RU2827722C1 - Heater for aerosol-forming substrate comprising ptc thermistor - Google Patents

Abstract

FIELD: heating.

SUBSTANCE: heater (10) for heating the aerosol-forming substrate. Heater (10) comprises a heating element configured to heat the aerosol-forming substrate, wherein the heating element comprises at least one PTC thermistor (24, 25, 260, 261, 262, 263, 264, 265, 27). Resistance of at least one PTC thermistor (24, 25, 260, 261, 262, 263, 264, 265, 27) increases when temperature of at least one PTC thermistor (24, 25, 260, 261, 262, 263, 264, 265, 27) increases within the stabilized temperature range. Lower limit of stabilized temperature range is control temperature (CT), at which resistance of at least one PTC thermistor (24, 25, 260, 261, 262, 263, 264, 265, 27) is twice greater than the value of minimum resistance of at least one PTC thermistor (24, 25, 260, 261, 262, 263, 264, 265, 27).

EFFECT: this makes it possible to effectively control the operating temperature of the heater while limiting the operating temperature of the heater by its configuration.

15 cl, 15 dwg

Description

The present invention relates to heaters for heating an aerosol-forming substrate and to aerosol-generating devices and aerosol-generating systems containing such heaters.

Aerosol generating articles are known in the art in which an aerosol forming substrate, such as a tobacco containing substrate, is heated rather than burned. The purpose of such heated aerosol generating articles is to reduce potentially harmful by-products formed as a result of combustion and pyrolytic degradation of tobacco in conventional cigarettes.

In heated aerosol-generating articles, an inhalable aerosol is typically generated by heat transfer from a heater to an aerosol-generating substrate. During heating, volatile compounds are released from the aerosol-generating substrate and are entrained in air. For example, volatile compounds may be entrained in air drawn through, above, around, or otherwise in the vicinity of the aerosol-generating article. As the released volatile compounds cool, they condense to form an aerosol. The aerosol may be inhaled by the user. The aerosol may contain aromatics, flavors, nicotine, and other desirable elements.

The heating element may be contained in an aerosol generating device. The combination of the aerosol generating article and the aerosol generating device may form an aerosol generating system.

The heating element may be a resistive heating element that may be inserted into or positioned around the aerosol-forming substrate when the article is placed in the aerosol-generating device. However, it may be difficult to regulate the temperature of the resistive heating element to provide the desired heating profile, as resistive heating elements may exhibit a slow thermal response. It may also be difficult to avoid potential overheating without providing additional elements.

It would be desirable to provide a heater in which the operating temperature of the heater can be effectively controlled. It would also be desirable to provide a heater in which the operating temperature of the heater is limited by the configuration of the heater.

A heater for heating an aerosol-forming substrate is proposed. The heater may comprise a heating element configured to heat the aerosol-forming substrate. The heating element may comprise at least one positive temperature coefficient (PTC) thermistor. The resistance of at least one PTC thermistor may increase when the temperature of at least one PTC thermistor increases within a stabilized temperature range. The lower limit of the stabilized temperature range may be a control temperature at which the resistance of at least one PTC thermistor is twice the minimum resistance value of at least one PTC thermistor.

The invention proposes a heater for heating an aerosol-forming substrate, wherein the heater comprises a heating element configured to heat the aerosol-forming substrate, wherein the heating element comprises at least one PTC thermistor, such that the resistance of at least one PTC thermistor increases when the temperature of at least one PTC thermistor increases within a stabilized temperature range, wherein the lower limit of the stabilized temperature range is a control temperature at which the resistance of at least one PTC thermistor is twice the value of the minimum resistance of at least one PTC thermistor.

The heating element may comprise at least one PTC thermistor. At least one PTC thermistor is a temperature-sensitive resistor that can be heated when an electric current is applied to at least one PTC thermistor. When at least one PTC thermistor is heated, the temperature and resistance of at least one PTC thermistor may change in accordance with a function that links both parameters. At least one PTC thermistor may have a good thermal response when the temperature changes in accordance with such a function. Therefore, it is possible to effectively control the operating temperature of at least one PTC thermistor. In particular, at least one PTC thermistor may be heated to a temperature that corresponds to the minimum resistance of at least one PTC thermistor.

In a similar manner, at least one PTC thermistor can be heated to a temperature corresponding to twice the minimum resistance of at least one PTC thermistor. If at least one PTC thermistor is heated to a temperature exceeding the temperature corresponding to twice the minimum resistance of at least one PTC thermistor, the resistance of at least one PTC thermistor increases when the temperature of at least one PTC thermistor increases within a stabilized temperature range. Therefore, the stabilized temperature range is limited by a lower limit corresponding to the temperature at which the resistance of at least one PTC thermistor is twice the minimum resistance value of at least one PTC thermistor. This lower limit of the stabilized temperature range is usually called the reference temperature of at least one PTC thermistor. Within the stabilized temperature range, the increase in the resistance of the at least one PTC thermistor with an increase in the temperature of the at least one PTC thermistor is typically sharp enough to ensure a very slow change in the temperature of the at least one PTC thermistor. It should be noted that in the context of this document, "stabilized temperature range" should be interpreted as a temperature range of the PTC thermistor in which the temperature is not necessarily constant, even if the change in temperature of the PTC thermistor may be insignificant in relation to the change in resistance of the PTC thermistor.

Therefore, at least one PTC thermistor can be stabilized at substantially a control temperature (or at a temperature slightly higher than the control temperature) within a stabilized temperature range for periods of time that may exceed the normal operating time of the aerosol generating device comprising the heater of the present invention. This provides a more consistent heating profile of the aerosol forming substrate, in which the maximum temperature of the heating element during the operating time can be determined and controlled by providing an appropriate PTC thermistor.

The reference temperature can essentially correspond to the Curie temperature for dielectric PTC thermistors such as semiconductor ceramics. The Curie temperature is usually defined as the threshold temperature above which certain materials transition from ferroelectricity to paraelectricity.

A heating element comprising at least one PTC thermistor may be less susceptible to overheating because the temperature of the at least one PTC thermistor may not significantly exceed a control temperature. The heater may not require additional special elements to reduce the potentially harmful effects of temperatures above a given temperature threshold by providing a PTC thermistor with control temperatures below such threshold.

The heater may not require a special element, such as a sensor, to measure and regulate the temperature of the heating element, since the control temperature may be an internal property of at least one PTC thermistor. Therefore, even without such special elements, the heating element can be designed to operate at maximum temperatures that do not significantly exceed the control temperature of at least one PTC thermistor.

The heater may comprise an external heating element, wherein at least one PTC thermistor is comprised in the external heating element. In the context of this document, the term "external heating element" refers to a heating element adapted to heat the outer surface of the aerosol-forming substrate. The external heating element may at least partially surround a cavity for accommodating the aerosol-forming substrate.

The heater may comprise an internal heating element, wherein at least one PTC thermistor is comprised in the internal heating element. In the context of this document, the term "internal heating element" refers to a heating element adapted for insertion into an aerosol-forming substrate. The internal heating element may be in the form of a blade, a pin, or a cone. The internal heating element may extend into a cavity for accommodating an aerosol-forming substrate.

In some embodiments, the heater comprises an internal heating element and an external heating element.

The heater is designed to heat the substrate that forms the aerosol.

In the context of this document, the term "aerosol-forming substrate" means a substrate capable of releasing volatile compounds that can form an aerosol. Such volatile compounds can be released by heating the aerosol-forming substrate. The aerosol-forming substrate is typically part of an aerosol-generating article.

The aerosol-forming substrate may contain nicotine. The nicotine-containing aerosol-forming substrate may be a nicotine salt matrix.

The aerosol-forming substrate may be a liquid. The aerosol-forming substrate may contain solid components and liquid components. Preferably, the aerosol-forming substrate is a solid.

The aerosol-forming substrate may comprise a material of plant origin. The aerosol-forming substrate may comprise tobacco. The aerosol-forming substrate may comprise a material comprising tobacco, which comprises volatile tobacco flavour compounds that are released from the aerosol-forming substrate upon heating. The aerosol-forming substrate may comprise a non-tobacco material. The aerosol-forming substrate may comprise a homogenised material of plant origin. The aerosol-forming substrate may comprise a homogenised tobacco material. The homogenised tobacco material may be formed by agglomerating tobacco in the form of particles. In a particularly preferred embodiment, the aerosol-forming substrate comprises an assembled corrugated sheet of homogenised tobacco material. In the context of the present document, the term "corrugated sheet" denotes a sheet having a plurality of substantially parallel folds or corrugations.

The aerosol forming substrate may comprise at least one aerosol forming agent. The aerosol forming agent is any suitable known compound or mixture of compounds that, when used, promote the formation of a dense and stable aerosol and that are substantially resistant to thermal degradation at the operating temperature of the system. Suitable aerosol forming agents are well known in the art and include, but are not limited to: polyhydric alcohols such as triethylene glycol, 1,3-butanediol and glycerol; esters of polyhydric alcohols such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids such as dimethyl dodecanedioate and dimethyl tetradecanedioate. Preferred aerosol forming agents may include polyhydric alcohols or mixtures thereof, such as triethylene glycol, 1,3-butanediol. Preferably, the aerosol forming agent is glycerol. If present, the homogenized tobacco material may have an aerosol forming substance content equal to or greater than about 5 percent by weight on a dry weight basis, such as from about 5 percent to about 30 percent by weight on a dry weight basis. The aerosol forming substrate may contain other additives and ingredients such as flavorings.

The control temperature of the at least one PTC thermistor may be from about 100 degrees Celsius to about 350 degrees Celsius when a DC voltage of 3.3 volts is applied to the at least one PTC thermistor.

This range of control temperatures may be useful for heating the aerosol-forming substrate sufficiently to release certain substances that may be contained in the aerosol-forming substrate, such as nicotine or processed tobacco leaves.

More preferably, the control temperature of at least one PTC thermistor may be from about 200 degrees Celsius to about 250 degrees Celsius.

This range of control temperatures may be sufficient to heat the aerosol-forming substrate sufficiently to release certain substances that may be contained in the aerosol-forming substrate, such as nicotine-containing e-liquids and gel substances.

The heating element may be configured to be inserted into an aerosol-forming substrate.

In other words, the heating element may be an internal heating element. The internal heating element may pierce the aerosol-forming substrate. The internal heating element may also be located in the internal cavity of the aerosol-forming substrate. The heater may comprise a cavity for accommodating the aerosol-forming substrate when the internal heating element is inserted into the aerosol-forming substrate. When an electric current is supplied to the internal heating element, the temperature of the internal heating element increases until it reaches the control temperature of at least one PTC thermistor contained in the internal heating element. If the supply of electric current is maintained after this point, the temperature of the internal heating element stabilizes at a temperature that substantially corresponds to the control temperature of at least one PTC thermistor contained in the internal heating element. Thus, the internal heating element may be used to heat the aerosol-forming substrate at substantially the control temperature of at least one PTC thermistor. The control temperature can be adjusted to optimize the release of volatile compounds from the substrate.

The heating element may be configured to heat the outer surface of the aerosol-forming substrate.

In other words, the heating element may be an external heating element. The external heating element may comprise a cavity for accommodating the aerosol-forming substrate. The cavity may comprise an internal wall configured to be in thermal contact with the outer surface of the aerosol-forming substrate. When an electric current is supplied to the external heating element, the temperature of the external heating element increases until it reaches the control temperature of at least one PTC thermistor contained in the external heating element. If the supply of the electric current is maintained after this point, the temperature of the external heating element stabilizes at a temperature that substantially corresponds to the control temperature of at least one PTC thermistor contained in the external heating element. Thus, the external heating element may be used to heat the aerosol-forming substrate at substantially the control temperature of the at least one PTC thermistor. The control temperature may be adjusted in such a way as to optimize the release of volatile compounds from the substrate.

The heater may comprise a heater body, wherein the heater body comprises an edge portion extending in the transverse direction between the edge inner wall and the edge outer wall, and a lower portion extending in the longitudinal direction between the lower inner wall and the lower outer wall; a cavity for accommodating an aerosol-forming substrate, extending in the longitudinal direction between the open end and the lower inner wall, wherein the cavity is limited in the transverse direction by the edge inner wall.

The edge inner wall and the lower inner wall may have appropriate dimensions and shape to form a cavity for accommodating the aerosol-forming substrate in such a way that heat transfer from the heating element to the aerosol-forming substrate can be optimized.

At least one PTC thermistor may be a PTC disk located inside the lower portion.

This can make it possible to provide a heater that is easy to manufacture and assemble, while providing a satisfactory heating profile for the aerosol-forming substrate when the substrate is placed in the cavity of the heater housing. In this embodiment, the temperature of the edge inner wall may differ slightly from the temperature of the PTC disk. Therefore, appropriate heat transfer between the PTC disk and the aerosol-forming substrate can be achieved.

At least one PTC thermistor may comprise a PTC tube located inside the edge portion to surround the edge inner wall.

In this device, the temperature of the inner edge wall can be substantially the same as the temperature of the PTC tube. This can lead to improved heat transfer between the PTC tube and the aerosol-forming substrate.

The outer edge wall may comprise at least three flat sections, at least one PTC thermistor comprising at least one PTC plate located on at least one of the at least three flat sections.

The presence of at least three flat sections on the outer edge wall may be advantageous in the sense that at least one PTC plate, which may be easy to manufacture, may be located on a flat surface of one or more of the at least three flat sections. Such an arrangement may result in optimized heat transfer from the at least one PTC plate to the aerosol-forming substrate when the substrate is placed in the cavity of the heater housing. The PTC plates are flat.

The outer edge wall may form a regular or irregular polygon according to the cross-section. In one example, the polygon is one of a triangle, rectangle, square, pentagon, and hexagon.

At least one PTC thermistor may comprise at least three PTC plates, such that each of the at least three PTC plates is located on a different flat section, wherein the number of PTC plates is equal to the number of flat sections.

In this embodiment, a PTC plate is located on each flat section. This can help improve the heat transfer from the PTC plates to the aerosol-forming substrate when the substrate is placed in the cavity of the heater body.

At least two of the at least three PTC plates may have different control temperatures.

This can be useful for heating different sections of the aerosol-forming substrate to different temperatures when the substrate is placed in the cavity of the heater housing. This can be used to ensure that different sections of the aerosol-forming substrate are heated sequentially, which can help reduce the mass of evaporated aerosol that can occur due to substrate depletion upon contact with the heater housing.

At least three PTC plates can be electrically connected in parallel to each other.

This can reduce the overall electrical resistance of the heater, thereby increasing power dissipation when using small batteries such as 3.0 volt to 6.0 volt batteries.

The outer edge wall may contain six flat sections.

It was found that a six-flat section arrangement could result in a compromise between optimal heat transfer between the PTC plates to the aerosol-forming substrate when the substrate is placed in the heater body cavity and the ease of fabrication of the flat sections.

The heater body may comprise an electrically conductive material, such as an electrically conductive metal, wherein the heater body forms a first electrode in electrical contact with at least one PTC plate. The heater may further comprise at least one external electrical contact comprising an electrically conductive material, such as an electrically conductive metal, and forming a second electrode in electrical contact with at least one PTC plate.

By using the heater housing as the first electrode for at least one PTC plate, the supply of electric current can be integrated into the heater in a more compact manner. The electrically conductive material contained in the housing can be a metal, such as aluminum.

Likewise, at least one external electrical contact is preferred in that it can provide an easy-to-assemble device for supplying electrical current.

In an embodiment in which the PTC thermistor comprises at least three PTC plates, so that each of the at least three PTC plates is located on a different flat section, at least three external electrical contacts can be provided, wherein each external electrical contact is in electrical contact with another PTC plate. This device can ensure a proper supply of electrical current to at least three PTC plates. In particular, in an embodiment comprising six PTC plates and, therefore, six external electrical contacts, it may be possible to reach a temperature substantially equal to the reference temperature of each PTC plate in 30 seconds.

In one embodiment, at least one PTC plate may have a length of approximately 7 millimeters. At least one PTC plate may have a width of approximately 3.8 millimeters. At least one PTC plate may have a thickness of approximately 0.5 millimeters.

At least one PTC thermistor may comprise a ceramic semiconductor, such as barium titanate.

The presence of a corresponding ceramic semiconductor may allow the control temperature of at least one PTC thermistor to be adjusted. When at least one PTC thermistor is made of a ceramic semiconductor, the control temperature of the PTC semiconductor may substantially correspond to the Curie temperature of the ceramic semiconductor.

At least one PTC thermistor may comprise a polymer material.

The presence of a polymeric material may be advantageous in that it may allow for simplified assembly of at least one PTC thermistor in the heater due to the high flexibility that some polymeric materials may have. It may also result in less brittle heaters. It may also result in heaters having a lower thermal mass, which may result in lower thermal latency during heating.

The polymer material may comprise polyethylene. The polymer material may comprise carbon grains, carbon ink, or other suitable conductive grains. The carbon grains may comprise carbon black. The carbon grains may comprise nickel powder.

The polymer material may contain a polymer film.

The heater may comprise a multilayer support that may be directly attached to the polymer film. The multilayer support may comprise a metal, such as copper.

At least one PTC thermistor may comprise a mixture of barium titanate and an alkaline earth metal element, such as a strontium or bismuth element. At least one PTC thermistor may comprise a mixture of barium titanate and lead titanate. These mixtures may provide additional control of the control temperature of at least one PTC thermistor.

Additional additives may be added to the at least one PTC thermistor to adjust the control temperature of the at least one PTC thermistor to a desired level.

The invention provides an aerosol generating device comprising any of the heaters described above. As used herein, the term "aerosol generating device" refers to a device that interacts with an aerosol-forming substrate to generate an aerosol.

Since the aerosol generating device according to the present invention comprises a heater according to the previous inventions, the advantages stated above for heaters also apply to the device itself.

The aerosol generating device may comprise a device housing. The device housing may at least partially form a cavity for accommodating an aerosol forming substrate. Preferably, the cavity for accommodating an aerosol forming substrate is located at the proximal end of the device.

The device body may be elongated. Preferably, the device body has a cylindrical shape. The device body 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 such materials, or thermoplastic materials suitable for use in the food or pharmaceutical industry, such as polypropylene, polyetheretherketone (PEEK) and polyethylene. Preferably, the material is light and non-brittle.

Preferably, the aerosol generating device is portable. The aerosol generating device may be of a size comparable to a traditional cigar or cigarette. The aerosol generating device may have a total length of about 30 millimeters to about 150 millimeters. The aerosol generating device may have an outer diameter of about 5 millimeters to about 30 millimeters. The aerosol generating device may be a hand-held device. In other words, the aerosol generating device may be sized and shaped to be held in the hand of a user.

The aerosol generating device may comprise a power source configured to supply electric current to the heating element.

The power source may be a DC power source. In preferred embodiments, the power source is a battery. The power source may be a nickel-metal hydride battery, a nickel-cadmium battery, or a lithium-based battery, such as a lithium-cobalt, lithium-iron phosphate, or lithium-polymer battery. However, in some embodiments, the power source may be another type of charge storage device, such as a capacitor. The power source may need to be recharged and may have a capacity that allows storing a sufficient amount of energy for one or more operations by the user. For example, the power source may have sufficient capacity to ensure continuous heating of the aerosol-forming substrate for a period of approximately six minutes, which corresponds to the typical time required to smoke a conventional cigarette, or for a period of multiples of six minutes. In another example, the power source may have sufficient capacity to ensure the possibility of performing a given number of puffs or individual activations of the aerosol generator. In another example, the power source may have a sufficient capacity to enable a given number of uses of the device or individual activations. In one embodiment, the power source is a DC power source having a DC power supply voltage in the range of about 2.5 volts to about 4.5 volts and a DC power supply current in the range of about 1 ampere to about 10 amperes (which corresponds to a DC power source in the range of about 2.5 watts to about 45 watts).

The aerosol generating device may comprise a controller connected to the heating element and a power source. The controller may be configured to control the power supply to the heating element from the power source. The controller may comprise a microprocessor, which may be a programmable microprocessor, a microcontroller, or an application-specific integrated circuit (ASIC), or another electronic circuit capable of providing control. The controller may comprise additional electronic components. The controller may be adapted to regulate the current supply to the heating element. The current may be supplied to the heating element continuously after activation of the aerosol generating device, or may be supplied intermittently, for example from puff to puff.

The controller may advantageously comprise a DC to AC converter, which may comprise a class D or class E power amplifier.

In some embodiments, the device body comprises a mouthpiece. The mouthpiece may comprise at least one air inlet and at least one air outlet. The mouthpiece may comprise more than one air inlet. One or more air inlets may reduce the temperature of the aerosol before it is delivered to the user and may reduce the concentration of the aerosol before it is delivered to the user.

In some embodiments, a mouthpiece is provided as part of an aerosol-generating article. As used herein, the term "mouthpiece" refers to a part of an aerosol-generating system that is placed in the mouth of a user for directly inhaling an aerosol generated by the aerosol-generating system from an aerosol-generating article housed in an aerosol-generating device.

The aerosol generating device may comprise a user interface for activating the device, such as a button for initiating heating of the aerosol generating article.

The aerosol generating device may comprise a display for indicating the state of the device or the aerosol generating substrate.

The invention provides an aerosol generating system comprising any of the above-mentioned aerosol generating devices. The aerosol generating system further comprises an aerosol generating article comprising an aerosol forming substrate.

As used herein, the term "aerosol-generating article" means an article that contains an aerosol-forming substrate capable of releasing volatile compounds that can form an aerosol. For example, an aerosol-generating article may be an article that generates an aerosol that is directly inhaled by a user who draws or puffs on a mouthpiece at the near or user end of the system. The aerosol-generating article may be disposable.

For the purposes of this document, the term "aerosol-generating system" refers to the combination of an aerosol-generating device and an aerosol-generating article. In an aerosol-generating system, the aerosol-generating article and the aerosol-generating device cooperate to generate an inhalable aerosol.

Since the aerosol generating system according to the present invention comprises a heater according to the previous inventions, the advantages stated above for heaters also apply to the system itself.

The aerosol-generating article may have any suitable shape. The aerosol-generating article may have a substantially cylindrical shape. The aerosol-generating article may be substantially elongated. The aerosol-generating article may have a length and a circumference substantially perpendicular to the length.

The aerosol-forming substrate may be provided as an aerosol-generating segment containing an aerosol-forming substrate. The aerosol-generating segment may contain a plurality of aerosol-forming substrates. The aerosol-generating segment may contain a first aerosol-forming substrate and a second aerosol-forming substrate. In some embodiments, the second aerosol-forming substrate is substantially the same as the first aerosol-forming substrate. In some embodiments, the second aerosol-forming substrate differs from the first aerosol-forming substrate.

The aerosol generating segment may have a substantially cylindrical shape. The aerosol generating segment may be substantially elongated. The aerosol generating segment may also have a length and a circumference substantially perpendicular to the length.

In case the aerosol generating segment comprises a plurality of aerosol forming substrates, the aerosol forming substrates may be arranged end to end along the axis of the aerosol generating segment. In some embodiments, the aerosol generating segment may comprise a partition between adjacent aerosol forming substrates.

In some preferred embodiments, the aerosol-generating article may have a total length of about 30 millimeters to about 100 millimeters. In some embodiments, the aerosol-generating article has a total length of about 45 millimeters. The aerosol-generating article may have an outer diameter of about 5 millimeters to about 12 millimeters. In some embodiments, the aerosol-generating article may have an outer diameter of about 7.2 millimeters.

The aerosol generating segment may have a length of about 7 millimeters to about 15 millimeters. In some embodiments, the aerosol generating segment may have a length of about 10 millimeters or 12 millimeters.

The aerosol generating segment preferably has an outer diameter that is approximately equal to the outer diameter of the aerosol generating article. The outer diameter of the aerosol generating segment may be from about 5 millimeters to about 12 millimeters. In one embodiment, the aerosol generating segment may have an outer diameter of about 7.2 millimeters.

The aerosol-generating article may comprise a filter rod. The filter rod may be located at the proximal end of the aerosol-generating article. The filter rod may be a cellulose acetate filter rod. In some embodiments, the filter rod may have a length of about 5 millimeters to about 10 millimeters. In some preferred embodiments, the filter rod may have a length of about 7 millimeters.

The aerosol-generating article may comprise an outer wrapper. The outer wrapper may be formed from paper. The outer wrapper may be permeable to gas in the aerosol-generating segment. In particular, in embodiments comprising a plurality of aerosol-generating substrates, the outer wrapper may comprise perforations or other air inlets at the boundary between adjacent aerosol-generating substrates. In the event that a partition is provided between adjacent aerosol-generating substrates, the outer wrapper may comprise perforations or other air inlets in the partition. This may ensure that the aerosol-generating substrate is directly supplied with air that is not drawn through another aerosol-generating substrate. This may increase the amount of air received by each aerosol-generating substrate. This may improve the characteristics of the aerosol generated from the aerosol-generating substrate.

The aerosol generating article may also comprise a partition between the aerosol forming substrate and the filter rod. The partition may have a size of approximately 18 millimeters, but may have a size in the range of approximately 5 millimeters to approximately 25 millimeters.

The invention proposes a method for operating any of the above-mentioned aerosol-generating systems. The method may include a step of determining the maximum operating temperature for an aerosol-generating substrate contained in an aerosol-generating article. The method may include a step of supplying an electric current to at least one PTC thermistor by means of a power source, wherein the electric current has a constant voltage. The constant voltage may be such that the control temperature of the PTC thermistor is essentially the maximum operating temperature for the aerosol-generating substrate.

The present invention provides a method of operating any of the above-mentioned aerosol generating systems, the method comprising the steps of:

- determining the maximum operating temperature for an aerosol-forming substrate contained in an aerosol-generating product;

- supplying an electric current to at least one PTC thermistor by means of a power source, wherein the electric current has a constant voltage, wherein the constant voltage is such that the control temperature of the PTC thermistor is essentially the maximum operating temperature for the aerosol-forming substrate.

These steps can be controlled by a controller. The aerosol generating device can comprise a controller. Alternatively, the controller can be provided in a device external to the aerosol generating system, such as a computer or a mobile phone. The controller can be configured to detect the type of aerosol generating substrate in the aerosol generating system. The controller can store a maximum operating temperature for each type of aerosol generating substrate in order to improve aerosol formation when the aerosol generating substrate is heated. The controller can be configured to receive external data to determine the maximum operating temperature for the aerosol generating substrate. The controller can use any other suitable configuration to determine the maximum operating temperature for the aerosol generating substrate.

The resistance of at least one PTC thermistor may depend on the resistance of the grains and on the transition resistance of the grain boundaries forming the material contained in at least one PTC thermistor. The higher the voltage applied to at least one PTC thermistor, the lower the resistance of at least one PTC thermistor may be. The decrease in the resistance of at least one PTC thermistor with increased voltage may be more significant when the temperature exceeds the reference temperature of at least one PTC thermistor, since the destruction of the barriers between the grains may occur with a higher probability; similarly, part of the applied voltage may not be absorbed by the resistance of the grain. However, it was found that the decrease in the resistance of at least one PTC thermistor with increased voltage may be noticeable at the reference temperature or at temperatures below the reference temperature of at least one PTC thermistor. Due to this effect, it was found that the reference temperature of at least one PTC thermistor may depend on the voltage applied to at least one PTC thermistor.

In the method of the present invention, it is possible to advantageously extract advantages from changing the control temperature of at least one PTC thermistor with a voltage supplied to at least one PTC thermistor. To achieve this, the controller can control the power supply to supply an electric current to at least one PTC thermistor having a constant voltage. The selected constant voltage can be determined by the controller to ensure that the control temperature of the PTC thermistor is substantially the maximum operating temperature for the substrate forming the aerosol. A table can be stored on the controller, which relates the voltage supplied to at least one PTC thermistor to the control temperature of at least one PTC thermistor.

Therefore, the method of the present invention can allow at least one PTC thermistor of the aerosol generating system to be substantially stabilized at the maximum operating temperature for the aerosol generating substrate. The temperature at which the at least one PTC thermistor is stabilized is substantially the same as the temperature applied to the aerosol generating substrate, or close enough to it, when the aerosol generating system is used to heat the aerosol generating substrate. Therefore, the temperature at which the PTC thermistor is stabilized can be selected to optimize the formation of an aerosol. This can be useful for providing an optimized aerosol formation experience.

The invention provides a method for operating any of the above-mentioned aerosol generating systems. The method may include a step of measuring the puff intensity when a puff occurs during use of the aerosol generating system. The method may include a step of determining a puff intensity threshold. When the puff intensity is equal to or exceeds the puff intensity threshold, the method may include a step of determining a first maximum operating temperature and a second maximum operating temperature for an aerosol-forming substrate contained in an aerosol-generating article. The method may include a step of selecting a first maximum operating temperature or a second maximum operating temperature. If the first maximum operating temperature is selected, the method may include a step of supplying an electric current to at least one PTC thermistor by means of a power source, wherein the electric current has a first constant voltage, wherein the first constant voltage is such that the control temperature of the PTC thermistor is essentially the first maximum operating temperature for the aerosol-forming substrate. If a second maximum operating temperature is selected, the method may include the step of supplying an electric current to at least one PTC thermistor by means of a power source, wherein the electric current has a second constant voltage, wherein the second constant voltage is such that the control temperature of the PTC thermistor is essentially the second maximum operating temperature for the aerosol-forming substrate.

The present invention provides a method of operating any of the above-mentioned aerosol generating systems, the method comprising the steps of:

- measuring the puff intensity when a puff is taken during use of an aerosol generating system;

- determining a puff intensity threshold such that when the puff intensity is equal to or exceeds the puff intensity threshold, the method includes additional steps:

- determining a first maximum operating temperature and a second maximum operating temperature for an aerosol-forming substrate contained in an aerosol-generating article;

- selection of the first maximum operating temperature or the second maximum operating temperature;

- if a first maximum operating temperature is selected, supplying an electric current to at least one PTC thermistor by means of a power source, wherein the electric current has a first constant voltage, wherein the first constant voltage is such that the control temperature of the PTC thermistor is essentially the first maximum operating temperature for the aerosol-forming substrate;

- if a second maximum operating temperature is selected, supplying an electric current to at least one PTC thermistor by means of a power source, wherein the electric current has a second constant voltage, wherein the second constant voltage is such that the control temperature of the PTC thermistor is essentially the second maximum operating temperature for the aerosol-forming substrate.

As explained for the method of the previous invention, a change in the control temperature of at least one PTC thermistor can be achieved by changing the voltage supplied to at least one PTC thermistor. This can allow the control temperature to be adjusted so that it substantially corresponds to the maximum operating temperature for the aerosol-forming substrate, thus optimizing the formation of the aerosol.

For some aerosol-generating substrates, it may be preferable to vary the maximum operating temperature. This may allow the aerosol generation to be tailored to a specific aerosol generation experience. Such an aerosol generation experience may be selected to suit the preferences of the user of the aerosol generating system.

However, as indicated for the method of the previous invention, the change in the control temperature of at least one PTC thermistor by changing the voltage supplied to at least one PTC thermistor may be relatively small. In other words, the methods of the present invention can generally provide a change in the control temperature of at least one PTC thermistor in a small temperature range.

The method of the present invention includes a step of measuring the intensity of a puff when a puff occurs during use of the aerosol generating system. The method also includes a step of determining a threshold of the intensity of a puff. These steps can also be performed by a controller.

The controller may be configured to determine a reference temperature of at least one PTC thermistor by determining a voltage supplied to at least one PTC thermistor only when the puff intensity is equal to or exceeds the puff intensity threshold. When the puff intensity is below the puff intensity threshold, the temperature of at least one PTC thermistor may typically depend on the puff intensity. The function may be stored on the controller.

When the puff intensity is equal to or exceeds the puff intensity threshold, the controller can regulate the voltage supplied to at least one PTC thermistor to determine the reference temperature of at least one PTC thermistor. The controller can control the power source to supply the first constant voltage to at least one PTC thermistor; the first constant voltage results in the first reference temperature of at least one PTC thermistor. The controller can control the power source to supply the second constant voltage, different from the first constant voltage, to at least one PTC thermistor; the second constant voltage results in the second reference temperature of at least one PTC thermistor. Preferably, the first reference temperature and the second reference temperature are equal to or exceed the temperature corresponding to the puff intensity threshold in the function relating the temperature of at least one PTC thermistor and the puff intensity.

By limiting the adjustment of the control temperature of at least one PTC thermistor to puff intensities equal to or greater than the puff intensity threshold, the specific range of control temperatures that can be achieved by changing the voltage supplied to at least one PTC thermistor is focused on temperatures that can lead to overheating of the aerosol generating device or to obtaining aerosols of lower quality. Within such a specific range, even if the change in the control temperature of at least one PTC thermistor can be relatively small, the corresponding change in the maximum operating temperature of the aerosol forming substrate can advantageously provide the ability to significantly change the properties of the formed aerosol, thus providing an aerosol formation experience that can be optimized or customized. The controller can select the first control temperature or the second control temperature to achieve the desired properties in the formed aerosol.

Similarly, since the first control temperature and the second control temperature of the PTC thermistor can be equal to or greater than the temperature corresponding to the puff intensity threshold in the function relating the temperature of at least one PTC thermistor and the puff intensity, the aerosol generating system comprising at least one PTC thermistor can be configured to change the temperature of at least one PTC thermistor in accordance with such a function, without achieving a stabilized temperature range when a puff occurs, the intensity of which is below the puff intensity threshold.

The method of the present invention may also provide for the possibility of determining and selecting additional control temperatures, such as a third control temperature, a fourth control temperature, a fifth control temperature, a seventh control temperature, an eighth control temperature, a ninth control temperature, a tenth control temperature, or any other control temperature.

Although the methods of the above inventions include the steps of providing a constant voltage, the controller may also be configured to control the power source to use pulse-width modulation or pulse-frequency modulation when the electric current is supplied to at least one PTC thermistor. In such cases, the resulting methods are identical to the methods of the above inventions, except that it is the pulse width or the pulse frequency that is respectively associated with a predetermined control temperature of the at least one PTC thermistor. Therefore, the control temperature of the at least one PTC thermistor can be adjusted by adjusting the pulse width or the pulse frequency of the electric current supplied to the at least one PTC thermistor.

These and other features and advantages of the present invention will become more apparent in light of the following detailed description of preferred embodiments, given by way of illustration only and not limitation, with reference to the accompanying figures:

Fig. 1 shows a temperature/resistance graph of a PTC thermistor contained in a heating element;

Fig. 2 illustrates a longitudinal section of a heater comprising a heater body and a PTC disk;

Fig. 3 shows a longitudinal section of a heater containing a heater body and a PTC tube;

Fig. 4 shows a longitudinal section of a heater containing a heater body and an internal heating element;

Fig. 5 shows a perspective view of the heater body, which in turn contains six flat sections;

Fig. 6 shows a cross-section of the heater body according to Fig. 5;

Fig. 7 shows a plurality of external electrical contacts;

Fig. 8 illustrates a perspective view of a heater comprising a heater housing of Fig. 5 and a plurality of external electrical contacts of Fig. 7;

Fig. 9 shows the temperature of the edge inner wall for four examples of the heater according to Fig. 8;

Fig. 10 shows an aerosol generating system comprising an aerosol generating article and an aerosol generating device which in turn comprises a heater according to Fig. 3;

Fig. 11 shows the aerosol generating system of Fig. 10, in which the aerosol generating article is placed in the cavity of the heater housing;

Fig. 12 illustrates an embodiment of an aerosol generating article;

Fig. 13 shows the process of changing the temperature of the edge inner wall and the temperature of the PTC tube for the heater according to Fig. 3;

Fig. 14 shows the process of changing the temperature of the edge inner wall and the temperature of the PTC disk for the heater according to Fig. 2;

Fig. 15 shows three temperature/resistance graphs of a PTC thermistor contained in a heating element when three different constant voltages are applied to the PTC thermistor.

Fig. 1 shows a graph of temperature T/resistance R of a PTC thermistor contained in the heating element of a heater for heating an aerosol-forming substrate.

The PTC thermistor heats up when an electric current is applied to the PTC thermistor. When the PTC thermistor heats up, the temperature T and the resistance R of the PTC thermistor change according to the function shown in Fig. 1.

In particular, the PTC thermistor can be heated to a temperature TMR, which corresponds to the minimum resistance MR of the PTC thermistor.

When the PTC thermistor is heated to a temperature T below the temperature corresponding to the minimum resistance TMR, the resistance R of the PTC thermistor decreases slightly as the temperature T of the PTC thermistor increases in accordance with the function shown in Fig. 1. In some PTC thermistors, the resistance R of the PTC thermistor remains substantially constant at a resistance slightly greater than the minimum resistance MR of the PTC thermistor until the minimum resistance MR of the PTC thermistor is reached at a temperature corresponding to the minimum resistance TMR.

Similarly, if the PTC thermistor is heated to a temperature T exceeding the temperature corresponding to the minimum resistance TMR, the resistance R of the PTC thermistor increases as the temperature T of the PTC thermistor increases in accordance with the function shown in Fig. 1.

If the PTC thermistor is heated to a temperature higher than the temperature corresponding to twice the minimum resistance TMR, the increase in the resistance of the PTC thermistor with increasing temperature of the PTC thermistor is so significant that the temperature of the PTC thermistor essentially stabilizes at a temperature T corresponding to twice the minimum resistance MR. Such a temperature is usually called the reference temperature CT of the PTC thermistor. In other words, the PTC thermistor has a high positive temperature coefficient α within a stabilized temperature range limited at the lower limit by the reference temperature CT. In dielectric materials, the reference temperature CT may essentially correspond to the Curie temperature of the dielectric material.

Temperatures T significantly higher than the reference temperature CT can be achieved if an electric current is applied to the PTC thermistor for a period of time sufficient to achieve the maximum resistance of the PTC thermistor. However, it should be noted that Fig. 1 shows the resistance R on a logarithmic scale. Therefore, the period of time required to achieve such a maximum resistance is usually significantly longer than the normal operating time of the heater for heating the substrate forming the aerosol. This can ensure effective stabilization of the PTC thermistor at a temperature that slightly exceeds the reference temperature CT.

Fig. 2 illustrates a heater 10 comprising a heater housing 20. The heater body 20 comprises an edge portion 21 extending in the transverse direction between the edge inner wall 210 and the edge outer wall 211. The heater body 20 comprises a lower portion 22 extending in the longitudinal direction between the lower inner wall 220 and the lower outer wall 221. A cavity 23 for accommodating an aerosol-forming substrate extends in the longitudinal direction between the open end 230 of the heater body 20 and the lower inner wall 220, wherein the cavity 23 is limited in the transverse direction by the edge inner wall 210. In the embodiment shown in Fig. 2, the heater comprises a heating element, which is made of a PTC disk 24 located inside the lower portion 22. When an electric current is supplied to the PTC disk 24, the temperature of the PTC disk 24 increases until it reaches the control temperature of the PTC disk 24. If the supply of electric current is maintained after this point, the temperature of the PTC disk 24 is stabilized at a temperature that substantially corresponds to the control temperature of the PTC disk 24. Thus, the marginal inner wall 210 reaches a temperature that may differ slightly from the temperature at which the PTC disk 24 is stabilized. Therefore, when the aerosol-forming substrate is placed in the cavity 23, the aerosol-forming substrate can be heated to the temperature of the marginal inner wall 210, so that an inhalable aerosol is formed.

In Fig. 3, a heater 10 is illustrated, comprising a heater housing 20. The heater housing 20 comprises an edge portion 21 extending in the transverse direction between an edge inner wall 210 and an edge outer wall 211. The heater housing 20 comprises a lower portion 22 extending in the longitudinal direction between a lower inner wall 220 and a lower outer wall 221. A cavity 23 for receiving an aerosol-forming substrate extends in the longitudinal direction between an open end 230 of the heater housing 20 and the lower inner wall 220, wherein the cavity 23 is limited in the transverse direction by the edge inner wall 210. In the embodiment shown in Fig. 3, the heater comprises a heating element which is made of a PTC tube 25 located inside the edge portion 21. When an electric current is supplied to the PTC tube 25, the temperature of the PTC tube 25 increases until it reaches the control temperature of the PTC tube 25. If the supply of electric current is maintained after this point, the temperature of the PTC tube 25 stabilizes at a temperature which substantially corresponds to the control temperature of the PTC tube 25. Thus, the edge inner wall 210 reaches a temperature which substantially corresponds to the control temperature of the PTC tube 25. Therefore, when the aerosol-forming substrate is placed in the cavity 23, the aerosol-forming substrate can be heated to a temperature which substantially corresponds to the control temperature of the PTC tube 25, so that an inhalable aerosol is formed.

In Fig. 4, a heater 10 is illustrated, comprising a heater housing 20. The heater housing 20 comprises an edge portion 21 extending in the transverse direction between an edge inner wall 210 and an edge outer wall 211. The heater housing 20 comprises a lower portion 22 extending in the longitudinal direction between a lower inner wall 220 and a lower outer wall 221. A cavity 23 for receiving an aerosol-forming substrate extends in the longitudinal direction between an open end 230 of the heater housing 20 and the lower inner wall 220, wherein the cavity 23 is limited in the transverse direction by the edge inner wall 210. In the embodiment shown in Fig. 4, the heater comprises a heating element which is formed by a PTC blade 27 extending in a longitudinal direction inside the cavity 23, so that the PTC blade 27 is configured to pierce the aerosol-forming substrate when the substrate is placed in the cavity 23. When an electric current is supplied to the PTC blade 27, the temperature of the PTC blade 27 increases until it reaches a control temperature of the PTC blade 27. If the supply of electric current is maintained after this point, the temperature of the PTC blade 27 stabilizes at a temperature which substantially corresponds to the control temperature of the PTC blade 27. Thus, the PTC blade 27 can be used to heat the aerosol-forming substrate at substantially the control temperature of the PTC blade, so that an inhalable aerosol is formed.

Fig. 5 shows a perspective view of the heater housing 20. The heater housing 20 has an edge portion 21 extending in the transverse direction between the edge inner wall 210 and the edge outer wall 211. The edge outer wall 211 has six flat sections 2110, 2111, 2112, 2113, 2114, 2115 formed in such a way that at least one PTC plate can be located on at least one flat section 2110, 2111, 2112, 2113, 2114, 2115. The PCT plate can be a round plate, a square plate or a polygonal plate. The plates are flat. Fig. 6 shows a cross-section of the heater housing 20 according to Fig. 5. The cavity 23 for accommodating the aerosol-forming substrate extends in the longitudinal direction between the open end 230 and the lower inner wall 220 (not shown in Figs. 5 and 6), wherein the cavity 23 is limited in the transverse direction by the marginal inner wall 210. In the embodiment according to Figs. 5 and 6, the cavity 23 limited by the marginal inner wall 210 is cylindrical, that is, the marginal inner wall 23 has a circular cross-section, as shown in Fig. 5. Such a shape may be convenient for accommodating a cylindrical aerosol-forming substrate.

In a preferred embodiment, the heater body 20 shown in Figs. 5 and 6 is provided with six PTC plates, one on each flat section 2110, 2111, 2112, 2113, 2114, 2115, thus forming the heater 10.

In one embodiment, the heater body 20 comprises an electrically conductive material, such as an electrically conductive metal. In this case, the heater body 20 forms a first electrode configured to be in electrical contact with the six PTC plates.

The heater 10 may also comprise at least one external electrical contact 30 comprising an electrically conductive material, such as an electrically conductive metal, and forming a second electrode configured to be in electrical contact with the six PTC plates. Fig. 7 shows at least one external electrical contact 30 comprising six elongated external electrical contacts 310, 311, 312, 313, 314, 315, each of which is configured to be in electrical contact with a PTC plate located on a flat section 2110, 2111, 2112, 2113, 2114, 2115.

Fig. 8 illustrates a heater 10 comprising a heater housing 20 shown in Fig. 5 and 6 and extended external electrical contacts 310, 311, 312, 313, 314, 315 of Fig. 7. Six PTC plates 260, 261, 262, 263, 264, 265 are provided, one on each flat section 2110, 2111, 2112, 2113, 2114, 2115. The six PTC plates 260, 261, 262, 263, 264, 265 form a heating element of the heater 10. The heater body 20 serves as a first electrode for the PTC plates 260, 261, 262, 263, 264, 265, since the PTC plates 260, 261, 262, 263, 264, 265 are in electrical contact with the flat sections 2110, 2111, 2112, 2113, 2114, 2115 of the heater housing 20. The extended external electrical contacts 310, 311, 312, 313, 314, 315, which are in electrical contact with the PTC plates 260, 261, 262, 263, 264, 265, serve as a second electrode for the PTC plates 260, 261, 262, 263, 264, 265.

When an electric current is applied to the first and second electrodes, the temperature of the PTC plates 260, 261, 262, 263, 264, 265 increases until the control temperature of the PTC plates 260, 261, 262, 263, 264, 265 is reached, as shown in Fig. 1. Thereafter, the temperature of the PTC plates 260, 261, 262, 263, 264, 265 stabilizes substantially at the control temperature of the PTC plates 260, 261, 262, 263, 264, 265 (or at a temperature slightly higher than the control temperature) for periods of time that typically last longer than the operating time of the aerosol generating device. This provides a consistent and predictable heating profile of the aerosol-forming substrate when the substrate is placed in the cavity 23, in which the maximum temperature of each of the PTC plates 260, 261, 262, 263, 264, 265 during the operating time can be determined and controlled by selecting the control temperature of the PTC plates 260, 261, 262, 263, 264, 265. The PTC plates 260, 261, 262, 263, 264, 265 can have the same or different control temperatures.

Fig. 9 shows the temperature of the edge inner wall 210 for four examples of the heater 10 of Fig. 8, in which the control temperature of the six PTC plates 260, 261, 262, 263, 264, 265 is identical.

In the first example CT190, the control temperature of the six PTC plates 260, 261, 262, 263, 264, 265 is 190 degrees Celsius. When the electric current is applied to the first and second electrodes, the six PTC plates 260, 261, 262, 263, 264, 265 reach the control temperature of 190 degrees Celsius in approximately 30 seconds and stabilize at a temperature slightly higher than the control temperature. Heat is transferred through the heater body 20 in such a way that the temperature of the inner wall 210 is substantially the same as the temperature of the six PTC plates 260, 261, 262, 263, 264, 265, that is, slightly higher than 190 degrees Celsius, as shown in Fig. 9. When the aerosol-forming substrate is placed in the cavity 23 after the inner wall 210 has reached a temperature of substantially 190 degrees Celsius, this temperature is successively applied to the aerosol-forming substrate during operation of the heater 10, thereby forming an inhalable aerosol.

In the second example CT200, the control temperature of the six PTC plates 260, 261, 262, 263, 264, 265 is 200 degrees Celsius. When the electric current is supplied to the first and second electrodes, the six PTC plates 260, 261, 262, 263, 264, 265 reach the control temperature of 200 degrees Celsius in approximately 30 seconds and stabilize at a temperature slightly higher than the control temperature. Heat is transferred through the heater body 20 in such a way that the temperature of the inner wall 210 is substantially the same as the temperature of the six PTC plates 260, 261, 262, 263, 264, 265, that is, slightly higher than 200 degrees Celsius, as shown in Fig. 9. When the aerosol-forming substrate is placed in the cavity 23 after the inner wall 210 has reached a temperature of substantially 200 degrees Celsius, this temperature sequentially acts on the aerosol-forming substrate during operation of the heater 10, thereby forming an inhalable aerosol.

In the third example CT210, the control temperature of the six PTC plates 260, 261, 262, 263, 264, 265 is 210 degrees Celsius. When the electric current is supplied to the first and second electrodes, the six PTC plates 260, 261, 262, 263, 264, 265 reach the control temperature of 210 degrees Celsius in approximately 30 seconds and stabilize at a temperature slightly higher than the control temperature. Heat is transferred through the heater body 20 in such a way that the temperature of the inner wall 210 is substantially the same as the temperature of the six PTC plates 260, 261, 262, 263, 264, 265, that is, slightly higher than 210 degrees Celsius, as shown in Fig. 9. When the aerosol-forming substrate is placed in the cavity 23 after the inner wall 210 has reached a temperature of substantially 210 degrees Celsius, this temperature sequentially acts on the aerosol-forming substrate during operation of the heater 10, thereby forming an inhalable aerosol.

In the fourth example CT220, the control temperature of the six PTC plates 260, 261, 262, 263, 264, 265 is 220 degrees Celsius. When the electric current is supplied to the first and second electrodes, the six PTC plates 260, 261, 262, 263, 264, 265 reach the control temperature of 220 degrees Celsius in approximately 30 seconds and stabilize at a temperature slightly higher than the control temperature. Heat is transferred through the heater body 20 in such a way that the temperature of the inner wall 210 is substantially the same as the temperature of the six PTC plates 260, 261, 262, 263, 264, 265, that is, slightly higher than 220 degrees Celsius, as shown in Fig. 9. When the aerosol-forming substrate is placed in the cavity 23 after the inner wall 210 has reached a temperature of substantially 220 degrees Celsius, this temperature is successively applied to the aerosol-forming substrate during operation of the heater 10, thereby forming an inhalable aerosol.

Fig. 10 and 11 show schematic cross-sections of an aerosol generating device 200 and an aerosol generating article 300. The aerosol generating device 200 and the aerosol generating article 300 form an aerosol generating system.

The aerosol generating device 200 comprises a substantially cylindrical device body 202 with a shape and size similar to a traditional cigar.

The aerosol generating device 200 further comprises a power source 206 in the form of a rechargeable nickel-cadmium battery, a PCB (printed circuit board) controller 208 comprising a microprocessor and a memory device, an electrical connector 209 and a heater 10. In the embodiment shown in Figs. 10 and 11, the heater 10 is similar to the heater shown in Fig. 3. However, other heaters may be used. In particular, the heaters shown in Figs. 2, 4 and 8 may be used.

All of the power source 206, controller 208 and heater 10 are located inside the device housing 202. The heater 10 of the aerosol generating device 200 is located at the near end of the device 200. The electrical connector 209 is located at the far end of the device housing 202.

As used herein, the term "proximal" refers to the user side or mouth end of an aerosol-generating device or aerosol-generating article, i.e., the end of the aerosol-generating device or aerosol-generating article that is configured to be closest to the user's mouth during normal use of the aerosol-generating device or aerosol-generating system comprising the aerosol-generating device and the aerosol-generating article. The proximal end of a component of the aerosol-generating device or aerosol-generating article is the end of the component closest to the user end, or mouthpiece end, of the aerosol-generating device or aerosol-generating article. As used herein, the term "distal" refers to the end opposite the proximal end.

The controller 208 is configured to control the supply of power from the power source 206 to the heater 10. The controller 208 further comprises a DC to AC converter comprising a class D power amplifier. The controller 208 is also configured to control the recharging of the power source 206 from the electrical connector 209. The controller 208 further comprises a puff sensor (not shown) configured to detect when the user puffs on the aerosol-generating article located in the cavity 23.

As explained in Fig. 3, the heater 10 comprises a heater body 20. The heater body 20 comprises an edge portion 21 extending in the transverse direction between the edge inner wall 210 and the edge outer wall 211. The heater body 20 comprises a lower portion 22 extending in the longitudinal direction between the lower inner wall 220 and the lower outer wall 221. A cavity 23 for accommodating an aerosol-forming substrate extends in the longitudinal direction between the open end 230 and the lower inner wall 220, wherein the cavity 23 is limited in the transverse direction by the edge inner wall 210. A PTC tube 25 is located inside the edge portion 21 to surround the edge inner wall 210.

The device body 202 also defines an air inlet 280 in close proximity to the distal end of the cavity 23 for containing the aerosol-forming substrate. The air inlet 280 is adapted to provide for drawing in ambient air into the device body 202. Air flow paths (not shown) are defined through the device 200 to provide for drawing in air from the air inlet 280 into the cavity 23.

The aerosol generating article 300 typically has the shape of a cylindrical rod having a diameter similar to the diameter of the marginal inner wall 210. The aerosol generating article 300 comprises a cylindrical cellulose acetate filter rod 304 and a cylindrical aerosol generating segment 310 wrapped together by an outer wrapper 320 made of cigarette paper.

The filter rod 304 is located at the proximal end of the aerosol generating article 300 and forms a mouthpiece of the aerosol generating system on which the user draws to receive the aerosol generated by the system.

The aerosol generating segment 310 is located at the distal end of the aerosol generating article 300 and has a length substantially equal to the length of the cavity 23. Although the aerosol generating segment 310 of Figs. 10 and 11 comprises only one aerosol generating substrate, the aerosol generating segment may equally comprise multiple aerosol generating substrates. When multiple aerosol generating substrates are present, the substrates may be arranged adjacent to each other in the longitudinal direction of the aerosol generating article 300. However, it is contemplated that in other embodiments, a partition may be provided between the aerosol generating substrates. It should be understood that in some embodiments, two or more aerosol generating substrates may be formed from the same materials, while in other embodiments, each of the aerosol generating substrates is different. For example, one or more aerosol-forming substrates may comprise an assembled corrugated sheet of homogenized tobacco material containing a menthol flavoring agent. The one or more aerosol-forming substrates may also contain a menthol flavoring agent and do not contain tobacco material or any other source of nicotine. The one or more aerosol-forming substrates may also contain additional components, such as one or more aerosol-forming agents and water, such that upon heating of the aerosol-forming substrate, an aerosol with the desired organoleptic properties is generated.

The near end of the aerosol generating segment 310 is open because it is not covered by the outer wrapper 320. When the aerosol generating segment 310 contains several aerosol generating substrates, the outer wrapper 320 may contain a line of perforations surrounding the aerosol generating article 300 at the boundary between the aerosol generating substrates. The perforations provide for the drawing of air into the aerosol generating segment 310.

Fig. 12 shows an aerosol generating article 300 similar to the article shown in Figs. 10 and 11. However, the filter rod 304 is a filter assembly 304 in the form of a rod. The filter assembly 304 comprises three segments: a cooling segment 307, a filter segment 309, and a mouth end segment 311. In the embodiment shown in Fig. 12, the cooling segment 307 is located between the second aerosol generating segment 310 and the filter segment 309, so that the cooling segment 307 is adjacent to the aerosol generating segment 310 and the filter segment 309. In other examples, a partition may be provided between the aerosol generating segment 310 and the cooling segment 307 and between the cooling segment 307 and the filter segment 309. The filter segment 309 is located between the cooling segment 307 and the mouth end segment 311. The mouth end segment 311 is located toward the near end of the article 300, adjacent to the filter segment 309. In the embodiment shown in FIG. 12, the filter segment 309 is adjacent to the segment 311 at the mouthpiece end. In one example, the overall length of the filter assembly 304 is from 37 millimeters to 45 millimeters, more preferably, the overall length of the filter assembly 304 is 41 millimeters.

In one example according to the embodiment shown in Fig. 12, the aerosol generating segment 310 has a length of 34 millimeters to 50 millimeters, more preferably the aerosol generating segment 310 has a length of 38 millimeters to 46 millimeters, even more preferably the aerosol generating segment 310 has a length of 42 millimeters.

In one example according to the embodiment shown in Fig. 12, the overall length of the article 300 is from 71 millimeters to 95 millimeters, more preferably the overall length of the article 300 is from 79 millimeters to 87 millimeters, even more preferably the overall length of the article 300 is 83 millimeters.

In one example, the cooling segment 307 is an annular tube and forms an air gap inside the cooling segment 307. The air gap provides a chamber for the passage of heated vaporized components generated from the aerosol generating segment 310. The cooling segment 307 is hollow to provide a chamber for collecting the aerosol, but nevertheless is rigid enough to withstand axial compressive forces and bending moments that may occur during the production and use of the article 300 during insertion into the aerosol generating device 200. In one example, the wall thickness of the cooling segment 307 is approximately 0.29 millimeters.

The cooling segment 307 provides a physical offset between the aerosol generating segment 310 and the filter segment 309. The physical offset provided by the cooling segment 307 will provide a temperature difference along the length of the cooling segment 307. In one example, the cooling segment 307 is adapted to provide a temperature difference of at least 40 degrees Celsius between the heated vaporized component entering the distal end of the cooling segment 307 and the heated vaporized component exiting the near end of the cooling segment 307. In one example, the cooling segment 307 is adapted to provide a temperature difference of at least 60 degrees Celsius between the heated vaporized component entering the distal end of the cooling segment 307 and the heated vaporized component exiting the near end of the cooling segment. 307. This temperature difference along the length of the cooling segment 307 protects the temperature sensitive filter segment 309 from the high temperatures of the aerosol formed from the aerosol generating segment 310.

In one example of the article 300 shown in Fig. 12, the length of the cooling segment 307 is at least 15 millimeters. In one example, the length of the cooling segment 307 is from 20 millimeters to 30 millimeters, more specifically from 23 millimeters to 27 millimeters, more specifically from 25 millimeters to 27 millimeters, and more specifically 25 millimeters.

The cooling segment 307 is made of paper, which means that it consists of a material that does not generate compounds that cause concern. In one example of the article 300 shown in Fig. 12, the cooling segment 307 is made of a spirally wound paper tube, which provides a hollow internal chamber, but at the same time maintains mechanical rigidity. Spiral wound paper tubes are able to meet the strict requirements for dimensional accuracy in high-speed manufacturing processes in terms of length, outer diameter, roundness and straightness of the tube. In another example, the cooling segment 307 is a recess created from a rigid wick or tipping paper. The rigid wick or tipping paper is made to have sufficient rigidity to withstand axial compressive forces and bending moments that can occur during the production and use of the article 300 during insertion into the device 200 generating an aerosol.

For each of the examples of cooling segment 307, the dimensional accuracy of the cooling segment is sufficient to meet the dimensional accuracy requirements of a high-speed manufacturing process.

The filter segment 309 can be formed from any filter material sufficient to remove one or more vaporized compounds from the heated vaporized components from the aerosol generating segment 310. In one example of the article 300 of Fig. 12, the filter segment 309 is made of a monoacetate material, such as cellulose acetate. The filter segment 309 provides cooling and reduces irritation from the heated vaporized components without depleting the amount of heated vaporized components to a level that is unsatisfactory for the user.

The density of the cellulose acetate tow material of the filter segment 309 controls the pressure drop across the filter segment 309, which in turn controls the draw resistance of the article 300. Therefore, the selection of the material of the filter segment 309 is important in controlling the draw resistance of the article 300. In addition, the filter segment performs the filtration function in the article 300.

The presence of the filter segment 309 provides an insulating effect by providing additional cooling for the heated vaporized components that exit the cooling segment 307. This additional cooling effect reduces the contact temperature of the user's lips on the surface of the filter segment 309.

One or more flavors may be added to the filter segment 309 either in the form of direct introduction of flavored liquids into the filter segment 309, or by embedding or placing one or more flavored breakable capsules or other flavor carriers within the cellulose acetate tow of the filter segment 309. In one example of the article 300 shown in Fig. 12, the filter segment 309 has a length of from 6 millimeters to 10 millimeters, more preferably 8 millimeters.

The segment 311 at the mouth end is an annular tube and forms an air gap inside the segment 311 at the mouth end. The air gap provides a chamber for the heated vaporized components that flow from the filter segment 309. The segment 311 at the mouth end is hollow to provide a chamber for collecting the aerosol, but nevertheless is rigid enough to withstand axial compressive forces and bending moments that may occur during production and use of the article during insertion into the device 200 generating an aerosol. In one example, the wall thickness of the segment 311 at the mouth end is approximately 0.29 millimeters.

In one example, the length of segment 311 at the mouthpiece end is from 6 millimeters to 10 millimeters, and more preferably 8 millimeters.

The 311 segment at the mouth end can be made from spirally wound paper tubing, which provides a hollow interior chamber while maintaining critical mechanical rigidity. Spiral wound paper tubing is capable of meeting the stringent dimensional accuracy requirements of high speed manufacturing processes in terms of length, outside diameter, roundness and straightness of the tube.

The segment 311 at the mouth end provides the function of preventing any liquid condensate that accumulates at the outlet of the filter segment 309 from coming into direct contact with the user.

It should be understood that in one example, the mouth end segment 311 and the cooling segment 307 may be formed from a single tube, and the filter segment 309 is located in this tube, separating the mouth end segment 311 and the cooling segment 307.

In the article 300 shown in Fig. 12, the ventilation holes 317 are located in the cooling segment 307 to help cool the article 300. In one example, the ventilation holes 317 provide one or more rows of holes, and preferably each row of holes is located circumferentially around the article 300 in a cross-section that is substantially perpendicular to the longitudinal axis of the article 300.

In one example of the article 300 shown in Fig. 12, one to four rows of ventilation holes 317 are provided to provide ventilation for the article 300. Each row of ventilation holes 317 can have from 12 to 36 ventilation holes 317. The ventilation holes 317 can have, for example, a diameter of 100 to 500 micrometers. In one example, the axial partition between the rows of ventilation holes 317 is from 0.25 millimeters to 0.75 millimeters, more preferably, the axial partition between the rows of ventilation holes 317 is 0.5 millimeters.

In one example of the article 300 shown in Fig. 12, the ventilation holes 317 have the same size. In another example, the ventilation holes 317 differ in size. The ventilation holes 317 can be formed using any suitable technique, such as one or more of the following techniques: laser technology, mechanical perforation of the cooling segment 307, or pre-perforation of the cooling segment 307 before it is formed into the article 300. The ventilation holes 317 are arranged so as to provide effective cooling for the article 300.

In one example of the article 300 shown in Fig. 12, the rows of ventilation holes 317 are located at least at a distance of 11 millimeters from the near end of the article 300, more preferably the ventilation holes 317 are located at a distance of 17 millimeters to 20 millimeters from the near end of the article 300. The location of the ventilation holes 317 is located such that the user does not block the ventilation holes 317 when the article 300 is used.

Advantageously, providing rows of ventilation holes at a distance of 17 millimeters to 20 millimeters from the near end of the article 300 allows the ventilation holes 317 to be located outside the aerosol-generating device 200 when the article 300 is fully inserted into the aerosol-generating device 200. Due to the location of the ventilation holes 317 outside the device 200, unheated air can enter the article 300 through the ventilation holes outside the device 200 to help cool the article 300.

The length of the cooling segment 307 is such that the cooling segment 307 will be partially inserted into the device 200 when the article 300 is completely inserted into the device 200.

In use, when the aerosol-generating article 300 is placed in the cavity 23, the user can puff on the near end of the aerosol-generating article 300 to inhale the aerosol generated by the aerosol-generating system. When the user puffs on the near end of the aerosol-generating article 300, air is drawn into the body 202 of the device at the air inlet 280 and is drawn into the aerosol-generating segment 310 of the aerosol-generating article 300.

In the embodiment shown in Fig. 11 and 12, the controller 208 of the aerosol generating device 200 is configured to supply electric current to the PTC tube 25 located in the edge portion 21 of the heater housing 20. The temperature of the PTC tube 25 increases until it reaches the control temperature of the PTC tube 25. After that, the temperature of the PTC tube 25 stabilizes at a temperature substantially equal to the control temperature of the PTC tube 25 for a period of time that typically exceeds the user session time for the aerosol generating device 200. Therefore, the heating profile of the aerosol-forming substrate contained in the aerosol generating segment 310 of the aerosol generating article 300 located in the cavity 23 can be determined depending on the control temperature of the PTC tube 25.

In the heater shown in Fig. 3 and 10, the temperature of the PTC tube TE is substantially the same as the temperature of the marginal inner wall TI, that is, substantially the same as the temperature that will be applied to the aerosol-forming substrate. This is shown in the graph in Fig. 13. The control temperature of the PTC tube 25 of the heater 10 in Fig. 13 is 200 degrees Celsius, which substantially corresponds to the temperature of the PTC tube TE and the temperature of the marginal inner wall TI after the stabilization time.

In the case of the heater shown in Fig. 8, the temperature of the six PTC plates TE also substantially corresponds to the temperature of the edge inner wall TI. However, in contrast to the example in Fig. 12, the stabilization time may be shorter. In particular, the temperature of the six PTC plates TE and the temperature of the edge inner wall TI may be stabilized at substantially the reference temperature of the six PTC plates after 30 seconds.

Fig. 14 shows a process for changing the temperature of the PTC disk TE and the temperature of the edge inner wall TI over time for the heater 10 of Fig. 2. In this embodiment, it should be understood that the temperature of the edge inner wall TI is lower than the temperature of the PTC disk TE. In particular, for the PTC disk 24 with a control temperature of 220 degrees Celsius, the temperature of the edge inner wall TI stabilizes at 210.

Fig. 15 shows a graph of temperature T/resistance R of a PTC thermistor included in a heating element of a heater for heating a substrate forming an aerosol, when different constant voltages V are applied to the PTC thermistor. In Fig. 15, the first voltage V1 is greater than the second voltage V2, which, in turn, is greater than the third voltage V3. As can be understood from Fig. 15, the control temperature CT of the PTC thermistor depends on the voltage V applied to the PTC thermistor. In particular, the first voltage V1 results in a first control temperature CT1, the second voltage V2 results in a second control temperature CT2, and the third voltage V3 results in a third control temperature CT3, so that the first control temperature CT1 is greater than the second control temperature CT2, which, in turn, is greater than the third control temperature CT3.

The controller may control the power source to supply electric current to the PTC thermistor having a first voltage V1, a second voltage V2, a third voltage V3 or any other suitable voltage. Therefore, the control temperature of the PTC thermistor will be adjusted to the first control temperature CT1, the second control temperature CT2, the third control temperature CT3 or any other suitable temperature. The relationship between the supplied voltage V and the control temperature CT for a particular PTC thermistor may be stored in the controller; in a preferred embodiment, such a relationship may be stored in a memory device contained in the controller. Similarly, the first control temperature CT1, the second control temperature CT2, the third control temperature CT3 or any other suitable temperature may be determined so that they correspond to the required maximum operating temperatures for one or more aerosol-forming substrates. The controller may also store one or more maximum operating temperatures for a given aerosol-forming substrate; In a preferred embodiment, such maximum operating temperatures may be stored in a memory device contained in the controller.

In this way, the PTC thermistor of the aerosol generating system can be substantially stabilized at a maximum operating temperature that is determined by the controller for a given aerosol generating substrate. The temperatures at which the PTC thermistor is stabilized are substantially the same as the temperature applied to the aerosol generating substrate, or sufficiently close to it, when the aerosol generating system is used to heat the aerosol generating substrate, as explained for the heaters of the above embodiments. Therefore, the temperatures at which the PTC thermistor is stabilized can be selected to optimize aerosol generation. This can be useful for providing an optimized aerosol generation experience.

Claims (29)

1. A heater for heating an aerosol-forming substrate, wherein the heater comprises a heating element configured to heat the aerosol-forming substrate, the heating element comprises at least one positive temperature coefficient (PTC) thermistor, and said at least one PTC thermistor is configured to supply an electric current to it to heat said at least one PTC thermistor, wherein the resistance of said at least one PTC thermistor increases when the temperature of said at least one PTC thermistor increases within a stabilized temperature range, wherein, when a constant voltage is applied to said at least one PTC thermistor, the lower limit of the stabilized temperature range is a control temperature at which the resistance of said at least one PTC thermistor is twice the value of the minimum resistance of said at least one PTC thermistor, and wherein the control temperature is from 100 degrees Celsius to 350 degrees Celsius, when a constant voltage of 3.3 volts is applied to said at least one PTC thermistor. 2. A heater according to any one of the preceding claims, wherein the control temperature is from 200 degrees Celsius to 250 degrees Celsius when a direct voltage of 3.3 volts is applied to said at least one PTC thermistor. 3. A heater according to any of the preceding claims, wherein the heating element is configured to be inserted into an aerosol-forming substrate. 4. A heater according to any of the preceding claims, wherein the heating element is configured to heat the outer surface of the aerosol-forming substrate. 5. A heater according to any of the preceding paragraphs, wherein the heater further comprises a cavity for accommodating an aerosol-forming substrate, and the heater is configured to heat the aerosol-forming substrate when the aerosol-forming substrate is placed in the cavity. 6. A heater according to claim 5, wherein the heater comprises a heater body, wherein the heater body comprises an edge portion extending in the transverse direction between the edge inner wall and the edge outer wall, and a lower portion extending in the longitudinal direction between the lower inner wall and the lower outer wall, wherein the cavity for accommodating the aerosol-forming substrate extends in the longitudinal direction between the open end and the lower inner wall, and the cavity is limited in the transverse direction by the edge inner wall. 7. The heater according to claim 6, wherein said at least one PTC thermistor comprises a PTC disk located in the lower part. 8. A heater according to any one of claims 6, 7, wherein said at least one PTC thermistor comprises a PTC tube located inside the edge portion to surround the edge inner wall. 9. A heater according to any one of claims 6, 7, wherein the peripheral outer wall comprises at least three flat sections, and wherein said at least one PTC thermistor comprises at least one PTC plate located on at least one of said at least three flat sections. 10. A heater according to any one of the preceding claims, wherein said at least one PTC thermistor comprises a ceramic semiconductor such as barium titanate. 11. A heater according to any one of the preceding claims, wherein said at least one PTC thermistor comprises a polymeric material. 12. An aerosol generating device comprising: - a heater according to any of the preceding paragraphs, - the device body; and - a power source electrically connected to the heating element for supplying electric current to said at least one PTC thermistor. 13. An aerosol generating system comprising: - an aerosol-generating article containing an aerosol-forming substrate; - an aerosol generating device according to paragraph 12. 14. A method for operating an aerosol generating system according to claim 13, wherein the method comprises the steps of: - determining the maximum operating temperature for an aerosol-forming substrate contained in an aerosol-generating product; - supplying an electric current to said at least one PTC thermistor by means of a power source, wherein the electric current has a constant voltage, so that the resistance of said at least one PTC thermistor increases when the temperature of said at least one PTC thermistor increases within a stabilized temperature range, wherein the lower limit of the stabilized temperature range is a reference temperature at which the resistance of said at least one PTC thermistor is twice the value of the minimum resistance of said at least one PTC thermistor, and the constant voltage is such that the reference temperature of the PTC thermistor is essentially the maximum operating temperature for the aerosol-forming substrate. 15. A method for operating an aerosol generating system according to claim 13, wherein the method comprises the steps of: - measuring the puff intensity when a puff is taken during use of an aerosol generating system; - determining a puff intensity threshold such that when the puff intensity is equal to or exceeds the puff intensity threshold, the method includes additional steps: - determining a first maximum operating temperature and a second maximum operating temperature for an aerosol-forming substrate contained in an aerosol-generating article; - selection of the first maximum operating temperature or the second maximum operating temperature; - if a first maximum operating temperature of supplying an electric current to said at least one PTC thermistor by means of a power source is selected, wherein the electric current has a first constant voltage, so that the resistance of said at least one PTC thermistor increases when the temperature of said at least one PTC thermistor increases within a stabilized temperature range, wherein the lower limit of the stabilized temperature range is a reference temperature at which the resistance of said at least one PTC thermistor is twice the value of the minimum resistance of the at least one PTC thermistor, and the first constant voltage is such that the reference temperature of the PTC thermistor is essentially the first maximum operating temperature for the aerosol-forming substrate; - if a second maximum operating temperature of supplying an electric current to said at least one PTC thermistor by means of a power source is selected, wherein the electric current has a second constant voltage, so that the resistance of said at least one PTC thermistor increases when the temperature of said at least one PTC thermistor increases within a stabilized temperature range, wherein the lower limit of the stabilized temperature range is a reference temperature at which the resistance of at least one PTC thermistor is twice the value of the minimum resistance of at least one PTC thermistor, and the second constant voltage is such that the reference temperature of the PTC thermistor is essentially the second maximum operating temperature for the aerosol-forming substrate.

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