Flow rate control device and control method for the same

Abstract

To prevent heat generation in a stepping motor and a motor driver while executing a stop operation where a valve body remains stationary.SOLUTION: A flow rate control device includes an ultrasonic flow rate measurement unit, a flow rate adjustment unit, and a flow rate setting unit, and a control unit that controls the flow rate adjustment unit and the flow rate setting unit. The flow rate adjustment unit has a stepping motor that moves a valve body along an axis by rotating around the axis and a motor driver that generates an excitation current for driving the stepping motor and outputs it to the stepping motor. The control unit controls the flow rate adjustment unit so as to move the valve body by an amount corresponding to the flow rate difference between the flow rate measurement value and the flow rate set value, thereby making the flow rate measurement value of a fluid measured by the flow rate measurement unit match a flow rate set value. The control unit also controls the motor driver to generate an excitation current of a first current value I1 during the execution of a movement operation in which the valve body is moved and to generate an excitation current of a second current value I2, which is lower than the first current value I1, during the execution of a stop operation in which the valve body remains stationary.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] The present invention relates to a flow rate adjusting device and a control method for the flow rate adjusting device.

Background Art

[0002] Conventionally, there has been known a flow rate adjusting device including a flow rate measuring unit that measures the flow rate of a fluid, and moving a valve body portion in a direction approaching or separating from a valve hole so that the flow rate measured by the flow rate measuring unit becomes a preset flow rate to adjust the flow rate of the fluid passing through the valve hole (see, for example, Patent Document 1). As the electric drive unit that moves the valve body portion, for example, a stepping motor driven by a motor driver can be used.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When moving the valve body portion by a stepping motor, the motor driver generates an excitation current corresponding to a pulse signal received from the control unit and outputs it to the stepping motor. Even when the valve body portion is stopped without being moved, the motor driver can hold the drive shaft of the stepping motor at a predetermined position so as not to rotate by outputting an excitation current having the same current value to the stepping motor.

[0005] However, in both the case of moving the valve body portion by a stepping motor and the case of stopping without moving the valve body portion, when the motor driver outputs an excitation current having the same current value to the stepping motor, the stepping motor and the motor driver generate heat even when the valve body portion is stopped, similar to the case of moving the valve body portion.

[0006] The present invention has been made in view of such circumstances, and an object thereof is to provide a flow rate adjusting device and a control method for the flow rate adjusting device capable of suppressing heat generation of a stepping motor and a motor driver during execution of a stop operation in which a valve body portion is not moved.

Means for Solving the Problems

[0007] In order to solve the above problems, the present invention employs the following means. The flow rate adjusting device according to the first aspect of the present invention includes a flow rate measuring unit that measures the flow rate of a fluid flowing in from an inflow port and flowing through a measurement flow path, and a valve body portion that moves in a direction approaching or separating from a valve hole along an axis, and adjusts the flow rate of the fluid flowing out from the downstream side of the measurement flow path to an outflow port. A flow rate adjusting unit, a flow rate setting unit that sets a flow rate set value of the fluid adjusted by the flow rate adjusting unit, and a control unit that controls the flow rate adjusting unit and the flow rate setting unit. The flow rate adjusting unit rotates around the axis to move the valve body portion along the axis. A stepping motor, and a motor driver that generates an exciting current for driving the stepping motor and outputs the exciting current to the stepping motor. The control unit moves the valve body portion by an amount of movement corresponding to a flow rate difference between the flow rate measurement value and the flow rate set value so that the flow rate measurement value of the fluid measured by the flow rate measuring unit becomes the flow rate set value. Control the flow rate adjusting unit, control the motor driver to generate the exciting current of the first current value during execution of the moving operation for moving the valve body portion, and execute the stop operation for not moving the valve body portion. The motor driver is controlled to generate the exciting current of the second current value lower than the first current value.

[0008] According to the flow rate adjusting device according to the first aspect of the present invention, the control unit controls the flow rate adjustment unit so as to move the valve body unit by an amount of movement corresponding to the flow rate difference between the measured flow rate value and the set flow rate value such that the measured flow rate value of the fluid measured by the flow rate measurement unit becomes the set flow rate value. Further, the control unit controls the motor driver to generate an exciting current having a first current value during the execution of the movement operation for moving the valve body unit. On the other hand, the control unit controls the motor driver to generate an exciting current having a second current value lower than the first current value during the execution of the stop operation for not moving the valve body unit.

[0009] According to the flow rate adjusting device according to the first aspect of the present invention, the second current value of the exciting current generated by the motor driver during the execution of the stop operation is lower than the first current value of the exciting current generated by the motor driver during the execution of the movement operation. Therefore, the heat generation of the stepping motor and the motor driver during the execution of the stop operation can be suppressed as compared with the case where the motor driver generates an exciting current having the same first current value during the execution of the stop operation as during the execution of the movement operation.

[0010] The flow rate adjusting device according to the second aspect of the present invention further includes the following configuration in the first aspect. That is, the second current value is set to be 0.5 times or more and 0.95 times or less of the first current value. According to the flow rate adjusting device according to the second aspect of the present invention, since the second current value is set to be 0.5 times or more and 0.95 times or less of the first current value, the heat generation of the stepping motor and the motor driver during the execution of the stop operation can be appropriately suppressed.

[0011] The flow rate adjusting device according to the third aspect of the present invention further includes the following configuration in the first aspect. That is, the control unit executes the stop operation during a stop period from when the first movement operation is completed to when the second movement operation is started, sets the first stop period when the flow rate difference is greater than a predetermined threshold value, and sets a second stop period longer than the first stop period when the flow rate difference is less than or equal to the predetermined threshold value.

[0012] According to the flow rate adjustment device according to the third aspect of the present invention, the second stop period when the flow rate difference is equal to or less than a predetermined threshold value is longer than the first stop period when the flow rate difference is greater than the predetermined threshold value. Therefore, by lengthening the stop period in a state where the flow rate difference is equal to or less than the predetermined threshold value and the flow rate fluctuation is relatively small, it is possible to effectively suppress the heat generation of the stepping motor and the motor driver during the execution of the stop operation. On the other hand, by shortening the stop period in a state where the flow rate difference is greater than the predetermined threshold value and the flow rate fluctuation is relatively large, the flow rate difference can be converged at an early stage.

[0013] The flow rate adjustment device according to the fourth aspect of the present invention further includes the following configuration in the third aspect. That is, the second stop period is set to be 1.1 times or more and 20 times or less the first stop period. According to the flow rate adjustment device according to the fourth aspect of the present invention, since the second stop period is set to be 1.1 times or more and 20 times or less the first stop period, it is possible to appropriately suppress the heat generation of the stepping motor and the motor driver when the flow rate difference is equal to or less than a predetermined threshold value.

[0014] The flow rate adjustment device according to the fifth aspect of the present invention further includes the following configuration in any one of the first aspect to the fourth aspect. That is, a temperature detection unit for detecting the temperature of the stepping motor or the motor driver is provided, and when the temperature detected by the temperature detection unit is less than a predetermined temperature value, the control unit controls the motor driver to generate the exciting current of the first current value during the execution of the moving operation, and when the temperature detected by the temperature detection unit is equal to or greater than the predetermined temperature value, the control unit controls the motor driver to generate the exciting current of a third current value lower than the first current value during the execution of the moving operation.

[0015] According to the flow rate adjustment device according to the fifth aspect of the present invention, when the temperature detected by the temperature detection unit is less than a predetermined temperature value, an exciting current of a first current value can be generated during the execution of the moving operation to surely hold the current position of the valve body portion. On the other hand, when the temperature detected by the temperature detection unit is equal to or higher than the predetermined temperature value, an exciting current of a third current value lower than the first current value can be generated during the execution of the moving operation to appropriately suppress the heat generation of the stepping motor and the motor driver.

[0016] In the control method of the flow rate adjustment device according to the sixth aspect of the present invention, the flow rate adjustment device includes a flow rate measurement unit that measures the flow rate of a fluid flowing in from an inflow port and flowing through a measurement flow path, and a flow rate adjustment unit that moves a valve body portion in a direction approaching or separating from a valve hole along an axis to adjust the flow rate of the fluid flowing out from the downstream side of the measurement flow path to an outflow port. The adjustment mechanism includes a stepping motor that rotates around the axis to move the valve body portion along the axis, and a motor driver that generates an exciting current for driving the stepping motor and outputs it to the stepping motor. The method includes a flow rate setting step of setting a flow rate set value of the fluid adjusted by the flow rate adjustment unit, and a control step of controlling the flow rate adjustment unit to move the valve body portion by an amount of movement corresponding to a flow rate difference between the flow rate measurement value and the flow rate set value so that the flow rate measurement value measured by the flow rate measurement unit becomes the flow rate set value. The control step controls the motor driver to generate the exciting current of the first current value during the execution of the moving operation for moving the valve body portion, and controls the motor driver to generate the exciting current of the second current value lower than the first current value during the execution of the stop operation for not moving the valve body portion.

[0017] According to the control method of the flow rate adjustment device according to the sixth aspect of the present invention, in the control step, the flow rate adjustment unit is controlled to move the valve body unit by an amount of movement corresponding to the flow rate difference between the measured flow rate value and the set flow rate value so that the measured flow rate value of the fluid measured by the flow rate measurement unit becomes the set flow rate value. Further, in the control step, the motor driver is controlled to generate an excitation current having a first current value during the execution of the movement operation for moving the valve body unit. On the other hand, in the control step, the motor driver is controlled to generate an excitation current having a second current value lower than the first current value during the execution of the stop operation for not moving the valve body unit.

[0018] According to the control method of the flow rate adjustment device according to the sixth aspect of the present invention, the second current value of the excitation current generated by the motor driver during the execution of the stop operation is lower than the first current value of the excitation current generated by the motor driver during the execution of the movement operation. Therefore, heat generation of the stepping motor and the motor driver during the execution of the stop operation can be suppressed as compared with the case where the motor driver generates an excitation current having the same first current value during the execution of the movement operation.

Effect of the Invention

[0019] According to the present invention, it is possible to provide a flow rate adjustment device and a control method of the flow rate adjustment device capable of suppressing heat generation of the stepping motor and the motor driver during the execution of the stop operation for not moving the valve body unit.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0021] Hereinafter, a flow rate adjustment device 100 according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a partial longitudinal sectional view showing an embodiment of the flow rate adjustment device 100. FIG. 2 is a partial longitudinal sectional view showing the ultrasonic flow rate measurement unit shown in FIG. 1.

[0022] The flow rate adjustment device 100 of the present embodiment shown in FIG. 1 includes an ultrasonic flow rate measurement unit 10 that measures the flow rate of a fluid flowing through a straight tubular measurement flow path 14 after flowing in from an inflow port 100a, a flow rate adjustment unit 20 that adjusts the flow rate of the fluid, a control device 30 that controls the flow rate adjustment unit 20, a housing unit 40 that houses the ultrasonic flow rate measurement unit 10, the flow rate adjustment unit 20, and the control device 30, an inflow side flow path unit 50 that guides the fluid flowing in from the inflow port 100a to the upstream side of the measurement flow path 14, an outflow side flow path unit 60 that guides the fluid flowing out from the downstream side of the measurement flow path 14 to an outflow port 100b, and a pressure sensor (pressure measurement unit) 70.

[0023] The fluid whose flow rate is adjusted by the flow rate adjustment device 100 of the present embodiment is, for example, a liquid such as a chemical solution or pure water used in a semiconductor manufacturing apparatus. Further, the temperature of the fluid is, for example, a temperature in a normal temperature range (for example, 10°C or higher and less than 50°C) or a high temperature range (for example, 50°C or higher and 80°C or lower).

[0024] The housing part 40 of the flow rate adjustment device 100 is fixed to the installation surface S by fastening bolts (not shown). Further, the flow rate adjustment device 100 is connected to an external device (not shown) via a cable 200, receives power supply from the external device via the cable 200, and transmits and receives various signals to and from the external device.

[0025] The signal received from the external device is, for example, a signal indicating the set value of the target flow rate adjusted by the flow rate adjustment device 100. Further, the signal transmitted to the external device is, for example, a signal indicating the flow rate of the fluid calculated by the control device 30 based on the signal measured by the ultrasonic flow rate measurement unit 10, or a signal indicating the pressure of the fluid measured by the pressure sensor 70.

[0026] The ultrasonic flow rate measurement unit 10 measures the propagation time difference of ultrasonic waves transmitted by a pair of vibrators, namely, an upstream vibrator 11 arranged on the upstream side of the measurement flow path 14 and a downstream vibrator 12 arranged on the downstream side of the measurement flow path 14, in order to obtain the flow rate of the fluid flowing through the straight pipe-shaped measurement flow path 14 after flowing in from the upstream side pipe (not shown).

[0027] As shown in FIG. 2, the ultrasonic flow rate measurement unit 10 includes an upstream vibrator 11 and a downstream vibrator 12 arranged on an axis X2 parallel to the installation surface S, an inflow channel 13 connected to the inflow side channel part 50, a straight pipe-shaped measurement flow path 14 connected to the inflow channel 13 and extending along the axis X2 (second axis), and an outflow channel 15 connected to the outflow side channel part 60. The axis X2 is in a direction parallel to the axis X1 (first axis), which is the advancing and retreating direction of the valve body part 21 described later.

[0028] The upstream vibrator 11 and the downstream vibrator 12 are arranged at positions facing each other via the measurement flow path 14 on the axis X2, and can each transmit and receive ultrasonic signals. The ultrasonic signal transmitted by the upstream vibrator 11 propagates through the fluid flowing through the measurement flow path 14 and is received by the downstream vibrator 12.

[0029] Similarly, the ultrasonic signal transmitted by the downstream oscillator 12 propagates through the fluid flowing in the measurement flow path 14 and is received by the upstream oscillator 11. Since the fluid flows through the measurement flow path 14 from the upstream side to the downstream side, the propagation time of the ultrasonic signal transmitted by the upstream oscillator 11 to the downstream oscillator 12 is shorter than the propagation time of the ultrasonic signal transmitted by the downstream oscillator 12 to the upstream oscillator 11. The ultrasonic flow measurement unit 10 measures the flow rate of the fluid flowing through the measurement flow path 14 by using this propagation time difference.

[0030] Note that the transmission of the ultrasonic signal by the upstream oscillator 11 and the downstream oscillator 12 is controlled by a control device 30 connected by signal lines 16, 17 shown in FIG. 2. Also, the reception of the ultrasonic signal by the upstream oscillator 11 and the downstream oscillator 12 is transmitted to the control device 30 via the signal lines 16, 17. As will be described later, the control device 30 calculates the propagation time difference from the transmission timing of the ultrasonic signal instructed to the upstream oscillator 11 and the downstream oscillator 12 and the reception timing of the ultrasonic signal received from the upstream oscillator 11 and the downstream oscillator 12 corresponding thereto, and calculates the flow rate of the fluid from the calculated propagation time difference.

[0031] The flow rate adjustment unit 20 adjusts the flow rate of the fluid flowing out to an outflow port 100b connected to a pipe (not shown) on the outflow side via an outflow side flow path unit 60 from the downstream side of the measurement flow path 14. As shown in FIG. 1, the flow rate adjustment unit 20 is disposed between the ultrasonic flow measurement unit 10 and the control device 30 in the direction of axis Y, which is the installation direction perpendicular to the installation surface S. As shown in FIG. 1, in the direction of axis Y, the ultrasonic flow measurement unit 10 is disposed at the position closest to the installation surface S, the control device 30 is disposed at the position farthest from the installation surface S, and the flow rate adjustment unit 20 is disposed between them.

[0032] FIG. 3 is a partial longitudinal sectional view showing the flow rate adjustment unit 20 and the outflow side flow path unit 60 shown in FIG. 1. As shown in FIG. 3, the flow rate adjustment unit 20 includes a valve body portion 21 inserted into a valve hole 62 formed in the outflow side flow path unit 60, and an electric drive unit 22 that moves the valve body portion 21 in a direction approaching or separating from the valve hole 62 along an axis X1 (first axis) parallel to the installation surface S. The flow rate adjustment unit 20 adjusts the flow rate of the fluid flowing out from the measurement flow path 14 by moving the valve body portion 21 in a direction approaching or separating from the valve hole 62 along the axis X1.

[0033] The electric drive unit 22 moves the valve body portion 21 forward and backward along the axis X1 between the closed state position shown by the solid line and the open state position shown by the broken line in FIG. 3. The flow rate adjustment unit 20 adjusts the amount of fluid flowing from the valve hole 62 into the valve chamber 63 by adjusting the position of the valve body portion 21 on the axis X1 by the electric drive unit 22.

[0034] Here, the configuration of the control device 30 will be described with reference to FIG. 5. FIG. 5 is a block diagram showing the configuration of the control device 30. As shown in FIG. 5, the control device 30 includes a control unit 31 and a flow rate setting unit 32. The control unit 31 controls the ultrasonic flow rate measurement unit 10, the flow rate adjustment unit 20, and the flow rate setting unit 32.

[0035] The control unit 31 controls the flow rate adjustment unit 20 based on the flow rate measurement value FRac of the fluid measured by the ultrasonic flow rate measurement unit 10. The control unit 31 moves the valve body portion 21 by a movement amount MV corresponding to the flow rate difference between the flow rate measurement value FRac and the flow rate setting value FRset so that the flow rate measurement value FRac of the fluid measured by the ultrasonic flow rate measurement unit 10 becomes the flow rate setting value FRset set by the flow rate setting unit 32, and controls the flow rate adjustment unit 20.

[0036] The control unit 31 can instruct each of the upstream side vibrator 11 and the downstream side vibrator 12 included in the ultrasonic flow rate measurement unit 10 to transmit an ultrasonic signal. Further, the control unit 31 can detect the timing at which an ultrasonic signal transmitted from either the upstream side vibrator 11 or the downstream side vibrator 12 is received by the other of the upstream side vibrator 11 and the downstream side vibrator 12.

[0037] The control unit 31 calculates a first propagation time based on the transmission timing of the ultrasonic signal instructed to the downstream oscillator 12 and the reception timing of the ultrasonic signal at the upstream oscillator 11 corresponding thereto. Further, the control device 30 calculates a second propagation time based on the transmission timing of the ultrasonic signal instructed to the upstream oscillator 11 and the reception timing of the ultrasonic signal at the downstream oscillator 12 corresponding thereto. The control unit 31 obtains the flow rate of the fluid flowing through the measurement flow path 14 based on the propagation time difference obtained by subtracting the second propagation time from the first propagation time and a predetermined flow rate calculation formula.

[0038] The flow rate setting unit 32 sets a flow rate setting value FRset [ml / min] included in the flow rate range from 0 [ml / min], which is the minimum flow rate of the flow rate adjustment device 100, to the maximum flow rate FRmax [ml / min]. The flow rate setting unit 32 sets the flow rate setting value FRset based on, for example, a flow rate setting signal received by the control device 30 from an external device via the cable 200.

[0039] The electric drive unit 22 of the flow rate adjustment unit 20 includes a stepping motor 22a that rotates around the axis X1 to move the valve body unit 21 along the axis X1, and a motor driver 22b that generates an excitation current for driving the stepping motor 22a and outputs it to the stepping motor 22a.

[0040] As shown in FIG. 1, in the housing unit 40, an air introduction port 40a and an air discharge port 40b are formed in order from the side closer to the installation surface S along the axis Y. The air introduction port 40a is a port for introducing the air supplied from an air supply source (not shown) into the inside of the housing unit 40. Further, the air discharge port 40b is a port for discharging the air that has flowed inside the housing unit 40 to the outside of the housing unit 40.

[0041] FIG. 4 is a longitudinal sectional view showing the inflow-side channel portion 50 and the pressure sensor 70 shown in FIG. 1. As shown in FIGS. 1 and 4, the inflow-side channel portion 50 is a member in which an inflow-side inclined channel 51 inclined in a direction approaching the installation surface S is formed inside, from the inflow port 100a toward the upstream inflow channel 13 of the measurement channel 14. A pressure sensor 70 for detecting the pressure of the fluid flowing through the inflow-side inclined channel 51 is attached to the inflow-side channel portion 50.

[0042] As shown in FIGS. 1 and 3, the outflow-side channel portion 60 is a member in which an outflow-side inclined channel 61 inclined in a direction approaching the installation surface S is formed inside, from the flow rate adjustment portion 20 toward the outflow port 100b. The outflow-side channel portion 60 guides the fluid to the upstream side of the outflow-side inclined channel 61 through the outflow channel 65 from the opening 64 provided above the valve chamber 63. The fluid guided to the upstream side of the outflow-side inclined channel 61 is guided to the outflow port 100b along the outflow-side inclined channel 61. As shown in FIGS. 2 and 3, the outflow-side channel portion 60 is provided with through-holes through which a plurality of fastening bolts 66 penetrate. The outflow-side channel portion 60 is fixed to the electric drive portion 22 by fastening the fastening bolts 66 to the electric drive portion 22.

[0043] The pressure sensor 70 measures the pressure (supply pressure) of the fluid flowing into the inflow-side inclined channel 51 on the upstream side of the measurement channel 14 from the inflow port 100a. The pressure sensor 70 is, for example, a strain gauge type pressure sensor. As shown in FIG. 4, the pressure sensor 70 is attached to the inflow-side channel portion 50 by a sensor holder 71. The pressure signal indicating the pressure of the fluid measured by the pressure sensor 70 is transmitted to the control device 30 and stored in a storage portion (not shown) provided in the control device 30. Further, the pressure signal is transmitted to an external device via the cable 200.

[0044] Next, the flow rate adjustment system 1 in which the flow rate adjustment device 100 of the present embodiment is installed will be described with reference to FIG. 6. FIG. 6 is a schematic configuration diagram showing the flow rate adjustment system 1 in which the flow rate adjustment device 100 is installed. As shown in FIG. 6, the flow rate adjustment system 1 includes a pump 2 that pumps a fluid, a pipe 3 that conveys the fluid from the inflow end 1a to the outflow end 1b, a flow rate adjustment device 100, an on-off valve 4 disposed in the pipe 3 on the upstream side of the flow rate adjustment device 100, and an on-off valve 5 disposed in the pipe 3 on the downstream side of the flow rate adjustment device 100.

[0045] The flow rate adjustment system 1 pumps the fluid flowing into the pipe 3 from the inflow end 1a by the pump 2 and supplies it to the flow rate adjustment device 100, and supplies the fluid whose flow rate has been adjusted by the flow rate adjustment device 100 to the outflow end 1b. The state of supplying and not supplying the fluid from the inflow end 1a to the flow rate adjustment device 100 is switched by the on-off valve 4. The state of supplying and not supplying the fluid from the flow rate adjustment device 100 to the outflow end 1b is switched by the on-off valve 5.

[0046] Next, the control method of the flow rate adjustment device 100 of the present embodiment will be described with reference to FIG. 7. FIG. 7 is a flowchart showing the control method of the flow rate adjustment unit 20 of the flow rate adjustment device 100 of the present embodiment. Each process shown in FIG. 7 is performed by the control device 30 executing a control program.

[0047] In step S101, the control unit 31 sets a flow rate set value FRset [ml / min] included in the flow rate range from 0 [ml / min], which is the minimum flow rate of the flow rate adjustment device 100, to the maximum flow rate FRmax [ml / min]. The flow rate setting unit 32 sets the flow rate set value FRset, for example, based on a flow rate setting signal received by the control device 30 from an external device via the cable 200.

[0048] In step S102, the control unit 31 acquires a flow rate measurement value FRac of the fluid flowing through the measurement flow path 14 from the ultrasonic flow rate measurement unit 10.

[0049] In step S103, the control unit 31 calculates the movement amount MV of the valve body unit 21 by the following formula (1). MV = (FRset - FRac) · α (1) Here, α is a positive coefficient.

[0050] In step S104, the control unit 31 controls the flow rate adjustment unit 20 to start an operation of moving the valve body portion 21 along the axis X1 by the moving amount MV determined in step S103.

[0051] When the flow rate measurement value FRac is smaller than the flow rate set value FRset, the moving amount MV of the valve body portion 21 becomes a positive value. When the moving amount MV is a positive value, the control unit 31 moves the valve body portion 21 in a direction away from the valve hole 62 by the moving amount MV to increase the flow rate of the fluid passing through the valve hole 62.

[0052] On the other hand, when the flow rate measurement value FRac is larger than the flow rate set value FRset, the moving amount MV of the valve body portion 21 becomes a negative value. When the moving amount MV is a negative value, the control unit 31 moves the valve body portion 21 in a direction approaching the valve hole 62 by the moving amount MV to decrease the flow rate of the fluid passing through the valve hole 62.

[0053] In step S105, the control unit 31 determines whether the moving amount of the valve body portion 21 has become the moving amount MV determined in step S103 and the movement of the valve body portion 21 is completed. If YES, the process proceeds to step S106, and if NO, step S105 is executed again. The control unit 31 determines that the movement of the valve body portion 21 is completed according to the fact that the number of pulses of the pulse signal transmitted to the motor driver 22b has become a predetermined number of pulses corresponding to the moving amount MV.

[0054] In step S106, the control unit 31 determines whether a predetermined stop period has elapsed since the movement of the valve body portion 21 was completed. If YES, the process proceeds to step S107, and if NO, step S106 is executed again.

[0055] In step S107, the control unit 31 determines whether to end the adjustment of the fluid flow rate by the flow rate adjustment unit 20. If YES, the processing of this flowchart ends; if NO, the processing of step S101 is executed again.

[0056] Next, with reference to FIG. 8, an example of the change in the measured value FRac of the fluid flow rate adjusted by the flow rate adjustment device 100 and the change in the opening degree of the valve body portion 21 will be described. FIG. 8 is a graph showing an example of the change in the measured value FRac of the fluid flow rate adjusted by the flow rate adjustment device 100 of the present embodiment and the change in the opening degree of the valve body portion 21.

[0057] As shown in FIG. 8, each period from time T1 to time T2, from time T3 to time T4, from time T5 to time T6, from time T7 to time T8, and from time T9 to time T10 is a period in which the valve body portion 21 executes a moving operation of the moving amount MV determined in step S103. On the other hand, each period from time T2 to time T3, from time T4 to time T5, from time T6 to time T7, and from time T8 to time T9 is a period in which the valve body portion 21 executes a stopping operation of stopping without moving.

[0058] In the example shown in FIG. 8, after the valve body portion 21 starts moving at time T1, the measured flow rate value FRac gradually approaches the set flow rate value FRset, and at time Tth, the flow rate difference between the measured flow rate value FRac and the set flow rate value FRset becomes a predetermined threshold value FRth. In the period before time Tth, the flow rate difference between the measured flow rate value FRac and the set flow rate value FRset is larger than the predetermined threshold value FRth, and in the period after time Tth, the flow rate difference between the measured flow rate value FRac and the set flow rate value FRset is equal to or less than the predetermined threshold value FRth.

[0059] As shown in FIG. 8, the control unit 31 executes a stopping operation of stopping the valve body portion 21 without moving during a stopping period (for example, the period from time T2 to time T3) from when the first moving operation (for example, the moving operation from time T1 to time T2) of the valve body portion 21 is completed until the second moving operation (for example, the moving operation from time T3 to time T4) is started.

[0060] As shown in FIG. 8, when the flow rate difference between the flow rate measurement value FRac and the flow rate set value FRset is greater than a predetermined threshold FRth, the control unit 31 sets a first stop period TS1, and when the flow rate difference is equal to or less than the predetermined threshold FRth, a second stop period TS2 longer than the first stop period TS1 is set.

[0061] The second stop period TS2 is set, for example, to be 1.1 times or more and 20 times or less the first stop period TS1. As will be described later, the second current value I2 output from the motor driver 22b to the stepping motor 22a during the second stop period TS2 is lower than the first current value I1 output from the motor driver 22b to the stepping motor 22a during the first stop period TS1. Therefore, the longer the second stop period TS2 is compared to the first stop period TS1, the more the heat generation of the stepping motor 22a and the motor driver 22b can be suppressed.

[0062] On the other hand, the longer the second stop period TS2 is compared to the first stop period TS1, the longer the stop period of the valve body portion 21 becomes, and thus the followability of the flow rate measurement value FRac with respect to the flow rate set value FRset decreases. It is desirable to set the first stop period TS1 and the second stop period TS2 in consideration of both the suppression of heat generation of the stepping motor 22a and the motor driver 22b and the followability of the flow rate measurement value FRac with respect to the flow rate set value FRset.

[0063] Next, an example of the change in the current value of the excitation current output from the motor driver 22b to the stepping motor 22a of the flow rate adjustment device 100 of the present embodiment will be described. FIG. 9 is a graph showing an example of the change in the current value of the excitation current output from the motor driver 22b to the stepping motor 22a of the flow rate adjustment device 100 of the present embodiment. The times T1 to T10 shown in FIG. 9 correspond to the times T1 to T10 shown in FIG. 8.

[0064] As shown in FIG. 9, during the execution of the moving operation for moving the valve body portion 21 (each period from time T1 to time T2, from time T3 to time T4, from time T5 to time T6, from time T7 to time T8, and from time T9 to time T10), the control unit 31 controls the motor driver 22b to generate an exciting current with a first current value I1. Further, during the execution of the stop operation in which the valve body portion 21 is not moved (each period from time T0 to time T1, from time T2 to time T3, from time T4 to time T5, from time T6 to time T7, and from time T8 to time T9), the control unit 31 controls the motor driver 22b to generate an exciting current with a second current value I2 that is lower than the first current value I1.

[0065] The second current value I2 is set, for example, to be 0.5 times or more and 0.95 times or less of the first current value I1. The second current value I2 output from the motor driver 22b to the stepping motor 22a in the second stop period TS2 is lower than the first current value I1 output from the motor driver 22b to the stepping motor 22a in the first stop period TS1. Therefore, the lower the second current value I2 is with respect to the first current value I1, the more the heat generation of the stepping motor 22a and the motor driver 22b can be suppressed.

[0066] On the other hand, the lower the second current value I2 is with respect to the first current value I1, the smaller the torque for holding the stop position of the valve body portion 21 becomes. It is desirable to set the first current value I1 and the second current value I2 in consideration of both the suppression of heat generation of the stepping motor 22a and the motor driver 22b and the decrease in the torque for holding the stop position of the valve body portion 21.

[0067] The operations and effects of the flow rate adjustment device 100 of the present embodiment described above will be described. According to the flow rate adjustment device 100 of the present embodiment, the control unit 31 controls the flow rate adjustment unit 20 to move the valve body unit 21 by a movement amount MV corresponding to the flow rate difference between the flow rate measurement value FRac measured by the ultrasonic flow meter 10 and the flow rate set value FRset so that the flow rate measurement value FRac of the fluid measured by the ultrasonic flow meter 10 becomes the flow rate set value FRset. Further, the control unit 31 controls the motor driver 22b to generate an excitation current with a first current value I1 during the execution of the movement operation for moving the valve body unit 21. On the other hand, the control unit 31 controls the motor driver 22b to generate an excitation current with a second current value I2 lower than the first current value I1 during the execution of the stop operation for not moving the valve body unit 21.

[0068] According to the flow rate adjustment device 100 of the present embodiment, the second current value I2 of the excitation current generated by the motor driver 22b during the execution of the stop operation is lower than the first current value I1 of the excitation current generated by the motor driver 22b during the execution of the movement operation. Therefore, the heat generation of the stepping motor 22a and the motor driver 22b during the execution of the stop operation can be suppressed as compared with the case where the motor driver 22b generates an excitation current with the same first current value I1 as during the execution of the movement operation.

[0069] According to the flow rate adjustment device 100 of the present embodiment, since the second current value I2 is set to be 0.5 times or more and 0.95 times or less of the first current value I1, the heat generation of the stepping motor 22a and the motor driver 22b during the execution of the stop operation can be appropriately suppressed.

[0070] According to the flow rate adjustment device 100 of the present embodiment, the second stop period TS2 when the flow rate difference between the flow rate measurement value FRac and the flow rate set value FRset is equal to or less than the predetermined threshold FRth is longer than the first stop period TS1 when the flow rate difference is larger than the predetermined threshold FRth. Therefore, by lengthening the stop period in a state where the flow rate difference is equal to or less than the predetermined threshold FRth and the flow rate fluctuation is relatively small, the heat generation of the stepping motor 22a and the motor driver 22b during the execution of the stop operation can be effectively suppressed. On the other hand, by shortening the stop period in a state where the flow rate difference is larger than the predetermined threshold FRth and the flow rate fluctuation is relatively large, the flow rate difference can be converged at an early stage.

[0071] Also, according to the flow rate adjustment device 100 of the present embodiment, since the second stop period TS2 is set to be 1.1 times or more and 20 times or less of the first stop period TS1, when the flow rate difference is equal to or less than the predetermined threshold value FRth, the heat generation of the stepping motor 22a and the motor driver 22b can be appropriately suppressed.

[0072] 〔Other Embodiments〕 The flow rate adjustment device 100 described above may be a modified example including a temperature detection unit 80 that detects the temperature of the stepping motor 22a or the motor driver 22b. FIG. 10 is a block diagram showing the configuration of the control device 30 included in the flow rate adjustment device 100 of the modified example. As shown in FIG. 10, the flow rate adjustment device 100 of the modified example includes a temperature detection unit 80 that detects the temperature of the stepping motor 22a or the motor driver 22b and transmits it to the control unit 31.

[0073] When the temperature detected by the temperature detection unit 80 is less than the predetermined temperature value, the control unit 31 of the modified example controls the motor driver 22b to generate an exciting current of the first current value I1 during the execution of the moving operation. When the temperature detected by the temperature detection unit 80 is equal to or greater than the predetermined temperature value, the control unit 31 controls the motor driver 22b to generate an exciting current of the third current value I3 that is lower than the first current value I1 during the execution of the stop operation. The third current value I3 is set to an arbitrary value in the range of, for example, 50% or more and 80% or less of the first current value I1.

[0074] According to the flow rate adjusting device 100 of this modification example, when the temperature detected by the temperature detection unit 80 is less than the predetermined temperature value, the exciting current of the first current value I1 can be generated during the execution of the moving operation to surely hold the current position of the valve body unit 21. On the other hand, when the temperature detected by the temperature detection unit 80 is equal to or higher than the predetermined temperature value, the exciting current of the third current value I3 lower than the first current value I1 can be generated during the execution of the moving operation to appropriately suppress the heat generation of the stepping motor 22a and the motor driver 22b. Further, by generating the exciting current of the third current value I3 lower than the first current value I1, the power consumption of the stepping motor 22a and the motor driver 22b can be reduced.

[0075] In the flow rate adjusting device 100 of the above modification example, the temperature detection unit 80 may be provided inside the motor driver 22b. In this case, status information indicating the temperature of the motor driver 22b is transmitted from the motor driver 22b to the control unit 31. When the status information transmitted from the motor driver 22b indicates that it is less than the predetermined temperature value, the control unit 31 controls the motor driver 22b to generate the exciting current of the first current value I1 during the execution of the moving operation. On the other hand, when the status information transmitted from the motor driver 22b indicates that it is equal to or higher than the predetermined temperature value, the control unit 31 controls the motor driver 22b to generate the exciting current of the third current value I3 during the execution of the moving operation.

[0076] In the above description, the flow rate adjusting device 100 accommodates the ultrasonic flow rate measuring unit 10 and the flow rate adjusting unit 20 in the same housing (housing unit 40), but other embodiments may be used. For example, the flow rate adjusting device 100 may accommodate the ultrasonic flow rate measuring unit 10 in a housing separate from other components including the flow rate adjusting unit 20. The flow rate of the fluid measured by the ultrasonic flow rate measuring unit 10 is preferably transmitted to the control device 30 of the flow rate adjusting device 100 via a cable (not shown).

[0077] In the above description, the flow rate adjustment device 100 measures the flow rate of the fluid by the ultrasonic flow meter 10, but other embodiments may be used. For example, the flow rate may be measured by other methods such as a differential pressure type flow meter that measures the flow rate of the fluid from the pressure difference at two locations.

Description of Reference Numerals

[0078] 1 Flow rate adjustment system 2 Pump 3 Pipe 4 On-off valve 5 On-off valve 10 Ultrasonic flow meter 11 Upstream oscillator 12 Downstream oscillator 13 Inflow channel 14 Measurement channel 15 Outflow channel 20 Flow rate adjustment unit 21 Valve body unit 22 Electric drive unit 22a Stepping motor 22b Motor driver 30 Control device 31 Control unit 32 Flow rate setting unit 40 Housing unit 50 Inflow side channel unit 60 Outflow side channel unit 62 Valve hole 63 Valve chamber 64 Opening 65 Outflow channel 66 Fastening bolt 70 Pressure sensor 80 Temperature detection unit 100 Flow rate adjustment device 100a Inflow port 100b Outflow port FRac Flow rate measurement value FRset Flow rate setting value FRth Predetermined threshold value I1 First current value I2 Second current value MV Movement amount TS1 First stop period TS2 Second Stop Period X1, X2, Y Axes

Claims

1. A flow rate measurement unit that measures the flow rate of a fluid flowing through a measurement flow path, A flow rate adjustment unit that moves a valve body portion in a direction approaching or separating from a valve hole along an axis to adjust the flow rate of the fluid flowing out from the measurement flow path, A flow rate setting unit that sets a flow rate set value of the fluid adjusted by the flow rate adjustment unit, A control unit that controls the flow rate adjustment unit and the flow rate setting unit, and includes: The flow rate adjustment unit, A stepping motor that rotates around the axis to move the valve body portion along the axis, A motor driver that generates an exciting current for driving the stepping motor and outputs it to the stepping motor, and has: The control unit, The flow rate adjustment unit is controlled to move the valve body portion by a movement amount corresponding to the flow rate difference between the flow rate measurement value and the flow rate set value so that the flow rate measurement value measured by the flow rate measurement unit becomes the flow rate set value, The motor driver is controlled to generate the exciting current of the first current value during the execution of the movement operation for moving the valve body portion, A flow rate adjustment device that controls the motor driver to generate the exciting current of the second current value lower than the first current value during the execution of the stop operation in which the valve body portion is not moved.

2. The flow rate adjustment device according to claim 1, wherein the second current value is set to be 0.5 times or more and 0.95 times or less of the first current value.

3. The control unit, The stop operation is executed during a stop period from when the first movement operation is completed until the second movement operation is started, The flow rate adjustment device according to claim 1, wherein the first stop period is set when the flow rate difference is greater than a predetermined threshold value, and the second stop period longer than the first stop period is set when the flow rate difference is equal to or less than the predetermined threshold value.

4. The flow rate adjustment device according to claim 3, wherein the second stop period is set to be 1.1 times or more and 20 times or less of the first stop period.

5. A temperature detection unit that detects the temperature of the stepping motor or the motor driver is provided, The control unit, When the temperature detected by the temperature detection unit is less than a predetermined temperature value, the motor driver is controlled to generate the exciting current of the first current value during the execution of the moving operation. When the temperature detected by the temperature detection unit is greater than or equal to the predetermined temperature value, the motor driver is controlled to generate the exciting current of a third current value lower than the first current value during the execution of the moving operation. The flow rate adjustment device according to any one of claims 1 to 4.

6. A control method for a flow rate adjustment device, wherein the flow rate adjustment device includes a flow rate measurement unit that measures the flow rate of a fluid flowing in from an inflow port and flowing through a measurement flow path, a flow rate adjustment unit that moves a valve body portion in a direction approaching or separating from a valve hole along an axis to adjust the flow rate of the fluid flowing out from the downstream side of the measurement flow path to an outflow port, wherein the flow rate adjustment unit includes a stepping motor that rotates around the axis to move the valve body portion along the axis, a motor driver that generates an exciting current for driving the stepping motor and outputs the exciting current to the stepping motor, a flow rate setting step of setting a flow rate set value of the fluid adjusted by the flow rate adjustment unit, a control step of controlling the flow rate adjustment unit to move the valve body portion by an amount of movement corresponding to a flow rate difference between the flow rate measurement value and the flow rate set value so that the flow rate measurement value of the fluid measured by the flow rate measurement unit becomes the flow rate set value, wherein the control step controls the motor driver to generate the exciting current of the first current value during the execution of a moving operation for moving the valve body portion, A control method for a flow rate adjustment device that controls the motor driver to generate the exciting current of a second current value lower than the first current value during the execution of a stop operation for not moving the valve body portion.

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