AEROSOL-GENERATING DEVICE FOR INDUCTIVE HEATING OF AN AEROSOL-FORMING SUBSTRATE

Abstract

An aerosol-generating device is provided for generating an aerosol by inductive heating of an aerosol-forming substrate, the device including: a device housing including a cavity to removably receive the substrate; first and second induction coils arranged and configured to generate an alternating magnetic field within first and second sections of the cavity, respectively; and a control circuit to selectively drive the first and the second coils to selectively generate an alternating magnetic field within the first and the second sections, respectively, the circuit including: a first LC resonator circuit including the first coil and a first capacitor, and a second LC resonator circuit including the second coil and a second capacitor, the first and the second circuits having a first and a second resonance frequency, respectively, and a driving oscillator circuit including a common oscillator coil to selectively generate an alternating magnetic oscillator field. An aerosol-generating system is also provided.

Claims

1.-15. (canceled)

16. An aerosol-generating device for generating an aerosol by inductive heating of an aerosol-forming substrate, the aerosol-generating device comprising: a device housing comprising a cavity configured to removably receive the aerosol-forming substrate; at least a first induction coil and a second induction coil, wherein the first induction coil is arranged and configured to generate an alternating magnetic field within a first section of the cavity, and wherein the second induction coil is arranged and configured to generate an alternating magnetic field within a second section of the cavity; and a control circuit configured to selectively drive the first induction coil and the second induction coil to selectively generate an alternating magnetic field within the first and the second sections, respectively, the control circuit comprising: a first LC resonator circuit including the first induction coil and a first capacitor, and a second LC resonator circuit including the second induction coil and a second capacitor, wherein the first LC resonator circuit has a first resonance frequency and the second LC resonator circuit has a second resonance frequency that is different from the first resonance frequency, and a driving oscillator circuit comprising a common oscillator coil configured to selectively generate an alternating magnetic oscillator field having a frequency either close to or at the first resonance frequency, or close to or at the second resonance frequency, wherein the common oscillator coil is inductively coupled to the first induction coil and to the second induction coil such that an alternating magnetic field is generated within the first section when the frequency of the oscillator field is close to or at the first resonance frequency and thus close to or on resonance with the first LC resonator circuit, and an alternating magnetic field is generated within the second section when the frequency of the oscillator field is close to or at the second resonance frequency and thus close to or on resonance with the second LC resonator circuit.

17. The aerosol-generating device according to claim 16, wherein the first resonance frequency is in a range between 1 percent and 20 percent of the second resonance frequency.

18. The aerosol-generating device according to claim 16, wherein the first resonance frequency differs from the second resonance frequency by at least 40 kHz.

19. The aerosol-generating device according to claim 16, wherein the first resonance frequency differs from the second resonance frequency by at least 500 kHz.

20. The aerosol-generating device according to claim 16, wherein the first resonance frequency differs from the second resonance frequency by at least 1 MHz.

21. The aerosol-generating device according to claim 16, wherein the first resonance frequency and the second resonance frequency are in a range between 100 kHz and 30 MHz, in a range between 5 MHz and 15 MHz, or in a range between 5 MHz and 10 MHz.

22. The aerosol-generating device according to claim 16, wherein the common oscillator coil is arranged coaxially with each one of the first induction coil and the second induction coil.

23. The aerosol-generating device according to claim 16, wherein the common oscillator coil, the first induction coil, and the second induction coil are helical coils.

24. The aerosol-generating device according to claim 16, wherein the common oscillator coil at least partially surrounds each one of the first induction coil and the second induction coil.

25. The aerosol-generating device according to claim 16, wherein the driving oscillator circuit further comprises a single transistor switch selectively operable either at the first resonance frequency or at the second resonance frequency to drive the common oscillator coil either at the first resonance frequency or at the second resonance frequency.

26. The aerosol-generating device according to claim 16, wherein at least one of the first capacitor and the second capacitor has a capacitance in a range between 1 nF and 10 μF.

27. The aerosol-generating device according to claim 16, wherein an inductance of the first induction coil is equal to an inductance of the second induction coil, and wherein a capacitance of the first capacitor is smaller or larger than a capacitance of the second capacitor.

28. The aerosol-generating device according to claim 16, wherein an inductance of the first induction coil is equal to an inductance of the second induction coil, and wherein a capacitance of the first capacitor is 2 percent smaller or larger than a capacitance of the second capacitor.

29. The aerosol-generating device according to claim 16, wherein an inductance of the first induction coil is equal to an inductance of the second induction coil, and wherein a capacitance of the first capacitor is 10 percent smaller or larger than a capacitance of the second capacitor.

30. The aerosol-generating device according to claim 16, wherein at least one of the first LC resonator circuit and the second LC resonator circuit has a quality factor in a range between 2 and 50.

31. The aerosol-generating device according to claim 16, wherein at least one of the first LC resonator circuit and the second LC resonator circuit has a quality factor in a range between 2 and 20.

32. The aerosol-generating device according to claim 16, further comprising a magnetic flux concentrator configured to inductively couple the common oscillator coil to the first induction coil and to the second induction coil.

33. The aerosol-generating device according to claim 16, further comprising at least one susceptor arranged at least partially within the cavity and surrounded by the first induction coil and the second induction coil.

34. An aerosol-generating system, comprising: an aerosol-generating device according to claim 16; and an aerosol-generating article received or receivable at least partially in the cavity of the aerosol-generating device, wherein the aerosol-generating article comprises at least one aerosol-forming substrate to be heated.

35. The aerosol-generating system according to claim 34, wherein the aerosol-generating article further comprises at least one susceptor positioned in thermal proximity to or in thermal contact with the at least one aerosol-forming substrate such that the at least one susceptor is inductively heatable by an induction source when the aerosol-generating article is received in the cavity of the aerosol-generating device.

Description

[0066] The invention will be further described, by way of example only, with reference to the accompanying drawings, in which:

[0067] FIG. 1 shows a schematic cross-section of an aerosol-generating system in accordance with a first embodiment of the present invention;

[0068] FIG. 2 schematically illustrates an exemplary embodiment of a control circuit that can be used within the aerosol-generating system according to FIG. 1;

[0069] FIG. 3 shows a schematic cross-section of an aerosol-generating system in accordance with a second embodiment of the present invention;

[0070] FIG. 4 shows a schematic cross-section of an aerosol-generating system in accordance with a third embodiment of the present invention; and

[0071] FIG. 5 shows a schematic cross-section of an aerosol-generating system in accordance with a fourth embodiment of the present invention.

[0072] FIG. 1 schematically illustrates a first exemplary embodiment of an aerosol-generating system 1 according to the present invention. The system 1 is configured for generating an aerosol by inductively heating an aerosol-forming substrate 91, in particular section-wise or portion-wise. The system 1 comprises two main components: an aerosol-generating article 90 including the aerosol-forming substrate to be heated, and an aerosol-generating device 10 for use with the article 90. The device 10 comprises a cavity 20 for receiving the article 90, and an inductive heating arrangement 30 for heating the substrate within the article 90 when the article 90 is inserted into the cavity 20.

[0073] The article 90 has a rod shape substantially resembling the shape of a conventional cigarette. In the present embodiment, the article 90 comprises four elements arranged in coaxial alignment: a substrate segment 91, a support segment 92, an aerosol-cooling segment 94, and a filter segment 95. The substrate segment is arranged at a distal end of the article 90 and comprises the aerosol-forming substrate 91 to be heated. The aerosol-forming substrate may include, for example, a crimped sheet of homogenized tobacco material including glycerine as an aerosol-former. The support segment 92 comprises a hollow core forming a central air passage 93. The aerosol-cooling segment 94 is used for cooling volatilized components of the aerosol-forming substrate. The filter segment 95 serves as a mouthpiece and may include, for example, cellulose acetate fibers. All four elements are substantially cylindrical elements being arranged sequentially one after the other. The segments have substantially the same diameter and are circumscribed by an outer wrapper 99 made of cigarette paper such as to form a cylindrical rod.

[0074] The device 10 comprises a substantially rod-shaped main body 11 formed by a substantially cylindrical device housing. Within a distal portion 13, the device 10 comprises a power supply 16, for example a lithium ion battery, and a control circuitry 17 for controlling operation of the device 10, in particular for controlling the inductive heating process.

[0075] Within a proximal portion 14 opposite to the distal portion 13, the device 10 comprises the cavity 20. The cavity 20 is open at the proximal end 12 of device 10, thus allowing the article 90 to be readily inserted into the cavity 20. A bottom portion 25 of the cavity 20 separates the distal portion 13 of the device 10 from the proximal portion 14 of the device 10, in particular from the cavity 20. Preferably, the bottom portion 25 is made of a thermally insulating material, for example, PEEK (polyether ether ketone). Thus, electric components of the control circuitry 17 within the distal portion 13 may be kept separate from heat, aerosol or residues produced by the within the cavity 20 during heating of the substrate 91.

[0076] The aerosol-generating device 10 according to the present embodiment is configured to heat the aerosol-forming substrate within the substrate segment 91 sections-wise, that is, to separately heat different portions of the aerosol-forming substrate. In the present embodiment, the device 10 is configured to separately heat a first portion 96 and a section 97 of the aerosol-forming substrate. The imaginary separation of the aerosol-forming substrate into the first and section portion 96, 97 is indicated by the dotted line 98 in FIG. 1.

[0077] In order to heat the first and section portion 96, 97 separately, the inductive heating arrangement 30 comprises a first induction coil 31 and a second induction coil 32. The first induction coil 31 is arranged and configured to generate an alternating magnetic field within a first section 21 of the cavity 20, whereas the second induction coil 32 is arranged and configured to generate an alternating magnetic field within a second section of the cavity 22. The first and second sections 21, 22 of the cavity 20 are assigned to the locations of the first and section portion 96, 97 of the aerosol-forming substrate when the aerosol-generating article 90 is received in the cavity 20.

[0078] The inductive heating arrangement 30 further comprises a susceptor 60 that is arranged within the cavity 20 such that a first portion 61 of the susceptor 60 experiences the electromagnetic field generated by the first induction coil 31 and that a second portion 62 of the susceptor 60 experiences the electromagnetic field generated by the second induction coil 32.

[0079] In the present embodiment, the susceptor 60 is a susceptor blade which is attached to the bottom portion 25 of the cavity 20 with its distal end. From there, the susceptor blade extends into the inner void of the cavity 20 towards the opening of the cavity 20 at the proximal end 12 of the device 10. The other end of the susceptor blade 60, that is, the distal free end is tapered such as to allow the susceptor blade to readily penetrate the aerosol-forming substrate within the distal end portion of the article 90. As can be seen in FIG. 1, when the aerosol-generating article 90 is received in the cavity 20, the first portion 61 of the susceptor 60 is arranged within the first portion 96 of the aerosol-forming substrate, whereas the second portion 62 of the susceptor 60 is arranged within the second portion 97 of the substrate. Instead of a blade, the susceptor may also be a susceptor pin or a susceptor rod.

[0080] Hence, when activating the first induction coil 31, an alternating electromagnetic field is generated substantially only within the first section 21 of the cavity 20. As a consequence, heating generating eddy currents and/or hysteresis losses are induced substantially only in the first portion 61 of the susceptor 60, depending on the magnetic and electric properties of the susceptor material. Thus, it is substantially only the first portion 61 of the susceptor 60 which is heated, while the second portion 62 of the susceptor 60 remains substantially unheated, when the second induction 32 coil is inactive. Accordingly, only the first portion 96 of the substrate is heated such as to form an aerosol which can be drawn downstream through the aerosol-generating article 90 for inhalation by the user. Likewise, when activating the second induction coil 32 an alternating electromagnetic field is generated substantially only within the second section 22 of the cavity 20 causing only the second portion 62 of the susceptor 60 to be inductively heated, while the first portion 61 of the susceptor 60 remains substantially unheated. As a consequence, only the second portion 97 of the substrate is heated such as to form an aerosol which can be drawn downstream through the aerosol-generating article 90 for inhalation by the user.

[0081] In order to allow the first induction coil 31 and the second induction coil 32 being activated independently from each other and, thus, to selectively generate an alternating magnetic field either within the first section 21 or the second section 22 of the cavity 20, each coil 31, 32 is made part of a LC resonator circuit which has a distinct resonance frequency. Each LC resonator circuit is inductively coupled to a (common) driving oscillator coil 32 which can be selectively operated close to or at the distinct resonance frequencies. That is, the present invention is based on inductively driving the first and second induction coil 31, 32, however, each coil at a different driving frequency such as to inductively decouple the operation of the first and second induction coil 31, 32 from each other.

[0082] FIG. 2 schematically illustrates an exemplary embodiment of a control circuit 18 that may be used within the aerosol-generating system according to FIG. 1. According to the basic idea described above, the control circuit 18 comprises a first LC resonator circuit 51 and a second LC resonator circuit 52, wherein the first LC resonator circuit 51 includes the first induction coil 31 and a first capacitor 41, and wherein the second LC resonator circuit 52 includes the second induction coil 32 and a second capacitor 42: The first LC resonator circuit 51 has a first resonance frequency, whereas the second LC resonator circuit 52 has a second resonance frequency f2 that is different from the first resonance frequency f1. The control circuit 18 further comprises a driving oscillator circuit 35 comprising an oscillator coil 33 (also shown in FIG. 1) for selectively generating an alternating magnetic oscillator field either close to or at the first resonance frequency f1 or close to or at the second resonance frequency f2. The oscillator coil 33 is inductively coupled to both, to the first induction coil 31 and to the second induction coil 32. However, due to the difference between the first resonance frequency f1 and the second resonance frequency f2, the alternating magnetic oscillator field generated by the oscillator coil 33 substantially only couples into the first induction coil 31 or the first LC resonator circuit 51, respectively, when the frequency of the magnetic oscillator field is close to or equal to the first resonance frequency f1 of the first LC resonator circuit 51. Vice versa, the alternating magnetic oscillator field generated by the oscillator coil 33 substantially only couples into the second induction coil 32 or the second LC resonator circuit 52, respectively, when the frequency of the magnetic oscillator field is close to or equal to the second resonance frequency f2 of the second LC resonator circuit 52.

[0083] Accordingly, with reference to FIG. 1, an alternating magnetic field is generated within the first section 21 of the cavity 20, when the oscillator field is close to or at the first resonance frequency f1 and thus close to or on resonance with the first LC resonator circuit 51. Likewise, an alternating magnetic field is generated within the second section 22 of the cavity 21, when the oscillator field is close to or at the second resonance frequency f2 and thus close to or on resonance with the second LC resonator circuit.

[0084] Advantageously, the difference between the first resonance frequency f1 and the second resonance frequency f2 also prevents the respective inactive coil from carrying a current induced by the active coil as the inactive coil is sufficiently off-resonant with respect to the current operating frequency of the oscillator coil 33.

[0085] Preferably, the difference between the first resonance frequency f1 and the second resonance frequency f2 is at least 40 kHz (kilo-Hertz), in particular at least 100 kHz (kilo-Hertz), preferably at least 100 kHz (kilo-Hertz), more preferably at least 500 kHz (kilo-Hertz) or at least 1 MHz (Mega-Hertz). For example, the first resonance frequency differs from the second resonance frequency by 120 kHz (kilo-Hertz). The first resonance frequency and the second resonance frequency are preferably chosen to be in a range between 100 kHz (kilo-Hertz) to 30 MHz (Mega-Hertz), in particular between 5 MHz (Mega-Hertz) and 15 MHz (Mega-Hertz), preferably between 5 MHz (Mega-Hertz) and 10 MHz (Mega-Hertz). For example, the first resonance frequency may be 150 kHz (kilo-Hertz) and the second resonance frequency may be 270 kHz (kilo-Hertz).

[0086] The first induction coil 31 and second induction coil 32 may have, for example, an inductance in a range between 0.3 μH (micro-Henry) and 1.2 μH (micro-Henry), preferably between 0.6 μH (micro-Henry) and 0.9 μH (micro-Henry). Depending on the frequency of the magnetic field to be achieved, the values of the capacitance of the first capacitor 41 and the second capacitor 42 may be chosen correspondingly. Preferably, the first capacitor 41 and the second capacitor 42 have a capacitance in a range between 1 nF (nano-Farad) and 10 μF (micro-Farad), in particular between 10 nF (nano-Farad) and 2 μF (micro-Farad).

[0087] For driving the oscillator coil 33 either close to or at the first resonance f1 frequency, or close to or at the second resonance frequency f2, the driving oscillator circuit 35 according to the embodiment shown in FIG. 2 comprises a single transistor switch 70 which is selectively operable either close to or at the first resonance frequency f1, or close to or at the second resonance frequency f2. In the present embodiment, the switch 70 is a field effect transistor (FET) which has a gate input 71 to control the gate terminal. A source input 72 and a drain output 73 of the field effect transistor are in series connection with the oscillator coil 33 and a power source 16, which may correspond to the power source 16 shown in FIG. 1. Accordingly, by applying an alternating driving signal to the gate input 71—having a driving frequency close to or at the first or second resonance frequency f1, f2—the oscillator coil 33 is alternatingly switched on and off at that driving frequency. This switching on and off causes the oscillator coil 32 to generate a magnetic oscillator field close to or at the first or the second resonance frequency f1, f2 due to the changing magnetic flux inside the oscillator coil 33. The alternating driving signal is schematically illustrated in FIG. 2 by two square-wave signal with frequencies f1 and f2. Preferably, the alternating driving signal is generated and provide to the oscillator circuit 35 by means of the control 17 shown in FIG. 1.

[0088] As can be seen in FIG. 1, the first and the second induction coils 31, 32 are helical coils circumferentially surrounding the first and second section 21, 22 of the cylindrical cavity 20, respectively. The first and the second induction coils 31, 32 are each formed from a plurality of wire windings extending along the length axis of the respective coil 31. The wire may have any suitable cross-sectional shape, such as square, oval, or triangular. In this embodiment, the wire has a circular cross-section. In other embodiments, the wire may have a flat cross-sectional shape. The same basically holds for the oscillator coil 33.

[0089] As can be further seen in FIG. 1, the oscillator coil 33 is arranged coaxially with and partially around each one of the first induction coil 31 and the second induction coil 32. Advantageously, this increases the overlap between the magnetic fields of the different coils and thus increases the inductive coupling between the oscillator coil and the first and the second induction coil, respectively.

[0090] FIG. 3 shows a schematic cross-section of an aerosol-generating system 101 in accordance with a second embodiment of the present invention. The system 101 according to FIG. 3 is very similar to the system 1 according to FIG. 1. Therefore, identical or similar features are denoted with same reference numbers, yet incremented by 100. In contrast to the aerosol-generating system 1 according to the first embodiment, the system 101 according to the second embodiment comprises an aerosol-generating article 190 which includes a first aerosol-forming substrate 196 and a second aerosol-forming substrate 197 arranged sequentially one after the other at a distal end portion of the article 190. The first and the second aerosol-forming substrates 196, 197 differ from each other with regard to their compositions and ingredients for enriching the user's experience. Further in contrast to the system 1 according to FIG. 1, the system 101 according to FIG. 3 comprises two susceptors which are not part of the aerosol-generating device 110, but rather part of the aerosol-generating article 190. A strip-like first susceptor 161 is arranged within the first aerosol-forming substrate 196. In a similar way, a strip-like second susceptor 162 is arranged within the second aerosol-forming substrate 197. Both susceptors 161, 162 are arranged centrally within the respective aerosol-forming substrate extending substantially along the longitudinal center axis of the aerosol-generating article 190. In particular, the susceptors 161, 162 are formed as separate parts being spaced apart from each other, which causes both susceptors 161, 162 being thermally decoupled from each other.

[0091] Upon insertion of the article 190 into the cavity 120 of the device 110, the first susceptor 161 and the first aerosol-forming substrate 196 are arranged within the first section 121 of the cavity 120. Likewise, the second susceptor 162 and the second aerosol-forming substrate 197 are arranged within the second section 122 of the cavity 120. Hence, in use of the system 101, the first susceptor 161 experiences the magnetic field of the first induction coil 131, whereas the second susceptor 162 experiences the magnetic field of the second induction coil 132 allowing the first and the second aerosol-forming substrates 196, 197 being heated separately from each other.

[0092] The aerosol-generating device 110 according to the second embodiment further differs from the device 10 according to the first embodiment by a flux concentrator 180 that is coaxially arranged around the first induction coil 131, the second induction coil 132 and the oscillator coil 133. In the present embodiment, the flux concentrator 180 is a cylindrical element made of a material having a high relative magnetic permeability, for example, a ferromagnetic stainless steel. The flux concentrator 180 is arranged and configured to distort the magnetic field of the oscillator coil 133 towards the region of the magnetic field of the first induction coil 131 and the second induction coil 132, thereby increasing the magnetic coupling between the oscillator coil 133 and the first and second induction coil 131, 132. In addition, as described further above, the flux concentrator acts as a magnetic shield.

[0093] Apart from that, the aerosol-generating device at FIG. 3 is identical to the device according to FIG. 1.

[0094] FIG. 4 shows a schematic cross-section of an aerosol-generating system 201 in accordance with a third embodiment of the present invention. The system 201 according to FIG. 4 is very similar to the system 101 according to FIG. 3. Therefore, identical or similar features are denoted with same reference numbers, yet incremented by 100. In contrast to the aerosol-generating system 101 according to the second embodiment, the system 201 according to the third embodiment comprises a first susceptor 261 and a second susceptor 262 which are part of the aerosol-generating device 210, but not part of the article 290. In the present embodiment, the first and the second susceptor 261, 262 are susceptor sleeves.

[0095] The sleeve-like first susceptor 261 is arranged at the inner surface of the cavity 220, within the outer circumferential periphery of the first section 221 of the cavity 220. There, in use of the device 210, the first susceptor 261 experiences substantially only the magnetic field of the first induction coil 231 Likewise, the sleeve-like second susceptor 262 is arranged at the inner surface of the cavity 220, within the outer circumferential periphery of the second section 222 of the cavity 220. There, in use of the device 210, the second susceptor 262 experiences substantially only the magnetic field of the second induction coil 232. In particular, the first and the second susceptors 261, 262 are formed as separate parts being spaced apart from each other, which causes both susceptors 261, 262 being thermally decoupled from each other.

[0096] As described above with regard to FIG. 3, a first and a second aerosol-forming substrate 296, 297 are arranged within the article 290 such that upon insertion of the article 290 into the cavity 220 of the device 210, the first aerosol-forming substrate 296 is arranged within the first section 221 of the cavity 220 and the second aerosol-forming substrate 297 is arranged within the second section 222 of the cavity 220. Thus, the first and the second aerosol-forming substrates 296, 297 may be heated separately from each other.

[0097] FIG. 5 shows a schematic cross-section of an aerosol-generating system 301 in accordance with a fourth embodiment of the present invention. The system 301 according to FIG. 5 is very similar to the system 201 according to FIG. 4. Therefore, identical or similar features are denoted with same reference numbers, yet incremented by 100. In contrast to the third embodiment, the aerosol-generating device 310 according to the fourth embodiment comprises a single sleeve-like susceptor 360. The single sleeve-like susceptor 360 is arranged at the inner surface of the cavity 320 relative to a first and a second induction coil 331, 332 such that in use a first portion 361 of the susceptor 360 experiences the electromagnetic field generated by the first induction coil 331 and a second portion 362 of the susceptor 360 experiences the electromagnetic field generated by the second induction coil 332. Thus, the heating arrangement 330 of the device 310 may be used to heat different portions of an aerosol-forming substrate 391 separately. That is, when inserting an article 390 into the cavity 320 and activating the first induction coil 331, the first portion 361 of the susceptor 360 heats a first portion 396 of the aerosol-forming substrate. Likewise, when activating the second induction coil 332, the second portion 362 of the susceptor 360 heats a second portion 397 of the aerosol-forming substrate 391.

[0098] Further in contrast to the embodiment shown in FIGS. 1, 3 and 4, the aerosol-generating article 390 according to FIG. 5 does not comprise a support segment. Instead, the article according to FIG. 5 comprises a substrate segment 391 including the aerosol-forming substrate to be heated, an aerosol-cooling segment 392 adjacent to the substrate segment 391 for cooling volatilized components of the aerosol-forming substrate, a filter segment 394 adjacent to the aerosol-cooling segment 392 for filtering volatilized components of the aerosol-forming substrate as well as a mouth end segment 395 adjacent to the filter segment 394 for being received in a mouth of a user. In addition, the article 390 may comprise an end member (not shown) at its distal end opposite to the proximal end, that is, opposite of the mouth end segment 395.

[0099] For example, the substrate segment 391 may include an aerosol-forming substrate which comprises strands of homogenized tobacco and an aerosol former, such as glycerol (glycerine), propylene glycol, triacetin (glycerin triacetate) or combinations thereof.

[0100] The cooling segment 392 may comprise a hollow tube which defines an air channel for volatilized components of the heated aerosol-forming substrate to flow through and cool down. A thickness of the tube wall may be, for example, 0.29 millimeters. The length of the cooling segment 392 is preferably such that the cooling segment 392 will be partially inserted into the cavity 320, when the article 390 is fully inserted into the device 310. The length of the cooling segment 392 may be between 20 millimeters and 30 millimeters, in particular 23 millimeters and 27 millimeters, preferably 25 millimeters to 27 millimeters, for example, 25 millimeters. The cooling segment 392 may be made of paper, for example, a spirally wound paper tube.

[0101] The filter segment 394 may be formed of any filter material sufficient to remove one or more compounds volatilized from the aerosol-forming substrate. For example, the filter segment 394 may be made of a mono-acetate material, such as cellulose acetate. One or more flavors may be added to the filter segment 394 in the form of either direct injection of flavored liquids into the filter segment 394 or by embedding or arranging one or more flavored breakable capsules or other flavor carriers within, for example, the cellulose acetate tow of the filter segment 394. The filter segment 394 may have a length between 6 millimeters and 10 millimeters, for example 8 millimeters.

[0102] The mouth end segment 395 serves to prevent any liquid condensate that accumulates at the exit of the filter segment 394 from coming into direct contact with a user. Like the cooling segment 392, mouth end segment 395 may comprise a hollow, in particular annular tube which defines an air channel for volatilized components of the heated aerosol-forming substrate to flow therethrough. The length of the mouth end segment 395 may be between 6 millimeters and 10 millimeters, for example, 8 millimeters. The mouth end segment 395 may be made of paper, for example, a spirally wound paper tube. A thickness of the tube wall may be, for example, 0.29 millimeters.

[0103] In addition, the aerosol-generating article 390 according to FIG. 5 comprises a ventilation region to enable air to flow into the interior of the article 390 from the exterior of the article 390. For example, the ventilation region may take the form of one or more ventilation holes formed through the outer layer of the article 390. In particular, the ventilation region may comprise one or more rows of ventilation holes, wherein each row of holes is arranged circumferentially around the article 390 in a cross-section that is substantially perpendicular to a longitudinal axis of the article 390. Each row of ventilation holes may have between 12 to 36 ventilation holes. The ventilation holes may be between 100 to 500 micrometers in diameter. An axial separation between rows of ventilation holes may be between 0.25 millimeters and 0.75 millimeters, for example, 0.5 millimeters. In the present embodiment, the ventilation region comprises two rows of ventilation holes 393, each row being arranged circumferentially around the article 390. As can be seen in FIG. 5, the ventilation holes 393 are located in the cooling segment 392 to aid with the aerosol cooling. In particular, the ventilation holes 393 are arranged such that the ventilation holes 393 are located outside of the cavity 320 when the article 390 is received in the cavity 320, thus allowing non-heated air to enter the article 390 through the ventilation holes 393 from outside. For example, the ventilation holes 393 may be located at least 11 millimeters, in particular between 17 millimeters and 20 millimeters from the proximal end of the article 390. In any case, the location of the ventilation holes is preferably chosen such that a user does not block the ventilation holes 393 during use.

[0104] Of course, a ventilation region as describe above, in particular one or more ventilation holes as described above, may also be provided in the aerosol-generating articles 90, 190 and 290 shown in FIGS. 1, 3 and 4.

[0105] Together, the cooling segment 392, the filter segment 394 and the mouth end segment 395 may for a filter assembly. For example, the total length of the filter assembly may be between 37 millimeters and 45 millimeters. Preferably, the total length of the filter assembly is about 41 millimeters. The length of the substrate segment 391 may be between 34 millimeters and 50 millimeters, preferably between 38 millimeters and 46 millimeters, for example, 42 millimeters. The total length of the article 390 may be between 71 millimeters and 95 millimeters, preferably between 79 millimeters and 87 millimeters, for example, about 83 millimeters.

[0106] Like in the other embodiments shown in FIGS. 1, 3 and 4, all segments 391, 392, 394 and 395 of the article 390 according to FIG. 5 have substantially the same diameter and are circumscribed by an outer wrapper 399 made of cigarette paper such as to form a cylindrical rod.