Aerosol generation system comprising a 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 invention relates to an aerosol generating system comprising a device part including a power source and a replaceable cartridge part including a consumable aerosol-forming substrate.

Background Art

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

[0003] The liquid aerosol-forming substrate becomes depleted during use and thus needs to be refilled. The most common way to supply refills of the liquid aerosol-forming substrate is in the form of a cartomizer-type cartridge. A cartomizer includes both a single dose of the liquid substrate and an atomizer, and is usually in the form of an electrically operated resistance heater wound around a capillary material soaked in the aerosol-forming substrate. Replacing the cartomizer as a single unit has the advantage of being convenient for the user and also avoids the need for the user to clean or otherwise maintain the atomizer.

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, it is desirable to provide a system that allows for a refill of the aerosol-forming substrate that can be manufactured more inexpensively and more robustly than currently available cartomizers, while still being easy and convenient for the consumer to use. Further, it is desirable to provide a system that allows for a sealed device that does not require soldered joints and is easy to clean.

Means for Solving the Problems

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

[0006] In operation, the high-frequency oscillating current passes through the flat spiral inductor coil to generate 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 causes Joule heating of the susceptor, which 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 can pass through the susceptor element and then cool to form an aerosol that is delivered to the user.

[0007] This array that utilizes induction heating has the advantage that no electrical contacts need to be formed 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 coupling elements. Further, a coil is provided as a component of the device that enables a simple, inexpensive, and robust cartridge configuration. The cartridge is a generally disposable item that is manufactured in much larger quantities than the devices it is used with. Thus, even when more expensive devices are required, reducing the cost of the cartridge can lead to significant cost savings for both the manufacturer and the consumer.

[0008] When used herein, high-frequency oscillating current means 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] When used herein, "susceptor element" means a conductor element that heats when exposed to a varying magnetic field. This can 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 geometric shape of the susceptor element can be selected to provide the desired electrical resistance and heat generation. The susceptor element may include, for example, a mesh, a flat spiral coil, a fiber, or a cloth.

[0010] When used herein, a "fluid-permeable" element means an element that permits a liquid or gas to permeate through it. The susceptor element can have within it a plurality of openings formed to permit fluid to permeate through the openings. In particular, this susceptor element permits an aerosol-forming substrate to permeate through the openings in either the gas phase or both the gas and liquid phases.

[0011] The susceptor element can be in the form of a sheet extending across an opening within the cartridge housing. The susceptor element can extend along the perimeter of the cartridge housing.

[0012] When the cartridge housing is engaged with the device housing, the device housing may include a recess for receiving at least a portion of the cartridge, and the recess has an inner surface. The inductor coil can be disposed on or adjacent to the surface of the recess closest to the power source. The inductor coil can have a shape that conforms to the inner surface of the recess.

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

[0014] Alternatively, the mouthpiece portion can be provided as a part of the cartridge. As used herein, the term "mouthpiece portion" means a device or portion of the cartridge that is placed in the user's mouth for directly inhaling the aerosol generated by the aerosol generating system. The aerosol is conveyed to the user's mouth through the mouthpiece portion.

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

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

[0017] An aerosol-forming substrate is a substrate having the ability to release volatile compounds capable of forming an aerosol. The volatile compounds can be released by heating the aerosol-forming substrate. The aerosol-forming substrate may be solid or liquid and may contain both solid and liquid components.

[0018] The aerosol-forming substrate may contain plant-derived materials. The aerosol-forming substrate may contain tobacco. The aerosol-forming substrate may contain a tobacco-containing material that contains volatile tobacco flavor compounds released from the aerosol-forming substrate upon heating. Alternatively, the aerosol-forming substrate may contain a non-tobacco-containing material. The aerosol-forming substrate may contain a homogenized plant-derived material. The aerosol-forming substrate may contain a homogenized tobacco material. The aerosol-forming substrate may contain at least one aerosol-forming agent. An aerosol-forming agent is any suitable known compound or mixture of compounds that, in use, facilitates the formation of a dense and stable aerosol and is substantially resistant to thermal decomposition at the operating temperature of the system. Suitable aerosol-forming agents are well known in the art and include, but are not limited to, polyhydric alcohols (such as triethylene glycol, 1,3-butanediol, and glycerol), 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-forming agents are polyhydric alcohols or mixtures thereof (such as triethylene glycol, 1,3-butanediol, and glycerol (most preferred)). The aerosol-forming substrate may contain other additives and components (such as flavorants).

[0019] The aerosol-forming substrate may be loaded onto a carrier or support by adsorption, coating, impregnation or other means. 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. The capillary material preferably 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 generally be arranged to move liquid towards 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 liquid can move 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, foamed metals or plastic materials, for example fibrous materials made of spun or extruded fibers (such as cellulose acetate, polyester, or bonded polyolefins, polyethylene, terylene or polypropylene fibers, nylon fibers or ceramics). The capillary material may have any suitable capillary and porosity to be used with different liquid physical properties. The liquid has physical properties including but not limited to viscosity, surface tension, density, thermal conductivity, boiling point and vapor pressure that allow it to move through the capillary material by capillary action. The capillary material may be configured to carry the aerosol-forming substrate to the susceptor element. The capillary material may extend into a gap within the susceptor element.

[0020] The susceptor element may be provided on a wall of a cartridge housing configured to be disposed adjacent to the inductor coil when the cartridge housing engages with the device housing. In use, it is advantageous to dispose the susceptor element close to the inductor coil in order to maximize the voltage induced in the susceptor element.

[0021] When the cartridge housing engages with the device housing, an air flow path can be provided between the inductor coil and the susceptor element. The vaporized aerosol-forming substrate can be mixed into the air flow within the air flow path and then cooled to form an aerosol.

[0022] The inductor coil can be a helical coil or a flat spiral coil. When used in this specification, the "flat spiral coil" generally means a planar coil where the axis of the coil windings is perpendicular to the surface on which the coil lies. However, when the term "flat spiral coil" is used in this specification, it encompasses not only planar coils but also flat spiral coils whose shape conforms to a curved surface. The use of a flat spiral coil allows for a compact device design with a robust and inexpensive simple design. The coil can be held within the device housing so as to prevent deposits on the coil and potential corrosion, and it does not need to be exposed to the generated aerosol. Also, the use of a flat spiral coil allows for a simple interface between the device and the cartridge, enabling a simple and inexpensive cartridge design.

[0023] The flat spiral inductor can have any desired shape within the plane of the coil. For example, the flat spiral coil can have a circular shape or generally an oval shape.

[0024] The diameter of the coil can be 5 mm to 10 mm.

[0025] The inductor coil can be arranged on or adjacent to the surface of the recess closest to the power source. This reduces the amount and complexity of the electrical connections within the device. The system can also include multiple inductor coils or multiple susceptor elements.

[0026] The inductor coil can have a shape that conforms to the shape of the susceptor element.

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

[0028] The material of the susceptor element may be selected based on its Curie temperature. Above its Curie temperature, hysteresis losses no longer occur, so the material is no longer ferromagnetic and thus does not heat 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 about 1 to 3%). This reduces the possibility of sudden overheating.

[0029] If the susceptor element is made of multiple materials, the material of the susceptor element can be optimized with respect to further aspects. For example, the material can be selected such that the first material of the susceptor element can have a Curie temperature above the maximum temperature to which the susceptor element should be heated. This first material of the susceptor element can then be optimized, for example, with respect to maximum heat generation, while moving to the aerosol-forming substrate to provide efficient heating of the susceptor. However, the susceptor element can then additionally comprise a second material having a Curie temperature corresponding to the maximum temperature to which the susceptor should be heated, and when the susceptor element reaches this Curie temperature, the magnetism of the entire susceptor element changes. This change can be detected and communicated to the microcontroller, and thereafter, the generation of AC power is interrupted until the temperature cools down again to a temperature below the Curie temperature, and the generation of AC power is resumed after cooling.

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

[0031] The system advantageously also comprises a power source (generally a power source such as a lithium-ion phosphate battery) 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 accumulation of sufficient energy for one or more smoking experiences. For example, the power source may have a capacity sufficient to allow for the continuous generation of aerosol for a time period of approximately one-sixth of the time typically taken to smoke one conventional cigarette, or a multiple of one-sixth of the time. In another example, the power source may have a capacity sufficient to allow for a predetermined number of smoking events, or for the discontinuous activation of the induction coil.

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

[0033] In a second aspect, there is provided a cartridge for use within an electrically heated aerosol generation system, wherein the electrically heated aerosol generation system comprises an aerosol generating device, the cartridge being configured for use with the device, the device comprising a device housing defining a recess for receiving at least a portion of the cartridge, an inductor coil disposed 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.

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

[0035] Features described in connection with one aspect may be applicable to other aspects of the present disclosure. In particular, advantageous or optional features described in connection with the first aspect of the present disclosure may be applicable to the second aspect of the invention.

[0036] Embodiments of the system according to the present disclosure will now be described in detail, by way of example only, with reference to the following accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

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Figure 13

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Figure 15

Figure 16A

Figure 16B

[0038] All of the embodiments shown in the figures rely on induction heating. Induction heating functions by placing a conductive article to be heated within a time-varying magnetic field. Eddy currents are induced within the conductive article. If the conductive article is electrically insulated, the eddy currents are dissipated by Joule heating of the conductive article. In an aerosol generating system that operates by heating an aerosol-forming substrate, the aerosol-forming substrate generally does not have sufficient conductivity on its own to be inductively heated in that manner. Therefore, in the embodiments shown in the figures, the susceptor element is used as the conductive article to be heated, and then the aerosol-forming substrate is heated by the susceptor element by heat conduction, heat convection, and / or heat radiation. When a ferromagnetic susceptor element is used, heat can also be generated by hysteresis losses when 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 receive significant Joule heating. In contrast, the susceptor element is designed to have significant Joule heating of the susceptor.

[0040] Figure 1 is a schematic cross-sectional view of an aerosol generating system according to a first embodiment of the present invention. The system comprises an apparatus 100 and a cartridge 200. The apparatus comprises a main housing 101 containing a lithium ion phosphate type battery 102 and control electronics 104. The main housing 101 also defines a recess 112 for receiving the cartridge 200 therein. The apparatus also includes a mouthpiece portion 120 including an outlet 124. The mouthpiece portion is connected to the main housing 101 by a hinged connection in this example, but any type of connection such as snap-fit or screw-mount may be used. 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 Figure 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 a copper plate. Coil 110 is clearly illustrated in FIG. 3. Coil 110 is positioned between air inlet 122 and air outlet 124 such that air drawn through inlet 122 and out outlet 124 passes through the coil. The coil can be sealed within a protective corrosion resistant coating or enclosure.

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

[0043] When cartridge 200 engages with the device and is received within recess 112, susceptor element 210 is positioned adjacent to flat spiral coil 110. Cartridge 200 can include keyed features to ensure that it cannot be inserted upside down within the device.

[0044] In use, the user inhales through the mouthpiece portion 120, draws air into the mouthpiece portion 120 through the air intake port 122, and exhales it from the outlet 124 into the user's mouth. The device includes an inhalation sensor 106 in the form of a microphone as part of the control electronic circuit 104. When the user inhales through the mouthpiece portion, a small air flow passes through the sensor inlet 121, through the microphone 106, and is drawn into the mouthpiece portion 120. When inhalation is detected, the control electronic circuit supplies a high-frequency oscillating current to the coil 110. This generates an oscillating magnetic field as shown by the dotted line in FIG. 1. Also, the LED 108 is activated to indicate that the device has been started. The oscillating magnetic field passes through the susceptor element and induces eddy currents within the susceptor element. The susceptor element is heated as a result of Joule heating and hysteresis losses, reaching a temperature sufficient to vaporize the aerosol-forming substrate near the susceptor element. The vaporized aerosol-forming substrate is mixed into the air flow from the air intake port to the air outlet and cools before entering the user's mouth to form an aerosol inside the mouthpiece portion. The control electronic circuit supplies the oscillating current to the coil for a predetermined duration (5 seconds in this example) when inhalation is detected, and then turns the current off until a new inhalation is detected.

[0045] It can be seen that the cartridge has a simple and robust design and can be manufactured at a lower cost compared to commercially available cartomisers. In this embodiment, the cartridge has a circular cylindrical shape and the susceptor element complements the circular open end of the cartridge housing. However, other configurations are possible. FIG. 4 is an end view of an alternative cartridge design where the susceptor element is a strip of steel mesh 220 that complements a rectangular opening in the cartridge housing 204. FIG. 5 is an end view of another alternative susceptor element. In FIG. 5, the susceptor is three concentric circles joined by radial bars. The susceptor element covers a circular opening within the cartridge housing.

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

[0047] In the embodiment shown in FIG. 6, the cartridge is of the same size and shape as the cartridge of FIG. 1 and has the same housing and susceptor element. However, the capillary material within the cartridge of FIG. 6 is different from that of FIG. 1. The cartridge of FIG. 6 has two separate capillary materials 202, 206. A disk of the first capillary material 206 is provided to contact the susceptor element 210 during use. The 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 capillary material and the second capillary material hold a liquid aerosol forming substrate. The first capillary material 206 that contacts the susceptor element has a higher thermal decomposition temperature (at least 160° C. or more, for example about 250° C., etc.) than the second capillary material 202. The first capillary material 206 effectively serves as a spacer that separates the heater susceptor element, which becomes very hot during use, from the second capillary material 202 so that the second capillary material is not exposed to a temperature above its thermal decomposition temperature. This is to ensure that the thermal gradient across the entire first capillary material keeps the second capillary material at a temperature below its thermal decomposition temperature. The second capillary material 202 can be selected to have excellent wicking performance to the first capillary material, 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 a glass fiber or an element containing glass fiber, and the second capillary material is a polymer such as high-density polyethylene (HDPE) or polyethylene terephthalate (PET).

[0048] Figure 7 illustrates a third embodiment. In Figure 7, only the front end of the system is shown as being able to use the same battery and control electronics as shown in Figure 1, including the inhalation detection mechanism. In Figure 7, the cartridge 240 is cubic and is formed by two strips of susceptor element 242 on opposite sides of the cartridge. The cartridge is shown alone in Figure 8. The device includes two flat spiral coils 142 located on opposite sides of the recess such that when the cartridge is received within the recess, the susceptor element strips 242 are adjacent to the coils 142. As shown in Figure 9, the coils 142 are rectangular so as to correspond to the shape of the susceptor strips. An air flow path is provided between the coils 142 and the susceptor element 242 such that when the user inhales at the mouthpiece portion 120, air from the inlet 144 passes through the susceptor strips and travels towards the outlet 124.

[0049] As shown in the embodiment of Figure 1, the cartridge includes a capillary material and a liquid aerosol forming substrate. The capillary material is arranged to carry the liquid substrate to the susceptor element strips 242.

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

[0051] In Figure 10, the cartridge 250 is cylindrical and is formed by a strip-shaped susceptor element 252 that extends around the central portion of the cartridge. The strip-shaped susceptor element covers an opening formed within a rigid cartridge housing. The cartridge is shown alone in Figure 11. The device includes a helical coil 152 located around the recess such that when the cartridge is received within the recess, the susceptor element 252 is within the coil 152. The coil 152 is shown alone in Figure 12. An air flow path is provided between the coil 152 and the susceptor element 252 such that when the user inhales at the mouthpiece portion 120, air from the inlet 154 passes through the susceptor strips and flows towards the outlet 124.

[0052] In use, the user inhales through the mouthpiece portion 120, passes air through the susceptor element 262 through the air inlet 154, draws the air out of the susceptor element into the mouthpiece portion 120, and exits through the outlet 124 into the user's mouth. When inhalation is detected, the control electronic circuit supplies a high-frequency oscillating current to the coil 152. This generates an oscillating magnetic field. The oscillating magnetic field passes through the susceptor element and induces eddy currents within the susceptor element. The susceptor element is heated as a result of Joule heating and hysteresis losses, reaching a temperature sufficient to vaporize the aerosol-forming substrate near the susceptor element. The vaporized aerosol-forming substrate passes through the susceptor element, mixes with the flow of air from the air inlet to the air outlet, cools before entering the user's mouth, and forms an aerosol inside the passage and the mouthpiece portion.

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

[0054] In use, the user inhales through the mouthpiece portion 120, passes the air through the air inlet 164 and into the central passage of the cartridge, through the susceptor element 262, draws the air out through the mouthpiece portion 120, and exits through the outlet 124 into the user's mouth. When inhalation is detected, the control electronic circuit supplies a high-frequency oscillating current to the coil 162. This generates an oscillating magnetic field. The oscillating magnetic field passes through the susceptor element and induces eddy currents in the susceptor element. The susceptor element is heated as a result of Joule heating and hysteresis losses, reaching a temperature sufficient to vaporize the aerosol-forming substrate close to the susceptor element. The vaporized aerosol-forming substrate passes through the susceptor element, mixes with the flow of air from the air inlet to the air outlet, cools before entering the user's mouth, and forms an aerosol inside the passage and the mouthpiece portion.

[0055] Figure 14 illustrates a sixth embodiment. In Figure 14, only the front end of the system is shown as being able to use the same battery and control electronic circuit as shown in Figure 1, including the inhalation detection mechanism. The cartridge 270 shown in Figure 14 is the same as that shown in Figure 13. However, the apparatus shown in Figure 14 has a different configuration in that it includes an inductor coil 172 on a holding blade 176 that extends into the central passage of the cartridge and generates an oscillating magnetic field near the susceptor element 272.

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

[0057] In use, the user inhales through the mouthpiece portion 120, draws air through the vapor-permeable portion of the cartridge 294 through the air inlet 194 and out of the air inlet 194 into the mouthpiece portion 120, and exits through the outlet 124 into the user's mouth. When an inhalation is detected, the control electronic circuit provides a high-frequency oscillating current to the coil 192. This generates an oscillating magnetic field. The oscillating magnetic field passes through the susceptor element of the cartridge housing and induces eddy currents in the susceptor element. The susceptor element is heated as a result of Joule heating and hysteresis losses and reaches a temperature sufficient to vaporize the aerosol-forming substrate. The vaporized aerosol-forming substrate is drawn through the vapor-permeable portion of the cartridge 294 by the air flowing from the air inlet to the air outlet, cools before entering the user's mouth, and forms an aerosol inside 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 from FIG. 16A, the circuit includes 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-source voltage) to the FET 1110, and a class E power amplifier including a transistor switch 1100 with a shunt capacitor C1 and an LC load network 1130 including a series connection of a capacitor C2 and an inductor L2. A DC power supply with a battery 101 includes a choke L1 and supplies a DC supply voltage. FIG. 16A also shows an ohmic resistor R representing a total ohmic load 1140, which is the sum of the ohmic resistance R of the inductor coil with the symbol L2 Coil and the ohmic resistance R of the susceptor element Load is the sum of.

[0059] Since the number of components is extremely small, the volume of the power supply circuit can be kept extremely small. This power supply circuit with an extremely small volume 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 since this volume is small, the overall dimensions of the induction heating device can be kept small.

[0060] The general operating principle of a class-E power amplifier is known and has been described in detail in the article "Class-E RF Power Amplifiers" (Nathan O. Sokal, published in the bimonthly QEX of the American Radio Relay League (ARRL), Newington, Connecticut, USA, January / February 2001, pages 9 - 20). Some general principles will be explained below.

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

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

[0063] The power loss in FET 1110 during one period of the AC voltage / current is the integral of the product of the transistor voltage and current at each point in time during that period of the AC voltage / current over the entire period, averaged over the entire period. Since FET 1110 must sustain a high voltage during some parts of that period and conduct a high current during some parts of that period, the occurrence of high voltage and high current simultaneously must be avoided. This is because it leads to significant power loss in FET 1110. In the "on" state of FET 1110, the transistor voltage is approximately zero and a high current flows through the FET. In the "off" state of FET 1110, the transistor voltage is high, but the current flowing through FET 1110 is approximately zero.

[0064] Also, the inevitable switching transitions span some portion of the period. Nevertheless, the high voltage-current product representing the high power loss in FET 1110 can be avoided by the following additional means. First, delay the rise of the transistor voltage until the current flowing through the transistor drops to zero. Second, return the transistor voltage to zero before the current flowing through the transistor begins to increase. This is achieved by a load network 1130 that includes a shunt capacitor C1 and a series connection of capacitor C2 and inductor L2, which is a network between FET 1110 and 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 stored energy of the shunt capacitor. Fourthly, the gradient of the transistor voltage at turn-on is zero. Next, the current injected into the turn-on transistor by the load network smoothly increases from zero at a controlled moderate rate, resulting in low power loss. On the other hand, the conductance of the transistor increases from zero during the turn-on transition. As a result, the voltage and current of the transistor never become high at the same time. The transitions of the voltage and current switching are mutually time-shifted. The values of L1, C1, and C2 can be selected such that the efficient dissipation of power within the susceptor element is maximized.

[0065] Although class E power amplifiers are preferred in most systems according to the present disclosure, other circuit configurations can also be used. FIG. 16B illustrates a second example of a 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, 1212. Two switching elements 1220, 1222 are provided for switching the on / off states of the two transistors 1210, 1212. The switches are controlled at a high frequency in such a way that one of the two transistors 1210, 1212 is surely turned off when the other one of the two transistors is on. The inductor coil is also denoted as L2 here, the total ohmic resistance of the coil and the susceptor element is denoted as R, and the values of C1 and C2 can be selected such that the efficient dissipation of power within the susceptor element is maximized.

[0066] The susceptor element can be manufactured from a material or combination of materials having a Curie temperature close to the desired temperature at which the susceptor element is to be heated. When the temperature of the susceptor element exceeds this Curie temperature, the material changes from ferromagnetic to paramagnetic. Thus, since the hysteresis loss of a paramagnetic material is much lower than that of a ferromagnetic material, the energy dissipation within the susceptor element is significantly reduced. This reduction in power loss within the susceptor element is detectable, and thus, for example, the generation of AC power by a DC / AC inverter can be interrupted until the susceptor element is cooled below the Curie temperature again and becomes ferromagnetic again. Thereafter, the generation of AC power by the DC / AC inverter can be resumed.

[0067] One skilled in the art can envision other cartridge designs incorporating the susceptor element according to the present disclosure. For example, the cartridge may include a mouthpiece portion and may have any desired shape. Moreover, the coil and susceptor arrangements according to the present disclosure can be used in other types of systems already described, including humidifiers, air fresheners, and other aerosol generating systems.

[0068] The above exemplary embodiments are illustrative but 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. An electrically heated aerosol generating system comprising an aerosol generator and a cartridge configured to be used with the aerosol generator, wherein the aerosol generator comprises 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, wherein the cartridge comprises a cartridge housing configured to engage with the device housing and contain an aerosol-forming substrate, the cartridge housing having an outer surface surrounding the aerosol-forming substrate, and the cartridge containing a fluid-permeable susceptor element, the system comprises an air flow passage extending from an air inlet to an air outlet, the fluid-permeable susceptor element being provided in the air flow passage, and the air flow passage extending through the inductor coil, the electrically heated aerosol generating system.

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

3. The electrically heated aerosol generating system according to claim 1 or 2, wherein the susceptor element extends around the periphery of the cartridge housing.

4. The electrically heated aerosol generating system according to any one of claims 1 to 3, wherein the inductor coil is a flat spiral coil.

5. The device housing includes a recess for receiving at least a portion of the cartridge when the device housing is engaged with the cartridge housing, the recess having an inner surface, and the inductor coil is disposed on or adjacent to the surface of the recess closest to the power supply. The electrically heated aerosol generating system according to any one of claims 1 to 4.

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

7. The electric heating aerosol generation system according to any one of claims 1 to 6, comprising a plurality of inductor coils.

8. The electric heating aerosol generation 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. The electric heating aerosol generation system according to any one of claims 1 to 8, wherein the susceptor element contacts the aerosol forming substrate.

10. The electric heating aerosol generation system according to any one of claims 1 to 9, wherein when the cartridge housing engages with the device housing, the air flow path extends through both the device housing and the cartridge housing.

11. The electric heating aerosol generation system according to any one of claims 1 to 10, wherein the susceptor element includes a mesh, a flat spiral coil, a fiber, or a cloth.

12. The electric heating aerosol generation system according to any one of claims 1 to 11, wherein the system is a handheld smoking system.

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