Aerosol generator equipped with multiple sensors

Abstract

An aerosol generating device (20) comprising: an air inlet (50), an air outlet (52), an airflow passage extending in a first direction between the air inlet (50) and the air outlet (52), a heating element (30) within the airflow passage for heating an aerosol-forming substrate, a first temperature sensor (80) for measuring a first temperature at a first position along the airflow passage, a second temperature sensor (82) for measuring a second temperature at a second position along the airflow passage spaced in the first direction from the first sensor, and a controller (14) configured to control operating parameters of the device (20) based on the measured first temperature and the measured second temperature. [Selected Figure] Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an aerosol generating device for generating an aerosol by heating an aerosol-forming substrate. In particular, but not exclusively, the present invention relates to an aerosol generating device comprising a plurality of temperature sensors for controlling the operating parameters of the aerosol generating device. [Background technology]

[0002] In many handheld aerosol generating devices, a resistive heating element may be used to heat an aerosol-forming substrate to generate an aerosol. The resistive heating element may be controlled by a controller. The controller may be configured to control the operation of the resistive heating element based on a heater temperature, which may be determined by measuring the electrical resistance across the resistive heating element. This may significantly reduce the chance that the resistive heating element will be damaged, for example by overheating, because the power supplied to the heating element may be limited when the measured heater temperature exceeds a given threshold. If the resistive heating element is used to heat a source of liquid aerosol-forming substrate, the controller may detect a significant increase in the temperature of the resistive heating element when the source of liquid aerosol-forming substrate is depleted. In response, the controller may prevent the resistive heating element from generating further heat by terminating the supply of power to the resistive heating element.

[0003] However, such temperature measurements may not detect local temperature variations in the resistive heating element because the electrical resistance is measured across the entire heater circuit and therefore represents the overall temperature of the entire resistive heating element. Furthermore, such temperature measurements do not indicate the temperature at locations other than the heating element within the device. For example, it is difficult to accurately derive the aerosol temperature based solely on the electrical resistance of the resistive heating element.

[0004] Furthermore, temperature measurement in a resistive heating element is based on measuring the electrical resistance when a current is passed through the resistive heating element. Thus, the temperature measurement stops when the resistive heating element is no longer in operation. This may be problematic or inconvenient. For example, if the controller stops supplying power to the resistive heating element because the temperature of the resistive heating element exceeds a threshold, the controller may not be able to continue to determine the temperature of the resistive heating element. This means that the controller cannot determine whether the temperature of the resistive heating element has decreased below the threshold without supplying power to the resistive heating element again. This may cause the temperature of the resistive heating element to rise again. It is clear that this type of temperature measurement only works with resistive heating elements. Thus, this technology cannot be used with other types of aerosol generating devices based on non-resistive heaters.

[0005] It would be desirable to provide an aerosol generating device with a heating arrangement which mitigates or overcomes at least some of these disadvantages in known devices.It would be desirable to provide an aerosol generating device which utilises more advanced sensor arrangements and which may implement improved control mechanisms. Summary of the Invention

[0006] According to a first aspect of the present invention, there is provided an aerosol generating device comprising an air inlet, an air outlet, an airflow passage extending in a first direction between the air inlet and the air outlet, a heating element within the airflow passage for heating an aerosol-forming substrate, a first temperature sensor for measuring a first temperature at a first location along the airflow passage, a second temperature sensor spaced in the first direction from the first sensor for measuring a second temperature at a second location along the airflow passage, and a controller configured to control operating parameters of the device based on the measured first temperature and the measured second temperature.

[0007] In some embodiments, the operating parameter may include multiple operating parameters.

[0008] The first temperature sensor and the second temperature sensor may be different types of temperature sensors. The first temperature sensor and the second temperature sensor may be the same type of temperature sensor.

[0009] As used herein, the term "temperature sensor" may refer to any suitable sensing means for sensing one or more signals indicative of temperature. For example, if the heating element includes a resistive heating element, the resistive heating element and a controller for measuring the electrical resistance across the resistive heating element function as the temperature sensor.

[0010] As used herein, the term "measured temperature" may refer to a direct temperature measurement or an indirect temperature measurement. An indirect temperature measurement may include a temperature determined by a controller based on one or more signals indicative of temperature.

[0011] The first and second locations may be located anywhere along the airflow path for measuring localized temperatures. The first temperature may include a temperature indicative of any one or combination of the ambient air at the first location, the air flowing through the airflow path at the first location, the aerosol generated in the airflow path at the first location, the heating element at the first location, and the aerosol-forming substrate supplied to the heating element at the first location. The second temperature may include a temperature indicative of any one or combination of the ambient air at the second location, the air flowing through the airflow path at the second location, the aerosol generated in the airflow path at the second location, the heating element at the second location, and the aerosol-forming substrate supplied to the heating element at the second location. The measured temperature may advantageously allow the controller to control one or more operating parameters of the device based on the localized temperature measured at a particular known location along the airflow path. The measured temperature may advantageously allow the controller to determine a temperature gradient in the airflow path along at least a first direction. The measured temperature may advantageously allow the controller to determine localized temperature variations in the heating element.

[0012] As described in the embodiments described below, each of the first and second locations may be selected to provide one or more advantageous effects.

[0013] The first location may be spaced from the heating element. The second location may be spaced from the heating element. This may allow for measurement of temperature at one or more locations along the airflow path, such as along a first direction along the airflow path, spaced from the heating element. Advantageously, this may simplify the design of the device, as the temperature sensor may be provided as a separate component from the heating element. This may make it easier to repair or replace the heating element. This may also be advantageous when it is desired to determine the temperature of the aerosol after it has been generated at the heating element. This may be advantageous when it is desired to determine the temperature of the air supply at a location before the air reaches the heating element, for example at a location where the temperature of the air supply is unlikely to be significantly affected by the heat generated by the heating element. The first and second locations may each be spaced an equal distance from the heating element along the airflow path.

[0014] The first location may be immediately adjacent to the heating element, either upstream or downstream relative to the heating element. The second location may be immediately adjacent to the heating element, either upstream or downstream relative to the heating element. This advantageously allows one or both of the first and second temperature sensors to provide an indication of air temperature just before the air reaches the heating element. This advantageously allows one or both of the first and second temperature sensors to provide an indication of aerosol temperature just after aerosol is generated at the heating element.

[0015] In some embodiments, one of the first location and the second location may be located upstream of the heating element, and the other of the first location and the second location may be located downstream of the heating element. In some embodiments, both the first location and the second location may be located upstream of the heating element. In some embodiments, both the first location and the second location may be located downstream of the heating element.

[0016] The controller may be configured to control the operating parameters of the device based on the measured first temperature and the measured second temperature. In some embodiments, the controller is configured to control the operating parameters of the device based on the difference between the first temperature and the second temperature. In some embodiments, the controller is configured to control the operating parameters based on the ratio between the first temperature and the second temperature. For example, in some embodiments, the difference between the first temperature and the second temperature may advantageously indicate that one or both of the air supply and the generated aerosol are flowing along at least a portion of the airflow path extending at least between the first and second positions. More specifically, a sudden increase in the first or second temperature relative to the other may indicate that such an airflow is occurring. This is particularly relevant when one of the first and second positions is located downstream of the heating element and the other of the first and second positions is located upstream of the heating element. This is because a sudden drop in temperature upstream of the heating element may indicate an inflow of the air supply into the airflow path. A sudden increase in temperature downstream of the heating element may indicate that aerosol is generated at the heating element and is flowing towards the air outlet. Thus, the relative difference or ratio between the first temperature and the second temperature may be indicative of such an event.

[0017] In some embodiments, one of the first and second locations may correspond to a location on the heating element, and the other of the first and second locations may be spaced from the heating element in a direction along the airflow passage. This may allow the measured heating element temperature to be compared to a temperature measured upstream or downstream of the heating element. This may advantageously allow for the determination of an airflow event. For example, a high airflow rate may result in a lower temperature being measured downstream of the heating element than would otherwise be measured if the airflow rate was lower. Thus, the controller may advantageously determine one or more airflow parameters, such as airflow rate, based on the first and second temperatures.

[0018] In some embodiments, the controller is configured to determine an airflow event, such as any one or more of an inhalation, exhalation or airflow rate, such as a volumetric airflow rate, based on the measured first temperature and the measured second temperature. This may advantageously enable the controller to control an operating parameter of the device based on the determined airflow event in addition to the first and second temperatures. Indeed, the airflow event may affect the measured first and second temperatures. By controlling the operating parameter based on both the airflow event and the first and second temperatures, the device may more accurately control the operating parameter.

[0019] In some embodiments, the heating element may include multiple heating sections. Each of the first and second locations may be located in a respective heating section of the heating element. The measured first temperature may thus be indicative of a temperature of a first section of the heating element corresponding to the first location. The measured second temperature may be indicative of a temperature of a second section of the heating element corresponding to the second location. This allows the temperature representative of different sections of the heating element to be determined using the sensors. Advantageously, this allows a temperature gradient across the heating element to be determined. In some embodiments, the controller is arranged to determine a temperature distribution across the heating element and to control an operating parameter based on the determined temperature distribution. In some embodiments, each heating section may be independently controllable. Advantageously, this allows for correction of undesirable local temperature variations across the heating element. Indeed, it will be appreciated that in some embodiments, more than one heating section may be provided, each heating section having a corresponding location at which a corresponding temperature may be measured. Multiple heating sections with multiple locations advantageously allow for a more accurate determination of a temperature gradient across the heating element.

[0020] In some embodiments, the heating element may include a resistive heating element. In such embodiments, one of the first temperature sensor and the second temperature sensor may include a resistive heating element, and the respective first or second measured temperature may be based on a measurement of an electrical resistance across the resistive heating element. The first temperature sensor and the second temperature sensor may be different types of temperature sensors. The first temperature sensor and the second temperature sensor may be the same type of temperature sensor.

[0021] The heating element can include a plasmonic heating element that includes a plurality of metal nanoparticles arranged to receive light from a light source and generate heat by surface plasmon resonance.

[0022] As used herein, the term "surface plasmon resonance" refers to the resonant oscillation of the free electrons of a metallic nanoparticle, and therefore the polarization of the charge at the surface of the metallic nanoparticle. The collective resonant oscillation of the free electrons, and therefore the polarization of the charge, is excited by light incident on the metallic nanoparticle from a light source. The energy from the oscillating free electrons can be dissipated by several mechanisms, including heat. Thus, when a metallic nanoparticle is illuminated by a light source, the metallic nanoparticle generates heat due to surface plasmon resonance.

[0023] As used herein, the term "metal nanoparticles" refers to metal particles having a maximum diameter of about 1 micrometer or less. Metal nanoparticles that generate heat through surface plasmon resonance when excited by incident light are also known as plasmonic nanoparticles.

[0024] Advantageously, plasmonic heating elements arranged to generate heat via surface plasmon resonance may provide more homogeneous heating of the aerosol-forming substrate compared to resistive and inductive heating systems: for example, the free electrons of metal nanoparticles are excited to the same extent regardless of the angle of incidence of the incident light.

[0025] Advantageously, a plasmonic heating element arranged to generate heat by surface plasmon resonance may provide more localized heating compared to resistive and inductive heating systems. Advantageously, the localized heating facilitates heating of individual portions of an aerosol-forming substrate or multiple individual aerosol-forming substrates. Advantageously, the localized heating increases the efficiency of the aerosol-generating device by increasing or maximizing the transfer of heat generated by the plasmonic heating element to the aerosol-forming substrate. Advantageously, the localized heating may reduce or eliminate undesired heating of other components of the aerosol-generating device.

[0026] The plasmonic heating element may be positioned to receive light from an external light source and generate heat by surface plasmon resonance. The external light source may include ambient light. The ambient light may include solar radiation. The ambient light may include at least one artificial light source external to the aerosol generation device.

[0027] The plasmonic heating element may receive the ambient light directly from the ambient light source, or the ambient light may be received via one or more additional optically transmitting elements within the device. The ambient light is received within the aerosol generating device via one or more windows or openings on the exterior surface of the aerosol generating device. The ambient light source may serve to complement the light source of the aerosol generating device. This may be advantageous when attempting to preheat the aerosol forming substrate to a high temperature before operating the internal light source of the device. This may also advantageously reduce the amount of power required by the aerosol generating device. The aerosol generating device may include an ambient light control means for controlling the amount of ambient light that the optically transmitting core receives from the ambient light source. The ambient light control means may include an automatic control means, such as an automatic shutter. The ambient light control means may include a manual control means, such as a removable cap for covering one or more windows or openings within the device.

[0028] The aerosol generating device may include a light source, where the plasmonic heating element is positioned to receive light from the light source and generate heat by surface plasmon resonance.

[0029] Advantageously, providing a light source to the aerosol generating device may enable the plasmonic heating element to generate heat without receiving light from an external light source. Advantageously, providing a light source to the aerosol generating device may provide improved control of the irradiation of the plasmonic heating element. Advantageously, controlling the irradiation of the plasmonic heating element controls the temperature to which the plasmonic heating element is heated by surface plasmon resonance.

[0030] The light source may include a light source arranged to emit light in the visible range of the electromagnetic spectrum. The light source may also include a light source arranged to emit light beyond the visible range of the electromagnetic spectrum, such as at least one of an ultraviolet light source and an infrared light source. This may advantageously excite a wider range of nanoparticles, such as nanoparticles of different sizes or compositions.

[0031] The light source is preferably configured to emit light including at least one wavelength between 380 nanometers and 700 nanometers. The light source is preferably configured for a peak emission wavelength between about 495 nanometers and about 580 nanometers. As used herein, "peak emission wavelength" means the wavelength at which the light source exhibits maximum intensity. Advantageously, a peak emission wavelength between about 495 nanometers and about 580 nanometers may provide maximum heating of the plasmonic heating element by surface plasmon resonance, particularly when the plurality of metal nanoparticles includes at least one of gold, silver, platinum, and copper.

[0032] The light source of the aerosol generating device may include at least one of a light emitting diode (LED) and a laser.

[0033] Advantageously, light emitting diodes and lasers may have a compact size suitable for use in an aerosol generating device. The light source of the aerosol generating device may not require a relatively large voltage drop to achieve surface plasmon resonance. For example, the light source of the aerosol generating device may include one or more light emitting diodes (LEDs). This may allow a safer and more cost-effective power source to be used to power the device. Furthermore, there is no need to provide a physical connection between the plasmonic heating element and the light source. Thus, the use of a plasmonic heating element may advantageously reduce the possibility of damage to the heating element during repair and maintenance. Indeed, since no physical connection between the plasmonic heating element and the light source needs to be provided, the plasmonic heating element may be easily repaired or replaced. The plasmonic heating element also means that the device is not vulnerable to the external environment, as the use of a plasmonic heating element removes the need for exposed electrical components.

[0034] The use of a laser as a light source may allow for the emission of light within a relatively narrow wavelength range. The laser may include at least one of a solid-state laser and a semiconductor laser. The narrow wavelength range may be a range of wavelengths that matches the size and composition of the nanoparticles, as described below. This may advantageously improve efficiency most when not all the light output by the light source is absorbed by the metal nanoparticles to generate heat through surface plasmon resonance. Furthermore, such light sources may be relatively robust and simple in construction compared to other light sources.

[0035] The light emitted by a light source, such as the number of photons emitted per second, can be varied by controlling the amplitude, or the frequency, or a combination of amplitude and frequency, of the emitted light. The amount of light emitted by a light source, such as the number of photons emitted per second, can be varied by emitting pulses of light.

[0036] The light source may include multiple light sources. The light sources may be of the same type. At least some of the light sources may be of different types. The multiple light sources may include any combination of the types of light sources described herein.

[0037] Advantageously, multiple light sources may facilitate customization of the heating profile generated by the aerosol generating device during use.

[0038] At least one of the light sources may be a primary light source and at least one of the light sources may be a supplemental light source. The aerosol generating device may be configured to emit light from the one or more supplemental light sources only when the one or more primary light sources are incapable of being activated.

[0039] At least one of the light sources may be positioned to illuminate only a portion of the plurality of metallic nanoparticles, and each of the plurality of light sources may be positioned to illuminate a different portion of the plurality of metallic nanoparticles.

[0040] The aerosol generating device may be configured such that multiple light sources simultaneously irradiate different portions of the metal nanoparticles. Advantageously, simultaneously irradiating different portions of the metal nanoparticles may facilitate homogenous heating of the plasmonic heating element. Advantageously, simultaneously irradiating different portions of the metal nanoparticles may facilitate simultaneous heating of multiple individual aerosol-forming substrates.

[0041] The aerosol generating device may be configured such that the multiple light sources irradiate different portions of the multiple metal nanoparticles at different times. Advantageously, irradiating different portions of the multiple metal nanoparticles at different times may facilitate heating of different portions of the aerosol-forming substrate at different times. Advantageously, irradiating different portions of the multiple metal nanoparticles at different times may facilitate heating of multiple individual aerosol-forming substrates at different times.

[0042] The aerosol generating device includes a power supply and a controller configured to provide power from the power supply to the light source.

[0043] In embodiments in which the aerosol generating device includes multiple light sources, the power supply may include a single power supply arranged to provide power to the multiple light sources.

[0044] In embodiments where the aerosol generating device includes multiple light sources, the power supply may include multiple power supplies arranged to provide power to the multiple light sources.

[0045] In embodiments where the aerosol generating device includes multiple light sources, the controller may be configured to selectively provide electrical power to at least some of the multiple light sources. The controller may be configured to selectively vary the supply of electrical power to at least some of the multiple light sources.

[0046] In embodiments in which a plurality of light sources irradiate different portions of the plurality of metal nanoparticles to heat a plurality of separate aerosol-forming substrates, the controller may be configured to selectively supply power to at least some of the plurality of light sources to selectively heat at least some of the plurality of separate aerosol-forming substrates, and the controller may selectively vary the supply of power to at least some of the plurality of light sources to vary the heating rate of at least some of the plurality of separate aerosol-forming substrates.

[0047] Advantageously, by varying the relative heating of at least some of the plurality of individual aerosol-forming substrates, the aerosol generating device may vary the composition of the aerosol delivered to a user.

[0048] The aerosol generating device preferably comprises a user input device. The user input device may include at least one of a push button, a scroll wheel, a touch button, a touch screen, and a microphone. Advantageously, the user input device allows a user to control one or more aspects of the operation of the aerosol generating device. In embodiments where the aerosol generating device includes a light source, a controller, and a power supply, the user input device may allow a user to activate the supply of power to the light source, deactivate the supply of power to the light source, or both.

[0049] In embodiments in which the controller selectively provides power to at least some of the plurality of light sources, the controller is preferably configured to selectively provide power to at least some of the plurality of light sources in response to user input received by the user input device.

[0050] In embodiments in which the controller is configured to selectively vary the supply of power to at least some of the plurality of light sources, the controller is preferably configured to selectively vary the supply of power to at least some of the plurality of light sources in response to user input received by the user input device.

[0051] The aerosol generating device can include one or more optical elements to facilitate the transfer of light from the light source to the plasmonic heating element. The one or more optical elements can include at least one of an aperture, a window, a lens, a reflector, and an optical fiber.

[0052] Advantageously, at least one of the opening and the window may facilitate transmission of light from an external light source to the plasmonic heating element. The aerosol generating device may comprise a housing, wherein at least one of the opening and the window is located on the housing.

[0053] Advantageously, at least one of a lens, a reflector, and an optical fiber may concentrate or focus the light emitted from the light source onto the plasmonic heating element. Advantageously, concentrating or focusing the light onto the plasmonic heating element may increase the temperature to which the plasmonic heating element is heated by surface plasmon resonance.

[0054] The metal nanoparticles may include at least one of gold, silver, platinum, copper, palladium, aluminum, chromium, titanium, rhodium, and ruthenium. The metal nanoparticles may include at least one metal in elemental form. The metal nanoparticles may include at least one metal in a metal compound. The metal compound may include at least one metal nitride.

[0055] The plurality of metal nanoparticles preferably comprises at least one of gold, silver, platinum, and copper. Advantageously, gold, silver, platinum, and copper nanoparticles may exhibit strong surface plasmon resonance when illuminated with visible light.

[0056] The metal nanoparticles may comprise a single metal. The metal nanoparticles may comprise a mixture of different metals.

[0057] The plurality of metallic nanoparticles can include a plurality of first nanoparticles including a first metal, and a plurality of second nanoparticles including a second metal.

[0058] At least a portion of the plurality of metal nanoparticles may each comprise a mixture of two or more metals. At least a portion of the plurality of metal nanoparticles may each comprise a metal alloy. At least a portion of the plurality of metal nanoparticles may each comprise a core-shell configuration, where the core comprises a first metal and the shell comprises a second metal.

[0059] In embodiments in which the aerosol generating device includes a light source, it is preferred that the plurality of metal nanoparticles include a number average maximum diameter less than or equal to the peak emission wavelength of the light source.

[0060] The plurality of metal nanoparticles can comprise a number average maximum diameter of less than about 700 nanometers, preferably less than about 600 nanometers, preferably less than about 500 nanometers, preferably less than about 400 nanometers, preferably less than about 300 nanometers, preferably less than about 200 nanometers, preferably less than about 150 nanometers, preferably less than about 100 nanometers.

[0061] The plasmonic heating element may be formed from a plurality of metal nanoparticles.

[0062] The plasmonic heating element may include a substrate layer and a coating layer positioned on at least a portion of the substrate layer, the coating layer including a plurality of metallic nanoparticles. Advantageously, the substrate layer may be formed from a material selected for desired mechanical properties. Advantageously, the coating layer may be formed to optimize surface plasmon resonance of the plurality of metallic nanoparticles when the coating layer is exposed to light from a light source.

[0063] The substrate layer may be formed from any suitable material. The substrate layer may comprise a metal. The substrate layer may comprise a polymeric material. The substrate layer may comprise a ceramic.

[0064] The substrate layer may be electrically conductive. The substrate layer may be electrically insulating.

[0065] The nanoparticles may be provided on the substrate layer using any suitable process. The metal nanoparticles may be deposited on the substrate layer using a physical vapor deposition process.

[0066] The plasmonic heating element may include a plurality of discrete regions of metal nanoparticles, the plurality of discrete regions being spaced apart from one another. Advantageously, the plurality of discrete regions of metal nanoparticles may facilitate heating of a plurality of discrete portions of an aerosol-forming substrate. Advantageously, the plurality of discrete regions of metal nanoparticles may facilitate heating of a plurality of discrete aerosol-forming substrates.

[0067] The aerosol generating device may comprise a light source arranged to illuminate a plurality of distinct regions of the metallic nanoparticles.The aerosol generating device may comprise a plurality of light sources arranged to illuminate a plurality of distinct regions of the metallic nanoparticles.Each of the plurality of light sources may be arranged to illuminate only one of the distinct regions of the metallic nanoparticles.

[0068] The plasmic heating element may include a first surface arranged to receive light from a light source and generate heat by surface plasmon resonance of a plurality of metal nanoparticles. The first surface may include a plurality of surface features defining a three-dimensional shape. The first surface may include at least one of a plurality of protrusions and a plurality of depressions. The first surface may have an undulating shape.

[0069] Advantageously, the first surface including the plurality of surface features may increase the surface area of ​​the first surface, which may advantageously increase heating of the plurality of metal nanoparticles by surface plasmon resonance when light is incident on the first surface.

[0070] In embodiments in which the plasmonic heating element includes a substrate layer and a cover layer, a first surface of the substrate layer may define a plurality of surface features, and a cover layer is provided on the first surface of the substrate layer to form the first surface of the plasmonic heating element.

[0071] The plasmonic heating element may include a second surface arranged to transfer heat to the aerosol-forming substrate during use. The second surface may be on an opposite side to the first surface of the plasmonic heating element. In embodiments in which the plasmonic heating element includes a substrate layer and a cover layer, the substrate layer preferably includes a first surface on which the cover layer is provided to form the first surface of the plasmonic heating element, and a second surface which forms the second surface of the plasmonic heating element. The substrate layer preferably includes a thermally conductive material to facilitate transfer of heat from the cover layer to the second surface of the plasmonic heating element.

[0072] In embodiments where the heating element includes a resistive heating element and a plasmonic heating element, the plurality of metal nanoparticles can form the resistive heating element.

[0073] In embodiments where the plasmonic heating element includes a substrate layer and a cover layer, at least one of the substrate layer and the cover layer may form a resistive heating element. The substrate layer may include an electrically resistive material. The electrically resistive material may include at least one of an electrically resistive metal and an electrically resistive ceramic. The substrate layer may be formed from an electrically resistive material. The substrate layer may include a woven material, with a plurality of threads of the electrically resistive material forming at least a portion of the woven material.

[0074] In embodiments in which the aerosol generating device includes a power supply and a controller, the controller is preferably arranged to provide a supply of power from the power supply to the resistive heating element.

[0075] The aerosol generating device may be arranged to generate heat using a resistive heating element in addition to generating heat by surface plasmon resonance of the plurality of metal nanoparticles. The aerosol generating device may be arranged to generate heat using a resistive heating element instead of generating heat by surface plasmon resonance of the plurality of metal nanoparticles.

[0076] The aerosol generating device may be arranged to generate heat using a resistive heating element as a back-up to generating heat by surface plasmon resonance of the plurality of metal nanoparticles, for example, when heating of the plurality of metal nanoparticles by surface plasmon resonance is insufficient.

[0077] The aerosol generating device may be arranged to generate heat using a resistive heating element at the start of a heating cycle. In other words, the resistive heating element may be used to generate heat to raise the temperature of the heating element to an initial operating temperature. The aerosol generating device may be arranged to reduce or terminate the supply of power to the resistive heating element when the temperature of the heating element reaches the initial operating temperature.

[0078] The operating parameters of the device may affect the operation of one or more components of the device. The operating parameters may include one or more process variables that may affect the operation of one or more components of the device. The one or more components preferably include one or more components used to generate the aerosol by the device, such as a heating element or a power source configured to provide power directly or indirectly to the heating element. For example, in some embodiments, the operating parameters may include a temperature of the heating element. The operating parameters may include a temperature profile of the heating element, such as an output temperature over time. The temperature or temperature profile may be controlled by the controller controlling power provided from the power source to the heating element. The power may be provided directly to the heating element. The power may be provided indirectly to the heating element, for example, by providing power to one or more light sources, the light sources being positioned to provide light to a plasmonic heating surface of the heating element. The controller may be configured to control an output temperature of at least a portion of the heating element based on the measured first temperature and the measured second temperature. In the above embodiments in which the first and second locations are located in different heating sections along the heating element, the controller may be configured to independently control an operating parameter associated with each of the heating sections based on the respective first and second measured temperatures. For example, the controller may be configured to determine a temperature distribution across the multiple heating sections and may individually control the power supplied to each of the multiple heating sections based on the determined temperature distribution. This may allow for more precise control of the heat generated by the heating element. Control of the power supplied to the multiple heating sections may be achieved by controlling the power supplied to one or more of the multiple light sources, the light sources being arranged to provide light to power each of the respective heating sections of the heating element.For example, if a first light source is positioned to provide light to a first heating section and a second light source is positioned to provide light to a second heating section, the controller may be configured to increase the amount of light emitted by the second light source relative to the amount of light emitted by the first light source when a measured temperature corresponding to the second section of the heating element is determined to be less than a measured temperature corresponding to the first section of the heating element.

[0079] In some embodiments, the controller may be configured to activate upon detection of airflow or to control the amount of heat dissipated by the heating element. In some embodiments, the controller may be configured to control an operating parameter based on the determined airflow rate. For example, the controller may be configured to control the temperature of the heating element based on the volumetric flow rate of airflow through the airflow passage.

[0080] In some embodiments, the aerosol generating device may include a liquid storage portion containing the aerosol-forming substrate and a pump for pumping the aerosol-forming substrate from the liquid storage portion to the heating element, where the operating parameters of the device include a flow rate of the aerosol-forming substrate from the liquid storage portion to the heating element, and the controller is arranged to control the flow rate of the aerosol-forming substrate based on the measured first temperature and the measured second temperature. In some embodiments, the controller may be arranged to control the pump to dispense a controlled volume of the liquid substrate based on an airflow event, such as a volumetric airflow rate through the airflow passage. The pump may be arranged to dispense a controlled amount of the liquid substrate based on an amount of airflow passed through the airflow passage. In some embodiments, the liquid storage portion may be a removable cartridge. For example, the aerosol generating device may include a connector for connecting to a connector, such as a luer fitting, of the cartridge.

[0081] In some embodiments, the first portion is a temperature at the heating element, the first temperature being a temperature of the heating element at a first location, the second location being a location downstream of the heating element, and the second temperature being an ambient temperature of the airflow passage at the second location. In some embodiments, the apparatus includes a third temperature sensor for sensing a third temperature at a third location along the airflow passage, the third location being a location upstream of the heating element, and the third temperature being an ambient temperature of the airflow passage at the third location, and the controller is configured to control an operating parameter of the apparatus based on the first temperature, the second temperature, and the third temperature. This may advantageously allow the controller to more accurately determine the airflow rate by taking into account the heater temperature as compared to the relative temperatures or temperature changes measured upstream and downstream of the heating element.

[0082] In some embodiments, the temperature sensor may be an on-chip temperature sensor. The temperature sensor may be planar. The temperature sensor may be embedded within the surface of the heating element. Thus, the use of such an on-chip temperature sensor may advantageously prevent excessive obstruction to the air flowing through the airflow passage. In some embodiments, the surface of such an on-chip temperature sensor may be coated with nanoparticles to achieve surface plasmon resonance. Advantageously, the inclusion of such an on-chip temperature sensor does not reduce the heating surface area available to achieve surface plasmon resonance.

[0083] The power source is preferably a power supply, which may include a DC power source. The power supply may include at least one battery. The at least one battery may include a rechargeable lithium ion battery. The power supply may include another form of charge storage device, such as a capacitor. The power supply may require recharging. The power supply may have a capacity that allows for the storage of sufficient energy for one or more uses of the aerosol generating device. For example, the power supply may have a capacity sufficient to allow continuous generation of aerosol for about 6 minutes, or a multiple of 6 minutes, corresponding to the typical time it takes to smoke one conventional cigarette. In another embodiment, the power supply may have a capacity sufficient to allow a predetermined number of puffs, or discontinuous activation.

[0084] In embodiments in which the aerosol generating device comprises a plasmonic heating element and a light source, the controller may be configured to initiate the supply of power from the power supply to the light source at the start of a heating cycle, and may be configured to terminate the supply of power from the power supply to the light source at the end of the heating cycle.

[0085] The controller may be configured to provide a continuous supply of power from the power supply to the light source.

[0086] The controller may be configured to provide an intermittent supply of power from the power supply to the light source. The controller may be configured to provide a pulsed supply of power from the power supply to the light source.

[0087] Advantageously, pulsing the power to the light source can facilitate control of the total output from the light source over a period of time. Advantageously, controlling the total output from the light source over a period of time can facilitate control of the temperature to which the plasmonic heating element is heated by surface plasmon resonance.

[0088] Advantageously, pulsing the power to the light source can increase the thermal relaxation of free electrons excited by surface plasmon resonance compared to other relaxation processes such as oxidation and reduction relaxation. Thus, pulsing the power to the light source can advantageously increase the heating of the plasmonic heating element. The controller is configured to provide pulsing of power from the power supply to the light source such that the time between successive pulses of light from the light source is about 1 picosecond or less. In other words, the time between the end of each pulse of light from the light source and the next pulse of light from the light source is about 1 picosecond or less.

[0089] The controller may be configured to vary the supply of power from the power supply to the light source. In embodiments in which the controller is configured to provide a pulsed supply of power to the light source, the controller may be configured to vary a duty cycle of the pulsed supply of power. The controller may be configured to vary at least one of a pulse width and a period of the duty cycle.

[0090] The aerosol-forming substrate may comprise a liquid aerosol-forming substrate. The aerosol generating device may comprise a liquid transfer element arranged to transfer the liquid aerosol-forming substrate from the storage portion towards the heating element. The liquid transfer element may comprise a capillary wick.

[0091] The liquid aerosol-forming substrate may comprise water.

[0092] The liquid aerosol-forming substrate may include an aerosol former. Suitable aerosol formers are well known in the art and include, but are not limited to, polyhydric alcohols (such as triethylene glycol, 1,3-butanediol, glycerin, etc.), esters of polyhydric alcohols (such as glycerol monoacetate, diacetate, or triacetate, etc.), and aliphatic esters of mono-, di-, or polycarboxylic acids (such as dimethyl dodecanedioate, dimethyl tetradecanedioate, etc.). Preferred aerosol formers are polyhydric alcohols or mixtures thereof (such as triethylene glycol, 1,3-butanediol, most preferably glycerin or polyethylene glycol).

[0093] The liquid aerosol-forming substrate may comprise at least one of nicotine or a tobacco product. Additionally or alternatively, the liquid aerosol-forming substrate may comprise another target compound for delivery to the user. In embodiments in which the liquid aerosol-forming substrate comprises nicotine, the nicotine may be included in the liquid aerosol-forming substrate along with the aerosol former.

[0094] The aerosol-generating device may comprise a first aerosol-forming substrate and a second aerosol-forming substrate. The heating element is preferably arranged to heat both the first aerosol-forming substrate and the second aerosol-forming substrate.

[0095] According to a second aspect of the present invention, there is provided a liquid storage cartridge including a connector for connecting the liquid storage cartridge to an aerosol generating device, the liquid storage cartridge including a liquid aerosol-forming substrate and configured to collapse upon depletion of the aerosol-forming substrate. Depletion of the aerosol-forming substrate may not cause negative pressure within the liquid storage cartridge. Thus, advantageously, air may be prevented from entering the cartridge. In some embodiments, the connector is a luer fitting.

[0096] According to a third aspect of the present invention there is provided an aerosol generation system comprising an aerosol generating device according to the first and second aspects of the present invention and an aerosol-generating article comprising an aerosol-forming substrate, optionally including a liquid storage cartridge comprising the aerosol-forming substrate.

[0097] As used herein, "aerosol-generating device" refers to a device that interacts with an aerosol-forming substrate to generate an aerosol.

[0098] The term "aerosol-forming substrate" as used herein relates to a substrate capable of releasing volatile compounds capable of forming an aerosol. Such volatile compounds may be released by heating the aerosol-forming substrate.

[0099] The aerosol-forming substrate may be part of an aerosol-forming article. The aerosol-forming substrate may have any suitable configuration and may include any of the features described in more detail below.

[0100] As used herein, the term "aerosol generating system" refers to the combination of an aerosol generating device and one or more aerosol forming articles for use in the device. The aerosol generating system may include additional components, such as a charging unit for recharging an on-board power supply in an electrically operated or electric aerosol generating device.

[0101] According to a fourth aspect of the present invention, there is provided a method for controlling an aerosol generating device comprising a heating element extending in a first direction within an airflow passage, the method comprising the steps of measuring a first temperature at a first location along the airflow passage, measuring a second temperature at a second location along the airflow passage, the second location being spaced apart in the first direction from the first location, and controlling operating parameters of the device based on the measured first temperature and the measured second temperature.

[0102] According to a fifth aspect of the present invention, there is provided an aerosol generating device comprising an air inlet, an air outlet, an airflow passage extending in a first direction between the air inlet and the air outlet, a heating element for heating an aerosol-forming substrate within the airflow passage, a first temperature sensor for measuring a first temperature at a first position along the airflow passage, and a controller configured to control operating parameters of the device based on at least the measured first temperature.

[0103] Features described with respect to one aspect may be equally applied to other aspects of the invention.

[0104] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which: [Brief description of the drawings]

[0105] [Figure 1] FIG. 1 is a perspective view of an aerosol generation system according to one embodiment of the present invention. [Diagram 2] Figure 2a is an exploded perspective view of the heater assembly of Figure 1. Figure 2b is a perspective view of the heater assembly of Figure 1. Figure 2c is a cross-sectional view of the heater assembly of Figures 2a and 2b. [Diagram 3] FIG. 3 is a cross-sectional view of a heater assembly according to one embodiment of the present invention. [Figure 4] FIG. 4 is a perspective view of a heating element of an aerosol generating device according to an embodiment of the present invention. [Diagram 5] Figure 5a is a schematic diagram of heat dissipation in the heating element of Figure 4 in a first state in which there is substantially no airflow across the heating element, and Figure 5b is a schematic diagram of heat dissipation in the heating element of Figure 4 in a second state in which an air supply is drawn across the heating element into the aerosol generation device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0106] FIG. 1 shows an aerosol generation system 10 comprising an aerosol generation device 20 and a liquid reservoir 100 containing a liquid aerosol-forming substrate for use in the aerosol generation device 20 .

[0107] The aerosol generating device 20 includes a housing configured to receive a liquid storage portion 100, for example in a storage compartment. The liquid storage portion 100 in the illustrated embodiment of FIG. 1 is a replaceable cartridge that includes an aerosol-forming substrate, such as a liquid aerosol-forming substrate. The replaceable cartridge is connectable to a dosing unit 60 of the aerosol generating device 20 by a leak-proof connection 62, such as a luer coupling and tubing 64. The dosing unit 60, which in the illustrated embodiment includes a pump, provides a controlled delivery of the liquid aerosol-forming substrate to the heater assembly 30, where the liquid substrate is heated to form a vapor. When a user puffs on the mouthpiece 66, an air supply is drawn into the aerosol generating device 20 through the air inlet 50. The air supply, at ambient temperature, condenses the vapor to form a flow of the generated aerosol. The mouthpiece 66 forms an air outlet 52. When a user puffs on the mouthpiece 66, the generated aerosol may exit the device and enter the user's mouth. Thus, the air supply and generated aerosol flow within an airflow passage defined between the air inlet 50 and the air outlet 52 .

[0108] The heater assembly 30 in the illustrated embodiment includes a plasmonic heating element. The plasmonic heating element generates heat by surface plasmon resonance (SPR). The plasmonic heating element typically includes a plurality of metal nanoparticles and may be based on excitation of the metal nanoparticles with light, e.g., visible light from a light source 40. Exposure to the incident light results in collective oscillation of the free electrons of the metal nanoparticles and polarization of the charge at the surface of the metal nanoparticles. In order to relax back to its initial state, the nanoparticles release this surplus of energy in the form of heat. Typically, the nanoparticles used in plasmonic heaters have a particle size equal to or smaller than the wavelength of visible light.

[0109] The aerosol generating device 20 includes an electrical energy source 12, such as a rechargeable lithium ion battery. The electrical energy source 12 includes a charging port 16 for charging the rechargeable battery. The device 10 further includes a controller 14 communicatively coupled to one or more light sources. In the illustrated embodiment, the light sources include light emitting diodes (LEDs) 40. The controller is also communicatively coupled to the electrical energy source 12 and a user interface 26. In this embodiment, the user interface 26 is a mechanical button. Upon activation of the user interface 26, the controller controls the power provided from the electrical energy source 12 to the light source 40 to heat the heating element 30 to a required operating temperature. In some embodiments, the controller controls the power provided to the light source 40 to provide a heating profile, such as a temperature profile of the heating element, over the period of time that the device 20 is in use.

[0110] 2a-c show an example of a heater assembly 30. In the illustrated embodiment, the heater assembly 30 includes a heating element 32. A light source 40 is positioned such that it radiates light toward the heating element 32 when the light source 40 is powered. The heater assembly 30 includes an aerosol-generation chamber 38 between the light source 40 and the heater assembly 30. The aerosol-generation chamber 38 provides a volume in which a liquid substrate may be vaporized to generate an aerosol along with an incoming air supply. The aerosol-generation chamber 38 forms part of an airflow passage between an air inlet 50 and an air outlet 52. The airflow passage extends along a first direction between the air inlet 50 and the air outlet 52. The first direction is coincident with or substantially parallel to a longitudinal axis of the device 20.

[0111] The heating element 32 in the illustrated embodiment comprises a planar element comprising a silicon-based material, e.g., quartz, which has the ability to maintain its mechanical strength at high temperatures. The heating element 32 includes a heating surface 34 that extends across at least a portion of the heating element 32 within the aerosol generation chamber 38 for heating and vaporizing an incoming dose of liquid substrate. The heating surface 34 includes a plurality of metal nanoparticles for achieving surface plasmon resonance.

[0112] In this particular example, the heating surface 34 is coated with a layer of silver nanoparticles with an average diameter of 100 nm, although other sizes of nanoparticles are applicable. Alternatively, other metal colloids or nanoparticles may be used, for example gold or platinum nanoparticles. Also, a mixture of metal nanoparticles, such as a mixture of gold and silver nanoparticles, may be applied to the heating surface 34 to perform plasmonic heating. Since the amount of nanoparticles is an important factor for managing the power output of the plasmonic heater, it is preferable to provide as many nanoparticles as possible on a given heating surface. Thus, to increase the nanoparticle density and therefore the heat generated by surface plasmon resonance, in some embodiments the heating surface includes multiple nanoparticle layers to increase the total number of available metal nanoparticles.

[0113] The illustrated light source 40 may include light emitting diodes (LEDs). More specifically, the light source 40 includes an array of LEDs arranged such that each is independently controllable by the controller 14. For example, the LEDs may each emit light sequentially, at different intensities or at different wavelengths, thereby varying the temperature rise across the heating surface. This is particularly beneficial for enabling selective localized heating of the heating surface 34.

[0114] The light source 40 is positioned to align with the heating surface 34 of the heating element 32. For example, the light source 40 is overlapped but spaced from the heating surface 34. This arrangement provides the metal nanoparticles with maximum exposure to the incident light emitted by the LED array. For example, multiple LEDs in the LED array may each emit light sequentially, at different intensities, or at different wavelengths. This causes a change in temperature across the heating surface. This is beneficial as it also allows for selective localized heating. This may be used to compensate for localized temperature variations across the heating surface 34 of the heating element 32. In use, the light source 40 is positioned to heat the heating surface 34 to a temperature of between 200 and 350 degrees Celsius.

[0115] As illustrated in Fig. 2c, the apparatus 20 includes a lens 44 that refracts and focuses the light emitted by the LED array toward the heating surface 34. The lens 44 is disposed between the LED light source 40 and the heating surface 34. For example, each of the LEDs in the LED array 40 includes a lens integrally formed with the LED. Additional lenses 44 are stacked above the LED array. The refracted light may be focused or dispersed by the lens 44 to control the amount of light transmitted to the heating surface 34 or a portion thereof.

[0116] In some embodiments, alternative light sources may be used as the light source. For example, the light source may include a laser diode. A laser diode allows for maximum excitation of certain types of nanoparticles. In some embodiments, the lens 36 of the heater assembly 30 may be connected to a light conduit (not shown) that extends toward the environment outside the housing 12 of the device 20 and captures and transmits light from an external source, such as natural daylight or ambient light, toward the heating surface 34 of the heating element 32. In such a case, the light collected at the lens 44 may be of lower intensity compared to the artificial light source 38. Nevertheless, the external light source may be used to preheat the aerosol-forming substrate 102 to an elevated temperature above ambient temperature, thus reducing power consumption in the artificial light source 38.

[0117] The heater assembly 30 includes a liquid channel 36 for delivering the liquid substrate to the heating surface 34. A single liquid channel 36 is shown having an outlet adjacent to the heating surface 34. Alternatively, multiple liquid channels may be provided. The use of multiple liquid channels may advantageously provide branched liquid delivery to the liquid substrate across the width of the heating surface 34.

[0118] A capillary fitting 65 is provided to connect the tubing 64 and the liquid channels 36. The capillary fitting 65 also forms a distributor for distributing a dose of liquid substrate evenly among the multiple liquid channels 36.

[0119] The heater assembly 30 further includes an air inlet 50 for drawing into the air supply. At least one air inlet 50 is in fluid communication with the airflow passageway. When a user draws on the mouthpiece 66, an air supply is drawn from the environment external to the device 20 through the air inlet 50 into the aerosol-generation chamber 38. When the heating element 32 is activated, the air drawn into the device is relatively cooler compared to the ambient air within the device proximate the heater. The relatively cooler air supply condenses at least a portion of the vaporized aerosol-forming substrate in the aerosol-formation chamber 38, thereby forming the generated aerosol stream.

[0120] Heat generated at the heating surface 34 by surface plasmon resonance radiates throughout the aerosol-generation chamber 38. This can heat the LED light source 40. Advantageously, the flow of air supply through the aerosol-generation chamber 38 via the air inlet 50 cools the light source 40, thus preventing it from overheating.

[0121] In some embodiments, the heating surface 34 may include multiple individual heating sections. This allows for more accurate determination of temperature gradients across the heating surface 34. In some embodiments, each heating section may include different densities of metal nanoparticles or different numbers of nanoparticle layers. This results in temperature variations across the different heating sections when all of the heating sections are exposed to a uniform light source. This is beneficial because it allows for selective localized heating. For example, upstream heating sections closer to the air inlet 50 may include relatively more nanoparticles compared to downstream heating sections proximal to the air outlet 52 and mouthpiece 66, since these heating sections are more affected by the relatively cooler incoming air. In some cases, multiple heating sections also allow for selective heating of the aerosol-forming substrate, thus allowing different liquid substrates and flavor compositions along the substrate to be heated at different temperatures.

[0122] The liquid storage portion 100 used in the illustrated embodiment is a replaceable cartridge. The replaceable cartridge 100 includes a flexible sidewall and is arranged to collapse upon depletion of the aerosol-forming substrate. Depletion of the liquid aerosol-forming substrate in the cartridge 100 does not cause negative pressure in the liquid storage portion. Thus, displacement of the aerosol-forming substrate does not result in air bubbles re-entering the cartridge 100. Thus, the possibility of intermittent liquid substrate delivery caused by such air bubbles and pump cavitation is reduced.

[0123] FIG. 3 shows a cross-section of another embodiment of the invention. An aerosol generation chamber 38b can include a tubular housing 22b. In this example, the aerosol generation device 20b includes the same components as the device 20 shown in FIGS. 2a-2c. A light source 40b and a lens 44b are formed on the outside of the tubular housing 22b. The lens 44b is positioned to refract and focus light emitted by the light source 40b onto a planar heating surface 34b in the heating element 32b. A portion of the tubular housing 22b includes a support 24b to provide a uniform platform for supporting a heating element 32b, such as the planar heating element 32b.

[0124] FIG. 4 is a perspective view of a portion of the heater assembly 30. The heater assembly 30 includes a heating element 32 and a plurality of temperature sensors 80, 82, 84. In the illustrated embodiment, the plurality of temperature sensors includes a heating element sensor 80 at the heating surface 34 to measure the temperature at the heating element. The plurality of temperature sensors 80, 82, 84 further includes an upstream sensor 82 and a downstream sensor 84 located upstream and downstream of the heating surface 34, respectively. In this example, the upstream sensor 82 and the downstream sensor 84 are spaced equal distances from the heating surface 34 to measure the temperature. The temperatures measured by the upstream sensor 82 and the downstream sensor 84 may include the air temperature at or proximate the respective sensor 82, 84, or the temperature of the generated aerosol at or proximate the respective sensor 82, 84. As used herein, the term "upstream" refers to a position relatively closer to the air inlet 50 than the air outlet 52. As used herein, the term “downstream” refers to a location relatively closer to the air outlet 52 than to the air inlet 50 .

[0125] The temperature sensors 80, 82, 84 may be on-chip temperature sensors. Such on-chip temperature sensors are generally planar and may be easily embedded within the heating element 32. Thus, the use of these on-chip temperature sensors does not cause undue disturbance of the airflow pattern in the aerosol generation chamber 38. Additionally, the surfaces of such on-chip temperature sensors may be coated with metal nanoparticles. This is particularly beneficial for the heating element sensor 80, as the inclusion does not reduce the amount of heating surface 34 available to achieve plasmonic heating.

[0126] The controller 14 is arranged to control operating parameters of the device 20 based on at least two temperatures along the airflow path. The temperature of the heating element 32 measured by the heating element sensor 80 may be sufficient for the controller 14 to provide feedback control over the power supply to the light source 40. More specifically, the controller 14 may be arranged to control the intensity, or pulse rate, or a combination of intensity and pulse rate, of the light as emitted by the light source 40 based on the measured heater temperature. This allows the temperature of the heating element 32 to be controlled and maintained at a desired temperature or within a desired temperature range. The controller may apply conventional temperature control based on the measured heater temperature.

[0127] The use of multiple temperature sensors 80, 82, 84 allows for the acquisition of additional operational information, such as temperature gradients across the heating surface 34, temperature gradients across the aerosol-generation chamber 38, or airflow events. Based thereon, new control mechanisms can be applied. For example, temperatures measured at different locations across the aerosol-generation chamber 38 by the temperature sensors 80, 82, 84 can be used to determine airflow events, such as inhalation, exhalation, or airflow, such as volumetric airflow of the air supply. FIG. 5a shows an air temperature profile along the aerosol-generation chamber 38 when there is no airflow through the airflow passage. The heating surface 34 is excited by incident light without the user sucking on the mouthpiece. For example, the user may engage the user interface 26 to initiate pre-heating of the heating element 32. The volume of stagnant air around the heating surface 34 is gradually heated by the heating surface 34, primarily by natural convection. As a result, the air temperature gradually decreases with increasing distance from the heating surface 34, as shown in FIG. 5a. As shown in Figure 5a, the temperature distribution of stagnant air around an activated heating element 32 is substantially symmetric. Because the temperature is the same in both the upstream and downstream directions, the upstream and downstream sensors 82, 84 detect similar air temperatures at each end of the heating surface 34. Such a temperature reading indicates that there is no airflow in the chamber, and therefore the controller may shut off power to the light source to prevent overheating at the heating surface 34 as well as to conserve energy.

[0128] FIG. 5b shows another temperature profile along the aerosol-generation chamber 38 as the user draws on the mouthpiece. In this embodiment, there is an air supply 90 flowing in a direction from the upstream sensor 82 toward the downstream sensor 84. The ambient air supply displaces stagnant air at the heated surface, thereby lowering the air temperature measured by the upstream sensor 82. Meanwhile, the downstream sensor 84 may detect an increase in air temperature as the heated air and generated aerosol are carried by convection toward the downstream sensor 84. The relative change in air temperature detected by the upstream sensor 82 and the downstream sensor 84 is related to the flow rate of the air supply 90. For example, a high air flow increases the difference in temperatures detected by the upstream sensor 82 and the downstream sensor 84. As a result, the air flow rate of the air supply 90 may be determined from two temperatures, such as the difference or ratio between the two temperatures measured by the sensors 82, 84 spaced apart from each other. This sensing may be used in combination with the heating element sensor 80 to provide a more accurate determination of the temperature gradient across the heated surface 34 of the heating element 32 within the aerosol generation chamber 38 .

[0129] The heater temperature measured by the heating element sensor 80 in combination with only one of the upstream sensor 82 and downstream sensor 84 may additionally be used to determine the airflow rate based on an enthalpy balance. The downstream temperature sensed by the downstream sensor 84 may be compared to the temperature of the heating element 32 to estimate the volume of air flowing between the heating element sensor 80 and the downstream temperature sensor 84. For example, for a given temperature of the heating element, a relatively large airflow rate will result in a relatively low downstream temperature sensed by the downstream sensor 84 because the heating element provides heating to a large volume of incoming air. Additional consideration of the temperature of the heating element 32 improves the accuracy of the airflow rate calculation.

[0130] The controller 14 may refer to information stored in the memory to process one or more temperatures sensed by the sensors 80, 82, 84, or to determine how to control the operating parameters based on one or more temperatures, or both. The memory may be a non-transitory computer-readable medium. The memory may be part of the aerosol generating device or may be remote to the device, such as a memory storage space on a cloud-based server. The information may include at least one look-up table. The information may include at least one algorithm. For example, the look-up table stored in the memory may provide empirical airflow rates corresponding to different temperature measurements. The look-up table may also provide empirical airflow rates corresponding to different temperature measurements and distances separating the temperature sensors.

[0131] The controller is arranged to control the operating parameters of the device 20 based directly on the temperatures measured from the plurality of temperature sensors 80, 82, 84. The controller may be arranged to control the operating parameters of the device 20 based indirectly on the temperatures measured from the plurality of temperature sensors 80, 82, 84. For example, the controller may be arranged to control the operating parameters of the device 20 based on airflow events, such as airflow rate, determined from the measured temperatures, as described above. The operating parameters may include a plurality of operating parameters. The operating parameters may include any one or more of the following: the temperature of the heating element 32, a temperature profile of the heating element 32, such as an output temperature over time, the power supplied directly or indirectly to the heating element 32, the flow rate of the aerosol-forming liquid substrate from the liquid storage portion 100 to the heating surface 34, and the dose volume of the aerosol-forming liquid substrate supplied to the heating surface 34. As described above, the temperature or temperature profile of the heating surface 34 may be controlled by the controller 14 controlling the power supplied to the heating element 32 from the electrical energy supply 12, from the power supply to the heating element 32. The power may be supplied directly to the heating element 32. Power may be supplied directly to the heating element 32 , for example, by supplying power to a light source 40 , which is positioned to provide light to a plasmonic heating surface 34 of the heating element 32 .

[0132] In an exemplary embodiment, the aerosol generating device 20 is arranged to control the flow rate of the aerosol-forming liquid substrate from the liquid storage portion 100 to the heated surface 34 in the following manner: First, a user activates the light source 40 by pressing a mechanical button on the user interface 26. Light is emitted from the light source 40 and incident on the metallic nanoparticles of the heated surface 34, initiating surface plasmon resonance. The nanoparticles on the heated surface 34 repeatedly undergo surface plasmon resonance after thermal relaxation, increasing the temperature of the heated surface 34 to a desired operating temperature. Typically, the heated surface 34 is heated to an operating temperature in the range of 200-350 degrees Celsius.

[0133] The controller 14 may determine when the heating surface 34 of the heating element 32 reaches a first threshold temperature, such as a desired operating temperature. When the heating surface 34 reaches the first threshold temperature, the controller 14 activates the pump of the dosing unit 60 to deliver a dose of aerosol-forming liquid substrate to the heating surface 34 upon reaching the desired operating temperature. The controller 14 may terminate or reduce power to the light source when the heater temperature exceeds a second threshold temperature. The second threshold temperature may be relatively higher than the first threshold temperature and may be related to a predetermined temperature limit. Thus, the controller 14 may prevent overheating of the heating element.

[0134] The controller 14 may analyze relationships, such as relative differences or ratios, between the temperature measurements obtained by the multiple sensors 80, 82, 84. The controller 14 then determines the instantaneous airflow rate across the aerosol-formation chamber 38 based on this analysis.

[0135] Based on the determined airflow rate, the controller 14 determines whether a temperature adjustment of the heating surface 34 is required. For example, when a user puffs on the mouthpiece 66, ambient air is drawn into the aerosol generation chamber 38 through the air inlet 50. This incoming air first has a cooling effect on at least a portion of the heating surface 34 of the heating element 32. Thus, upon detecting an inhalation, the controller 14 may determine that a temperature adjustment is required, such as an increase in temperature at the heating surface 34. If the controller determines that a temperature adjustment is required, the controller 14 may determine to provide the required amount of power to the light source 40 to achieve the determined temperature adjustment. Thus, the controller 14 controls the temperature of the heating surface 34 to compensate for the cooling induced by the incoming air supply when the user puffs on the mouthpiece 66. This maintains a consistent operating temperature at the heating surface 34 of the heating element 32 while the user operates the device. Thus, overheating of the heating element 32 may be prevented. Excessive cooling of the heating surface 34 due to fluctuations in the incoming air may also be prevented.

[0136] In some embodiments, based on the determined airflow rate, the controller may also determine the amount of aerosol-forming liquid substrate that needs to be dispensed at the heated surface 34. The controller 14 then adjusts the operation of the pump of the dosing unit 60 to control the rate of aerosol-forming liquid substrate delivery to the heated surface 34. More specifically, the amount of liquid substrate dispensed onto the heated surface 34 may be proportional to the airflow rate. This allows for a consistent aerosol concentration in each puff, regardless of how hard the user draws on the mouthpiece 66.

[0137] In some embodiments, the pump of the dosing unit 60 is arranged to deliver a fixed amount of liquid substrate upon detection of an airflow, such as an airflow indicating that a user has taken a puff on the mouthpiece 66 of the device 20. For example, upon detection of a temperature difference between the upstream sensor 82 and the downstream sensor 84, the controller 14 outputs a signal to the dosing unit 60 to deliver a fixed dose of aerosol-forming liquid substrate onto the heated surface 34. Compared to a continuous pumping system in which the aerosol-forming liquid substrate is delivered continuously upon heater activation, this arrangement limits the amount of aerosol generated per puff. Thus, if the aerosol-forming liquid substrate contains nicotine, the nicotine in the aerosol delivered with each puff is limited. This provides a consistent nicotine delivery throughout a session of use of the device.

[0138] In some embodiments, the controller 14 is arranged to provide power to the light source 40 only when airflow is detected passing through the aerosol-generation chamber 38. In such embodiments, the heated surface 34 may be heated only as the generated aerosol is drawn through the aerosol-generation chamber 38. This may not only prevent the liquid substrate from drying out on the heated surface 34, but may also protect the heater assembly 30 from overheating.

[0139] In some embodiments, the controller 14 is arranged to monitor the user's puffing behavior based on the determined airflow rate. The controller 14 may determine a puff rate, a puff frequency, a puff volume, or any combination thereof. The controller 14 may then determine a total amount of aerosol-forming liquid substrate inhaled by the user over each use cycle. If the aerosol-forming liquid substrate includes nicotine, the controller 14 may determine a total amount of nicotine inhaled by the user over each use cycle. This allows for the implementation of safety limits to limit the amount of nicotine that can be inhaled by the user over a given period of time. For example, the aerosol generating device 20 may reduce the dosage of the aerosol-forming liquid substrate or cease operation when the user approaches or exceeds a predefined nicotine limit in each use cycle.

[0140] In some embodiments, the controller 14 may modify the feedback control provided to the pump and heater assembly 30 of the dosing unit 60 with reference to the monitored puff behavior. For example, the controller 14 may determine the average puff duration for a particular user, or the average pause duration between puffs. The controller 14 may then apply this information to control the heating and dosing of the aerosol-forming liquid substrate. The controller 14 may automatically stop heating and dosing of the liquid substrate as the average puff duration elapses. The controller 14 may resume heating the heating surface 34 when the average pause duration is nearing expiration. This may facilitate aerosol generation and delivery while improving the efficiency of the device 20.

[0141] In some embodiments, the aerosol generating device 20 includes only two or less of the multiple temperature sensors 80, 82, 84. This arrangement reduces the amount of data that needs to be analyzed, and therefore reduces the complexity of the process control. For example, the determination of the airflow rate across the aerosol generating chamber 38 can be accomplished using only two temperature sensors spaced apart from one another. More specifically, in one embodiment, there is no heating element sensor 80, and only an upstream sensor 82 and a downstream sensor 84 are provided. Thus, control of the heater temperature and the dosing of the liquid substrate can be based on the temperature across the two sensors 82, 84, and the airflow rate determined as described in the embodiment above with respect to FIG. 5b.

[0142] In some embodiments, only the heating element sensor 80 and the downstream sensor 84 are provided in the aerosol generating device 20. The airflow rate through the aerosol generating chamber 38 may be determined based on the difference between the heater temperature and the air temperature downstream of the heating surface 34. More specifically, the airflow rate may be determined by determining the amount of heat dissipation at a particular temperature of the heating surface 34 of the heating element 32. The controller 14 may reference a look-up table stored in memory to improve the accuracy of the airflow rate determination. The look-up table may provide empirical airflow rates corresponding to different downstream temperatures and heater temperatures. The look-up table may provide empirical airflow rates corresponding to different downstream temperatures, different heater temperatures, and distances separating the downstream sensor 84 relative to the heating surface 34.

[0143] In some embodiments, only one upstream sensor 82 is provided in the vicinity of the heated surface 34. For example, the temperature reading at the upstream sensor 82 may enable the controller 14 to determine the frequency and duration of each puff based on the amount of cooling upstream of the heated surface 34 induced by the incoming air supply. As shown in FIG. 5a, in the absence of airflow in the airflow channel, the upstream air temperature gradually increases while the heated surface 34 is activated. As the user puffs on the mouthpiece 66, the incoming air supply causes a drop in the measured upstream temperature. Thus, the time history of the upstream temperature, or the temperature change over time, is indicative of the flow of the air supply and thus the puffing behavior of the user. The use of the upstream sensor 82 may also serve as an automatic trigger for heating the heated surface 34 and pumping the liquid substrate.

[0144] In some embodiments, only the downstream sensor 84 is provided in the aerosol generating device 20. More specifically, the heating element sensor 80 and the upstream sensor 82 are omitted. By referring to a look-up table, the controller 14 is arranged to estimate the heater temperature from the power consumed by the light source 40. The controller may then determine the airflow rate based on the difference between the estimated heater temperature and the air temperature measured by the downstream sensor 84, using the method described in relation to the embodiment shown in FIG. 5b.

[0145] In some embodiments, multiple heating element sensors 80 are provided along the length of the heating surface 34. The heating surface 34 includes multiple heating sections. Each of the heating element sensors 80 is provided in a respective heating section to detect the local heating section temperature. Each of the heating sections is independently excitable by a respective local light source. For example, each of the local light sources is an LED in the LED array 40.

[0146] In use, a lack of airflow across the aerosol-generation chamber 38 results in a lack of air cooling at the heated surface 34, and therefore the heated section temperatures measured by each of the heating element sensors 80 will return similar values. When a user draws on the mouthpiece 66, the incoming air supply cools a portion of the heated surface 34 closest to the air inlet, such as the upstream heated surface. This results in different temperature readings at the heating element sensors 80 across the different heated sections. Thus, the airflow rate can be determined based on the relative difference between the heater temperatures measured across the different heated sections.

[0147] Additionally, multiple heating element sensors 80 mounted along the heating surface 34 allow for localized heating control. For example, the controller is arranged to control the power as supplied to each of the localized light sources based on the respective heating element sensor 80. This is particularly beneficial when more power is supplied to the localized light sources to energize the upstream heating section to compensate for cooling induced by the ambient air supply.

[0148] The above exemplary embodiments are illustrative and not limiting. In light of the exemplary embodiments discussed above, other embodiments consistent with the above exemplary embodiments will be apparent to those skilled in the art.

Claims

1. An aerosol generating device, comprising: An air intake; An air outlet; an airflow passage extending in a first direction between the air inlet and the air outlet; a heating element for heating the aerosol-forming substrate within the airflow passage; a first temperature sensor for measuring a first temperature at a first location along the airflow passage, the first location being a location at the heating element, and the first temperature being a temperature of the heating element at the first location; and a second temperature sensor for measuring a second temperature at a second location along the airflow passage spaced in the first direction from the first temperature sensor, the second location being a location downstream of the heating element, and the second temperature being an ambient temperature of the airflow passage at the second location; a third temperature sensor for measuring a third temperature at a third location along the airflow passage, the third location being a location upstream of the heating element, and the third temperature being an ambient temperature of the airflow passage at the third location; and and a controller configured to control operating parameters of the aerosol generating device based on the measured first temperature, the measured second temperature, and the measured third temperature.

2. 2. The aerosol generating device of claim 1, wherein the heating element comprises a plurality of heating sections, and the first temperature sensor is positioned in each heating section of the heating element.

3. 3. The aerosol generating device of claim 2, wherein the controller is configured to determine a temperature distribution across the plurality of heating sections and to control power supplied to the plurality of heating sections based on the determined temperature distribution.

4. An aerosol generating device as described in any one of claims 1 to 3, wherein the controller is arranged to determine a temperature distribution across the heating element and to control the operating parameters based on the determined temperature distribution.

5. An aerosol generating device as described in any one of claims 1 to 4, wherein the operating parameters of the aerosol generating device include the temperature of the heating element, and the controller is configured to control the output temperature of at least a portion of the heating element based on the measured first temperature and the measured second temperature.

6. An aerosol generating device as described in any one of claims 1 to 5, wherein the controller is configured to determine an airflow rate through the airflow passage based on the measured first temperature and the measured second temperature.

7. 7. The aerosol generating device of claim 6, wherein the controller is configured to control the operating parameters based on the determined airflow rate.

8. An aerosol generating system comprising the aerosol generating device according to any one of claims 1 to 7 and an aerosol-generating article including an aerosol-forming substrate.

9. 1. A method of controlling an aerosol generating device, the aerosol generating device comprising a heating element extending in a first direction within an airflow passage, the method comprising: - measuring a first temperature at a first location along the airflow passage, the first location being a location at the heating element, the first temperature being the temperature of the heating element at the first location; - measuring a second temperature at a second location along the airflow passage, the second location being spaced in the first direction from the first location, the second location being a location downstream of the heating element, the second temperature being an ambient temperature of the airflow passage at the second location; - measuring a third temperature at a third location along the airflow passage, the third location being a location upstream of the heating element, the third temperature being an ambient temperature of the airflow passage at the third location; - controlling operating parameters of the aerosol generating device based on the measured first temperature, the measured second temperature, and the measured third temperature.

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