Aerosol-generating system comprising a planar induction coil

Abstract

There is provided an electrically heated aerosol-generating system comprising an aerosol-generating device and a cartridge configured for use with the device.SOLUTION: The device comprises a device housing, a flat spiral inductor coil, and a power supply connected to the flat spiral inductor coil and configured to provide a high frequency oscillating current to the flat spiral inductor coil, wherein the cartridge comprises a cartridge housing containing an aerosol-forming substrate and configured to engage the device housing, and wherein the susceptor element is arranged to heat the aerosol-forming substrate. In operation, a high frequency oscillating current is passed through the flat spiral inductor coil to generate heat in the 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 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; a flat spiral inductor coil; a power supply connected to the flat spiral inductor coil and configured to provide a high frequency oscillating current to the flat spiral inductor coil; This cartridge is a cartridge housing including an aerosol-forming substrate and configured to engage the device housing; a susceptor element positioned to heat the aerosol-forming substrate.

[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 in the susceptor element. The induced voltage causes a current to flow in the susceptor element, which causes Joule heating of the susceptor element, which in turn heats the aerosol-forming substrate. If the susceptor element is ferromagnetic, hysteresis losses in the susceptor element can also generate heat.

[0007] As used herein, the term "flat spiral coil" generally refers to a planar coil, in which the axis of the coil's windings is perpendicular to the surface of the coil. In some embodiments, the flat spiral coil may be planar, meaning that it lies within a flat Euclidean plane. However, the term "flat spiral coil," as used herein, also encompasses coils shaped to conform to a curved or other three-dimensional surface. For example, a flat spiral coil may be shaped to conform to a cylindrical housing or cavity in a device. The flat spiral coil may then be called "planar," but the axis of the coil's windings is perpendicular to the cylindrical surface at the center of the coil and coincides with the cylindrical surface. When the flat spiral coil conforms to a cylindrical surface or a non-Euclidean plane, the flat spiral coil preferably lies in a plane with a radius of curvature of the region of the flat spiral coil that is greater than the diameter of the flat spiral coil. When the flat spiral coil is curved, for example, to conform to a cylindrical or other shaped housing, it is preferable for the susceptor element to have a complementary shape, so that the distance between the flat spiral coil and the susceptor is substantially constant throughout the extent of the susceptor element. In particular, in an embodiment where there is an airflow path between the flat spiral coil and the susceptor, the shortest distance between the susceptor element and the flat spiral coil is preferably 0.5 to 1 mm.

[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] "Susceptor element," as used herein, means 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.

[0010] 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 cartridges, even when more expensive devices are required, can result in significant cost savings for both manufacturers and consumers.

[0011] Furthermore, the use of induction heating rather than coil design offers improved energy conversion because coil-related power losses, particularly losses due to contact resistance at the connection between the coil and the device's power supply system, are not present in induction heating systems. To function, the coil is connected to a power source through leads that are provided in the device, either permanently or replaceably. Even with improved automated manufacturing techniques, coil systems generally have contact resistance in the leads that create parasitic losses. Replaceable coil devices may suffer from the buildup of films or other materials that increase contact resistance between the replaceable cartridge and the device's leads. In contrast, induction heating systems do not require contact between the heating element and the device's leads and therefore do not suffer from the contact resistance issues present in coil-based devices.

[0012] 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, preventing fouling and corrosion on the coil and simplifying device cleaning, and does not need to be exposed to the aerosols generated. 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.

[0013] The device housing includes a recess for receiving at least a portion of the cartridge, the recess having an interior surface. The flat spiral inductor coil can be disposed on or adjacent to a surface of the recess closest to the power source. The flat spiral coil can be shaped to conform to the interior surface of the recess.

[0014] 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 flat spiral inductor coil can be in the mouthpiece portion or in the body.

[0015] 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 generating system. The aerosol is delivered to the user's mouth through the mouthpiece portion.

[0016] The system may include an air path extending from an air inlet to an air outlet, where the air path passes through a flat spiral inductor. By allowing the air flow through the system and past the coil, a compact system can be achieved.

[0017] The system may include multiple inductor coils, some or all of which may be flat spiral coils. For example, in one possible configuration, the system may include two flat spiral coils positioned on opposite sides of a recess in the device housing that receives the cartridge.

[0018] Flat spiral inductors can have any desired shape in the plane of the coil. For example, flat spiral coils can have a circular shape or a generally oblong shape. The coil diameter can be between 5 mm and 10 mm.

[0019] 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.

[0020] 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.

[0021] 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 that includes volatile tobacco flavor compounds that are released from the aerosol-forming substrate upon heating. Alternatively, the aerosol-forming substrate may comprise a non-tobacco-containing material. The aerosol-forming substrate may comprise a homogenized plant-derived material. The aerosol-forming substrate may comprise a homogenized tobacco material. The aerosol-forming substrate may comprise at least one aerosol-forming agent. The aerosol-forming agent is any suitable known compound or mixture of compounds that, in use, facilitates the formation of a dense, stable aerosol and that is substantially resistant to thermal decomposition at the operating temperature of the system. Suitable aerosol formers are well known in the art and include, but are not limited to, polyhydric alcohols (such as triethylene glycol, 1,3-butanediol, and glycerin), esters of polyhydric alcohols (such as glycerol monoacetate, diacetate, or triacetate), and aliphatic esters of monocarboxylic, dicarboxylic, or polycarboxylic acids (such as dimethyl dodecanedioate and dimethyl tetradecanedioate). Preferred aerosol formers are polyhydric alcohols or mixtures thereof (such as triethylene glycol, 1,3-butanediol, and glycerin, most preferred). The aerosol-forming substrate may contain other additives and ingredients, such as flavorings.

[0022] 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 spongy 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 element 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 made from 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.

[0023] The susceptor element may be in contact with the aerosol-forming substrate, or alternatively, the susceptor element may be spaced apart from the aerosol-forming substrate but positioned close to the aerosol-forming substrate to heat it.

[0024] The susceptor element may be provided on a wall of the cartridge housing configured to be positioned adjacent to the flat spiral inductor coil when the cartridge housing is engaged with the device housing. In use, it is advantageous to position the susceptor element close to the flat spiral coil to maximize the voltage induced in the susceptor element.

[0025] When the cartridge housing is engaged with the device housing, an airflow passage can be provided between the flat spiral 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.

[0026] The susceptor element may comprise a mesh, a flat spiral coil, an inner foil, a fiber, or a rod. The susceptor element may be fluid permeable to allow the liquid aerosol-forming substrate or the vaporized aerosol-forming substrate to pass through the susceptor.

[0027] If a capillary material is used in the cartridge (e.g., if the susceptor is in the form of a mesh or filament array), the capillary material may extend into interstices in the susceptor. The susceptor elements may be provided in the form of sheets and may extend across openings in the cartridge housing. Alternatively, the susceptor elements may be embedded in the aerosol-forming substrate.

[0028] The susceptor element may include a capillary material. The susceptor may include a capillary wick that extends across the air path through the system.

[0029] 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.

[0030] 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.

[0031] 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.

[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] 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 flat spiral coil. Current may be supplied to the flat spiral coil element continuously after activation of the system, or may be supplied 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.

[0034] Advantageously, the system 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 require recharging and may have a capacity that allows for the storage of sufficient energy for one or more user actions, e.g., one or more smoking experiences. For example, the power source may have a capacity sufficient to allow for continuous production of aerosol for a period of approximately six minutes, corresponding to the typical time it takes to smoke a conventional cigarette, or for 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 flat spiral coil.

[0035] In a second aspect, there is provided an electrically heated aerosol generating device comprising: an apparatus housing defining a recess for receiving at least a portion of a cartridge, the cartridge including an aerosol-forming substrate and a susceptor element in contact with the aerosol-forming substrate, the recess having an interior surface; a flat spiral inductor coil disposed on an interior surface of the recess; a power supply connected to the flat spiral inductor coil and configured to provide a high frequency oscillating current to the flat spiral inductor coil.

[0036] In a third aspect, a method of generating an aerosol is provided, the method comprising: providing a cartridge comprising a susceptor and an aerosol-forming substrate in contact with or adjacent to the susceptor; positioning the cartridge so that the susceptor is adjacent to a flat spiral inductor coil; and passing a high frequency oscillating current through a flat spiral induction coil to induce a current in the susceptor, thereby heating the aerosol-forming substrate.

[0037] 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 and third aspects of the invention.

[0038] 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]

[0039] [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 is a schematic diagram of the fifth embodiment. [Figure 13] FIG. 13 is a schematic diagram of the sixth embodiment. [Figure 14] FIG. 14 is a schematic diagram of the seventh 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

[0040] 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 isolated, 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 itself is generally not sufficiently conductive 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 ferromagnetic susceptor elements are used, heat can also be generated by hysteresis losses as magnetic domains switch within the susceptor element.

[0041] Each embodiment uses a flat spiral coil to generate a time-varying magnetic field. The flat spiral coil is designed not to experience significant Joule heating. In contrast, the susceptor element is designed to experience significant Joule heating of the susceptor element.

[0042] FIG. 1 is a schematic diagram of an aerosol generation system according to a first embodiment of the present invention. The system includes a device 100 and a cartridge 200. The device includes 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.

[0043] 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 out outlet 124 passes through the coil. The coil may be covered by a corrosion-resistant coating or enclosure.

[0044] 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. In this embodiment, the susceptor element is a ferrite mesh. The aerosol-forming substrate is capable of forming a meniscus within the interstices of the mesh. Another option for the susceptor is graphite fiber with an open mesh structure.

[0045] 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.

[0046] During use, a user inhales into mouthpiece portion 120, drawing air through air inlet 122 into mouthpiece portion 120 and out 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, reaching a temperature sufficient to vaporize the aerosol-forming substrate adjacent to the susceptor element. As previously mentioned, hysteresis losses can also result in significant heating of 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.

[0047] 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.

[0048] 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 in the device body 101 relative to the mouthpiece portion 120, 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 from inlet 132 to outlet 124 that passes through the susceptor. In the embodiment shown in FIG. 6, some air can flow directly 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.

[0049] 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. There are two separate capillary materials 202, 206 in the cartridge of Figure 6. 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 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).

[0050] 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, the 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 the susceptor element strips 242 are adjacent to the coils 142 when the cartridge is received in the cavity. The coils 142 are rectangular to correspond to the shape of the susceptor strips, as shown in FIG. 9. The rectangular shape is advantageous because it allows for a higher density of eddy currents and minimizes the effect on the skin. 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.

[0051] 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.

[0052] FIG. 10 illustrates a fourth embodiment. In FIG. 10, only the front end of the system is shown, which may use the same battery and control electronics as shown in FIG. 1, including the inhalation detection mechanism. The device of FIG. 10 has a structure similar to that shown in FIG. 6, including a flat spiral inductor coil 152 positioned within the device body 101 at the end of the cavity opposite the mouthpiece portion 120. However, the cartridge shown in FIG. 10 has a different structure than that shown in FIG. 6. The cartridge of FIG. 10 is shown in end view in FIG. 11. The cartridge housing 250 has a cylindrical shape but has a central passageway 256 therethrough. The aerosol-forming substrate is held within the annular space surrounding the central passageway and may be held within a capillary material within the housing 250, similar to that previously described. A capillary wick is provided at one end of the cartridge across the central passageway 256. The capillary wick is formed of ferrite fibers and serves both as a wick for the aerosol-forming substrate and as a susceptor that is inductively heated by the coil 152.

[0053] In use, the aerosol-forming substrate is drawn into the ferrite core 252. When inhalation is detected, the coil 152 is activated, generating an oscillating magnetic field. The varying magnetic flux across the core induces eddy currents and hysteresis losses in the core, heating it and vaporizing the aerosol-forming substrate within the wick. The vaporized aerosol-forming substrate is entrained in air drawn through the system from the air inlet 154 to the outlet 124 upon the user's inhalation on the mouthpiece. Air flows through the internal passage 256, which serves as the aerosol-forming chamber, cooling the air and vapor as it moves toward the outlet 124. The use of a hollow cartridge allows for a shorter overall length for the system, as the vapor cools within the hollow space defined by the cartridge.

[0054] FIG. 12 illustrates a fifth embodiment. In FIG. 12, only the front end of the system is shown, which may use the same battery and control electronics as shown in FIG. 1, including the inhalation detection mechanism. The device of FIG. 12 has a similar structure to the device of FIG. 7, with a flat spiral coil located on the side wall of the housing surrounding the cavity in which the cartridge is received and shaped to match the shape of the housing. However, the cartridge has a different structure. Cartridge 260 of FIG. 12 has a hollow cylindrical shape similar to that 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 may line the entire interior surface of the cartridge, or only a portion of the interior surface of the cartridge.

[0055] During use, a user inhales into mouthpiece portion 120, drawing air through air inlet 164, through the cartridge's central passageway, 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 and hysteresis losses within the susceptor element. The susceptor element heats up and reaches 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.

[0056] A sixth embodiment is illustrated in Figure 13. Only the front end of the system is shown in Figure 13, 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 13 is identical to that shown in Figure 12. However, the device in Figure 13 has a different configuration, including a flat spiral 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.

[0057] A seventh embodiment is illustrated in Figure 14. Only the front end of the system is shown in Figure 14, which can use the same battery and control electronics as shown in Figure 1, including the inhalation detection mechanism. In Figure 14, the device has a similar structure to that shown in Figure 12, except that the cartridge in Figure 14 is filled with susceptor elements 280 that are soaked with an aerosol-forming substrate. The cartridge housing includes a vapor-permeable membrane 282 that allows vaporized aerosol-forming substrate to escape from the cartridge. The vapor-permeable membrane 282 is positioned adjacent to an airflow channel extending from the air inlet 184 to the air outlet 124.

[0058] In use, a user inhales into mouthpiece portion 120, drawing air through air inlet 184, through the vapor-permeable portion of cartridge 282, 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 182, which generates an oscillating magnetic field. The oscillating magnetic field passes through the susceptor element within the cartridge, inducing eddy currents and hysteresis losses within the susceptor element. The susceptor element heats up and reaches a temperature sufficient to vaporize the aerosol-forming substrate. The vaporized aerosol-forming substrate is drawn through the vapor-permeable membrane of cartridge 282 by the air flow 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.

[0059] It is of course possible to use susceptor elements to fill the cartridges shown in Figures 1, 2, 4, 5, 6, 7, 8, 10, 11, 12, and 13 in the same manner into hollow cartridges such as those shown in Figures 12 and 13, providing a vapor-permeable portion of the cartridge housing within the portion through which air passes as it flows from the air inlet to the air outlet.

[0060] FIG. 15 illustrates an eighth 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 the aerosol-forming substrate 290. 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.

[0061] In use, a user inhales into mouthpiece portion 120, drawing air from air inlet 194 through 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 and hysteresis losses within the susceptor element. The susceptor element heats up and reaches 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 the air flow 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.

[0062] 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 flat spiral inductor coil, designated L2. コイル and the ohmic resistance of the susceptor element R Load It is the sum of.

[0063] The volume of the power supply circuit can be kept extremely small due to the very small number of components, which 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 inductive heating device can be kept small.

[0064] The general operating principles of Class-E power amplifiers are known and are 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, pages 9-20), and some general principles will be explained below.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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 supply 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 for switching 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 flat spiral 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.

[0070] 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.

[0071] Those of ordinary skill 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.

[0072] 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.

[0073] 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; a flat spiral inductor coil; a power supply connected to the flat spiral inductor coil and configured to provide a high frequency oscillating current to the flat spiral inductor coil; The cartridge a cartridge housing including an aerosol-forming substrate and configured to engage the device housing; a susceptor element positioned to heat the aerosol-forming substrate. 2. An electrically heated aerosol generating system as described in 1, wherein the device housing has a recess for receiving at least a portion of the cartridge, the recess having an inner surface. 3. The electrically heated aerosol generating system described in 2, wherein the flat spiral inductor coil is located on or adjacent to the surface of the recess closest to the power source. 4. The electrically heated aerosol generating system described in 2, 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 flat spiral inductor coil is within the mouthpiece portion. 5. An electrically heated aerosol generating system described in any one of 1 to 4, wherein the device has an air path from an air inlet to an air outlet, the air path passing through the flat spiral inductor. 6. An electrically heated aerosol generating system according to any one of 1 to 5, comprising a plurality of inductor coils. 7. The electrically heated aerosol generating system according to any one of 1 to 6, wherein the susceptor element is in contact with the aerosol-forming substrate. 8. An electrically heated aerosol generating system described in any one of 1 to 7, wherein the susceptor element is provided on a wall of the cartridge housing configured to be positioned adjacent to the flat spiral inductor coil when the cartridge housing is engaged with the device housing. 9. An electrically heated aerosol generating system described in any one of 1 to 8, wherein an airflow passage is provided between the flat spiral inductor coil and the susceptor element when the cartridge housing is engaged with the device housing. 10. An electrically heated aerosol generating system according to any one of 1 to 9, wherein the susceptor element is fluid-permeable. 11. An electrically heated aerosol generating system as described in any one of 1 to 10, wherein the susceptor element is in the form of a sheet and extends across the entire opening in the cartridge housing. 12. An electrically heated aerosol generating system described in any one of 1 to 11, wherein the system is a handheld smoking system. 13. An electrically heated aerosol generator, a device housing; a flat spiral inductor coil within the device housing; a power source connected to the flat spiral inductor coil and configured to provide a high frequency oscillating current to the flat spiral inductor coil. 14. An electrically heated aerosol generating device as described in 13, wherein the device housing defines a recess for receiving at least a portion of a cartridge, the cartridge comprising a housing containing an aerosol-forming substrate and a susceptor element in contact with the aerosol-forming substrate. 15. A method for generating an aerosol, comprising: providing a cartridge comprising a susceptor and an aerosol-forming substrate in contact with or adjacent to the susceptor; positioning the cartridge so that the susceptor is adjacent to a flat spiral inductor coil; passing a high frequency oscillating current through the flat spiral induction coil to induce a current in the susceptor, thereby heating the aerosol-forming substrate.

[0074] 16. 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; a flat spiral inductor coil; Power supply and an electrical circuit connected to the flat spiral inductor coil and the power source; Equipped with the electrical circuit comprises a DC / AC inverter comprising a class D or class E power amplifier and configured to provide a high frequency oscillating current to the flat spiral inductor coil; The cartridge a cartridge housing including an aerosol-forming substrate and configured to engage the device housing; a susceptor element positioned to heat the aerosol-forming substrate; An electrically heated aerosol generating system, wherein an airflow passage is provided between the flat spiral inductor coil and the susceptor element when the cartridge housing is engaged with the device housing. 17. The electrically heated aerosol generating system described in 16, wherein the device housing has a recess for receiving at least a portion of the cartridge, the recess having an inner surface. 18. The electrically heated aerosol generating system described in 17, wherein the flat spiral inductor coil is located on or adjacent to the surface of the recess closest to the power source. 19. The electrically heated aerosol generating system described in 17, wherein the device housing comprises a body and a mouthpiece portion, the recess is within the 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 flat spiral inductor coil is within the mouthpiece portion. 20. An electrically heated aerosol generating system described in any one of 16 to 19, wherein the shortest distance between the susceptor element and the flat spiral inductor coil is 0.5 to 1 mm. 21. An electrically heated aerosol generating system according to any one of 16 to 20, wherein the high-frequency oscillating current has a frequency of 500 kHz to 30 MHz, more preferably 1 to 10 MHz. 22. An electrically heated aerosol generating system described in any one of 16 to 21, wherein the flat spiral inductor coil has a diameter of 5 mm to 10 mm. 23. An electrically heated aerosol generating system described in any one of 16 to 22, wherein the device has an air path from an air inlet to an air outlet, the air path passing through the flat spiral inductor coil. 24. An electrically heated aerosol generating system described in any one of 16 to 23, comprising multiple inductor coils. 25. An electrically heated aerosol generating system according to any one of 16 to 24, wherein the susceptor element is in contact with the aerosol-forming substrate. 26. An electrically heated aerosol generating system described in any one of 16 to 25, wherein the aerosol-forming substrate in the cartridge housing is a liquid. 27. The electrically heated aerosol generating system of claim 26, wherein the liquid aerosol-forming substrate is held within a capillary material. 28. The electrically heated aerosol generating system of claim 27, wherein the capillary material is configured to convey the aerosol-forming substrate to the susceptor element. 29. An electrically heated aerosol generating system described in any one of 16 to 28, wherein the susceptor element is provided on a wall of the cartridge housing configured to be positioned adjacent to the flat spiral inductor coil when the cartridge housing is engaged with the device housing. 30. An electrically heated aerosol generating system according to any one of 16 to 29, wherein the susceptor element is fluid-permeable. 31. An electrically heated aerosol generating system as described in any one of 16 to 30, wherein the susceptor element is in the form of a sheet and extends across the entire opening in the cartridge housing. 32. An electrically heated aerosol generating system according to any one of 16 to 30, wherein the susceptor element is embedded in the aerosol-forming substrate. 33. An electrically heated aerosol generating system according to any one of 16 to 32, wherein the susceptor element comprises a capillary material. 34. An electrically heated aerosol generating system as described in 33, wherein the susceptor element includes a capillary wick extending across an air path through the system. 35. An electrically heated aerosol generating system described in any one of 16 to 34, wherein the system is a handheld smoking system.

[0075] 41. 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 including a recess for receiving at least a portion of the cartridge when the device housing is engaged with the cartridge; a first flat spiral inductor coil and a second flat spiral inductor coil, the first flat spiral inductor coil being on an opposite side of the recess from the second flat spiral inductor coil; a power supply connected to the first flat spiral inductor coil and the second flat spiral inductor coil, the power supply configured to provide a high frequency oscillating current to the first flat spiral inductor coil and the second flat spiral inductor coil; Equipped with The cartridge a cartridge housing including an aerosol-forming substrate and configured to engage the device housing; a susceptor element positioned to heat the aerosol-forming substrate; An electrically heated aerosol generating system comprising: 42. The electrically heated aerosol generating system described in 41, wherein the device housing has a recess for receiving at least a portion of the cartridge, the recess having an interior surface. 43. The electrically heated aerosol generating system of 42, wherein the first flat spiral inductor coil is located on or adjacent to the surface of the recess closest to the power source. 44. The electrically heated aerosol generating system described in 42, wherein the device housing comprises a body and a mouthpiece portion, the recess is within the 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 first flat spiral inductor coil is within the mouthpiece portion. 45. An electrically heated aerosol generating system described in any one of 41 to 44, wherein the device has an air path from an air inlet to an air outlet, the air path passing through the first flat spiral inductor coil. 46. ​​An electrically heated aerosol generating system according to any one of items 41 to 45, wherein the susceptor element is in contact with the aerosol-forming substrate. 47. An electrically heated aerosol generating system described in any of 41 to 46, wherein the susceptor element is provided on a wall of the cartridge housing configured to be positioned adjacent to the first flat spiral inductor coil when the cartridge housing is engaged with the device housing. 48. An electrically heated aerosol generating system described in any one of 41 to 47, wherein an airflow passage is provided between the first flat spiral inductor coil and the susceptor element when the cartridge housing is engaged with the device housing. 49. An electrically heated aerosol generating system according to any one of items 41 to 48, wherein the susceptor element is fluid-permeable. 50. An electrically heated aerosol generating system described in any one of 41 to 49, wherein the susceptor element is in the form of a sheet and extends across the entire opening in the cartridge housing. 51. An electrically heated aerosol generating system described in any one of 41 to 50, wherein the system is a handheld smoking system. 52. An electrically heated aerosol generator comprising: a device housing having a recess for receiving at least a portion of a cartridge when the device housing is engaged with the cartridge, the cartridge comprising a housing containing an aerosol-forming substrate and a susceptor element in contact with the aerosol-forming substrate; a first flat spiral inductor coil and a second flat spiral inductor coil, the first flat spiral inductor coil being on an opposite side of the recess from the second flat spiral inductor coil; a power supply connected to the first flat spiral inductor coil and the second flat spiral inductor coil, the power supply configured to provide a high frequency oscillating current to the first flat spiral inductor coil and the second flat spiral inductor coil; An electrically heated aerosol generating device comprising: 53. A method for generating an aerosol, comprising: providing a cartridge comprising a susceptor and an aerosol-forming substrate in contact with or adjacent to the susceptor; placing the cartridge in a recess in an aerosol generator housing such that the susceptor is adjacent to a first flat spiral inductor coil and a second flat spiral inductor coil disposed on an opposite side of the recess from the first flat spiral inductor coil; passing a high frequency oscillating current through the first flat spiral inductor coil and the second flat spiral inductor coil to induce a current in the susceptor, thereby heating the aerosol-forming substrate; A method comprising:

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; a flat spiral inductor coil; a power supply connected to the flat spiral inductor coil and configured to provide a high frequency oscillating current to the flat spiral inductor coil; The cartridge is a cartridge housing including an aerosol-forming substrate and configured to engage the device housing; a susceptor element positioned to heat the aerosol-forming substrate; the system comprising an air path extending through the system from an air inlet to an air outlet when the cartridge housing is engaged with the device housing; An electrically heated aerosol generating system, wherein the susceptor element comprises a capillary wick extending across the air path.

2. 2. The electrically heated aerosol generating system of claim 1, wherein the device housing comprises a recess for receiving at least a portion of the cartridge, the recess having an interior surface.

3. 3. The electrically heated aerosol generating system of claim 2, wherein the flat spiral inductor coil is located on or adjacent to the surface of the recess closest to the power source.

4. 3. The electrically heated aerosol generating system of claim 2, wherein the device housing comprises a main body and a mouthpiece portion, the recess being in the main body, the mouthpiece portion having an outlet through which the aerosol generated by the system can be drawn into the user's mouth, and the flat spiral inductor coil being within the mouthpiece portion.

5. The electrically heated aerosol generating system of any one of claims 1 to 4, wherein the air path passes through the flat spiral inductor coil.

6. An electrically heated aerosol generating system according to any one of claims 1 to 5, comprising a plurality of flat spiral inductor coils.

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

8. 8. The electrically heated aerosol generating system according to claim 1, wherein at least a portion of the capillary wick is in contact with the aerosol-forming substrate.

9. An electrically heated aerosol generation system as described in any one of claims 1 to 8, wherein an airflow passage is provided between the flat spiral inductor coil and the susceptor element when the cartridge housing is engaged with the device housing.

10. 10. The electrically heated aerosol generating system according to claim 1, wherein the susceptor element is fluid permeable.

11. An electrically heated aerosol generating system according to any one of claims 1 to 10, wherein the system is a handheld smoking system.

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