WO2023194533A1

WO2023194533A1 - Aerosol generating device comprising a heating plate comprising a ceramic part and a metal part and associated method for controlling

Info

Publication number: WO2023194533A1
Application number: PCT/EP2023/059136
Authority: WO
Inventors: Alec WRIGHT
Original assignee: Jt International S.A.
Priority date: 2022-04-06
Filing date: 2023-04-06
Publication date: 2023-10-12

Abstract

The invention concerns an aerosol generating device configured to operate with a flat-shaped tobacco article (12) and comprising a flat-shaped heating chamber (50); the heating chamber (50) being configured to receive the flat-shaped tobacco article (12) and comprising a heating plate (70) forming at least partially a wall (54A, 54B) of the heating chamber (50); the heating plate (70) comprising a ceramic part (72) and a metal part (74) different from the ceramic part (72) and engaged with this ceramic part (72), both parts (72, 74) being arranged to heat the flat-shaped tobacco article (12).

Description

Aerosol generating device comprising a heating plate comprising a ceramic part and a metal part and associated method for controlling

FIELD OF THE INVENTION

The present invention concerns an aerosol generating device comprising a heating plate comprising a ceramic part and a metal part.

Particularly, the aerosol generating device according to the invention is configured to operate with a tobacco article, for example a flat-shaped tobacco article, which comprises for example a solid substrate able to form aerosol when being heated. Thus, such type of aerosol generating devices, also known as heat-not-burn devices, is adapted to heat, rather than burn, the substrate by conduction, convection and/or radiation, to generate aerosol for inhalation.

The present invention also concerns a method for controlling the aerosol generating device.

BACKGROUND OF THE INVENTION

The popularity and use of reduced-risk or modified-risk devices (also known as vaporisers) has grown rapidly in the past few years as an aid to assist habitual smokers wishing to quit smoking traditional tobacco products such as cigarettes, cigars, cigarillos, and rolling tobacco. Various devices and systems are available that heat or warm vaporizable substances as opposed to burning tobacco in conventional tobacco products.

A commonly available reduced-risk or modified-risk device is the heated substrate aerosol generation device or heat-not-burn device. Devices of this type generate aerosol or vapour by heating an aerosol substrate that typically comprises moist leaf tobacco or other suitable vaporizable material to a temperature typically in the range 150°C to 350°C. Heating an aerosol substrate, but not combusting or burning it, releases aerosol that comprises the components sought by the user but not the toxic and carcinogenic byproducts of combustion and burning. Furthermore, the aerosol produced by heating the tobacco or other vaporizable material does not typically comprise the burnt or bitter taste resulting from combustion and burning that can be unpleasant for the user and so the substrate does not therefore require the sugars and other additives that are typically added to such materials to make the smoke and/or vapour more palatable for the user.

Tobacco articles, usable with such type of aerosol generating devices can take various forms. Some of them can present an elongated stick or any other suitable shape, like for example a flat shape. However, design of a tobacco article is often a trade-off between its aesthetics and efficiency in heating.

Some of known aerosol generating devices operating with tobacco article comprise a heater which consumes a lot of energy to bring the heater up to a predefined temperature and thus to heat the tobacco article to the target temperature.

For example, WO 2019/128551 describes an aerosol generating device comprising a heating zone comprising at least one electromagnetic induction heating device or at least one resistance heating device, and a heating chamber configured to receive a sheet of tobacco.

SUMMARY OF THE INVENTION

One of the aims of the invention is to provide an aerosol generating device requiring less energy to heat a tobacco article to a target temperature.

For this purpose, the invention relates to an aerosol generating device configured to operate with a flat-shaped tobacco article and comprising a flat-shaped heating chamber; the heating chamber being configured to receive the flat-shaped tobacco article and comprising a heating plate forming at least partially a wall of the heating chamber; the heating plate comprising a ceramic part and a metal part different from the ceramic part and engaged with this ceramic part, both parts being arranged to heat the flat-shaped tobacco article.

Thank to these features, it is possible to provide an aerosol generating device requiring less energy to heat a tobacco article to a target temperature while heating the tobacco article in an optimal way. Particularly, the metal part enables to rapidly heat the tobacco article with little energy, allowing a fast puff by a user. Additionally, the metal part is advantageously configured to heat the ceramic part by thermal conduction. High thermal mass of the ceramic part allows a homogenous heating of the surface of the tobacco article. Additionally, the ceramic part has a high thermal penetration into the tobacco article, which enables to generate more vapour as compared to a heater comprising a unique metal part. Thus, the user experience while using the aerosol generating device can be improved. A heating plate comprising a metal part and a ceramic part thus enables to use less energy to heat the heating plate to a predetermined temperature as compared to the energy used to heat a heating plate comprising a unique ceramic part to said predetermined temperature, and to obtain a homogeneous heating of the heating plate during a vaping session. The combination of the metal part and the ceramic part thus enables to optimize the heating of the flat-shaped tobacco article.

The ceramic part may be made in a single element. In variant, the ceramic part may be made of at least two elements.

The metal part may be made of a single element. In variant, the metal part may be made of at least two elements. The metal part may form a resistive element designed to be powered by a power source. The supply of power may be controlled by a control unit of the aerosol generating device. The metal part may be connected to electrical wires supplying power, for example by welding of the electrical wires to the metal part. According to other embodiments, a polyimide film heater, is arranged adjacent, in particular, in contact with the metal part to heat the metal part by thermal conduction. According to other embodiments of the invention, the heating chamber comprises a magnetic element able to cause heating of the metal part by magnetic induction.

According to some embodiments, the ceramic part extends around the metal part .

Thanks to this feature, heat transmission from the metal part to the ceramic part is enhanced. The metal part and the ceramic part extending around the metal part may be in contact. Thus, having a ceramic part extending around the metal part enables to increase the areas of the ceramic part and the metal part in contact so that thermal conduction from the metal part to the ceramic part can be enhanced.

According to some embodiments, the ceramic part defines a recess portion receiving the metal part.

Thanks to this feature, the heating plate can be easily manufactured since performing a recess can be made by known tools and known manufacturing methods. Moreover, thanks to this feature, it is possible to obtain a compact heating plate adapted to its integration in an aerosol generating device. The recess portion may correspond to a blind hole.

According to some embodiments, the ceramic part and the metal part engaged with the ceramic part form a flat surface designed to be in contact with or face the flat-shaped tobacco article.

Thanks to this feature, the heating plate has a surface designed to be in contact with or face the flat-shaped tobacco article whose shape is complementary to the flat shape of the flat-shaped tobacco article. The portion of the flat surface formed by ceramic part may be continuous. In variant, the portion of the flat surface formed by ceramic part has zones disjointed from each other. The portion of the flat surface formed by metal part may be continuous. In variant, the portion of the flat surface formed by metal part has zones disjointed from each other. As an alternative, the surface formed by the ceramic part and the metal part has another shape from a flat shape, for example a rounded shape.

According to some embodiments, the metal part forms at least 50%, preferably at least 60% and advantageously at least 70%, of the total area of the flat surface.

Thanks to this feature, heating of the flat-shaped tobacco article by the metal part is efficient and fast. Additionally, thanks to this feature, heating the ceramic part by the metal part is optimal. Additionally, thanks to this feature, it is possible to arrange the parts of the flat surface formed by the ceramic part in contact with or in front of the ends of a tobacco portion of the tobacco article so that an efficient heating of said tobacco portion is obtained. This results in a better extraction of tobacco from the tobacco portion of the flat-shaped tobacco article.

According to some embodiments, the recess portion forms a shape complementary to the external shape of the metal part to tightly fit the metal part.

Thanks to this feature, a compact heating plate is obtained. Thus, thanks to this feature, the heating plate can be easily integrated in the aerosol generating device.

According to some embodiments, the recess portion forms a substantially parallelepiped shape, preferably with rounded corners. Thanks to this feature, the heating plate is easily manufactured since the parallelepiped shape can be performed using well known tools and manufacturing methods.

According to some embodiments, the heating plate is designed to extend substantially along the whole area of a tobacco portion comprised in the flat-shaped tobacco article.

Thanks to this feature, the entire area of the tobacco portion is heated. According to some embodiments, the heating plate is designed to protrude from the ends of the tobacco portion defined along a device axis. This ensures a proper heating of the ends of the tobacco portion defined along the device axis and thus a better extraction of tobacco from the tobacco portion of the flat-shaped tobacco article.

According to some embodiments, both ceramic and metal parts are designed to be in contact with or face said tobacco portion of the flat-shaped tobacco article.

For example, the ceramic part is directly in contact with or directly face the ends of the tobacco portion so that the ends of the tobacco portion are heated during all the vaping session. By “directly” it is understood that no intermediate element extend between the ceramic plate and the ends of the tobacco portion.

According to some embodiments, the ceramic part is configured to be heated by thermal conduction by the metal part.

Thanks to this feature, a little amount of energy is required to heat the metal part and thus the ceramic part while enabling to obtain an optimal heating of the heating plate during a vaping session.

According to some embodiments, the heating chamber comprises two heating plates forming at least partially opposite walls of the heating chamber.

Thanks to this feature, a homogeneous heating is obtained.

The invention also relates to a method for controlling an aerosol generating device as described above, comprising a step of heating the metal part, the heated metal part heating the ceramic part by thermal conduction. BRIEF DESCRIPTION OF THE DRAWINGS

The invention and its advantages will be better understood upon reading the following description, which is given solely by way of non-limiting example and which is made with reference to the appended drawings, in which:

- Figure 1 is a perspective view of an aerosol generating assembly according to the invention, the aerosol generating assembly comprising an aerosol generating device according to the invention and a tobacco article usable with the aerosol generating device;

- Figure 2 is a perspective view of the tobacco article of Figure 1 ;

- Figure 3 is a partial cross-sectional view of the aerosol generating assembly of Figure 1 according to plane III, the aerosol generating device comprising a heating plate according to the invention;

- Figure 4 is a partial cross-sectional view of the aerosol generating assembly of Figure 1 according to plane IV;

- Figure 5 is a detailed view of the heating plate of Figure 3;

- Figure 6 a front view of the heating plate of Figure 5 along arrow VI;

- Figure 7 is a front view of a ceramic part of the heating plate of Figure 5; and

- Figure 8 is a cross-sectional view of the ceramic part of Figure 7 according to plane VIII.

DETAILED DESCRIPTION OF THE INVENTION

Before describing the invention, it is to be understood that it is not limited to the details of construction set forth in the following description. It will be apparent to those skilled in the art having the benefit of the present disclosure that the invention is capable of other embodiments and of being practiced or being carried out in various ways. The expression “substantially equal to” is understood hereinafter as an equality at plus or minus 10% and preferably at plus or minus 5%.

As used herein, the term “aerosol generating device” or “device” may include a vaping device to deliver an aerosol to a user, including an aerosol for vaping, by means of a heater element explained in further detail below. The device may be portable. “Portable” may refer to the device being for use when held by a user. The device may be adapted to generate a variable amount of aerosol, e.g. by activating the heater element for a variable amount of time (as opposed to a metered dose of aerosol), which can be controlled by a trigger. The trigger may be user activated, such as a vaping button and/or inhalation sensor. The inhalation sensor may be sensitive to the strength of inhalation as well as the duration of inhalation to enable a variable amount of vapour to be provided (so as to mimic the effect of smoking a conventional combustible smoking article such as a cigarette, cigar or pipe, etc.). The device may include a temperature regulation control to drive the temperature of the heater and/or the heated aerosol generating substance (aerosol pre-cursor) to a specified target temperature and thereafter to maintain the temperature at the target temperature that enables efficient generation of aerosol.

As used herein, the term “aerosol” may include a suspension of vaporizable material as one or more of: solid particles; liquid droplets; gas. Said suspension may be in a gas including air. Aerosol herein may generally refer to/include a vapour. Aerosol may include one or more components of the vaporizable material.

As used herein, the term “vaporizable material” or “precursor” may refer to a smokable material which may for example comprise nicotine or tobacco and an aerosol former. Tobacco may take the form of various materials such as shredded tobacco, granulated tobacco, tobacco leaf and/or reconstituted tobacco. Suitable aerosol formers include: a polyol such as sorbitol, glycerol, and glycols like propylene glycol or triethylene glycol; a non-polyol such as monohydric alcohols, acids such as lactic acid, glycerol derivatives, esters such as triacetin, triethylene glycol diacetate, triethyl citrate, glycerin or vegetable glycerin. In some embodiments, the aerosol generating agent may be glycerol, propylene glycol, or a mixture of glycerol and propylene glycol. The substrate may also comprise at least one of a gelling agent, a binding agent, a stabilizing agent, and a humectant. Figure 1 shows an aerosol generating assembly 10 comprising an aerosol generating device 1 1 and a tobacco article 12. The aerosol generating device 11 is intended to operate with the tobacco article 12 which is shown in more detail in Figure 2.

In the example of this Figure 2, the tobacco article 12 is a flat-shaped tobacco article presenting for example a flat-shaped cuboid extending along an article axis X and having external dimensions L12xW12xD12. In a typical example, the length L12 of the article 12 according to the article axis X equals substantially to 33 millimeters (mm) while its width W12 and depth D12 are substantially equal respectively to 12 mm and 1 .2 mm. According to different examples, the values L12, W12 and D12 can be selected within a range of +/- 40%, for example. The depth D12 of the tobacco article 12 is formed by a pair of parallel walls 13A, 13B, called hereinafter narrow walls 13A, 13B, and the width W12 of the tobacco article 12 is formed by a pair of parallel walls 14A, 14B, called hereinafter wide walls 14A, 14B. In some embodiments, the edges between the wide and narrow walls 13A, 13B, 14A, 14B can be rounded. According to other embodiments of the invention, the tobacco article 12 can have any other suitable flat shape and/or external dimensions. According to still other embodiments, the tobacco article 12 can present any other suitable shape, as for example a stick shape.

The tobacco article 12 comprises a tobacco portion 15 and a mouthpiece portion 16 arranged along the article axis X. The tobacco portion 15 may for example be slightly longer than the mouthpiece portion 16. The tobacco portion 15 is formed by parallel walls 15A, 15B which are parts of the wide walls 14A, 14B of the tobacco article 12. For example, the length L15 of the tobacco portion 15 according to the article axis X may be substantially equal to 18 mm. The width W15 of the tobacco portion 15 is equal to the width W12 of the tobacco article 12. The length L16 of the mouthpiece portion 16 according to the article axis X may be substantially equal to 15 mm. The tobacco portion 15 defines an abutting end 18 of the article 12 and the mouthpiece portion 16 defines a mouth end 20 of the article 12. The tobacco portion 15 and the mouthpiece portion 16 may be fixed one to the other by a wrapper 21 extending around the substrate axis X. The wrapper 21 forms the narrow and wide walls 13A, 13B, 14A, 14B of the tobacco article 12. In some embodiments, the wrapper 21 is formed from a same wrapping sheet. In some other embodiments, the wrapper 21 is formed by separate wrapping sheets wrapping separately the portions 15, 16 and fixed one to the other by any other suitable mean. The wrapper 21 may, for example, comprise paper and/or non-woven fabric and/or aluminium foil. The wrapper 21 may be porous or air impermeable and forms a plurality of airflow channels extending inside the article 12 between the abutting end 18 and the mouth end 20.

The mouthpiece portion 16 comprises a core 27 intended to act for example as a cooler to cool slightly the vapour before it is inhaled by the user. The core 27 may comprise for this purpose for example corrugated paper. The core 27 may be formed through an extrusion and/or rolling process into a stable shape. Advantageously, the core 27 is arranged inside the mouthpiece portion 16 to be entirely in contact with the internal surface of the wrapper 21 delimiting this mouthpiece portion 16.

The tobacco portion 15 comprises a vaporizable material and is intended to be heated by a heating chamber, as it will be explained in further detail below.

Referring again to Figure 1 , the aerosol generating device 1 1 comprises a device body 40 extending along a device axis Y and a mouthpiece 42. According to the example described below, the mouthpiece 42 and the device body 40 form two different pieces. Particularly, according to this example, the mouthpiece 42 is designed to be fixed on a fixing end of the device body 40.

As it is shown in Figure 3, the mouthpiece 42 comprises a central part 43 and a peripheral part 44 extending around the central part 43. The peripheral part 44 defines for example a collar covering partially an external surface of the device body 40 when the mouthpiece 42 is fixed on the fixing end of the device body 40. For example, the peripheral part 44 can be designed to cooperate with a gasket 45 arranged on the fixing end of the device body 40 in order to seal the space formed between the peripheral part 44 and the external surface of the device body 40. The peripheral part 44 also defines an intermediate portion extending for example transversally to the device axis Y and forming a transition between the central part 43 of the mouthpiece 42 and the collar defined by the peripheral part 44. The central part 43 of the mouthpiece 42 defines a through hole 46 adapted to receive at least partially the tobacco article 12. Particularly, the through hole 46 can be adapted to receive at least a part of the mouthpiece portion 16 of the tobacco article 12 as it is shown in Figure 3. Advantageously, the through hole 46 can be adapted to fit tightly the mouthpiece portion 16 of the tobacco article 12 so as to avoid or minimise flow leakage between a wall delimiting the through hole 46 and an external surface of the tobacco article 12. In some embodiments, the tobacco article 12 can be retained for example by friction in the through hole 46. In this case, it is possible for example to insert first the mouthpiece portion 16 of the tobacco article 12 inside the through hole 46 and when fix both elements on the fixing end of the device body 40.

As it is also shown in Figure 3, an inner volume 47 is formed between an inner surface 48 of the mouthpiece 42 and the fixing end of the device body 40. This inner volume 47 is crossed by the tobacco article 12 when it is inserted inside the device body 40. For example, the tobacco article 12 can divide the inner volume 47 in two symmetric parts.

The device body 40 delimits an internal space of the device 1 1 receiving various elements designed to carry out different functionalities of the device 1 1 . This internal space can for example receive a battery for powering the device 1 1 , a control module for controlling the operation of the device 11 , a flat-shaped heating chamber 50 (hereinafter “heating chamber 50”) for heating the tobacco portion 15 of the tobacco article 12, etc. Among these elements, only the flat-shaped heating chamber 50 will be explained in further detail in reference to Figure 3.

Particularly, as it is shown in this Figure 3, the heating chamber 50 is configured to receive the tobacco article 12. The heating chamber 50 has a flat shape adapted to receive at least the tobacco portion 15 of the tobacco article 12 and in some cases, at least a part of the mouthpiece portion 16. As the tobacco article 12, the heating chamber 50 may also form a cuboid shape extending along the device axis Y and comprising a pair of parallel narrow walls 53A, 53B (shown in Figures 4) extending along the device axis Y, a pair of parallel wide walls 54A, 54B extending also along the device axis Y and a bottom wall 58 adjacent to each of said walls and extending perpendicularly to the device axis Y. The bottom wall 58 forms thus a closed end of the chamber 50. Opposite to the bottom wall 58, the heating chamber 50 defines an opening 60 configured to receive the tobacco article 12 so as the corresponding wide walls 14A, 14B of the tobacco article 12 face the corresponding wide walls 54A, 54B of the heating chamber 50, the corresponding narrow walls 13A, 13B of the tobacco article 12 face the corresponding narrow walls 53A, 53B of the heating chamber 50 and the abutting end 18 of the tobacco article 12 abuts against the bottom wall 58 or at least a rib extending from this bottom wall 58. Alternatively, the abutting end 18 faces the bottom wall 58 without being in contact with it. The flat-shaped heating chamber 50 is thus configured to receive the tobacco article 12 so as the narrow wall 13A (respectively 13B) of the tobacco article 12 faces the narrow wall 53B (respectively 53A) of the heating chamber 50, and the wide wall 14A (respectively 14B) of the tobacco article 12 faces the wide wall 54B (respectively 54A) of the heating chamber 50. The facing wide walls 14A, 14B, 54A, 54B and the facing narrow walls 13A, 13B, 53A, 53B can be in contact one with the other or spaced one from the other.

The heating chamber 50 comprises a heating plate forming at least partially a wall of the heating chamber 50. Such wall is for example one of the wide walls 54A, 54B of the heating chamber 50. The heating plate is designed to be in contact with or face the tobacco portion 15 of the tobacco article 12. In particular, the heating plate is designed to be in contact with or face one of the wide walls 15A, 15B of the tobacco portion 15. According to a particular example, the heating plate is designed to extend along the whole area of the tobacco portion 15 comprised in the tobacco article 12. That is to say, the heating plate extends at least along the whole length L15 of the tobacco portion 15 and at least along the whole width W15 of the tobacco portion 15. According to a specific example, the length of the heating plate along the device axis Y is greater than the length of the tobacco portion 15. Thus, each heating plate 70 protrudes from both ends of the tobacco portion 15 defined along the device axis Y.

In the specific example shown on Figure 3, the heating chamber 50 comprises two heating plates 70 forming at least partially opposite walls of the heating chamber 50. The opposite walls are for example the wide walls 54A, 54B of the heating chamber 50. Each heating plate 70 is designed to be in contact with or face the tobacco portion 15 of the tobacco article 12. In particular, each heating plate 70 is designed to be in contact with or face a respective wide wall 15A, 15B of the tobacco article 15. In the example shown on Figure 3, each heating plate 70 faces a respective wide wall 15A, 15B of the tobacco article 15 and a gap is defined between the heating plate 70 and said respective wide wall 15A, 15B of the tobacco article 15. The gap is inferior or equal to 0.1 mm. Each heating plate 70 has a length W70 defined along the device axis Y, a width W70 (see Figure 6 showing the dimensions L70 and W70 for one of the two heating plates 70) and a depth D70 (see Figure 5 showing the dimension D70). Each heating plate 70 is designed to extend along the whole area of the tobacco portion 15. In other words, the length L70 of the heating plate 70 is at least equal to the length L15 of the tobacco portion 15 and the width W70 of the heating plate 70 is at least equal to the width W15 of the tobacco portion 15. According to a specific example shown on Figure 3, the length L70 of each heating plate 70 is greater than the length L15 of the tobacco portion 15. Thus, each heating plate 70 protrudes from both ends of the tobacco portion 15 defined along the device axis Y. This ensures a proper heating of the ends of the tobacco portion 15 defined along the device axis Y. The depth D70 of the heating plate 70 depends on the dimensions of the tobacco article 15. For example, the depth D70 of the heating plate 70 is greater or equal to 0.25 mm and less than or equal to 0.75 mm. As also shown on Figure 3, the tobacco portion 15 is arranged in sandwich between the two heating plates 70.

According to an example, the two heating plates 70 are structurally identical. In the following, only one heating plate 70 is described in reference to Figures 3 to 8. The other heating plate 70 is structurally similar to the described heating plate 70 and is thus not described in detail. According to another example, two heating plates 70 are different. In this case, the non-described below heating plate 70, may correspond to any conventional heating plate made for example from metal or ceramics.

The heating plate 70 comprises a ceramic part 72 and a metal part 74 different from the ceramic part 72 and engaged with this ceramic part 72, both parts 72, 74 being arranged to heat the tobacco article 12. Both ceramic and metal parts 72, 74 of the heating plate 70 are designed to be in contact with or face said tobacco portion 15 of the tobacco article 12, and in particular to be in contact with or face one of the wide faces 15A, 15B of the tobacco article 12. The ceramic part 72 and the metal part 74 of the heating plate 70 are engaged to form a flat surface 76 designed to be in contact with or face the tobacco article 12, shown on Figures 3, 5 and 6. As an alternative, the surface formed by the ceramic part 72 and the metal part 74 has a shape different from the flat shape, as for example a rounded shape.

In the present example, the flat surface 76 is designed to be in contact with or face at least the tobacco portion 15 comprised in the tobacco article 12. More specifically, the flat surface 76 is designed to be in contact with or face one of the wide faces 15A, 15B of the tobacco article 12. In the example shown on Figure 3, the flat surface 76 faces one of the wide faces 15A, 15B of the tobacco article 12 and said gap extends between the flat surface 76 and said wide face 15A, 15B of the tobacco article 15. The length of the flat surface 76 is equal to the length L70 of the heating plate 70 and the width of the flat surface 76 is equal to the width W70 of the heating plate 70.

The flat surface 76 is formed by a ceramic flat surface portion 72S delimited by the ceramic part 72 and a metal flat surface portion 74S delimited by the metal part 74. The ceramic flat surface portion 72S and the metal flat surface portion 74S are substantially flush. By “substantially flush”, it is understood that the difference in level between the ceramic flat surface portion 72S and the metal flat surface portion 74S along a direction perpendicular to these portions 72S, 74S is less than or equal for example to 0.2 mm. The ceramic flat surface portion 72S is configured to be in contact with or face a part of the tobacco portion 15. Advantageously, as shown in Figure 3, the ceramic flat surface portion 72S is configured to be directly in contact with or face directly the ends of the tobacco portion 15 defined along the device axis Y. By “directly” it is understood that no intermediate element extends between the ceramic flat surface portion 72S and the ends of the tobacco portion 15. According to an example, the ceramic flat surface portion 72S protrudes from both ends of the tobacco portion 15 defined along the device axis Y.

As shown on Figure 6, the ceramic flat surface portion 72S surrounds all the edges of the metal flat surface portion 74S. In other words, in each plane perpendicular to the flat surface 76, the ceramic flat surface portion 72S extends on both sides of the metal flat surface portion 74S. The ceramic flat surface portion 72S is for example continuous. In each plane perpendicular to the flat surface 76 crossing both the metal portion 74 and the ceramic portion 72 and extending along the device axis Y, the length of the ceramic flat surface portion 72S is equal to the length difference between the length of the flat surface 76 and the length of the metal flat surface portion 74S. In each plane perpendicular to the flat surface 76 crossing both the metal portion 74 and the ceramic portion 72 and extending along the device axis Y, the width of the ceramic flat surface portion 72S is equal to the length difference between the width of the flat surface 76 and the width of the metal flat surface portion 74S. In variant, the ceramic flat surface portion 72S has zones disjointed from each other.

The metal flat surface portion 74S is configured to be in contact with or face a central part of the tobacco portion 15. The metal flat surface portion 74S forms a substantially central zone of the flat surface 76. Moreover, in each plane perpendicular to the flat surface 76 crossing both the metal part 74 and the ceramic part 72, the metal flat surface portion 74S is arranged between two parts of the ceramic flat surface portion 74S. The metal flat surface portion 74S of the flat surface 76 is for example continuous. In this case, the length of the metal flat surface portion 74S is equal to the length of the metal part 74 described in details in the following. Additionally, the width of the metal flat surface portion 74S is equal to the width of the metal part 74. In variant, the metal flat surface portion 74S has zones disjointed from each other.

More specifically, as shown in Figures 3, 5 and 6, the ceramic part 72 extends around the metal part 74. The ceramic part 72 extends around all the external faces of the metal part 74 excluding the metal flat surface portion 74S. The length L72 of the ceramic part 72 is equal to the length L70 of the heating plate 70. The length L72 of the ceramic part 72 is strictly greater than the length L74 of the metal part 74. According to an example, the width W72 of the ceramic part 72 is equal to the width W70 of the heating plate 70. The width W72 of the ceramic part 72 is strictly greater than the width W74 of the metal part 74. The ceramic part 72 is in contact with the metal part 74. The ceramic part 72 has a substantially parallelepiped shape, preferably with rounded corners.

As shown on Figures 7 and 8, the ceramic part 72 defines a recess portion 78 receiving the metal part 74. The recess portion 78 is a concave area in the ceramic part 72. The recess portion 78 forms a shape complementary to the external shape of the metal part 74 to tightly fit the metal part 74. The recess portion 78 forms a substantially parallelepiped shape, preferably with rounded corners. The depth of the recess portion may for example be substantially equal to 50% of the depth D70 of the heating plate 70. The depth D72i of the ceramic part 72 in front of the recess portion 78 is thus substantially equal to 50% of the depth D70 of the metal plate 70. The depth D72₂ of the ceramic part 72 arranged at the periphery of the recess 78 is equal to the depth D70 of the metal plate 70. The part of the surface of the ceramic part 72 arranged surrounding the recess portion 78 defines the ceramic flat surface portion 72S. The ceramic part 72 is made in a single piece. In variant, the ceramic part 72 is made of at least two pieces.

Advantageously, the ceramic part 72 is configured to be heated by thermal conduction by the metal part 74. According to other embodiments, the heating chamber 50 may further comprise a heating element configured to heat the ceramic part 72. The heating element may be a resistive heating element arranged adjacent to the ceramic part 72. Advantageously, the resistive heating element, as for example a heating track or a polyimide film heater, is arranged adjacent to the ceramic part 72, for example on an external surface of the ceramic part 72. According to still another embodiment, the heating element may comprise a magnetic element and a plurality of susceptors comprised in the ceramic part 72, the magnetic element being able to cause heating of the plurality of susceptors by magnetic induction.

As an example, the metal part 74 is engaged inside the recess portion 78 by clipping. The metal part 74 is for example held by force in the recess portion 78. The recess portion 78 corresponds to a blind hole. The metal part 74 forms at least 50%, preferably at least 60% and advantageously at least 70%, of the total area of the flat surface 76. The metal part 74 has for example a parallelepiped shape. The free face of the metal part 74 engaged inside the recess portion 78 forms the metal flat surface portion 74S. The depth D74 of the metal part 74 is substantially equal to 50% of the depth of the heating plate 70. The metal of the metal part 74 is for example stainless steel or tungsten. The metal part 74 is made of a single piece. In variant, the metal part 74 is made of at least two pieces.

According to an embodiment, the metal part 74 forms a resistive element designed to be powered by a power source (not shown). The supply of power may be controlled by a control unit (not shown) of the aerosol generating device 1 1. According to some example, the metal part 74 is connected to electrical wires supplying power, for example by welding of the electrical wires to the metal part 74. According to other embodiments, a polyimide film heater, is arranged adjacent, in particular, in contact with the metal part 74 to heat the metal part 74 by thermal conduction. According to other embodiments of the invention, the heating chamber 50 comprises a magnetic element able to cause heating of the metal part 74 by magnetic induction.

In order to ensure user’s puffs, an airflow channel extending from an airflow inlet 65 (shown in Figure 4) until the closed end of the heating chamber 50 is formed inside the aerosol generating device 1 1. Thus, air can enter the heating chamber 50 through the airflow channel and pass first to the tobacco portion 15 and then through the mouthpiece portion 16 of the tobacco article 12 before being delivered to the user. According to the invention, the airflow inlet 65 is arranged in the mouthpiece 42, advantageously in the intermediate portion of the peripheral part 44 of this mouthpiece 42. The airflow inlet 65 can be formed by a through hole.

A controlling method for controlling an aerosol generating device 11 of the aerosol generating assembly 10 is explained in the following.

The controlling method comprises a step of heating of the metal part 74.

The heating of the metal part 74 is carried out by supplying power to the metal part 74 via the electric wires. More specifically, the supply of power is controlled by the control unit of the aerosol generating device 11 . The control unit may control the supply of power according to a control law. The control law may comprise supplying the metal part 74 with a predetermined current during a predetermined duration. The heated metal part 74 heats the ceramic part 72 by thermal conduction.

Said predetermined current supplying the metal part 74 and said predetermined duration may be chosen based on a predetermined heating temperature of the ceramic part 72.

According to another embodiment, the control law may comprise supplying the metal part 74 with a predetermined current during a predetermined duration so that the metal part 74 is heated, stopping supplying the metal part 74 with the predetermined current and then activating the heating element heating the ceramic part 72.

According to another embodiment, the control law comprises simultaneously supplying the metal part 74 with a predetermined current so that the metal part 74 is heated and activating the heating element heating the ceramic part 72.

According to still another embodiment, the control law comprises first activating the heating element heating the ceramic part 72 during a predetermined period and, once the predetermined period is over, supplying the metal part 74 with a predetermined current. The control law may comprise the activation of the heating element heating the ceramic part 72 after the predetermined period.

Claims

1. An aerosol generating device (11 ) configured to operate with a flat-shaped tobacco article (12) and comprising a flat-shaped heating chamber (50); the heating chamber (50) being configured to receive the flat-shaped tobacco article (12) and comprising a heating plate (70) forming at least partially a wall (54A, 54B) of the heating chamber (50); the heating plate (70) comprising a ceramic part (72) and a metal part (74) different from the ceramic part (72) and engaged with this ceramic part (72), the metal part (74) forming a metal flat surface portion (74S), both parts (72, 74) being arranged to heat the flat-shaped tobacco article (12).

2. The aerosol generating device according to claim 1 , wherein the ceramic part (72) extends around the metal part (74).

3. The aerosol generating device according to claim 1 or 2, wherein the ceramic part (72) defines a recess portion (78) receiving the metal part (74), the recess portion (78) preferably being a blind hole and having a depth substantially equal to 50% of a depth (D70) of the heating plate (70).

4. The aerosol generating device according to any one of claims 1 to 3, wherein the ceramic part (72) and the metal part (74) engaged with the ceramic part (72) form a flat surface (76) designed to be in contact with or face the flat-shaped tobacco article (12), the flat surface (76) comprising the metal flat surface portion (74S).

5. The aerosol generating device according to claim 4, wherein the metal part (74) forms at least 50%, preferably at least 60% and advantageously at least 70%, of the total area of the flat surface (76).

6. The aerosol generating device according to any one of claims 3 to 5, wherein the recess portion (78) forms a shape complementary to the external shape of the metal part (74) to tightly fit the metal part (74).

7. The aerosol generating device according to any one of claims 3 to 6, wherein the recess portion (78) forms a substantially parallelepiped shape with rounded corners.

8. The aerosol generating device according to any one of the preceding claims, wherein the heating plate (70) is designed to extend substantially along the whole area of a tobacco portion (15) comprised in the flat-shaped tobacco article (12).

9. The aerosol generating device according to claim 8, wherein both ceramic and metal parts (72, 74) are designed to be in contact with or face said tobacco portion (15) of the flat-shaped tobacco article (12).

10. The aerosol generating device according to any one of the preceding claims, wherein the ceramic part (72) is configured to be heated by thermal conduction by the metal part (74).

1 1 . The aerosol generating device according to any one of the preceding claims, wherein the heating chamber (50) comprises two heating plates (70) forming at least partially opposite walls of the heating chamber.

12. The aerosol generating device according to any one of the preceding claims, wherein the heating chamber (50) further comprises a heating element configured to heat the ceramic part (72).

13. The aerosol generating device according to claim 12, wherein the heating element is a resistive heating element arranged adjacent to the ceramic part (72), advantageously a heating track or a polyimide film heater arranged adjacent to the ceramic part (72), for example on an external surface of the ceramic part (72).

14. The aerosol generating device according to claim 13, wherein the heating element comprises a magnetic element and a plurality of susceptors comprised in the ceramic part (72), the magnetic element being able to cause heating of the plurality of susceptors by magnetic induction.

15. Method for controlling an aerosol generating device (11 ) according to any one of the preceding claims, comprising a step of heating the metal part (74), the heated metal part (74) heating the ceramic part (72) by thermal conduction.