Aerosol generation system and method using dielectric heating

Abstract

To provide a system and method for generating an aerosol from an aerosol-forming substrate.SOLUTION: There is provided an aerosol-generating device for heating an aerosol-forming substrate to generate an aerosol, the aerosol-generating device comprising: a substrate cavity (28 / 49 / 58 / 78 / 88 / 108) configured to receive an aerosol-forming substrate; and an electromagnetic field generator (23 / 43 / 53 / 73 / 83 / 103) configured to generate a radio frequency (RF) electromagnetic field in the substrate cavity (28 / 49 / 58 / 78 / 88 / 108), the electromagnetic field generator (23 / 43 / 53 / 73 / 83 / 103) comprising a solid state RF transistor. The device can give rise to dielectric heating of the aerosol-forming substrate (36).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a system and method for generating an aerosol from an aerosol-forming substrate. In particular, the present disclosure relates to a system and method for heating an aerosol-forming substrate to generate an aerosol for inhalation by a user.

Background Art

[0002] Many different types of personal vaporizers and heat-not-burn products are available for generating inhalable aerosols from aerosol-forming substrates. Some of these systems heat a liquid composition, and others heat a solid tobacco mixture. Nearly all available systems heat the aerosol-forming substrate by conduction of heat from a heating element to the aerosol-forming substrate. Most commonly, this is achieved by passing an electric current through a resistive heating element to cause Joule heating of the heating element. Inductive heating systems have also been proposed, where Joule heating occurs as a result of induced eddy currents in a susceptor heating element.

[0003] One problem with these systems is that they cause non-uniform heating of the aerosol-forming substrate. The portion of the aerosol-forming substrate closest to the heating element is heated faster or to a higher temperature than the portion of the aerosol-forming substrate further away from the heating element. To mitigate this problem, various designs have been used. Some designs use multiple heating elements to provide the ability to distribute heat or heat different portions of the substrate at different times. Other designs transport only a small portion of the aerosol-forming substrate to the heating element, so that only that small portion is vaporized before another portion of the aerosol-forming substrate is transported to the heating element.

[0004] It is desirable to provide uniform heating of the aerosol-forming substrate in a manner that allows for greater design flexibility while being achievable in a compact, handheld system and allows for heating control.

Summary of the Invention

[0005] This disclosure provides an aerosol generating apparatus for generating aerosols by heating an aerosol-forming substrate, and the aerosol generating apparatus is A substrate recess configured to receive an aerosol-forming substrate, An electromagnetic field generator configured to generate a radio frequency (RF) electromagnetic field in a recess in a substrate, comprising an electromagnetic field generator including a solid-state RF transistor.

[0006] The apparatus can generate dielectric heating of an aerosol-forming substrate. Dielectric heating can be uniform within a large volume of the aerosol-forming substrate without the generation of hot spots. Heating also does not require contact between the heating element and the aerosol-forming substrate. This means that there is no need to clean the heating element, which may accumulate aerosol residue on it. The apparatus allows for considerable design flexibility with respect to the shape, volume, and composition of the aerosol-forming substrate, as well as the shape and volume of the substrate recesses.

[0007] Using solid-state RF converters allows for more compact devices. It's possible to manufacture devices that easily fit in a user's hand. The conventional method for generating RF frequency radiation for heating, such as in household microwave ovens, is the magnetron. Magnetrons are bulky and require very high voltages to operate, making them unsuitable for handheld devices. Furthermore, magnetrons have relatively unstable frequency output and a relatively short lifespan. RF transistors offer consistent operation over many more usage cycles and require much lower operating voltages.

[0008] Advantageously, solid-state RF transistors are configured to generate and amplify RF electromagnetic fields. Using a single transistor to provide both RF field generation and amplification makes it possible to fabricate compact devices.

[0009] As used herein, radio frequency (RF) means a frequency between 3 Hz and 3 THz, and includes microwaves. The RF electromagnetic field preferably has a frequency between 500 MHz and 50 GHz, and more preferably between 900 MHz and 30 GHz. The RF electromagnetic field may also have a frequency between 900 MHz and 5 GHz. In one embodiment, the RF electromagnetic field has a frequency of approximately 2.4 GHz.

[0010] As used herein, the term “aerosol-forming substrate” refers to a substrate having the ability to release volatile compounds that can form aerosols. Such volatile compounds may be released by heating the aerosol-forming substrate. An aerosol-forming substrate is typically part of an aerosol-generating article.

[0011] As used herein, the term “aerosol-generating article” refers to an article comprising an aerosol-forming substrate capable of releasing volatile compounds that can form aerosols. For example, an aerosol-generating article may be an article that generates an aerosol that can be directly inhaled by a user who inhales or smokes a mouthpiece. Aerosol-generating articles may be disposable. An article comprising an aerosol-forming substrate, including tobacco, may be called a tobacco stick.

[0012] As used herein, the term “aerosol generator” refers to a device that generates an aerosol by interacting with an aerosol-forming substrate. The aerosol-generating article is separate from the aerosol generator for heating the aerosol-generating article and is configured to be combined with it.

[0013] As used herein, the term "aerosol generating system" refers to a combination of an aerosol generating article and an aerosol generating device. In an aerosol generating system, the aerosol generating article and the aerosol generating device work together to generate an aerosol.

[0014] The substrate recess may comprise one or more outer walls formed from a material that does not transmit RF electromagnetic fields. One or more slots may be formed in one or more outer walls to allow the electromagnetic field to penetrate the substrate recess. It is desirable to contain the electromagnetic radiation generated by the electromagnetic field generator within the substrate recess. This is to provide efficient heating and to avoid radiation leakage. Such radiation leakage can damage other components of the system, including the electromagnetic field generator itself. It is also desirable to minimize user exposure to RF radiation. The outer walls may include any suitable material that does not transmit RF radiation, such as aluminum, stainless steel, silver, or gold. The outer walls may have polished surfaces to improve the reflection of RF radiation within the recess.

[0015] However, it is necessary that radiation be allowed to enter the substrate cavity. By providing one or more slots through which the electromagnetic field can pass, the electromagnetic field can enter the substrate cavity. At least one of the one or more slots may be L-shaped, S-shaped, T-shaped, or I-shaped.

[0016] The substrate recess may include a wall that allows an RF electromagnetic field to pass through. The aerosol-forming substrate may be enclosed in a wrapper or container made of a material that does not allow an RF electromagnetic field to pass through, and one or more slots may be formed in the wrapper or container to allow the electromagnetic field to penetrate.

[0017] The substrate recess may include a blind recess having an open end and a closed end. The substrate recess may be configured to receive an aerosol-forming article containing an aerosol-forming substrate through the open end. The substrate recess may be configured to hold the aerosol-forming substrate within the substrate recess.

[0018] The device may include a closure or mouthpiece to cover the open end of the substrate recess when in use. The closure or mouthpiece may include a radiation shield configured to reflect RF electromagnetic radiation. Alternatively, or additionally, the aerosol-forming article may include a radiation shield configured to reflect RF electromagnetic radiation. One or more radiation shields may be fluid-permeable to allow the generated aerosol to pass through them. For example, the radiation shield may include a metal mesh.

[0019] The device may include an air intake and an air outlet. The airflow path may be defined between the air intake and the air outlet. The airflow path may pass through or over a substrate recess. In embodiments in which the airflow path passes through a substrate recess or over a generated RF electromagnetic field, the airflow path may include a labyrinthine portion beyond one or more radiation shielding elements to prevent the escape of RF radiation through the air intake or air outlet. Alternatively, or additionally, one or more fluid-permeable radiation shielding elements may be provided in the airflow path.

[0020] The apparatus may include an apparatus housing. The apparatus may have a radiation containment recess within the housing, which surrounds or is adjacent to a substrate recess. The radiation containment recess may be provided to allow an RF electromagnetic field to enter the substrate recess through one or more slots or entry points. RF radiation can propagate freely within the radiation containment recess. The radiation containment recess may include a waveguide. The radiation containment recess may have an outer wall that does not allow RF electromagnetic radiation to pass through.

[0021] The aerosol generator may further comprise a resonant recess between the substrate recess and the electromagnetic field generator. As used herein, the term “resonant recess” is a structure capable of confining electromagnetic waves of a given frequency. In this case, the selected frequency of the electromagnetic wave corresponds to the RF region of the spectrum. To confine the electromagnetic wave, the resonant recess is fabricated from a reflective material (e.g., a metal) for that frequency. The structure may be hollow or filled with a dielectric material. The goal of the resonant recess is to allow the electromagnetic wave to bounce back and forth within it in order to enhance the formation of standing waves and minimize power loss.

[0022] The resonant recess can be designed to match the impedance of the electromagnetic field generator and the load (in this case, the aerosol-forming substrate in the substrate recess) to amplify the RF electromagnetic field at the resonant frequency, optimize energy absorption by the load, and minimize reflection of radiation from the load. This improves heating efficiency and minimizes radiation leakage from the system. The resonant recess may be positioned between the electromagnetic field generator and the substrate recess.

[0023] The aerosol generator may further include one or more antennas connected to an electromagnetic field generator and configured to direct an RF electromagnetic field. One or more antennas may be positioned at least partially within a substrate recess. During use, one or more antennas may be positioned at least partially within the substrate recess together with the aerosol-forming substrate. During use, one or more antennas may be configured to pierce a container holding the aerosol-forming substrate. One or more antennas may pass through slots in the outer wall of the substrate recess. One or more antennas may be positioned at least partially within a radiation containment recess. One or more antennas may be positioned within a resonance recess.

[0024] Providing an antenna that directs the radiation generated by an electromagnetic field generator can improve the efficiency of the device. One or more antennas may include conductive pins.

[0025] By using an RF transistor to generate an RF electromagnetic field, it is possible to use a closed-loop control scheme. The apparatus may include a sensor in or adjacent to the substrate recess that provides a signal indicative of the temperature in the substrate recess, and a controller connected to receive the signal from the sensor and configured to control the electromagnetic field generating device in accordance with the signal from the sensor.

[0026] The sensor may include a temperature sensor that directly measures temperature. As another method or additionally, the sensor may include one or more sampling antennas configured to detect perturbations in the electromagnetic field in the substrate recess indicative of the temperature in the substrate recess. The dielectric properties of the aerosol-forming substrate vary depending on temperature. The frequency or amplitude of the electromagnetic field, or both the frequency and amplitude, may be adjusted by the controller based on the signal from the sensor to control the heating provided by the apparatus. In particular, overheating may be detected, insufficient heating may be detected, and the frequency and amplitude of the electromagnetic field may be adjusted accordingly. Malfunctions may be detected. It may also be possible to detect the presence of an inappropriate material in the substrate recess. If an inappropriate material is detected, the apparatus can be automatically turned off. Similarly, if the signal from the sensor suggests that the aerosol-forming substrate is not present in the substrate recess, the apparatus can be automatically turned off. This type of control is not possible when using a magnetron to generate RF radiation.

[0027] It may be desirable to maintain the temperature within the substrate recess within a predetermined temperature range. It may be desirable to maintain the temperature of the aerosol-forming substrate below the temperature of the aerosol-forming substrate combustion product.

[0028] The ability to control the amount of heating provided by the device based on the feedback signal also allows for the use of different aerosol-forming substrates. It may be desirable to heat different aerosol-forming substrates to different temperatures. Therefore, by providing a mechanism for temperature control, it becomes possible to achieve optimal conditions for different aerosol-forming substrates or different designs of aerosol-forming articles.

[0029] The aerosol generating device may further comprise a liquid storage unit and a liquid pump configured to deliver liquid from the liquid storage unit to the substrate recess. The liquid in the liquid storage unit may include water. The liquid in the liquid storage unit may also include polar molecules that are susceptible to the effects of dielectric heating. For efficient dielectric heating, it is beneficial for the aerosol-forming substrate to include molecules that absorb RF radiation in the frequency range generated by the electromagnetic field generating device. It may be advantageous to add additional liquid to the aerosol-forming substrate immediately before or during heating.

[0030] The liquid pump may be connected to a control circuit. The control circuit may also be connected to the electromagnetic field generating device. The control circuit may coordinate the operation of the liquid pump and the electromagnetic field generating device.

[0031] The liquid pump may include a stepper motor, a syringe pump, and a peristaltic pump combined with an osmotic pump or a piezoelectric pump.

[0032] The solid state RF transistor may be, for example, an LDMOS transistor, a GaAs FET, a SiC MESFET, or a GaN HFET.

[0033] The aerosol generating device may comprise a smoking detector configured to detect when a user smokes the aerosol generating system. As used herein, the term "smoking" is used to refer to a user inhaling the aerosol generating system to receive the aerosol.

[0034] The aerosol generator is preferably portable. The aerosol generator may be comparable in size to a conventional cigar or cigarette. The aerosol generator may have an overall length of about 30 mm to about 150 mm. The aerosol generator may have an outer diameter of about 5 mm to about 30 mm. The base recess may have a diameter of 2 mm to 20 mm. The base recess may have a length of 2 mm to 20 mm. The aerosol generator may be a personal vaporizer, an e-cigarette, or a heated non-combustion device.

[0035] The device may include a control circuit. The control circuit may be configured to control the supply of power from a power source to an electromagnetic field generator. The control circuit may include a microprocessor, a programmable microprocessor, a microcontroller, or an application-specific integrated circuit chip (ASIC) or other electronic circuitry capable of providing control. The control circuit may include further electronic components. For example, in some embodiments, the control circuit may include a sensor, a switch, or a display element. The control circuit may include an RF power sensor. The control circuit may include a power amplifier. The power source may be a DC power source. The power source may include at least one battery. At least one battery may be a rechargeable lithium-ion battery. Alternatively, the power source may be another form of charge storage device, such as a capacitor.

[0036] The power supply can provide 0.5 watts to 30 watts of power. The impedance of the electromagnetic field generator may be less than 100 ohms, and is preferably between 50 and 75 ohms.

[0037] During use, the aerosol-forming substrate is received in the substrate cavity. An aerosol generation system is provided that includes the aerosol generator described above and the aerosol-forming substrate received in the substrate cavity.

[0038] The aerosol-forming substrate may include a solid. The aerosol-forming substrate may include a liquid. The aerosol-forming substrate may include a gel. The aerosol-forming substrate may include any combination of two or more of the solid, liquid, and gel.

[0039] The aerosol-forming substrate may contain nicotine, nicotine derivatives, or nicotine analogs. The aerosol-forming substrate may contain one or more nicotine salts. One or more nicotine salts may be selected from the list consisting of nicotine citrate, nicotine lactate, nicotine pyruvate, nicotine beetartrate, nicotine pectinate, nicotine alginate, and nicotine salicylate.

[0040] Aerosol-forming substrates may include aerosol-forming compounds. As used herein, “aerosol-forming compound” is any suitable known compound or mixture of compounds that, upon use, promotes the formation of a high-density, stable aerosol and is substantially resistant to thermal degradation at the operating temperature of the aerosol-generating article. Suitable aerosol-forming compounds are well known in the art and are not limited to, but include 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 acids, dicarboxylic acids, or polycarboxylic acids such as dimethyl dodecanediol and dimethyl tetradecanediol. Preferred aerosol-forming compounds are polyhydric alcohols or mixtures thereof, such as triethylene glycol, 1,3-butanediol, and glycerin.

[0041] The aerosol-forming substrate may further contain a flavoring agent. The flavoring agent may contain volatile flavor components. The flavoring agent may contain menthol. As used herein, the term "menthol" refers to the compound 2-isopropyl-5-methylcyclohexanol in any of its isomers. The flavoring agent may provide a flavor selected from the group consisting of menthol, lemon, vanilla, orange, wintergreen, cherry, and cinnamon. The flavoring agent may also contain volatile tobacco flavor compounds released from the substrate upon heating.

[0042] The aerosol-forming substrate may further contain tobacco or tobacco-containing material. For example, the aerosol-forming substrate may contain any of tobacco leaves, tobacco stem fragments, reconstituted tobacco, homogenized tobacco, extruded tobacco, tobacco slurry, cast tobacco, and puffed tobacco. Optionally, the aerosol-forming substrate may also contain tobacco powder compressed with an inert material, such as glass or ceramic, or another suitable inert material.

[0043] When the aerosol-forming substrate contains a liquid or gel, in some embodiments the aerosol-generating article may include an absorbent carrier. The aerosol-forming substrate may be coated onto the absorbent carrier or impregnated within the absorbent carrier. For example, the nicotine compound and the aerosol-forming substance may be mixed with water as a liquid. In some embodiments, the liquid may further include a flavoring agent. Such a liquid may then be absorbed by the absorbent carrier or coated onto the surface of the absorbent carrier. The absorbent carrier may be a sheet or tablet of a cellulose-based material on which the nicotine compound and the aerosol-forming substance may be coated or absorbed. The absorbent carrier may be a metal, polymer, or plant-based foam having liquid-retaining and capillary properties on which the liquid or gel aerosol-forming substrate is coated or absorbed.

[0044] Different categories of aerosol-generating articles may exist, each offering a different user experience. For example, different categories may include articles with different recipes or compositions of aerosol-forming substrates, different concentrations of nicotine or other components, and different amounts or thicknesses of aerosol-forming substrates. Aerosol-generating articles belonging to the same category may have the same shape, size, or color to make them identifiable to the user or the aerosol-generating system or device. An aerosol-generating system or device may be configured to accept only aerosol-generating articles of a specific category, for example, by having recesses or spaces shaped and sized to accept only a particular type of aerosol-generating article. Recesses or spaces may be keyed to accept only aerosol-generating articles of complementary shapes.

[0045] The aerosol-forming substrate may include a liquid-filled capsule. The aerosol-forming substrate may include a gel-filled capsule. The liquid-filled capsule or gel-filled capsule may be configured to rupture when the liquid or gel is heated by an RF electromagnetic field in the substrate cavity. The liquid-filled capsule or gel-filled capsule may include one or more valves. One or more valves may be configured to open when the liquid or gel is heated by an RF electromagnetic field in the substrate cavity due to an increase in pressure within the capsule. One or more valves may be configured to open when the user draws air through the aerosol-generating system.

[0046] An aerosol generating article is provided, comprising an aerosol-forming substrate, a mouthpiece through which a user can draw out an aerosol or vapor, and a fluid-permeable radio frequency electromagnetic radiation shield positioned between the aerosol-forming substrate and the mouthpiece.

[0047] The aerosol-generating article may be used in conjunction with the aerosol-generating device described above. The aerosol-generating article may be received in a recess in the substrate, or partially received. The aerosol-forming substrate may be as described above. The fluid-permeable radio frequency electromagnetic radiation shield may be a metal mesh.

[0048] The article is preferably configured such that the generated aerosol or vapor must pass through a fluid-permeable radio frequency electromagnetic radiation shield to reach the mouthpiece. The fluid-permeable radio frequency electromagnetic radiation shield may be positioned adjacent to the mouthpiece or attached to the mouthpiece.

[0049] The aerosol generating article may include a filter in the mouthpiece. The aerosol generating article may include a cooling element. The aerosol generating article may include a spacer.

[0050] A method for generating aerosols from an aerosol-forming substrate is provided, and this method is The aerosol-forming substrate is placed in a recess in the substrate of the aerosol generator, This includes using a solid-state RF transistor to generate a radio frequency (RF) electromagnetic field in a substrate recess.

[0051] The aerosol-forming substrate may be one of the aerosol-forming substrates described above. The aerosol generator may be one of the aerosol-generating devices described above.

[0052] The radio frequency (RF) electromagnetic field preferably has a frequency of 500 MHz to 50 GHz, and more preferably 900 MHz to 30 GHz. The RF electromagnetic field may also have a frequency of 900 MHz to 5 MHz. In one embodiment, the RF electromagnetic field has a frequency of approximately 2.4 GHz. Generally, heating efficiency is higher at higher frequencies. Therefore, it is desirable to use frequencies in the microwave portion of the RF spectrum.

[0053] The method may further include sensing parameters within a substrate recess and adjusting a radio frequency (RF) electromagnetic field based on the sensed parameters. The parameters may be temperature; the parameters may be electromagnetic field intensity; the parameters may be electromagnetic field frequency. The method may also include adjusting a radio frequency (RF) electromagnetic field based on a combination of the sensed parameters.

[0054] The method may further include injecting a liquid into an aerosol-forming substrate in a substrate cavity.

[0055] Furthermore, it is naturally possible to independently implement, supply, or use specific combinations of the various features described above.

[0056] Herein, embodiments of the present disclosure will be described, for illustrative purposes only, with reference to the attached drawings. [Brief explanation of the drawing]

[0057] [Figure 1] Figure 1 is a schematic diagram of a dielectric heating system. [Figure 2] Figure 2 is a schematic diagram of the first embodiment of the aerosol generation system. [Figure 3] Figure 3 is a schematic diagram of an aerosol generating article for use in the system shown in Figure 2. [Figure 4] Figure 4 is a schematic diagram of a second embodiment of the aerosol generation system. [Figure 5] Figure 5 is a schematic diagram of a third embodiment of the aerosol generation system. [Figure 6] Figure 6 is a schematic diagram of a fourth embodiment of the aerosol generation system. [Figure 7] Figure 7 is a schematic diagram of the fifth embodiment of the aerosol generation system. [Figure 8] Figure 8 is a schematic diagram of the sixth embodiment of the aerosol generation system. [Figure 9] Figure 9 is a schematic diagram of possible configurations of slots in the substrate recess. [Figure 10] Figure 10 is a schematic diagram of the seventh embodiment of the aerosol generation system. [Figure 11] Figure 11 is a schematic diagram of the eighth embodiment of the aerosol generation system. [Figure 12] Figure 12 is a schematic diagram of a liquid capsule. [Figure 13] Figure 13 is a schematic diagram of a closed-loop control system for an aerosol generation system according to one of the embodiments described.

[0058] Figure 1 is a schematic diagram of a heating system using radio frequency electromagnetic radiation, sometimes called dielectric heating. The system comprises a radio frequency signal generator 10, a power amplifier 12 connected to the signal generator to amplify the radio frequency signal, and an antenna 16 positioned inside a heating cavity 14, the antenna connected to the output of the power amplifier 12. The output of the amplifier is fed back to the signal generator to provide closed-loop control. The object to be heated 18 is placed in the cavity 14 and receives radio frequency electromagnetic radiation. Polar molecules within the object 18 align with the vibrating electromagnetic field and are stirred by the electromagnetic field as it vibrates. This causes an increase in the temperature of the object 18. This type of heating has the advantage of being uniform throughout the object (if the polar molecules are uniformly distributed). It also has the advantage of being a non-contact form of heating that does not require heat conduction or convection from a high-temperature heating element. Embodiments described with reference to Figures 2-13 use the basic heating principle illustrated in Figure 1.

[0059] In addition, the embodiments described use solid-state radio frequency (RF) transistors to perform both the signal generation function and power amplification function illustrated in Figure 1. However, it would be possible to implement the embodiments described using separate electronic components for signal generation and for power amplification.

[0060] Figure 2 is a schematic diagram of a heated, non-combustible aerosol generation system. The system 21 includes an aerosol generating article 22 received within a housing 26 of the aerosol generator. The aerosol generator includes a power source 25, such as a lithium-ion battery, a control circuit 24, an RF electromagnetic field generator 23 including a solid-state RF transistor, and a substrate recess 28 in which the aerosol generating article 22 is received. The RF electromagnetic field generator 23 is powered by the battery 25 under the control of the control circuit 24 and generates radio frequency electromagnetic radiation within the substrate recess 28. Surrounding the substrate recess 28 and positioned between the RF electromagnetic field generator and the substrate recess is a radiation containment recess 27 through which the electromagnetic radiation generated by the RF electromagnetic field generator travels before reaching the substrate recess 28.

[0061] The substrate recess is a generally cylindrical blind recess having an open end and a closed end, and a side wall extending between the open and closed ends. The aerosol-generating article is inserted into the substrate recess through its open end. Both the substrate recess 28 and the radiation containment recess 27 have outer walls formed from a suitable metallic material such as aluminum that does not transmit RF radiation. This concentrates the electromagnetic field within the substrate recess, preventing radiation leakage from the device. Slots 29 are formed in the outer wall of the substrate recess 28 to allow radiation to pass from the radiation containment recess into the substrate recess. In the example shown in Figure 2, one slot is formed in the wall at the closed end of the substrate recess, and two more slots are formed in the side wall of the substrate recess.

[0062] The aerosol generating article 22 of this embodiment has the appearance and feel of a cigarette. It is equipped with a mouthpiece end from which the user can inhale and draw aerosol from the aerosol generating system. On the opposite side of the mouthpiece end, the aerosol generating article holds an aerosol forming substrate. In this embodiment, the aerosol forming substrate includes a reconstituted cigarette along with an aerosol forming agent such as glycerol and water. The mouthpiece may be equipped with a filter.

[0063] The aerosol generator is designed to be a portable, handheld device that can be easily held by the user with one hand. The housing 26 may be formed of a suitable plastic material such as polyetheretherketone (PEEK). An air inlet (not shown) may be provided in the housing, allowing air to be drawn into the device through a substrate recess 28 and exit through the mouthpiece of the aerosol generating article.

[0064] During operation, the device is activated after the aerosol-generating article is placed in the substrate recess. RF radiation from the electromagnetic field generator is then directed into the substrate recess, causing dielectric heating of the aerosol-forming substrate. In this example, the frequency of the electromagnetic field is 900 MHz to 2.4 GHz. As will be described in detail, the temperature inside the substrate recess can be regulated using a feedback control mechanism. The temperature inside the substrate recess can be sensed, or another parameter indicating the temperature inside the substrate recess can be sensed, in order to provide a feedback signal to the control circuit 24. The control circuit then adjusts the frequency or amplitude of the electromagnetic field, or both, to maintain the temperature inside the substrate recess within a desired temperature range.

[0065] As mentioned above, the walls of the substrate recess and the radiation containment recess are made from a material that does not transmit RF radiation. For example, aluminum, stainless steel, silver, and gold can be used. Ideally, the walls of the substrate recess should have a polished surface to improve the reflection of RF radiation. It is also desirable to minimize the escape of RF radiation through the mouthpiece edge of the aerosol generating article. To this end, a radiation shielding element may be included within the aerosol generating article, as shown in Figure 3.

[0066] The aerosol generating article 22 shown in Figure 3 includes an aerosol generating substrate portion 36, which may be a crumpled reconstructed cigarette plug along with an aerosol former and water. The aerosol generating article also includes a support element 35, which may be a hollow acetate tube, a ventilation portion 34 including laser perforations 33 in an outer wrapper to allow air ingress for cooling the generated vapor aerosol, and a mouthpiece filter 31. A metal mesh radiation shielding element 32 is provided between the mouthpiece filter 31 and the cooling portion 34. The radiation shielding element reflects any RF radiation (indicated by arrows in Figure 3) escaping from the substrate recess toward the mouthpiece. The provision of the radiation shielding element minimizes radiation leakage toward the mouthpiece and therefore toward the user of the device. For the generated aerosol to pass into the user's mouth, the radiation shielding element must be fluid permeable.

[0067] Figure 4 shows another embodiment of the aerosol generating system, similar to the embodiment illustrated in Figure 2. However, in the embodiment of Figure 4, the substrate recess has walls that allow the RF electromagnetic field to pass through. For example, the walls of the substrate recess 49 may include, for example, Teflon®, high-purity quartz, or polytetrafluoroethylene. These materials can withstand high temperatures and provide a smooth, easy-to-clean surface. Similar to the embodiment of Figure 2, the system includes an aerosol generating article 22 received in a housing 46 of the aerosol generator. The aerosol generator includes a power source 45, such as a lithium-ion battery, a control circuit 44, an RF electromagnetic field generator 43 including a solid-state RF transistor, and a substrate recess 49 in which the aerosol generating article 22 is received. The RF electromagnetic field generator 43 is powered by the battery 45 under the control of the control circuit 44 and generates RF electromagnetic radiation within the substrate recess 49.

[0068] Figure 5 shows a further embodiment of the present invention in which the delivery of the electromagnetic field to the substrate recess is improved by providing an antenna or waveguide 59. The components of the system in the embodiment of Figure 5 are otherwise identical to those described with reference to Figure 2. The system includes an aerosol generating article 22 received in a housing 56 of an aerosol generator. The aerosol generator includes a power supply 55, a control circuit 54, an RF electromagnetic field generator 53 including a solid-state RF transistor, and a substrate recess 58 in which the aerosol generating article 22 is received. Surrounding the substrate recess 58 and positioned between the RF electromagnetic field generator and the substrate recess is a radiation containment recess 57 through which electromagnetic radiation generated by the RF electromagnetic field generator travels before reaching the substrate recess 58.

[0069] The antenna 59 extends from the electromagnetic field generator 53 into the substrate recess 58 through a slot 51 formed in the base of the substrate recess. When an aerosol-generating article is inserted into the substrate recess, the antenna pierces the aerosol-forming substrate. The antenna 59 delivers RF electromagnetic radiation directly into the substrate recess. The antenna 59 may also help to hold the aerosol-generating article inside the device. The antenna 59 may also be a conductive pin. The RF electromagnetic field can also propagate freely in the radiation containment recess 57 and enter the substrate recess through a slot 51 in the side wall of the substrate recess.

[0070] Figure 6 shows a further embodiment substantially identical to the embodiment in Figure 5. The features of Figure 6 are identical to those of Figure 5 and are labeled with the same reference numerals. In the embodiment of Figure 6, the antenna 59 extends into a substrate recess, but in this case, the antenna 59 does not penetrate the aerosol-forming substrate. A stopping surface 60 is provided within the substrate recess to prevent aerosol-generating articles from being pushed down onto the antenna 59. This has the advantage that condensation or debris does not accumulate on the antenna. However, the antenna can still deliver the electromagnetic field directly into the substrate recess.

[0071] Heating efficiency and reduced radiation leakage can also be improved by using a resonant recess positioned between the RF electromagnetic field generator and the substrate recess. A system including the resonant recess is shown in Figure 7.

[0072] The system in Figure 7 includes an aerosol generating article 22 received within a housing 76 of an aerosol generator. The aerosol generator includes a power supply 75, a control circuit 74, an RF electromagnetic field generator 73 including a solid-state RF transistor, and a substrate recess 78 in which the aerosol generating article 22 is received. Surrounding the substrate recess 78 is a radiation containment recess 77 through which electromagnetic radiation generated by the RF electromagnetic field generator can travel.

[0073] A resonant recess 65 is positioned between the electromagnetic field generator and the substrate recess. The antenna 79, connected to the output of the electromagnetic field generator 73, is located within the resonant recess. The walls of the resonant recess are configured to reflect RF radiation. The dimensions of the resonant recess match the operating frequency of the system so that electromagnetic field resonance occurs and the electromagnetic field is amplified at the resonant frequency. The use of the resonant recess allows for impedance matching between the source (in this case, the electromagnetic field generator 73) and the load (in this case, the aerosol-forming substrate). When the impedances of the load and the source are matched, there is no reflection of the electromagnetic field back from the load to the source.

[0074] In one embodiment, the operating frequency is 2.4 GHz. The resonant recess is generally cylindrical and has a length of 22.75 mm (extending in the direction between the electromagnetic field generator and the substrate recess) and a diameter of 21.75 mm. The antenna has a length of 8.74 mm. The radiative containment recess has the same dimensions as the resonant recess. The substrate recess within the radiative containment recess has a length of 13 mm and a diameter of 7 mm. The slots between the resonant recess and the radiative containment recess, and between the radiative containment recess and the substrate recess, may be rectangular and have dimensions of 1 mm × 3 mm.

[0075] Dielectric heating is typically most efficient for liquid-phase molecules that move more freely than solid-phase molecules. Gels, especially gels that liquefy upon heating, can also be heated effectively. For this reason, it is advantageous for aerosol-forming substrates to have a certain amount of gel or liquid content. The liquid or gel content may also be beneficial for generating high-density aerosols. In the examples described so far, the aerosol-forming substrate includes tobacco material. Only reconstituted tobacco can be heated using dielectric heating. However, it may be advantageous to immerse or moisten the tobacco with liquid glycerin and water. The water and aerosol-forming substrate may be provided in a capsule within the tobacco in a liquid or gel phase at room temperature. When the liquid or gel in the capsule is heated by dielectric heating, it expands. The capsule wall may be configured to burst as the liquid or gel expands, or to melt or collapse as the temperature rises. The capsule may burst immediately before use by the application of mechanical pressure. Alternatively, or additionally, the tobacco material may be coated with a composition that is a gel at room temperature but liquefies as the temperature rises. In these methods, the aerosol-forming substrate can be stored for extended periods without the liquid content drying out completely, and the liquid is released only during use.

[0076] A further option is to embed a non-rupturing liquid capsule within the aerosol-forming substrate. The liquid in the capsule is heated by RF radiation, and the heat is transferred from the capsule to the rest of the aerosol-forming substrate by conduction.

[0077] At least a portion of the gel or liquid is heated by RF radiation, but may be selected so as not to vaporize significantly at the operating temperature. In this way, the gel or liquid imparts heat to the aerosol-forming substrate, but the liquid or gel content of the substrate, which could affect heating efficiency, does not decrease during heating.

[0078] Another possibility is to inject or pump liquid into the substrate cavity immediately before or during use. Figure 8 is a schematic diagram of an embodiment of an aerosol generating system similar to the embodiment in Figure 2, where liquid from the liquid storage unit is pumped into the aerosol-forming substrate while the substrate is being heated.

[0079] The system in Figure 8 includes an aerosol generating article 22 received within a housing 86 of an aerosol generator. The aerosol generator includes a power supply 85, a control circuit 84, an RF electromagnetic field generator 83 including a solid-state RF transistor, and a substrate recess 88 in which the aerosol generating article 22 is received. Surrounding the substrate recess 88 is a radiation containment recess 87 through which electromagnetic radiation generated by the RF electromagnetic field generator can travel. A slot 81 is provided within the substrate recess to allow radiation to pass from the radiation containment recess into the substrate recess.

[0080] The aerosol generator comprises a liquid reservoir containing a liquid aerosol-forming material such as glycerol and water. A liquid conduit 95 leads from the liquid reservoir 94 to a substrate recess 88. A pump 94 is configured to pump the liquid from the liquid reservoir into the substrate recess at a controlled rate. Pumping the liquid into the substrate recess can improve heating efficiency. A control module 92 is connected to a control circuit 84 of an electromagnetic field generator 83. The operation of the pump 94 can be synchronized with the operation of the electromagnetic field generator in response to the sensed temperature in the substrate recess. The pump may be, for example, a piezoelectric micropump.

[0081] The slots provided to enable RF radiation to the aerosol-forming substrate may be in various positions. Figure 9 shows various possibilities for slot placement. Option a) includes a single slot at the closed end of the substrate recess. Option b) includes an opposite slot on the side wall of the recess. Option c) includes both a slot at the closed end and an opposite slot on the side wall of the recess. Option d) includes two slots at the closed end and an opposite slot on the side wall of the recess. Option e) includes only two slots at the closed end of the recess. Option f) includes two slots at the closed end and a single slot on the side wall of the recess. Option g) includes three slots at the closed end of the recess. Option h) includes three slots at the closed end of the recess and two opposite slots on the side wall of the recess. Option i) includes three slots at the closed end of the recess and two pairs of opposite slots on the side wall of the recess. These are just a few examples of configurations. Each slot may have a specific shape. For example, some or all of the slots may be I-shaped, L-shaped, S-shaped, or T-shaped. Some or all of the slots may also be circular, elliptical, or rectangular.

[0082] In embodiments in which the walls of the substrate recess allow RF radiation to pass through, the aerosol-generating article may have a wrapper or casing that does not allow RF radiation to pass through, and it is clear that slots or windows may be provided in various configurations in the wrapper or casing to allow RF radiation to penetrate the aerosol-forming substrate.

[0083] In the embodiments described herein, the aerosol-forming substrate is provided within an aerosol-generating article that the user inhales. Figure 10 illustrates an alternative embodiment in which the aerosol-generating article is positioned together with an aerosol-generating device. The aerosol-generating system in Figure 10 includes a mouthpiece portion which is part of the device and inhales the user, and a capsule 110 containing an aerosol-forming substrate that is fully contained within the device housing 106.

[0084] The system in Figure 10 includes an aerosol generating capsule 110 housed within a housing 106 of an aerosol generator. The aerosol generator includes a power supply 105, a control circuit 104, an RF electromagnetic field generator 103 including a solid-state RF transistor, and a substrate recess 108 in which the aerosol generating capsule 110 is housed. A resonant recess 107 is located between the electromagnetic field generator 103 and the substrate recess. An antenna 109 connected to the output of the electromagnetic field generator 103 is located within the resonant recess, as described with reference to the embodiment in Figure 7. The outer surface of the capsule is generally opaque to RF radiation, but a window 112 that allows RF electromagnetic fields to pass through is provided, allowing radiation to penetrate the capsule. The capsule may be provided with, for example, a plastic coating that allows RF radiation to pass through.

[0085] The mouthpiece portion 101 is secured to the housing 106 to cover the capsule. The mouthpiece can be attached to the device housing by screw fittings, snap fasteners, hinges or any other method. The mouthpiece portion 101 includes a metal mesh radiation shield 102 through which the generated aerosol can pass.

[0086] An air inlet (not shown) may be provided in the housing 106 to allow air to be drawn into the device, pass through (or through) the outlet of the capsule 110, and exit through the mouthpiece of the aerosol generator.

[0087] Figure 11 shows another embodiment similar to the embodiment in Figure 10, but with a waveguide instead of a resonant recess. Features identical to those in the embodiment in Figure 10 are provided by the same reference numerals. The aerosol generator includes a power supply 105, a control circuit 104, an RF electromagnetic field generator 103 including a solid-state RF transistor, and a substrate recess 108 that receives the aerosol generation capsule 120. In the embodiment of Figure 11, RF radiation is directed from the electromagnetic field generator 103 through the waveguide 124 to an antenna 126 positioned adjacent to a window in the side wall of the capsule 120. Again, the outer surface of the capsule is generally impermeable to RF radiation, but a window 122 that allows the RF electromagnetic field to pass through is provided, allowing the radiation to penetrate the capsule. The window 122 is located on the opposite side of the capsule, allowing the radiation to enter the recess, as will be described below, and the RF electromagnetic field to be sampled by a sampling antenna.

[0088] In the embodiments shown in Figures 10 and 11, the capsules are filled with a gel or liquid aerosol-forming substrate, but the same range of substrates may be used as described with reference to the embodiments above. The gel may contain a large amount of glycerol, along with nicotine and flavoring agents. The liquid may contain a mixture of glycerol and one or more aerosol-forming agents such as propylene glycol, water, nicotine, and flavoring agents. In one embodiment, the liquid in the capsule of Figure 11 contains 39% (by weight) glycerol, 39% propylene glycol, 20% water, and 2% nicotine. In another embodiment, the liquid contains 58% (by weight) glycerol, 20% propylene glycol, 20% water, and 2% nicotine.

[0089] Figure 12 is a schematic diagram of a possible mechanism for use in the embodiments of Figure 10 or 11, which allows for the escape of an aerosol from a gel or liquid-filled capsule. The capsule in Figure 12 includes a metal housing 130 that can be refilled with a gel or liquid aerosol-forming substrate 132. A window is formed in the capsule housing to allow the entry of RF radiation so that the gel or liquid may be heated. A valve 134 is provided at the mouthpiece end of the capsule. When the user inhales the mouthpiece of the system, the pressure drop in the mouthpiece pulls open the valve, allowing vapor and aerosol to escape from the capsule and be drawn into the user's mouth. Heating of the gel or liquid may also increase the pressure in the capsule, providing further opening force to the valve 134.

[0090] In all of the embodiments described, it is desirable that the temperature of the aerosol-forming substrate can be controlled. The ability to adjust the frequency or amplitude of the electromagnetic field using feedback control is one of the advantages of using solid-state RF transistors.

[0091] Figure 13 shows a control scheme that may be used in any of the embodiments described. As previously stated, the system includes a control circuit for the electromagnetic field generator. In the embodiment of Figure 13, the electromagnetic field generator 11 includes a solid-state RF LDMOS transistor that performs both the functions of an RF signal generator 10 and a power amplifier 12, and amplifies the generated RF electromagnetic signal. The output of the RF solid-state transistor 11 is passed to a radiating antenna 149, which is positioned to radiate an aerosol-forming substrate 152 located within an aerosol-generating article 150 received in a substrate recess 148.

[0092] The control circuit includes a microcontroller 140 capable of controlling both the frequency and power output of the RF solid-state transistor. One or more sensors provide input to the microcontroller. Based on the sensor inputs, the microcontroller adjusts the frequency or power output of the electromagnetic field generator, or both. In the embodiment shown in Figure 13, there is a temperature sensor 142 positioned to sense the temperature within the substrate recess. A sampling antenna 144 may be provided in the recess as an alternative to or in addition to the temperature sensor. The sampling antenna is configured as a receiver and can detect perturbations of the electromagnetic field in the substrate recess, which are an indicator of the efficiency of energy absorption by the aerosol-forming substrate. An RF power sensor 147 is also provided to detect the power output from the electromagnetic field generator.

[0093] The microcontroller 140 receives signals from the RF power sensor, the temperature sensor 142, and the sampling antenna 144. The signals can be used to determine whether the temperature in the substrate cavity is too low, too high, defective, or absent or improperly dielectric. A substrate with improper dielectric properties may be one whose liquid or gel content has been depleted through use and therefore needs to be replaced.

[0094] Based on a decision made by the microcontroller 140, the frequency and power of the electromagnetic field generated by the RF solid-state transistor 11 are adjusted, or the electromagnetic field is turned off. Typically, it is desirable to provide a stable and consistent volume of aerosol, which means maintaining the aerosol-forming substrate within a specific temperature range. However, the desired target temperature may change over time as the composition of the aerosol-forming substrate changes and the temperature of the surrounding system changes. Also, since the dielectric properties of the aerosol-forming substrate change with temperature, it may be necessary to adjust the electromagnetic field as the temperature rises or falls.

[0095] It is clear that features described in one embodiment may also be applicable to other embodiments. The described embodiments offer the advantages of uniform, non-contact heating of an aerosol-forming substrate in a manner that can be controlled to provide specific, desirable aerosol properties. Compared to conventional microwave heating using a magnetron, the use of a solid-state RF transistor provides a compact system that can be implemented as a handheld system. Furthermore, the use of a solid-state RF transistor enables better control of frequency and power, as well as a longer operating life.

Claims

1. an aerosol generating system comprising an aerosol generating device and an aerosol forming substrate, A substrate recess configured to receive an aerosol-forming substrate, The system includes an electromagnetic field generator configured to generate a radio frequency (RF) electromagnetic field in the recess of the substrate, The aerosol-forming substrate is configured to be received in a substrate recess, and the aerosol-forming substrate includes or contains a liquid-filled capsule or a gel-filled capsule, and the liquid-filled capsule or gel-filled capsule is configured to rupture when the liquid or gel is dielectrically heated by the radio frequency (RF) electromagnetic field in the substrate recess. Aerosol generation system.

2. The aerosol generating system according to claim 1, wherein the aerosol-forming substrate includes tobacco.

3. The aerosol generating system according to claim 2, wherein the tobacco is coated with a composition configured to be a gel at room temperature but to liquefy as the temperature rises.

4. The electromagnetic field generating device includes a solid-state RF transistor, and is an aerosol generating system according to any one of claims 1 to 3.

5. The aerosol generation system according to claim 4, wherein the solid-state RF transistor is configured to generate the RF electromagnetic field.

6. The aerosol generating system according to any one of claims 1 to 5, further comprising a resonance recess between the substrate recess and the electromagnetic field generating device.

7. The aerosol generating system according to claim 6, further comprising an antenna connected to the electromagnetic field generating device and configured to direct the RF electromagnetic field, wherein the antenna is positioned in the resonant recess.

8. The aerosol generating system according to claim 6 or 7, wherein the resonance recess is located adjacent to the window of the capsule.

9. The aerosol generating system according to any one of claims 6 to 8, wherein the outer surface of the capsule is generally impermeable to RF radiation, and the capsule includes a first window through which the RF electromagnetic field passes.

10. The aerosol generating system according to claim 9, further comprising an antenna connected to the electromagnetic field generating device and configured to direct the RF electromagnetic field, wherein the antenna is positioned adjacent to the first window.

11. The aerosol generating system according to claim 9 or 10, wherein the capsule includes a second window through which the RF electromagnetic field passes, the second window being positioned on the opposite side of the capsule from the first window.

12. The aerosol generating system according to any one of claims 1 to 11, wherein the substrate recess comprises one or more outer walls formed of a material that does not allow the RF electromagnetic field to pass through, and one or more slots are formed in the one or more outer walls.

13. The aerosol generating system according to any one of claims 1 to 12, comprising: a sensor located in or adjacent to the substrate recess, which provides a signal indicating the temperature in the substrate recess; and a controller connected to receive the signal from the sensor and connected to control the electromagnetic field generator depending on the signal from the sensor.

14. The aerosol generating system according to any one of claims 1 to 13, further comprising: a liquid storage unit; and a liquid pump configured to deliver liquid from the liquid storage unit to the substrate recess.

15. A method for generating an aerosol from an aerosol-forming substrate, wherein the aerosol-forming substrate includes or is contained within a liquid-filled capsule or a gel-filled capsule, and the method is The aerosol-forming substrate is placed in a recess in the substrate of the aerosol generator, To generate a radio frequency (RF) electromagnetic field in the recess of the substrate, To rupture the liquid-filled capsule or gel-filled capsule, the RF electromagnetic field is used to heat the liquid-filled capsule or gel-filled capsule in the recess of the substrate, Methods that include...

16. A capsule for insertion into a substrate recess of an aerosol generator, wherein the aerosol generator has an electromagnetic field generator configured to generate a radio frequency (RF) electromagnetic field in the substrate recess, the capsule is filled with a liquid or gel, the liquid or gel comprises an aerosol-forming substrate, and the capsule is configured to rupture when the liquid or gel is heated by the radio frequency (RF) electromagnetic field.

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