JP5113722B2 - Flow measuring device - Google Patents

Description

  The present invention relates to a flow rate measuring device that measures the flow rate of a fluid flowing in a pipe line.

  Conventionally, both a flow meter and a valve are arranged in the pipeline, and the opening degree of the valve is controlled based on the flow rate measured by the flow meter. However, in such a method, both the flow meter and the valve must be connected, which increases the cost. Therefore, a flow control valve having both a flow measurement function and a valve opening control function is desired and put into practical use (for example, see Patent Document 1).

  This flow control valve controls a valve body provided with a pipe forming a fluid flow path and a valve body for regulating a flow rate of fluid flowing in the pipe, and an opening degree of the valve body attached to the valve main body. Actuator. The valve body includes a first pressure sensor for detecting a fluid pressure P1 upstream of the valve body, a second pressure sensor for detecting a fluid pressure P2 downstream of the valve body, and an opening degree of the valve body (valve A valve opening sensor for detecting (opening) θ is provided. A CPU and memory are mounted on the actuator.

  The CPU of the actuator obtains a differential pressure ΔP between the upstream and downstream of the valve body from the fluid pressure P1 from the first pressure sensor and the fluid pressure P2 from the second pressure sensor, and the valve opening from the valve opening sensor. A flow rate coefficient Cv corresponding to θ is read from a characteristic table stored in the memory, and a flow rate Q of the fluid flowing in the pipe body of the valve body is calculated from the flow rate coefficient Cv and the differential pressure ΔP by the following equation (1). Then, the calculated flow rate Q is compared with the set flow rate Qsp as the measured flow rate Qpv, and the valve opening degree θ is controlled so that the measured flow rate Qpv matches the set flow rate Qsp.

Q = A · Cv · (ΔP) ^1/2 ··· (1)
However, A is a constant.

  In this flow control valve, the relationship between the valve opening θ and the flow coefficient Cv differs depending on the diameter and type of the valve body (gate valve, disk valve, ball valve, butterfly valve, spool valve, flapper valve, etc.). For this reason, a characteristic table indicating the relationship between the appropriate valve opening θ and the flow coefficient Cv is obtained according to the diameter and type of the valve body, and the memory of the actuator is shipped at the time of shipment according to the valve body to which this characteristic table can be attached. Is writing. FIG. 10 shows an example of the characteristic table.

  In general, a reference differential pressure (for example, 0.1 MPa) is determined with respect to the differential pressure between the upstream and downstream of the valve body, and the valve opening θ of the valve body is set to a predetermined value under this reference differential pressure. A flow coefficient Cv corresponding to each opening when changing in increments (for example, every few percent) is obtained, and a characteristic table in which the flow coefficient Cv is associated with each opening θ is written in the memory of the actuator at the time of shipment.

  At the time of actual flow rate measurement, interpolation calculation is performed using the flow rate coefficient Cv corresponding to two points before and after the current valve opening degree θ on the characteristic table written in the memory, and the current valve opening degree θ is calculated. The corresponding flow rate coefficient Cv is calculated and substituted into the above equation (1) to obtain the flow rate Q.

JP-A-4-232514 JP 60-168974 A

  The applicant changed the differential pressure ΔP variously, and obtained the flow coefficient Cv corresponding to the valve opening θ at that time. In this case, the deviation of the flow coefficient Cv at the reference differential pressure of the same opening is within about 5% at a high differential pressure beyond the reference differential pressure (for example, 0.1 MPa). Thus, it was found that a large deviation of 10 to several tens of percent occurs at a low differential pressure lower than the reference differential pressure. Further, when the valve opening θ is lower than a certain opening (for example, 30% to 40% or less), the deviation of the flow coefficient Cv may become very large regardless of the high differential pressure and the low differential pressure. I understood. FIG. 11 illustrates the result.

  However, in the conventional flow control valve, only the characteristic table indicating the relationship between the valve opening θ and the flow coefficient Cv at the reference differential pressure is used as the characteristic table indicating the relationship between the valve opening θ and the flow coefficient Cv. Therefore, there is a problem that a large error occurs in the flow coefficient Cv required at the time of low opening even at a low differential pressure or a high differential pressure lower than the reference differential pressure, and the reliability of the measured flow rate value is very low.

  Some flow control valves do not measure the flow rate, but some flow measurement devices connected to the flow control valve measure the flow rate of the fluid flowing in the pipe of the flow control valve (for example, patents) Reference 2). In this case, the flow measuring device obtains the differential pressure ΔP between the upstream and downstream of the valve body from the fluid pressures P1 and P2 from the flow control valve, and stores the flow coefficient Cv according to the valve opening θ from the flow control valve. The flow rate Q of the fluid flowing in the pipe of the flow control valve is measured from the flow coefficient Cv and the differential pressure ΔP. Even in such a case, since only the characteristic table showing the relationship between the valve opening θ at the reference differential pressure and the flow coefficient Cv is written in the memory of the flow measurement device, it is the same as that of the flow control valve having the flow measurement function. Problem arises.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a flow rate measuring device capable of improving the reliability of a measured flow rate value.

In order to achieve such an object, a first invention (invention according to claim 1) is provided in a memory in which a valve of a valve body at a reference differential pressure that is predetermined with respect to a pressure difference between upstream and downstream of the valve body At least a reference characteristic table indicating the relationship between the opening and the flow coefficient, and a low differential pressure characteristic table indicating the relationship between the valve opening and the flow coefficient at a differential pressure lower than the reference differential pressure are stored. If the current differential pressure is lower than the reference differential pressure, the flow coefficient corresponding to the differential pressure and the current valve opening is obtained from the characteristic table at the time of low differential pressure, and the obtained flow coefficient and the current differential pressure Based on the above, the flow rate of the fluid flowing in the pipe is calculated.
According to the present invention, when the differential pressure between the upstream and downstream of the valve body is lower than the reference differential pressure, the current differential pressure and the current valve opening are determined from the characteristic table at the time of low differential pressure instead of the reference characteristic table. A corresponding flow coefficient is determined. As a result, even when the differential pressure is lower than the reference differential pressure, the flow coefficient is obtained with high accuracy, and as a result, accurate flow measurement can be performed.

In the second invention (the invention according to claim 1), the relationship between the valve opening degree and the flow coefficient of the valve body at a reference differential pressure predetermined with respect to the differential pressure between the upstream and downstream of the valve body is shown in the memory. A reference characteristic table, a characteristic table at the time of low differential pressure showing the relationship between the valve opening degree and the flow coefficient at a differential pressure lower than the reference differential pressure, and a valve characteristic at a differential pressure higher than the reference differential pressure When storing at least a characteristic table at the time of high differential pressure and low opening indicating the relationship between a valve opening and a flow coefficient equal to or lower than a predetermined low opening threshold, and the current differential pressure is lower than the reference differential pressure, The flow coefficient corresponding to the differential pressure and the current valve opening is obtained from the characteristic table at the time of low differential pressure, and the flow rate of the fluid flowing in the pipeline is calculated based on the obtained flow coefficient and the current differential pressure, If the current differential pressure is higher than the reference differential pressure and the current valve opening is below the low opening threshold, the difference And the flow coefficient corresponding to the valve opening is obtained from the characteristic table at the time of high differential pressure and low opening, and the flow rate of the fluid flowing in the pipe line is calculated based on the obtained flow coefficient and the current differential pressure. Is.
According to the present invention, when the differential pressure between the upstream and downstream of the valve body is lower than the reference differential pressure, the current differential pressure and the current valve opening are determined from the characteristic table at the time of low differential pressure instead of the reference characteristic table. A corresponding flow coefficient is determined. In addition, when the differential pressure between the upstream and downstream of the valve body is higher than the reference differential pressure and the valve opening is below the low opening threshold, not the reference characteristic table, but the characteristic table at the time of high differential pressure and low opening Thus, a flow coefficient corresponding to the current differential pressure and the current valve opening is obtained. As a result, the flow coefficient can be calculated with high accuracy even when the differential pressure is lower than the reference differential pressure or even when the opening is high and higher than the reference differential pressure. It is possible to measure the flow rate.

According to a third invention (invention according to claim 3), in the second invention, when the current differential pressure is higher than the reference differential pressure and the current valve opening is larger than the low opening threshold, the differential pressure and the valve A flow coefficient corresponding to the opening is obtained from a reference characteristic table, and the flow rate of the fluid flowing in the pipeline is calculated based on the obtained flow coefficient and the current differential pressure.
According to the present invention, when the differential pressure between the upstream and downstream of the valve body is higher than the reference differential pressure and the valve opening of the valve body is larger than the low opening threshold, the current differential pressure is calculated from the reference characteristic table. A flow coefficient corresponding to the current valve opening is obtained. In this case, since the deviation of the flow coefficient obtained from the reference characteristic table is small compared to the actual flow coefficient, the flow rate can be accurately adjusted even at a high opening with a high differential pressure higher than the reference differential pressure. As a result, a flow rate can be measured with high accuracy.
In the third invention, since the flow coefficient is obtained from the reference characteristic table at the time of high differential pressure and high opening, the storage capacity of the memory is reduced compared to the case where the characteristic table at the time of high differential pressure and high opening is provided. Can be small.

  According to the first invention, when the differential pressure between the upstream and downstream of the valve body is lower than the reference differential pressure, the current differential pressure and the current valve opening are not based on the characteristic table at the time of low differential pressure but the reference characteristic table. Therefore, even when the differential pressure is lower than the reference differential pressure, the flow coefficient can be obtained with high accuracy, and as a result, accurate flow measurement can be performed.

  According to the second invention, when the differential pressure between the upstream and downstream of the valve body is lower than the reference differential pressure, the current differential pressure and the current valve opening are not based on the characteristic table at the time of low differential pressure, but on the characteristic table at the time of low differential pressure. If the differential pressure between the upstream and downstream of the valve body is higher than the reference differential pressure and the current valve opening is below the low opening threshold, the difference between the upstream and downstream is not a reference characteristic table. It is obtained from the characteristic table at the time of the low pressure opening, so that even at a low differential pressure lower than the reference differential pressure, even at a low opening at a high differential pressure higher than the reference differential pressure, The flow coefficient is obtained with high accuracy, and as a result, accurate flow measurement is possible.

  According to the third invention, when the differential pressure between the upstream and downstream of the valve body is higher than the reference differential pressure and the valve opening degree of the valve body is larger than the low opening threshold value, the current differential pressure is calculated from the reference characteristic table. The flow coefficient corresponding to the current valve opening is calculated, and the flow coefficient is calculated accurately even at high opening when the differential pressure is higher than the reference differential pressure, resulting in accurate flow measurement. Is possible. In this case, since the flow coefficient is obtained from the reference characteristic table at the time of high differential pressure and high opening, the memory capacity of the memory is reduced compared with the case where the characteristic table at the time of high differential pressure and high opening is provided. Will be able to.

Hereinafter, the present invention will be described in detail with reference to the drawings.
[Embodiment 1: Flow control valve]
FIG. 1 is a diagram showing an outline of an embodiment of a flow rate control valve incorporating a flow rate measuring device according to the present invention. In the figure, reference numeral 100 denotes a flow control valve, which comprises a valve body 1 and an actuator 2 attached to the valve body 1.

  The valve body 1 includes a pipe line 1-1 that forms a fluid flow path, and a valve body 1-2 that regulates the flow rate of the fluid flowing in the pipe line 1-1. A first pressure sensor S1 that detects a fluid pressure (upstream fluid pressure) P1 in the pipeline is provided on the upstream side, and a fluid pressure (in the pipeline on the downstream side of the valve body 1-2 ( A second pressure sensor S2 for detecting the downstream fluid pressure (P2) is provided.

  The actuator 2 includes a CPU 2-1, a memory 2-2, a display unit 2-3, and a motor 2-4, and the drive shaft of the motor 2-4 is connected to the valve element 1-2. . A valve opening degree sensor S3 for detecting the valve opening degree θ of the valve body 1-2 is provided at a connecting portion between the drive shaft of the motor 2-4 and the valve body 1-2.

  The CPU 2-1 of the actuator 2 has a fluid pressure P1 upstream of the valve body 1-2 detected by the first pressure sensor S1, and a fluid downstream of the valve body 1-2 detected by the second pressure sensor S2. The pressure P2, the valve opening degree θ of the valve body 1-2 detected by the valve opening degree sensor S3, and the set flow rate Qsp from the host device are given.

  In the memory 2-2 of the actuator 2, as shown in FIG. 2, a reference indicating the relationship between the valve opening degree θ of the valve body 1-2 and the flow coefficient Cv at a reference differential pressure (0.1 MPa in this example). Characteristic table TB and a low differential pressure indicating the relationship between the valve opening degree θ of the valve body 1-2 and the flow coefficient Cv at a differential pressure lower than the reference differential pressure (in this example, 0.02 MPa, 0.35 MPa). Characteristic table TL and a predetermined low opening degree of the valve body 1-2 at a differential pressure higher than the reference differential pressure (in this example, 0.15 MPa, 0.2 MPa, 0.25 MPa, 0.3 MPa) A characteristic table TH at the time of high differential pressure and low opening indicating the relationship between the opening θ and the flow coefficient Cv below the threshold θth (32.63% in this example) is stored. In this embodiment, a table combining the characteristic tables TB, TL, and TC is referred to as a characteristic table TCv.

  Hereinafter, with reference to the flowchart shown in FIG. 3, processing operations unique to the present embodiment executed by the CPU 2-1 of the actuator 2 according to the program stored in the memory 2-2 will be described.

  The CPU 2-1 reads the valve opening degree θ (current valve opening degree θ) of the valve body 1-2 from the valve opening degree sensor S3 (step S101). Also, the fluid pressure P1 upstream of the valve body 1-2 from the first pressure sensor S1 and the fluid pressure P2 downstream of the valve body 1-2 from the second pressure sensor S2 are read (step S102), A differential pressure ΔP (current differential pressure ΔP) between the upstream and downstream of the valve body 1-2 is calculated from the read fluid pressures P1 and P2 (step S103).

  Then, the flow coefficient Cv corresponding to the current valve opening θ of the valve body 1-2 read in step S101 and the current differential pressure ΔP between the upstream and downstream of the valve body 1-2 calculated in step S103 is stored in the memory 2- 2 is obtained by interpolation calculation from the characteristic table TCv in step 2 (step S104).

  Here, when the current differential pressure ΔP is lower than the reference differential pressure, the CPU 2-1 obtains a flow coefficient Cv corresponding to the differential pressure ΔP and the current valve opening θ from the characteristic table TL at the time of low differential pressure, When the current differential pressure ΔP is equal to the reference differential pressure, a flow coefficient Cv corresponding to the differential pressure ΔP and the current valve opening degree θ is obtained from the reference characteristic table TB.

  Further, when the current differential pressure ΔP is higher than the reference differential pressure and the current valve opening degree θ is equal to or less than the low opening threshold value θth, the flow coefficient Cv corresponding to the differential pressure ΔP and the valve opening degree θ is highly different. When the current differential pressure ΔP is higher than the reference differential pressure and the current valve opening θ is larger than the low opening threshold θth, the pressure difference ΔP and the valve opening are obtained. A flow coefficient Cv corresponding to the degree θ is obtained from the reference characteristic table TB.

Then, the CPU 2-1 determines the flow rate Q (Q = A · Cv) of the fluid flowing in the pipe line 1-1 of the valve body 1 from the flow coefficient Cv obtained in step S104 and the current differential pressure ΔP obtained in step S103. (ΔP) ^1/2 ) is calculated (step S105), and the calculated flow rate Q is displayed on the display unit 2-3 as the measured flow rate Qpv (step S106).

  Then, the set flow rate Qsp from the host device is read (step S107), the measured flow rate Qpv is compared with the set flow rate Qsp, and the valve opening degree of the valve element 1-2 is adjusted so that the measured flow rate Qpv matches the set flow rate Qsp. θ is controlled (step S108). The CPU 2-1 repeats the processing operations in steps S <b> 101 to S <b> 108 at regular intervals.

  FIG. 4 shows a functional block diagram of the flow rate measuring unit 3 realized as the processing operation of the CPU 2-1. The flow rate measuring unit 3 inputs the fluid pressure P1 on the upstream side of the valve body 1-2 from the first pressure sensor S1 and the fluid pressure P2 on the downstream side of the valve body 1-2 from the second pressure sensor S2. From the differential pressure calculation unit 3A for calculating the differential pressure ΔP (current differential pressure ΔP) between the upstream and downstream of the valve body 1-2, the differential pressure ΔP from the differential pressure calculation unit 3A and the valve opening sensor S3 The valve opening 1-2 of the valve body 1-2 (current valve opening θ) is input, and the current differential pressure ΔP and the current valve opening from the characteristic table TCv (TB, TL, TC) in the memory 2-2. The flow path coefficient Cv corresponding to the degree θ, the Cv value calculation unit 3B, the current differential pressure ΔP from the differential pressure calculation unit 3A, and the flow coefficient Cv from the Cv value calculation unit 3B 1 and a flow rate calculation unit 3C that calculates the flow rate Q of the fluid flowing in the inside.

  In the present embodiment, as can be seen from the processing operation in step S104, when the differential pressure ΔP between the upstream and downstream of the valve body 1-2 is lower than the reference differential pressure, not the reference characteristic table TB but the low differential pressure The flow rate coefficient Cv corresponding to the current differential pressure ΔP and the current valve opening θ is obtained from the current characteristic table TL. Further, when the differential pressure ΔP between the upstream and downstream of the valve body 1-2 is higher than the reference differential pressure and the valve opening θ is equal to or less than the low opening threshold θth, the high differential pressure is not the reference characteristic table TB. It is obtained from the characteristic table TH at the time of low opening. As a result, the flow coefficient can be calculated with high accuracy even when the differential pressure is lower than the reference differential pressure or even when the opening is high and higher than the reference differential pressure. It is possible to measure the flow rate.

  Further, in the present embodiment, as can be seen from the processing operation in step S104, the differential pressure ΔP between the upstream and downstream of the valve body 1-2 is higher than the reference differential pressure, and the valve opening degree of the valve body 1-2. When θ is larger than the low opening threshold θth, the current differential pressure ΔP and the flow coefficient Cv corresponding to the current valve opening θ are obtained from the reference characteristic table TB. In this case, since the deviation of the flow coefficient Cv obtained from the reference characteristic table TB is smaller than the actual flow coefficient, the accuracy can be improved even at a high opening degree at a high differential pressure higher than the reference differential pressure. A flow coefficient is often obtained, and as a result, accurate flow measurement is possible.

  In this embodiment, since the flow coefficient Cv is obtained from the reference characteristic table TB at the time of high differential pressure and high opening, it is compared with the case where a characteristic table at the time of high differential pressure and high opening is provided. That is, the storage capacity of the memory 2-2 can be reduced as compared with the case where the characteristic table corresponding to the hatched portion in FIG. 2 is provided.

[Embodiment 2: Flow measurement device]
FIG. 5 is a diagram showing an outline of an embodiment of a system in which a flow rate measuring device incorporating a flow rate measuring device according to the present invention is connected to a flow rate control valve. 1, the same reference numerals as those in FIG. 1 denote the same or equivalent components as those described with reference to FIG. 1, and the description thereof will be omitted.

  In this embodiment, the flow rate measuring device 5 is connected to the flow rate control valve 101, and the flow rate measuring device 5 calculates the flow rate Q (measured flow rate Qpv) of the fluid flowing in the pipe 1-1 of the flow rate control valve 101. I have to.

  In this embodiment, the actuator 4 in the flow control valve 101 includes a CPU 4-1, a memory 4-2, and a motor 4-3. The CPU 5 of the actuator 4 includes a valve opening sensor. The valve opening degree θ of the valve body 1-2 detected by S3, the measured flow rate Qpv from the flow rate measuring device 5, and the set flow rate Qsp from the host device are provided.

  The flow rate measuring device 5 includes a CPU 5-1, a memory 5-2, a display unit 5-3, and an interface 5-4. The CPU 5-1 of the flow rate measuring device 5 detects the fluid pressure P1 on the upstream side of the valve body 1-2 detected by the first pressure sensor S1 and the second pressure sensor S2 via the interface 5-4. The fluid pressure P2 on the downstream side of the valve body 1-2 and the valve opening degree θ of the valve body 1-2 detected by the valve opening sensor S3 are given.

  In the memory 5-2 of the flow rate measuring device 5, as in the first embodiment, a reference characteristic table TB indicating the relationship between the valve opening degree θ of the valve body 1-2 and the flow coefficient Cv at the reference differential pressure, A characteristic table TL at the time of low differential pressure showing the relationship between the valve opening degree θ of the valve body 1-2 and the flow coefficient Cv at a differential pressure lower than the reference differential pressure, and the valve body 1 at a differential pressure higher than the reference differential pressure -2 is stored as a characteristic table TH at the time of high differential pressure and low opening indicating the relationship between the opening θ below the predetermined low opening threshold θth and the flow coefficient Cv. That is, the characteristic table TCv (TL, TB, TH) shown in FIG. 2 is stored.

  Hereinafter, processing operations executed by the CPU 5-1 of the flow rate measuring device 5 according to a program stored in the memory 5-2 will be described with reference to a flowchart shown in FIG.

  The CPU 5-1 reads the valve opening degree θ (current valve opening degree θ) of the valve element 1-2 from the valve opening degree sensor S3 (step S201). Further, the fluid pressure P1 on the upstream side of the valve body 1-2 from the first pressure sensor S1 and the fluid pressure P2 on the downstream side of the valve body 1-2 from the second pressure sensor S2 are read (step S202), A differential pressure ΔP (current differential pressure ΔP) between the upstream and downstream of the valve body 1-2 is calculated from the read fluid pressures P1 and P2 (step S203).

  Then, the flow coefficient Cv corresponding to the current valve opening θ of the valve body 1-2 read in step S201 and the current differential pressure ΔP between the upstream and downstream of the valve body 1-2 calculated in step S203 is stored in the memory 2- 2 is obtained by interpolation calculation from the characteristic table TCv in step 2 (step S204).

  Here, when the current differential pressure ΔP is lower than the reference differential pressure, the CPU 5-1 obtains a flow coefficient Cv corresponding to the differential pressure ΔP and the current valve opening θ from the characteristic table TL at the time of low differential pressure, When the current differential pressure ΔP is equal to the reference differential pressure, a flow coefficient Cv corresponding to the differential pressure ΔP and the current valve opening degree θ is obtained from the reference characteristic table TB.

  Further, when the current differential pressure ΔP is higher than the reference differential pressure and the current valve opening degree θ is equal to or less than the low opening threshold value θth, the flow coefficient Cv corresponding to the differential pressure ΔP and the valve opening degree θ is highly different. When the current differential pressure ΔP is higher than the reference differential pressure and the current valve opening θ is larger than the low opening threshold θth, the pressure difference ΔP and the valve opening are obtained. A flow coefficient Cv corresponding to the degree θ is obtained from the reference characteristic table TB.

The CPU 5-1 then determines the flow rate Q (Q = A ·) of the fluid flowing in the pipe 1-1 of the flow rate control valve 101 from the flow rate coefficient Cv obtained in step S 204 and the current differential pressure ΔP obtained in step S 203. Cv · (ΔP) ^1/2 ) (step S205), the calculated flow rate Q is displayed on the display unit 2-3 as the measured flow rate Qpv (step S206), and the flow rate is controlled via the interface 5-4. It sends to the actuator 4 of the valve 101 (step S207). The CPU 5-1 repeats the processing operations of steps S201 to S207 at regular intervals.

  When the measured flow rate Qpv is sent from the flow rate measuring device 5, the CPU 4-1 of the actuator 4 compares the sent measured flow rate Qpv with the set flow rate Qsp, and the measured flow rate Qpv matches the set flow rate Qsp. In this way, the valve opening degree θ of the valve body 1-2 is controlled. The control of the valve opening degree θ is performed according to a program stored in the memory 4-2.

  FIG. 7 shows a functional block diagram of the flow rate measuring unit 6 realized as the processing operation of the CPU 5-1. The flow rate measuring unit 6 inputs the fluid pressure P1 upstream of the valve body 1-2 from the first pressure sensor S1 and the fluid pressure P2 downstream of the valve body 1-2 from the second pressure sensor S2. From the differential pressure calculation unit 6A for calculating the differential pressure ΔP between the upstream and downstream of the valve body 1-2 (current differential pressure ΔP), the differential pressure ΔP from the differential pressure calculation unit 6A and the valve opening sensor S3 The valve opening 1-2 of the valve body 1-2 (current valve opening θ) is input, and the current differential pressure ΔP and the current valve opening from the characteristic table TCv (TB, TL, TC) in the memory 5-2. The flow path coefficient Cv corresponding to the degree θ, the Cv value calculation unit 6B, the current differential pressure ΔP from the differential pressure calculation unit 6A, and the flow coefficient Cv from the Cv value calculation unit 6B 1 and a flow rate calculation unit 6C that calculates the flow rate Q of the fluid flowing through the inside.

  Also in the second embodiment, as in the first embodiment, when the differential pressure ΔP between the upstream and downstream of the valve body 1-2 is lower than the reference differential pressure, not the reference characteristic table TB but at the time of the low differential pressure. The flow rate coefficient Cv corresponding to the current differential pressure ΔP and the current valve opening θ is obtained from the characteristic table TL, the differential pressure ΔP between the upstream and downstream of the valve element 1-2 is higher than the reference differential pressure, and the valve is opened. When the degree θ is equal to or lower than the low opening threshold θth, the pressure difference ΔP between the upstream and downstream of the valve body 1-2 is obtained from the characteristic table TH at the time of high differential pressure and low opening instead of the reference characteristic table TB. When the valve opening degree θ is higher than the reference differential pressure and the valve element 1-2 is larger than the low opening threshold value θth, the flow rate corresponding to the current differential pressure ΔP and the current valve opening degree θ from the reference characteristic table TB. A coefficient Cv is obtained. As a result, regardless of the low differential pressure and the high differential pressure, the flow coefficient can be obtained with high accuracy, and as a result, accurate flow measurement can be performed. Further, the storage capacity of the memory 5-2 can be reduced.

[Embodiment 3: Flow measurement device]
FIG. 8 is a diagram showing an outline of another embodiment of a system in which a flow rate measuring device incorporating a flow rate measuring device according to the present invention is connected to a flow rate control valve. 5, the same reference numerals as those in FIG. 5 denote the same or equivalent components as those described with reference to FIG. 5, and the description thereof will be omitted.

  In this embodiment, a plurality of flow control valves 101 are connected to the flow measurement device 7, and the flow measurement device 7 calculates the flow rate Q of the fluid flowing in the pipe lines 1-1 of the plurality of flow control valves 101. I have to. In this example, the plurality of flow control valves 101 are two flow control valves 101A and 101B, and the flow rates QA and QB (measured flow rates) of the fluid flowing in the pipes 1-1 and 1-1 of the flow control valves 101A and 101B. QApv, QBpv) is calculated.

  The flow rate measuring device 7 includes a CPU 7-1, a memory 7-2, a display unit 7-3, and an interface 7-4. The fluid pressure P1A on the upstream side of the valve body 1-2 detected by the first pressure sensor S1 in the flow control valve 101A is connected to the CPU 7-1 of the flow rate measuring device 7 via the interface 7-4. The fluid pressure P2A on the downstream side of the valve body 1-2 detected by the sensor S2, the valve opening θA of the valve body 1-2 detected by the valve opening sensor S3, and the first pressure sensor S1 in the flow control valve 101B are detected. Fluid pressure P1B upstream of the valve body 1-2, fluid pressure P2B downstream of the valve body 1-2 detected by the second pressure sensor S2, and valve body 1-2 detected by the valve opening sensor S3. A valve opening θB is given.

  In the memory 7-2 of the flow rate measuring device 7, as in the first embodiment, a reference characteristic table TB indicating the relationship between the valve opening degree θ of the valve body 1-2 and the flow coefficient Cv at the reference differential pressure, A characteristic table TL at the time of low differential pressure showing the relationship between the valve opening degree θ of the valve body 1-2 and the flow coefficient Cv at a differential pressure lower than the reference differential pressure, and the valve body 1 at a differential pressure higher than the reference differential pressure -2 is stored as a characteristic table TH at the time of high differential pressure and low opening indicating the relationship between the opening θ below the predetermined low opening threshold θth and the flow coefficient Cv. That is, the characteristic table TCv (TL, TB, TH) shown in FIG. 2 is stored.

  Hereinafter, with reference to the flowchart shown in FIG. 9, the processing operation unique to the present embodiment executed by the CPU 7-1 of the flow rate measuring device 7 according to the program stored in the memory 7-2 will be described.

  The CPU 7-1 reads the valve opening degree θA (current valve opening degree θA) of the valve body 1-2 from the valve opening degree sensor S3 of the flow control valve 101A (step S301). Further, the fluid pressure P1A upstream of the valve body 1-2 from the first pressure sensor S1 of the flow control valve 101A and the fluid pressure P2A downstream of the valve body 1-2 from the second pressure sensor S2 are read. (Step S302) A differential pressure ΔP between the upstream and downstream of the valve body 1-2 of the flow control valve 101A is calculated from the read fluid pressures P1A and P2A (Step S303).

  The current differential pressure ΔP between the current valve opening θA of the valve body 1-2 of the flow control valve 101A read in step S301 and the upstream and downstream of the valve body 1-2 of the flow control valve 101A calculated in step S303. Is obtained from the characteristic table TCv in the memory 7-2 by interpolation calculation (step S304).

  Here, when the current differential pressure ΔP is lower than the reference differential pressure, the CPU 7-1 obtains a flow coefficient Cv corresponding to the differential pressure ΔP and the current valve opening θ from the characteristic table TL at the time of low differential pressure, When the current differential pressure ΔP is equal to the reference differential pressure, a flow coefficient Cv corresponding to the differential pressure ΔP and the current valve opening degree θ is obtained from the reference characteristic table TB.

  Further, when the current differential pressure ΔP is higher than the reference differential pressure and the current valve opening degree θ is equal to or less than the low opening threshold value θth, the flow coefficient Cv corresponding to the differential pressure ΔP and the valve opening degree θ is highly different. When the current differential pressure ΔP is higher than the reference differential pressure and the current valve opening θ is larger than the low opening threshold θth, the pressure difference ΔP and the valve opening are obtained. A flow coefficient Cv corresponding to the degree θ is obtained from the reference characteristic table TB.

Then, the CPU 7-1 determines the flow rate Q (Q = A ·) of the fluid flowing in the pipe 1-1 of the flow control valve 101A from the flow coefficient Cv obtained in step S304 and the current differential pressure ΔP obtained in step S303. Cv · (ΔP) ^1/2 ) (step S305), the calculated flow rate Q is displayed on the display unit 7-3 as the measured flow rate QApv (step S306), and the flow rate is controlled via the interface 7-4. This is sent to the actuator 4 of the valve 101A (step S307).

  When the measured flow rate QApv is sent from the flow rate measuring device 7, the CPU 4-1 of the actuator 4 in the flow rate control valve 101 A compares the sent measured flow rate QApv with the set flow rate QAsp, and the measured flow rate QApv is set. The valve opening degree θA of the valve element 1-2 is controlled so as to coincide with the flow rate QAsp.

  Next, the CPU 7-1 checks whether there is a next flow control valve connected to the flow measuring device 7 (step S308). In this case, since the flow rate control valve 101B is connected to the flow rate measuring device 7 as the next flow rate control valve, the flow returns to step S301 in response to YES in step S308.

  In step S301, the CPU 7-1 reads the valve opening degree θB (current valve opening degree θB) of the valve body 1-2 from the valve opening degree sensor S3 of the flow control valve 101B. Then, the fluid pressure P1 upstream of the valve body 1-2 from the first pressure sensor S1 of the flow control valve 101B and the fluid pressure P2 downstream of the valve body 1-2 from the second pressure sensor S2 are read. (Step S302) A differential pressure ΔP between the upstream and downstream of the valve body 1-2 of the flow control valve 101B is calculated from the read fluid pressures P1B and P2B (Step S303).

  Then, the current differential pressure ΔP between the current valve opening θB of the valve body 1-2 of the flow control valve 101B read in step S301 and the upstream and downstream of the valve body 1-2 of the flow control valve 101B calculated in step S103. Is obtained from the characteristic table TCv in the memory 7-2 by interpolation calculation (step S304).

  Here, when the current differential pressure ΔP is lower than the reference differential pressure, the CPU 7-1 obtains a flow coefficient Cv corresponding to the differential pressure ΔP and the current valve opening θ from the characteristic table TL at the time of low differential pressure, When the current differential pressure ΔP is equal to the reference differential pressure, a flow coefficient Cv corresponding to the differential pressure ΔP and the current valve opening degree θ is obtained from the reference characteristic table TB.

  Further, when the current differential pressure ΔP is higher than the reference differential pressure and the current valve opening degree θ is equal to or less than the low opening threshold value θth, the flow coefficient Cv corresponding to the differential pressure ΔP and the valve opening degree θ is highly different. When the current differential pressure ΔP is higher than the reference differential pressure and the current valve opening θ is larger than the low opening threshold θth, the pressure difference ΔP and the valve opening are obtained. A flow coefficient Cv corresponding to the degree θ is obtained from the reference characteristic table TB.

Then, the CPU 7-1 determines the flow rate Q (Q = A ·) of the fluid flowing in the pipe line 1-1 of the flow control valve 101B from the flow coefficient Cv obtained in step S304 and the current differential pressure ΔP obtained in step S303. Cv · (ΔP) ^1/2 ) (step S305), the calculated flow rate Q is displayed on the display unit 7-3 as the measured flow rate QBpv (step S306), and the flow rate is controlled via the interface 7-4. This is sent to the actuator 4 of the valve 101B (step S307).

  When the measured flow QBpv is sent from the flow measuring device 7, the CPU 4-1 of the actuator 4 in the flow control valve 101 B compares the sent measured flow QBpv with the set flow QBsp, and the measured flow QBpv is set. The valve opening degree θB of the valve element 1-2 is controlled so as to coincide with the flow rate QBsp.

  Next, the CPU 7-1 checks whether there is a next flow control valve connected to the flow measuring device 7 (step S308). In this case, since the next flow rate control valve is not connected to the flow rate measuring device 7, the processing loop of steps S301 to S308 is removed in accordance with NO in step S308. The CPU 7-1 repeats this processing operation at regular intervals.

  In the third embodiment, similarly to the first embodiment, when the differential pressure ΔP between the upstream and downstream of the valve body 1-2 is lower than the reference differential pressure, not the reference characteristic table TB but the low differential pressure. The flow rate coefficient Cv corresponding to the current differential pressure ΔP and the current valve opening θ is obtained from the characteristic table TL, the differential pressure ΔP between the upstream and downstream of the valve element 1-2 is higher than the reference differential pressure, and the valve is opened. When the degree θ is equal to or lower than the low opening threshold θth, the pressure difference ΔP between the upstream and downstream of the valve body 1-2 is obtained from the characteristic table TH at the time of high differential pressure and low opening instead of the reference characteristic table TB. When the valve opening degree θ is higher than the reference differential pressure and the valve element 1-2 is larger than the low opening threshold value θth, the flow rate corresponding to the current differential pressure ΔP and the current valve opening degree θ from the reference characteristic table TB. A coefficient Cv is obtained. As a result, regardless of the low differential pressure and the high differential pressure, the flow coefficient can be obtained with high accuracy, and as a result, accurate flow measurement can be performed. In addition, the storage capacity of the memory 7-2 can be reduced.

  Further, in the third embodiment, since the flow rate measurement in the plurality of flow control valves 101 can be performed by one flow measurement device 7, the flow rate is individually applied to the actuator 2 of the flow control valve 101 as in the first embodiment. It is not necessary to provide a measurement function, and it is not necessary to connect the flow rate control devices 5 to the flow rate control valve 101 one by one as in the second embodiment, and the cost of the system can be greatly reduced.

  In the first embodiment, the memory 2-2 is provided with the characteristic table TH at the time of high differential pressure and low opening. However, the memory 2-2 is provided with the characteristic table TH at the time of high differential pressure and low opening. Instead, the reference characteristic table TB may be used as in the case of the high differential pressure and high opening. Although the memory capacity of the memory 2-2 increases, in addition to the reference characteristic table TB, the characteristic table TL at the time of low differential pressure, and the characteristic table TH at the time of high differential pressure and low opening, at the time of high differential pressure and high opening. The characteristic table may be provided. The same applies to the second and third embodiments.

  In the first embodiment described above, the valve opening degree θ of the valve element 1-2 is controlled so that the flow rate Qpv measured by the actuator 2 and the set flow rate Qsp coincide with each other. The valve opening degree θ of the valve body 1-2 is controlled so that the set opening degree θsp and the valve opening degree θ (θpv) detected by the valve opening degree sensor S3 coincide with each other. Also good. In this case, the flow rate Qpv measured by the actuator 2 is only displayed.

  Similarly, in the second embodiment, the valve opening degree θ of the valve body 1-2 may be controlled so that the set opening degree θsp and the detected valve opening degree θpv in the flow control valve 101 coincide with each other. . In this case, it is not necessary to send the measured flow rate Qpv from the flow rate measuring device 5 to the flow rate control valve 101. The same applies to the third embodiment.

It is a figure which shows the outline of one Embodiment of the flow control valve which incorporated the flow measuring device which concerns on this invention. It is a figure which illustrates the characteristic table (The characteristic table TL at the time of low differential pressure, the reference | standard characteristic table TB, the characteristic table TH at the time of high differential pressure low opening degree) used with this flow control valve. It is a flowchart explaining the processing operation which CPU in the actuator of this flow control valve performs. It is a functional block diagram of the flow measurement part implement | achieved as a processing operation of CPU in this actuator. It is a figure which shows the outline of one Embodiment of the system which connected the flow measuring device incorporating the flow measuring device which concerns on this invention to the flow control valve. It is a flowchart explaining the processing operation which CPU in this flow measuring device performs. It is a functional block diagram of the flow measurement part implement | achieved as processing operation of CPU in this flow measurement apparatus. It is a figure which shows the outline of other embodiment of the system which connected the flow measuring device incorporating the flow measuring device which concerns on this invention to the flow control valve. It is a flowchart explaining the processing operation which CPU in this flow measurement apparatus performs. It is a figure which shows an example of the characteristic table used conventionally. It is a figure which illustrates the deviation with respect to the flow coefficient Cv corresponding to the valve opening degree (theta) at the time of the reference | standard differential pressure at the time of changing differential pressure (DELTA) P variously.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Valve main body, 1-1 ... Pipe line, 1-1 ... Valve body, 2 ... Actuator, 2-1 ... CPU, 2-2 ... Memory, 2-3 ... Display part, 2-4 ... Motor, S1 ... 1st pressure sensor, S2 ... 2nd pressure sensor, S3 ... Valve opening sensor, 3 ... Flow rate measurement part, 3A ... Differential pressure calculation part, 3B ... Cv value calculation part, 3C ... Flow rate calculation part, 4 ... Actuator 4-1 ... CPU, 4-2 ... memory, 4-3 ... motor, 5 ... flow rate measuring device, 5-1 ... CPU, 5-2 ... memory, 5-2 ... display unit, 5-4 ... interface, DESCRIPTION OF SYMBOLS 6 ... Flow measurement part, 6A ... Differential pressure calculation part, 6B ... Cv value calculation part, 6C ... Flow rate calculation part, 7 ... Flow measurement apparatus, 7-1 ... CPU, 7-2 ... Memory, 7-3 ... Display part , 7-4 ... interface, 100, 101, 101A, 101B ... flow control valve, TL ... characteristic table at low differential pressure, TB Criteria characteristic table, TH ... high differential pressure drop opening when the characteristic table.

Claims (3)

A memory for storing a characteristic table showing the relationship between the valve opening degree of the valve body that regulates the flow rate of the fluid flowing in the pipe line and the flow coefficient, and the current valve opening degree of the valve body from the characteristic table in this memory A flow rate measuring device comprising: a flow rate calculating unit that calculates a flow rate coefficient that corresponds, and calculates a flow rate of the fluid flowing in the pipe line based on the calculated flow rate coefficient and a current differential pressure between the upstream and downstream of the valve body In
The memory is
As the characteristic table, a reference characteristic table showing a relationship between a valve opening degree of the valve body and a flow coefficient at a reference differential pressure predetermined with respect to a differential pressure between the upstream and downstream of the valve body, and the reference difference Storing at least a characteristic table at the time of low differential pressure indicating a relationship between a valve opening degree of the valve body and a flow coefficient at a differential pressure lower than the pressure,
The flow rate calculation means includes
When the current differential pressure is lower than the reference differential pressure, a flow coefficient corresponding to the differential pressure and the current valve opening is obtained from the characteristic table at the time of the low differential pressure, and the obtained flow coefficient and the current differential pressure The flow rate of the fluid flowing in the pipe line is calculated based on the flow rate measuring device. A memory for storing a characteristic table showing the relationship between the valve opening degree of the valve body that regulates the flow rate of the fluid flowing in the pipe line and the flow coefficient, and the current valve opening degree of the valve body from the characteristic table in this memory A flow rate measuring device comprising: a flow rate calculating unit that calculates a flow rate coefficient that corresponds, and calculates a flow rate of the fluid flowing in the pipe line based on the calculated flow rate coefficient and a current differential pressure between the upstream and downstream of the valve body In
The memory is
As the characteristic table, a reference characteristic table showing a relationship between a valve opening degree of the valve body and a flow coefficient at a reference differential pressure predetermined with respect to a differential pressure between the upstream and downstream of the valve body, and the reference difference A characteristic table at the time of low differential pressure indicating the relationship between the valve opening degree and the flow coefficient of the valve body at a differential pressure lower than the pressure, and a predetermined low value of the valve body at a differential pressure higher than the reference differential pressure. Storing at least a characteristic table at the time of high differential pressure and low opening indicating a relationship between a valve opening less than an opening threshold and a flow coefficient;
The flow rate calculation means includes
When the current differential pressure is lower than the reference differential pressure, a flow coefficient corresponding to the differential pressure and the current valve opening is obtained from the characteristic table at the time of the low differential pressure, and the obtained flow coefficient and the current differential pressure And calculating the flow rate of the fluid flowing in the pipe line based on
When the current differential pressure is higher than the reference differential pressure and the current valve opening is less than or equal to the low opening threshold, the flow coefficient corresponding to the differential pressure and the valve opening is set at the high differential pressure and low opening. A flow rate measuring device characterized in that the flow rate of the fluid flowing in the pipe is calculated based on the flow rate coefficient and the current differential pressure. In the flow rate measuring device according to claim 2,
The flow rate calculation means includes
When the current differential pressure is higher than the reference differential pressure and the current valve opening is larger than the low opening threshold, a flow coefficient corresponding to the differential pressure and the valve opening is obtained from the reference characteristic table. A flow rate measuring apparatus, wherein the flow rate of the fluid flowing in the pipe line is calculated based on the obtained flow rate coefficient and the current differential pressure.

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