JP2008286761A - Piston prover - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To smooth the movements of a piston, make leaks hard to occur, and prevent errors from occurring in a fluid having a standard volume being fed to a flowmeter to be calibrated. <P>SOLUTION: The moving speed of the piston 2 is controlled in such a way that the differential pressure between the pressure of the fluid on the upstream side and the pressure of the fluid on the downstream side may be zero while the piston 2 passes through at least a measuring section A-B in a cylinder 1. The piston 2 thereby exhibits no resistance (noload) to the fluid and smoothly moves in the cylinder 1 to make leaks hard to occur and prevent errors from occurring in the fluid having a standard volume being fed to the flowmeter 10 to be calibrated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a piston prober suitable for use in calibration of a flow meter and inspection of measurement accuracy.

  Conventionally, a reference volume of fluid discharged from the cylinder while the piston moves a predetermined distance in the cylinder is sent to the flow meter to be calibrated (flow meter to be tested), and the reference volume of fluid sent to the flow meter to be calibrated There is known a single-tube type piston prober that compares a flow rate (reference flow rate) with a measured flow rate measured by a calibrated flow meter and calibrates a measured flow rate of the calibrated flow meter based on the comparison result.

  For example, Patent Document 1 shows a typical structure of the above-described single pipe type piston prober. In the piston prober shown in Patent Document 1, a water flow valve (poppet valve) is provided inside the piston. When non-calibration, the poppet valve is opened to allow fluid to pass, and during calibration, the poppet valve is closed to flow the fluid. The piston is moved in the direction, the fluid in the cylinder is discharged while the piston moves a predetermined distance, and this fluid is sent to the flowmeter to be calibrated as a reference volume fluid. After the calibration is completed, the piston is pulled back in the direction opposite to the fluid flow direction with the poppet valve opened.

  In addition, since such a piston prober can be directly inserted into a pipe line to test an electric or mechanical flow meter, it can correct an error from the reference volume flow rate even when the density or viscosity changes. Used for transaction and tank load management. In addition, it is used as a school standard for various flowmeter-side devices of mechanical and electrical types. For example, it is used as a calibration device for an electromagnetic flow meter, or as a standard for a water meter.

Japanese Examined Patent Publication No. 60-608 (refer to FIG. 2, FIG. 3, FIG. 3A, description on pages 5-6)

  However, in the piston prober disclosed in Patent Document 1, in order to reliably close the poppet valve inside the piston during the movement of the piston, the upstream side must be maintained to maintain a high pressure. As a result, the piston is braked, and the smooth movement of the piston is disturbed and the occurrence of leakage is likely to occur. The reference volume fluid sent to the flow meter to be calibrated (the flow meter to be tested) An error will occur.

  The present invention has been made in order to solve such problems. The object of the present invention is to make the movement of the piston smooth and to prevent the occurrence of leakage, and to provide a reference volume of fluid to be sent to the flow meter to be tested. An object of the present invention is to provide a piston prober in which no error occurs.

In order to achieve such an object, the present invention comprises a cylinder having a fluid inlet and outlet and a piston moving in the cylinder, the cylinder being filled with fluid and the inlet. The fluid discharged from the outlet while the piston moves from the start position to the end position of the metering section defined between the inlet and outlet in the cylinder in a state where the outlet and the outlet are not in communication. In the piston prober that sends the fluid as a reference volume fluid to the flow meter under test, the differential pressure measuring means for measuring the differential pressure between the fluid pressure upstream of the piston and the fluid pressure downstream of the piston, and the piston is a cylinder The moving speed control means for controlling the moving speed of the piston is provided so that the differential pressure measured by the differential pressure measuring means becomes zero during at least the passage of the measuring section.
According to the present invention, while the piston passes through the measuring section in the cylinder, the moving speed of the piston is controlled so that the differential pressure between the upstream fluid pressure and the downstream fluid pressure becomes zero. This makes the piston no-resistance (no load) against the fluid, makes the piston move smoothly in the cylinder, makes it difficult for leaks to occur, and causes an error in the reference volume fluid sent to the flow meter under test. It will not be.

In the present invention, in addition to the above-described differential pressure measuring means and moving speed control means, the fluid speed measuring means for measuring the speed of the fluid flowing into the cylinder, and the movement of the piston to the measuring section, You may make it provide the piston movement start means which starts the movement of a piston at the same speed as the present speed of the fluid which a speed measurement means measures. By providing such means, when the piston starts to move to the metering section, the moving speed becomes the same as the speed of the fluid that has been flowing in the cylinder until then, and the fluid suddenly changes in flow rate when the piston starts moving. It becomes possible not to generate.
Further, in the present invention, a moving speed increasing means for increasing the moving speed of the piston after the piston has passed through the measuring section may be provided. By providing such means, after the reference volume of fluid is sent to the flow meter to be tested, the moving speed of the piston is increased and the time required for calibration is shortened.

  According to the present invention, the piston is moved so that the differential pressure between the fluid pressure upstream of the piston and the fluid pressure downstream of the piston becomes zero while the piston passes at least the metering section in the cylinder. Since the speed is controlled, the piston has no resistance to the fluid, the piston moves smoothly in the cylinder, and the occurrence of leakage is less likely to occur. As a result, the calibration accuracy of the flow meter under test can be improved by preventing an error from occurring in the fluid of the reference volume sent to the flow meter under test.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a side sectional view showing an essential part of one embodiment of a piston prober according to the present invention.

  In FIG. 1, reference numeral 1 denotes a cylinder. The cylinder 1 includes a reference volume tube 1-1 including a measuring section AB, and a first volume attached to one end side opening 1a of the reference volume tube 1-1. The retraction chamber 1-2 and a second retraction chamber 1-3 attached to the other end side opening 1b of the reference volume tube 1-2 are configured.

  The first evacuation chamber 1-2 has a wider opening than the one end side opening 1a of the reference volume tube 1-1, that is, its inner diameter L1 (L1> L0) is larger than the inner diameter L0 of the reference volume tube 1-1. An internal space 1c is provided, and a fluid inflow port 1d communicating with the internal space 1c is provided in the first evacuation chamber 1-2.

  The second evacuation chamber 1-3 is wider than the opening 1b on the other end side of the reference volume tube 1-1, that is, its inner diameter L2 (L2> L0, L2) than the inner diameter L0 of the reference volume tube 1-1. = L1) has a large internal space 1e, and the second escape chamber 1-3 is provided with a fluid outlet 1f communicating with the internal space 1e.

  In the present embodiment, the first evacuation chamber 1-2 and the second evacuation chamber 1-3 are configured with the same material and the same structure, that is, the first evacuation chamber 1-2 and the second evacuation chamber. By using the chamber 1-3 as a common member, the types of parts are reduced, and management costs and manufacturing costs are reduced.

  A piston 2 moves in the cylinder 1. The piston 2 is fixed to a shaft 3 provided through the cylinder 1. The shaft 3 is pivotally supported so as to be slidable in the horizontal direction in the figure. The piston 2 moves integrally with the shaft 3 in the cylinder 1.

  In order to prevent fluid from flowing through the outer peripheral surface 2a of the piston 2 through the gap between the outer peripheral surface 2a and the inner peripheral surface of the cylinder 1 (inner peripheral surface of the reference volume tube 1-1) 1g. Rings (seal rings) 2-1 and 2-2 are mounted as seal portions. The rings 2-1 and 2-2 are attached back and forth at the center of the outer peripheral surface 2a of the piston 2.

  A servo motor 4 is connected to the shaft end of the shaft 3 through a mechanism such as a ball screw, a trapezoidal screw, a rack & pinion, or the like as an auxiliary drive device (auxiliary drive device). An encoder 5 for detecting the moving position of the piston 2 in the cylinder 1 is provided in the mechanism of the auxiliary drive device.

  The state of FIG. 1 shows a case where the piston 2 is located at the start end position ST defined on the inflow port 1d side with respect to the start position A of the measuring section AB in the cylinder 1. At the start end position ST, the portion of the piston 2 exposed from the one end side opening 1a of the reference volume tube 1-1 is located in the internal space 1c of the first retraction chamber 1-2, and between the piston 2 and the cylinder 1. A communication path H1 that connects the inflow port 1d and the outflow port 1f is formed. In the present embodiment, a notch (opening) 2b is formed in front of the outer peripheral surface 2a of the piston 2, and this notch 2b serves as a communication path H1 (FIG. 3A).

  FIG. 2 shows a case where the piston 2 is located at the end position END determined on the outlet 1f side from the end position B of the measuring section AB in the cylinder 1. FIG. At the end position END, the portion of the piston 2 exposed from the other end side opening 1b of the reference volume tube 1-1 is located in the internal space 1e of the second retreat chamber 1-3, and between the piston 2 and the cylinder 1. A communication path H2 that connects the inflow port 1d and the outflow port 1f is formed. In the present embodiment, a notch (opening) 2c is formed behind the outer peripheral surface 2a of the piston 2, and this notch 2c serves as a communication path H2 (see FIG. 3C).

  FIG. 4 shows a system configuration diagram of a flow rate calibration system using this piston prober. 1, the same reference numerals as those in FIG. 1 denote the same or equivalent components as those described with reference to FIG. 1, and the description thereof will be omitted.

  In FIG. 4, 6 is a tank, 7 is a pump that sucks up the fluid stored in the tank 6, 8 is a control valve for adjusting the flow rate of the fluid flowing from the pump 7 to the pipe, and 9 is the flow rate of the fluid flowing through the pipe. 10 is a flow meter to be calibrated, 11 is a first valve provided in the middle of a pipe P1 connecting the pump 7 and the inlet 1d of the cylinder 1, and 12 is an outlet 1f of the cylinder 1 and calibrated. A second valve 13 provided in the middle of the pipe P2 connecting the flow meter 10, a third valve 13 provided in the middle of the pipe P3 connecting the pump 7 and the outlet 1f of the cylinder 1, and 14 a cylinder 1 Is a fourth valve provided in the middle of the pipe P4 connecting the fluid inlet 1d and the fluid inlet to the flow meter 10 to be calibrated, between the fluid outlet of the flow meter 10 to be calibrated and the tank 6. Are connected by a pipe P5.

  15 is a control device, 16 is a sequencer, 17 is a servo amplifier, 18 is a clock generator for generating a reference clock, 19 is a fluid pressure in the first retreat chamber 1-2 of the cylinder 1 and a second retreat chamber 1-3. It is a differential pressure gauge which measures differential pressure (DELTA) P with an internal fluid pressure.

  In the present embodiment, a personal computer is used as the control device 15. The control device 15 and the servo amplifier 17 are connected via a sequencer 16, and the servo motor 4 is driven in accordance with a command from the control device 15 via the sequencer 16. The control device 15 is also connected to the encoder 5, the control valve 8, the monitor flow meter 9, the flow meter 10 to be calibrated, the valves 11 to 14, the clock generator 18, and the differential pressure gauge 19 via the sequencer 16. Instead of the clock generator 18, a frequency oscillator may be used.

  The control device 15 is realized by hardware including a processor and a storage device, and a program that realizes various functions in cooperation with the hardware. Specifically, a program is installed in the hard disk, and the processing operation of the CPU according to the installed program is realized. The hard disk stores a measurement flow rate calibration program for calibrating the measurement flow rate of the flow meter 10 to be calibrated as a program unique to the present embodiment.

  Hereinafter, processing operations executed by the CPU of the control device 15 in accordance with the measured flow rate calibration program will be described with reference to flowcharts shown in FIGS.

  In this embodiment, the main configuration of the piston prober is shown in FIG. 1, but the configuration of the piston prober includes a control device 15, a sequencer 16, a servo amplifier 17, a clock generator 18, a differential pressure gauge 19, and the like. Is also included. In practice, the CPU of the control device 15 executes the following processing operation via the sequencer 16, but the description will be given assuming that the control device 15 executes the following processing operation. In addition, the upstream pipe of the flow meter 10 to be calibrated is considered to have a piping length or straight pipe length considering flow stability according to the type and standard of the flow meter 10 to be calibrated.

[Before calibration]
Now, as a state before calibration, the pump 7 is in an operating state, and the control valve 8 is opened at a predetermined opening degree. Further, it is assumed that the control device 15 opens the valves 11 and 12 and closes the valves 13 and 14. In addition, the piston 2 in the cylinder 1 is assumed to be located in the first retreat chamber 1-2 at a portion exposed from the reference volume tube 1-1. FIG. 4 shows this state.

  In this case, the flow rate of the fluid sucked up from the tank 6 by the pump 7 is reduced by the control valve 8 and sent to the inlet 1d of the cylinder 1 through the valve 11 (pipe P1). The fluid flowing in from the inlet 1d of the cylinder 1 passes through the notch 2b in front of the outer peripheral surface 2a of the piston 2 (see FIG. 3A), passes through the reference volume pipe 1-1, and flows into the downstream outlet 1f. It flows to. The fluid that flows out from the outlet 1f passes through the valve 12 (pipe P2), is sent to the flow meter 10 to be calibrated, passes through the flow meter 10 to be calibrated, and is returned to the tank 6. As a result, a normal fluid flow to the flowmeter 10 to be calibrated is created as a state before calibration.

[Calibration on the outward trip]
Upon receiving an instruction to start calibration from the operator (FIG. 6: YES in step 101), the control device 15 sets the set flow rate to QS (step 102), and uses the flow rate QR of the current fluid flowing through the pipeline as the monitor flow rate. A total of 9 is measured, and the opening degree of the control valve 8 is controlled so that the flow rate QR becomes the set flow rate QS (steps 103 to 105). In this embodiment, the monitor flow meter 9 is provided on the upstream side of the cylinder 1, but may be provided on the downstream side.

  If the flow rate QR becomes the set flow rate QS (YES in step 105), the set flow rate QS is divided by the effective sectional area S of the piston 2 to obtain the velocity Vp of the fluid in the reference volume tube 1-1 (step 106). The rotation speed N of the servo motor 4 is set so that the moving speed of the piston 2 becomes Vp (step 107). That is, the current velocity Vp of the fluid flowing in the reference volume tube 1-1 is obtained, and this velocity Vp is set as the initial velocity of the piston 2.

  Then, an operation start command is sent to the servo motor 4 (step 108), and the piston 2 is advanced at the initial speed Vp. As the piston 2 advances, the piston 2 enters the reference volume tube 1-1 of the cylinder 1, and the notch 2b in front of the outer peripheral surface 2a of the piston 2 is blocked by the inner peripheral surface of the reference volume tube 1-1. Thereby, the inflow port 1d and the outflow port 1f of the cylinder 1 are brought into a non-communication state in a state where the fluid is filled in the cylinder 1.

  When the notch 2b of the outer peripheral surface 2a of the piston 2 is closed, the fluid from the inflow port 1d does not flow to the downstream side of the piston 2, but presses the upstream side of the piston 2 to move the piston 2 to the downstream side. The fluid in the cylinder 1 is discharged from the outlet 1f. At this time, since the moving speed of the piston 2 is the same as the speed Vp of the fluid that has been flowing in the reference volume tube 1-1 until then, the piston 2 receives the pressure of the fluid from the inlet 1d and suddenly moves to the fluid. It smoothly enters the reference volume tube 1-1 without causing a flow rate change. Further, the shape of the notch 2b gives a characteristic to a change in the passage area of the fluid accompanying the movement of the piston 2, and a rapid flow rate change that occurs when the piston 2 starts to move and closes the reference volume tube 1-1. Alleviated.

  During the movement of the piston 2, the fluid tends to flow through the gap between the outer peripheral surface 2a of the piston 2 and the inner peripheral surface 1g of the reference volume tube 1-1. This fluid flow is blocked by the rings 2-1 and 2-2 attached to the outer peripheral surface 2 a of the piston 2. In other words, out of the rings 2-1 and 2-2 attached to the center of the outer peripheral surface 2a of the piston 2, the outlet 1f in the reference volume pipe 1-1 is attached by the ring 2-1 attached to the front. Is prevented from flowing from the inlet to the inlet 1d side, and the fluid 2-2 is attached to the rear side from the inlet 1d in the reference volume tube 1-1 to the outlet 1f. Is blocked.

  When the movement position of the piston 2 reaches the seal position S1 (YES in Step 109), that is, when both the rings 2-1 and 2-2 start to act as seal portions, the control device 15 causes the cylinder from the differential pressure gauge 19 to The pressure difference ΔP between the fluid pressure in the first first retracting chamber 1-2 and the fluid pressure in the second retracting chamber 1-3 is checked (FIG. 7: step 110). The rotational speed N of the servo motor 4 is adjusted so as to be (step 111). As a result, the piston 2 moves in a state of no resistance (no load) with respect to the fluid, and the piston 2 moves smoothly in the cylinder 1 so that leakage does not easily occur.

  When the movement position of the piston 2 reaches the start position A of the measuring section A-B in the cylinder 1 (YES in step 112, see FIG. 3B), the control device 15 sends the reference clock from the clock generator 18. Is started (step 113). Thereby, measurement of the elapsed time TC after the piston 2 reaches the start position A of the measuring section AB in the cylinder 1 is started. Further, simultaneously with the start of the measurement of the elapsed time TC, the control device 15 starts counting pulses (flow rate signals) corresponding to the flow rate of the fluid passing from the calibration flow meter 10 (step 114). The reference clock from the clock generator 18 is started with the pulse of the flow meter to be calibrated as a trigger.

  When the movement position of the piston 2 reaches the end position B of the measuring section AB in the cylinder 1 (YES in step 115), the control device 15 causes the piston 2 to move from the start position A to the end position B of the measuring section AB. The flow rate of the fluid discharged from the outlet 1f during the movement is set as the reference volume fluid, and the flow rate of the reference volume fluid is calculated as the reference flow rate QC (step 116). Further, the measured flow rate QV with respect to the reference flow rate QC in the calibrated flow meter 10 is calculated from the count value of the flow rate signal transmitted from the calibrated flow meter 10 (step 117).

  Then, the reference flow rate QC is divided by the elapsed time TC therebetween to obtain an average reference flow rate Qc (Qc = QC / TC) (step 118), and the measured flow rate QV is divided by the elapsed time TC between them to obtain the average measured flow rate Qv. (Qv = QV / TC) is obtained (step 119), and the average reference flow rate Qc is compared with the average measured flow rate Qv (FIG. 8: step 120).

  Here, if Qc = Qv (YES in step 120), the control device 15 determines that no error has occurred in the measured flow rate QV, and displays that fact on the display (step 121). , Go to step 124.

  On the other hand, if Qc ≠ Qv (NO in step 120), an error amount is obtained as Qc−Qv = ΔQc (step 122), and this error amount ΔQc is set in the calibrated flow meter 10 as correction information for the measured flow rate. (Step 123), the process proceeds to step 124.

  In step 124, the control device 15 increases the rotation speed N of the servo motor 4 to the rotation speed Nmax. When the piston 2 reaches the end position END in the cylinder 1 (YES in step 125), an operation stop command is sent to the servo motor 4 to stop the movement of the piston 2 (step 126). As a result, the piston 2 moves at a high speed to the end position END in the cylinder 1 after passing through the measuring section A-B, thereby shortening the time required for calibration.

  The piston 2 has a portion exposed from the reference volume tube 1-1 at the end position END in the cylinder 1 positioned in the second retreat chamber 1-3 (see FIG. 3C). In this case, the fluid flowing in from the inlet 1d of the cylinder 1 and flowing in the reference volume pipe 1-1 passes through the notch 2c behind the outer peripheral surface 2a of the piston 2 and flows to the downstream outlet 1f. Go. The fluid that flows out from the outlet 1f passes through the valve 12 (pipe P2), is sent to the flow meter 10 to be calibrated, passes through the flow meter 10 to be calibrated, and is returned to the tank 6.

  In the above description, the measuring section AB in the cylinder 1 is selected so that the pulse (flow rate pulse) generated by the flow meter 10 to be calibrated is the measured flow rate (flow velocity) at the time of measurement, and is 10000 pulses or more in that section. It is good to use. This time measurement is preferably performed by a so-called pulse interpolation method.

[Calibration on the return trip]
When receiving the next calibration start instruction from the operator (YES in step 127), the control device 15 closes the valves 11 and 12, opens the valves 13 and 14, and the flow path between the cylinder 1 and the flow meter 10 to be calibrated. Are switched (step 128). As a result, as shown in FIG. 5, the outlet 1f of the cylinder 1 serves as an inlet, and the inlet 1d serves as an outlet. Hereinafter, the outlet 1f is the inlet, the inlet 1d is the outlet, the end position END is the start position, the start position ST is the end position, the end position B of the measurement section AB is the start position, and the start of the measurement section AB Position A is called the end position.

  In this case, the flow of the fluid sucked up from the tank 6 by the pump 7 is throttled by the control valve 8 and sent to the inlet 1 f of the cylinder 1 through the valve 13 (pipe P3). At this time, the portion of the piston 2 in the cylinder 1 exposed from the reference volume tube 1-1 is located in the second retreat chamber 1-3.

  As a result, the fluid flowing in from the inlet 1f of the cylinder 1 passes through the notch 2c in front of the outer peripheral surface 2a of the piston 2, passes through the reference volume pipe 1-1, and flows to the downstream outlet 1d. . The fluid exiting from the outlet 1d passes through the valve 14 (pipe P4), is sent to the flow meter 10 to be calibrated, passes through the flow meter 10 to be calibrated, and is returned to the tank 6.

  Thereafter, the control device 15 sets the set flow rate to QS (FIG. 6: step 102), measures the flow rate QR of the current fluid flowing through the pipeline with the monitor flow meter 9, and this flow rate QR is set to the set flow rate QS. Thus, the opening degree of the control valve 8 is controlled (steps 103 to 105).

  If the flow rate QR becomes the set flow rate QS (YES in step 105), the set flow rate QS is divided by the effective sectional area S of the piston 2 to obtain the velocity Vp of the fluid in the reference volume tube 1-1 (step 106). The rotation speed N of the servo motor 4 is set so that the moving speed of the piston 2 becomes Vp (step 107). Then, an operation start command is sent to the servo motor 4 (step 108), and the piston 2 is moved backward at the speed Vp.

  Thereafter, the piston 2 moves to the end position END (steps 108 to 128), that is, moves to the first start position ST in the same way as in the case of calibration in the forward path, during which the average reference flow rate in the measuring section AB is measured. Qc and average measured flow rate Qv are obtained (steps 118 and 119), and when Qc ≠ Qv (YES in step 120), Qc−Qv = ΔQc is set in the calibrated flow meter 10 as correction information for the measured flow rate. (Step 123).

  In this example, it is described that the next calibration start instruction is received from the operator in step 127. However, it is possible to set whether the calibration is only for the forward path or the calibration for the forward path and the return path. In the case of calibration in which the forward path and the backward path are combined, the processing after step 128 may be automatically executed.

  As can be seen from the above description, according to the present embodiment, the notches 2b and 2c formed in the outer peripheral surface 2a of the piston 2 serve as poppet valves. As a result, the poppet valve inside the piston, which is necessary for the piston prober of Patent Document 1, can be eliminated, the structure can be simplified, and the cost can be reduced. In addition, the number of seals can be reduced to make it difficult for leaks to occur and to improve reliability.

  Further, in the present embodiment, since the piston 2 is fixed to the shaft 3, the movement position of the piston 2 can be controlled so that the reference volume can be measured at the same position in the cylinder 1 at any time. it can. On the other hand, in the thing using the poppet valve shown by patent document 1, the piston is not restrained by the rod for position detection, but is in an idle state. In this case, if the position of the poppet valve is changed when the poppet valve is closed, the measuring pipe moves in a different position, and the shape error of the measuring pipe causes repeatability uncertainties. In the present embodiment, since the reference volume can always be measured at the same position in the cylinder 1, such an uncertainty does not occur.

  In the present embodiment, the cutouts (openings) 2b and 2c have a shape close to a rectangle. However, the notches (openings) 2b and 2c have a semicircular shape as shown in FIG. 9A or a triangular shape as shown in FIG. 9B. Or a stepped shape as shown in FIG. 9 (c), a semi-circular shape as shown in FIG. 9 (d), or a through hole as shown in FIG. 9 (e). May be. Such a change in shape gives a characteristic to a change in the passage area of the fluid accompanying the movement of the piston 2, and mitigates a rapid flow rate change that occurs when the piston 2 starts moving and closes the reference volume tube 1-1. The flow control characteristics can be made freely.

  In the present embodiment, the cylinder 1 has a structure in which the first evacuation chamber 1-2 and the second evacuation chamber 1-3 are attached to the openings at both ends of the reference volume tube 1-1. An integrated tube structure may be used. In the case of an integrated structure, for example, three chambers (a reference volume tube, a first evacuation chamber, and a second evacuation chamber) of the cylinder 1 are manufactured by all processing, and the end surface is closed with a mirror plate. As in the present embodiment, the reference volume tube 1 has a structure in which the first evacuation chamber 1-2 and the second evacuation chamber 1-3 are attached to the openings at both ends of the reference volume tube 1-1. The outer diameter of -1 can be reduced, that is, the thickness of the reference volume tube 1-1 can be reduced to reduce the weight.

  Further, in the present embodiment, the piston 2 is electrically stopped at the start end position ST and the end position END in the cylinder 1, but the start end position ST and the end position END are provided by providing a locking member or the like. The piston 2 may be mechanically stopped. That is, the means for restricting the movement of the piston 2 at the start end position ST or the end position END in the cylinder 1 may be a means for electrically stopping at that position, or a means for mechanically stopping at that position. There may be.

  Moreover, in this Embodiment, although the to-be-calibrated flowmeter 10 was provided in the most downstream side in the piping through which the fluid flows, you may make it provide in the upstream of piping. For example, it is provided immediately after the monitor flow meter 9 and before the valves 11 and 13. When the flow meter 10 to be calibrated is provided on the upstream side of the pipe, the fluid that has passed through the flow meter 10 to be calibrated is sent to the cylinder 1, but the fluid of the reference volume discharged from the cylinder 1 is the flow meter 10 to be calibrated. There is no change in being sent to.

  In the present embodiment, the flow meter to be calibrated is described as one, but a configuration in which a plurality of flow meters to be calibrated are connected in series may be used. In this case, if the flow rate measurement ranges (ranges) of the flow meters to be calibrated connected in series are the same, the flow rate signals are individually taken from the flow meters to be calibrated and the end position from the start position ST of the piston 2 is obtained. By moving to END, the flow rate calibration for all the flow meters to be calibrated can be performed at a time by the same processing as described above.

  When the flowmeter to be calibrated is a combination having a different range, the metering may be performed in different sections of the cylinder 1. The data to be measured at this time may be obtained by communicating with the flow meter to be calibrated from the control device 15 or obtained by reading the value of the multi-channel counter provided in the sequencer 16 from the channel.

  In addition, when a single flow meter to be calibrated has a plurality of range settings, it is only necessary to perform measurement in an appropriate measurement section after changing the settings by communication. In this case, since one cylinder 1 is provided, the order of measurement may be determined in advance in order to perform all measurements in a short time.

  In the present embodiment, the monitor flow meter 9 is provided to determine the initial speed of the piston 2, but the accuracy of the monitor flow meter 9 may not be so high. That is, if necessary, the monitor flow meter 9 can be corrected (calibrated) with a piston prober, so the accuracy of the monitor flow meter 9 may be low.

  In the present embodiment, the differential pressure ΔP between the fluid pressure in the first retracting chamber 1-2 of the cylinder 1 and the fluid pressure in the second retracting chamber 1-3 is measured by the differential pressure gauge 19. However, a first pressure gauge that measures the fluid pressure in the first evacuation chamber 1-2 and a second pressure gauge that measures the fluid pressure in the second evacuation chamber 1-3 are provided. The measured values of the first and second pressure gauges may be sent to the control device 15, and the control device 15 may determine the differential pressure ΔP.

  Further, the pressure difference between the fluid pressure in the first evacuation chamber 1-2 and the fluid pressure in the second evacuation chamber 1-3 is not necessarily measured as the differential pressure ΔP. The pressure difference between the fluid pressure inside and the fluid pressure in the downstream pipe may be measured as the differential pressure ΔP.

  In this embodiment, the notches 2b and 2c are formed before and after the outer peripheral surface 2a of the piston 2, but only the notches 2b may be formed. For example, when the control method is such that after the piston 2 passes through the measuring section A-B in the cylinder 1 and the flow direction of the fluid is switched halfway to return the piston 2 to the start position ST, the outer periphery of the piston 2 It is possible to omit the notch 2c of the surface 2a and make only the notch 2b.

  Moreover, in this Embodiment, although the flow path between the cylinder 1 and the to-be-configured flowmeter 10 was switched by opening and closing the valves 11-14 provided in piping, for example, the tank 6 and the to-be-calibrated flowmeter 10 A second pump may be provided between the two, and the fluid may be caused to flow in the reverse direction by the second pump. Further, a valve for switching between the outflow path and the inflow path may be provided on the tank 6 side so that the fluid flows in the opposite direction.

  In this embodiment, the inflow port 1d and the outflow port 1f are provided on the axial end surfaces of the first retraction chamber 1-2 and the second retraction chamber 1-3, but the first retraction chamber You may make it provide the inflow port 1d and the outflow port 1f in the upper surface and lower surface of 1-2 and the 2nd retraction | saving room 1-3. Further, by providing an appropriate taper at the end of the reference volume tube 1-1, it is possible to easily make the structure such that the rings 2-1 and 2-2 attached to the piston 2 are not damaged.

  Further, in this embodiment, the notches 2a and 2b are provided in the piston 2, but such notches need not necessarily be provided in the piston 2. For example, as shown in FIGS. 10A and 10B, the piston 2 ′ not having the notches 2a and 2b is stopped at a position completely removed from the reference volume tube 1-1, and the piston 2 generated in this case is stopped. A communication gap H1 or H2 may be used as a clearance between the reference volume tube 1-1 and the reference volume tube 1-1 to allow communication between the inlet 1d and the outlet 1f.

  Further, in the present embodiment, the flow rate calibration of the flow meter 10 to be calibrated is performed, but the measurement accuracy of the flow meter 10 to be calibrated may be inspected. When the measurement accuracy is inspected, the flow meter to be calibrated is a flow meter to be tested. In the present invention, the flow meter including the flow meter to be calibrated and the flow meter to be tested is called the flow meter to be tested. In the present invention, correction information for performing flow rate calibration and information including measurement accuracy are referred to as verification information.

  Further, in the present embodiment, since the measurement can be performed in the forward, reverse, and both directions, the piston 2 is provided with rings (seal rings) 2-1 and 2-2, and two positions (seal positions) ). In this case, strictly speaking, the volumes of different sections are moved in the forward direction and the reverse direction. In order to correct this, the same measurement interval is used by starting and ending the time measurement by correcting the measurement start and END positions on the seal position difference and control device 15. can do. If a single seal ring is used, such a problem does not occur.

It is a sectional side view which shows the principal part (when a piston is located in a starting end position) of one Embodiment of the piston prober which concerns on this invention. It is a sectional side view which shows the principal part (when a piston is located in the terminal position) of one Embodiment of the piston prober which concerns on this invention. It is a figure which shows the flow of the fluid in case a piston moves from the starting end position in a cylinder to an end position. It is a system configuration figure (when a piston is located in a starting end position) of a flow rate calibration system using this piston prober. It is a system configuration figure (when a piston is located in a termination position) of a flow rate calibration system using this piston prober. It is a flowchart which shows the processing operation according to the measurement flow volume calibration program which this control device of a piston prober performs. It is a flowchart following FIG. It is a flowchart following FIG. It is a figure which shows the other example of the notch (opening) formed in the outer peripheral surface of a piston. It is a figure which shows the example which made it stop in the position which removed the piston completely from the reference | standard volume pipe | tube.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Cylinder, 1-1 ... Reference | standard volume tube, 1-2 ... 1st evacuation chamber, 1-3 ... 2nd evacuation chamber, 1a ... One end side opening, 1b ... Other end side opening, 1c ... Internal space, 1d ... inlet, 1e ... inside space, 1f ... outlet, 1g ... inner peripheral surface, 2,2 '... piston, 2a ... outer peripheral surface, 2b, 2c ... notch, 2-1, 2-2 ... ring (seal 3) Shaft, 4 ... Servo motor, 5 ... Encoder, 6 ... Tank, 7 ... Pump, 8 ... Control valve, 9 ... Monitor flow meter, 10 ... Flow meter to be calibrated, 11 ... First valve, 12 2nd valve, 13th valve, 14th valve, 15 control device, 16 sequencer, 17 servo amplifier, 18 clock generator, 19 differential pressure gauge, P1 to P5, piping, ST: Start position, S1: Seal position, AB: Weighing section, END: End position, 1, H2 ... communication passage.

Claims (3)

A cylinder having a fluid inlet and outlet and a piston moving in the cylinder, the cylinder is filled with fluid, and the inlet and outlet are not in communication. In this state, the fluid discharged from the outlet during the movement of the piston from the start position to the end position of the metering section defined between the inlet and the outlet in the cylinder is covered as a reference volume fluid. In the piston prober to send to the test flow meter,
Differential pressure measuring means for measuring the differential pressure between the fluid pressure upstream of the piston and the fluid pressure downstream of the piston;
A moving speed control means for controlling the moving speed of the piston so that the differential pressure measured by the differential pressure measuring means becomes zero while the piston passes at least the measuring section in the cylinder. A characteristic piston prover. The piston prober according to claim 1, wherein
Fluid velocity measuring means for measuring the velocity of the fluid flowing into the cylinder;
A piston movement start means for starting the movement of the piston at a speed substantially the same as the current speed of the fluid measured by the fluid speed measurement means when the movement of the piston to the measuring section is started. Piston prober characterized by In the piston prober according to claim 1 or 2,
A piston prober comprising: a moving speed increasing means for increasing a moving speed of the piston after the piston has passed through the measuring section.

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