JP2014006227A - Flow measurement instrument and flow measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flow measurement instrument and a flow measurement method which are capable of accurately measuring a flow rate of a liquid sample by a simple structure.SOLUTION: The flow measurement instrument includes: a measuring tube 11 provided in a liquid feed path 4 above a tube pump 9; bubble generation means 7 which injects gas into the liquid feed path above the measuring tube 11 to generate a bubble having such a size that a liquid flowing in the measuring tube is divided to the downstream side and the upstream side; a pair of photointerrupters 13a and 13b which are arranged above and below the measuring tube 11 respectively to detect the bubble on the basis of the difference between characteristics to light of the liquid passing the photointerrupters and those of the bubble; and calculation means which calculates a flow rate of the liquid flowing in the measuring tube on the basis of the elapsed time from detecting the bubble by the photointerrupter 13a on the upstream side to detecting the bubble by the photointerrupter 13b on the downstream side, the interval between the pair of photointerrupters, and an inside diameter of the measuring tube.

Description

  The present invention relates to a flow rate measuring device and a flow rate measuring method, and more particularly to a flow rate measuring device and a flow rate measuring method suitable for accurately measuring the flow rate of a liquid sample supplied to a reaction column of a flow reactor.

  When supplying a liquid sample (reaction solution) to a reaction column of a flow reactor (microreactor), it is necessary to precisely control the supply amount of the liquid sample. In addition, an accurate flow rate is measured using a pressure sensor, a mass flow meter, or the like. Moreover, as a pump for liquid feeding, the plunger pump for high performance liquid chromatography which can obtain an exact flow volume may be used (for example, refer patent document 1 and 2).

JP 2007-93266 A JP 2008-215873 A

  However, as described in Patent Document 2, when the flow rate is measured using a pressure sensor, the flow rate around 10 microliters / minute (0.01 milliliters / minute) required for the flow reactor is accurately measured. In order to do this, it is necessary to use other various sensors in combination, and there is a possibility that the apparatus configuration becomes large and the cost is greatly increased. In addition, the mass flow meter not only has a problem that the mass flow meter itself is expensive, but when measuring liquid samples having different specific gravity, it is necessary to correct the measured value according to the specific gravity of each liquid sample. It was not suitable for experiments in which different liquid samples were used.

  Accordingly, an object of the present invention is to provide a flow rate measuring apparatus and a flow rate measuring method capable of accurately measuring the flow rate of a liquid sample with a simple structure.

  In order to achieve the above object, the flow rate measuring device of the present invention is the flow rate measuring device for measuring the flow rate of the liquid fed from the liquid supply source to the liquid feed destination through the liquid feed path by the liquid feed unit. A measurement tube formed of a transparent tube provided in the liquid supply path on the upstream side of the liquid, and the liquid flowing through the measurement tube by injecting gas into the liquid supply path on the upstream side of the measurement tube Bubble generating means for generating bubbles of a size that divides into the upstream side, characteristics with respect to the light of the liquid that passes through the measurement tube and is arranged on the upstream side and the downstream side of the measurement tube, and the light of the bubble A pair of photo-interrupters that detect the bubbles based on the difference in characteristics with respect to the time, and an elapsed time from when the upstream photo interrupter detects the bubbles until the downstream photo interrupter detects the bubbles, It is characterized in that it comprises a calculating means for calculating the flow rate of the liquid flowing through the measurement tube on the basis of the inner diameter of spacing and the measuring tube pairs of the photo-interrupter.

  Further, it is preferable that the liquid of the liquid supply source is maintained at atmospheric pressure, and is sucked into the liquid feeding path and fed by the suction force of the liquid feeding means. Further, the liquid feeding destination may be a reaction column of a flow reactor. The flow rate of the liquid is preferably 200 microliters per minute at the maximum. Further, the bubble generating means includes a liquid straight pipe provided on the upstream side of the measuring pipe, a bubble injection branch pipe branched from the liquid straight pipe, and a gas supply source for supplying a gas for forming bubbles. And an electromagnetic pump for sending the gas having a predetermined volume to the bubble injection branch pipe. Further, the liquid straight pipe may have the same inner diameter as the inner diameter of the path connected to the upstream side and the downstream side of the liquid straight pipe. Further, it is preferable that the liquid feeding means is a tube pump including a flexible tube and a pressing roller that presses the flexible tube and sends out an internal fluid. The flexible tube is preferably a polytetrafluoroethylene tube. Further, it is preferable that the liquid supply path downstream of the liquid supply means is provided with a bubble discharge means for discharging the bubbles moving along with the liquid in the liquid supply path from the liquid supply path. .

  Further, the flow rate measuring method of the present invention is a flow rate measuring method using the flow rate measuring device, wherein the calculation means detects the front end portion of the bubble by the photo interrupter arranged on the upstream side of the measuring tube. Measurement of the elapsed time is started, and when the photo interrupter arranged on the downstream side of the measurement tube detects the front end of the bubble, the measurement of the elapsed time is terminated, and the measured elapsed time and a pair of photo The liquid flow rate per unit time is calculated based on the interval between the interrupters and the inner diameter of the measuring tube.

  The control means increases the liquid feeding amount of the liquid feeding means when the calculated liquid flow rate is smaller than a preset flow rate, and the liquid feeding amount when the calculated liquid flow rate is larger than a preset flow rate. It is preferable to reduce the liquid feeding amount of the means.

  The flow rate measuring device of the present invention can be composed of a measuring tube provided in the middle of the liquid supply path, bubble generating means for injecting gas into the liquid, a pair of photo interrupters, a general personal computer, and other computing means, Since the flow rate of the liquid is obtained from the movement state of the bubbles in the measurement tube, the flow rate of various liquids can be measured accurately, and the apparatus configuration can be simplified and the cost can be reduced.

  Also, the liquid supply source liquid is held at a constant pressure, usually atmospheric pressure, and sucked into the liquid feeding path by the suction force of the liquid feeding means, thereby suppressing the pressure change of the liquid flowing through the measuring tube. Precise flow measurement can be performed. In particular, the flow rate measuring device of the present invention is suitable for a case where the liquid delivery destination is a reaction column of a flow reactor and the maximum flow rate of liquid is 200 microliters per minute, and the reaction in the flow reactor is reliably performed. be able to.

  As a bubble generating means, by injecting gas into the liquid through the bubble injection branch pipe branched from the liquid straight pipe, bubbles that can be reliably detected by the photo interrupter can be easily formed. By forming the tube with the same inner diameter as the liquid feeding path, it is possible to reliably form bubbles and prevent the formed bubbles from being destroyed. In addition, by using a tube pump as the liquid feeding means, liquid with high crystallinity can be reliably delivered, and by using a flexible tube made of polytetrafluoroethylene having excellent chemical resistance It is possible to cope with liquid feeding of various liquids. Furthermore, by providing the bubble discharging means on the downstream side of the liquid feeding means, it is possible to deal with a liquid sending destination that dislikes mixing of bubbles.

  Therefore, according to the flow rate measurement method of the present invention, the elapsed time from when the upstream photo interrupter detects a bubble until the downstream photo interrupter detects the bubble, the interval between the photo interrupters, and the inner diameter of the measurement tube The liquid flow rate per unit time can be easily and accurately calculated on the basis of this, and the liquid supply amount of the liquid supply means is increased or decreased based on the calculated change state of the liquid flow rate, thereby supplying a liquid at a predetermined flow rate. The liquid can be stably fed to the liquid tip.

It is sectional drawing of the flow measuring device which shows one example of this invention. It is an expanded sectional view which similarly shows the measurement pipe part of a flow measuring device. It is an expanded sectional view which similarly shows the bubble generation means part of a flow measuring device. It is a systematic diagram which shows an example of the flow reactor using the flow volume measuring apparatus of this invention. It is a systematic diagram which shows the other example of the flow reactor using the flow measuring device of this invention.

  1 to 4 show an embodiment in which the flow rate measuring device of the present invention capable of implementing the flow rate measuring method of the present invention is applied to a liquid feeding device of a flow reactor. As shown in FIG. 4, the liquid feeding device shown in this embodiment includes a liquid storage tank 1 that is a liquid supply source for storing a liquid sample for reaction (reaction liquid, hereinafter referred to as liquid L), and the liquid storage tank 1. And a tube pump 3 which is a liquid feeding means for feeding the liquid L to the reaction column 2 of the flow reactor which is a liquid sending destination, in the middle of the liquid feeding path 4 from the liquid storage tank 1 to the tube pump 3. A flow rate measuring device 5 is provided.

  On the upstream side of the flow rate measuring device 5, bubble generating means 7 having a three-way joint 6 is provided. The three-way joint 6 includes a liquid straight pipe 6a formed linearly in the main body, and a bubble injection branch pipe 6b branched at right angles from the central portion of the liquid straight pipe 6a. An upstream side of the liquid straight pipe 6a is connected via a suction tube 8, a first union 9, a connecting pipe 10 and a connector 10a for sucking the liquid L from the liquid storage tank 1, and the liquid straight pipe 6a On the downstream side, a measuring tube 11 made of a transparent tube having a constant inner diameter in the length direction, for example, a glass tube, is connected through the connector 11a in the horizontal direction. Further, on the downstream side of the measuring tube 11, A flexible tube 3 a attached to the tube pump 3 is connected via the second union 12.

  In the bubble injection branch pipe 6b, a gas for forming the bubble B in the liquid L flowing in the liquid straight pipe 6a is sucked into the gas suction pipe 7a from a gas supply source (not shown). In addition, an electromagnetic pump 7c for sending to the bubble injection branch pipe 6b is connected via the gas injection pipe 7b. The electromagnetic pump 7c has a size that closes the measuring tube 11 in the liquid L that flows from the liquid straight tube 6a toward the measuring tube 11, and has a size that divides the liquid L into the downstream side and the upstream side. A constant-capacity electromagnetic pump capable of delivering a minimum volume of gas that generates bubbles B is used. Although the gas injected into the liquid L can use the atmosphere, it does not dissolve in a large amount in the liquid L or does not react with the liquid L, and also adversely affects the reaction in the reaction column 2. It is preferable to use an inert gas such as nitrogen or argon. Furthermore, depending on the reaction conditions in the reaction column 2, a reaction gas to be reacted with the liquid L, for example, a part of hydrogen can be used as a gas to be injected into the liquid L.

  Furthermore, the path from the connecting pipe 10 through the liquid straight pipe 6a to the measuring pipe 11 is set to have the same inner diameter that is larger than the inner diameter of the suction tube 8 or the flexible tube 3a. Bubbles formed by the gas injected from the branch pipe 6b into the liquid straight pipe 6a can pass through the measuring pipe 11 smoothly without breaking the shape due to a step or the like.

 On the other hand, since the gas injection branch pipe 6b only needs to flow at a moderate flow rate, the inner diameter can be kept smaller than the liquid straight pipe 6a, and by appropriately reducing the inner diameter, The liquid L can be prevented from flowing into the bubble injection branch tube 6b, and no crystal is precipitated in the bubble injection branch tube 6b.

  Further, since the downstream flow of the gas injected into the liquid from the bubble injection branch pipe 6b is regulated by the tube pump 3, the liquid L flows from the branch portion of the bubble injection branch pipe 6b toward the upstream side. Since the bubble B is formed by pushing back, the pressure on the liquid storage tank 1 side is maintained at a constant, usually atmospheric pressure, and sucked by the tube pump 3, so that the upstream side The bubble B generated toward the front can always be generated under a certain condition. Furthermore, by forming the part from the branch part of the bubble injection branch pipe 6b to the upstream connection pipe 10 with the same inner diameter as the downstream side within the range where the bubble B is generated, it grows toward the upstream side. The bubbles B can be formed more smoothly, and damage to the bubbles B that move downstream as the liquid L moves can be prevented.

  In the flow rate measuring device 5, a pair of photointerrupters 13 a and 13 b are arranged at a predetermined interval on the upstream side and the downstream side in the measurement tube 11 located on the downstream side of the bubble generating means 7. The photo interrupters 13a and 13b sandwich a measuring tube 11 between a light emitting portion that emits light of a constant intensity and a light receiving portion that receives light passing through the measuring tube 11 and generates a signal corresponding to the received light intensity. Based on the difference between the characteristics of the liquid L that passes through the measurement tube 11 and the characteristics of the bubble B, the presence of the bubbles B that move in the measurement tube 11 It is formed to detect the presence or absence.

  If the bubble B formed in the liquid feeding path 4 by the bubble generating means 7 is smaller than the inner diameter of the measuring tube 11, the bubble B is attached to the inner surface of the liquid straight tube 6 a or the measuring tube 11 and the liquid L The movement speed may be different from the movement speed of the bubble B, and the bubble B may not be reliably detected by the photo interrupters 13a and 13b. However, as described above, the measurement tube 11 is closed. The bubble B having a size that divides the liquid L into the downstream side and the upstream side reliably moves in the measuring tube 11 as the liquid L moves, and the presence or absence of the bubble B is reliably detected by the photo interrupters 13a and 13b. Can be detected.

  The photo interrupters 13a and 13b output a constant intensity signal from the light receiving unit when the measuring tube 11 is in the liquid L, and when the leading end and the rear end of the bubble B reach the photo interrupters 13a and 13b, the gas-liquid interface Due to the refraction of light, the light receiving portion hardly receives light, and the intensity of the signal changes. For example, a signal having the maximum intensity is output. Further, when the inside of the measurement tube 11 is a bubble B, a signal having a different intensity from that of the liquid L due to a difference in light transmittance or refraction at the interface with the measurement tube 11, for example, the inside of the measurement tube 11 is the liquid L. A signal having a greater strength than the current strength is output. Therefore, by measuring the intensity of the signal from the light receiving unit, it can be determined whether the inside of the measurement tube 11 of the photo interrupters 13a and 13b is the liquid L, the bubble B, or the leading end or the trailing end of the bubble B. Can be determined.

  The computing means 14 that operates based on the signals from the photo interrupters 13a and 13b is formed in the liquid by the bubble generating means 7 when the tube pump 3 is operated to send the liquid L from the liquid storage tank 1 to the reaction column 2. The moving speed of the liquid in the measuring tube 11 is obtained from the elapsed time from when the upstream photo interrupter 13a provided in the measuring tube 11 detects the bubble until the downstream photo interrupter 13a detects the bubble. The flow rate per unit time of the liquid L supplied to the reaction column 2 is obtained from the moving speed and the inner diameter of the measuring tube 11. The detection of the bubble B by the photo interrupters 13a and 13b accurately reflects the movement of the liquid L sucked into the tube pump 3 by performing based on a change in signal intensity when the tip of the bubble B passes. Thus, the moving state of the liquid L in the measuring tube 11 can be accurately detected. The calculation means 14 may be set to constantly monitor the signals of the photointerrupters 13a and 13b, but is set so as to read the signals of the photointerrupters 13a and 13b at an appropriate time interval, for example, every 50 milliseconds. The configuration of the calculation means 14 can be simplified.

  The tube pump 3 is a known tube pump that presses a flexible tube with a plurality of pressing rollers that revolve around a rotating shaft driven by a drive motor, and sends out the fluid in the tube so as to squeeze out. Thus, the fluid delivery amount increases as the rotational speed of the rotating shaft is increased. As the flexible tube 3a, a flexible tube made of various materials can be used, but the corrosion resistance is improved by using a fluororesin tube having excellent chemical resistance, for example, a polytetrafluoroethylene tube. It is possible to cope with the delivery of various liquids.

  Further, in the case of a liquid feeding means having a valve mechanism such as a plunger pump, if crystals are deposited in the liquid feeding path 4 and adhere to the valve portion, there is a possibility that a liquid feeding failure occurs and the liquid cannot be delivered. However, since the tube pump 3 does not have a valve mechanism, it is possible to continue the liquid delivery even if crystals are deposited in the liquid feed path 4, and to cope with the delivery of a liquid with high crystallinity. Can do. On the other hand, in the plunger pump, liquid feeding at a constant volume is possible by the operation of the plunger, but the tube pump 3 relies on the elastic restoring force of the flexible tube 3a for sucking the liquid during liquid feeding. There is a possibility that the flow rate becomes unstable due to the influence of ambient temperature, change of the tube over time, wear of the tube and the pressing roller, and the like.

  Therefore, the flow rate measuring device 5 including the bubble generating means 7, the measuring tube 11 in which the pair of photointerrupters 13a and 13b are arranged at predetermined intervals, and the calculating means 14 is arranged in the front stage of the tube pump 3, and is appropriately used during liquid feeding. The flow rate of the liquid L is measured at a proper time interval, and the tube pump 3 is controlled based on the measured flow rate. Can be fed to the reaction column 2. In addition, when crystals are deposited in the flow path in the pump, it takes a lot of time and labor to remove the crystals in the plunger pump, but in the case of the tube pump 3, it is only necessary to replace the flexible tube 3a. Also, there is an advantage that the liquid feeding operation can be resumed in a short time by a simple work.

  For example, a tube pump 3 having a liquid flow rate range of 10 to 200 microliters / minute is used, a glass tube having an outer diameter of 3 mm, an inner diameter of 1.8 mm, and a length of 80 mm is used as the measurement tube 11, and the upstream photointerrupter 13a. When the interval between the photointerrupter 13b and the downstream photointerrupter 13b is 20 mm, it is possible to form a bubble B having a size that closes the measuring tube 11 by injecting 10 microliters of gas. In order to form the bubbles B, it is preferable to inject about 30 microliters of gas into the liquid L.

  Since the internal volume of the measuring tube 11 between the photo interrupters 13a and 13b is 50.89 microliters, the upstream side photo when the liquid feed rate of the tube pump 3 is 50 microliters / minute (0.05 milliliters / minute). The elapsed time from when the interrupter 13a detects the bubble until the downstream photo interrupter 13a detects the bubble is about 1 minute. In addition, the elapsed time at a flow rate of 10 microliters / minute is about 5 minutes, and the elapsed time at a flow rate of 200 microliters / minute is about 15 seconds, so the flow rate measured at a set flow rate of 50 microliters / minute. Is less than 50 microliters / minute, the flow rate can be brought close to 50 microliters / minute by increasing the rotational speed of the tube pump 3 and increasing the liquid feed amount of the tube pump 3, and the measured flow rate is 50 micrometers. If it exceeds 1 liter / minute, the set flow rate can be adjusted to 50 microliters / minute by lowering the rotational speed of the tube pump 3. As a result, the liquid L can be stably fed at a predetermined flow rate over a long period of time. In addition, by appropriately setting the inner diameter of the measuring tube 11 and the interval between the photo interrupters 13a and 13b, it is possible to select an optimum elapsed time corresponding to the flow rate of the liquid L.

  The time interval for forming the bubble B and measuring the flow rate can be arbitrarily set. However, if the previously formed bubble B exists between the measurement tube 11 and the tube pump 3, the bubble B is The tube B 3 expands and contracts with intermittent liquid feeding, and the bubbles B that are formed later may not be able to move smoothly, so the next flow rate after the bubbles B that have been formed first pass through the tube pump 3. It is desirable to set to perform measurement. The amount and flow rate of the gas when the gas is injected from the bubble injection branch pipe 6b to the liquid straight pipe 6a by the electromagnetic pump 7c of the bubble generation means 7 are the conditions such as the moving speed, viscosity, and pipe inner diameter of the liquid L. It may be set according to

  When the liquid delivery destination of the reaction column 2 or the like dislikes mixing of bubbles, bubble detection means such as a photo interrupter that detects bubbles downstream of the tube pump 3 and valve opening when the bubble detection means detects bubbles Thus, by providing a bubble discharge portion 15 equipped with a solenoid valve or the like for discharging bubbles from the liquid feed path 4 (flexible tube 3a) to the outside, it is possible to avoid mixing gas into the reaction column 2 or the like. it can.

  The calculation means 14 may be set to constantly monitor the signals of the photo interrupters 13a and 13b, but by setting to read the signals of the photo interrupters 13a and 13b at an appropriate time interval, for example, every 50 milliseconds, The configuration of the calculation means 14 can be simplified, and there is no problem even if a delay of about 50 milliseconds occurs in the detection of the bubble B from the above-described elapsed time. In particular, the elapsed time is about 5 minutes with a small flow rate. In this case, the difference of about 50 milliseconds can be completely ignored, and the measurement accuracy improves as the flow rate decreases.

  As shown in FIG. 5, when a plurality of, for example, three types of liquid samples are sent, the liquid supply sources 1 a and 1 b storing the liquid samples via the three-way switching cock 16 and the container main valves 17, 1c can be connected. As described above, when a plurality of liquid samples are switched and fed, the flow rate can be accurately measured by the same procedure as described above even if the specific gravity and viscosity of the liquid samples are different. In FIG. 5, the same components as those in the above-described embodiment are designated by the same reference numerals, and detailed description thereof is omitted.

  In addition, a liquid sending destination is arbitrary and a liquid feeding means is also arbitrary. The liquid to be fed may be any liquid as long as it can be detected by distinguishing the liquid and the bubbles with a photo interrupter, and the bubble generating means may manually inject gas. Further, by installing the measuring tube in the horizontal direction, it is possible to prevent the liquid and bubbles in the measuring tube having a large inner diameter from being replaced by gravity.

  DESCRIPTION OF SYMBOLS 1 ... Liquid storage tank, 2 ... Reaction column, 3 ... Tube pump, 3a ... Flexible tube, 4 ... Liquid supply path, 5 ... Flow measuring device, 6 ... Three-way joint, 6a ... Straight pipe for liquid, 6b ... Bubble injection Branch pipe, 7 ... Bubble generating means, 7a ... Gas suction pipe, 7b ... Gas injection pipe, 7c ... Electromagnetic pump, 8 ... Suction tube, 9 ... First union, 10 ... Connecting pipe, 11 ... Measuring pipe, 10a, DESCRIPTION OF SYMBOLS 11a ... Connector, 12 ... 2nd union, 13a, 13b ... Photo interrupter, 14 ... Calculation means, 15 ... Bubble discharge part, 16 ... Three-way switching cock, 17 ... Container original valve

Claims (11)

In the flow rate measuring device for measuring the flow rate of the liquid fed from the liquid supply source to the liquid feed destination by the liquid feed means, formed by a transparent tube provided in the liquid feed path upstream of the liquid feed means Generation of a gas bubble that generates a bubble having a size that injects a gas into a liquid supply path upstream of the measurement tube and divides the liquid flowing inside the measurement tube into a downstream side and an upstream side A pair of means for detecting the bubble based on the difference between the characteristic of the liquid that passes through the measurement pipe and the characteristic of the bubble with respect to the light, which are respectively arranged on the upstream side and the downstream side of the measurement pipe Elapsed time from detection of bubbles by the photo interrupter and the upstream photo interrupter to detection of bubbles by the downstream photo interrupter, the interval between the pair of photo interrupters, and the inside of the measurement tube Flow measuring apparatus characterized by and a calculating means for calculating the flow rate of the liquid flowing through the measuring tube based on. 2. The flow rate measuring device according to claim 1, wherein the liquid of the liquid supply source is held at atmospheric pressure, and is sucked into the liquid feeding path and fed by the suction force of the liquid feeding means. The flow rate measuring device according to claim 1, wherein the liquid feeding destination is a reaction column of a flow reactor. 4. The flow rate measuring device according to claim 1, wherein the flow rate of the liquid is 200 microliters per minute at the maximum. The bubble generating means includes a liquid straight pipe provided on the upstream side of the measurement pipe, a bubble injection branch pipe branched from the liquid straight pipe, a gas supply source for supplying a gas forming a bubble, The flow rate measuring device according to any one of claims 1 to 4, further comprising an electromagnetic pump for sending the gas having a preset volume to the branch pipe for bubble injection. 6. The flow rate measuring device according to claim 5, wherein the liquid straight pipe has the same inner diameter as an inner diameter of a path connected to the upstream side and the downstream side of the liquid straight pipe. The said liquid feeding means is a tube pump provided with the flexible tube and the press roller which presses this flexible tube and sends out the fluid inside. The flow rate measuring device according to 1. The flow rate measuring device according to claim 7, wherein the flexible tube is a polytetrafluoroethylene tube. The liquid supply path downstream of the liquid supply means is provided with bubble discharge means for discharging the bubbles moving along with the liquid in the liquid supply path from the liquid supply path. Item 9. The flow measurement device according to any one of Items 1 to 8. 10. The flow rate measurement method using the flow rate measurement device according to claim 1, wherein the calculation unit detects the front end portion of the bubble by the photo interrupter disposed upstream of the measurement tube. Measurement of the elapsed time is started, the measurement of the elapsed time is terminated when the photo interrupter arranged on the downstream side of the measurement tube detects the front end of the bubble, and the measured elapsed time and a pair of A flow rate measuring method, comprising: calculating a flow rate of a liquid per unit time based on an interval between photo interrupters and an inner diameter of the measuring tube. The control means increases the liquid feeding amount of the liquid feeding means when the calculated flow rate of the liquid is smaller than a preset flow rate, and when the calculated liquid flow rate is larger than the preset flow rate, The flow rate measuring method according to claim 10, wherein the liquid feeding amount is reduced.

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