WO2023030853A1

WO2023030853A1 - Control unit for an inhalation device and method performed by a control unit for an inhalation device

Info

Publication number: WO2023030853A1
Application number: PCT/EP2022/072544
Authority: WO
Inventors: Simon Dodd; Domenico Giusti; Gianluca GULLI; James Alan Mott; Ari BADAL
Original assignee: Jt International Sa
Priority date: 2021-08-31
Filing date: 2022-08-11
Publication date: 2023-03-09

Abstract

A control unit for an inhalation device with at least one liquid jet device for producing drops of a liquid on demand, the control unit being configured to: control supply of power to one or more heating elements of the liquid jet device based on a pulse train having pulses defined by a voltage and a pulse width; monitor a value indicative of a fluid temperature of the liquid jet device, and reduce the power supplied to the one or more heating elements of the liquid jet device when the monitored value exceeds a first threshold value.

Description

CONTROL UNIT FOR AN INHALATION DEVICE AND METHOD PERFORMED BY A CONTROL UNIT FOR AN INHALATION DEVICE

[Technical Field]

The present invention generally relates to the field of inhalation devices . In particular, the present invention is directed to a control unit for an inhalation device with at least one liquid j et device for producing drops of a liquid on demand, an inhalation device comprising such a control unit , and method performed by such a control unit .

[ Background ]

Inhalation devices , also referred to as aerosol generation devices , such as e-cigarettes , vaping devices and aerosol inhalers , are known .

Such inhalation devices are hand-held devices and conventionally include an atomizer , a power supply, and a liquid-filled capsule , or similar means disposed therein in order to generate an aerosol ( that is , a vapour ) to be inhaled by a user . By way of example , conventional inhalation devices generally change the phase of a fluid before inhalation with, for example , a wick and a coil so as to significantly raise the vapor temperature above human body temperature or deliver drops a room temperature by, for example , employing an ultrasonic mesh .

The generated aerosol may contain, for example , a form of nicotine such that user of the inhalation device may, for example , simulate smoking tobacco by inhaling the generated aerosol .

Inhalation devices generally have to be of a relatively small size and relatively low weight in order to be handheld and easily portable . Normally, this requirement results in limited power supply as the battery ( or any other suitable power supply means ) must be relatively small and light .

As such, the present inventors have recognised a general need to improve inhalation devices , e . g . in terms of efficiency, size and/or weight .

[Summary of the Invention]

The present invention is intended to address one or more of the above technical problems . One or more of these problems may be remedied by the subj ect-matter of the independent claims . Further preferred embodiments are defined in the dependent claims .

In particular, in view of the limitations discussed above , the present inventors have devised, in accordance with a first aspect herein, a control unit for an inhalation device with at least one liquid j et device for producing drops of a liquid on demand . The control unit is configured to control supply of power to one or more heating elements of the liquid j et device based on a pulse train having pulses defined by a voltage and a pulse width . The control unit is further configured to monitor a value indicative of a temperature of the liquid j et device , and to reduce the power supplied to the one or more heating elements of the liquid j et device when the monitored value exceeds a first threshold value .

The present inventors have further devised, in accordance with a second aspect herein, an inhalation device with at least one liquid j et device for producing drops of a liquid on demand . The liquid j et device comprises a fluid chamber , at least one ej ection noz zle , a supply channel and a heating element configured to heat the liquid in order to cause ej ection through the at least one ej ection nozzle . The inhalation device further comprises a control unit according to the first aspect herein . The present inventors have further devised, in accordance with a third aspect herein, a method performed by a control unit for an inhalation device with at least one liquid j et device for producing drops of a liquid on demand . The method comprises steps of controlling supply of power to one or more heating elements of the liquid j et device based on a pulse train having pulses defined by a voltage and a pulse width; monitoring a value indicative of a temperature of the liquid j et device , and reducing the power supplied to the one or more heating elements of the liquid j et device when the monitored value exceeds a first threshold value .

The present inventors have further devised, in accordance with a fourth aspect herein, a computer program comprising instructions which, when executed by a control unit of an inhalation device with at least one liquid j et device for producing drops of a liquid on demand, cause the control unit to perform a method according to the third aspect herein .

[Brief Description of the Drawings ]

Embodiments of the invention will now be explained in detail , by way of non-limiting example only, with reference to the accompanying figures , described below . Like reference numerals appearing in different ones of the figures can denote identical or functionally similar elements , unless indicated otherwise .

Figure 1 is a schematic illustration of an inhalation device in accordance with an embodiment of the present invention .

Figure 2A is a schematic view of a first liquid j et device as employed in an inhalation device in accordance with an embodiment of the present invention .

Figure 2B is a schematic view of a second liquid j et device as employed in an inhalation device in accordance with an embodiment of the present invention . Figures 3A and 3B are schematic illustrations of exemplary layouts of ej ection noz zles associated with a heating element in a liquid j et device .

Figure 4 is a flow diagram illustrating a process performed by the control unit of Figure 1 in accordance with an embodiment of the present invention .

Figure 5 shows a graph of the pulse width versus the counted number of drops .

[Detailed Description]

Example embodiments of the present invention will now be described in detail with reference to the accompanying drawings .

Where technical features in the drawings , detailed description or any claim are followed by reference signs , the reference signs have been included for the sole purpose of increasing the intelligibility of the drawings , detailed description, and claims . Accordingly, neither the reference signs nor their absence have any limiting effect on the scope of any claim elements .

The present inventors have recognised that inhalation device may use drop-on demand technology similar to inkj et printers in order to generate an aerosol by providing at least one liquid et device in an inhalation device . Such liquid j et devices , which may also be referred to as thermal inkj et microfluidic devices , allow liquid drops to be produced on demand so as to form an aerosol .

Firing a liquid j et device ( i . e . producing a drop of liquid by the inkj et device ) typically takes a specific amount of energy . This amount of energy may be referred to as the Turn-On Energy (TOE ) , which is defined as the amount of energy needed to initiate drop ej ection . It is known that when firing a liquid j et device with a single heater and a single noz zle the efficiency of the liquid et device ( electricity in vs . mechanical momentum/energy out ) decreases as the drop size decreases . This may result in a presumed decrease in efficiency of a liquid j et device when drop size decreases , particularly to the size required for aerosol generation .

The present inventors have recognised that such a limited power supply may be incompatible with the above-identified decrease in efficiency of a liquid j et device as the drop size decreases . As such, the present inventors have recognised a need to improve efficiency of use of liquid j et devices , so as to allow the use of liquid j et devices in an inhalation device without exceeding any power supply limitations of the inhalation device .

In view of the limitations discussed above , there is described, in accordance with a first aspect herein, a control unit for an inhalation device with at least one liquid j et device for producing drops of a liquid on demand . The control unit is configured to control supply of power to one or more heating elements of the liquid j et device based on a pulse train having pulses defined by a voltage and a pulse width . The control unit is further configured to monitor a value indicative of a temperature of the liquid j et device , and to reduce the power supplied to the one or more heating elements of the liquid j et device when the monitored value exceeds a first threshold value .

In accordance with a second aspect herein, there is described an inhalation device with at least one liquid j et device for producing drops of a liquid on demand . The liquid j et device comprises a fluid chamber, at least one ej ection nozzle , a supply channel and a heating element configured to heat the liquid in order to cause ej ection through the at least one ej ection nozzle . The inhalation device further comprises a control unit according to the first aspect herein .

In accordance with a third aspect herein, there is described a method performed by a control unit for an inhalation device with at least one liquid j et device for producing drops of a liquid on demand . The method comprises steps of controlling supply of power to one or more heating elements of the liquid j et device based on a pulse train having pulses defined by a voltage and a pulse width; monitoring a value indicative of a temperature of the liquid j et device , and reducing the power supplied to the one or more heating elements of the liquid j et device when the monitored value exceeds a first threshold value .

In accordance with a fourth aspect herein, there is described a computer program comprising instructions which, when executed by a control unit of an inhalation device with at least one liquid j et device for producing drops of a liquid on demand, cause the control unit to perform a method according to the third aspect herein .

According to the first to fourth aspect , supply of power to one or more heating elements of the liquid j et device is controlled by a pulse train having pulses defined by a voltage and a pulse width . By way of more particular example , to generate sufficient drops to create an aerosol , the control unit creates the pulse train at a desired frequency, which repeatedly energizes the one or more heating element , causing fluid drops to be ej ected . The present inventors have recognised that the initial drops produced by the liquid j et device require more energy to produce . More specifically, the energy required to produce drops goes down as the fluid temperature in the liquid j et device increases ( due to the die heating up from previous drop ejections) . That is, the TOE required by the liquid jet device to produce a drop on demand may decrease as the number of drops produced increases.

Therefore, according to each of first to fourth aspects herein, the power supplied to the one or more heating elements of the liquid jet device is reduced when a monitored value indicative of a temperature of the liquid jet device exceeds a first threshold value. By way of example, this may be achieved by reducing the pulse width of the pulses of the pulse train and/or by reducing the voltage of the pulses of the pulse train.

This reduces the energy used by the liquid jet device to produce drops after the first threshold value has been exceeded, in accordance with the decreasing TOE. In particular, the energy consumed by the liquid jet device to produce a drop on demand is proportional to the square of the voltage applied to the heating element of the liquid jet device multiplied by the time (i.e.

V²t) . As such, reducing the pulse width (i.e. time t) or the voltage of the pulses (i.e. the voltage V) reduces the energy consumed by the liquid jet device.

Accordingly, by adapting control of supply of power to the liquid jet device so as to account for the decrease in TOE as the number of drops produced increases, the overall amount of energy consumed by the liquid jet device during production of an aerosol may be reduced. In this way, the efficiency of the use of a liquid jet device in an inhalation device may be improved.

This may in turn allow the use of liquid jet devices in an inhalation device without exceeding any limitations of the power supply of the inhalation device or enable for a decrease in the size of the battery (or other power supply means) of the inhalation device. Figure 1 is a schematic illustration of an inhalation device 100 in accordance with an embodiment of the present invention. The inhalation device 100 comprises a liquid jet device 210 for producing drops of a liquid on demand. The liquid jet device 210 comprises a fluid chamber, at least one ejection nozzle, a supply channel and a heating element configured to heat the liquid in order to cause ejection through the at least one ejection nozzle.

Details of the elements of the liquid jet device 210 are shown and described below in relation to Figures 2A, 2B, 3A and 3B. The term fluid chamber is meant to cover jet technologies generally, including at least piezo jet and thermal jet devices, wherein in the latter case the fluid chamber is then usually referred to as a firing chamber.

The inhalation device 100 further comprises a control unit 110 in accordance with an embodiment herein. Operation of the control unit 110 will be described in more detail below in relation to Figure 4.

More generally, the control unit 110 may, as in the present example embodiment, be configured to control operation of the inhalation device 100. By way of example, in example embodiments such as the present example embodiment in which the inhalation device 100 comprises a power supply unit 120, the control section 110 may control charging of a power supply unit. Additionally or alternatively, the control section 11 may optionally control supply of power to, and receive and process signals from any sensors or I/O units (e.g. optional button 130) included in the inhalation device 100 and control operation of the inhalation device 100 based on the received signals.

The control unit 110 may comprise one or more processing units or modules (e.g. a central processing unit (CPU) such as a microprocessor, or a suitably programmed field programmable gate array (FPGA) or application-specific integrated circuit (ASIC) ) . Additionally or alternatively, the control unit 110 may be provided with any memory sections (not shown) necessary to perform its function of controlling operation of the inhalation device 100. Such memory sections may be provided as part of (comprised in) the control unit 110 (e.g. integrally formed or provided on the same chip) or provided separately, but electrically connected to the control unit 110. By way of example, the memory sections may comprise both volatile and non-volatile memory resources, including, for example, a working memory (e.g. a random access memory) . In addition, the memory sections may include an instruction store (e.g. a ROM in the form of an electrically- erasable programmable read-only memory (EEPROM) or flash memory) storing a computer program comprising the computer-readable instructions which, when executed by the control unit 110, cause the control unit 110 to perform various functions described herein .

A computer program comprising the computer-readable instructions which, when executed by the control unit 110, cause the control unit 110 to perform various functions described herein may, for example, be a software or a firmware program.

The inhalation device 100 may, as in the present example embodiment, further comprise a power supply unit 120. The power supply unit 120 may, as in the present example embodiment, be a rechargeable power supply. The power supply unit 120 may, as in the present example embodiment, be a lithium ion battery. Alternatively, the power supply unit 120 may be, for example, a chargeable secondary battery or an electric double layer capacitor (EDLC) or any other suitable power supply means known in the art.

Additionally or alternatively, the inhalation device 100 may, as in the present example embodiment, comprise a reservoir 220 for storing an amount of said liquid to be vaporized. By way of nonlimiting example, the liquid may contain nicotine and/or flavours (e.g. mint, menthol, herbs, and/or fruit flavours) . Optionally, the liquid stored in the reservoir 220 may include additional substances , such as glycerin, propylene glycol and/or water , to aid formation of an aerosol .

By way of example , the reservoir 220 and/or the liquid stored therein may be replaceable . By way of example , at least the reservoir 220 of the inhalation device 100 may be provided in the form of a replaceable cartridge .

Preferably, the inhalation device may further comprise a reservoir heating element ( not shown ) arranged to heat the liquid in said reservoir 220 and/or in a flow path between said reservoir 220 and liquid j et device 210 to a predetermined liquid reservoir temperature . This may allow the liquid to be provided to the liquid j et device 210 from the reservoir 220 at an optimal temperature for producing drops by the liquid j et device 210 .

Additionally or alternatively, the inhalation device 100 may, as the present example embodiment , comprise an air conduit 230 and a mixing chamber ( not shown ) in which air from said air conduit 230 is mixed with the liquid drops generated by the liquid j et device 210 . The air conduit 230 further comprises at least one air inlet orifice 240 at some suitable site of said inhalation device 100 .

Additionally or alternatively, the inhalation device 100 may, as in the present example embodiment , comprise a mouthpiece opening 310 through which a user may inhale the inhalation vapour . The mouthpiece 300 may be integral with the housing of the inhalation device 100 , it may be replaceable , or may form part of a capsule or cartridge . The latter may comprise further elements , such as the mixing chamber, the liquid j et device 210 or the reservoir 220 so as to provide a replaceability of further elements for achieving convenience , flexibility, reliability and/or safety . Figure 2A is a schematic view of a first liquid jet device 210 as employed in an inhalation device in accordance with an embodiment of the present invention.

The liquid jet device 210 comprises a fluid chamber 211, at least one ejection nozzle 214, a supply channel 213 and a heating element 212 configured to heat the liquid 216 in order to cause ejection through the at least one ejection nozzle 214.

The heating element 212 may, as in the present example embodiment, be arranged in the vicinity of the fluid chamber 211. In such embodiments, the control unit 110 may control the heating element 212 to heat up a portion of the liquid 216 to vaporized and form a gas bubble 217. The resulting expansion leads to the ejection of an amount of the liquid 216 in the form of a drop or droplet 215 through the ejection nozzle 214. By way of example, the drop 215 may then form a vapour or aerosol in the mixing chamber.

By way of example, the fluid chamber 211 may, as in the present example embodiment, be in liquid communication with the reservoir 220 for providing liquid 216 to the fluid chamber 211 so as to be vaporized or atomized.

The heating element 212 may, for example, be a resistive heating element. By way of more specific example, the heating element 212 may be a resistor embedded in the substrate.

The liquid jet device 210 may, as in the present example embodiment, be formed as a MEMS in a substrate of any suitable material, for example silicon. In such example embodiments, the fluid chamber 211, the ejection nozzle 214, and the supply channel 213 may be formed on the substrate. In addition, in a case where the heating element 212 comprises a resistor, the resistor may be deposited on a substrate of the MEMs. Such a MEMs liquid jet device may, by way of non-limiting example, be mounted on a printed circuit board. In the liquid jet device 210 showing in Figure 2A, the liquid jet device 210 comprises a single ejection nozzle 214 in association with the heating element 212. Alternatively, the liquid jet device may comprise two or more ejection nozzles in association with the heating element 212. That is, the liquid jet device 210 may have a 'shower head' type design in which there are multiple ejection nozzles per heating element.

By way of example, Figure 2B shows a schematic view of a second liquid jet device 210 as employed in an inhalation device in accordance with an embodiment of the present invention. In the liquid jet device 210 shown in Figure 2B, the heating element 212 is associated with three ejection nozzles 214-1 to 214-3.

As such, the control unit 110 may control the heating element 212 to heat up a portion of the liquid 216 to vaporized and form a gas bubble 217. The resulting expansion leads to the ejection of an amount of the liquid 216 in the form of respective drops (or droplets) 215-1 to 215-3 through each of the ejection nozzle 214-1 to 214-3. By way of example, the drops 215-1 to 215-3 may then form a vapour or aerosol in the mixing chamber.

By way of further alternative, the heating element 212 of the liquid jet device 210 may be associated with any suitable number of ejection nozzles in any suitable layout. By way of non-limiting example, Figures 3A and 3B are schematic illustrations of alternative exemplary layouts of ejection nozzles 214-1 to 214-9 associated with the heating element 212 in the liquid jet device 210.

As shown in Figure 3A, the ejection nozzles 214-1 to 214-9 may be arranged at the edge of the fluid chamber only. Alternatively, as shown in Figure 3B, the ejection nozzles 214-1 to 214-9 may be arranged at the edge and the centre of the fluid chamber. The use of liquid j et devices having such ' shower head' type designs may, in combination with the control device of the present invention, allow for further improvement in the efficiency of the use of a liquid j et device in an inhalation device , particularly where smaller drops suitable for generation of an aerosol are to be produced . In particular, such ' shower head' type designs allow for multiple drops to be produced with each energy pulse ( i . e . pulse of the pulse train ) , thereby further improving efficiency . In particular, when compared to a single noz zle per resistor, the shower head type design improves both the mechanical and electrical efficiencies of the drop generation .

In Figures 2A and 2B, the liquid j et device 210 comprises a single heating element 212 . Alternatively, the liquid j et device 210 may comprise multiple heating elements 212 , each heating element 212 being associated with a respective one or more ej ection noz zles 214 . In example embodiments in which the liquid j et device 210 comprises multiple heating elements 212 , the control unit 110 may be configured to control the supply of power to each of the heating elements 212 based on the pulse train .

As discussed in detail above , the present inventors have recognised a need to improve efficiency of use of liquid j et devices , so as to allow the use of liquid j et devices in an inhalation device without exceeding any power supply limitations of the inhalation device . This obj ective may be achieved by the control unit 110 configured to perform a process as described in relation to Figure 4 .

Figure 4 is a flow diagram illustrating a process performed by the control unit 110 of Figure 1 in accordance with an embodiment of the present invention .

In process step S41 of Figure 4 , control unit 110 controls supply of power to one or more heating elements 212 of the liquid j et device based on a pulse train having pulses defined by a voltage and a pulse width .

That is , the control unit 110 may control supply of power ( e . g . from the power supply unit 120 or a connected external power supply) to the heating element 212 such that the heating element 212 receives voltage in the form of a pulsed waveform . The control unit 110 may control the width of the pulses of the pulse train ( i . e . the length of time the waveform is ON or positive ) so as to control the length of time for which voltage is continuously supplied to the heating element . Alternatively, the control unit 110 may control the voltage of the pulses of the pulse train so as to control the amount of voltage that is continuously supplied to the heating element during a pulse of a given pulse width .

As such, the control unit may control the amount of voltage and the resulting current applied to the heating element 212 of the liquid j et device 210 .

The heating element 212 may, as in the present example embodiment , be configured to heat up a portion of the liquid 216 to vaporized and form a gas bubble 217 so as to ej ect an amount of the liquid 216 in the form of one or more drops ( dependent on the number of ej ection nozzles ) in response to the voltage supplied thereto with each pulse of the pulse train .

Additionally, the control unit 100 may, as in the present example embodiment , control other aspects of the pulse train such as the frequency and/or duty cycle of the pulse train . By way of example , the pulse train may be in the form of a square wave , a rectangular wave , a sawtooth wave , a triangular wave , or any other suitable wave form.

In process step S42 of Figure 4 , control unit 110 monitors a value indicative of a temperature of the liquid j et device 210 . The monitored value may be indicative of the fluid temperature in the liquid j et device . That is , the monitored value may be indicative of the temperature of the liquid 216 stored in the fluid chamber 211. As such, the increase in the temperature of the liquid (fluid) 216 due to drops being ejected (which causes the die to heat up) may be monitored directly or indirectly.

By way of example, the value indicative of a temperature of the liquid jet device 210 may, as in the present example embodiment, comprise a number of drops produced by the liquid jet device 210. Alternatively, the value indicative of a temperature of the liquid jet device 210 may comprise a temperature of the liquid jet device 210. By way of further example, the control unit 110 may be configured to calculate the value indicative of a temperature of the liquid jet device 210 as a function of one or both a number of drops produced by the liquid jet device 210 and a temperature of the liquid jet device 210.

In some example embodiments, process step S42 may, as in the present example embodiment, be performed concurrently with process step S41.

As noted above, the control unit 110 may, as in the present example embodiment, be configured to count the number of drops produced by the liquid jet device 210. This value may be indicative of the temperature of the liquid jet device 210 because the fluid temperature in the liquid jet device increases with the number of drops to ejected (due to the die heating up from previous drop ejections) .

The control unit 110 may be configured to count the number of drops produced by the liquid jet device 210 in any suitable way. By way of example, the control unit 110 may, as in the present example embodiment, be configured to count the number of pulses in the pulse train and to determine a count of a corresponding number of drops using stored information regarding the liquid jet device 210 (e.g. the number of ejection nozzles) . Alternatively, the control unit 110 or the liquid jet device 210 (or any other suitable element of the inhalation device 100) may comprise one or more sensors for detecting whether a drop has been produced by the liquid jet device 210. In such embodiments, the control unit 110 may be configured to receive signals output by the one or more sensors and to count the number of drops produced by the liquid jet device 210 based on the received signals.

Furthermore, the control unit 110 may be configured to count, as the number of drops produced by the liquid jet device 210, the number of individual drops produced by the liquid jet device 210 or the number of times the liquid jet device 210 is fired (caused to produce one or more drops) , regardless of the number of drops that would result from such a firing.

Similarly, in example embodiments in which the control unit 110 is configured to measure a temperature of the liquid jet device 210, this may be achieved in any suitable way. By way of example, the control unit 110 or the liquid jet device 210 (or any other suitable element of the inhalation device 100) may comprise one or more sensors for detecting the temperature of the liquid jet device 210. In such embodiments, the control unit 110 may be configured to receive signals output by the one or more sensors and to determine the temperature of the liquid jet device 210 based on the received signals.

The control unit 110 may be configured to initiate monitoring of the value indicative of a temperature of the liquid jet device 210by any suitable means. By way of example, the control unit 110 may be caused to initiate monitoring by any action or input of a user of the inhalation device 100 that causes the inhalation device to generate an aerosol. For example, the control unit 110 initiate monitoring in response to detecting that the user has provided input to an I/O device of the inhalation device 100 (e.g. optional button 130 shown in Figure 1) , in a response to a detection of the user inhaling through the mouthpiece opening 310 by suitable sensing means, etc. In process step S43 of Figure 4, control unit 110 reduces the power supplied to the one or more heating elements 212 of the liquid jet device 210 when the monitored value exceeds a first threshold value.

By way of example, the control unit 110 may, as in the present example embodiment, be configured to reduce the power supplied to the one or more heating elements 212 of the liquid jet device 210 by reducing the pulse width of the pulses of the pulse train. Alternatively, the control unit 110 may be configured to reduce the power supplied to the one or more heating elements 212 of the liquid jet device 210 by reducing the voltage of the pulses of the pulse train or by reducing both the pulse width of the pulses of the pulse train the voltage of the pulses of the pulse train.

Thus, the control unit 110 may reduce the amount of time for which current is continuously supplied to the heating element and/or the amount of voltage that is continuously supplied to the heating element during a pulse of a given pulse width. The energy consumed by the liquid jet device 210 to produce a drop on demand is proportional to the square of the voltage applied to the heating element g the liquid jet device 210 multiplied by the time (i.e. V²t) . As such, reducing the pulse width (i.e. time t) or the voltage of the pulses (i.e. the voltage V) reduces the energy consumed by the liquid jet device.

By way of example, the initial pulse width and/or the initial voltage (i.e. the pulse width and/or voltage before process step S43 is performed by the control unit 110) may be appropriately selected based on the required Turn-On Energy (TOE) , which is defined as the amount of energy needed to initiate drop ejection. The TOE for a liquid jet device may be determined experimentally, for example, by sweeping through a series of voltages with a given pulse width to visually detect when a drop is first ejected. Alternatively, in order to prevent overheating a system when no drops are ejected, the TOE for a liquid jet device may be determined experimentally by starting at a high voltage and decreasing voltage until no drop is ejected. By way of further alternative, the TOE may be determined experimentally by sweeping through a series of pulse widths with the voltage being held constant, starting with a long pulse width and gradually reducing the pulse width, to visually detect when a drop is first ejected. The voltage and pulse width at which a drop eject is first detected may then be used to derive the TOE and/or the initial pulse width and/or initial voltage.

Additionally or alternatively, the reduced pulse width and/or the reduced voltage (i.e. the pulse width and/or voltage after process step S43 has been performed by the control unit 110) may be appropriately selected based on the required TOE. By way of example, the reduced pulse width of the pulses of the pulse train may, as in the present example embodiment, be less than or equal to Ips (e.g. less than or equal to 0.9 ps or 0.8ps) .

More generally, the reduced pulse width and/or the reduced voltage may be determined by the control unit 110 as an absolute value or as a reduction (e.g. in terms of a fixed amount or a percentage reduction) . Such absolute values or reductions may be determined by the control unit 110 from a lookup table or a formula, the details of which may be stored in a memory of or accessible to the control unit 110.

The pulses having the reduced pulse width may, as in the present example embodiment, have a voltage of greater than or equal to 10V.

Furthermore, the first threshold value may be selected in any suitable manner based on the decrease of the TOE as the monitored value varies (e.g. as a number of drops produced or a temperature of the liquid jet device 210 increases) . By way of example, the first threshold value may be selected to correspond to a value indicative of the temperature of the liquid jet device 210 (e.g. a number of produced drops) at which the TOE is, for example, 5%, 10%, 15%, or 20% less than the TOE required by the liquid jet device 210 to produce a first drop of the liquid.

By way of more specific example, the first threshold value may be between 50 and 1,000 counted drops, preferably between 100 and 500 counted drops (e.g. 200 drops) .

In the above described example embodiments, in which the value indicative of a temperature of the liquid jet device 210 is a number of drops produced or a temperature of the liquid jet device 210, the monitored value increases as the temperature of the liquid jet device 210 increases. In such embodiments, the monitored value may be considered to exceed the first threshold value when the monitored value is greater than or equal to the first threshold value. Alternatively, in example embodiments in which the monitored value decreases as the temperature of the liquid jet device 210 increases (e.g. where the monitored value is calculated as a function of one or both a number of drops produced by the liquid jet device 210 and a temperature of the liquid jet device 210) , the monitored value may be considered to exceed the first threshold value when the monitored value is less than or equal to the first threshold value.

As previously discussed, the present inventors have recognised that the initial drops produced by the liquid jet device 210 require more energy to produce. That is, the TOE required by the liquid jet device 210 to produce a drop on demand may decrease as the number of drops produced increases and the temperature of the liquid jet device 210 increases. Later drops in a consecutive series of produced drops may require as much as 20% less energy to produce compared to the initial drops produced by the liquid jet device 210.

By reducing the power supplied to the one or more heating elements of the liquid jet device when the monitored value exceeds a first threshold value , the energy used by the liquid j et device 210 to produce drops after the first threshold value has been exceeded, in accordance with the decreasing TOE . Accordingly, the overall amount of energy consumed by the liquid j et device 210 during production of an aerosol may be reduced . In this way, the efficiency of the use of a liquid j et device 210 in an inhalation device 100 may be improved .

In particular, energy inefficiency in liquid j et devices produces excess heat , which may be transferred to silicon or other substrates forming the liquid j et devices . In order to compensate for the excess heat generated by less efficient parts , conventional liquid j et devices and associated control units relied on thermal throttling ( that is , decreasing speed in order to decrease heat ) or increasing a silicon area to dissipate the heat .

By adapting control of supply of power to the liquid j et device 210 in accordance with the process of Figure 4 , the efficiency of the use of a liquid j et device 210 in an inhalation device 100 may be improved . This may result in less excess heat being generating , thereby reducing the need to rely on thermal throttling and/or increasing silicon area . Furthermore , in example embodiments such as the present example embodiment , in which the power supply unit 120 is rechargeable , improving efficiency may result in the power supply unit 120 lasting longer for every charge cycle , thereby increasing life of the inhalation device 100 or allowing for a decrease in size of the power supply unit 120 .

Additionally, the process of Figure 4 may comprise optional process step S44 . In process step S44 , the control unit 110 further reduces the power supplied to the one or more heating elements 212 of the liquid j et device 210 when the monitored value exceeds a second threshold value greater than the first threshold value . The second threshold value may be selected by any of the means described above in relation to the first threshold value. By way of example, the second threshold value may be selected to correspond to a value indicative of the temperature of the liquid jet device 210at which the TOE is, for example, 5%, 10%, 15%, or 20% less than the TOE required by the liquid jet device 210 to produce a drop of the liquid when the first threshold value is exceeded .

By way of more specific example, the second threshold value may be between 200 and 1,500 counted drops, preferably between 250 and 750 counted drops (e.g. 500 drops) .

Additionally or alternatively, the further reduced pulse width (i.e. the pulse width after optional process step S44 has been performed by the control unit 110) may be appropriately selected based on the required TOE. By way of example, the reduced pulse width of the pulses of the pulse train may, as in the present example embodiment, be less than or equal to Ips (e.g. less than or equal to 0.9 ps or 0.8ps) . The pulses having the reduced pulse width may, as in the present example embodiment, have a voltage of greater than or equal to 10V.

Figure 5 shows an exemplary graph of the pulse width versus the counted number of drops. In the example of Figure 5, the initial pulse width is Ips, the first threshold value is 200 drops, the reduced pulse width is 0.9ps, the second threshold value is500 drops, and the further reduced pulse width is 0.8ps.

In the example of Figure 5, the control unit 110 reduces the power supplied to the one or more heating elements 212 of the liquid jet device 210 twice, based on a comparison of the monitored value with a respective first and second threshold value. However, this is merely by way of non-limiting example.

More generally, the control unit 110 may be configured to further reduce the power supplied to the one or more heating elements 212 of the liquid j et device 210 each time the monitored value exceeds a series of threshold values ( e . g . two or more additional threshold values ) . As such, the supply of power to the one or more heating elements 212 of the liquid j et device 210 may be reduced any suitable number of times .

As discussed above , the TOE required by the liquid j et device 210 to produce a drop on demand may decrease as the number of drops produced increases . As such, by further reducing the power supplied to the one or more heating elements of the liquid j et device 210 so as to further reduce the energy used by the liquid j et device 210 to produce drops in accordance with the decreasing TOE , further improvements in energy eff iciency may be achieved .

Additionally or alternatively, in example embodiments such as the present example embodiment in which the monitored value comprises a number of drops produced by the liquid j et device 210 , the process of Figure 4 may comprise optional process step S45 . In process step S45 , the control unit 110 initializes the counted number of drops to zero when a predetermined number of drops have been produced or after a predetermined time interval .

By way of example , the inhalation device 100 may be configured to generate aerosol only for a predetermined length of time following an action or input of a user of the inhalation device 100 to cause the inhalation device to generate an aerosol . This may help to ensure safe and reliable operation of the inhalation device 100 . For example , the inhalation device 100 may be configured so as to allow aerosol to be continuously generated for up to a maximum time limit only, e . g . Is , 3s , or 5 s .

Accordingly, the control unit 110 may be configured to initialize ( set ) the counted number of drops to zero at such a maximum time limit or when a predetermined number of drops corresponding to such a maximum time limit or to a predetermined maximum volume of aerosol have been produced. As such time, the control unit 110 may be further configured to control to stop supply of current from the power supply unit 120 to the liquid jet device 210, e.g. until a next action or input of a user of the inhalation device 100 to cause the inhalation device to generate an aerosol is received.

Alternatively, in example embodiments in which the monitored value comprises a temperature of the liquid jet device 210, the control unit 110 may be configured to monitor the temperature of the liquid jet device 210 only when the inhalation device 100 is in use, e.g. for a predetermined length of time following an action or input of a user of the inhalation device 100 to cause the inhalation device to generate an aerosol. This may help to ensure safe and reliable operation of the inhalation device 100. For example, the inhalation device 100 may be configured so as to allow aerosol to be continuously generated for up to a maximum time limit only, e.g. Is, 3s, or 5s.

Although detailed embodiments have been described, they only serve to provide a better understanding of the invention defined by the independent claims, and are not to be seen as limiting.

Claims

24 Claims

1 . A control unit for an inhalation device with at least one liquid j et device for producing drops of a liquid on demand, the control unit being configured to : control supply of power to one or more heating elements of the liquid j et device based on a pulse train having pulses defined by a voltage and a pulse width; monitor a value indicative of a fluid temperature of the liquid j et device , and reduce the power supplied to the one or more heating elements of the liquid j et device when the monitored value exceeds a first threshold value .

2 . The control unit according to claim 1 , wherein the control unit is configured to reduce the power supplied to the one or more heating elements of the liquid j et device by reducing the pulse width of the pulses of the pulse train and/or by reducing the voltage of the pulses of the pulse train .

3 . The control unit according to claim 1 or claim 2 , wherein the value indicative of the fluid temperature of the liquid j et device comprises a number of drops produced by the liquid j et device or a fluid temperature of the liquid j et device .

4 . The control unit according to any preceding claim, wherein the control unit is configured to further reduce the power supplied to the one or more heating elements of the liquid j et device when the monitored value exceeds a second threshold value greater than the first threshold value .

5 . The control unit according to any preceding claim, wherein an initial pulse width of the pulses of the pulse train is less than or equal to 1 . 5ps and/or wherein a reduced pulse width of the pulses of the pulse train is less than or equal to 0 . 8ps .

6 . An inhalation device with at least one liquid j et device for producing drops of a liquid on demand, the liquid j et device comprising a fluid chamber, at least one ej ection noz zle , a supply channel and a heating element configured to heat the liquid in order to cause ej ection through the at least one ej ection noz zle , the inhalation device further comprising a control unit according to any of claims 1 to 5 .

7 . The inhalation device according to claim 6 wherein the liquid j et device comprises multiple heating elements , each heating element being associated with a respective one or more ej ection noz zles ; and wherein the control unit is configured to control the supply of power to each of the heating elements based on the pulse train .

8 . The inhalation device according to claim 6 or claim 7 , wherein the heating element is arranged in a vicinity o f the fluid chamber ; and wherein the control unit is configured to control the heating element to heat a first amount of the liquid to at least a vapori zation temperature , so that a vapour bubble expels a drop of the liquid through the at least one ej ection noz zle .

9 . The inhalation device according to any of claims 6 to 8 , wherein the liquid j et device is in the form of a microelectromechanical system, MEMS .

10 . The inhalation device according to claim 9 , wherein the heating element is a resistor deposited on a substrate of the MEMS .

11 . The inhalation device according to claim 10 , further comprising a temperature sense resistor, TSR, deposited on the substrate and configured to detect the fluid temperature of the liquid j et device .

12 . The inhalation device according to any of claims 6 to 11 , wherein the inhalation device further comprises an air conduit and a mixing chamber in which air from the air conduit is mixed with the drops of the liquid .

13 . The inhalation device according to any of claims 6 to 12 , further comprising a reservoir configured to store an amount of the liquid .

14 . A method performed by a control unit for an inhalation device with at least one liquid j et device for producing drops of a liquid on demand, the method comprising : controlling supply of power to one or more heating elements of the liquid j et device based on a pulse train having pulses defined by a voltage and a pulse width; monitoring a value indicative of a fluid temperature of the liquid j et device , and reducing the power supplied to the one or more heating elements of the liquid j et device when the monitored value exceeds a first threshold value .

15 . A computer program comprising instructions which, when executed by a control unit of an inhalation device with at 27 least one liquid j et device for producing drops of a liquid on demand, cause the control unit to perform the method of claim 14 .