Improved control of aerosol production in aerosol-generating system

Abstract

To provide control of aerosol production in an aerosol-generating system.SOLUTION: A system (100) includes an aerosol-generating element (119), and a housing (101) having an air inlet (123) and an air outlet (125). A flow channel from the air inlet (123) to the air outlet (125) configured to provide a flow of air passing through the aerosol-generating element (119). The system (100) includes a flow sensor (109) configured to detect an air flow in the flow channel. A method includes increasing the power supplied to the aerosol-generating element (119) for at least a second time if the flow sensor (109) detects that the flow rate of the air flow exceeds a threshold. There is also provided an aerosol-generating system comprising circuitry configured to practice the method.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for controlling aerosol generation within an aerosol generation system. The present invention further relates to an aerosol generation system. The present invention has a particular application as a method for controlling aerosol generation within an aerosol generation system through the control of the power supplied to an aerosol generating element of the aerosol generation system.

Background Art

[0002] WO2012 / 072790 discloses a method for controlling at least one electric heating element of an electrically heated aerosol generation system in order to heat an aerosol forming substrate. The aerosol generation system has a sensor for detecting an airflow indicative of a user smoking having an airflow period. The method includes increasing the heating power to at least one heating element when the sensor detects that the airflow rate has increased to a first threshold value, and decreasing the heating power to at least one heating element when the sensor detects that the airflow rate has decreased to a second threshold value.

[0003] As disclosed in WO2012 / 072790, the energy consumption can be optimized by controlling the heating power supplied to at least one heating element. The heating power can be adjusted for a particular smoking profile such that desired aerosol characteristics such as a particular aerosol concentration or particle size can be achieved. Also, unnecessary overheating or underheating, especially towards the start or end of smoking, can be avoided. The decrease in power towards the end of smoking affects the cooling of the heating element and thus the temperature of the heating element and its vicinity. This in turn affects the amount of condensation that can form within the system, which can affect liquid leakage.

[0004] The disclosure of WO2012 / 072790 teaches a method of minimizing the condensation of aerosol generated within an aerosol generating device by reducing the heating power supplied to the aerosol generating element prior to the end of a user's smoking. However, this may frustrate the user, especially when an insufficient amount of aerosol is delivered to the user after the power supplied to the aerosol generating element has been reduced, particularly during a more complex smoking profile.

[0005] It is an object of the present invention to provide an improved method of controlling aerosol generation within an aerosol generating system. In particular, it is an object of the present invention to provide an improved method of controlling aerosol generation during a complex smoking profile. SUMMARY OF THE INVENTION

[0006] According to a first aspect of the present invention, there is provided a method of controlling aerosol generation within an aerosol generating system. The system comprises an aerosol generating element and a housing having an air inlet and an air outlet. A flow path is defined through the housing from the air inlet to the air outlet, the flow path providing an air flow through the aerosol generating element when a user smokes on the system. The system further comprises a flow sensor configured to detect an air flow within the flow path indicative of the user smoking. The method comprises the following chronological steps, increasing the power supplied to the aerosol generating element from power P0 to at least power P1 when the flow sensor detects that the flow rate of the air flow is greater than a first threshold; reducing the power supplied to the aerosol generating element to power P2, where power P2 is less than power P1, when the flow sensor detects that the flow rate of the air flow is less than a second threshold, the second threshold being a flow rate that is a predetermined first percentage of a first maximum flow rate detected by the flow sensor; Before detecting that the flow rate of the airflow is less than the smoking end threshold, when the flow sensor detects that the flow rate of the airflow is greater than a third threshold, a step of increasing the power supplied to the aerosol generating element, wherein the third threshold is greater than the second threshold and the smoking end threshold is less than the second threshold, the step of increasing, is included.

[0007] The steps of the method are shown in chronological order. That is, the order of the above steps is the order in which the steps are performed. However, there may be more steps performed before, after, or in between any of the steps of the above method.

[0008] As used herein, the term "aerosol generation system" can be used to describe a system configured to generate an aerosol. The aerosol can be for inhalation by a user. The aerosol generation system can include an aerosol generator and a cartridge. The aerosol generator can include a power source. The cartridge can include an aerosol forming substrate.

[0009] As used herein, the term "aerosol generating element" can be used to describe one or more elements configured to generate an aerosol or vapor from an aerosol forming substrate. One or more of the aerosol generating elements, or the elements forming the aerosol generating element, can be connected to a power source. That is, the aerosol generation system can include a power source configured to supply power to the aerosol generating element.

[0010] As used herein, the term "aerosol-forming substrate" is used to mean a substrate having the ability to release volatile compounds capable of forming an aerosol. The volatile compounds may be released by heating the aerosol-forming substrate. The aerosol generated from the aerosol-forming substrate of the aerosol generating system according to the present invention may be visible or invisible, and may also include vapors (e.g., particulate matter in a gaseous state of a substance that is normally liquid or solid at room temperature), as well as droplets of liquids of gases and condensed vapors.

[0011] As used herein, the term "flow rate" can be used to describe any parameter indicating the flow rate through an aerosol generating system. For example, the defined "flow rate" can be one or more of pressure, flow velocity, temperature, mass flow rate or volumetric flow rate. Thus, the defined "flow sensor" can detect one or more of pressure, flow velocity, temperature, mass flow rate or volumetric flow rate.

[0012] As used herein, the term "smoking detection system" can refer to a system comprising a flow sensor.

[0013] As used herein, the term "airflow" may be used to refer to a flow of only air, or may be used to refer to a flow of air combined with aerosol droplets.

[0014] As used herein, the term "droplet" can be used to mean a droplet or particle. That is, the term "droplet" can refer to a liquid droplet. Alternatively, or additionally, the term "droplet" can refer to a solid particle.

[0015] The flow sensor can include an electromechanical device, or a mechanical device, or an optical device, or an optomechanical device, or a microelectromechanical system (MEMS)-based sensor, an acoustic sensor, or any combination of the foregoing.

[0016] As used herein, the term "smoking" is used to describe inhalation by a user that causes a flow of air through an aerosol generating system. The start point of smoking is defined by the point at which a flow sensor detects that the flow rate is greater than a smoking start threshold, and the end point of smoking is defined by the point at which the flow sensor detects that the flow rate has decreased below a smoking end threshold.

[0017] As used herein, the term "predetermined" is used to mean determined prior to the start point of smoking.

[0018] According to a first aspect of the present invention, a method of controlling aerosol generation includes increasing the power supplied to an aerosol generating element when a flow sensor detects that the flow rate of an air stream is greater than a third threshold, before detecting that the flow rate of the air stream is less than a smoking end threshold. That is, the power supplied to the aerosol generating element can increase two or more times during smoking according to a smoking profile. Thereby, advantageously, the aerosol generating system can deliver sufficient aerosol to the user during smoking having a complex smoking profile. In this context, the term "complex smoking profile" is used to mean a smoking profile having at least one local maximum when plotting a graph of flow rate versus time. For example, this step can mitigate potential problems in an exemplary smoking profile including the following steps: · Step 1: The user smokes with the system and increases the detected air stream flow rate from zero to a first maximum flow rate. · Step 2: Next, the detected flow rate decreases to a first local minimum flow rate that is greater than a smoking end threshold. · Step 3: Next, the flow rate increases to a second maximum flow rate. · Step 4: Next, the flow rate decreases below a smoking end threshold, indicating that smoking has ended.

[0019] If the power supplied to the aerosol generating element decreases between the second and third stages of smoking and does not increase again, the user may become frustrated with the improper delivery of aerosol during the third and fourth stages of smoking. In the method according to the present invention, the power supplied to the aerosol generating element can be increased during the third stage. Thus, the user can be delivered an appropriate aerosol during the third and fourth stages.

[0020] The power P0 may be zero. Advantageously, this can result in power savings. This may mean that the aerosol generating system does not need to be frequently recharged.

[0021] Alternatively, the power P0 may be a non-zero power. Advantageously, this can enable the system to more quickly deliver an appropriate aerosol in response to detected smoking.

[0022] The power P2 may be zero. Advantageously, this can result in power savings. This may mean that the aerosol generating system does not need to be frequently recharged.

[0023] Alternatively, the power P2 may be a non-zero power. Advantageously, this can enable the system to more quickly deliver an appropriate aerosol in response to the detected flow rate being greater than a third threshold.

[0024] The third threshold may be a predetermined second percentage of the first maximum flow rate. The predetermined second percentage needs to be greater than the predetermined first percentage so that the third threshold is greater than the second threshold.

[0025] Alternatively, the third threshold may be a predetermined multiple of the second threshold. The predetermined multiple needs to be greater than 1 so that the third threshold is greater than the second threshold. The predetermined multiple does not need to be an integer.

[0026] The first threshold may be a first constant.

[0027] The smoking end threshold can be a smoking end constant.

[0028] The step of increasing the power supplied to the aerosol generating element from power P0 to at least power P1 may include increasing the power supplied to the aerosol generating element to power PX, where PX is greater than or equal to power P1. Before detecting that the flow rate of the air flow is less than the smoking end threshold, when the flow sensor detects that the flow rate of the air flow is greater than a third threshold, the step of increasing the power supplied to the aerosol generating element may include increasing the power supplied to the aerosol generating element to power P3, where P3 is less than or equal to PX. P3, which is less than PX, may be advantageous for a typical smoking profile where the first maximum flow rate is the maximum flow rate during smoking.

[0029] The method may include, after the step of increasing the power supplied to the aerosol generating element when the flow sensor detects that the flow rate of the air flow is greater than a third threshold, before detecting that the flow rate of the air flow is less than the smoking end threshold, a step of decreasing the power supplied to the aerosol generating element to power P4 when the flow sensor detects that the flow rate of the air flow is less than the smoking end threshold.

[0030] Power P4 may be zero. Advantageously, this may result in power savings. This may mean that the aerosol generating system does not need to be recharged frequently.

[0031] Alternatively, power P4 may not be zero. Advantageously, this may enable the system to more quickly deliver an appropriate aerosol in response to the next detected smoking.

[0032] The power P4 may not be zero, and the method may further include a step of reducing the power supplied to the aerosol generating element to zero after a step of reducing the power supplied to the aerosol generating element to the power P4 when the flow sensor detects that the flow rate of the air flow is less than the smoking end threshold value. Reducing the power supplied to the aerosol generating element from the power P4 to zero may occur when another smoking is not detected within a given time interval, for example, within 5 minutes or within 3 minutes after the power supplied to the aerosol generating element has been reduced to the power P4. That is, reducing the power supplied to the aerosol generating element from the power P4 to zero may occur when a flow rate greater than the first threshold value is not detected within a given time interval after the power supplied to the aerosol generating element has been reduced to the power P4.

[0033] The step of increasing the power supplied to the aerosol generating element from the power P0 to at least the power P1 may include increasing the power from the power P0 to at least the power P1 substantially instantaneously. That is, the power may be increased from the power P0 to at least the power P1 over a period that is substantially equal to zero. On a plot of heating power on the vertical axis versus time on the horizontal axis, this may be represented by a vertical or substantially vertical line from the power P0 to at least the power P1. For example, the term "substantially instantaneously" may be used to mean that the power can be increased from the power P0 to at least the power P1 within 0.1 seconds. Advantageously, increasing the power supplied to the aerosol generating element substantially instantaneously may result in a more rapid generation of aerosol and less lag for the user.

[0034] As another method, the step of increasing the power supplied to the aerosol generating element from power P0 to at least power P1 may include increasing the power stepwise from power P0 to at least power P1. That is, the power may be increased stepwise from power P0 to at least power P1 over a period of time. The longer the period, the more stepwise the power increase. On a plot of heating power on the vertical axis versus time on the horizontal axis, this may be represented by a line having a positive average gradient from power P0 to at least power P1. The gradient of the line may or may not be constant. That is, the rate of change of power may or may not be constant. For example, the term "stepwise" may be used to mean that the power may be increased from power P0 to at least power P1 over a period of 0.1 seconds to 1 second, or 0.2 seconds to 0.6 seconds, or 0.2 seconds to 0.4 seconds.

[0035] The step of decreasing the power supplied to the aerosol generating element to power P2 may include decreasing the power supplied to the aerosol generating element from at least power P1 to power P2.

[0036] The step of decreasing the power supplied to the aerosol generating element to power P2 may include decreasing the power supplied to the aerosol generating element substantially instantaneously to power P2. That is, the power may be decreased to power P2 over a period that is substantially equal to zero. On a plot of heating power on the vertical axis versus time on the horizontal axis, this may be represented by a vertical, or substantially vertical, line to power P2. For example, the term "substantially instantaneously" may be used to mean that the power may be increased to power P2 within 0.1 seconds.

[0037] As another method, the step of reducing the power supplied to the aerosol generating element to power P2 may include gradually reducing the power supplied to the aerosol generating element to power P2. That is, the power can be reduced over a period that is not equal to zero. That is, the power can be gradually reduced to power P2 over a period of time. The longer the period, the more gradual the power reduction. On a plot of heating power on the vertical axis versus time on the horizontal axis, this can be represented by a line with a negative average gradient to power P2. The gradient of the line may or may not be constant. For example, the term "gradually" can be used to mean that after the flow sensor detects that the flow rate of the air flow is less than a second threshold value, the power can be reduced to power P2 within a period of 0.1 second to 1 second, or 0.2 second to 0.6 second, or 0.2 second to 0.4 second.

[0038] The method is after the step of increasing the power supplied to the aerosol generating element from power P0 to at least power P1, but may include a step of increasing the power supplied to the aerosol generating element from at least power P1 to power P5 before the step of reducing the power supplied to the aerosol generating element to power P2.

[0039] The power supplied to the aerosol generating element can be increased from at least power P1 to power P5 after, preferably substantially immediately after, the step of increasing the power supplied to the aerosol generating element from power P0 to at least power P1. In this context, the term "substantially immediately" can be used to mean within 0.1 second.

[0040] As another method, the step of increasing the power supplied to the aerosol generating element from power P0 to at least power P1 may include increasing the power supplied to the aerosol generating element from power P0 to power P5, where power P5 is greater than power P1.

[0041] Advantageously, this can provide a power burst near the start of smoking. The high power near the start of smoking can result in an early start of appropriate aerosol generation. This can provide good responsiveness to the user. This can also reduce the aerosol droplet size near the start of smoking. The power P5 may be predefined. The power P5 may depend on a number of factors including, but not limited to, the aerosol generating element, the type of aerosol forming substrate, the amount of aerosol desired to be formed, and the droplet size required for the aerosol. After the initial power burst, the power preferably decreases, for example, to power P1.

[0042] Supplying power to the aerosol generating element can include supplying a current pulse to the aerosol generating element.

[0043] Increasing or decreasing the power supplied to the aerosol generating element can include changing the frequency or magnitude, or both the frequency and magnitude, of the current pulse supplied to the aerosol generating element.

[0044] According to a second aspect of the present invention, an aerosol generating system is provided. The system comprises an aerosol generating element and a flow path configured to allow an airflow to pass through the aerosol generating element. The system further comprises a flow sensor configured to detect the airflow, wherein the airflow indicates that the user is smoking, and a power source for supplying power to the aerosol generating element. The system further comprises an electrical circuit for controlling the power supply from the power source to the aerosol generating element, and the electrical circuit is arranged to implement the method according to the first aspect of the present invention.

[0045] According to a third aspect of the present invention, an electrical circuit for an aerosol generating system is provided, and the electrical circuit is arranged to implement the method according to the first aspect of the present invention.

[0046] According to a fourth aspect of the present invention, there is provided a computer program which, when executed on a programmable electrical circuit for an aerosol generation system, causes the programmable electrical circuit to perform the method according to the first aspect of the present invention.

[0047] According to a fifth aspect of the present invention, there is provided a computer-readable storage medium having stored thereon the computer program according to the fourth aspect of the present invention.

[0048] According to a sixth aspect of the present invention, there is provided a method of controlling aerosol generation within an aerosol generation system. The system comprises an aerosol generating element and a housing having an air inlet and an air outlet. An air flow path is defined through the housing from the air inlet to the air outlet, the air flow path providing an air flow through the aerosol generating element when a user smokes on the system. The system further comprises a flow sensor configured to detect an air flow, the air flow indicating that the user is smoking. The method includes increasing the power supplied to the aerosol generating element from power p20 to at least power p21 when the flow sensor detects that the flow rate of the air flow is greater than a first threshold t21. The method is subject to the following conditions: · the flow sensor detecting that the flow rate of the air flow is less than a second threshold t22, the second threshold t22 being or indicating a predetermined flow rate, or · the flow sensor detecting that the flow rate of the air flow is less than a third threshold t23, the third threshold t23 being or indicating a flow rate that is a predetermined percentage of the maximum detected flow rate of the air flow, whichever occurs first, further including reducing the power supplied to the aerosol generating element to power p22 after detecting that the flow rate of the air flow is greater than the first threshold t21, power p22 being less than power p21.

[0049] Both the second threshold t22 and the third threshold t23 are greater than zero.

[0050] Advantageously, reducing the power supplied to the aerosol generating element before the flow rate drops to zero can reduce the amount of condensation that can form within the system, which can affect liquid leakage.

[0051] Advantageously, as either condition occurs first, by reducing the power supplied to the aerosol generating element, the power can be reduced at a greater flow rate for smoking having a greater maximum detected flow rate. However, regardless of the maximum detected flow rate of smoking, the second threshold t22 provides the minimum flow rate at which the power supplied to the aerosol generating element is reduced.

[0052] The power p22 may be zero.

[0053] The step of increasing the power supplied to the aerosol generating element from power p20 to at least power p21 can include increasing the power substantially instantaneously from power p20 to at least power p1. That is, the power can be increased from power P20 to at least power P21 over a period that is substantially equal to zero. On a plot of heating power on the vertical axis versus time on the horizontal axis, this can be represented by a vertical, or substantially vertical, line from power p20 to at least power P21. For example, the term "substantially instantaneously" can be used to mean that the power can be increased from power P20 to at least power P21 within 0.1 seconds.

[0054] Alternatively, according to a sixth aspect, the step of increasing the power supplied to the aerosol generating element from power p20 to at least power p21 may include increasing the power stepwise from power p20 to at least power p21. That is, the power may be increased stepwise from power p20 to at least power p21 over a period of time. The longer the period, the more stepwise the power increase. On a plot of heating power on the vertical axis against time on the horizontal axis, this may be represented by a line having a positive average gradient from power p20 to at least power p21. The gradient of the line may or may not be constant. For example, the term "stepwise" may be used to mean that the power may be increased from power p20 to at least power p21 over a period of 0.1 seconds to 1 second, or 0.2 seconds to 0.6 seconds, or 0.2 seconds to 0.4 seconds.

[0055] According to a sixth aspect, the step of decreasing the power supplied to the aerosol generating element to power p22 may include decreasing the power supplied to the aerosol generating element from at least power p21 to power p22.

[0056] According to a sixth aspect, the step of decreasing the power supplied to the aerosol generating element to power p22 may include decreasing the power supplied to the aerosol generating element to power p22 substantially instantaneously. That is, the power may be decreased to power p22 over a period of time that is substantially equal to zero. On a plot of heating power on the vertical axis against time on the horizontal axis, this may be represented by a vertical or substantially vertical line to power p22. For example, the term "substantially instantaneously" may be used to mean that the power may be increased to power p22 within 0.1 seconds.

[0057] Alternatively, according to a sixth aspect, the step of reducing the power supplied to the aerosol generating element to power p22 may include gradually reducing the power supplied to the aerosol generating element to power p22. That is, the power can be reduced over a period that is not equal to zero. That is, the power can be gradually reduced to power p22 over a period of time. The longer the period, the more gradual the power reduction. On a plot of heating power on the vertical axis versus time on the horizontal axis, this can be represented by a line with a negative average gradient to power p22. The gradient of the line may or may not be constant. For example, the term "gradually" can be used to mean that the power can be reduced to power p22 within a period of 0.1 seconds to 1 second, or 0.2 seconds to 0.6 seconds, or 0.2 seconds to 0.4 seconds after the flow sensor detects that the flow rate of the air flow is less than the second threshold t22.

[0058] According to a sixth aspect, the method may include a step of increasing the power supplied to the aerosol generating element from power p20 to at least power p21, but before the step of reducing the power supplied to the aerosol generating element to power p22, increasing the power supplied to the aerosol generating element from at least power p21 to power p25.

[0059] According to a sixth aspect, the power supplied to the aerosol generating element can be increased from at least power p21 to power p25 after, preferably substantially immediately after, the step of increasing the power supplied to the aerosol generating element from power p20 to power p21. In this context, the term "substantially immediately" can be used to mean within 0.1 seconds.

[0060] Alternatively, the step of increasing the power supplied to the aerosol generating element from power p20 to at least power p21 may include increasing the power supplied to the aerosol generating element from power p20 to power p25, where power p25 is greater than power p21.

[0061] This can provide a burst of power near the start of smoking. Such a burst of power near the start of smoking can result in an early start of appropriate aerosol generation. This can provide good responsiveness to the user. This can also reduce the aerosol droplet size near the start of smoking. The power p25 may be predefined. The power p25 may depend on a number of factors including, but not limited to, the aerosol generating element, the type of aerosol forming substrate, the amount of aerosol desired to be formed, and the droplet size required for the aerosol. After the initial burst of power, the power preferably decreases, for example, to the power p21.

[0062] According to a sixth aspect, supplying power to the aerosol generating element may include supplying a current pulse to the aerosol generating element.

[0063] According to a seventh aspect, there is provided an aerosol generating system arranged to carry out the method of the sixth aspect. The system comprises an aerosol generating element and a flow path configured to allow an airflow to pass through the aerosol generating element. The system further comprises a flow sensor configured to detect the airflow, wherein the airflow indicates that the user is smoking, and a power source for supplying power to the aerosol generating element. The system further comprises an electrical circuit for controlling the supply of power from the power source to the aerosol generating element, and the electrical circuit is arranged to carry out the method according to the sixth aspect.

[0064] According to an eighth aspect, there is provided an electrical circuit for an aerosol generating system, the electrical circuit being arranged to carry out the method of the sixth aspect.

[0065] According to a ninth aspect, there is provided a computer program which, when executed on a programmable electrical circuit for an aerosol generating system, causes the programmable electrical circuit to carry out the method of the sixth aspect.

[0066] According to a tenth aspect, there is provided a computer-readable storage medium having a computer program which, when executed on a programmable electrical circuit for an aerosol generation system, causes the programmable electrical circuit to implement the method of the sixth aspect.

[0067] According to an eleventh aspect, there is provided a method of controlling aerosol generation within an aerosol generation system. The system comprises an aerosol generating element, a housing having an air inlet and an air outlet, and a flow path defined through the housing from the air inlet to the air outlet, the flow path providing an air flow through the aerosol generating element when a user smokes on the system. The system further comprises a flow sensor configured to detect an air flow, the air flow indicating that the user is smoking. The method according to the eleventh aspect comprises the following chronological steps: increasing the power supplied to the aerosol generating element from power p30 to at least power p31 when the flow sensor detects that the flow rate of the air flow is greater than a first threshold t31; decreasing the power supplied to the aerosol generating element to power p32, where power p32 is less than power p31, when the flow sensor detects that the flow rate of the air flow is less than a second threshold t32; increasing the power supplied to the aerosol generating element to power p33, where the third threshold t33 is less than the second threshold t32, when the flow sensor detects that the flow rate of the air flow is greater than a third threshold t33 within a predetermined time interval after the flow sensor has detected that the flow rate of the air flow is less than the second threshold t32, or · When the flow sensor detects that the flow rate of the air current is smaller than a fourth threshold value t34, where the fourth threshold value t34 is smaller than the second threshold value t32, and when the time difference between the time when the flow rate of the air current is detected to be smaller than the second threshold value t32 and the time when the flow rate of the air current is detected to be smaller than the fourth threshold value t34 is smaller than a fifth threshold value t35, it includes any one of the steps of increasing the power supplied to the aerosol generating element to power p34.

[0068] According to the eleventh aspect, the third threshold value t33 is smaller than the second threshold value t32, and the fourth threshold value t34 is smaller than the second threshold value t32. Advantageously, this enables the aerosol generation system to deliver sufficient aerosol to the user during a slowly ending smoking.

[0069] According to the eleventh aspect, the second threshold value t32 is a flow rate that is a predetermined first ratio of the first maximum flow rate sensed by the flow sensor or can indicate it.

[0070] According to the eleventh aspect, the flow sensor can detect the flow rate continuously or intermittently.

[0071] According to the eleventh aspect, the flow sensor can detect the flow rate during a first predetermined period after the flow sensor detects that the flow rate has decreased to less than the second threshold value t32. The flow sensor can then compare the detected flow rate during this first predetermined period after detecting that the flow rate has decreased to less than the second threshold value t32 with the third threshold value t33.

[0072] According to the eleventh aspect, the flow sensor can regularly detect the flow rate throughout the smoking, which means that the flow rate is detected every period tp3. After detecting that the flow rate has decreased below the second threshold t32, the flow sensor can compare the nth detected flow rate with the third threshold t33, where n is an integer greater than 1. Advantageously, this means that the nth flow rate is not compared with the third threshold until at least a period of (n - 1) multiplied by the period tp3 has elapsed since the flow sensor first detected that the flow rate has decreased below the second threshold.

[0073] According to the eleventh aspect, any increase or decrease in the power supplied to the aerosol generating element can occur substantially instantaneously or stepwise. In connection with the claimed invention and as explained with reference to the method of the sixth aspect, the term "stepwise" may be used to mean within a period of 0.1 second to 1 second, or 0.2 second to 0.6 second, or 0.2 second to 0.4 second, and the term "substantially instantaneously" may be used to mean within 0.1 second.

[0074] According to the eleventh aspect, the power p32 may be zero. The power p33 may be a predetermined power. The power p34 may be a predetermined power. The power p33 and the power p34 may be the same power. Alternatively, the power p33 and the power p34 may be different powers.

[0075] The method according to the eleventh aspect may include a step of increasing the power supplied to the aerosol generating element from at least power p31 to power p35 after a step of increasing the power supplied to the aerosol generating element from power p30 to at least power p31, but before a step of decreasing the power supplied to the aerosol generating element to power p32.

[0076] According to an eleventh aspect, the power supplied to the aerosol generating element can be increased from at least power p31 to power p35, preferably substantially immediately after, the step of increasing the power supplied to the aerosol generating element from power p30 to at least power p31. In this context, the term "substantially immediately" can be used to mean within 0.1 seconds.

[0077] As another method, according to an eleventh aspect, the step of increasing the power supplied to the aerosol generating element from power p30 to at least power p31 can include increasing the power supplied to the aerosol generating element from power p30 to power p35, where power p35 is greater than power p31.

[0078] This can provide a burst of power near the start of smoking. Such a burst of power near the start of smoking can result in an early start of appropriate aerosol generation. This can reduce the lag for the user. This can also reduce the aerosol droplet size near the start of smoking. Power p35 may be predefined. Power p35 can depend on a number of factors including, but not limited to, the aerosol generating element, the type of aerosol forming substrate, the amount of aerosol desired to be formed, and the droplet size required for the aerosol. After the initial burst of power, the power preferably decreases, for example, to power p31.

[0079] The method according to the eleventh aspect can further include the step of reducing the power supplied to the aerosol generating element to power p36 when the flow sensor detects that the flow rate of the air stream has decreased below a smoking end threshold t3e, after either the step of increasing the power supplied to the aerosol generating element to power p33 or the step of increasing the power supplied to the aerosol generating element to power p34.

[0080] Power p36 may be zero. The smoking end threshold t3e can be a smoking end constant.

[0081] According to an eleventh aspect, supplying power to the aerosol generating element may include supplying a current pulse to the aerosol generating element.

[0082] According to a twelfth aspect, there is provided an aerosol generating system arranged to carry out the method according to the eleventh aspect. The system comprises an aerosol generating element and a flow path configured to allow an air flow to pass through the aerosol generating element. The system further comprises a flow sensor configured to detect the air flow, the air flow indicating that the user is smoking, and a power source for supplying power to the aerosol generating element. The system further comprises an electrical circuit for controlling the supply of power from the power source to the aerosol generating element, the electrical circuit being arranged to carry out the method according to the eleventh aspect.

[0083] According to a thirteenth aspect of the present invention, there is provided an electrical circuit for an aerosol generating system, the electrical circuit being arranged to carry out the method according to the eleventh aspect.

[0084] According to a fourteenth aspect, there is provided a computer program which, when executed on a programmable electrical circuit for an aerosol generating system, causes the programmable electrical circuit to carry out the method according to the eleventh aspect.

[0085] According to a fifteenth aspect, there is provided a computer-readable storage medium having a computer program which, when executed on a programmable electrical circuit for an aerosol generating system, causes the programmable electrical circuit to carry out the method according to the eleventh aspect.

[0086] According to a sixteenth aspect of the present invention, there is provided a method of controlling aerosol generation within an aerosol generation system. The system comprises data storage means and an aerosol generating element. The system further comprises a housing having an air inlet and an air outlet, and a flow path defined through the housing from the air inlet to the air outlet, the flow path providing an air flow through the aerosol generating element when a user smokes with the system. The system further comprises a flow sensor configured to detect an air flow, the air flow indicating that the user is smoking. The method includes increasing the power supplied to the aerosol generating element from power p4x to at least power p41 when the flow sensor detects that the flow rate of the air flow is greater than a first threshold value t41. The method further includes storing a measured value measured by the flow sensor in the data storage means, and intermittently calculating an estimated value of the remaining volume of the smoking using the measured value stored in the data storage means. The method further includes reducing the power supplied to the aerosol generating element to power t42 when the estimated value of the remaining volume of the smoking is less than a second threshold value t42, the second threshold value t42 being a measured value of the volume or indicating the same.

[0087] Advantageously, the method of the sixteenth aspect can allow an approximate volume, herein referred to as the air flushing volume, to pass through the aerosol generation system after the power supplied to the aerosol generating element has been reduced. The second threshold value t42 is a flushing volume or indicates the same.

[0088] According to the sixteenth aspect, the second threshold value t42 may be a predetermined value.

[0089] According to the sixteenth aspect, the second threshold t42 may be approximately equal to or indicative of a volume substantially equal to the internal volume of the flow passage within the mouthpiece of the aerosol generation system. That is, when an air flow passes through the flow passage within the mouthpiece of the aerosol generation system, the flushing volume may advantageously be approximately equal to the volume of the flow passage within the mouthpiece. In this context, "substantially equal to the volume of the flow passage" may be used to mean within 1.5 to 0.5 times, or 0.75 to 1.25 times, or 0.9 to 1.1 times the volume of the flow passage, or within 5 ml, or 3 ml, or 1 ml of the flow passage.

[0090] According to the sixteenth aspect, the second threshold t42 may be or indicate a volume of 0.1 ml to 10 ml, or 0.1 ml to 5 ml, or 0.1 ml to 3 ml, or 0.1 ml to 1 ml, or 1 ml to 10 ml, or 1 ml to 5 ml.

[0091] The method of the sixteenth aspect may include a step of increasing the power supplied to the aerosol generation element to power p43 after a step of decreasing the power supplied to the aerosol generation element to power p42 when an estimated value of the remaining volume of smoking is less than the second threshold t42. The step of increasing the power supplied to the aerosol generation element to power p43 may occur when an estimated value of the remaining volume of smoking is greater than a third threshold t43, and the third threshold t43 is greater than the second threshold t42.

[0092] According to the sixteenth aspect, the flow sensor may measure the measured value continuously or intermittently.

[0093] According to the sixteenth aspect, the intermittent calculation of the estimated value of the remaining volume of smoking may be calculated by one or more of several methods.

[0094] As a first example of how the calculation is performed, the flow sensor may intermittently store the volumetric flow rate value. In this context, "intermittently" may be used to mean periodically, for example, every period T P each. Period T PFor the second and each subsequent stored value, the processor calculates the average rate of change of the current flow rate A c The average rate of change of this current flow rate A c is the current flow rate value Q c The flow rate value Q stored just before c-1 After subtracting, period T P The processor then calculates the average rate of change of this current flow rate, A c remains constant. This means that the average rate of change of the current flow rate A c If is negative, the remaining time of the current puff T C is the current flow rate value Q c The average rate of change of the current flow rate A c This means that the current remaining volume of the puff, V, can be estimated to be equal to the negative of c The estimated value of the current flow rate Q is set to -0.5. c The average rate of change of the current flow rate A c Of course, this calculation can be done by dividing the average rate of change of the current flow rate A c When is negative, the current remaining volume V c The current remaining volume of the puff, V, is positive. c and the current remaining time T C The processor returns a negative value for such a current remaining volume V. c The processor may ignore all of the current average rate of change of flow rate A c In particular, we do not need to calculate the estimate until the current remaining time T C is the current remaining volume V c In equation form, the first embodiment can be summarized as follows:

number

[0095] Alternatively, as a second example, the average rate of change of the current flow rate A cis the flow rate value Q immediately after c+1 subtracted from the flow rate value Q stored immediately before c-1 and then divided by the period T p can be estimated. Naturally, this estimation cannot be carried out until immediately after the flow rate value Q c+1 is measured. In the form of an equation, the second embodiment can be summarized as follows.

Equation

[0096] As another method, as a third embodiment, non-linear extrapolation of the flow rate may be used. Non-linear extrapolation may use a predetermined polynomial. Non-linear extrapolation may use a predetermined polynomial that more accurately represents the change in the flow rate of smoking towards the end of a general smoking profile. As another method, non-linear extrapolation may depend on previously stored measurement values measured by a flow sensor during the current smoking. For example, if the average rate of change of the flow rate appears to decrease in each of the measurement values after being measured near the end of smoking, a polynomial that more accurately estimates the change in the flow rate for such smoking may be selected, and a different polynomial may be selected for smoking where the rate of change of the flow rate is constant or increasing. Advantageously, this can more accurately estimate the change in the flow rate towards the end of smoking and thus provide a better estimate of the remaining volume of smoking.

[0097] According to a sixteenth aspect, the intermittent calculation of the estimated remaining volume of smoking may not start until the flow sensor detects that the flow rate has decreased below an estimated start threshold t4s. Alternatively, the intermittent calculation of the estimated remaining volume of smoking may not operate until the flow sensor detects that the flow rate has decreased below an estimated start threshold t4s, which means that the power supplied to the aerosol generating element does not change. The estimated start threshold t4s can be a predetermined percentage of the detected maximum flow rate. Advantageously, this can help avoid changing the power supplied to the aerosol generating element based on an inaccurately small estimated value of the remaining volume of smoking. For example, if the flow rate decreases significantly after the maximum flow rate is detected, the calculated estimated value for the remaining volume of smoking may be much smaller than the actual remaining volume of smoking.

[0098] According to a sixteenth aspect, any increase or decrease in the power supplied to the aerosol generating element can occur substantially instantaneously or in steps. In relation to the claimed invention, and as described with reference to the method of the sixth aspect, the term "in steps" may be used to mean within a period of 0.1 second to 1 second, or 0.2 second to 0.6 second, or 0.2 second to 0.4 second, and the term "substantially instantaneously" may be used to mean within 0.1 second.

[0099] The method of the sixteenth aspect can include a step of increasing the power supplied to the aerosol generating element from at least power p41 to power p45 after a step of increasing the power supplied to the aerosol generating element from power p4x to at least power p41, but before a step of decreasing the power supplied to the aerosol generating element to power p42.

[0100] According to a sixteenth aspect, the power supplied to the aerosol generating element can be increased from at least power p41 to power p45 after, preferably substantially immediately after, a step of increasing the power supplied to the aerosol generating element from power p4x to power p41. In this context, the term "substantially immediately" can be used to mean within 0.1 second.

[0101] As another method, the step of increasing the power supplied to the aerosol generating element from power p4x to at least power p41 may include increasing the power supplied to the aerosol generating element from power p4x to power p45, where power p45 is greater than power p41.

[0102] This can provide a burst of power near the start of smoking. Such a burst of power near the start of smoking can result in an early start of proper aerosol generation. This can provide good responsiveness to the user. This can also reduce the aerosol droplet size near the start of smoking. Power p45 may be predefined. Power p45 may depend on a number of factors including, but not limited to, the aerosol generating element, the type of aerosol forming substrate, the amount of aerosol desired to be formed, and the droplet size required for the aerosol. After the initial burst of power, the power preferably decreases, for example, to power p41.

[0103] According to a sixteenth aspect, supplying power to the aerosol generating element may include supplying a current pulse to the aerosol generating element.

[0104] According to another aspect, an aerosol generating system is provided that is arranged to implement the method of the sixteenth aspect. The system comprises an aerosol generating element and a flow path configured to allow an airflow to pass through the aerosol generating element. The system further comprises a flow sensor configured to detect the airflow, where the airflow indicates that the user is smoking, and a power source for supplying power to the aerosol generating element. The system further comprises an electrical circuit for controlling the power supply from the power source to the aerosol generating element, and the electrical circuit is arranged to implement the method according to the sixteenth aspect.

[0105] According to another aspect, an electrical circuit for an aerosol generating system is provided, and the electrical circuit is arranged to implement the method of the sixteenth aspect.

[0106] According to another aspect, there is provided a computer program which, when executed on a programmable electrical circuit for an aerosol generation system, causes the programmable electrical circuit to perform the method of the sixteenth aspect.

[0107] According to another aspect, there is provided a computer-readable storage medium storing a computer program which, when executed on a programmable electrical circuit for an aerosol generation system, causes the programmable electrical circuit to perform the method of the sixteenth aspect.

[0108] The aerosol generation system may comprise an aerosol-forming substrate, and the aerosol generating element may include one or more elements configured to interact with the aerosol-forming substrate to generate an aerosol or vapor, for example, by adding aerosol droplets to an air stream to generate an aerosol.

[0109] The aerosol generating element may include a mechanical device such as a vibrating orifice transducer or a piezoelectric device. The aerosol generating element may include an electrical heater including at least one heater element. At least one electrical heating element may be arranged to heat the aerosol-forming substrate to form an aerosol.

[0110] The aerosol generating element may include a single heating element. Alternatively, the aerosol generating element may include a plurality of heating elements, for example two, or three, or four, or five, or six, or more heating elements. The heating element(s) may be appropriately arranged to most effectively heat the aerosol-forming substrate.

[0111] The aerosol generating element may include at least one electrical heating element. The at least one electrical heating element preferably includes an electrically resistive material. Suitable electrically resistive materials include, for example, semiconductors such as doped ceramics, "conductive" ceramics (such as molybdenum disilicide), carbon, graphite, metals, alloys, and composite materials made of ceramic materials and metal materials, but are not limited thereto. Such composite materials may include doped ceramics or undoped ceramics. An example of a suitable doped ceramic is doped silicon carbide. Examples of suitable metals include titanium, zirconium, tantalum, and platinum group metals. Examples of suitable metal alloys include stainless steel, constantan, nickel-containing, cobalt-containing, chromium-containing, aluminum-containing, titanium-containing, zirconium-containing, hafnium-containing, niobium-containing, molybdenum-containing, tantalum-containing, tungsten-containing, tin-containing, gallium-containing, manganese-containing, and iron-containing alloys, as well as nickel, iron, cobalt, stainless steel-based superalloys, Timetal® (registered trademark), iron-aluminum-based alloys, and iron-manganese-aluminum-based alloys. Timetal® is a registered trademark of Titanium Metals Corporation (1999 Broadway Suite 4300, Denver Colorado). In the composite material, the electrically resistive material may optionally be embedded in, encapsulated in, or coated with a heat insulating material, or vice versa, depending on the required energy transfer kinetics and external physico-chemical properties. The heating element may include a metal etched foil insulated between two layers of inert material. In that case, the inert material may include Kapton® (registered trademark), all-layer polyimide, or mica foil. Kapton® is a registered trademark of E.I. du Pont de Nemours and Company (1007 Market Street, Wilmington, Delaware 19898, United States of America).

[0112] Alternatively, or in addition, the aerosol generating element may include an infrared heater, a photon source, or an inductive heater.

[0113] At least one electric heater may take any suitable form. For example, at least one electric heater may take the form of a heating blade.

[0114] At least one electric heater may include a casing or substrate having different conductive parts or an electrically resistive metal tube. If the aerosol-forming substrate is a liquid provided within a container, the container may incorporate a disposable heater.

[0115] At least one electric heater may include a heating needle or rod that passes through the center of the aerosol-forming substrate.

[0116] At least one electric heater may include a disk-shaped (end) heater or a combination of a disk-shaped heater and a heating needle or rod.

[0117] At least one electric heater may be provided with a flexible material sheet arranged to surround or partially surround the aerosol-forming substrate. Other alternatives include heating wires or filaments, such as wires or heating plates made of Ni-Cr, platinum, tungsten, or alloys. Optionally, the heater may be disposed within or on a rigid carrier material.

[0118] Alternatively, or in addition, the aerosol generating element may include a heating element, which includes a plurality of conductive filaments. As used herein, the term "filament" refers to an electrical path disposed between two electrical contacts. The filaments may optionally be branched and divided into several paths or filaments respectively, or may converge from several electrical paths into one path. The filaments may have a round, square, flat, or any other cross-sectional shape. The filaments may be arranged in a straight manner or in a curved manner.

[0119] The heating element may be, for example, an array of filaments arranged parallel to each other. Preferably, the filaments can form a mesh. The mesh may be woven or non-woven. The mesh may be formed using different types of weaving structures or lattice structures. Alternatively, the conductive heating element consists of an array of filaments or a fabric of filaments. The mesh, array, or fabric of conductive filaments may also be characterized by its ability to hold liquid in some cases.

[0120] In a preferred embodiment, the substantially flat heating element may be constructed of wires formed into a wire mesh. The mesh preferably has a plain weave design. The heating element is preferably a wire grill made from mesh strips.

[0121] The filaments of the heating element may be formed of any material having suitable electrical properties. Suitable materials include, but are not limited to, semiconductors such as doped ceramics, "conductive" ceramics, carbon, graphite, metals, alloys, and composite materials made of ceramic materials and metal materials.

[0122] Preferred materials for the conductive filaments are stainless steel and graphite, with 300 series stainless steels such as AISI 304, 316, 304L, 316L being more preferred. To improve the control of the resistance of the heating element, a combination of materials may be used for the conductive heating element. For example, a material with a high resistivity may be combined with a material with a low resistivity. This may be advantageous when one of the materials is more beneficial from other viewpoints, such as price, machinability, or other physical or chemical parameters. Advantageously, a substantially flat filament arrangement with increased resistance reduces parasitic losses. Advantageously, a heater with a high resistance enables more efficient use of battery energy.

[0123] The filament is preferably made of wire. The wire is preferably made of metal, and most preferably made of stainless steel.

[0124] The conductive filaments may define gaps between the filaments. The gaps may have a width of from 10 micrometers to 100 micrometers. It is preferred that the filaments cause capillary action within the gaps such that a liquid that is to be vaporized during use is drawn into the gaps, increasing the contact area between the heating element and the liquid aerosol forming substrate.

[0125] At least one heating element may heat the aerosol forming substrate by conduction. The heating element may be at least partially in contact with the substrate or with a carrier on which the substrate is deposited.

[0126] Heat from the heating element may be conducted to the substrate by means of a thermally conductive element.

[0127] At least one heating element may transfer heat to the incoming ambient air drawn through an electrically heated aerosol generating system during use, which in turn heats the aerosol forming substrate by convection. The ambient air may be heated before passing through the aerosol forming substrate.

[0128] When the aerosol-forming substrate is a liquid substrate, ambient air may first be drawn through the substrate and then heated.

[0129] The aerosol-forming substrate may be a solid aerosol-forming substrate. The aerosol-forming substrate preferably comprises a tobacco-containing material comprising volatile tobacco flavor compounds emitted from the substrate upon heating. The aerosol-forming substrate may comprise a non-tobacco material. The aerosol-forming substrate may comprise a tobacco-containing material and a non-tobacco material. The aerosol-forming substrate preferably further comprises an aerosol-forming agent. Examples of suitable aerosol-forming agents are glycerin and propylene glycol.

[0130] The aerosol-forming substrate may be a liquid aerosol-forming substrate. The aerosol generation system may comprise a liquid storage portion. The liquid aerosol-forming substrate is preferably stored within the liquid storage portion. The aerosol generating element may comprise a capillary core in communication with the liquid storage portion. The aerosol generation system may comprise a capillary core for holding the liquid without having a liquid storage portion. In that case, the capillary core may be pre-loaded with liquid.

[0131] It is preferable to dispose the capillary core so as to contact the liquid in the liquid storage portion. In that case, during use, the liquid is moved from the liquid storage portion toward at least one electric heating element by capillary action within the capillary core. In one embodiment, the capillary core has a first end and a second end, the first end extending into the liquid storage portion for contacting the liquid therein, and at least one electric heating element may be arranged to heat the liquid within the second end. When the heating element is activated, the liquid at the second end of the capillary core is vaporized by the heater to form supersaturated vapor. The supersaturated vapor is mixed with the air stream and carried within the air stream. During the flow, the vapor is condensed to form an aerosol, and the aerosol is carried toward the user's mouth. The heating element combined with the capillary core may provide a quick response, which may be because this arrangement may provide a large surface area of the liquid to the heating element. Therefore, the control of the heating element according to the present invention may depend on the structure of the arrangement of the capillary core.

[0132] The liquid matrix may be absorbed by any suitable absorbent plug or body, such as a porous carrier material made of a foamy metal or plastic material, polypropylene, terylene, nylon fiber or ceramic. The liquid matrix may be held within the porous carrier material before using an electrically heated aerosol generation system, or alternatively, the liquid matrix material may be released into the porous carrier material during or immediately before use. For example, the liquid matrix may be provided within a capsule. It is preferable that the shell of the capsule melts with heating to release the liquid matrix into the porous carrier material. The capsule may optionally contain a solid combined with the liquid.

[0133] When the aerosol-forming substrate is a liquid substrate, the liquid has physical properties, such as a boiling point suitable for use in an aerosol-generating system. If the boiling point is too high, at least one electrical heating element cannot vaporize the liquid in the wick, but if the boiling point is too low, the liquid may vaporize without activating at least one electrical heating element. The control of at least one electrical heating element may depend on the physical properties of the liquid substrate. The liquid preferably contains a tobacco-containing material that includes volatile tobacco flavor compounds released from the liquid when heated. Alternatively or additionally, the liquid may contain non-tobacco materials. The liquid may include water, solvents, ethanol, plant extracts, and natural or artificial flavors. The liquid preferably further contains an aerosol former. Examples of suitable aerosol formers are glycerin and propylene glycol.

[0134] The advantage of providing a liquid storage portion is that a high level of hygiene can be maintained. By using a wick extending between the liquid and the electrical heating element, the structure of the system can be made relatively simple. The liquid has physical properties including viscosity and surface tension such that the liquid is carried through the wick by capillary action. The liquid storage portion is preferably a container. The liquid storage portion may not be refillable. Thus, when the liquid in the liquid storage portion is exhausted, the aerosol-generating system is replaced. Alternatively, the liquid storage portion may be refillable. In that case, the aerosol-generating system may be replaced after a certain number of refills of the liquid storage portion. The liquid storage portion is preferably arranged to hold liquid for a predetermined number of smoking sessions.

[0135] The wick may have a fibrous or spongy structure. The wick preferably comprises a bundle of capillaries. For example, the wick may include a plurality of fibers or threads, or other fine tubes. The fibers or threads can generally be arranged in the longitudinal direction of the aerosol-generating system.

[0136] Alternatively, the capillary core may comprise a sponge-like or foam-like material formed in a rod shape. The rod shape may extend along the long axis direction of the aerosol generation system. The core structure forms a plurality of small holes or tubes through which the liquid can move to the electrothermal heater by capillary action. The capillary core may comprise any suitable material or combination of materials. Examples of suitable materials include materials based on ceramics or graphite in the form of fibers or sintered powders. The capillary core may have any suitable capillary and porosity such that it combines different liquid physical properties such as density, viscosity, surface tension, and vapor pressure. The capillary nature of the core, combined with the nature of the liquid, ensures that the core is always wet within the heating region. If the core is dry, overheating may occur, which can lead to degradation of the liquid.

[0137] During operation, the substrate may be fully contained within the aerosol generation system. In that case, the user may smoke through the mouthpiece of the electrically heated aerosol generation system. Alternatively, during operation, the substrate may be partially contained within the aerosol generation system. In that case, the substrate may form part of a separate article, and the user may smoke the separate article directly.

[0138] The aerosol generation system is preferably an electrically heated aerosol generation system. More preferably, the aerosol generation system is an electrically heated smoking system.

[0139] The aerosol generation system comprises a flow path, a part of which may be called the aerosol formation chamber. In the aerosol formation chamber, the aerosol is formed from supersaturated vapor and can then be carried into the user's mouth. The air inlet, air outlet, and chamber are preferably arranged to define a path of airflow from the air inlet, through the aerosol formation chamber, to the air outlet so as to carry the aerosol to the air outlet and into the user's mouth. Condensation may form on the walls of the aerosol formation chamber. The amount of condensation may depend on the heating profile, especially towards the end of smoking.

[0140] The housing of the aerosol generation system is preferably elongated. The structure of the housing, including the surfaces available for the formation of condensation, will affect the aerosol properties and whether there is leakage of liquid from the aerosol generation system. The housing may comprise a shell and a mouthpiece. In that case, all components may be included either in the shell or in the mouthpiece. The housing may comprise any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics, or composite materials containing one or more of these materials, or thermoplastic resins suitable for food or pharmaceutical applications, such as polypropylene, polyetheretherketone (PEEK), and polyethylene. The material is preferably light and not brittle. The material of the housing may affect the amount of condensation formed in the housing, which in turn will affect the leakage of liquid from the system.

[0141] The aerosol generation system is preferably portable. The aerosol generation system can be a smoking system and can have a size comparable to that of a conventional cigar or cigarette. The overall length of the smoking system may be approximately 30 mm to approximately 150 mm. The outer diameter of the smoking system may be approximately 5 mm to approximately 30 mm.

[0142] Two or more of the methods described herein may be used in combination. For example, the smoking end threshold of the method of the first aspect may be calculated using the method according to the sixteenth aspect. That is, the smoking end threshold of the first aspect may be equal to the flushing volume of the sixteenth aspect.

[0143] Two or more of the methods described herein may be provided as different operating modes in a single aerosol generation system. The user may be able to select which method to implement using a user interface.

[0144] The features described in connection with one aspect described herein may be applicable to another aspect described herein. It will be apparent to those skilled in the art that features described in connection with one aspect may be applicable to another aspect.

[0145] Here, by way of example only, the present invention will be further described with reference to the following accompanying drawings.

Brief Description of the Drawings

[0146]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Best Mode for Carrying Out the Invention

[0147] FIG. 1 is a schematic diagram of an aerosol generating system. The system 100 includes two main components, a cartridge 102 and a control body 104. The connection end 106 of the cartridge 102 is removably connected to the corresponding connection end 108 of the control body 104. The aerosol generating system 100 is portable and has a size comparable to that of a conventional cigarette or a roll-up tobacco cigarette.

[0148] The control body 104 houses a battery 110 (a rechargeable lithium-ion battery in this embodiment) and a control circuit 112. The control circuit 112 includes a smoking detection system 111.

[0149] The cartridge 102 includes a housing 114 that houses an atomization assembly 116 and a liquid storage compartment 118. The liquid storage compartment includes a capillary material immersed in a liquid aerosol forming matrix. In this example, the aerosol forming matrix includes 39% by weight glycerin, 39% by weight propylene glycol, 20% by weight water and flavorant, and 2% by weight nicotine. The capillary material is a material that actively transports liquid from one end to the other end and may be made of any suitable material. In this example, the capillary material is formed from polyester.

[0150] In this embodiment, the atomization assembly includes a plurality of conductive heater filaments that form an electrically heated mesh heating element. When the cartridge 102 is connected to the control body 104, the power source 110 is electrically connected to the mesh heating element. The air flow path extends from the air inlet 122 through the atomization assembly 116 and through the cartridge to the opening 124 at the mouth side end within the housing 114.

[0151] The system is configured such that a user can draw an aerosol into their mouth by sucking on the opening 124 at the mouth-side end of the cartridge 102. During operation, when the user sucks on the opening 124 at the mouth-side end, air is drawn from the air inlet 122 through the air flow path. The smoking detection system 111 detects the air flow through the air flow path and activates the atomization assembly 116. The control circuit 112 controls the power supply from the power source 110 to the atomization assembly 116. Air flows through the atomization assembly 116. The atomization assembly 116 generates vapor that is mixed into the air flow passing through the air flow path. The amount and characteristics of the vapor generated by the atomization assembly 116 are at least partially controlled by the power supplied from the power source 110 to the atomization assembly 116. The air and the mixed vapor, or aerosol, flow into the user's mouth through the opening 124 at the mouth-side end.

[0152] Figure 1 shows an example of an electrically heated aerosol generation system that can be used in the present invention. However, numerous other examples can be used in combination with the present invention. The present invention can be used in any electrically heated aerosol generation system comprising an aerosol generation element that is powered by a power source under the control of an electrical circuit. For example, the system does not necessarily have to be a smoking system. For example, the aerosol-forming substrate can be a fixed substrate rather than a liquid substrate. Alternatively, this aerosol-forming substrate may be in the form of other substrates such as gels or pastes. The aerosol generation element can take any suitable form. The overall shape and size of the housing can be changed, and the housing may comprise another shell and a mouthpiece. Other variations are, of course, possible.

[0153] In the embodiment of FIG. 1, the control circuit 112 including the smoking detection system 111 is programmable to control the power supply to the mesh heating element. This in turn affects the heating profile that can affect the characteristics of the vapor, or aerosol. The term "heating profile" refers to a graphical representation of the power (or some other similar measurement, such as the heat generated by the heating element) supplied to the heating element over the time taken for a puff. However, if the control circuit 112 and the smoking detection system 111 are wired to control the power supply to the heating element, the aerosol generation system can function in much the same way. Again, this can affect the heating profile and in turn the droplet size of the aerosol.

[0154] FIG. 2 is a plot showing airflow rate versus time and heating power versus time in a known aerosol generation system implementing a known method of controlling aerosol generation.

[0155] FIG. 2 is a plot showing airflow rate 201 and heating power 203 on the vertical axis and time 205 on the horizontal axis. The airflow rate 201 is shown by a solid line and the heating power 203 is shown by a dotted line. The airflow rate is sensed by a smoking detection system such as the smoking detection system 111 of FIG. 1. The heating power, measured in watts, is the power provided from a power source to the heating element under the control of an electrical circuit such as the control circuit 112 of FIG. 1. FIG. 2 shows a single puff by a user in an electrically heated aerosol generation system such as that shown in FIG. 1.

[0156] As can be seen in FIG. 2, in this embodiment, the airflow rate for a puff is illustrated as taking the shape of a normal or Gaussian distribution. The airflow rate starts at zero, increases stepwise to a maximum of 201max, and then decreases back to zero. However, the airflow rate usually does not have a precise Gaussian distribution. However, in all cases, the airflow rate during a puff increases from zero to a maximum and then decreases from the maximum to zero. The area below the airflow rate curve is the total air volume for that puff.

[0157] When the smoking detection system senses that the air flow rate 201 has increased to the threshold value 201a at time 205a, the electric circuit controls the power to turn on the heating element and directly increases the heating power 203 from zero to the power 203a. When the smoking detection system senses that the air flow rate 201 has decreased back to the threshold value 201a at time 205b, the electric circuit controls the power to turn off the heating element and immediately decreases the heating power 203 from the power 203a to zero. During the time between 205a and 205b, the smoking detection system detects that the air flow rate remains greater than the threshold value 201a, and the heating power to the heating element is maintained at the power 203a. Therefore, the heating period is from time 205b to 205a.

[0158] In the embodiment of FIG. 2, the air flow rate threshold for turning on the heating element is the same as the air flow rate threshold for turning off the heating element. The advantage of the arrangement of FIG. 2 is the simplification of the design. However, in this arrangement, there is a possibility of overheating towards the end of smoking, such as in the region 207 surrounded by the circle in FIG. 2. Further, if the air flow rate of smoking increases again after the power supplied to the heater has decreased to zero at time 205b, the user may become frustrated with inappropriate aerosol delivery after time 205b because the heater remains without power.

[0159] FIG. 3 includes two plots. One plot shows the air flow rate 301 on the vertical axis and the time 305 on the horizontal axis, and the other plot shows the heating power 303 on the vertical axis and the time 305 on the horizontal axis. The time 305 shown in both plots is the same time. That is, the plots in FIG. 3 show the air flow rate and the heating power for the same smoking. The air flow rate 301 is indicated by a solid line, and the heating power 303 is indicated by a dotted line. The air flow rate is measured in volume per unit time, generally in cubic centimeters per second. The air flow rate is sensed by a smoking detection system such as the smoking detection system 111 in FIG. 1. The heating power is the power provided from the power source to the heating element under the control of an electric circuit such as the control circuit 112 in FIG. 1. FIG. 3 shows a single smoking by a user in an electrically heated aerosol generation system such as that shown in FIG. 1.

[0160] As can be seen in FIG. 3, in this embodiment, the smoking profile is more complex than the smoking profile shown in FIG. 2. In this embodiment, the air flow rate 301 increases from zero to a first maximum flow rate 301max1. Next, the air flow rate decreases to a flow rate 301min1. Next, the air flow rate increases to a second maximum flow rate 301max2. The air flow rate then decreases to zero.

[0161] When the smoking detection system senses that the air flow rate 301 has increased to the threshold value 301a at time 305a, the electric circuit controls the power to turn on the heating element and substantially instantaneously increases the heating power 303 from zero to the power 303a. When the smoking detection system senses that the air flow rate 301 has decreased to the threshold value 301b at time 305b, the electric circuit controls the power to turn off the heating element and substantially instantaneously decreases the heating power 303 from the power 303a to zero. During the time 305a to time 305b, the heating power to the heating element is maintained at the power 303a.

[0162] When the smoking detection system then senses that the air flow rate 301 has increased to the threshold value 301c at time 305c, the electric circuit controls the power to turn on the heating element and substantially instantaneously increases the heating power 303 from zero to the power 303c. When the smoking detection system senses that the air flow rate 301 has decreased to the threshold value 301d at time 305d, the electric circuit controls the power to turn off the heating element and substantially instantaneously decreases the heating power 303 from the power 303c to zero. During the time 305c to time 305d, the heating power to the heating element is maintained at the power 303c.

[0163] In the embodiment of FIG. 3, the threshold value 301a is a predetermined constant, and the threshold value 301d is another predetermined constant for the end of smoking. The threshold value 305d is smaller than the threshold value 301a. The threshold value 301b is 50% of 301max1, and the threshold value 301c is 65% of 301max1. The power 303a and the power 303c are equal.

[0164] Figure 4 includes two plots. The first plot in Figure 4 shows the same smoking profile as that shown in Figure 3. This is copied onto Figure 4 only for comparison with the second plot in Figure 4. The second plot shows heating power 403 on the vertical axis and time 405 on the horizontal axis. The time shown in both plots is the same time. That is, the plots in Figure 4 show the air flow rate and heating power for the same smoking. The air flow rate 301 is indicated by a solid line, and the heating power 403 is indicated by a dotted line. The air flow rate is sensed by a smoking detection system such as the smoking detection system 111 in Figure 1. The heating power is the power provided from a power source to a heating element under the control of an electrical circuit such as the control circuit 112 in Figure 1. Figure 4 shows a single smoking by a user in an electrically heated aerosol generation system such as that shown in Figure 1.

[0165] At time 305z, the user presses a button on the aerosol generation system. In response, the electrical circuit controls the power to turn on the heating element and increases the heating power to the heating element to power level 403z. As shown in Figure 4, the user presses the button immediately after starting to smoke in the system. However, it is possible that the user presses the button before starting to smoke in the system and the power is supplied at power level 403z before the air flow rate increases. In this embodiment, if the user presses the button but the smoking detection system does not detect an air flow rate exceeding the threshold 301a within 10 seconds after the user presses the button, the power supplied to the heating element can be reduced back to zero.

[0166] When the smoking detection system senses that the air flow rate 301 has increased to the threshold 301a at time 305a, the electrical circuit controls the power to the heating element and immediately increases the heating power 403 from 403z to power 403a. The power supplied to the heating element is held at this level for a short period, approximately 0.2 seconds, for the average smoking time before decreasing to power level 403x at time 305x. This provides an initial burst of power towards the start of smoking.

[0167] When the smoking detection system senses that the air flow rate 301 has decreased to the threshold value 301b at time 305b, the electric circuit controls the power to turn off the heating element and reduces the heating power 403 from the power 403x to zero. As shown in FIG. 4, this decrease in power occurs stepwise at a constant rate between times 305b and 305b2.

[0168] When the smoking detection system then senses that the air flow rate 301 has increased to the threshold value 301c at time 305c, the electric circuit controls the power to turn on the heating element and immediately increases the heating power 403 from zero to the power 403c. When the smoking detection system senses that the air flow rate 301 has decreased to the threshold value 301d at time 305d, the electric circuit controls the power to turn off the heating element and immediately reduces the heating power 403 from the power 403c to zero. Between time 305c and time 305d, the heating power to the heating element is maintained at the power 403c.

[0169] In the embodiment of FIG. 4, the threshold value 301a is a predetermined constant, and the threshold value 301d is another predetermined constant for the end of smoking. The threshold value 305d is smaller than the threshold value 301a. The threshold value 301b is 50% of 301max1, and the threshold value 301c is 65% of 301max1. The power 403a is greater than the power 403x, the power 403x is greater than the power 403c, and the power 403c is greater than the power 403z.

[0170] FIG. 5 includes two plots. One plot shows the air flow rate 501 on the vertical axis and time 505 on the horizontal axis, and the other plot shows the heating power 503 on the vertical axis and time 505 on the horizontal axis. The time 505 shown in both plots is the same time. That is, the plots in FIG. 5 show the air flow rate and heating power for the same smoking. The air flow rate 501 is shown by a solid line, and the heating power 503 is shown by a dotted line. The air flow rate is sensed by a smoking detection system such as the smoking detection system 111 of FIG. 1. The heating power is the power provided from the power source to the heating element under the control of an electric circuit such as the control circuit 112 of FIG. 1. FIG. 5 shows a single smoking by a user in an electrically heated aerosol generation system such as that shown in FIG. 1.

[0171] As can be seen in FIG. 5, in this embodiment, the smoking profile is more complex than the smoking profile shown in FIG. 3. In this embodiment, the air flow rate 501 increases from zero to a first maximum flow rate 501max1. Next, the air flow rate experiences another local maximum 501maxz before decreasing to a local minimum flow rate 501min1. Next, the air flow rate increases to another local maximum flow rate 501max2 before decreasing to another local minimum flow rate 501min2. The air flow rate then increases to another local maximum 501max3 before decreasing to zero. In FIG. 5, the flow rate 501max2 is greater than 501max1, 501max1 is greater than 501maxz, 501maxz is greater than 501min3, 501min3 is greater than 501min1, and 501min1 is greater than 501min2.

[0172] When the smoking detection system senses that the air flow rate 501 has increased to the threshold value 501a at time 505a, the electric circuit controls the power to turn on the heating element and directly increases the heating power 503 from zero to the power 503a. When the smoking detection system senses that the air flow rate 501 has decreased to the threshold value 501b at time 505b, the electric circuit controls the power to the heating element to immediately decrease the heating power 503 from the power 503a to 503w1. During the time between 505a and 505b, the heating power to the heating element is maintained at the power 503a.

[0173] When the smoking detection system then senses that the air flow rate 501 has increased to the threshold value 501c at time 505c, the electric circuit controls the power to the heating element to immediately increase the heating power 503 from 503w1 to the power 503c. When the smoking detection system senses that the air flow rate 501 has decreased to the threshold value 501d at time 505d, the electric circuit controls the power to the heating element to immediately decrease the heating power 503 from the power 503c to 503w2. During the time between 505c and 505d, the heating power to the heating element is maintained at the power 503c.

[0174] When the smoking detection system subsequently senses that the air flow rate 501 has increased to the threshold value 501e at time 505e, the electric circuit controls the power to the heating element to immediately increase the heating power 503 from 503w2 to the power 503e. When the smoking detection system senses that the air flow rate 501 has decreased to the threshold value 501f at time 505f, the electric circuit controls the power to the heating element to immediately decrease the heating power 503 from the power 503e to 503w3. During the time period from time 505e to time 505f, the heating power to the heating element is maintained at the power 503e.

[0175] When the smoking detection system senses that the air flow rate 501 has decreased to less than the threshold value 501g, the electric circuit controls the power to the heating element to immediately decrease the heating power 503 from the power 503w3 to zero.

[0176] In the embodiment of FIG. 5, the threshold value 501a is a predetermined constant, and the threshold value 501g is another predetermined constant for the end of smoking. The threshold value 501g is smaller than the threshold value 501a.

[0177] Since the local maximum flow rate 501maxz is between the flow rate 501max1 and the threshold value 501b and the local maximum flow rate 501maxz is smaller than the flow rate 501max1, the local maximum flow rate 501maxz does not affect the threshold value 501b. If the flow rate 501maxz is larger than the flow rate 501max1, the threshold value 501b can be calculated as a percentage of the flow rate 501maxz.

[0178] The threshold value 501b is 70% of 501max1. The threshold value 501c is 80% of 501max1. The threshold value 501d is 70% of 501max2. The threshold value 501e is 80% of 501max2. The powers 503a, 503c, 503e, 503w1, 503w2, and 503w3 are predetermined powers, where the largest of the powers 503w1, 503w2, and 503w3 is smaller than the smallest of the powers 503a, 503c, and 503e.

[0179] It should be noted that according to the embodiment of FIG. 5, the power supplied to the heating element increases indefinitely in response to the air flow rate increasing by more than a threshold value defined by the local maximum, and can decrease indefinitely in response to the air flow rate decreasing below the threshold value defined by the local maximum. That is, FIG. 5 shows three increases in the power supplied to the heating element, although different smoking profiles may show four, or five or more increases in the power supplied to the heating element.

[0180] FIG. 6 is a plot showing the air flow rate against time and a plot showing the heating power against time in an aerosol generation system according to the sixth aspect described herein. FIG. 6 is a plot showing the air flow rate 601 for the first smoking 6A and the second smoking 6B on the vertical axis and time 605 on the horizontal axis, and the second plot shows the heating power 603 for the first smoking 6A and the second smoking 6B on the vertical axis and time 605 on the horizontal axis. The air flow rate 601 and the heating power 603 for the smoking 6A are shown by solid lines, and the air flow rate 601 and the heating power 603 for the smoking 6B are shown by dotted lines. The air flow rate is sensed by a smoking detection system such as the smoking detection system 111 of FIG. 1. The heating power is the power provided from the power source to the heating element under the control of an electrical circuit such as the control circuit 112 of FIG. 1. FIG. 6 shows a single smoking by a user in an electrically heated aerosol generation system such as that shown in FIG. 1.

[0181] As can be seen in FIG. 6, in this embodiment, the air flow rate for smoking is illustrated as taking the shape of a normal distribution or a Gaussian distribution.

[0182] For the smoking 6A, the air flow rate starts at zero, increases stepwise to a maximum value 601maxA, and then decreases stepwise back to zero. For the smoking 6B, the air flow rate starts at zero, increases stepwise to a maximum 601maxB, and then decreases stepwise back to zero.

[0183] The threshold value 601a is a predetermined constant. Also, the threshold value 601end is a predetermined constant for the end of smoking. The threshold value 601bA is applicable to smoking A but not to smoking B and is 50% of the local maximum 601maxA. The threshold value 601bB is applicable to smoking B but not to smoking A and is 50% of the local maximum 601maxB.

[0184] Regarding smoking 6A, when the smoking detection system senses that the air flow rate 601 has increased to the threshold value 601a at time 605aA, the electric circuit controls the power to turn on the heating element and immediately increases the heating power 603 from zero to power 603a. As can be seen in Figure 6, the threshold value 601end is smaller than the threshold value 601bA, and for smoking A, the threshold value 601bA is reached before the threshold value 601end. Therefore, when the smoking detection system senses that the air flow rate 601 has decreased to the threshold value 601bA at time 605bA, the electric circuit controls the power to turn off the heating element and immediately decreases the heating power 603 from power 603a to zero. During the time from 605a to 605b, the heating power to the heating element is maintained at power 603a.

[0185] Regarding smoking 6B, when the smoking detection system senses that the air flow rate 601 has increased to the threshold value 601a at time 605aB, the electric circuit controls the power to turn on the heating element and immediately increases the heating power 603 from zero to power 603a. As can be seen in Figure 6, for smoking B, the threshold value 601end is reached before the threshold value 601bB. Therefore, when the smoking detection system senses that the air flow rate 601 has decreased to the threshold value 601end at time 605endB, the electric circuit controls the power to turn off the heating element and immediately decreases the heating power 603 from power 603a to zero. The power supplied to the heating element does not change when the air flow rate subsequently decreases to the threshold value 601bB. During the time from 605a to 605b, the heating power to the heating element is maintained at power 603a.

[0186] FIG. 7 is a plot showing the air flow rate against time and a plot showing the heating power against time in the aerosol generation system according to the eleventh aspect described in this specification. The first plot in FIG. 7 shows the air flow rate against time, and the second plot in FIG. 7 shows the heating power against time. Both plots are related to a single smoking by a user in an electrically heated aerosol generation system such as that shown in FIG. 1.

[0187] The first plot shows the air flow rate 701 on the vertical axis and the time 705 on the horizontal axis, and the second plot shows the heating power 703 on the vertical axis and the time 705 on the horizontal axis. The time 705 shown in both plots is the same time. That is, the plots in FIG. 7 show the air flow rate and the heating power for the same smoking. The air flow rate 701 is indicated by a solid line, and the heating power 703 is indicated by a dotted line. The air flow rate is sensed by a smoking detection system such as the smoking detection system 111 in FIG. 1. The heating power is the power provided from the power source to the heating element under the control of an electric circuit such as the control circuit 112 in FIG. 1. FIG. 7 shows a single smoking by a user in an electrically heated aerosol generation system such as that shown in FIG. 1.

[0188] The first plot in FIG. 7 shows a smoking profile in which the air flow rate increases from zero to the air flow rate 701max and then decreases from 701max to zero. The plot exhibits a shape similar to a normal distribution that is positively skewed, or skewed to the right.

[0189] When the smoking detection system senses that the air flow rate 701 has increased to the threshold value 701a at time 705a, the electric circuit controls the power to turn on the heating element and directly increases the heating power 703 from zero to the power 703a. In this embodiment, the threshold value 701a is a predetermined constant.

[0190] When the smoking detection system senses that the air flow rate 701 has decreased to the threshold value 701b at time 705b, the electric circuit controls the power to turn off the heating element and immediately decreases the heating power 703 from the power 703a to zero. In this embodiment, the threshold value 701b is 70% of the flow rate 701max.

[0191] Next, the smoking detection system waits for a fixed time of 0.3 seconds from time 705b to time 705c. At time 705c, the smoking detection system measures the flow rate as flow rate 701c and compares flow rate 701c with a restart threshold flow rate (not shown). In this embodiment, the restart threshold flow rate is 60% of flow rate 701max. If flow rate 705c is greater than the restart threshold flow rate, the electric circuit controls the power to turn on the heating element and increases the heating power. If flow rate 705c is less than the restart threshold flow rate, the heating element remains off until the end of smoking or until there is another reason to turn the heating element back on. In the embodiment of FIG. 7, flow rate 705c is greater than the restart threshold flow rate, and thus the electric circuit controls the power to turn on the heating element and immediately increases the heating power 703 from zero to power 703c. In this embodiment, power 703c is less than power 703a.

[0192] The power to the heating element remains at power 703c until the smoking detection system detects that the flow rate is less than the flow rate threshold 701d. At the flow rate threshold 701d, the electric circuit controls the power to turn off the heating element and immediately decreases the heating power 703 from power 703c to zero.

[0193] In this embodiment, the smoking detection system measures the flow rate for a given time after reaching the flow rate threshold 701b. This given time is equal to the time obtained by subtracting time 705b from time 705c. However, similar or identical effects can be achieved in a number of alternative ways. Some of these alternatives can be described with reference to FIG. 7.

[0194] In one exemplary alternative, the smoking detection system may periodically measure the flow rate. The smoking detection system may compare the measured flow rate 701c with a restart threshold, where the flow rate 701c is measured by a given number of flow rate measurements after the first measurement after the flow rate has decreased below the threshold 701b. Next, similar to the method implemented in the embodiment of FIG. 7, if the flow rate 705c is greater than the restart threshold flow rate, the electrical circuit controls the power to turn on the heating element and increases the heating power, but if the flow rate 705c is less than the restart threshold flow rate, the heating element remains off until the end of smoking or until there is another reason to turn the heating element back on.

[0195] In a second exemplary alternative, the smoking detection system may continuously or intermittently measure the flow rate. When the smoking detection system detects that the air flow rate is less than the threshold 701c, the aerosol generation system may compare the approximate time difference with a restart time threshold, where the approximate time difference is approximately the time between the time when it is detected that the flow rate is less than the threshold 701b and the time when it is detected that the flow rate is less than the threshold 701c, and where the threshold 701b is greater than the threshold 701c. Thus, if the approximate time difference is greater than the restart time threshold, the electrical circuit controls the power to turn on the heating element and increases the heating power, or if the approximate time difference is less than the restart time threshold, the heating element remains off until the end of smoking or until there is another reason to turn the heating element back on.

[0196] FIG. 8 is a plot showing the air flow rate versus time and a plot showing the heating power versus time in an aerosol generation system according to the sixteenth aspect described herein.

[0197] FIG. 8 is a plot showing air flow rate 801 on the vertical axis and time 805 on the horizontal axis, and a second plot shows heating power 803 on the vertical axis and time 805 on the horizontal axis. The air flow rate 801 is indicated by a solid line, and the heating power 803 is indicated by a dotted line. The air flow rate is sensed by a smoking detection system such as the smoking detection system 111 of FIG. 1. The heating power is the power provided from a power source to a heating element under the control of an electrical circuit such as the control circuit 112 of FIG. 1. FIG. 8 shows a single smoking by a user in an electrically heated aerosol generation system such as that shown in FIG. 1. In this embodiment, the control circuit 112 shown in FIG. 1 needs to include data storage means capable of storing the measured values measured by the smoking detection system 111.

[0198] As can be seen in FIG. 8, in this embodiment, the air flow rate for smoking is illustrated as taking a shape similar to a normal distribution or a Gaussian distribution. The air flow rate starts at zero, increases stepwise to a maximum of 801max, and then decreases back to zero.

[0199] In this embodiment, the aerosol generation system intermittently stores the measured values measured by the smoking detection system in the data storage means.

[0200] When the smoking detection system senses that the air flow rate 801 has increased to the threshold value 801a at time 805a, the electrical circuit controls the power to turn on the heating element and directly increases the heating power 803 from zero to the power 803a.

[0201] When the smoking detection system senses that the air flow rate 801 has decreased to the threshold value 801s at time 805s, the aerosol generation system starts to intermittently calculate an estimated value for the remaining volume of smoking based on the currently detected flow rate and an estimated value of the change rate of the current flow rate. In this embodiment, the flow rate threshold value 801s is 80% of the maximum detected flow rate 801max.

[0202] In this embodiment, the flow sensor stores the volumetric flow rate value intermittently. In this context, "intermittently" means that if the value is not stored periodically, the system may not function in the same way, but it is used to mean periodically, every period T P each. The time T P is short compared to the average smoking period. In this embodiment, the period T P is 0.01 seconds. After reaching the threshold value 801s, the processor of the aerosol generation system calculates the average rate of change A c of the current flow rate. The average rate of change A c of the current flow rate is calculated by subtracting the flow rate value Q c-5 which are five flow rate values stored before the current flow rate value from the current flow rate value A c , then dividing by 5, and then dividing by the period T P . Next, the processor assumes that this average rate of change A c of the current flow rate remains constant. This means that when the average rate of change A c of the current flow rate is negative, the remaining time T C of the current smoking can be estimated to be equal to the negative of the current flow rate value Q c divided by the average rate of change A c of the current flow rate. The processor then calculates the estimated value of the remaining volume V c of the current smoking as the product of -0.5 times the square of the current flow rate value divided by the average rate of change of the current flow rate. The processor compares each of the calculated estimated values of the remaining volume V c of the current smoking with the threshold volume. In this embodiment, the threshold volume is 3 ml.

[0203] In the first plot of FIG. 8, at time 805b, the flow rate 801b is measured and stored in the data storage means. Next, an estimated value of the remaining volume of smoking is calculated. This estimated value of the remaining volume of smoking is shown as the shaded volume in the first plot of FIG. 8. In the embodiment of FIG. 8, this estimated value for the remaining volume of smoking is a first estimated value less than 3 ml. Thus, the electric circuit controls the power to turn off the heating element and immediately reduces the heating power 803 from the power 803a to zero.

[0204] The figures illustrate specific embodiments of the aspects described herein. However, it is apparent that changes can be made to the described embodiments within the scope of the present invention. It will be apparent to those skilled in the art that features described in connection with one aspect or embodiment may be applicable to one or more of the other aspects or embodiments as appropriate.

[0205] Advantageously, all of the embodiments described herein provide an improved method of controlling aerosol generation within an aerosol generating system. Specifically, the claimed invention provides an improved method of controlling aerosol generation during complex smoking profiles.

Claims

1. 1. A method for controlling aerosol generation in an aerosol generating system, the system comprising: An aerosol-generating element; a housing having an air inlet and an air outlet, a flow path defined through the housing from the air inlet to the air outlet, the flow path providing a flow of air through the aerosol generation element when a user takes a puff on the system; a flow sensor configured to detect airflow in the flow path indicative of the user taking a puff, the method comprising the following chronological steps: increasing the power supplied to the aerosol generation element from power P0 to at least power P1 when the flow sensor detects that the airflow rate is greater than a first threshold; reducing the power supplied to the aerosol generation element to a power P2, the power P2 being less than the power P1, when the flow sensor detects that the flow rate of the airflow is less than a second threshold, the second threshold being at or indicative of a flow rate that is a predetermined first percentage of a first maximum flow rate detected by the flow sensor; and increasing the power supplied to the aerosol generation element when the flow sensor detects that the flow rate of the airflow is greater than a third threshold before detecting that the flow rate of the airflow is less than a puff end threshold, wherein the third threshold is greater than the second threshold and the puff end threshold is less than the second threshold.

2. The method of claim 1 , wherein the power P0 is zero, or the power P2 is zero, or both the power P0 is zero and the power P2 is zero.

3. 3. The method of claim 1, wherein the third threshold is a predetermined second percentage of the first maximum flow rate, the predetermined second percentage being greater than the predetermined first percentage, or the third threshold is a predetermined multiple of the second threshold, the predetermined multiple being greater than one.

4. 4. The method of claim 1, wherein the first threshold is a first constant, or the puff termination threshold is a puff termination constant, or the first threshold is a first constant and the puff termination threshold is a puff termination constant.

5. 5. The method of claim 1, wherein the step of increasing the power supplied to the aerosol generation element from power P0 to at least power P1 comprises increasing the power supplied to the aerosol generation element to power PX, where PX is equal to or greater than power P1, and wherein if the flow sensor detects that the flow rate of the airflow is greater than a third threshold before detecting that the flow rate of the airflow is less than an end-of-puff threshold, the step of increasing the power supplied to the aerosol generation element comprises increasing the power supplied to the aerosol generation element to power P3, where P3 is equal to or less than PX.

6. If the flow sensor detects that the flow rate of the airflow is greater than a third threshold before the method detects that the flow rate of the airflow is less than an end-of-puff threshold, then after the step of increasing the power supplied to the aerosol generation element, The method of any one of claims 1 to 5, further comprising the step of reducing the power supplied to the aerosol generation element to power P4 when the flow sensor detects that the flow rate of the airflow is less than the end-of-puff threshold.

7. The method of claim 6 , wherein the power P4 is zero.

8. or the step of increasing the power supplied to the aerosol generation element from the power P0 to at least the power P1 comprises increasing the power from the power P0 to at least the power P1 substantially instantly; or or the step of reducing the power supplied to the aerosol generation element to the power P2 comprises substantially instantly reducing the power supplied to the aerosol generation element to the power P2; or 8. The method of claim 1, wherein the step of increasing the power supplied to the aerosol generation element from the power P0 to at least the power P1 comprises substantially instantaneously increasing the power from the power P0 to at least the power P1, and the step of decreasing the power supplied to the aerosol generation element to power P2 comprises substantially instantaneously decreasing the power supplied to the aerosol generation element to power P2.

9. or the step of increasing the power supplied to the aerosol generation element from the power P0 to at least the power P1 comprises increasing the power stepwise from the power P0 to at least the power P1; The step of reducing the power supplied to the aerosol generation element to power P2 comprises reducing the power supplied to the aerosol generation element stepwise to power P2, or 7. The method of claim 1, wherein the step of increasing the power supplied to the aerosol generation element from the power P0 to at least the power P1 comprises increasing the power stepwise from the power P0 to at least the power P1, and the step of decreasing the power supplied to the aerosol generation element to power P2 comprises decreasing the power supplied to the aerosol generation element stepwise to the power P2.

10. The method further comprises the steps of: after the step of increasing the power supplied to the aerosol generation element from the power P0 to at least the power P1, but before the step of decreasing the power supplied to the aerosol generation element to the power P2; The method of any of claims 1 to 9, further comprising increasing the power supplied to the aerosol generation element from at least power P1 to power P5.

11. The method of any one of claims 1 to 10, wherein supplying power to the aerosol generation element comprises supplying a current pulse to the aerosol generation element.

12. 1. An aerosol generation system, comprising: An aerosol-generating element; a flow path configured to allow airflow through the aerosol generating element; a flow sensor configured to detect the airflow, the airflow indicating that a user is taking a puff; and a power source for providing power to the aerosol generation element; An aerosol generation system comprising: an electrical circuit for controlling the supply of power from the power source to the aerosol generation element, the electrical circuit being arranged to carry out a method according to any one of claims 1 to 11.

13. An electrical circuit for an aerosol generating system, said electrical circuit being arranged to carry out the method according to any one of claims 1 to 11.

14. A computer program which, when executed on a programmable electrical circuit for an aerosol generating system, causes said programmable electrical circuit to carry out any of the methods according to claims 1 to 11.

15. A computer readable storage medium storing a computer program according to claim 14.

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