Heating type aerosol generation device, and method for generating aerosol of consistent characteristics

Abstract

To provide a method for controlling the generation of aerosol in an aerosol generation device.SOLUTION: An aerosol generation device includes a heater including at least one heating element configured so as to heat an aerosol forming base material and a power source for supplying power to the heating element. A method for controlling the generation of aerosol includes a step to control the power to be supplied to the heating element so that power is supplied in order for the temperature of the heating element to increase from an initial temperature to a first temperature in a first stage, power is supplied in order for the temperature of the heating element to decrease to a second temperature lower than the first temperature in a second stage, and power is supplied in order for the temperature of the heating element to increase again in a third stage. When the temperature of the heating element is caused to increase in a final stage of the heating process, a decrease in aerosol delivery by a lapse of time is reduced or prevented.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an aerosol generating device and a method for generating an aerosol by heating an aerosol forming substrate. In particular, the present invention relates to an apparatus and method for generating an aerosol of consistent desired properties from an aerosol forming substrate over a continuous or repeated heating period of the aerosol forming substrate.

Background Art

[0002] In the art, aerosol generating devices are known that operate by heating an aerosol forming substrate, such as a heated smoking device. WO 2009 / 118085 describes a heated smoking device that generates an aerosol by heating a substrate while controlling the temperature within a temperature range desirable to prevent combustion of the substrate.

[0003] It is desirable for an aerosol generating device to be able to produce a consistent aerosol over time. This is particularly true when the aerosol is consumed by a human, such as in the case of a heated smoking device. In devices where a consumable substrate is heated continuously or repeatedly over a period of time, consistent aerosol generation can be difficult because the properties of the aerosol forming substrate can change significantly with continuous or repeated heating, both in terms of the amount and distribution of the aerosol forming components remaining in the substrate and the temperature of the substrate. In particular, users of continuous or repeated heating devices may experience a fading of the aroma, taste, and feel of the aerosol as the nicotine and, in some cases, the aerosol forming bodies that convey flavorants deplete from the substrate. Therefore, achieve consistent aerosol delivery over time such that the aerosol initially delivered during operation is approximately the same as the aerosol delivered last.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present disclosure is to provide an aerosol generating device and a system that provide an aerosol with more consistent characteristics over a continuous or repeated heating period of an aerosol-forming substrate.

Means for Solving the Problems

[0006] In a first aspect, the present disclosure provides a method for controlling the generation of an aerosol in an aerosol generating device, the device comprising: a heater including at least one heating element configured to heat an aerosol-forming substrate; a power source for supplying power to the heating element; and the method includes controlling the power supplied to the heating element such that in a first stage, power is supplied so that the temperature of the heating element rises from an initial temperature to a first temperature, in a second stage, power is supplied so that the temperature of the heating element drops to a second temperature lower than the first temperature, and in a third stage, power is supplied so that the temperature of the heating element rises to a third temperature higher than the second temperature.

[0007] As used herein, an "aerosol generating device" relates to a device that interacts with an aerosol-forming substrate to generate an aerosol. The aerosol-forming substrate can be part of an aerosol-generating article, such as part of a smoking article. The aerosol generating device can be a smoking device that interacts with the aerosol-forming substrate of the aerosol-generating article to generate an aerosol that can be directly inhaled into the user's lungs through the user's mouth. The aerosol generating device can be a holder.

[0008] As used herein, the term "aerosol-forming substrate" relates to a substrate capable of releasing a volatile compound capable of forming an aerosol. Such a volatile compound can be released by heating the aerosol-forming substrate. The aerosol-forming substrate can, for the sake of convenience, be part of an aerosol-generating article or a smoking article.

[0009] As used herein, the terms "aerosol-generating article" and "smoking article" mean an article comprising an aerosol-forming substrate capable of releasing a volatile compound capable of forming an aerosol. For example, the aerosol-generating article can be a smoking article that generates an aerosol that can be directly inhaled into the user's lungs through the user's mouth. The aerosol-generating article can be disposable. Hereinafter, the term "smoking article" will generally be used. The smoking article can be a tobacco stick or can include a tobacco stick.

[0010] Typically, existing aerosol-generating devices that generate an aerosol by repeatedly or continuously heating a substrate are controlled to achieve a single constant temperature over time. However, the aerosol-forming substrate is depleted by heating, i.e., the amount of the main aerosol component in the substrate decreases, which means that the generation of the aerosol at a given temperature decreases. Furthermore, when the temperature of the aerosol-forming substrate reaches a steady state, the delivery of the aerosol decreases due to the reduction of the heat diffusion effect. As a result, in the case of a heated smoking device, the delivery of the aerosol, measured with respect to the main aerosol component such as nicotine, decreases over time. Increasing the temperature of the heating element during the final stage of the heating process can reduce or prevent the decrease in aerosol delivery over time.

[0011] In this context, continuous or repeated heating means heating a substrate or a part of the substrate over a duration that is usually longer than 5 seconds and, in some cases, longer than 30 seconds to generate an aerosol. In the context of a heated smoking device or other device where a user smokes and draws an aerosol from the device, this means heating the substrate such that an aerosol is continuously generated over a period that includes multiple puffs by the user, regardless of whether the user is puffing on the device. In this context, depletion of the substrate is an important issue. This is in contrast to momentary heating where a separate substrate or part of the substrate is heated for each puff by the user and the substrate part is not heated for a longer duration than a single puff that has a duration of about 2 - 3 seconds.

[0012] In this specification, the terms "puff" and "inhale" are used synonymously and mean the act by which a user inhales an aerosol into their body through the mouth or nose. Inhaling includes situations where the aerosol is inhaled into the user's lungs and also situations where the aerosol is inhaled only into the user's mouth or nasal cavity before being exhaled from the user's body.

[0013] Select the first, second, and third temperatures such that an aerosol is continuously generated during the first, second, and third stages. The first, second, and third temperatures are preferably determined based on a temperature range corresponding to the volatilization temperature of the aerosol former present in the substrate. For example, when using glycerin as the aerosol former, a temperature of 290 degrees Celsius to 320 degrees Celsius or higher (i.e., a temperature higher than the boiling point of glycerin) is used. During the second stage, power can be supplied to the heating element to ensure that the temperature does not fall below the minimum allowable temperature.

[0014] In the first stage, the temperature of the heating element is raised to a first temperature at which aerosol is generated from the aerosol-forming substrate. In many devices, particularly heated smoking devices, it is desirable to generate an aerosol containing the desired components as soon as possible after the device is activated. The "time to first puff" is considered extremely important to provide a satisfactory consumer experience for a heated smoking device. Consumers do not want to have to wait a long time from when the device is activated until the first puff. Therefore, in the first stage, power can be supplied to the heating element to raise the temperature of the heating element to the first temperature as quickly as possible. The first temperature can be selected to fall within an acceptable temperature range, but can be selected near the maximum allowable temperature in order to generate a satisfactory amount of aerosol for the first delivery to the consumer. During the initial operating time of the device, the delivery of the aerosol is reduced by condensation within the device.

[0015] The acceptable temperature range depends on the aerosol-forming substrate. The aerosol-forming substrate releases various ranges of volatile compounds at different temperatures. Some of the volatile compounds released from the aerosol-forming substrate are only formed through the heating process. Each volatile compound is released above its respective release temperature. By controlling the maximum operating temperature below the release temperatures of some of the volatile compounds, the release or formation of the components of these volatile compounds can be avoided. The maximum operating temperature can also be selected to ensure that the substrate does not burn under normal operating conditions.

[0016] The allowable temperature range can have a lower limit of 240 degrees Celsius to 340 degrees Celsius and an upper limit of 340 degrees Celsius to 400 degrees Celsius, and preferably can be 340 degrees Celsius to 380 degrees Celsius. The first temperature can be 340 degrees Celsius to 400 degrees Celsius. The second temperature can be 240 degrees Celsius to 340 degrees Celsius, preferably 270 degrees Celsius to 340 degrees Celsius, and the third temperature can be 340 degrees Celsius to 400 degrees Celsius, preferably 340 degrees Celsius to 380 degrees Celsius. The maximum operating temperature of the first, second, and third temperatures is preferably not more than the combustion temperature of undesirable compounds present in conventional cigarettes with a lit tip or about 380 degrees Celsius.

[0017] In the second and third stages, it is advantageous to perform the step of controlling the power supplied to the heating element so as to maintain the temperature of the heating element within the allowable temperature range or a desired temperature range.

[0018] There are many possibilities for determining when to transition from the first stage to the second stage and similarly when to transition from the second stage to the third stage. In one embodiment, each of the first, second, and third stages can have a predetermined duration. In this embodiment, the time after the operation of the device is used to determine when to start and end the second and third stages. In another example, the first stage can be ended as soon as the heating element reaches the first target temperature. In yet another example, the first stage ends based on a predetermined time after the heating element reaches the first target temperature. In another example, the first and second stages can be ended based on the total energy delivered to the heating element after activation. In yet another example, the device can be configured to detect smoking by the user using, for example, a dedicated flow sensor, and the first and second stages can be ended after a predetermined number of smoking times. It will be apparent that combinations of these options can be applied to the transition between any two stages. It will also be apparent that the operating stages of the heating element can be more than three different ones.

[0019] When the first stage ends, the second stage begins, and the power to the heating element is controlled such that the temperature of the heating element decreases to a second temperature that is lower than the first temperature but within an acceptable temperature range. The reason for this desired decrease in the temperature of the heating element is that as the device and the substrate warm up, condensation is suppressed at a predetermined heating element temperature and aerosol delivery increases. After the first stage, it is also desirable to lower the temperature of the heating element to suppress the possibility of the substrate burning. Also, reducing the temperature of the heating element decreases the amount of energy consumed by the aerosol generator. Further, by varying the temperature of the heating element during operation of the device, a time-modulated temperature gradient can be introduced into the substrate.

[0020] In the third stage, the temperature of the heating element is increased. During the third stage, it is desirable to continuously increase the temperature as the substrate becomes increasingly depleted. By increasing the temperature of the heating element during the third stage, the decrease in aerosol delivery due to substrate depletion and reduced heat diffusion is compensated for. However, the increase in the temperature of the heating element during the third stage can have any desired temporal profile and can depend on the shape of the device and the substrate, the composition of the equipment, and the duration of the first and second stages. It is desirable for the temperature of the heating element to be maintained within an acceptable range throughout the third stage. In one embodiment, the step of controlling the power to the heating element is performed to continuously increase the temperature of the heating element during the third stage.

[0021] The step of controlling the power to the heating element can include measuring the temperature of the heating element or the temperature near the heating element to provide a measured temperature, comparing the measured temperature with a target temperature, and adjusting the power supplied to the heating element based on this comparison result. The target temperature preferably varies with the time resulting from the first, second, and third stages after the operation of the device. For example, during the first stage, the target temperature can be set to a first target temperature, during the second stage, the target temperature can be set to a second target temperature, and during the third stage, the target temperature can be set to a third target temperature, and the third target temperature gradually increases with time. It will be apparent that the target temperature can be selected to have any desired temporal profile within the constraints of the first, second, and third operating stages.

[0022] The heating element can be an electrically resistive heating element, and the step of controlling the power supplied to the heating element can include measuring the electrical resistance of the heating element and adjusting the current supplied to the heating element depending on the measured electrical resistance. The electrical resistance of the heating element indicates the temperature of the heating element, and thus the measured electrical resistance can be compared with a target electrical resistance and the supplied power adjusted accordingly. A PID control loop can be used to lead the measured temperature to the target temperature. Further, in addition to or instead of detecting the electrical resistance of the heating element, mechanisms for detecting temperature such as a bimetal plate, a thermocouple or a dedicated thermistor, or an electrical resistance element electrically separated from the heating element can also be used. These alternative temperature detection mechanisms can be used in addition to or instead of temperature measurement by monitoring the electrical resistance of the heating element. For example, a separate temperature detection mechanism can be used within a control mechanism for reducing the power to the heating element when the temperature of the heating element exceeds an acceptable temperature range.

[0023] The method can further include the step of identifying the characteristics of the aerosol-forming substrate. Thereafter, the step of controlling the power can be adjusted depending on the identified characteristics. For example, different target temperatures can be used for different substrates.

[0024] In a second aspect of the present invention, there is provided an electrically operated aerosol generator, the apparatus comprising: at least one heating element configured to heat an aerosol-forming substrate to generate an aerosol; a power source for supplying power to the heating element; an electrical circuit for controlling the supply of power from the power source to the at least one heating element; wherein the electrical circuit is configured to control the power supplied to the heating element such that in a first stage, the temperature of the heating element rises from an initial temperature to a first temperature, in a second stage, the temperature of the heating element drops below the first temperature, and in a third stage, the temperature of the heating element rises again, with power being continuously supplied during the first, second, and third stages.

[0025] The options regarding the duration of each stage and the temperature of the heating element during each stage are as described in relation to the first aspect. The electrical circuit can be configured such that each of the first, second, and third stages has a constant duration. The electrical circuit can be configured to control the power supplied to the heating element such that the temperature of the heating element continuously rises during the third stage.

[0026] The circuit can be configured to supply power to the heating element as current pulses. The power supplied to the heating element can be adjusted by adjusting the duty cycle of the current. The duty cycle can be adjusted by changing the pulse width or the frequency of the pulses, or both. Alternatively, the circuit can be configured to supply power to the heating element as a continuous DC signal.

[0027] The electrical circuit can include temperature detection means configured to measure the temperature of the heating element or the temperature near the heating element to provide a measured temperature, and can be configured to compare the measured temperature with a target temperature and, based on this comparison, adjust the power supplied to the heating element. The target temperature can be stored in an electronic memory and preferably varies with the times resulting in the first, second, and third stages after the operation of the device.

[0028] The temperature detection means can be a dedicated electrical component such as a thermistor or a circuit configured to measure the temperature based on the electrical resistance of the heating element.

[0029] The electrical circuit can further include means for identifying the characteristics of the aerosol-forming substrate within the device and a memory holding a look-up table of power control instructions and the corresponding characteristics of the aerosol-forming substrate.

[0030] In the first and second aspects of the present invention, in both cases, the heating element can include an electric resistance material. Suitable electric resistance materials include, but are not limited to, doped ceramics, "conductive" ceramics (such as molybdenum disilicide), carbon, graphite, metals, metal alloys, and semiconductors such as composite materials composed of ceramic materials and metal materials. Such composite materials can include doped ceramics or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbide. Examples of suitable metals include titanium, zirconium, tantalum, platinum, gold, and silver. Examples of suitable metal alloys include stainless steel, nickel-containing alloys, cobalt-containing alloys, chromium-containing alloys, aluminum-containing alloys, titanium-containing alloys, zirconium-containing alloys, hafnium-containing alloys, niobium-containing alloys, molybdenum-containing alloys, tantalum-containing alloys, tungsten-containing alloys, tin-containing alloys, gallium-containing alloys, manganese-containing alloys, gold-containing alloys, and iron-containing alloys, and superalloys based on nickel, iron, cobalt, stainless steel, Timetal® (registered trademark), and iron-manganese-aluminum-based alloys. In the composite material, depending on the dynamics of energy transfer and the required external physico-chemical properties, the electric resistance material can optionally be embedded in an insulating material, or encapsulated or coated with an insulating material, or vice versa.

[0031] In the first and second aspects of the present invention, the aerosol generating device can include an internal heating element, an external heating element, or both, where "internal" and "external" relate to the aerosol-forming substrate. The internal heating element can take any suitable form. For example, the internal heating element can take the form of a heating blade. Alternatively, the internal heater can also take the form of a casing or substrate having different conductive parts, or an electrically resistive metal tube. Alternatively, the internal heating element can be one or more heating needles or rods passing through the center of the aerosol-forming substrate. Other options include, for example, heating wires or filaments such as Ni-Cr (nickel-chromium), platinum, tungsten, or alloy wires, or heating plates. Optionally, the internal heating element can be deposited within or on a rigid carrier material. In such an embodiment, an electrically resistive heating element can be formed using a metal having a defined temperature-resistivity relationship. In such an exemplary device, the metal can be formed as a track on a suitable insulating material such as a ceramic material and sandwiched between another insulating material such as glass. The heater thus formed can be used to both heat the heating element and monitor the temperature during operation.

[0032] The external heating element can take any suitable form. For example, the external heating element can take the form of one or more flexible heating foils on a dielectric substrate such as polyimide. This flexible foil can be shaped to conform to the outer periphery of the substrate receiving cavity. Alternatively, the external heating element can also take the form of one or more metal grids, flexible circuit boards, molded interconnect devices (MIDs), ceramic heaters, flexible carbon fiber heaters, or can be formed on a suitable shaped substrate using coating techniques such as plasma deposition. The external heating element can also be formed using a metal having a defined temperature-resistivity relationship. In such an exemplary device, this metal can be formed as a track between two layers of suitable insulating materials. Using the external heating element formed in this way, both heating and temperature monitoring of the external heating element can be performed during operation.

[0033] The internal or external heating element can include a heat sink or a heat storage body containing a material that can absorb heat and store it and then release the heat to the aerosol-forming substrate over time. The heat sink can be formed of any suitable material such as a suitable metal or ceramic material. In one embodiment, this material has a high heat capacity (sensible heat storage material) or is a material that can release heat through a reversible process such as a high-temperature phase change after absorbing heat. Suitable sensible heat storage materials include silica gel, alumina, carbon, glass mat, glass fiber, minerals, metals or alloys such as aluminum, silver or lead, and cellulose materials such as paper. Other suitable materials that release heat through a reversible phase change include paraffin, sodium acetate, naphthalene, wax, polyethylene oxide, metals, metal salts, mixtures of eutectic salts, or alloys. The heat sink or heat storage body can be configured to be in direct contact with the aerosol-forming substrate so as to directly transfer the stored heat to the substrate. Alternatively, the heat stored in the heat sink or heat storage body can also be transferred to the aerosol-forming substrate using a heat conductor such as a metal tube.

[0034] The heating element advantageously heats the aerosol-forming substrate by heat conduction. The heating element can be in at least partial contact with the substrate or the carrier on which the substrate is deposited. Alternatively, heat from either an internal or external heating element can be conducted to the substrate by a heat-conducting element.

[0035] In both the first and second aspects of the invention, during operation, the aerosol-forming substrate can be completely accommodated within the aerosol-generating device. In this case, the user can puff on the mouthpiece of the aerosol-generating device. Alternatively, during operation, a smoking article containing the aerosol-forming substrate can be partially accommodated within the aerosol-generating device. In this case, the user can puff directly on the smoking article. The heating element can be located within a cavity of the device, which is configured to receive the aerosol-forming substrate such that during use the heating element is present within the aerosol-forming substrate.

[0036] The smoking article can be substantially cylindrical in shape. The smoking article can be substantially elongated. The smoking article can have a length and an outer perimeter that is substantially perpendicular to this length. The aerosol-forming substrate can be substantially cylindrical in shape. The aerosol-forming substrate can be substantially elongated. The aerosol-forming substrate can also have a length and an outer perimeter that is substantially perpendicular to this length.

[0037] The smoking article can have an overall length of from about 30 mm to about 100 mm. The smoking article can have an outer diameter of from about 5 mm to about 12 mm. The smoking article can include a filter plug. The filter plug can be located at the downstream end of the smoking article. The filter plug can be a cellulose acetate filter plug. The filter plug can be about 7 mm in length in one embodiment, but can have a length of from about 5 mm to about 10 mm.

[0038] In one embodiment, the smoking article has an overall length of about 45 mm. The smoking article can have an outer diameter of about 7.2 mm. Further, the aerosol-forming substrate can have a length of about 10 mm. Alternatively, the aerosol-forming substrate can have a length of about 12 mm. Further, the diameter of the aerosol-forming substrate can be from about 5 mm to about 12 mm. The smoking article can include an outer paper wrapper. Further, the smoking article can have a separation distance between the aerosol-forming substrate and the filter plug. This separation distance can be about 18 mm, but can be from about 5 mm to about 25 mm. This separation distance is preferably filled within the smoking article by a heat exchanger that cools the aerosol as it passes from the substrate to the filter plug within the smoking article. The heat exchanger can be, for example, a polymer filter such as a wrinkled PLA material.

[0039] In the first and second aspects of the present invention, the aerosol-forming substrate can be a solid aerosol-forming substrate in both cases. Alternatively, the aerosol-forming substrate can also include both a solid component and a liquid component. The aerosol-forming substrate can include a tobacco-containing material that includes volatile tobacco flavor compounds released from the substrate upon heating. Alternatively, the aerosol-forming substrate can also include a non-tobacco material. The aerosol-forming substrate can further include an aerosol-forming body. Examples of suitable aerosol-forming bodies include glycerin and propylene glycol.

[0040] When the aerosol-forming substrate is a solid aerosol-forming substrate, the solid aerosol-forming substrate can comprise, for example, one or more of powdered, granular, pelletized, flaked, filamentous, strip or sheet forms containing one or more of herb leaves, tobacco leaves, fragments of tobacco stems, reconstituted tobacco, homogenized tobacco, extracted tobacco, shaped leaf tobacco and expanded tobacco. The solid aerosol-forming substrate can be in a loose form or provided in a suitable container or cartridge. Optionally, the solid aerosol-forming substrate can also contain additional tobacco or non-tobacco volatile flavor compounds released upon heating of the substrate. The solid aerosol-forming substrate can also contain capsules containing additional tobacco or non-tobacco volatile flavor compounds, such capsules being capable of dissolving during heating of the solid aerosol-forming substrate.

[0041] As used herein, homogenized tobacco means a material formed by agglomerating particulate tobacco. Homogenized tobacco can take the form of a sheet. The homogenized tobacco material can have an aerosol-forming agent content of more than 5% dry weight. Alternatively, the homogenized tobacco material can also have an aerosol-forming agent content of 5-30% dry weight. The sheet of homogenized tobacco material can be formed by agglomerating particulate tobacco obtained by grinding or otherwise pulverizing one or both of the blade of the tobacco leaf and the stem of the tobacco leaf into a mass. Separately or in addition thereto, the sheet of homogenized tobacco material can also contain one or more of, for example, tobacco scraps, tobacco powder and other particulate tobacco formed as by-products during the processing, handling and shipping of tobacco. The sheet of homogenized tobacco material can contain one or more endogenous binders sourced from within the tobacco, one or more exogenous binders sourced from outside the tobacco, or a combination thereof, to assist in agglomerating the particulate tobacco into a mass. Separately or in addition thereto, the sheet of homogenized tobacco material can also contain other additives including, but not limited to, tobacco and non-tobacco fibers, aerosol-forming agents, humectants, plasticizers, flavorants, fillers, aqueous and non-aqueous solvents, and combinations thereof.

[0042] Optionally, the solid aerosol-forming substrate can be provided on or embedded in a thermally stable carrier. The carrier can take the form of a powder, granule, pellet, chip, filament, strip or sheet. Alternatively, the carrier can be a tubular carrier having a thin layer of the solid substrate deposited on its inner or outer surface, or both. Such a tubular carrier can be formed, for example, from paper or paper-like material, a non-woven carbon fiber mat, a low-mass mesh metal screen or a perforated metal foil, or any other thermally stable polymer matrix.

[0043] The solid aerosol-forming substrate can be deposited on the surface of the carrier, for example, in the form of a sheet, foam, gel or slurry. The solid aerosol-forming substrate can be deposited over the entire surface of the carrier or in a defined pattern such that non-uniform fragrance delivery occurs during use.

[0044] Having described the solid aerosol-forming substrate above, it will be apparent to those skilled in the art that in other embodiments other forms of aerosol-forming substrates can be used. For example, the aerosol-forming substrate can be a liquid aerosol-forming substrate. When providing a liquid aerosol-forming substrate, the aerosol generating device preferably has means for holding the liquid. For example, the liquid aerosol-forming substrate can be held within a container. Alternatively or in addition to this, the liquid aerosol-forming substrate can be absorbed into a porous carrier material. The porous carrier material can be formed from any suitable absorbent plug or absorber such as, for example, a foamed metal or plastic material, polypropylene, terylene, nylon fiber or ceramic. The liquid aerosol-forming substrate can be held within the porous carrier material prior to use of the aerosol generating device or the liquid aerosol-forming substrate material can be released into the porous carrier material during or immediately prior to use. For example, the liquid aerosol-forming substrate can be provided in capsules. The shell of the capsule preferably dissolves upon heating to release the liquid aerosol-forming substrate into the porous carrier material. The capsule can optionally also contain a solid in combination with the liquid.

[0045] Alternatively, the carrier can also be a non-woven fabric or a fiber bundle incorporated with tobacco components. The non-woven fabric or fiber bundle can include, for example, carbon fibers, natural cellulose fibers, or cellulose-derived fibers.

[0046] In the first and second aspects of the present invention, the aerosol generating device can further include a power source for supplying power to the heating element. The power source can be any suitable power source such as, for example, a DC voltage source. In one embodiment, the power source is a lithium-ion battery. Alternatively, the power source can be a nickel-metal hydride battery, a nickel-cadmium battery, or a lithium-based battery such as, for example, a lithium cobalt battery, a lithium iron phosphate battery, a lithium titanate battery, or a lithium polymer battery.

[0047] In the third aspect of the present invention, there is provided an electric circuit for an electrically operated aerosol generating device configured to execute the method of the first aspect of the present invention.

[0048] In the fourth aspect of the present invention, there is provided a computer program that causes a programmable electric circuit for an electrically operated aerosol generating device to execute the method of the first aspect of the present invention when executed on the programmable electric circuit. In the fifth aspect of the present invention, there is provided a computer-readable storage medium storing the computer program according to the fourth aspect of the present invention.

[0049] Although the present disclosure has been described with reference to different aspects, it will be apparent that the features described in connection with one aspect of the present disclosure can also be applied to other aspects of the present disclosure.

[0050] Hereinafter, embodiments of the present invention will be described in detail by way of example with reference to the accompanying drawings.

Brief Description of the Drawings

[0051]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0052] In FIG. 1, the components of an embodiment of an electrically heated aerosol generating device 100 are shown in a simplified form. Specifically, in FIG. 1, the elements of the electrically heated aerosol generating device 100 are not shown to scale. In FIG. 1, elements not relevant to the understanding of the present embodiment are omitted for simplification.

[0053] The electrically heated aerosol generating device 100 includes a housing 10 and an aerosol forming substrate 12 such as a cigarette. The aerosol forming substrate 12 is pushed into the housing 10 and is thermally proximate to the heating element 14. The aerosol forming substrate 12 releases various ranges of volatile compounds at different temperatures. By controlling the operating temperature of the electrically heated aerosol generating device 100 to be below the release temperatures of some of the volatile compounds, the release or formation of the components of these volatile compounds can be avoided.

[0054] Inside the housing 10, there is an electrical energy supply source 16 such as, for example, a rechargeable lithium-ion battery. A controller 18 is connected to the heating element 14, the electrical energy supply source 16, and a user interface 20 such as, for example, a button or a display. The controller 18 controls the power supplied to the heating element 14 in order to adjust the temperature of the heating element 14. Usually, the aerosol-forming substrate is heated to a temperature between 250 degrees Celsius and 450 degrees Celsius.

[0055] In the embodiment to be described, the heating element 14 is one or more electrical resistance tracks deposited on a ceramic substrate. The ceramic substrate is in the form of a blade and is inserted into the aerosol-forming substrate 12 during use. FIG. 2 is a schematic view of the front end of the device and shows the air flow through the device. Note that in FIG. 2, the relative dimensions of the elements of the device are not shown accurately. The smoking article 102 including the aerosol-forming substrate 12 is received within the cavity 22 of the device 100. Air is drawn into the device by the user's act of sucking on the mouthpiece 24 of the smoking article 102. The air is drawn in through an inlet 26 that forms the proximal surface of the housing 10. The air drawn into the device passes through an air channel 28 around the outer periphery of the cavity 22. The drawn air enters the aerosol-forming substrate 12 at the distal end of the smoking article 102 adjacent to the proximal end of the blade-shaped heating element 14 provided within the cavity 22. The drawn air travels through the aerosol-forming substrate 12 and, together with the aerosol, reaches the lip-side end of the smoking article 102. The aerosol-forming substrate 12 is a cylindrical plug of tobacco-based material.

[0056] As shown in FIG. 3, the current aerosol generator is configured to provide a constant temperature during operation. After the device is activated, power is supplied to the heating element until the target temperature of 50 is reached. When the target temperature of 50 is reached, the heating element is maintained at this temperature until the device stops. FIG. 4 is a schematic diagram showing the delivery of the main aerosol components using the flat temperature profile shown in FIG. 3. Line 52 represents the amount of the main aerosol components such as glycerol or nicotine delivered during the operation of the device. It can be seen that the delivery of the components reaches a peak and then decreases over time as the substrate is depleted and the heat diffusion effect weakens.

[0057] FIG. 5 is a schematic diagram of the temperature profile of the heating element according to an embodiment of the present invention. Line 60 represents the temperature of the heating element over time.

[0058] In the first stage 70, the temperature of the heating element rises from the ambient temperature to the first temperature 62. The temperature 62 is within the allowable temperature range between the minimum temperature 66 and the maximum temperature 68. The allowable temperature change is set so that the desired volatile compounds volatilize from the substrate, but the undesirable compounds that volatilize at higher temperatures do not volatilize. Also, the allowable temperature range is below the temperature at which combustion of the substrate can occur under normal operating conditions, i.e., normal temperature, pressure, humidity, the user's smoking action, and air composition.

[0059] In the second stage 72, the temperature of the heating element drops to a second temperature. The second temperature is within the allowable temperature range but lower than the first temperature.

[0060] In the third stage 74, the temperature of the heating element gradually rises until the stop time 76. The temperature of the heating element is maintained within the allowable temperature range throughout the third stage.

[0061] FIG. 6 is a schematic diagram of the delivery profile of the main aerosol components according to the temperature profile of the heating element shown in FIG. 5. After the initial delivery increase after the activation of the heating element, the delivery remains constant until the heating element stops. The increase in temperature in the third stage compensates for the depletion of the aerosol-forming material of the substrate.

[0062] Figure 7 shows a control circuit used to implement the described temperature profile according to one embodiment of the present invention.

[0063] The heater 14 is connected to the battery via the connection part 42. This battery (not shown in Figure 7) supplies a voltage V2. A further resistor 44 with a known resistance r is inserted in series with the heating element 14 and connected to the voltage V1 intermediate between the ground and the voltage V2. The frequency modulation of the current is controlled by the microcontroller 18 and delivered via its analog output 47 to a transistor 46 that functions as a simple switch.

[0064] This adjustment is based on a PID regulator which is part of the software incorporated in the microcontroller 18. The temperature of the heating element (or indication of temperature) is determined by measuring the electrical resistance of the heating element. To keep the heating element at the target temperature or to adjust the temperature of the heating element towards the target temperature, the determined temperature is used to adjust the duty cycle (frequency modulation in this example) of the pulses of the current supplied to the heating element. The temperature is determined at a frequency selected to conform to the control of the duty cycle and can be determined at a frequency of once every 100 ms.

[0065] The analog input 48 to the microcontroller 18 is used to collect the voltage of the resistor 44 and provides an image of the current flowing through the heating element. Using the battery voltage V+ and the voltage of the resistor 44, the resistance variation and / or the temperature of the heating element are calculated.

[0066] Let the resistance of the heater measured at a specific temperature be R heater . For the microprocessor 18 to measure the resistance R heater of the heater 14, both the current of the heater 14 and the voltage of the heater 14 need to be determined. As a result, the resistance can be determined using the following well-known formula. JPEG2025100924000002.jpg620(1)

[0067] In Figure 6, the voltage of the heater is V2 - V1 and the current of the heater is I. Therefore, the following equation can be obtained. JPEG2025100924000003.jpg1437(2)

[0068] Using an additional resistor 44 with a known resistance r, the current I is obtained again using the above (1). The current of resistor 44 is I and the voltage of resistor 24 is V1. Therefore, the following equation can be obtained. JPEG2025100924000004.jpg1417(3)

[0069] Therefore, by combining (2) and (3), the following equation can be obtained. JPEG2025100924000005.jpg1446(4)

[0070] In this way, the microprocessor 18 can measure V2 and V1 when the aerosol generation system is in use, and with the known value of r, the resistance R of the heater at a specific temperature heater can be obtained.

[0071] The resistance of the heater is correlated with temperature. Using linear approximation, the temperature T and the resistance R heater measured at temperature T can be associated according to the following equation. JPEG2025100924000006.jpg1439(5) In the equation, A is the thermal resistivity coefficient of the heating element material and R0 is the resistance of the heating element at room temperature T0.

[0072] If a simple linear approximation is not sufficient over the operating temperature range, other more complex methods can be used to approximate the relationship between resistance and temperature. For example, in another embodiment, the relationship can be derived based on a combination of two or more linear approximations, each covering a different temperature range. This scheme relies on three or more temperature calibration points at which the resistance of the heater is measured. At temperatures intermediate these calibration points, the resistance value is interpolated from the values at the calibration points. The calibration point temperatures are selected to cover the expected temperature range of the heater during operation.

[0073] The advantage of these embodiments is that they do not require a temperature sensor, which can be large and expensive. Also, the PID regulator can use the resistance value directly instead of the temperature. This resistance value is directly correlated to the temperature of the heating element as shown in equation (5). Thus, if the measured resistance value is within the desired range, the temperature of the heating element is also within the desired range. Therefore, it is not necessary to calculate the actual temperature of the heating element. However, it is also possible to use a separate temperature sensor connected to the microcontroller to provide the necessary temperature information.

[0074] Figure 8 shows an example of a target temperature profile where three operating stages can be clearly identified. In the first stage 70, the target temperature is set to T0. Power is supplied to the heating element to raise its temperature to T0 as quickly as possible. As described above, the PID regulator is used to keep the temperature of the heating element as close as possible to the target temperature throughout the operation of the device. At time t1, the target temperature changes to T1, which means that the first stage 70 has ended and the second stage has started. The target temperature is maintained at T1 until time t2. At time t2, the second stage ends and the third stage 74 starts. During the third stage 74, the target temperature rises linearly with the increase in time until time t3, at which point the target temperature reaches T2 and no more power is supplied to the heating element.

[0075] The target temperature profile of the shape shown in FIG. 8 results in the actual temperature profile of the shape shown in FIG. 5. The values of T0, T1, and T2 can be adjusted to suit a particular substrate and particular apparatus, heating element, and substrate shape. Similarly, the values of t1, t2, and t3 can also be selected to suit the situation.

[0076] In one example, the first stage is 45 seconds in length and T0 is set to 360 °C, the second stage is 145 seconds in length and T1 is 320 °C, and the third stage is 170 seconds in length and T2 is 380 °C. The smoking experience lasts for a total of 360 seconds.

[0077] In another example, the first stage is 60 seconds in length and T0 is set to 340 °C, the second stage is 180 seconds in length and T1 is 320 °C, and the third stage is 120 seconds in length and T2 is 360 °C. Again, the heating cycle or smoking experience lasts for a total of 360 seconds.

[0078] In yet another example, the first stage is 30 seconds in length and T0 is set to 380 °C, the second stage is 110 seconds in length and T1 is 300 °C, and the third stage is 220 seconds in length and T2 is 340 °C.

[0079] The duration and temperature targets of each operating stage are stored in the memory within the controller 18. This information can be part of the software executed by the microcontroller. On the other hand, this information can also be stored in a look-up table so that the microcontroller can select different profiles. Consumers can select different profiles via the user interface based on the user's preferences or the particular substrate to be heated. The apparatus can include substrate identification means such as an optical reader, and a heating profile automatically selected based on the identified substrate.

[0080] In another embodiment, only the target temperatures T0, T1, and T2 are stored in the memory, and the transitions between the stages are caused by the number of puffs. For example, the microcontroller can receive puff count data from the flow sensor and can be configured to end the first stage after two puffs and end the second stage after an additional five puffs.

[0081] In each of the above-described embodiments, when compared with the flat heating profile shown in FIG. 3, the aerosol is delivered more evenly during heating of the substrate. The optimal heating profile depends on a plurality of factors and can be determined experimentally for a given device, the shape of the substrate, and the composition of the substrate. For example, the device can include more than one heating element, and the configuration of the heating elements affects the depletion of the substrate and the heat dissipation effect. Each heating element can be controlled to have a different heating profile. The shape and size of the substrate with respect to the heating elements are also important factors.

[0082] It will be apparent that the above exemplary embodiments are illustrative and not limiting. Given the above exemplary embodiments, other embodiments in accordance with these exemplary embodiments will already be apparent to those skilled in the art.

Description of Reference Numerals

[0083] 60 wire 62 First temperature 66 Minimum temperature 68 Maximum temperature 70 First stage 72 Second stage 74 Third stage 76 Stop time

Claims

1. A method for controlling the generation of aerosol in an aerosol generating device, the device comprising: a heater including at least one heating element configured to heat an aerosol forming substrate; a power source for supplying power to the heating element; and the method comprises: controlling the power supplied to the heating element such that in a first stage, power is supplied so that the temperature of the heating element rises from an initial temperature to a first temperature, in a second stage, power is supplied so that the temperature of the heating element drops to a second temperature lower than the first temperature, and in a third stage, power is supplied so that the temperature of the heating element rises again. A method characterized by the above.

2. The step of controlling the power supplied to the heating element is performed so as to maintain the temperature of the heating element within a desired temperature range in the second stage and the third stage. The method according to claim 1, characterized by the above.

3. The desired temperature range has a lower limit of 240 degrees Celsius to 340 degrees Celsius and an upper limit of 340 degrees Celsius to 400 degrees Celsius. The method according to claim 1, characterized by the above.

4. The first temperature is 340 degrees Celsius to 400 degrees Celsius. The method according to any one of claims 1 to 3, characterized by the above.

5. The first stage, the second stage or the third stage has a predetermined duration. The method according to any one of claims 1 to 4, characterized by the above.

6. The first stage ends when the heating element reaches the first temperature. The method according to any one of claims 1 to 5, characterized by the above.

7. The duration of the second stage is determined based on the total amount of power supplied to the heating element during the second stage. The method according to any one of claims 1 to 6, characterized by the above.

8. The method further includes the step of detecting smoking of the aerosol generating device by a user, and the first, second or third stage ends after detecting a predetermined number of smoking times by the user. The method according to any one of claims 1 to 7, characterized by the above.

9. The method further includes the step of identifying the characteristics of the aerosol forming substrate, and the step of controlling the power is adjusted depending on the identified characteristics. The method according to any one of claims 1 to 8, characterized by the above.

10. An electrically operated aerosol generating device, At least one heating element configured to heat an aerosol-forming substrate to generate an aerosol, A power source for supplying power to the heating element, An electrical circuit for controlling the supply of power from the power source to at least the one heating element, Comprising, the electrical circuit, The power supplied to the heating element is controlled such that in a first stage the temperature of the heating element rises from an initial temperature to a first temperature, in a second stage the temperature of the heating element drops below the first temperature, and in a third stage the temperature of the heating element rises again, with power being continuously supplied during the first, second and third stages. An electrically-operated aerosol generating device, characterized in that.

11. The electrical circuit is configured such that at least one of the first stage, the second stage and the third stage has a constant duration. The electrically-operated aerosol generating device according to claim 10, characterized in that.

12. Further comprising means for detecting smoking of the aerosol generating device by a user, the electrical circuit being configured such that at least one of the first, second or third stages ends after a predetermined number of smoking detections by the user. The electrically-operated aerosol generating device according to claim 10 or 11, characterized in that.

13. Further comprising means for identifying the characteristics of the aerosol-forming substrate within the device, the control circuit including a memory holding a look-up table of power control instructions and the corresponding characteristics of the aerosol-forming substrate. The electrically-operated aerosol generating device according to claim 10, 11 or 12, characterized in that.

14. The heating element is located within a cavity of the device, the cavity being configured to receive the aerosol-forming substrate such that during use the heating element is present within the aerosol-forming substrate. The electrically-operated aerosol generating device according to any one of claims 10 to 13, characterized in that.

15. An electrical circuit for an electrically-operated aerosol generating device, configured to perform the method according to claim 1. An electrical circuit, characterized in that.

16. When executed on a programmable electrical circuit for an electrically-operated aerosol generating device, causing the programmable electrical circuit to perform the method according to claim 1. A computer program, characterized in that.

17. A computer-readable storage medium storing the computer program according to claim 1, characterized in that.

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