EP4247118A1

EP4247118A1 - A method for measuring the temperature of a susceptor

Info

Publication number: EP4247118A1
Application number: EP22162934.8A
Authority: EP
Inventors: Branislav ZIGMUND; Stanislav SLIVA; Daniel Vanko
Original assignee: JT International SA
Current assignee: JT International SA
Priority date: 2022-03-18
Filing date: 2022-03-18
Publication date: 2023-09-20

Abstract

A method comprising inductively heating a susceptor (10), detecting the thermal radiation emitted from the susceptor (10), and measuring the temperature of the susceptor (10) based on the emitted thermal radiation to provide a measured susceptor temperature.

Description

Technical Field

The present disclosure relates generally to a method for measuring the temperature of a susceptor, and more particularly to a method for measuring the temperature of an inductively heated susceptor.

Technical Background

Aerosol generating devices (also known as vaporisers) which heat, rather than burn or combust, an aerosol generating substrate to produce an aerosol for inhalation by a user of the device have become popular with consumers in recent years as an alternative to the use of traditional tobacco products.
Various devices and systems are available which can use one of a number of different approaches to provide heat to the aerosol generating substrate. One such approach is to provide an induction heating assembly. Such assemblies employ an electromagnetic field generator, such as an induction coil, to generate an alternating electromagnetic field that couples with, and inductively heats, a susceptor heating element. Heat from the susceptor is transferred, for example by conduction, to the substrate and an aerosol is generated as the substrate is heated for inhalation by a user of the device.
The temperature of an inductively heated susceptor can be estimated. Based on the estimated temperature, adjustments can be made to one or more operating parameters, such as moderating power supply to the induction coil, to maintain a target operating temperature to ensure a sufficient amount of vapour is generated during use.
To ascertain the accuracy of such temperature estimates, a comparison is required with a measurement of the actual temperature of an inductively heated susceptor. Based on any differences observed between the estimated and measured temperatures, modifications can be made to the method used to provide the temperature estimate to improve accuracy and correspondence. Modifications can also be made to the geometry, materials and/or manufacturing process of the susceptor to improve susceptor performance towards an ideal on which temperature estimation methods may be based.
Methods are therefore required for measuring the temperature of an inductively heated susceptor.

Summary of the Disclosure

According to a first aspect of the present disclosure, there is provided a method, the method comprising:

inductively heating a susceptor;
detecting the thermal radiation emitted from the susceptor; and
measuring the temperature of the susceptor based on the emitted thermal radiation to provide a measured susceptor temperature.

The thermal radiation emitted from the susceptor may be detected by a thermal imaging camera.
The susceptor may be inductively heated by an induction coil. The induction coil may be arranged to surround the susceptor.
Possibly, the method comprises:

detecting a reflection of the thermal radiation emitted from the susceptor; and
measuring the temperature of the susceptor based on the reflected thermal radiation.

The thermal radiation may be reflected by a mirror. A reflective surface of the mirror may comprise gold.
The method may comprise comparing the measured susceptor temperature with an estimated susceptor temperature.
Possibly, the method comprises:

varying the temperature of the susceptor over a time period; and
measuring the temperature of the susceptor over the time period to provide a measured susceptor temperature profile over the time period. The method may comprise comparing the measured susceptor temperature profile with an estimated susceptor temperature profile over the time period.

The susceptor may be substantially cylindrical. The susceptor may be a susceptor tube. Alternatively, the susceptor may be substantially planar. The susceptor may be a susceptor strip. Possibly, the susceptor is useable as a heating element as part of an induction heating assembly of an aerosol generating system, wherein the aerosol generating system comprises an aerosol generating device and an aerosol generating substrate.
The method according to examples of the disclosure provides accurate measurement of the actual temperature of an inductively heated susceptor in real time allowing comparison to an estimated susceptor temperature.

Brief Description of the Drawings

Figure 1 is a diagrammatic view of an aerosol generating system;
Figure 2 is a diagrammatic perspective view of a susceptor;
Figure 3 is a diagrammatic perspective view of another susceptor;
Figure 4 illustrates a method for measuring the temperature of a susceptor; and
Figure 5 is a graphical representation showing a comparison between estimated susceptor temperature and measured susceptor temperature.

Detailed Description of Embodiments

Embodiments of the present disclosure will now be described by way of example only and with reference to the accompanying drawings.
Examples of the disclosure provide a method for measuring the temperature of an inductively heated susceptor 10. Accordingly, a method is provided for measuring the temperature of a susceptor 10 which has been inductively heated or is being inductively heated. The method is a non-contact method.
As shown diagrammatically in Figure 1, a susceptor 10 according to examples of the disclosure is useable as a heating element 12 as part of an induction heating assembly 14, i.e., an induction heating system, of an aerosol generating system 16. An aerosol generating system 16 comprises an aerosol generating device 18 (also known as a vaporiser) and an aerosol generating substrate 20. An aerosol generating device 18 is a hand-held, portable, device, by which it is meant that a user is able to hold and support the device 18 unaided, in a single hand.
In use, an induction coil 22, i.e., an electromagnetic field generator, comprised in the induction heating assembly 14 is arranged to be energised to generate an alternating electromagnetic field that couples with, and inductively heats, the susceptor 10 due to eddy currents and magnetic hysteresis losses resulting in a conversion of energy from electromagnetic to heat. Heat from the susceptor 10 is transferred, for example by conduction, radiation and convection, to the aerosol generating substrate 20 to heat the aerosol generating substrate 20 (without burning or combusting the aerosol generating substrate 20) thereby generating a vapour which cools and condenses to form an aerosol for inhalation by a user of the aerosol generating device 18.
In general terms, a vapour is a substance in the gas phase at a temperature lower than its critical temperature, which means that the vapour can be condensed to a liquid by increasing its pressure without reducing the temperature, whereas an aerosol is a suspension of fine solid particles or liquid droplets, in air or another gas. It should, however, be noted that the terms 'aerosol' and 'vapour' may be used interchangeably in this specification, particularly with regard to the form of the inhalable medium that is generated for inhalation by a user.
The induction coil 22 is energised by a power source 24 of the aerosol generating device 18, such as a battery. Aerosol generating devices 10 typically include a controller 26 and a user interface for controlling the operation of the aerosol generating device 18 via the controller 26.
The controller 26 is configured to detect the initiation of use of the aerosol generating device 18, for example, in response to a user input, such as a button press to activate the aerosol generating device 18, or in response to a detected airflow through the aerosol generating device 18. As will be understood by one of ordinary skill in the art, an airflow through the aerosol generating device 18 is indicative of a user inhalation or 'puff. The aerosol generating device 18 may, for example, include a puff detector, such as an airflow sensor (not shown), to detect an airflow through the aerosol generating device 18.
The controller 26 includes electronic circuitry. The power source 24 and the electronic circuitry may be configured to operate at a high frequency. For example, the power source 24 and the electronic circuitry may be configured to operate at a frequency of between approximately 80 kHz and 500 kHz, possibly between approximately 150 kHz and 250 kHz, and possibly at approximately 200 kHz. The power source 24 and the electronic circuitry could be configured to operate at a higher frequency, for example in the MHz range, if required.
The induction coil 22 may be arranged around the susceptor 10, for example to surround or fully surround the susceptor 10. The induction coil 22 may be substantially helical in shape. The induction coil 22 may be annular. The induction coil 22 may comprise a Litz wire or a Litz cable. It will, however, be understood that other materials could be used. The induction coil 22 may be arranged to operate in use with a fluctuating electromagnetic field having a magnetic flux density of between approximately 20mT and approximately 2.0T at the point of highest concentration.
The induction heating assembly 14 may have an arrangement in which one or more susceptors 10 are arranged around the periphery of a heating compartment (not shown) configured for receiving an aerosol generating substrate 20. Alternatively, in other arrangements a susceptor 10 may be arranged to project into a heating compartment (not shown) from an end of the heating compartment to penetrate the aerosol generating substrate 20 when the aerosol generating substrate 20 is received in the heating compartment. In such examples, the susceptor 10 may be a blade or pin as described below. In these examples, the susceptor 20 is comprised in the aerosol generating device 18, as illustrated diagrammatically in Figure 1.
In other arrangements, the susceptor 10 is instead provided in the aerosol generating substrate 20 during manufacture.
In examples of the disclosure, the susceptor 10 comprises an electrically conductive material. The susceptor 10 may comprise one or more, but not limited to, of graphite, molybdenum, silicon carbide, niobium, aluminium, iron, nickel, nickel containing compounds, titanium, mild steel, stainless steel, low carbon steel and alloys thereof, e.g., nickel chromium or nickel copper, and composites of metallic materials. In some examples, the susceptor 10 comprises a metal selected from the group consisting of mild steel, stainless steel, and low carbon stainless steel.
Susceptors 10 according to examples of the disclosure may comprise a variety of geometrical configurations. For instance, a susceptor 10 may be cylindrical (i.e., a cylindrical susceptor or substantially cylindrical susceptor), or planar (i.e., a planar susceptor or substantially planar susceptor). Susceptors 10 may be open-ended, hollow and/or elongate. Specific examples of susceptors 10 according to examples of the disclosure include, but are not limited to, a particulate susceptor, a susceptor filament, a susceptor mesh, a susceptor wick, a susceptor pin, a susceptor rod, a susceptor blade, a susceptor strip, a susceptor sleeve, a susceptor tube, a susceptor ring, and a susceptor cup. A susceptor strip may be elongate.
Figures 2 and 3, respectively show examples of different types of susceptor tubes 28, 30 each having a tube wall 32.
Regarding the susceptor tube 28 shown in Figure 2, openings 34 extend through the tube wall 32. The openings 34 are apertures, through-holes, or perforations. Accordingly, the tube wall 32 comprises a plurality of openings 34. The openings 34 are substantially circular shaped openings. In other examples, the openings 34 may have a different shape. The openings 34 are distributed over the majority of the tube wall 32. The openings 34 are arranged in rows. Each row extends around the circumference of the susceptor tube 28. Accordingly, the openings 34 are arranged in circumferentially adjacent rows. The openings 34 in adjacent rows are staggered. Accordingly, the openings 34 in each row are axially offset from the openings 34 in circumferentially adjacent rows to provide a staggered arrangement of the openings 34. The openings 34 in each row are uniformly spaced apart. The rows are uniformly spaced apart.
The susceptor tube 28 may be an outer susceptor or peripheral susceptor, i.e., locatable on the outside of an aerosol generating substrate.
Referring to Figure 3, the susceptor tube 30 has a longer axial length and a reduced diameter compared to the susceptor tube 28 shown in Figure 2. Furthermore, the tube wall 32 of the susceptor tube 30 does not comprise openings extending therethrough. The susceptor tube 30 may be a central or inner susceptor, i.e., locatable within an aerosol generating substrate or on the inside of an aerosol generating substrate.
Susceptors 10 according to examples of the disclosure may have a thickness up to 150 µm, or up to 300 µm, or preferably may have a thickness from 30 µm to 300 µm, or more preferably may have a thickness from 100 µm to 150 µm, or most preferably may have a thickness of 100 µm. A susceptor 10 having these thickness dimensions may be particularly suitable for being inductively heated during use.
During use of an aerosol generating system 16, the temperature of an inductively heated susceptor 10, i.e., a susceptor 10 which has been inductively heated or is being inductively heated, can be estimated, for instance by the controller 26, using one of a number of different methods. Such methods may rely on an algorithm.
In some examples, the temperature estimation may be based on the electrical resistance of the susceptor 10. Electrical resistance changes proportionally with susceptor 10 temperature. During induction heating, the change in the electrical resistance of the susceptor 10 can be observed as a change in resonance frequency and/or a change in the amplitude of resonance peak voltage. Preferably, in such examples an estimation of susceptor 10 temperature is based on resonance peak voltage because this is generally more sensitive to a change in electrical resistance of the susceptor 10.
Based on the estimated temperature, adjustments can be made to one or more operating parameters, such as moderating power supply from the power source 24 to the induction coil 22, to maintain a target operating temperature to ensure a sufficient amount of vapour is generated during use. The normal operational temperature of a susceptor 10 in an induction heating assembly 14 of an aerosol generating system 16 is about 350°C, or up to 350°C.
To ascertain the accuracy of such temperature estimates, a comparison is required with a measurement of the actual temperature of an inductively heated susceptor 10. Based on any differences observed between the estimated and measured temperatures, modifications can be made to the method used to provide the temperature estimate to improve accuracy and correspondence. Modifications can also be made to the geometry, materials and/or manufacturing process of the susceptor 10 to improve susceptor 10 performance towards an ideal on which temperature estimation methods may be based.
Figure 4 illustrates a method for measuring the temperature of a susceptor 10. The method is a non-contact method.
With reference to block 36, the method comprises inductively heating a susceptor 10, detecting the thermal radiation emitted from the susceptor 10, and measuring the temperature of the susceptor 10 based on the emitted thermal radiation. A measured susceptor temperature is provided corresponding to the actual temperature of the susceptor.
In some examples, the thermal radiation emitted from the susceptor 10 is detected by a thermal imaging camera.
In some examples, the susceptor 10 is inductively heated by an induction coil 22. The induction coil 22 may be arranged to surround, or fully surround, the susceptor 10. The induction coil 22 may be as described above.
Regarding block 38, in some examples the method comprises detecting a reflection of the thermal radiation emitted from the susceptor 10 and measuring the temperature of the susceptor 10 based on the reflected thermal radiation. The thermal radiation is reflected by a mirror. A reflective surface of the mirror may comprise gold.
At block 40, in some examples the method comprises comparing the measured susceptor temperature with an estimated susceptor temperature.
With reference to block 42, in some examples the method comprises varying the temperature of the susceptor over a time period and measuring the temperature of the susceptor over the time period. A measured susceptor temperature profile over the time period is provided corresponding to the actual temperature profile of the susceptor. The measured susceptor temperature profile may be compared with an estimated susceptor temperature profile over the same time period.
The graph of Figure 5 compares the measured temperature of an inductively heated susceptor 10 (i.e., the actual susceptor temperature) with an estimation of the susceptor temperature over the same time period.
The susceptor 10 was inductively heated using an induction coil 22 arranged to fully surround the susceptor 10. The induction coil 22 is of the type described above and had seven turns, an inductance of 0.340 µH and a resistance of 9.7 mOhm. The susceptor 10 had an outer diameter of 5 mm, a wall thickens of 150 µm and an axial length of 7 mm.
The temperature of the susceptor 10 was varied over the time period indicated in the graph. The power supply to the induction coil 22 was moderated to vary the temperature of the susceptor 10 over the time period.
The thermal radiation emitted from the susceptor 10 over the time period was reflected using a mirror having a reflective surface comprising gold. The reflection of the thermal radiation was detected using a thermal imaging camera to provide a measured susceptor temperature profile over the time period. In the graph of Figure 5, the measured susceptor temperature profile (corresponding to the actual temperature profile of the susceptor 10) is compared with an estimated susceptor temperature profile over the same time period.
It is apparent from a consideration of Figure 5 that the estimated and measured temperature profiles are different. Accordingly, in this example modification may be required to the method used to provide the temperature estimate to improve accuracy and correspondence. Additional or alternatively, modifications may also be required to the geometry, materials and/or manufacturing process of the susceptor to improve susceptor performance towards an ideal on which temperature estimation methods may be based. In other examples, there may be correspondence, i.e., a close similarity, between the estimated temperature and the actual measured temperature of the susceptor 10, suggesting that modifications are not required to the method used to provide the temperature estimate and/or to the geometry, materials and/or manufacturing process of the susceptor 10.
The method according to examples of the disclosure provides accurate measurement of the actual temperature of an inductively heated susceptor 10 in real time allowing comparison to an estimated susceptor temperature.
Although exemplary embodiments have been described in the preceding paragraphs, it should be understood that various modifications may be made to those embodiments without departing from the scope of the appended claims. Thus, the breadth and scope of the claims should not be limited to the above-described exemplary embodiments.
Any combination of the above-described features in all possible variations thereof is encompassed by the present disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.
Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like, are to be construed in an inclusive as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".

Claims

A method, the method comprising:
inductively heating a susceptor (10);

detecting the thermal radiation emitted from the susceptor (10); and

measuring the temperature of the susceptor (10) based on the emitted thermal radiation to provide a measured susceptor temperature.
A method according to claim 1, wherein the thermal radiation emitted from the susceptor (10) is detected by a thermal imaging camera.
A method according to claim 1 or 2, wherein the susceptor (10) is inductively heated by an induction coil (22).
A method according to claim 3, wherein the induction coil (22) is arranged to surround the susceptor (10).
A method according to any of the preceding claims, wherein the method comprises:
detecting a reflection of the thermal radiation emitted from the susceptor (10); and

measuring the temperature of the susceptor (10) based on the reflected thermal radiation.
A method according to claim 5, wherein the thermal radiation is reflected by a mirror.
A method according to claim 6, wherein a reflective surface of the mirror comprises gold.
A method according to any of the proceeding claims, wherein the method comprises:
comparing the measured susceptor temperature with an estimated susceptor temperature.
A method according to any of the proceeding claims, wherein the method comprises:
varying the temperature of the susceptor (10) over a time period; and

measuring the temperature of the susceptor (10) over the time period to provide a measured susceptor temperature profile over the time period.
A method according to claim 9, wherein the method comprises:
comparing the measured susceptor temperature profile with an estimated susceptor temperature profile over the time period.
A method according to any of the preceding claims, wherein the susceptor (10) is substantially cylindrical.
A method according to claim 11, wherein the susceptor (10) is a susceptor tube.
A method according to any of claim 1 to 10, wherein the susceptor (10) is substantially planar.
A method according to claim 13, wherein the susceptor (10) is a susceptor strip.
A method according to any of the preceding claims, wherein the susceptor (10) is useable as a heating element (12) as part of an induction heating assembly (14) of an aerosol generating system (16), wherein the aerosol generating system (16) comprises an aerosol generating device (18) and an aerosol generating substrate (20).