An aerosol generating system having means for determining depletion of a liquid substrate

European).

THE AEROSOL MANUFACTURING SYSTEM HAVING A CLEARANCE TO DEFINE THE USE

LIQUID SUBSTRATE

The present invention relates to an electric aerosol generating system. In particular, the present invention relates to an electric aerosol generating system in which the aerosol-generating substrate is liquid and is located in a fluid storage part.

WO 2009/132793 A1 discloses an electric heating system having a fluid storage part. The fluid storage part comprises a substrate for generating an aerosol and is connected to a vaporizer containing an electric heater which is powered by a battery. In use, the electric heater is actuated by suction on the mouthpiece by the user to switch on the power source. The heated aerosol-generating substrate contained in the vaporizer will be evaporated.

The sucking on the mouthpiece by the user causes the air to be sucked along or through the vaporizer, and thus the generation of an aerosol, which is known to the person skilled in the art, is a suspension of solid particles or liquid droplets in a gas such as air. The generated aerosol is sucked into the mouthpiece and then into the mouth of the user.

WO 2007/078273 discloses an electronic smoking device comprising an evaporator for evaporating liquid stored in a container. The device includes LED diodes for indicating the liquid level in the container.

Electrical prior art aerosol generating systems, including the smoking system mentioned above, have many advantages, but there are still chances for improvement, especially regarding the handling of the aerosol-forming substrate contained in the fluid storage part.

According to a first aspect of the invention there is provided an electric aerosol generating system for receiving a substrate for generating an aerosol, which comprises: a part for storing fluid for storage of a liquid aerosol-generating substrate; an electric heater comprising at least one heating element for heating a liquid substrate for generating an aerosol; and an assembly of electrical circuits configured to determine the consumption of a liquid substrate for generating an aerosol based on the relationship between the supply provided to the heating element and the resulting change in temperature of the heating element.

The electric circuits are preferably configured to determine the amount of liquid substrate for aerosol production in a liquid aerosol generating substrate based on specific consumption.

The amount of liquid substrate for aerosol production in the fluid storage part can be an absolute or relative value, e.g.

the percentage or it can be determined that in the fluid storage part there is more or less than the threshold amount of liquid aerosol generating substrate.

Providing electrical circuits for determining the consumption of a liquid aerosol generating substrate supplied to the heater is advantageous for a number of reasons. For example, when the fluid storage portion is empty or nearly empty, an insufficient liquid aerosol-generating substrate may be provided to the electric heater.

This may mean that the aerosol produced does not have the desired properties, for example the size of the aerosol particles or the chemical composition.

This can cause a poor smoking experience for the user.

Furthermore, if it is possible to determine when the fluid storage part will be empty or almost empty, it is possible to inform the user. The user can then be prepared to replace or refill the fluid storage parts.

The relationship between the temperature of the heating element and the power applied to the heating element can be, for example, the rate of temperature change of the heating element for a given power used, the absolute temperature of the heating element at a predetermined time in the heating cycle for a given power used, the temperature integral in a part of the heating cycle for a given heating element power or power applied to the heating element to maintain a given temperature. In general, the less the aerosol-generating substrate is supplied to the heater for evaporation, the higher the temperature of the heating element for a given power applied. For a given power, the evolution of the temperature of the heating element of the heating cycle and the way in which this evolution changes over many heating cycles can be used to detect

For a liquid substrate for the production of an aerosol, certain physical properties, e.g. steam pressure or substrate viscosity, are selected to be suitable for use in an aerosol generating system. The fluid preferably comprises a tobacco-containing material containing volatile tobacco aromatic compounds that are released from the liquid upon heating. Alternatively or additionally, the fluid may contain a non-tobacco material. The fluid may include water, solvents, ethanol and other solvents, vegetable extracts, nicotine solutions, and natural or artificial flavors.

Preferably, the fluid further comprises an aerosol former.

Examples of suitable aerosol forming agents are glycerol and propylene glycol.

The advantage of providing the fluid storage part is that the liquid in the liquid storage portion is protected from ambient air. In some embodiments, ambient light can not also enter the fluid storage part to avoid the risk of degradation of the liquid caused by the light. In addition, you can maintain a high level of hygiene.

Preferably, the fluid storage part is arranged to divide fluid into a predetermined number of puffs.

If the fluid storage part is non-refillable and the liquid in the fluid storage part has been used, the fluid storage part must be replaced by the user. During such a replacement, contamination of the user with liquid should be prevented. Alternatively, the fluid reservoir part may be refillable. In this case, the aerosol generating system can be replaced after a number of fillings of the fluid storage part.

The electric heater may comprise a single heating element.

Alternatively, the electric heater may comprise more than one heating element, e.g. two or three or four or five or six or more heating elements. The heating element or heating elements may be arranged in order to heat the liquid aerosol generating substrate most effectively.

Preferably, at least one heating element comprises a material that causes electrical resistance. Suitable materials for causing electrical resistance include, but are not limited to: semiconductors, such as doped ceramics, electrically conductive ceramics (such as, for example, molybdenum disilicate), carbon, graphite, metals, metal alloys, and composite materials made of ceramic material and metallic material . Such composite materials may comprise doped or non-doped ceramics. Examples of suitable doped ceramics include doped silicon carbides. Examples of suitable metals include titanium, zirconium, tantalum and platinum group metals. Examples of suitable metal alloys include stainless steel, constantate, nickel alloys, cobalt, chromium, aluminum, titanium, zirconium, hafnium, niobium, molybdenum, tantalum, tungsten, tin, gallium, manganese and containing iron and superalloys based on nickel, iron, cobalt, stainless steel, Timetal®, iron-aluminum alloys and alloys based on iron-manganese-aluminum. Timetal® is a registered trademark of Titanium Metals

Corporation. In composite materials, the electrically resistive material may optionally be embedded, encapsulated or coated with insulating material or vice versa, depending on the energy transfer kinetics and the required external physicochemical properties. The heating element may comprise an etched metallic foil insulated with two layers of inert material. In this case, the inert material may contain

Kapton®, polyimide or mica foil. Kapton® is a registered trademark of EI Du Pont de Nemours and the Company.

At least one electric heating element may have any suitable form. For example, at least one electric heating element may be in the form of a heating blade. Alternatively, at least one electric heating element may be in the form of a sheath or substrate having different electrically conductive parts or a metallic tube for causing electrical resistance. The liquid reservoir part may include a disposable heating element. Alternatively, one or more heating pins or sticks that run through the liquid substrate for aerosol production may also be suitable.

Alternatively, at least one electric heating element may comprise a flexible material sheet. Other possibilities include a heating wire or fiber, e.g. a Ni-Cr (Nickel-Chrome), platinum, tungsten wire or alloy wire or a hot plate. Optionally, the heating element may be embedded in or on the rigid carrier material.

The at least one electric heating element may comprise a heat sink or heat accumulator containing a material capable of absorbing and storing heat and then releasing heat over time to heat the aerosol forming substrate.

The radiator can be made of any suitable material, such as a suitable metal or ceramic material. Preferably, the material has a high heat capacity (material with perceptible heat storage) or is a material that can absorb and then release heat in a reversible process, such as a high temperature phase transition. Suitable materials with palpable heat storage include silica gel, clay, carbon, glass mat, glass fiber, minerals, metal or alloy, such as aluminum, silver or lead, and cellulosic material, such as paper. Other suitable materials that release heat in a reversible phase change include paraffin, sodium acetate, naphthalene, wax, polyethylene oxide, metal, metal salt, eutectic salt mixture or alloy.

The heat sink or heat accumulator can be arranged to be in direct contact with the liquid aerosol generating substrate and able to transfer the accumulated heat directly to the substrate. Alternatively, the heat accumulated in the heat sink or heat container can be transferred to the aerosol generating substrate by means of heat conductors, such as a metallic tube.

At least one heating element may heat the liquid substrate for generating the aerosol via conduction means. The heating element may at least partially be in contact with the substrate. Alternatively, the heat from the heating element can be conducted to the substrate by a heat conducting element.

Alternatively, at least one heating element may transfer heat to the incoming ambient air, which is sucked in by the heated electric aerosol generating system during use, which in turn heats the aerosol generating substrate.

The surrounding air can be heated before it passes through the aerosol-generating substrate. Alternatively, the surrounding air may first be sucked in by the liquid substrate and then heated.

Preferably, the electric aerosol generating system further comprises a capillary wick for conveying the liquid substrate for generating an aerosol from the fluid storage portion to the electric heater.

Preferably, the capillary wick is disposed in such a way that it is in contact with the fluid in the liquid reservoir part.

Preferably, the capillary wick extends to the fluid storage part. In this case, during use, the fluid is transferred from the fluid storage portion to the electric heater based on capillary phenomena in the capillary wick. In one embodiment, the capillary wick has a first end and a second end, the first end extends to the fluid storage portion to contact the liquid therein, while the electric heater is arranged to heat the fluid at the other end. Upon actuation of the heater, the fluid at the other end of the capillary wick is vaporized by the heater element of the heater to produce a supersaturated steam. The supersaturated pair is mixed with and carried in the air stream. During the flow, the vapor condenses to form an aerosol and the aerosol is transferred towards the user's mouth. The liquid aerosol-generating substrate has suitable physical properties, including surface tension and viscosity, which allow liquid to be transported through the capillary material based on capillary phenomena.

The capillary wick may have a fibrous or spongy structure. The capillary wick preferably has a bundle of capillaries. For example, the capillary wick may comprise a plurality of fibers or threads or other thin tubes with an opening. The fibers or threads may be generally arranged in a row in the longitudinal direction of the aerosol generating system. Alternatively, the capillary wick may comprise a sponge-like material or foam, formed in the shape of a stick. The shape of the rod may extend along the direction of the longitudinal aerosol generating system. The structure of the wick creates many small holes or tubes through which the fluid can be transported based on capillary phenomena. The capillary wick can comprise any suitable material or combination of materials.

Examples of suitable materials are capillary materials, e.g. spongy or foam material, graphite or ceramic based materials in the form of fibers or sintered powders, foam metal or plastic materials, a fibrous material, e.g. made of yarn or extruded fibers, such as acetate cellulose, polyester or bonded polyolefin, polyethylene, terylene or polypropylene fibers, nylon fibers or ceramics.

The capillary material may have any suitable capillarity and porosity, so as to be applicable to the various physical properties of the fluid. The fluid has appropriate physical properties, including, but not limited to, viscosity, surface tension, density, thermal conductivity, boiling point and vapor pressure, which allow fluid to be transported through the capillary material based on capillary phenomena.

Preferably, the at least one heating element is in the form of a heating conductor or circumferential fiber, and optionally supporting the capillary wick. Capillary properties of the wick, combined with properties

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The fluid storage can be removable from the aerosolization system as a single component.

In the first embodiment, the electric aerosol generating system further comprises a temperature sensor for measuring the temperature of the at least one heating element and an electrical circuitry adapted to monitor the temperature of the at least one heating element detected by the temperature sensor and determining the consumption of the liquid substrate for generating the aerosol heated by the heater in based on the temperature of at least one heating element detected by the temperature sensor.

If the amount of aerosol-forming liquid substrate is reduced, e.g. if the fluid storage portion is empty or almost empty, a insufficient liquid aerosol-generating substrate may be provided to the heater. This can lead to an increase in the temperature of the heating element. Thus, the temperature of the heating element detected by the temperature sensor may allow the electric circuits to determine that the amount of liquid aerosol-forming substrate in the fluid storage part has decreased to a predetermined threshold and may be able to provide an absolute indication of the liquid aerosol-generating substrate in the part fluid storage.

In another embodiment, the electrical circuits are adapted to measure the electrical resistance of the at least one heating element to determine the temperature of the heating element from the measurement of electrical resistance.

If the amount of aerosol-forming liquid substrate is reduced, e.g. if the fluid storage portion is empty or almost empty, a insufficient liquid aerosol-generating substrate may be provided to the heater. This can lead to an increase in the temperature of the heating element. If the at least one heating element has the appropriate resistance coefficient parameters, the measurement of the electrical resistance of the at least one heating element will make it possible to determine the temperature of the heating element. Thus, the temperature of the heating element determined by the electrical circuits from the measurement of the electrical resistance may allow the electric circuits to determine the amount of liquid substrate for generating the aerosol in the fluid storage part.

An advantage of this embodiment is that it is not necessary to switch on a temperature sensor that can take up valuable space in the aerosol generating system, and can also be expensive. It is emphasized that the electrical resistance, in this embodiment, is used both as an 'actuator' (heating element) and as a 'sensor' (temperature measurement).

In this embodiment, the electrical circuits may be arranged to measure the electrical resistance of the at least one heating element by measuring current through at least one heating element and voltage in at least one heating element and determining the electrical resistance of at least one heating element from current and voltage measurement. . In this case, the electrical circuits may include a resistive resistor in series with at least one heating element, and the electrical circuits may be adapted to measure current through at least one heating element by measuring a voltage in a resistor of known resistance and determining the current for at least one one heating element with voltage measurement and known resistance.

The electrical circuitry may be adapted to determine the consumption of a liquid substrate for generating an aerosol heated by a heater by monitoring the rise in temperature detected or set in subsequent heating cycles when a liquid substrate for generating an aerosol in a fluid storage part is consumed.

The electric circuits may be adapted to determine the consumption of a liquid aerosol-generating substrate heated by the heater by monitoring the rate of temperature rise detected or determined at the start of the heating cycle in subsequent heating cycles when the liquid aerosol-generating substrate in the fluid storage part is consumed.

The electric circuits may be adapted to determine the amount of liquid aerosol-forming substrate in the fluid storage part by monitoring the rise of the integral over time of the detected or set temperature in a portion of each heating cycle in subsequent heating cycles when the liquid aerosol-generating substrate in the storage portion the fluid is consumed.

In another embodiment, the electric circuitry is adapted to limit the temperature of the heating element to a maximum temperature and is adapted to determine the consumption of the substrate to produce an aerosol heated by the heater by monitoring the amount of power applied to the heating element to maintain the maximum temperature.

In this embodiment, the electrical systems can be arranged to provide the heating element with a pulse width modulation signal and wherein the electrical circuitry is adapted to monitor the amount or power applied to the heating element by monitoring the pulse width modulation signal cycle. .

The electric circuits may be adapted to calibrate other systems to determine the amount of substrate for generating the aerosol in the fluid storage part based on a predetermined amount.

In addition to allowing determination of the amount of substrate for aerosol production in the fluid storage part, the same principle of monitoring the temperature evolution of the heating element during each heating cycle can be used to protect the user from overheating and malfunction if, for example, the viscosity of the aerosol change due to extreme external conditions, so that it is no longer delivered to the heating element in sufficient quantity.

In a preferred embodiment, the electric circuitry is constructed such that when it is determined that the amount of liquid aerosol-forming substrate in the fluid storage part has dropped to a predetermined threshold to deactivate the electric heater.

This is advantageous because the user may then no longer use the aerosol generating system after the liquid aerosol-generating substrate is insufficient. This will avoid the formation of an aerosol that has no desired properties. This will allow the user to avoid a poor smoking experience.

The electrical circuits may be adapted to deactivate the electric heater by burning an electrical fuse between the electric heater and the power supply.

The electrical circuits may be adapted to deactivate the electric heater by switching off the switch between the electric heater and the power supply. Alternative methods for deactivating an electric heater will be apparent to those skilled in the art.

In a preferred embodiment, the electric circuitry is constructed such that when the amount of liquid substrate for aerosol formation is determined in the fluid storage part, it falls to a predetermined threshold to indicate to the user. This is advantageous because the indicator enables the user to refill or replace the fluid storage parts.

The electric aerosol generating system may include a user display. In this case, the indicator may contain an indication on the user's display. Alternatively, the indicator may include an audible indication or other appropriate type of indication to the user.

The aerosol generating system may further comprise an electric power source. Preferably, the aerosol generating system includes a housing. Preferably, the housing is elongated. If the aerosol formation system includes capillary accounts, the longitudinal axis of the capillary wick and the longitudinal axis of the housing may be substantially parallel. The housing may include a shield and a mouthpiece. In this case, all components can be included either in the shell or in the mouthpiece. In one embodiment, the housing includes a removable insert including a fluid storage portion, a capillary wick and a heater. In this embodiment, these parts of the aerosol generating system can be removable from the housing as a single component. This can be useful, for example, when refilling or replacing fluid storage parts.

The housing may contain any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics or composite materials containing one or more of such materials or thermoplastics suitable for food or pharmaceutical applications, e.g. polypropylene, polyetheretherketone (PEEK) and polyethylene.

Preferably, the material is light and non-breakable.

Preferably, the aerosol generating system is portable. The aerosol generating system may be a smoking system and may have a size comparable to a traditional cigar or cigarette. The total length of the smoking system can be between approximately 30 mm and approximately 150 mm. The outer diameter of the smoking system can be between approximately 5 mm and approximately 30 mm.

Preferably, the electric aerosol generating system is a smoking system with electric heating.

According to a second aspect of the invention, there is provided a method comprising: providing an electric aerosol generating system comprising a fluid storage section for a liquid aerosol-generating substrate and an electric heater comprising at least one heating element for heating a liquid aerosol generating substrate; and determining the consumption of the liquid substrate for generating the aerosol heated by the heater based on the relationship between the power applied to the heating element and the resulting temperature change of the heating element.

The amount of liquid aerosol-forming substrate may be an absolute or relative value, e.g. a percentage or it may be determined that in the fluid storage part there is more or less than a threshold amount of a liquid aerosol generating substrate.

According to a third aspect of the invention, electrical circuits for an electric aerosol generating system are provided, the electrical circuits being arranged to perform the method of the second aspect of the invention.

According to a fourth aspect of the invention there is provided a computer program which when it activates a programmed electric circuit for an electric aerosol generating system, causes the programmed electric circuit to perform the method of the second aspect of the invention.

According to a fifth aspect of the invention there is provided a computer readable data medium having a computer program stored therein according to a fourth aspect of the invention.

The features shown with respect to the aerosolization system of the invention may also apply to other methods of the invention. In contrast, the features described in relation to the method of the invention may also apply to the aerosol generating system of the invention.

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

Fig. 1 shows one example of an electric aerosol generating system having a fluid storage part;

Fig. 2 is a graph showing five medians of temperature profiles of a heating element during repeated inhalation of an electric aerosol generating system;

Fig. 3 is a graph showing the rate of increase of the temperature of the heating element throughout the duration of the fluid storage part calculated at three different time intervals;

Fig. 4 is a graph showing, on the y axis, the resistance of the heating element, and on the x-axis the temperature of the heating element of the electric heater from the electric aerosol generating system; and

Fig. 5 is a schematic of electrical circuits that allows measuring the resistance of a heating element according to one embodiment of the invention.

Fig. 1 shows one example of an electric aerosol generating system having a fluid storage part. In Fig. 1, the system is a smoking system. The smoking system 100 of Fig. 1 includes a housing

101 having an end at the mouthpiece 103 and the end of the body 105. At the end of the body an electrical power source in the form of a battery is provided

107 and electrical circuits 109. A puff detection system 111 is also provided in cooperation with electrical circuits 109. Finally, a fluid storage portion 113 in the form of a fluid-containing insert 113, a capillary wound 117, and a heater 119 are provided at the mouthpiece.

It should be noted that the heater is shown schematically in Fig. 1. In the embodiment shown in Fig. 1, one end of capillary wick 117 extends to cartridge 113 and the other end of capillary wick 117 is surrounded by heater 119.

The heater is connected to electrical circuits through connections

121, which extend along the exterior of the cartridge 113 (not shown in FIG

Fig.1). The housing 101 also includes an air inlet 123, an air outlet 125 at the end of the mouthpiece, and an aerosol generating chamber 127.

In use, the operation of the device is as follows. Liquid

115 is transmitted based on capillary phenomena from the insert end wick end 113, which protrudes into the cartridge to the other end of the wick which is surrounded by the heater 119. When the user sucks off the aerosol generating system, the air surrounding 125 is sucked through the air inlet 123 In the setting shown on

1, the puff detection system 111 detects puffing and activates the heater 119. The battery 107 provides electrical energy to the heater 119 to heat the end of the capillary wick 117 surrounded by the heater. The fluid at the end of the wick 117 is vaporized by the heater 119 to create a supersaturated vapor. At the same time that the liquid is evaporated, it is replaced by the fluid passing further along the wick 117 based on capillary phenomena.

(This is sometimes presented to us as a "pumping action".)

The resulting supersaturated couple is mixed with and distributed in the air stream flowing from the air inlet 123. In the aerosolization chamber 127, the vapor condenses to form an inhalable aerosol that is transferred towards the outlet 125 and to the mouth of the user.

In the embodiment shown in Fig. 1, electrical circuits

109 and the puff detection system 111, preferably are programmable.

The electric circuits 109 and the puff detection system 111 can be used to manage the process of the aerosol generating system.

This supports the regulation of particle size in the aerosol.

Fig. 1 shows one example of an electric aerosol generating system according to the present invention. Nevertheless, many other examples are possible. In addition, it should be noted that Fig. 1 is schematic. In particular, the components shown are necessarily not singularly or in relation to each other.

The electric aerosol generating system must comprise or obtain a liquid aerosol-generating substrate located in the fluid storage part. An electric aerosol generating system requires a type of electric heater comprising at least one heating element for heating a liquid aerosol generating substrate. Finally, the electric aerosol generating system requires electrical circuits to determine the amount of liquid aerosol-forming substrate in the fluid storage part. This will be described below with reference to Figures 2 to 5. For example, the system need not be a smoking system. A puff detection system may not be provided. Instead, the system can be operated by manual actuation, for example a user-operated switch when it is on. For example, you can change the overall dimensions and shape of the housing. In addition, the system may not comprise a capillary wick. In this case, the system may include a different fluid delivery mechanism for evaporation.

However, in a preferred embodiment, the system comprises a capillary wick for transferring liquid from the fluid storage portion to the at least one heating element. The capillary wick can be made of various capillary or porous materials and preferably has a known, predetermined capillarity. Examples include ceramics or graphite materials in the form of fibers or sintered powders. Wicks of different porosity can be used, providing them with various physical properties of the fluid, such as density, viscosity, surface tension and vapor pressure. The wick must be suitable so that the required amount of fluid can be supplied to the heater. Preferably, the heater comprises at least one heating conductor or a fiber extending around the capillary wick.

Several embodiments of the invention will now be described with reference to Figs. 2 to 5. Embodiments are based on the example shown in Fig. 1, although they are applicable to other embodiments of electric aerosol generating systems.

As already mentioned, the aerosol generating system of the invention includes electrical circuits for determining the amount of liquid aerosol-forming substrate in the fluid storage part. This is advantageous because when the fluid storage part is empty or almost empty, insufficient liquid aerosol generating substrate may be provided to the heater. This may mean that the aerosol formed and inhaled by the user does not have the desired properties, for example the size of the aerosol particles. This can cause a poor smoking experience for the user. Furthermore, it is advantageous to provide a mechanism by which the user can be informed that the fluid storage part is empty or almost empty. The user can then be prepared to replace or refill the fluid storage parts. If a capillary wick is provided, it means that the capillary wick will become dry. The temperature of the heating element will increase. This increase in temperature of the heating element is used in the first and second embodiments of the invention.

Fig. 2 is a graph showing five median temperature profiles measured during multiple puffs of an aerosol generating system. The temperature T of the heating element is shown on the y axis and the puff time t is shown on the x-axis. The curve 201 is the median of the first set of puffs, each puff being

2-second time of taking. Similarly, curve 203 is the median of the second set of puffs, curve 205 is the median of the third set of puffs, curve 207 is the median of the fourth set of puffs and curve 208 is the median of the fifth set of puffs. In each curve, vertical bars (e.g. shown in 209) indicate a standard deviation around the median for these temperatures. In this way, the evolution of the measured temperature during the measurement period of the fluid storage part is shown. This behavior was observed and confirmed for all evaporated liquid compositions and at all feed levels.

As can be seen in Fig. 2, the temperature data of the heating element is relatively stable on the curves 201, 203 and 205. This means that the standard deviation around the median in the first three puff sets is relatively small. There are two effects on curve 207. First, the standard deviation around the median for the third set of hauls is greater. Second, the temperature of the heating element increased significantly during each puff. These two effects indicate that the fluid storage part becomes empty.

On curve 208, the standard deviation around the median for the fifth set of puffs is smaller again. This means that the temperature range during puffs is relatively stable. However, the temperature of the heating element increases during each puff. This indicates that the fluid storage part is essentially empty.

The temperature increase on the curve 207 compared to the curve 205 is particularly evident after about 0.4 seconds of puffing (shown in dotted line 211). The detection that the amount of fluid in the fluid storage part has dropped to a threshold value can therefore be accurately based on the temperature level of the heating element after 0.4 s of puff time.

Experimental data on specific substrate models for aerosol generation and for a given system model can be stored in memory in electrical circuits. Empirical data can associate the temperature of the heating element at a given puff point or heating cycle operating at a given power with the amount of fluid remaining in the fluid storage part. Empirical data can then be used to determine the amount of residual liquid and can be used to provide the user with an indication of when it is estimated that there will be less than a predetermined number of remaining puffs.

Thus, Fig. 2 shows that there is a marked increase in temperature of the heating element when the fluid storage part becomes empty. This is particularly evident after the first 0.4 seconds of contracting. This temperature rise can be used to determine when the fluid storage part is empty or almost empty.

It can also be seen in Fig. 2 that the temperature profile slope in the range of 0 to 0.2 seconds increases as the fluid storage part becomes empty. Thus, measuring the temperature rise rate at the initial puff time during the measurement period of the fluid storage part may provide an alternative or additional means for detecting the amount of residual liquid in the fluid storage part. This measurement may indeed be a more desirable measurement than that of Fig. 2, because this measurement can be taken in a shorter period of time, i.e. 0.2 seconds instead of 2 seconds. This can provide quicker insight into changes in temperature levels and can help reduce the risk of poor aerosol properties.

Fig. 3 is a graph showing the temperature rise rate calculated for different time ranges while consuming the aerosol generating substrate in the liquid power storage part at constant power. The points determined in this way were calculated on the basis of the formula:

AT T - T a = - = -⁰ .

At t - t

Graph 301 shows the rate of temperature increase and slope factor with t1 = 2ms and t2 = 50ms with the beginning of each puff, graph 302 shows the slope factor with t1 = 20ms and t2 = 100ms with the beginning of each puff and the graph

303 shows the slope factor with t1 = 20ms and t2 = 200 ms with the beginning of each puff. It can be seen that the coefficient of inclination when puffing is fairly constant from the puff number when the liquid storage part is full in sequence to the puff number "X1" for all three plots. Between the puff number "X1" and the puff number "X2" is the increase in the slope factor when the puff number increases. It can be seen that the increase in the slope factor is approximately linear with the puff number for all three plots. The increase in the rate of temperature rise for a given applied power is the result of wear of the substrate to produce an aerosol in the vicinity of the heater as a result of emptying the fluid storage part. In this example, this leads to the drying of the wick.

X2 further, the slope factor is also fairly constant. This corresponds to the empty part for storing the fluid and the dry wick. There is no substrate for producing an evaporation aerosol, and thus the energy supplied to the heating element is simply directed to heating. This phenomenon was observed and confirmed for the liquid formulations used and at all feed levels.

The phenomenon of the rope growth rate of temperature in the "emptied" area between puffs X1 and X2 can be used to provide measurement of the amount of substrate to produce the aerosol remaining in the fluid storage part. It may also be used to calibrate any other techniques for measuring or determining residual aerosol generating substrate. It can be seen in Fig. 3 that curve 301 corresponds to a temperature increase rate between 2 to 50 ms with the start of each puff representing the largest change between puffs X1 and X2, and therefore can be used to ensure the largest decomposition of the aerosol-producing substrate amount remaining parts for fluid storage.

It should be clear that the initiation of draining area and the rate of temperature increase in the emptying area is dependent on the composition of the substrate for generating the aerosol and the physical properties of the system, such as dimensions. Thus, by using a different device model or other substrate, the behavior of the device in the evacuation area will change. The threshold in which the decision is made that the storage part is "empty" can be set according to the design of the system and the substrate being used.

An alternative to measuring the slope shown in Fig. 3 is the integration of the curves in Fig. 2. It can be performed in the same time range between 0 and 0.2 seconds from each puff. It may also be a more desirable measurement than that of Fig. 2, since this measure will be taken over in just 0.2 seconds and thus can provide faster insight into changes in the temperature level.

Thus, Fig. 2 and 3 show that temperature measurement of the heating element, or the rate of change of temperature or integral of temperature over time, all can provide a sufficiently accurate measurement when the amount of fluid storage part has decreased to the threshold.

According to a first embodiment of the invention, the amount of liquid in the fluid storage part is determined by measuring the temperature in the vicinity of the heating element. As discussed above, if the measured temperature increases from puff to puff, this may indicate that the fluid storage portion is empty or nearly empty.

According to a first embodiment of the present invention, a temperature sensor is provided in a system for generating an aerosol in the vicinity of a heating element. The electrical circuits can monitor the temperature measured by the temperature sensor, hence determine the amount of liquid in the fluid storage part. An advantage of this embodiment is that no calculation or discharge is required because the temperature sensor directly measures the temperature near the heating element.

Once it has been determined that the amount of liquid in the fluid storage part has dropped to a limit value, a series of actions can be taken, which will be described below.

According to a second embodiment of the invention, the amount of liquid in the fluid storage part is determined by measuring the electrical resistance of the heating element. If the heating element has the appropriate temperature coefficient of resistance (see, for example, equation (5) below), the resistance may be the measurement of the temperature of the electric heating element.

Fig. 4 is a graph showing the resistance R of the heater element of the electric heater on the y axis in relation to the temperature

T of the heating element on the x-axis. As can be seen in Fig. 4, when the temperature T of the heating element increases, also the resistance R increases. Within the selected range (in the temperature range T1 and T2 and the resistance R1 and R2 on

Fig. 4), wherein the temperature T and the resistance R can be proportional to one another.

As discussed above with respect to the first embodiment of the invention, if the fluid storage part is empty or almost empty, insufficient liquid aerosol generating substrate will be supplied to the heater. This means that each capillary wick will become dry and the temperature of the heating element will increase.

Fig. 4 shows that such a temperature increase can be determined by measuring the resistance of the heating element, because when the temperature rises, the measured resistance increases.

Fig. 5 is a diagram of electric circuits showing how the resistance of the heating element can be measured in accordance with the second embodiment of the invention. In Fig. 5, the heater 501 is connected to the battery 503, which supplies the voltage V2. The resistance of the heater measured at a given temperature is Rogrzewacz. In a series with the heater 501, an additional resistor 505 with known resistance r is placed connected to the voltage V1, mediates between ground and voltage V2. To measure the resistance of the heater heater 501 for the microprocessor 507, both the current flowing through the heater 501 and the voltage on the heater 501 can be determined. Then a well-known equation can be used to determine the resistance:

V = IR

In Figure 5, the voltage on the heater is V2-V1 through the heater is I. Thus:

and flowing current

I ^ .ogizev.aęz -

An additional resistor 505, whose resistance r is used to determine the current I, again above. The current flowing through the resistor 505 is I and the resistor 505 is V1. Therefore:

I - V1

1)

2) is known using (1) voltage on

Thus, combining (2) and (3) we get:

3) p _ (V 2 - V1) ^^ heater -

V1

4)

Thus, when an aerosol generating system is used, the microprocessor 507 can measure V2 and V1, and knowing the value of r, can determine the resistance of the heater for a particular temperature, the Warmer.

By monitoring the Cochlea during the lifetime of the fluid storage part, the growth in the heater can be fixed. Hence the increase in resistance can be detected, which may indicate an increase in temperature because the capillary wick is dry.

Then, the following formula can be used to determine the temperature {T} from the measured resistance Reheater _R rj-i _ heater + rp ¹ at temperature T:

aR ,, where α is the coefficient of thermal resistance of the heating element material and R0 is the resistance of the heating element at room temperature T0. Thus, an increase in temperature can be detected, which may correspond to emptying the fluid storage part such that it becomes empty or almost empty.

The advantage of this embodiment is that no temperature sensor is required, which can be cumbersome and expensive.

In this way, the temperature measurement of the heating element can be derived. It can be used to determine when the amount of fluid in the fluid storage part has dropped to the threshold and to determine the absolute amount of substrate for producing the aerosol remaining in the fluid storage part.

In a third embodiment of the invention, the aerosol generating system may be configured to maintain or control the temperature of the heating element during puffing or may be configured to limit the temperature of the heating element to a maximum temperature to avoid undesired chemical degradation. In this embodiment, instead of using the temperature as a liquid level consumption indicator, the power required to maintain the predetermined temperature can be used to calculate the amount of substrate for generating the aerosol. For example, if a capillary wick is used, when the wick dries out, less power will be required to maintain the predetermined temperature.

The power can be supplied to the heater with pulse width modulation (PWM) with a predetermined amplitude. The power waveform operation cycle, i.e. the ratio of the time period in which the power is switched to the time period in which the power is turned off, then a parameter may be used to calculate the amount of substrate for generating the aerosol in the fluid storage part. Again, the empirical power data for the amount of aerosol-forming substrate in the fluid storage part can be stored in memory in the electrical circuits.

In all of the embodiments described above, after determining when the amount of liquid aerosol generating substrate in the fluid storage part has decreased to a threshold value, one or more actions may be taken. The electric heater can be turned off. For example, the system may be called to make the fluid storage part not be usable. For example, electric circuits, as a result of determining that the amount of aerosol-forming liquid substrate in the fluid storage part has decreased to a threshold value, can burn an electrical fuse between at least one heating element of the electric heater and the power supply. An electric fuse may be provided as part of a removable component containing a fluid storage part. Alternatively, the electrical circuits determining that the amount of liquid aerosol-generating substrate in the fluid storage portion is reduced to a threshold value, can switch off the switch between the at least one heating element of the electric heater and the power supply. Of course, alternative methods for deactivating the electric heater are possible. The advantage of deactivating the electric heater is that it is impossible to use the aerosol generating system. Of course, alternative methods for deactivating the electric heater are possible. The advantage of deactivating the electric heater is that it is impossible to use the aerosol generating system. Of course, alternative methods for deactivating the electric heater are possible. The advantage of deactivating the electric heater is that it is impossible to use the aerosol generating system.

This prevents the user from inhaling an aerosol that has no desired properties.

When it is determined when the amount of liquid in the fluid storage part has dropped to a threshold value, the user may be informed. For example, electric circuits specifying that the amount of liquid aerosol-forming substrate in the fluid storage part decreased to a threshold value may indicate to the user. For example, if the aerosol generating system includes a user display, this can be indicated to the user by means of a user display that the fluid storage portion is empty or nearly empty and can provide a determination of the number of remaining puffs. Alternatively or additionally, the audible signal may indicate to the user that the fluid storage part is empty or almost empty. Alternative ways to indicate to the user that the fluid storage part is empty or almost empty, are of course possible. The advantage of informing the user is that the user is prepared to replace or refill the fluid storage parts.

Thus, according to the invention, the electric aerosol generating system comprises electric circuits for determining when the amount of liquid aerosol generating substrate in the fluid storage part has decreased to a predetermined threshold. Various methods for determining that the amount of liquid aerosol-forming substrate in the fluid storage portion decreased to a predetermined threshold have been described with reference to Figs. 2 to 5. The features described in relation to one embodiment can also be applied to another embodiment.