JP4978994B2 - Electromagnetic flow meter - Google Patents

Description

  The present invention relates to an electromagnetic flowmeter that measures an integrated value of a flow of a fluid that is caused to flow in a pulsating manner by operation of a metering pump.

The electromagnetic flow meter is configured to apply a magnetic field to a fluid and measure a flow rate and a flow rate integrated value based on an induced voltage generated in the fluid (for example, see Patent Document 1). Therefore, a fluid (for example, foreign matter) that is not suitable for measurement by a flow meter having a movable part that contacts the fluid, such as an impeller flow meter (for example, see Patent Document 2) and a gear type flow meter (a positive displacement flow meter). It can also be used for fluids that can be mixed with crystals and crystals.
Japanese Patent No. 2568620 (Claim 1, FIG. 10) JP 2003-207377 A (paragraphs [0023], [0041] claim 1, FIG. 1)

  By the way, in general, in an electromagnetic flow meter, since the measured value of the flow rate is unstable when the fluid is stationary (the actual flow rate is zero), the average of the measured values of the flow rate in a predetermined period is set in advance. When it is less than the average reference value, the flow rate during the predetermined period is regarded as uniformly zero, and the flow rate integrated value is calculated (in other words, excluded from the flow rate integrated value).

  However, when the fluid flowing with the flow rate pulsatingly changed by the operation of a metering pump or the like is measured with a conventional electromagnetic flow meter having the above-described function, when the generation interval of the pulsating flow becomes long, a predetermined period In other words, the average of the measured values of the flow rate becomes lower than the average reference value, and the flow rate due to the pulsating flow generated during the predetermined period cannot be included in the integrated flow rate value. For this reason, the conventional electromagnetic flowmeter has not been suitable for measurement of fluid flowing with the flow rate changing pulsatingly.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electromagnetic flow meter suitable for measuring a flow integrated value of a fluid that is flowed with a pulsating change.

An electromagnetic flow meter according to the invention of claim 1 made to achieve the above object is an electromagnetic flow meter for measuring a flow integrated value of a fluid that is caused to flow in a pulsating manner by an operation of a metering pump. Thus, when the reference pulsation period and the reference peak value are preset and the flow rate exceeds the reference peak value, it is detected that there is a pulsating flow, and when the flow rate does not exceed the reference peak value, it is detected that there is no pulsating flow. When the generation interval of the pulsating flow detected by the detecting means and the pulsating flow detecting means is shorter than the reference pulsation period, it is determined that the metering pump is operating, and when longer than the reference pulsating period, the metering pump is operating. not equal and a working discriminating means for discriminating, the flow rate during inactive periods metering pump is determined to not being operated by the actuation determining means excluded from the flow accumulation value, a metering pump is in operation by the operation determination means Operating period determined as Having the characteristics, including the flow rate in the flow rate integrated value was equipped with a flow rate integrated value computing means for computing.

  It should be noted that the “flow rate” in the present invention is the volume of the fluid that has passed through a cross section per unit time, and the “flow integrated value” is the per unit time. It is a value obtained by integrating the passed volume over a certain period.

  The invention according to claim 2 is the electromagnetic flow meter according to claim 1, wherein an average reference value smaller than the reference peak value is set in advance, and the average value of the flow rate in a predetermined period is greater than or equal to the average reference value. Average flow rate determining means for determining whether or not the flow rate integrated value calculating means is determined by the operation determining means that the metering pump is not in operation, and the average flow rate determining means is determined to be in fluid flow. The present invention is characterized in that the calculation is performed by including the flow rate during the abnormal flow period in the integrated flow rate value.

  According to a third aspect of the present invention, in the electromagnetic flowmeter according to the second aspect, when it is determined that the metering pump is not in operation by the operation determining means and the fluid flow is determined by the average flow determining means. It has a feature in that it is provided with abnormality notifying means for notifying abnormality.

[Invention of Claim 1]
When the metering pump is actually operating, a pulsating flow whose flow rate exceeds the reference peak value is generated unless there is an abnormality, and the generation interval is shorter than the reference pulsation period. At this time, in the electromagnetic flow meter of the present invention, it is determined that the metering pump is in operation, and the flow rate during the operation period is included in the integrated flow rate. On the other hand, when the metering pump is stopped, the fluid is stationary as long as there is no abnormality, and the flow rate becomes substantially zero. That is, since the pulsating flow does not occur until the metering pump is actuated again, the pulsating flow generation interval becomes longer than the reference pulsation period. At this time, in the electromagnetic flow meter of the present invention, it is determined that the metering pump is not operating, and the flow rate during this non-operation period is excluded from the integrated flow rate. As described above, the electromagnetic flowmeter of the present invention does not include the flow rate during the period in which the flow rate is substantially zero in the integrated flow rate value, but the pulsating flow is generated at an interval shorter than the reference pulsation period. Since the flow rate during a certain period can be included in the integrated flow rate value, it is also suitable for measurement of the integrated flow rate value of fluid that flows by changing the flow rate in a pulsating manner.

[Invention of claim 2]
According to the invention of claim 2, when it is determined that the metering pump is not in operation, the average value of the flow rate during the predetermined period is compared with the average reference value. Determine that there is. The flow rate during the abnormal flow period is included in the integrated flow rate. That is, if it is determined that the fluid is actually flowing not only in the operation period in which it is determined that the metering pump is operating, but also in the flow rate during the non-operation period in which it is determined that the metering pump is not operating. The flow rate can be included in the integrated flow value. In other words, only the flow rate when it is determined that the metering pump is stopped and the fluid is stationary is excluded from the integrated flow rate. Thereby, for example, the flow rate when flowing due to a factor other than the operation of the metering pump or when the pulsating flow is less than the reference peak value due to an abnormality of the metering pump can be included in the integrated flow rate value, Accumulated leakage of the flow rate can be reliably prevented.

[Invention of claim 3]
According to invention of Claim 3, it becomes possible to respond early to the abnormal flow of fluid.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a chemical liquid mixing device 20. The chemical liquid mixing device 20 includes a feed pipe 16 and a feed water pump 17 for drawing water into the feed pipe 16 from a water storage tank (not shown). The water supply pump 17 is disposed at the end of the feed pipe 16 and can be driven and controlled by, for example, a water supply control unit 18. And the chemical | medical solution (for example, liquid fertilizer, agrochemicals, etc.) as "fluid" concerning the present invention is mixed with the water drawn into the feed pipe 16 by the feed water pump 17 at a predetermined mixing rate, and is fed to a predetermined location. Is done. In addition to liquid fertilizers and pesticides, chemicals include industrial chemicals and water treatment chemicals.

  For example, the water supply control unit 18 is provided with a timer function. When a predetermined time is reached, the water supply pump 17 is activated and continuously operated for a predetermined operation time Ton (for example, 20 to 30 minutes). Thereafter, the water supply pump 17 is stopped for a predetermined stop time Toff (for example, 20 to 30 minutes) (see FIG. 3A). Thereby, the start and stop of water supply are performed automatically. The operation time Ton and the stop time Toff of the water supply pump 17 can be arbitrarily set.

  The chemical liquid mixing apparatus 20 includes a chemical liquid tank 22 that stores the chemical liquid. A pipe line 23 extends from the bottom surface of the chemical liquid tank 22, and the tip of the pipe line 23 is connected to the feed pipe 16. A metering pump 24 is provided in the middle of the conduit 23.

  The metering pump 24 is, for example, a diaphragm type electromagnetic metering pump, and has a known structure commercially available from many manufacturers. The metering pump 24 operates intermittently according to the period during which the feed water pump 17 is continuously operated over the operation time Ton (20 to 30 minutes), and the feed water pump 17 is stopped over the stop time Toff. Stop intermittent operation according to the period. In other words, the metering pump 24 intermittently repeats a discharge operation for discharging a fixed amount of chemical liquid by reciprocation of the diaphragm in accordance with the operation of the water supply pump 17, and stops the discharge operation in accordance with the stop of the water supply pump 17. .

  As shown in FIG. 1, the chemical liquid mixing apparatus 20 is provided with a controller 26 for controlling the discharge timing of the chemical liquid by the metering pump 24. The controller 26 gives a discharge command signal R to the metering pump 24. As shown in FIGS. 3A and 3B, the discharge command signal R is always off and is switched on and off at a preset cycle T1 only during the operation period Ton of the water supply pump 17. Each time the discharge command signal R is switched from OFF to ON, a discharge operation is performed by the diaphragm, and a fixed amount of chemical solution is discharged from the metering pump 24 each time.

  As shown by the dotted lines in FIG. 3B and FIG. 3C, when the discharge command signal R is switched on and off with the operation of the water supply pump 17, the actual flow rate dSr of the chemical solution changes in a pulsating manner. (Pulsating flow is generated). Further, when the discharge command signal R is held off as the feed water pump 17 is stopped, the chemical liquid does not flow, so the actual flow rate dSr becomes zero and constant. Here, since the flow rate is obtained by multiplying the flow rate by the cross-sectional area of the flow path, the actual flow rate dSr and the actual flow rate Vr are shown in the same scale in FIG.

  Here, the delivery amount of the chemical solution by the metering pump 24 can be changed according to the magnitude of the reciprocating stroke amount of the diaphragm. It changes depending on the length. In FIG. 1, the controller 26 and the metering pump 24 are shown as separate devices. However, the controller 26 and the metering pump 24 may be integrated (for example, the metering pump 24 incorporates the controller 26). Of course.

  As described above, the metering pump 24 operates intermittently only when the feed water pump 17 is in continuous operation. Therefore, the controller 26 acquires a pump operation identification signal for identifying whether or not the water supply pump 17 is in continuous operation from the water supply control unit 18.

  The controller 26 determines a target value for the delivery amount of the chemical solution by the metering pump 24 according to a preset reference mixing ratio and the flow rate of water flowing through the feed pipe 16. In order to measure the flow rate of water, an electromagnetic flow meter 28 having a known structure is provided between the feed pipe 16 and a connection portion of the metering pump 24 connected to the discharge port and the feed water pump 17. Yes. The electromagnetic flow meter 28 measures both the flow rate of the water that has flowed when the water supply pump 17 is operated and its integrated value, and applies the measured value to the controller 26.

  Further, in order for the controller 26 to check whether or not the chemical solution according to the target delivery amount is being delivered by the metering pump 24, an electromagnetic flow meter according to the present invention is provided on the downstream side of the metering pump 24 in the conduit 23. 40 is provided.

  The electromagnetic flow meter 40 includes a measurement channel (not shown) communicating with the conduit 23, an electromagnetic coil (not shown) facing the measurement channel from the side, and a pair of electrodes (not shown) that contact the chemical solution in the measurement channel. And applying a magnetic field to the chemical liquid flowing through the measurement flow path, thereby detecting the induced voltage E generated in the chemical liquid. A CPU (not shown) provided in the electromagnetic flow meter 40 multiplies the induced voltage E by a predetermined constant to calculate the flow velocity V of the chemical solution, and multiplies the flow velocity V by the cross-sectional area A of the measurement flow path in the electromagnetic flow meter 40. The flow rate dS is calculated, and the flow rate dS is integrated to calculate the integrated flow rate value Q. The electromagnetic flow meter 40 gives the above-described flow rate dS and integrated flow rate Q to the controller 26.

  Here, FIG. 4A shows an example of a graph showing the time change of the flow rate dS calculated from the induced voltage E by the electromagnetic flow meter 40. FIG. 4B shows an example of a graph showing the change over time in the flow rate dS applied to the controller 26 by the electromagnetic flow meter 40. The value obtained by integrating the flow rate dS shown in FIG. 4B (the total area of the hatched portion in FIG. 4B) is the integrated flow value Q that the electromagnetic flow meter 40 gives to the controller 26.

  The CPU of the electromagnetic flow meter 40 repeatedly executes the calculation control program PG1 (corresponding to "flow rate integrated value calculation means" according to the present invention) shown in FIG. 2 at a predetermined cycle. When the calculation control program PG1 is executed, the flow velocity V and the flow rate dS are measured as described above (S1).

  Next, it is determined whether or not the metering pump 24 is operating based on the pulsating flow generation interval. That is, when the metering pump 24 is actually operating, unless there is an abnormality, the generation interval of the pulsating flow is shorter than the preset reference pulsation period Ls, and when the metering pump 24 is stopped, As long as there is no abnormality, the pulsation generation interval is longer than the reference pulsation period Ls.

  Therefore, in step S2, it is determined based on a timer or a counter whether or not a preset reference pulsation period Ls has elapsed since the previous pulsating flow was detected. If the reference pulsation period Ls has not been reached (NO in S2), it is determined that the metering pump 24 is in operation, and the measurement interval ΔT (the execution cycle of the calculation control program PG1) is added to the flow rate dS measured at that time. ) Is added to the integrated flow rate Q (S5).

  On the other hand, if the reference pulsation period Ls has elapsed since the previous detection of pulsating flow (YES in S2), it is determined whether or not the flow rate dS has exceeded a preset reference peak value PK1 (see FIG. 4A). Discriminate (S3).

  When the flow rate dS exceeds the reference peak value PK1 (YES in S3), that is, when a new pulsating flow is detected, as a pulsating flow detection process (S4), for example, a timer or counter is cleared to 0 Start timing. Then, a value obtained by multiplying the flow rate dS at that time by the measurement interval ΔT is added to the flow rate integrated value Q (S5).

  On the other hand, if the flow rate dS does not exceed the reference peak value PK1 in step S3 (NO in S3), that is, the next pulsating flow is detected even if the reference pulsation period Ls has elapsed since the previous pulsating flow detection. If not, it is determined that the metering pump 24 is not operating, and it is determined whether or not the chemical is flowing.

  Specifically, it is determined whether or not the average value AdS of the flow rate dS in a predetermined period (for example, from the previous pulsating flow detection to the present) exceeds a preset average reference value AV1 (S6). When the average value AdS of the flow rate dS is equal to or greater than the average reference value AV1 (YES in S6), the chemical solution is actually flowing although the metering pump 24 is not operating “during abnormal flow period” For example, abnormality notification (S7) is performed by a lamp or buzzer (not shown) provided in the electromagnetic flow meter 40. Then, a value obtained by multiplying the flow rate dS at that time by the measurement interval ΔT is added to the flow rate integrated value Q (S5).

  On the other hand, when the average value AdS of the flow rate dS is equal to or less than the preset average reference value AV1 (NO in S6), the chemical solution is not flowing and the flow rate dS is substantially “0”. Without including the flow rate dS at that time in the flow rate integrated value Q, the operation control program PG1 is immediately exited.

  Here, the set values Ls, PK1, and AV1 used in steps S2, S3, and S6 of the arithmetic control program PG1 are as follows. That is, the reference pulsation period Ls is set to a period sufficiently longer than the cycle T1 at which the discharge command signal R switches from off to on, for example. The reference peak value PK1 is set to a value smaller than the peak value of the pulsating flow rate dS that can be generated by the normal operation of the metering pump 24 (for example, a value obtained by multiplying the peak value by a coefficient less than “1”). ing. The average reference value AV1 is smaller than the reference peak value PK1. In the present embodiment, for example, a value smaller than the peak value of the pulsating flow rate dS generated when the diaphragm reciprocating stroke amount is minimized (for example, 30% of the maximum) (for example, the peak value is “0.5”). ”).

  In the present embodiment, the above-described step S3 constitutes the “pulsating flow detection means” according to the present invention, and the above-described steps S2 and S3 constitute the “operation determination means” according to the present invention. The “average flow rate discriminating means” according to the present invention is configured, and the “abnormality notifying means” according to the present invention is configured by the step S7, the lamp, and the buzzer.

  The configuration of the present embodiment is as described above. Next, the effect of this embodiment is demonstrated. The controller 26 recognizes whether or not the water supply pump 17 is in the operation period Ton based on the pump operation identification signal acquired from the water supply control unit 18. Then, during the operation period Ton of the water supply pump 17, the controller 26 switches the discharge command signal R on and off at a predetermined cycle T1 (see FIG. 3B). Each time the discharge command signal R is turned on, the diaphragm provided in the metering pump 24 performs a discharge operation, and a certain amount of chemical liquid flows through the pipe line 23 each time. As a result, the chemical solution is intermittently fed from the metering pump 24 through the electromagnetic flow meter 40 to the feed pipe 16 by a certain amount.

  The electromagnetic flow meter 40 applies a magnetic field to the chemical solution in order to measure the flow rate dS and the integrated flow rate Q of the chemical solution, and detects an induced voltage E generated in the chemical solution. Then, the flow rate dS is obtained based on the induced voltage E (S1 in FIG. 2), and the flow rate dS is integrated to obtain the flow rate integrated value Q (S5 in FIG. 2).

  Here, a noise voltage component is generally superimposed on the induced voltage E actually measured by the electromagnetic flow meter 40. Therefore, as shown in comparison with FIG. 3C, the noise voltage component is always present between the flow rate dS calculated from the induced voltage E and the actual flow rate dSr regardless of the magnitude of the flow rate dS. The resulting error dSc (= dS−dSr) occurs.

  On the other hand, in the electromagnetic flow meter 40 of the present embodiment, the flow rate dS when it is determined that the metering pump 24 is in operation (NO in step S2 of FIG. 2) is included in the integrated flow rate value Q without exception. The flow rate during the period (denoted by L1 in FIG. 4) when it is determined that the metering pump 24 is not operating (NO in S3 in FIG. 2) and the chemical is not flowing (NO in step S6 in FIG. 2). dS is not included in the integrated flow rate Q.

  That is, as the metering pump 24 stops, the flow rate dS calculated from the induced voltage E (noise voltage component) when the flow rate is substantially “0” is not included in the flow rate integrated value Q. Thereby, the flow volume integrated value Q of a chemical | medical solution can be measured accurately. Note that the flow rate dS during the period in which it is determined that the metering pump 34 is operating is included in the integrated flow rate Q even if the average value AdS is less than the average reference value AV1.

  Also, if for some reason, the state where the peak value of the pulsating flow is less than the reference peak value PK1, the metering pump 24 is not in operation even though the chemical solution is actually flowing intermittently. (YES in step S2, NO in step S3). However, if the chemical solution is actually flowing, the average value AdS of the flow rate dS increases correspondingly and becomes equal to or higher than the average reference value AV1. The flow rate dS during such an “abnormal flow period” is included in the integrated flow rate value Q even if it is determined that the metering pump 24 is not operating.

  As described above, the electromagnetic flow meter 40 of the present embodiment does not detect the next pulsating flow even after the reference pulsation period Ls has elapsed since the previous pulsating flow was detected by stopping the metering pump 24, and the flow rate was substantially reduced. The flow rate dS during the period determined to be zero is not included in the integrated flow rate Q, and the flow rate during the period when the metering pump 24 operates normally and the pulsation is generated at an interval shorter than the reference pulsation period Ls. Since dS is included in the integrated flow rate value Q, it is suitable for the measurement of the integrated flow rate value Q of the fluid that flows with the flow rate dS changing in a pulsating manner.

  Even if it is determined that the metering pump 24 is not operating, the flow rate dS during that period can be included in the flow rate integrated value Q if the chemical solution is actually flowing. In other words, out of the flow rate dS obtained from the induced voltage E, only the flow rate dS when the chemical solution is stationary due to the stop of the metering pump 24 (when the flow rate dS is substantially “0”) is used as the integrated flow rate value Q. To eliminate. Thereby, for example, the flow rate dS in the case of flowing due to unforeseen factors other than the operation of the metering pump 24, or in the case where the metering pump 24 is pulsating in a state of less than the reference peak value PK1 due to the abnormality of the metering pump 24, Q can be included, and the accumulated leakage of the flow rate dS can be reliably prevented.

  In addition, when it is determined that the metering pump 24 is not in operation and it is determined that the chemical liquid is flowing, the lamp or buzzer notifies that an abnormal flow is occurring. Can be dealt with early.

[Other Embodiments]
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.

  (1) In the above-described embodiment, the magnitude of the flow rate dS and the reference peak value PK1 is compared. However, the flow rate V and the predetermined reference peak value PK2 may be compared. Here, since the flow velocity V is included in the calculation formula (dS = A · V) for determining the flow rate dS, the configuration for comparing the flow velocity V with the predetermined reference peak value PK2 (= PK1 / A) is substantially the same. Is the same as the configuration comparing the flow rate dS and the reference peak value PK1. Therefore, the electromagnetic flow meter 40 configured to compare the flow velocity V with the predetermined reference peak PK2 value instead of the flow rate dS is also within the technical scope of the present invention.

  (2) In the above embodiment, the electromagnetic flow meter 40 is provided downstream of the metering pump 24. However, the electromagnetic flow meter 40 may be provided upstream of the metering pump 24.

  (3) In the above embodiment, when it is determined that the electromagnetic metering pump 24 is not operating and it is determined that the chemical solution is not flowing, the flow rate dS measured at that time is not included in the integrated flow value Q. However, if it is determined that the electromagnetic metering pump 24 is not in operation, the flow rate dS at that time is not included in the flow rate integrated value Q regardless of whether the chemical solution is flowing or not. You may do it.

  Specifically, as in the calculation control program PG2 shown in FIG. 5, the steps S6 and S7 in the calculation control program PG1 of the first embodiment are omitted, and the flow rate dS exceeds the preset reference peak value PK1. If it is determined that it is not (NO in S3), the calculation control program PG2 may be immediately exited without executing the integration process in step S5.

  (4) In the above embodiment, the flow rate dS during the period when the metering pump 24 is determined to be operating is included in the flow rate integrated value Q. The flow rate dS during the period when the flow rate dSr is zero may not be included in the integrated flow value Q. As a result, the flow rate integrated value Q can be measured with higher accuracy.

  (5) In the above embodiment, the diaphragm type electromagnetic metering pump is exemplified as an example of the “metering pump”, but the metering pump is not limited to the diaphragm type or the electromagnetic type, and other structures (for example, piston type) The metering pump may be used.

  (6) If the reference peak value PK1 is set to a value sufficiently smaller than the peak value of the flow rate dS of the pulsating flow generated when the reciprocating stroke amount of the diaphragm is minimized, for example, the metering pump As long as 24 is operating (as long as the metering pump 24 is stopped and the actual flow rate dSr does not become “0”), the flow rate dS is included in the flow rate integrated value Q and is calculated.

The conceptual diagram of the chemical | medical solution mixing apparatus which concerns on one Embodiment of this invention. Flow chart of calculation control program (A) A graph showing the operating state of the feed water pump, (B) a graph showing a change in the discharge command signal, (C) a graph showing a change in the flow rate calculated from the induced voltage and a change in the actual flow rate (A) Graph showing change in flow rate calculated from induced voltage, (B) Graph showing change in flow rate applied to controller Flowchart of calculation control program according to another embodiment (5)

Explanation of symbols

24 Metering pump 40 Electromagnetic flow meter AdS Flow average value AV1 Average reference value Ls Reference pulsation period PG1, PG2 Calculation control program (flow rate integrated value calculation means)
PK1 Reference peak value Q Flow rate integrated value dS Flow rate

Claims (3)

An electromagnetic flowmeter that measures the integrated value of the flow of fluid that is caused to flow pulsatically by the operation of a metering pump,
A reference pulsation period and a reference peak value are preset,
A pulsating flow detecting means for detecting the presence of pulsating flow when the flow rate exceeds the reference peak value, and detecting no pulsating flow when not exceeding the reference peak value ;
When the generation interval of the pulsating flow detected by the pulsating flow detecting means is shorter than the reference pulsation period, it is determined that the metering pump is in operation, and when longer than the reference pulsation period, the metering pump is operated. An operation determining means for determining that it is not in the middle ,
The operation period in which the flow rate during the non-operation period determined that the metering pump is not operating by the operation determining unit is excluded from the integrated flow value, and the metering pump is determined to be operating by the operation determining unit An electromagnetic flowmeter comprising flow integrated value calculation means for calculating the flow rate included in the integrated flow rate value. An average reference value smaller than the reference peak value is preset,
An average flow rate discriminating means for discriminating whether or not the average value of the flow rate in a predetermined period is in fluid flow that is equal to or greater than the average reference value;
The flow rate integrated value calculation means determines the flow rate during the abnormal flow period determined by the operation determination means that the metering pump is not operating and the average flow rate determination means determines that the fluid is flowing. The electromagnetic flow meter according to claim 1, wherein the electromagnetic flow meter is configured to perform calculation by including in the integrated flow rate value.   When the operation determining unit determines that the metering pump is not operating and the average flow rate determining unit determines that the fluid is flowing, the abnormality notifying unit is configured to notify an abnormality. The electromagnetic flow meter according to claim 2.

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