JP7451875B2 - flow measuring device - Google Patents

Description

The present invention relates to a flow rate measuring device.

2. Description of the Related Art There is known a flow rate measuring device (for example, see Patent Documents 1 and 2) that measures the flow rate of a fluid flowing in a path using a thermal flow sensor that includes a heater and two temperature sensors. Furthermore, as such a flow rate measuring device, there is also known a device equipped with a dew condensation sensor consisting of two electrode patterns arranged at a predetermined interval in order to be able to detect the occurrence of dew condensation (for example, see Patent Document 3). It is being

Patent No. 3658321 Patent No. 5652315 Japanese Patent Application Publication No. 2018-151307

If a dew condensation sensor is provided, it becomes possible to detect the occurrence of dew condensation. However, the dew condensation that can be detected by the dew condensation sensor is only the dew condensation that is larger in size than the interval between the two electrode patterns forming the dew condensation sensor. The first thing that occurs when the humidity becomes high (when the humidity reaches 100%) is minute condensation that cannot be detected by a dew condensation sensor.

The present invention has been made in view of the above-mentioned current situation, and an object of the present invention is to provide a flow rate measuring device capable of detecting high humidity.

A flow rate measuring device according to one aspect of the present invention includes: a first sensor that measures a value correlated with the flow rate of a fluid to be measured; two temperature measuring sections; and a heating section disposed at the center of the two temperature measuring sections. a second sensor, wherein the two temperature measurement units and the heating unit are arranged in a position where the fluid to be measured flows in a second predetermined direction, and the direction in which the two temperature measuring units and the heating unit are arranged is perpendicular to the second predetermined direction. a second sensor, a flow rate calculation process for calculating the flow rate of the fluid to be measured based on the value measured by the first sensor, and a flow rate calculation process for calculating the flow rate of the fluid to be measured based on the value measured by the first sensor; Obtain temperature measurement results from the two temperature measurement units, and determine whether the humidity of the fluid to be measured is equal to or higher than a predetermined humidity based on whether each of the obtained temperature measurement results is equal to or less than a predetermined threshold. and a control unit configured to be able to execute determination processing.

That is, the flow rate measurement device includes a second sensor arranged so that the temperature measurement results by each temperature measurement section are not influenced by the flow rate (flow velocity) of the fluid to be measured. Then, by increasing the temperature of the heating section of the second sensor, obtaining temperature measurement results from the two temperature measurement sections of the second sensor, and comparing each of the obtained temperature measurement results with a threshold value, the humidity of the fluid to be measured can be determined. It has been confirmed through various experiments that it is possible to determine whether or not the humidity corresponds to the threshold value. Therefore, according to the flow rate measuring device, it is possible to detect that the humidity is high (humidity according to a predetermined threshold value).

The second sensor of the flow rate measuring device may be a sensor used only to determine whether the humidity has reached a predetermined humidity or higher. Further, the control unit is configured to set the temperature measurement result obtained by one of the two temperature measurement units obtained by increasing the temperature of the heating unit to the first temperature and the temperature of the heating unit to the first temperature. It is possible to execute a correction coefficient calculation process of calculating a correction coefficient used when calculating the flow rate in the flow rate calculation process from the temperature measurement result obtained by the one temperature measurement unit raised to a second temperature different from the temperature measurement unit. By configuring this, the second sensor may also be used for calculating the correction coefficient.

A condensation sensor consisting of two electrode patterns arranged side by side at a predetermined interval is added to the flow rate measuring device, and a control section is configured to determine whether or not condensation is occurring based on the resistance value of the condensation sensor. 2 determination processing may be configured to be executable.

Each temperature measuring section of the second sensor may be a resistance temperature sensor or a thermocouple, but if each temperature measuring section is a thermopile with a large output voltage, a flow rate measuring device that is less susceptible to noise can be obtained. I can do it. In addition, if sensors with the same configuration are used as the first sensor and the second sensor, the manufacturing cost of the flow rate measuring device can be reduced compared to the case where the first sensor and the second sensor are sensors with different configurations. can be reduced.

According to the present invention, it is possible to provide a flow rate measuring device capable of detecting high humidity.

FIG. 1 is an exploded perspective view of a flow rate measuring device 1 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the flow rate measuring device. FIG. 3 is a plan view of the sub-flow path section included in the flow rate measurement device. FIG. 4 is a plan view of a sensor used as a flow rate detection sensor and a physical property detection sensor. FIG. 5A is an explanatory diagram of a flow rate detection sensor. FIG. 5B is an explanatory diagram of a sensor for detecting physical property values. FIG. 6 is a diagram for explaining the principle of flow measurement in the flow measurement device. FIG. 7 is a flowchart of the state detection process executed by the control unit of the flow rate measuring device. FIG. 8 is an explanatory diagram of the connection form between the control section and each sensor on the circuit board of the flow rate measuring device. FIG. 9 is an explanatory diagram of the results of an experiment conducted to develop a flow rate measuring device.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an exploded perspective view of a flow rate measuring device 1 according to an embodiment of the present invention, and FIG. 2 shows a sectional view of the flow rate measuring device 1.

The flow rate measuring device 1 according to the present embodiment is a device that is used by being incorporated into a device (such as a gas meter, a fuel cell, etc.) that requires monitoring and adjustment of the flow rate of fluid. As shown in FIG. 1, the flow rate measuring device 1 includes a main flow path section 2, a sub flow path section 3, a seal 4, a circuit board 5, and a cover 6.

The main flow path portion 2 is a tubular member through which a fluid whose flow rate is to be measured (hereinafter referred to as a fluid to be measured) flows. As shown in FIG. 2, an inlet 34A is provided on the inner circumferential surface of the main flow path section 2 on the upstream side in the flow direction of the fluid to be measured. Further, an outflow port 35A is provided on the inner peripheral surface of the main flow path section 2 on the downstream side in the flow direction of the fluid to be measured. Furthermore, an orifice 21 is provided between the inlet 34A and the outlet 35A of the main flow path 2 to adjust the amount of fluid flowing through the sub flow path 3 (details will be described later).

The circuit board 5 (FIG. 1) is a unit (printed circuit board) in which a flow rate detection sensor 11, a physical property value detection sensor 12, a control section 13, and a dew condensation sensor 14 (see FIG. 3) are attached to a printed wiring board. The flow rate detection sensor 11, the physical property value detection sensor 12, and the dew condensation sensor 14 are provided on the surface of the circuit board 5 (the surface facing the sub-flow path section 3; the lower surface in FIG. 1), The control unit 13 is provided on the back surface of the circuit board 5. Details of the sensors 11, 12, and 14 and the control unit 13 will be described later.

The sub-flow path section 3 (FIGS. 1 and 2) is a bypass flow path for a fluid to be measured, which is provided for measuring flow rate and the like. The sub-channel portion 3 is sealed by fixing the circuit board 5 with the seal 4 sandwiched therebetween.

FIG. 3 shows a plan view of the sub-channel section 3. In this plan view, the positions of the sensors 11, 12, and 14 in a state where the circuit board 5 is fixed to the sub-channel section 3 are also shown by dotted lines.

As shown in FIGS. 3 and 2, the sub-channel section 3 has an inflow channel 34 that communicates with the inflow port 34A, and an outflow channel 35 that communicates with the outflow port 35A. It includes a physical property value detection flow path 32 and a flow rate detection flow path 33, which are flow paths that connect between the flow path 34 and the outflow flow path 35. As shown in FIG. 3, the shape of each flow path in the sub-flow path section 3, the position of each sensor on the circuit board 5, etc. are determined when the circuit board 5 is fixed to the sub-flow path section 3. The detection sensor 11 is in contact with the fluid flowing through the flow path 33, the physical property value detection sensor 12 is in contact with the fluid flowing through the physical property value detection flow path 32, and the dew condensation sensor 14 is in contact with the fluid flowing through the physical property value detection flow path 32 and the flow rate. It is determined to be in contact with the fluid flowing through the detection flow path 33.

Further, the physical property value detection channel 32 has a smaller cross-sectional area than the flow rate detection channel 33. Therefore, as schematically shown by the sizes of arrows P and Q, the amount of fluid flowing through the physical property value detection channel 32 is smaller than the amount of fluid flowing through the flow rate detection channel 33. There is. The reason why the amount of fluid flowing through the flow rate detection channel 33 is reduced will be described later.

The cover 6 (FIG. 1) is a member for protecting the circuit board 5 fixed to the sub-channel section 3.

Each component of the circuit board 5 will be explained below.
The dew condensation sensor 14 (see FIG. 3) is a sensor composed of two electrode patterns (comb-like electrode patterns in this embodiment) formed so that the intervals between each part are a predetermined interval.

Both the flow rate detection sensor 11 and the physical property value detection sensor 12 are sensors 100 having the configuration shown in FIG. 4 . Note that this sensor 100 is a so-called MEMS flow sensor in which an insulating film including a microheater 103 and thermopiles 101 and 102 provided symmetrically with the microheater 103 in between is formed on a silicon base. The insulating film of the sensor 100 is also provided with a temperature sensor 104 for measuring a reference temperature. In addition, a cavity is provided in the central part of the silicon base of the sensor 100 in order to reduce the heat capacity of the opposing part of the insulating film (the part where the micro-heater 103 is provided, etc.). (See Figure 6).

As described above, the flow rate detection sensor 11 and the physical property value detection sensor 12 are the sensors 100 having the same configuration. However, the sensor 100 used as the flow rate detection sensor 11 can form the state shown in FIG . It is attached to the circuit board 5 in a posture. Furthermore, the sensor 100 used as the physical property value detection sensor 12 is circuited in the state shown in FIG. It is attached to the board 5. Hereinafter, the thermopile 101, thermopile 102, and microheater 103 of the sensor 100 used as the flow rate detection sensor 11 will be referred to as thermopile 111, thermopile 112, and microheater 113, respectively, as shown in FIG. 5B . do. Furthermore, as shown in FIG. 5A , the thermopile 101, thermopile 102, and microheater 103 of the sensor 100 used as the physical property value detection sensor 12 are referred to as the thermopile 121, thermopile 122, and microheater 123, respectively. write.

The control unit 13 is a unit (ASIC in this embodiment) that includes a communication interface circuit for communicating with an external device and executes a flow rate calculation process, a sensitivity correction coefficient calculation process, and a state detection process. The control unit 13 according to the present embodiment performs each process periodically, but the control unit 13 executes each process when an instruction to execute each process is given from an external device. Also good.

The contents of each process executed by the control unit 13 will be explained below.

《Flow rate calculation process》
The flow rate calculation process involves increasing the temperature of the microheater 113 of the flow rate detection sensor 11 and measuring the difference ΔV between the output voltages of the thermopiles 111 and 112 of the flow rate detection sensor 11 (hereinafter referred to as sensor output value ΔV). , is a process of calculating the flow rate of the fluid to be measured based on the measured sensor output value ΔV.

That is, when the temperature of the micro-heater 113 of the flow rate detection sensor 11 is increased in a state where gas is not flowing, the temperature distribution of the gas changes to the upstream side of the micro-heater 113 as shown in FIG. 6(A). It is a target on the downstream side. On the other hand, when the temperature of the micro-heater 113 is increased while gas is flowing, the temperature of the gas downstream of the micro-heater 113 becomes higher, as shown in FIG. 6(B). The temperature difference between the upstream side and the downstream side when gas is flowing is proportional to the square root of the gas flow rate unless there are special circumstances such as a large influence of natural convection. Further, the flow rate of the fluid to be measured in the main flow path section 2 is proportional to the flow rate of the fluid to be measured in the flow path 33 for flow rate detection.

Therefore, the flow rate of the fluid to be measured in the main flow path section 2 can be determined from the sensor output value (difference between the output voltages of the thermopiles 111 and 112) ΔV. However, even if the flow rate and temperature of the fluid to be measured do not change, if the physical properties of the fluid to be measured, such as thermal conductivity, density, and specific heat capacity, change, the sensor output value ΔV also changes. Therefore, the flow rate calculation process is a process of converting the sensor output value ΔV into the sensor output value ΔV when the various physical property values of the fluid to be measured are reference values by multiplying it by a sensitivity correction coefficient, and then calculating the flow rate. It becomes.

《Sensitivity correction coefficient calculation process》
The sensitivity correction coefficient calculation process is a process in which a sensitivity correction coefficient used during the flow rate calculation process is calculated. During this sensitivity correction coefficient calculation process, the control section 13 operates as follows.

The control unit 13 that has started the sensitivity correction coefficient calculation process first increases the temperature of the microheater 123 of the physical property value detection sensor 12 by applying a first predetermined voltage, and then increases the temperature of the microheater 123 of the physical property value detection sensor 12. 121 is obtained. Next, the control unit 13 increases the temperature of the microheater 123 by applying a second predetermined voltage (>first predetermined voltage), and then acquires the output voltage V2 of the thermocouple 121.

Thereafter, the control unit 13 calculates a sensitivity correction coefficient by multiplying the voltage difference "V2-V1" by a predetermined coefficient. Then, the control unit 13 stores the calculated sensitivity correction coefficient as a sensitivity correction coefficient to be used in the subsequent flow rate calculation process, and then ends the sensitivity correction coefficient calculation process.

As already explained (see FIG. 5B), the flow rate measurement device 1 is configured such that the fluid to be measured is distributed in the length direction of the microheater 123 of the physical property value detection sensor 12 (in other words, between the thermopiles 121 and 122 and the microheater). 123), and the amount of fluid flowing through the physical property value detection channel 32 is smaller than the amount of fluid flowing through the flow rate detection channel 33. ing. The reason why the flow measuring device 1 is configured as such is that the output voltages V1 and V2 of the thermocouple 121 are set to values that are not affected by the flow velocity of the fluid to be measured (physical property values of the fluid to be measured other than the flow velocity). This is to make it a value indicating .

《Status detection processing》
The contents of the state detection process executed by the control unit 13 will be described below with reference to FIGS. 7 and 8. FIG. 7 is a flowchart of the state detection process. FIG. 8 is an explanatory diagram of the connection form between the control unit 13 and each sensor on the circuit board 5. As shown in FIG. In FIG. 8, illustrations of the microheaters 111 and 121 and signal lines for communicating with external devices are omitted.

The state detection process is a process for detecting a state related to the humidity of the fluid to be measured. As shown in FIG. 7, the control unit 13 that has started the state detection process first measures the resistance of the dew condensation sensor 14 (step S101). Next, the control unit 13 determines whether the resistance measurement result is less than or equal to a predetermined resistance threshold (step S102). If the measurement result is less than or equal to the resistance threshold (step S102; YES), the control unit 13 determines that condensation of a size that can be detected by the condensation sensor 14 has occurred, and notifies the external device of the determination result. (Step S107). The process of step S107 may be a process of storing the determination result in order to notify the external device of the determination result upon request. After completing the process of step S107, the control unit 13 then ends the state detection process.

Note that in order to avoid the need to increase the number of input terminals, the control unit 13 and each sensor are connected as shown in FIG. 8. Therefore, the resistance actually measured in step S101 is not the resistance of the dew condensation sensor 14, but the resistance of the circuit in which the dew condensation sensor 14 and the thermocouple 122 are connected in parallel. However, the resistance of the condensation sensor 14 changes greatly depending on whether or not condensation is occurring, so if the resistance threshold is appropriately determined, the above process will ensure that condensation of a size that can be detected by the condensation sensor 14 occurs. It can be determined whether there is a

If the measurement result is not below the resistance threshold (step S102; YES), the control unit 13 increases the temperature of the microheater 123 by applying a predetermined voltage to the microheater 123 of the physical property value detection sensor 12. (Step S103). Next, the control unit 13 acquires the output voltage TA1 of the thermopile 121 of the physical property value detection sensor 12 and the output voltage TB2 of the thermopile 122 of the physical property value detection sensor 12 (step S104). The process of step S104 is a process of acquiring the single detection result of the output voltage of the thermopiles 121, 122 as TA2, TB2, or the average value of the multiple detection results of the output voltage of the thermopiles 121, 122. Alternatively, the integrated value may be acquired as TA2 and TB2.

After completing the process of step S104, the control unit 13 determines whether the conditions that TA2 is less than or equal to a predetermined threshold value A and TB2 is less than or equal to a predetermined threshold value B are satisfied. (Step S104).

If the above conditions are not satisfied (step S104; NO), the control unit 13 ends the state detection process without performing any particular process. On the other hand, if the above conditions are met (step S104; YES), the control unit 13 determines that the humidity is 100% (minor condensation that cannot be detected by the dew condensation sensor 14 has occurred), and the determination result is is notified to the external device (step S105). The process in step S105 may also be a process in which the determination result is stored in order to notify the external device of the determination result upon request.

After completing the process in step S105, the control unit 13 then ends the state detection process.

The processing in steps S103 to S105 of the state detection processing was conceived based on the following knowledge.

It is desired that the flow rate measuring device 1 be able to detect dew condensation of a size that cannot be detected by the dew condensation sensor 14. Therefore, when measuring TA2 and TB2 when fluids to be measured with various humidity levels are introduced into the flow rate measurement device 1, as shown in FIG. It was confirmed that TA2 and TB2 at the time of introducing the dry fluid to be measured were significantly different. It was also confirmed that even if the humidity of the fluid to be measured is not 100%, one of TA2 and TB2 may become smaller if there is a disturbance (such as vibration due to an external force of the flow rate measuring device 1). Then, by determining appropriate thresholds A and B based on the experimental results and using the conditions TA2≦Threshold A and TB2≦Threshold B, the humidity will be 100% even though the humidity is not near 100%. % can be prevented, so the processing of steps S103 to S105 of the state detection processing is performed according to the above procedure.

Note that the processing in steps S103 to S105 of the state detection processing was conceived based on the above knowledge. Therefore, what can actually be determined in the processing of steps S103 to S105 is whether the humidity has become equal to or higher than the humidity corresponding to the threshold values A and B. Also, the reason why the threshold value for TA2 ("threshold value A") and the threshold value for TB2 ("threshold value B") are set separately is because there is manufacturing error, so the temperature difference between the hot junction and the cold junction is the same. Even if there is, the output voltage of the thermopile 121 and the output voltage of the thermopile 122 are usually different (see FIG. 9). Therefore, when the thermopile 121 and the thermopile 122 have the same performance or can be considered to have the same performance, the same value can be used as the threshold value A and the threshold value B.

As described above, the flow rate measuring device 1 according to the present embodiment includes the physical property value detection sensor 12 arranged so that the temperature measurement results by the thermopiles 121 and 122 are not affected by the flow velocity of the fluid to be measured. . Then, if it is determined whether the output voltages of the thermopiles 121 and 122 are below a predetermined threshold when the temperature of the microheater 121 of the physical property value detection sensor 12 is increased, the humidity of the fluid to be measured can be determined. It has been confirmed through various experiments that it is possible to determine whether or not it is approximately 100%. Therefore, according to the flow rate measuring device 1 according to the present embodiment, it is possible to detect that the humidity has become high humidity (humidity higher than the humidity corresponding to the threshold values A and B).

The flow rate measuring device 1 also includes a dew condensation sensor 14 . According to the flow rate measuring device 1, it is also possible to determine whether or not large condensation is occurring (whether or not immediate countermeasures are required).

Further, in the flow rate measurement device 1, sensors 100 having the same configuration are used as the flow rate detection sensor 11 and the physical property value detection sensor 12, respectively. Therefore, the flow rate measuring device 1 can be manufactured at a lower cost than when separate sensors are used as the flow rate detection sensor 11 and the physical property value detection sensor 12.

《Modified example》
The flow rate measuring device 1 described above can be modified in various ways. For example, if correction using a sensitivity correction coefficient is not required, the flow rate measuring device 1 may be modified to a device including a control unit 13 that cannot perform sensitivity correction coefficient calculation processing. Furthermore, the flow rate measuring device 1 may be modified into a device that does not include the dew condensation sensor 14.

The state detection process is modified to a process that repeats steps S104 and S105 multiple times and determines that the humidity has reached 100% when the conditions "TA2≦Threshold A and TB2≦Threshold B" are continuously satisfied. You may do so.

Further, the positions of the flow rate detection sensor 11 and the physical property value detection sensor 12 are not limited to those described above. For example, the flow rate detection sensor 11 and the physical property value detection sensor 12 may be arranged on the inner surface of the main flow path 2.

The flow rate detection sensor 11 and the physical property value detection sensor 12 may be provided as separate sensors. Instead of the flow rate detection sensor 11 and/or the physical property value detection sensor 12, a sensor equipped with a temperature sensor other than a thermopile (resistance temperature sensor, thermocouple, etc.) may be used.

《Additional notes》
a first sensor (11) that measures a value correlated with the flow rate of the fluid to be measured;
A second sensor (12) comprising two temperature measuring sections (121, 122) and a heating section (123) arranged in the center of the two temperature measuring sections (121, 122), the second sensor (12) comprising: a second sensor () disposed at a position where the fluid flows in a second predetermined direction, with a direction in which the two temperature measurement units (121, 122) and the heating unit (123) are arranged in a direction perpendicular to the second predetermined direction; 12) and
a flow rate calculation process of calculating the flow rate of the fluid to be measured based on the value measured by the first sensor (11); and a process of calculating the flow rate of the fluid to be measured based on the value measured by the first sensor (11); Temperature measurement results by the two temperature measuring units (121, 122) of the two sensors are acquired, and the humidity of the fluid to be measured is determined to be higher than a predetermined humidity depending on whether each of the acquired temperature measurement results is below a predetermined threshold. a control unit (13) configured to be able to execute a determination process for determining whether or not the
A flow rate measuring device (1) characterized by comprising:

1 Flow rate measurement device 2 Main flow path section 3 Sub flow path section 4 Seal 5 Circuit board 11 Flow rate detection sensor 12 Physical property value detection sensor 13 Control section 14 Condensation sensor 21 Orifice 32 Physical property value detection flow path 33 Flow rate detection flow path 34 Inflow channel 34A Inflow port 35 Outflow channel 35A Outlet port 100 Sensor 101, 102, 111, 112, 121, 122 Thermopile 103, 113, 123 Micro heater 104 Temperature sensor

Claims (4)

a first sensor that measures a value correlated with the flow rate of the fluid to be measured;
A second sensor comprising two temperature measuring sections and a heating section disposed at the center of the two temperature measuring sections, wherein the two temperature measuring sections are arranged at a position where the fluid to be measured flows in a second predetermined direction. a second sensor arranged in a posture in which the direction in which the part and the heating part are arranged is orthogonal to the second predetermined direction;
a flow rate calculation process of calculating the flow rate of the fluid to be measured based on the value measured by the first sensor; and increasing the temperature of the heating section of the second sensor to increase the temperature of the two temperature measuring sections of the second sensor. The humidity of the fluid to be measured is determined to be higher than a predetermined humidity depending on whether each of the obtained temperature measurement results is below a predetermined threshold set separately for the two temperature measurement units. a control unit configured to be able to execute a determination process for determining whether or not the
Equipped with
further comprising a dew condensation sensor consisting of two electrode patterns arranged at a predetermined interval,
The control unit executes a second determination process for determining whether or not condensation is occurring based on the resistance value of the dew condensation sensor,
The control unit determines that dew condensation has occurred in the second determination process when the resistance value of the dew condensation sensor is less than or equal to a resistance threshold;
A flow rate measuring device characterized in that the determination process is executed when the resistance value of the dew condensation sensor is greater than a resistance threshold value . The control unit sets the temperature measurement result obtained by one of the two temperature measurement units obtained by raising the temperature of the heating unit to a first temperature and the temperature of the heating unit to the first temperature. is configured to be able to execute a correction coefficient calculation process of calculating a correction coefficient to be used when calculating the flow rate in the flow rate calculation process from the temperature measurement result obtained by the one temperature measurement unit obtained by raising the temperature to a different second temperature. has been,
The flow rate measuring device according to claim 1, characterized in that: Each temperature measuring part of the second sensor is a thermopile,
The flow rate measuring device according to claim 1 or 2, characterized in that: the first sensor and the second sensor have the same configuration;
The flow rate measuring device according to any one of claims 1 to 3, characterized in that:

Images