system, wherein the system comprises a device and a removable cartridge, the power supply and the electrical circuit are within the device, the heating element is within the removable cartridge, and the cartridge contains a liquid aerosol forming substrate. 2. The electrically operated aerosol generating system according to 1, wherein the electrical circuit is configured to determine a harmful state only after the temperature of the heating element has risen from an initial temperature to a target temperature. 3. The electrically operated aerosol generating system according to 1 or 2, wherein the predefined range is based on a maximum threshold of a rate of change of the supplied power or a minimum threshold of a decrease in the supplied power over a continuous heating cycle. 4. The electrically operated aerosol generating system according to any one of 1 to 3, wherein the temperature sensor is configured to measure the electrical resistance of the heating element. 5. The electrically operated aerosol generating system according to any one of 1 to 4, further comprising a smoking detector for detecting when a user is smoking with the system, the smoking detector communicating with the electrical circuit, and the electrical circuit being configured to supply power from the power supply to the heating element when smoking is detected by the smoking detector such that each smoking corresponds to a heating cycle, and the electrical circuit being configured to determine whether there is a harmful state during each heating cycle. 6. A method for controlling power supply to a heating element of an electrically operated aerosol generating system, comprising: measuring the temperature of the heating element; adjusting the power supply to the heating element based on the measured temperature; determining a harmful state when i) a rate of change of the power supplied to the heating element required to achieve or maintain a predetermined temperature, or ii) a decrease in the supplied power required to achieve or maintain a predetermined temperature over a continuous heating cycle, is outside a predefined range, the predefined range being stored in the memory. A method comprising a step of controlling the power supplied to the heating element based on whether there is a harmful state, or a step of providing a display when there is a harmful state. 7. A computer program product directly loadable into an internal memory of a microprocessor, comprising software code portions for performing the steps according to claim 6 when the computer program product is executed on the microprocessor in an electrically operating aerosol generation system, the system comprising a heating element for heating an aerosol-forming substrate, a sensor for sensing the temperature of the heating element, and a power supply for supplying power to the heating element, the microprocessor being connected to the electric heater, the sensor and the power supply.

Claims

1. A heating element for heating an aerosol-forming substrate, a power source for supplying power to the heating element, a temperature sensor for sensing the temperature of the heating element, and an electrically-operated aerosol generation system comprising an electrical circuit in communication with the heating element, the temperature sensor, and the power source, wherein the electrical circuit comprises a memory and is configured to adjust the power supply to the heating element based on the measured temperature from the temperature sensor, by comparing the power supplied to the heating element in a certain heating cycle with the power supplied in one or more preceding cycles, and determining a harmful state when a decrease in the power supplied to the heating element required to achieve or maintain a predetermined temperature over successive heating cycles is outside a predefined range, the predefined range being stored in the memory, and is configured to control the power supplied to the heating element based on whether there is a harmful state, or to provide an indication when there is a harmful state, wherein the system comprises a device and a removable cartridge, the power source and the electrical circuit being within the device, the heating element being within the removable cartridge, and the cartridge containing a liquid aerosol-forming substrate, an electrically-operated aerosol generation system.

2. The electrically-operated aerosol generation system according to claim 1, wherein the electrical circuit is configured to determine a harmful state only after the temperature of the heating element has risen from an initial temperature to a target temperature.

3. The electrically-operated aerosol generation system according to claim 1 or 2, wherein the predefined range is based on a maximum threshold of the rate of change of the power supplied or a minimum threshold of the decrease in the power supplied over successive heating cycles.

4. The electrically-operated aerosol generation system according to any one of claims 1 to 3, wherein the temperature sensor is configured to measure the electrical resistance of the heating element.

5. The electrically operated aerosol generating system according to any one of claims 1 to 4, further comprising a smoking detector for detecting when a user is smoking in the system, the smoking detector communicating with the electrical circuit, and the electrical circuit being configured to supply power from the power source to the heating element when smoking is detected by the smoking detector so that each smoking corresponds to a heating cycle, and the electrical circuit being configured to determine whether there is a harmful condition during each heating cycle.

6. A method for controlling power supply to a heating element of an electrically operated aerosol generating system, comprising: measuring the temperature of the heating element; adjusting the power supply to the heating element based on the measured temperature; determining a harmful condition by comparing the power supplied to the heating element in a certain heating cycle with the power supplied in one or more preceding cycles to determine if a decrease in supplied power required to achieve or maintain a predetermined temperature over successive heating cycles is outside a predefined range, the predefined range being stored in a memory; controlling the power supplied to the heating element based on whether there is a harmful condition, or providing a display when there is a harmful condition.

7. A computer program product directly loadable into an internal memory of a microprocessor, comprising software code portions for performing the steps according to claim 6 when the computer program product is executed on the microprocessor in an electrically operated aerosol generating system, the system comprising a heating element for heating an aerosol-forming substrate, a sensor for sensing the temperature of the heating element, and a power source for supplying power to the heating element, the microprocessor being connected to the electric heater, the sensor, and the power source.

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