Flow rate adjustment device and control method for flow rate adjustment device

Abstract

In the event that the ultrasonic flow measurement unit becomes unable to perform flow measurement due to air bubbles present in the measurement channel, this system quickly resolves the abnormal condition and prevents the occurrence of flow rate fluctuations. [Solution] A control method for a flow rate adjustment device is provided, comprising: a flow rate adjustment step S107 that controls the flow rate adjustment unit to perform a flow rate adjustment operation so that the flow rate measurement value of the liquid measured by the ultrasonic flow rate measurement unit becomes the flow rate set value; an abnormality detection step S105 that detects whether the ultrasonic flow rate measurement unit is in an abnormal state where it cannot perform a flow rate measurement operation due to bubbles present in the measurement channel; and a bubble release step S106 that controls the flow rate adjustment unit to move the valve body a predetermined distance away from the valve hole and then stop it in response to the abnormality detection step detecting an abnormal state.

Description

Technical Field

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

Background Art

[0002] Conventionally, there has been known a flow rate adjustment device that includes a flow rate measurement unit for measuring the flow rate of liquid, and adjusts the flow rate of liquid passing through a valve hole by moving a valve body in a direction toward or away from the valve hole so that the flow rate measured by the flow rate measurement unit matches a preset set flow rate (see, for example, Patent Document 1). The flow rate adjustment device disclosed in Patent Document 1 includes an ultrasonic flow rate measurement unit that performs a flow rate measurement operation of measuring the flow rate of liquid flowing through a measurement flow path based on the propagation time difference of ultrasonic waves oscillated by a pair of vibrators arranged upstream and downstream of the measurement flow path through which the liquid flows.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] If the liquid flowing through the measurement flow path contains air bubbles, the air bubbles existing between the pair of vibrators of the ultrasonic flow rate measurement unit may cause an abnormal state in which the flow rate measurement operation cannot be properly performed. In the abnormal state, for example, the ultrasonic flow rate measurement unit may measure that the flow rate of the liquid is zero even when the liquid is flowing through the measurement flow path.

[0005] In abnormal conditions, if the flow rate measured by the ultrasonic flow measurement unit is less than the set flow rate, the valve body moves away from the valve opening, causing the opening to increase excessively. In this case, the opening when bubbles present in the measurement channel are released becomes excessively large relative to the set flow rate, resulting in flow rate fluctuations such as a temporary increase in the measured flow rate relative to the set flow rate (overshoot) or a periodic repetition of states where the measured flow rate is excessively high and excessively low relative to the set flow rate (hunting).

[0006] For example, to prevent overshoot or hunting, one might consider stopping the movement of the valve body in response to an abnormal condition where the flow measurement operation cannot be properly performed due to bubbles, thereby preventing the valve body opening from becoming excessively large relative to the set flow rate. However, if the movement of the valve body is stopped in response to an abnormal condition, a state in which bubbles are difficult to release will be maintained when the valve body opening is small. In this case, the condition in which the flow measurement operation cannot be properly performed will not be resolved, or it will take a long time to resolve.

[0007] This invention has been made in view of these circumstances, and aims to provide a flow rate adjustment device and a control method for a flow rate adjustment device that can quickly resolve an abnormal condition and prevent the occurrence of flow rate fluctuations when the ultrasonic flow rate measurement unit becomes unable to perform flow rate measurement operations due to bubbles present in the measurement channel. [Means for solving the problem]

[0008] To solve the above problems, the present invention employs the following means. A flow rate adjustment device according to one aspect of the present invention includes: an ultrasonic flow rate measurement unit that performs a flow rate measurement operation to measure the flow rate of liquid flowing through a measurement channel based on the propagation time difference of ultrasonic waves emitted by a pair of transducers arranged on the upstream and downstream sides of the measurement channel through which the liquid flows; a flow rate adjustment unit that adjusts the flow rate of liquid flowing out of the measurement channel by moving a valve body along an axis in a direction toward or toward the valve hole; a flow rate setting unit that sets a set value for the liquid flow rate adjusted by the flow rate adjustment unit; a control unit that controls the flow rate adjustment unit to perform a flow rate adjustment operation to move the valve body to a target position that changes according to the flow rate difference between the flow rate measurement value and the flow rate setting value so that the liquid flow rate measurement value measured by the ultrasonic flow rate measurement unit becomes the set value; and an abnormal state in which the ultrasonic flow rate measurement unit cannot perform the flow rate measurement operation due to bubbles present in the measurement channel. The control unit includes an abnormality detection unit that detects whether or not an abnormal state exists, and the control unit controls the flow rate adjustment unit to move the valve body a predetermined distance away from the valve hole and then stop it in response to the abnormality detection unit detecting that an abnormal state exists.

[0009] According to one aspect of the present invention, when the abnormality detection unit detects that the ultrasonic flow measurement unit is in an abnormal state where it cannot perform flow measurement due to bubbles present in the measurement channel, the valve body moves a predetermined distance away from the valve hole, and then the movement of the valve body is stopped. Since the opening of the valve body becomes larger than the opening at the time the abnormal state was detected, bubbles are more easily released from the measurement channel compared to when the opening of the valve body at the time the abnormal state was detected, and the abnormal state can be resolved quickly. Furthermore, since the opening of the valve body is set regardless of the measurement results of the ultrasonic flow measurement unit, it is possible to prevent flow rate fluctuations caused by the opening of the valve body becoming excessively large relative to the flow rate set value.

[0010] In a flow rate adjustment device according to one aspect of the present invention, the control unit may be configured to stop the execution of the flow rate adjustment operation when the abnormality detection unit detects that an abnormal state exists, and to start the execution of the flow rate adjustment operation when the abnormality detection unit detects that an abnormal state does not exist. With this flow rate adjustment device configuration, it is possible to appropriately switch whether or not to perform a flow rate adjustment operation depending on whether or not the abnormality detection unit detects an abnormal condition.

[0011] In a flow rate adjustment device according to one aspect of the present invention, the control unit may be configured to control the flow rate adjustment unit such that the predetermined distance becomes longer the smaller the flow rate setting value set by the flow rate setting unit when the abnormality detection unit detects that an abnormal state exists.

[0012] With this flow rate adjustment device configuration, the smaller the flow rate setting value when an abnormal condition is detected, the longer the predetermined distance can be made. This effectively eliminates the phenomenon where the opening of the valve body becomes smaller as the flow rate setting value decreases, making it difficult for bubbles to be released from the measurement channel.

[0013] In a flow rate adjustment device according to one aspect of the present invention, the control unit may be configured to control the flow rate adjustment unit so that when the abnormality detection unit detects an abnormal state and the flow rate setting value set by the flow rate setting unit is less than or equal to a predetermined value, the valve body is moved a predetermined distance away from the valve hole and then stopped, and when the abnormality detection unit detects an abnormal state and the flow rate setting value set by the flow rate setting unit is greater than the predetermined value, the valve body is stopped without being moved away from the valve hole.

[0014] According to this flow rate adjustment device configuration, when an abnormal condition is detected and the flow rate setting value is below a predetermined value, the valve body is moved a predetermined distance away from the valve body, thereby appropriately resolving the phenomenon in which bubbles are difficult to release from the measurement channel due to the small opening of the valve body when the flow rate setting value is below a predetermined value.

[0015] In a control method for a flow rate adjustment device according to one aspect of the present invention, the flow rate adjustment device comprises: an ultrasonic flow rate measurement unit that performs a flow rate measurement operation to measure the flow rate of liquid flowing through a measurement channel based on the propagation time difference of ultrasonic waves emitted by a pair of transducers arranged on the upstream and downstream sides of the measurement channel through which the liquid flows; a flow rate adjustment unit that adjusts the flow rate of liquid flowing out of the measurement channel by moving a valve body along an axis in a direction toward or toward the valve hole; and a flow rate setting unit that sets a set value for the liquid flow rate adjusted by the flow rate adjustment unit, wherein the flow rate measurement value of the liquid measured by the ultrasonic flow rate measurement unit The system includes a flow rate adjustment step that controls the flow rate adjustment unit to perform a flow rate adjustment operation to move the valve body to a target position that changes according to the flow rate difference between the measured flow rate and the set flow rate, so that the flow rate becomes the set flow rate; an abnormality detection step that detects whether the ultrasonic flow rate measuring unit is in an abnormal state where it cannot perform the flow rate measurement operation due to bubbles present in the measuring channel; and a bubble release step that controls the flow rate adjustment unit to move the valve body a predetermined distance away from the valve hole and then stop it in response to the abnormality detection step detecting the abnormal state.

[0016] According to a control method for a flow rate adjustment device according to one aspect of the present invention, when an abnormality detection step detects that the ultrasonic flow rate measuring unit is in an abnormal state where it cannot perform flow rate measurement due to bubbles present in the measurement channel, the valve body moves a predetermined distance away from the valve hole, and then the movement of the valve body is stopped. Since the opening of the valve body becomes larger than the opening of the valve body at the time the abnormal state was detected, bubbles are more easily released from the measurement channel compared to when the opening of the valve body at the time the abnormal state was detected is maintained, and the abnormal state can be resolved quickly. Furthermore, since the opening of the valve body is set regardless of the measurement results of the ultrasonic flow rate measuring unit, it is possible to prevent the occurrence of flow rate fluctuations due to the opening of the valve body becoming excessively large relative to the flow rate set value.

[0017] In a control method for a flow rate adjustment device according to one aspect of the present invention, the method may include a flow rate adjustment stop step that stops the execution of the flow rate adjustment operation when the abnormality detection step detects that the abnormal state is present, and the flow rate adjustment step may be configured to start the execution of the flow rate adjustment operation when the abnormality detection step detects that the abnormal state is not present. According to the control method for the flow rate adjustment device in this configuration, it is possible to appropriately switch whether or not to perform the flow rate measurement operation depending on whether or not the abnormality detection process detects an abnormal condition.

[0018] In a control method for a flow rate adjustment device according to one aspect of the present invention, the bubble release step may be configured to control the flow rate adjustment unit such that the predetermined distance becomes longer the smaller the flow rate setting value set by the flow rate setting unit when the abnormality detection step detects that the abnormal state is present.

[0019] According to the control method of the flow rate adjustment device with this configuration, the smaller the flow rate setting value when an abnormal condition is detected, the longer the predetermined distance can be made, thereby appropriately resolving the phenomenon in which the opening degree of the valve body becomes smaller as the flow rate setting value decreases, making it difficult for bubbles to be released from the measurement channel.

[0020] In a control method for a flow rate adjustment device according to one aspect of the present invention, the bubble release step may be configured such that, when the abnormality detection step detects that an abnormal state is present and the flow rate setting value set by the flow rate setting unit is less than or equal to a predetermined value, the valve body is moved a predetermined distance away from the valve hole and then stopped; and when the abnormality detection step detects that an abnormal state is present and the flow rate setting value set by the flow rate setting unit is greater than the predetermined value, the flow rate adjustment unit is stopped without moving the valve body away from the valve hole.

[0021] According to the control method for the flow rate adjustment device of the present configuration, when the flow rate setting value detected upon detection of an abnormal state is equal to or less than a predetermined value, the valve body portion is moved by a predetermined distance in a direction away from the valve seat portion, whereby the phenomenon that air bubbles are less likely to be discharged from the measurement flow path due to the small opening degree of the valve body portion when the flow rate setting value is equal to or less than the predetermined value can be appropriately eliminated.

Effects of the Invention

[0022] According to the present invention, when an abnormal state in which an ultrasonic flow rate measurement unit cannot perform a flow rate measurement operation due to air bubbles present in a measurement flow path occurs, it is possible to provide a flow rate adjustment device and a control method for the flow rate adjustment device that can quickly resolve the abnormal state and prevent the occurrence of flow rate fluctuations.

Brief Description of the Drawings

[0023] [Figure 1] It is a partial longitudinal cross-sectional view showing one embodiment of a flow rate adjustment device. [Figure 2] It is a partial longitudinal cross-sectional view showing the ultrasonic flow rate measurement unit shown in FIG. 1. [Figure 3] It is a partial longitudinal cross-sectional view showing the flow rate adjustment unit and the outflow-side flow path unit shown in FIG. 1. [Figure 4] It is a longitudinal cross-sectional view showing the inflow-side flow path unit and the pressure sensor shown in FIG. 1. [Figure 5] It is a block diagram showing the configuration of a control device. [Figure 6] It is a schematic configuration diagram showing a flow rate adjustment system in which the flow rate adjustment device is installed. [Figure 7] It is a flowchart showing an operation executed by the flow rate adjustment device. [Figure 8] It is a flowchart showing an operation in an air bubble discharge mode. [Figure 9] It is a graph showing an example of changes in the opening degree of the valve body portion and the flow rate setting value.

Mode for Carrying Out the Invention

[0024] Hereinafter, a flow rate adjustment device 100 according to one embodiment of the present invention will be described with reference to the drawings. Figure 1 is a partial longitudinal cross-sectional view showing one embodiment of the flow rate adjustment device 100. Figure 2 is a partial longitudinal cross-sectional view showing the ultrasonic flow measurement unit 10 shown in Figure 1.

[0025] The flow rate adjustment device 100 of this embodiment shown in Figure 1 comprises an ultrasonic flow rate measuring unit 10 that measures the flow rate of liquid flowing in from the inlet port 100a and through the straight-tube measuring channel 14, a flow rate adjustment unit 20 that adjusts the flow rate of the liquid, a control device 30 that controls the flow rate adjustment unit 20, a housing unit 40 that houses the ultrasonic flow rate measuring unit 10, the flow rate adjustment unit 20 and the control device 30, an inlet-side channel unit 50 that guides the fluid flowing in from the inlet port 100a to the upstream side of the measuring channel 14, an outlet-side channel unit 60 that guides the fluid flowing out from the downstream side of the measuring channel 14 to the outlet port 100b, and a pressure sensor 70.

[0026] The liquid whose flow rate is adjusted by the flow rate adjustment device 100 of this embodiment is, for example, a chemical solution used in semiconductor manufacturing equipment (e.g., hydrogen peroxide solution), pure water, etc. The temperature of the liquid is, for example, in the room temperature range (e.g., 10°C or higher and less than 40°C) or the high temperature range (e.g., 40°C or higher and 90°C or lower).

[0027] The housing portion 40 of the flow rate adjustment device 100 is fixed to the installation surface S by fastening bolts (not shown). The flow rate adjustment device 100 is also connected to a higher-level device 200 (see Figure 6) via a cable 101, and receives power from an external device via the cable 101, as well as transmitting and receiving various signals with the higher-level device 200.

[0028] The signals received from the higher-level device 200 are, for example, flow rate setting signals indicating the target flow rate set by the flow rate adjustment device 100. The signals transmitted to the higher-level device 200 are, for example, signals indicating the liquid flow rate calculated by the control device 30 based on the signal measured by the ultrasonic flow measurement unit 10, and signals indicating the liquid pressure measured by the pressure sensor 70.

[0029] The ultrasonic flow rate measurement unit 10 measures the propagation time difference of ultrasonic signals emitted by a pair of transducers: an upstream transducer 11 located upstream of the measurement channel 14 and a downstream transducer 12 located downstream of the measurement channel 14, in order to obtain the flow rate of the liquid flowing through the straight measurement channel 14 from the inflow side piping (not shown). The ultrasonic flow rate measurement unit 10 performs a flow rate measurement operation to measure the flow rate of the liquid flowing through the measurement channel 14 based on the propagation time difference.

[0030] As shown in Figure 2, the ultrasonic flow measurement unit 10 includes an upstream transducer 11 and a downstream transducer 12 arranged on an axis X2 parallel to the installation surface S, an inlet channel 13 connected to the inlet channel section 50, a straight tubular measurement channel 14 connected to the inlet channel 13 and extending along axis X2 (second axis), and an outlet channel 15 connected to the outlet channel section 60. Axis X2 is parallel to axis X1 (first axis), which is the direction of movement of the valve body section 21 described later.

[0031] The upstream transducer 11 and the downstream transducer 12 are positioned opposite each other on the axis X2 via the measurement channel 14, and are capable of transmitting and receiving ultrasonic signals, respectively. The ultrasonic signal transmitted by the upstream transducer 11 propagates through the liquid flowing in the measurement channel 14 and is received by the downstream transducer 12.

[0032] Similarly, the ultrasonic signal emitted by the downstream transducer 12 propagates through the liquid flowing through the measurement channel 14 and is received by the upstream transducer 11. Since the liquid flows through the measurement channel 14 from upstream to downstream, the propagation time of the ultrasonic signal emitted by the upstream transducer 11 to the downstream transducer 12 is shorter than the propagation time of the ultrasonic signal emitted by the downstream transducer 12 to the upstream transducer 11. The ultrasonic flow rate measurement unit 10 uses this propagation time difference to measure the flow rate of the liquid flowing through the measurement channel 14.

[0033] The transmission of ultrasonic signals by the upstream transducer 11 and the downstream transducer 12 is controlled by the control device 30, which is connected by signal lines 16 and 17 as shown in Figure 2. The reception of ultrasonic signals by the upstream transducer 11 and the downstream transducer 12 is transmitted to the control device 30 via signal lines 16 and 17. As will be described later, the control device 30 calculates the propagation time difference from the transmission timing of the ultrasonic signals instructed to the upstream transducer 11 and the downstream transducer 12, and the corresponding reception timing of the ultrasonic signals received from the upstream transducer 11 and the downstream transducer 12, and calculates the liquid flow rate from the calculated propagation time difference.

[0034] The flow rate adjustment unit 20 adjusts the flow rate of the liquid flowing from the downstream side of the measurement channel 14 to the outlet port 100b, which is connected to the outlet piping (not shown) via the outlet channel section 60. As shown in Figure 1, the flow rate adjustment unit 20 is positioned between the ultrasonic flow measurement unit 10 and the control device 30 in the axial Y direction, which is the installation direction perpendicular to the installation surface S. As shown in Figure 1, in the axial Y direction, the ultrasonic flow measurement unit 10 is positioned closest to the installation surface S, the control device 30 is positioned furthest from the installation surface S, and the flow rate adjustment unit 20 is positioned between them.

[0035] Figure 3 is a partial longitudinal cross-sectional view showing the flow rate adjustment unit 20 and the outlet side flow path 60 shown in Figure 1. As shown in Figure 3, the flow rate adjustment unit 20 has a valve body 21 that is inserted into a valve hole 62 formed in the outlet side flow path 60, and an electric drive unit 22 that moves the valve body 21 in a direction toward or toward 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 liquid flowing out of the measurement flow path 14 by moving the valve body 21 toward or toward the valve hole 62 along the axis X1.

[0036] The electric drive unit 22 moves the valve body 21 back and forth along axis X1 between the closed position shown by the solid line and the open position shown by the dashed line in Figure 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 21 on axis X1 using the electric drive unit 22.

[0037] The configuration of the control device 30 will now be explained with reference to Figure 5. Figure 5 is a block diagram showing the configuration of the control device 30. As shown in Figure 5, the control device 30 includes a control unit 31, a flow rate setting unit 32, and a bubble detection unit (abnormality detection unit) 33. The control unit 31 controls the ultrasonic flow rate measurement unit 10, the flow rate adjustment unit 20, the flow rate setting unit 32, and the bubble detection unit 33.

[0038] The control unit 31 controls the flow rate adjustment unit 20 based on the liquid flow rate measurement value FRac measured by the ultrasonic flow rate measurement unit 10. The control unit 31 controls the flow rate adjustment unit 20 in one of the following modes: flow rate adjustment mode, bubble release mode, or standby mode.

[0039] When executing the flow rate adjustment mode, the control unit 31 controls the flow rate adjustment unit 20 to move the valve body 21 to a target position that fluctuates according to the flow rate difference between the measured liquid value FRac and the set flow rate value FRset, so that the measured liquid flow rate value FRac measured by the ultrasonic flow rate measurement unit 10 becomes the set flow rate value FRset set by the flow rate setting unit 32.

[0040] The control unit 31 controls the flow rate adjustment unit 20 to execute the bubble release mode when it detects that the bubble detection unit 33 is in an abnormal state, as described later. In response to the bubble detection unit 33 detecting an abnormal state, the control unit 31 controls the flow rate adjustment unit 20 to move the valve body 21 a predetermined distance away from the valve hole 62 and then stop it.

[0041] The bubble detection unit 33 detects whether the ultrasonic flow measurement unit 10 is in an abnormal state where it cannot perform flow measurement due to bubbles present in the measurement channel 14. If bubbles are present in the measurement channel 14, the downstream transducer 12 will not be able to receive the signal transmitted by the upstream transducer 11, and the upstream transducer 11 will not be able to receive the signal transmitted by the downstream transducer 12.

[0042] In this case, the downstream transducer 12 may not be able to receive the signal transmitted by the upstream transducer 11 if the signal transmitted by the upstream transducer 11 is attenuated by air bubbles and falls below a signal level that can be received by the downstream transducer 12, or if the transmission of the signal transmitted by the upstream transducer 11 is delayed due to the effect of air bubbles and does not reach the downstream transducer 12 within a predetermined time after transmission.

[0043] Similarly, if the upstream transducer 11 cannot receive the signal transmitted by the downstream transducer 12, this includes cases where the signal transmitted by the downstream transducer 12 is attenuated by air bubbles and falls below a signal level that can be received by the upstream transducer 11, or where the transmission of the signal transmitted by the downstream transducer 12 is delayed due to the effect of air bubbles and does not reach the upstream transducer 11 within a predetermined time after transmission.

[0044] The ultrasonic flow measurement unit 10 operates so that the upstream transducer 11 and the downstream transducer 12 alternately transmit and receive signals. The bubble detection unit 33 detects an abnormal condition when the downstream transducer 12 cannot receive a signal transmitted by the upstream transducer 11, or when the upstream transducer 11 cannot receive a signal transmitted by the downstream transducer 12. The valve body 21 is moved a predetermined distance away from the valve hole 62 in response to the bubble detection unit 33 detecting an abnormal condition in order to facilitate the release of bubbles present in the measurement channel 14 to the downstream side of the measurement channel 14.

[0045] The control unit 31 sets a predetermined distance D for moving the valve body 21 based on the following equations (1) and (2) in response to the bubble detection unit 33 detecting an abnormal state. O = -Omax·FRset / FRmax+Omax (1) D = O·Xmax (2)

[0046] Here, Xmax is the distance from the position on axis X1 where the valve body 21 contacts the valve hole 62 to the position on axis X1 of the valve body 21 corresponding to the maximum flow rate FRmax of the flow rate setting value FRset that can be set by the flow rate setting unit 32; O is the percentage [%] of the opening degree of the valve body 21 that the bubble detection unit 33 increases when it detects an abnormal state; and Omax is the maximum value of O. Omax is set to, for example, 0.2.

[0047] As shown in equations (1) and (2), the predetermined distance D is 0 when the flow rate setting value FRset is the maximum flow rate FRmax. That is, when the flow rate setting value FRset is the maximum flow rate FRmax, the valve body 21 is already near Xmin, which corresponds to the maximum opening, so there is no need to further increase the opening of the valve body 21 in order to release bubbles, and therefore the predetermined distance D is set to 0. Furthermore, as shown in equations (1) and (2), the smaller the flow rate setting value FRset set by the flow rate setting unit 32, the longer the predetermined distance D becomes. This is to resolve the situation where the opening of the valve body 21 is smaller and bubbles are less likely to be released when the flow rate setting value FRset is small.

[0048] The control unit 31 executes a standby mode if neither the flow rate adjustment mode nor the bubble release mode is executed. When the control unit 31 executes the standby mode, it controls the flow rate adjustment unit 20 to move the valve body 21 to a standby position where the valve body 21 does not contact the valve hole 62, and then maintains that standby position. The control unit 31 sets the standby position to a predetermined position between the closed position (lower limit position) corresponding to FRmin (lower limit value), which is the minimum flow rate of the flow rate setting value FRset that can be set by the flow rate setting unit 32, and the upper limit position corresponding to the maximum flow rate FRmax (upper limit value) of the flow rate setting value FRset that can be set by the flow rate setting unit 32.

[0049] The control unit 31 can instruct the upstream transducer 11 and the downstream transducer 12 of the ultrasonic flow measurement unit 10 to transmit ultrasonic signals. The control unit 31 can also detect the timing at which the ultrasonic signal transmitted from either the upstream transducer 11 or the downstream transducer 12 is received by the other of the two transducers.

[0050] The control unit 31 calculates a first propagation time from the timing of the ultrasonic signal transmission instructed to the downstream transducer 12 and the corresponding timing of the ultrasonic signal reception at the upstream transducer 11. The control device 30 also calculates a second propagation time from the timing of the ultrasonic signal transmission instructed to the upstream transducer 11 and the corresponding timing of the ultrasonic signal reception at the downstream transducer 12. The control unit 31 obtains the flow rate of the liquid flowing through the measurement channel 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.

[0051] The flow rate setting unit 32 sets the flow rate setting value FRset [ml / min] which is included in the flow rate range from the minimum flow rate of 0 [ml / min] 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 the flow rate setting signal that the control device 30 receives from the host device 200 via the cable 101.

[0052] The electric drive unit 22 of the flow rate adjustment unit 20 includes a stepping motor 22a that moves the valve body 21 along the axis X1 by rotating around the axis X1, and a motor driver 22b that generates an excitation current to drive the stepping motor 22a and outputs it to the stepping motor 22a.

[0053] Figure 4 is a longitudinal cross-sectional view showing the inlet-side flow path section 50 and pressure sensor 70 shown in Figure 1. As shown in Figures 1 and 4, the inlet-side flow path section 50 is a member in which an inlet-side inclined flow path 51 is formed inside, which is inclined from the inlet port 100a toward the upstream inlet flow path 13 of the measurement flow path 14 toward the installation surface S. A pressure sensor 70 is attached to the inlet-side flow path section 50 for detecting the pressure of the liquid flowing through the inlet-side inclined flow path 51.

[0054] As shown in Figures 1 and 3, the outlet-side flow path section 60 is a member in which an outlet-side inclined flow path 61 is formed inside, which is inclined in a direction toward approaching the installation surface S toward the outlet port 100b from the flow rate adjustment section 20. The outlet-side flow path section 60 guides fluid to the upstream side of the outlet-side inclined flow path 61 via the outlet flow path 65 from an opening 64 provided above the valve chamber 63.

[0055] The liquid guided upstream of the outflow-side inclined channel 61 is guided along the outflow-side inclined channel 61 to the outflow port 100b. As shown in Figures 2 and 3, the outflow-side channel section 60 is provided with through holes through which multiple fastening bolts 66 pass. The outflow-side channel section 60 is fixed to the electric drive unit 22 by fastening the fastening bolts 66 to the electric drive unit 22.

[0056] The pressure sensor 70 measures the pressure (supply pressure) of the liquid flowing from the inlet port 100a into the inlet-side inclined channel 51 on the upstream side of the measurement channel 14. The pressure sensor 70 is, for example, a strain gauge type pressure sensor. As shown in Figure 4, the pressure sensor 70 is attached to the inlet-side channel section 50 by a sensor holder 71. The pressure signal indicating the liquid pressure measured by the pressure sensor 70 is transmitted to the control device 30 and stored in the memory unit (not shown) of the control device 30. The pressure signal is also transmitted to the host device 200 via cable 101.

[0057] Next, the flow rate adjustment system 1 in which the flow rate adjustment device 100 of this embodiment is installed will be described with reference to Figure 6. Figure 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 Figure 6, the flow rate adjustment system 1 includes a pump 2 for pressurizing the liquid, piping 3 for transporting the liquid from the inlet end 1a to the outlet end 1b, the flow rate adjustment device 100, an on-off valve 4 located in the piping 3 upstream of the flow rate adjustment device 100, an on-off valve 5 located in the piping 3 downstream of the flow rate adjustment device 100, and a higher-level device 200. The higher-level device 200 is a device that controls the flow rate adjustment device 100, the pump 2, the on-off valve 4, and the on-off valve 5.

[0058] The flow rate adjustment system 1 pumps the liquid flowing from the inlet end 1a into the piping 3 using a pump 2 and supplies it to the flow rate adjustment device 100. The flow rate adjustment device 100 then adjusts the liquid flow rate and supplies it to the outlet end 1b. The state in which liquid is supplied from the inlet end 1a to the flow rate adjustment device 100 and the state in which it is not supplied is switched by an on-off valve 4. The state in which liquid is supplied from the flow rate adjustment device 100 to the outlet end 1b and the state in which it is not supplied is switched by an on-off valve 5.

[0059] Next, the processes performed by the flow rate adjustment device 100 of this embodiment will be described with reference to Figure 7. Figure 7 is a flowchart showing the operations performed by the flow rate adjustment device 100.

[0060] In step S101, the control unit 31 checks the flow rate setting signal received from the host device 200 and recognizes the flow rate setting value FRset set by the flow rate setting signal.

[0061] In step S102, the control unit 31 determines whether the flow rate setting value FRset is less than FRmin (lower limit). If YES, the process proceeds to step S103; otherwise, the process proceeds to step S104.

[0062] In step S103, the control unit 31 executes standby mode. When executing standby mode, the control unit 31 controls the flow rate adjustment unit 20 to move the valve body 21 to a standby position where the valve body 21 does not contact the valve hole 62, and then maintain that standby position.

[0063] In step S104, the control unit 31 controls the ultrasonic flow measurement unit 10 to perform a flow measurement operation. The ultrasonic flow measurement unit 10 performs a flow measurement operation to measure the flow rate of the liquid flowing through the measurement channel 14 based on the propagation time difference of ultrasonic signals emitted by a pair of transducers.

[0064] In step S105, the control unit 31 determines whether the bubble detection unit 33 has detected an abnormal condition in which the ultrasonic flow measurement unit 10 is unable to perform flow measurement due to bubbles present in the measurement channel 14. If the result is YES, the process proceeds to step S106; otherwise, the process proceeds to step S107. In step S106, the control unit 31 executes the bubble release mode. The bubble release mode will be described later.

[0065] In step S107, the control unit 31 controls the flow rate adjustment unit 20 to perform a flow rate adjustment operation. The control unit 31 controls the flow rate adjustment unit 20 to move the valve body 21 to a target position that changes according to the flow rate difference between the flow rate measurement value FRac and the flow rate setting value FRset, so that the liquid flow rate measurement value FRac measured by the ultrasonic flow rate measurement unit 10 becomes the flow rate setting value FRset set by the flow rate setting unit 32.

[0066] In step S108, the control unit 31 determines whether to stop the flow rate adjustment device 100. If it is YES, it terminates the process in this flowchart; otherwise, it repeats step S101.

[0067] Next, the bubble release mode performed in step S106 of Figure 7 will be described with reference to Figure 8. Figure 8 is a flowchart showing the operation of the bubble release mode.

[0068] In step S201, the control unit 31 determines whether this is the first operation since the bubble detection unit 33 detected an abnormal condition. If it is YES, it proceeds to step S202; otherwise, it terminates the process shown in this flowchart.

[0069] In step S202, the control unit 31 controls the flow rate adjustment unit 20 to stop the flow rate adjustment operation if it is currently performing the flow rate adjustment operation.

[0070] In step S203, the control unit 31 inputs the flow rate setting value FRset, which was confirmed in step S101 of Figure 7, into equation (1) to calculate the predetermined distance D. The control unit 31 then calculates the number of pulses to be output from the motor driver 22b to the stepping motor 22a as the predetermined distance D. This number of pulses is the value required to move the valve body 21 along the axis X1 by a predetermined distance D.

[0071] In step S204, the control unit 31 controls the flow rate adjustment unit 20 to start moving the valve body 21 away from the valve hole 62. The control unit 31 controls the flow rate adjustment unit 20 to start outputting pulses for the motor driver 22b to drive the stepping motor 22a.

[0072] In step S205, the control unit 31 determines whether the valve body 21 has moved a predetermined distance D away from the valve hole 62 relative to its position at the time the bubble detection unit 33 detected an abnormal condition in step S105. If the determination is YES, the process proceeds to step S206; otherwise, the determination in step S205 is repeated. The control unit 31 determines that the determination is YES if the number of pulses required to move the valve body 21 by the predetermined distance D is output from the motor driver 22b to the stepping motor 22a.

[0073] In step S206, the control unit 31 controls the flow rate adjustment unit 20 to stop the operation of moving the valve body 21 away from the valve hole 62. The control unit 31 controls the flow rate adjustment unit 20 to stop the motor driver 22b from outputting pulses to drive the stepping motor 22a.

[0074] As explained in Figures 7 and 8 above, the control unit 31 stops the execution of the flow rate adjustment operation when the bubble detection unit 33 detects an abnormal state in step S105 (S202), and controls the flow rate adjustment unit 20 to start the execution of the flow rate adjustment operation when the bubble detection unit 33 detects that there is no abnormal state in step S105 (S107).

[0075] Furthermore, the control unit 31 calculates a predetermined distance D in step S203 using equation (1), and controls the flow rate adjustment unit 20 such that the predetermined distance D becomes longer the smaller the flow rate setting value FRset set by the flow rate setting unit 32 when the bubble detection unit 33 detects an abnormal state.

[0076] In the above explanation, the predetermined distance D was calculated from equation (1), but other configurations are also possible. For example, the control unit 31 may calculate a predetermined distance D greater than 0 when the flow rate setting value FRset is less than or equal to a predetermined value, and may calculate zero as the predetermined distance D when the flow rate setting value FRset is less than or equal to a predetermined value. In this case, when the bubble detection unit 33 detects that an abnormal state has occurred, the control unit 31 moves the valve body 21 a predetermined distance D away from the valve hole 62 and then stops it if the flow rate setting value FRset set by the flow rate setting unit 32 is less than or equal to a predetermined value, and when the bubble detection unit 33 detects that an abnormal state has occurred, the control unit 31 controls the flow rate adjustment unit 20 to stop the valve body 21 without moving it away from the valve hole 62 if the flow rate setting value FRset set by the flow rate setting unit 32 is greater than a predetermined value.

[0077] Next, an example of performing the operations shown in Figures 7 and 8 will be explained with reference to Figure 9. Figure 9 is a graph showing an example of the changes in the opening degree of the valve body 21 and the flow rate set value FRset. The opening degree of the valve body 21 is defined as 100% for the position of the valve body 21 corresponding to the maximum flow rate FRmax (upper limit), and 0% for the position of the valve body 21 when it is in contact with the valve hole 62.

[0078] In Figure 9, the periods from time T0 to time T1, from time T2 to time T4, and from time T5 onward are periods during which the bubble detection unit 33 detects that it is not in an abnormal state. On the other hand, in Figure 9, the periods from time T1 to time T2 and from time T4 to time T5 are periods during which the bubble detection unit 33 detects that it is in an abnormal state.

[0079] Furthermore, for the period from time T0 to time T3, a flow rate setting value FRset1 is set, which corresponds to a 20% opening of the valve body 21, and for the period from time T3 onward, a flow rate setting value FRset2 is set, which corresponds to a 70% opening of the valve body 21.

[0080] As shown in Figure 9, the control unit 31 controls the flow rate adjustment unit 20 to perform a flow rate adjustment operation during the period when the bubble detection unit 33 detects that there is no abnormal condition. During this period, the control unit 31 adjusts the position of the valve body 21 to maintain an opening of 20%, which corresponds to the flow rate set value FRset1.

[0081] Furthermore, as shown in Figure 9, the control unit 31 increases the opening of the valve body 21 to an opening greater than 20%, which corresponds to the flow rate setting value FRset1, during the period from time T1 to time T2 when the bubble detection unit 33 detects an abnormal state. This is to facilitate the release of bubbles from the measurement channel 14 and encourage the abnormal state to be resolved.

[0082] Similarly, as shown in Figure 9, the control unit 31 increases the opening of the valve body 21 to an opening greater than 70%, which corresponds to the flow rate setting value FRset2, during the period from time T4 to time T5 when the bubble detection unit 33 detects an abnormal state. This is to facilitate the release of bubbles from the measurement channel 14 and encourage the abnormal state to be resolved.

[0083] Furthermore, the increase in the opening degree of the valve body 21 from 20% corresponding to the flow rate setting value FRset1 during the period from time T1 to time T2 is greater than the increase in the opening degree of the valve body 21 from 70% corresponding to the flow rate setting value FRset2 during the period from time T4 to time T5. This is because, when an abnormal condition is detected, the smaller the flow rate setting value FRset, the longer the predetermined distance D required to move the valve body 21 is made, thereby appropriately resolving the phenomenon in which the opening degree of the valve body 21 becomes smaller as the flow rate setting value FRset decreases, making it difficult for bubbles to be released from the measurement channel 14.

[0084] The operation and effects of the flow rate adjustment device 100 of this embodiment, as described above, will now be explained.

[0085] According to the flow rate adjustment device 100 of this embodiment, when the bubble detection unit 33 detects that the ultrasonic flow rate measurement unit 10 is in an abnormal state where it cannot perform flow rate measurement due to bubbles present in the measurement channel 14, the valve body 21 moves a predetermined distance D in the direction away from the valve hole 62, and then the movement of the valve body 21 is stopped. Since the opening degree of the valve body 21 becomes larger than the opening degree of the valve body 21 at the time the abnormal state was detected, bubbles are more easily released from the measurement channel 14 compared to when the opening degree of the valve body 21 at the time the abnormal state was detected, and the abnormal state can be resolved quickly. In addition, since the opening degree of the valve body 21 is set regardless of the measurement results of the ultrasonic flow rate measurement unit 10, it is possible to prevent the occurrence of flow rate fluctuations due to the opening degree of the valve body 21 becoming excessively large relative to the flow rate setting value FRset.

[0086] According to the flow rate adjustment device 100 of this embodiment, the predetermined distance D is increased as the flow rate setting value FRset becomes smaller when an abnormal condition is detected. This appropriately eliminates the phenomenon in which the opening degree of the valve body 21 becomes smaller as the flow rate setting value FRset becomes smaller, making it difficult for bubbles to be released from the measurement channel 14.

[0087] According to the flow rate adjustment device 100 of this embodiment, when an abnormal condition is detected and the flow rate setting value FRset is below a predetermined value, the valve body 21 is moved a predetermined distance D in the direction away from the valve body 21, thereby appropriately resolving the phenomenon in which bubbles are difficult to release from the measurement channel 14 due to the small opening of the valve body 21 when the flow rate setting value FRset is below a predetermined value. [Explanation of Symbols]

[0088] 1. Flow rate adjustment system 1a Inlet end 1b Outflow end 2 pumps 3 Piping 4. Shut-off valves 5. Shut-off valves 10. Ultrasonic flow measurement unit 11 Upstream transducer 12 Downstream transducer 13 Inflow channel 14 Measurement channel 15 Outlet channel 16,17 Signal lines 20 Flow rate adjustment section 21 Valve body 22 Electric drive unit 30 Control device 31 Control Unit 32 Flow rate setting section 33. Bubble detection unit (anomaly detection unit) 40 Housing section 50 Inlet flow path section 51 Inlet inclined channel 60 Outlet flow path section 61 Outflow side inclined channel 62 valve holes 63 valve chambers 64 openings 65 Outlet channel 66 fastening bolts 70 Pressure Sensor 100 Flow rate adjustment device 100a Inflow Port 100b Outflow Port 101 Cable 200 Higher-level equipment S Setting surface X1, X2, Y axes

Claims

1. An ultrasonic flow rate measuring unit performs a flow rate measurement operation that measures the flow rate of liquid flowing through a measurement channel based on the difference in propagation time of ultrasonic waves emitted by a pair of transducers positioned upstream and downstream of the measurement channel through which the liquid flows, A flow rate adjustment unit adjusts the flow rate of liquid flowing out of the measurement channel by moving the valve body along the axis in a direction toward or toward the valve hole, A flow rate setting unit for setting the flow rate of the liquid adjusted by the flow rate adjustment unit, A control unit controls the flow rate adjustment unit to perform a flow rate adjustment operation that moves the valve body to a target position that changes according to the flow rate difference between the measured flow rate and the set flow rate, so that the measured flow rate of the liquid measured by the ultrasonic flow rate measurement unit becomes the set flow rate. The ultrasonic flow measurement unit includes an abnormality detection unit that detects whether the ultrasonic flow measurement unit is in an abnormal state where it cannot perform the flow measurement operation due to bubbles present in the measurement channel, The control unit controls the flow rate adjustment unit to move the valve body a predetermined distance away from the valve hole and then stop it, in response to the abnormality detection unit detecting the abnormal state.

2. The flow rate adjustment device according to claim 1, wherein the control unit controls the flow rate adjustment unit to stop the execution of the flow rate adjustment operation when the abnormality detection unit detects that an abnormal state exists, and to start the execution of the flow rate adjustment operation when the abnormality detection unit detects that an abnormal state does not exist.

3. The flow rate adjustment device according to claim 1 or 2, wherein the control unit controls the flow rate adjustment unit such that the predetermined distance becomes longer the smaller the flow rate setting value set by the flow rate setting unit when the abnormality detection unit detects that an abnormal state exists.

4. The flow rate adjustment device according to claim 1 or 2, wherein the control unit controls the flow rate adjustment unit so that if the flow rate setting value set by the flow rate setting unit when the abnormality detection unit detects that an abnormal state is present is less than or equal to a predetermined value, the valve body is moved a predetermined distance away from the valve hole and then stopped, and if the flow rate setting value set by the flow rate setting unit when the abnormality detection unit detects that an abnormal state is present is greater than the predetermined value, the valve body is stopped without being moved away from the valve hole.

5. A control method for a flow rate adjustment device, The aforementioned flow rate adjustment device is An ultrasonic flow rate measuring unit performs a flow rate measurement operation that measures the flow rate of liquid flowing through a measurement channel based on the difference in propagation time of ultrasonic waves emitted by a pair of transducers positioned upstream and downstream of the measurement channel through which the liquid flows, A flow rate adjustment unit adjusts the flow rate of liquid flowing out of the measurement channel by moving the valve body along the axis in a direction toward or toward the valve hole, The system includes a flow rate setting unit for setting a set value for the flow rate of the liquid adjusted by the flow rate adjustment unit, A flow rate adjustment step involves controlling the flow rate adjustment unit to perform a flow rate adjustment operation that moves the valve body to a target position that fluctuates according to the flow rate difference between the measured flow rate and the set flow rate, so that the measured flow rate of the liquid measured by the ultrasonic flow rate measurement unit becomes the set flow rate value. An abnormality detection step for detecting whether the ultrasonic flow measurement unit is in an abnormal state where it cannot perform the flow measurement operation due to bubbles present in the measurement channel, A control method for a flow rate adjustment device, comprising: a bubble release step, which controls the flow rate adjustment unit to move the valve body a predetermined distance away from the valve hole and then stop it in response to the abnormality detection step detecting that the abnormal state is present.

6. The abnormality detection step includes a flow rate adjustment stop step that stops the execution of the flow rate adjustment operation in response to the detection of the abnormal state, The flow rate adjustment step is a control method for a flow rate adjustment device according to claim 5, wherein the flow rate adjustment step is initiated in response to the abnormality detection step detecting that the abnormal state is not present.

7. The control method for a flow rate adjustment device according to claim 5 or 6, wherein the bubble release step controls the flow rate adjustment unit such that the predetermined distance becomes longer the smaller the flow rate setting value set by the flow rate setting unit when the abnormality detection step detects that the abnormal state is present.

8. A control method for a flow rate adjustment device according to claim 5 or 6, wherein the bubble release step is stopped after moving the valve body a predetermined distance away from the valve hole if the flow rate setting value set by the flow rate setting unit when the abnormality detection step detects that an abnormal state is present is less than or equal to a predetermined value, and the flow rate adjustment unit is stopped without moving the valve body in the direction away from the valve hole if the flow rate setting value set by the flow rate setting unit when the abnormality detection step detects that an abnormal state is present is greater than the predetermined value.

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