Induction heating device with ring-shaped channel

Abstract

An induction heating device (10) is provided. The induction heating device (10) includes a first inductor coil (12) arranged to generate a first time-varying magnetic field when a time-varying current flows through the first inductor coil (12). The induction heating device (10) also includes a second inductor coil (14) arranged to generate a second time-varying magnetic field when a time-varying current flows through the second inductor coil (14). The induction heating device (10) also includes a flux concentrator (20) positioned around the first inductor coil (12) to distort the first time-varying magnetic field generated by the first inductor coil (12). The flux concentrator (20) has a tubular shape and includes a main portion (24) positioned around the first inductor coil (12). The main portion (24) has an inner diameter, a first end, and a second end. The flux concentrator (20) also includes a first end portion (26) at the first end of the main portion (24). The first end portion (26) has an inner diameter, where the inner diameter of the first end portion (26) is less than the inner diameter of the main portion (24). The flux concentrator (20) also includes a second end portion (28) at the second end of the main portion (24). The second end portion (28) has an inner diameter, where the inner diameter of the second end portion (28) is less than the inner diameter of the main portion (24). An inner surface (30) of the flux concentrator (20) defines an annular channel (32) between the first end portion (26) and the second end portion (28). The first inductor coil (12) is positioned within the annular channel (32) between the first end portion (26) and the second end portion (28).

Description

Technical Field

[0001] The present invention relates to an induction heating device comprising an annular channel. The present invention also relates to an aerosol generating device comprising the induction heating device. Background Art

[0002] Many electrically powered aerosol-generating systems have been proposed in the art, in which an aerosol-generating device with an electric heater is used to heat an aerosol-forming substrate, such as a tobacco filter segment. One purpose of such aerosol-generating systems is to reduce the known types of harmful smoke components produced by the combustion and pyrolytic degradation of tobacco in conventional cigarettes. Typically, the aerosol-generating substrate is provided as part of an aerosol-generating article, which is inserted into the cavity of the aerosol-generating device. In some known systems, in order to heat the aerosol-forming substrate to a temperature capable of releasing volatile components that can form an aerosol, a resistive heating element (such as a heating blade) is inserted into or around the aerosol-forming substrate when the article is received in the aerosol-generating device. In other aerosol-generating systems, an induction heater is used instead of a resistive heating element. The induction heater typically comprises an inductor coil forming part of the aerosol-generating device, and a susceptor arranged so that it is thermally adjacent to the aerosol-forming substrate. The inductor coil generates a varying magnetic field to generate eddy currents and hysteresis losses in the susceptor, causing the susceptor to heat, thereby heating the aerosol-forming substrate.

[0003] Induction heating allows aerosols to be generated without exposing the inductor coil to the aerosol generating article. This may improve the ease with which the device can be cleaned. However, in the case of induction heating, the inductor coil may also induce eddy currents and hysteresis losses in adjacent parts of the aerosol generating device. This may reduce the efficiency of the induction heater and therefore the efficiency of the aerosol generating device. This may also lead to undesired heating of adjacent parts of the aerosol generating device. This may be particularly problematic in aerosol generating devices comprising more than one inductor coil, wherein each inductor coil is arranged to heat a different part of a susceptor or a different susceptor. For example, a changing magnetic field generated by a first inductor coil may induce a current in a second inductor coil, which in turn may heat a susceptor that is arranged to be heated using only the second inductor coil.

[0004] It would be desirable to provide an induction heating apparatus that alleviates or overcomes these problems of known systems. Summary of the Invention

[0005] According to the present disclosure, an induction heating device is provided. The induction heating device may include an inductor coil. The inductor coil may be arranged to generate a varying magnetic field when a varying current flows through the inductor coil. The induction heating device may include a flux concentrator. The flux concentrator may be positioned around the inductor coil. The flux concentrator may distort the varying magnetic field generated by the inductor coil. The flux concentrator may have a tubular shape. The flux concentrator may include a main portion positioned around the inductor coil. The main portion may have an inner diameter. The main portion may have a first end. The main portion may have a second end. The flux concentrator may include a first end portion. The first end portion may be at the first end of the main portion. The first end portion may have an inner diameter. The inner diameter of the first end portion may be smaller than the inner diameter of the main portion. The flux concentrator may include a second end portion. The second end portion may be at the second end of the main portion. The second end portion may have an inner diameter. The inner diameter of the second end portion may be smaller than the inner diameter of the main portion. An inner surface of the flux concentrator may define an annular channel between the first end portion and the second end portion. An inductor coil may be positioned within the annular channel between the first end portion and the second end portion.

[0006] According to the present disclosure, an induction heating device is provided. The induction heating device includes an induction coil arranged to generate a varying magnetic field when a varying current flows through the induction coil. The induction heating device also includes a flux concentrator positioned around the induction coil to distort the varying magnetic field generated by the induction coil. The flux concentrator has a tubular shape and includes a main portion positioned around the induction coil. The main portion has an inner diameter, a first end, and a second end. The flux concentrator also includes a first end portion at the first end of the main portion. The first end portion has an inner diameter, wherein the inner diameter of the first end portion is smaller than the inner diameter of the main portion. The flux concentrator also includes a second end portion at the second end of the main portion. The second end portion has an inner diameter, wherein the inner diameter of the second end portion is smaller than the inner diameter of the main portion. An inner surface of the flux concentrator defines an annular channel between the first end portion and the second end portion. The induction coil is positioned within the annular channel between the first end portion and the second end portion.

[0007] According to the present disclosure, an induction heating device is provided. The induction heating device may include an inductor coil. The inductor coil may be arranged to generate a varying magnetic field when a varying current flows through the inductor coil. The induction heating device may also include a flux concentrator. The flux concentrator may be positioned around the inductor coil. The flux concentrator may distort the varying magnetic field generated by the inductor coil. The flux concentrator may have a tubular shape. The flux concentrator may include an annular channel defined by an inner surface of the flux concentrator. The inductor coil may be positioned within the annular channel.

[0008] According to the present disclosure, an induction heating device is provided, comprising an inductor coil and a flux concentrator. The inductor coil is arranged to generate a varying magnetic field when a varying current flows through the inductor coil. The flux concentrator is positioned around the inductor coil to distort the varying magnetic field generated by the inductor coil. The flux concentrator has a tubular shape and includes an annular channel defined by an inner surface of the flux concentrator. The inductor coil is positioned within the annular channel.

[0009] The flux concentrator may include a main portion positioned around the inductor coil, the main portion having an inner diameter, a first end, and a second end. The flux concentrator may also include a first end portion at the first end of the main portion. The first end portion has an inner diameter, wherein the inner diameter of the first end portion is smaller than the inner diameter of the main portion. The flux concentrator may also include a second end portion at the second end of the main portion. The second end portion has an inner diameter, wherein the inner diameter of the second end portion is smaller than the inner diameter of the main portion. An annular channel may be defined between the first end portion and the second end portion.

[0010] According to the present disclosure, an induction heating device is provided. The induction heating device may include an inductor coil. The inductor coil may be arranged to generate a varying magnetic field when a varying current flows through the inductor coil. The induction heating device may include a flux concentrator positioned around the inductor coil. The flux concentrator may be arranged to distort the varying magnetic field generated by the inductor coil. The flux concentrator may have a tubular shape. The flux concentrator and the inductor coil may be positioned concentrically about a longitudinal axis. The cross-sectional shape of the flux concentrator in a longitudinal direction along the longitudinal axis may include a U-shaped portion. The inductor coil may be positioned within the U-shaped portion.

[0011] According to the present disclosure, an induction heating device is provided, comprising an inductor coil and a flux concentrator. The inductor coil is arranged to generate a varying magnetic field when a varying current flows through the inductor coil. The flux concentrator is positioned around the inductor coil to distort the varying magnetic field generated by the inductor coil. The flux concentrator has a tubular shape. The flux concentrator and the inductor coil are positioned concentrically about a longitudinal axis. The cross-sectional shape of the flux concentrator in the longitudinal direction along the longitudinal axis includes a U-shaped portion. The inductor coil is positioned within the U-shaped portion.

[0012] The inductor coil may be a first inductor coil arranged to generate a first varying magnetic field when a varying current flows through the first inductor coil. The induction heating device may include a second inductor coil arranged to generate a second varying magnetic field when a varying current flows through the second inductor coil.

[0013] A cross-sectional shape of the flux concentrator in the longitudinal direction may include a first U-shaped portion in which the first inductor coil is positioned and a second U-shaped portion in which the second inductor coil is positioned.

[0014] The flux concentrator may be a first flux concentrator positioned around the first inductor coil. The induction heating device may include a second flux concentrator positioned around the second inductor coil to distort the second changing magnetic field generated by the second inductor coil. The second flux concentrator may have a tubular shape, wherein the second flux concentrator and the second inductor coil are concentrically positioned around the longitudinal axis. The cross-sectional shape of the second flux concentrator in the longitudinal direction may include a U-shaped portion in which the second inductor coil is positioned.

[0015] As used herein, the term "aerosol-forming substrate" refers to a substrate that is capable of releasing volatile compounds that can form an aerosol. Such volatile compounds can be released by heating the aerosol-forming substrate. The aerosol-forming substrate is part of an aerosol-generating article.

[0016] As used herein, the term "aerosol-generating article" refers to an article comprising an aerosol-forming substrate capable of releasing volatile compounds that can form an aerosol. For example, an aerosol-generating article can be an article that generates an aerosol that can be directly inhaled by a user drawing or puffing on a mouthpiece at the proximal or user end of the system. The aerosol-generating article can be disposable. An article comprising an aerosol-forming substrate comprising tobacco can be referred to as a tobacco stick.

[0017] As used herein, the term "aerosol-generating device" refers to a device that interacts with an aerosol-forming substrate to generate an aerosol.

[0018] As used herein, the term "aerosol-generating system" refers to the combination of an aerosol-generating device and an aerosol-generating article. In an aerosol-generating system, the aerosol-generating article and the aerosol-generating device cooperate to generate an aerosol.

[0019] As used herein, the term "length" refers to the principal dimension in the longitudinal direction of an induction heating device, an aerosol-generating device or an aerosol-generating article, or a component of an induction heating device, an aerosol-generating device or an aerosol-generating article.

[0020] As used herein, the term "longitudinal section" is used to describe a cross-section of an induction heating device, an aerosol-generating device or an aerosol-generating article, or a component of an induction heating device, an aerosol-generating device or an aerosol-generating article in the longitudinal direction.

[0021] An induction heating device according to the present disclosure includes a flux concentrator. Advantageously, the flux concentrator distorts the varying magnetic field generated by the inductor coil. Advantageously, distorting the varying magnetic field can concentrate or focus the varying magnetic field. For example, the flux concentrator can concentrate or focus the varying magnetic field toward a susceptor. Advantageously, for a given current within the inductor coil, this can increase the level of heat generated in the susceptor.

[0022] The flux concentrator defines an annular channel or U-shaped portion in which the inductor coil is received.

[0023] Advantageously, the annular channel or U-shaped portion can reduce or minimize the extent to which the varying magnetic field propagates beyond the inductor coil. In other words, the annular channel or U-shaped portion can act as a magnetic shield. Advantageously, this can reduce the induction of undesirable currents in adjacent conductive components.

[0024] Advantageously, the annular channel or U-shaped portion may facilitate retaining the inductor coil within the flux concentrator.For example, the inductor coil may be retained within the annular channel or U-shaped portion by an interference fit.

[0025] The inductor coil may be a first inductor coil arranged to generate a first varying magnetic field when a varying current flows through the first inductor coil. The induction heating device may include a second inductor coil arranged to generate a second varying magnetic field when a varying current flows through the second inductor coil.

[0026] Advantageously, the first and second inductor coils may facilitate separate heating of the first and second susceptors. Advantageously, the first and second inductor coils may facilitate separate heating of the first and second portions of a single inductor. Advantageously, the first and second inductor coils may facilitate separate heating of the first and second aerosol-forming substrates. Advantageously, the first and second inductor coils may facilitate separate heating of the first and second portions of a single aerosol-forming substrate.

[0027] The flux concentrator may be a first flux concentrator, wherein the main portion is a first main portion positioned around the first inductor coil, and the annular channel is a first annular channel. The induction heating device may include a second flux concentrator positioned around the second inductor coil to distort the second varying magnetic field generated by the second inductor coil, wherein the second flux concentrator has an annular shape. The second flux concentrator may include a second main portion positioned around the second inductor coil, the second main portion having an inner diameter, a first end, and a second end. The second flux concentrator may include a third end portion at the first end of the second main portion, the third end portion having an inner diameter, wherein the inner diameter of the third end portion is smaller than the inner diameter of the second main portion. The second flux concentrator may also include a fourth end portion at the second end of the second main portion, the fourth end portion having an inner diameter, wherein the inner diameter of the fourth end portion is smaller than the inner diameter of the second main portion. An inner surface of the second flux concentrator may define a second annular channel between the third and fourth end portions, wherein the second inductor coil is positioned within the second annular channel between the third and fourth end portions.

[0028] Advantageously, the first and second end portions of the first flux concentrator can facilitate magnetic shielding of the second inductor coil from the varying magnetic field generated by the first inductor coil. Advantageously, this can reduce or minimize current induction in the second inductor coil by the varying magnetic field generated by the first inductor coil.

[0029] Advantageously, the third and fourth end portions of the second flux concentrator can facilitate magnetic shielding of the first inductor coil from the varying magnetic field generated by the second inductor coil. Advantageously, this can reduce or minimize current induction in the first inductor coil by the varying magnetic field generated by the second inductor coil.

[0030] A flux concentrator may be positioned around the first and second inductor coils to distort the first and second varying magnetic fields generated by the first and second inductor coils. A main portion of the flux concentrator may be a first main portion positioned around the first inductor coil, and the annular channel may be the first annular channel. The flux concentrator may include a second main portion positioned around the second inductor coil, the second main portion having an inner diameter, a first end, and a second end. The flux concentrator may include a third end portion at the first end of the second main portion, the third end portion having an inner diameter, wherein the inner diameter of the third end portion is smaller than the inner diameter of the second main portion. The second end portion may be at the second end of the second main portion, such that the second end portion is positioned between the first and second main portions. The second end portion has an inner diameter smaller than the inner diameter of the second main portion. An inner surface of the flux concentrator may define a second annular channel between the second and third end portions. The second inductor coil may be positioned within the second annular channel between the second and third end portions.

[0031] Advantageously, the first and second end portions of the flux concentrator can facilitate magnetic shielding of the second inductor coil from the varying magnetic field generated by the first inductor coil. Advantageously, this can reduce or minimize current induction in the second inductor coil by the varying magnetic field generated by the first inductor coil.

[0032] Advantageously, the second and third end portions of the flux concentrator can facilitate magnetic shielding of the first inductor coil from the varying magnetic field generated by the second inductor coil. Advantageously, this can reduce or minimize current induction in the first inductor coil by the varying magnetic field generated by the second inductor coil.

[0033] The inductor coil and the annular channel may be positioned concentrically about the longitudinal axis. The annular channel may have a U-shaped cross-sectional shape in the longitudinal direction along the longitudinal axis. The U-shaped cross-sectional shape may be a rectangular U-shaped cross-sectional shape. The rectangular U-shaped cross-sectional shape may include a center segment that defines a main portion of the flux concentrator. The rectangular U-shaped cross-sectional shape may include a first end segment that extends substantially orthogonally relative to the main portion and defines a first end portion of the flux concentrator. The rectangular U-shaped cross-sectional shape may include a second end segment that extends substantially orthogonally relative to the main portion and defines a second end portion of the flux concentrator.

[0034] In embodiments in which the induction heating device includes a second annular passage and a second inductor coil, the second inductor coil and the second annular passage can be positioned concentrically about the longitudinal axis. A cross-sectional shape of the second annular passage in the longitudinal direction can be U-shaped. The U-shaped cross-sectional shape can be a rectangular U-shaped cross-sectional shape.

[0035] The inductor coil and the annular passage defined by the flux concentrator can be positioned concentrically about the longitudinal axis. The flux concentrator can be formed from a discrete first portion having a half-annular shape and a discrete second portion having a half-annular shape, wherein the first portion and the second portion together define the tubular shape of the flux concentrator.

[0036] Advantageously, forming the flux concentrator from a first portion and a second portion each having a half-annular shape can facilitate assembly of the induction heating device. For example, the flux concentrator can be assembled about the inductor coil by positioning the first portion and the second portion about the inductor coil.

[0037] In embodiments in which the induction heating device includes a first flux concentrator and a second flux concentrator, at least one of the first flux concentrator and the second flux concentrator can be formed from a discrete first portion having a half-annular shape and a discrete second portion having a half-annular shape, wherein the first portion and the second portion together define the tubular shape of the flux concentrator. The first flux concentrator and the second flux concentrator can each be formed from a discrete first portion having a half-annular shape and a discrete second portion having a half-annular shape, wherein the first portion and the second portion together define the tubular shape of the flux concentrator.

[0038] The flux concentrator can include a plurality of discrete annular segments positioned in series to define the tubular shape of the flux concentrator.

[0039] Advantageously, forming the flux concentrator from a plurality of discrete annular segments can facilitate assembly of the induction heating device. For example, the flux concentrator can be assembled about the inductor coil by positioning the discrete annular segments in series about the inductor coil.

[0040] The induction heating device can include a first discrete annular segment defining a first end portion of the flux concentrator. The induction heating device can include a second discrete annular segment defining a second end portion of the flux concentrator. The induction heating device can include at least one intermediate discrete annular segment defining a main portion of the flux concentrator.

[0041] In embodiments where the flux concentrator includes a first main portion and a second main portion, the at least one intermediate discrete annular segment may include at least one first intermediate discrete annular segment defining the first main portion and at least one second intermediate discrete annular segment defining the second main portion. The induction heating device may include a third discrete annular segment defining a third end portion of the flux concentrator.

[0042] In embodiments where the induction heating device comprises a first flux concentrator and a second flux concentrator, at least one of the first flux concentrator and the second flux concentrator may comprise a plurality of discrete annular segments positioned consecutively to define a tubular shape of the flux concentrator. The first flux concentrator and the second flux concentrator may each comprise a plurality of discrete annular segments positioned consecutively to define a tubular shape of the flux concentrator.

[0043] The at least one intermediate discrete annular segment may be at least one first intermediate discrete annular segment defining a first main portion of the first flux concentrator. The induction heating device may include a third discrete annular segment defining a third end portion of the second flux concentrator. The induction heating device may include a fourth discrete annular segment defining a fourth end portion of the second flux concentrator. The induction heating device may include at least one second intermediate discrete annular segment defining a second main portion of the second flux concentrator.

[0044] The preferred features and optional features of a flux concentrator for an induction heating device according to the present disclosure will now be described. In embodiments where the induction heating device includes a first flux concentrator and a second flux concentrator, each of the preferred features and optional features may be applied to the first flux concentrator, the second flux concentrator, or both.

[0045] Preferably, the flux concentrator has a high relative magnetic permeability. Advantageously, the high relative magnetic permeability acts to concentrate or focus the varying magnetic field generated by the inductor coil.

[0046] As used herein and within the art, the term "relative magnetic permeability" refers to the ratio of the magnetic permeability of a material or medium such as a flux concentrator to the magnetic permeability "μ0" of free space, where μ0 is 4π×10 -7 Newtons per ampere squared.

[0047] Preferably, the flux concentrator has a relative permeability at 25 degrees Celsius of at least about 5, for example at least about 10, at least about 20, at least about 30, at least about 40, at least about 50, at least about 60, at least about 80, or at least about 100. These example values ​​refer to values ​​of relative permeability at frequencies between 6 and 8 megahertz and a temperature of 25 degrees Celsius.

[0048] The flux concentrator may be formed from any suitable material or combination of materials. Preferably, the flux concentrator comprises a ferromagnetic material. The flux concentrator may comprise a ferrite material, ferrite powder held in a binder, or any other suitable material comprising a ferrite material. Suitable ferrite materials include ferritic iron, ferromagnetic steel, and stainless steel.

[0049] The preferred features and optional features of the inductor coil for an induction heating device according to the present disclosure will now be described. In an embodiment in which the induction heating device includes a first inductor coil and a second inductor coil, each of the preferred features and optional features may be applied to the first inductor coil, the second inductor coil, or both.

[0050] When a varying current is supplied to the inductor coil, the inductor coil generates a varying magnetic field. In a preferred embodiment, the varying current is an alternating current. When an alternating current is supplied to the inductor coil, the inductor coil generates an alternating magnetic field. Therefore, in a preferred embodiment, the term "varying current" refers to an alternating current, and the term "varying magnetic field" refers to an alternating magnetic field.

[0051] Preferably, the inductor coil is a tubular inductor coil. The inductor coil may be helically wound about a longitudinal axis. The inductor coil may be elongated. Particularly preferably, the inductor coil may be an elongated tubular inductor coil. The inductor coil may have any suitable cross-section. For example, the inductor coil may have a circular, oval, square, rectangular, triangular, or other polygonal cross-section.

[0052] The inductor coil may be formed from any suitable material. The inductor coil is formed from a conductive material. Preferably, the inductor coil is formed from a metal or a metal alloy.

[0053] In some embodiments, the second inductor coil is substantially identical to the first inductor coil. In other words, the first inductor coil and the second inductor coil have the same shape, size, and number of turns. Advantageously, the identical first and second inductor coils can simplify the manufacture of the induction heating device.

[0054] In some embodiments, the second inductor coil is different from the first inductor coil. For example, the second inductor coil may have at least one of a different length, a different number of turns, or a different cross-section than the first inductor coil. Advantageously, the different first and second inductor coils may generate different varying magnetic fields. Advantageously, the different varying magnetic fields may be used to heat different portions of the susceptor to different temperatures. Advantageously, the different varying magnetic fields may be used to heat different susceptors to different temperatures.

[0055] The first inductor coil and the second inductor coil may be arranged in any suitable arrangement. Particularly preferably, the first inductor coil and the second inductor coil are coaxially aligned along an axis. In the case where the first inductor coil and the second inductor coil are elongated tubular inductor coils, the first inductor coil and the second inductor coil may be coaxially aligned along a longitudinal axis.

[0056] An induction heating device may include a susceptor. As used herein, the term "susceptor" refers to an element comprising a material capable of converting magnetic energy into heat. When the susceptor is exposed to a varying magnetic field, the susceptor is heated. The heating of the susceptor may be the result of at least one of hysteresis losses and eddy currents induced in the susceptor, depending on the electrical and magnetic properties of the susceptor material.

[0057] Preferably, the inductor coil is positioned around at least a portion of the susceptor.

[0058] In embodiments where the induction heating device comprises a first inductor coil and a second inductor coil, the first inductor coil may be positioned around a first portion of the susceptor and the second inductor coil may be positioned around a second portion of the susceptor.

[0059] The susceptor may be a first susceptor, wherein the first inductor coil is positioned around at least a portion of the first susceptor.The induction heating apparatus may include a second susceptor, wherein the second inductor coil is positioned around at least a portion of the second susceptor.

[0060] Preferably, the induction heating device comprises a space between the first susceptor and the second susceptor, wherein the space thermally insulates the first susceptor from the second susceptor.The space may be of any suitable size to thermally insulate the first susceptor from the second susceptor.

[0061] The induction heating device may include an intermediate element disposed between a first susceptor and a second susceptor. The intermediate element may be disposed in a space between the first and second susceptors. The intermediate element may extend between the first and second susceptors. The intermediate element may contact an end of the first susceptor. The intermediate element may contact an end of the second susceptor. The intermediate element may be fixed to an end of the first susceptor. The intermediate element may be fixed to an end of the second susceptor. The intermediate element may connect the second susceptor to the first susceptor.

[0062] In some preferred embodiments, the first susceptor and the second susceptor are tubular susceptors, and the intermediate element is a tubular intermediate element. In these embodiments, the tubular first susceptor, the tubular second susceptor, and the tubular intermediate element can be substantially aligned.

[0063] The intermediate element may be formed from any suitable material. The intermediate element may include a thermally insulating material for thermally insulating the first susceptor from the second susceptor. Suitable materials include polyetheretherketone, liquid crystal polymer, cement, glass, zirconium dioxide, silicon nitride, aluminum oxide, and combinations thereof.

[0064] The preferred features and optional features of a susceptor for an induction heating device according to the present disclosure will now be described. In embodiments where the induction heating device includes a first susceptor and a second susceptor, each of the preferred features and optional features may be applied to the first susceptor, the second susceptor, or both.

[0065] Preferably, the susceptor is a tubular susceptor. Preferably, the tubular susceptor defines a cavity for receiving at least a portion of the aerosol-forming substrate. The cavity may be open at one end. The cavity may be open at both ends.

[0066] Where the susceptor is a tubular susceptor defining a lumen open at one or both ends, the susceptor is preferably substantially airtight from the outer surface of the susceptor to the inner surface of the susceptor. In other words, the susceptor is preferably substantially impermeable to air through the sidewalls of the susceptor.

[0067] The susceptor may comprise any suitable material. The susceptor may be formed of any material that can be inductively heated to a temperature sufficient to aerosolize the aerosol-forming substrate. Preferred susceptors may be heated to a temperature exceeding about 250 degrees Celsius. Preferred susceptors may be formed of electrically conductive materials. As used herein, "electrically conductive" means having a conductivity of less than or equal to 1×10 at 20 degrees Celsius. -4 The preferred susceptor may be formed of a thermally conductive material. As used herein, the term "thermally conductive material" is used to describe a material having a thermal conductivity of at least 10 watts per meter Kelvin at 23 degrees Celsius and 50% relative humidity as measured using the Modified Transient Planar Thermal Source (MTPS) method.

[0068] Suitable materials for the susceptor include graphite, molybdenum, silicon carbide, stainless steel, niobium, aluminum, nickel, nickel-containing compounds, titanium, and composites of metallic materials. Some preferred susceptors include metal or carbon. Some preferred susceptors include ferromagnetic materials, such as ferritic iron, ferromagnetic alloys (such as ferromagnetic steel or stainless steel), ferromagnetic particles, and ferrites. Some preferred susceptors are composed of ferromagnetic materials. Suitable susceptors may include aluminum. Suitable susceptors may be composed of aluminum. The susceptor may include at least about 5%, at least about 20%, at least about 50%, or at least about 90% ferromagnetic or paramagnetic material.

[0069] According to the present disclosure, there is provided an aerosol generating device comprising any of the induction heating devices described herein.

[0070] The aerosol generating device may comprise a power source. Preferably, the aerosol generating device comprises a power source.

[0071] The aerosol generating device may comprise a controller. The controller may be arranged to supply a varying current from a power supply to each inductor coil. Preferably, the aerosol generating device comprises a controller arranged to supply a varying current from said power supply to each inductor coil.

[0072] The power supply can be a DC power supply. In some preferred embodiments, the power supply is a battery, such as a rechargeable lithium-ion battery. The power supply can be another form of charge storage device, such as a capacitor. The power supply may need to be recharged. The power supply can have a capacity that allows sufficient energy to be stored for one or more uses of the device. For example, the power supply can have enough capacity to allow continuous aerosol generation for a period of about six minutes, corresponding to the typical time spent smoking a conventional cigarette, or for a period of multiple six minutes. In another example, the power supply can have enough capacity to allow a predetermined number of uses or discontinuous activation of the device. In one embodiment, the power supply is a DC power supply having a DC supply voltage in the range of about 2.5 volts to about 4.5 volts and a DC supply current in the range of about 1 ampere to about 10 amperes (corresponding to a DC power supply between about 2.5 watts to about 45 watts).

[0073] The controller may include a microprocessor, which may be a programmable microprocessor, a microcontroller, or an application specific integrated circuit (ASIC) or other circuit capable of providing control. The controller may include other electronic components. The controller may be configured to regulate the current supply to each inductor coil. The current may be supplied to the inductor coil continuously after activation of the aerosol generating device, or may be supplied intermittently, such as on a puff-by-puff basis.

[0074] The controller may be configured to supply a current to the inductor coil that varies in frequency between approximately 5 kilohertz and approximately 500 kilohertz.

[0075] The controller may be configured to supply a high-frequency varying current to the inductor coil. As used herein, the term "high-frequency varying current" refers to a varying current having a frequency between about 500 kilohertz and about 30 megahertz. The high-frequency varying current may have a frequency between about 1 megahertz and about 30 megahertz, for example, between about 1 megahertz and about 10 megahertz, or, for example, between about 5 megahertz and about 8 megahertz.

[0076] In an embodiment where the induction heating device includes a first inductor coil and a second inductor coil, the controller may supply a first varying current to the first inductor coil during a first time period, and the controller may supply a second varying current to the second inductor coil during a second time period.

[0077] The first time period may be the same as the second time period. In other words, the controller may supply the first varying current and the second varying current simultaneously.

[0078] The first time period may be different from the second time period. The first time period may be longer than the second time period. The first time period may be shorter than the second time period. The first time period may partially overlap with the second time period. The first time period may completely overlap with the second time period. There may not be any overlap between the first time period and the second time period. The first time period and the second time period may be consecutive.

[0079] The controller may advantageously comprise a DC / AC inverter.The DC / AC inverter may comprise a class C, class D or class E power amplifier.

[0080] The aerosol generating device may include a device housing. The device housing may be elongated. The device housing may comprise any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics, or composite materials comprising one or more of those materials, or thermoplastic materials suitable for food or pharmaceutical applications, such as polypropylene, polyetheretherketone (PEEK), and polyethylene. Preferably, the material is lightweight and non-brittle.

[0081] The device housing may define an induction heating chamber. Preferably, the induction heating device is positioned within the induction heating chamber.

[0082] The device housing may include an air inlet. The air inlet may be configured to allow ambient air to enter the device housing. The device housing may include any number of air inlets. The device housing may include multiple air inlets.

[0083] The device housing may include an air outlet. The air outlet may be configured to allow air to enter the device cavity from within the device housing. The device housing may include any suitable number of air outlets. The device housing may include multiple air outlets.

[0084] In some embodiments, the aerosol generating device housing includes a mouthpiece. The mouthpiece may include at least one air inlet and at least one air outlet. The mouthpiece may include more than one air inlet. The one or more air inlets may reduce the temperature of the aerosol before delivery to the user and may reduce the concentration of the aerosol before delivery to the user.

[0085] The aerosol-generating device can comprise a temperature sensor. The temperature sensor can be arranged to sense a temperature of the induction heating device. In embodiments in which the induction heating device comprises a susceptor, the temperature sensor can be arranged to sense a temperature of the susceptor. In embodiments in which the induction heating device comprises a first susceptor and a second susceptor, the aerosol-generating device can comprise a first temperature sensor arranged to sense a temperature of the first susceptor and a second temperature sensor arranged to sense a temperature of the second susceptor.

[0086] The aerosol-generating device can comprise a user interface to activate the device, for example a button to initiate heating of the aerosol-forming substrate.

[0087] The aerosol-generating device can comprise a display to indicate a status of the device or the aerosol-forming substrate.

[0088] The aerosol-generating device can comprise a puff sensor to sense inhalation by a user on the aerosol-generating system.

[0089] Preferably, the aerosol-generating device is portable. The aerosol-generating device can have a size comparable to a conventional cigar or cigarette. The aerosol-generating device can have an overall length of between about 30 millimetres and about 150 millimetres. The aerosol-generating device can have an outer diameter of between about 5 millimetres and about 30 millimetres.

[0090] According to the present disclosure, there is provided an aerosol-generating system comprising any of the aerosol-generating devices as described herein.

[0091] The aerosol-generating system can further comprise an aerosol-generating article. The aerosol-generating article can comprise an aerosol-forming substrate.

[0092] Preferably, the aerosol-generating article is configured to be received at least partially within a cavity of the aerosol-generating device. The induction heating device can define a cavity for receiving the aerosol-generating article. In embodiments in which the induction heating device comprises a susceptor, the susceptor can define the cavity.

[0093] The aerosol-forming substrate can comprise nicotine. The nicotine-containing aerosol-forming substrate can be a nicotine salt substrate.

[0094] The aerosol-forming substrate can be a liquid. The aerosol-forming substrate can comprise a solid component and a liquid component. Preferably, the aerosol-forming substrate is a solid.

[0095] The aerosol-forming substrate may comprise a plant-based material. The aerosol-forming substrate may comprise tobacco. The aerosol-forming substrate may comprise a tobacco-containing material comprising volatile tobacco flavoring compounds that are released from the aerosol-forming substrate upon heating. The aerosol-forming substrate may comprise a non-tobacco material. The aerosol-forming substrate may comprise a homogenized plant-based material. The aerosol-forming substrate may comprise a homogenized tobacco material. The homogenized tobacco material may be formed by agglomerating particulate tobacco. In a particularly preferred embodiment, the aerosol-forming substrate comprises a curled sheet of aggregated homogenized tobacco material. As used herein, the term "curled sheet" refers to a sheet having a plurality of generally parallel ridges or wrinkles.

[0096] The aerosol-forming matrix may include at least one aerosol-forming agent. An aerosol-forming agent is any suitable known compound or mixture of compounds that, in use, facilitates the formation of a dense and stable aerosol and is substantially resistant to thermal degradation at the operating temperature of the system. Suitable aerosol-forming agents are well known in the art and include, but are not limited to, polyols such as triethylene glycol, 1,3-butylene glycol, and glycerol; esters of polyols such as glycerol mono-, di-, or triacetate; and fatty acid esters of mono-, di-, or polycarboxylic acids such as dimethyl dodecanedioate and dimethyl tetradecanoic acid. Preferred aerosol-forming agents may include polyols or mixtures thereof such as triethylene glycol, 1,3-butylene glycol. Preferably, the aerosol-forming agent is glycerol. If present, the aerosol-forming agent content of the homogenized tobacco material may be equal to or greater than 5 weight percent on a dry weight basis, for example, between about 5 weight percent and about 30 weight percent on a dry weight basis. The aerosol-forming matrix may include other additives and ingredients, such as flavorings.

[0097] The aerosol-generating article may have any suitable form. The aerosol-generating article may be substantially cylindrical in shape. The aerosol-generating article may be generally elongate. The aerosol-generating article may have a length and a circumference substantially perpendicular to the length.

[0098] The aerosol-forming substrate may be provided as an aerosol-generating segment comprising an aerosol-forming substrate. The aerosol-generating segment may comprise a plurality of aerosol-forming substrates. The aerosol-generating segment may comprise a first aerosol-forming substrate and a second aerosol-forming substrate. In some embodiments, the second aerosol-forming substrate is substantially identical to the first aerosol-forming substrate. In some embodiments, the second aerosol-forming substrate is different from the first aerosol-forming substrate.

[0099] Where the aerosol-generating segment comprises a plurality of aerosol-forming substrates, the number of aerosol-forming substrates may be the same as the number of inductor coils in the induction heating device.

[0100] The aerosol-generating segment may be generally cylindrical in shape.The aerosol-generating segment may be substantially elongated.The aerosol-generating segment may also have a length and a circumference substantially perpendicular to the length.

[0101] Where the aerosol-generating segment comprises a plurality of aerosol-forming substrates, the aerosol-forming substrates may be arranged end-to-end along the axis of the aerosol-generating segment.In some embodiments, the aerosol-generating segment may comprise spaces between adjacent aerosol-forming substrates.

[0102] In some preferred embodiments, the aerosol-generating article can have an overall length of between about 30 mm and about 100 mm. In some embodiments, the aerosol-generating article has an overall length of about 45 mm. The aerosol-generating article can have an outer diameter of between about 5 mm and about 12 mm. In some embodiments, the aerosol-generating article can have an outer diameter of about 7.2 mm.

[0103] The aerosol-generating segment may have a length of between about 7 mm and about 15 mm. In some embodiments, the aerosol-generating segment may have a length of about 10 mm or 12 mm.

[0104] The aerosol-generating segment preferably has an outer diameter approximately equal to the outer diameter of the aerosol-generating article. The outer diameter of the aerosol-generating segment may be between about 5 mm and about 12 mm. In one embodiment, the aerosol-generating segment may have an outer diameter of about 7.2 mm.

[0105] The aerosol-generating article may include a filter segment. The filter segment may be located at the mouth end of the aerosol-generating article. The filter segment may be a cellulose acetate filter plug. In some embodiments, the filter segment may have a length of about 5 mm to about 10 mm. In some preferred embodiments, the filter segment may have a length of about 7 mm.

[0106] The aerosol-generating article may include an outer wrapping material. The outer wrapping material may be formed from paper. The outer wrapping material may be air-permeable at the aerosol-generating section. Specifically, in embodiments comprising a plurality of aerosol-forming substrates, the outer wrapping material may include perforations or other air inlets at the interfaces between adjacent aerosol-forming substrates. Where spaces are provided between adjacent aerosol-forming substrates, the outer wrapping material may include perforations or other air inlets at the spaces. This may enable an aerosol-forming substrate to be directly supplied with air that has not been drawn through another aerosol-forming substrate. This may increase the amount of air received by each aerosol-forming substrate. This may improve the properties of the aerosol generated from the aerosol-forming substrate.

[0107] The aerosol-generating article may further comprise a spacing between the aerosol-forming substrate and the filter segment. The spacing may be in the range of about 5 mm to about 25 mm. The spacing may be about 18 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0108] Embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0109] Figure 1 shows a longitudinal sectional view of an induction heating device according to a first embodiment of the present disclosure;

[0110] Figure 2 Shown along line 1-1 Figure 1 A partially exploded cross-sectional view of an induction heating device;

[0111] Figure 3 A cross-sectional view of an aerosol-generating system comprising an aerosol-generating article and an aerosol-generating device comprising Figure 1 Induction heating device;

[0112] Figure 4 Shown Figure 3 an aerosol generating system, wherein the aerosol generating article is received in the aerosol generating device;

[0113] Figure 5 A longitudinal sectional view showing an induction heating device according to a second embodiment of the present disclosure; and

[0114] Figure 6 A longitudinal sectional view showing an induction heating device according to a third embodiment of the present disclosure. DETAILED DESCRIPTION

[0115] Figure 1 A longitudinal cross-sectional view of an induction heating device 10 according to a first embodiment of the present disclosure is shown. The induction heating device 10 comprises a first inductor coil 12 and a second inductor coil 14 coaxially positioned about a tubular susceptor 16 along a longitudinal axis 18 of the induction heating device 10. The susceptor 16 defines a cavity 19 in which an aerosol-forming substrate can be received for heating by the induction heating device 10.

[0116] The induction heating device 10 includes a first flux concentrator 20 positioned around the first inductor coil 12 and a second flux concentrator 22 positioned around the second inductor coil 14. The first flux concentrator 20 and the second flux concentrator 22 are each formed of a ferromagnetic material.

[0117] First flux concentrator 20 has a tubular shape and includes a first main portion 24 positioned around first inductor coil 12, a first end portion 26 at a first end of first main portion 24, and a second end portion 28 at a second end of first main portion 24. First end portion 26 and second end portion 28 each have an inner diameter that is smaller than the inner diameter of first main portion 24. An inner surface 30 of first flux concentrator 20 defines a first annular channel 32 between first end portion 26 and second end portion 28. First inductor coil 12 is positioned within first annular channel 32 between first end portion 26 and second end portion 28.

[0118] Second flux concentrator 22 has a tubular shape and includes a second main portion 34 positioned around second inductor coil 14, a third end portion 36 at a first end of second main portion 34, and a fourth end portion 38 at a second end of second main portion 34. Third end portion 36 and fourth end portion 38 each have an inner diameter that is smaller than the inner diameter of second main portion 34. An inner surface 40 of second flux concentrator 22 defines a second annular channel 42 between third end portion 36 and fourth end portion 38. Second inductor coil 14 is positioned within second annular channel 42 between third end portion 36 and fourth end portion 38.

[0119] When a varying current is supplied to first inductor coil 12, first inductor coil 12 generates a varying magnetic field. The shape of first flux concentrator 20, and in particular the shapes of first end portion 26 and second end portion 28, distorts the varying magnetic field, causing it to be concentrated in a first portion of susceptor 16 positioned within first inductor coil 12. The varying magnetic field generated by first inductor coil 12 induces eddy currents in the first portion of susceptor 16, causing the first portion of susceptor 16 to heat. Advantageously, concentrating the varying magnetic field in the first portion of susceptor 16 by first flux concentrator 20 reduces or minimizes heating of the second portion of susceptor 16 positioned within second inductor coil 14 by the varying magnetic field generated by first inductor coil 12.

[0120] When a varying current is supplied to second inductor coil 14, second inductor coil 14 generates a varying magnetic field. The shape of second flux concentrator 22, and in particular the shapes of first end portion 36 and second end portion 38, distorts the varying magnetic field, causing it to be concentrated in the second portion of susceptor 16 positioned within second inductor coil 14. The varying magnetic field generated by second inductor coil 14 induces eddy currents in the second portion of susceptor 16, causing the second portion of susceptor 16 to be heated. Advantageously, concentrating the varying magnetic field in the second portion of susceptor 16 by second flux concentrator 22 reduces or minimizes heating of the first portion of susceptor 16 positioned within first inductor coil 12 by the varying magnetic field generated by second inductor coil 14.

[0121] Figure 2 Shown along line 1-1 Figure 1 FIG1 is a partially exploded cross-sectional view of the induction heating device 10. The first flux concentrator 20 includes a discrete first portion 44 having a semi-annular shape and a discrete second portion 46 having a semi-annular shape. When the discrete first portion 44 and second portion 46 are brought together, they define the tubular shape of the first flux concentrator 20. Advantageously, forming the first flux concentrator 20 from the first portion 44 and second portion 46, each having a semi-annular shape, facilitates assembly of the induction heating assembly 10. For example, Figure 2 , the first inductor coil 12 can be positioned above the first portion of the susceptor 16. Then, the first portion 44 and the second portion 46 can be positioned around the first inductor coil 12 and contact each other to form the first flux concentrator 20. The same arrangement can be used to assemble the second flux concentrator 22. In other words, the second flux concentrator 22 can also be formed from separate first and second portions each having a semi-annular shape.

[0122] Figure 3 1 shows a cross-sectional view of an aerosol generating system 100 according to an embodiment of the present disclosure. The aerosol generating system 100 comprises an aerosol generating device 102 comprising Figure 1 The induction heating device 10. The aerosol generating system 100 also includes an aerosol generating article 200.

[0123] The aerosol-generating device 102 includes a generally cylindrical device housing 103 having a shape and size similar to that of a conventional cigar. The device housing 103 defines a device cavity 104 at a proximal end. The device cavity 104 is substantially cylindrical, open at the proximal end, and substantially closed at a distal end opposite the proximal end. The device cavity 104 is configured to receive a portion of the aerosol-generating article 200. Thus, the diameter of the device cavity 104 is substantially similar to the diameter of the aerosol-generating article 200.

[0124] The aerosol generating device 102 further comprises a power source 106 in the form of a rechargeable nickel-cadmium battery, a controller 108 in the form of a printed circuit board including a microprocessor, an electrical connector 109, and an induction heating device 10. The power source 106, the controller 108, and the induction heating device 10 are all housed within a device housing 103. The induction heating device 10 of the aerosol generating device 102 is arranged at the proximal end of the device 102 and is generally arranged around the device cavity 104. The electrical connector 109 is arranged at the distal end of the device housing 103, opposite the device cavity 104.

[0125] The controller 108 is configured to control the supply of power from the power source 106 to the induction heating device 10. The controller 108 further includes a DC / AC inverter (which includes a Class D power amplifier) ​​and is configured to supply at least one varying current to the induction heating device 10. The controller 108 is also configured to control the recharging of the power source 106 from the electrical connector 109. Additionally, the controller 108 includes a puff sensor (not shown) configured to sense when a user inhales on the aerosol-generating article received in the device cavity 104.

[0126] The first inductor coil 12 is connected to the controller 108 and the power supply 106, and the controller 108 is configured to supply a varying current to the first inductor coil 12. When the varying current is supplied to the first inductor coil 12, the first inductor coil 12 generates a varying magnetic field that heats the first portion of the susceptor 16 by induction.

[0127] The second inductor coil 14 is connected to the controller 108 and the power supply 106, and the controller 108 is configured to supply a varying current to the second inductor coil 14. When the varying current is supplied to the second inductor coil 14, the second inductor coil 14 generates a varying magnetic field that heats the second portion of the susceptor 16 by induction.

[0128] The device housing 103 also defines an air inlet 180 proximate the distal end of the device cavity 106. The air inlet 180 is configured to allow ambient air to be drawn into the device housing 103. An air flow path is defined through the device between the air inlet 180 and an air outlet in the distal end of the device cavity 104 to allow air to be drawn from the air inlet 180 into the device cavity 104.

[0129] The aerosol-generating article 200 comprises an aerosol-forming substrate 202 in the form of a cylindrical rod comprising tobacco. The cylindrical rod of the aerosol-forming substrate 202 has a length substantially equal to the length of the device cavity 104. The aerosol-generating article 200 further comprises a tubular cooling segment 204, a filter segment 206, and a mouth-end segment 208. The aerosol-forming substrate 202, the tubular cooling segment 204, the filter segment 206, and the mouth-end segment 208 are held together by an overwrap material 210.

[0130] like Figure 4 As shown in , when the aerosol-forming substrate 202 of the aerosol-generating article 200 is received in the device cavity 104 , the length of the aerosol-forming substrate 202 is such that the aerosol-forming substrate 202 extends along the length of the induction heating device 10 .

[0131] In use, when the aerosol-generating article 200 is received in the device cavity 104, a user can inhale on the proximal end of the aerosol-generating article 200 to exhale the aerosol generated by the aerosol-generating system 100. When the user inhales on the proximal end of the aerosol-generating article 200, air is drawn into the device housing 103 at the air inlet 180 and along the airflow path into the device cavity 104. Air is drawn into the aerosol-generating article 200 at the proximal end of the aerosol-forming substrate 202, through an outlet in the distal end of the device cavity 104.

[0132] The controller 108 of the aerosol generating device 102 is configured to supply power to the first inductor coil 12 and the second inductor coil 14 of the induction heating device 10 according to a predetermined heating profile. The predetermined heating profile includes supplying a varying current to the first inductor coil 12 during a first time period to heat a first portion of the susceptor 16 to an operating temperature. The predetermined heating profile also includes supplying a varying current to the second inductor coil 14 during a second time period to heat a second portion of the susceptor 16 to an operating temperature. In this embodiment, the first and second time periods partially overlap. In other words, the second time period begins when a portion of the first time period has elapsed, and the first time period ends when a portion of the second time period has elapsed. However, it should be understood that the controller 108 may be configured to supply power to the first and second inductor coils 12, 14 according to different heating profiles, depending on the desired aerosol delivery to the user. In some embodiments, the aerosol generating device 102 is user-controllable to change the heating profile.

[0133] Figure 5 A longitudinal sectional view of an induction heating device 310 according to a second embodiment of the present disclosure is shown. Figure 5 The induction heating device 310 shown in FIG is similar to Figure 1The induction heating device 10 is shown in FIG. 1 , and the same reference numerals are used to designate the same parts.

[0134] The induction heating device 310 includes a single flux concentrator 313 having a tubular shape and including a first main portion 24 positioned around the first inductor coil 12, a second main portion 34 positioned around the second inductor coil 14, a first end portion 26 at a first end of the first main portion 24, a second end portion 28 at a second end of the first and second main portions 24, 34, and a third end portion 36 at a first end of the second main portion 34. An inner surface 331 of the flux concentrator 313 defines a first annular channel 32 between the first and second end portions 26, 28, and a second annular channel 42 between the second and third end portions 28, 36. Preferably, the flux concentrator 313 includes a first end portion 26, 28, and a second end portion 36, each having a first end portion 26, 28, and a second end portion 36. Figure 2 The induction heating device 10 is described with respect to the separate first and second portions of the semi-annular shape.

[0135] Figure 6 A longitudinal sectional view of an induction heating device 410 according to a third embodiment of the present disclosure is shown. Figure 6 The induction heating device 410 shown in FIG. 1 is similar to Figure 5 1 and 2. The induction heating device 310 of FIG. 1 is shown in FIG. 2 and the same reference numerals are used to designate the same parts.

[0136] The induction heating device 410 includes a single flux concentrator 413 comprising a plurality of discrete annular segments 411 positioned serially to define the tubular shape of the flux concentrator 413. The plurality of discrete annular segments 411 include a first discrete annular segment 427 defining a first end portion 26 of the flux concentrator 413, a second discrete annular segment 429 defining a second end portion 28 of the flux concentrator 413, and a third discrete annular segment 437 defining a third end portion 36 of the flux concentrator 413. The plurality of discrete annular segments 411 also includes a plurality of first intermediate discrete annular segments 425 defining a first main portion 24 of the flux concentrator 413, and a plurality of second intermediate discrete annular segments 435 defining a second main portion 34 of the flux concentrator 413.

[0137] It should be understood that Figure 1 The first flux concentrator 20 and the second flux concentrator 22 of the induction heating device 10 can each be connected to Figure 6 The flux concentrator 413 is formed in the same manner from a plurality of discrete annular segments.

Claims

1. An induction heating device, comprising: a first inductor coil arranged to generate a first varying magnetic field when a varying current flows through the first inductor coil; a second inductor coil arranged to generate a second varying magnetic field when a varying current flows through the second inductor coil; and a flux concentrator positioned around the first inductor coil to distort a first varying magnetic field generated by the first inductor coil, wherein the flux concentrator has a ring shape and comprises: a main portion positioned about the first inductor coil, the main portion having an inner diameter, a first end, and a second end; a first end portion at a first end of the main portion, the first end portion having an inner diameter, wherein the inner diameter of the first end portion is smaller than the inner diameter of the main portion; and a second end portion at a second end of the main portion, the second end portion having an inner diameter, wherein the inner diameter of the second end portion is smaller than the inner diameter of the main portion; Wherein an inner surface of the flux concentrator defines an annular channel between the first end portion and the second end portion, and wherein the first inductor coil is positioned within the annular channel between the first end portion and the second end portion.

2. The induction heating device of claim 1 , wherein the flux concentrator is a first flux concentrator, wherein the main portion is a first main portion positioned around the first inductor coil, wherein the annular channel is a first annular channel, wherein the induction heating device includes a second flux concentrator positioned around the second inductor coil to distort the second changing magnetic field generated by the second inductor coil, and wherein the second flux concentrator has a tubular shape and comprises: a second main portion positioned about the second inductor coil, the second main portion having an inner diameter, a first end, and a second end; a third end portion at the first end of the second main portion, the third end portion having an inner diameter, wherein the inner diameter of the third end portion is smaller than the inner diameter of the second main portion; as well as a fourth end portion at the second end of the second main portion, the fourth end portion having an inner diameter, wherein the inner diameter of the fourth end portion is smaller than the inner diameter of the second main portion; wherein an inner surface of the second flux concentrator defines a second annular channel between the third end portion and the fourth end portion, and wherein the second inductor coil is positioned within the second annular channel between the third end portion and the fourth end portion.

3. The induction heating device of claim 1 , wherein the flux concentrator is positioned around the first inductor coil and the second inductor coil to distort the first and second changing magnetic fields generated by the first and second inductor coils, wherein the main portion is a first main portion positioned around the first inductor coil, wherein the annular channel is a first annular channel, wherein the flux concentrator further comprises: a second main portion positioned about the second inductor coil, the second main portion having an inner diameter, a first end, and a second end; as well as a third end portion at the first end of the second main portion, the third end portion having an inner diameter, wherein the inner diameter of the third end portion is smaller than the inner diameter of the second main portion; wherein the second end portion is at a second end of the second main portion such that the second end portion is positioned between the first main portion and the second main portion; wherein the inner diameter of the second end portion is smaller than the inner diameter of the second main portion; Wherein an inner surface of the flux concentrator defines a second annular channel between the second end portion and the third end portion, and wherein the second inductor coil is positioned within the second annular channel between the second end portion and the third end portion.

4. The induction heating device of claim 1, wherein each inductor coil and each corresponding annular channel are concentrically positioned about a longitudinal axis, and wherein a cross-sectional shape of each annular channel in a longitudinal direction along the longitudinal axis is U-shaped. 5 . The induction heating device according to claim 4 , wherein the U-shaped cross-sectional shape of each annular channel is a rectangular U-shaped cross-sectional shape.

6. The induction heating device of claim 1 , wherein each inductor coil and each corresponding annular channel are concentrically positioned about a longitudinal axis, wherein each flux concentrator is formed from a discrete first portion having a semi-annular shape and a discrete second portion having a semi-annular shape, wherein the first portion and the second portion together define a tubular shape of the flux concentrator.

7. The induction heating device of claim 1, wherein each flux concentrator comprises a plurality of discrete annular segments positioned serially to define a tubular shape of the flux concentrator.

8. The induction heating device according to claim 7, comprising: a first discrete annular segment defining a first end portion of said flux concentrator; a second discrete annular segment defining a second end portion of said flux concentrator; as well as At least one intermediate discrete annular segment defines a major portion of the flux concentrator.

9. The induction heating device according to claim 8, wherein: The flux concentrator is a first flux concentrator, wherein the main portion is a first main portion positioned around the first inductor coil, wherein the annular channel is a first annular channel, wherein the induction heating device includes a second flux concentrator positioned around the second inductor coil to distort the second changing magnetic field generated by the second inductor coil, and wherein the second flux concentrator has a tubular shape and comprises: a second main portion positioned about the second inductor coil, the second main portion having an inner diameter, a first end, and a second end; a third end portion at the first end of the second main portion, the third end portion having an inner diameter, wherein the inner diameter of the third end portion is smaller than the inner diameter of the second main portion; and a fourth end portion at the second end of the second main portion, the fourth end portion having an inner diameter, wherein the inner diameter of the fourth end portion is smaller than the inner diameter of the second main portion; wherein an inner surface of the second flux concentrator defines a second annular channel between the third end portion and the fourth end portion, and wherein the second inductor coil is positioned within the second annular channel between the third end portion and the fourth end portion; wherein the at least one intermediate discrete annular segment is at least one first intermediate discrete annular segment defining a first main portion of the first flux concentrator, the induction heating device further comprising: a third discrete annular segment defining a third end portion of said second flux concentrator; a fourth discrete annular segment defining a fourth end portion of the second flux concentrator; and At least one second intermediate discrete annular segment defines a second main portion of said second flux concentrator.

10. The induction heating device of claim 8, wherein the flux concentrator is positioned around the first inductor coil and the second inductor coil to distort the first and second changing magnetic fields generated by the first and second inductor coils, wherein the main portion is a first main portion positioned around the first inductor coil, wherein the annular channel is a first annular channel, wherein the flux concentrator further comprises: a second main portion positioned about the second inductor coil, the second main portion having an inner diameter, a first end, and a second end; as well as a third end portion at the first end of the second main portion, the third end portion having an inner diameter, wherein the inner diameter of the third end portion is smaller than the inner diameter of the second main portion; wherein the second end portion is at a second end of the second main portion such that the second end portion is positioned between the first main portion and the second main portion; wherein the inner diameter of the second end portion is smaller than the inner diameter of the second main portion; wherein an inner surface of the flux concentrator defines a second annular channel between the second end portion and the third end portion, and wherein the second inductor coil is positioned within the second annular channel between the second end portion and the third end portion; The at least one intermediate discrete annular segment defining the main portion of the flux concentrator includes at least one first intermediate discrete annular segment defining the first main portion and at least one second intermediate discrete annular segment defining the second main portion, and the induction heating device further includes a third discrete annular segment defining a third end portion of the flux concentrator.

11. The induction heating device of claim 1 , wherein each flux concentrator comprises a material having a relative magnetic permeability of at least 5 at a frequency of 6 to 8 MHz and a temperature of 25 degrees Celsius.

12. The induction heating device of claim 1, wherein each flux concentrator comprises a ferromagnetic material.

13. An aerosol generating device comprising: The induction heating device according to any one of claims 1 to 12; power supply; as well as A controller is arranged to supply a varying current from the power supply to each inductor coil.

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