RU2789673C2 - Aerosol generator - Google Patents

Abstract

FIELD: tobacco industry; smoking devices.

SUBSTANCE: group of inventions relates to vaporization devices with heating and, in particular, to electrically resistive heaters for vaporization and spraying of liquids in order to obtain inhaled aerosols. The aerosol generation device contains a heating element containing a sheet of electrically conductive material having a first surface and a second surface opposite to the first surface, and containing many channels located in the area of the sheet and passing through the sheet from the first surface to the second surface, while the channels are made with the possibility of forming a directed vapor flow of liquid medium from the channels. The parameters of the power supply that supplies current through the sheet area in the form of pulses are set for pulsed heating of liquids above the boiling point. The node in which the porous medium is paired with a sheet to suppress the growth of bubbles during vaporization is removed for replacement. The temperature of the heating element is limited by means of a temperature sensor controlling the power supply unit, made with the possibility of matching the parameters of the pulse sequence with the thermal time constant of the heating element. Heat is removed through the air duct contained in the housing in which the heating element is enclosed. Channels in the area of the sheet are performed with a laser. Channels in a sheet made of a plate of highly alloyed silicon are performed by micro-processing using photolithography followed by etching of silicon.

EFFECT: formation of a high-density aerosol is ensured with significantly reduced levels of health risk, as well as standardized less expensive production.

20 cl, 18 dwg, 4 tbl

Description

CROSS-REFERENCE TO RELATED STATEMENT

This application claims the benefit of U.S. Provisional Application 62/683,991, filed June 12, 2018, which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to heated vaporization devices, and in particular to electrically resistive heaters for vaporizing and aerosolizing liquids to produce respirable aerosols.

BACKGROUND OF THE INVENTION

Typical high-powered vaporizers and e-cigarettes designed to generate large amounts of aerosol during puffs typically use heater blocks with bulky heating elements, resulting in intense heating of the devices due to heat dissipation around the heater blocks. Because of the bulkiness, the heating blocks cool slowly. This feature makes the devices hot and uncomfortable to use. In addition, "after-use" residual heat due to long cooling times can cause long-term chemical reactions to form toxic solutions such as acrolein, especially in the aerosol liquid in close proximity to the heating blocks. This toxic substance is then vaporized and inhaled by the user during the first puffs of the next puff session.

From the application documents US2016/0138795A1, US2017/0360100A1, aerosol generating devices are known, containing flat liquid heating elements, in which the heating conductor is made in the form of an electrically conductive coating or film deposited on a non-conductive substrate with a plurality of openings (ports, apertures). Also known are the flat liquid heating elements described in US2017/360100A1, in which the heating conductor is made in the form of an electrically conductive mesh. During heating, the liquid is drawn due to capillary forces into the openings (ports, apertures) of the substrate and cells of the grid of heating elements on one side and is vaporized with the release of steam from the opposite side. In this case, the vapor freely expands randomly in all possible directions in the surrounding air due to the temperature difference, which is accompanied by a sharp drop in the density of the vapor and, accordingly, the aerosol. To increase the vapor density, the electric power is increased, which is associated either with overheating of the heater, or with an increase in its size and, as a result, heat losses. In both cases, excess heat increases health risks, for the reasons mentioned above. The present invention solves the problem of aerosol intensification while reducing the size of the heating conductor and reducing health risks.

SUMMARY OF THE INVENTION

Embodiments of the present invention, which are described below, provide improved heating and vaporization devices, as well as methods for their use, in particular for the production of aerosols.

In accordance with an embodiment of the invention, an aerosolization device is thus provided, comprising a reservoir configured to contain a liquid medium.

The heating element includes a sheet of electrically conductive material having a first surface in physical contact with the liquid medium and a second surface opposite the first surface, and an array of micronozzles located in the area of the sheet and passing through the sheet from the first surface to the second surface.

The power supply unit is designed to supply electric current pulses through the area of the sheet, with the pulse energy selected in such a way as to heat the conductive material enough to vaporize the liquid medium and thereby cause the release of the corresponding liquid vapor jets through the micronozzles from the second surface.

The term "micronozzle" throughout the description refers to a narrow, long or elongated hollow object, or in other words a channel having a cylindrical or conical shape, which is made with the ability to control, in particular to give direction and accelerate the movement of the vapor of a liquid medium moving in this channel in vaporization time. Due to the negative pressure created by accelerated hot vapors, narrowly directed steam jets are formed in the area of the micronozzle ejection hole, and cold ambient air is drawn from the sides into the hot vapor jet, causing aerosol generation during the sharp cooling of hot vapors in the jet.

The reduction in accelerated vapor pressure may also be accompanied by a vapor acceleration-induced temperature decrease in the micronozzle ejection port region, which may favorably influence aerosol generation in the micronozzle ejection port region in addition to ambient air cooling. The formation of high-velocity steam jets, which, due to the pressure drop, significantly contribute to the generation of aerosol, is a characteristic and essential feature introduced by micronozzles. The ability of micronozzles to generate a dense aerosol enables miniaturization and more standard mass production of heating elements, for example using micromachining techniques.

In some embodiments, the device includes an air duct comprising at least a second surface of the heating element and including an air intake through which ambient air passes into the duct and over the second surface, thereby forming an aerosol containing a vaporized liquid medium, and an outlet, through which the aerosol leaves the duct. In one embodiment, the duct includes at least one air nozzle for generating and directing turbulent airflow onto the second surface of the sheet to promote aerosol generation.

The micronozzles are generally identical and evenly distributed over the area of the sheet of conductive material.

The sheet of electrically conductive material may be flat or curved. The electrically conductive material sheet may include one or more of a metal, a doped semiconductor, and an electrically conductive foil.

In the disclosed embodiments, the sheet of conductive material has a thickness between the first and second surfaces of less than 1 mm, and the micronozzles have a diameter of less than 0.2 mm.

In one embodiment, the micronozzles are truncated cone shaped. In another embodiment, the micronozzles are Laval nozzles. The micronozzles may be pierced through the sheet of electrically conductive material and protrude outward from the second surface. Alternatively, the micronozzles may be etched through a sheet of electrically conductive material and positioned flush with the second surface.

In some embodiments, the reservoir includes a porous medium that is saturated with a liquid medium. In the disclosed embodiment, the porous medium is adjacent to the first surface of the sheet and has a liquid transmission capacity greater than 3 µl/mm ² s. Additionally or alternatively, the porous medium includes a hydrophilic fibrous material that may be included in a layer having a thickness in the range of 0.1 mm to 1 mm.

In some embodiments, the heating element includes a plurality of electrical contacts located on a sheet of electrically conductive material on opposite sides of the array of micronozzles, and the power supply includes springy electrical leads connected to the electrical contacts to supply an electric current through them. In one embodiment, the electrical contacts include micro molds formed on at least one of the surfaces of the electrically conductive material, and the electrical leads are pressed against the micro molds. Alternatively, the electrical contacts include one or more cutouts formed on at least one of the surfaces of the electrically conductive material, and the resilient electrical leads are cylindrical in shape that mates with the one or more cutouts.

In the disclosed embodiment, at least the heating element is replaceable.

In some embodiments, the heating element is configured and the power supply is configured such that the temperature of the liquid medium that is in contact with the first surface of the sheet of electrically conductive material in the heating element rises above the boiling point of the liquid medium during pulses and falls below the boiling point during delay. between pulses in a sequence of pulses supplied by the power supply to the heating element. In one embodiment, the power supply includes a temperature sensor and is configured to control at least one pulse train parameter in response to an output of the temperature sensor.

In the disclosed embodiment, the power supply includes a pulse generator circuit and an isolation transformer that couples the pulse generator circuit to the heating element.

Also provided, in accordance with an embodiment of the invention, is an aerosol generation method that includes providing a heating element including a sheet of electrically conductive material with opposite first and second surfaces, and including an array of micronozzles positioned in a region of the sheet and extending through the sheet from the first surface to a second surface.

The liquid medium comes into contact with the first surface of the heating element. Electric current pulses are applied through the area of the sheet, the energy of the pulse being chosen to heat the conductive material sufficiently to vaporize the liquid medium and thereby cause the corresponding liquid vapor jets to be ejected through the micronozzles from the second surface.

In the disclosed embodiment, providing the liquid medium includes filling a reservoir with the liquid medium and delivering the liquid medium from the reservoir to the first surface of the heating element.

The present invention will be more fully understood from the following detailed description of its embodiments, together with the drawings, in which:

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 is a schematic perspective view of a heating element with an array of micronozzles in accordance with an embodiment of the invention;

Fig. 2A, 2B and 2C are schematic side views of micronozzles and liquid-saturated media in accordance with embodiments of the invention;

Fig. 3A is a schematic perspective view of a cylindrical heating element with cylindrical contact pads in accordance with an embodiment of the invention;

Fig. 3B is a schematic perspective view of a curved paddle heating element in accordance with an embodiment of the invention;

Fig. 3C is a schematic perspective view of a flat micronozzle etched heating element in accordance with an embodiment of the invention;

Fig. 3D is a schematic perspective view of a flat heating element with longitudinal micronozzles according to an embodiment of the invention;

Fig. 4A is a schematic side view of a rough impulse contact interface in accordance with an embodiment of the invention;

Fig. 4B is a schematic side view of a structured impulse contact interface in accordance with an embodiment of the invention;

Fig. 5A is a schematic perspective view of a strip interface of a clamp-on electrical contact according to an embodiment of the invention;

Fig. 5B is a schematic perspective view of a strip interface of a clamp-on electrical contact according to another embodiment of the invention;

Fig. 5C is a schematic perspective view of a clamp-on electrical contact strip interface, in accordance with yet another embodiment of the invention;

Fig. 6 is a schematic perspective view of an electronic cigarette device with airway nozzles according to an embodiment of the invention;

Fig. 7 is a circuit diagram of an aerosol generator with a galvanically isolated output power supply in accordance with an embodiment of the invention;

Fig. 8A is a schematic perspective view of a flat replaceable heating element in accordance with an embodiment of the invention;

Fig. 8B is a schematic perspective view of a cylindrical replaceable heating element in accordance with an embodiment of the invention; and

Fig. 9 is a schematic diagram of pulses used in an aerosolization device according to an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

For safe and convenient electronic cigarettes and similar vaporization devices, it would be beneficial to have an alternative system and method to generate high density aerosol at significantly reduced levels of risk while allowing more standardized, lower cost production.

In response to this need, embodiments of the present invention provide a heating system for generating an aerosol that includes a thin conductive heating element, a plurality of narrow micronozzles for vaporizing liquid and accelerating vapor in the heating element, and non-adiabatic electrical contacts on the element for power supply. The heating element and micronozzles are designed for fast thermal relaxation. The components of the system are designed, shaped and configured to provide a vaporization device capable of rapid, repetitive heating and rapid thermal relaxation.

In some embodiments, the liquid medium (eg, e-liquid) located at the inlet of the hot heating body micronozzles first quickly evaporates there to form saturated vapors in each heating cycle. The vapors are then accelerated by micronozzles and exit as high-velocity hot gas jets into the surrounding air. The jets are rapidly cooled when mixed with ambient air, providing a succession of aerosol shots that accumulate in a puff. The higher the steam jet velocity and the degree of supersaturation, the more concentrated the aerosol is.

After each vaporization pulse, the heating element is rapidly cooled, allowing a new portion of the liquid to fill the area at the entrance to the micronozzles until the cycle repeats. Thus, the device can create a sequence of discrete portions of intense aerosol in response to a series of short powerful electrical pulses. Such pulse operation of the heating element causes only little heat dissipation to the surroundings, as opposed to continuous heating, thus protecting the surroundings from overheating.

The disclosed system includes, but is not limited to, a liquid vaporization heating system having at least one electrical heating conductor specially adapted for pulsed operation. The conductor is made in the form of a double-sided element configured for fast thermal relaxation, with areas of electrical contact on the element and with a plurality of through micronozzles in the element, also configured for fast thermal relaxation, having injection holes on one side and ejection holes on the other side of the element for liquid vaporization and formation of steam jets.

In some embodiments of the invention, the aerosolization device includes a reservoir, which may include a container for storing liquid, wicks for transporting liquid and/or other components containing and source liquid medium, and a double-sided heating element containing a thin sheet of electrically conductive material capable of rapid repetitive heating. The heating element has a first surface on the first side of the element, which is in physical contact with the liquid medium, and a second surface on the second side of the element, opposite the first surface. An array of narrow micronozzles, which are also capable of rapid repetitive heating, are placed over the area of the sheet and extend through the sheet from the first surface to the second surface. The power supply unit generates and delivers electric current pulses through the sheet area, with the pulse energy selected in such a way as to heat the conductive material enough to vaporize the liquid medium and thereby cause the corresponding liquid vapor jets to be ejected through the micronozzles from the second surface.

In the disclosed embodiment, the reservoir contains a porous medium, such as a glass fiber medium, which is saturated with liquid medium and which, for example, supplies liquid medium from the container and is in physical contact with the first surface of the sheet of electrically conductive material.

In one embodiment, at least the second side of the heating element is contained in an air duct containing an air intake through which ambient air passes into the air duct and along the second side, thereby forming an aerosol containing a vaporized liquid medium. The aerosol leaves the duct through the outlet. The airflow in the duct can be initiated by a pressure difference between the air inlet and the outlet, created, for example, by inhaling a vape. The more intense the air is mixed with saturated vapors, the denser the aerosol. In another embodiment, the air duct contains specially shaped air nozzles to create air turbulence over the heating element to improve steam mixing and promote aerosol formation.

The electrically conductive element may be flat or curved, and may comprise, for example, a suitably shaped metal sheet or doped semiconductor material. Typically, the element is formed from a sheet of conductive material having a dimension between the first and second sides of less than about 1 mm. The micronozzles have an appropriate length equal to the element size and diameters less than about 0.2 mm. These dimensions allow them to instantly respond to repetitive heating pulses that have a duration and a delay time between pulses of less than 100 ms. The sheet may be thinner than the feature dimension between the first and second sides, such as less than 0.5 mm, less than 0.3 mm, or even less than 0.05 mm. In this case, the micronozzles are shaped to protrude from the surface of the sheet on the second side of the element. The diameter of the micronozzle is determined by the thermodynamics of the processes of heating and cooling of the liquid inside and therefore can be wider or narrower than the thickness of the sheet.

In some embodiments, the micronozzles are truncated cone shaped. Alternatively, the micronozzles may be Laval nozzles. In both cases, the micronozzles may be pierced through a sheet of electrically conductive material (and thus protrude outward from the second surface) or may be etched through a sheet of electrically conductive material (so that they are flush with the second surface). Etching and punching can also be done with laser perforation.

Each of the micronozzles advantageously includes an injection port and a steam boost segment to create discrete sub- or possibly even supersonic jets of hot saturated steam coherently with each pulse of the electric current pulse train. The injection port of the micronozzle is configured to trap, move, and accelerate liquid vapor towards the ejection port. Further, it is preferable that the plurality of micronozzles be arranged in an array of evenly spaced identical micronozzles, which promotes uniform heating.

Furthermore, it is preferable that the conductive heating element with its micronozzles and electrical contact pads be in a form with a fast thermal response, which allows its temperature to cycle up and down from the boiling point of the liquid medium coherently with each pulse and the delay between pulses of the train of electrical pulses applied. during every puff. Typically, the conductor body is made of a thermomechanically stable material that is resistant to thermal shock, thermomechanical fatigue and microcracks.

In one possible embodiment, the heating element is flat, formed in the form of a thin sheet or plate of electrically conductive material with micronozzles lying in the plane of the plate, with the first and second sides formed by one pair of plate edges, and electrical contact pads located on the other pair of plate edges.

In other possible embodiments, the heating element is tubular and formed as an electrically conductive thin-walled tube or thin sheet bent into a cylindrical shape with micronozzles directed radially in or out of the cylinder. Electrocontact pads are formed on the edges of the cylinder.

In an additional embodiment, the heating element is made in the form of a thin plate with micronozzles located across or perpendicular to the plane of the plate.

In some embodiments, the heating element includes electrical contacts located on a sheet of electrically conductive material on opposite sides of the micronozzle array, and the power supply includes electrical leads connected to supply electrical current through the electrical contacts. In one embodiment, the electrical contacts comprise non-adiabatic micro molds formed to dissipate the heat generated by the contact resistance during each pulse on at least one of the surfaces of the electrically conductive material, and the electrical leads are pressed against the micro molds. In another embodiment, the electrical contacts comprise one or more cutouts formed on at least one of the surfaces of the electrically conductive material, and the electrical leads are cylindrical in shape that mates with the one or more cutouts. The electrical terminals form a narrow strip-like interface with the electrical pads and may also have non-adiabatic micro-shapes. Mating can be formed by connecting or clamping the leads with uniform pressure on the contact surface.

As noted earlier, the power supply typically pulses the heating element in sequence with a pulse duration and a delay between pulses chosen such that the temperature of the liquid medium that contacts the first surface of the sheet of conductive material rises above the boiling point of the liquid medium during the pulses and falls below boiling point during the delay between pulses. In one embodiment, the power supply includes a temperature sensor that has a fast response and is configured to sense changes in temperature instantly. The power supply unit regulates the parameters of the pulse train, such as the magnitude of the pulse power, duration and interval between pulses, in response to the output signal of the temperature sensor. In another embodiment, a simple temperature sensor having a long response time can be used to monitor the average power during a puff.

In some embodiments, the implementation of the power supply contains a battery, such as a lithium battery. In other embodiments, the pulse generator circuit in the power supply may be connected by an isolation transformer to a heating element to protect the user from possible electric shock, such as in the case of mains power.

In some embodiments, a layer of porous media that is saturated with liquid media is in physical contact with the first side of the heating element, with the porous media partially filling the injection holes of the micronozzles. In other embodiments, liquid medium is continuously supplied to the porous media layer from a liquid storage container via hydraulic connection means, such as fiberglass tows. Thus, all components containing a liquid medium constitute a liquid reservoir. The layer of porous medium at the boundary with the heating element supplies the liquid medium to the heating element during each heating pulse. In additional embodiments, the implementation of the layer of porous media can also be immersed in a container for storing liquid. To suppress hydraulic communication between adjacent micronozzles, the pore size of the porous medium is much smaller than the injection holes of the micronozzle. The thickness of the porous medium is usually much greater than the thermal diffusion length in the liquid medium, so that sufficient liquid can be provided by the porous medium layer for vaporization during the heating pulse.

Some embodiments may include a replaceable unit containing at least a heating element and/or a fluid storage container. The refill may also be in the form of a disposable cartridge containing a liquid storage container, a porous medium, electrical leads, and an electrical interface, eg for disposable use.

In some exemplary embodiments, the micronozzle and electrical pad heating element may be fabricated using silicon micromachining.

In other embodiments, the implementation of the heating element is formed from a foil of electrically conductive heat-resistant material, such as, for example, metals, alloys or heavily doped semiconductors, such as silicon. The foil can be clamped, for example, by springy leads and stretched over a region of a porous medium saturated with liquid.

In some embodiments, the reservoir and heating element are enclosed in a housing that includes at least one duct (also referred to as an air duct) to supply air to the heating element, remove vapors and aerosols from the heating element, and remove heat from the device. As noted above, the heating element, including micronozzles and electrical pads, has a fast thermal response, allowing it to cycle above and below the boiling point of the liquid in concert with the electrical pulses and inter-pulse delay of the applied pulse trains during each puff. The device may include a power supply unit connected to the conductor through electrical contact pads, with an electrical control unit for controlling the parameters of the output pulse.

Fig. 1 is a schematic perspective view of a heating element 100 in accordance with an embodiment of the invention. The heating element 100 includes a sheet 102 of conductive material having a first surface 104 for interaction with the liquid aerosolization medium and a second surface 106 for interaction with ambient air. A pair of electrical contact pads 108 on sheet 102 conduct electrical current through the area of the sheet in which the array of micronozzles 110 is formed.

The micronozzles 110 serve to increase the rate of expanding vapors generated by the vaporization of the liquid medium that is in contact with the first surface 104. surface 104 and vaporize it in the micronozzles 110 to form supersaturated vapors which are accelerated by the micronozzles 110 and discharged into the ambient air on the second side 106 as high velocity steam jets. The aerosol is formed due to the rapid cooling of the hot saturated vapors of the liquid medium by collision with the cold air above the heating element 100 with each puff. The particles and molecules of the vapor lose their kinetic energy and coagulate into larger droplets, which are thus an aerosol. The higher the degree of supersaturation and the faster the cooling of the vapor, the denser the aerosol will be and the smaller the aerosol particles will be.

Sheet 102 may be made from a thermomechanically stable electrically conductive material such as metals, alloys, heavily doped low resistivity semiconductors, such as n-type or p-type monocrystalline, polycrystalline, or amorphous silicon, or conductive glasses, ceramics, composites, or other materials, having a specific electrical resistance of not more than 0.01 Ohm cm and resistance to thermal shock.

Fig. 2A, 2B, and 2C are schematic side views of micronozzles 110, 114, and 116, respectively, and liquid-saturated fibrous porous media 210, in accordance with embodiments of the invention. Each micronozzle has a liquid injection port 200 on the first surface 104 and a steam ejection port 202 on the second surface 106 of the sheet 102. The cross sections of the micronozzles 110, 114, and 116 may be circular, rectangular, or square. The first surface 104 with the liquid injection port 200 is in physical contact with the liquid medium, which is bound by the capillary forces of the fibrous porous medium 210 to prevent leakage to the environment.

The sheet 102 heats the liquid by heat transfer to a temperature above the boiling point in the region of the injection port 200, allowing the liquid-vapour phase to pass into the micronozzle 110, 114, 116 and completely vaporize it into supersaturated vapors due to the heat transferred from the sheet 102. The ejection port 202 for steam contributes to the release of expanding vapors in the form of a jet into the surrounding air. To help accelerate the naturally expanding hot vapors from the liquid-filled injection port 200 to the free ejection port 202, the micronozzles 110 and 114 are formed as hollow frustocones 204, in which the injection port 200 is formed at the base of the frustocone 204 and the ejection port 202 is formed by a frustocone. part of the cone 204. A supersonic jet can be created in the micronozzle 116 as a result of strong acceleration by the micronozzle 116 having the shape of a Laval nozzle 206.

Regardless of the shape of the nozzle, a plurality of micronozzles are arranged as an array of identical micronozzles 110 evenly distributed in the conductive sheet 102, for example in a rectangular shape between the electrical contact pads 108, as shown in FIG. 1, so that the current density in the region of the conductive sheet array is also uniformly distributed.

In the embodiment shown in FIG. 2B, in order to generate more vapor, the micronozzle 114 is shaped at its injection port 200 so as to form a short section 208 of a truncated cone-shaped interface portion that increases the liquid vaporization area and assists in collecting vapor from the first surface 104 and the inclined interface portion 208 into the micronozzle. 114. In another embodiment of this type, the aperture and apex angle of the cone may gradually change along its axis from 90° at opening 200 to 0° at opening 202.

The conductive sheet 102, the electrical pads 108, and the micronozzles 110 (or 114 or 116) of the heating element 100 are configured to allow the heating element 100 to produce an aerosol in discrete portions. Sheet 102 has a fast thermal response and low inductance and is made of a material with high thermal diffusivity α _M . Thus, the temperature of the heating element 100 is able to instantly respond to a sequence of short electric current pulses of duration τ and a delay between pulses δ, totaling the puff duration T, rising sharply above the boiling temperature of the liquid T _B during each of the electric current pulses and falling below the temperature Boiling TB liquid during the delay between pulses.

В таблице 1 ниже перечислены примеры вариантов осуществления с вычисленным верхним пределом толщины H_B листа 102 для различных материалов и значений длительности τ импульса.In some embodiments, the material of sheet 102 has a sufficiently high thermal diffusivity α _M such that the thickness H _B of sheet 102 satisfies the condition

Table 1 below lists exemplary embodiments with calculated upper limit thickness H _B of sheet 102 for different materials and pulse durations τ.

TABLE 1

Material α _M , mm ² /s τ, ms

мм

mm H _B , mm Silicon 88 0.1 0.3 <0.03 1 0.93 <0.093 10 2.95 <0.295 Steel, Nichrome 4.2 0.1 0.064 <0.0064 1 0.2 <0.02 10 0.64 <0.064

, чтобы избежать узких путей с высоким сопротивлением не только току, но также и быстрому тепловому перераспределению и релаксации в нагревательном элементе 100 за время длительности импульса τ.For a pulse duration τ of about 1 ms to 10 ms, sheet 102 can be made from silicon wafers or metal foils that are thin enough to respond to power pulses with a large temperature difference. For shorter pulse durations τ of about 0.1 ms to 1 ms, both silicon and metal foils may be suitable. In these embodiments, the distance or wall thickness between the micronozzles 110 is preferably not too small, such as not less than the limit

to avoid narrow paths with high resistance not only to current but also to rapid thermal redistribution and relaxation in the heating element 100 during the pulse duration τ.

On FIG. 3A shows a heating element 300 which has a cylindrical sheet geometry 102 and radial micronozzles 110.

Electrical contact pads 108 are located on a pair of circular edges of sheet 102. This embodiment can have two versions: in one embodiment, the first surface 104 is the outside, and the second surface 106 is the inside of the cylindrical sheet 102. In another embodiment, the first surface 104 is the inside, and the second surface 106 is the outside of the cylindrical sheet 102.

On FIG. 3B shows another heating element 302 that has a curved sheet geometry 102 and radial micronozzles 110 in which contact pads 108 are located on a pair of flat edges of sheet 102.

As in Fig. 1 in FIG. 3C shows a heating element having a flat sheet 102 geometry and through micronozzles 110 perpendicular to the plane of the sheet 102, in which electrical pads 108 are located on a pair of flat edges of the sheet 102. However, in this embodiment, the micronozzles 110 are etched through the sheet 102 rather than pierced, for example , as can be done in previous embodiments.

For the manufacture of the heating element, the sheet 102 may be formed in various ways, depending on the material.

For example, the sheet 102 in the heating elements 100, 300, and 302 may be made by microforming or micropunching thin strips of metal foil. Due to the natural ductility of metals, micronozzles 110 will form with each puncture. The sheet 102 in the heating elements 300 and 302 can then be folded into a curved shape and cut to the desired size. In the heating element 304, the sheet 102 may be fabricated from a wafer or other substrate of a metallic or semiconductor material such as silicon using micromachining techniques such as photoetching or photolithography followed by etching of the materials, such as deep reactive ion etching of semiconductor materials to form microcavities in sheet 102. These microcavities can be formed as micronozzles 110 by controlling process parameters relating to anisotropy and etch rate.

Alternatively, laser micropunch, microperforation, or microetching, such as with ultrashort pulse lasers, can be used to create micronozzles 110 in semiconductor substrates, metal foils, glass, or ceramic materials. Alternatively, microerosion or other electrochemical and micromachining technologies can be used for metals. Alternatively, some materials can be extruded and fused into a polycapillary rod, followed by cross-cutting into plates with multiple microcavities.

On FIG. 3D shows a heating element 306 which has longitudinal micronozzles 110 in the plane of the flat sheet 102 and electrical contact pads 108 located on a pair of plate edges that do not have micronozzle openings 110. substrates that are first micromachined and then clamped and spliced together.

и

In some embodiments, each of the micronozzles 110 has a maximum diameter D _N determined by the conditions

And

where α _l is the temperature conductivity of the liquid or steam. Table 2 lists exemplary embodiments with a calculated upper limit of micronozzle diameter D _N 110 for a typical example of glycerol as a liquid and various pulse widths τ:

TABLE 2

Liquid α _L , mm ² /s τ, ms

, мм

, mm D _N , mm Glycerol 0.1 0.1 0.02 ≤0.02 1 0.062 ≤0.093 10 0.198 ≤0.2

For pulse durations τ, for example, from about 1 ms to 10 ms, the micronozzles 110 may have a diameter of from about 0.05 to 0.1 mm.

In some embodiments, the heating system may have a sensing element 112, such as a temperature sensor, located on or within the sheet 102, such as in one of the micronozzles 110, as shown in FIG. 1. Sensor 112 can be used to control process parameters such as the temperature of sheet 102. To provide peak detection, sensor 112 can be configured for fast thermal response to provide adequate measurement resolution over pulse width τ and time delay δ. Depending on the material and dimensions of the sheet 102, in some embodiments, the sensor 112 may comprise a thermocouple, possibly using a thermoelectric effect in contact with the material of the sheet 102. In other embodiments, the sensor 112 may comprise a glass hermetically sealed thermistor. In another embodiment, the sensor 112 may comprise a thin film resistance and/or a silicon bandgap temperature sensor deposited on the sheet 102 in the form of a thin coating. As an alternative for temperature sensors, thermoelements based on the thermoelectric effect at the junction between the semiconductor and metal leads can be used.

и

и распределены таким образом, что расстояние Δ между соседними микропятнами контактной поверхности 402 удовлетворяет условию

.In some embodiments, electrical contact is provided by electromechanical spring clips. For example, in FIG. 4A shows an electrical contact 400 in which the contact surface 402 is on distributed microforms, such as microspots 408 of surface irregularities due to natural or artificial roughness at the interface between the electrical contact pad 108 of the sheet 102 and the leads 404. The electrical contact pad 108 has a low electrical impedance, fast thermal response and high resistance to thermal shock, so that when passing short powerful electrical pulses, the contact surface 402 quickly reaches thermal equilibrium due to the rapid dissipation of transient heat from the micro-spots 408 of the contact surface 402. To protect the electrical pad 108 from local sparking and overheating, micro-spots 408 of the contact surface 402 are evenly distributed over the electrical contact pad 108. In one embodiment, the microspots 408 of the contact surface 402 have a diameter D _I satisfying the conditions

And

and distributed in such a way that the distance Δ between adjacent microspots of the contact surface 402 satisfies the condition

.

,

и

. Количество микропятен 408 на контактной поверхности 402 электрических контактов 400 и 406 может быть настолько большим, насколько это необходимо для перераспределения вклада контактного сопротивления в пиковое повышение температуры в каждом микропятне при каждом импульсе.In another embodiment of electrical contact 406 shown in FIG. 4B, contact surface 402 between terminals 404 and electrical pad 108 may comprise a plurality, such as an array, of micro-spots 408 of predetermined diameter D _I and distance Δ between adjacent micro-spots. These micro-spots are formed by artificially created micro-shapes, such as spherical or conical micro-shapes, etched into the surface of the sheet 102, satisfying the conditions

,

And

. The number of microspots 408 on contact surface 402 of electrical contacts 400 and 406 may be as large as necessary to redistribute the contribution of contact resistance to the peak temperature rise in each microspot on each pulse.

Table 3 below lists exemplary embodiments with a calculated upper microspot diameter limit DI for a typical example of gold plated copper and silicon surfaces and various pulse widths τ.

TABLE 3

Material α _M , mm ² /s τ, ms

, мм

, mm D _I , mm Δ, mm Gold plating on copper 111 0.1 0.105 <0.01 >0.01 1 0.333 <0.03 >0.03 10 1.05 <0.1 >0.1 Silicon 88 0.1 0.09 <0.01 >0.01 1 0.297 <0.03 >0.03 10 0.938 <0.1 >0.1

For pulse durations τ, for example, from about 1 ms to 10 ms, diameters D _I of microspots 408 may range from about 0.01 to 0.1 mm.

On FIG. 5A shows an electrical contact 500 in which the contact surface 402 between the terminal 404 and the sheet 102 on the electrical contact pad 108 is formed as at least one narrow strip formed by the cylindrical terminal 404 and the flat surface of the electrical pad 108.

In another embodiment shown in FIG. 5B, the contact surface 402 in contact 502 includes two narrow strips formed by a cylindrical tab 404 and a stepped notch 504 in the contact area 108.

In the next embodiment shown in FIG. 5C, the contact surface 402 in contact 506 includes two narrow strips formed by a cylindrical tab 404 and a stepped notch 508 in the contact area 108.

At contacts 500, 502, and 506, narrow strips of contact surface 402 provide an electrical connection path for electrical current from terminals 404 through contact surface 402 to conductive sheet 102, while reducing heat transfer from hot sheet 102 through contact surface 402 to electrical terminals 404.

и

.Reducing heat leakage from the sheet 102 through the contact surface 402 promotes uniform temperature distribution across the sheet 102 during each pulse with a duration τ. The narrow interfaces of the contact strips 500, 502 and 506 may advantageously have a narrow strip width D _S satisfying the conditions

And

.

.When there are two or more narrow strips on the contact surface 402, as in contacts 502 and 506, the distance Δ between adjacent narrow strips may advantageously satisfy the condition

.

It is preferable to connect the electrical leads 404 and pad 108 by applying sufficient force to the contact surface 402 to ensure that the contact does not heat up due to contact resistance and arc is not ignited during the pulses (which can cause oxidation and/or breakage of the circuit after the pulses) .

For contact surfaces between metal parts and between metals and heavily doped semiconductors, the contact resistance depends on the contact pressure. For this reason, it is desirable that the contact pressure exceeds 1 N/mm ² . Such contacts may be formed from micro-bent spring metal, such as brass, wire, or micro-stamped metal pieces such as SMD contact springs, formed as clamps to mechanically secure the sheet 102 while providing reliable galvanic contact at the contact surface 402.

In embodiments where contact surface 402 is formed by metal leads 404 and sheet 102 is made of a semiconductor, such as heavily doped n-type silicon, it is desirable that the contact resistance at interface 402 be lower than the volume resistance of sheet 102. This condition is satisfied rather not a Schottky, but an ohmic contact, which thus allows the free transfer of majority charge carriers between the terminals 404 and the semiconductor sheet 102 and does not limit the electric current. Heavy doping of the semiconductor reduces the possible Schottky barrier, turning it into an ohmic contact.

In other embodiments where sheet 102 is made from a low resistivity semiconductor, pad 108 may be further processed to reduce Schottky type contact resistance. One such treatment may be electrical conductivity plating with gold (Au) or copper (Cu) or a suitable laminate. For this purpose, metallized silicon wafers, which are widely available commercially, can be used.

An appropriate photolithography step, followed by a metal etching step to form metalized contacts, is added to the sheet 102 fabrication process. diffusion of phosphorus into the semiconductor from special pastes containing an n-type doping agent, applied through masks or stencils, as in the case of surface mounting pastes.

In some implementations, as shown in FIG. 2A-C, fluid-saturated, highly porous fibrous media 210 is fluidly coupled to a source of aerosolization fluid and abuts first surface 104 of sheet 102. At its interface with first surface 104, media 210 partially fills micronozzles 110 (or 114 or 116) to increase contact area with sheet 102, thereby increasing the amount of liquid that can be vaporized. Preferably, the medium 210 partially fills the micronozzles 110 at the sloped interface 208 to produce more steam.

The medium 210 has a small pore size, such as less than 20 microns, compared to the distance between adjacent micronozzles 110. The small pore size prevents free fluid communication between the micronozzles and reduces splashing of liquid from one of the micronozzles 110 due to the pressure created by the bubbles formed in the hole injection 200 adjacent micronozzle 110.

The reduced pore size of medium 210 creates additional resistance to fluid flow, even at high porosity.

. В таблице 4 ниже перечислены примеры вариантов осуществления с расчетным значением толщины D_M для типичного примера глицерина в среде 210, такой как сетка из стекловолокна, с пористостью, близкой к 100%, и различными значениями длительности импульса τ.It is desirable, especially if the medium 210 has a limited thickness, to ensure that this medium is able to supply the required amount of liquid for vaporization during the pulse duration τ, and, on the other hand, to replenish the vaporized amount of liquid during the interpulse period τ+δ. The minimum thickness D _M of this medium is also limited by the length of heat diffusion into the liquid medium 210, defined as

. Table 4 below lists exemplary embodiments with a calculated thickness D _M for a typical example of glycerol in a medium 210, such as a glass fiber mesh, with a porosity close to 100%, and various pulse widths τ.

TABLE 4

Liquid α _L , mm ² /s τ, ms

мм

mm D _M , mm Glycerol 88 0.1 0.01 >0.01 1 0.031 >0.03 10 0.099 >0.1

For pulse durations τ, for example, from about 1 ms to 10 ms, the porous medium 210 desirably has a thickness greater than 0.1 mm.

Advantageously, the porous media 210 has sufficient fluid hydrophilicity and porosity to ensure a high liquid refill rate at a thickness D _M for a delay time δ after each pulse of the pulse train. This characteristic is useful for preventing the formation of a layer of Leidenfrost.

The porous hydrophilic medium 210 desirably has a porosity or void fraction of at least 70-90% with a pore diameter in the range of about 1 micron to 10 microns to promote capillary flow and fast filling rates. Media 210 must be stable at high temperature and provide a fluid flow rate of at least 3 μl/mm ² s, withstanding a pressure of at least 0.3 g/mm ² to maintain integrity in the presence of hot gases from the micronozzles 110. Porous media 210 retains fluid due to capillary forces, but releases liquid when sheet 102 is heated due to the resulting drop in liquid viscosity and capillary forces. For this purpose, the porous medium 210 can be formed, for example, in the form of a microfiber matrix consisting of high temperature resistant fibers of borosilicate or quartz glass with a thickness of 0.5 - 1 micron, having a weight of the order of 100 g/m ² . The microfiber matrix has a thickness greater than 0.3 mm and mechanical stability at 0.5 psi, similar to glass or quartz fiber filters known in the art. Such filters usually have a higher fluid flow rate than cotton.

To avoid excessive back pressure at high fluid flow rates, the thickness of the porous medium 210 is typically no greater than about 1 mm.

In another embodiment, the porous media 210 may actively control fluid delivery using electrically actuated changes in the fluid's viscosity and surface tension, such as by preheating or electrowetting, thereby changing the capillary forces to retain the fluid in the media 210. In this case, the porous media can be made electrically conductive fiberglass.

On FIG. 6 shows an aerosol generating device 600, such as that used as an electronic cigarette or a similar type of vaping device, in accordance with an embodiment of the invention.

The aerosol generating device 600 may comprise at least one heating element, for example in the form of a conductive sheet 102 as in heating elements 100, 300, 302, 304, or 306 described above. , one duct 604 containing the heating element. The air duct includes at least one air inlet 606 and one air outlet 608 for air from the housing, allowing the flow of ambient air from the air inlet 606 to the conductive plate 102. Ambient air flows over the second surface 106, promoting the formation of aerosol there and delivering the aerosol to the outlet 608. The duct 604 is not necessarily a separate element, but rather may be limited to one or more air-permeable portions within the housing allowing air to flow from the air inlet 606 to the outlet 608.

The device 600 may further comprise a switching power supply unit 612, which may include a battery connected by electrical leads 404 to the conductive sheet 102. The device 600 also includes a liquid reservoir with an aerosolization liquid mixture storage container unit 614 hydraulically coupled to the heating element. In the embodiment shown in FIG. 6, a fluid source in the form of a storage unit 614 with a fluid transport means is located below the sheet 102. In other possible embodiments, the liquid storage unit may be integrated into the housing 602 in the form of a coaxial reservoir around the sheet 102 while the accessible area under the sheet 102 may be used for the 612 power supply battery.

In one embodiment, the duct 604 includes at least one air nozzle 616 for creating turbulence at the outlet of the air nozzle 616 and directing the turbulent airflow onto and/or over the second surface 106 of the sheet 102.

This turbulent flow contributes to the intense mixing of the air above the heating element and hence the intense formation of aerosols. The speed of the air flow from the nozzle 616 may preferably exceed 1 m/s. For example, the nozzle 616 may be formed together with the plastic housing 602, for example, using injection molding. Desirably, the portion of duct 604 from sheet 102 to outlet 608 maintains laminar airflow to prevent recondensation of aerosol to liquid on the walls of duct 604.

In some embodiments, to reduce residual heat flow from the heating element, duct 604 may include at least one heat sink element 618, such as a pinned heat sink or winding section of duct 604. The heat sink element may comprise a high thermal conductivity ceramic base, connected to the sheet 102. The thermal response time of the heat sink element can advantageously be much longer than the pulse duration τ in order to remove residual heat without affecting the peak heating temperature.

On FIG. 7 is a circuit diagram of a power supply unit 612 of a device 600 in accordance with an embodiment of the invention. The power supply 612 may include an isolated output circuit similar to that used in medical devices. In the depicted embodiment, the power supply unit 612 includes a flyback converter 702 using an isolation transformer 700 to separate an electrical output 706, which is connected via electrical leads 708 to a conductive sheet, from an input 704, which is powered by a main power source, such as an AC/DC converter. or battery.

The galvanically isolated interface allows the safe use of more power to produce intense aerosol output while maintaining battery capacity. To power the heating element 102 using pulses with a duration τ and a delay δ, the frequency controller 710 of the flyback converter 702 modulates the switching frequency and duty cycle.

On FIG. 8A shows a flat replaceable heating element 800 comprising a flat conductive sheet 102, which may be similar to the sheet shown in FIG. 1 and FIG. 3C, along with liquid-saturated porous media 210. These elements are sandwiched in substrate 802 with electrical leads 404. Replaceable heating element 800 may include a flat liquid storage container block 614 that may be reusable or disposable.

If the porous media 210 is soft, such as a glass microfiber media, it may be supported by an additional support mesh layer 804 made of a mechanically stable hydrophilic (relative to the composition of the liquid media) material, such as polycarbonate, polyethylene terephthalate (PET), or polyetheretherketone (PEEK) , or ceramic, glass or composite material. Fixing the porous medium 210 with the mesh layer 804 prevents the medium 210 from delamination from the sheet 102 due to the sudden increase in gas pressure inside the micronozzles 110 with each pulse heating.

To control operating parameters, plug-in 800 may include a sensor, such as a temperature sensor 806. Substrate 802 may be a DBC (Direct Connected Copper) substrate with 808 leads as on a printed circuit board. The liquid storage container block 614 may be injection molded from a suitable plastic.

On FIG. 8B shows a cylindrical replaceable heating element 810 in which the conductive sheet 102 is bent into a cylindrical shape, such as in the heating element 300 shown in FIG. 3A. In this embodiment, the liquid medium is supplied from the coaxial cylindrical block of the liquid storage container 614, located outside the cylindrical sheet 102, through the coaxial liquid-saturated porous medium 210, as well as the coaxial support layer 804. The micronozzles 110 are positioned to create jets of vapor in the inner radial direction to the axis of the cylindrical sheet 102.

In another embodiment (not shown in the figures), the fluid storage unit, the porous media, and the support layer may be located within the cylindrical conductive sheet, thereby supplying the fluid from within the heating body. In this case, the micronozzles create jets of steam in a radial direction outward from the axis of the cylindrical heating body.

Fig. 9 is a schematic diagram of pulses applied in an aerosolization device according to an embodiment of the invention. To produce an aerosol, the amount of current I _M provided by the power supply 612 in each pulse 652 having a duration τ is sufficiently high that the liquid temperature 654 at the interface with the conductive sheet 102 preferentially cycles with the power pulses 652 in the temperature range below the boiling point T _B and Leidenfrost points T _L . In this temperature range, the liquid medium boils in the nucleation and transition regions of the liquid boiling curve 656, thus providing the highest critical power flow FM from the heating element to the liquid and the most intense vaporization of V _M 658 to a state of saturated vapor. For example, the power flow determined by an electric current is 1-10 W/mm2 to vaporize a layer of a glycerin-based composition having a thickness of 0.01 mm to 0.1 mm in less than or about 10 ms. The pulse duration τ is chosen to be large enough to vaporize the heated liquid mixture.

. The duration of the power pulse τ is pre-set no more than the time required for heating and vaporization of the liquid layer adjacent to the conductive sheet to a thickness of the order of the thermal diffusion length D _M in a liquid medium or a porous medium 210 defined as

.

, чтобы избежать переохлаждения жидкости в микросоплах 110. Например, временная задержка δ может быть порядка длительности τ импульса.Desirably, the time delay δ between successive power pulses 652 is not less than the time required to replenish the vaporized liquid in the region of the liquid-saturated porous medium 210 adjacent to the interface with the first surface of the conductive sheet 102 at the injection port 200. It is further preferred so that the time delay δ correlates with the size D _N of the micronozzles 110 through the condition

to avoid overcooling the liquid in the micronozzles 110. For example, the time delay δ may be on the order of pulse duration τ.

It should be understood that the embodiments described above are by way of example and that the present invention is not limited to what has been specifically shown and described above.

Rather, the scope of the present invention includes both combinations and subcombinations of the various features described above, as well as variations and modifications thereof, which may occur to those skilled in the art upon reading the foregoing description and which are not disclosed in the prior art.

Claims (26)

1. An aerosol generating device comprising a heating element containing a sheet of electrically conductive material having a first surface and a second surface opposite the first surface, and containing a plurality of channels located in the area of the sheet and passing through the sheet from the first surface to the second surface, while the channels are made with the possibility of forming a directed flow of vapor of a liquid medium from the channels. 2. The device according to claim. 1, while the channels have a variable cross-section along the length or at least in the region of the edge. 3. The device according to claim 1, wherein the sheet is made of a heavily doped silicon wafer. 4. The device according to claim. 1, wherein the plurality of channels is made in the form of a rectangular or square array of identical channels. 5. The device of claim. 1, wherein the sheet contains containing metal or dopant pads, in which the contact resistance is less than outside the pads on the sheet. 6. The device according to claim 1, wherein the sheet comprises a surface portion configured to measure the temperature of the heating element. 7. The device according to claim 1, also containing a reservoir for containing a liquid medium, containing a layer of hydrophilic porous medium mated with the surface of the sheet on the first surface of the sheet, made in one node with the sheet with the possibility of suppressing the growth of bubbles during vaporization in the interface area. 8. The device according to claim 7, in which the pore size of the porous medium is smaller than the transverse size of the channels and the distance between the channels. 9. The device according to claim. 7, while the node is made with the possibility of removal. 10. The device according to one of paragraphs. 7-9, also comprising a power supply unit for delivering electrical current through the sheet region in the form of pulses, configured to match at least one pulse train parameter with a heating element thermal time constant for pulsed heating of the heating element. 11. The device according to claim. 10, wherein the power supply contains electrodes, made with the possibility of pressing against the sheet, the body of which is limited by a cylindrical surface at the place of pressing against the sheet. 12. The device according to claim 10, wherein the power supply and the heating element are configured so that at least one pulse train parameter of the power supply and the thermal time constant of the heating element are mutually matched for pulsed heating of the liquid medium above the boiling point of the liquid medium. 13. The apparatus of claim. 10, comprising a control unit configured to control the power supply in response to the output signal of the temperature sensor of the heating element. 14. The apparatus of claim. 10, wherein the heating element is enclosed in a housing containing an air duct configured to remove heat through the air flow. 15. A method for generating an aerosol, comprising: providing the device according to claim 12; bringing the liquid medium into contact with the first surface of the sheet; applying electric current pulses through the area of the sheet to initiate a directed flow of liquid medium vapor from the channels; as well as setting the pulse parameters for pulsed heating of the liquid medium above the boiling point of the liquid medium. 16. A method for generating an aerosol, comprising: providing a device according to claim 10, containing a removable node according to claim 9; bringing the liquid medium into contact with the first surface of the sheet; applying electric current pulses through the area of the sheet to initiate a directed flow of liquid medium vapor from the channels; as well as removal of the assembly for replacement. 17. A method for generating an aerosol, comprising: providing the device according to claim 13; bringing the liquid medium into contact with the first surface of the sheet; applying electric current pulses through the area of the sheet to initiate a directed flow of liquid medium vapor from the channels; and limiting the heating temperature of the sheet in response to the temperature sensor output. 18. The method of generating an aerosol, containing: providing the device p. 14; bringing the liquid medium into contact with the first surface of the sheet; applying electric current pulses through the area of the sheet to initiate a directed flow of liquid medium vapor from the channels; as well as directing air through the duct to remove heat. 19. A method for manufacturing a heating element of an aerosol generation device according to claim 3, comprising: providing a silicon wafer according to claim 3; formation of channels in the wafer by micromachining using photolithography followed by silicon etching. 20. A method for manufacturing a heating element of an aerosol generation device according to claim 1, comprising: providing a sheet according to paragraph 1; formation of channels in the sheet with a laser.

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