Induction heating arrangement for use in an induction heated aerosol generator - Patent Application 20070122997

Abstract

The present invention relates to an induction heating arrangement for use in an induction heating aerosol generating apparatus, the heating arrangement comprising a cylindrically helical induction coil for generating an alternating magnetic field within the interior space of the induction coil that enables induction heating of a susceptor for heating an aerosol-forming substrate in thermal contact or proximity to the susceptor. The heating arrangement comprises a magnetic flux concentrator disposed around the induction coil and configured to distort the alternating magnetic field of the induction heating arrangement toward the interior space of the induction coil during use. The magnetic flux concentrator includes a sleeve portion circumferentially surrounding the induction coil and annular protruding portions at each axial end of the sleeve portion that protrude radially inward beyond the sleeve portion, the induction coil being axially disposed between the annular protruding portions. The present invention further relates to an induction heating module, an aerosol generating apparatus, and an aerosol generating system comprising such a heating arrangement.

Description

[Technical Field]

[0001] The present disclosure relates to an induction heating arrangement for use in an induction heated aerosol generating device. The present disclosure further relates to an induction heating module, an aerosol generating device and an aerosol generating system comprising such a heating arrangement. [Background technology]

[0002] Aerosol-generating devices used to generate inhalable aerosols by inductively heating an aerosol-forming substrate are generally known in the prior art. Such systems and devices may include an induction heating arrangement including an induction coil for generating an alternating magnetic field. The magnetic field is used to induce at least one of heat-generating eddy currents or hysteresis losses in a susceptor disposed in thermal proximity or direct physical contact with the aerosol-forming substrate, which is capable of forming an inhalable aerosol upon heating. The susceptor and substrate may be part of an aerosol-generating article receivable within the interior space of the induction coil. In particular, the substrate may be a liquid aerosol-forming substrate stored in a liquid reservoir of the article. The reservoir may be in fluid communication with the susceptor located in an evaporation portion of the article, where the aerosol-forming liquid can be evaporated by interaction of the susceptor with the alternating magnetic field of the induction coil. Alternatively, the aerosol-forming substrate may be a solid or gel-like aerosol-forming substrate in thermal proximity or direct physical contact with the susceptor, with both the susceptor and the substrate being contained in the evaporation portion of the article. Alternatively, the susceptor may be part of the aerosol generating device.

[0003] In some articles, the susceptor may have a flat shape, such as a sheet-like shape, that provides a large surface-to-mass ratio, which is beneficial for efficiently utilizing the heat generated by the susceptor and for enhancing heat transfer from the susceptor to the aerosol-forming substrate.

[0004] During a user experience, the induction heating arrangement may operate either continuously or on demand, specifically in an intermittent mode such as after each puff. In a continuous operating mode, the susceptor is permanently maintained at a temperature level sufficient to form a satisfactory amount of aerosol, but when the heating system is operated intermittently, such as on user demand, it may be difficult to reach a sufficient temperature level within a short period of time.

[0005] It would therefore be desirable to have an induction heating arrangement for inductively heating an aerosol-forming substrate, an aerosol generator, and an aerosol generation system that have the advantages of the prior art solutions while alleviating their limitations. In particular, it would be desirable to have an induction heating arrangement for inductively heating an aerosol-forming substrate, an aerosol generator, and an aerosol generation system that each enable higher heating efficiency, particularly reaching sufficient temperature levels within a short period of time. Summary of the Invention

[0006] According to the present invention, there is provided an induction heating arrangement for use in an induction heating aerosol generating apparatus, the heating arrangement comprising at least one cylindrically helical induction coil, in particular a single cylindrically helical induction coil, for generating an alternating magnetic field within the interior space of the induction coil that enables inductive heating of a susceptor for heating an aerosol-forming substrate in thermal contact with or in thermal proximity to the susceptor. The heating arrangement also comprises a magnetic flux concentrator disposed around the induction coil and configured to distort the alternating magnetic field of the induction heating arrangement toward the interior space of the induction coil during use. The magnetic flux concentrator includes a sleeve portion circumferentially surrounding the induction coil, and additional annular protrusions at each axial end of the sleeve portion that protrude radially inward beyond the sleeve portion such that the induction coil is axially disposed between the annular protrusions.

[0007] In accordance with the present invention, it has been found that the heating efficiency of an induction heating arrangement for a given operating power can be improved by increasing the density of the magnetic field within the interior space of the induction coil in which the susceptor is placed during use. In particular, it has been found that the density of the magnetic field at the susceptor location can be increased by using a magnetic flux concentrator shaped as described above to distort the magnetic field toward the interior space of the induction coil. In particular, the annular protrusions at each axial end of the sleeve portion that protrude radially inward beyond the sleeve portion lead to a concentration or focusing of the magnetic field within the interior space of the induction coil. Therefore, the level of heat generated in the susceptor for a given level of power passing through the induction coil is increased compared to an induction coil without a magnetic flux concentrator or having only a sleeve-shaped magnetic flux concentrator without annular protrusions at each axial end.

[0008] Additionally, the magnetic flux concentrator acts as a magnetic shield, capable of reducing the extent to which the magnetic field propagates beyond the induction coil. Thus, the magnetic flux concentrator can help reduce unwanted heating of adjacent sensitive components, such as the metal outer housing of an aerosol generating device used in the heating arrangement. Similarly, the magnetic flux concentrator can help reduce unwanted heating of adjacent sensitive components outside the device. Thus, by reducing unwanted heating losses, the efficiency of the induction heating arrangement can be further improved.

[0009] The efficiency of the induction heating arrangement is further enhanced due to the use of a cylindrical helical induction coil, which advantageously makes it possible to generate a homogeneous alternating magnetic field.

[0010] As used herein, the term "magnetic flux concentrator" refers to a component having a high relative permeability that acts to concentrate and direct the magnetic field or lines of force generated by an induction coil. As used herein, the term "high relative permeability" refers to a relative permeability of at least 50 or 100, particularly at least 1000, preferably at least 10,000, even more preferably at least 50,000, and most preferably at least 80,000. These exemplary values refer to maximum relative permeability values at frequencies up to 50 kHz and temperatures of 25°C. The term "relative permeability" refers to the ratio of the permeability of a material or medium, such as a magnetic flux concentrator, to the permeability of free space, μ_0, where μ_0 is 4π·10 -7 N.A. -2 (4·Pi·10E-07 Newtons per square ampere).

[0011] The magnetic flux concentrator preferably includes or is made of one or more layers of magnetic flux concentrator foil. Magnetic flux concentrators including or made of one or more layers of magnetic flux concentrator foil are more flexible than other magnetic flux concentrator configurations, such as solid ferrite bodies. Therefore, foil-based magnetic flux concentrators offer improved shock absorption characteristics and can therefore withstand higher excessive force impacts or shocks without breaking. For example, compared to susceptors made from sintered ferrite powder, foil-based magnetic flux concentrators offer significantly improved resistance to shock loads, such as those resulting from an accidental drop. Furthermore, foil-based magnetic flux concentrators enable a more compact design of the heating arrangement. Furthermore, in contrast to solid-body magnetic flux concentrators, foil-based magnetic flux concentrators also allow for compensation for manufacturing tolerances and fine-tuning of the inductivity. Magnetic flux concentrator foil can advantageously help enhance the impedance stability of the induction coil over temperature. Generally, the impedance of an induction coil is affected by the presence of a flux concentrator. When using foil-based flux concentrators, the conductance of the induction heating arrangement may vary less with temperature due to the small volume of the foil, especially compared to larger-volume solid-body flux concentrators. As a result, the impedance may also vary less with temperature. Additionally, foil-based flux concentrators are easier to manufacture.

[0012] According to a preferred setup of the magnetic flux concentrator, each of the annular protrusions may be made of one or more layers of magnetic flux concentrator foil, which extend radially outward at least to, and preferably beyond, the outer periphery of the induction coil. On top of the annular protrusions, a sleeve portion may be made of one or more layers of magnetic flux concentrator foil surrounding the induction coil and each of the annular protrusions. That is, the magnetic flux concentrator may be realized by, in a first step, providing one or more turns of magnetic flux concentrator foil at each axial end of the induction coil such that the induction coil is axially sandwiched between these two turns forming the annular protrusions, and then, in a second step, winding one or more layers of magnetic flux concentrator foil over the annular protrusions and the induction coil to form the sleeve portion.

[0013] According to an alternative setup of the flux concentrator, the sleeve portion may be made of one or more layers of flux concentrator foil surrounding the induction coil, and each of the annular protruding portions may be made of one or more layers of flux concentrator foil and terminate radially flush with the outer periphery of the sleeve portion, i.e., the one or more layers of flux concentrator foil forming the sleeve portion are sandwiched between two windings of the flux concentrator coil forming the annular protruding portion.

[0014] Generally, the flux concentrator foil used to form the annular protruding portion may be the same as the flux concentrator foil used to form the sleeve portion, however, the flux concentrator foil used to form the annular protruding portion may be different from the flux concentrator foil used to form the sleeve portion.

[0015] As used herein, the term "foil" refers to a thin sheet material having a thickness that is much smaller than any dimension perpendicular to the thickness direction. As used herein, the term "thickness" refers to the dimension of the foil perpendicular to the major surface of the foil.

[0016] The magnetic flux concentrator foil may have a foil thickness ranging from 50 micrometers to 250 micrometers, in particular from 80 micrometers to 150 micrometers, such a thickness value allowing for easy winding of the foil while ensuring that the magnetic flux concentrator has sufficient mechanical stability.

[0017] The magnetic flux concentrator foil is preferably a multi-layer magnetic flux concentrator foil including at least one ferrite layer sandwiched between an adhesive layer and a cover layer.

[0018] The adhesive layer advantageously aids in the wrapping and securing of one or more layers of magnetic flux concentrator foil that form the sleeve portion and the annular projection portion.

[0019] The cover layer may be or include a polymer film. The polymer film may be selected from polyester, polyimide, polyolefin, or a combination thereof. For example, the cover layer may be a PET (polyethylene terephthalate) cover layer.

[0020] At least one of the adhesive layer and the cover layer, and preferably both, may be edge layers of the multi-layer magnetic flux concentrator foil, i.e., the outermost layers of the multi-layer magnetic flux concentrator foil.

[0021] By way of example, the flux concentrator foil may be a flexible ferrite sheet available from Laird under the tradenames MHLL6060-300 or MULL6060-300. MHLL6060-300 has a real permeability of about 130 and an imaginary permeability of about 5 at a frequency of 13.56 MHz. MULL6060-300 has a real permeability of about 150 and an imaginary permeability of about 5 at a frequency of 13.56 MHz.

[0022] The sleeve portion may be radially spaced from the induction coil by a radial gap. The radial gap may have a width (radial extension) in the range of 0.5 mm to 1.5 mm, in particular 0.8 mm to 1 mm. Advantageously, the radial gap may help to reduce losses in the induction coil and increase losses in the heated susceptor, i.e., increase the heating efficiency of the aerosol-generating device.

[0023] Similarly, at least one, and preferably each, of the annular protruding portions may be axially spaced from the induction coil by an axial gap.

[0024] The radial and / or axial gaps may be voids or spaces at least partially filled with a filler material, for example, a polyimide such as poly(4,4'-oxydiphenylene-pyromellitic imide), also known as Kapton®, or any other suitable dielectric material.

[0025] To ensure sufficient concentration of the magnetic field within the interior space of the induction coil, the annular protruding portions preferably extend radially inward beyond the outer periphery of the induction coil, such that the induction coil is at least partially sandwiched between the annular protruding portions.

[0026] The opposite is also possible, and it has been found that the concentration of the magnetic field within the internal space of the induction coil is sufficient when the annular protrusion extends radially inward up to the inner circumference of the induction coil, i.e., when the annular protrusion does not protrude radially inward beyond the inner circumference of the induction coil.

[0027] The width of each of the axial annular projections may be in the range of 1.5 to 2.5 mm, particularly 1.8 to 2.2 mm. These width dimensions have proven advantageous for distorting the magnetic field sufficiently within the interior space of the induction coil while still allowing for a compact design of the induction heating arrangement. The latter is particularly important when the induction heating arrangement is implemented in a handheld / portable aerosol generating device.

[0028] Similarly, the height dimension of each of the radial annular projections may be in the range of 1.5 mm to 2.5 mm, in particular 1.8 mm to 2.2 mm. Advantageously, the height dimension is a function of the thickness of the sleeve and the cross section of the wire from which the coil is formed.

[0029] The radial thickness of the sleeve portion may be in the range of 100 micrometers to 500 micrometers, particularly 150 micrometers to 250 micrometers. In this respect, it has been found that the sleeve portion may be fairly thin in order to still adequately focus and shield the magnetic field. Thin sleeve portions also present advantages with regard to the compact design of the induction heating arrangement.

[0030] The axial width dimension of each of the sleeve portions may be in the range of 7 mm to 12 mm, especially 9 mm to 11 mm.

[0031] In general, the magnetic flux concentrator may have any transverse cross-sectional shape. Preferably, the shape of the magnetic flux concentrator matches the shape of the cylindrical spiral guide. Thus, the sleeve portion and the annular protrusion portion may each have a cylindrical shape.

[0032] As viewed in a longitudinal cross section through the flux concentrator along the length axis of the induction coil, the flux concentrator may have a U- or C-shape, with the sleeve portion being part of the base of the U- or C-shape and the annular protruding portion being part of the arm or leg of the U- or C-shape.

[0033] At least one of the annular protruding portions, preferably the more distal annular protruding portion, may include a recess or feed-through opening for passing a connecting lead of the induction coil. If the magnetic flux concentrator is formed by winding a magnetic flux concentrator foil, the recess or feed-through opening may be cut into the annular protruding portion after winding the magnetic flux concentrator foil.

[0034] The interior space of the induction coil is preferably configured to removably receive at least a portion of an aerosol-generating article, particularly an evaporation portion of the aerosol-generating article. The evaporation portion of the article may include a susceptor, particularly a flat susceptor, more particularly a sheet-like susceptor, for heating an aerosol-forming substrate contained within the article by interaction of the susceptor with the alternating magnetic field of the induction coil. That is, the susceptor inductively heated by the induction coil may be part of the aerosol-generating article. Alternatively, the susceptor inductively heated by the induction coil may be part of an aerosol-generating device in / with which the induction heating arrangement is configured to be used.

[0035] Generally, the cylindrical helical induction coil may be formed by one or more turns of coil wire. For example, the induction coil may include 3 to 6 turns, particularly 4 to 5 turns. The number of turns does not necessarily have to be an integer; the number of turns may be any number between two integers.

[0036] The coil wire may preferably have a circular cross section.

[0037] The coil wire may be one of a solid wire, a stranded wire, and a Litz wire.

[0038] Because induction coils are driven by AC current, the current through the coil wire flows only near the outer surface of the coil wire, so the diameter of the coil wire does not need to be large to carry a large current.

[0039] This can be beneficial if the coil wire has a diameter in the range of 0.8 mm to 1.5 mm, especially 1 mm to 1.2 mm, to achieve a compact coil design with a sufficiently large number of turns per unit of length.

[0040] The induction coil preferably has an axial length extension similar to that of the susceptor, measured in the same direction when received within the interior space of the induction coil. The induction coil may have an axial length in the range of 4 mm to 12 mm, particularly 5 mm to 8 mm.

[0041] It is preferable to have a gap between adjacent turns of the induction coil. That is, the pitch of the helical induction coil may be greater than the axial extension of the cross-section of the coil wire, as seen in the longitudinal cross-section of the induction coil. In particular, if the coil wire has a circular cross-section, the pitch of the helical induction coil may be greater than the diameter of the coil wire. As a result, the coil wire of adjacent turns does not contact each other. This allows the use of coil wire without wire insulation. However, the coil wire may also be insulated. For example, the coil wire may be coated copper wire, e.g., enamel-coated copper wire. Furthermore, the gap between adjacent turns of the induction coil serves to improve heat dissipation, thus reducing resistive power losses in the coil winding. The gap between adjacent turns also helps to reduce undesirable ring / crossover effects. The distance (center-to-center) between adjacent portions of the coil wire of adjacent turns may be in the range of 1.1 to 1.4 times, particularly 1.2 to 1.3 times, the axial extension of the cross-section of the coil wire, as seen in the longitudinal cross-section of the induction coil. In particular, when the coil wire has a circular cross section, the distance (center-to-center) between adjacent portions of the coil wire of adjacent turns is in the range of 1.1 to 1.4 times, and especially 1.2 to 1.3 times, the diameter of the coil wire. These ranges have proven to provide a sufficiently long distance that still allows for a compact coil design, i.e., a sufficiently large number of turns per unit of length.

[0042] When an induction heating arrangement is intended to heat a flat, particularly sheet-like, susceptor, it may be advantageous to adapt the geometry of the magnetic field within the interior space of the induction coil in which the susceptor is placed to the flat shape of the susceptor. Thus, a cylindrical, helical induction coil may have a non-circular, flat transverse cross-sectional shape, including, in particular consisting of, two opposing flat sections connected by two opposing, at least partially curved sections. Advantageously, flattening the transverse cross-sectional shape of the induction coil can reduce the radial distance between the induction coil and the main surface of the flat susceptor, given that the susceptor is placed so that its main surfaces are aligned with the two opposing flat sections of the transverse cross-sectional shape of the outer periphery of the support tube. The reduction in radial distance leads to an increase in the magnetic field strength at the susceptor, which in turn leads to an increase in heating efficiency. Therefore, the level of heat generated in the susceptor for a given level of power passing through the induction coil increases, which, among other things, allows the desired temperature level to be reached within a shorter period of time.

[0043] The non-circular flat transverse cross-sectional shape of the induction coil preferably includes a minor axis of symmetry and a major axis of symmetry. The minor axis of symmetry may extend between two opposing flat sections of the induction coil. Conversely, the major axis of symmetry may extend between two opposing at least partially curved sections of the induction coil.

[0044] The ratio of the maximum distance along the major axis of symmetry between two opposing at least partially curved sections to the maximum distance along the minor axis of symmetry between two opposing flat sections is preferably in the range of 1.2 to 3, especially 1.5 to 2.5, which is particularly advantageous for a good match between the geometry of the magnetic field and the flat shape of the susceptor to be heated.

[0045] In order to arrange the induction coil as close as possible to the interior space of the induction coil in which the susceptor is placed, the maximum distance along the minor axis of symmetry between the two opposing flat sections may be in the range of 4 to 7 mm, in particular 5 to 6 mm, while the maximum distance along the major axis of symmetry between the two opposing at least partially curved sections may be in the range of 7 to 10 mm, in particular 8 to 9 mm.

[0046] Preferably, the two opposing flat sections are substantially parallel to one another. A parallel configuration is particularly useful for matching the magnetic field geometry to a susceptor having a sheet-like shape. In particular, each of the two opposing flat sections is substantially straight.

[0047] In particular, the non-circular flattened transverse cross-sectional shape of the induction coil is an ellipse. As used herein, the term "ellipse" defines a shape consisting of two semicircles connected by parallel lines tangent to their endpoints. Thus, the induction coil may have an elliptical cylindrical shape.

[0048] Like the induction coil, the magnetic flux concentrator may have a non-circular flat transverse cross-sectional shape that corresponds to the non-circular flat transverse cross-sectional shape of the induction coil, i.e., a non-circular flat transverse cross-sectional shape that includes, in particular consists of, two opposing flat sections connected by two opposing at least partially curved sections. In particular, the cross-sectional shape of the magnetic flux concentrator may be oval.

[0049] In addition to the induction coil and magnetic flux concentrator, the induction heating arrangement may include an alternating current (AC) generator. The AC generator may be powered by a power source, particularly a DC power source. The power source may be part of the aerosol generation device in which the induction heating arrangement is configured to be used. The AC generator is operably coupled to at least one induction coil. Specifically, the induction coil may be an integral part of the AC generator. The AC generator is configured to generate a high-frequency oscillating current that passes through the induction coil to generate a changing magnetic field. The AC current may be supplied to the induction coil continuously after activation of the system, or may be supplied intermittently (e.g., with each puff).

[0050] The induction heating arrangement preferably comprises a DC / AC converter connectable to a DC power source, which may be part of the aerosol generating device in which the induction heating arrangement is configured to be used.

[0051] The DC / AC converter may include an LC network. For example, the DC / AC converter may include a power amplifier, particularly a switching power amplifier, more specifically a single-ended switching power amplifier, preferably one of a Class C power amplifier, a Class D power amplifier, or a Class E power amplifier. In particular, the DC / AC converter may include at least one transistor switch, particularly a single transistor switch, at least one transistor switch driver circuit, and at least one LC network. The LC network may include a series connection of a capacitor and an inductor, where the inductor is a cylindrical spiral induction coil of the induction heating arrangement according to the present invention, which is used to generate an alternating magnetic field for heating a susceptor of an article received within the interior space of the induction coil. The LC network may further include a shunt capacitor in parallel with the transistor switch. In addition, the DC / AC converter may include a choke inductor for supplying a DC supply voltage from a DC power source.

[0052] The induction heating arrangement is preferably configured to generate a high frequency varying magnetic field. As referred to herein, the high frequency varying magnetic field may have a frequency in the range of 500 kHz (kilohertz) to 30 MHz (megahertz), in particular 5 MHz (megahertz) to 15 MHz (megahertz), preferably 5 MHz (megahertz) to 10 MHz (megahertz).

[0053] The induction heating arrangement, including the induction coil and the magnetic flux concentrator, may be part of an induction module that is used and is particularly adapted to be disposed within an induction heated aerosol generating device.

[0054] In this regard, the present invention further relates to an induction heating module for use in an inductively heated aerosol generating device, the induction heating module comprising an induction heating arrangement according to the present invention and as described herein. The induction heating module may, for example, be arranged within the device housing of the inductively heated aerosol generating device.

[0055] Preferably, the induction heating module further comprises a coil support on which the induction coil and flux concentrator are supported.

[0056] The coil support may comprise a support tube, in particular a cylindrical support tube, with the induction coil disposed around the outer periphery of the support tube.

[0057] The interior space of the support tube may form a receiving cavity for removably receiving at least a portion of the aerosol-generating article, in particular at least an evaporation portion of the aerosol-generating article, which may include a susceptor for heating an aerosol-forming substrate contained within the article by interaction of the susceptor with the alternating magnetic field of the induction coil.

[0058] The coil support may include a circumferential collar at each axial end of the support tube to provide lateral axial confinement of the coil windings.

[0059] At least one of the collars may include a recess or feed-through opening for passing connecting leads for the induction coil.

[0060] When the induction heating arrangement is intended to heat a flat, particularly sheet-like, susceptor, the outer periphery of the support tube, like the induction coil, may advantageously also have a non-circular, flattened cross-sectional shape, including, in particular consisting of, two opposing flat sections connected by two opposing, at least partially curved sections. That is, the outer surface of the support tube along its periphery may include, in particular consist of, two opposing flat outer portions connected by two opposing, at least partially curved outer portions. In this configuration, the induction coil may be wound around the periphery of the support tube such that the cross-sectional shape of the induction coil follows the non-circular, flattened cross-sectional shape of the periphery of the support tube. As already mentioned above with respect to the heating arrangement, flattening the cross-sectional shape of the induction coil leads to an increase in the magnetic field strength at the susceptor, which in turn leads to an increase in heating efficiency.

[0061] The non-circular flattened transverse cross-sectional shape of the support tube is preferably elliptical, especially when the transverse cross-sectional shape of the induction coil is also elliptical. As used herein, the term "ellipse" defines a shape consisting of two semicircles connected by parallel lines tangent to their endpoints. Thus, the support tube and induction coil may have an elliptical cylindrical shape, i.e., a flattened cylinder with two opposing parallel planar sidewall portions and two opposing hemispherical sidewall portions between the two opposing planar sidewall portions.

[0062] Similarly, the cross-sectional shape of the magnetic flux concentrator may be oval.

[0063] When the outer periphery of the support tube has a non-circular flattened cross-sectional shape as described above, each of the above-mentioned collars, if present, may have a non-circular flattened cross-sectional shape corresponding to the non-circular flattened cross-sectional shape of the outer periphery of the support tube. In particular, each collar may have an oval cross-sectional shape.

[0064] To stabilize the coil winding, the outer periphery of the support tube may include a wire recess pattern into which the coil wire is received. The wire recess pattern is preferably selected to correspond to the winding pattern of the desired induction coil. Because the induction is a cylindrical helical induction coil, the wire recess pattern is also preferably a helical wire recess pattern.

[0065] Furthermore, the wire recess pattern allows for a further reduction in the radial distance between the induction coil and the susceptor location within the induction coil's internal space. As already mentioned above, a reduction in radial distance increases the magnetic field strength at the susceptor location, which in turn increases heating efficiency. Therefore, the level of heat generated within the susceptor for a given level of power passing through the induction coil increases, which, in addition to the non-circular, flattened cross-sectional shape of the support tube's outer periphery, further facilitates reaching the desired temperature level within a shorter period of time. The greater the recess depth of the wire recess pattern, the better the magnetic field strength at the susceptor location within the induction coil's internal space. For example, when the coil wire has a circular cross section, the recess depth of the radial wire recess pattern is preferably in the range of 0.2 to 0.8 times, particularly 0.3 to 0.5 times, the diameter of the coil wire.

[0066] The outer periphery of the support tube may further include a flux concentrator recess for each of the annular protruding portions of the flux concentrator into which a radially inner end of the respective annular protruding portion is received, thereby providing secure support for the annular protruding portions, which helps prevent the flux concentrator from displacing, which could otherwise lead to undesirable changes in the inductance of the induction coil and undesirable changes in the magnetic field density within the interior space of the induction coil.

[0067] For easy and inexpensive manufacture, the coil support may include or be made of plastic. If the induction heating module must meet certain regulatory requirements, the coil support may include or be made of bisphenol A-free plastic.

[0068] Further features and advantages of the induction heating module, particularly the induction coil and flux concentrator, have been described with respect to the induction heating arrangement of the present invention and apply equally.

[0069] The present invention also relates to an inductively heated aerosol generating apparatus for use with an aerosol-generating article, the article comprising an aerosol-forming substrate that is heated by interaction of a susceptor with an alternating magnetic field provided by the aerosol generating apparatus, the apparatus comprising an inductive heating arrangement according to the invention and as described herein, or an inductive heating module according to the invention and as described herein.

[0070] As used herein, the term "aerosol-generating device" is used to describe an electrically operated device capable of interacting with an aerosol-forming substrate, particularly at least one aerosol-generating article including an aerosol-forming liquid, and a susceptor, to generate an aerosol by inductively heating the substrate through interaction of the susceptor with an alternating magnetic field provided by the device. The aerosol-generating device is preferably a smoking device for generating an aerosol that can be directly inhaled by a user through the user's mouth. Specifically, the aerosol-generating device is a handheld aerosol-generating device.

[0071] The aerosol generating device may comprise a device housing in which the induction heating arrangement or induction heating module according to the present invention is located or disposed.

[0072] The aerosol generating device, and in particular the device housing, may be provided with an insertion opening giving access to the interior space of the induction coil or the interior space of the support tube of the induction heating module to allow the insertion of an aerosol-generating article therein.

[0073] The aerosol-generating device may further comprise a receiving cavity for removably receiving at least a portion of the aerosol-generating article, in particular the evaporative portion. The receiving cavity may be located at least partially within the interior space of the induction coil or the interior space of the support tube of the induction heating module. In particular, the receiving cavity may be at least partially formed by the interior space of the induction coil or the interior space of the support tube of the induction heating module, in particular by the interior space of the support tube of the induction heating module. The induction coil may be arranged to surround at least a portion of the receiving cavity, in particular to surround at least the evaporative portion of the aerosol-generating article, when the aerosol-generating article is received in the receiving cavity.

[0074] The aerosol generating device may further include a puff detector, such as a microphone or pressure sensor, for detecting a user puff, i.e., the start of a user experience when the user begins puffing on the device. The puff detector may be operably connected to the heating arrangement and / or the controller, such that detection of the occurrence of a puff by the puff detector may trigger delivery of power to the induction coil for generating the aerosol. That is, the heating arrangement and / or the controller may be configured to initiate operation of the heating arrangement, in particular generation of the alternating magnetic field, in response to the puff detector detecting the occurrence of a user puff.

[0075] The aerosol-generating device may further comprise a controller configured to control operation of the device. In particular, the controller may be configured to control operation of the induction heating arrangement, preferably in a closed-loop configuration, to control heating of the aerosol-forming substrate to a predetermined operating temperature. Depending on at least one of the type of aerosol-forming substrate to be heated, the configuration of the susceptor, and the arrangement of the susceptor relative to the aerosol-forming substrate, the operating temperature may be in the range of 180°C to 370°C, particularly 180°C to 240°C, or 280°C to 370°C.

[0076] The controller may comprise a microprocessor (e.g., a programmable microprocessor), a microcontroller, or an application specific integrated circuit (ASIC) or other electronic circuit capable of providing control. The controller may include further electronic components such as at least part of the induction heating arrangement, in particular part of an alternating current (AC) generator, e.g., part of a DC / AC inverter and / or a power amplifier. In particular, the induction heating arrangement may be at least partly part of the controller.

[0077] The aerosol generating device may include a power source, particularly a DC power source configured to provide a DC supply voltage and a DC supply current to the induction heating arrangement. The power source is preferably a battery, such as a lithium iron phosphate battery. The power source may have a capacity sufficient to allow continuous generation of aerosol for approximately six minutes or a multiple of six minutes. Similarly, the power source may have a capacity sufficient to allow a predetermined number of puffs or discontinuous activation of the induction heating arrangement.

[0078] The susceptor used to heat the aerosol-forming substrate by interaction of the susceptor with the alternating magnetic field provided by the aerosol-generating device may be part of an article configured for use with the device. In particular, the susceptor may be disposed within the evaporation portion of the article. In this configuration, the interior space of the induction coil, the interior space of the support tube of the induction heating module, and / or the receiving cavity of the aerosol-generating device are preferably configured to removably receive at least the evaporation portion of the aerosol-generating article.

[0079] Alternatively, the susceptor used to heat the aerosol-forming substrate by interaction of the susceptor with the alternating magnetic field provided by the aerosol-generating device may be part of the aerosol-generating device itself, i.e., the aerosol-generating device may comprise a susceptor for heating the aerosol-forming substrate. Further features and advantages of the aerosol-generating device have been described with respect to the induction heating arrangement and induction heating module of the present invention and apply equally.

[0080] The present invention further relates to an aerosol-generating system comprising an aerosol-generating device according to the present invention and as described herein, and an aerosol-generating article for use with the aerosol-generating device, the article comprising a susceptor and an aerosol-forming substrate that is heated by interaction with an alternating magnetic field provided by the aerosol-generating device.

[0081] As used herein, the term "aerosol-generating system" refers to the combination of an aerosol-generating article as further described herein and an aerosol-generating device according to the present invention and as described herein, in which the article and device cooperate to generate a respirable aerosol.

[0082] The term "aerosol-generating article" as used herein refers to an article comprising at least one aerosol-forming substrate that, when heated, releases a volatile compound capable of forming an aerosol. The aerosol-generating article is preferably a heated aerosol-generating article, i.e., an aerosol-generating article comprising at least one aerosol-forming substrate that is intended to be heated, rather than combusted, to release a volatile compound capable of forming an aerosol. The aerosol-generating article may be a consumable product, particularly a consumable product that is discarded after a single use. Preferably, the article may comprise a liquid aerosol-forming substrate, i.e., an aerosol-forming liquid. Alternatively, the article may comprise a solid aerosol-forming substrate or a gel-like aerosol-forming substrate, or a combination thereof.

[0083] As used herein, the term "aerosol-forming substrate" generally refers to a substrate formed from or including an aerosol-forming material capable of releasing volatile compounds upon heating to generate an aerosol. The aerosol-forming substrate is intended to be heated, rather than combusted, to release the aerosol-forming volatile compounds. The aerosol-forming substrate may be a solid aerosol-forming substrate, a liquid aerosol-forming substrate, a gel-like aerosol-forming substrate, or any combination thereof. The aerosol-forming substrate is preferably a liquid aerosol-forming substrate, i.e., an aerosol-forming liquid. The aerosol-forming liquid may include both solid and liquid aerosol-forming materials or components. The aerosol-forming substrate, particularly the aerosol-forming liquid, may include a tobacco-containing material containing volatile tobacco flavor compounds that are released from the substrate upon heating. Alternatively, or additionally, the aerosol-forming substrate, particularly the aerosol-forming liquid, may include a non-tobacco material. The aerosol-forming substrate, particularly the aerosol-forming liquid, may further include an aerosol former. Examples of suitable aerosol formers are glycerin and propylene glycol. The aerosol-forming substrate, particularly the aerosol-forming liquid, may also contain other additives and ingredients, such as nicotine or flavorings. In particular, the aerosol-forming liquid may contain water, a solvent, ethanol, a plant extract, and a natural or artificial flavor. The aerosol-forming liquid may be an aqueous aerosol-forming liquid or an oil-based aerosol-forming liquid. The aerosol-forming substrate may also be a paste-like material, a sachet of porous material containing the aerosol-forming substrate, or loose tobacco mixed with, for example, a gelling agent or adhesive, which may contain a common aerosol former, such as glycerin, which is compressed or molded into a plug.

[0084] As described above in relation to the aerosol-generating device according to the invention, the susceptor for heating the aerosol-forming substrate may be part of either the aerosol-generating device or the aerosol-generating article, i.e. either the aerosol-generating device or the aerosol-generating article comprises a susceptor for heating the aerosol-forming substrate.

[0085] In the latter case, the aerosol-generating article may comprise an evaporation portion, and a susceptor for heating the aerosol-forming substrate is disposed in the evaporation zone. In this configuration, the interior space of the induction coil of the aerosol-generating device and / or the interior space of the support tube of the induction heating module is preferably configured to removably receive at least the evaporation portion of the aerosol-generating article.

[0086] As used herein, the term "susceptor element" refers to an element capable of converting electromagnetic energy into heat when subjected to a changing magnetic field. This may be the result of at least one of hysteresis loss or eddy currents induced in the susceptor, depending on the electrical and magnetic properties of the susceptor material. Hysteresis loss occurs in ferromagnetic or ferrimagnetic susceptors due to magnetic domains in the susceptor material switching under the influence of the changing magnetic field. Eddy currents may be induced if the susceptor is conductive. In the case of a conductive ferromagnetic or ferrimagnetic susceptor, heat can be generated due to both eddy currents and hysteresis loss.

[0087] Thus, the susceptor may be formed from any material that can be inductively heated to a temperature sufficient to generate an aerosol from the aerosol-forming substrate. Preferred susceptors include metal or carbon. Preferred susceptors may include ferromagnetic materials, such as ferritic iron, or ferromagnetic steel or stainless steel. Suitable susceptors may be or include aluminum. Preferred susceptors may be formed from 400 series stainless steel, such as grade 410, or grade 420, or grade 430 stainless steel.

[0088] The susceptor can include a variety of geometric configurations depending, among other things, on the type of aerosol-forming substrate.

[0089] The susceptor may include or be a susceptor pin, susceptor rod, susceptor blade, susceptor strip, or susceptor plate. Preferably, the susceptor is a flat susceptor, more particularly a sheet-like susceptor. Similarly, the susceptor may include or be a susceptor sleeve, susceptor cup, cylindrical susceptor, or tubular susceptor.

[0090] Specifically, when the substrate is a liquid, i.e., an aerosol-forming liquid, the susceptor may include or be a filament susceptor, a mesh susceptor, or a wick susceptor. In any of these configurations, the susceptor advantageously has the ability to perform both the functions of wicking (transporting) and heating the aerosol-forming liquid. Thus, with any of the foregoing configurations, the susceptor may be considered a liquid-transporting susceptor.

[0091] If the aerosol-forming substrate is a liquid substrate, the article may comprise a liquid reservoir for storing the aerosol-forming liquid. The susceptor is preferably in fluid communication with the liquid reservoir in which the aerosol-forming liquid is stored.

[0092] Further features and advantages of the aerosol generation system have already been described above with respect to the induction heating arrangement, the induction heating module and the aerosol generation device according to the invention and apply equally.

[0093] As used herein, the terms "radial" and "axial" refer to the cylindrical geometry of a cylindrical induction coil. [Example]

[0094] The present invention is defined in the claims. However, below is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

[0095] Example 1: 1. An induction heating arrangement for use in an induction heated aerosol generating apparatus, the heating arrangement comprising: a single cylindrical helical induction coil for generating an alternating magnetic field that allows inductive heating of the susceptor within the interior space of the induction coil in order to heat an aerosol-forming substrate that is in thermal contact or proximity to the susceptor; an induction heating arrangement comprising: a magnetic flux concentrator disposed around the induction coil and configured to distort an alternating magnetic field of the induction heating arrangement toward an interior space of the induction coil during use, the magnetic flux concentrator including a sleeve portion circumferentially surrounding the induction coil and annular protrusion portions at each axial end of the sleeve portion that protrude radially inward beyond the sleeve portion, the induction coil being disposed axially between the annular protrusion portions. Example 1a: An induction heating arrangement as described in Example 1, wherein the interior space of the induction coil is configured to removably receive at least a portion of an aerosol-generating article, in particular the evaporation portion, and the evaporation portion of the article preferably includes a susceptor, in particular a flat susceptor, more particularly a sheet-like susceptor, for heating an aerosol-forming substrate contained within the article by interaction of the susceptor with the alternating magnetic field of the induction coil. Example 2: The induction heating arrangement of any one of Example 1 or Example 1a, wherein the magnetic flux concentrator comprises or is made of one or more layers of magnetic flux concentrator foil. Example 3: 3. The induction heating arrangement of claim 1 or 2, wherein each of the annular protrusions is made of one or more layers of magnetic flux concentrator foil, the one or more layers of the annular protrusions extending radially outward at least to, and preferably beyond, the outer periphery of the induction coil, and the sleeve portion is made of one or more layers of magnetic flux concentrator foil surrounding the induction coil and each of the annular protrusions. Example 4: 3. The induction heating arrangement of claim 1 or 2, wherein the sleeve portion is made of one or more layers of magnetic flux concentrator foil surrounding the induction coil, and wherein each of the annular protrusions is made of one or more layers of magnetic flux concentrator foil and terminates radially flush with the outer periphery of the sleeve portion. Example 5: 5. The induction heating arrangement according to any one of Examples 2 to 4, wherein the magnetic flux concentrator foil has a foil thickness in the range of 50 micrometers to 250 micrometers, in particular 80 micrometers to 150 micrometers. Example 6: 6. The induction heating arrangement of any one of Examples 2-5, wherein the magnetic flux concentrator foil is a multi-layer magnetic flux concentrator foil including at least one ferrite layer sandwiched between an adhesive layer and a cover layer. Example 7: 7. The induction heating arrangement of any one of Examples 1-6, wherein the sleeve portion is radially spaced from the induction coil by a radial gap. Example 8: 8. The induction heating arrangement of embodiment 7, wherein the radial gap has a width in the range of 0.5 millimeters to 1.5 millimeters, in particular 0.8 millimeters to 1 millimeter. Example 9: 9. The induction heating arrangement of any one of Examples 1-8, wherein each of the annular protrusions is axially spaced from the induction coil by an axial gap. Example 10: 10. The induction heating arrangement of any one of Examples 1-9, wherein the annular protrusion extends radially inward beyond the outer periphery of the induction coil. Example 11: 11. The induction heating arrangement according to any one of Examples 1 to 10, wherein the annular protruding portion extends radially inward up to the inner circumference of the induction coil. Example 12: An induction heating arrangement according to any one of Examples 1 to 11, wherein the width dimension of each of the annular projections in the axial direction is in the range of 1.5 mm to 2.5 mm, in particular 1.8 mm to 2.2 mm. Example 13: An induction heating arrangement according to any one of Examples 1 to 12, wherein the height dimension of each of the annular projections in the radial direction is in the range of 1.5 mm to 2.5 mm, in particular 1.8 mm to 2.2 mm. Example 14: An induction heating arrangement according to any one of Examples 1 to 13, wherein the thickness of the sleeve portion in the radial direction is in the range of 100 micrometers to 500 micrometers, in particular 150 micrometers to 250 micrometers. Example 15: 15. The induction heating arrangement of any one of Examples 1-14, wherein the sleeve portion and the annular protrusion portion each have a cylindrical shape. Example 16: An induction heating module for use in an induction heating aerosol generator, the induction heating module comprising the induction heating arrangement according to any one of Examples 1-15. Example 17: 17. The induction heating module of example 16, further comprising a coil support on which the induction coil and magnetic flux concentrator are supported. Example 18: The induction heating module of any one of examples 16 or 17, wherein the coil support comprises a support tube and the induction coil is disposed around an outer periphery of the support tube. Example 19: 19. The induction heating module of example 18, wherein the interior space of the support tube forms a receiving cavity for removably receiving at least a portion of the aerosol-generating article. Example 20: 20. An induction heating module as described in any one of Examples 18 or 19, wherein the outer periphery of the support tube includes a flux concentrator recess for each of the annular protrusions of the flux concentrator, into which the radially inner end of each annular protrusion is received. Example 21: An inductively heated aerosol generating apparatus for use with an aerosol-generating article, the article comprising an aerosol-forming substrate that is heated by interaction of a susceptor with an alternating magnetic field provided by the aerosol-generating apparatus, the apparatus comprising an inductive heating arrangement as described in any one of Examples 1 to 15 or an inductive heating module as described in any one of Examples 16 to 20. Example 22: 22. An inductively heated aerosol generator as described in Example 21, wherein the apparatus further comprises a susceptor for heating the aerosol-forming substrate. Example 23: An aerosol-generating system comprising the aerosol-generating device of Example 21 or 22 and an aerosol-generating article for use with the aerosol-generating device, the article comprising an aerosol-forming substrate that is heated by interaction of the susceptor with an alternating magnetic field provided by the aerosol-generating device. Example 24: 24. The aerosol-generating system of Example 23, wherein either the aerosol-generating device or the aerosol-generating article comprises a susceptor for heating the aerosol-forming substrate. Example 25: 25. An aerosol-generating system according to any one of Examples 23 or 24, wherein the article comprises an evaporation portion, and a susceptor for heating the aerosol-forming substrate is disposed within the evaporation zone. Example 26: An aerosol generating system as described in Example 25, wherein the internal space of the induction coil and / or the internal space of the support tube of the induction heating module are configured to removably receive at least the evaporated portion of the aerosol generating article.

[0096] The embodiments will now be further described with reference to the figures. [Brief explanation of the drawings]

[0097] [Figure 1] FIG. 1 shows an exemplary embodiment of an aerosol generation system according to the present invention in longitudinal cross section. [Figure 2] FIG. 2 shows a detailed longitudinal cross-section of the aerosol generation system according to FIG. [Figure 3] FIG. 3 shows a detail of the aerosol generation system according to FIG. 1 in a longitudinal perspective cross-sectional view. [Figure 4] FIG. 4 shows details of the coil support used in the aerosol generating device according to FIG. [Figure 5] FIG. 5 shows details of an induction heating arrangement used in the aerosol generating device according to FIG. [Figure 6] FIG. 6 shows further details of the coil support used in the aerosol generating device according to FIG. [Figure 7] FIG. 7 shows details of a first embodiment of a power supply electronic circuit that can be used in the aerosol generating device according to FIG. [Figure 8] FIG. 8 shows details of a second embodiment of power supply electronics that can alternatively be used in the aerosol generating device according to FIG. DETAILED DESCRIPTION OF THE INVENTION

[0098] 1-3 show schematic cross-sectional views of an aerosol-generating system 1 according to an exemplary embodiment of the present invention. System 1 is configured to generate an inhalable aerosol by inductively heating a susceptor in thermal contact with a liquid aerosol-forming substrate 25, also referred to hereinafter as aerosol-forming liquid 25. System 1 comprises two main components: an aerosol-generating article 2 and an aerosol-generating device 1 for use with article 2. While article 2 includes a susceptor 22 and aerosol-forming liquid 25 to be heated, device 1 comprises a receiving cavity 16 for receiving article 2 and an induction heating arrangement 10 configured to generate an alternating magnetic field for inductively heating susceptor 22 and thus vaporizing aerosol-forming liquid 25 within article 2 when article 2 is inserted into cavity 16 of device 1.

[0099] 1 , which shows the device 1 and the article 2 separated from each other, the aerosol generating device 1 comprises a substantially rod-shaped body having a substantially cylindrical device housing 15. Within the distal portion 4, the device 1 comprises a power source 12, e.g., a lithium-ion battery, and an electrical circuit 11 including a controller 160 for controlling the operation of the device 1, and in particular for controlling the heating process. Within the proximal portion 5, opposite the distal portion 4, the device 1 comprises a receiving cavity 16 and at least a portion of the induction heating arrangement 10. The receiving cavity 16 is an open-ended cavity including an insertion opening 19 at the proximal end of the device 1 to allow the article 2 to be inserted into the receiving cavity 16.

[0100] The induction heating arrangement 10 includes an induction coil 13 for generating an alternating magnetic field within the cavity 16. The induction coil 13 is a cylindrical helical coil that circumferentially surrounds the cylindrical receiving cavity 16. In this embodiment, the induction coil 13 has an axial length of approximately 8 millimeters and is formed by a single layer of 4.25 turns of coil wire with a circular cross-section. The turns of the induction coil 13 extend along the entire length of the cavity 16. It is preferable that there be a gap between adjacent turns of the induction coil 13. That is, the pitch of the helical induction coil 13 may be greater than the diameter of the coil wire. As a result, adjacent turns of the coil wire do not contact each other, which allows the use of coil wire without wire insulation. However, the coil wire in this embodiment is enamel-coated copper wire with a diameter of 1.1 millimeters. Furthermore, the gap between adjacent turns of the induction coil serves to improve heat dissipation, thereby reducing resistive power losses in the coil windings. In this embodiment, the distance (center to center) between adjacent portions of the coil wire of adjacent turns is about 1.1 times the diameter of the coil wire. These ranges have been proven to provide a sufficiently long distance that still allows for a compact coil design, i.e., a sufficiently large number of turns per unit of length.

[0101] The induction coil 13 is part of an induction module 30 that, in addition to the induction coil 13, further comprises a coil support 17 disposed within the device housing 15 to support the induction coil 13. The coil support 17 is shown in detail in FIG. 4. The coil support 17 includes a cylindrical support tube 32 and circumferential collars 33 at each axial end of the support tube 32. The more distal collars 33 include recesses or feed-through openings 34 for passing connecting leads 60 to the induction coil 13, as shown in FIG. 5. As can be seen in FIGS. 1-3, the interior space of the support tube 32 at least partially defines the receiving cavity 16 of the device 1 for removably receiving at least a portion of the aerosol-generating article 2. That is, the inner surface of the support tube 32 along its inner circumference forms at least a portion of the inner surface of the receiving cavity 16. For easy and inexpensive manufacture, the coil support 17 may be made of plastic. If the induction heating module 30 must comply with certain regulatory requirements, the coil support 17 may be made of, for example, a bisphenol A-free plastic.

[0102] In addition to induction coil 13, induction heating arrangement 10 includes power electronics that may be at least partially integrated within electrical circuit 11 and coupled to induction coil 13 via connecting electrical pads 131 (see FIG. 1 ). In combination with induction coil 13, power electronics functions to generate a high-frequency alternating current that passes through induction coil 13, causing induction coil 31 to generate a high-frequency varying magnetic field within the interior space of induction coil 12 and thus cavity 16, as indicated by the dashed line in FIG. 2 . The frequency of the high-frequency varying magnetic field may range from 500 kHz (kilohertz) to 30 MHz (megahertz), particularly from 5 MHz (megahertz) to 15 MHz (megahertz), and preferably from 5 MHz (megahertz) to 10 MHz (megahertz). As explained in more detail below, the alternating magnetic field is used to induce at least one of heat-generating eddy currents or hysteresis losses in susceptor 22 of article 2 to vaporize aerosol-forming liquid 25 contained within article 2.

[0103] Next to the device 1, FIG. 1 also shows details of the aerosol-generating article 2. In this embodiment, the article 2 is a mushroom-shaped cartridge that can be coupled to the device 1. At its distal end, the article 2 comprises an elongated evaporation portion 29 configured to be inserted into the receiving cavity 16 of the device 1, as shown in FIGS. 2 and 3 . Within the evaporation portion 29, the article 2 comprises a susceptor 22 disposed within the article 2 such that the susceptor 22 is located within the interior space of the induction coil 13 when the evaporation portion 29 of the article 2 is inserted into the cavity 16. Therefore, in order to be heated, the susceptor 22 can experience an alternating magnetic field generated by the induction coil 13 during operation of the heating arrangement 10.

[0104] In this embodiment, the susceptor 22 is a flat sheet-like mesh made of induction-heated ferromagnetic stainless steel. Therefore, the susceptor 22 may also be referred to as a sheet-like mesh susceptor 22 capable of performing both the functions of wicking (transporting) and heating the aerosol-forming liquid 25. Because the material of the susceptor 22 is both conductive and magnetic, the alternating electromagnetic field of the induction coil 13 can induce both heat-generating eddy currents and hysteresis losses in the susceptor material.

[0105] The susceptor mesh 22 is in fluid communication with the aerosol-forming liquid 25 contained within the reservoir 24 of the article 2 by means of the wicking porous element 28. The wicking porous element 28 is configured to directly contact the liquid 25 in the reservoir 24 and transport the liquid 25 to the mesh susceptor 22. Thus, the susceptor mesh 22 is continuously humidified. Upon inserting the article 2 into the cavity 16 (see FIGS. 2 and 3) and activating the heating arrangement 10, the mesh susceptor 22 is heated to a temperature sufficient to vaporize the aerosol-forming liquid 25 in contact with the mesh susceptor 22.

[0106] As can be further seen in particular in FIG. 1 , mesh susceptor 22 is disposed within airflow channel 26, which passes through article 2 along its central axis. Airflow channel 26 has an air inlet at the distal end of article 2 and an outlet at the proximal end of article 2. The outlet is formed by mouthpiece 21, through which a user can inhale. Thus, when a user inhales through mouthpiece 21 during use of the system, air is entrained into airflow channel 26 via the air inlet and passes along mesh susceptor 22. There, vaporized aerosol-forming liquid material is entrained within the airflow through airflow channel 26. Thereafter, as it passes further downstream within airflow channel 26 toward mouthpiece 21, the airflow containing the vaporized material is cooled to form an aerosol that exits article 2 through the outlet in mouthpiece 21.

[0107] The aerosol generating device 1 according to this embodiment further comprises a smoke detector 14 for detecting a puff by the user. The smoke detector 14 is operatively connected to the power supply electronics such that detection of a puff by the smoke detector 14 triggers the delivery of power to the induction coil 13 to generate the aerosol. In this respect, the aerosol generating device 1 according to this embodiment may be referred to as an on-demand smoke suction device. Once the user stops puffing, the delivery of power to the induction coil is interrupted to avoid unnecessary generation of unused aerosol. That is, the induction heating arrangement is operated intermittently according to the user's request.

[0108] During a continuous mode of operation, the susceptor may permanently maintain a temperature sufficient to form a satisfactory amount of aerosol, but when the heating arrangement is operated intermittently upon user demand (on-demand puffing), it may be difficult to reach a sufficient temperature within a short period of time.

[0109] To achieve higher heating efficiency, particularly to reach a sufficient temperature level within a short period of time, the induction heating arrangement 10 of this embodiment includes a magnetic flux concentrator 50 disposed around the induction coil 13 and configured to distort the alternating magnetic field of the induction heating arrangement 10 toward the interior space of the induction coil 13 during use. To this end, the magnetic flux concentrator 50 has a specific configuration including a sleeve portion 52 circumferentially surrounding the induction coil 13 and, in addition, annular protrusions 51 at each axial end of the sleeve portion 52 that protrude radially inward beyond the sleeve portion 51 so that the induction coil 13 is axially disposed between the annular protrusions 51, as can be particularly seen in FIGS. 1 and 2. Thus, as seen in a longitudinal cross section through the magnetic flux concentrator 50 along the length axis of the induction coil 13 (see FIGS. 1 and 2), the magnetic flux concentrator 50 has a U- or C-shape, with the sleeve portion 52 being part of the base of the U- or C-shape and the annular protrusions 51 being part of the arms or legs of the U- or C-shape. In this regard, it has been discovered that the magnetic field density at the susceptor 22 can be increased by distorting the magnetic field toward the interior space of the induction coil 13 using the magnetic flux concentrator 50 shaped as described above. In particular, the annular protrusions 51 at each axial end of the sleeve portion 52, which extend radially inward beyond the sleeve portion 52, lead to a concentration or focusing of the magnetic field within the interior space of the induction coil 13. Therefore, the level of heat generated within the susceptor 22 for a given level of power passing through the induction coil 13 is increased compared to an induction coil without a magnetic flux concentrator or an induction coil having only a sleeve-shaped magnetic flux concentrator without annular protrusions at each axial end. In addition, the magnetic flux concentrator 50 acts as a magnetic shield, capable of reducing the extent to which the magnetic field propagates beyond the induction coil 13. Therefore, the magnetic flux concentrator 50 can help reduce undesired heating of other sensitive components in the system or external to the apparatus 1.

[0110] To ensure sufficient concentration of the magnetic field, the annular protrusion 51 should extend radially inward beyond the outer periphery of the induction coil 13, but the magnetic field concentration may be sufficient if the annular protrusion 51 extends radially inward up to the inner periphery of the induction coil 13, i.e., if the annular protrusion does not protrude radially inward beyond the inner periphery of the induction coil 13.

[0111] In this embodiment, the magnetic flux concentrator 50 is constructed from magnetic flux concentrator foil. More specifically, each annular protrusion 51 is made of magnetic flux concentrator foil that is spirally wound in multiple layers onto the coil support 17 so as to extend radially outward beyond the outer periphery of the induction coil 13. Over the annular protrusion 51, a sleeve portion 52 is formed of several layers of the same magnetic flux concentrator foil material to surround the induction coil 13 and each annular protrusion 51. As an example, a flexible three-layer ferrite sheet, including a ferrite layer sandwiched between an adhesive layer and a cover layer, available from Laird Corporation under the trade name MHLL6060-300, can be used as the magnetic flux concentrator foil. MHLL6060-300 has a foil thickness of approximately 90 micrometers, a real permeability of approximately 130, and an imaginary permeability of approximately 5 at a frequency of 13.56 MHz. 1-3 each have a height dimension (radial) of 2 millimeters and a width dimension (axial) of 2 millimeters. Sleeve portion 52 has a thickness dimension (radial) of approximately 180 micrometers and a width dimension (axial) of 10 millimeters. Thus, using a foil material having a foil thickness of 90 micrometers would require approximately 22 wraps to form a 2 millimeter high annular protrusion portion 51 and approximately 2 wraps to form a 180 micrometer thick sleeve portion 52.

[0112] The sleeve portion 52 is radially spaced apart from the induction coil 13 by a radial gap having a width (radial extension) in the range of 0.5 mm to 1.5 mm, in particular 0.8 mm to 1 mm. Advantageously, the radial gap may help to avoid heat loss from the induction coil to the sleeve portion, reducing losses in the induction coil and increasing losses in the heated susceptor 22, i.e., increasing the heating efficiency of the aerosol generation device 1. Similarly, each of the annular protruding portions 51 is axially spaced apart from the induction coil 13 by an axial gap. The radial gap and / or the axial gap may be a void or gap at least partially filled with a filler material.

[0113] 6, the more distal annular protruding portion 51 includes a recess or feed-through opening 501 for passing connecting leads 60 for the induction coil. The recess or feed-through opening 501 may be cut into the annular protruding portion 51 after the flux concentrator foil has been wound.

[0114] In particular, with respect to the flat, sheet-like shape of the susceptor 22, it has been found that the heating efficiency can be further improved by adapting the geometry of the magnetic field within the interior space of the induction coil 13 in which the susceptor 22 is placed to the flat shape of the susceptor 22. In particular, it has been found that by flattening the transverse cross-sectional shape of the induction coil 13, the radial distance between the induction coil 13 and the main surface of the flat susceptor 22 can be reduced. The reduction in radial distance leads to an increase in the magnetic field strength at the susceptor, which in turn causes an increase in heating efficiency. Therefore, the level of heat generated in the susceptor for a given level of power passing through the induction coil increases, which, among other things, allows the desired temperature level to be reached within a shorter period of time. Therefore, in this embodiment, the outer periphery of the support tube 32 has a non-circular, flat transverse cross-sectional shape (see dashed lines in FIG. 4 ) consisting of two opposing flat sections 32.1 connected by two opposing, at least partially curved sections 32.2. Because the induction coil 13 is wound around the outer periphery of the support tube 32, the cross-sectional shape of the induction coil 13 follows the non-circular flattened cross-sectional shape of the outer periphery of the support tube 32. That is, the cylindrical helical induction coil 13 also has a non-circular flattened cross-sectional shape (see the dotted line on the right side of Figure 5) consisting of two opposing flat sections 13.1 connected by two opposing at least partially curved sections 13.2.

[0115] In this embodiment, the non-circular flattened cross-sectional shape of the support tube 32 and induction coil 13 is elliptical, i.e., it is made up of two semicircles 13.2, 32.2 connected by parallel lines 13.1, 32.1 tangent to their end points. Thus, the induction coil 13 and support tube 17 have an elliptical cylindrical shape.

[0116] Due to the parallel and semicircular oval sections, the non-circular, flattened transverse cross-sectional shape of the induction coil 13 and support tube 32 includes a minor axis of symmetry and a major axis of symmetry. As shown by the dashed arrows for the induction coil 13 on the right side of FIG. 5, the minor axis of symmetry extends between the two opposing flat sections 13.1 of the induction coil 13, and the major axis of symmetry extends between the two opposing curved sections 13.2 of the induction coil. Preferably, the ratio of the maximum distance along the major axis of symmetry between the two opposing at least partially curved sections 13.2, 32.2 to the maximum distance along the minor axis of symmetry between the two opposing flat sections 13.1, 32.1 ranges from 1.2 to 3, particularly from 1.5 to 2.5. These ratios are particularly advantageous for achieving a good match between the geometry of the magnetic field and the flat shape of the susceptor 22 to be heated. Like the support tube 32 and induction coil 13, the magnetic flux concentrator 50 may also have a non-circular flattened cross-sectional shape that corresponds to the non-circular flattened cross-sectional shapes of the support tube 32 and induction coil 13. In particular, the cross-sectional shape of the magnetic flux concentrator 50 may be oval.

[0117] To further increase heating efficiency, the outer periphery of the support tube 32 in this embodiment includes a helical wire recess pattern 39 into which the coil wire is received, as shown in Figures 4 and 6. Advantageously, the wire recess pattern 39 allows for a further reduction in the radial distance between the induction coil 13 and the susceptor position within the interior space of the induction coil 13. As already mentioned above, a reduction in the radial distance increases the magnetic field strength at the susceptor position, which in turn increases heating efficiency.

[0118] The greater the depth of the recesses in the wire recess pattern 39, the better the magnetic field strength at the susceptor position within the internal space of the induction coil 13. For example, when the coil wire has a circular cross section, the radial depth of the recesses in the wire recess pattern 39 is preferably in the range of 0.2 to 0.8 times, particularly 0.3 to 0.5 times, the diameter of the coil wire. The radial distance between the induction coil 13 and the inner periphery of the coil support 17 may be in the range of 0.1 to 1 mm, particularly 0.2 to 0.5 mm, and preferably approximately 0.3 mm, as shown in FIG. 6. This ensures that the radial distance between the induction coil 13 and the internal space of the support tube 32, in which the susceptor 22 is received, is particularly short. That is, the radial distance a between the inner periphery of the support tube 32 and the bottom of the recess pattern 39 is in the range of 0.1 to 1 mm, particularly 0.2 to 0.5 mm, and preferably approximately 0.3 mm.

[0119] 2 and 6, the outer periphery of the support tube 32 may further include flux concentrator recesses 38 for each of the annular protruding portions 51 of the flux concentrator 50, into which the radially inner end of the respective annular protruding portion 51 is received. Thus, the annular protruding portions 51 are securely supported, which helps prevent the flux concentrator 50 from being displaced, which could otherwise result in an undesirable change in the inductance of the induction coil 13 and an undesirable change in the magnetic field density within the interior space of the induction coil 13.

[0120] FIG. 7 shows further details of the power supply electronics that can be used in the induction heating arrangement 10, particularly the aerosol generating device shown in FIGS. 1-3. According to this embodiment, the induction heating arrangement 10 comprises a DC / AC inverter connected to the DC power supply 12 shown in FIG. 1. The DC / AC inverter includes a class E power amplifier, which includes the following components: a transistor switch 111 including a field-effect transistor (FET), e.g., a metal-oxide semiconductor field-effect transistor (MOSFET); a transistor switch supply circuit, indicated by arrow 112, for supplying a switching signal (gate-source voltage) to the transistor switch 111; and an LC load network 113 including a shunt capacitor C1 and a series connection of a capacitor C2 and an inductor L2. Inductor L2 corresponds to the induction coil 13 shown in FIGS. 1-3, which is used to generate an alternating magnetic field in the cavity 16. Additionally, a choke L1 is provided for supplying a DC supply voltage +V_DC from the DC power supply 12. 7, the ohmic resistance R representing the total equivalent resistance or total resistive load 114 when the system is in use, i.e. when an item 2 is inserted into the cavity 16 of the device 1, is the sum of the ohmic resistance of the induction coil 13 marked with L2 and the ohmic resistance of the susceptor 22. Otherwise, when no item is inserted into the cavity 16, the equivalent resistance or resistive load 114 corresponds only to the ohmic resistance of the induction coil 13.

[0121] Figure 8 shows another embodiment of power supply electronics that can alternatively be used in the aerosol generating device shown in Figures 1-3 to provide a high-frequency oscillating current to the induction coil 13. The configuration shown in Figure 8 corresponds to a Class D amplifier configuration. The DC power supply 12 is connected to two transistors 1210 and 1212. Two switching elements 1220 and 1222 are provided to switch the two transistors 1210 and 1212 on and off. The switching elements 1220 and 1222 are controlled at high frequency to ensure that one of the two transistors 1210 and 1212 is off when the other is on. The induction coil 13, used to generate the alternating magnetic field for induction heating, is again designated L2, while the combined ohmic resistance of the induction coil 13 and susceptor 22 is designated R. The values of C1 and C2 can be selected to maximize the efficient dissipation of power within the susceptor element. Capacitor C1 is not required to configure the architecture as Class D and can therefore be omitted.

[0122] For purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing amounts, quantities, percentages, and the like should be understood in all instances to be modified by the term "about." Also, all ranges include the disclosed maximum and minimum points, and include any intermediate ranges therein, which may or may not be specifically recited herein. Thus, in this context, the number A is understood as A ± 5%. Within this context, the number A may be considered to include a numerical value that is within the typical standard error for the measurement of the property that the number A modifies. In some cases, as used in the appended claims, the number A may deviate by the percentages recited above, provided that the amount by which A deviates does not materially affect the basic and novel characteristics of the claimed invention. Also, all ranges include the disclosed maximum and minimum points, and include any intermediate ranges therein, which may or may not be specifically recited herein.

Claims

1. 1. An induction heating module for use in an induction heated aerosol generating device, the induction heating module comprising an induction heating arrangement, the heating arrangement comprising: a single cylindrical helical induction coil for generating an alternating magnetic field making it possible to inductively heat a susceptor within the interior space of the induction coil in order to heat an aerosol-forming substrate in thermal contact or thermal proximity with said susceptor; a magnetic flux concentrator disposed around the induction coil and configured to distort the alternating magnetic field of the induction heating arrangement towards the interior space of the induction coil during use, the magnetic flux concentrator including a sleeve portion circumferentially surrounding the induction coil and annular protruding portions at each axial end of the sleeve portion protruding radially inwardly beyond the sleeve portion, the induction coil being disposed axially between the annular protruding portions; a coil support on which the induction coil and the magnetic flux concentrators are supported, the coil support including a support tube, the induction coil being disposed around an outer periphery of the support tube, the outer periphery of the support tube including a magnetic flux concentrator recess for each annular protruding portion of the magnetic flux concentrators, into which a radially inner end of the respective annular protruding portion is received.

2. 10. The induction heating module of claim 1, wherein the magnetic flux concentrator comprises or is made of one or more layers of magnetic flux concentrator foil.

3. 3. The induction heating module of claim 1, wherein each of the annular protrusions is made of one or more layers of magnetic flux concentrator foil, the one or more layers of the annular protrusions extending radially outward at least to, and preferably beyond, an outer periphery of the induction coil, and the sleeve portion is made of one or more layers of magnetic flux concentrator foil surrounding the induction coil and each of the annular protrusions, or the sleeve portion is made of one or more layers of magnetic flux concentrator foil surrounding the induction coil, and each of the annular protrusions is made of one or more layers of magnetic flux concentrator foil and terminates radially flush with the outer periphery of the sleeve portion.

4. 1. An induction heating module for use in an induction heated aerosol generating device, the induction heating module comprising an induction heating arrangement, the heating arrangement comprising: a single cylindrical helical induction coil for generating an alternating magnetic field making it possible to inductively heat a susceptor within the interior space of the induction coil in order to heat an aerosol-forming substrate in thermal contact or thermal proximity with said susceptor; a magnetic flux concentrator disposed around the induction coil and configured to distort the alternating magnetic field of the induction heating arrangement towards the interior space of the induction coil in use, the magnetic flux concentrator comprising a sleeve portion circumferentially surrounding the induction coil and annular protruding portions at each axial end of the sleeve portion protruding radially inwardly beyond the sleeve portion, the induction coil being disposed axially between the annular protruding portions, the magnetic flux concentrator comprising or made from one or more layers of magnetic flux concentrator foil; each of the annular protruding portions is made of one or more layers of magnetic flux concentrator foil, the one or more layers of the annular protruding portion extending radially outward at least to, and preferably beyond, the outer periphery of the induction coil, and the sleeve portion is made of one or more layers of magnetic flux concentrator foil surrounding the induction coil and each of the annular protruding portions; or 1. An induction heating module, wherein the sleeve portion is made of one or more layers of magnetic flux concentrator foil surrounding the induction coil, and wherein each of the annular protrusion portions is made of one or more layers of magnetic flux concentrator foil and terminates radially flush with the outer periphery of the sleeve portion.

5. The induction heating module of any one of claims 1 to 4, wherein each of the annular protruding portions is spaced axially from the induction coil by an axial gap.

6. 1. An induction heating module for use in an induction heated aerosol generating device, the induction heating module comprising an induction heating arrangement, the heating arrangement comprising: a single cylindrical helical induction coil for generating an alternating magnetic field making it possible to inductively heat a susceptor within the interior space of the induction coil in order to heat an aerosol-forming substrate in thermal contact or thermal proximity with said susceptor; an induction heating module, comprising: a magnetic flux concentrator disposed around the induction coil and configured to distort the alternating magnetic field of the induction heating arrangement toward the interior space of the induction coil during use, the magnetic flux concentrator including a sleeve portion circumferentially surrounding the induction coil and annular protruding portions at each axial end of the sleeve portion protruding radially inward beyond the sleeve portion, the induction coil being disposed axially between the annular protruding portions, each of the annular protruding portions being spaced axially from the induction coil by an axial gap.

7. An induction heating module according to any preceding claim, wherein the sleeve portion is spaced radially from the induction coil by a radial gap.

8. An induction heating module according to any preceding claim, wherein the annular protruding portion extends radially inward beyond the outer periphery of the induction coil.

9. The induction heating module according to any one of claims 1 to 8, wherein the annular protruding portion extends radially inward up to an inner circumference of the induction coil.

10. 10. An induction heating module according to any one of the preceding claims, wherein the width dimension of each of the annular projections in the axial direction is in the range of 1.5 mm to 2.5 mm, in particular 1.8 mm to 2.2 mm.

11. 11. An induction heating module according to any one of claims 1 to 10, wherein the height dimension of each of the annular protruding portions in the radial direction is in the range of 1.5 mm to 2.5 mm, in particular 1.8 mm to 2.2 mm.

12. 12. The induction heating module according to claim 1, wherein the thickness dimension of the sleeve portion in the radial direction is in the range of 100 micrometers to 500 micrometers, in particular 150 micrometers to 250 micrometers.

13. 13. An induction heating module according to any one of claims 1 to 12, wherein the outer periphery of the cylindrical helical induction coil, and preferably the support tube, if present, has a non-circular flattened transverse cross-sectional shape comprising, in particular consisting of, two opposing flat sections connected by two opposing at least partially curved sections, and preferably the magnetic flux concentrator has a non-circular flattened transverse cross-sectional shape corresponding to the non-circular flattened transverse cross-sectional shape of the induction coil.

14. 14. An inductively heated aerosol generating apparatus for use with an aerosol-generating article, the article comprising an aerosol-forming substrate that is heated by interaction of a susceptor with an alternating magnetic field provided by the aerosol-generating apparatus, the apparatus comprising an inductively heated aerosol module according to any one of claims 1 to 13.

15. 15. An aerosol generation system comprising: an aerosol generating device according to claim 14; and an aerosol-generating article for use with the aerosol generating device, the article including an aerosol-forming substrate that is heated by interaction of a susceptor with an alternating magnetic field provided by the aerosol generating device.

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