Aerosol generator

Abstract

The aerosol generator (10) includes a heating chamber (18) configured to receive consumables (100) including an aerosol generating substrate (102), a heating assembly operable to supply heat to the aerosol generating substrate during a usage session, and a controller (24). The controller is operable to monitor an observable quantity indicating the moisture content of the aerosol generating substrate during a usage session and to progressively present an index of the moisture content of the aerosol generating substrate to the user during the usage session. The observable quantity may be a delay associated with an RC monitoring circuit having a predetermined time constant. A method for operating the aerosol generator is also described.

Description

Technical Field

[0001] The present disclosure generally relates to an aerosol generating device that heats an aerosol generating substrate to generate an aerosol inhaled by a user of the aerosol generating device. The present disclosure is particularly applicable to portable aerosol generating devices. Such devices generate an aerosol for the user to inhale by heating, rather than burning, an aerosol generating substrate, such as tobacco or other suitable material, by conduction, convection, and / or radiation.

Background Art

[0002] Risk reduction or risk improvement devices (also known as aerosol generating devices or vapor generating devices) have rapidly gained popularity and usage frequency in recent years as an alternative to the use of conventional tobacco products. A variety of devices and systems are available that heat or warm an aerosol generating substance to generate an aerosol for the user to inhale.

[0003] Generally available risk reduction or risk improvement devices are heated substrate aerosol generating devices, or so-called heat-not-burn devices. This type of device generates an aerosol or vapor by heating an aerosol generating substrate to a temperature typically in the range of 150°C to 300°C. By heating the aerosol generating substrate to a temperature within this range without burning or combusting the aerosol generating substrate, vapor is generated, and the vapor typically cools and condenses to form an aerosol for the user of the device to inhale.

[0004] Currently available aerosol generators can supply heat to the aerosol-generating substrate using one of several different approaches. One such approach utilizes an induction heating system. In such a device, an induction coil is provided within the device, and an induction-heatable susceptor is provided to heat the aerosol-generating substrate. When the user starts the device, electrical energy is supplied to the induction coil, generating an alternating current electromagnetic field. The susceptor couples with the electromagnetic field to generate heat, which is then transferred to the aerosol-generating substrate, for example by conduction. As the aerosol-generating substrate heats up, an aerosol is generated.

[0005] Another heating method uses a resistance heating system. In such a device, a resistance heating element is provided to heat the aerosol-generating substrate. When the user starts the device, electrical energy is supplied to the resistance heating element to generate heat, which is then transferred to the aerosol-generating substrate, for example by conduction. As the aerosol-generating substrate heats up, an aerosol is generated.

[0006] In the vast majority of such aerosol generators, the heater operates in a predetermined manner when commanded to start, for example, in response to the user pressing a start button, or in response to the device determining, via an airflow sensor, that the user has inhaled vapor through the device. The heater typically operates for a predetermined session duration, which can be measured over a predetermined time (e.g., 4.5 minutes) or over a predetermined number of inhalations. The session duration or predetermined number of inhalations is selected to consume all or substantially all of the aerosol-generating material in the consumables. [Overview of the project] [Problems that the invention aims to solve]

[0007] Typically, slight variations can exist between different types of consumables, and even between different batches of the same type of consumable, due to manufacturing tolerances, for example. This can lead to situations where a session ends even though some usable aerosol-generating material remains in the consumable, potentially causing user dissatisfaction. Conversely, it can lead to situations where the aerosol generator continues to heat the consumable even after all of the aerosol-generating material in the consumable has been consumed. This can result in an unpleasant session ending for the user (e.g., a bad taste) and an increased risk of the consumable burning in the heating chamber. The objective of the present invention is to mitigate one or more of the above-mentioned problems. [Means for solving the problem]

[0008] According to a first aspect of the present invention, A heating chamber configured to receive consumables including an aerosol generating substrate, A heating assembly that can be operated to supply heat to the aerosol-generating substrate during a usage session, Controller and We provide an aerosol generating device that includes, The controller is During the usage session, an observable amount indicating the water content of the aerosol-generating substrate is monitored. During the usage session, the user will be progressively presented with an indicator of the water content of the aerosol-generating substrate. It is operable for that purpose.

[0009] New consumables suitable for use in aerosol generators typically have a specific moisture content. This moisture content decreases with heating, and used consumables typically have a significantly reduced moisture content, possibly little to no moisture remaining. The moisture content in unheated consumables therefore indicates the expected session length of the consumable. By progressively displaying an indicator of the moisture content of the aerosol-generating substrate within the consumable to the user throughout the session, the expected remaining time of the session can be presented to the user along with a visual representation of the consumption status of the aerosol-generating substrate.

[0010] The controller can operate to select the duration of each session by using monitored observables to determine when to terminate the session. Since moisture content indicates the expected session length, selecting the duration of each session using monitored observables allows for more precise setting of the session length specific to each session.

[0011] The controller may be operable to terminate the session if the monitored observable quantity indicates that the water content of the aerosol-generating substrate is below a first predetermined threshold. The first predetermined threshold may be a water content of 1 to 6%, for example, 5%.

[0012] The controller may be operable to measure an initial value of the observable quantity when the consumable is inserted into the heating chamber before heating begins. The initial value of the observable quantity may therefore represent the initial moisture content of the aerosol-generating substrate. The controller may further be operable to compare the measured initial observable quantity with a further predetermined threshold. The controller may be operable to prevent the heating assembly from operating if the measured initial value of the observable quantity is less than or equal to a further predetermined threshold, which may be the same as the first predetermined threshold. Alternatively, the controller may be operable to cause the heating assembly to operate only if the measured initial value of the observable quantity is greater than or equal to a further predetermined threshold, which may be an observable value representing the expected minimum initial moisture content. If the initial moisture content is unexpectedly low (i.e., the measured initial value of the observable quantity indicates a moisture content below the expected minimum initial moisture content), it may indicate that the consumable is already heated. Therefore, by comparing the measured initial observable quantity with a further predetermined threshold, the aerosol generator can prevent further heating of the already heated consumable.

[0013] The controller may be operable to generate an indicator that the session is nearing its end. Such an indicator may be provided to the user in addition to a progressive indicator of moisture content provided throughout the session. The indicator that the session is nearing its end may be provided when the monitored observable amount indicates that the moisture content of the aerosol-generating substrate is below a second predetermined threshold, which is reached before the first predetermined threshold. The second predetermined threshold may be in the range of 8–3%, or 7–5%, or 6–5%. The second predetermined threshold may be equal to the estimated remaining session time, e.g., 10%, 15%, or 20% of the session remaining (e.g., 30 seconds, 45 seconds, or 1 minute).

[0014] Observable quantities are periodically monitored during the usage session. These may be measured, for example, every 5-100 ms or every 10-50 ms.

[0015] The aerosol generator may further include a monitoring circuit having a predetermined time constant, where the observable quantity is the time delay associated with the monitoring circuit.

[0016] The time constant τ (tau) of a circuit is a parameter that characterizes the circuit's response to a step input. For example, in an RC circuit containing one resistor and one capacitor, the time constant τ (in seconds) = RC, where R is resistance (in ohms) and C is capacitance (in farads).

[0017] Since the capacitance of consumables is non-zero, introducing them into a monitoring circuit with a known time constant changes the circuit's capacitance, and therefore the circuit's time constant. The consumables do not need to be in physical contact with the monitoring circuit to affect its capacitance.

[0018] The capacitance of a consumable depends at least partially on its moisture content. Since the time constant of the monitoring circuit varies with capacitance, the time constant of the monitoring circuit represents an observable indicator of the moisture content of the consumable present in the heating chamber of the aerosol formation apparatus. Changes in the moisture content of the consumable during a session can therefore be observed by monitoring the change in the time constant of a monitoring circuit with a known time constant.

[0019] The monitoring circuit may include an RC circuit having predetermined resistance and capacitance. RC circuits are simple in structure and inexpensive, and the calculation of the measured time constant of such a circuit is straightforward. Since the wiring of the circuit inevitably has a certain capacitance, it will be understood that the use of an RC circuit does not necessarily imply the presence of a capacitor.

[0020] The controller may be capable of supplying a signal to the input of the monitoring circuit and receiving the modified signal from the output of the monitoring circuit. The controller may also be capable of determining the time delay from the modified signal.

[0021] Observable quantities may include rise and / or fall times associated with the signal. In this specification, the term "rise time" refers to the time (in seconds) it takes for a signal (e.g., voltage) to change from a specified low to a specified high. Similarly, the term "fall time" refers to the time it takes for a signal to change from a specified high to a specified low. The controller may therefore be operable to monitor changes in rise and / or fall times rather than monitoring the time constant itself. The relative change in rise time between the presence of a consumable in the heating chamber and the absence of a consumable may be greater than the relative change between the known time constant of the monitoring circuit and the time constant altered due to the presence of the consumable. Therefore, utilizing rise and / or fall times can improve the accuracy of the determination.

[0022] The signal input to the monitoring circuit may include a voltage pulse such as a rectangular wave. The controller may be operable to periodically input the signal to the monitoring circuit. By using an acute signal such as a pulse, it becomes easier to observe the rise and / or fall time.

[0023] A monitoring circuit such as an RC circuit may be electrically connected to the heating circuit of the heating assembly. The change in the time constant of the monitoring circuit is typically small, especially when the consumable is not physically in contact with the monitoring circuit. The inventors have found that by electrically connecting the monitoring circuit to the heating circuit of the aerosol forming device, the magnitude of the change in the time constant increases, and thus the detection sensitivity is improved. Since the heating circuit is necessarily provided in the aerosol forming device, even if the sensitivity is increased in this way, no costs such as the circuit becoming complex or additional manufacturing costs being incurred occur.

[0024] Measurements during the heating session are possible, but it is desirable not to measure exactly at the same time as the heater power pulse. Therefore, the timing of the measurement of the observable quantity may be inserted between the heating pulses, and / or the heating assembly may be stopped when the observable quantity is being monitored. This can reduce the risk of damage to the monitoring circuit by the voltage supplied to the heating assembly, and / or improve the monitoring accuracy by reducing interference in the monitoring signal. The observable quantity may be measured, for example, every 5 to 100 ms, or every 10 to 50 ms.

[0025] The aerosol generating device may be switchable between a heating mode in which a voltage is supplied to a heating circuit and a time delay monitoring mode in which a signal is supplied to a monitoring circuit. The controller may be operable to determine the moisture content of the consumable using only the time delay associated with the monitoring circuit when the aerosol generating device is in the time delay monitoring mode. Thereby, it is possible to prevent the monitoring circuit from being damaged when a voltage is supplied to the heating circuit in the heating mode. The aerosol generating device may include a first switch that can be closed in the time delay monitoring mode and opened in the heating mode, and a second switch that can be closed in the heating mode and opened in the time delay monitoring mode.

[0026] The heating circuit may include a resistive heater such as a resistive wire or a thin film heater.

[0027] The heating chamber may be substantially cup-shaped and may have an open first end operable to receive the consumable. For example, the heating chamber may include a substantially cylindrical sidewall that defines an open first end by being open at the first end and defines the bottom surface of the heating chamber by being closed at the second end. The resistive heater may be outside the heating chamber and may be wound around the heating chamber.

[0028] The aerosol generating device may further include a user interface having an output display, and the aerosol generating device may be operable to progressively present an indicator to the user using the display. The progressive indicator may be presented to the user in any suitable manner. For example, the display may include a light emitting element such as one or more LEDs, and the light emitting element may initially be lit at the start of the session and may be progressively turned off as the session progresses to present a visual indicator of the monitored moisture content. In an alternative example, the output display may include a display screen, and a graphic illustration may be presented to the user via the display screen. Thus, the user can visually observe the depth of consumption of the consumable by the progressive indicator.

[0029] According to a second aspect of the present invention, a method for operating an aerosol generating apparatus is provided, and this apparatus is A heating chamber configured to receive consumables containing aerosol products, A heating assembly that can be operated to supply heat to the aerosol-generating substrate during a usage session, Controller and Includes, This method, During the usage session, monitor the observable amount indicating the water content of the aerosol-generating substrate, During the usage session, the user will be progressively presented with an indicator of the water content of the aerosol-generating substrate. It includes.

[0030] This method may further include determining when to terminate the session using monitored observable quantities.

[0031] This method may further include providing the user with an indicator that the session is nearing its end.

[0032] The method may further include measuring an initial value of the monitored observable quantity before starting heating, and having the controller compare the measured initial value with a further predetermined threshold. The controller may use the comparison to determine whether or not to start heating.

[0033] This method may further be implemented in an aerosol generating apparatus according to the first aspect of the present invention, and may further include any features of the first aspect of the present invention.

[0034] The features of the above-described aspects of the present invention may be combined with features selected from this specification in any order, unless otherwise explicitly stated.

[0035] The present invention will be described in more detail below, primarily illustratively, with reference to the accompanying drawings. [Brief explanation of the drawing]

[0036] [Figure 1] This is a cross-sectional view illustrating an aerosol generation system, including an aerosol generator and consumables placed inside the heating chamber of the aerosol generator. [Figure 2] Figure 1 is a schematic diagram of a thin-film heater suitable for use in an aerosol generating apparatus. [Figure 3] Figure 2 shows the thin-film heater wrapped around the heating chamber. [Figure 4] This diagram schematically shows the time-dependent changes in the measured, observable quantity indicating moisture content. [Figure 5] Figure 1 shows an exemplary monitoring circuit suitable for use in the aerosol generator, illustrating the first time-delay monitoring mode and the second heating mode. [Figure 6] A schematic diagram of a time delay monitoring method is shown. [Figure 7] This shows the variation in rise and / or fall times measured before, during, and after insertion of consumables into the heating chamber. [Figure 8] This shows the variation in rise and / or fall times measured before, during, and after insertion of already heated consumables into the heating chamber. [Figure 9] This is a close-up of the region shown in the graph in Figure 7. [Modes for carrying out the invention]

[0037] First, referring to Figure 1, an example of an aerosol generation system 1 is illustrated. The aerosol generation system 1 includes an aerosol generating device 10 and consumables 100, also referred to herein as aerosol products, used with the device 10. The aerosol generating device 10 may have a size that fits the elements described in the various embodiments disclosed herein and may have any shape that can be comfortably held by a user with one hand without the use of assistive devices.

[0038] The first end 14 of the aerosol generator 10, shown towards the bottom of Figure 1, is conveniently referred to as the distal end, bottom, base, or lower end of the aerosol generator 10. The second end 16 of the aerosol generator 10, shown towards the top of Figure 1, is referred to as the proximal end, uppermost, or upper end of the aerosol generator 10. During use, the user typically orients the aerosol generator 10 so that the first end 14 is downward and / or distal to the user's mouth, and the second end 16 is upward and / or proximal to the user's mouth.

[0039] The aerosol generator 10 includes a heating chamber 18. The heating chamber 18 defines its internal volume in the form of a cavity 20 having a substantially cylindrical cross-section. The cavity 20 of the heating chamber 18 opens toward the second end 16 of the aerosol generator 10. The heating chamber 18 has a longitudinal axis defining its longitudinal direction and is made of a metallic material such as stainless steel.

[0040] The heating assembly 15, including the heating element 22, is positioned in close proximity to the heating chamber 18 and is operable to supply heat to the heating chamber. The heating element 22 is contained within a heating circuit 40 that is electrically connected to a controller 24.

[0041] The aerosol generator 10 further includes a power supply 26, which may consist of one or more rechargeable batteries. The controller 24 connects the power supply 26 to the heating element 22. The controller 24 may also be connected to a user interface 23 which includes input terminals such as a power button for receiving commands from the user, and / or output terminals such as indicator lights, a display screen, or an audio or vibration alarm for providing information to the user. The controller 24 may also have an interface with an antenna 25 for wireless communication with a remote device such as the user's smartphone, and can be used not only for input and output but also for data relay between the aerosol generator 10 and the manufacturer of the device.

[0042] The heating chamber 18, specifically the cavity 20, is arranged to receive a moderately shaped, roughly cylindrical or rod-shaped aerosol product 100. Typically, the aerosol product 100 includes a pre-packaged aerosol generating substrate 102. The aerosol product 100 is a disposable and replaceable article (also known as a “consumable”) which may contain, for example, tobacco as the aerosol generating substrate 102. The aerosol product 100 has a proximal end 104 (or mouth end) and a distal end 106. The distal end 106 is inserted into the heating chamber 18 of the aerosol generating device 10 so that at least the aerosol generating substrate 102 is housed within the heating chamber 18. The aerosol product 100 further includes a mouthpiece 108 located downstream of the aerosol generating substrate 102. At least a portion of the mouthpiece 108 protrudes from the heating chamber 18 so that the proximal end 104 of the aerosol product 100 is accessible to the user's mouth. Once the aerosol generator 10 heats the aerosol product 100, heated vapor is released from the aerosol generating substrate 102. As air is drawn towards the proximal end 104 of the aerosol product 100 by the user's inhalation, the vapor cools and condenses as it passes through the mouthpiece 108 to form an aerosol with properties suitable for inhalation. The mouthpiece 108 may further include a filter (not shown) to remove particles or droplets larger than a certain size from the airflow.

[0043] The aerosol-generating substrate 102 and the mouthpiece 108 are coaxially aligned within a wrapper 110 (e.g., wrapping paper) that holds the elements in place to form a rod-shaped aerosol product 100. Typically, the wrapper 110 does not cover the ends 104, 106 of the aerosol product 100, allowing air to flow through the aerosol product 100 from the distal end 106 to the proximal end 104.

[0044] The aerosol generating substrate 102 may be provided as a solid or paste material in the form of shredded, pelletized, powdered, granular flakes, or sheets, or optionally a combination thereof. The aerosol generating substrate may contain tobacco, for example, in a dried or hardened state, and in some cases may contain additional components for flavoring, making it milder, or otherwise more pleasant. In some examples, the aerosol generating substrate 102, such as tobacco, may be treated with a vaporizer. The vaporizer can improve the generation of vapor from the aerosol substrate. The vaporizer may contain, for example, a polyol such as glycerol, or a glycol such as propylene glycol. In some cases, the aerosol generating substrate may not contain tobacco or even nicotine, and instead may contain natural or artificially derived components to provide flavoring, volatility, improved mildness, and / or other pleasurable effects. The aerosol generating substrate 102, such as tobacco, may contain one or more humectants, such as glycol, that retain moisture.

[0045] Before use, the aerosol-generating substrate 102 has an initial moisture content that may depend on its design, shape, packaging, type, flavor, etc. As used herein, "moisture content" refers to the amount of water and any other humectants that may be present in the aerosol-generating substrate 102, and may be defined by the mass (e.g., weight moisture content), volume (e.g., volumetric moisture content), or any other measurable physical quantity of the aerosol-generating substrate. In practice, it will be understood that moisture content may vary slightly between consumables. Typically, the moisture content of a tobacco stick before use (i.e., initial moisture content) is about 15%. After use, the moisture content of a tobacco stick typically decreases to about 5%.

[0046] In the illustrated embodiment of the present invention, the heating chamber 18 includes a first end 28 that is open to a second end and a closed base 30. That is, the heating chamber 18 is cup-shaped. This ensures that air drawn in from the open end 28 is guided around the consumable towards the base 30, and at certain points the air is drawn in through the aerosol-generating substrate 102.

[0047] As described above with respect to Figure 1, the aerosol generator 10 includes a heating chamber 18 configured to receive consumables 100 including an aerosol generating substrate 102, a heating assembly 15 configured to supply heat to the heating chamber 18, and a controller 24. The controller 24 is operable to monitor an observable amount indicating the moisture content of the aerosol generating substrate during a usage session and to progressively present an index of the moisture content of the aerosol generating substrate to the user during a usage session.

[0048] Figure 2 shows an example of a heating element 22 used in the type of heating circuit 40 shown in Figure 1. The heating element 22 is a resistance heating element, specifically a thin-film heater. This heating element includes a heating track 32 embedded in a thin film and a pair of contacts 34, 36 that enable connection to the controller 24.

[0049] Figure 3 shows the heating chamber 18 of the aerosol generator 10 in more detail. The heating chamber 18 has a cylindrical side wall 38 connecting an open first end 28 and a closed base 30. The heating element 22 is wrapped around the outer surface of the side wall 38.

[0050] Figure 4 illustrates how the measured observable quantity may fluctuate during a usage session. Figure 4 shows the initial state 400 of the aerosol formation apparatus with no consumables present in the heating chamber. During this initial period, since no consumables are present in the heating chamber, the measurement of the observable quantity indicates that the water content is zero or close to zero.

[0051] During the second period 402, the consumable is inserted into the heating chamber. The measurement of the observable quantity shows a rapid increase in moisture content. If the consumable is fully inserted, the first measured observable quantity m1 can be considered to represent the initial moisture content of the consumable. As mentioned above, the first measured observable quantity m1 can be considered to be equal to the moisture content of approximately 15% in the aerosol-generating substrate.

[0052] Heating of the consumable begins at start time 404 following insertion of the consumable and continues throughout session 406. An observable quantity indicating moisture content is measured during session 406 and generally decreases throughout the session as moisture and / or humectants in the consumable vaporize during heating. The session ends when the measured observable quantity reaches a second value m2, indicating that the moisture and / or humectants in the consumable have been substantially consumed. This does not necessarily mean that the moisture content is zero, but rather that it has fallen below a first predetermined threshold below which the quality of the inhalation experience is expected to deteriorate. Such a threshold may be a moisture content of, for example, 6% or less, 5% or less, 4% or less, or below.

[0053] Once the first predetermined threshold is reached, heating stops at time 408, and therefore the second value of the measured observable quantity m2, which indicates the residual moisture content, remains constant for a period of 410 after the end of the session.

[0054] To support the monitoring of observable quantities, the aerosol generator 10 shown in Figure 1 further includes a monitoring circuit 50. The monitoring circuit may be contained within the controller 24 or be in signal communication with the controller 24. The monitoring circuit may be operable to monitor any observable quantity indicating the water content of the aerosol generating substrate. An example of such an observable quantity is a time delay associated with a monitoring circuit having a known time constant.

[0055] Referring now to Figure 5, an exemplary monitoring circuit 50 is shown in more detail together with the heating circuit 40. The monitoring circuit 50 includes a resistor R and an optional capacitor C, thus forming an RC circuit. The monitoring circuit includes an electrical input terminal 52 and an electrical output terminal 54 connected to a microcontroller μC. It will be understood that the microcontroller μC may be included in the controller 24, or it may be separate from the controller 24 and subject to the instructions of the controller 24.

[0056] In Figure 5, the monitoring circuit 50 is shown connected to the heating circuit 40, particularly to the contact 34 of the heating circuit 40. However, this is not mandatory, and the monitoring circuit 50 may be connected to another part of the heating assembly 15, or to another part of the aerosol forming apparatus, such as the heating chamber 18, if necessary.

[0057] Resistor R is connected between input terminal 52 and output terminal 54, and is connected in parallel with capacitor C, which is connected to ground. The value of resistor R is in the range of 500kΩ to 10MΩ. Capacitor C is optional, but if present, it helps clean up the signal.

[0058] The monitoring circuit 50 further includes a first switch 56 connected between the monitoring circuit 50 and the heating circuit 40, specifically between the monitoring circuit 50 and the contact 34 of the heating track 32. When the first switch 56 is in the closed position, the monitoring circuit is electrically connected to the heating circuit 40. In this state, the aerosol generator 10 is considered to be in time-delay monitoring mode. When the first switch 56 is in the open position, the monitoring circuit 50 is not electrically connected to the heating circuit 40 so that no current flows between the monitoring circuit 50 and the heating circuit 40.

[0059] The heating circuit 40 includes a second switch 42 positioned between the heating element 22 and the input voltage (supplied, for example, by the power supply 26), and a third switch 44 positioned between the heating element 22 and ground. When the second and third switches 42 and 44 are closed, the heating element 22 is electrically connected to the input voltage so that a voltage is supplied to the heating element and the heating element 22 generates heat. In this state, the aerosol generator is considered to be in heating mode. When the second and third switches 42 and 44 are open, the heating element 22 is disconnected from the input voltage and cannot generate heat.

[0060] The aerosol generator may be in heating mode and time-delay monitoring mode simultaneously, such that all three switches 56, 42, and 44 are closed at the same time. However, in this example, the aerosol generator can be operated to switch between time-delay monitoring mode and heating mode so that time-delay monitoring does not occur during heating.

[0061] Referring now to Figure 6, the operation of the aerosol generator 10 in time-delay monitoring mode is described. In time-delay monitoring mode, the microcontroller μC can be operated to send a signal 60 to the input terminal 52 of the monitoring circuit 50 (for example, from a pin labeled "send"). The signal 60 is a voltage pulse such as a square wave defined by a low value 62 and a high value 64, and may repeat periodically.

[0062] In time-delay monitoring mode, switch 56 is closed, so the signal also passes through the monitoring circuit 50 and the heating circuit 40. The signal from output terminal 54 is received by the microcontroller μC (for example, on a pin labeled "return"), but the received signal is modified by the system's capacitance. This modification is characterized by a rise time d, which constitutes the time it takes for the signal to change from a low value 62 to a high value 64, and / or a fall time, which constitutes the time it takes for the signal to return from a high value 64 to a low value 62. In the original signal, these changes are virtually instantaneous, but in the received signal, there is a delay when the signal rises from a low value to a high value and when the signal falls from a high value to a low value. The rise time is proportional to the circuit's time constant. Similarly, the fall time is also proportional to the circuit's time constant.

[0063] Figure 6 includes a graph 70 plotting the rise and fall times 72 against time 74, allowing us to recognize the changes in rise and fall times over time. It can be seen that the rise time d1 at the first time point 76 is shorter than the rise time d2 at the second time point 78. This indicates that the system's capacitance changed between the first and second time points. In particular, the system's capacitance increased between the first time point 76 and the second time point 78.

[0064] Figure 7 shows how the rise and / or fall time variations shown in Figure 6 can be used to determine the moisture content of the consumable 100 in the heating chamber 18 of the aerosol generator 10. Figure 7 includes a graph plotting the measured rise and fall times 72 (in this example, rise and fall times are represented by the time it takes to transmit a signal from input to output) against the time 74 between the initial time point t0 and the end time point t5.

[0065] During the first period 82 between time points t0 and t1, the reference transmission time, such as the average rise and fall times, is the first reference time a1. During this period, no consumables are present in the heating chamber. The rise and fall times applied to the signal during this period therefore represent the time constant τ of the monitoring circuit in the absence of consumables, and are considered to be a predetermined time constant.

[0066] At time point t1, the measured rise and fall times increase, averaging the third reference time a3 over the second period 84 between time points t1 and t2. The increase in rise and fall times indicates an increase in the system's capacitance, and therefore a change, particularly an increase, in the time constant τ of the monitoring circuit. During this period, the consumable is being inserted into the heating chamber 18 (i.e., it is in the process of being inserted, not yet fully inserted but partially inserted, and / or close to the heating chamber). The increase in capacitance during this period is due to the consumable 100 being close to and / or partially inside the cavity of the heating chamber, and potentially also affected by contact between the consumable and the user's fingers.

[0067] At time t2, the measured rise and fall times decrease, averaging the second reference time a2 over the third period 86 between time t2 and time t3. The decrease in rise and fall times indicates a decrease in the system's capacitance, and therefore a change, particularly a decrease, in the time constant τ of the monitoring circuit. However, it should be noted that the relation a2 > a1 holds, meaning that the system's capacitance, and therefore its time constant, is greater than a given time constant τ of the monitoring circuit without the consumable. During the period, the consumable 100 is present in the heating chamber 18 of the aerosol generator. The consumable is heated over time, and therefore the third period 86 is also considered an inhalation session.

[0068] Figure 9 shows a close-up of the measurements taken during the third period 86. The rise and fall times measured during the third period 86 are averaged over the second reference time a2, but it can be seen that the measured rise and fall times generally decrease throughout the entire third period 86 94. The reason for this is that, as mentioned above in relation to Figure 4, the rise and fall times indicate the moisture content of the consumables in the heating chamber, and the moisture content decreases as the session progresses as the moisture and / or humectants in the aerosol-forming substrate are depleted.

[0069] At time t3, the rise / fall time increases, averaging the further rise / fall time over a fourth period 88 between time t3 and time t4. The fourth period 88 is the inverse of the second period 84 in the sense that the consumables are removed from the heating chamber during the fourth period. The average rise / fall time during the fourth period is therefore similar to and approximately equal to the average rise / fall time a3 of the second period.

[0070] Similarly, the average rise-fall time in the fifth period 90 between time points t4 and t5 is similar to and approximately equal to the first average rise-fall time a1 in the first period, indicating that the consumables are no longer present in the heating chamber.

[0071] For example, changes in the time constant of a monitoring circuit, measured using changes in time delay such as the rise and / or fall times mentioned above, can therefore be used to monitor the moisture content of consumables present in the heating chamber.

[0072] In one example, the controller is only operational to begin monitoring the observable quantity after the stick has been inserted and heating has started. A state machine or scheduler or time interrupt or watchdog timer will disconnect the heater and reconnect the measurement line every 10-50 ms to periodically acquire measurements of the observable quantity. The acquired data is stored in memory (internal or external to the controller), and signal processing of the stored data can be used to display the decrease in moisture level.

[0073] The aerosol generator 10 is configured to progressively present an indicator of the moisture content of consumables to the user of the device throughout the session using monitored observable amounts. The indicator may be presented to the user on the user interface 23 of the aerosol generator, and / or displayed on a connected device such as the user's smartphone, for example, via an app paired with the aerosol generator. This indicator can provide the user with a progressive visual representation of the consumption depth of consumables throughout the session, so that at any given point in time the user can instantly see how much of the aerosol generating substrate has been consumed.

[0074] For comparison, Figure 8 shows the variation in rise and / or fall times when a preheated consumable is inserted into the heating chamber of the aerosol generating apparatus. During the first period 96 and the third period 97, no consumable is present in the heating chamber. However, during the second period 98, consumable 100' is inserted into the heating chamber. Since consumable 100' is already heated, the measured observable amount indicating its moisture content is less than or equal to the observable amount m2 indicating residual moisture content. The controller of the aerosol generating apparatus can therefore determine, using the measured observable amount, that the consumable inserted into the heating chamber has already been used. In such a situation, the controller can prevent further heating of the already heated stick. For example, the controller can prevent the heating circuit from operating in such a situation.

[0075] While the preceding paragraphs have described exemplary embodiments, it should be understood that various modifications may be made to these embodiments without departing from the attached claims. For example, although the present invention has been described primarily in relation to resistance heating assemblies, it may also be applicable to other types of heating assemblies, such as induction heating assemblies. Therefore, the scope and application of the claims should not be limited to the exemplary embodiments described above.

Claims

1. A heating chamber (18) configured to receive a consumable (100) containing an aerosol generating substrate (102), A heating assembly that is operable to supply heat to the aerosol generating substrate during a usage session, Controller (24) and an aerosol generating apparatus (10) including, The aforementioned controller During the aforementioned usage session, an observable amount indicating the water content of the aerosol-generating substrate is monitored, By using the monitored observable quantity, the duration of each usage session is selected by determining when to terminate the usage session, and the controller is capable of terminating each session when the monitored observable quantity indicates that the water content of the aerosol generating substrate is below a first predetermined threshold. Throughout the entire usage session, an indicator showing the decrease in the water content of the aerosol-generating substrate is progressively presented to the user. Therefore, it is operable. Aerosol generating device (10).

2. The aerosol generating apparatus according to claim 1, wherein the controller is operable to generate an indicator that the session is nearing its end when the monitored observable quantity indicates that the water content of the aerosol generating substrate is below a second predetermined threshold, and the second predetermined threshold is reached before the first predetermined threshold.

3. The aerosol generating apparatus according to claim 1 or 2, wherein the observable amount is periodically monitored throughout the entire usage session.

4. The aerosol generating apparatus according to claim 1, further comprising a monitoring circuit (50) having a predetermined time constant, wherein the observable quantity is a time delay associated with the monitoring circuit.

5. The aerosol generating apparatus according to claim 4, wherein the controller (24) is operable to supply a signal to the input of the monitoring circuit (50) and to receive the modified signal from the output of the monitoring circuit, and the controller is operable to determine the time delay from the modified signal.

6. The aerosol generating apparatus according to claim 5, wherein the monitoring circuit (50) includes an RC circuit having predetermined resistance and capacitance, and the observable quantity is the rise and / or fall time associated with the modified signal.

7. The aerosol generating apparatus according to claim 6, wherein the RC circuit is electrically connected to the heating circuit (40) of the heating assembly.

8. The aerosol generating apparatus according to claim 1, wherein the heating assembly is stopped when the observable amount is being monitored.

9. The aerosol generating apparatus according to claim 4, wherein the aerosol generating apparatus (10) is switchable between a heating mode in which voltage is supplied to the heating assembly and a time-delay monitoring mode in which a signal is supplied to the monitoring circuit (50).

10. The aerosol generating apparatus according to claim 9, further comprising a first switch (56) that is closed in the time-delay monitoring mode and opened in the heating mode, and a second switch (42) that is closed in the heating mode and opened in the time-delay monitoring mode.

11. The aerosol generating apparatus according to claim 7, wherein the heating circuit includes a resistance heater (22) and preferably a thin-film heater.

12. The aerosol generating apparatus according to claim 1, further comprising a user interface (23) having an output display, wherein the aerosol generating apparatus is operable to progressively present the indicator to the user using the output display.

13. The aforementioned controller further, The initial value of the observable quantity is determined by measuring an initial value that indicates the initial moisture content. The measured initial value is compared with a further predetermined threshold, Based on the above comparison, it is determined whether or not to allow the heating assembly to start. It is operational for that purpose, The controller is operable to prevent the heating assembly from operating when the measured initial value for the observable quantity is below a further predetermined threshold. The aerosol generating apparatus according to claim 2.

14. The aerosol generating apparatus according to claim 13, wherein the further predetermined threshold is the same as the first predetermined threshold or the second predetermined threshold.

15. A heating chamber (18) configured to receive consumables including an aerosol generating substrate, A heating assembly that is operable to supply heat to the aerosol generating substrate during a usage session, Controller (24) and A method for operating an aerosol generating device containing, During the aforementioned usage session, an observable amount indicating the water content of the aerosol-generating substrate is monitored, The duration of each usage session is selected by determining when to terminate the usage session using the monitored observable quantity, wherein the controller can operate to terminate each usage session when the monitored observable quantity indicates that the water content of the aerosol generating substrate is below a first predetermined threshold. Throughout the entire usage session, an indicator showing the decrease in the water content of the aerosol-generating substrate is progressively presented to the user. Methods that include...

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