JP2004212103A - Thermal flowmeter and smoking apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal flowmeter which reliably prevents aerosol from easily adhering onto the surface of a thermal flow sensor. <P>SOLUTION: The thermal flow sensor 1 has a pair of temperature sensors (temperature-sensing sections) Tu, Rd provided in the conducting direction of fluid at a specific interval while a heater element Rh is sandwiched. In the thermal flow sensor 1, a drive voltage or a drive current is increased for allowing the temperature-sensing sections to generate heat. Or, a heater 1a provided near the temperature-sensing section is driven to generate heat for allowing thermal migration in the fluid to occur near the surface of the thermal flow sensor 1. The thermal migration prevents particles contained in the fluid from adhering to the thermal flow sensor (a temperature control means). <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a thermal type flow meter which effectively prevents the aerosol (particles) contained in a fluid from adhering to the surface of a thermal type flow sensor and enables a stable flow rate measurement for a long period of time, and uses the thermal type flow meter. Smoking device.
[0002]
[Related background art]
As a sensor for detecting the flow rate of a fluid such as gas or air, a pair of temperature measuring sections (temperature detecting elements) are provided at a predetermined distance in the direction of fluid flow with a heating section (heater element) therebetween. There is a type flow sensor. This thermal type flow sensor focuses on the fact that the temperature distribution near the sensor surface formed by the heat generated by the heat generating portion changes with the flow velocity of the fluid, and detects the temperature distribution as a temperature difference using a pair of temperature measuring portions. The mass flow rate of the fluid is measured from the temperature difference (for example, see Patent Document 1). In addition, there is an apparatus that does not include a heat generating unit and detects a flow rate by causing a pair of temperature measuring units to generate heat by themselves (for example, see Patent Document 2). By the way, in this type of thermal flow sensor, since the self-heating of the temperature measuring section causes an error in the temperature measurement, the flow rate measuring accuracy should be ensured exclusively by minimizing the driving power of the temperature measuring section as much as possible. ing.
[0003]
On the other hand, in order to solve the problem of smoke caused by smoking of cigarettes, a smoking device has been proposed in which cigarettes are heated using a heater at the time of inhaling cigarettes, thereby extracting only the flavor of the cigarettes without burning the cigarettes. (See, for example, Patent Document 3). In this smoking device, the suction of the cigarette is detected, for example, from the flow of air generated by the suction, and the heater is driven to generate heat.
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 4-230808 [Patent Document 2]
JP-A-2-259527 [Patent Document 3]
US Pat. No. 5,878,752
[Problems to be solved by the invention]
However, when the above-described thermal flow sensor is used for a long period of time, aerosols (particles) contained in fluid gas or air gradually adhere to the surface of the thermal flow sensor. Then, the aerosol adhering to the sensor surface hinders heat conduction to the heat generating portion and the temperature measuring portion, so that the measurement accuracy is deteriorated. Further, such adhesion of the aerosol also causes problems such as slowing down the response speed of the flow rate detection. In particular, when it is assumed that the thermal flow sensor is used as the power supply control means of the heater in the smoking device described above, the aerosol leaking from the cigarette as so-called sidestream smoke easily adheres to the surface of the thermal flow sensor. Is big.
[0006]
The present invention has been made in view of such circumstances, and an object of the present invention is to easily and reliably prevent aerosol from adhering to the surface of a thermal flow sensor, and to provide a stable flow rate for a long period of time. An object of the present invention is to provide a thermal flow meter that enables measurement.
Another object of the present invention is to provide a smoking apparatus having high operation reliability using the above-described thermal flow meter as a heater power supply control means.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a thermal type flow meter according to the present invention includes a thermal type flow sensor having a pair of temperature measuring units (temperature detecting elements) provided at predetermined intervals in a flow direction of a fluid; Flow rate measuring means for determining the flow rate of the fluid flowing along the surface of the thermal type flow rate sensor from the difference between the temperatures respectively detected by the pair of temperature measuring sections, and in particular, the pair of temperature measuring sections To increase the driving voltage or the driving current to generate heat in the temperature measuring section, or to generate heat by driving a heating element provided in the vicinity of the temperature measuring section to cause thermophoresis of fluid near the surface of the thermal flow sensor. And temperature control means for preventing particles contained in the fluid from adhering to the thermal flow sensor by the thermophoresis is provided. The thermophoresis of a fluid refers to a phenomenon in which aerosol (particles) contained in a fluid such as gas or air moves from a higher temperature to a lower temperature.
[0008]
According to the thermal type flow meter configured as described above, normally, the drive voltage or the drive current of the temperature measuring unit which reduces the driving power as much as possible to suppress self-heating is increased to cause the temperature measuring unit to generate heat. Alternatively, by simply driving a heating element provided near the temperature measuring unit to generate heat, and causing thermophoresis near the surface of the thermal flow sensor, the aerosol contained in gas or air is exposed to the surface of the thermal flow sensor. Therefore, it is possible to effectively prevent the aerosol from adhering to the thermal type flow sensor, and it is possible to perform a long-term stable flow rate measurement using the thermal type flow meter. When the temperature measurement unit generates heat, the measurement accuracy can be easily ensured by temperature-correcting the flow measurement value according to the heat generation temperature.
[0009]
Incidentally, the heating element provided in the vicinity of the temperature measuring section is, for example, a heating element incorporated in a substrate of a thermal flow sensor to heat the entire thermal flow sensor, or a heating section provided between a pair of temperature measuring sections. It may be. Further, the temperature control means is configured to increase the surface temperature of the thermal flow rate sensor for a predetermined time when the flow rate measured by the flow rate measurement means is greatly reduced. That is, the thermophoresis may be generated only in a situation where the flow rate is low and the aerosol easily stays on the surface of the thermal flow sensor.
[0010]
Further, the smoking device according to the present invention has a cylindrical holder surrounding the cigarette except for the mouthpiece of the cigarette, and a cigarette provided in communication with the bottom of the holder and attached to the tip of the cigarette loaded in the holder. An outside air introduction path for introducing outside air, a flow meter provided in the outside air introduction path to detect introduction of outside air into the holder, and when the introduction of outside air is detected by the flow meter incorporated in the holder. And a heater that is driven to heat the cigarette loaded in the holder,
Particularly, the present invention is characterized in that the above-mentioned thermal flow meter is used as the flow meter.
[0011]
According to the smoking device having such a configuration, it is possible to effectively prevent the aerosol that leaks from the cigarette toward the outside air introduction path from adhering to the surface of the thermal flow sensor particularly as so-called sidestream smoke, particularly after sucking the cigarette. Can be. Therefore, it is possible to stably maintain the flow detection performance of the thermal flow sensor over a long period of time.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a thermal flow meter according to the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a schematic configuration of a thermal flow meter according to one embodiment of the present invention, and 1 is a thermal flow sensor. The thermal type flow sensor 1 is basically made of a temperature measuring resistor in a fluid flow direction F with a heater element (heating portion) Rh made of a heating resistor provided on a silicon base B interposed therebetween. It has an element structure provided with a pair of temperature sensors (temperature measuring units) Ru and Rd. The thermal flow meter utilizes the fact that the degree of diffusion (temperature distribution) of the heat generated from the heater element Rh changes due to the flow of the fluid, and the thermal sensor measures the resistance value change of the temperature sensors Ru and Rd by the heat. It is configured to detect the flow rate Q of the fluid. In the drawing, Rr is a temperature sensor for measuring the ambient temperature, which is composed of a temperature measuring resistor provided at a position distant from the heater element Rh.
[0013]
That is, the thermal type flow meter uses the flow rate measuring unit 3 to change the resistance value of the temperature sensors Ru and Rd due to the temperature while driving the heater element Rh of the thermal type flow sensor 1 at a constant temperature by the driving unit 2. Configured to be detected. Specifically, as shown in FIG. 2, the driving unit 2 of the heater element Rh forms a bridge circuit 2a using the heater element Rh, a temperature sensor Rr for measuring the ambient temperature, and a pair of fixed resistors R1 and R2. Is configured to apply a voltage Vcc supplied from a predetermined power supply to the bridge circuit 2a via a transistor TR. Then, the bridge output voltage of the bridge circuit 2a is obtained by the differential amplifier 2b, and the transistor TR is feedback-controlled so that the bridge output voltage becomes zero so that the heater drive voltage applied to the bridge circuit 2a is adjusted. Be composed. The heater driving unit configured as described above controls the heating temperature of the heater element Rh so as to be always higher than the ambient temperature by a constant temperature difference.
[0014]
On the other hand, the flow rate detector 3 for detecting the flow rate Q of the fluid flowing along the surface of the thermal type flow rate sensor 1 from the change in the resistance value of the pair of temperature sensors Ru and Rd due to the heat, , Rd and a pair of fixed resistors Rx, Ry to form a bridge circuit 3a for flow measurement, and detects a bridge output voltage according to a change in the resistance value of the temperature sensors Ru, Rd via a differential amplifier 3b. It is configured as follows. A fluid flowing along the surface of the thermal type flow sensor 1 from the bridge output voltage detected via the differential amplifier 3b under the condition that the heating value of the heater element Rh is fixed by the heater driving unit 2. Is determined.
[0015]
Basically, the present invention is characterized in a thermal type flow meter including the above-mentioned thermal type flow sensor 1 and its drive unit 2 and flow rate measuring unit 3. Is increased, and thermophoresis is generated near the surface of the thermal flow sensor 1 to prevent particles contained in the fluid to be measured by the thermal flow sensor 1 from adhering to the thermal flow sensor 1. The point is that the temperature controller 4 is provided. The temperature control unit 4 uses, for example, a voltage Vh of about 2.5 V higher than the drive voltage Vcc instead of the drive voltage Vcc of about 1 V constantly applied to the bridge circuits 2a and 3a shown in FIG. It comprises means for applying to the bridge circuits 2a and 3a or means for driving the heater element 1a for heating the substrate embedded in the substrate B of the thermal type flow sensor 1 to generate heat.
[0016]
That is, the temperature control unit 4 increases the drive voltage applied to the heater element Rh or the temperature sensors Ru, Rd formed by a resistor such as platinum (Pt), or increases the drive current to increase the heater element. Rh and the temperature sensors Ru and Rd generate a large amount of heat and generate thermophoresis in the vicinity of the surface, thereby playing a role of keeping the aerosol (particles) contained in the fluid away from the substrate surface. Alternatively, the temperature control unit 4 generates thermophoresis near the surface of the thermal flow sensor 1 by driving the heater element 1a provided near the temperature sensors Ru and Rd of the thermal flow sensor 1 to generate heat. It plays a role in keeping the aerosol (particles) contained in the fluid away from the substrate surface by using electrophoresis.
[0017]
When the flow rate is measured while such thermophoresis is generated, the temperature distribution near the surface of the thermal flow rate sensor 1 naturally changes. The flow rate measured in step 3 may be corrected for temperature. For this temperature correction, information on the surface temperature of the thermal type flow sensor 1 is given to a temperature correction unit 5 realized by using, for example, a microprocessor. What is necessary is just to make an external output after correcting.
[0018]
Thus, according to the thermal flow meter configured as described above, the temperature sensors Ru and Rd are caused to generate heat under the control of the temperature control unit 4, or the heater 1a provided in the thermal flow sensor 1 is driven to generate heat. Only by causing thermophoresis near the surface of the flow sensor 1, the aerosol (particles) contained in the fluid can be kept away from the surface of the thermal flow sensor 1 using this thermophoresis. As a result, it is possible to effectively prevent the aerosol (particles) from adhering to the surface of the thermal flow sensor 1 with only simple control.
[0019]
That is, the temperature of the fluid in the vicinity of the temperature sensors Ru and Rd is increased, and the aerosol contained in the fluid is thermophoresed so as not to touch the temperature sensors Ru and Rd. Adhesion can be prevented. Then, since the surfaces of the temperature sensors Ru and Rd are not contaminated by the adhesion of the aerosol, the flow measurement using the thermal flow sensor 1 can be stably performed over a long period of time.
[0020]
Here, the thermal type flow sensor 1 in which the heater element Rh is provided between the pair of temperature sensors Ru and Rd has been described as an example, but the heater element Rh is not provided, and the pair of temperature sensors Ru and Rd are self-heating. The present invention can be similarly applied to a case where a flow rate sensor of a type that performs flow rate measurement is used. In addition, the pair of temperature sensors Ru and Rd may be driven not only with a constant current but also with a constant voltage. In addition, the temperature measuring unit is not limited to a temperature measuring resistor, but may be a thermistor or a thermoelectric device. Alternatively, an element such as a thermopile may be used.
[0021]
Next, an electric smoking apparatus using the thermal flowmeter configured as described above will be described.
This smoking apparatus uses a heater driven to generate heat by energization to heat a cigarette, thereby generating the flavor of the cigarette as a gas (volatile component) equivalent to smoke without burning the cigarette, thereby providing a smoker. To offer. In addition to preventing the generation of smoke at the time of smoking, the generation of ash, which is burnt out of tobacco leaves, and its scattering are prevented. Such an electric smoking device is as described in detail in Patent Document 2 described above.
[0022]
Schematically, this smoking apparatus comprises a cylindrical holder 11 surrounding a main body of the cigarette C except for a mouth portion provided with a filter, for example, as shown in FIG. And a heater 12 incorporated in the holder 11 to heat the cigarette C loaded in the holder 11. Further, the holder 11 is provided with an outside air introduction passage 13 which communicates with the bottom of the holder 11 and introduces outside air into the tip of the cigarette C loaded in the holder 11. A thermal flow meter 14 for detecting the introduction of outside air into the holder 11 is provided in the outside air introduction path 13. As described with reference to FIGS. 1 and 2, the thermal flow meter 14 can prevent the aerosol from adhering by causing the temperature sensors Ru and Rd to generate heat or driving the heater 1 a to generate heat. It consists of what was constituted. In the figure, reference numeral 15 denotes a mesh filter provided at a position facing the tip of the cigarette C.
[0023]
This smoking apparatus uses a secondary battery 20 as a drive source as shown in FIG. 4 as an electric configuration. The heater 12 and the thermal flow meter described above are connected to the secondary battery 20 via a power switch 21. 14 are connected. A control circuit (control unit) 22 for controlling the operation of the heater 12 and the thermal flow meter 14 is also connected to the secondary battery 20 via the power switch 21. The control circuit 22 controls the operation of an energization control unit 23 inserted in series with a power supply line of the heater 12 to control on / off of energization of the heater 12 and, for example, to control the energization of the thermal flow meter 14. It is configured to control the operation of the voltage control unit 23 inserted in series with the power supply line to control the drive voltage applied to the thermal flow meter 14.
[0024]
Specifically, when the power switch 21 is turned on (turned on), the control circuit 22 lowers the output voltage of the voltage control unit 24 to set the flow detection mode by the thermal flow meter 14, and sets the power supply control unit 23. Is turned off to set the heater 12 in the power supply standby state. The power switch 21 may be configured to automatically conduct (turn on) when the cigarette C is loaded into the holder 11 described above.
[0025]
When the cigarette C loaded in the holder 11 is sucked by the smoker, the control circuit 22 controls the flow of the air flowing into the holder 11 from the outside air introduction passage 13 by the suction through the thermal flow meter 14. As shown in FIG. 5, a function is provided to drive the heater 12 by generating heat by turning on the power supply control unit 23 during the suction period (smoking period) as shown in FIG. The control circuit 22 stops the heat generation drive of the heater 12 and stops the output voltage of the voltage control unit 24 for a predetermined time T when the suction stop of the cigarette C is detected via the thermal flow meter 14. The aerosol adhesion prevention mode by the thermal type flow meter 14 is set by setting the temperature to be high.
[0026]
In this aerosol adhesion prevention mode, the output voltage of the voltage control unit 24 is increased to drive the temperature sensors Ru and Rd of the thermal flow sensor 1 to generate heat, as described above, to generate thermophoresis and to cause the outside air introduction path 13 to move. This is a state in which the aerosol that has entered is prevented from adhering to the surface of the thermal flow sensor 1. In particular, a state in which a large amount of aerosol enters the outside air introduction passage 13 is a state in which when the suction of the cigarette C is stopped, its volatile components leak out from the cigarette C as so-called sidestream smoke.
[0027]
Therefore, in this embodiment, when the stoppage of the suction of the cigarette C is detected, the aerosol adhesion prevention mode is set for a predetermined time T, and the thermophoresis is generated near the surface of the thermal flow sensor 1 to stop the suction. The aerosol contained in the sidestream smoke generated later is prevented from adhering to the surface of the thermal flow sensor 1. In particular, in this embodiment, by increasing the drive voltage of the thermal flow sensor 1 (thermal flow meter 14) for a predetermined time T immediately after the energization of the heater 12 is stopped, a large amount of sidestream smoke is generated. Care is taken so that the limited battery capacity of the battery 20 is not unnecessarily consumed.
[0028]
Thus, according to the electric smoking apparatus configured as described above, the adhesion of the aerosol contained in the sidestream smoke generated by smoking of the cigarette C to the surface of the thermal flow sensor 1 is simply and effectively prevented. Therefore, the flow of air in the outside air introduction passage 13 caused by the suction of the cigarette C can be reliably detected by the thermal flow meter 14. Therefore, when the cigarette C is sucked, the heater 12 is immediately energized to heat the cigarette C to volatilize the volatile component that is the source of the flavor, and when the suction is stopped, the energization of the heater 12 is immediately stopped. As a result, wasteful power consumption can be suppressed.
[0029]
When the energization of the heater 12 is stopped, the drive voltage of the thermal type flow meter 14 is simply increased over a predetermined time T to prevent the aerosol from adhering to the surface of the thermal type flow sensor 1. In particular, since the thermal flow meter 14 is only temporarily driven with high power by using the time when the power supply to the heater 12 is stopped, the power load on the secondary battery 20 does not increase so much, and the overall power consumption thereof is reduced. Can be kept low. In addition, since the contamination of the thermal flow meter 14 (thermal flow sensor 1) by the aerosol can be effectively prevented, it is possible to guarantee a long-term stable operation of the electric smoking device. A great effect can be obtained in practical use.
[0030]
Note that the present invention is not limited to the embodiment described above. For example, the drive voltage or the drive current of the temperature sensors Ru, Rd (temperature measuring unit) in the thermal flow sensor 1 may be increased to drive only the temperature sensors Ru, Rd to generate heat, or the temperature sensors Ru, Rd. Only the heater element Rh provided between them may be driven to generate heat at a high temperature.
[0031]
In this case, thermophoresis is generated near the surface of the thermal flow sensor 1 to prevent the aerosol from adhering. However, it is only necessary to prevent the aerosol from adhering to the thermal flow sensor 1 by using electric means. If, for example, as shown in FIG. 6, a charger 31 is provided on the upstream side of the portion where the thermal flow sensor 1 is provided in the flow path through which the fluid flows to charge the aerosol contained in the fluid at the same time. The thermal flow sensor 1 may also be charged to the same polarity to repel the aerosol from the surface of the thermal flow sensor 1. As shown in FIG. 7, a charger 32 having a polarity opposite to that of the charger 31 is provided between the charger 31 and the thermal flow sensor 1, and the aerosol is adsorbed on the electrode plate 32a of the charger 32. Thus, the aerosol may be prevented from flowing onto the thermal flow sensor 1. However, when such chargers 31 and 32 are provided, it is unavoidable that the flow path length as a flow meter becomes longer, and a high voltage is required to drive the chargers 31 and 32. It is simpler to generate thermophoresis in the vicinity of the surface of the thermal type flow sensor 1 and the configuration as a flow meter can be simplified.
[0032]
Further, the thermal flow meter according to the present invention can be realized by modifying the drive circuit section of an existing flow meter, and thus has an advantage that its application range is wide. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.
[0033]
【The invention's effect】
As described above, according to the present invention, the drive voltage or the drive current of the temperature measuring unit in the thermal flow sensor is increased to cause the temperature measuring unit to generate heat, or the heating element provided near the temperature measuring unit is heated. Generates thermophoresis of the fluid near the surface of the thermal flow sensor by driving heat generation, so it is easy to attach the aerosol (particles) contained in the fluid guided to the surface of the thermal flow sensor to the surface of the thermal flow sensor. And a practically significant effect can be achieved.
[0034]
Further, according to the electric smoking apparatus according to the present invention, it is possible to prevent the aerosol emitted from the cigarette from adhering to the surface of the thermal flow sensor, and to ensure its stable operation for a long time. A great effect can be obtained in practical use.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a thermal flow meter according to an embodiment of the present invention.
FIG. 2 is a diagram showing a configuration example of a drive unit and a flow measurement unit of the thermal flow meter shown in FIG.
FIG. 3 is a diagram showing a schematic configuration of an electric smoking device.
FIG. 4 is a diagram showing an electrical configuration of an electric smoking device according to an embodiment of the present invention.
FIG. 5 is a timing chart showing an operation mode of the smoking device shown in FIG. 4;
FIG. 6 is a diagram showing an example of an aerosol adhesion preventing means using a charger.
FIG. 7 is a diagram showing another example of an aerosol adhesion preventing means using a charger.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Thermal type flow sensor 1a Heater element for substrate heating 2 Drive part 3 Flow rate measuring part 4 Temperature control part 5 Temperature correction part 11 Holder 12 Heater 13 Outside air introduction path 14 Thermal flow meter 20 Secondary battery 22 Control part 23 Power supply control Unit 24 voltage control unit Rh heater element (heating unit)
Ru, Rd Temperature sensor (temperature measuring part)

Claims (5)

A thermal flow sensor having a pair of temperature measuring units,
Flow rate measuring means for determining the flow rate of the fluid flowing along the surface of the thermal flow rate sensor from the difference between the temperatures detected by the pair of temperature measurement units,
The thermal flow rate of particles contained in the fluid by increasing the drive voltage or drive current for the pair of temperature measurement sections to cause the temperature measurement sections to generate heat and generate thermophoresis near the surface of the thermal flow rate sensor. A thermal flow meter, comprising: temperature control means for preventing adhesion to a sensor. A thermal flow sensor having a pair of temperature measuring units,
Flow rate measuring means for determining the flow rate of the fluid flowing along the surface of the thermal flow rate sensor from the difference between the temperatures detected by the pair of temperature measurement units,
A heating element provided in the vicinity of the temperature measuring section is driven to generate heat to cause thermophoresis near the surface of the thermal flow sensor to prevent particles contained in the fluid from adhering to the thermal flow sensor. A thermal flow meter comprising a temperature control means. The thermal flow meter according to claim 2, wherein the heating element is incorporated into a substrate of the thermal flow sensor and heats the entire thermal flow sensor. The thermal flow rate according to claim 1 or 2, wherein the temperature control means increases the surface temperature of the thermal flow rate sensor over a predetermined time when the flow rate measured by the flow rate measurement means is greatly reduced. Total. A cylindrical holder surrounding the cigarette except for the mouthpiece of the cigarette;
An outside air introduction passage that is provided in communication with the bottom of the holder and that introduces outside air to the tip of a cigarette loaded in the holder;
The thermal flow meter according to claim 1, wherein the thermal flow meter is provided in the outside air introduction passage and detects introduction of outside air into the holder.
A smoking apparatus, comprising: a heater incorporated in the holder and driven when the introduction of outside air is detected by the thermal flow meter to heat a cigarette loaded in the holder.

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