INDUCTIVE HEATING ARRANGEMENT COMPRISING A TEMPERATURE SENSOR

Abstract

A method is provided for measuring a temperature of a susceptor of an inductive heating arrangement configured to heat an aerosol-forming substrate, the inductive heating arrangement including: a cavity to receive the substrate, at least one inductor coil configured to generate a varying magnetic field when a varying electric current flows through the at least one inductor coil, at least one susceptor arranged relative to the at least one inductor coil such that the at least one susceptor is heatable by penetration of the varying magnetic field, the at least one susceptor being configured to heat the substrate, and at least one temperature sensor; and the method including: providing the at least one temperature sensor in thermal contact with the at least one susceptor, and measuring the temperature of the at least one susceptor when the varying electric current does not flow through the at least one inductor coil.

Claims

1-25. (canceled)

26. A method for measuring a temperature of a susceptor of an inductive heating arrangement configured to heat an aerosol-forming substrate, the inductive heating arrangement comprising: a cavity configured to receive the aerosol-forming substrate heatable by the inductive heating arrangement, at least one inductor coil configured to generate a varying magnetic field when a varying electric current flows through the at least one inductor coil, at least one susceptor arranged relative to the at least one inductor coil such that the at least one susceptor is heatable by penetration of the varying magnetic field, the at least one susceptor being configured to heat the aerosol-forming substrate, and at least one temperature sensor; and the method comprising: providing the at least one temperature sensor in thermal contact with the at least one susceptor, and measuring the temperature of the at least one susceptor when the varying electric current does not flow through the at least one inductor coil.

27. The method of claim 26, further comprising: avoiding measuring the temperature of the at least one susceptor when the varying electric current flows through the at least one inductor coil.

28. The method of claim 26, wherein the at least one temperature sensor is a thermocouple.

29. The method of claim 28, wherein the at least one temperature sensor is a thermocouple comprising a first thermocouple wire and a second thermocouple wire, the first thermocouple wire extending from a first proximal end to a first distal end, the second thermocouple wire extending from a second proximal end to a second distal end, the first proximal end being joined to the second proximal end, thus forming a joint, the joint being in thermal contact with the at least one susceptor.

30. The method of claim 29, wherein the joint is in thermal contact with the at least one susceptor by means of a welding point.

31. The method of claim 29, wherein the first thermocouple wire and the second thermocouple wire have a diameter between about 5 micrometres and about 100 micrometres.

32. The method of claim 29, wherein the first thermocouple wire is surrounded by a first electrical insulation layer and the second thermocouple wire is surrounded by a second electrical insulation layer, the first and the second electrical insulation layers having a thickness between about 2 micrometres and about 10 micrometres.

33. The method of claim 32, wherein the first electrical insulation layer and the second electrical insulation layer comprise parylene.

34. The method of claim 29, wherein the at least one susceptor comprises a thermal insulator arranged for thermally insulating the at least one susceptor from the first thermocouple wire and the second thermocouple wire.

35. The method of claim 29, wherein the first thermocouple wire comprises chromel and the second thermocouple wire comprises alumel.

36. The method of claim 26, wherein the at least one temperature sensor is a resistive temperature device, the resistive temperature device comprising a resistive element such that a resistance of the resistive element increases when a temperature of the resistive element increases.

37. The method of claim 36, wherein the resistive element of the resistive temperature device comprises platinum.

38. The method of claim 26, wherein the at least one inductor coil comprises a first inductor coil and a second inductor coil, the first inductor coil being configured to generate a first varying magnetic field when a first varying electric current flows through the first inductor coil and the second inductor coil being configured to generate a second varying magnetic field when a second varying electric current flows through the second inductor coil, wherein the at least one susceptor comprises a first susceptor and a second susceptor, the first susceptor arranged relative to the first inductor coil such that the first susceptor is heatable by penetration of the first varying magnetic field, the second susceptor arranged relative to the second inductor coil such that the second susceptor is heatable by penetration of the second varying magnetic field, the first susceptor and the second susceptor being configured to heat the aerosol-forming substrate, and the method further comprising: providing the at least one temperature sensor in thermal contact with the first susceptor, and measuring the temperature of the first susceptor when the first varying electric current does not flow through the first inductor coil.

39. The method of claim 38, further comprising: avoiding measuring the temperature of the first susceptor when the first varying electric current flows through the first inductor coil.

40. The method of claim 38, wherein the at least one temperature sensor comprises a first temperature sensor and a second temperature sensor, and the method further comprising: providing the first temperature sensor in thermal contact with the first susceptor, measuring the temperature of the first susceptor when the first varying electric current does not flow through the first inductor coil, providing the second temperature sensor in thermal contact with the second susceptor, and measuring the temperature of the second susceptor when the second varying electric current does not flow through the second inductor coil.

41. The method of claim 40, further comprising: avoiding measuring the temperature of the first susceptor when the first varying electric current flows through the first inductor coil; and avoiding measuring the temperature of the second susceptor when the second varying electric current flows through the second inductor coil.

42. An inductive heating arrangement, comprising: a cavity configured to receive an aerosol-forming substrate heatable by the inductive heating arrangement; at least one inductor coil configured to generate a varying magnetic field when a varying electric current flows through the at least one inductor coil; at least one susceptor arranged relative to the at least one inductor coil such that the at least one susceptor is heatable by penetration of the varying magnetic field, the at least one susceptor being configured to heat the aerosol-forming substrate; and a thermocouple comprising a first thermocouple wire and a second thermocouple wire, the first thermocouple wire extending from a first proximal end to a first distal end, the second thermocouple wire extending from a second proximal end to a second distal end, the first proximal end being joined to the second proximal end, thus forming a joint, the joint being in thermal contact with the at least one susceptor, wherein the first thermocouple wire and the second thermocouple wire have a diameter between about 5 micrometres and about 100 micrometres.

43. The inductive heating arrangement of claim 42, wherein the at least one susceptor is a tubular susceptor.

44. The inductive heating arrangement of claim 43, wherein the tubular susceptor at least partially defines the cavity configured to receive the aerosol-forming substrate.

45. The inductive heating arrangement of claim 43, wherein the tubular susceptor comprises a tubular support body and a susceptor layer provided on an internal surface of the tubular support body.

46. The inductive heating arrangement of claim 42, wherein the first thermocouple wire is surrounded by a first electrical insulation layer and the second thermocouple wire is surrounded by a second electrical insulation layer, the first and the second electrical insulation layers having a thickness between about 2 micrometres and about 10 micrometres.

47. The inductive heating arrangement of claim 46, wherein the first electrical insulation layer and the second electrical insulation layer comprise parylene.

48. The inductive heating arrangement of claim 42, wherein the first thermocouple wire comprises chromel and the second thermocouple wire comprises alumel.

49. An aerosol-generating device, comprising: the inductive heating arrangement of claim 42; a device housing; and a power supply electrically connected to the inductive heating arrangement and configured to provide a varying electric current to the at least one inductor coil.

50. An aerosol-generating system, comprising: an aerosol-generating article comprising an aerosol-forming substrate; and the aerosol-generating device of claim 49.

Description

[0112] These and other features and advantages of the invention will become more evident in the light of the following detailed description of preferred embodiments, given only by way of illustrative and non-limiting example, in reference to the attached figures:

[0113] FIG. 1 shows a schematic flow diagram of a method for measuring the temperature of a susceptor of an inductive heating arrangement.

[0114] FIG. 2 illustrates an inductive heating arrangement comprising an inductor coil, a susceptor, a cavity for receiving an aerosol-forming substrate and a temperature sensor.

[0115] FIG. 3 depicts an inductive heating arrangement comprising a first and a second inductor coil, a first and a second susceptor, a first and a second portion of the cavity for receiving an aerosol-forming substrate and a first and a second temperature sensor.

[0116] FIG. 4 depicts an inductive heating arrangement comprising a first and a second inductor coil, a susceptor, a cavity for receiving an aerosol-forming substrate and a first and a second temperature sensor.

[0117] FIG. 5 shows a thermocouple in thermal contact with the susceptor.

[0118] FIG. 6 shows a resistive temperature device in thermal contact with the susceptor.

[0119] FIG. 7 is a representation of an aerosol-generating system comprising an aerosol-generating article and an aerosol-generating device, the aerosol-generating device comprising an inductive heating arrangement.

[0120] FIG. 8 shows the aerosol-generating system of FIG. 7 when the aerosol-forming substrate of the aerosol-generating article is received in the cavity of the inductive heating arrangement.

[0121] FIG. 9 shows an aerosol-generating article comprising a filter assembly which includes a cooling segment, a filter segment and a mouth end segment.

[0122] FIG. 1 schematically represents a method for measuring the temperature of a susceptor in an inductive heating arrangement 10. Detailed embodiments of such inductive heating arrangement 10 are described with respect to FIGS. 2 to 8. The method of FIG. 1 comprises a step A whereby a temperature sensor 13 of the inductive heating arrangement 10 is provided in thermal contact with a susceptor 11 of the inductive heating arrangement 10. The method of FIG. 1 further comprises a step B whereby the temperature of the susceptor 11 is measured when a varying electric current does not flow through an inductor coil 12 of the inductive heating arrangement 10. The inductor coil 12 is configured to generate a varying magnetic field when such varying current flows through the inductor coil 12. The susceptor 11 is arranged relative to the inductor coil 12 coil in such a way that the susceptor 11 is heatable by penetration of the varying magnetic field. The susceptor 11 is configured to heat an aerosol-forming substrate. In an example of the embodiment of FIG. 1, the method further comprises a step C, represented in dashed lines. Step C consists of avoiding measuring the temperature of the susceptor 11 when the varying electric current flows through the inductor coil 12.

[0123] FIG. 2 shows the inductive heating arrangement 10 comprising the susceptor 11 and the inductor coil 12. As has been explained for FIG. 1, the inductor coil 12 is configured to generate a varying magnetic field when a varying electric current flows through the inductor coil 12. The susceptor 11 is arranged relative to the inductor coil 12 in such a way that the susceptor 11 is heatable by penetration of the varying magnetic field that may be generated by the inductor coil 12. The susceptor 11 is configured to heat an aerosol-forming substrate. Put another way, when the susceptor 11 is heated by penetration of the varying magnetic field, the aerosol-forming substrate may be heated by the susceptor. The aerosol-forming substrate heatable by the susceptor may be received in a cavity 14 of the inductive heating arrangement 10. In the embodiment of FIG. 2, the susceptor 11 is a tubular susceptor 11, the tubular susceptor defining the cavity 14 for receiving the aerosol-forming substrate.

[0124] A temperature sensor 13 is provided in thermal contact with the susceptor 11. As a result, the temperature sensor 13 may be used to measure the temperature of the susceptor 11. The measurement of the temperature of the susceptor 11 may be carried out when the varying electric current does not flow through the inductor coil 12. In particular, it may be avoided measuring the temperature of the susceptor 11 when the varying electric current flows through the inductor coil 12. This method improves the accuracy of the measurement of the temperature of the susceptor 11, since currents that may be induced in the temperature sensor 13 by the magnetic field generated by the inductor coil 12 are minimised. Such induced currents may lead to erroneous measurements of the temperature of the susceptor 11.

[0125] FIG. 3 illustrates an inductive heating arrangement 10 comprising a first susceptor 11 and a second susceptor 15. The inductive heating arrangement 10 also comprises a first inductor coil 12 and a second inductor coil 16. The first inductor coil 12 is configured to generate a first varying magnetic field when a first varying electric current flows through the first inductor coil 12. The second inductor coil 16 is configured to generate a second varying magnetic field when a second varying electric current flows through the second inductor coil 16. The first susceptor 11 is arranged relative to the first inductor coil 12 in such a way that the first susceptor 11 is heatable by penetration of the first varying magnetic field. The second susceptor 15 is arranged relative to the second inductor coil 16 in such a way that the second susceptor 15 is heatable by penetration of the second varying magnetic field. Therefore, when the first susceptor 11 is heated by penetration of the first varying magnetic field, the aerosol-forming substrate may be heated by the first susceptor 11. Likewise, when the second susceptor 15 is heated by penetration of the second varying magnetic field, the aerosol-forming substrate may be heated by the second susceptor 15.

[0126] The temperature sensor of the embodiment of FIG. 3 comprises a first temperature sensor 13 and a second temperature sensor 17. The first temperature sensor 13 is provided in thermal contact with the first susceptor 11. As a result, the first temperature sensor 13 may be used to measure the temperature of the first susceptor 11. The measurement of the temperature of the first susceptor 11 may be carried out when the first varying electric current does not flow through the first inductor coil 12. In particular, it may be avoided measuring the temperature of the first susceptor 11 when the first varying electric current flows through the first inductor coil 12.

[0127] The second temperature sensor 17 is provided in thermal contact with the second susceptor 15. As a result, the second temperature sensor 17 may be used to measure the temperature of the second susceptor 15. The measurement of the temperature of the second susceptor 15 may be carried out when the second varying electric current does not flow through the second inductor coil 16. In particular, it may be avoided measuring the temperature of the second susceptor 15 when the second varying electric current flows through the second inductor coil 16.

[0128] This method improves the accuracy of the measurements of the temperatures of the first susceptor 11 and the second susceptor 15, since currents that may be induced in the first temperature sensor 13 and the second temperature sensor 17 by the first and second magnetic fields respectively generated by the first inductor coil 12 and the second inductor coil 16 are minimised. Such induced currents may lead to erroneous measurements of the temperatures of the first susceptor 11 and the second susceptor 15.

[0129] In the embodiment of FIG. 3, the first susceptor 11 is a tubular susceptor, the tubular susceptor defining a first portion 14 of the cavity for receiving the aerosol-forming substrate. Likewise, the second susceptor 15 is a tubular susceptor, the tubular susceptor defining a second portion 18 of the cavity for receiving the aerosol-forming substrate.

[0130] The embodiment of FIG. 3 enables selective heating of the first susceptor 11 and the second susceptor 15. Such selective heating enables the inductive heating arrangement 10 to heat different portions of an aerosol-forming substrate at different times, when the aerosol-forming substrate is received in the first portion 14 and the second portion 18 of the cavity, and may enable one of the susceptors 11, 15 to be heated to a different temperature than the other susceptor 15, 11. Such temperatures may be advantageously measured by using the method of FIG. 1.

[0131] FIG. 4 illustrates an inductive heating arrangement 10 comprising a single susceptor 11 having a first region 111 and a second region 112. The inductive heating arrangement 10 also comprises a first inductor coil 12 and a second inductor coil 16. The first inductor coil 12 is configured to generate a first varying magnetic field when a first varying electric current flows through the first inductor coil 12. The second inductor coil 16 is configured to generate a second varying magnetic field when a second varying electric current flows through the second inductor coil 16. The first region 111 is arranged relative to the first inductor coil 12 in such a way that the first region 111 is heatable by penetration of the first varying magnetic field. The second region 112 is arranged relative to the second inductor coil 16 in such a way that the second region 112 is heatable by penetration of the second varying magnetic field. Therefore, when the first region 111 is heated by penetration of the first varying magnetic field, the aerosol-forming substrate may be heated by the first region 111. Likewise, when the second region 112 is heated by penetration of the second varying magnetic field, the aerosol-forming substrate may be heated by the second region 112.

[0132] The temperature sensor of the embodiment of FIG. 4 comprises a first temperature sensor 13 and a second temperature sensor 17. The first temperature sensor 13 is provided in thermal contact with the first region 111. As a result, the first temperature sensor 13 may be used to measure the temperature of the first region 111. The measurement of the temperature of the first region 111 may be carried out when the first varying electric current does not flow through the first inductor coil 12. In particular, it may be avoided measuring the temperature of the first region 111 when the first varying electric current flows through the first inductor coil 12.

[0133] The second temperature sensor 17 is provided in thermal contact with the second region 112. As a result, the second temperature sensor 17 may be used to measure the temperature of the second region 112. The measurement of the temperature of the second region 112 may be carried out when the second varying electric current does not flow through the second inductor coil 16. In particular, it may be avoided measuring the temperature of the second region 112 when the second varying electric current flows through the second inductor coil 16.

[0134] This method improves the accuracy of the measurements of the temperatures of the first region 111 and the second region 112 of the susceptor 11, since currents that may be induced in the first temperature sensor 13 and the second temperature sensor 17 by the first and second magnetic fields respectively generated by the first inductor coil 12 and the second inductor coil 16 are minimised. Such induced currents may lead to erroneous measurements of the temperatures of the first region 111 and the second region 112.

[0135] In the embodiment of FIG. 4, the susceptor 11 is a tubular susceptor, the tubular susceptor defining a cavity 14 for receiving the aerosol-forming substrate.

[0136] The embodiment of FIG. 4 enables selective heating of the first region 111 and the second region 112. Such selective heating enables the inductive heating arrangement 10 to heat different portions of an aerosol-forming substrate at different times, when the aerosol-forming substrate is received in the cavity 14, and may enable one of the regions 111, 112 to be heated to a different temperature than the other region 112, 111. Such temperatures may be advantageously measured by using the method of FIG. 1.

[0137] FIG. 5 represents in more detail the thermal contact between the temperature sensor 13 and the susceptor 11. In particular, the temperature sensor 13 of the embodiment of FIG. 5 is a thermocouple 131. The thermocouple 131 comprises a first thermocouple wire 132 and a second thermocouple wire 133. The first thermocouple wire 132 extends from a first proximal end 136 to a first distal end (not represented). The second thermocouple wire 133 extends from a second proximal end 137 to a second distal end (not represented). The first proximal end 136 is joined to the second proximal end 137 forming a joint 138 in thermal contact with susceptor 11. In the embodiment of FIG. 5, the joint 138 is in thermal contact with the susceptor 11 through a welding point 139.

[0138] In the embodiment of FIG. 5, the first thermocouple wire 132 has a first diameter D1 and the second thermocouple wire 133 has a second diameter D2. The first diameter D1 and the second diameter D2 are between about 5 micrometres and about 100 micrometres, preferably between about 45 micrometres and about 55 micrometres. Such diameters D1, D2 may contribute to a quick temperature stabilisation of the first thermocouple wire 132 and the second thermocouple wire 133.

[0139] In FIG. 5, the first thermocouple wire 132 is surrounded by a first electrical insulation layer 134 and the second thermocouple wire 133 is surrounded by a second electrical insulation layer 135. The first electrical insulation layer 134 has a first thickness t1 and the second electrical insulation layer 135 has a second thickness t2. Such thicknesses t1, t2 are between about 2 micrometres and about 10 micrometres, which may help achieve a quick temperature stabilisation in the first thermocouple wire 132 and the second thermocouple wire 133.

[0140] The first electrical insulation layer 134 and the second electrical insulation layer 135 of the embodiment of FIG. 5 comprise parylene. Likewise, the first thermocouple wire 132 comprises chromel and the second thermocouple wire 133 comprises alumel.

[0141] In FIG. 5, the susceptor 11 comprises a thermal insulator 19 arranged for thermally insulating the susceptor 11 from the first thermocouple wire 132 and the second thermocouple wire 133. This arrangement may help ensure that the thermocouple 131 is in thermal contact with the susceptor 11 only through the joint 138 and the welding point 139. This may also enhance the accuracy of the measurement of the temperature of the susceptor 11.

[0142] In FIG. 6, the temperature sensor 13 is a resistive temperature device 139. The resistive temperature device 139 comprises a resistive element 140 whose resistance increases when its temperature increases. Wiring 141 is provided to connect the resistive element 139 to a measuring device configured to measure a resistance of a circuit formed from the resistive element 140 and the wiring 141.

[0143] A correlation may be established between the resistance of the resistive element 140 and the temperature of the resistive element 140. This way, the temperature of the resistive element 140, which corresponds to the temperature of the susceptor 11 in thermal contact with the resistive element 140, may be obtained by measuring the resistance of the resistive element 140. The resistive element 140 is preferably formed from metal. More preferably, the resistive element 140 comprises at least one of platinum and nickel.

[0144] The wiring 141 may be designed in such a way that the resistance of the circuit formed from the resistive element 140 and the wiring 141 is substantially the same as the resistance of the resistive element 141. Put another way, the configuration of the wiring 141 may reduce the error in the measurement of the resistance of the resistive element 140.

[0145] In an example, the wiring 141 comprises two wires connecting opposite ends of the resistive element 141 to the measuring device. In this example, the resistance of the circuit formed from the resistive element 140 and the wiring 141 is equal to the resistance of the resistive element 141 plus the resistance of each one of the two wires. This may cause that the temperature measured by the resistive temperature device 139 is greater than the temperature of the resistive element 140, which corresponds to the temperature of the susceptor 11.

[0146] In another example, the wiring 141 comprises three wires. Two wires connect one end of the resistive element 141 to the measuring device. The remaining wire connects the opposite end of the resistive element 141 to the measurement device. The three wires of the wiring 141 may be identical in material and length. Such three wires may have a similar resistance. The resistance of the circuit formed from the resistive element 140 and the wiring 141 may be measured exclusively through the two wires on the same end of the resistive element 140. Such first measurement will indicate the total resistance of those two wires. Likewise, the resistance of the circuit formed from resistive element 140 and the wiring 141 may be measured through the wire on the opposite end of the resistive element 140 and one of the other two wires. Such second measurement will indicate the resistance of the resistive element 140 plus the total resistance of the two wires used for the measurement. When the resistance of the three wires is the same, a more accurate measurement of the resistance of the resistive element 140 may be obtained by subtracting the value of the first measurement from the value of the second measurement.

[0147] Other configurations of wiring 141 known in the art, such as a wiring 141 comprising four wires, can also be used in the present invention.

[0148] FIGS. 7 and 8 show schematic cross-sections of an aerosol-generating device 200 and the aerosol-generating article 300.

[0149] The aerosol-generating device 200 comprises a substantially cylindrical device housing 202, with a shape and size similar to a conventional cigar.

[0150] The aerosol-generating device 200 further comprises a power supply 206, in the form of a rechargeable nickel-cadmium battery, a controller 208 in the form of a printed circuit board including a microprocessor, an electrical connector 209, and the inductive heating arrangement 10. In the embodiment of FIGS. 7 and 8, the inductive heating arrangement 10 is similar to that of FIG. 3. However, other inductive heating arrangements may be used. In particular, inductive heating arrangements comprising one inductor coil and one susceptor may be used. Alternatively, inductive heating arrangements comprising more than two inductor coils and more than two susceptors may be used. In a preferred alternative, inductive heating arrangements comprising one susceptor, two inductor coils and two temperature sensors may be used; in particular, the inductive heating arrangement of FIG. 4 can be used.

[0151] The power supply 206, controller 208 and inductive heating arrangement 10 are all housed within the device housing 202. The inductive heating arrangement 10 of the aerosol-generating device 200 is arranged at the proximal end of the device 200. The electrical connector 209 is arranged at a distal end of the device housing 202.

[0152] As used herein, the term “proximal” refers to a user end, or mouth end of the aerosol-generating device or aerosol-generating article. The proximal end of a component of an aerosol-generating device or an aerosol-generating article is the end of the component closest to the user end, or mouth end of the aerosol-generating device or the aerosol-generating article. As used herein, the term “distal” refers to the end opposite the proximal end.

[0153] The controller 208 is configured to control the supply of power from the power supply 206 to the inductive heating arrangement 10. The controller 208 further comprises a DC/AC inverter, including a Class-D power amplifier. The controller 208 is also configured to control recharging of the power supply 206 from the electrical connector 209. The controller 208 further comprises a puff sensor (not shown) configured to sense when a user is drawing on an aerosol-generating article received in the cavity 14, 18.

[0154] The inductive heating arrangement 10 comprises a first inductor coil 12 and a second inductor coil 16. The inductive heating arrangement 10 also comprises a first susceptor 11 and a second susceptor 15. As described for FIG. 3, the first susceptor 11 is a tubular susceptor, the tubular susceptor defining a first portion 14 of the cavity for receiving the aerosol-forming substrate. Likewise, the second susceptor 15 is a tubular susceptor, the tubular susceptor defining a second portion 18 of the cavity for receiving the aerosol-forming substrate. The first 12 and second 16 inductor coils are also tubular in the embodiment of FIGS. 7 and 8, and they are disposed concentrically around, respectively, the first susceptor 11 and the second susceptor 15.

[0155] The first inductor coil 12 is connected to the controller 208 and the power supply 206, and the controller 208 is configured to supply a first varying electric current to the first inductor coil 12. When the first varying electric current is supplied to the first inductor coil 12, the first inductor coil 12 generates a first varying magnetic field, which heats the first susceptor 11 by induction.

[0156] The second inductor coil 16 is connected to the controller 208 and the power supply 208, and the controller 208 is configured to supply a second varying electric current to the second inductor coil 16. When the second varying electric current is supplied to the second inductor coil 16, the second inductor coil 16 generates a second varying magnetic field, which heats the second susceptor 15 by induction.

[0157] The inductive heating arrangement 10 comprises a first temperature sensor 13 in thermal contact with the first susceptor 11. The inductive heating arrangement 10 comprises a second temperature sensor 17 in thermal contact with the second susceptor 15. The first 13 and second 17 temperature sensors may be used to respectively measure the temperatures of the first susceptor 11 and the second susceptor 15 as described for FIG. 3.

[0158] The device housing 202 also defines an air inlet 280 in close proximity to the distal end of the cavity 14, 18 for receiving the aerosol-forming substrate. The air inlet 280 is configured to enable ambient air to be drawn into the device housing 202. Airflow pathways are defined through the device to enable air to be drawn from the air inlet 280 into the cavity 14, 18.

[0159] The aerosol-generating article 300 is generally in the form of a cylindrical rod, having a diameter similar to the inner diameter of the cavity 14, 18 for receiving the aerosol-forming substrate. The aerosol-generating article 300 comprises a cylindrical cellulose acetate filter plug 304 and a cylindrical aerosol-generating segment 310 wrapped together by an outer wrapper 320 of cigarette paper.

[0160] The filter plug 304 is arranged at a proximal end of the aerosol-generating article 300, and forms the mouthpiece of the aerosol-generating system, on which a user draws to receive aerosol generated by the system.

[0161] The aerosol-generating segment 310 is arranged at a distal end of the aerosol-generating article 300, and has a length substantially equal to the length of the cavity 14, 18. The aerosol-generating segment 310 comprises a plurality of aerosol-forming substrates, including: a first aerosol-forming substrate 312 at a distal end of the aerosol-generating article 300 and a second aerosol-forming substrate 314 at a proximal end of the aerosol-generating segment 210, adjacent the first aerosol-forming substrate 312. It will be appreciated that in some embodiments two or more of the aerosol-forming substrates may be formed from the same materials. However, in this embodiment, each of the aerosol-forming substrates 312, 314 is different. The first aerosol-forming substrate 312 comprises a gathered and crimped sheet of homogenised tobacco material, without additional flavourings. The second aerosol-forming substrate 314 comprises a gathered and crimped sheet of homogenised tobacco material including a flavouring in the form of menthol. In other examples, an aerosol-forming substrate may comprise a flavouring in the form of menthol, and not comprise tobacco material or any other source of nicotine. Each of the aerosol-forming substrates 312, 314 may also comprise further components, such as one or more aerosol formers and water, such that heating the aerosol-forming substrate generates an aerosol with desirable organoleptic properties.

[0162] The proximal end of the first aerosol-forming substrate 312 is exposed, as it is not covered by an outer wrapper 320. The outer wrapper 320 comprises a line of perforations 322 circumscribing the aerosol-generating article 300 at the interface between the first aerosol-forming substrate 312 and the second aerosol-forming substrate 314. The perforations 322, enable air to be drawn into the aerosol-generating segment 310.

[0163] In this embodiment, the first aerosol-forming substrate 312 and the second aerosol-forming substrate 314 are arranged end-to-end. However, it is envisaged that in other embodiments, a separation may be provided between the first aerosol-forming substrate 312 and the second aerosol-forming substrate 314.

[0164] FIG. 9 shows an aerosol-generating article similar to those of FIGS. 7 and 8. However, the filter plug 304 is a filter assembly 304 in the form of a rod. The filter assembly 304 includes three segments: a cooling segment 307, a filter segment 309 and a mouth end segment 311. In the embodiment of FIG. 9, the cooling segment 307 is located adjacent the second aerosol-forming substrate 314, between the second aerosol-forming substrate 314 and the filter segment 309, such that the cooling segment 307 is in an abutting relationship with the second aerosol-forming substrate 314 and the filter segment 309. In other examples, there may be a separation between the second aerosol-forming substrate 314 and the cooling segment 307 and between the cooling segment 307 and the filter segment 309. The filter segment 309 is located in between the cooling segment 307 and the mouth end segment 311. The mouth end segment 311 is located towards the proximal end of the article 300, adjacent the filter segment 309. In the embodiment of FIG. 9, the filter segment 309 is in an abutting relationship with the mouth end segment 311. In one example, the total length of the filter assembly 304 is between 37 millimetres and 45 millimetres, more preferably, the total length of the filter assembly 304 is 41 millimetres.

[0165] In one example of the embodiment of FIG. 9, the aerosol-generating segment 310 is between 34 millimetres and 50 millimetres in length, more preferably, the aerosol-generating segment 310 is between 38 millimetres and 46 millimetres in length, more preferably still, the aerosol-generating segment 310 is 42 millimetres in length.

[0166] In one example of the embodiment of FIG. 9, the total length of the article 300 is between 71 millimetres and 95 millimetres, more preferably, the total length of the article 300 is between 79 millimetres and 87 millimetres, more preferably still, the total length of the article 300 is 83 millimetres.

[0167] In one example, the cooling segment 307 is an annular tube and defines an air gap within the cooling segment 307. The air gap provides a chamber for heated volatilised components generated from the aerosol-generating segment 310 to flow. The cooling segment 307 is hollow to provide a chamber for aerosol accumulation yet rigid enough to withstand axial compressive forces and bending moments that might arise during manufacture and whilst the article 300 is in use during insertion into the aerosol-generating device 200. In one example, the thickness of the wall of the cooling segment 307 is approximately 0.29 millimetres.

[0168] The cooling segment 307 provides a physical displacement between the aerosol-generating segment 310 and the filter segment 309. The physical displacement provided by the cooling segment 307 will provide a thermal gradient across the length of the cooling segment 307. In one example the cooling segment 307 is configured to provide a temperature differential of at least 40 degrees Celsius between a heated volatilised component entering a distal end of the cooling segment 307 and a heated volatilised component exiting a proximal end of the cooling segment 307. In one example the cooling segment 307 is configured to provide a temperature differential of at least 60 degrees Celsius between a heated volatilised component entering a distal end of the cooling segment 307 and a heated volatilised component exiting a proximal end of the cooling segment 307. This temperature differential across the length of the cooling element 307 protects the temperature sensitive filter segment 309 from the high temperatures of the aerosol formed from the aerosol-generating segment 310.

[0169] In one example of the article 300 of FIG. 9, the length of the cooling segment 307 is at least 15 millimetres. In one example, the length of the cooling segment 307 is between 20 millimetres and 30 millimetres, more particularly 23 millimetres to 27 millimetres, more particularly 25 millimetres to 27 millimetres and more particularly 25 millimetres.

[0170] The cooling segment 307 is made of paper, which means that it is comprised of a material that does not generate compounds of concern. In one example of the article 300 of FIG. 9, the cooling segment 307 is manufactured from a spirally wound paper tube which provides a hollow internal chamber yet maintains mechanical rigidity. Spirally wound paper tubes are able to meet the tight dimensional accuracy requirements of high-speed manufacturing processes with respect to tube length, outer diameter, roundness and straightness. In another example, the cooling segment 307 is a recess created from stiff plug wrap or tipping paper. The stiff plug wrap or tipping paper is manufactured to have a rigidity that is sufficient to withstand the axial compressive forces and bending moments that might arise during manufacture and whilst the article 300 is in use during insertion into the aerosol-generating device 200.

[0171] For each of the examples of the cooling segment 307, the dimensional accuracy of the cooling segment is sufficient to meet the dimensional accuracy requirements of high-speed manufacturing process.

[0172] The filter segment 309 may be formed of any filter material sufficient to remove one or more volatilised compounds from heated volatilised components from the aerosol-generating segment 310. In one example of the article 300 of FIG. 9, the filter segment 309 is made of a mono-acetate material, such as cellulose acetate. The filter segment 309 provides cooling and irritation-reduction from the heated volatilised components without depleting the quantity of the heated volatilised components to an unsatisfactory level for a user.

[0173] The density of the cellulose acetate tow material of the filter segment 309 controls the pressure drop across the filter segment 309, which in turn controls the draw resistance of the article 300. Therefore the selection of the material of the filter segment 309 is important in controlling the resistance to draw of the article 300. In addition, the filter segment performs a filtration function in the article 300.

[0174] The presence of the filter segment 309 provides an insulating effect by providing further cooling to the heated volatilised components that exit the cooling segment 307. This further cooling effect reduces the contact temperature of the user's lips on the surface of the filter segment 309.

[0175] One or more flavours may be added to the filter segment 309 in the form of either direct injection of flavoured liquids into the filter segment 309 or by embedding or arranging one or more flavoured breakable capsules or other flavour carriers within the cellulose acetate tow of the filter segment 309. In one example of the article 300 of FIG. 9, the filter segment 309 is between 6 millimetres to 10 millimetres in length, more preferably 8 millimetres.

[0176] The mouth end segment 311 is an annular tube and defines an air gap within the mouth end segment 311. The air gap provides a chamber for heated volatilised components that flow from the filter segment 309. The mouth end segment 311 is hollow to provide a chamber for aerosol accumulation yet rigid enough to withstand axial compressive forces and bending moments that might arise during manufacture and whilst the article is in use during insertion into the aerosol-generating device 200. In one example, the thickness of the wall of the mouth end segment 311 is approximately 0.29 millimetres.

[0177] In one example, the length of the mouth end segment 311 is between 6 millimetres to 10 millimetres and more preferably 8 millimetres.

[0178] The mouth end segment 311 may be manufactured from a spirally wound paper tube which provides a hollow internal chamber yet maintains critical mechanical rigidity. Spirally wound paper tubes are able to meet the tight dimensional accuracy requirements of high-speed manufacturing processes with respect to tube length, outer diameter, roundness and straightness.

[0179] The mouth end segment 311 provides the function of preventing any liquid condensate that accumulates at the exit of the filter segment 309 from coming into direct contact with a user.

[0180] It should be appreciated that, in one example, the mouth end segment 311 and the cooling segment 307 may be formed of a single tube and the filter segment 309 is located within that tube separating the mouth end segment 311 and the cooling segment 307.

[0181] In the article 300 of FIG. 9, ventilation holes 317 are located in the cooling segment 307 to aid with the cooling of the article 300. In one example, the ventilation holes 317 comprise one or more rows of holes, and preferably, each row of holes is arranged circumferentially around the article 300 in a cross-section that is substantially perpendicular to a longitudinal axis of the article 300.

[0182] In one example of the article 300 of FIG. 9, there are between one to four rows of ventilation holes 317 to provide ventilation for the article 300. Each row of ventilation holes 317 may have between 12 to 36 ventilation holes 317. The ventilation holes 317 may, for example, be between 100 to 500 micrometres in diameter. In one example, an axial separation between rows of ventilation holes 317 is between 0.25 millimetres and 0.75 millimetres, more preferably, an axial separation between rows of ventilation holes 317 is 0.5 millimetres.

[0183] In one example of the article 300 of FIG. 9, the ventilation holes 317 are of uniform size. In another example, the ventilation holes 317 vary in size. The ventilation holes can be made using any suitable technique, for example, one or more of the following techniques: laser technology, mechanical perforation of the cooling segment 307 or pre-perforation of the cooling segment 307 before it is formed into the article 300. The ventilation holes 317 are positioned so as to provide effective cooling to the article 300.

[0184] In one example of the article 300 of FIG. 9, the rows of ventilation holes 317 are located at least 11 millimetres from the proximal end of the article 300, more preferably the ventilation holes 317 are located between 17 millimetres and 20 millimetres from the proximal end of the article 300. The location of the ventilation holes 317 is positioned such that user does not block the ventilation holes 317 when the article 300 is in use.

[0185] Advantageously, providing the rows of ventilation holes between 17 millimetres and 20 mm from the proximal end of the article 300 enables the ventilation holes 317 to be located outside of the aerosol-generating device 200 when the article 300 is fully inserted in the aerosol-generating device 200. By locating the ventilation holes 317 outside of the device 200, non-heated air is able to enter the article 300 through the ventilation holes from outside the device 200 to aid with the cooling of the article 300.

[0186] The length of the cooling segment 307 is such that the cooling segment 307 will be partially inserted into the device 200 when the article 300 is fully inserted into the device 200.

[0187] As shown in FIG. 8, the length of the first aerosol-forming substrate 312 is such that the first aerosol-forming substrate 312 extends from the distal end of the cavity 14, 18 for receiving the aerosol-forming substrate along the first portion 14 of the cavity. The length of the second aerosol-forming substrate 314 is such that the second aerosol-forming substrate 314 extends along the second portion 18 of the cavity until the proximal end of the cavity 14, 18.

[0188] In use, when an aerosol-generating article 300 is received in the cavity 14, 18, a user may draw on the proximal end of the aerosol-generating article 300 to inhale aerosol generated by the aerosol-generating system. When a user draws on the proximal end of the aerosol-generating article 300, air is drawn into the device housing 202 at the air inlet 280, and is drawn into the aerosol-generating segment 310 of the aerosol-generating article 300. Air is drawn into the proximal end of the first aerosol-forming substrate 312 and into the proximal end of the second aerosol-forming substrate 314.

[0189] In this embodiment, the controller 208 of the aerosol-generating device 200 is configured to supply power to the inductor coils 12, 16 of the inductive heating arrangement 10 in a predetermined sequence. The predetermined sequence comprises supplying a first varying electric current to the first inductor coil 12 during a first draw from the user, subsequently supplying a second varying electric current to the second inductor coil 16 during a second draw from the user, after the first draw has finished. On the third draw, the sequence starts again at the first inductor coil 12. This sequence results in heating of the first aerosol-forming substrate 312 on a first puff and in heating of the second aerosol-forming substrate 314 on a second puff. Since the aerosol forming substrates 312, 314 of the article 300 are all different, this sequence results in a different experience for a user on each puff on the aerosol-generating system.

[0190] The measurement of the temperature of the first susceptor 11 may be carried out during the second draw from the user, that is, when the first varying electric current does not flow through the first inductor coil 12. Likewise, it may be avoided measuring the temperature of the first susceptor 11 during the first draw from the user, that is, when the first varying electric current flows through the first inductor coil 12.

[0191] The measurement of the temperature of the second susceptor 15 may be carried out during the first draw from the user, that is, when the second varying electric current does not flow through the second inductor coil 16. Likewise, it may be avoided measuring the temperature of the second susceptor 15 during the second draw from the user, that is, when the second varying electric current flows through the second inductor coil 16.

[0192] This method improves the accuracy of the measurements of the temperatures of the first susceptor 11 and the second susceptor 15.

[0193] In an example of this embodiment, the first temperature sensor 13 is a thermocouple 131 as illustrated in FIG. 5. In another example, the first temperature sensor 13 is a resistive temperature device 139, as shown in FIG. 6. In another example, the second temperature device 17 is a thermocouple 131. In another example, the second temperature sensor 17 is a resistive temperature device 139.