Heater assembly with measurement contact

Abstract

A heater assembly for an aerosol-generating system, comprising: an electrical heating element for heating a liquid aerosol-forming substrate to form an aerosol; a porous body for supplying the liquid aerosol-forming substrate to the electrical heating element, the electrical heating element being arranged along a porous outer surface of the porous body; a protective layer arranged to extend across at least a portion of the electrical heating element to protect the electrical heating element; and a measurement contact arranged to allow an electrical parameter of the heater assembly to be measured to detect whether a sufficient amount of liquid aerosol-forming substrate is supplied to the electrical heating element.

Description

Technical Field

[0001] The present disclosure relates to a heater assembly for an aerosol-generating system. In particular but not exclusively, the present disclosure relates to a heater assembly for a handheld electrically-operated aerosol-generating system, the heater assembly being configured to heat an aerosol-forming substrate to generate an aerosol and to deliver the aerosol to a user's mouth. The present disclosure also relates to a cartridge and an aerosol-generating system including the heater assembly, and also to a method of operating the heater assembly. Background Art

[0002] Aerosol-generating systems that heat a liquid aerosol-forming substrate to generate an aerosol for delivery to a user are generally known in the art. These systems typically include an aerosol-generating device and a replaceable cartridge. The cartridge includes a liquid aerosol-forming substrate that is capable of releasing volatile compounds upon heating. The cartridge typically includes a heater for heating the liquid aerosol-forming substrate. In known aerosol-generating systems, the heater includes a resistive heating element wound around a core that supplies the liquid aerosol-forming substrate to the heating element. The aerosol-generating device or the cartridge also includes a mouthpiece. When a negative pressure is applied at the mouthpiece, an electric current passes through the heating element, causing it to be heated by resistive heating or Joule heating, and the heating element in turn heats the liquid aerosol-forming substrate supplied by the core. This causes volatile compounds to be released from the liquid aerosol-forming substrate, and the volatile compounds cool to form an aerosol. The aerosol is then drawn into the user's mouth via the mouthpiece.

[0003] Such known aerosol-generating systems have a number of disadvantages. For example, they may be difficult to manufacture with consistent manufacturing tolerances, which may result in inconsistent vapor production and flavor generation. Inconsistent manufacturing tolerances may also affect the heat transfer from the heating element to the core, thereby reducing the energy efficiency of such devices. Another problem encountered by such known aerosol-generating systems is "dry heating" or "dry puffing", which occurs when the heating element is heated in the absence of an adequate supply of liquid aerosol-forming substrate to the heating element. For example, this may occur when the user has consumed all of the liquid aerosol-forming substrate in the cartridge such that the cartridge is depleted of the liquid aerosol-forming substrate and needs to be replaced. During operation, it is preferred to maintain the supply of liquid aerosol-forming substrate to the heating element such that the heating element remains in a wet state, as this helps to ensure that a satisfactory aerosol is generated when a negative pressure is applied at the mouthpiece. Dry heating may cause overheating of the heating element and potentially thermal decomposition of the liquid aerosol-forming substrate, which may produce undesirable by-products and an unsatisfactory aerosol. Allowing the aerosol-generating system to continue operating when no liquid aerosol-forming substrate is supplied to the heating element may result in a poor user experience.

[0004] A known aerosol - generating system has a ceramic body and a heating element, and electricity is supplied to the heating element through electrical contacts. The ceramic body has a coating or protective layer on a single surface. Liquid is supplied from a liquid reservoir to the heating element via pores within the ceramic body. This known aerosol - generating system can also experience "dry heating" or "dry puffing" situations and thus has associated drawbacks, namely undesirable by - products, unsatisfactory aerosols, and a poor user experience.

[0005] There is a desire to provide a more energy - efficient heater assembly that can generate a more consistent aerosol. There is a desire to provide a heater assembly that reduces the likelihood of a user experiencing dry heating or dry puffing and that limits the ability of the user to continue using the aerosol - generating system when no liquid aerosol - forming substrate is supplied to the heating element. Summary of the Invention

[0006] According to an example of the present disclosure, there is provided a heater assembly for an aerosol - generating system. The heater assembly may include an electrical heating element for heating a liquid aerosol - forming substrate to form an aerosol. The heater assembly may include a porous body for supplying the liquid aerosol - forming substrate to the electrical heating element. The heater assembly may include an electrical heating element. The electrical heating element may be arranged along a porous outer surface of the porous body. The porous outer surface on which the electrical heating element is provided may be substantially flat. The electrical heating element may at least partially extend into the pores of the porous outer surface. The heater assembly may include a protective layer. The protective layer may be arranged to extend across at least a portion of the electrical heating element to protect the electrical heating element. The heater assembly may include measurement contacts arranged to allow measurement of electrical parameters of the heater assembly to detect whether a sufficient amount of liquid aerosol - forming substrate is supplied to the electrical heating element.

[0007] According to an example of the present disclosure, there is provided a heater assembly for an aerosol - generating system. The heater assembly includes an electrical heating element for heating a liquid aerosol - forming substrate to form an aerosol. The heater assembly includes a porous body for supplying the liquid aerosol - forming substrate to the electrical heating element. The heater assembly includes an electrical heating element arranged along a porous outer surface of the porous body. The heater assembly includes a protective layer arranged to extend across at least a portion of the electrical heating element to protect the electrical heating element. The heater assembly includes measurement contacts arranged to allow measurement of electrical parameters of the heater assembly to detect whether a sufficient amount of liquid aerosol - forming substrate is supplied to the electrical heating element.

[0008] With this arrangement, the presence, absence or amount of liquid can be accurately measured despite the presence of the protective layer. This reduces the likelihood of dry heating events. When the protective layer is present, it is extremely difficult to measure the change in resistance of the electrically heated element. The advantage of the claimed arrangement is that the resistance across the heating assembly can be accurately measured during heating to detect the presence, absence or amount of liquid, and the temperature of the electrically heated element can be controlled to avoid dry heating situations.

[0009] Advantageously, the heater assembly allows the aerosol generating system to detect and control the occurrence of overheating or dry heating situations. By measuring electrical parameters using measurement contacts, overheating or dry heating situations can be detected, and if overheating or dry heating situations are prevented, the likelihood of generating unwanted by-products and the user receiving a poor user experience can be reduced. By measuring electrical parameters using measurement contacts, it can be determined when the liquid level is below a predetermined value and is thus approaching an overheating or dry heating situation.

[0010] As used herein, the term "aerosol generating device" relates to a device that interacts with a liquid aerosol-forming substrate to generate an aerosol.

[0011] As used herein, the term "aerosol generating cartridge" relates to a component that interacts with a liquid aerosol generating device to generate an aerosol. The aerosol generating cartridge contains or is configured to contain a liquid aerosol-forming substrate.

[0012] As used herein, the term "liquid aerosol-forming substrate" relates to a liquid substrate capable of releasing volatile compounds that can form an aerosol. Such volatile compounds can be released by heating the aerosol-forming substrate.

[0013] As used herein, the term "electrically heated element" refers to a component that transfers thermal energy to a liquid aerosol-forming substrate. It should be understood that the electrically heated element can be directly deposited on a porous body.

[0014] As used herein, the term "electrical parameter" refers to an electrical property or characteristic, including but not limited to voltage or potential difference, current or resistance. Electrical parameters can be monitored by directly measuring a parameter such as voltage, or can be determined indirectly from another or more electrical parameters. For example, resistance can be determined using Ohm's law by first determining the voltage across a component and the current through the component and dividing the voltage by the current.

[0015] As used herein, the term "porous body" refers to a component having a plurality of pores, at least some of which are interconnected. The porous body is configured to contain liquid within the plurality of pores.

[0016] As used herein, the term "protective layer" refers to a component configured to protect an electroheating element. Specifically, the protective layer is configured to extend the life of the electroheating element.

[0017] As used herein, the term "sufficient" when used in the phrase "sufficient amount of liquid aerosol-forming substrate" refers to the amount of aerosol-forming substrate that prevents dry heating or dry puffing conditions when present at the electroheating element.

[0018] The liquid aerosol-forming substrate can be liquid at room temperature. The liquid aerosol-forming substrate can include both liquid and solid components. The liquid aerosol-forming substrate can include nicotine. The nicotine-containing liquid aerosol-forming substrate can be a nicotine salt substrate. The liquid aerosol-forming substrate can include plant-based materials. The liquid aerosol-forming substrate can include tobacco. The liquid aerosol-forming substrate can include tobacco-containing materials that contain volatile tobacco flavor compounds that are released from the aerosol-forming substrate upon heating. The liquid aerosol-forming substrate can include homogenized tobacco materials. The liquid aerosol-forming substrate can include tobacco-free materials. The liquid aerosol-forming substrate can include homogenized plant-based materials.

[0019] The liquid aerosol-forming substrate can include one or more aerosol formers. An aerosol former is any suitable known compound or mixture of compounds that promotes the formation of a dense and stable aerosol during use and is substantially heat-resistant to degradation at the operating temperature of the system. Examples of suitable aerosol formers include glycerol and propylene glycol. Suitable aerosol formers are well known in the art and include, but are not limited to: polyols such as triethylene glycol, 1,3-butanediol, and glycerol; esters of polyols such as glycerol mono-, di-, or triacetate; and aliphatic esters of mono-, di-, or polycarboxylic acids such as dimethyl dodecanedioate and dimethyl tetradecanedioate. The liquid aerosol-forming substrate can include water, solvents, ethanol, plant extracts, and natural or artificial flavors.

[0020] The liquid aerosol-forming substrate can include nicotine and at least one aerosol former. The aerosol former can be glycerol or propylene glycol. The aerosol former can include both glycerol and propylene glycol. The liquid aerosol-forming substrate can have a nicotine concentration between about 0.5% and about 10%, for example about 2%.

[0021] The electrical parameter can be the electrical parameter of the protective layer. The measurement contacts can be disposed on opposite sides of the surface of the protective layer on the surface of the protective layer. The measurement contacts can be disposed on opposite sides of the surface of the protective layer such that the measurement contacts can measure the electrical parameter across the protective layer. The protective layer has a thickness, a width, and a length. The thickness can be less than the width or the length. The measurement contacts can be spaced apart from each other in a direction orthogonal to the thickness. This has the advantage of accurately allowing determination of the presence or absence of liquid at the protective layer.

[0022] The electrical parameter can be the electrical parameter of the porous body. The measurement contacts can be disposed on opposite surfaces of the porous body. This is a particularly advantageous arrangement in which the likelihood of a dry heating event is reduced. The heater assembly can be configured such that the liquid aerosol-forming substrate travels from the non-heated surface of the porous body to the heated surface of the porous body. There may be a situation where the liquid aerosol-forming substrate is present at the heated surface of the porous body but not within the porous body. In such a case, measurement of the electrical parameter of the porous body can be used to identify and pre-empt a dry heating event. By measuring the electrical parameter of the porous body, the likelihood of a dry heating event is reduced.

[0023] The measurement contacts can be disposed on opposite sides of the surface of the porous body such that the measurement contacts can measure the electrical parameter across the porous body. The measurement contacts can be disposed on the surface of the porous body. The measurement contacts can be disposed on opposite sides of the surface of the porous body such that the measurement contacts can measure the electrical parameter across the porous body.

[0024] The measurement contacts can be spaced apart from each other in a direction aligned with or parallel to the outer surface of the porous body. The porous body can have a liquid absorption side and an aerosolization side. The measurement contacts can be arranged on the aerosolization side of the porous body.

[0025] The electrical parameter can indicate resistance.

[0026] The electrical parameter can be used to determine whether the porous body or the protective layer is being supplied with a sufficient amount of the liquid aerosol-forming substrate. The value of the electrical parameter can be stored in a memory of the aerosol generation system. By comparing the electrical parameter with one or more values stored in the memory, the aerosol generation system can determine whether the electrical heating element is being supplied with a sufficient amount of the liquid aerosol-forming substrate.

[0027] The electric heating element can be electrically connected to the electrical contact. The electric heating element can be configured to heat the liquid aerosol-forming substrate when a potential difference is applied to the electrical contact. The electric heating element can be one or more of the following: a curved shape or a serpentine shape. The electric heating element can include a resistive heating element. The electric heating element can be made of any suitable electrically conductive material. Suitable materials include, but are not limited to: semiconductors (such as doped ceramics), "electrically conductive" ceramics (such as molybdenum disilicide), carbon, graphite, metals, metal alloys, and composite materials made of ceramic materials and metal materials. Such composite materials can include doped or undoped ceramics. Examples of suitable doped ceramics include doped silicon carbide. Examples of suitable metals include titanium, zirconium, tantalum, and platinum group metals. Examples of suitable metal alloys include stainless steel; constantan; nickel-containing alloys, cobalt-containing alloys, chromium-containing alloys, aluminum-containing alloys, titanium-containing alloys, zirconium-containing alloys, hafnium-containing alloys, niobium-containing alloys, molybdenum-containing alloys, tantalum-containing alloys, tungsten-containing alloys, tin-containing alloys, gallium-containing alloys, manganese-containing alloys, and iron-containing alloys; and nickel-, iron-, cobalt-based superalloys; stainless steel, iron-aluminum-based alloys, and iron-manganese-aluminum-based alloys. is a registered trademark of Titanium Metals Corporation. The electric heating element can be made of stainless steel, such as 300 series stainless steel, such as AISI 304, 316, 304L, 316L.

[0028] Additionally, the electric heating element can include a combination of the above materials. The combination of materials can be used to improve the control of the resistance of the electric heating element. For example, a material with a high intrinsic resistance can be combined with a material with a low intrinsic resistance. This can be advantageous if one of the materials is more favorable in other aspects, such as price, processability, or other physical and chemical parameters. Advantageously, high resistivity heating allows for more efficient use of battery energy.

[0029] According to an example of the present disclosure, a cartridge for an aerosol generating system is provided. The cartridge can include a heater assembly. The cartridge can include a liquid storage portion configured to hold a liquid aerosol-forming substrate. The liquid storage portion can be disposed on a side of the heater assembly opposite to the porous outer surface.

[0030] According to an example of the present disclosure, a cartridge for an aerosol generating system is provided. The cartridge includes a heater assembly. The cartridge includes a liquid storage portion configured to hold a liquid aerosol-forming substrate. The liquid storage portion is disposed on a side of the heater assembly opposite to the porous outer surface.

[0031] According to an example of the present disclosure, an aerosol - generating system is provided. The aerosol - generating system may include a cartridge. The aerosol - generating system may include a power source for supplying power to an electrically - heated element. The aerosol - generating system may include a control circuitry configured to control the power supply from the power source to the electrically - heated element. The control circuitry may also be configured to receive a signal from a measurement contact and determine based on the signal whether a liquid aerosol - forming substrate is supplied to the electrically - heated element.

[0032] According to an example of the present disclosure, an aerosol - generating system is provided. The aerosol - generating system includes a cartridge. The aerosol - generating system includes a power source for supplying power to an electrically - heated element. The aerosol - generating system includes a control circuitry configured to control the power supply from the power source to the electrically - heated element. The control circuitry is also configured to receive a signal from a measurement contact and determine based on the signal whether a liquid aerosol - forming substrate is supplied to the electrically - heated element.

[0033] The electrical parameter may be greater than a maximum threshold or less than a minimum threshold, indicating that the liquid aerosol - forming substrate supplied to the electrically - heated element is below a threshold amount. The maximum threshold may be a maximum threshold indicating resistance. Based on a 7 - mm distance between a glycerol aerosol - forming substrate and the measurement contact, the maximum threshold may relate to a maximum threshold resistance value of 7×10 7 ohms. Based on a 7 - mm distance between a glycerol aerosol - forming substrate and the measurement contact, the maximum threshold may be 7×10 7 ohms of maximum threshold resistance value. The minimum threshold may be a minimum threshold indicating conductance. The minimum threshold may relate to a minimum threshold conductance value of (1 / 7)×10 -7 siemens. The minimum threshold may be (1 / 7)×10 -7 siemens - ohm of minimum threshold conductance value.

[0034] The controller may be configured to prevent power supply to the electrically - heated element if the liquid aerosol - forming substrate is not supplied to the electrically - heated element or if the liquid aerosol - forming substrate in the electrically - heated element is below a threshold amount.

[0035] According to an example of the present disclosure, a method of controlling heating in an aerosol - generating system including a heater assembly is provided. The heater assembly may include an electrically - heated element for heating a liquid aerosol - forming substrate to form an aerosol. The heater assembly may include a porous body for supplying the liquid aerosol - forming substrate to the electrically - heated element. The electrically - heated element may be arranged along a porous outer surface of the porous body. A protective layer may be arranged to extend across at least a portion of the electrically - heated element to protect the electrically - heated element. The heater assembly may include measurement contacts arranged to allow measurement of electrical parameters of the heater assembly to detect whether a sufficient amount of the liquid aerosol - forming substrate is supplied to the electrically - heated element. The method may include measuring the electrical parameters of the heater assembly between the measurement contacts to detect whether the liquid aerosol - forming substrate is supplied to the electrically - heated element.

[0036] According to an example of the present disclosure, a method of controlling heating in an aerosol - generating system including a heater assembly is provided. The heater assembly includes an electrically - heated element for heating a liquid aerosol - forming substrate to form an aerosol. The heater assembly includes a porous body for supplying the liquid aerosol - forming substrate to the electrically - heated element. The electrically - heated element is arranged along a porous outer surface of the porous body. A protective layer is arranged to extend across at least a portion of the electrically - heated element to protect the electrically - heated element. The heater assembly includes measurement contacts arranged to allow measurement of electrical parameters of the heater assembly to detect whether a sufficient amount of the liquid aerosol - forming substrate is supplied to the electrically - heated element. The method includes measuring the electrical parameters of the heater assembly between the measurement contacts to detect whether the liquid aerosol - forming substrate is supplied to the electrically - heated element.

[0037] A sufficient amount of the liquid aerosol - forming substrate may be an amount that provides an electrical connection between the measurement contacts. This electrical connection may be made without a short - circuit, i.e., the aerosol - forming substrate may form a current path between the measurement contacts. A sufficient amount of the liquid aerosol - forming substrate in the porous body may be an amount that produces sufficient aerosol to allow the user to inhale at least once. Preferably, a sufficient amount of the liquid aerosol - forming substrate in the porous body is an amount that produces sufficient aerosol to allow the user to inhale at least five times. A sufficient amount of the liquid aerosol - forming substrate in the porous body may be between 0.3 mg and 32.5 mg, preferably between 1.5 mg and 32.5 mg. A sufficient amount of the liquid aerosol - forming substrate in the porous body may be at least 20 mg, preferably at least 30 mg. A sufficient amount of the liquid aerosol - forming substrate in the porous body may be 32.5 mg. A sufficient amount of the liquid aerosol - forming substrate on the protective layer may be an amount that produces sufficient aerosol to allow the user to inhale once. A sufficient amount of the liquid aerosol - forming substrate on the protective layer may be between 0.3 mg and 15 mg, preferably between 10 mg and 15 mg. A sufficient amount of the liquid aerosol - forming substrate on the protective layer may be at least 1 mg, preferably at least 5 mg, more preferably at least 10 mg.

[0038] The method may include determining an indication of one or more of the following based on the measured value of the electrical parameter: absence of a liquid aerosol-forming substrate, presence of a liquid aerosol-forming substrate, amount of the liquid aerosol-forming substrate.

[0039] The method may include preventing power supply to the electrical heating element when it is determined that the amount of the liquid aerosol-forming substrate in the porous body is small.

[0040] The method may include preventing power supply to the electrical heating element when it is detected that there is no liquid aerosol-forming substrate in the porous body.

[0041] The porous body may have a very high resistance when dry. The porous body may have a liquid absorption side and an aerosolization side. The electrical heating element may be disposed along the aerosolization side of the porous body. The porous body may be configured to supply a liquid aerosol-forming substrate from the liquid absorption side of the porous body to the aerosolization side. The porous body may be a ceramic body. The porous body may be an open porous body, i.e., may include a plurality of interconnected open pores. The porous body may define a series of capillary tubes. The porous body may have been manufactured by sintering. The porous body may have been manufactured by directly sintering ceramic powder to form a porous body with pores between interconnected powder particles. The porous body may have been manufactured by using a sacrificial material within the ceramic powder, and the sacrificial material serves as a spacer to form pores. The sacrificial material may have been burned out during sintering.

[0042] The protective layer may have a very high resistance when dry. The protective layer may include or consist of an inorganic material. The protective layer may be arranged to substantially cover the porous body. The protective layer may have a conductivity of at most 1×10 -11 Siemens / cm. The protective layer may have a conductivity of at most 1×10 -14 Siemens / cm. The protective layer may have a conductivity of 1×10 -14 Siemens / cm. The protective layer may have a conductivity of at most 1×10 -12 Siemens / cm. The protective layer may have a conductivity of 1×10 -12 Siemens / cm.

[0043] The aerosol generating system may be portable. The aerosol generating system may have a size comparable to that of a conventional cigar or cigarette.

[0044] An aerosol generating device may comprise a control circuitry. The control circuitry may include any suitable controller or electrical component. The controller may include a memory. Information for performing the above method may be stored in the memory. The control circuitry may include a microprocessor. The microprocessor may be a programmable microprocessor, a microcontroller or an application specific integrated circuit (ASIC) or other electronic circuitry capable of providing control. The control circuitry may be configured to continuously supply power to the electrical heating element after activation of the device, or may be configured to supply power intermittently, such as on a puff-by-puff basis. The power may be supplied to the electrical heating element in the form of current pulses, for example by means of pulse width modulation (PWM). The control circuitry may include additional electronic components. For example, in some embodiments, the control circuitry may include any of a sensor, a switch, a display element.

[0045] The aerosol generating device may comprise a power source in the form of a battery. The battery may be rechargeable. The battery may be a lithium-based battery, such as lithium cobalt, lithium iron phosphate, lithium titanate or lithium polymer battery. The battery may be a nickel metal hydride battery or a nickel cadmium battery. The power source may be another form of charge storage device, such as a capacitor. The power source may be rechargeable and configured for a number of charge and discharge cycles. The power source may have a capacity that allows storage of sufficient energy for one or more user experiences of the aerosol generating system; for example, the power source may have sufficient capacity to allow continuous generation of aerosol for a period of about six minutes (corresponding to the typical time taken to smoke a conventional cigarette), or for a period that is a multiple of six minutes. In another example, the power source may have sufficient capacity to allow a predetermined number of puffs or discontinuous activation of the aerosol generating system.

[0046] The aerosol generating device may include a housing. The housing may be elongated. The housing may include any suitable material or combination of materials. Examples of suitable materials include metals, alloys, plastics or composite materials containing one or more of those materials, or thermoplastics suitable for food or pharmaceutical applications, such as polypropylene, polyetheretherketone (PEEK) and polyethylene. Preferably, the material is lightweight and non-brittle.

[0047] The cartridge may be releasably coupled to the aerosol generating device.

[0048] The cartridge of the aerosol generating system may have a connection end. At the connection end, the cartridge may be connected or connectable to the aerosol generating device. The connection end of the cartridge may have electrical contacts that may be electrically connected to electrical contacts on the aerosol generating device. The cartridge may include one or more of the following: a mouthpiece, a cartridge body, an external air inlet, an internal air passage and an aerosol outlet.

[0049] The mouthpiece can be connected to or connectable to the cartridge body. The mouthpiece can be connected to or connectable to the cartridge body so as to define one or more external air inlets between the mouthpiece and the cartridge body. The mouthpiece can be disposed at one end of the cartridge body. The mouthpiece can be disposed at an end of the cartridge body opposite to the connection end. The mouthpiece can include an aerosol outlet.

[0050] The cartridge body can include a heater assembly. The cartridge body can include a liquid storage portion. The heater assembly can be disposed adjacent to or at the connection end. The liquid storage portion can be disposed between the heater assembly and the mouthpiece.

[0051] The liquid storage portion can be disposed at a first side of the heater assembly. An air flow channel can be disposed at a side of the heater assembly opposite to the first side. The air flow channel can be adjacent to the electrical heating element. The air flow path can extend through the electrical heating element. The air flow path can be configured to convey the aerosol. The cartridge body can be configured such that the air flow passing through the heater assembly entrains the evaporated aerosol to form a matrix. The cartridge can be configured such that air can flow from outside the system through the external air inlet and flow within the cartridge body. The cartridge can be configured such that the air can then flow towards the connection end. At the connection end, the air can be guided to return by itself to flow through the center of the cartridge. In doing so, the air flow can pass through the heater assembly. At the heater assembly, the air can be combined with the aerosol. The cartridge can be configured such that after being combined with the aerosol, the air flow passes through the center of the cartridge to reach the mouthpiece. The air flow can then flow out of the aerosol outlet hole.

[0052] The mouthpiece can include an internal baffle. The internal baffle can be integrally molded with the outer wall of the mouthpiece portion. The baffle can ensure that when air is drawn from the inlet to the aerosol outlet hole, the air flows above the heater assembly on the cartridge, where the aerosol forming matrix is evaporating. When the air passes through the heater assembly, the evaporated matrix can be entrained in the air flow and can be cooled to form an aerosol before leaving the aerosol outlet hole.

[0053] Features described with respect to one of the above examples can equally apply to other examples of the present disclosure.

[0054] The present invention is defined in the claims. However, a non-exhaustive list of non-limiting examples is provided below. Any one or more features of these examples can be combined with any one or more features of another example, embodiment, or aspect described herein.

[0055] Example Ex1: A heater assembly for an aerosol generating system, comprising:

[0056] an electrical heating element for heating a liquid aerosol forming matrix to form an aerosol;

[0057] A porous body for supplying the liquid aerosol-forming substrate to the electroheating element, the electroheating element being arranged along the porous outer surface of the porous body; and

[0058] A protective layer arranged to extend across at least a portion of the electroheating element to protect the electroheating element.

[0059] Example Ex2: The heater assembly according to Example Ex1 further includes measurement contacts arranged to allow measurement of the electrical parameters of the heater assembly to detect whether a sufficient amount of the liquid aerosol-forming substrate is supplied to the electroheating element.

[0060] Example Ex3: The heater assembly according to Example Ex1 or Ex2, wherein the protective layer comprises an inorganic material.

[0061] Example Ex4: The heater assembly according to any one of Examples Ex1 to Ex3, wherein the protective layer has a conductivity of at most 1×10 -11 Siemens per centimeter.

[0062] Example Ex5: The heater assembly according to any one of Examples Ex1 to Ex4, wherein the protective layer has a conductivity of at most 1×10 -12 Siemens per centimeter.

[0063] Example Ex6: The heater assembly according to any one of Examples Ex2 to Ex5, wherein the electrical parameter is the electrical parameter of the protective layer.

[0064] Example Ex7: The heater assembly according to any one of Examples Ex2 to Ex6, wherein the measurement contacts are provided on opposite sides of the surface of the protective layer such that the measurement contacts can measure the electrical parameter across the protective layer.

[0065] Example Ex8: The heater assembly according to any one of Examples Ex2 to Ex7, wherein the electrical parameter is the electrical parameter of the porous body.

[0066] Example Ex9: The heater assembly according to any one of Examples Ex1 to Ex8, wherein the protective layer has a conductivity of at most 1×10 -12 Siemens per centimeter.

[0067] Example Ex10: The heater assembly according to any one of Examples Ex1 to Ex9, wherein the protective layer has a conductivity of at most 1×10 -14 Siemens per centimeter.

[0068] Example Ex11: The heater assembly according to any one of Examples Ex1 to Ex10, wherein the porous body comprises a sintered ceramic material.

[0069] Example Ex12: A heater assembly according to any one of Examples Ex2 to Ex11, wherein the measurement contacts are provided on opposite surfaces of the porous body such that the measurement contacts are capable of measuring an electrical parameter across the porous body.

[0070] Example Ex13: A heater assembly according to any one of Examples Ex2 to Ex12, wherein the electrical parameter indicates resistance.

[0071] Example Ex14: A heater assembly according to any one of Examples Ex1 to Ex13, wherein the electrical heating element is electrically connected to an electrical contact.

[0072] Example Ex15: A heater assembly according to any one of Examples Ex14, wherein the electrical heating element is configured to heat the liquid aerosol-forming substrate when a potential difference is applied to the electrical contact.

[0073] Example Ex16: A cartridge for an aerosol-generating system, comprising:

[0074] A heater assembly according to any one of Examples Ex1 to Ex15; and

[0075] A liquid storage portion configured to hold a liquid aerosol-forming substrate;

[0076] wherein the liquid storage portion is arranged on a side of the heater assembly opposite to the porous outer surface.

[0077] Example Ex17: An aerosol-generating system, comprising:

[0078] A cartridge according to Example Ex16;

[0079] A power source for supplying power to the electrical heating element;

[0080] A control circuitry configured to control the power supply from the power source to the electrical heating element, wherein the control circuitry is further configured to receive a signal from the measurement contacts and determine based on the signal whether a liquid aerosol-forming substrate is supplied to the electrical heating element.

[0081] Example Ex18: An aerosol-generating system according to Example Ex17, wherein the electrical parameter is greater than a maximum threshold or less than a minimum threshold, indicating that the liquid aerosol-forming substrate supplied to the electrical heating element is below a threshold amount.

[0082] Example Ex19: An aerosol-generating system according to Example Ex18, wherein the maximum threshold or the minimum threshold is related to at least 1×10 measured across the measurement contacts -10related to a minimum conductivity of 1 Siemens / cm.

[0083] Example Ex20: The aerosol-generating system according to Example Ex19, wherein the maximum threshold or the minimum threshold is related to a minimum conductivity of at least 1×10 -9 Siemens / cm measured across the measurement contacts.

[0084] Example Ex21: The aerosol-generating system according to Example Ex20, wherein the maximum threshold or the minimum threshold is related to a minimum conductivity of at least 1×10 -8 Siemens / cm measured across the measurement contacts.

[0085] Example Ex22: The aerosol-generating system according to Example Ex21, wherein the maximum threshold or the minimum threshold is related to a minimum conductivity of at least 1×10 -7 Siemens / cm measured across the measurement contacts.

[0086] Example Ex23: The aerosol-generating system according to any one of Examples Ex17 to Ex22, wherein the controller is configured to prevent power from being supplied to the electroheating element if a liquid aerosol-forming substrate is not supplied to the electroheating element.

[0087] Example Ex24: The aerosol-generating system according to any one of Examples Ex17 to Ex23, wherein the controller is configured to prevent power from being supplied to the electroheating element if the amount of the liquid aerosol-forming substrate in the porous body is below a threshold amount.

[0088] Example Ex25: A method of controlling heating in an aerosol-generating system including a heater assembly:

[0089] The heater assembly includes:

[0090] An electroheating element for heating a liquid aerosol-forming substrate to form an aerosol;

[0091] A porous body for supplying the liquid aerosol-forming substrate to the electroheating element, the electroheating element being arranged along a porous outer surface of the porous body;

[0092] A protective layer arranged to extend across at least a portion of the electroheating element to protect the electroheating element; and

[0093] Measurement contacts arranged to allow measurement of an electrical parameter of the heater assembly to detect whether a sufficient amount of the liquid aerosol-forming substrate is supplied to the electroheating element,

[0094] The method includes:

[0095] Measure an electrical parameter of the heater assembly between the measurement contacts to detect whether a liquid aerosol-forming substrate is supplied to the electroheating element.

[0096] Example Ex26: The method according to Example Ex25, comprising:

[0097] Determine an indication of one or more of the following based on the measured electrical parameter value: the absence of a liquid aerosol-forming substrate, the presence of a liquid aerosol-forming substrate, the amount of the liquid aerosol-forming substrate.

[0098] Example Ex27: The method according to Example Ex26, wherein determining an indication of one or more of the following: the absence of a liquid aerosol-forming substrate, the presence of a liquid aerosol-forming substrate, the amount of the liquid aerosol-forming substrate involves comparing the measured electrical parameter with one or more predetermined reference parameters.

[0099] Example Ex28: The method according to Example Ex26 or Ex27, wherein the one or more predetermined reference parameters are resistance values or conductance values indicating the absence of a liquid aerosol-forming substrate, the presence of a liquid aerosol-forming substrate, the amount of the liquid aerosol-forming substrate.

[0100] Example Ex29: The method according to any one of Examples Ex26 to Ex28, comprising:

[0101] When it is determined that the amount of the liquid aerosol-forming substrate in the porous body is small, prevent power supply to the electroheating element.

[0102] Example Ex30: The method according to any one of Examples Ex26 to Ex29, comprising:

[0103] When it is determined that the amount of the liquid aerosol-forming substrate on the protective layer is small, prevent power supply to the electroheating element.

[0104] Example Ex31: The method according to any one of Examples Ex30, wherein it is determined that the amount of the liquid aerosol-forming substrate is small by a measured value of an electrical parameter indicating that the conductivity across the measurement contacts is less than 1×10 -8 Siemens / cm.

[0105] Example Ex32: The method according to any one of Examples Ex26 to Ex31, comprising:

[0106] When it is detected that there is no liquid aerosol-forming substrate in the porous body, prevent power supply to the electroheating element.

[0107] Example Ex33: The method according to any one of Examples Ex26 to Ex32, comprising:

[0108] When it is detected that there is no liquid aerosol forming matrix on the protective layer, power supply to the electric heating element is prevented.

[0109] Example Ex34: The method according to any one of Examples Ex26 to Ex33, comprising:

[0110] wherein the absence of the liquid aerosol forming matrix is determined by indicating a measured value of the conductivity across the measurement contacts to be less than 1×10 -11 Siemens / cm. BRIEF DESCRIPTION OF THE DRAWINGS

[0111] Examples will now be further described with reference to the drawings, in which:

[0112] Figure 1 is a schematic diagram of a heater assembly according to an example of the present disclosure, wherein measurement contacts are provided on a protective layer;

[0113] Figure 2 is a schematic diagram of a heater assembly according to an example of the present disclosure, wherein measurement contacts are provided on a porous body;

[0114] Figure 3 is a schematic diagram of a cartridge having a heater assembly according to an example of the present disclosure;

[0115] Figure 4 is a schematic diagram of an aerosol generating system according to an example of the present disclosure;

[0116] Figure 5 is a flowchart showing a method of controlling heating in an aerosol generating system according to an example of the present disclosure; and

[0117] Figure 6 is a circuit showing the conversion of a resistance measurement value to an electrical signal. DETAILED DESCRIPTION

[0118] The above and other features and advantages of the exemplary embodiments will become more apparent by referring to the drawings and describing the exemplary embodiments in detail. However, for the purpose of describing the exemplary embodiments, the specific structural and functional details disclosed herein are only representative. However, the exemplary embodiments can be implemented in many alternative forms and should not be construed as limited to the embodiments set forth herein.

[0119] Accordingly, while exemplary embodiments are capable of various modifications and alternative forms, embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intention to limit the exemplary embodiments to the particular forms disclosed, and on the contrary, exemplary embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of the exemplary embodiments. Throughout the description of the figures, like reference numerals refer to like elements.

[0120] For ease of description, spatial relative terms (such as "below") may be used herein to describe the relationship of one element or feature to another element or feature as illustrated in the figures. It should be understood that the spatial relative terms are intended to cover different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, an element described as "below" other elements or features would then be oriented "above" the other elements or features. Thus, the term "below" can include both an orientation of "above" and "below". The device may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatial relative descriptors used herein can be interpreted accordingly.

[0121] It should be understood that when an element or layer is referred to as being "on" another element or layer, it can be directly on the other element or layer, connected to, coupled to, or covering the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on" another element or layer, there are no intervening elements or layers.

[0122] The terms used herein are for the purpose of describing various embodiments only and are not intended to limit the exemplary embodiments. As used herein, unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" are also intended to include the plural forms. It will be further understood that the terms "comprising" and "including" when used in this specification specify the presence of the stated features, integers, steps, operations, elements, or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, or groups thereof.

[0123] Exemplary embodiments are described herein with reference to cross-sectional views that are schematic illustrations of idealized embodiments (and intermediate structures) of the exemplary embodiments. Thus, for example, variations in the illustrated shapes due to manufacturing techniques or tolerances are to be expected. Accordingly, the exemplary embodiments should not be construed as limited to the shapes of the regions shown herein, but should include, for example, shape deviations caused by manufacturing. Thus, the regions shown in the figures are schematic in nature, and their shapes are not intended to depict the actual shape of the regions of the device, nor are they intended to limit the scope of the exemplary embodiments. In all of the figures, the same reference numerals represent the same elements. Unless otherwise specified, the drawings should not be considered to be drawn to scale. It should be understood that the drawings in the present application are schematic and some features have been omitted for clarity.

[0124] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the exemplary embodiments belong. It will be further understood that terms, including those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0125] The drawings are intended to depict exemplary embodiments and should not be construed as limiting the intended scope of the claims.

[0126] Reference Figure 1 , shows a schematic view of a heater assembly 100 for an aerosol generation system according to an example of the present disclosure. The heater assembly 100 includes: an electric heating element 120, a porous body 110, a protective layer 140, and measurement contacts 150, a circuit 160, an electrical parameter measurement device 170, and a control circuitry (not shown for clarity).

[0127] The porous body 110 is configured to supply a liquid aerosol-forming matrix to the electric heating element 120. Specifically, the porous body 110 is configured to transfer the liquid aerosol-forming matrix from a liquid reservoir (not shown for clarity in Figure 1 ) to the electric heating element 120. The porous body 110 is configured to store some of the liquid aerosol-forming matrix until it is aerosolized by the electric heating element 120.

[0128] The porous body 110 is a rectangular block. The porous body 110 includes a plurality of open pores. The plurality of open pores are interconnected to provide a fluid path for the aerosol-generating liquid to pass through the porous body 110. The porous body 110 includes a material that does not chemically interact with the liquid aerosol-forming matrix. The porous body 110 includes ceramics. The porous body 110 contains Ca2SiO3 or SiO2 (or Ca2SiO3 and SiO2). It should be understood that the porous body 110 may have different shapes or include different materials.

[0129] The electric heating element 120 is configured to heat a liquid aerosol-forming substrate to form an aerosol. The electric heating element 120 is configured to convert electrical energy into heat energy by the material resistance of the electric heating element 120 to an electric current.

[0130] The electric heating element 120 is elongate. The electric heating element 120 comprises NiCr or TiZr (or NiCr and TiZr). It should be understood that the electric heating element 120 may have different shapes or comprise different materials.

[0131] The electric heating element 120 is arranged along the porous outer surface of the porous body 110. The electric heating element 120 is in direct contact with the porous body 110. The electric heating element 120 is disposed on a single surface of the porous body 110.

[0132] The electric heating element 120 is electrically connected to the electrical contact 130. The electric heating element 120 is configured to heat the liquid aerosol-forming substrate when a potential difference is applied to the electrical contact 130. The electrical contacts 130 are provided at each end of the elongate electric heating element 120. The electrical contacts 130 and the electric heating element 120 are directly disposed on the same surface of the porous body 110. The electrical contacts 130 comprise CuZnAu. The electrical contacts 130 are provided at opposite edges of the porous outer surface of the porous body 110. The electrical contacts 130 are aligned with the opposite edges of the porous outer surface of the porous body 110.

[0133] The protective layer 140 is arranged to extend across at least a portion of the electric heating element 120 to protect the electric heating element 120. The protective layer 140 is configured to protect the electric heating element 120 and extend the life of the electric heating element 120. The protective layer 140 is configured to prevent oxidation of the electric heating element 120.

[0134] The protective layer 140 is planar. The protective layer 140 has a size and shape configured to cover the electric heating element 120. The protective layer 140 is configured to completely cover the surface of the electric heating element 120. The protective layer 140 is configured to substantially cover the porous body 110 below the electric heating element 120. The protective layer 140 comprises an inorganic material such as Al2O3, SiO2, MgO, BaO, CaO, ZrO2 or ZnO. It should be understood that the protective layer 140 may have different shapes or comprise different materials.

[0135] The protective layer 140 is arranged along the electric heating element 120. The protective layer 140 is in direct contact with the electric heating element 120. The protective layer 140, the electric heating element 120 and the porous body 110 are arranged such that the electric heating element 120 is between the protective layer 140 and the porous body 110.

[0136] The measurement contacts 150 are disposed directly on the surface of the protective layer 140 at opposite sides of the surface of the protective layer 140 such that the measurement contacts 150 can measure the electrical parameters across the protective layer 140. The measurement contacts 150 are arranged to allow measurement of the electrical parameters of the heater assembly 100 to detect whether a sufficient amount of the liquid aerosol-forming matrix is supplied to the electrical heating element 120.

[0137] Two measurement contacts 150 are provided. The measurement contacts 150 are identical to each other in terms of material, shape, and size. The measurement contacts 150 are attached to the protective layer 140. The measurement contacts 150 extend from the inorganic protective layer 140.

[0138] A circuit 160 is provided to connect the measurement contacts 150 to each other via an electrical parameter measuring device 170, which in this instance is a device configured to measure the resistance between the measurement contacts 150. The circuit 160 is capable of measuring up to 0.1×10 7 ohms.

[0139] In this instance, the electrical parameter measured across the measurement contacts 150 is the electrical parameter of the protective layer 140. In this instance, the electrical parameter indicates the resistance across the protective layer 140. The protective layer 140 is configured to have a very low electrical conductivity such that when there is no liquid, the measured resistance value across the measurement contacts 150 will be high, corresponding to an open-circuit measurement value. As described above, the porous body 110 may comprise SiO2, the electrical conductivity of which may be 1×10 -12 . When there is a liquid film on the protective layer, the measured resistance value across the measurement contacts 150 can measurably decrease due to the higher electrical conductivity of the liquid. The liquid may comprise, for example, propylene glycol, the electrical conductivity of which may be 0.1×10 -6 . The liquid may comprise glycerol, the electrical conductivity of which may be 0.06×10 -6 . Therefore, the resistance measured across the protective layer 140 indicates whether there is liquid on, at, or within the protective layer 140. The resistance measured across the protective layer 140 may decrease as the amount of liquid on, at, or within the protective layer increases.

[0140] The control circuitry (not shown for clarity in Figure 1 ) is configured to allow power to be supplied to the electrical heating element 120 only when the measured resistance value indicates that there is liquid on, at, or within the inorganic protective layer 140. This has the advantage of reducing the likelihood that the user experiences dry heating or dry puffing when using the aerosol generating device.

[0141] Reference Figure 2, which shows a heater assembly 100 for an aerosol generation system according to a second example of the present disclosure. The heater assembly 100 includes: an electrical heating element 120, a porous body 110, a protective layer 140, and measurement contacts 150, a circuit 160, an electrical parameter measurement device 170, and a control circuitry (not shown for clarity).

[0142] The electrical heating element 120, the porous body 110, and the protective layer 140 are as described in the example shown in Figure 1 the.

[0143] The measurement contacts 150 of the second example are directly disposed on opposite surfaces of the porous body 110 such that the measurement contacts 150 can measure the electrical parameters across the porous body 110.

[0144] Two measurement contacts 150 are provided. The measurement contacts 150 are identical to each other in terms of material, shape, and size. The measurement contacts 150 are attached to the porous body 110. Each measurement contact 150 extends along the side of the porous body 110 on which it is disposed.

[0145] The circuit 160 is provided to connect the measurement contacts 150 to each other via the electrical parameter measurement device 170, which in this example is a device configured to measure the resistance between the measurement contacts 150.

[0146] In this example, the electrical parameter measured across the measurement contacts 150 is the electrical parameter of the porous body 110. In this example, the electrical parameter indicates the resistance across the porous body 110. The resistance across the porous body 110 indicates whether liquid is present on or within the porous body 110. When liquid is present on or within the porous body 110, the resistance measured across the porous body 110 is significantly lower than when the liquid is absent. The resistance measured across the porous body 110 can decrease as the amount of liquid within the porous body 110 increases.

[0147] Refer to Figure 3 and 4 , which shows a schematic diagram of an exemplary aerosol generation cartridge 400 and a schematic diagram of an exemplary aerosol generation system 600. The aerosol generation system 600 includes two main components, the cartridge 400 and the body portion or aerosol generation device 500.

[0148] The aerosol generation cartridge 400 includes: the heater assembly 100 and liquid storage portions 430, 435 configured to hold a liquid aerosol-forming substrate. The liquid storage portions 430, 435 are arranged on a side of the heater assembly opposite to the porous outer surface.

[0149] The aerosol generating system 600 includes: a cartridge 400; a power source 510 for supplying power to a heating element; a control circuitry 520 configured to control the power supply from the power source 510 to the heating element, wherein the control circuitry 520 is further configured to receive a signal from a measurement contact and determine based on the signal whether a liquid aerosol-forming substrate is supplied to the porous body. The electrical parameter measured by the measurement contact is greater than a maximum threshold or less than a minimum threshold, indicating that the liquid aerosol-forming substrate supplied to the porous body is below a threshold amount.

[0150] The connecting end 415 of the cartridge 400 is removably connected to a corresponding connecting end 505 of the aerosol generating device 500. The connecting end 415 of the cartridge 400 and the connecting end 505 of the aerosol generating device 500 each have electrical contacts or connections (not shown) arranged to cooperate to provide an electrical connection between the cartridge 400 and the aerosol generating device 500. The aerosol generating device 500 includes a power source in the form of a battery 510 and a control circuitry 520, which in this example is a rechargeable lithium-ion battery. The aerosol generating system is portable and has a size comparable to that of a conventional cigar or cigarette. A mouthpiece 425 is disposed at an end of the cartridge 400 opposite the connecting end 415.

[0151] The cartridge 400 includes a housing 405 containing Figure 1 or Figure 2 a heater assembly 100 and a liquid storage compartment or section having a first storage portion 430 and a second storage portion 435. The liquid aerosol-forming substrate is held in the liquid storage compartment. Although not shown in Figure 3 or 4, the first storage portion 430 of the liquid storage compartment is connected to the second storage portion 435 of the liquid storage compartment such that the liquid in the first storage portion 430 can be transferred to the second storage portion 435. The heater assembly 100 receives liquid from the second storage portion 435 of the liquid storage compartment. At least a portion of the porous body of the heater assembly 100 extends into the second storage portion 435 of the liquid storage compartment to contact the liquid aerosol-forming substrate therein.

[0152] Air flow passages 440, 445 extend through the cartridge 400 from an air inlet 450 formed in one side of the housing 405 past the electrically heated element of the heater assembly 100 and from the heater assembly 100 to a mouthpiece opening 410 formed in the housing 405 at an end of the cartridge 400 opposite the connecting end 415.

[0153] The components of the cartridge 400 are arranged such that a first storage portion 430 of the liquid storage compartment is between the heater assembly 100 and the mouthpiece opening 410, and a second storage portion 435 of the liquid storage compartment is located on the side of the heater assembly 100 opposite the mouthpiece opening 410. In other words, the heater assembly 100 is located between the two portions 430, 435 of the liquid storage compartment and receives liquid from the second storage portion 435. The first storage portion 430 of the liquid storage compartment is closer to the mouthpiece opening 410 than the second storage portion 435 of the liquid storage compartment. The air flow passages 440, 445 pass through the electrically heated element of the heater assembly 100 and extend between the first portion 430 and the second portion 435 of the liquid storage compartment.

[0154] The aerosol generating system is configured such that a negative pressure can be applied at the mouthpiece 425 of the cartridge to draw the aerosol out of the mouthpiece opening 410. In operation, when a negative pressure is applied to the mouthpiece 425, air passes through the air flow passages 440, 445 from the air inlet 450, through the heater assembly 100, and is drawn into the mouthpiece opening 410. When the system is activated, the control circuitry 520 controls the power supply from the battery 510 to the cartridge 400. This in turn controls the amount and nature of the vapor generated by the heater assembly 100. The control circuitry 520 may include an air flow sensor (not shown), and when a user draw is detected by the air flow sensor, the control circuitry 520 may supply power to the heater assembly 100. This type of control arrangement has been in use for a long time in aerosol generating systems such as inhalers and electronic cigarettes. When a negative pressure is applied to the mouthpiece opening 410 of the cartridge 400, the heater assembly 100 is activated and generates vapor, which is entrained in the air flow passing through the air flow passage 440. The vapor cools in the air flow within the passage 445 to form an aerosol, which is then drawn through the mouthpiece opening 410 into the user's mouth.

[0155] In operation, the mouthpiece opening 410 is typically the highest point of the system. The construction of the cartridge 400, and in particular the arrangement of the heater assembly 100 between the first storage portion 430 and the second storage portion 435 of the liquid storage compartment, is advantageous because it utilizes gravity to ensure delivery of the liquid matrix to the heater assembly 100, even when the liquid storage compartment is empty, but prevents over-supply of liquid to the heater assembly 100, which over-supply could cause liquid to leak into the air flow passage 440.

[0156] In Figure 5 the flowchart shows a method of controlling heating in an aerosol generating system. The heater assembly controlled by the method includes:

[0157] an electrically heated element for heating a liquid aerosol-forming matrix to form an aerosol;

[0158] A porous body for supplying a liquid aerosol-forming substrate to an electrical heating element disposed along a porous outer surface of the porous body;

[0159] A protective layer disposed to extend across at least a portion of the electrical heating element to protect the electrical heating element; and

[0160] Measurement contacts arranged to allow measurement of electrical parameters of the heater assembly to detect whether a sufficient amount of liquid aerosol-forming substrate is supplied to the electrical heating element.

[0161] In a first step 61, the method includes measuring electrical parameters of the heater assembly between the measurement contacts to detect whether a liquid aerosol-forming substrate is supplied to the electrical heating element.

[0162] In a second step 62, the method includes determining an indication of one or more of the following based on the measured electrical parameter values: absence of liquid aerosol-forming substrate, presence of liquid aerosol-forming substrate, amount of liquid aerosol-forming substrate.

[0163] In a third step 63, the method includes preventing power supply to the electrical heating element when it is determined that the amount of liquid aerosol-forming substrate in the porous body is low.

[0164] In a fourth step 64, the method includes preventing power supply to the electrical heating element when it is detected that there is no liquid aerosol-forming substrate in the porous body.

[0165] The third step 63 may be performed without the fourth step 64. Similarly, the fourth step 64 may be performed without the third step 63. It should be understood that the method need not be performed in the order of the steps shown in Figure 5 .

[0166] Figure 6 Is shown in more detail Figure 4 A schematic circuit diagram of a portion of the control circuitry 520 of the aerosol generation system of Figure 6 The circuit 200 of is used to determine one or more electrical parameters of the heater assembly.

[0167] The circuit 200 includes a resistor R Z , which corresponds to or is equivalent to the resistance of the protective layer or the porous body between two measurement contacts 210, 211 and is connected to a power supply via a connection 202. The power supply provides a voltage Vin. An additional resistor R with a known value is inserted in series with the heater R Z . The resistor R Z and the known resistor R form a voltage divider. At the heater R ZThere is a voltage V at point Z in circuit 200 between the additional resistor R Z . The voltage V Z is in the middle between ground and voltage Vin.

[0168] Circuit 200 determines the electrical parameters of resistor R Z , in this example, determines the resistance of resistor R Z . The analog input 204 on the microcontroller MCU is used to monitor the voltage Vin provided by connection 202. The analog input 206 on the microcontroller MCU is used to monitor the voltage V at point Z Z . The analog input 206 is connected to the analog-to-digital converter (ADC) input of the microcontroller MCU. In order for the microprocessor MCU to measure the resistance of resistor R Z , the current passing through resistor R Z and the voltage across resistor R Z are determined. Then, Ohm's law is used to determine resistor R Z .

[0169] The voltage across resistor R Z is V Z , and the current passing through resistor R Z is I. Therefore, the resistance of resistor R Z can be determined by Equation 1:

[0170] R Z = V Z / I (1)

[0171] The current passing through the known resistor R is the same as the current passing through resistor R Z because they are connected in series. That is, the current passing through resistor R and the current passing through resistor R Z are current I. As described above, resistor R has a known value. The voltage across resistor R is Vin - V Z . By applying Ohm's law, the current passing through resistor R can be determined by Equation 2:

[0172] I = Vin - V Z / R (2)

[0173] Therefore, combining (1) and (2) gives:

[0174] R Z = (V Z / (Vin – V Z )) x R (3)

[0175] Therefore, when the aerosol generating system is in use, the microprocessor MCU can measure Vin and V Z, and given the value of resistor R, the resistance of resistor R can be determined. Z resistance.

[0176] The microprocessor MCU is configured to prevent power supply to the electroheating element if the liquid aerosol forming matrix is not supplied to the porous body or if the liquid aerosol forming matrix in the porous body is below a threshold amount.

[0177] The microprocessor can determine the conductance by determining the reciprocal of the measured resistance R H resistance.

[0178] For the purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing quantities, amounts, percentages, etc. are to be understood as being modified in all instances by the term "about." Moreover, all ranges include the disclosed maximum and minimum points, and include any intermediate ranges that may be specifically recited or may not be recited herein. Thus, in this context, the number A is understood as A ± 10% (10 percent) of A. In this context, the number A may be regarded as including values within the general standard error for the measurement of the property modified by the number A. In certain instances used in the appended claims, the number A may deviate from the percentage recited above, provided that the amount by which A deviates does not materially affect the basic and novel features of the claimed invention. Moreover, all ranges include the disclosed maximum and minimum points, and include any intermediate ranges that may be specifically recited or may not be recited herein.

Claims

1. A heater assembly for an aerosol generating system, comprising: an electrical heating element configured to heat a liquid aerosol-forming substrate to form an aerosol; a porous body configured to supply the liquid aerosol-forming substrate to the electrical heating element, the electrical heating element being arranged along a porous outer surface of the porous body; a protective layer arranged to extend across at least a portion of the electrical heating element to protect the electrical heating element; and measurement contacts arranged to allow measurement of an electrical parameter of the heater assembly to detect whether a sufficient amount of the liquid aerosol-forming substrate is supplied to the electrical heating element.

2. The heater assembly according to claim 1, wherein the electrical parameter is an electrical parameter of the protective layer.

3. The heater assembly according to claim 1 or claim 2, wherein the measurement contacts are provided on opposite sides of a surface of the protective layer such that the measurement contacts are able to measure the electrical parameter across the protective layer.

4. The heater assembly according to claim 1, wherein the electrical parameter is an electrical parameter of the porous body.

5. The heater assembly according to claim 1 or claim 4, wherein the measurement contacts are provided on opposite surfaces of the porous body such that the measurement contacts are able to measure the electrical parameter across the porous body.

6. The heater assembly according to any one of the preceding claims, wherein the electrical parameter indicates resistance.

7. The heater assembly according to any one of the preceding claims, wherein the electrical heating element is electrically connected to electrical contacts, and the electrical heating element is configured to heat the liquid aerosol-forming substrate when a potential difference is applied to the electrical contacts.

8. A cartridge for an aerosol generating system, comprising: the heater assembly according to any one of claims 1 to 7; and a liquid storage portion configured to hold the liquid aerosol-forming substrate; wherein the liquid storage portion is arranged on a side of the heater assembly opposite to the porous outer surface.

9. An aerosol generating system, comprising: the cartridge according to claim 8; and an aerosol generating device, the aerosol generating device comprising: a power source for supplying power to the electrical heating element; and control circuitry configured to control the power supply from the power source to the electrical heating element, wherein the control circuitry is further configured to receive a signal from the measurement contacts and determine based on the signal whether the liquid aerosol-forming substrate is supplied to the electrical heating element.

10. The aerosol generating system according to claim 9, wherein the electrical parameter being greater than a maximum threshold or less than a minimum threshold indicates that the liquid aerosol-forming substrate supplied to the porous body is below a threshold amount.

11. The aerosol-generating system according to claim 9 or claim 10, wherein the controller is configured to prevent power from being supplied to the electrical heating element if a liquid aerosol-forming substrate is not supplied to the porous body, or if the liquid aerosol-forming substrate in the porous body is below a threshold amount.

12. A method of controlling heating in an aerosol-generating system comprising a heater assembly: The heater assembly comprises: an electrical heating element for heating a liquid aerosol-forming substrate to form an aerosol; a porous body for supplying the liquid aerosol-forming substrate to the electrical heating element, the electrical heating element being arranged along a porous outer surface of the porous body; a protective layer arranged to extend across at least a portion of the electrical heating element to protect the electrical heating element; and measurement contacts arranged to allow measurement of an electrical parameter of the heater assembly to detect whether a sufficient amount of the liquid aerosol-forming substrate is supplied to the electrical heating element, The method comprises: measuring an electrical parameter of the heater assembly between the measurement contacts to detect whether a liquid aerosol-forming substrate is supplied to the electrical heating element.

13. The method according to claim 12, comprising: determining an indication of one or more of the following based on the measured value of the electrical parameter: absence of a liquid aerosol-forming substrate, presence of a liquid aerosol-forming substrate, amount of the liquid aerosol-forming substrate.

14. The method according to claim 13, comprising: preventing power from being supplied to the electrical heating element when it is determined that the amount of the liquid aerosol-forming substrate in the porous body is low.

15. The method according to claim 13 or claim 14, comprising: preventing power from being supplied to the electrical heating element when it is detected that there is no liquid aerosol-forming substrate in the porous body.

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