Induction heating array having annular channels

Abstract

An induction heating array (10) is provided. The induction heating array (10) includes a first inductor coil (12) arranged to generate a first variable magnetic field when a variable current flows through the first inductor coil (12). The induction heating array (10) may also include a second inductor coil (14) arranged to generate a second variable magnetic field when a variable current flows through the second inductor coil (14). The induction heating array (10) also includes a flux concentrator (20) positioned around the first inductor coil (12) to distort the first variable magnetic field generated by the first inductor coil (12). The flux concentrator (20) has a tubular shape and includes a main part (24) positioned around the first inductor coil (12). The main part (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, wherein the inner diameter of the first end portion (26) is smaller 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, wherein the inner diameter of the second end portion (28) is smaller than the inner diameter of the main portion (24). The 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 located within the annular channel (32) between the first end portion (26) and the second end portion (28).

Description

Technology Field

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

[0002] A number of electrically operated aerosol generating systems are proposed in the art in which an aerosol generating device having an electric heater is used to heat an aerosol-forming substrate, such as a cigarette plug. One objective of such aerosol generating systems is to reduce known harmful smoke components of the type produced by the combustion and thermal degradation of tobacco in conventional cigarettes. Typically, the aerosol generating substrate is provided as part of an aerosol generating article that is inserted into the cavity of the aerosol generating device. In some known systems, 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 order to heat the aerosol-forming substrate to a temperature at which it is possible to release volatile components capable of forming an aerosol. In other aerosol generating systems, an induction heater is used rather than a resistive heating element. The induction heater typically comprises an inductor that forms part of the aerosol generating device and a susceptor arranged in thermal proximity to the aerosol-forming substrate. The inductor coil generates an alternating magnetic field to cause eddy currents and hysteresis losses in the susceptor element, thereby heating the susceptor element and heating the aerosol-forming substrate.

[0003] Induction heating can allow aerosols to be generated without exposing the inductor coil to the aerosol generating article. This can improve the ease with which the device can be cleaned. However, due to induction heating, the inductor coil can also cause eddy currents and hysteresis losses in adjacent parts of the aerosol generating device. This can reduce the efficiency of the inductive heater, thereby reducing the efficiency of the aerosol generating device. This can also lead to undesirable heating of adjacent parts of the aerosol generating device. This can be a particular problem in aerosol generating devices containing more than one inductor coil, where each inductor coil is arranged to heat a susceptor or a different part of a different susceptor. For example, a variable magnetic field generated by a first inductor coil can induce a current in a second inductor coil, which can eventually heat a susceptor arranged to be heated using only the second inductor coil.

[0004] It would be desirable to provide an induction heating array that mitigates or overcomes these problems of the disclosed systems.

[0005] According to the present disclosure, an induction heating array is provided. The induction heating array may include an inductor coil. The inductor coil may be arranged to generate a variable magnetic field when a variable current flows through the inductor coil. The induction heating array may include a flux concentrator. The flux concentrator may be located around the inductor coil. The flux concentrator may distort the variable magnetic field generated by the inductor coil. The flux concentrator may have a tubular shape. The flux concentrator may include a principal portion located around the inductor coil. The principal portion may have an inner diameter. The principal portion may have a first end. The principal 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 principal 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 principal portion. The flux concentrator may include a second end portion. The second end portion may be located 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. The 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 located within the annular channel between the first end portion and the second end portion.

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

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

[0009] A flux concentrator may include a main portion located around an inductor coil, and the main portion has 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, and 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, and 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 array is provided. The induction heating array may include an inductor coil. The inductor coil may be arranged to generate a variable magnetic field when a variable current flows through the inductor coil. The induction heating array may include a flux concentrator located around the inductor coil. The flux concentrator may be arranged to distort the variable 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 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 array comprising an inductor coil and a flux concentrator is provided. The inductor coil is arranged to generate a variable magnetic field when a variable current flows through the inductor coil. A flux concentrator is positioned around the inductor coil to distort the variable 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. Along the longitudinal axis, the cross-sectional shape of the flux concentrator 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 variable magnetic field when a variable current flows through the first inductor coil. The induction heating arrangement may include a second inductor coil arranged to generate a second variable magnetic field when a variable current flows through the second inductor coil.

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

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

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

[0016] As used herein, the term “aerosol generating article” refers to an article comprising an aerosol-forming material capable of releasing a volatile compound capable of forming an aerosol. For example, an aerosol generating article may be an article that generates an aerosol that can be inhaled directly by a user inhaling or puffing over a mouthpiece at the proximal end of the system or at the user-side end. An aerosol generating article may be disposable. An article comprising an aerosol-forming material containing tobacco may be referred to herein as a tobacco stick.

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

[0018] As used herein, the term "aerosol generating system" refers to a 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 array, an aerosol generator or an aerosol generating article, or a component of an induction heating array, an aerosol generator or an aerosol generating article.

[0020] As used herein, the term "longitudinal section" is used to describe a longitudinal section of an induction heating array, an aerosol generator or an aerosol generating article, or a component of an induction heating array, an aerosol generator or an aerosol generating article.

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

[0022] The flux concentrator defines an annular channel or U-shaped section that accommodates the inductor coil.

[0023] Advantageously, the annular channel or U-shaped portion can reduce or minimize the extent to which a variable magnetic field propagates through the inductor coil. That is, the annular channel or U-shaped portion can function as a magnetic shield. Advantageously, this can reduce the induction of unwanted current in adjacent electrically conductive parts.

[0024] Advantageously, an annular channel or U-shaped section can facilitate the retention of the inductor coil within the flux concentrator. For example, the inductor coil can be retained within the annular channel or U-shaped section by interference fitting.

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

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

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

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

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

[0031] Advantageously, the first and second end portions of the flux concentrator can facilitate magnetic shielding of the second inductor coil from the variable magnetic field generated by the first inductor coil. Advantageously, this can reduce or minimize the induction of current in the second inductor coil by the variable 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 variable magnetic field generated by the second inductor coil. Advantageously, this can reduce or minimize the induction of current in the first inductor coil by the variable 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 cross-sectional shape of the annular channel along the longitudinal axis may be U-shaped. 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 central portion defining the main portion of the flux concentrator. The rectangular U-shaped cross-sectional shape may include a first end portion extending substantially orthogonally to the main portion and defining the first end portion of the flux concentrator. The rectangular U-shaped cross-sectional shape may include a second end portion extending substantially orthogonally to the main portion and defining the second end portion of the flux concentrator.

[0034] In an embodiment in which the induction heating array includes a second annular channel and a second inductor coil, the second inductor coil and the second annular channel may be positioned concentrically about a longitudinal axis. In the longitudinal direction, the cross-sectional shape of the second annular channel may be U-shaped. The U-shaped cross-sectional shape may be a rectangular U-shaped cross-sectional shape.

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

[0036] Advantageously, forming a flux concentrator from first and second parts, each having a semi-circular shape, can facilitate the assembly of an induction heating array. For example, the flux concentrator can be assembled around an inductor coil by positioning the first and second parts around the inductor coil.

[0037] In an embodiment in which an induction heating array comprises a first flux concentrator and a second flux concentrator, at least one of the first flux concentrator and the second flux concentrator may be formed of a discrete first part having a semi-circular shape and a discrete second part having a semi-circular shape, wherein the first part and the second part together define the tubular shape of the flux concentrator. The first flux concentrator and the second flux concentrator may each be formed of a discrete first part having a semi-circular shape and a discrete second part having a semi-circular shape, wherein the first part and the second part together define the tubular shape of the flux concentrator.

[0038] The flux concentrator may include a plurality of discrete annular regions positioned in succession to define the tubular shape of the flux concentrator.

[0039] Advantageously, forming a flux concentrator from multiple discrete annular sections can facilitate the assembly of an induction heating array. For example, the flux concentrator can be assembled around an inductor coil by positioning a continuous discrete annular section around the inductor coil.

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

[0041] In an embodiment in which the flux concentrator comprises a first major portion and a second major portion, at least one intermediate discrete annular portion may include at least one first intermediate discrete annular portion defining the first major portion and at least one second intermediate discrete annular portion defining the second major portion. The induction heating array may include a third discrete annular portion defining the third end portion of the flux concentrator.

[0042] In an embodiment in which the induction heating array includes a first flux concentrator and a second flux concentrator, at least one of the first flux concentrator and the second flux concentrator may include a plurality of discrete annular portions arranged in succession to define the tubular shape of the flux concentrator. The first flux concentrator and the second flux concentrator may each include a plurality of discrete annular portions arranged in succession to define the tubular shape of the flux concentrator.

[0043] At least one intermediate discrete annular region may be at least one first intermediate discrete annular region defining a first major portion of the first flux concentrator. The induction heating array may include a third discrete annular region defining a third major portion of the second flux concentrator. The induction heating array may include a fourth discrete annular region defining a fourth major portion of the second flux concentrator. The induction heating array may include at least one second intermediate discrete annular region defining a second major portion of the second flux concentrator.

[0044] Preferred and optional features of a flux concentrator for an induction heating array according to the present disclosure will now be described. In an embodiment in which the induction heating array comprises a first flux concentrator and a second flux concentrator, each of the preferred and optional features may be applied to the first flux concentrator, the second flux concentrator, or the first flux concentrator and the second flux concentrator.

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

[0046] As used in this application and in the technical field, the term "relative magnetic permeability" refers to the ratio of the magnetic permeability of a medium, such as a material or flux concentrator, to the magnetic permeability of free space, "μ0," where μ0 is 4π×10 -7 It is N·A-2.

[0047] Preferably, the flux concentrator has a relative magnetic transmittance 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 at 25°C. These exemplary values ​​refer to relative magnetic transmittance values ​​for a frequency of 6 to 8 MHz and a temperature of 25°C.

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

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

[0050] An inductor coil generates a variable magnetic field when a variable current is supplied to the inductor coil. In a preferred embodiment, the variable current is an alternating current. The inductor coil generates an alternating magnetic field when an alternating current is supplied to the inductor coil. Thus, in a preferred embodiment, the term "variable current" is an alternating current, and the term "variable magnetic field" is an alternating magnetic field.

[0051] Preferably, the inductor coil is a tubular inductor coil. The inductor coil may be wound spirally around a longitudinal axis. The inductor coil may be slender. Particularly preferably, the inductor coil may be a slender tubular inductor coil. The inductor coil may have any suitable cross-section. For example, the inductor coil may have a circular, elliptical, square, rectangular, triangular, or other polygonal cross-section.

[0052] The inductor coil can be formed from any suitable material. The inductor coil is formed from an electrically 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. That is, the first inductor coil and the second inductor coil have the same shape, dimensions, and number of turns. Advantageously, identical first and second inductor coils can simplify the manufacture of the induction heating array.

[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 with respect to the first inductor coil. Advantageously, the different first and second inductor coils may generate different variable magnetic fields. Advantageously, different variable magnetic fields may be used to heat different parts of the susceptor to different temperatures. Advantageously, different variable 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 aligned coaxially along an axis. If the first inductor coil and the second inductor coil are slender tubular inductor coils, the first inductor coil and the second inductor coil may be aligned coaxially along a longitudinal axis.

[0056] An induction heating array 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 placed in a variable magnetic field, the susceptor is heated. The heating of the susceptor may be the result of at least one of hysteresis loss or eddy current 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 an embodiment in which the induction heating array includes a first inductor coil and a second inductor coil, the first inductor coil may be located around a first part of the susceptor, and the second inductor coil may be located around a second part of the susceptor.

[0059] The susceptor may be a first susceptor, and a first inductor coil is located around at least a portion of the first susceptor. The induction heating array may include a second susceptor, where a second inductor coil is located around at least a portion of the second susceptor.

[0060] Preferably, the induction heating array includes a separator between a first susceptor and a second susceptor, wherein the separator thermally insulates the first susceptor from the second susceptor. The separator may be of any suitable size for thermally insulating the first susceptor from the second susceptor.

[0061] The induction heating array may include an intermediate element positioned between the first susceptor and the second susceptor. The intermediate element may be positioned at the separation portion between the first susceptor and the second susceptor. The intermediate element may extend between the first susceptor and the second susceptor. The intermediate element may contact the end of the first susceptor. The intermediate element may contact the end of the second susceptor. The intermediate element may be fixed to the end of the first susceptor. The intermediate element may be fixed to the 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 thermal insulating material for thermally insulating the first susceptor from the second susceptor. Suitable materials include polyether ether ketone, liquid crystal polymer, cement, glass, zirconium dioxide, silicon nitride, aluminum oxide, and combinations thereof.

[0064] Preferred and optional features of a susceptor for an induction heating array according to the present disclosure will now be described. In an embodiment in which the induction heating array comprises a first susceptor and a second susceptor, each of the preferred and optional features may be applied to the first susceptor, the second susceptor, or the first susceptor and the second susceptor.

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

[0066] If the susceptor is a tubular susceptor defining a cavity that opens at one or both ends, preferably the susceptor is substantially impermeable to gas from the outer surface of the susceptor to the inner surface of the susceptor. That is, preferably the susceptor is substantially impermeable to gas through the sidewalls of the susceptor.

[0067] The susceptor may comprise any suitable susceptor material. The susceptor may be formed of any material capable of induction heating to a temperature sufficient to aerosolize the aerosol-forming substrate. A preferred susceptor may be heated to a temperature exceeding 250°C. A preferred susceptor may be formed of an electrically conductive material. As used herein, "electrically conductive" refers to 1 x 10⁻⁶ at 20°C. -4 It refers to a material having an electrical resistivity of Ωm or less. A 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 about 10 W (W / (m·K)) per meter Kelvin at 23°C and 50% relative humidity as measured using the modified transient plan 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 like ferromagnetic steel or stainless steel, ferromagnetic particles, and ferrite. Some preferred susceptors are made of ferromagnetic materials. Suitable susceptors may include aluminum. Suitable susceptors may be composed of aluminum. The susceptor may contain at least about 5%, at least about 20%, at least about 50%, or at least about 90% of a ferromagnetic or paramagnetic material.

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

[0070] The aerosol generating device may include a power supply unit. Preferably, the aerosol generating device includes a power supply unit.

[0071] The aerosol generator may include a controller. The controller may be arranged to supply a variable current from a power supply to each inductor coil. Preferably, the aerosol generator includes a controller arranged to supply a variable current from a power supply to each inductor coil.

[0072] The power supply may 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 may be another form of charge storage device, such as a capacitor. The power supply may require recharging. The power supply may have a capacity that allows for the storage of energy sufficient for one or more uses of the device. For example, the power supply may have a capacity sufficient to continuously generate an aerosol for a period of about 6 minutes, corresponding to the usual time taken to smoke a regular cigarette, or for a period of several times 6 minutes. In other examples, the power supply may have a capacity sufficient to allow for a predetermined number of uses of the device or individual activations. 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 in the range of about 2.5 watts to about 45 watts).

[0073] The controller may include a programmable microprocessor, a microcontroller, an application-specific integrated chip (ASIC), or a microprocessor capable of providing control. The controller may include additional electronic components. The controller may be configured to regulate the current supply to each inductor coil. Current may be supplied to the inductor coil continuously following the activation of the aerosol generator, or intermittently, for example, on a per-puff basis.

[0074] The controller may be configured to supply a variable current having a frequency of about 5 kHz to about 500 kHz to the inductor coil.

[0075] The controller may be configured to supply a high-frequency variable current to an inductor coil. As used herein, the term “high-frequency variable current” means a variable current having a frequency of about 500 kHz to about 30 MHz. The high-frequency variable current may have a frequency of about 1 MHz to about 30 MHz, such as about 1 MHz to about 10 MHz, or about 5 MHz to about 8 MHz.

[0076] In an embodiment in which the induction heating array includes a first inductor coil and a second inductor coil, the controller can supply a first variable current to the first inductor coil during a first period, and the controller can supply a second variable current to the second inductor coil during a period.

[0077] The first period may be the same as the second period. That is, the controller can supply the first and second variable currents simultaneously.

[0078] The first period may differ from the second period. The first period may be longer than the second period. The first period may be shorter than the second period. The first period may partially overlap with the second period. The first period may completely overlap with the second period. There may be no overlap between the first period and the second period. The first time and the second time may be continuous.

[0079] The controller may advantageously include a DC / AC inverter. The DC / AC inverter may include 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 include any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics, or composite materials comprising one or more of these materials, or thermoplastic resins suitable for food or pharmaceutical applications, such as polypropylene, polyetheretherketone (PEEK), and polyethylene. The material is preferably lightweight and non-brittle.

[0081] The device housing can define an induction heating chamber. Preferably, the induction heating array is located within the induction heating chamber.

[0082] The above device housing includes an air inlet. The air inlet may be configured to allow ambient air to enter the device housing. The device housing may include any appropriate number of air inlets. The device housing may include a plurality of air inlets.

[0083] The device housing may include an air inlet. An air outlet may be configured to allow air to enter the device cavity from inside the device housing. The device housing may include any suitable number of air outlets. The device housing may include a plurality of air outlets.

[0084] In some embodiments, the aerosol generating device 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. One or more of the air inlets may reduce the temperature of the aerosol before the aerosol is delivered to the user and may reduce the concentration of the aerosol before the aerosol is delivered to the user.

[0085] The aerosol generator may include a temperature sensor. The temperature sensor may be arranged to detect the temperature of an induction heating array. In an embodiment in which the induction heating array includes a susceptor, the temperature sensor may be arranged to detect the temperature of the susceptor. In an embodiment in which the induction heating array includes a first susceptor and a second susceptor, the aerosol generator may include a first temperature sensor arranged to detect the temperature of the first susceptor and a second temperature sensor arranged to detect the temperature of the second susceptor.

[0086] The aerosol generating device may include a user interface for activating the device, for example, a button for initiating heating of an aerosol-forming substrate.

[0087] The aerosol generating device may include a display for indicating the state of the device or the aerosol forming substrate.

[0088] The aerosol generating device may include a puff sensor to detect inhalation by a user on the aerosol generating system.

[0089] Preferably, the aerosol generator is portable. The aerosol generator may have a size similar to a conventional cigar or cigarette. The aerosol generator may have a total length of about 30 mm to about 150 mm. The aerosol generator may have an outer diameter of about 5 mm to about 30 mm.

[0090] According to the present disclosure, an aerosol generating system is provided that includes any one of the aerosol generating devices described herein.

[0091] The aerosol generating system may additionally include an aerosol generating article. The aerosol generating article may include an aerosol forming substrate.

[0092] Preferably, the aerosol generating article is configured to be at least partially accommodated within the cavity of the aerosol generating device. An induction heating array may define the cavity for accommodating the aerosol generating article. In an embodiment in which the induction heating array includes a susceptor, the susceptor may define the cavity.

[0093] The aerosol-forming substrate may contain nicotine. The nicotine-containing aerosol-forming substrate may be a nicotine salt matrix.

[0094] The aerosol-forming substrate may be a liquid. The aerosol-forming substrate may include a solid component and a liquid component. Preferably, the aerosol-forming substrate may be a solid.

[0095] The aerosol-forming substrate may include a plant-based material. The aerosol-forming substrate may include tobacco. The aerosol-forming substrate may include a tobacco-containing material containing a volatile tobacco flavor compound that is released from the aerosol-forming substrate upon heating. The aerosol-forming substrate may include a non-tobacco material. The aerosol-forming substrate may include a homogenized plant-based material. The aerosol-forming substrate may include a homogenized tobacco material. The homogenized tobacco material may be formed by aggregating fine tobacco particles. In a particularly preferred embodiment, the aerosol-forming substrate includes a crimped sheet of homogenized tobacco material. As used herein, the term 'crimped sheet' refers to a sheet having a plurality of substantially parallel ridges or wavy folds.

[0096] The aerosol-forming substrate may comprise at least one aerosol-forming agent. The aerosol-forming agent is any suitable known compound or mixture of compounds that facilitates the formation of a dense and stable aerosol upon use and is substantially resistant to thermal sensitivity at the operating temperature of the system. Suitable aerosol-forming agents are well known in the art and include, but are not limited to, polyhydric alcohols such as triethylene glycol, 1,3-butanediol, and glycerin; esters of polyhydric alcohols such as glycerol mono-, di-, or triacetate; and aliphatic esters of mono-, di-, or polycarboxylic acids such as dimethyl dodecanedioate and dimethyl tetradecanedioate. Preferred aerosol-forming agents may comprise polyhydric alcohols or mixtures thereof, such as triethylene glycol and 1,3-butanediol. Preferably, the aerosol-forming agent is glycerin. The homogenized tobacco material may have an aerosol-forming agent content of 5% by weight or more based on dry weight, such as 5% by weight to 30% by weight, where present. The aerosol-forming agent may include other additives and components, such as flavoring agents.

[0097] The aerosol generating article may have any suitable shape. The aerosol generating article may be substantially cylindrical in shape. The aerosol generating article may be substantially elongated. The aerosol generating article may have a length and a circumference substantially perpendicular to this length.

[0098] An aerosol-forming substrate may be provided as an aerosol-forming site containing an aerosol-forming substrate. The aerosol-generating site may include a plurality of components comprising aerosol-forming substrates. The aerosol-generating site may include 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] When the aerosol generating site includes a plurality of aerosol-forming materials, the number of aerosol-forming materials may be equal to the number of inductor coils in the induction heating array.

[0100] The aerosol-forming site may be substantially cylindrical in shape. The aerosol-generating site may be substantially elongated. The aerosol-forming site may have a length and a circumference substantially perpendicular to that length.

[0101] When the aerosol generating site comprises a plurality of aerosol-forming substrates, the aerosol-forming substrates may be arranged from one end to the other along the axis of the aerosol generating site. In some embodiments, the aerosol generating site may include a separator between adjacent aerosol-forming substrates.

[0102] In some preferred embodiments, the aerosol generating article may have a total length of 30 mm and 100 mm. In some embodiments, the aerosol generating article has a total length of approximately 45 mm. The aerosol generating article may have an outer diameter of approximately 5 mm to approximately 12 mm. In some embodiments, the aerosol generating article may have an outer diameter of approximately 7.2 mm.

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

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

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

[0106] The aerosol generating article may include an outer wrapper. The outer wrapper may be formed of paper. The outer wrapper may be gas permeable at the aerosol generating site. In particular, in an embodiment comprising a plurality of aerosol generating substrates, the outer wrapper may include perforations or other air inlets at the interface between adjacent aerosol generating substrates. If a separation portion is provided between adjacent aerosol generating substrates, the outer wrapper may include perforations or other air inlets upon separation. This may allow the aerosol generating substrate to directly provide air that is not drawn in through other aerosol generating substrates. This may increase the amount of air received by each aerosol generating substrate. This improves the characteristics of the aerosol generated from the aerosol generating substrate.

[0107] Additionally, the aerosol generating article may include a separator between the aerosol forming substrate and the filter plug. The separator may be in the range of about 5 mm to about 25 mm. The separator may be about 18 mm. Brief explanation of the drawing

[0108] Embodiments of the present disclosure will now be described by way of example with reference to the accompanying drawings, where: FIG. 1 shows a longitudinal cross-sectional view of an induction heating array according to a first embodiment of the present disclosure; FIG. 2 shows a partially exploded cross-sectional view of the induction heating array of FIG. 1 along line 1-1; FIG. 3 shows a cross-sectional view of an aerosol generating system comprising an aerosol generating article and an aerosol generating device comprising the induction heating array of FIG. 1; FIG. 4 shows an aerosol generating system of FIG. 3 having an aerosol generating article housed inside an aerosol generating device; FIG. 5 shows a longitudinal cross-sectional view of an induction heating array according to a second embodiment of the present disclosure; and FIG. 6 shows a longitudinal cross-sectional view of an induction heating array according to a third embodiment of the present disclosure. Specific details for implementing the invention

[0109] FIG. 1 shows a longitudinal cross-sectional view of an induction heating array (10) according to a first embodiment of the present disclosure. The induction heating array (10) includes a first inductor coil (12) and a second inductor coil (14) positioned coaxially around a tubular susceptor (16) along the longitudinal axis (18) of the induction heating array (10). The susceptor (16) defines a cavity (19) in which an aerosol-forming substrate can be received for heating by the induction heating array (10).

[0110] The induction heating array (10) includes a first flux concentrator (20) located around a first inductor coil (12) and a second flux concentrator (22) located around a second inductor coil (14). The first and second flux concentrators (20, 22) are each formed of a ferromagnetic material.

[0111] The first flux concentrator (20) has a tubular shape and includes a first main part (24) located around the first inductor coil (12), a first end part (26) at the first end of the first main part (24), and a second end part (28) at the second end of the first main part (24). The first and second end parts (26, 28) each have an inner diameter smaller than the inner diameter of the first main part (24). The inner surface (30) of the first flux concentrator (20) defines a first annular channel (32) between the first end part (26) and the second end part (28). The first inductor coil (12) is located within the first annular channel (32) between the first end part (26) and the second end part (28).

[0112] The second flux concentrator (22) has a tubular shape and includes a second main part (34) located around the second inductor coil (14), a third end part (36) at the first end of the second main part (34), and a fourth end part (38) at the second end of the second main part (34). The third and fourth end parts (36, 38) each have an inner diameter smaller than the inner diameter of the second main part (34). The inner surface (40) of the second flux concentrator (22) defines a second annular channel (42) between the third end part (36) and the fourth end part (38). The second inductor coil (14) is located within the second annular channel (42) between the third end part (36) and the fourth end part (38).

[0113] When a variable current is supplied to the first inductor coil (12), the first inductor coil (12) generates a variable magnetic field. The shape of the first flux concentrator (20), and in particular the first and second end portions (26, 28), distorts the variable magnetic field so that the variable magnetic field is concentrated in the first portion of the susceptor (16) located within the first inductor coil (12). The variable magnetic field generated by the first inductor coil (12) induces eddy currents in the first portion of the susceptor (16), causing the first portion of the susceptor (16) to heat up. Advantageously, the concentration of the variable magnetic field within the first portion of the susceptor (16) by the first flux concentrator (20) reduces or minimizes the heating of the second portion of the susceptor (16) located within the second inductor coil (14) by the variable magnetic field generated by the first inductor coil (12).

[0114] When a variable current is supplied to the second inductor coil (14), the second inductor coil (14) generates a variable magnetic field. The shape of the second flux concentrator (22), and in particular the first and second end portions (36, 38), distorts the variable magnetic field so that the variable magnetic field is concentrated in the second portion of the susceptor (16) located within the second inductor coil (14). The variable magnetic field generated by the second inductor coil (14) induces eddy currents in the second portion of the susceptor (16), causing the second portion of the susceptor (16) to heat up. Advantageously, the concentration of the variable magnetic field within the second portion of the susceptor (16) by the second flux concentrator (22) reduces or minimizes the heating of the first portion of the susceptor (16) located within the first inductor coil (12) by the variable magnetic field generated by the second inductor coil (14).

[0115] FIG. 2 shows a partially disassembled cross-sectional view of the induction heating array (10) of FIG. 1 along line 1-1. The first flux concentrator (20) comprises a discrete first component (44) having a semi-circular shape and a discrete second component (46) having a semi-circular shape. When the discrete first and second components (44, 46) are assembled together, they define the tubular shape of the first flux concentrator (20). Advantageously, forming the first flux concentrator (20) from the first and second components (44, 46), each having a semi-circular shape, facilitates the assembly of the induction heating assembly (10). For example, as shown in FIG. 2, the first inductor coil (12) can be positioned over the first part of the susceptor (16). Then, the first and second parts (44, 46) can be positioned around the first inductor coil (12) and come into contact with each other to form a first flux concentrator (20). The same arrangement can be used to assemble a second flux concentrator (22). That is, the second flux concentrator (22) can also be formed from discrete first and second parts, each having a return-type shape.

[0116] FIG. 3 shows an exploded cross-sectional view of an aerosol generating system (100) according to an embodiment of the present disclosure. The aerosol generating system (100) includes an aerosol generating device (102) that includes the induction heating array (10) of FIG. 1. The aerosol generating system (100) also includes an aerosol generating article (200).

[0117] The aerosol generating device (102) comprises a substantially cylindrical device housing (103) having a shape and size similar to 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 the distal end opposite the proximal end. The device cavity (104) is configured to accommodate a portion of an aerosol generating article (200). Thus, the diameter of the device cavity (104) is substantially similar to the diameter of the aerosol generating article (200).

[0118] The aerosol generator (102) further comprises a power supply (106) in the form of a rechargeable nickel-cadmium battery, a controller (108) in the form of a printed circuit board containing a microprocessor, an electrical connector (109), and an induction heating array (10). The power supply (106), the controller (108), and the induction heating array (10) are all housed within a device housing (103). The induction heating array (10) of the aerosol generator (102) is arranged at the proximal end of the device (102) and is generally positioned around the device cavity (104). The electrical connector (109) is arranged at the distal end of the device housing (103) facing the device cavity (104).

[0119] The controller (108) is configured to control the power supply from the power supply unit (106) to the induction heating array (10). The controller (108) further includes a DC / AC inverter including a Class-D power amplifier and is configured to supply at least one variable current to the induction heating array (10). The controller (108) is also configured to control the recharging of the power supply unit (106) from the electrical connector (109). Additionally, the controller (108) includes a puff sensor (not shown) configured to detect when a user inhales an aerosol generating item contained within the device cavity (104).

[0120] The first inductor coil (12) is connected to a controller (108) and a power supply unit (106), and the controller (108) is configured to supply a variable current to the first inductor coil (12). When the variable current is supplied to the first inductor coil (12), the first inductor coil (12) generates a variable magnetic field, which heats the first part of the susceptor (16) by induction.

[0121] The second inductor coil (14) is connected to a controller (108) and a power supply unit (106), and the controller (108) is configured to supply a variable current to the second inductor coil (14). When the variable current is supplied to the second inductor coil (14), the second inductor coil (14) generates a variable magnetic field, which heats the second part of the susceptor (16) by induction.

[0122] The device housing (103) also defines an air inlet (180) very close to the distal end of the device cavity (106). The air inlet (180) is configured so that ambient air can be drawn into the device housing (103). An airflow path is defined through the device between the air inlet (180) and the air outlet within the distal end of the device cavity (104), allowing air to be drawn from the air inlet (180) into the device cavity (104).

[0123] The aerosol generating article (200) comprises an aerosol forming material (202) which is in the form of a cylindrical rod and contains tobacco. The cylindrical rod of the aerosol forming material (202) has a length substantially equal to the length of the device cavity (104). The aerosol generating article (200) also comprises a tubular cooling portion (204), a filter portion (206), and a mouse end portion (208). The aerosol forming material (202), the tubular cooling portion (204), the filter portion (206), and the mouse end portion (208) are held together by an external wrapper (210).

[0124] As illustrated in FIG. 4, when the aerosol forming substrate (202) of the aerosol generating article (200) is received within 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 array (10).

[0125] When in use, when the aerosol generating item (200) is received within the device cavity (104), the user can inhale the aerosol generated by the aerosol generating system (100) by inhaling the proximal end of the aerosol generating item (200). When the user inhales the proximal end of the aerosol generating item (200), air is drawn into the device housing (103) from the air inlet (180) and into the device cavity (104) along the airflow path. Air is drawn into the aerosol generating item (200) from the proximal end of the aerosol forming material (202) through the outlet within the distal end of the device cavity (104).

[0126] The controller (108) of the aerosol generator (102) is configured to supply power to the first and second inductor coils (12, 14) of the induction heating array (10) according to a predetermined heating profile. The predetermined heating profile includes the step of supplying a variable current to the first inductor coil (12) to heat a first portion of the susceptor (16) to an operating temperature during a first period. The predetermined heating profile also includes the step of supplying a variable current to the second inductor coil (14) to heat a second portion of the susceptor (16) to an operating temperature during a second period. In this embodiment, the first period and the second period partially overlap. That is, the second period begins when a portion of the first period has elapsed, and the first period ends when a portion of the second period has elapsed. However, it will be understood that the controller (108) may be configured to power 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 generator (102) may be controlled by the user to change the heating profile.

[0127] FIG. 5 shows a longitudinal cross-sectional view of an induction heating array (310) according to a second embodiment of the present disclosure. The induction heating array (310) shown in FIG. 5 is similar to the induction heating array (10) of FIG. 1, and the same reference numerals are used to designate the same parts.

[0128] The induction heating array (310) has a tubular shape and includes a single flux concentrator (313) comprising a first main part (24) located around a first inductor coil (12), a second main part (34) located around a second inductor coil (14), a first end part (26) at the first end of the first main part (24), a second end part (28) at the second end of the first and second main parts (24, 34), and a third end part (36) at the first end of the second main part (34). The inner surface (331) of the flux concentrator (313) defines a first annular channel (32) between the first end part (26) and the second end part (28), and a second annular channel (42) between the second end part (28) and the third end part (36). Preferably, the flux concentrator (313) includes discrete first and second parts having a semi-circular shape as described with reference to FIG. 2 for each induction heating array (10).

[0129] FIG. 6 shows a longitudinal cross-sectional view of an induction heating array (410) according to a third embodiment of the present disclosure. The induction heating array (410) shown in FIG. 6 is similar to the induction heating array (310) shown in FIG. 5, and the same reference numerals are used to refer to the same parts.

[0130] The induction heating array (410) includes a single flux concentrator (413) comprising a plurality of discrete annular portions (411) arranged in succession to define the tubular shape of the flux concentrator (413). The plurality of discrete annular portions (411) include a first discrete annular portion (427) defining a first end portion (26) of the flux concentrator (413), a second discrete annular portion (429) defining a second end portion (28) of the flux concentrator (413), and a third discrete annular portion (437) defining a third end portion (36) of the flux concentrator (413). A plurality of discrete annular portions (411) also include a plurality of first intermediate discrete annular portions (425) defining a first major portion (24) of the flux concentrator (413), and a plurality of second intermediate discrete annular portions (435) defining a second major portion (34) of the flux concentrator (413).

[0131] It will be understood that the first and second flux concentrators (20, 22) of the induction heating array (10) of FIG. 1 can each be formed from a plurality of discrete annular portions in the same manner as the flux concentrator (413) of FIG. 6.

Claims

Claim 1 An induction heating array comprising: a first inductor coil arranged to generate a first variable magnetic field when a variable current flows through the first inductor coil; a second inductor coil arranged to generate a second variable magnetic field when a variable current flows through the second inductor coil; and a flux concentrator positioned around the first inductor coil to distort the first variable magnetic field generated by the first inductor coil, wherein the flux concentrator has a tubular shape and is a main part positioned around the first inductor coil, the main part having an inner diameter, a first end, and a second end; a first end part at the first end of the main part, the first end part having an inner diameter, and the inner diameter of the first end part being smaller than the inner diameter of the main part; and a second end portion at the second end of the main portion, wherein the second end portion has an inner diameter, and the inner diameter of the second end portion is smaller than the inner diameter of the main portion; an induction heating array, wherein the inner surface of the flux concentrator defines an annular channel between the first end portion and the second end portion, and the first inductor coil is located within the annular channel between the first end portion and the second end portion. Claim 2 In claim 1, the flux concentrator is a first flux concentrator, the main part is a first main part located around the first inductor coil, the annular channel is a first annular channel, and the induction heating array includes a second flux concentrator located around the second inductor coil to distort a second variable magnetic field generated by the second inductor coil, wherein the second flux concentrator has a tubular shape and is a second main part located around the second inductor coil, the second main part having an inner diameter, a first end and a second end; a third end part located at the first end of the second main part, the third end part having an inner diameter, and the inner diameter of the third end part is smaller than the inner diameter of the second main part; An induction heating arrangement comprising a fourth end portion at the second end of the second main portion, wherein the fourth end portion has an inner diameter, and the inner diameter of the fourth end portion is smaller than the inner diameter of the second main portion; and the inner surface of the second flux concentrator defines a second annular channel between the third end portion and the fourth end portion, and the second inductor coil is located within the second annular channel between the third end portion and the fourth end portion. Claim 3 In claim 1, the flux concentrator is positioned around the first inductor coil and the second inductor coil to distort the first and second variable magnetic fields generated by the first and second inductor coils, the main part is a first main part positioned around the first inductor coil, the annular channel is a first annular channel, and the flux concentrator is: a second main part positioned around the second inductor coil, the second main part having an inner diameter, a first end and a second end; An induction heating arrangement comprising: a third end portion located at the first end of the second main portion, wherein the third end portion has an inner diameter, and 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 located at the 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; and the inner diameter of the second end portion is smaller than the inner diameter of the second main portion; and wherein the inner surface of the flux concentrator defines a second annular channel between the second end portion and the third end portion, and the second inductor coil is positioned within the second annular channel between the second end portion and the third end portion. Claim 4 An induction heating array according to any one of claims 1 to 3, wherein each inductor coil and each annular channel are positioned concentrically about a longitudinal axis, and the cross-sectional shape of each annular channel along the longitudinal axis is U-shaped. Claim 5 In paragraph 4, the induction heating array wherein the U-shaped cross-sectional shape of each annular channel is a rectangular U-shaped cross-sectional shape. Claim 6 An induction heating array according to any one of claims 1 to 3, wherein each inductor coil and each annular channel are positioned concentrically about a longitudinal axis, and each flux concentrator is formed of a discrete first component having a semi-annular shape and a discrete second component having a semi-annular shape, and said first component and said second component together define the tubular shape of said flux concentrator. Claim 7 An induction heating array according to any one of claims 1 to 3, wherein each flux concentrator comprises a plurality of discrete annular portions arranged in succession to define the tubular shape of the flux concentrator. Claim 8 In claim 7, an induction heating array comprising: a first discrete annular portion defining a first end portion of the flux concentrator; a second discrete annular portion defining a second end portion of the flux concentrator; and at least one intermediate discrete annular portion defining a main portion of the flux concentrator. Claim 9 In paragraph 2, each flux concentrator comprises a plurality of discrete annular portions arranged in succession to define the tubular shape of the flux concentrator, and the induction heating array further comprises: a first discrete annular portion defining a first end portion of the flux concentrator; a second discrete annular portion defining a second end portion of the flux concentrator; and at least one intermediate discrete annular portion defining a main portion of the flux concentrator, wherein the at least one intermediate discrete annular portion is at least one first intermediate discrete annular portion defining a first main portion of the first flux concentrator, and the induction heating array further comprises: a third discrete annular portion defining a third end portion of the second flux concentrator; a fourth discrete annular portion defining a fourth end portion of the second flux concentrator; and at least one second intermediate discrete annular portion defining a second main portion of the second flux concentrator. Claim 10 In paragraph 3, each flux concentrator comprises a plurality of discrete annular portions arranged in succession to define the tubular shape of the flux concentrator, and the induction heating array further comprises a first discrete annular portion defining a first end portion of the flux concentrator; a second discrete annular portion defining a second end portion of the flux concentrator; and at least one intermediate discrete annular portion defining a main portion of the flux concentrator, wherein the at least one intermediate discrete annular portion defining the main portion of the flux concentrator comprises at least one first intermediate discrete annular portion defining the first main portion and at least one second intermediate discrete annular portion defining the second main portion, and the induction heating array further comprises a third discrete annular portion defining a third end portion of the flux concentrator. Claim 11 An induction heating array according to any one of claims 1 to 3, 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°C. Claim 12 An induction heating array according to any one of claims 1 to 3, wherein each flux concentrator comprises a ferromagnetic material. Claim 13 An aerosol generating device comprising: an induction heating array according to any one of claims 1 to 3; a power supply unit; and a controller arranged to supply a variable current from the power supply unit to each inductor coil.

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