Induction heating assembly for an aerosol generating device - Patent Application 20070123633

Abstract

An inductive heating assembly (11) for an aerosol-generating device (10) includes a heating chamber (18) for receiving at least a portion of an aerosol-generating substrate (102), an induction coil (58) positioned outside the heating chamber (18) for generating an electromagnetic field, an inductively heatable susceptor (48) positioned inside the heating chamber (18) around (31) the aerosol-generating substrate (102), and a temperature sensor (64) in thermal contact with the inductively heatable susceptor (48). The inductively heatable susceptor (48) is positioned relative to the induction coil (58) to be inductively heated by the generated electromagnetic field and has geometric features (70) positioned to shield the temperature sensor (64) from the generated electromagnetic field.

Description

[Technical field]

[0001] The present disclosure relates generally to an induction heating assembly for an aerosol generating device, and more particularly to an induction heating assembly for heating an aerosol-generating substrate to generate an aerosol for inhalation by a user of the aerosol generating device. Embodiments of the present disclosure also relate to an aerosol generating device including an induction heating assembly. The present disclosure is particularly applicable to portable (handheld) aerosol generating devices. Such devices heat an aerosol-generating substrate, such as tobacco or other suitable material, by conduction, convection and / or radiation, rather than combustion, to generate an aerosol for inhalation by a user. The present disclosure particularly relates to an inductively heated aerosol generating device. [Background technology]

[0002] In recent years, the popularity and use of risk-reducing or risk-modifying devices (also known as aerosol-generating devices, or vapor-generating devices, or personal vaporizers) has grown rapidly as an alternative to the use of traditional tobacco products. A variety of devices and systems are available that heat or warm an aerosol-generating material to generate an aerosol for inhalation by the user.

[0003] A commonly available risk reduction or risk modification device is the substrate heated aerosol generating device, i.e. the so-called non-combustion heated device. This type of device generates an aerosol or vapour by heating an aerosol-generating substrate, typically to a temperature in the range of 150° C. to 300° C. Heating the aerosol-generating substrate to a temperature within this range, without burning or combusting the aerosol-generating substrate, generates a vapour which typically cools and condenses to form an aerosol which is inhaled by the user of the device.

[0004] Currently available aerosol-generating devices can provide heat to the aerosol-generating substrate using one of several different approaches. One such approach is to provide an aerosol-generating device that employs an induction heating system. In such devices, an induction coil is provided within the device and an inductively heatable susceptor is provided to heat the aerosol-generating substrate. When a user activates the device, electrical energy is supplied to the induction coil, which in turn generates an alternating electromagnetic field. The susceptor couples with the electromagnetic field to generate heat, which is transferred to the aerosol-generating substrate, for example, by one or more of conduction, radiation, and convection, and as the aerosol-generating substrate heats up, aerosol is generated. Summary of the Invention [Problem to be solved by the invention]

[0005] In general, it is desirable to rapidly heat an aerosol-generating substrate to a temperature high enough to generate vapor, and to maintain the aerosol-generating substrate at that temperature. In order to generate a vapor aerosol having suitable properties, the temperature of the aerosol-generating substrate must be carefully controlled, and therefore it is desirable to be able to precisely control the heating temperature. The present disclosure seeks to address this need. [Means for solving the problem]

[0006] According to a first aspect of the present disclosure, there is provided an inductive heating assembly for an aerosol generating device, comprising: a heating chamber for receiving at least a portion of the aerosol-generating substrate; an induction coil positioned outside the heating chamber for generating an electromagnetic field; an inductively heatable susceptor positioned within and around the heating chamber external to the aerosol-generating substrate, the inductively heatable susceptor being positioned relative to the induction coil so as to be inductively heated by the generated electromagnetic field; A temperature sensor in thermal contact with an inductively heatable susceptor. wherein the inductively heatable susceptor has geometric features arranged to shield the temperature sensor from the generated electromagnetic field.

[0007] According to a second aspect of the present disclosure there is provided an aerosol generation device comprising an induction heating assembly according to the first aspect. The induction heating assembly may further comprise a power supply arranged to provide power to the induction coil.

[0008] The induction heating assembly is configured to heat the aerosol-generating substrate without burning the aerosol-generating substrate to volatilize at least one component of the aerosol-generating substrate, thereby generating a heated vapor that cools and condenses to form an aerosol for inhalation by a user of the aerosol-generating device. The aerosol-generating device is typically a handheld, portable device.

[0009] Generally speaking, a vapor is a substance that is in the gas phase below its critical temperature, meaning that it can be condensed into a liquid by increasing the pressure without decreasing the temperature, while an aerosol is fine solid particles or liquid droplets suspended in air or another gas. However, it should be noted that, in this specification, the terms "aerosol" and "vapor" may be used interchangeably, particularly with respect to the form of inhalable medium that is generated for a user to inhale.

[0010] The geometric features are arranged to concentrate the generated electromagnetic field away from the temperature sensor, and thus the temperature sensor is shielded from the generated electromagnetic field. In particular, the geometric features are shaped (i.e. have a shape and / or volume arranged in such a way) to concentrate the generated electromagnetic field away from the temperature sensor. The geometric features may be formed from a susceptor material and may be at least partially formed within or by the inductively heatable susceptor. The inductively heatable susceptor is not positioned within the aerosol-generating substrate (i.e. does not function as an internal heating element) but is instead positioned outside the aerosol-generating substrate, and thus the temperature sensor is also positioned outside the aerosol-generating substrate (e.g. between the aerosol-generating substrate and the induction coil), where the electromagnetic field concentration may be highest. Shielding the temperature sensor from the generated electromagnetic field minimizes the effect of the generated electromagnetic field on the temperature sensor. In particular, inductive heating of the temperature sensor is substantially or completely avoided, thereby ensuring that an accurate measurement of the temperature of the inductively heatable susceptor can be obtained by the temperature sensor. This ensures that the heating of the aerosol-generating substrate can be precisely controlled.

[0011] We now describe optional features, which may be applied alone or in any combination with any aspect of the present disclosure.

[0012] The temperature sensor may be accommodated within the geometric feature, which minimizes the effect of electromagnetic fields on the temperature sensor and allows for a more accurate measurement of the temperature of the inductively heatable susceptor.

[0013] The temperature sensor may be a thermocouple and may include a first thermocouple wire that may be received within the geometric feature and may include a second thermocouple wire that may be received within the geometric feature. The geometric feature has a shape and / or volume operable to receive the first and second thermocouple wires. By locating the first and second thermocouple wires within the geometric feature, the effect of the generated electromagnetic field on the first and second thermocouple wires is minimized, resulting in a more accurate measurement of the temperature of the inductively heatable susceptor.

[0014] The induction coil may extend around the heating chamber. The heating chamber may have a longitudinal axis defining a longitudinal direction. The induction coil may be a helical coil extending around the heating chamber about the longitudinal axis. Providing an induction coil that helically extends around the heating chamber ensures reliable heating of the inductively heatable susceptor by the generated electromagnetic field.

[0015] The inductively heatable susceptor may be elongated in the longitudinal direction of the heating chamber. An elongated inductively heatable susceptor heats efficiently in the presence of the generated electromagnetic field, and its elongated shape ensures rapid and uniform heating of the aerosol-generating substrate along its length, thereby maximizing the energy efficiency of the aerosol-generating device.

[0016] The inductively heatable susceptor may have an inner surface and may have an outer surface. The heating chamber may include a chamber wall that defines an interior volume of the heating chamber. There may be an outer gap between the inductively heatable susceptor (e.g., an outer surface of the inductively heatable susceptor) and the chamber wall, and when the aerosol-generating substrate (or an aerosol-generating article including the aerosol-generating substrate) is received in the heating chamber, there may be an inner gap between the inductively heatable susceptor (e.g., an inner surface of the inductively heatable susceptor) and the aerosol-generating substrate (or an aerosol-generating article including the aerosol-generating substrate). Thus, efficient heat transfer from the inductively heatable susceptor to the aerosol-generating substrate may be achieved.

[0017] The induction heating assembly may include a holder positioned within the heating chamber, and an inductively heatable susceptor may be mounted on the holder, and the use of a holder may facilitate positioning the inductively heatable susceptor within the heating chamber, around the periphery of the heating chamber and outside the aerosol-generating substrate, such that the inductively heatable susceptor is positioned externally adjacent to the aerosol-generating substrate, but does not penetrate the aerosol-generating substrate.

[0018] The geometric feature may include a groove that may be formed on an inner or outer surface of the inductively heatable susceptor. The groove may extend along a longitudinal direction. The temperature sensor may be positioned within the groove. The temperature sensor and its component parts, such as the first and second thermocouple wires, may be fully contained within the groove, ensuring minimal effects of the generated electromagnetic field on the temperature sensor and its component parts, resulting in a more accurate measurement of the temperature of the inductively heatable susceptor. The groove may be easily formed on an inner or outer surface of the inductively heatable susceptor, thereby improving the manufacturability of the induction heating assembly.

[0019] The groove may extend longitudinally from the location of the temperature sensor to an end of the inductively heatable susceptor. Component parts of the temperature sensor, such as first and second thermocouple wires, may be received within the groove.

[0020] In embodiments where the groove is formed in the inner surface of the inductively heatable susceptor, the temperature sensor may be recessed from the inner surface. In embodiments where the groove is formed in the outer surface of the inductively heatable susceptor, the temperature sensor may be recessed from the outer surface. Recessing from the inner or outer surface of the inductively heatable susceptor minimizes the effect of the generated electromagnetic fields on the temperature sensor and its component parts, resulting in a more accurate measurement of the temperature of the inductively heatable susceptor.

[0021] The groove may be covered by a conductive, non-magnetically permeable strip of material that may enclose the temperature sensor within the groove. The material strip should ideally have high electrical conductivity (i.e. low electrical resistivity) so that little heat is generated within the material strip when eddy currents (e.g., generated within an adjacent inductively heatable susceptor) pass through the material strip.

[0022] The geometric features may include a channel that may be disposed on an inner or outer surface of the inductively heatable susceptor. The channel may extend along a longitudinal direction. The temperature sensor may be positioned within the channel. The temperature sensor and its component parts, such as the first and second thermocouple wires, may be completely contained within the channel, ensuring minimal effects of the generated electromagnetic fields on the temperature sensor and its component parts, resulting in a more accurate measurement of the temperature of the inductively heatable susceptor. The channel may be easily formed on the inner or outer surface of the inductively heatable susceptor, thereby improving the manufacturability of the induction heating assembly.

[0023] The channel may extend longitudinally from the location of the temperature sensor to an end of the inductively heatable susceptor. Component parts of the temperature sensor, such as first and second thermocouple wires, may be housed within the channel.

[0024] The channel may be formed by a pair of longitudinally extending sidewalls. The sidewalls may comprise an electrically conductive and magnetically permeable material. The sidewalls may be configured and dimensioned to maximize the shielding effect of the channel with respect to the temperature sensor. The sidewalls should ideally be spaced a sufficient distance from the temperature sensor such that heat generated at the sidewalls (e.g., by eddy currents and / or magnetic hysteresis losses) does not affect the temperature sensor (and thus the measured temperature) but is instead transferred to the inductively heatable susceptor.

[0025] The channel may be covered by a conductive, non-magnetically permeable strip of material that may enclose the temperature sensor within the channel. As mentioned above, the strip of material should ideally have high electrical conductivity (i.e. low electrical resistivity) so that little heat is generated within the strip of material when eddy currents (e.g., generated within an adjacent inductively heatable susceptor) pass through the strip of material.

[0026] The induction heating assembly may include a plurality of said inductively heatable susceptors, which may be mounted on a holder and extend around the inner surface of the chamber wall. By providing a plurality of inductively heatable susceptors, more rapid and uniform heating of the aerosol-generating substrate may be achieved.

[0027] The chamber wall may include a coil support structure that may be formed in or on the outer surface to support the induction coil. The coil support structure facilitates mounting of the induction coil and allows for optimal positioning of the induction coil relative to the inductively heatable susceptor, thereby efficiently heating the inductively heatable susceptor, thereby improving the energy efficiency of the induction heating assembly and the aerosol generating device. The provision of the coil support structure also facilitates manufacture and assembly of the induction heating assembly.

[0028] The coil support structure may include a coil support groove. The coil support groove may extend helically around the outer surface of the chamber wall. The coil support groove is particularly suitable for receiving a helical induction coil. Thus, a helical induction coil may extend around the heating chamber. The induction coil may comprise a Litz wire or Litz cable. However, it should be understood that other materials may be used. The circular cross section of the helical induction coil may facilitate insertion of the aerosol-generating substrate into the heating chamber and may ensure uniform heating of the inductively heatable susceptor and thus the aerosol-generating substrate.

[0029] The induction coil may be arranged, in use, to operate with a varying electromagnetic field having a magnetic flux density of about 20 mT to about 2.0 T (at the point of highest density).

[0030] The heating chamber may be generally tubular and the or each inductively heatable susceptor may be mounted in a holder such that the or each inductively heatable susceptor extends around the generally tubular heating chamber. The heating chamber may be generally cylindrical and the or each inductively heatable susceptor may be mounted in a holder such that the or each inductively heatable susceptor extends around the generally cylindrical heating chamber. The heating chamber may thus be configured to receive a generally cylindrical aerosol-generating substrate, which may be advantageous as aerosol-generating substrates in the form of aerosol-generating articles are often packaged and sold in cylindrical form. The induction heating assembly may include two inductively heatable susceptors. Each of the inductively heatable susceptors may be longitudinally elongated and may have a generally semicircular cross section.

[0031] The heating chamber and / or holder may comprise a substantially non-conductive and non-magnetically permeable material. For example, the heating chamber and / or holder may comprise a heat-resistant plastic material such as polyetheretherketone (PEEK). The heating chamber and / or holder are not heated by the electromagnetic field generated by the induction coil during operation of the aerosol generating device, ensuring that the energy input to the inductively heatable susceptor is maximized. This therefore helps to ensure that the energy efficiency of the induction heating assembly and the aerosol generating device is maximized. The aerosol generating device also remains cool to the touch, ensuring that user comfort is maximized.

[0032] The temperature sensor may be selected from the group consisting of a thermocouple, a thermistor, and a resistance temperature detector (RTD), however, other types of temperature sensors may also be employed.

[0033] The inductively heatable susceptor may comprise a metal. The metal is typically selected from the group consisting of stainless steel and carbon steel. However, the inductively heatable susceptor may comprise any suitable material, including, but not limited to, one or more of aluminum, iron, nickel, stainless steel, carbon steel, and alloys thereof, such as nickel-chromium or nickel-copper. The inductively heatable susceptor generates heat when an electromagnetic field is applied in the vicinity of the susceptor due to eddy currents and magnetic hysteresis losses resulting in energy conversion from electromagnetic to thermal.

[0034] The aerosol generating device may include, for example, a controller including control circuitry, which may be configured to operate at high frequencies. The power source and circuitry may be configured to operate at frequencies between about 80 kHz and 1 MHz, optionally between about 150 kHz and 250 kHz, optionally about 200 kHz. The power source and circuitry may be configured to operate at higher frequencies, such as in the MHz range, depending on the type of inductively heatable susceptor used.

[0035] The aerosol-generating substrate may comprise any type of solid or semi-solid material. Exemplary types of aerosol-generating solids include, for example, powders, granules, pellets, shreds, strands, particles, gels, strips, loose-leaf, cut fillers, porous materials, foamed materials, or sheets. The aerosol-generating substrate may comprise a plant-derived material, and in particular tobacco. The aerosol-generating substrate may advantageously comprise reconstituted tobacco, for example, tobacco and any one or more of cellulose fibers, tobacco stem fibers, and inorganic fillers, such as CaCO3.

[0036] Thus, aerosol-generating devices may be referred to as "heated tobacco devices," "heated non-combustion tobacco devices," "devices for vaporizing tobacco products," etc., and are to be construed as devices suitable for achieving these effects. The features disclosed herein are equally applicable to devices designed to vaporize any aerosol-generating substrate.

[0037] The aerosol-generating substrate may form part of the aerosol-generating article and may be surrounded by a paper wrapper.

[0038] The aerosol-generating article may be substantially formed in the shape of a stick and may generally resemble a cigarette with a tubular region having the aerosol-generating substrate arranged in a suitable configuration. The aerosol-generating article may include a filter segment, for example comprising cellulose acetate fibers, at the proximal end of the aerosol-generating article. The filter segment may constitute a mouthpiece filter and may be coaxially aligned with the aerosol-generating substrate. Some designs may also include one or more vapor collection regions, cooling regions, and other structures. For example, the aerosol-generating article may include at least one tubular segment upstream of the filter segment. The tubular segment may function as a vapor cooling region. The vapor cooling region may advantageously allow the heated vapor generated by heating the aerosol-generating substrate to cool and condense to form an aerosol having suitable properties for inhalation by a user, for example through the filter segment.

[0039] The aerosol-generating substrate may include an aerosol-forming agent. Examples of aerosol-forming agents include polyhydric alcohols, such as glycerin or propylene glycol, and mixtures thereof. Typically, the aerosol-generating substrate may include an aerosol-forming agent content of about 5% to about 50% on a dry weight basis. In some embodiments, the aerosol-generating substrate may include an aerosol-forming agent content of about 10% to about 20% on a dry weight basis, and in some cases about 15% on a dry weight basis.

[0040] Upon heating, the aerosol-generating substrate may release volatile compounds, which may include flavor compounds such as nicotine or tobacco flavorings. [Brief description of the drawings]

[0041] [Figure 1]1 is a schematic cross-sectional view of an aerosol generating system including an aerosol generating device and an aerosol-generating article to be positioned within a heating chamber of the aerosol generating device. [Diagram 2] 2 is a schematic cross-sectional view of the aerosol generating system of FIG. 1 showing an aerosol-generating article positioned within a heating chamber of the aerosol generating device. [Diagram 3] FIG. 3 is a cutaway schematic perspective view of a first example of an inductive heating assembly of the aerosol generating device of FIGS. 1 and 2, showing a holder and an inductively heatable susceptor positioned within a heating chamber. [Figure 4] FIG. 2 is a schematic perspective view of a holder and an inductively heatable susceptor. [Diagram 5] FIG. 5 is an exploded view of the holder and inductively heatable susceptor of FIG. [Figure 6-7] 1 is a schematic perspective view of a portion of a first example of an inductively heatable susceptor having grooves formed in an outer surface of the inductively heatable susceptor; [Figure 8-9] 1 is a schematic perspective view of a portion of a second example of an inductively heatable susceptor having grooves formed in an inner surface of the inductively heatable susceptor; FIG. [Figure 10-11] FIG. 13 is a schematic perspective view of a portion of a third example of an inductively heatable susceptor having channels disposed on an outer surface of the inductively heatable susceptor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] Embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0043] 1 and 2, an example of an aerosol generating system 1 is shown generally. The aerosol generating system 1 includes an aerosol generating device 10 and an aerosol generating article 100 for use with the device 10. The aerosol generating device 10 includes a body 12 that houses the various components of the aerosol generating device 10. The body 12 can have any shape that is compatible with the components described in the various embodiments presented herein and is sized to be comfortably held by a user in one hand without assistance.

[0044] A first end 14 of the aerosol generating device 10, shown at the bottom in Figures 1-2, is for convenience described as the distal, bottom, base or lower end of the aerosol generating device 10. A second end 16 of the aerosol generating device 10, shown at the top in Figures 1-2, is described as the proximal, top or upper end of the aerosol generating device 10. During use, a user typically orients the aerosol generating device 10 with the first end 14 facing downward and / or distal to the user's mouth and the second end 16 facing upward and / or proximal to the user's mouth.

[0045] The aerosol generating device 10 includes an induction heating assembly 11 positioned within a body 12. The induction heating assembly 11 includes a heating chamber 18. The heating chamber 18 defines an interior volume in the form of a cavity 20 having a substantially cylindrical cross-section for receiving an aerosol generating article 100. The heating chamber 18 has a longitudinal axis defining a lengthwise direction and is formed from a heat resistant plastic material such as polyetheretherketone (PEEK). The aerosol generating device 10 further includes a power source 22, for example one or more batteries, which may be rechargeable, and a controller 24.

[0046] The heating chamber 18 is open towards the second end 16 of the aerosol generating device 10. In other words, the heating chamber 18 has a first end 26 that is open towards the second end 16 of the aerosol generating device 10. The heating chamber 18 is typically maintained spaced apart from the inner surface of the body 12 to minimize heat transfer to the body 12.

[0047] The aerosol generating device 10 may optionally include a slide cover 28 that is movable in a transverse direction between a closed position (see FIG. 1 ) in which the slide cover 28 covers the open first end 26 of the heating chamber 18 to prevent access to the heating chamber 18, and an open position (see FIG. 2 ) in which the slide cover 28 exposes the open first end 26 of the heating chamber 18 to provide access to the heating chamber 18. In some embodiments, the slide cover 28 may be biased to the closed position.

[0048] The heating chamber 18, and more particularly the cavity 20, is arranged to receive a correspondingly shaped, generally cylindrical or rod-shaped aerosol-generating article 100. Typically, the aerosol-generating article 100 comprises a pre-packaged aerosol-generating substrate 102. The aerosol-generating article 100 is a disposable and replaceable article (also known as a "consumable") that may, for example, comprise tobacco as the aerosol-generating substrate 102. The aerosol-generating article 100 has a proximal end 104 (or mouth end) and a distal end 106. The aerosol-generating article 100 further comprises a mouthpiece segment 108 positioned downstream of the aerosol-generating substrate 102. The aerosol-generating substrate 102 and the mouthpiece segment 108 are arranged in coaxial alignment within a wrapper 110 (e.g., a paper wrapper) to hold the components in place and form the rod-shaped aerosol-generating article 100.

[0049] The mouthpiece segment 108 may include one or more of the following components (not shown in detail) arranged sequentially and in coaxial alignment in a downstream direction, i.e., from the distal end 106 toward the proximal (mouth) end 104 of the aerosol-generating article 100: a cooling segment, a central hole segment, and a filter segment. The cooling segment typically includes a hollow paper tube having a thickness greater than that of the wrapper 110. The central hole segment may include a hardened mixture containing cellulose acetate fibers and a plasticizer, and functions to increase the strength of the mouthpiece segment 108. The filter segment typically includes cellulose acetate fibers and functions as a mouthpiece filter. As heated vapor flows from the aerosol-generating substrate 102 toward the proximal (mouth) end 104 of the aerosol-generating article 100, the vapor cools and condenses as it passes through the cooling segment and the central hole segment to form an aerosol having suitable properties for a user to inhale through the filter segment.

[0050] The heating chamber 18 has a sidewall (chamber wall) 30 extending between a base 32 at a second end 34 of the heating chamber 18 and the open first end 26. The sidewall 30 and the base 32 may be connected together and integrally formed as a single piece. In the illustrated embodiment, the sidewall 30 is tubular, more specifically cylindrical. In other embodiments, the sidewall 30 may be of other suitable shapes, such as tubular with an elliptical or polygonal cross section. In yet other embodiments, the sidewall 30 may be tapered.

[0051] In the illustrated embodiment, the base 32 of the heating chamber 18 is closed, e.g., sealed or airtight, i.e., the heating chamber 18 is cup-shaped. This may ensure that air drawn in from the open first end 26 is prevented by the base 32 from exiting the second end 34, but is instead directed through the aerosol-generating substrate 102.

[0052] 3-5, the induction heating assembly 11 includes a holder 36 (or frame) positioned within the cavity 20 of the heating chamber 18, the holder 36 (or frame) also being formed of a heat resistant plastic material such as polyetheretherketone (PEEK). The holder 36 is not shown in FIGS. 1 and 2 for simplicity. The holder 36 has a proximal end 38 and a distal end 40, and includes a rim 42 at the proximal end 38 that cooperates with a circumferential lip 44 at the open first end 26 of the heating chamber 18 (best seen in FIG. 3). The holder 36 includes two longitudinally extending susceptor mounts 46 that extend from the rim 42 toward the distal end 40 of the holder 36. Two elongated, generally semicircular inductively heatable susceptors 48 in the form of bent plates are attached to the holder 36 by susceptor mounts 46 such that the inductively heatable susceptors 48 together form a tubular susceptor. Each of the inductively heatable susceptors 48 has an inner surface 48a and an outer surface 48b. The inductively heatable susceptors 48, and more specifically the inner surface 48a, may be spaced apart from the aerosol-generating substrate 102 to form an interior gap that allows air to flow between the inner surface 48a of the inductively heatable susceptor 48 and the outer surface of the wrapper 110 of the aerosol-generating article 100.

[0053] The sidewall 30 of the heating chamber 18 has an inner surface 50 and an outer surface 52, and the inductively heatable susceptor 48 is positioned at the periphery 31 of the heating chamber 18. More specifically, the inductively heatable susceptor 48 extends around the periphery 50 of the sidewall 30. The outer surface 48b of the inductively heatable susceptor 48 faces the inner surface 50 of the sidewall 30 but is spaced from the inner surface 50 of the sidewall 30 to form an outer gap that allows air to flow between the outer surface 48b of the inductively heatable susceptor 48 and the inner surface 50 of the sidewall 30.

[0054] The induction heating assembly 11 includes an electromagnetic field generator 56 for generating an electromagnetic field. The electromagnetic field generator 56 includes a generally helical induction coil 58. The induction coil 58 has a circular cross-section and extends helically around the generally cylindrical heating chamber 18. The induction coil 58 may be energized by the power source 22 and the controller 24. The controller 24 includes, among other electronic components, an inverter arranged to convert direct current from the power source 22 to alternating high frequency current for the induction coil 58.

[0055] The sidewall 30 of the heating chamber 18 includes a coil support structure 60 formed on the outer surface 52. In the illustrated example, the coil support structure 60 includes a coil support groove 62 that extends helically around the outer surface 52. The induction coil 58 is positioned within the coil support groove 62 such that it is securely and optimally positioned relative to the inductively heatable susceptor 48.

[0056] 6-11, the induction heating assembly 11 further includes a temperature sensor 64, which may be, for example, a thermocouple, a thermistor, a resistance temperature detector (RTD), or any other suitable temperature sensor. The temperature sensor 64 is operatively coupled to the controller 24 and in thermal contact with the inductively heatable susceptor 48 to allow the temperature of the inductively heatable susceptor 48 to be measured. In the illustrated example, the temperature sensor 64 includes first and second connecting wires 66, 68 connecting the temperature sensor 64 to the controller 24. In the case of a thermocouple, the first and second connecting wires 66, 68 may include first and second thermocouple wires. The inductively heatable susceptor 48 has a geometric feature 70 arranged to shield the temperature sensor 64 from the electromagnetic field generated by the induction coil 58 by concentrating the generated electromagnetic field away from the temperature sensor 64. Note that the geometric feature 70 has been omitted from FIGS. 1-5 for simplicity.

[0057] 6 and 7, a first example of an inductively heatable susceptor 48 is shown in which a geometric feature 70 includes a groove 72 formed in the outer surface 48b of the inductively heatable susceptor 48. The groove 72 extends longitudinally from a location where the temperature sensor 64 is located to an end of the inductively heatable susceptor 48. The temperature sensor 64 is positioned within the groove 72 so as to be recessed from the outer surface 48b. In the example of FIG. 7, the groove 72 is covered by an electrically conductive, non-magnetically permeable material strip 74. The material strip 74 encloses the temperature sensor 64 and the first and second connecting wires 66, 68 within the groove 72 and comprises a material having a high electrical conductivity (i.e., low electrical resistivity) such that little heat is generated within the material strip 74 when eddy currents generated in the adjacent inductively heatable susceptor 48 pass therethrough.

[0058] 8 and 9, a second example of an inductively heatable susceptor 48 is shown in which a geometric feature 70 includes a groove 72 formed in the inner surface 48a of the inductively heatable susceptor 48. The groove 72 extends longitudinally from a location where the temperature sensor 64 is located to an end of the inductively heatable susceptor 48. The temperature sensor 64 is positioned within the groove 72 so as to be recessed from the inner surface 48a. In the example of FIG. 9, the groove 72 is covered by an electrically conductive, non-magnetically permeable strip of material 74. The strip of material 74 encloses the temperature sensor 64 and the first and second connecting wires 66, 68 within the groove 72 and includes a material having a high electrical conductivity as discussed above.

[0059] 10 and 11, a third example of an inductively heatable susceptor 48 is shown in which the geometric feature 70 includes a channel 76 disposed on the outer surface 48b of the inductively heatable susceptor 48. The channel 76 extends longitudinally from the location where the temperature sensor 64 is located to the end of the inductively heatable susceptor 48. The channel 76 is formed by a pair of longitudinally extending sidewalls 76a. The sidewalls 76a include an electrically conductive and magnetically permeable material and may be formed of the same material as the inductively heatable susceptor 48. The sidewalls 76a are spaced from the temperature sensor 64 by a sufficient distance to minimize heat transfer from the sidewalls 76a to the temperature sensor 64 that may affect the temperature measurement. In the example of FIG. 11, the channel 76 is covered by an electrically conductive and non-magnetically permeable material strip 74. The material strip 74 encloses the temperature sensor 64 and the first and second connecting wires 66, 68 within the channel 76 and includes a material having a high electrical conductivity as discussed above.

[0060] To use the aerosol generating device 10, a user displaces the sliding cover 28 (if present) from the closed position shown in Figure 1 to the open position shown in Figure 2. The user then inserts the aerosol-generating article 100 through the open first end 26 into the heating chamber 18, and more specifically into the holder 36 positioned within the heating chamber 18, such that the aerosol-generating substrate 102 is received within the cavity 20 and the proximal end 104 of the aerosol-generating article 100 is positioned at the open first end 26 of the heating chamber 18 with at least a portion of the mouthpiece segment 108 protruding from the open first end 26 to allow engagement by the user's lips.

[0061] When a user activates the aerosol generating device 10, the induction coil 58 is energized by the power supply 22 and controller 24, which provide an alternating current to the induction coil 58, thereby generating an alternating and time-varying electromagnetic field by the induction coil 58. This electromagnetic field couples with the inductively heatable susceptor 48, generating eddy currents and / or magnetic hysteresis losses in the susceptor 48, causing the susceptor 48 to heat up. Heat is transferred from the inductively heatable susceptor 48 to the aerosol-generating substrate 102, for example, by conduction, radiation and convection. This results in non-combustion heating of the aerosol-generating substrate 102, which in turn generates vapor. The generated vapor cools and condenses into an aerosol that can be inhaled by a user of the aerosol generating device 10 through the mouthpiece segment 108 (more specifically, the filter segment).

[0062] Evaporation of the aerosol-generating substrate 102 is facilitated by adding air, for example, from the ambient environment, through the open first end 26 of the heating chamber 18, which is heated as it flows through an inner air flow passage defined by an inner gap between the inner surface 48a of each inductively heatable susceptor 48 and the outer surface of the wrapper 110, and through an outer air flow passage defined by an outer gap between the outer surface 48b of each inductively heatable susceptor 48 and the inner surface 50 of the sidewall 30. More specifically, as a user inhales through the filter segment, air is drawn into the heating chamber 18 through the open first end 26, as shown by arrow A in FIG. 2, and the air is heated as it flows from the open first end 26 through the heating chamber 18 along the inner and outer air flow passages toward the closed second end 34. When this heated air reaches the closed second end 34 of the heating chamber 18, it turns approximately 180° to enter the distal end 106 of the aerosol-generating article 100. The heated air is then drawn through the aerosol-generating article 100 from the distal end 106 towards the proximal (mouth) end 104, as shown by arrow B in Figure 2. This causes heating, without combustion, of the aerosol-generating substrate 102, thereby generating vapor. As described above, the generated vapor cools and condenses into an aerosol that can be inhaled by a user of the aerosol-generating device 10 through the mouthpiece segment 108 (more specifically, the filter segment).

[0063] The user can continue to inhale the aerosol so long as the aerosol-generating substrate 102 can continue to generate vapor, e.g., so long as there are vaporizable components remaining in the aerosol-generating substrate 102 for vaporization into a suitable vapor. The controller 24 can adjust the magnitude of the alternating current flowing through the induction coil 58 to ensure that the temperature of the inductively heatable susceptor 48, and therefore the temperature of the aerosol-generating substrate 102, does not exceed a threshold level. Specifically, at a certain temperature, depending on the configuration of the aerosol-generating substrate 102, the aerosol-generating substrate 102 will begin to burn. This is not a desired effect, and temperatures above this temperature are avoided.

[0064] To assist in this, the controller 24 is configured to receive an indication of the temperature of the aerosol-generating substrate 102, and more specifically the temperature of the inductively heatable susceptor 48, from the temperature sensor 64, and use the temperature indication to control the magnitude of the alternating current supplied to the induction coil 58. Thus, heating of the aerosol-generating substrate 102 can be precisely controlled, particularly because the geometric features 70 (e.g. grooves 72 or channels 76) shield the temperature sensor 64 from the generated electromagnetic field, thereby minimizing or preventing inductive heating of the temperature sensor 64.

[0065] Although exemplary embodiments have been described in the preceding paragraphs, it should be understood that various modifications to those embodiments may be made without departing from the scope of the appended claims. Thus, the breadth and scope of the claims should not be limited to the above-described exemplary embodiments.

[0066] Any combination of the above-described features in all possible variations thereof is encompassed by the present disclosure unless otherwise indicated herein or clearly contradicted by context.

[0067] Unless the context clearly dictates otherwise, throughout this specification and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense, i.e., including but not limited to, rather than in an exclusive or exhaustive sense.

Claims

1. An induction heating assembly (11) for an aerosol generating device (10), a heating chamber (18) for receiving at least a portion of an aerosol generating substrate (102), an induction coil (58) positioned outside the heating chamber (18) for generating an electromagnetic field, an induction heatable susceptor (48) positioned around (31) inside the heating chamber (18) outside the aerosol generating substrate (102), the induction heatable susceptor (48) being arranged relative to the induction coil (58) to be inductively heated by the generated electromagnetic field, a temperature sensor (64) in thermal contact with the induction heatable susceptor (48), comprising, the induction heatable susceptor (48) having geometric features (70) arranged to shield the temperature sensor (64) from the generated electromagnetic field, the induction heating assembly (11).

2. The induction heating assembly according to claim 1, wherein the temperature sensor (64) is received within the geometric features (70).

3. The induction heating assembly according to claim 2, wherein the temperature sensor (64) is a thermocouple and comprises a first thermocouple wire (66) received within the geometric features (70) and a second thermocouple wire (68) received within the geometric features (70).

4. The induction heating assembly according to claim 1, wherein the induction coil (58) extends around the heating chamber (18).

5. The heating chamber (18) has a longitudinal axis defining a longitudinal direction, the induction heatable susceptor (48) is elongated in the longitudinal direction of the heating chamber (18), and the induction heatable susceptor (48) has an inner surface (48a) and an outer surface (48b), the induction heating assembly according to claim 4.

6. The heating chamber (18) includes a chamber wall (30) defining an internal volume of the heating chamber (18), and when the aerosol generating substrate (102) is received within the heating chamber (18), there is an inner gap between the inner surface (48a) of the induction heatable susceptor (48) and the aerosol generating substrate (102), and an outer gap between the outer surface (48b) of the induction heatable susceptor (48) and the chamber wall (30), the induction heating assembly according to claim 5.

7. The geometric feature (70) includes a groove (72) formed on the inner surface (48a) or the outer surface (48b) of the induction heatable susceptor (48), the groove (72) extends in the longitudinal direction, and the temperature sensor (64) is positioned within the groove (72). The induction heating assembly according to claim 5.

8. The induction heating assembly according to claim 7, wherein the groove (72) extends in the longitudinal direction from the position of the temperature sensor (64) to the end of the induction heatable susceptor (48).

9. The induction heating assembly according to claim 7, when the groove (72) is formed on the inner surface (48a) of the induction heatable susceptor (48), the temperature sensor (64) is recessed from the inner surface (48a).

10. The induction heating assembly according to claim 7, when the groove (72) is formed on the outer surface (48b) of the induction heatable susceptor (48), the temperature sensor (64) is recessed from the outer surface (48b).

11. The induction heating assembly according to claim 7, wherein the groove (72) is covered by a strip (74) of electrically conductive and non-magnetic material to surround the temperature sensor (64) within the groove (72).

12. The geometric feature (70) includes a channel (76) disposed on the inner surface (48a) or the outer surface (48b) of the induction heatable susceptor (48), the channel (76) extends in the longitudinal direction, and the temperature sensor (64) is positioned within the channel (76). The induction heating assembly according to claim 5.

13. The induction heating assembly according to claim 12, wherein the channel (76) extends in the longitudinal direction from the position of the temperature sensor (64) to the end of the induction heatable susceptor (48).

14. The induction heating assembly according to claim 12, wherein the channel (76) is formed by a pair of side walls (76a) extending in the longitudinal direction, and the side walls (76a) include an electrically conductive and magnetic material.

15. The induction heating assembly according to any one of claims 12 to 14, wherein the channel (76) is covered by a strip (74) of electrically conductive and non-magnetic material to surround the temperature sensor (64) within the channel (76).

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