WO2024126645A1

WO2024126645A1 - Aerosol generating device with heater control

Info

Publication number: WO2024126645A1
Application number: PCT/EP2023/085749
Authority: WO
Inventors: Jaakko MCEVOY
Original assignee: Jt International Sa
Priority date: 2022-12-16
Filing date: 2023-12-14
Publication date: 2024-06-20

Abstract

An aerosol generating device (1), comprising: a heater (12) configured to heat an aerosol forming substrate so that it can release an aerosol for inhalation; a timer (16) configured to measure a time elapsed from the start of a vaping session; and a processor (20) configured to calculate a temperature profile (105) that varies continuously as a function of time, using a temperature profile function, wherein the processor (20) is configured to send the calculated temperature profile (105) to the heater (12) in a control signal.

Description

AEROSOL GENERATING DEVICE WITH HEATER CONTROL

FIELD OF THE INVENTION

The present invention relates to an aerosol generating device, and more specifically to control of a heater in the aerosol generating device.

BACKGROUND

The popularity and use of aerosol-generating devices and systems (also known as vaporisers) has grown rapidly in the past few years as an alternative to traditional tobacco products such as cigarettes, cigars, cigarillos, and rolling tobacco. Various devices and systems are available that heat or warm aerosolisable substances, that may or may not comprise nicotine or other active substances, as opposed to burning tobacco in conventional tobacco products.

A commonly available aerosol-generating system is the heated substrate aerosol generation or heat-not-burn type. Systems of this type generate an aerosol or vapour by heating a consumable article (i.e. a “heat-not-burn stick”) containing an aerosol substrate such as reconstituted tobacco to a temperature typically in the range of 150°C to 350°C. Heating an aerosol substrate, but not combusting or burning it, releases an aerosol that comprises the components sought by the user but not the undesirable by-products of combustion. In addition, the aerosol produced by heating the tobacco or other aerosolisable material does not typically comprise the burnt or bitter taste that may result from combustion which can be unpleasant for the user.

Typically, a heat-not-burn consumable article, for example in stick form, is inserted into a cavity of a heat-not-burn device, with an end of the stick left protruding from the device and forming an inhalation mouthpiece. The heat-not-burn device subsequently supplies heat to the stick to aerosolise aerosolisable material contained in the aerosol substrate in the stick, and the aerosol produced is supplied to the user from the protruding end of the stick. The heat supplied to the stick by the heater may be varied using a control signal that alters the power supplied to the heater. Typically, the control signal used to control the heater in an aerosol generating device is defined via a discrete set of temperature values at specific times, thereby defining a discrete temperature profile. For example, a discrete temperature profile may include a list with a sequence of discrete temperature values each with a corresponding duration.

The use of discrete temperature profiles may cause problems. Firstly, thermal shock may be caused by sudden changes in the heater due to repeated switching on and off of the power supply. Secondly, sudden changes in the heater control may lead to inhomogeneous heating of the aerosol generating substrate by the heater. Thirdly, discontinuities in temperature profile may lead to unexpected and undesirable control signals that may result in damage to the heater, undesirable combustion by-products, and danger to the user. Fourthly, discrete temperature profiles are not easy to customize and optimize for a particular type of device or consumable article.

Therefore, it is an aim of the present invention to address the problems discussed above.

SUMMARY OF INVENTION

According to a first aspect of the present invention there is provided an aerosol generating device, comprising: a heater configured to heat an aerosol forming substrate so that it can release an aerosol for inhalation; a timer configured to measure a time elapsed from a start of a vaping session; and a processor configured to calculate a temperature profile that varies continuously as a function of time, using a temperature profile function, wherein the processor is configured to send the calculated temperature profile to the heater in a control signal.

The calculated temperature profile may define the setpoint temperature of the heater, where the control signal sent to the heater is based on the setpoint temperature. For example, the control signal may be provided via a PID controller or a bang-bang controller. Thus, the setpoint temperature profile varies continuously as a function of time (prior to being converted to a control signal to be sent to the heater). Advantageously, the aerosol generating device may enable the heater to use smooth heating profiles that vary continuously in time, based on a temperature profile function such as a Fourier series or a polynomial function. The aerosol generating device may have an ideal heating profile that depends on the aerosol forming substrate and/or the heater being used.

As used herein, the term “as a function of time” preferably connotes that the temperature profile function takes time as an input in order to provide the temperature profile, though it will be appreciated that the temperature profile function may take other inputs as well as time. Thus, the temperature profile is preferably a function that is dependent upon time. Preferably, the time taken as an input to the temperature profile function is the time elapsed since the start of the vaping session. As used herein, the term “continuously variable” or “varies continuously” preferably connotes that the temperature profile does not include any discrete (or instantaneous) changes or discontinuities. Preferably the first order derivative of the temperature profile does not include any discontinuities and may itself be continuous or smoothly varying.

The processor may be configured to modify one or more parameters of the temperature profile function based on a user input. For example, the location and/or number of temperature rises and falls may be provided by the user input. Advantageously, this enables the heater temperature to be defined precisely by the user.

The processor may be configured to verify whether the user input satisfies one or more predetermined conditions. Advantageously, the one or more predetermined conditions may reduce the risk of damage to the aerosol generating device and/or may reduce the risk of danger to the user. For example, the one or more predetermined conditions may prevent the temperature profile from: defining a temperature above a maximum value, maintaining a temperature above a threshold value for longer than a predetermined time, and/or changing faster than a maximum rate.

The aerosol generating device may further comprise a temperature sensor for measuring an ambient temperature, wherein the processor is configured to modify one or more parameters of the temperature profile function based on the measured ambient temperature. Alternatively, the ambient temperature may be provided as a user input, such as from the separate device.

The processor may be configured to reduce the temperature profile during a time period when a puff is not being taken by a user. Advantageously, during this time period the power consumption of the device may be reduced, thereby improving battery performance. Furthermore, vapour generation may be reduced, thereby minimizing vapour leakage and increasing lifetime of the aerosol generating substrate.

The aerosol generating device may further comprise a puff detector, wherein the processor is configured to reduce the temperature profile for a heat reduction time period after a puff is detected by the puff detector. The heat reduction time period may begin after a first time period from detection of a puff, and end after a second time period from detection of a puff. In other words, the temperature profile is reduced after the first time period, and is restored to the normal temperature profile after the second time from detection of a puff (i.e. the temperature reduction is removed). By reducing the temperature profile after the first time period (rather than immediately when a puff is detected), the initial puff is not affected by the reduced temperature profile. By restoring the temperature profile after the second time period, subsequent puffs are not affected by the temperature reduction. The second time period may be less than the time that the user typically takes between puffs. Since, a user is unlikely to take two puffs in quick succession, the temperature profile is only reduced during a time window (i.e. the heat reduction time period) when the user is unlikely to be taking a puff. Thus, the temperature profile may be reduced and then increased after a puff is detected. The temperature reduction may result in a local minimum (or dip) in the temperature profile.

The aerosol generating device may further comprise an orientation sensor, wherein the processor is configured to reduce the temperature profile for a heat reduction time period when the orientation sensor detects a predetermined position of the device and/or a predetermined change in position of the device. The heat reduction time period may begin after a first time period from the orientation detection, and end after a second time period from the orientation detection. In other words, the temperature profile is reduced after the first time period, and is restored to the normal temperature profile after the second time from the orientation detection (i.e. the temperature reduction is removed). For example, the temperature profile may be reduced in response to the user lowering the device and/or putting the device down, such as on a table. Since the user is unlikely to take a puff in these positions, the temperature profile may be reduced without affecting the user experience. By restoring the temperature profile to its normal value after the second time period from the orientation change, the temperature profile can be reduced and then increased again during a period when a user is unlikely to be inhaling; this can result in a power saving.

The heat reduction time period may be predetermined or may have a dynamically adjusted value. The heat reduction time period may be based on data collected by the processor on usage of the device by the user. For example, where the temperature profile is reduced for a heat reduction time period after a puff is detected, the length of the heat reduction time period may be less than a minimum time that the user typically takes between puffs. In a similar manner, where the temperature profile is reduced for a heat reduction time period after an orientation detection, the length of the heat reduction time period may less than a minimum time period that the user typically takes from such an orientation detection to a subsequent puff. In this way, the device may optimize the battery usage of the device for each user, even though different users may take puffs at a different frequency or at a different time after lowering the device or putting the device down. The heat reduction time period may be updated based on further data collected by the processor during ongoing usage of the device by the user, thereby accounting for changes in habits of a particular user, and/or changes in behaviour over the course of a vaping session. Accordingly, the device may provide dynamic adjustment of the length of the reduced portion of the temperature profile.

The temperature profile function may be a Fourier series. Advantageously, a Fourier series makes use of trigonometric functions and mathematical operations that may be performed quickly by the processor. Furthermore, a Fourier series may approximate a more complex function with a variable level of accuracy, simply by changing the number of terms in the Fourier series, thereby allowing the aerosol generating device to adapt the amount of processing power required by the processor.

The timer may be configured to measure the time elapsed from the start of the vaping session up to a maximum session length. For example, a maximum session length may be about 300s, such as about 280 seconds. The maximum session length may be determined by a user input.

The processor may be configured to receive the user input from a separate device. Advantageously, the separate device may enable precise control of the heater temperature without the need for a complex user interface to be provided on the aerosol generating device. For example, a user may input instructions into a device such as a mobile phone, for example via an application with a graphical user interface. The aerosol generating device may comprise a communication unit connected to the processor. The communication unit may receive the user input from the separate device via Wi-Fi, Bluetooth, and/or any other suitable wireless communication protocol. Alternatively, the processor may be configured to receive the user input from a user interface of the aerosol generating device.

According to another aspect of the present invention, there is provided a method of controlling a heater in an aerosol generating device, the method comprising the steps of: measuring a time elapsed from the start of a vaping session; and controlling the heater based on a calculated temperature profile that varies continuously as a function of time.

Also described herein is an aerosol generating device, comprising: a heater configured to heat an aerosol forming substrate so that it can release an aerosol for inhalation; a timer configured to measure a time elapsed from a start of a vaping session; and a processor configured to calculate a temperature profile that varies continuously with respect to time, using a temperature profile function, wherein the processor is configured to send the calculated temperature profile to the heater in a control signal. Preferable features of this aerosol generating device correspond to those already described above in relation to the first aspect.

It will be understood by a skilled person that any device or apparatus feature described herein may be provided as a method feature, and vice versa. It will be understood that particular combinations of the various features described and defined in any aspects described herein can be implemented and/or supplied and/or used independently. Moreover, it will be understood that the present invention is described herein purely by way of example, and modifications of detail can be made within the scope of the invention.

BRIEF DESCRIPTION OF DRAWINGS

One or more embodiments will now be described, purely by way of example, with reference to the accompanying figures, in which:

Figure 1 shows a schematic cross section of an embodiment of an aerosol generating device;

Figure 2 shows setpoint temperature profiles that may be used in a typical aerosol generating device;

Figure 3 shows an embodiment of a setpoint temperature profile that is continuous; and Figures 4A shows an embodiment of a setpoint temperature profile that is continuous, and Figure 4B shows the setpoint temperature profile of Figure 4A including a temperature reduction portion.

DETAILED DESCRIPTION

Figure 1 depicts a schematic cross section of an aerosol generating device 1 , showing various internal components. It will be appreciated that the positions of the components in the device are merely schematic and should not be taken as limiting to the present invention. It will also be appreciated that multiple instances of the components of the device 1 may be provided. Furthermore, the device 1 may contain a number of additional components that are not relevant to the understanding of the present invention and thus will not be depicted or described in detail herein.

As shown in Figure 1 , the device 1 has a housing 10 with a cavity 11 that is configured to receive an aerosol generating consumable article 5. The device 1 also comprises a heater 12 configured to supply heat to the aerosol generating consumable article 5 when it is located within the cavity 11. The aerosol generating consumable article 5 contains an aerosol forming substrate (not shown) that produces an inhalable aerosol when heated.

As described herein, a vapour is generally understood to refer to a substance in the gas phase at a temperature lower than its critical temperature, which means that the vapour can be condensed to a liquid by increasing its pressure without reducing the temperature, whereas an aerosol is a suspension of fine solid particles or liquid droplets, in air or another gas. It should, however, be noted that the terms ‘aerosol’ and ‘vapour’ may be used interchangeably in this specification, particularly with regard to the form of the inhalable medium that is generated for inhalation by a user. As such, the term “vaping” or “vaping session” may refer to any use of the aerosol generating device 1 that produces an aerosol and/or a vapour that is supplied to the user. In this example, the aerosol generating device 1 is a heat-not-burn device 1 and the aerosol generating consumable article 5 is a heat-not-burn stick 5, though it will be appreciated that the present invention is applicable to any form of aerosol generating device 1 that uses a heater to generate an aerosol from an aerosol forming substrate. For example, the aerosol generating device 1 may be a vaporizer that may supply heat to a fluid aerosol forming substrate.

The device 1 also comprises a power supply such as a battery 14 for supplying electrical power to the heater 12 and to other components of the device 1 .

The device 1 also comprises a timer 16. The timer 16 is configured to measure a time (t) elapsed from the start of a vaping session. For example, the timer 16 may begin counting (i.e., from t = 0) when the user activates or starts the vaping session and will continue to monitor the time elapsed until the session ends. The start of a vaping session may be manually triggered by the user, such as via a user interface or button (not shown). The start of a vaping session may also be measured by the start of an inhalation as measured by an airflow sensor. The end of a vaping session may be when the user manually stops the vaping session or stops inhaling. The end of the vaping session may also occur when a predetermined maximum session length is reached. This length may be about 300 seconds, such as 280 seconds.

The device 1 also comprises a processor 20 that controls operation of the device 1. As will be described later in more detail, the processor 20 is used to control the temperature of the heater 12. More specifically, the processor 20 is configured to calculate a time dependent temperature profile. This temperature profile may be referred to as a “setpoint temperature profile”, which may represent a target or desired temperature profile for the heater 12 with respect to time. The processor 20 may include a control unit that generates a control signal to be provided to the heater 12, where the control signal is based on the temperature profile. For example, the control unit may comprise a PID controller, a bang-bang controller, or any other suitable type of controller. The control signal may vary the power supplied to the heater 12 by the power supply 14. While the control unit is described herein as being part of the processor 20, it will be appreciated that a separate control unit may be provided anywhere in the device 1 , and that the processor 20 and control unit may each perform processing and/or control operations.

One or more temperature sensors 31 , 32 may be provided in the aerosol generating device 1 to provide data to the processor 20. For example, a first temperature sensor 31 may be configured to measure the temperature of the cavity and/or the heater 12. The first temperature sensor 31 (i.e., the “heater temperature sensor 31”) may directly measure the temperature of the cavity 11 and/or the heater 12 or may calculate the temperature in another way, such as by monitoring the resistance of the heater 12. The first temperature sensor 31 may provide a feedback signal that is used by the control unit to vary the control signal to the heater 12. For example, the control unit may compare the measured temperature to the setpoint temperature profile and adjust the control signal based on a difference between them. A second temperature sensor 32 (i.e., an “ambient temperature sensor 32”) may be configured to measure an ambient temperature of the surroundings of the device 1 , which may also be used by the processor 20 in a manner that will be described in detail later. As described later in relation to Figures 4A and 4B, the device 1 may also include a puff detector (not shown) and/or an orientation sensor 22.

Temperature control in a typical aerosol generating device will now be described in relation to Figure 2. Generally, a typical setpoint temperature profile is discrete, where a set of discrete values are provided for the temperature and time, such as in an array. In the example shown in Figure 2, two example setpoint temperature profiles are shown for use with a single heater. The solid line indicates the setpoint temperature profile 101a in a first example and the dashed line indicates the setpoint temperature profile 101 b for a second example. As noted above, these setpoint temperature profiles 101 may be provided to a control unit that generates a control signal. Since the setpoint temperature profiles 101 in Figure 2 are discrete, the profiles 101 change instantaneously leading to discontinuities in the profiles 101 at certain times (e.g., at 50, 100, and 150 seconds). As such, at the times when the change occurs, the setpoint temperature profile 101 may not be well-defined.

Data that may be used to represent the setpoint temperature profiles 101 in Figure 2 is shown in Table 1. As demonstrated by Table 1 , typical setpoint temperature profiles 101 only require a few parameters in order to control the temperature of the heater, thereby reducing the amount of storage space, and the amount of processing power required.

TABLE 1

The use of conventional setpoint temperature profiles 101 such as those in examples 1 and 2 may lead to a number of problems. Firstly, they only define discrete temperatures that are maintained for predetermined times; as a result, the profile is discontinuous leading to sudden changes in temperature being required by the heater. This can lead to thermal shock in the heater and/or components connected to the heater, which may decrease the lifetime of the aerosol generating device. The sudden changes may also lead to non-uniform heating of the aerosol forming substrate in the device. Additionally, sudden changes in the setpoint temperature profile 101 may be difficult to process by the control unit; for example, in a PI D controller, an instantaneous or sudden change in the setpoint may cause an overshoot in the control signal which may damage the device or the aerosol forming substrate. In particular, this may lead to a spike in the power supplied by the battery 14, which may damage electrical components in the device. Furthermore, this may lead to a spike in the temperature of the heater 12, which may be dangerous to the user, and/or may cause unwanted aerosol substances to be produced by the aerosol forming substrate. Tuning or modification of the control unit to mitigate this problem may increase the computation burden required by the control unit. Furthermore, the discontinuous setpoint temperature profile 101 is inflexible, and difficult to customize or optimise for a certain type of aerosol generating device or aerosol generating consumable article.

Figure 3 depicts an exemplary setpoint temperature profile 105 according to the present invention. The setpoint temperature profile 105 shown in Figure 3 may be calculated using the equation or function:

where t is the time elapsed from the start of the vaping session (such as measured by the timer 16) and parameters a to m and T_o take the values shown in Table 2.

TABLE 2

It will be appreciated that equation (1), which may alternatively be referred to as a function, and corresponding parameters above are merely exemplary and that other equations may be used within the scope of the present invention. More generally, the setpoint temperature profile 105 may be given by a function such as an equation of the form:

T = f(t, a, b, c, ... ) (2) where t is the time elapsed from the start of the vaping session, and where the other parameters (a, b, c, ...) may be functions of other parameters and/or a function of time. The parameters may alternatively be referred to as coefficients.

In contrast to the example shown in Figure 2, the setpoint temperature profile 105 is continuous. As used herein, the term “continuous” preferably indicates that the line is smooth and does not include any instantaneous changes or discontinuities. The first order derivative of the temperature profile may also not include any discontinuities and may itself be continuous or smoothly varying. For each time value the setpoint temperature may be uniquely defined and can be calculated for any instant in time in a vaping session using the function. More specifically, the setpoint temperature profile function may be used to calculate the setpoint temperature at any instant in time during a vaping session, without needing to approximate or interpolate using other time or temperature values. In this way, the setpoint temperature profile 105 may be considered to have an arbitrarily high resolution. This is achieved even though the temperature profile function itself can be defined using only a few parameters.

In this way, the device 1 may provide a precise setpoint temperature profile 105 defined only by a few parameters. Advantageously, the setpoint temperature profile 105 does not define any discontinuous or sudden jumps in temperature; instead, the setpoint temperature profile 105 may gradually ramp the temperature. This reduces the risk of thermal shock, damage due to thermal cycling stress, and/or non-uniform heating of the aerosol forming substrate. Furthermore, a continuous setpoint temperature profile 105 is more easily processed by the control unit, thereby reducing the risk of overshoot that may damage the heater or other electronics in the device. Furthermore, having a continuous profile may allow the setpoint temperature profile 105 to be more customizable for certain types of device 1 or stick 5. For example, it may be beneficial to change the temperature of the heater 12 throughout a vaping session in order to facilitate a more continuous delivery of the aerosol to the user; more specifically, a gradual increase in heater temperature may provide a constant delivery of the aerosol even as the aerosol forming substrate is depleted.

The setpoint temperature profile 105 may contain trigonometric functions, including sums, products, and/or powers of such trigonometric functions in any suitable combination. In this way, the setpoint temperature profile 105 may be calculated using only simple arithmetic and well-defined functions, thereby allowing the calculations to be performed in only milliseconds on current microcontrollers, with no noticeable lag. It will be appreciated that the number of parameters required to define the continuous setpoint temperature profile 105 may be much less than required in an array containing discrete values for temperature and time. Therefore, the continuous setpoint temperature profile 105 may be more data efficient and less computationally intense than existing control methods.

In one embodiment, a Fourier series may be used to define the setpoint temperature profile 105, with the period of the Fourier series being given by the maximum session length (e.g., 280 seconds). When the session ends, the heater 12 may be switched off, and the timer 16 may reset to t=Q. Advantageously, a Fourier series makes use of only well-defined trigonometric functions and simple mathematical operations that may be performed quickly by the processor 20. Furthermore, a Fourier series may be used to approximate any suitable optimal function for the heater temperature, with the accuracy of the approximation being easily modified by changing the number of terms in the Fourier series. A large number of terms may add complexity to the setpoint temperature profile 105. Therefore, the setpoint temperature profile 105 may be adapted to best make use of the processing power available in the device 1 . Optionally, the setpoint temperature profile 105 may also have a continuous first derivative. In this configuration, the setpoint temperature profile 105 may be referred to as a setpoint temperature curve. Advantageously, having a continuous first derivative may avoid any discontinuities when controlling the heater 12 when using certain types of control unit, such as PID controllers, thereby further reducing the risk of temperature spikes or other undesirable behaviour. In some embodiments even the second derivative may be continuous.

Any of the parameters in the setpoint temperature profile 105 may be made a variable that is user controlled, and/or environment controlled. Specifically, the processor 20 may be configured to modify one or more of the parameters of the setpoint temperature profile 105 based on a user input. For example, the location and/or number of temperature rises and falls may be provided by the user input with a fine level of precision. Alternatively or additionally, the user may specify the maximum session length, such as if the user wants to vape for 1 minute instead of 4 minutes; in the example in equation (1) above, this may be achieved by varying the parameter d. It will be appreciated that the user may adjust any of the other parameters that define the setpoint temperature profile 105.

The processor 20 may be configured to verify whether the user input satisfies one or more predetermined conditions. If the user input satisfies the one or more predetermined conditions, then the processor 20 may update the setpoint temperature profile 105 based on the user input. However, if the user input does not satisfy the one or more predetermined conditions, then the setpoint temperature profile 105 is not updated, and an error indication may be provided to the user. The one or more predetermined conditions may prevent the temperature profile 105 from: reaching a temperature above a maximum value, maintaining a temperature above a threshold value for longer than a predetermined time, and/or changing faster than a maximum rate. In this way, the one or more predetermined conditions may reduce the risk of the heater overheating, thereby reducing the risk of damage to the aerosol generating device 1 and/or reducing the risk of danger to the user. The one or more predetermined conditions may be hardcoded limits to limit modification of the temperature profile 105 to dangerous configurations.

The user input may be provided to the processor 20 with a user interface (not shown) of the device 1 . Alternatively or additionally, the processor 20 may be configured to receive the user input from a separate device. The separate device may be a mobile phone, which may run an application that may have a graphical user interface. By using the graphical user interface, the user may build their own vape profiles or modify existing ones, and subsequently send them to the device 1 . The separate device may communicate with the processor 20 via a communication unit 18 in the aerosol generating device 1. The communication unit 18 may receive the user input from the separate device via Wi-Fi, Bluetooth, and/or any other suitable wireless communication protocol.

The processor 20 may be configured to modify one or more parameters of the temperature profile function based on an ambient temperature surrounding the device 1. More specifically, measurements taken by the second temperature sensor 32 may be used to modify one or more parameters of the temperature profile function. For example, the ambient temperature may provide a temperature offset to the temperature profile function. In equation (1), the parameter T_o may define a temperature offset that is based on the ambient temperature. Optionally, the user may also provide a user input to change the temperature offset, in addition to data from the second temperature sensor 32.

Advantageously, by accounting for the ambient temperature, it may be possible to compensate for external conditions. For example, in a cold environment (such as when outdoors in winter) the setpoint temperature profile 105 may be boosted to provide more optimal heating of the aerosol generating substrate. Subsequently, if the user moves indoors, such as into an office, the setpoint temperature profile 105 may be reduced again.

Figures 4A and 4B depict further exemplary setpoint temperature profiles 110a, 110b according to the present invention. The setpoint temperature profile 110a closely corresponds to the one shown in Figure 3, and may be referred to as a “normal” profile. The setpoint temperature profile 110b includes at least one temperature reduction portion 111 , and thus the profile may be referred to as a “reduced temperature” profile. While only a single temperature reduction portion 111 is shown in Figure 4B, it will be appreciated that more than one temperature reduction portion 111 may be present.

The setpoint temperature profiles 110a, 110b shown in Figures 4A and 4B may be calculated using the equation or function:

where t is the time elapsed from the start of the vaping session (such as measured by the timer 16) and parameters a to w take the values shown in Table 3.

TABLE 3 Parameter p acts as a Boolean function. When it is 0, the profile is normal (as shown in Figure 4A), and when it is 1 , the reduced temperature profile is in effect (as shown in Figure 4B). Alternatively, the parameter p may be a continuous parameter that may be varied to any value from 0 to 1 . The processor 20 may change the value of the parameter p to switch between the normal profile 110a and the reduced temperature profile 110b.

The processor 20 may be configured to reduce the temperature profile during a time period when a puff is not being taken by the user. In other words, the processor 20 may adjust one or more parameters of the temperature profile function so that the temperature reduction portion 111 occurs during a time when a puff is not being taken by the user. In this way, the puff is not affected by the temperature reduction portion 111 , so the user experience is not affected. Advantageously, by reducing the temperature profile, the power consumption of the device 1 is reduced, thereby improving battery 12 performance. Furthermore, vapour generation may be reduced, thereby minimizing vapour leakage and increasing lifetime of the aerosol generating substrate.

For example, the aerosol generating device 1 may comprise a puff detector (not shown), and the processor 20 may be configured to reduce the temperature profile for a heat reduction time period after a puff is detected by the puff detector. After detection of a puff, the heat reduction time period may begin after a first time period from detection of a puff, and end after a second time period from detection of a puff. In other words, the temperature profile is reduced after the first time period and is restored to the normal temperature profile after the second time period from detection of a puff (i.e. the temperature reduction is removed).

More specifically, as shown in Figure 4B, a puff may be detected at time to. The temperature reduction portion 111 may begin to reduce the temperature profile at time ti and may increase the temperature profile to return it to its normal level at time t₂. It will be appreciated that the particular values and positions shown in Figure 4B are merely exemplary and are not necessarily drawn to scale. The first time period is given by Ati = ti - to. The first time period may have a predefined value so that the temperature reduction portion 111 does not affect the initial puff occurring at time to. The value for the first time period may be personalised and adjusted depending on the user. For example, the first time period may be about 2 seconds.

The second time period is given by At? = t? ~ to. The second time period may have a predefined value so that the temperature reduction portion 111 does not affect a subsequent puff taken by the user. The duration of the second time period is preferably selected based on the minimum period between successive puffs. The value for the second time period may be personalised and adjusted depending on the user. In this way, during the reduced temperature profile the user is unlikely to be taking a subsequent puff, such that the user experience is unaffected.

Therefore, the temperature profile 110b is only reduced within the heat reduction time period given by At_r = t? - ti. The time periods Ati, At?, At_r may be selected by varying one or more parameters of the temperature profile function 110b. For example, in equation (3), the timing of the temperature reduction portion 111 depends on parameter w, and the length of the temperature reduction portion 111 depends on parameter q. Additional temperature reduction portions 111 may be provided for each puff taken by the user.

The puff detector may be provided by a temperature sensor, which may be attached to a wall of the cavity 11 such as an inner or outer bottom face. The temperature sensor 31 may be used for this purpose, or a separate temperature sensor may be used. The temperature sensor detects a rapid temperature drop caused by the user’s puff. Alternatively or additionally, a pressure sensor may detect a reduction in pressure or within the cavity 11 caused by the user’s puff. Other puff detectors, such as flow sensors may be used.

The heat reduction time period may be predetermined or may have a dynamically varying value. The heat reduction time period may be based on data collected by the processor 20 on usage of the device 1 by the user. In other words, the heat reduction time period may be personalised. More specifically, the length of the heat reduction time period may be less than a minimum time that the user typically takes between puffs. This minimum time may be determined by the device for each user since different users may take puffs at a different frequency to each other. In this way, the device 1 may optimize battery usage and reduce unwanted vapour leakage in a way that is tailored for each user. The heat reduction time period may be updated based on further data collected by the processor 20 during ongoing usage of the device 1 by the user, thereby accounting for changes in habits of a particular user. Furthermore, if the processor 20 determines that the user takes puffs at a different frequency at the start of a session compared to the end, the heat reduction time period may be adjusted accordingly, thereby maximising efficiency of the device 1 without compromising the user experience. Accordingly, the device 1 may provide dynamic adjustment of the length of the reduced portion of the temperature profile.

Alternatively or additionally, the temperature reduction portion 111 may be set to occur in response to the device 1 being in a predetermined position, and/or in response to a predetermined change in position. In order to detect such positional information, the device 1 may comprise an orientation sensor 22, which may be able to detect the position (i.e. orientation) of the device 1 and/or a change in the position (i.e. motion) of the device 1. For example, the orientation sensor 22 may comprise a gyroscope and/or an accelerometer. For example, the temperature reduction portion 111 may be set to occur when the user has lowered the device 1 or put the device 1 down, such as on a table. Since the user is unlikely to take a puff when the device 1 is lowered or moved to a certain position, the power supplied to the heater 12 may be reduced without affecting the user experience. More specifically, after an orientation detection at time to, the temperature reduction portion 111 may begin to reduce the temperature profile at time ti and may increase the temperature profile to return it to its normal level at time t₂, in a similar manner to as already described above. Accordingly, the processor 20 is configured to reduce the temperature profile for a heat reduction time period (A_r = t₂ - ti) when the orientation sensor 22 detects a predetermined position of the device 1 and/or a predetermined change in position of the device 1.

In a similar manner to as described above, the heat reduction time period may be predetermined or may have a dynamically varying value. The heat reduction time period may be based on data collected by the processor 20 on usage of the device 1 by the user. In other words, the heat reduction time period may be personalised. More specifically, the length of the heat reduction time period may be less than a minimum time period that a user typically takes from such an orientation detection to a subsequent puff. This minimum time may be determined by the device for each user since different users may take a subsequent puff more quickly after changing an orientation of the device 1 or putting the device 1 down. In this way, the device 1 may optimize battery usage and reduce unwanted vapour leakage in a way that is tailored for each user. The heat reduction time period may be updated based on further data collected by the processor 20 during ongoing usage of the device 1 by the user, thereby accounting for changes in habits of a particular user. Accordingly, the device 1 may provide dynamic adjustment of the length of the reduced portion of the temperature profile.

The amount of temperature reduction may be changed by modifying the parameters n, o, and/or v. A greater reduction may further reduce power consumption and vapour leakage, but may increase the time for the temperature to return to its normal level before a subsequent puff is taken.

While the foregoing is directed to exemplary embodiments of the present invention, it will be understood that the present invention is described herein purely by way of example, and modifications of detail can be made within the scope of the invention. Furthermore, one skilled in the art will understand that the present invention may not be limited by the embodiments disclosed herein, or to any details shown in the accompanying figures that are not described in detail herein or defined in the claims. Moreover, other and further embodiments of the invention will be apparent to those skilled in the art from consideration of the specification, and may be devised without departing from the basic scope thereof, which is determined by the claims that follow.

Claims

1. An aerosol generating device, comprising: a heater configured to heat an aerosol forming substrate so that it can release an aerosol for inhalation; a timer configured to measure a time elapsed from a start of a vaping session; and a processor configured to calculate a temperature profile that varies continuously as a function of time, using a temperature profile function, wherein the processor is configured to send the calculated temperature profile to the heater in a control signal.

2. The aerosol generating device of claim 1 , wherein the processor is configured to modify one or more parameters of the temperature profile function based on a user input.

3. The aerosol generating device of claim 2, wherein the processor is configured to verify whether the user input satisfies one or more predetermined conditions.

4. The aerosol generating device of any preceding claim, further comprising a temperature sensor for measuring an ambient temperature, wherein the processor is configured to modify one or more parameters of the temperature profile function based on the measured ambient temperature.

5. The aerosol generating device of any preceding claim, wherein the processor is configured to reduce the temperature profile during a time period when a puff is not being taken by a user.

6. The aerosol generating device of claim 5, further comprising a puff detector, wherein the processor is configured to reduce the temperature profile for a heat reduction time period after a puff is detected by the puff detector.

7. The aerosol generating device of claim 5 or 6, further comprising an orientation sensor, wherein the processor is configured to reduce the temperature profile for a heat reduction time period when the orientation sensor detects a predetermined position of the device and/or a predetermined change in position of the device.

8. The aerosol generating device of claim 6 or 7, wherein the heat reduction time period is determined based on data collected by the processor on usage of the device by the user.

9. The aerosol generating device of any of the preceding claims, wherein the temperature profile function is a Fourier series.

10. The aerosol generating device of any of the preceding claims, wherein the timer is configured to measure the time elapsed from the start of the vaping session up to a maximum session length.

11. The aerosol generating device of any of the preceding claims, wherein the first time derivative of the temperature profile is continuous with respect to time.

12. The aerosol generating device of claim 2, wherein the processor is configured to receive the user input from a separate device.

13. A method of controlling a heater in an aerosol generating device, the method comprising the steps of: measuring a time elapsed from the start of a vaping session; and controlling the heater based on a calculated temperature profile that varies continuously as a function of time.