NZ624113B2 - An electrically operated aerosol generating system having aerosol production control - Google Patents
An electrically operated aerosol generating system having aerosol production control Download PDFInfo
- Publication number
- NZ624113B2 NZ624113B2 NZ624113A NZ62411312A NZ624113B2 NZ 624113 B2 NZ624113 B2 NZ 624113B2 NZ 624113 A NZ624113 A NZ 624113A NZ 62411312 A NZ62411312 A NZ 62411312A NZ 624113 B2 NZ624113 B2 NZ 624113B2
- Authority
- NZ
- New Zealand
- Prior art keywords
- aerosol
- parameter
- flow rate
- aerosol generating
- heating element
- Prior art date
Links
- 239000000443 aerosol Substances 0.000 title claims abstract description 147
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 18
- 238000010438 heat treatment Methods 0.000 claims abstract description 74
- 239000000758 substrate Substances 0.000 claims abstract description 56
- 239000000203 mixture Substances 0.000 claims abstract description 22
- 230000001276 controlling effect Effects 0.000 claims abstract description 19
- 230000001419 dependent Effects 0.000 claims description 4
- 238000004590 computer program Methods 0.000 claims description 3
- 239000007788 liquid Substances 0.000 description 72
- 239000003570 air Substances 0.000 description 64
- 239000000463 material Substances 0.000 description 39
- 210000001736 Capillaries Anatomy 0.000 description 33
- 238000003860 storage Methods 0.000 description 21
- 238000005485 electric heating Methods 0.000 description 18
- 238000009833 condensation Methods 0.000 description 11
- 230000005494 condensation Effects 0.000 description 11
- 230000000391 smoking Effects 0.000 description 11
- -1 aluminium- titanium- zirconium- Chemical compound 0.000 description 10
- 229910052751 metal Inorganic materials 0.000 description 10
- 239000002184 metal Substances 0.000 description 10
- 241000208125 Nicotiana Species 0.000 description 8
- 235000002637 Nicotiana tabacum Nutrition 0.000 description 8
- 229910045601 alloy Inorganic materials 0.000 description 7
- 239000000956 alloy Substances 0.000 description 7
- 239000000969 carrier Substances 0.000 description 6
- 238000001514 detection method Methods 0.000 description 6
- 230000000051 modifying Effects 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- 239000000919 ceramic Substances 0.000 description 5
- 230000000704 physical effect Effects 0.000 description 5
- 230000004913 activation Effects 0.000 description 4
- 239000012080 ambient air Substances 0.000 description 4
- 230000006399 behavior Effects 0.000 description 4
- 239000002131 composite material Substances 0.000 description 4
- 238000001816 cooling Methods 0.000 description 4
- 150000002739 metals Chemical class 0.000 description 4
- DNIAPMSPPWPWGF-UHFFFAOYSA-N propylene glycol Chemical compound CC(O)CO DNIAPMSPPWPWGF-UHFFFAOYSA-N 0.000 description 4
- 239000007787 solid Substances 0.000 description 4
- REDXJYDRNCIFBQ-UHFFFAOYSA-N aluminium(3+) Chemical class [Al+3] REDXJYDRNCIFBQ-UHFFFAOYSA-N 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 3
- 239000002775 capsule Substances 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000000796 flavoring agent Substances 0.000 description 3
- 235000019634 flavors Nutrition 0.000 description 3
- 239000010439 graphite Substances 0.000 description 3
- 229910002804 graphite Inorganic materials 0.000 description 3
- 239000011133 lead Substances 0.000 description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 3
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical group [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 3
- 239000004696 Poly ether ether ketone Substances 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 229910010293 ceramic material Inorganic materials 0.000 description 2
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 2
- 230000003247 decreasing Effects 0.000 description 2
- 238000009795 derivation Methods 0.000 description 2
- 239000003814 drug Substances 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- PEDCQBHIVMGVHV-UHFFFAOYSA-N glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 2
- 235000011187 glycerol Nutrition 0.000 description 2
- 238000005338 heat storage Methods 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 229910001092 metal group alloy Inorganic materials 0.000 description 2
- UFWIBTONFRDIAS-UHFFFAOYSA-N naphthalene Chemical compound C1=CC=CC2=CC=CC=C21 UFWIBTONFRDIAS-UHFFFAOYSA-N 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 229920003223 poly(pyromellitimide-1,4-diphenyl ether) Polymers 0.000 description 2
- 229920002530 poly[4-(4-benzoylphenoxy)phenol] polymer Polymers 0.000 description 2
- 229920001155 polypropylene Polymers 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 230000002441 reversible Effects 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 239000011232 storage material Substances 0.000 description 2
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 239000010936 titanium Substances 0.000 description 2
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N AI2O3 Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 229910001006 Constantan Inorganic materials 0.000 description 1
- VBJZVLUMGGDVMO-UHFFFAOYSA-N Hafnium Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 description 1
- 229910018487 Ni—Cr Inorganic materials 0.000 description 1
- 239000004677 Nylon Substances 0.000 description 1
- 229920003171 Poly (ethylene oxide) Polymers 0.000 description 1
- 239000004698 Polyethylene (PE) Substances 0.000 description 1
- 229920001721 Polyimide Polymers 0.000 description 1
- 239000004642 Polyimide Substances 0.000 description 1
- 229920004933 Terylene® Polymers 0.000 description 1
- 230000002745 absorbent Effects 0.000 description 1
- 239000002250 absorbent Substances 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminum Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 239000001913 cellulose Substances 0.000 description 1
- 229920002678 cellulose Polymers 0.000 description 1
- 238000002144 chemical decomposition reaction Methods 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 235000019506 cigar Nutrition 0.000 description 1
- 235000019504 cigarettes Nutrition 0.000 description 1
- 229910052803 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 230000000875 corresponding Effects 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 230000005496 eutectics Effects 0.000 description 1
- 235000013305 food Nutrition 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 239000003365 glass fiber Substances 0.000 description 1
- 239000000383 hazardous chemical Substances 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000010445 mica Substances 0.000 description 1
- 229910052618 mica group Inorganic materials 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 229910021343 molybdenum disilicide Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 229920001778 nylon Polymers 0.000 description 1
- 230000003287 optical Effects 0.000 description 1
- 239000012188 paraffin wax Substances 0.000 description 1
- 239000000419 plant extract Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 239000005020 polyethylene terephthalate Substances 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 238000010926 purge Methods 0.000 description 1
- 230000001105 regulatory Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000000717 retained Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000000741 silica gel Substances 0.000 description 1
- 229910002027 silica gel Inorganic materials 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- VMHLLURERBWHNL-UHFFFAOYSA-M sodium acetate Chemical compound [Na+].CC([O-])=O VMHLLURERBWHNL-UHFFFAOYSA-M 0.000 description 1
- 235000017281 sodium acetate Nutrition 0.000 description 1
- 239000001632 sodium acetate Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 229910000601 superalloy Inorganic materials 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N tin hydride Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- 238000009834 vaporization Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 239000001993 wax Substances 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Classifications
-
- A—HUMAN NECESSITIES
- A24—TOBACCO; CIGARS; CIGARETTES; SIMULATED SMOKING DEVICES; SMOKERS' REQUISITES
- A24F—SMOKERS' REQUISITES; MATCH BOXES; SIMULATED SMOKING DEVICES
- A24F40/00—Electrically operated smoking devices; Component parts thereof; Manufacture thereof; Maintenance or testing thereof; Charging means specially adapted therefor
- A24F40/10—Devices using liquid inhalable precursors
-
- A—HUMAN NECESSITIES
- A24—TOBACCO; CIGARS; CIGARETTES; SIMULATED SMOKING DEVICES; SMOKERS' REQUISITES
- A24F—SMOKERS' REQUISITES; MATCH BOXES; SIMULATED SMOKING DEVICES
- A24F40/00—Electrically operated smoking devices; Component parts thereof; Manufacture thereof; Maintenance or testing thereof; Charging means specially adapted therefor
- A24F40/50—Control or monitoring
- A24F40/51—Arrangement of sensors
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M11/00—Sprayers or atomisers specially adapted for therapeutic purposes
- A61M11/04—Sprayers or atomisers specially adapted for therapeutic purposes operated by the vapour pressure of the liquid to be sprayed or atomised
- A61M11/041—Sprayers or atomisers specially adapted for therapeutic purposes operated by the vapour pressure of the liquid to be sprayed or atomised using heaters
- A61M11/042—Sprayers or atomisers specially adapted for therapeutic purposes operated by the vapour pressure of the liquid to be sprayed or atomised using heaters electrical
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M15/00—Inhalators
- A61M15/06—Inhaling appliances shaped like cigars, cigarettes or pipes
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
- A61M16/0003—Accessories therefor, e.g. sensors, vibrators, negative pressure
- A61M2016/0015—Accessories therefor, e.g. sensors, vibrators, negative pressure inhalation detectors
- A61M2016/0018—Accessories therefor, e.g. sensors, vibrators, negative pressure inhalation detectors electrical
- A61M2016/0024—Accessories therefor, e.g. sensors, vibrators, negative pressure inhalation detectors electrical with an on-off output signal, e.g. from a switch
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M2205/00—General characteristics of the apparatus
- A61M2205/36—General characteristics of the apparatus related to heating or cooling
- A61M2205/3653—General characteristics of the apparatus related to heating or cooling by Joule effect, i.e. electric resistance
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M2205/00—General characteristics of the apparatus
- A61M2205/82—Internal energy supply devices
- A61M2205/8206—Internal energy supply devices battery-operated
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H1/00—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters
- F24H1/0018—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters using electric energy supply
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
- F24H9/00—Details
- F24H9/20—Arrangement or mounting of control or safety devices
- F24H9/2007—Arrangement or mounting of control or safety devices for water heaters
- F24H9/2014—Arrangement or mounting of control or safety devices for water heaters using electrical energy supply
Abstract
electrically operated aerosol generating device (100) is disclosed. The device comprises at least one heating element (119) for heating an aerosol-forming substrate, a power source (107) for providing power to the heating element (119), and electric circuitry (109) for controlling the supply of power to the heating element. The electric circuitry (109) includes a sensor for detecting air flow past the aerosol generating element. The electric circuitry (109) is arranged to determine a first parameter related to change in flow rate of the air flow, compare the first parameter to a threshold value, and subsequently reduce or suspend the supply of power to the heating element (119). The first parameter is derived from a combination of second and third parameters, wherein the second parameter relates to an air flow rate through the device, and the third parameter relates to one, or a combination of, temperature , power supplied to the heating element (119), a maximum detected flow rate, or a rate of change of flow rate. A method of controlling aerosol production in an aerosol generating device is also disclosed. ower to the heating element. The electric circuitry (109) includes a sensor for detecting air flow past the aerosol generating element. The electric circuitry (109) is arranged to determine a first parameter related to change in flow rate of the air flow, compare the first parameter to a threshold value, and subsequently reduce or suspend the supply of power to the heating element (119). The first parameter is derived from a combination of second and third parameters, wherein the second parameter relates to an air flow rate through the device, and the third parameter relates to one, or a combination of, temperature , power supplied to the heating element (119), a maximum detected flow rate, or a rate of change of flow rate. A method of controlling aerosol production in an aerosol generating device is also disclosed.
Description
AN ELECTRICALLY OPERATED AEROSOL GENERATING SYSTEM
HAVING AEROSOL PRODUCTION CONTROL
The present invention relates to a method for controlling aerosol production.
The present invention further relates to an aerosol generating system and more
specifically to an electrically operated aerosol generation system. The present
invention finds particular application as a method for controlling aerosol production
in an aerosol generation system through at least one electric element of an
electrically operated smoking system.
WO-A-2009/132793 discloses an electrically heated smoking system. A
liquid is stored in a liquid storage portion, and a capillary wick has a first end which
extends into the liquid storage portion for contact with the liquid therein, and a
second end which extends out of the liquid storage portion. A heating element
heats the second end of the capillary wick. The heating element is in the form of a
spirally wound electric heating element in electrical connection with a power supply,
and surrounding the second end of the capillary wick. In use, the heating element
may be activated by the user to switch on the power supply. Suction on a
mouthpiece by the user causes air to be drawn into the electrically heated smoking
system over the capillary wick and heating element and subsequently into the
mouth of the user.
It is an objective of the present invention to provide an improved method of
controlling the electric heating element of such an electrically heated aerosol
generating system, and/or to at least provide the public with a useful choice.
One particular problem with an aerosol generating devices is condensation
of the aerosol inside the device. The aerosol can condense into a liquid within the
aerosol condensation chamber and the liquid can then leak out of the device. In
particular, for aerosol generation devices used for inhalation, the liquid in the
aerosol condensation chamber could leak while the device is not in use or while the
device is in use, entering a user’s mouth. Any liquid which enters the user’s mouth
could be unpleasant and potentially hazardous.
A further problem with condensation within aerosol generating devices is
that the condensates of the aerosol can migrate or settle onto the aerosol
generating element and interfere with its operation. In the case of thermal
vaporization, if an aerosol condensate is subsequently re-evaporated this can lead
to chemical degradation of the original liquid formulation. This could result in an
unpleasant taste or hazardous chemicals.
It would be desirable to minimise condensation of aerosols generated by,
and within, such aerosol generating devices.
According to one aspect of the invention, there is provided a method of
controlling aerosol production in an aerosol-generating device, the device
comprising:
an aerosol generating element;
a flow channel configured to allow an air flow past the aerosol generating
element;
and a flow sensor configured to detect the air flow in the flow channel,
comprising the steps of:
determining a value of a first parameter related to a change in flow rate of
the air flow; and
changing the supply of power to the aerosol generating element depending
on a result of a comparison between the value of the first parameter and a
threshold value, wherein the first parameter is derived from a combination of a
second parameter that is a measure of a flow rate detected by the flow sensor and
a third parameter related to the flow rate,
and wherein the third parameter is temperature, power supplied to the
aerosol generating element, a maximum detected flow rate, or a rate of change of
flow rate, or is derived from a combination of two or more of temperature, power
supplied to the aerosol generating element, a maximum detected flow rate, and a
rate of change of flow rate.
The term ‘comprising’ as used in this specification and claims means
‘consisting at least in part of’. When interpreting statements in this specification and
claims which include the term ‘comprising’, other features besides the features
prefaced by this term in each statement can also be present. Related terms such
as ‘comprise’ and ‘comprised’ are to be interpreted in a similar manner.
Preferably, the device is configured to allow the air flow to be generated by
a user inhalation. Preferably, the step of determining comprises determining a value
of the first parameter during an inhalation period. Preferably the step of changing
the power supply comprises reducing the supply of power to zero.
An aerosol is a suspension of solid particles or liquid droplets in a gas, such
as air. By controlling the power supplied to the aerosol generating element, the rate
of aerosol generation can be controlled. By reducing or suspending power to the
aerosol generating element before the end of a period of air flow, such as a user
inhalation or puff, the remaining portion of the air flow can be used to remove or
purge already generated aerosol, and thus reduce condensation within the device.
However, the most desirable time to stop aerosol generation depends on the rate
and variance of the air flow during a defined period. For a device driven by user
inhalation, different users have different inhalation behaviour, and a single user can
have different inhalation behaviour at different times. So it is desirable to have a
control method that compensates for or normalises between different user
behaviours. A set flow rate threshold for controlling aerosol production does not
work equally well in removing produced aerosol for short sharp user inhalations and
long slow inhalations. A flow threshold appropriate for a short sharp inhalation may
never be reached by a user taking long slow inhalations.
Preferably, the present invention provides a method of controlling aerosol
production, and in particular reducing or suspending aerosol production, based on a
detected flow rate and on another measure called the first parameter which is
indicative of the evolution of the flow characteristics of the air flow. However, it
does not have to be only the detected flow rate, but could be based on different puff
parameters.
The second parameter may be a parameter that does not have units of flow
rate but is nevertheless a measure of flow rate. For example, the flow sensor may
operate by determining the resistance of an electrical filament in the air flow, and so
the second parameter may be a resistance value rather than a flow rate calculated
from a resistance value. In other words the second parameter may be a parameter
having a constant relationship with flow rate rather than the actual flow rate. The
invention does not require an actual flow rate to be calculated.
If the third parameter is temperature or maximum flow rate, then
advantageously the first parameter is proportional to a ratio between the second
and third parameters.
If the third parameter is power supplied to the aerosol generating element or
rate of change of flow rate, the first parameter is advantageously proportional to a
product of the second and third parameters.
Alternatively, the first parameter may simply be proportional to a rate of
change of flow rate.
However, many possibilities exist for the first parameter. The most
appropriate first parameter depends on the design of the aerosol-generating device.
Different designs may have different flow characteristics past a flow sensor, and
different types of aerosol-generating devices may behave differently. Although the
preferred examples are simple products or ratios of two detected or derived
parameters, more complex combinations may be used.
The aerosol generating element may be a mechanical device, such as a
vibrating orifice transducer or a piezoelectric device. However, preferably, the
aerosol generating element is an electrical heater comprising at least one heater
element. The at least one electric heating element may be arranged to heat an
aerosol-forming substrate to form the aerosol.
If a constant power is provided to the heating element, the temperature of
the heating element is a parameter that is indicative of the flow characteristics
within the device. This may be used as the third parameter. For lower temperatures
there is a high flow rate as the air flow provides a cooling effect. So, the
temperature of the heating element will increase as the flow rate drops at the end of
a user inhalation. The resistance of the heating element may be dependent on the
temperature of the heating element, so that the resistance of the heating element
may be used as the third parameter.
If the temperature is controlled to remain constant, then the power supplied
to the heater element to maintain a constant temperature is indicative of the flow
rate and so may be used as the third parameter. The higher the flow rate the more
power is required to maintain a given temperature. The constant temperature may
be a predetermined value or may be dynamically calculated based on one or more
other measured parameters, such as flow rate.
According to another aspect of the invention, there is provided an
electrically operated aerosol generating device, the device comprising: at least one
electric aerosol generating element for forming an aerosol from a substrate; a
power supply for supplying power to the at least one aerosol generating element;
and electric circuitry for controlling supply of power from the power supply to the at
least one aerosol generating element, the electric circuitry including a sensor for
detecting air flow past the aerosol generating element and wherein the electric
circuitry is arranged to:
determine a value of a first parameter related to a change in flow rate of the
air flow; and
reduce or suspend the supply of power to the aerosol generating element to
zero dependent on a result of a comparison between the value of the first
parameter and a threshold value, wherein the first parameter is derived from a
combination of a second parameter that is a measure of a flow rate detected by the
flow sensor and a third parameter related to the flow rate,
and wherein the third parameter is temperature, power supplied to the
aerosol generating element, a maximum detected flow rate, or a rate of change of
flow rate, or is derived from a combination of two or more of temperature, power
supplied to the aerosol generating element, a maximum detected flow rate, and a
rate of change of flow rate.
Preferably, the device is configured to allow the air flow to be generated by
a user inhalation. Preferably, the device is configured to determine a value of the
first parameter during an inhalation period.
If the third parameter is temperature or maximum flow rate, then preferably
the first parameter is proportional to a ratio between the second and third
parameters.
If the third parameter is power supplied to the aerosol generating element or
rate of change of flow rate, the first parameter is preferably proportional to a product
of the second and third parameters.
Alternatively, the first parameter may simply be proportional to a rate of
change of flow rate.
The device may be configured to receive an aerosol-forming substrate. The
aerosol generating element may be a mechanical device, such as a vibrating orifice
transducer. However, preferably, the aerosol generating element is an electrical
heater comprising at least one heater element. The at least one electric heating
element may be arranged to heat an aerosol-forming substrate to form the aerosol.
If a constant power is provided to the heating element, the temperature of
the heating element is a parameter that is indicative of the flow characteristics
within the device. Temperature may then be used as the third parameter. For lower
temperatures there is a high flow rate as the air flow provides a cooling effect. So,
the temperature of the heating element will increase as the flow rate drops
at the end of a user inhalation (or other air flow period). The electrical resistance of
the heating element may be dependent on the temperature of the heating element,
so that the electrical resistance of the heating element may be used as the third
parameter.
If the temperature is controlled to remain constant, then the power supplied
to the heater element to maintain a constant temperature is indicative of the flow
rate and so may be used as the third parameter. The higher the flow rate the more
power is required to maintain a given temperature. The constant temperature may
be a predetermined value or may be dynamically calculated based on one or more
other measured parameters, such as flow rate.
Preferably, the electric circuitry is arranged to perform the method steps of
the previous aspect of the invention. To perform the method steps of the previous
aspect of the invention, the electric circuitry may be hardwired. More preferably,
however, the electric circuitry is programmable to perform the method steps of the
previous aspect of the invention.
The sensor may be any sensor which can detect airflow. The sensor may
be an electro-mechanical device. Alternatively, the sensor may be any of: a
mechanical device, an optical device, an opto-mechanical device, a micro electro
mechanical systems (MEMS) based sensor and an acoustic sensor. The sensor
can be a thermal conductive flow sensor, a pressure sensor, an anemometer and
should be able to not only detect an airflow but should be able to measure the
airflow. So, the sensor should be able to deliver an analogue electrical signal or
digital information that is representative of the amplitude of the air flow.
The electric heater may comprise a single heating element. Alternatively,
the electric heater may comprise more than one heating element, for example two,
or three, or four, or five, or six or more heating elements. The heating element or
heating elements may be arranged appropriately so as to most effectively heat the
aerosol-forming substrate.
The at least one electric heating element preferably comprises an
electrically resistive material. Suitable electrically resistive materials include but are
not limited to: semiconductors such as doped ceramics, electrically “conductive”
ceramics (such as, for example, molybdenum disilicide), carbon, graphite, metals,
metal alloys and composite materials made of a ceramic material and a metallic
material. Such composite materials may comprise doped or undoped ceramics.
Examples of suitable doped ceramics include doped silicon carbides. Examples of
suitable metals include titanium, zirconium, tantalum and metals from the platinum
group. Examples of suitable metal alloys include stainless steel, Constantan,
nickel-, cobalt-, chromium-, aluminium- titanium- zirconium-, hafnium-, niobium-,
molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese- and iron-containing
alloys, and super-alloys based on nickel, iron, cobalt, stainless steel, Timetal®, iron-
aluminium based alloys and iron-manganese-aluminium based alloys. Timetal® is a
registered trade mark of Titanium Metals Corporation, 1999 Broadway Suite 4300,
Denver Colorado. In composite materials, the electrically resistive material may
optionally be embedded in, encapsulated or coated with an insulating material or
vice-versa, depending on the kinetics of energy transfer and the external
physicochemical properties required. The heating element may comprise a metallic
etched foil insulated between two layers of an inert material. In that case, the inert
material may comprise Kapton®, all-polyimide or mica foil. Kapton® is a registered
trade mark of E.I. du Pont de Nemours and Company, 1007 Market Street,
Wilmington, Delaware 19898, United States of America.
Alternatively, the at least one electric heating element may comprise an
infra-red heating element, a photonic source, or an inductive heating element.
The at least one electric heating element may take any suitable form. For
example, the at least one electric heating element may take the form of a heating
blade. Alternatively, the at least one electric heating element may take the form of
a casing or substrate having different electro-conductive portions, or an electrically
resistive metallic tube. If the aerosol-forming substrate is a liquid provided within a
container, the container may incorporate a disposable heating element.
Alternatively, one or more heating needles or rods that run through the centre of the
aerosol-forming substrate may also be suitable. Alternatively, the at least one
electric heating element may be a disk (end) heater or a combination of a disk
heater with heating needles or rods. Alternatively, the at least one electric heating
element may comprise a flexible sheet of material arranged to surround or partially
surround the aerosol-forming substrate. Other alternatives include a heating wire or
filament, for example a Ni-Cr, platinum, tungsten or alloy wire, or a heating plate.
Optionally, the heating element may be deposited in or on a rigid carrier material.
The at least one electric heating element may comprise a heat sink, or heat
reservoir comprising a material capable of absorbing and storing heat and
subsequently releasing the heat over time to the aerosol-forming substrate. The
heat sink may be formed of any suitable material, such as a suitable metal or
ceramic material. Preferably, the material has a high heat capacity (sensible heat
storage material), or is a material capable of absorbing and subsequently releasing
heat via a reversible process, such as a high temperature phase change. Suitable
sensible heat storage materials include silica gel, alumina, carbon, glass mat, glass
fibre, minerals, a metal or alloy such as aluminium, silver or lead, and a cellulose
material such as paper. Other suitable materials which release heat via a
reversible phase change include paraffin, sodium acetate, naphthalene, wax,
polyethylene oxide, a metal, metal salt, a mixture of eutectic salts or an alloy.
The heat sink or heat reservoir may be arranged such that it is directly in
contact with the aerosol-forming substrate and can transfer the stored heat directly
to the substrate. Alternatively, the heat stored in the heat sink or heat reservoir
may be transferred to the aerosol-forming substrate by means of a heat conductor,
such as a metallic tube.
The at least one heating element may heat the aerosol-forming substrate by
means of conduction. The heating element may be at least partially in contact with
the substrate, or the carrier on which the substrate is deposited. Alternatively, the
heat from the heating element may be conducted to heat conductive element.
Alternatively, the at least one heating element may transfer heat to the
incoming ambient air that is drawn through the electrically heated aerosol
generating device during use, which in turn heats the aerosol-forming substrate by
convection. The ambient air may be heated before passing through the aerosol-
forming substrate. Alternatively, if the aerosol-forming substrate is a liquid
substrate, the ambient air may be first drawn through the substrate and then
heated.
The aerosol-forming substrate may be a solid aerosol-forming substrate.
The aerosol-forming substrate preferably comprises a tobacco-containing material
containing volatile tobacco flavour compounds which are released from the
substrate upon heating. The aerosol-forming substrate may comprise a non-
tobacco material. The aerosol-forming substrate may comprise tobacco-containing
material and non-tobacco containing material. Preferably, the aerosol-forming
substrate further comprises an aerosol former. Examples of suitable aerosol
formers are glycerine and propylene glycol.
Alternatively, the aerosol-forming substrate may be a liquid aerosol-forming
substrate. In one embodiment, the electrically heated aerosol generating device
further comprises a liquid storage portion. Preferably, the liquid aerosol-forming
substrate is stored in the liquid storage portion. In one embodiment, the electrically
heated aerosol generating device further comprises a capillary wick in
communication with the liquid storage portion. It is also possible for a capillary wick
for holding liquid to be provided without a liquid storage portion. In that
embodiment, the capillary wick may be preloaded with liquid.
Preferably, the capillary wick is arranged to be in contact with liquid in the
liquid storage portion. In that case, in use, liquid is transferred from the liquid
storage portion towards the at least one electric heating element by capillary action
in the capillary wick. In one embodiment, the capillary wick has a first end and a
second end, the first end extending into the liquid storage portion for contact with
liquid therein and the at least one electric heating element being arranged to heat
liquid in the second end. When the heating element is activated, the liquid at the
second end of the capillary wick is vaporized by the heater to form the
supersaturated vapour. The supersaturated vapour is mixed with and carried in the
airflow. During the flow, the vapour condenses to form the aerosol and the aerosol
is carried towards the mouth of a user. The heating element in combination with a
capillary wick may provide a fast response, because that arrangement may provide
a high surface area of liquid to the heating element. Control of the heating element
according to the invention may therefore depend on the structure of the capillary
wick arrangement.
The liquid substrate may be absorbed into a porous carrier material, which
may be made from any suitable absorbent plug or body, for example, a foamed
metal or plastics material, polypropylene, terylene, nylon fibres or ceramic. The
liquid substrate may be retained in the porous carrier material prior to use of the
electrically heated aerosol generating device or alternatively, the liquid substrate
material may be released into the porous carrier material during, or immediately
prior to use. For example, the liquid substrate may be provided in a capsule. The
shell of the capsule preferably melts upon heating and releases the liquid substrate
into the porous carrier material. The capsule may optionally contain a solid in
combination with the liquid.
If the aerosol-forming substrate is a liquid substrate, the liquid has specific
physical properties. These include, for example, a boiling point, vapour pressure,
and surface tension characteristics to make them suitable for use in the aerosol
generating device. Control of the at least one electric heating element may depend
upon the physical properties of the liquid substrate. The liquid preferably comprises
a tobacco-containing material comprising volatile tobacco flavour compounds which
are released from the liquid upon heating. Alternatively, or in addition, the liquid
may comprise a non-tobacco material. The liquid may include water, solvents,
ethanol, plant extracts and natural or artificial flavours. Preferably, the liquid further
comprises an aerosol former. Examples of suitable aerosol formers are glycerine
and propylene glycol.
An advantage of providing a liquid storage portion is that a high level of
hygiene can be maintained. Using a capillary wick extending between the liquid and
the electric heating element, allows the structure of the device to be relatively
simple. The liquid has physical properties, including viscosity and surface tension,
which allow the liquid to be transported through the capillary wick by capillary
action. The liquid storage portion is preferably a container. The liquid storage
portion may not be refillable. Thus, when the liquid in the liquid storage portion has
been used up, the liquid storage portion, or the entire aerosol generating device, is
replaced. Alternatively, the liquid storage portion may be refillable. In that case, the
aerosol generating device may be replaced after a certain number of refills of the
liquid storage portion. Preferably, the liquid storage portion is arranged to hold liquid
for a pre-determined number of puffs.
The capillary wick may have a fibrous or spongy structure. The capillary
wick preferably comprises a bundle of capillaries. For example, the capillary wick
may comprise a plurality of fibres or threads, or other fine bore tubes. The fibres or
threads may be generally aligned in the longitudinal direction of the aerosol
generating device. Alternatively, the capillary wick may comprise sponge-like or
foam-like material formed into a rod shape. The rod shape may extend along the
longitudinal direction of the aerosol generating device. The structure of the wick
forms a plurality of small bores or tubes, through which the liquid can be
transported to the electric heating element, by capillary action. The capillary wick
may comprise any suitable material or combination of materials. Examples of
suitable materials are ceramic- or graphite-based materials in the form of fibres or
sintered powders. The capillary wick may have any suitable capillarity and porosity
so as to be used with different liquid physical properties such as density, viscosity,
surface tension and vapour pressure. The capillary properties of the wick, combined
with the properties of the liquid, ensure that the wick is always wet in the heating
area.
The aerosol-forming substrate may alternatively be any other sort of
substrate, for example, a gas substrate, or any combination of the various types of
substrate. During operation, the substrate may be completely contained within the
electrically heated aerosol generating device. In that case, a user may puff on a
mouthpiece of the electrically heated aerosol generating device. Alternatively,
during operation, the substrate may be partially contained within the electrically
heated aerosol generating device. In that case, the substrate may form part of a
separate article and the user may puff directly on the separate article.
Preferably, the electrically heated aerosol generating device is an
electrically heated smoking device.
The electrically heated aerosol generating device may comprise an aerosol-
forming chamber in which aerosol forms from a super saturated vapour, which
aerosol is then carried into the mouth of the user. An air inlet, air outlet and the
chamber are preferably arranged so as to define an airflow route from the air inlet to
the air outlet via the aerosol-forming chamber, so as to convey the aerosol to the air
outlet and into the mouth of a user. Condensation may form on the walls of the
aerosol-forming chamber. The amount of condensation may depend on the amount
of power supplied, particularly towards the end of the puff.
Preferably, the aerosol generating device comprises a housing. Preferably,
the housing is elongate. The structure of the housing, including the surface area
available for condensation to form, will affect the aerosol properties and whether
there is liquid leakage from the device. The housing may comprise a shell and a
mouthpiece. In that case, all the components may be contained in either the shell or
the mouthpiece. The housing may comprise any suitable material or combination of
materials. Examples of suitable materials include metals, alloys, plastics or
composite materials containing one or more of those materials, or thermoplastics
that are suitable for food or pharmaceutical applications, for example
polypropylene, polyetheretherketone (PEEK) and polyethylene. Preferably, the
material is light and non-brittle. The material of the housing may affect the amount
of condensation forming on the housing which will, in turn, affect liquid leakage from
the device
Preferably, the aerosol generating device is portable. The aerosol
generating device may be a smoking device and may have a size comparable to a
conventional cigar or cigarette. The smoking device may have a total length
between approximately 30 mm and approximately 150 mm. The smoking device
may have an external diameter between approximately 5 mm and approximately 30
mm.
The method and electrically heated aerosol generating device according to
the present invention provide the advantage that the amount of power supplied to
the heating element may be tailored to the air flow profile, thereby providing
an improved experience for the user and reducing the amount of aerosol that
condenses within the housing of the device, without requiring any additional user or
device actions.
According to another aspect of the invention, there is provided electric
circuitry for an electrically operated aerosol generating device, the electric circuitry
being arranged to perform the method of the other aspects of the invention.
Preferably, the electric circuitry is programmable to perform the method of
the other aspects of the invention. Alternatively, the electric circuitry may be
hardwired to perform the method of the other aspects of the invention.
According to another aspect of the invention, there is provided a computer
program which, when run on programmable electric circuitry for an electrically
operated aerosol generating device, causes the programmable electric circuitry to
perform the method of the other aspects of the invention.
According a another aspect of the invention, there is provided a computer
readable storage medium having stored thereon a computer program according to
the previous aspect of the invention.
Features described in relation to one aspect of the invention may be
applicable to another aspect of the invention.
The invention will be further described, by way of example only, with
reference to the accompanying drawings, in which:
Figure 1 shows one example of an electrically heated aerosol generating
device;
Figure 2 illustrates a method of controlling aerosol production in accordance
with a first embodiment of the invention;
Figure 3 illustrates a method of controlling aerosol production in accordance
with the first embodiment, for a different puff profile;
Figure 4 illustrates a method of controlling aerosol production in accordance
with a second embodiment of the invention; and
Figure 5 illustrates a method of controlling aerosol production in accordance
with the second embodiment, for a different puff profile.
Figure 1 shows one example of an electrically heated aerosol generating
device. In Figure 1, the device is a smoking device having a liquid storage portion.
The smoking device 100 of Figure 1 comprises a housing 101 having a mouthpiece
end 103 and a body end 105. In the body end, there is provided an electric power
supply in the form of battery 107 and electric circuitry in the form of hardware 109
and a puff detection device 111. In the mouthpiece end, there is provided a liquid
storage portion in the form of cartridge 113 containing liquid 115, a capillary wick
117 and a heater 119 comprising at least one heating element. Note that the heater
is only shown schematically in Figure 1. One end of the capillary wick 117
extends into the cartridge 113 and the other end of the capillary wick 117 is
surrounded by the heater 119. The heater is connected to the electric circuitry via
connections 121. The housing 101 also includes an air inlet 123, an air outlet 125 at
the mouthpiece end and an aerosol-forming chamber 127.
In use, operation is as follows. Liquid 115 is transferred or conveyed by
capillary action from the cartridge 113 from the end of the wick 117 which extends
into the cartridge to the other end of the wick 117 which is surrounded by the heater
119. When a user draws on the device at the air outlet 125, ambient air is drawn
through air inlet 123. In the arrangement shown in Figure 1, the puff detection
device 111 senses the puff and activates the heater 119. The battery 107 supplies
energy to the heater 119 to heat the end of the wick 117 surrounded by the heater.
The liquid in that end of the wick 117 is vaporized by the heater 119 to create a
supersaturated vapour. At the same time, the liquid being vaporized is replaced by
further liquid moving along the wick 117 by capillary action. (This is sometimes
referred to as "pumping action".) The supersaturated vapour created is mixed with
and carried in the airflow from the air inlet 123. In the aerosol-forming chamber 127,
the vapour condenses to form an inhalable aerosol, which is carried towards the
outlet 125 and into the mouth of the user.
The capillary wick can be made from a variety of porous or capillary
materials and preferably has a known, pre-defined capillarity. Examples include
ceramic- or graphite-based materials in the form of fibres or sintered powders.
Wicks of different porosities can be used to accommodate different liquid physical
properties such as density, viscosity, surface tension and vapour pressure. The
wick must be suitable so that the required amount of liquid can be delivered to the
heating element. The wick and heating element must be suitable so that the
required amount of aerosol can be conveyed to the user.
In the embodiment shown in Figure 1, the hardware 109 and the puff
detection device 111 are preferably programmable. The hardware 109 and puff
detection device 111 can be used to manage the device operation. This assists with
control of the particle size in the aerosol.
Figure 1 shows one example of an electrically heated aerosol generating
device which may be used with the present invention. Many other examples are
usable with the invention, however. The electrically heated aerosol generating
device simply needs to include or receive an aerosol forming substrate which can
be heated by at least one electric heating element, powered by a power supply
under the control of electric circuitry. For example, the device need not be a
smoking device. For example, the aerosol forming substrate may be a solid
substrate, rather than a liquid substrate. Alternatively, the aerosol forming substrate
may be another form of substrate such as a gas substrate. The heating
element may take any appropriate form. The overall shape and size of the housing
could be altered and the housing could comprise a separable shell and mouthpiece.
Other variations are, of course, possible.
As already mentioned, preferably, the electric circuitry, comprising hardware
109 and the puff detection device 111, is programmable in order to control the
supply of power to the heating element. This, in turn, affects the temperature profile
which will affect the density of the aerosol produced. The term “temperature profile”
refers to a graphic representation of the temperature of the heating element (or
another similar measure, for example, the heat generated by the heating element)
over the time taken for a puff. Alternatively, the hardware 109 and the puff detection
device 111 may be hardwired to control the supply of power to the heating element.
Again, this will affect the temperature profile which will affect the density of the
aerosol generated.
Problems arise in an aerosol generating device of the type shown in Figure
1 if aerosol continues to be generated when there is insufficient airflow through the
device to remove the produced aerosol. This results in condensation of the aerosol
on the interior of the housing, which may subsequently leak from the device into the
user’s mouth or hands. It can also lead to a build up of material that might migrate
on heating element which can be subsequently be chemically degraded into
undesirable compounds. If, for example, power is switched off at the same fixed
flow threshold as it is switched on, aerosol will continue to be generated when there
is little or no air flow through the device.
Figure 2 illustrates a method for controlling power to the heater of Figure 1
in accordance with a first embodiment of the invention. Curve 200 is the detected
air flow through the device during a user inhalation period or puff. Curve 210 is the
temperature of the heater during the same period. Power is applied to the heater
when air flow through the device is first detected and is continuously applied at the
same level until it is switched off. So the temperature of the heater initially rises until
it reaches a fairly stable level, at which the cooling of the air flow balances the
heating provided by the power supply. Towards the end of the user puff, as air flow
is decreasing, the temperature of the heater rises more sharply again. This is
because the cooling effect of the air flow is reducing. The heater temperature at is
therefore sensitive to a change in air flow during a puff.
Curve 220 is a plot of the temperature of the heater divided by the air flow.
This curve is used to provide a normalised threshold for switching off power to the
heater and will be referred to as the end of puff variable. The curve 220 is
calculated using the following formula:
EP = A or EP=
Q AQ
Where:
- EP is the End of puff Variable.
- T is the temperature of the heating element.
- Q is the Air flow
- A is a compensation coefficient.
Power to the heater is stopped when curve 220 reaches a threshold value
(but only after the maximum flow rate has passed). In this embodiment the
threshold value is preset and stored in the electric circuitry during manufacture.
However, it is possible to have a threshold that is changed over time to be most
appropriate for a particular user behavior. The power stop is shown by line 230, at
1.6 seconds into the puff. After power is stopped, the temperature of the heater
goes down (dotted line 215). The corresponding end of puff variable curve is
obtained for the decreasing temperature and is shown in dotted line 225. The
threshold is selected so that the temperature of heater decreases enough to
significantly reduce the generation of the aerosol up to the end of the puff, but not
so early as to frustrate the device user.
Figure 3 shows another example in accordance with the first embodiment,
with a more complex flow profile during a puff. Curve 300 shows the air flow, curve
310 shows the heater temperature and curve 320 shows the end of puff variable
EP, where:
EP = A
Power to the heater is stopped when the end of puff variable reaches the
predetermined threshold value, in this case at 1.7 seconds into the puff, shown at
line 330.
Reactivation of the heater for subsequent puffs is based on a simple air flow
threshold, referred to as the first activation threshold. Once the heating power is
stopped, the air flow must go down below the first activation threshold, for the user
to be able to take another puff and for the device to be reinitialized.
The temperature of the heating element can be calculated from its electrical
resistance, which is continuously measured. Therefore the temperature variable
can be replaced by the electrical resistance value of the heating element in the
calculation of the end of puff variable, reducing the calculation load for the electric
circuitry.
If the temperature of the heater is regulated during a puff, such that it is held
constant once it has reached the desired temperature, heater temperature can not
be used in calculated the end of puff variable due to the fact that it will remain
constant, independently of the air flow level. Therefore another variable input must
be used. The power supplied in order to maintain a constant temperature may be
used in calculating the end of puff variable. As air flow drops less power is required
to maintain the temperature constant.
Power is supplied to the heater in the form of a pulsed signal. In order to
regulate the temperature of the heater, the power voltage is modulated. The power
voltage modulation can be done by either varying the width of the power voltage
pulses or by varying the frequency of the pulses.
The average power that is applied to the heating element can be varied by
changing the frequency (or “PFM” - pulse frequency modulation) of the modulations
of the power voltage at fixed duty cycle to keep constant the temperature of the
heating element. In that case the end of puff variable may be calculated as:
1+Δf
EP = P
Where:
- Q is the Air flow
- ∆f is the variation of the modulation frequency
- P is a compensation coefficient
The other way of altering the power applied is PWM (pulse width
modulation), which consists of varying the duty cycle at constant frequency. The
duty cycle is the ratio of the time that the power is switched on to the time the power
is switched off. In other words, the ratio of the width of the voltage pulses to the
time between the voltage pulses. A low duty cycle of 5% will provide much less
power than a duty cycle of 95%. In that case the end of puff variable may be
calculated as:
(1+Δd)
EP = B
Where:
- Q is the Air flow
- ∆d is the variation of the duty cycle
- B is a compensation coefficient
A combination of the frequency and the duty cycle variation can also be
used in a calculation of the end of puff variable.
There are several alternative ways of providing a “normalized” parameter to
compare with a threshold for stopping power to the heater or any alternative aerosol
generating element. One alternative is the use of the rate of change of air flow.
Figure 4 shows the air flow and the rate of change of air flow for a first puff
profile. Curve 400 is the air flow rate. Curve 410 is the derivation of the air flow with
respect to time. The threshold for stopping power to the heater can be set at a fixed
rate of change of air flow, as illustrated by line 420. The rate of change of air flow
normalizes between large and small inhalations.
Figure 5 shows the use of rate of change or air flow for a more complex puff
profile. Curve 500 is the air flow rate and curve 510 is the rate of change of air flow.
The power to the heater is stopped when the rate of change of air flow reaches a
threshold value. With the puff shown in Figure 5 the heating power stop will happen
several times during the puff, as shown by line 530 and 540. The first power stop
occurs after 0.6 s. the second power stop will appear after 1.2 s.
The device needs to be reactivated after the first power stop in order to
avoid frustrating the user. The reactivation threshold can take place at the
discontinuity of the derivation curve 550 or when the rate of change of air flow goes
positive. Once the air flow falls below the first activation threshold, the device can
be reset to provide power again when the air flow exceeds the first activation
threshold.
The rate of change of air flow can be calculated using the formula.
dQ (Q −Q )
n n−1
dt (t −t )
n n−1
Where Q is the air flow measured at time t .
Other alternative end of puff parameters include Q /Q, where Q is the
max max
maximum detected air flow during a puff, A/(Q.dQ/dt), AQ /(Q.dQ/dt) or AT/Q .
For different designs of aerosol generating device, and different users, different end
of puff parameters may be appropriate. Whichever end of puff parameter is used it
should normalize in some way the different kinds of flow profiles found in user
inhalations. This means using a parameter related to the change in air flow over a
particular flow period and, as can be seen from the example above, that parameter
may be derived from one, two or more detected parameters relating to air flow. The
threshold should be set to ensure that the last portion of a user inhalation is used to
remove generated aerosol from the device.
Although the invention has been described with reference to an electric
smoking device, all aerosol generators, vaporizers or inhalers activated on demand
suffer from the same problem of having part of the generated aerosol trapped in the
consumable housing. According the present invention can be applied to all aerosol
generators, vaporizers or inhalers activated on demand.
In case of medical devices, if the medication dose delivered to the patient
has to be estimated and counted, then controlling aerosol production in accordance
with the present invention can ensure that all of the generated aerosol is delivered
to the patient. By stopping aerosol production before the end of an inhalation
substantially all of the aerosol is delivered to the patient and so medication dosage
can be more accurately monitored.
Although the invention has been described with reference to electrically
heated aerosol-forming substrates, other types of aerosol generator can be used
with the present invention. For example, a vibrating orifice transducer may be used
to generate aerosol. With such an aerosol generator, the temperature variable used
with the heater to calculate the end of puff variable can be replaced by an actuator
pressure, power, frequency or amplitude of displacement variables.
Claims (10)
1. A method of controlling aerosol production in an aerosol-generating device, the device comprising: an aerosol generating element; 5 a flow channel configured to allow an air flow past the aerosol generating element; and a flow sensor configured to detect the air flow in the flow channel, comprising the steps of: determining a value of a first parameter related to a change in flow rate of 10 the air flow; and changing the supply of power to the aerosol generating element depending on a result of a comparison between the value of the first parameter and a threshold value, wherein the first parameter is derived from a combination of a second parameter that is a measure of a flow rate detected by the flow sensor and 15 a third parameter related to the flow rate, and wherein the third parameter is temperature, power supplied to the aerosol generating element, a maximum detected flow rate, or a rate of change of flow rate, or is derived from a combination of two or more of temperature, power supplied to the aerosol generating element, a maximum detected flow rate, and a 20 rate of change of flow rate.
2. A method according to claim 1, wherein the third parameter is temperature or maximum flow rate and comprising a step of deriving the first parameter by calculating a ratio between the second and third parameters.
3. A method according to claim 1, wherein the third parameter is power 25 supplied to the aerosol generating element or rate of change of flow rate, and further comprising a step of deriving the first parameter by calculating a product of the second and third parameters.
4. A method according to claim 1, wherein the first parameter is proportional to a rate of change of flow rate. 30
5. A method according to any preceding claim, wherein the aerosol- generating element is an electrically heated heating element and the first parameter is proportional to a temperature of the heating element divided by a flow rate detected by the flow sensor.
6. A method according to any preceding claim, further comprising the step of re-supplying power to the aerosol-generating element based on a flow rate 5 detected by the flow sensor.
7. An electrically operated aerosol generating device, the device comprising: at least one electric aerosol generating element for forming an aerosol from a substrate; a power supply for supplying power to the at least one aerosol generating element; and electric circuitry for controlling supply of power from the 10 power supply to the at least one aerosol generating element, the electric circuitry including a sensor for detecting air flow past the aerosol generating element and wherein the electric circuitry is arranged to: determine a value of a first parameter related to a change in flow rate of the air flow; and 15 reduce or suspend the supply of power to the aerosol generating element to zero dependent on a result of a comparison between the value of the first parameter and a threshold value, wherein the first parameter is derived from a combination of a second parameter that is a measure of a flow rate detected by the flow sensor and a third parameter related to the flow rate, 20 and wherein the third parameter is temperature, power supplied to the aerosol generating element, a maximum detected flow rate, or a rate of change of flow rate, or is derived from a combination of two or more of temperature, power supplied to the aerosol generating element, a maximum detected flow rate, and a rate of change of flow rate. 25
8. An electrically operated aerosol generating device according to claim 7, wherein the aerosol-generating element is an electrically heated heating element and the first parameter is proportional to a temperature of the heating element divided by a flow rate detected by the flow sensor.
9. Electric circuitry for an electrically operated aerosol generating 30 device, the electric circuitry being arranged to perform the method of claim 1.
10. A computer program which, when run on programmable electric circuitry for an electrically operated aerosol generating device, causes the
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP11250874.2 | 2011-10-27 | ||
EP11250874 | 2011-10-27 | ||
PCT/EP2012/071169 WO2013060784A2 (en) | 2011-10-27 | 2012-10-25 | An electrically operated aerosol generating system having aerosol production control |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ624113A NZ624113A (en) | 2016-01-29 |
NZ624113B2 true NZ624113B2 (en) | 2016-05-03 |
Family
ID=
Similar Documents
Publication | Publication Date | Title |
---|---|---|
AU2012330373B2 (en) | An electrically operated aerosol generating system having aerosol production control | |
JP6674429B2 (en) | Aerosol generation system with improved aerosol generation | |
US9532600B2 (en) | Electrically heated aerosol generating system having improved heater control | |
US11950634B2 (en) | Control of aerosol production in an aerosol-generating system | |
NZ624113B2 (en) | An electrically operated aerosol generating system having aerosol production control | |
NZ624108B2 (en) | Aerosol generating system with improved aerosol production |