Patent Description:
Aerosol generating apparatuses (electronic vaporization apparatuses), such as so-called electronic cigarettes and nebulizers (inhalers), that atomize (aerosolize) a liquid or a solid, which is an aerosol source, using a load that operates when supplied with power from a power source, such as a heater or an actuator, to allow a user to inhale the atomized liquid or solid are known.

For example, a system for generating inhalable vapor using an electronic vaporization apparatus is proposed (for example, PTL1). With this technology, whether or not vaporization is occurring is determined by monitoring power supplied to a coil that corresponds to a heater for atomizing an aerosol source. It is described that a reduction in power required to keep the coil at a set temperature indicates that there is not enough liquid in a fluid wick for normal vaporization to occur.

Also, an aerosol generating apparatus is proposed (for example, PTL2) that detects the presence of an aerosol forming substrate that includes or corresponds to an aerosol source in the proximity of a heating element configured to heat the aerosol forming substrate, by comparing, with a threshold value, power or energy that needs to be supplied to the heating element to keep the temperature of the heating element at a target temperature. <CIT> relates to vaporization device systems. As illustrated in the basic block diagram of FIG. 17A of this document, the device utilizes a proportional-integral-derivative controller or PID control law. A PID controller calculates an "error" value as the difference between a measured process variable and a desired setpoint. When PID control is enabled, power to the coil is monitored to determine whether or not acceptable vaporization is occurring. With a given airflow over the coil, more power will be required to hold the coil at a given temperature if the device is producing vapor (heat is removed from the coil to form vapor). If power required to keep the coil at the set temperature drops below a threshold, the device indicates that it cannot currently produce vapor. Under normal operating conditions, this indicates that there is not enough liquid in the wick for normal vaporization to occur. <CIT> relates to vaporization device control systems.

When an aerosol is generated using an ordinary aerosol generating apparatus, power supply from a power source to a heater is controlled such that the temperature of the heater is near the boiling point of an aerosol source. If a sufficient quantity of the aerosol source is remaining and the aerosol generation quantity is controlled, power supplied from the power source to the heater has a constant value or shows a continuous change. In other words, if a sufficient quantity of the aerosol source is remaining and feedback control is performed to keep the heater temperature at a target temperature or in a target temperature range, power supplied from the power source to the heater has a constant value or shows a continuous change.

The remaining quantity of the aerosol source is an important variable that is used in various kinds of control performed by the aerosol generating apparatus. If the remaining quantity of the aerosol source is not detected or cannot be detected with sufficiently high precision, for example, there is a risk that power supply from the power source to the heater will be continued even if the aerosol source has been already depleted, and the charge amount of the power source will be wasted.

Therefore, the aerosol generating apparatus proposed in PTL2 determines whether there is a sufficient quantity of the aerosol source based on power required to maintain the temperature of the heater. However, power is generally measured using a plurality of sensors, and it is difficult to accurately estimate the remaining quantity of the aerosol source or depletion thereof based on the measured power unless errors of these sensors are accurately calibrated or control that takes errors into consideration is established.

As other methods for detecting the remaining quantity of the aerosol source, methods that use the temperature of the heater or the electric resistance value of the heater as described in PTL3 and PTL4 are proposed. It is known that the temperature and the electric resistance value of the heater take different values between a case in which a sufficient quantity of the aerosol source is remaining and a case in which the aerosol source is depleted. However, dedicated sensors or a plurality of sensors are necessary for these methods, and therefore it is also difficult to accurately estimate the remaining quantity of the aerosol source or depletion thereof using these methods.

Therefore, the present invention aims to provide an aerosol generating apparatus, a method for controlling an aerosol generating apparatus, and a program for causing a processor to execute the method, that improve precision of estimation of the remaining quantity of the aerosol source or depletion thereof.

An aerosol generating apparatus according to the present invention includes a power source, a load configured to have an electric resistance value that varies according to a temperature and atomize an aerosol source or heat a flavor source when supplied with power from the power source, a sensor configured to output a measurement value corresponding to a current value of a current flowing through the load, and control means for controlling power supply from the power source to the load and performing a determination operation for determining that there is an abnormality if the measurement value becomes smaller than a threshold value within a determination period that is included, on a time axis, in a feeding sequence during which power is supplied from the power source to the load, wherein the control means adjusts a length of the determination period based on the measurement value.

With this configuration, a reference used in the determination operation can be adjusted by changing the determination period based on the measurement value, and precision of the determination can be improved when compared to a case in which a constant reference is always used. Namely, precision of the remaining quantity of the aerosol source estimated by the aerosol generating apparatus can be improved, for example.

A configuration is also possible in which the feeding sequence is performed a plurality of times, and based on the measurement value obtained in a preceding feeding sequence, the control means adjusts the length of the determination period included in a following feeding sequence that is performed later than the preceding feeding sequence along the time axis. In this case, the determination period can be changed based on a chronological change in a plurality of measurement values, rather than a single measurement value. Therefore, precision of the determination can be improved using the determination period determined by estimating the state of the aerosol generating apparatus.

A configuration is also possible in which the control means adjusts the determination period included in the following feeding sequence based on a period it takes for the measurement value to become smaller than the threshold value in the preceding feeding sequence. Thus, the current determination period is adjusted based on a change in the measurement value in the preceding feeding period or the next determination period is adjusted based on a change in the measurement value in the current feeding period, for example.

A configuration is also possible in which the control means adjusts the determination period included in the following feeding sequence based on a shorter one of a period it takes for the measurement value to become smaller than the threshold value in the preceding feeding sequence and a period for which power supply from the power source to the load has been continued in the preceding feeding sequence.

A configuration is also possible in which, if the number of determination periods within which the measurement value has become smaller than the threshold value exceeds a prescribed number, the control means ceases to supply power from the power source to the load. A configuration is also possible in which, if the number of feeding sequences in which the measurement value has become smaller than the threshold value within the determination period is not larger than a prescribed number, the control means continues to supply power from the power source to the load. A configuration is also possible in which, if the number of consecutive determination periods within which the measurement value has become smaller than the threshold value is equal to or larger than a prescribed number, the control means ceases to supply power from the power source to the load. A configuration is also possible in which, if the number of consecutive determination periods within which the measurement value has become smaller than the threshold value is smaller than a prescribed number, the control means continues to supply power from the power source to the load. If the prescribed number is set, erroneous determination can be suppressed, when compared to a case in which the prescribed number is not set.

A configuration is also possible in which the aerosol generating apparatus further includes a feed circuit that electrically connects the power source to the load, wherein the feed circuit includes a first power supply path and a second power supply path that are connected in parallel, the control means selectively causes one of the first power supply path and the second power supply path to function, and the control means controls the second power supply path such that power supplied from the power source to the load is small when compared to a case in which the first power supply path is caused to function, and executes the determination operation while causing the second power supply path to function. With this configuration, the control means can suppress power loss when generating an aerosol using the first power supply path and suppress effects of a reduction of the voltage output from the power source when performing the determination operation using the second power supply path. Therefore, the use efficiency of power stored in the power source is improved, when compared to a case in which a single power supply path that serves as both the first power supply path and the second power supply path is provided.

A configuration is also possible in which the aerosol generating apparatus further includes a feed circuit that electrically connects the power source to the load, wherein the feed circuit includes a first power supply path and a second power supply path that are connected in parallel, the second power supply path is configured such that a current that flows through the second power supply path is smaller than a current that flows through the first power supply path, the control means selectively causes one of the first power supply path and the second power supply path to function, and performs the determination operation while causing the second power supply path to function. This configuration may also be employed to suppress power loss when an aerosol is generated using the first power supply path and suppress effects of a reduction of the voltage output from the power source in the determination operation performed using the second power supply path. Therefore, the use efficiency of power stored in the power source is improved, when compared to a case in which a single power supply path that serves as both the first power supply path and the second power supply path is provided.

A configuration is also possible in which the aerosol generating apparatus further includes a mouthpiece end that is provided at an end portion of the aerosol generating apparatus to emit an aerosol, and the control means controls the second power supply path such that the aerosol is not emitted from the mouthpiece end while the second power supply path is caused to function. A configuration is also possible in which the control means controls the feed circuit such that the load generates an aerosol only when the first power supply path out of the first and second power supply paths is caused to function. Thus, generation of the aerosol may be suppressed in the determination operation.

A configuration is also possible in which the control means causes the second power supply path to function, after causing the first power supply path to function. In this case, determination can be performed immediately after the aerosol is generated, i.e., in a state in which the aerosol source is likely to be depleted, and precision of the determination can be easily improved.

An aerosol generating apparatus according to another aspect of the present invention includes a power source, a load configured to have an electric resistance value that varies according to a temperature and atomize an aerosol source or heat a flavor source when supplied with power from the power source, a sensor configured to output a measurement value corresponding to a current value of a current flowing through the load, and control means capable of executing a feeding sequence during which power is supplied from the power source to the load such that the sensor can output the measurement value, and determining that there is an abnormality if the measurement value becomes smaller than a first threshold value within a determination period, wherein the determination period is shorter than the feeding sequence. A configuration is also possible in which the control means sets the determination period to be shorter than the feeding sequence only when a possibility of depletion of the aerosol source or the flavor source estimated based on the measurement value is at least a second threshold value.

Thus, a reference used in the determination operation can be adjusted by setting the determination period to be short, and precision of the determination can be improved when compared to a case in which the reference is not adjusted. Namely, precision of the remaining quantity of the aerosol source estimated by the aerosol generating apparatus can be improved, for example.

A configuration is also possible in which an aerosol generating apparatus according to another aspect of the present invention includes a power source, a load configured to have an electric resistance value that varies according to a temperature and atomize an aerosol source or heat a flavor source when supplied with power from the power source, a sensor configured to output a measurement value corresponding to a current value of a current flowing through the load, and control means for controlling a plurality of feeding sequences during which power is supplied from the power source to the load, wherein, based on the measurement value obtained in a preceding feeding sequence, the control means determines a length of a following feeding sequence that is performed later than the preceding feeding sequence along a time axis.

If the length of the following determination period is changed based on the measurement value obtained in the preceding feeding sequence as described above, determination can be made based on a change in the measurement value during a plurality of periods, and a reference used in the determination operation can be adjusted, and accordingly precision of the determination can be improved. Namely, precision of the remaining quantity of the aerosol source estimated by the aerosol generating apparatus can be improved.

A configuration is also possible in which an aerosol generating apparatus according to another aspect of the present invention includes a power source, a load configured to have an electric resistance value that varies according to a temperature and atomize an aerosol source or heat a flavor source when supplied with power from the power source, a sensor configured to output a measurement value that is affected by a remaining quantity of the aerosol source or the flavor source, and control means for controlling power supply from the power source to the load and performing a determination operation for determining that there is an abnormality if the measurement value becomes smaller than a threshold value within a determination period that is included, on a time axis, in a feeding sequence during which power is supplied from the power source to the load, wherein the control means sets the determination period shorter as a possibility of depletion of the aerosol source or the flavor source estimated based on the measurement value increases.

With this configuration, the length of the determination period can be appropriately set based on the possibility of depletion of the aerosol source or the flavor source, and precision of the determination can be improved. Namely, precision of the remaining quantity of the aerosol source estimated by the aerosol generating apparatus can be improved.

A configuration is also possible in which an aerosol generating apparatus according to another aspect of the present invention includes a power source, a load configured to have an electric resistance value that varies according to a temperature and atomize an aerosol source or heat a flavor source when supplied with power from the power source, a sensor configured to output a measurement value corresponding to a current value of a current flowing through the load, and control means for controlling a plurality of feeding sequences during which power is supplied from the power source to the load, wherein, based on the measurement value obtained in a currently performed feeding sequence, the control means determines a length of a feeding sequence to be performed later than the currently performed feeding sequence along a time axis.

As described above, it is also possible to determine the length of the following feeding sequences based on the measurement value obtained in the currently performed feeding sequence, other than determining the length of the currently performed feeding sequence based on the measurement value obtained in a past feeding sequence.

Note that what are described in the solution to problem can be combined within a scope not departing from the problem to be solved by the present invention and the technical idea of the present invention. Also, what are described in the solution to problem can be provided as a system that includes one or more apparatuses that include a computer, a processor, an electric circuit, etc., a method to be executed by an apparatus, or a program to be executed by an apparatus. The program can also be executed on a network. A storage medium that holds the program may also be provided.

According to the present invention, it is possible to provide an aerosol generating apparatus that improves precision of estimation of the remaining quantity of the aerosol source or depletion thereof.

An embodiment of an aerosol generating apparatus according to the present invention will be described based on the drawings. Dimensions, materials, shapes, relative arrangements, etc. of constitutional elements described in the present embodiment are examples. Also, the order of processes is one example, and the order can be changed or processes can be executed in parallel within a scope not departing from the problem to be solved by the present invention and the technical idea of the present invention. Therefore, the technical scope of the present invention is not limited to the following examples unless otherwise specified.

<FIG> is a perspective view showing one example of the external appearance of an aerosol generating apparatus. <FIG> is an exploded view showing one example of the aerosol generating apparatus. An aerosol generating apparatus <NUM> is an electronic cigarette, a nebulizer, etc. and generates an aerosol in response to inhalation performed by a user and provides the aerosol to the user. Note that a single continuous inhaling action performed by a user will be referred to as a "puff". Also, in the present embodiment, the aerosol generating apparatus <NUM> adds a flavor component etc. to the generated aerosol and emits the aerosol into the mouth of the user.

As shown in <FIG>, the aerosol generating apparatus <NUM> includes a main body <NUM>, an aerosol source holding portion <NUM>, and an additive component holding portion <NUM>. The main body <NUM> supplies power and controls operations of the entire apparatus. The aerosol source holding portion <NUM> holds an aerosol source to be atomized to generate an aerosol. The additive component holding portion <NUM> holds components such as a flavor component, nicotine, etc. A user can inhale the aerosol with added flavor etc. while holding a mouthpiece, which is an end portion on the additive component holding portion <NUM> side, in their mouth.

The aerosol generating apparatus <NUM> is formed as a result of the main body <NUM>, the aerosol source holding portion <NUM>, and the additive component holding portion <NUM> being assembled by the user, for example. In the present embodiment, the main body <NUM>, the aerosol source holding portion <NUM>, and the additive component holding portion <NUM> have a cylindrical shape, a truncated cone shape, etc. with a predetermined diameter, and can be coupled together in the order of the main body <NUM>, the aerosol source holding portion <NUM>, and the additive component holding portion <NUM>. The main body <NUM> and the aerosol source holding portion <NUM> are coupled to each other by screwing together a male screw portion and a female screw portion that are respectively provided in end portions of the main body <NUM> and the aerosol source holding portion <NUM>, for example. The aerosol source holding portion <NUM> and the additive component holding portion <NUM> are coupled to each other by fitting the additive component holding portion <NUM>, which includes a side surface having tapers, into a tubular portion provided at one end of the aerosol source holding portion <NUM>, for example. The aerosol source holding portion <NUM> and the additive component holding portion <NUM> may be disposable replacement parts.

<FIG> is a schematic diagram showing one example of the inside of the aerosol generating apparatus <NUM>. The main body <NUM> includes a power source <NUM>, a control unit <NUM>, and an inhalation sensor <NUM>. The control unit <NUM> is electrically connected to the power source <NUM> and the inhalation sensor <NUM>. The power source <NUM> is a secondary battery, for example, and supplies power to an electric circuit included in the aerosol generating apparatus <NUM>. The control unit <NUM> is a processor, such as a microcontroller (MCU: Micro-Control Unit), and controls operations of the electric circuit included in the aerosol generating apparatus <NUM>. The inhalation sensor <NUM> is an air pressure sensor, a flow rate sensor, etc. When a user inhales from the mouthpiece of the aerosol generating apparatus <NUM>, the inhalation sensor <NUM> outputs a value according to a negative pressure or the flow rate of a gas flow generated inside the aerosol generating apparatus <NUM>. Namely, the control unit <NUM> can detect inhalation based on the output value of the inhalation sensor <NUM>.

The aerosol source holding portion <NUM> of the aerosol generating apparatus <NUM> includes a storage portion <NUM>, a supply portion <NUM>, a load <NUM>, and a remaining quantity sensor <NUM>. The storage portion <NUM> is a container for storing a liquid aerosol source to be atomized through heating. Note that the aerosol source is a polyol-based material, such as glycerin or propylene glycol, for example. The aerosol source may also be a liquid mixture (also referred to as a "flavor source") that further contains a nicotine liquid, water, a flavoring agent, etc. Assume that such an aerosol source is stored in the storage portion <NUM> in advance. Note that the aerosol source may also be a solid for which the storage portion <NUM> is unnecessary.

The supply portion <NUM> includes a wick that is formed by twisting a fiber material, such as fiberglass, for example. The supply portion <NUM> is connected to the storage portion <NUM>. The supply portion <NUM> is also connected to the load <NUM> or at least a portion of the supply portion <NUM> is arranged in the vicinity of the load <NUM>. The aerosol source permeates through the wick by capillary action, and moves to a portion at which the aerosol source can be atomized as a result of being heated by the load <NUM>. In other words, the supply portion <NUM> soaks up the aerosol source from the storage portion <NUM> and carries the aerosol source to the load <NUM> or the vicinity of the load <NUM>. Note that porous ceramic may also be used for the wick, instead of fiberglass.

The load <NUM> is a coil-shaped heater, for example, and generates heat as a result of a current flowing through the load <NUM>. For example, the load <NUM> has Positive Temperature Coefficient (PTC) characteristics, and the resistance value of the load <NUM> is substantially in direct proportion to the generated heat temperature. Note that the load <NUM> does not necessarily have to have Positive Temperature Coefficient characteristics, and it is only required that there is a correlation between the resistance value of the load <NUM> and the generated heat temperature. For example, a configuration is also possible in which the load <NUM> has Negative Temperature Coefficient (NTC) characteristics. Note that the load <NUM> may be wrapped around the wick or conversely, the circumference of the load <NUM> may be covered by the wick. The control unit <NUM> controls power supply to the load <NUM>. When the aerosol source is supplied from the storage portion <NUM> to the load <NUM> by the supply portion <NUM>, the aerosol source evaporates under heat generated by the load <NUM>, and an aerosol is generated. If an inhaling action of the user is detected based on the output value of the inhalation sensor <NUM>, the control unit <NUM> supplies power to the load <NUM> to generate the aerosol. If the remaining quantity of the aerosol source stored in the storage portion <NUM> is sufficiently large, a sufficient quantity of the aerosol source is supplied to the load <NUM> and heat generated by the load <NUM> is transferred to the aerosol source, in other words, heat generated by the load <NUM> is used for heating and vaporizing the aerosol source, and therefore the temperature of the load <NUM> almost never becomes higher than a predetermined temperature set in advance. On the other hand, if the aerosol source stored in the storage portion <NUM> is depleted, the quantity of the aerosol source supplied to the load <NUM> per unit time decreases. As a result, heat generated by the load <NUM> is not transferred to the aerosol source, in other words, heat generated by the load <NUM> is not used for heating and vaporizing the aerosol source, and therefore the load <NUM> is excessively heated and the resistance value of the load <NUM> is accordingly increased.

The remaining quantity sensor <NUM> outputs sensing data for estimating the remaining quantity of the aerosol source stored in the storage portion <NUM> based on the temperature of the load <NUM>. The remaining quantity sensor <NUM> includes, for example, a resistor (shunt resistor) that is connected in series to the load <NUM> to measure a current, and a measurement apparatus that is connected in parallel to the resistor to measure the voltage value of the resistor. Note that the resistance value of the resistor is a constant value that is determined in advance and does not substantially vary according to the temperature. Therefore, the current value of a current flowing through the resistor can be determined based on the known resistance value and a measured voltage value.

Note that a measurement apparatus in which a hall element is used may also be used instead of the above-described measurement apparatus in which the shunt resistor is used. The hall element is arranged at a position in series to the load <NUM>. Namely, a gap core that includes the hall element is arranged around a conducting wire that is connected in series to the load <NUM>. The hall element detects a magnetic field generated by a current passing therethrough. In a case in which the hall element is used, the "current passing therethrough" means a current that flows through the conducting wire that is arranged at the center of the gap core and is not in contact with the hall element, and the current value of the current is the same as that of a current flowing through the load <NUM>. In the present embodiment, the remaining quantity sensor <NUM> outputs the current value of a current flowing through the resistor. Alternatively, the voltage value of a voltage applied between opposite ends of the resistor may also be used, or a value obtained by performing a predetermined operation on the current value or the voltage value may also be used, rather than the current value or the voltage value itself. These measurement values that can be used instead of the current value of a current flowing through the resistor are values that vary according to the current value of a current flowing through the resistor. Namely, the remaining quantity sensor <NUM> is only required to output a measurement value corresponding to the current value of a current flowing through the resistor. It goes without saying that the technical idea of the present invention encompasses cases in which these measurement values are used instead of the current value of a current flowing through the resistor.

The additive component holding portion <NUM> of the aerosol generating apparatus <NUM> holds chopped tobacco leaves and a flavor component <NUM>, such as menthol, therein. The additive component holding portion <NUM> includes air vents on the mouthpiece side and in a portion to be coupled to the aerosol source holding portion <NUM>, and when the user inhales from the mouthpiece, a negative pressure is generated inside the additive component holding portion <NUM>, the aerosol generated in the aerosol source holding portion <NUM> is sucked, nicotine, a flavor component, etc. are added to the aerosol in the additive component holding portion <NUM>, and the aerosol is emitted into the mouth of the user.

Note that the internal configuration shown in <FIG> is one example. A configuration is also possible in which the aerosol source holding portion <NUM> is provided along a side surface of a cylinder and have a torus shape that includes a cavity extending along a center of a circular cross section. In this case, the supply portion <NUM> and the load <NUM> may be arranged in the central cavity. Furthermore, an output portion, such as an LED (Light Emitting Diode) or a vibrator, may be further provided to output the state of the apparatus to the user.

<FIG> is a circuit diagram showing one example of a portion of a circuit configuration in the aerosol generating apparatus relating to detection of the remaining quantity of the aerosol source and control of power supply to the load. The aerosol generating apparatus <NUM> includes the power source <NUM>, the control unit <NUM>, a voltage conversion unit <NUM>, switches (switching elements) Q1 and Q2, the load <NUM>, and the remaining quantity sensor <NUM>. A portion that connects the power source <NUM> to the load <NUM> and includes the switches Q1 and Q2 and the voltage conversion unit <NUM> will also be referred to as a "feed circuit" according to the present invention. The power source <NUM> and the control unit <NUM> are provided in the main body <NUM> shown in <FIG>, and the voltage conversion unit <NUM>, the switches Q1 and Q2, the load <NUM>, and the remaining quantity sensor <NUM> are provided in the aerosol source holding portion <NUM> shown in <FIG>, for example. As a result of the main body <NUM> and the aerosol source holding portion <NUM> being coupled together, constitutional elements therein are electrically connected to each other and a circuit as shown in <FIG> is formed. Note that a configuration is also possible in which at least some of the voltage conversion unit <NUM>, the switches Q1 and Q2, and the remaining quantity sensor <NUM> are provided in the main body <NUM>, for example. In a case in which the aerosol source holding portion <NUM> and the additive component holding portion <NUM> are configured as disposable replacement parts, the cost of the replacement parts can be reduced by reducing the number of components included in the replacement parts.

The power source <NUM> is directly or indirectly electrically connected to each constitutional element and supplies power to the circuit. The control unit <NUM> is connected to the switches Q1 and Q2 and the remaining quantity sensor <NUM>. The control unit <NUM> acquires an output value of the remaining quantity sensor <NUM> to calculate an estimated value regarding the aerosol source remaining in the storage portion <NUM>, and controls opening and closing of the switches Q1 and Q2 based on the calculated estimated value, an output value of the inhalation sensor <NUM>, etc..

The switches Q1 and Q2 are semiconductor switches such as MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), for example. One end of the switch Q1 is connected to the power source <NUM> and another end of the switch Q1 is connected to the load <NUM>. By closing the switch Q1, power can be supplied to the load <NUM> to generate an aerosol. The control unit <NUM> closes the switch Q1 upon detecting an inhaling action of the user, for example. Note that a path that passes the switch Q1 and the load <NUM> will also be referred to as an "aerosol generation path" and a "first power supply path".

One end of the switch Q2 is connected to the power source <NUM> via the voltage conversion unit <NUM> and another end of the switch Q2 is connected to the load <NUM> via the remaining quantity sensor <NUM>. By closing the switch Q2, an output value of the remaining quantity sensor <NUM> can be acquired. Note that a path that passes the switch Q2, the remaining quantity sensor <NUM>, and the load <NUM> and through which the remaining quantity sensor <NUM> outputs a prescribed measurement value will also be referred to as a "remaining quantity detection path" and a "second power supply path" according to the present invention. Note that, if a hall element is used in the remaining quantity sensor <NUM>, the remaining quantity sensor <NUM> need not be connected to the switch Q2 and the load <NUM> and is only required to be provided to be able to output a prescribed measurement value at a position between the switch Q2 and the load <NUM>. In other words, it is only required that a conducting wire that connects the switch Q2 to the load <NUM> passes through the hall element.

The above-described circuit shown in <FIG> includes a first node <NUM> from which a path extending from the power source <NUM> branches into the aerosol generation path and the remaining quantity detection path and a second node <NUM> that is connected to the load <NUM> and at which the aerosol generation path and the remaining quantity detection path merge with each other.

The voltage conversion unit <NUM> is capable of converting a voltage output by the power source <NUM> and outputting the converted voltage to the load <NUM>. Specifically, the voltage conversion unit <NUM> is a voltage regulator, such as an LDO (Low Drop-Out) regulator shown in <FIG>, and outputs a constant voltage. One end of the voltage conversion unit <NUM> is connected to the power source <NUM> and another end of the voltage conversion unit <NUM> is connected to the switch Q2. The voltage conversion unit <NUM> includes a switch Q3, resistors R1 and R2, capacitors C1 and C2, a comparator Comp, and a constant voltage source that outputs a reference voltage VREF. Note that, if the LDO regulator shown in <FIG> is used, an output voltage Vout of the LDO regulator can be determined using the following expression (<NUM>).

The switch Q3 is a semiconductor switch, for example, and is opened or closed according to output of the comparator Comp. One end of the switch Q3 is connected to the power source <NUM>, and the output voltage is changed according to the duty ratio of opening and closing of the switch Q3. The output voltage of the switch Q3 is divided by the resistors R1 and R2 that are connected in series, and is applied to one input terminal of the comparator Comp. The reference voltage VREF is applied to another input terminal of the comparator Comp. Then, a signal that indicates the result of comparison between the reference voltage VREF and the output voltage of the switch Q3 is output. Even if the voltage value of a voltage applied to the switch Q3 varies, so long as the voltage value is at least a predetermined value, the output voltage of the switch Q3 can be made constant based on feedback received from the comparator Comp, as described above. The comparator Comp and the switch Q3 will also be referred to as a "voltage conversion unit" according to the present invention.

Note that one end of the capacitor C1 is connected to an end portion of the voltage conversion unit <NUM> on the power source <NUM> side and another end of the capacitor C1 is connected to the ground. The capacitor C1 stores power and protects the circuit from a surge voltage. One end of the capacitor C2 is connected to an output terminal of the switch Q3 and the capacitor C2 smooths the output voltage.

If a power source such as a secondary battery is used, the power source voltage decreases as the charge rate decreases. With the voltage conversion unit <NUM> according to the present embodiment, a constant voltage can be supplied even if the power source voltage varies to some extent.

The remaining quantity sensor <NUM> includes a shunt resistor <NUM> and a voltmeter <NUM>. One end of the shunt resistor <NUM> is connected to the voltage conversion unit <NUM> via the switch Q2. Another end of the shunt resistor <NUM> is connected to the load <NUM>. Namely, the shunt resistor <NUM> is connected in series to the load <NUM>. The voltmeter <NUM> is connected in parallel to the shunt resistor <NUM> and is capable of measuring a voltage drop amount at the shunt resistor <NUM>. The voltmeter <NUM> is also connected to the control unit <NUM> and outputs the measured voltage drop amount at the shunt resistor <NUM> to the control unit <NUM>.

<FIG> is a block diagram showing processing for estimating the quantity of the aerosol source stored in the storage portion <NUM>. Assume that a voltage Vout that is output by the voltage conversion unit <NUM> is a constant. Also, a resistance value Rshunt of the shunt resistor <NUM> is a known constant. Therefore, a current value Ishunt of a current flowing through the shunt resistor <NUM> can be determined from a voltage Vshunt between opposite ends of the shunt resistor <NUM> using the following expression (<NUM>).

Note that a current value IHTR of a current flowing through the load <NUM> connected in series to the shunt resistor <NUM> is equal to Ishunt. The shunt resistor <NUM> is connected in series to the load <NUM>, and a value corresponding to the current value of a current flowing through the load is measured at the shunt resistor <NUM>.

Here, the output voltage Vout of the voltage conversion unit <NUM> can be expressed by the following expression (<NUM>) using a resistance value RHTR of the load <NUM>.

By transforming the expression (<NUM>), the resistance value RHTR of the load <NUM> can be expressed by the following expression (<NUM>).

The load <NUM> has the above-described Positive Temperature Coefficient (PTC) characteristics, and the resistance value RHTR of the load <NUM> is substantially in direct proportion to a temperature THTR of the load <NUM> as shown in <FIG>. Therefore, the temperature THTR of the load <NUM> can be calculated based on the resistance value RHTR of the load <NUM>. In the present embodiment, information that indicates a relationship between the resistance value RHTR and the temperature THTR of the load <NUM> is stored in a table in advance, for example. Therefore, the temperature THTR of the load <NUM> can be estimated without using a dedicated temperature sensor. Note that, in a case in which the load <NUM> has Negative Temperature Coefficient (NTC) characteristics as well, the temperature THTR of the load <NUM> can be estimated based on information indicating a relationship between the resistance value RHTR and the temperature THTR.

In the present embodiment, even if the aerosol source around the load <NUM> is evaporated by the load <NUM>, the aerosol source is continuously supplied via the supply portion <NUM> to the load <NUM> so long as a sufficient quantity of the aerosol source is stored in the storage portion <NUM>. Therefore, if the quantity of the aerosol source remaining in the storage portion <NUM> is at least a predetermined quantity, normally, the temperature of the load <NUM> is not significantly increased exceeding the boiling point of the aerosol source. However, as the quantity of the aerosol source remaining in the storage portion <NUM> decreases, the quantity of the aerosol source supplied via the supply portion <NUM> to the load <NUM> also decreases, and the temperature of the load <NUM> is increased exceeding the boiling point of the aerosol source. Assume that information that indicates such a relationship between the remaining quantity of the aerosol source and the temperature of the load <NUM> is known in advance through experiments etc. Based on this information and the calculated temperature THTR of the load <NUM>, a remaining quantity of the aerosol source held by the storage portion <NUM> can be estimated. Note that the remaining quantity may also be determined as the ratio of the remaining quantity to the capacity of the storage portion <NUM>.

Since there is a correlation between the remaining quantity of the aerosol source and the temperature of the load <NUM>, it is possible to determine that the aerosol source in the storage portion <NUM> is depleted if the temperature of the load <NUM> exceeds a threshold value of the temperature that corresponds to a threshold value of the remaining quantity determined in advance. Furthermore, since there is correspondence between the resistance value and the temperature of the load <NUM>, it is possible to determine that the aerosol source in the storage portion <NUM> is depleted if the resistance value of the load <NUM> exceeds a threshold value of the resistance value that corresponds to the above-described threshold value of the temperature. Also, the current value Ishunt of a current flowing through the shunt resistor <NUM> is the only variable in the above-described expression (<NUM>), and accordingly a threshold value of the current value that corresponds to the above-described threshold value of the resistance value is uniquely determined. Here, the current value Ishunt of a current flowing through the shunt resistor <NUM> is equal to the current value IHTR of a current flowing through the load <NUM>. Therefore, it is also possible to determine that the aerosol source in the storage portion <NUM> is depleted if the current value IHTR of a current flowing through the load <NUM> is smaller than a threshold value of the current value determined in advance. Namely, with respect to a measurement value, such as the current value of a current caused to flow through the load <NUM>, it is possible to determine a target value or a target range in a state in which a sufficient quantity of the aerosol source is remaining, for example, and determine whether the remaining quantity of the aerosol source is sufficiently large depending on whether or not the measurement value belongs to a prescribed range that includes the target value or the target range. The prescribed range can be determined using the above-described threshold value, for example.

As described above, according to the present embodiment, the resistance value RHTR of the load <NUM> can be calculated using one measurement value, i.e., the value Ishunt of a current flowing through the shunt resistor <NUM>. Note that the current value Ishunt of a current flowing through the shunt resistor <NUM> can be determined by measuring the voltage Vshunt between opposite ends of the shunt resistor <NUM> as shown by the expression (<NUM>). Here, a measurement value output by a sensor generally includes various errors, such as an offset error, a gain error, a hysteresis error, and a linearity error. In the present embodiment, the voltage conversion unit <NUM> that outputs a constant voltage is used, and accordingly, when estimating the remaining quantity of the aerosol source held by the storage portion <NUM> or determining whether or not the aerosol source in the storage portion <NUM> is depleted, the number of variables for which measurement values are to be substituted is one. Therefore, precision of the calculated resistance value RHTR of the load <NUM> is improved, when compared to a case in which the resistance value of the load etc. is calculated by substituting output values of different sensors for a plurality of variables, for example. As a result, precision of the remaining quantity of the aerosol source, which is estimated based on the resistance value RHTR of the load <NUM>, is also improved.

<FIG> is a processing flow diagram showing one example of remaining quantity estimation processing. <FIG> is a timing chart showing one example of a state in which a user uses the aerosol generating apparatus. In <FIG>, the direction of an arrow indicates passage of time t (s) and graphs respectively show opening and closing of the switches Q1 and Q2, the value IHTR of a current flowing through the load <NUM>, the calculated temperature THTR of the load <NUM>, and a change in the remaining quantity of the aerosol source. Note that threshold values Thre1 and Thre2 are predetermined threshold values for detecting depletion of the aerosol source. The aerosol generating apparatus <NUM> estimates the remaining quantity when used by a user, and if a reduction in the aerosol source is detected, performs predetermined processing.

The control unit <NUM> of the aerosol generating apparatus <NUM> determines whether the user has performed an inhaling action, based on output of the inhalation sensor <NUM> (<FIG>: step S1). In this step, if the control unit <NUM> detects generation of a negative pressure, a change in the flow rate, etc. based on output of the inhalation sensor <NUM>, the control unit <NUM> determines that an inhaling action of the user is detected. If inhalation is not detected (step S1: No), the process performed in step S1 is repeated. Note that inhalation performed by the user may also be detected by comparing a negative pressure or a change in the flow rate with a threshold value other than <NUM>.

On the other hand, if inhalation is detected (step S1: Yes), the control unit <NUM> performs Pulse Width Modulation (PWM) control on the switch Q1 (<FIG>: step S2). Assume that inhalation is detected at time t1 in <FIG>, for example. After time t1, the control unit <NUM> opens and closes the switch Q1 at a predetermined cycle. As the switch Q1 is opened and closed, a current flows through the load <NUM> and the temperature THTR of the load <NUM> increases up to approximately the boiling point of the aerosol source. The aerosol source is heated with the temperature of the load <NUM> and evaporates, and the remaining quantity of the aerosol source decreases. Note that Pulse Frequency Modulation (PFM) control may also be used, instead of the PWM control, when controlling the switch Q1 in step S2.

The control unit <NUM> determines whether the inhaling action of the user has ended, based on output of the inhalation sensor <NUM> (<FIG>: step S3). In this step, the control unit <NUM> determines that the user has ceased to inhale if generation of a negative pressure, a change in the flow rate, etc. is no longer detected based on output of the inhalation sensor <NUM>. If inhalation has not ended (step S3: No), the control unit <NUM> repeats the process in step S2. Note that the end of the inhaling action of the user may also be detected by comparing a negative pressure or a change in the flow rate with a threshold value other than <NUM>. Alternatively, when a predetermined period has elapsed from detection of the inhaling action of the user in step S1, the processing may be advanced to step S4 regardless of the determination made in step S3.

On the other hand, if inhalation has ended (step S3: Yes), the control unit <NUM> ceases the PWM control of the switch Q1 (<FIG>: step S4). Assume that it is determined at time t2 in <FIG> that inhalation has ended, for example. After time t2, the switch Q1 enters an open state (OFF) and power supply to the load <NUM> ceases. The aerosol source is supplied from the storage portion <NUM> via the supply portion <NUM> to the load <NUM> and the temperature THTR of the load <NUM> gradually decreases through dissipation. As a result of the temperature THTR of the load <NUM> decreasing, evaporation of the aerosol source ceases and a reduction in the remaining quantity also ceases.

As described above, as a result of the switch Q1 being turned ON, a current flows through the aerosol generation path shown in <FIG> in steps S2 to S4 surrounded by a rounded rectangle indicated by a dotted line in <FIG>.

Thereafter, the control unit <NUM> continuously closes the switch Q2 for a predetermined period (<FIG>: step S5). As a result of the switch Q2 being turned ON, a current flows through the remaining quantity detection path shown in <FIG> in steps S5 to S9 surrounded by a rounded rectangle indicated by a dotted line in <FIG>. At time t3 in <FIG>, the switch Q2 is in a closed state (ON). In the remaining quantity detection path, the shunt resistor <NUM> is connected in series to the load <NUM>. The remaining quantity detection path has a larger resistance value than the aerosol generation path as a result of the shunt resistor <NUM> being added, and the current value IHTR of a current flowing through the load <NUM> via the remaining quantity detection path is smaller than the current value IHTR of a current flowing through the load <NUM> via the aerosol generation path.

In the state in which the switch Q2 is closed, the control unit <NUM> acquires a measurement value from the remaining quantity sensor <NUM> and detects the current value of a current flowing through the shunt resistor <NUM> (<FIG>: step S6). In this step, the current value Ishunt at the shunt resistor <NUM> is calculated using the above-described expression (<NUM>) from a voltage between opposite ends of the shunt resistor <NUM> measured using the voltmeter <NUM>, for example. Note that the current value Ishunt at the shunt resistor <NUM> is equal to the current value IHTR of a current flowing through the load <NUM>.

In the state in which the switch Q2 is closed, the control unit <NUM> determines whether or not the current value of a current flowing through the load <NUM> is smaller than a threshold value of the current determined in advance (<FIG>: step S7). Namely, the control unit <NUM> determines whether the measurement value belongs to a prescribed range that includes a target value or a target range. Here, the threshold value (<FIG>: Thre1) of the current corresponds to a threshold value (<FIG>: Thre2) of the remaining quantity of the aerosol source determined in advance, with which it is to be determined that the aerosol source in the storage portion <NUM> is depleted. Namely, if the current value IHTR of a current flowing through the load <NUM> is smaller than the threshold value Thre1, it is possible to determine that the remaining quantity of the aerosol source is smaller than the threshold value Thre2.

If the current value IHTR becomes smaller than the threshold value Thre1 (step S7: Yes) within a predetermined period for which the switch Q2 is closed, the control unit <NUM> detects depletion of the aerosol source and performs predetermined processing (<FIG>: step S8). If the voltage value measured in step S6 and the current value determined based on the voltage value are smaller than predetermined threshold values, the remaining quantity of the aerosol source is small, and accordingly control is performed in this step to further reduce the voltage value measured in step S6 and the current value determined based on the voltage value. For example, the control unit <NUM> may cease operations of the aerosol generating apparatus <NUM> by ceasing operations of the switch Q1 or Q2 or cutting off power supply to the load <NUM> using a power fuse (not shown), for example.

Note that, as is the case with the period from time t3 to time t4 in <FIG>, if the remaining quantity of the aerosol source is sufficiently large, the current value IHTR is larger than the threshold value Thre1.

After step S8 or if the current value IHTR is at least the threshold value Thre1 (step S7: No) over the predetermined period for which the switch Q2 is closed, the control unit <NUM> opens the switch Q2 (<FIG>: step S9). At time t4 in <FIG>, the predetermined period has elapsed and the current value IHTR has been at least the threshold value Thre1, and therefore the switch Q2 is turned OFF. Note that the predetermined period (corresponding to the period from time t3 to time t4 in <FIG>) for which the switch Q2 is closed is shorter than a period (corresponding to the period from time t1 to time t2 in <FIG>) for which the switch Q1 is closed in steps S2 to S4. If it is determined in step S7 that the measurement value belongs to the prescribed range, when inhalation is detected thereafter (step S1: Yes), control is performed such that the current value (measurement value) to be calculated in step S6 approaches the target value or the target range by opening and closing the switch Q1 (step S2) while adjusting the duty ratio of the switching, for example. Here, control is performed such that the amount of change in the measurement value is larger in a case in which the feed circuit is controlled to reduce the amount of a current flowing to the load <NUM> (also referred to as a "second control mode" according to the present invention) when the measurement value does not belong to the prescribed range, than in a case in which the feed circuit is controlled to make the measurement value approach the target value or the target range (also referred to as a "first control mode" according to the present invention) when the measurement value belongs to the prescribed range.

Thus, the remaining quantity estimation processing ends. Thereafter, the processing returns to the process performed in step S1, and if an inhaling action of the user is detected, the processing shown in <FIG> is executed again.

At time t5 in <FIG>, an inhaling action of the user is detected (<FIG>: step S1: Yes), and PWM control of the switch Q1 is started. At time t6 in <FIG>, it is determined that the inhaling action of the user has ended (<FIG>: step S3: Yes), and the PWM control of the switch Q1 is ceased. At time t7 in <FIG>, the switch Q2 is turned ON (<FIG>: step S5), and the current value at the shunt resistor is calculated (<FIG>: step S6). Thereafter, as shown in the period after time t7 in <FIG>, the remaining quantity of the aerosol source becomes smaller than the threshold value Thre2 and the temperature THTR of the load <NUM> increases. The current value IHTR of a current flowing through the load <NUM> decreases, and at time t8, the control unit <NUM> detects that the current value IHTR is smaller than the threshold value Thre1 (<FIG>: step S7: Yes). In this case, it is found that the aerosol cannot be generated due to depletion of the aerosol source, and accordingly the control unit <NUM> does not open and close the switch Q1 even if an inhaling action of the user is detected at time t8 or later, for example. In the example shown in <FIG>, the predetermined period thereafter elapses at time t9, and the switch Q2 is turned OFF (<FIG>: step S9). Note that the control unit <NUM> may also turn the switch Q2 OFF at time t8 at which the current value IHTR becomes smaller than the threshold value Thre1.

As described above, in the present embodiment, the voltage conversion unit <NUM> that converts voltage is provided, and therefore it is possible to reduce errors that might be included in variables used for control when estimating the remaining quantity of the aerosol source or depletion thereof, and precision of control performed according to the remaining quantity of the aerosol source can be improved, for example.

In the remaining quantity determination processing performed in the above-described embodiment, the control unit <NUM> acquires the measurement value of the remaining quantity sensor <NUM> while keeping the switch Q2 ON for the predetermined period. Note that the period for which the switch Q2 is closed will be referred to as a "feeding sequence" for supplying power to the remaining quantity sensor <NUM> and the load <NUM>. Here, a "determination period" for determining the remaining quantity of the aerosol source may also be used to determine the remaining quantity. The determination period is included in the feeding sequence on a time axis, for example, and the length of the determination period is changeable.

<FIG> is a diagram showing one example of a method for determining the length of the determination period. In the graph shown in <FIG>, the horizontal axis indicates passage of time t and the vertical axis indicates the current value IHTR of a current flowing through the load <NUM>. In the example shown in <FIG>, the current value IHTR of a current that flows when the switch Q1 is opened or closed is omitted for the sake of convenience, and only the current value IHTR of a current that flows through the load <NUM> in feeding sequences during which the switch Q2 is closed is shown.

Periods p1 shown in <FIG> are normal feeding sequences, and the current value IHTR shown on the left represents a schematic profile in a case in which a sufficient quantity of the aerosol source is remaining. Assume that the determination period is initially equal to the feeding sequence (p1). In the example shown on the left, the temperature THTR of the load <NUM> increases as power is supplied, and the current value IHTR gradually decreases as a result of the resistance value RHTR of of the load <NUM> increasing with the increase in the temperature THTR of the load <NUM>, but the current value IHTR does not become smaller than the threshold value Thre1. In such a case, the determination period is not changed.

The current value IHTR shown at the center represents a case in which the current value IHTR becomes smaller than the threshold value Thre1 within the determination period (p1). Here, a period p2 from the start of the feeding sequence to a time at which the current value IHTR becomes smaller than the threshold value Thre1 is set as the determination period to be included in the following feeding sequence. Namely, the determination period in the following feeding sequence is adjusted based on the period it takes for the current value IHTR to become smaller than the threshold value Thre1 in the preceding feeding sequence. In other words, the higher the possibility of depletion of the aerosol source is, the shorter the determination period is set. A configuration is also possible in which the length of the feeding sequence is used as a reference, and if the current value IHTR becomes smaller than the threshold value Thre1 within the feeding sequence (determination period), it is determined that the possibility of depletion of the aerosol source is at least a threshold value (also referred to as a "second threshold value" according to the present invention). In other words, the determination period is set to be shorter than the feeding sequence only when the possibility of depletion of the aerosol source is at least the threshold value.

The current value IHTR shown on the right represents a case in which the current value IHTR becomes smaller than the threshold value Thre1 within the determination period (p2). The quantity of the aerosol source held by the storage portion <NUM> continuously decreases while the aerosol generating apparatus <NUM> is used. Therefore, as the aerosol source is depleted, the period from the start of power supply to a time at which the current value IHTR becomes smaller than the threshold value Thre1 normally gets shorter and shorter. In the example shown in <FIG>, it is determined that the aerosol source is depleted (i.e., abnormal) if more than a prescribed number of cases have consecutively occurred in which the current value IHTR becomes smaller than the threshold value Thre1 within the determination period, when the determination period is repeated while being changed as described above. Note that, if the aerosol source is depleted, power supply to the remaining quantity detection circuit may also be ceased as shown in <FIG>.

<FIG> is a diagram showing another example of changes in the current value of a current flowing through the load. The changes in the current value IHTR shown on the left and at the center of <FIG> are the same as those shown in <FIG>. The current value IHTR shown on the right of <FIG> has the same profile as that in the case in which a sufficient quantity of the aerosol source is remaining, and does not become smaller than the threshold value Thre1 within the determination period (p2). Here, the aerosol generating apparatus <NUM> as shown in <FIG> is configured to supply the aerosol source from the storage portion <NUM> to the supply portion <NUM> using capillary action, and therefore, depending on the manner of inhalation performed by the user, it is difficult to control supply of the aerosol source using the control unit <NUM> etc. If the user inhales for a longer period than an envisaged period for a single puff or inhales at a shorter interval than an envisaged normal interval, the quantity of the aerosol source around the load <NUM> may temporarily become smaller than a normal quantity. In such a case, the current value IHTR may become smaller than the threshold value Thre1 within the determination period, as shown at the center of <FIG>. If the user thereafter inhales in a different manner, the current value IHTR does not become smaller than the threshold value Thre1 within the determination period, as shown on the right of <FIG>. Therefore, in the example shown in <FIG>, the number of consecutive cases in which the current value IHTR becomes smaller than the threshold value Thre1 within the determination period is not larger than the prescribed number when the determination period is repeated, and accordingly it is determined that the aerosol source stored in the storage portion <NUM> is not depleted.

If the above-described determination period is employed, precision of the determination as to whether or not the aerosol source is depleted can be further improved. Namely, the reference used in the determination operation can be adjusted by changing the determination period, and precision of the determination can be improved.

<FIG> is a processing flow diagram showing one example of processing for setting the determination period. In this variation, the control unit <NUM> executes determination processing shown in <FIG> instead of the processes performed in steps S5 to S9 in the remaining quantity estimation processing shown in <FIG>.

First, the control unit <NUM> of the aerosol generating apparatus <NUM> turns the switch Q2 ON (<FIG>: step S5). This step is the same as step S5 in <FIG>.

Also, the control unit <NUM> activates a timer and starts to count an elapsed time t (<FIG>: step S11).

Then, the control unit <NUM> determines whether the elapsed time t is at least the determination period (<FIG>: step S12). If the elapsed time t is shorter than the determination period (step S12: No), the control unit <NUM> counts the elapsed time (<FIG>: step S21). In this step, a difference Δt of a time elapsed from when the timer has been activated or the process in step S21 has been previously performed is added to t.

Also, the control unit <NUM> detects the current value IHTR of a current flowing through the load <NUM> (<FIG>: step S6). The process performed in this step is the same as that performed in step S6 in <FIG>.

Then, the control unit <NUM> determines whether the calculated current value IHTR is smaller than the predetermined threshold value Thre1 (<FIG>: step S7). This step is similar to step S7 in <FIG>. If the current value IHTR is equal to or larger than the threshold value Thre1 (step S7: No), the processing returns to the process performed in step S12.

In contrast, if the current value IHTR is smaller than the threshold value Thre1 (step S7: Yes), the control unit <NUM> adds <NUM> to a counter for counting the number of determination periods within which depletion is detected (<FIG>: step S22).

Then, the control unit <NUM> determines whether the counter indicates a value that is larger than a prescribed value (threshold value) (step S23). If it is determined that the counter indicates a value larger than the prescribed value (step S23: Yes), the control unit <NUM> determines that depletion of the aerosol source is detected, and performs predetermined processing (<FIG>: step S8). This step is the same as step S8 in <FIG>.

In contrast, if it is determined that the counter indicates a value that is not larger than the prescribed value (step S23: No), the control unit <NUM> determines whether the feeding sequence has ended (<FIG>: step S31). If the feeding sequence has not elapsed (step S31: No), the control unit <NUM> updates the elapsed time t and returns to the process performed in step S31.

In contrast, if it is determined that the feeding sequence has ended (step S31: Yes), the control unit <NUM> updates the determination period (<FIG>: step S32). In this step, the elapsed time t at the point in time when it is determined in step S7 that the current value IHTR is smaller than the threshold value Thre1 is set as a new determination period. Namely, the determination period in the following feeding sequence is adjusted based on the period it takes for the measurement value to become smaller than the threshold value in the preceding feeding sequence. In other words, the length of the determination period in the following feeding sequence is adjusted based on the measurement value obtained in the preceding feeding sequence. This can also be said as adjusting the length of the determination period in a future feeding sequence based on the measurement value obtained in the current feeding sequence.

If it is determined in step S12 that the elapsed time t is at least the determination period (step S12: Yes), the control unit <NUM> determines whether the feeding sequence has ended (<FIG>: step S13). If the feeding sequence has not ended (step S13: No), the control unit <NUM> continues to supply power until the feeding sequence ends. A state in which the determination period has elapsed and the feeding sequence has not elapsed is the state after the period p2 has elapsed and before the period p1 elapses in the period shown on the right of <FIG>.

If it is determined that the feeding sequence has ended (step S13: Yes), the control unit <NUM> sets the length of the determination period to be equal to the length of the feeding sequence (<FIG>: step S14).

Also, the control unit <NUM> resets the counter (<FIG>: step S15). Namely, the counter for counting the number of consecutive determination periods within which depletion is detected is reset because the current value IHTR has not become smaller than the threshold value Thre1 within the determination period defined along with the feeding period. Note that a configuration is also possible in which the counter is not reset and, it is determined that there is an abnormality if the number of determination periods within which depletion is detected exceeds a predetermined threshold value.

After step S15, S8, or S32, the control unit <NUM> turns the switch Q2 OFF (<FIG>: step S9). This step is the same as step S9 in <FIG>.

Through the above-described processing, the changeable determination period shown in <FIG> and <FIG> can be realized.

The control unit <NUM> estimates the remaining quantity of the aerosol source by causing the remaining quantity detection path to function during a period for which the user does not inhale using the aerosol generating apparatus <NUM>. However, it is not preferable that the aerosol is emitted from the mouthpiece during the period for which the user does not inhale. Namely, it is desirable that the quantity of the aerosol source evaporated by the load <NUM> while the switch Q2 is closed is as small as possible.

On the other hand, it is preferable that the control unit <NUM> can precisely detect a change in the remaining quantity of the aerosol source when the remaining quantity is small. Namely, the resolution increases as the measurement value of the remaining quantity sensor <NUM> largely changes according to the remaining quantity of the aerosol source, which is desirable. The following describes the resistance value of the shunt resistor based on these standpoints.

<FIG> is a diagram schematically showing energy consumed in the storage portion, the supply portion, and the load. Q<NUM> represents the quantity of heat generated by the wick of the supply portion <NUM>, Q<NUM> represents the quantity of heat generated by the coil of the load <NUM>, Q<NUM> represents the quantity of heat required for increasing the temperature of the aerosol source in a liquid state, Q<NUM> represents the quantity of heat required for changing the aerosol source from the liquid state to a gas state, and Q<NUM> represents heat generation in air through radiation etc. Consumed energy Q is the sum of Q<NUM> to Q<NUM>.

The heat capacity C (J/K) of an object is a product of the mass m (g) of the object and the specific heat c (J/g K) of the object. A heat quantity Q (J/K) required for changing the temperature of the object by T (K) can be expressed as m × C × T. Accordingly, if the temperature THTR of the load <NUM> is lower than the boiling point Tb of the aerosol source, the consumed energy Q can be schematically expressed by the following expression (<NUM>). Note that m<NUM> represents the mass of the wick of the supply portion <NUM>, C<NUM> represents the specific heat of the wick of the supply portion <NUM>, m<NUM> represents the mass of the coil of the load <NUM>, C<NUM> represents the specific heat of the coil of the load <NUM>, m<NUM> represents the mass of the aerosol source in the liquid state, C<NUM> represents the specific heat of the aerosol source in the liquid state, and T<NUM> represents an initial value of the temperature of the load <NUM>.

If the temperature THTR of the load <NUM> is equal to or higher than the boiling point Tb of the aerosol source, the consumed energy Q can be expressed by the following expression (<NUM>). Note that m<NUM> represents the mass of an evaporated portion of the liquid aerosol source and H<NUM> represents heat of evaporation of the liquid aerosol source.

Therefore, in order to prevent generation of the aerosol through evaporation, a threshold value Ethre needs to satisfy a condition shown by the following expression (<NUM>).

<FIG> is a graph schematically showing a relationship between energy (electric energy) consumed by the load <NUM> and the quantity of the generated aerosol. In <FIG>, the horizontal axis indicates the energy and the vertical axis indicates TPM (Total Particle Matter: the quantity of substances forming the aerosol). As shown in <FIG>, generation of the aerosol starts when the energy consumed by the load <NUM> exceeds the predetermined threshold value Ethre, and the quantity of the generated aerosol increases substantially in direct proportion to the consumed energy. Note that the vertical axis in <FIG> does not necessarily have to indicate the quantity of the aerosol generated by the load <NUM>. For example, the vertical axis may also indicate the quantity of the aerosol generated through evaporation of the aerosol source. Alternatively, the vertical axis may also indicate the quantity of the aerosol emitted from the mouthpiece.

Here, energy EHTR consumed by the load <NUM> can be expressed by the following expression (<NUM>). Note that WHTR represents the power of the load <NUM> and tQ2_ON represents a period (s) for which the switch Q2 is turned ON. Note that the switch Q2 needs to be turned ON for a certain period to measure the current value at the shunt resistor.

The following expression (<NUM>) is obtained by transforming the expression (<NUM>) using a current value IQ2 of a current flowing through the remaining quantity detection path, a resistance value RHTR (THTR) of the load <NUM> that varies according to the temperature THTR of the load <NUM>, and a measured voltage Vmeas of the shunt resistor.

Therefore, if the energy EHTR consumed by the load <NUM> is smaller than the threshold value Ethre shown in <FIG> as expressed by the following expression (<NUM>), the aerosol is not generated.

This can be transformed to the following expression (<NUM>). Namely, if the resistance value Rshunt of the shunt resistor satisfies the expression (<NUM>), the aerosol is not generated in the remaining quantity estimation processing, which is preferable.

Generally, it is preferable that the shunt resistor has a small resistance value, such as about several dozens of mQ, to reduce effects on the circuit to which the shunt resistor is added. However, in the present embodiment, the lower limit of the resistance value of the shunt resistor is determined as described above from the standpoint of suppressing generation of the aerosol. The lower limit value is preferably about several Ω, for example, which is larger than the resistance value of the load <NUM>. As described above, the resistance value of the shunt resistor is preferably set to satisfy a first condition that the quantity of the aerosol generated by the load in the feeding sequence during which power is supplied from the power source to the resistor is not larger than a predetermined threshold value.

Note that a configuration is also possible in which the resistance value of the shunt resistor is not increased, and an adjustment resistor is additionally provided in series to the shunt resistor to increase the total resistance value. In this case, a configuration is also possible in which a voltage between opposite ends of the added adjustment resistor is not measured.

<FIG> is one example of a graph that shows a relationship between the remaining quantity of the aerosol source and the resistance value of the load <NUM>. In the graph shown in <FIG>, the horizontal axis indicates the remaining quantity of the aerosol source and the vertical axis indicates the resistance value of the load <NUM> determined according to the temperature of the load <NUM>. RHTR (TDepletion) represents a resistance value at a time when the aerosol source is depleted. ) represents a resistance value at the room temperature. Here, precision of estimation of the remaining quantity of the aerosol source can be improved by appropriately setting not only the voltage and the current, but also a measurement range of the resistance value or the temperature of the load <NUM>, with respect to the resolution of the control unit <NUM> including the number of bits. On the other hand, as the difference between the resistance values RHTR (TDepletion) and RHTR (TR. ) of the load <NUM> increases, the width of variation according to the remaining quantity of the aerosol source increases. In other words, precision of the estimated value of the remaining quantity calculated by the control unit <NUM> can be improved by increasing the width of variation of the resistance value of the load <NUM> that varies according to the temperature of the load <NUM>, other than setting the resolution of the control unit <NUM> and the measurement range.

A current value IQ2_ON (TDepletion) that is detected based on an output value of the remaining quantity sensor <NUM> at a time when the aerosol source is depleted can be expressed by the following expression (<NUM>) using the resistance value RHTR (TDepletion) of the load <NUM> at the time.

Likewise, a current value IQ2_ON (TR. ) that is detected based on an output value of the remaining quantity sensor <NUM> at a time when the load <NUM> is at the room temperature can be expressed by the following expression (<NUM>) using the resistance value RHTR (TR. ) of the load <NUM> at the time.

Further, a difference ΔIQ2_ON obtained by subtracting the current value IQ2_ON (TDepletion) from the current value IQ2_ON (TR. ) can be expressed by the following expression (<NUM>).

It can be found from the expression (<NUM>) that, if Rshunt is increased, the difference ΔIQ2_ON between the current value IQ2_ON (TR. ) and the current value IQ2_ON (TDepletion) is reduced, and the remaining quantity of the aerosol source cannot be precisely estimated. Therefore, the resistance value Rshunt of the shunt resistor is determined such that the difference ΔIQ2_ON is larger than a desired threshold value ΔIthre as shown by the following expression (<NUM>).

By solving the expression (<NUM>) with respect to the resistance value Rshunt, a condition that is to be satisfied by the resistance value Rshunt to sufficiently increase the resolution regarding the estimated value of the remaining quantity can be expressed by the following expression (<NUM>) using the desired threshold value ΔIthre. Therefore, the resistance value Rshunt is set to satisfy the expression (<NUM>).

In the present embodiment, the resistance value Rshunt is set such that the difference ΔIQ2_ON between the current value IQ2_ON (TR. ) of a current flowing through the load <NUM> at the room temperature and the current value IQ2_ON (TDepletion) of a current flowing through the load <NUM> when the aerosol source is depleted is large enough to be detected by the control unit <NUM>. Alternatively, a configuration is also possible in which the resistance value Rshunt is set such that a difference between the current value of a current flowing through the load <NUM> at approximately the boiling point of the aerosol source and the current value of a current flowing through the load <NUM> when the aerosol source is depleted is large enough to be detected by the control unit <NUM>, for example. Generally, precision of estimation of the remaining quantity of the aerosol source is improved as the temperature difference corresponding to a current difference that can be detected by the control unit <NUM> is smaller.

The following more specifically describes effects that the resolution of the control unit <NUM> and settings of the remaining quantity detection circuit including the resistance value of the load <NUM> have on the precision of estimation of the remaining quantity of the aerosol source. If an n-bit microcontroller is used for the control unit <NUM> and VREF is applied as a reference voltage, the resolution of the control unit <NUM> can be expressed by the following expression (<NUM>).

A difference ΔVQ2_ON between a value that is detected by the voltmeter <NUM> when the load <NUM> is at the room temperature and a value that is detected by the voltmeter <NUM> when the aerosol source is depleted can be expressed by the following expression (<NUM>) based on the expression (<NUM>).

Therefore, according to the expressions (<NUM>) and (<NUM>), the control unit <NUM> can detect a value expressed by the following expression (<NUM>) and integral multiples of this value as voltage differences, in the range from <NUM> to ΔVQ2_ON.

Furthermore, according to the expression (<NUM>), the control unit <NUM> can detect a value expressed by the following expression (<NUM>) and integral multiples of this value as temperatures of the heater, in the range from the room temperature to the temperature of the load <NUM> at the time when the aerosol source is depleted.

Table <NUM> below shows one example of the resolution of the control unit <NUM> with respect to the temperature of the load <NUM> in cases in which variables in the expression (<NUM>) are changed.

As apparent from Table <NUM>, there is a tendency that the resolution of the control unit <NUM> with respect to the temperature of the load <NUM> largely changes when values of the variables are adjusted. In order to determine whether or not the aerosol source is depleted, the control unit <NUM> needs to be capable of distinguishing at least the room temperature, which is the temperature at a time when control is not performed or is started by the control unit <NUM>, and the temperature at the time when the aerosol source is depleted. Namely, a measurement value of the remaining quantity sensor <NUM> obtained at the room temperature and a measurement value of the remaining quantity sensor <NUM> obtained at the temperature at the time when the aerosol source is depleted need to have a significant difference therebetween to be distinguishable for the control unit <NUM>. In other words, the resolution of the control unit <NUM> with respect to the temperature of the load <NUM> needs to be not larger than a difference between the temperature at the time when the aerosol source is depleted and the room temperature.

As described above, if the remaining quantity of the aerosol source is sufficiently large, the temperature of the load <NUM> is kept near the boiling point of the aerosol source. In order to more accurately determine whether the aerosol source is depleted, it is preferable that the control unit <NUM> is capable of distinguishing the boiling point of the aerosol source and the temperature at the time when the aerosol source is depleted. Namely, it is preferable that a measurement value of the remaining quantity sensor <NUM> obtained at the boiling point of the aerosol source and a measurement value of the remaining quantity sensor <NUM> obtained at the temperature at the time when the aerosol source is depleted have a significant difference therebetween to be distinguishable for the control unit <NUM>. In other words, it is preferable that the resolution of the control unit <NUM> with respect to the temperature of the load <NUM> is not larger than a difference between the temperature at the time when the aerosol source is depleted and the boiling point of the aerosol source.

Furthermore, if the remaining quantity sensor <NUM> is used not only for obtaining a measurement value to be used for determining whether or not the aerosol source is depleted, but also as a sensor for determining the temperature of the load <NUM>, it is preferable that the control unit <NUM> is capable of distinguishing the room temperature, which is the temperature at a time when control is not performed or is started by the control unit <NUM>, and the boiling point of the aerosol source. Namely, it is preferable that a measurement value of the remaining quantity sensor <NUM> obtained at the room temperature and a measurement value of the remaining quantity sensor <NUM> obtained at the boiling point of the aerosol source have a significant difference therebetween to be distinguishable for the control unit <NUM>. In other words, it is preferable that the resolution of the control unit <NUM> with respect to the temperature of the load <NUM> is not larger than a difference between the boiling point of the aerosol source and the room temperature.

In order to use the remaining quantity sensor <NUM> for more precisely determining the temperature of the load <NUM>, it is preferable that the resolution of the control unit <NUM> with respect to the temperature of the load <NUM> is not larger than <NUM>. More preferably, the resolution is not larger than <NUM>. Further preferably, the resolution is not larger than <NUM>. In order to accurately distinguish a case in which the aerosol source is going to be depleted and a case in which the aerosol source has actually been depleted, it is preferable that the resolution of the control unit <NUM> with respect to the temperature of the load <NUM> is a divisor of a difference between the temperature at the time when the aerosol source is depleted and the room temperature.

Note that, as apparent from Table <NUM>, the resolution of the control unit <NUM> with respect to the temperature of the load <NUM> can be easily improved by increasing the number of bits of the control unit <NUM>, in other words, by improving the performance of the control unit <NUM>. However, an increase in the performance of the control unit <NUM> leads to an increase in cost, weight, size, etc..

As described above, the resistance value of the shunt resistor can be determined to satisfy at least a first condition that the quantity of the aerosol generated by the load <NUM> is not larger than the predetermined threshold value or a second condition that a reduction in the remaining quantity of the aerosol source can be detected by the control unit <NUM> based on an output value of the remaining quantity sensor <NUM>, and it is more preferable that the resistance value of the shunt resistor is determined to satisfy both the first condition and the second condition. A configuration is also possible in which the resistance value of the shunt resistor is closer to the largest value of values with which the second condition is satisfied than to the smallest value of values with which the first condition is satisfied. With this configuration, the resolution regarding detection of the remaining quantity can be improved as far as possible while suppressing generation of the aerosol during measurement. As a result, the remaining quantity of the aerosol source can be estimated not only precisely but also in a short period of time, and accordingly generation of the aerosol during measurement can be further suppressed.

It can be said that both the first condition and the second condition relate to responsiveness of a change in the current value of a current flowing through the load <NUM>, which is the measurement value of the remaining quantity sensor <NUM>, with respect to a change in the temperature of the load <NUM>. A case in which responsiveness of a change in the current value of a current flowing through the load <NUM> with respect to a change in the temperature of the load <NUM> is strong is a case in which the load <NUM> is dominant in a combined resistance constituted by the shunt resistor <NUM> and the load <NUM> connected in series. Namely, the resistance value Rshunt of the shunt resistor is small, and therefore the second condition can be easily satisfied, but the first condition is difficult to satisfy.

On the other hand, a case in which responsiveness of a change in the current value of a current flowing through the load <NUM> with respect to a change in the temperature of the load <NUM> is weak is a case in which the shunt resistor <NUM> is dominant in the combined resistance constituted by the shunt resistor <NUM> and the load <NUM> connected in series. Namely, the resistance value Rshunt of the shunt resistor is large, and therefore the first condition can be easily satisfied, but the second condition is difficult to satisfy.

Namely, in order to satisfy the first condition, responsiveness of a change in the current value of a current flowing through the load <NUM> with respect to a change in the temperature of the load <NUM> needs to be not higher than a prescribed upper limit. On the other hand, in order to satisfy the second condition, responsiveness of a change in the current value of a current flowing through the load <NUM> with respect to a change in the temperature of the load <NUM> needs to be at least a prescribed lower limit. In order to satisfy both the first condition and the second condition, responsiveness of a change in the current value of a current flowing through the load <NUM> with respect to a change in the temperature of the load <NUM> needs to belong to a range that is defined by the prescribed upper limit and the prescribed lower limit.

<FIG> is a diagram showing a variation of the circuit included in the aerosol generating apparatus <NUM>. In the example shown in <FIG>, the remaining quantity detection path also serves as the aerosol generation path. Namely, the voltage conversion unit <NUM>, the switch Q2, the remaining quantity sensor <NUM>, and the load <NUM> are connected in series. Generation of an aerosol and estimation of the remaining quantity are performed using the single path. The remaining quantity can also be estimated with this configuration.

<FIG> is a diagram showing another variation of the circuit included in the aerosol generating apparatus <NUM>. The example shown in <FIG> includes a voltage conversion unit <NUM> that is a switching regulator, instead of a linear regulator. In one example, the voltage conversion unit <NUM> is a step-up converter and includes an inductor L1, a diode D1, a switch Q4, and capacitors C1 and C2 that function as smoothing capacitors. The voltage conversion unit <NUM> is provided upstream of a position at which a path extending from the power source <NUM> branches into the aerosol generation path and the remaining quantity detection path. Accordingly, mutually different voltages can be respectively output to the aerosol generation path and the remaining quantity detection path as a result of opening and closing of the switch Q4 of the voltage conversion unit <NUM> being controlled by the control unit <NUM>. Note that, in a case in which a switching regulator is used instead of a linear regular as well, the switching regulator may be provided at the same position as that of the linear regulator shown in <FIG>.

A configuration is also possible in which the voltage conversion unit <NUM> is controlled such that, when the aerosol generation path, which has less restrictions regarding voltage applied thereto when compared to the remaining quantity detection path to the entirety of which a constant voltage needs to be applied to detect the remaining quantity of the aerosol source, is caused to function, power loss is smaller than that occurs when the remaining quantity detection path is caused to function. With this configuration, wasting of the charge amount of the power source <NUM> can be suppressed. Also, the control unit <NUM> performs control such that a current that flows through the load <NUM> via the remaining quantity detection path is smaller than a current that flows through the load <NUM> via the aerosol generation path. Thus, generation of the aerosol at the load <NUM> can be suppressed while the remaining quantity of the aerosol source is estimated by causing the remaining quantity detection path to function.

A configuration is also possible in which, while the aerosol generation path is caused to function, the switching regulator is caused to operate in a "direct coupling mode" (also referred to as a "direct coupling state") in which switching of the low side switch Q4 is ceased and the switch Q4 is kept ON. Namely, the duty ratio of the switch Q4 may also be set to <NUM>%. Loss that occurs when the switching regulator is switched includes transition loss and switching loss that accompany switching, in addition to conduction loss. However, if the switching regulator is caused to operate in the direct coupling mode, only conduction loss occurs at the switching regulator, and accordingly the use efficiency of the charge amount of the power source <NUM> is improved. A configuration is also possible in which the switching regulator is caused to operate in the direct coupling mode for a portion of a period for which the aerosol generation path is caused to function. In one example, if the charge amount of the power source <NUM> is sufficiently large and the output voltage of the power source <NUM> is high, the switching regulator is caused to operate in the direct coupling mode. On the other hand, if the charge amount of the power source <NUM> is small and the output voltage of the power source <NUM> is low, the switching regulator may be switched. With this configuration as well, the remaining quantity can be estimated, and loss can be reduced when compared to a case in which a linear regulator is used. Note that a step-down converter or a step-up/down converter may also be used instead of a step-up converter.

The target to be heated by the aerosol generating apparatus may be a liquid flavor source that contains nicotine and other additive materials. In this case, a generated aerosol is inhaled by the user without passing through the additive component holding portion. In a case in which such a flavor source is used as well, the remaining quantity can be precisely estimated using the above-described aerosol generating apparatus.

The control unit <NUM> performs control such that the switches Q1 and Q2 are not turned ON at the same time. Namely, the control unit <NUM> performs control such that the aerosol generation path and the remaining quantity detection path do not function at the same time. A configuration is also possible in which a dead time for which both of the switches Q1 and Q2 are turned OFF is provided when switching opening and closing of the switches Q1 and Q2. This can prevent a situation in which a current flows through the two paths. On the other hand, it is preferable to make the dead time short to keep the temperature of the load <NUM> from decreasing during the dead time as far as possible.

The processing shown in <FIG> is described assuming that the remaining quantity estimation processing is performed one time for a single puff performed by a user. However, a configuration is also possible in which the remaining quantity estimation processing is performed one time for a plurality of puffs, rather than being performed for every puff. A configuration is also possible in which, after the aerosol source holding portion <NUM> is replaced, the remaining quantity estimation processing is started after a predetermined number of puffs, because a sufficient quantity of the aerosol source is remaining after the replacement. Namely, a configuration is also possible in which the frequency of power supply to the remaining quantity detection path is lower than the frequently of power supply to the aerosol generation path. With this configuration, the remaining quantity estimation processing is kept from being excessively performed and is executed only at appropriate timings, and accordingly the use efficiency of the charge amount of the power source <NUM> is improved.

Claim 1:
An aerosol generating apparatus (<NUM>) comprising:
a power source (<NUM>);
a load (<NUM>) configured to have an electric resistance value that varies according to a temperature and atomize an aerosol source or heat a flavor source when supplied with power from the power source;
a sensor (<NUM>) configured to output a measurement value corresponding to a current value of a current flowing through the load; and
control means (<NUM>) for controlling power supply from the power source to the load and performing a determination operation for determining that there is an abnormality if the measurement value becomes smaller than a threshold value within a determination period that is included, on a time axis, in a feeding sequence during which power is supplied from the power source to the load,
wherein the control means adjusts a length of the determination period based on the measurement value.