Aerosol-generating system comprising fluid permeable susceptor element

Abstract

To provide aerosol-generating systems that operate by heating an aerosol-forming substrate.SOLUTION: An electrically heated aerosol-generating system includes an aerosol-generating device and a cartridge configured to be used with the device. The device includes: a device housing configured to engage at least a portion of the cartridge; an inductor coil positioned around or adjacently to the cavity; and a power supply connected to the inductor coil and configured to provide a high frequency oscillating current to the inductor coil. The cartridge includes a cartridge housing configured to engage the device housing and containing an aerosol-forming substrate, the cartridge housing having an external surface surrounding the aerosol-forming substrate, at least a portion of the external surface being formed by a fluid-permeable susceptor element.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an aerosol generating system that operates by heating an aerosol-forming substrate. In particular, the present disclosure relates to an aerosol generating system that includes a device portion that includes a power source and a replaceable cartridge portion that includes a consumable aerosol-forming substrate. [Background technology]

[0002] One type of aerosol-generating system is the electronic cigarette. Electronic cigarettes typically use a liquid aerosol-forming substrate that is vaporized to form an aerosol. Electronic cigarettes typically include a power source, a liquid reservoir for holding a dose of the liquid aerosol-forming substrate, and an atomizer.

[0003] Liquid aerosol-forming substrates become depleted during use and therefore need to be replenished. The most common way to provide refills of liquid aerosol-forming substrates is in cartomizer-type cartridges. A cartomizer contains both a single dose of liquid substrate and an atomizer, usually in the form of an electrically operated resistance heater wrapped around a capillary material immersed in the aerosol-forming substrate. Replacing the cartomizer as a single unit has the advantage of convenience for the user and also avoids the need for the user to clean or otherwise maintain the atomizer. Summary of the Invention [Problem to be solved by the invention]

[0004] However, it would be desirable to provide a system that is cheaper to manufacture and more robust than currently available cartomizers, allowing for refills of the aerosol-forming substrate, while still being easy and convenient for the consumer to use. Additionally, it would be desirable to provide a system that eliminates the need for soldered seams, allowing for a sealed device that is easy to clean. [Means for solving the problem]

[0005] In a first aspect, there is provided an electrically heated aerosol generation system comprising an aerosol generation device and a cartridge configured for use with the device, the device comprising: a device housing; an inductor coil disposed around or adjacent to the recess; a power supply connected to the inductor coil and configured to provide a high frequency oscillating current to the inductor coil; The cartridge is The cartridge housing is configured to engage the device housing and contain the aerosol-forming substrate, the housing having an exterior surface surrounding the aerosol-forming substrate, at least a portion of the exterior surface being formed by a fluid-permeable susceptor element.

[0006] In operation, a high-frequency oscillating current is passed through the flat spiral inductor coil, generating an alternating magnetic field that induces a voltage within the susceptor element. The induced voltage causes a current to flow within the susceptor element, which in turn causes Joule heating of the susceptor, which in turn heats the aerosol-forming substrate. If the susceptor element is ferromagnetic, hysteresis losses within the susceptor element may also generate heat. The vaporized aerosol-forming substrate is allowed to pass through the susceptor element, where it subsequently cools to form an aerosol that is delivered to the user.

[0007] This induction heating arrangement has the advantage that no electrical contacts need to be made between the cartridge and the device. Also, the heating element (in this case, the susceptor element) does not need to be electrically coupled to any other components, eliminating the need for solder or other bonding elements. Furthermore, the coil is provided as a component of the device, allowing for the construction of a simple, inexpensive, and robust cartridge. Cartridges are generally disposable items manufactured in much larger quantities than the devices they operate. Therefore, reducing the cost of the cartridge can result in significant cost savings for both the manufacturer and the consumer, even when more expensive devices are required.

[0008] As used herein, high frequency oscillating current refers to an oscillating current having a frequency of 500 kHz to 30 MHz. The frequency of the high frequency oscillating current can be 1 to 30 MHz, preferably 1 to 10 MHz, and more preferably 5 to 7 MHz.

[0009] As used herein, "susceptor element" refers to a conductive element that heats up when exposed to a fluctuating magnetic field. This may be the result of eddy currents and / or hysteresis losses induced within the susceptor element. Possible materials for the susceptor element include graphite, molybdenum, silicon carbide, stainless steel, niobium, aluminum, and almost any other conductive element. Advantageously, the susceptor element is a ferrite element. The material and geometry of the susceptor element can be selected to provide the desired electrical resistance and heat generation. The susceptor element may comprise, for example, a mesh, a flat spiral coil, a fiber, or a cloth.

[0010] As used herein, a "fluid-permeable" element means an element that allows a liquid or gas to permeate therethrough. The susceptor element may have a plurality of openings therein that are formed to allow a fluid to permeate through the openings. In particular, the susceptor element allows the aerosol-forming substrate, either in the gas phase or in both the gas and liquid phases, to permeate through the openings.

[0011] The susceptor element may be in the form of a sheet that extends across an opening in the cartridge housing.The susceptor element may extend around the periphery of the cartridge housing.

[0012] The device housing may include a recess for receiving at least a portion of the cartridge when the cartridge housing is engaged with the device housing, the recess having an interior surface. The inductor coil may be disposed on or adjacent to a surface of the recess closest to the power source. The inductor coil may be shaped to conform to the interior surface of the recess.

[0013] The device housing can include a body and a mouthpiece portion. The cavity can be in the body, and the mouthpiece portion can have an outlet through which aerosol generated by the system is drawn into the user's mouth. The inductor coil can be in the mouthpiece portion or in the body.

[0014] Alternatively, the mouthpiece portion may be provided as part of the cartridge. As used herein, the term mouthpiece portion refers to the portion of the device or cartridge that is placed in the user's mouth for direct inhalation of the aerosol generated by the aerosol generation system. The aerosol is delivered to the user's mouth through the mouthpiece portion.

[0015] The system may include an air path extending from an air inlet to an air outlet, where the air path passes through an inductor coil. By allowing air flow through the system and past the coil, a compact system may be achieved.

[0016] The cartridge may have a simple design. The cartridge has a housing within which the aerosol-forming substrate is held. The cartridge housing is preferably a rigid housing comprising a material that is impermeable to liquids. As used herein, "rigid housing" means a free-standing housing.

[0017] An aerosol-forming substrate is a substrate capable of releasing a volatile compound capable of forming an aerosol. The volatile compound can be released by heating the aerosol-forming substrate. The aerosol-forming substrate can be solid or liquid, or can contain both solid and liquid components.

[0018] The aerosol-forming substrate may comprise a plant-derived material. The aerosol-forming substrate may comprise tobacco. The aerosol-forming substrate may comprise a tobacco-containing material comprising volatile tobacco flavour compounds that are released from the aerosol-forming substrate upon heating. Alternatively, the aerosol-forming substrate may comprise a non-tobacco-containing material. The aerosol-forming substrate may comprise a homogenised plant-derived material. The aerosol-forming substrate may comprise a homogenised tobacco material. The aerosol-forming substrate may comprise at least one aerosol former. The aerosol-forming agent is any suitable known compound or mixture of compounds that is substantially resistant to thermal decomposition at the operating temperature of the system, which facilitates the formation of a dense, stable aerosol in use. Suitable aerosol formers are well known in the art and include, but are not limited to, polyhydric alcohols (such as triethylene glycol, 1,3-butanediol, and glycerin), esters of polyhydric alcohols (such as glycerol monoacetate, diacetate, or triacetate), and aliphatic esters of monocarboxylic, dicarboxylic, or polycarboxylic acids (such as dimethyl dodecanedioate and dimethyl tetradecanedioate). Preferred aerosol formers are polyhydric alcohols or mixtures thereof (such as triethylene glycol, 1,3-butanediol, and glycerin, most preferred). The aerosol-forming substrate may contain other additives and ingredients, such as flavorings.

[0019] The aerosol-forming substrate may be adsorbed, coated, impregnated, or otherwise loaded onto a carrier or support. In one example, the aerosol-forming substrate is a liquid substrate held within a capillary material. The capillary material may have a fibrous or spongy structure. Preferably, the capillary material comprises a bundle of capillaries. For example, the capillary material may comprise a plurality of fibers or threads or other fine tubes. The fibers or threads may be generally aligned to transport the liquid to the heater. Alternatively, the capillary material may comprise a sponge-like or foam-like material. The structure of the capillary material forms a plurality of small holes or tubes through which the liquid can travel by capillary action. The capillary material may comprise any suitable material or combination of materials. Examples of suitable materials include sponge or foam materials, ceramic or graphite-based materials in the form of fibers or sintered powders, expanded metal or plastic materials, and fibrous materials, such as spun or extruded fibers (such as cellulose acetate, polyester, or bonded polyolefin, polyethylene, terylene, or polypropylene fibers, nylon fibers, or ceramics). Capillary materials may have any suitable capillary and porosity for use with different liquid physical properties. Liquids have physical properties, including, but not limited to, viscosity, surface tension, density, thermal conductivity, boiling point, and vapor pressure, that allow them to move through the capillary material by capillary action. The capillary material may be configured to transport the aerosol-forming substrate to the susceptor element. The capillary material may extend into interstices within the susceptor element.

[0020] The susceptor elements may be provided on a wall of the cartridge housing configured to be positioned adjacent to the inductor coil when the cartridge housing is engaged with the device housing. In use, it is advantageous to position the susceptor elements close to the inductor coil to maximize the voltage induced in the susceptor elements.

[0021] When the cartridge housing is engaged with the device housing, an airflow passage can be provided between the inductor coil and the susceptor element. The vaporized aerosol-forming substrate can be entrained in the airflow passage and then cools to form an aerosol.

[0022] The inductor coil can be a helical coil or a flat spiral coil. As used herein, "flat spiral coil" generally refers to a planar coil, with the axis of the coil's windings perpendicular to the surface on which the coil lies. However, as used herein, the term "flat spiral coil" encompasses flat coils as well as flat spiral coils shaped to conform to curved surfaces. The use of a flat spiral coil allows for a compact device design with a simple design that is robust and inexpensive to manufacture. The coil can be retained within the device housing to prevent deposits and potential corrosion on the coil and does not need to be exposed to generated aerosols. The use of a flat spiral coil also allows for a simple interface between the device and cartridge, allowing for a simple and inexpensive cartridge design.

[0023] A flat spiral inductor can have any desired shape in the plane of the coil. For example, a flat spiral coil can have a circular shape or a generally oblong shape.

[0024] The coil diameter can be between 5mm and 10mm.

[0025] The inductor coil may be located on or adjacent to the surface of the cavity closest to the power source, thereby reducing the amount and complexity of electrical connections within the apparatus. The system may include multiple inductor coils and may also include multiple susceptor elements.

[0026] The inductor coil may have a shape that matches the shape of the susceptor element.

[0027] Advantageously, the susceptor element has a relative permeability of 1 to 40,000. A lower permeability material may be used when it is desired to rely on eddy currents for the majority of the heating, and a higher permeability material may be used when a hysteresis effect is desired. Preferably, the relative permeability of the material is 500 to 40,000. This provides efficient heating.

[0028] The material of the susceptor element may be selected because of its Curie temperature, above which hysteresis losses no longer occur and the material is no longer ferromagnetic and therefore no longer heats up. If the susceptor element is made of a single material, the Curie temperature may correspond to the maximum temperature the susceptor element should have (i.e., the Curie temperature is equal to the maximum temperature to which the susceptor element should be heated or deviates from this maximum temperature by approximately 1-3%). This reduces the possibility of rapid overheating.

[0029] When the susceptor element is made of multiple materials, the materials of the susceptor element can be optimized for further aspects. For example, materials can be selected so that a first material of the susceptor element has a Curie temperature that exceeds the maximum temperature to which the susceptor element should be heated. This first material of the susceptor element can then be optimized, for example, for maximum heat generation while transferring to the aerosol-forming substrate to provide efficient heating of the susceptor. However, the susceptor element can then additionally comprise a second material with a Curie temperature corresponding to the maximum temperature to which the susceptor should be heated. When the susceptor element reaches this Curie temperature, the magnetic properties of the entire susceptor element change. This change can be detected and communicated to a microcontroller, after which AC power generation is interrupted until the temperature cools back down below the Curie temperature, at which point AC power generation resumes.

[0030] The system may further comprise an electrical circuit connected to the inductor coil and a power source. The electrical circuit may comprise a microprocessor, which may be a programmable microprocessor, a microcontroller, or an application specific integrated circuit chip (ASIC) or other electronic circuit with control capabilities. The electrical circuit may comprise additional electronic components. The electrical circuit may be configured to regulate the current supply to the coil. Current may be supplied to the inductor coil continuously after activation of the system, or intermittently, such as with each inhalation. The electrical circuit may advantageously comprise a DC / AC inverter, which may comprise a class D or class E power amplifier.

[0031] The system advantageously includes a power source (typically a lithium-ion phosphate battery or similar power source) within the body of the housing. Alternatively, the power source may be another form of charge storage device, such as a capacitor. The power source may be rechargeable and may have a capacity that allows for the storage of energy sufficient for one or more smoking experiences. For example, the power source may have a capacity sufficient to allow for continuous generation of aerosol for a period of approximately six minutes, corresponding to the typical time it takes to smoke one conventional cigarette, or a multiple of six minutes. In another example, the power source may have a capacity sufficient to allow for a predetermined number of smokes or for discontinuous activation of the inductor coil.

[0032] The system may be an electrically operated smoking system. The system may be a handheld aerosol generating system. The aerosol generating system may have a size comparable to a conventional cigar or cigarette. The overall length of the smoking system may be between about 30 mm and about 150 mm. The outer diameter of the smoking system may be between about 5 mm and about 30 mm.

[0033] In a second aspect, there is provided a cartridge for use in an electrically heated aerosol generation system, the electrically heated aerosol generation system comprising an aerosol generation device, the cartridge configured to be used in the device, the device comprising: a device housing defining a recess for receiving at least a portion of the cartridge; an inductor coil arranged around or adjacent to the recess; and a power source connected to the inductor coil and configured to provide a high-frequency oscillating current to the inductor coil, the cartridge comprising a cartridge housing containing an aerosol-forming substrate, the housing having an outer surface, at least a portion of the outer surface formed by a fluid-permeable susceptor element, the susceptor element being electrically insulated from any other conductive components.

[0034] The susceptor element may be in the form of a sheet and may extend across an opening in the cartridge housing. The susceptor element may extend around the periphery of the cartridge housing.

[0035] Features described in relation to one aspect may be applied to other aspects of the present disclosure, and in particular advantageous or optional features described in relation to the first aspect of the present disclosure may be applied to the second aspect of the invention.

[0036] Embodiments of systems according to the present disclosure will now be described in detail, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0037] [Figure 1] FIG. 1 is a schematic diagram of a first embodiment of an aerosol generation system using a flat spiral inductor coil. [Figure 2] FIG. 2 shows the cartridge of FIG. [Figure 3] FIG. 3 shows the inductor coil of FIG. [Figure 4] FIG. 4 shows an alternative susceptor element for the cartridge of FIG. [Figure 5] FIG. 5 shows a further alternative susceptor element for the cartridge of FIG. [Figure 6] FIG. 6 is a schematic diagram of a second embodiment using a flat spiral inductor coil. [Figure 7] FIG. 7 is a schematic diagram of a third embodiment using a flat spiral inductor coil. [Figure 8] FIG. 8 shows the cartridge of FIG. [Figure 9] FIG. 9 shows the inductor coil of FIG. [Figure 10] FIG. 10 is a schematic diagram of the fourth embodiment. [Figure 11] FIG. 11 shows the cartridge of FIG. [Figure 12] FIG. 12 shows the coil of FIG. [Figure 13] FIG. 13 is a schematic diagram of the fifth embodiment. [Figure 14] FIG. 14 is a schematic diagram of the sixth embodiment. [Figure 15] FIG. 15 is a schematic diagram of an eighth embodiment using a unit dose cartridge. [Figure 16A] FIG. 16A is a first example of a drive circuit for generating a high frequency signal for an inductor coil. [Figure 16B] FIG. 16B is a second example of a drive circuit for generating a high frequency signal for an inductor coil. DETAILED DESCRIPTION OF THE INVENTION

[0038] All of the illustrated embodiments rely on induction heating. Induction heating works by placing a conductive article to be heated in a time-varying magnetic field. Eddy currents are induced in the conductive article. If the conductive article is electrically insulated, the eddy currents are dissipated by Joule heating of the conductive article. In aerosol-generating systems that operate by heating an aerosol-forming substrate, the aerosol-forming substrate generally does not have sufficient electrical conductivity to be inductively heated in this manner. Therefore, in the illustrated embodiments, a susceptor element is used as the conductive article to be heated, and the aerosol-forming substrate is then heated by the susceptor element via thermal conduction, thermal convection, and / or thermal radiation. When a ferromagnetic susceptor element is used, heat can also be generated by hysteresis losses as magnetic domains switch within the susceptor element.

[0039] Each of the described embodiments uses an inductor coil to generate a time-varying magnetic field. The inductor coil is designed not to experience significant Joule heating. In contrast, the susceptor element is designed to experience significant Joule heating of the susceptor.

[0040] FIG. 1 is a schematic cross-sectional view of an aerosol generation system according to a first embodiment of the present invention. The system comprises a device 100 and a cartridge 200. The device comprises a main housing 101 containing a lithium-ion phosphate battery 102 and control electronics 104. The main housing 101 also defines a recess 112 for receiving the cartridge 200 therein. The device also includes a mouthpiece portion 120 including an outlet 124. The mouthpiece portion is connected to the main housing 101 with a hinged connection in this example, although any type of connection may be used, such as a snap-fit ​​or threaded attachment. An air inlet 122 is defined between the mouthpiece portion 120 and the body 101 when the mouthpiece portion is in the closed position, as shown in FIG. 1.

[0041] Inside the mouthpiece portion is a flat spiral inductor coil 110. Coil 110 is formed by stamping or cutting a spiral coil from copper sheet. Coil 110 is best seen in FIG. 3. Coil 110 is located between air inlet 122 and air outlet 124 so that air drawn through inlet 122 and outlet 124 passes through the coil. The coil may be sealed within a protective corrosion-resistant coating or enclosure.

[0042] The cartridge 200 comprises a cartridge housing 204 that holds a capillary material and is filled with a liquid aerosol-forming substrate. The cartridge housing 204 is fluid-impermeable but has an open end that is covered by a permeable susceptor element 210. The cartridge 200 is best seen in FIG. 2. The susceptor element in this embodiment comprises a ferrite mesh comprising ferritic steel. The aerosol-forming substrate can form a meniscus within the interstices of the mesh. Another option for the susceptor is a woven graphite fabric with an open mesh structure.

[0043] When cartridge 200 is engaged with the device and received within recess 112, susceptor element 210 is located adjacent to flat spiral coil 110. Cartridge 200 may include a keyed feature to ensure it cannot be inserted into the device upside down.

[0044] During use, a user inhales into mouthpiece portion 120, drawing air into mouthpiece portion 120 through air inlet 122 and out through outlet 124 to the user's mouth. The device includes an inhalation sensor 106 in the form of a microphone as part of control electronics 104. When a user inhales into the mouthpiece, a small stream of air is drawn through sensor inlet 121, past microphone 106, and into mouthpiece portion 120. When inhalation is detected, the control electronics supplies a high-frequency oscillating current to coil 110, which generates an oscillating magnetic field, as shown by the dotted line in FIG. 1 , and activates LED 108, indicating that the device is activated. The oscillating magnetic field passes through the susceptor element, inducing eddy currents within the susceptor element. The susceptor element heats as a result of Joule heating and hysteresis losses, reaching a temperature sufficient to vaporize the aerosol-forming substrate adjacent to the susceptor element. The vaporized aerosol-forming substrate is entrained in the airflow from the air inlet to the air outlet, where it cools before entering the user's mouth and forms an aerosol inside the mouthpiece portion. When an inhalation is detected, the control electronics supplies an oscillating current to the coil for a predetermined duration (5 seconds in this example), after which the current is turned off until a new inhalation is detected.

[0045] It can be seen that the cartridge has a simple and robust design and is inexpensive to manufacture compared to commercially available cartomizers. In this embodiment, the cartridge has a circular cylindrical shape, and the susceptor element spans the circular open end of the cartridge housing. However, other configurations are possible. Figure 4 is an end view of an alternative cartridge design in which the susceptor element is a strip of steel mesh 220 that spans a rectangular opening in the cartridge housing 204. Figure 5 is an end view of another alternative susceptor element. In Figure 5, the susceptor is three concentric circles connected by radial bars. The susceptor element spans the circular opening in the cartridge housing.

[0046] FIG. 6 illustrates a second embodiment. In FIG. 6, only the front end of the system is shown, which can use the same battery and control electronics as shown in FIG. 1, including the inhalation detection mechanism. In FIG. 6, the flat spiral coil 136 is located at the opposite end of the recess relative to the mouthpiece portion 120 within the device body 101, but the system operates in essentially the same manner. A spacer 134 ensures airflow space between the coil 136 and the susceptor element 210. Vaporized aerosol-forming substrate is entrained in the airflow passing through the susceptor from inlet 132 to outlet 124. In the embodiment shown in FIG. 6, some air is allowed to flow from inlet 132 to outlet 124 without passing through the susceptor element. This direct airflow mixes with the vapor at the mouthpiece, increasing the rate of cooling and ensuring optimal droplet size in the aerosol.

[0047] In the embodiment shown in Figure 6, the cartridge is the same size and shape as the cartridge of Figure 1, and has the same housing and susceptor element. However, the capillary material in the cartridge of Figure 6 is different from that of Figure 1. The cartridge of Figure 6 has two separate capillary materials 202, 206. A disk of the first capillary material 206 is provided for contacting the susceptor element 210 during use. A larger body of the second capillary material 202 is provided on the opposite side of the first capillary material 206 to the susceptor element. Both the first and second capillary materials hold a liquid aerosol-forming substrate. The first capillary material 206, which contacts the susceptor element, has a higher pyrolysis temperature (at least 160°C or higher, e.g., about 250°C) than the second capillary material 202. The first capillary material 206 effectively acts as a spacer separating the heater-susceptor element, which can become very hot during use, from the second capillary material 202 so that the second capillary material is not exposed to temperatures above its thermal decomposition temperature. A thermal gradient across the first capillary material ensures that the second capillary material is exposed to temperatures below its thermal decomposition temperature. The second capillary material 202 can be selected to have good wicking properties to the first capillary material 206, can hold more liquid per unit volume than the first capillary material, and can be less expensive than the first capillary material. In this example, the first capillary material is a heat-resistant element such as glass fiber or a glass fiber-containing element, and the second capillary material is a polymer such as high density polyethylene (HDPE) or polyethylene terephthalate (PET).

[0048] FIG. 7 illustrates a third embodiment. Only the front end of the system is shown in FIG. 7, which may utilize the same battery and control electronics as shown in FIG. 1, including the inhalation detection mechanism. In FIG. 7, cartridge 240 is cubic and formed with two strips of susceptor element 242 on opposite sides of the cartridge. The cartridge is shown alone in FIG. 8. The device includes two flat spiral coils 142 positioned on opposite sides of the cavity, such that when the cartridge is received in the cavity, the susceptor element strips 242 are adjacent to the coils 142. The coils 142 are rectangular to correspond to the shape of the susceptor strips, as shown in FIG. 9. An airflow passage is provided between the coils 142 and the susceptor strips 242 so that air from the inlet 144 passes through the susceptor strips and toward the outlet 124 when the user inhales through the mouthpiece portion 120.

[0049] 1, the cartridge includes a capillary material and a liquid aerosol-forming substrate. The capillary material is arranged to convey the liquid substrate to the susceptor element strips 242.

[0050] Figure 10 is a schematic diagram of a fourth embodiment, in which only the front end of the system is shown, which may use the same battery and control electronics as shown in Figure 1, including the inhalation detection mechanism.

[0051] In FIG. 10, cartridge 250 is cylindrical and formed with a strip-shaped susceptor element 252 extending around a central portion of the cartridge. The strip-shaped susceptor element covers an opening formed in a rigid cartridge housing. The cartridge is shown alone in FIG. 11. The device includes a helical coil 152 positioned around the cavity such that when the cartridge is received in the cavity, the susceptor element 252 is within the coil 152. Coil 152 is shown alone in FIG. 12. An airflow passage is provided between coil 152 and susceptor element 252 so that when a user inhales on mouthpiece portion 120, air from inlet 154 flows past the susceptor strip toward outlet 124.

[0052] During use, a user inhales into mouthpiece portion 120, drawing air through air inlet 154, past susceptor element 262, into mouthpiece portion 120, and out outlet 124 into the user's mouth. When inhalation is detected, control electronics supplies a high-frequency oscillating current to coil 152, which generates an oscillating magnetic field. The oscillating magnetic field passes through the susceptor element, inducing eddy currents within the susceptor element. The susceptor element heats as a result of Joule heating and hysteresis losses, reaching a temperature sufficient to vaporize the aerosol-forming substrate proximate to the susceptor element. The vaporized aerosol-forming substrate passes through the susceptor element and is entrained in the airflow from the air inlet to the air outlet, where it cools and forms an aerosol within the passageway and mouthpiece portion before entering the user's mouth.

[0053] FIG. 13 illustrates a fifth embodiment. In FIG. 13, only the front end of the system is shown, which can use the same battery and control electronics as shown in FIG. 1, including the inhalation detection mechanism. The device of FIG. 13 has a similar structure to the device of FIG. 7, with a flat spiral coil located on the side wall of the housing surrounding a cavity in which the cartridge is received. However, the cartridge has a different structure. Cartridge 260 of FIG. 13 has a hollow cylindrical shape similar to the shape of the cartridge shown in FIG. 10. The cartridge includes a capillary material and is filled with a liquid aerosol-forming substrate. The interior surface of cartridge 260, i.e., the surface surrounding interior passage 166, is provided with a fluid-permeable susceptor element, in this example, a ferrite mesh. The ferrite mesh can line the entire interior surface of the cartridge, or only a portion of the interior surface of the cartridge.

[0054] During use, a user inhales into mouthpiece portion 120, drawing air through air inlet 164, through the central passageway of the cartridge, past susceptor element 262, into mouthpiece portion 120, and out outlet 124 into the user's mouth. When inhalation is detected, control electronics supplies a high-frequency oscillating current to coil 162, which generates an oscillating magnetic field. The oscillating magnetic field passes through the susceptor element, inducing eddy currents within the susceptor element. The susceptor element heats as a result of Joule heating and hysteresis losses, reaching a temperature sufficient to vaporize the aerosol-forming substrate adjacent to the susceptor element. The vaporized aerosol-forming substrate passes through the susceptor element and is entrained in the airflow from the air inlet to the air outlet, where it cools and forms an aerosol within the passageway and mouthpiece portion before entering the user's mouth.

[0055] A sixth embodiment is illustrated in Figure 14. Only the front end of the system is shown in Figure 14, which may use the same battery and control electronics as shown in Figure 1, including the inhalation detection mechanism. The cartridge 270 shown in Figure 14 is identical to that shown in Figure 13. However, the device in Figure 14 has a different configuration, including an inductor coil 172 on a retaining blade 176 that extends into the central passage of the cartridge and generates an oscillating magnetic field adjacent to the susceptor element 272.

[0056] FIG. 15 illustrates a seventh embodiment. In FIG. 15, only the front end of the system is shown, which can use the same battery and control electronics as shown in FIG. 1, including the inhalation detection mechanism. In the embodiment of FIG. 15, the cartridge is very small, holding just enough aerosol-forming substrate for a single use (e.g., a single smoking session or a single dose of medication). The cartridge includes a susceptor foil housing 292 made of ferrite material that holds an aerosol-forming substrate 290 made of ferrite material. The front end 294 of the cartridge housing is perforated to be vapor permeable. The cartridge is engaged in a recess in the device adjacent to the flat spiral inductor coil 192.

[0057] During use, a user inhales into mouthpiece portion 120, drawing air through air inlet 194, past the vapor-permeable portion of cartridge 294, into mouthpiece portion 120, and out outlet 124 into the user's mouth. When inhalation is detected, control electronics provides a high-frequency oscillating current to coil 192, which generates an oscillating magnetic field. The oscillating magnetic field passes through the susceptor element of the cartridge housing, inducing eddy currents within the susceptor element. The susceptor element heats as a result of Joule heating and hysteresis losses, reaching a temperature sufficient to vaporize the aerosol-forming substrate. The vaporized aerosol-forming substrate is drawn through the vapor-permeable portion of cartridge 294 by air flowing from the air inlet to the air outlet, where it cools before entering the user's mouth and forming an aerosol within the mouthpiece portion.

[0058] All of the described embodiments can be driven by essentially the same electronic circuit 104. FIG. 16A illustrates a first example of a circuit used to provide a high-frequency oscillating current to an inductor coil using a class-E power amplifier. As can be seen in FIG. 16A, the circuit includes a class-E power amplifier including a transistor switch 1100 with a field-effect transistor (FET) 1110 (e.g., a metal-oxide semiconductor field-effect transistor (MOSFET)), a transistor switch supply circuit, indicated by arrow 1120, for supplying a switching signal (gate-to-source voltage) to the FET 1110, and an LC load network 1130 including a shunt capacitor C1 and a series connection of a capacitor C2 and an inductor L2. A DC power supply including a battery 101 includes a choke L1 and provides the DC supply voltage. Also shown in FIG. 16A is an ohmic resistance R representing the total ohmic load 1140, which is the ohmic resistance R of the inductor coil, designated L2. Coil and the ohmic resistance of the susceptor element R Load It is the sum of.

[0059] The volume of the power supply circuit can be kept extremely small because the number of components is very small. This extremely small volume of the power supply circuit is possible because the inductor L2 of the LC load network 1130 is directly used as an inductor for inductive coupling with the susceptor element, and because of this small volume, the overall size of the induction heating device can be kept small.

[0060] The general principles of operation of Class-E power amplifiers are known and described in detail in the already mentioned article "Class-E RF Power Amplifiers" (Nathan O. Sokal, published in QEX, bimonthly magazine of the American Radio Relay League (ARRL), Newington, Connecticut, USA, January / February 2001, pp. 9-20), and some general principles will be explained below.

[0061] Assume that transistor switch supply circuit 1120 supplies a switching voltage (the gate-to-source voltage of the FET) with a rectangular profile to FET 1110. As long as FET 1321 is conducting ("on" state), it essentially constitutes a short circuit (low resistance) and all of the current flows through choke L1 and FET 1110. When FET 1110 is non-conducting ("off" state), FET 1110 essentially represents an open circuit (high resistance) and all of the current flows into the LC load network. Switching the transistor between these two states converts the supplied DC voltage and current into AC voltage and current.

[0062] To efficiently heat the susceptor element, as much of the supplied DC power as possible is transferred in the form of AC power to inductor L2, which then transfers it to the susceptor element, which is inductively coupled to inductor L2. As explained in more detail above, power dissipated within the susceptor element (eddy current losses, hysteresis losses) generates heat within the susceptor element. In other words, power loss in FET 1110 should be minimized and power loss in the susceptor element should be maximized.

[0063] The power dissipated in FET 1110 during a period of AC voltage / current is the product of the transistor voltage and current at each point during that period, integrated over that period and averaged over that period. Because FET 1110 must sustain a high voltage for part of that period and conduct a high current for part of that period, the simultaneous occurrence of high voltage and high current must be avoided, as this would result in significant power dissipation in FET 1110. In the "on" state of FET 1110, the transistor voltage is near zero and a high current flows through the FET. In the "off" state of FET 1110, the transistor voltage is high but the current passing through FET 1110 is near zero.

[0064] Also, the unavoidable switching transitions span some portion of the period. Nevertheless, the high voltage-current product, which represents high power dissipation in the FET 1110, can be avoided by the following additional measures: First, delaying the rise of the transistor voltage until the current through the transistor has fallen to zero. Second, ensuring that the transistor voltage returns to zero before the current through the transistor starts to increase. This is achieved by the load network 1130, which includes a shunt capacitor C1 and a series combination of capacitor C2 and inductor L2, between the FET 1110 and the load 1140. Third, the transistor voltage at turn-on is effectively zero (for a bipolar junction transistor "BJT," the saturation offset voltage V o). The turn-on transistor does not discharge the charged shunt capacitor C1, thus avoiding the dissipation of the shunt capacitor's stored energy. Fourth, the transistor voltage slope is zero at turn-on. Second, the current injected into the turn-on transistor by the load network increases smoothly from zero at a controlled, moderate rate, resulting in low power losses, while the transistor conductance increases from zero during the turn-on transition. As a result, the transistor voltage and current never go high simultaneously. The voltage and current switching transitions are staggered with respect to each other. The values ​​of L1, C1, and C2 can be selected to maximize the efficient dissipation of power within the susceptor element.

[0065] While a Class E power amplifier is preferred in most systems according to the present disclosure, other circuit configurations can be used. FIG. 16B illustrates a second example circuit used to provide a high-frequency oscillating current to an inductor coil using a Class D power amplifier. The circuit of FIG. 16B includes a battery 101 connected to two transistors 1210 and 1212. Two switching elements 1220 and 1222 are provided to switch the two transistors 1210 and 1212 on and off. The switches are controlled at high frequency in a manner that ensures that one of the two transistors 1210 and 1212 is off when the other is on. The inductor coil is again designated L2, the total ohmic resistance of the coil and susceptor element is designated R, and the values ​​of C1 and C2 can be selected to maximize the efficient distribution of power within the susceptor element.

[0066] The susceptor element can be made of a material or combination of materials that has a Curie temperature close to the desired temperature to which the susceptor element should be heated. When the temperature of the susceptor element exceeds this Curie temperature, the material changes from ferromagnetic to paramagnetic. Therefore, the hysteresis loss of a paramagnetic material is much lower than that of a ferromagnetic material, and energy dissipation within the susceptor element is significantly reduced. This reduction in power dissipation within the susceptor element is detectable, and therefore, for example, generation of AC power by a DC / AC inverter can be interrupted until the susceptor element cools below its Curie temperature again and becomes ferromagnetic again. Then, generation of AC power by the DC / AC inverter can be resumed.

[0067] Those skilled in the art will appreciate other cartridge designs incorporating susceptor elements according to the present disclosure. For example, the cartridge may include a mouthpiece portion and may have any desired shape. Moreover, coil and susceptor arrangements according to the present disclosure may be used in other types of systems previously described, such as humidifiers, air fresheners, and other aerosol generating systems.

[0068] The above-described exemplary embodiments are illustrative and not limiting. In light of the exemplary embodiments discussed above, other embodiments consistent with the above exemplary embodiments will now be apparent to those skilled in the art.

Claims

1. 1. An electrically heated aerosol generating system comprising an aerosol generating device and a cartridge configured for use with said device, said device comprising: a device housing; an inductor coil disposed around or adjacent to the recess; a power supply connected to the inductor coil and configured to provide a high frequency oscillating current to the inductor coil; The cartridge An electrically heated aerosol generating system comprising: a cartridge housing configured to engage the device housing and contain an aerosol-forming substrate, the housing having an exterior surface surrounding the aerosol-forming substrate, at least a portion of the exterior surface being formed by a fluid-permeable susceptor element.

2. 2. The electrically heated aerosol generating system of claim 1, wherein the susceptor element is in the form of a sheet and spans an opening in the cartridge housing.

3. 3. The electrically heated aerosol generating system of claim 1, wherein the susceptor element extends around the periphery of the cartridge housing.

4. 4. The electrically heated aerosol generating system according to claim 1, wherein the inductor coil is a flat spiral coil.

5. An electrically heated aerosol generation system as described in any one of claims 1 to 4, wherein the device housing has a recess for receiving at least a portion of the cartridge when the device housing engages with the device housing, the recess having an inner surface, and the inductor coil is positioned on or adjacent to the surface of the recess closest to the power source.

6. An electrically heated aerosol generating system as described in any one of claims 1 to 4, wherein the device housing comprises a main body and a mouthpiece portion, the recess is within the main body, the mouthpiece portion has an outlet through which the aerosol generated by the system can be drawn into the user's mouth, and the inductor coil is within the mouthpiece portion.

7. An electrically heated aerosol generating system according to any one of claims 1 to 6, comprising a plurality of inductor coils.

8. The electrically heated aerosol generating system according to any one of claims 1 to 7, wherein the inductor coil has a shape that matches the shape of the susceptor element.

9. 9. The electrically heated aerosol generating system according to claim 1, wherein the susceptor element is in contact with the aerosol-forming substrate.

10. 10. The electrically heated aerosol generating system of claim 1, wherein an airflow passage is provided between the inductor coil and the susceptor element when the cartridge housing is engaged with the device housing.

11. The electrically heated aerosol generating system of any one of claims 1 to 10, wherein the susceptor element comprises a mesh, a flat spiral coil, a fiber, or a cloth.

12. An electrically heated aerosol generating system according to any one of claims 1 to 11, wherein the system is a handheld smoking system.

13. A cartridge for use in an electrically heated aerosol generating system, the electrically heated aerosol generating system comprising an aerosol generating device, the cartridge being configured to be used in the device, the device comprising: a device housing defining a recess for receiving at least a portion of the cartridge; an inductor coil arranged around or adjacent to the recess; and a power source connected to the inductor coil and configured to provide a high-frequency oscillating current to the inductor coil, the cartridge comprising a cartridge housing containing an aerosol-forming substrate, the housing having an outer surface, at least a portion of the outer surface being formed by a fluid-permeable susceptor element, the susceptor element being electrically insulated from any other conductive components.

14. The cartridge of claim 13 , wherein the susceptor element is in the form of a sheet and spans the entire opening of the cartridge housing.

15. 15. The cartridge of claim 13 or 14, wherein the susceptor element extends around the periphery of the cartridge housing.

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