Heating assembly, aerosol-generating device and a method for heating an aerosol-forming substrate

Abstract

The present invention relates to a heating assembly (10) of an aerosol-generating device for heating aerosol-forming substrate. The heating assembly comprises a chemical heating device (200) configured to generate primary heat by an exothermic chemical reaction and to supply the primary heat to an aerosol-forming substrate for heating the substrate. The heating assembly further comprises an electrical heating device (100) configured to electrically generate and supply secondary heat to the aerosol-forming substrate for heating the substrate. The invention further relates to an aerosol-generating device including such a heating assembly. A method for generating an aerosol by heating aerosol-forming substrate comprises at least one of a sequential or a parallel performance of the following steps: generating primary heat by an exothermic chemical reaction and supplying the primary heat to the aerosol-forming substrate for heating the substrate; and electrically generating secondary heat and supplying the secondary heat to the aerosol-forming substrate for further heating the substrate.

Claims

1. A heating assembly of an aerosol-generating device for heating aerosol-forming substrate, the heating assembly comprising: a chemical heating device configured to generate primary heat by an exothermic chemical reaction and to supply the primary heat to an aerosol-forming substrate for heating the substrate, an electrical heating device configured to electrically generate and supply secondary heat to the aerosol-forming substrate for heating the substrate, and a controller operatively connected at least to the electrical heating device for controlling the temperature of the aerosol-forming substrate.

2. The heating assembly according to claim 1, wherein the heating assembly is configured for at least one of: parallel heating of the aerosol-forming substrate by using the chemical heating device and the electrical heating device in combination; sequential heating of the aerosol-forming substrate using the chemical heating device and the electrical heating device sequentially.

3. The heating assembly according to anyone of claim 1, wherein the chemical heating device is configured for heating the substrate to a pre-target temperature, and the electrical heating device is configured for further heating the substrate to a target temperature above the pre-target temperature in addition to the chemical heating device.

4. The heating assembly according to claim 1, wherein the chemical heating device comprises a reaction chamber for executing the exothermic chemical reaction and a heat transfer element for transferring primary heat out of the reaction chamber.

5. The heating assembly according to claim 1, wherein the heating assembly comprises a controllable supply system for supplying at least one reactant to the exothermic chemical reaction and for controlling the generation of primary heat.

6. The heating assembly according to claim 1, wherein the electrical heating device comprises a resistive heating element.

7. The heating assembly according to claim 1, further comprising an energy converting device for converting heat generated by the chemical heating device into electrical power.

8. The heating assembly according to claim 7, wherein the energy converting device is operatively connected to the electrical heating device for supplying the electrical heating device with converted electrical power.

9. An aerosol-generating device comprising a heating assembly according to claim 1.

10. A method for generating an aerosol by heating an aerosol-forming substrate, the method comprising at least one of a sequential or a parallel performance of the following steps: generating primary heat by an exothermic chemical reaction and supplying the primary heat to the aerosol-forming substrate for heating the substrate; electrically generating secondary heat and supplying the secondary heat to the aerosol-forming substrate for heating the substrate; and adjusting the temperature of the aerosol-forming substrate to a target temperature by controlling at least the generation of secondary heat.

11. The method according to claim 10, wherein the primary heat and the secondary heat are used for heating the aerosol-forming substrate during different phases of generating an aerosol.

12. The method according to claim 10, wherein the primary heat is used for heating the aerosol-forming substrate to a pre-target temperature and wherein the secondary heat is used in addition to the primary heat for further heating the aerosol-forming substrate to the target temperature above the pre-target temperature.

13. The method according to anyone of claim 10, further comprising the step of converting heat from the exothermic chemical reaction into electrical power and providing the converted electrical power for electrically generating secondary heat.

Description

(1) The invention will be further described, by way of example only, with reference to the accompanying drawings, in which:

(2) FIG. 1 is a schematic illustration of an aerosol-generating device comprising a hybrid heating assembly according to a first embodiment of the invention;

(3) FIG. 2 is a schematic illustration of an aerosol-generating device comprising a hybrid heating assembly according to a second embodiment of the invention;

(4) FIG. 3 shows a cross-section through a portion of the hybrid heating assembly according to FIG. 1 and FIG. 2,

(5) FIG. 4 is a schematic illustration of an aerosol-generating device comprising a hybrid heating assembly according to a third embodiment of the invention; and

(6) FIGS. 5-8 show details of the hybrid heating assembly according to FIG. 4.

(7) FIG. 1 schematically shows an aerosol-generating device 1 comprising a heating assembly 10 according to a first embodiment to the invention. The heating assembly 10 comprises two heating devices, a chemical heating device 200 and an electrical heating device 100, for combined heating of aerosol-forming substrate. The chemical heating device 200 provides primary heat by an exothermic chemical reaction for pre-heating of the aerosol-forming substrate to a pre-target temperature which is below a desired target temperature of the aerosol-forming substrate to form an aerosol. In order to reach the target temperature, the electrical heating device 100 provides secondary heat in addition to the primary heat. Due to the high energy density of exothermic chemical reactions, the chemical heating device preferably provides a major amount of heat for a coarse adjustment of the temperature, whereas the electrical heating device preferably provides a minor amount of heat used for fine adjustment of the temperature.

(8) With regard to the embodiment according to FIG. 1, the chemical heating device 200 is a catalytic heater configured to generate primary heat by catalyzed fuel combustion in a reaction chamber 201. For this, fuel is provided in a reactant reservoir or fuel reservoir 202 that is in fluid communication with the reaction chamber 201 via a dispensing tube 204. The fuel reservoir 202 may be refillable via a fill inlet (not shown). The chemical heating device 200 also comprises pressure means 208 for pressurizing the fuel in the fuel reservoir 208, causing the pressure in the fuel reservoir 202 to be higher than in the reaction chamber 201, the latter being typically at atmosphere pressure. Due to this, fuel is automatically dispensed via the dispenser tube 204 into the reaction chamber 201 upon opening a valve 203 that is configured to control the fuel flow from the reservoir 202 into the reaction chamber 201.

(9) Apart from the inlet for the dispenser tube 204, the reaction chamber 201 comprises air inlets 207 for providing oxygen for the catalytic reaction. Furthermore, the reaction chamber 201 comprises outlets 206 for discharging water and exhaust gases of the catalytic reaction to the environment.

(10) A thermal barrier 205 is provided between the reaction chamber 201 and the fuel reservoir 202 for thermal shielding such that the fuel reservoir and other components beyond the thermal barrier 205 stay at reasonable temperatures.

(11) In the reaction chamber 201, the fuel is combusted by a catalyzed exothermic reaction, thereby generating primary heat for heating aerosol-forming substrate.

(12) The fuel may be any organic compound capable of supplying energy through its oxidation. For example, the fuel may comprise one of a short chain alcohol (methanol, ethanol, propanol or isopropanol and butanol and isomers), ketone, aldehyde or carboxylic acid that is readily oxidized. Catalytically combustible gases may comprise, for example, one of hydrogen, methane, propane, pentane, ether, ethane, or butane and their isomers.

(13) The catalyst used to catalyze the fuel combustion may be a catalyst having high oxygen reduction reactivity. The catalyst may comprise, for example, one or more metals or an alloy of one or more metals selected from the group comprising Fe, Co, Ni, Rh, Pd, Pt, Cu, Ag, Au, Zn and Cd. In particular, the catalyst may comprise at least one precious metal, at least one transition metals or a combination of at least one metal and at least one transition metal, for example, Pt, Pd, Rh, Ir, Ru, Ni, Os, Re, Co, Fe, Mn, Ag, Cu. The catalyst may be supported for example on a surface of a substrate article within the reaction chamber 201.

(14) Primary heat generated by the catalyzed exothermic reaction of the fuel-oxygen mixture is transferred via a heat transfer element 210 from the reaction chamber 201 to a cavity 2 defined within a housing 3 of the aerosol-generating device 1. The cavity 2 is open at the proximal end of the aerosol-generating device 1 for receiving an aerosol-generating article that includes the aerosol-forming substrate to be heated. For example, the aerosol-forming substrate may be compressed or molded into a plug forming the aerosol-generating article (not shown).

(15) FIG. 3 shows further details of the heat transfer element 210 used within the embodiment shown in FIG. 1 and FIG. 2. The heat transfer element 210 comprises a metallic blade 214 fed through the wall of the reaction chamber 201 next to the cavity 2. The heat transfer element 210 comprises a first portion 212 which is arranged in the reaction chamber 201 and on which the catalyzed exothermic reaction is preferably performed directly in order to optimize heat transfer. A second portion 211 of the heat transfer element 210 is arranged in the cavity 2 separated from the reaction chamber 201. The proximate end of the second portion 211 is tapered, thus facilitating to plug on and hold an aerosol-generating article when it is pushed into the cavity 2 of the housing 3. By this, the aerosol-forming substrate may be brought into direct thermal contact with the catalyzed exothermic reaction, however, without direct contact to the reaction itself.

(16) Further referring to FIGS. 1 and 3, the heat transfer element 210 comprises ceramic cover members 213 sandwiching the metallic core of the blade 214 along the second portion 211. The ceramic cover members 214 provide an electrically non-conductive substrate to support an electrically conductive heating element 103 which is part of the resistive heating device 100. In the present embodiment, the heating element comprises metal tracks 103 on both sides of the blade-like heat transfer element 210. In order to optimize heat transfer to the aerosol-forming substrate, the metal tracks 103 are arranged in meandering configuration. Alternatively, the tracks may be arranged in a spiral configuration. To electrically generate heat, the heating element 103 consists of a resistive material. Preferably, the metal tracks are made of platinum.

(17) The tracks may be heated up to the desired target temperature by running an electrical current through. For this, the tracks on both sides of the heat transfer element 210 are connected in parallel via electrical connections 102 to a power supply 104. In present embodiment, the power supply is a rechargeable battery, for example a Lithium-ion battery.

(18) Advantageously, the heating tracks 103 may simultaneously be used to measure the temperature on the surfaces of the heat transfer element 210 which is indicative for the actual temperature of an aerosol-forming substrate attached thereto. Assuming that the material of the heating element 103 has an appropriate temperature coefficient of resistance characteristic, the temperate may be determined by measuring the resistance of the heating element 103, for example by measuring the voltage across and the current through the electrically conductive heating element 103. Using the heating element as temperature sensor may help to reduce the number of components within the heating assembly 10 since no separate temperature sensor will be required. However, in addition or alternatively, the heating assembly 10 may also comprise a separate temperature sensor, of course.

(19) A controller 101, such as a micro controller unit implemented on an electronic circuit board, may be used for controlling the temperature of the aerosol-forming substrate. According to the invention, this is realized by controlling at least the secondary heat provided by the electrically heating device 100 on top of the primary heat provided by the chemical heating device 200. Therefore, the controller 101 is operatively connected at least to the electrical heating device 100. In particular, the controller 101 may be configured to determine the actual temperature on the surface of the heat transfer element 210 by determining the temperature dependent resistance of the heating element 103 as described above. The temperature on the surface of the heat transfer element 210 is indicative of the actual temperature of aerosol-forming substrate. Based upon a comparison of the actual temperature with the desired target temperature of the aerosol-forming substrate or the corresponding temperatures on the heat transfer element, respectively, the controller 101 is further configured to control the electrical power from the power supply 104 to the electrically heating element 103. The heat electrical power is preferably supplied intermittently to the heating element 103. Advantageously, the control of secondary heat for fine adjustment of the temperature of the aerosol-forming substrate is closed-loop.

(20) The controller 101 may be also used for controlling the recharge of the power supply 104, for example the recharge of the battery from an external power supply. The controller may be also used for controlling the generation of primary heat, for example by controlling the fuel valve 203, thereby controlling the amount of fuel to be dispensed from the fuel reservoir 202 to the reaction chamber 201. For this, the controller 101 may access a table (for example stored in a storage unit of the controller 101) which contains pre-calibrated fuel flow rates versus generated primary heat in the reaction chamber 201. Additionally or alternatively, the controller 101 may also act on the air inlet 207 to modulate the oxygen supply into the reaction chamber 201. The generation of primary heat is limited to a pre-target temperature well below the actual target temperature so that a complete shut-off of secondary heat will be enough to easily reduce the actual temperature to reasonable temperatures in case of overheating. Preferably, the pre-target temperature is about 250° C., whereas the target temperature is typically between 300° C. and 350° C.

(21) In general, the controller 101 and/the power supply 104 may be either part of the heating assembly 10 or the overall aerosol-generating device 1.

(22) FIG. 2 schematically shows an aerosol-generating device 1 comprising a heating assembly 10 according to a second embodiment to the invention. The basic concept of generating and supplying first and second heat to the aerosol-forming substrate is similar to the first embodiment according to FIG. 1. Therefore, identical features are denoted with identical reference numerals unless otherwise explicitly indicated.

(23) In contrast to the first embodiment according to FIG. 1, the heating assembly according to the second embodiment comprises an energy converting device 107 for converting heat generated by the chemical heating 200 device into electrical power. In the present embodiment, the energy converting device 107 may comprise at least one thermoelectrical generator capable of generating electricity from a temperature gradient based on the Seebeck principle. Such thermoelectrical generator are generally known from prior art. For this, the thermoelectrical generator may be arranged between the fuel reservoir and the reaction chamber in lieu of the thermal barrier 205 in the first embodiment according to FIG. 1. Alternatively or additionally, the thermoelectrical generator may be arranged laterally attached to reaction chamber, having its “cold” side facing outwards from the reaction chamber 201.

(24) Preferably, electrical power generated by the energy converting device 107 is fed into the power supply 104 of the heating assembly 10 of the overall aerosol-generating device 1. In the present embodiment, the heating assembly 10 comprises a battery charger 105 using the electricity provided by the energy converting device 107 to at least partially recharge the battery 104. For this, the battery charger 105 is operatically connected to the energy converting device 107 and the power supply 104 via electrical connections 106.

(25) FIGS. 4, 5, 6, 7 and 8 show an aerosol-generating device 1 comprising a heating assembly 10 according to a third embodiment to the invention. The basic concept of generating and supplying first and second heat to the aerosol-forming substrate is similar to the first and second embodiment according to FIG. 1 and FIG. 2. Therefore, identical features are denoted with identical reference numerals unless otherwise explicitly indicated.

(26) In contrast to the embodiments according to FIG. 1 and FIG. 2, the heating assembly 10 according to this third embodiment comprises a cup-like heat transfer element 210.

(27) The heat transfer element 210 comprises a plate-like first portion 212 (not shown in top view of FIG. 6 and perspective view of FIG. 8) and a hollow-cylindrical second portion 211. The first portion 212 may be attached to or may form a bottom of the second portion 211 (see cross-sectional view of FIG. 5).

(28) The first portion 212 is at least partially arranged in or exposed to the reaction chamber 201 such that the exothermic chemical reaction occurs directly on the exposed surface of the first portion 212. The first portion 212 is made of metal allowing for efficiently transferring primary heat to the aerosol-forming substrate which may be received within the hollow-cylindrical second portion 211.

(29) The second portion 211 is also involved in transferring of primary heat. For this, the hollow-cylindrical second portion 211 is made of a ceramic material, providing good thermal conductivity and high thermal resistance.

(30) As can be seen in particular from the side view of FIG. 7 and the perspective view of FIG. 8, the outside surface of the electrically non-conductive second portion 211 supports an electrically conductive heating element 103 which is part of the resistive heating device 100. In the present embodiment, the heating element comprises a metal track 103 (dashed-dotted-line in FIG. 4 and FIG. 5) circumferentially arranged in meandering configuration on the outside surface of the second portion 211. The meandering configuration advantageously optimizes heat transfer from the heating element 103 to the aerosol-forming substrate via the second portion 211. In the same way as for the heating assemblies shown in FIG. 1 and FIG. 2, the track 103 may be heated up by running an electrical current through. For this, the track is connected via electrical connections 102 to a power supply 104.

(31) In order to avoid a user of the device to sustain contact burns, a thermal barrier 108 is arranged in the clearance between the outside surface of the second portion 211 and the inner surface of the cavity 2 defined at the distal end of the housing 3 of the aerosol-generating device 1.