JP2002062168A - Flow measurement system - Google Patents

Abstract

(57) [Summary] [Problem] To provide a flow rate measurement system capable of performing highly accurate abnormality detection. The present invention relates to a flow measurement system provided with a flow meter (5) for detecting a flow rate of a fluid on a pipe (2) through which the fluid is sucked by driving a pump (3). A predetermined number of density values are obtained based on the density signal, a difference value indicating a difference between the maximum value and the minimum value of these density values is obtained, and the difference value is compared with a first threshold value for a preset difference value test. At the same time, a predetermined number of the difference values are obtained, a ratio of the abnormal difference value exceeding the first threshold value in the predetermined number of the difference values is obtained, and the ratio is set to a predetermined second threshold value for the abnormality test. And a control means 10 for comparing with.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate measuring system used for measuring a flow rate of a fluid,
The present invention relates to a flow measurement system capable of detecting an abnormality occurring in a flow measurement system.

[0002]

2. Description of the Related Art A flow rate measuring system 1 'shown in FIG. 7 has been known for measuring the flow rate of gas, liquid, or the like flowing in a pipe. This flow rate measuring system 1 'is provided in, for example, a traveling milk collection vehicle that collects milk, which is an example of a fluid, stored in a milk storage tank around a dairy farm, and is connected to the milk storage tank. It has a pipeline 2 which is connected to the milk collection tank of the milk collection truck as much as possible and in which a pump 3, an air separator 4 and a flow meter 5 'are provided, and these are controlled by a control means 6. It is configured as follows.

The air separator 4 is for separating air bubbles mixed in milk, and is configured to separate and remove air bubbles from a fluid at a predetermined processing speed. The flow meter 5 'is a Coriolis mass flow meter that has been widely used recently. This Coriolis mass flowmeter is a well-known two-tube type provided with a vibrator that is provided to support both ends of a sensor tube through which a fluid flows and that applies vibration to a central portion of the sensor tube. This Coriolis mass flow meter
When a fluid is caused to flow through the vibrating sensor tube, the flow rate of the fluid is detected by detecting the occurrence of a vibration phase difference proportional to the mass flow rate at two symmetrical positions between the support portions at both ends and the central portion of the sensor tube due to the Coriolis force. Is configured to seek.

In the above-mentioned conventional flow rate measuring system 1 ',
When the pump 3 is operated and milk is sucked into the pipeline 2, first, air bubbles in the milk are separated and removed by the air separator 4. Thereafter, the milk passes through a flow meter 5 ', where the mass flow is measured.

[0005]

In the conventional flow rate measuring system 1 ', fine air bubbles cannot be removed by the air separator 4. In addition, cavitation (cavitation phenomenon) occurs due to the flow rate of milk in the pipeline, the shape of the pipeline, and the like, which also causes air bubbles in the fluid. On the other hand, the flow meter 5 'has such a characteristic that when bubbles exist in the fluid, the Coriolis force changes greatly due to the influence of the bubbles, and the vibration phase difference of the sensor tube increases. For this reason, if air bubbles are contained in the fluid, the flow rate detected by the flow meter 5 'becomes larger than the actual flow rate. However, conventionally, such an abnormality could not be detected.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a flow rate meter provided with a flow meter for detecting the flow rate of a fluid on a pipe through which the fluid is sucked by driving a pump. In the measurement system, a predetermined number of the first comparison basic data based on the measurement signal of the fluid output from the flow meter is obtained, a difference value between the maximum value and the minimum value of the comparison basic data is obtained, and the difference value is set in advance. And a predetermined number of the difference values are obtained, the number of abnormal difference values exceeding the first threshold value among the difference values is obtained, and a second comparison based on the number of the abnormal difference values is performed. Control means for comparing the basic data with a preset second threshold value is provided.

Preferably, the second comparison basic data is a ratio of an abnormal difference value in a predetermined number of difference values, and the control means determines whether or not the comparison result between the second comparison basic data and the second threshold value is equal. Preferably, the speed of the pump is changed accordingly. Further, the control means is configured to, when the speed of the pump is switched to the low speed, determine from the comparison result of the second comparison basic data and the second threshold value that an abnormality has occurred continuously a predetermined number of times. If the pump is further decelerated and the abnormality does not occur continuously for a predetermined number of times, the pump is switched to a high speed, or the second comparison basic data and the second If it is found from the comparison result with the threshold that the abnormality has occurred continuously for a predetermined number of times, the pump is stopped, and if no abnormality occurs continuously for a predetermined number of times, the pump is switched at a high speed. Is desirable.

[0008]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described with reference to FIGS. The same components as those of the flow rate measuring system 1 'introduced in the section of the related art are denoted by the same reference numerals, and the description thereof will be omitted. The fluid to be measured is milk as in the conventional example.

FIG. 1 shows a flow rate measuring system 1 according to the present invention.
The flow rate measuring system 1 comprises a pipeline 2, a pump 3, and an air separator 4, the outflow side of which is connected to a milk collection tank (not shown) of a traveling milk collection truck introduced in the conventional example. , A Coriolis mass flow meter 5 (hereinafter simply referred to as a flow meter 5), and a control means 10. In addition, a joint (not shown) that can be connected to a milk storage tank (not shown) provided to the dairy farmer is provided on the inflow side of the pipe line 2 in this flow rate measurement system.

The flow meter 5 in the flow measurement system 1 measures the mass flow rate according to the same principle as the flow meter 5 'described in the prior art, and the flow meter 5 is based on the frequency of the sensor tube. The flow rate of milk flowing through the sensor tube is calculated, the flow rate signal output unit 5a capable of outputting a flow rate signal corresponding thereto, and the density indicating the density of milk is calculated from the frequency of the sensor tube, and the density signal corresponding thereto is calculated. And a density signal output unit 5b capable of outputting the same. In the embodiment of the present invention, an example in which a density signal which is an example of a measurement signal output from the density signal output unit 5b of the flowmeter 5 is used for abnormality detection will be described.

The control means 10, as shown in FIG.
A control unit 11, a pump driving unit 12 for driving and controlling the pump 3, a display unit 13 for displaying various information such as abnormality information and a flow rate detected by the flow meter 5, and a density signal output from the flow meter 5 Storage unit 14 for storing density values, first and second threshold values, abnormality occurrence limit values, stability judgment values, various control programs, other various control parameters, and the like corresponding to.
Work start command signal, work end command signal, first and second
An operation unit 15 is provided for inputting information necessary for control such as a threshold value, an abnormality occurrence limit value, and a stability determination value.

The density signal output from the flow meter 5 is input to the control unit 11, and the control unit 11 calculates a density value as an example of the first comparison basic data described in the claims based on the density signal. Calculation is performed, and this is stored in the storage unit 14.
On the other hand, the storage unit 15 has a density value storage table T1 in which n density values can be registered, and always registers the latest n density values in this table T1. That is, the control unit 1
1 performs a process of replacing a new density value obtained for each control cycle with the oldest density value in the density value storage table T1 (the density value obtained in the nth previous control cycle). The first threshold value stored in the storage unit 14 is:
The first threshold value is set by the operator in advance from the operation unit, and an allowable value of a difference (hereinafter referred to as a difference value) between the maximum value and the minimum value of the n density values is set as the first threshold value. Is done.

In the storage unit 14, a comparison result storage table T2 is set in addition to the density value storage table T1. In the comparison result storage table T2, a predetermined number p of comparison results between the difference value ΔD obtained from the n density values stored in the density value storage table T1 and the first threshold value k can be registered. Always have the latest p comparison results R
Is stored. That is, the control unit 11 stores the new comparison result R obtained for each control cycle in the comparison result storage table T.
2 is replaced with the oldest comparison result data (comparison result obtained in the pth previous control cycle).
The above-mentioned second threshold value x is a ratio A (the first threshold value of the comparison result R determined to be abnormal when exceeding the first threshold value k in the p comparison results R stored in the comparison result storage table T2). Assuming that the number of comparison results R exceeding q is q, the ratio A = q /
p) is an allowable limit value, and the second threshold value x is set by an operator inputting from the operation unit 15 in advance. The p comparison results stored in the comparison result storage table T2 are digital data, and 1 is determined to be normal as a result of comparison with the first threshold k, and 0 is determined to be abnormal. expressed.

Further, the storage unit 14 stores an abnormality occurrence number storage area (not shown) in which the number of consecutive times determined as abnormal as a result of the comparison between the comparison result R and the second threshold value x can be stored as the number of consecutive abnormality occurrences. ) And a normal operation number storage area (not shown) capable of storing the number of continuous operations determined to be normal as the number of continuous normal operations.

Further, the control unit 11 is provided with the control unit shown in FIGS.
(S01) Wait for a work start command signal. (S02) A high-speed drive command signal is output to the pump drive unit 17. (The pump operates at high speed in steady state.) At this time, the timer starts at the same time. (S03) Wait until the timer expires. (S04) The density signal of the flow meter 5 is obtained to obtain a density value, and this density value is stored in the density value storage table T1 of the storage unit 14.
Write to. At this time, if n pieces of density data already exist in the table T1, the data is written by replacing the oldest density data. (S05) It is confirmed whether or not predetermined n density values are stored. If not, the process returns to (S04). (S06) The maximum value and the minimum value among the n density values are determined, and a difference value ΔD, which is the difference, is determined. (S07) The difference value ΔD is compared with the first threshold value k. ΔD
“1” if <k, and “0” if ΔD ≧ k
4 is written to the comparison result storage table T2. At this time, if p pieces of comparison result data already exist in the table T2, the data is replaced with the oldest comparison result data and written. (S08) It is confirmed whether or not predetermined p pieces of comparison result data are stored. If not, the process returns to (S04). (S09) The number (q) of “0” which is the comparison result regarded as abnormal among the p comparison result data is determined, and the ratio A = q / p is obtained. (S10) The ratio A is compared with the second threshold x. If A <x, the process jumps to (S17). (S11) The number of continuous normal operations, the number of continuous abnormal occurrences, and the abnormal occurrence limit value are read from the storage unit. (S12) The number of continuous normal operations is confirmed, and if this is "0", the routine jumps to (S14). (S13) The number of continuous normal operations is reset. (S14) One is added to the number of consecutive abnormal occurrences. (S15) The number of continuous abnormal occurrences is confirmed, and if this is not "1", the flow jumps to (S17). (S16) A low-speed drive command signal is output to the pump drive unit 12, and an abnormality occurrence display command signal is output to the display unit 13, and the process jumps to (S26). (S17) It is confirmed whether or not the number of consecutive abnormal occurrences does not exceed the abnormal occurrence limit value. If not exceeded, (S2
Jump to 6). (S18) A stop command signal is output to the pump drive unit 12, an abnormal stop display command signal is output to the display unit 13, and the process jumps to (S29). (S19) The number of continuous normal operations, the number of abnormal occurrences, and the stability determination value in the storage unit 14 are read. (S20) The number of continuous abnormal occurrences is confirmed, and if this is "0", the flow jumps to (S22). (S21) The number of continuous abnormal occurrences is reset. (S22) One is added to the number of continuous normal operations. (S23) When the number of continuous normal operations is “1”, (S2
Jump to 6) (S24) Check whether the number of continuous normal operations exceeds the stability judgment value. If not, the process jumps to (S26). (S25) A high-speed drive command signal is output to the pump drive unit 12. (S26) It is confirmed whether or not a work end command signal has been input. If not, jump to (S04). (S27) The flow rate measured by the flow meter 5 is read. (S28) A stop command signal is output to the pump drive unit 12, and a flow rate display command signal is output to the display unit 13. (S29) The density data and the comparison result data of each table T1 and T2 of the storage unit 14, the number of continuous normal operations and the number of continuous abnormal occurrences, the measured flow value of the flow meter 5, and the like are reset. (S30) End. The following control is performed. Section number indicating each section (number such as (S01) above)
Corresponds to the reference numerals in FIGS.

In the above flow rate measuring system, the pipe 2
Is connected to the milk storage tank of the dairy farmer, and when a work start command signal is input from the operation unit 17, the pump 3 is driven and controlled by the pump drive unit 12, and the milk enters the pipeline 2. Is inhaled. At the same time, the air separator 4 starts separation and removal of air bubbles in the flowing milk. At this time, timing of a timer (not shown) is started in synchronization with the start of the pump 3. This timer measures the time required until air bubbles in the pipe line 2 are removed by the air separator 4 and the flow signal of the flow meter 5 is stabilized to some extent.

When the timer expires, the control unit 11
Obtains the density signal of the flow meter, obtains the density value, and writes the density value in the density storage table of the storage unit 14. Since there are no n density values stored in the storage unit 14 at the beginning of the measurement, the control unit 11 repeats this density value acquisition processing until n density values are secured. In this case, since the calculation regarding the difference value, the comparison result, and the like is not performed, the cycle for acquiring the density value is shortened. As described above, since the density value can be acquired in a short cycle at first, fine control can be performed when the flow rate of milk in the pipeline 2 at the start of the flow rate measurement is in an unstable state.

When n density values D are obtained, the control unit 11
Calculates the difference between the maximum value and the minimum value of the _n density values D _{1 to} D _n as a difference value ΔD ₁ , and compares the difference value with a first threshold value k to obtain a comparison result R ₁ . The comparison result _{R 1} is
The data is written to the comparison result storage table T2 of the storage unit 14. At the beginning of the measurement, a predetermined number p
Since there are no comparisons, the control unit 11
The comparison between the difference value of the density value and the first threshold value k is repeated. That is, the control unit 11 acquires a new density value D _{n + 1} and replaces it with the density value D _{1 in the} storage unit 14. This allows
The density values stored in the storage unit 14 are density values D _{2 to} D _{n + 1}
N. Then, the control unit 11 obtains a difference value [Delta] D ₂ from the n-number of density values _D 2 _{to D n + 1,} performs a process of comparing this with a threshold value k. In this way, the n density values are sequentially updated, and each time the density value is updated, the difference values ΔD ₃ , ΔD
₄ ... ΔD _p are obtained and compared with the first threshold value k. The control unit 11 calculates the difference value ΔD for each control cycle.
And the first threshold value k is sequentially written into the comparison result storage table T2 of the storage unit 14.

[0019] Comparison result storage table T2 has been compared result storing in is p number, the control unit 11, the p number of comparison results R ₁ to R _p abnormal comparison result the number of data occupied in the q ratio A ₁ Then, this is compared with a second threshold value x. This ratio A
_{If 1} is smaller than the second threshold value x, the control unit 11 obtains a new density value D _{p + 1} and sets n including this density value D _{p + 1.}
New difference value ΔD from the density values D _{p to} D _{n + p−1
Find p + 1} . Then, this ΔD _{p + 1} and the first threshold value k
Replacing the oldest comparison result R ₁ of the comparison result storage table T2 the comparison result R _{p + 1} and. Thus, the comparison result storage table T2, the comparison result _R 2 _{to R p + 1} of p
Pieces of data will be stored. Control unit 11 obtains a new ratio A ₂ from the updated p number of comparison results, performs a process of comparing this with a second threshold value x. In this way, the ratios A ₃ , A ₄ ... Are sequentially obtained, and each is compared with the second threshold value x. In the embodiment of the present invention,
The aforementioned ratio A is an example of the second comparison basic data described in the claims.

When air bubbles are generated in milk due to cavitation or the like, the ratio A _m (the ratio A obtained in the m-th control cycle) becomes equal to or more than the second threshold value x. After switching the driving speed of the pump 3 to a low speed, the unit 11 outputs the next comparison result R as described above.
Get the _{p + m + 1,} comparing the ratio _{A m + 1} obtained therefrom with a second threshold value x. In this way, the ratio _{Am + 2} ,
When the ratio A becomes a value equal to or more than the second threshold value x for a predetermined number of consecutive times during the successive comparison of A _{m + 3} ...
While the driving of the pump 3 is stopped, the display unit 13 displays, for example, “cavitation does not disappear”
An error message such as "There is an error in the pipeline" is displayed. On the other hand, the ratio A continuously becomes the second threshold x
If it becomes smaller, that is, if the normal operation in which no abnormality occurs continues for a predetermined number of times, the drive of the pump 3 is switched at high speed and the steady operation is resumed.

As described above, the present flow rate measuring system 1
The abnormality occurrence rate calculated for each section, that is, the ratio A,
Is sequentially compared with a second threshold value x, and the pump 3
This is for switching the driving speed of. As described above, by sequentially comparing the ratio of each section with the second threshold, it is possible to identify whether the abnormality has occurred instantaneously or continuously based on a certain reference (second threshold). Therefore, highly accurate abnormality detection and pump speed control can be performed. Moreover, even after the drive of the pump 3 is switched to the low speed, the ratio A is compared with the second threshold value x, and the pump 3 is stopped or the pump 3
Since it is determined whether or not to return to a high speed, it is possible to identify whether or not the generation of bubbles due to cavitation or the like has stopped and to perform correct control.

In order to efficiently flow the fluid while realizing accurate flow rate measurement, it is preferable to supply the fluid in a limit region where cavitation does not occur.
The speed of the pump may be switched more finely in multiple stages according to the number of continuous abnormal occurrences and the number of continuous normal operations. In the above description, the case where the density value is obtained from the density signal of the flow meter is described. However, in addition to the density value, for example, a flow signal output from the flow signal output unit 5a of the flow meter is obtained, and the flow value is obtained from this. It is also possible to determine and use this flow rate value as an index for abnormality detection, and the effect obtained in such a case is the same.

[0023]

The flow rate measuring system according to the present invention calculates the difference (difference value) between the maximum value and the minimum value of a predetermined number n of density values output from the flow meter, and determines the difference value as a first threshold value. And a predetermined number p of this comparison result is obtained,
The ratio of q abnormalities in p is compared with a second threshold value. Thereby, for example, it becomes possible to identify whether the flow rate fluctuation when a small amount of air bubbles is mixed in the fluid due to the occurrence of cavitation or the like occurs instantaneously or continuously. High-precision abnormality detection can be performed, and accurate pump drive control can be performed. Therefore, the error between the measured flow rate and the actual flow rate is extremely small. Further, since the ratio of the number of abnormal difference values is used as the basic data for comparison with the second threshold value, for example, even if the setting value of the acquisition number n of the density value or the acquisition number p of the difference value is changed, the setting change of the second threshold value is performed. You don't have to. Therefore, there is an advantage that the number of setting items before the work of measuring the flow rate is reduced and work efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory diagram of a flow measurement system according to the present invention.

FIG. 2 is a flowchart showing a part of a control process of the flow rate measuring system according to the present invention.

FIG. 3 is a flowchart showing a part of a control process of the flow measurement system according to the present invention.

FIG. 4 is a flowchart showing a part of a control process of the flow rate measuring system according to the present invention.

FIG. 5 is a flowchart showing a part of a control process of the flow rate measuring system according to the present invention.

FIG. 6 is a flowchart showing a part of a control process of the flow measurement system according to the present invention.

FIG. 7 is a schematic explanatory view of a conventional flow measurement system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flow rate measurement system 2 Pipe line 3 Pump 4 Air separator 5 Coriolis mass flow meter 5a Flow rate signal output part 5b Density signal output part 10 Control means 11 Control part 12 Pump drive part 13 Display part 14 Storage part 15 Operation part

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B67D 5/08 B67D 5/08 A

Claims (5)

[Claims] 1. A flow measurement system having a flow meter for detecting a flow rate of a fluid on a pipe through which a fluid is sucked by driving a pump, wherein a first comparison basis based on a measurement signal of the fluid output from the flow meter. A predetermined number of data is obtained, a difference value between the maximum value and the minimum value of the comparison basic data is obtained, the difference value is compared with a first threshold value set in advance, and a predetermined number of the difference values are obtained. The number of abnormal difference values exceeding the first threshold value among the difference values is obtained, and the second based on the number of abnormal difference values is obtained.
A flow rate measuring system comprising a control unit for comparing comparison basic data with a second threshold value set in advance. 2. The flow measurement system according to claim 1, wherein the second comparison basic data is a ratio of an abnormal difference value in a predetermined number of difference values. 3. The flow rate measuring system according to claim 1, wherein the control means changes the speed of the pump in accordance with a result of comparison between the second comparison basic data and the second threshold value. 4. The control means recognizes that an abnormality has occurred continuously a predetermined number of times based on a comparison result between the second comparison basic data and the second threshold value in a state where the pump speed is switched to a low speed. 4. The flow measuring system according to claim 3, wherein the pump is further decelerated in the case, and the pump is switched to the high speed when no abnormality occurs continuously for a predetermined number of times. 5. The control means recognizes that an abnormality has occurred continuously a predetermined number of times from a comparison result between the second comparison basic data and the second threshold value in a state where the pump speed is switched to a low speed. 4. The flow measurement system according to claim 3, wherein the pump is stopped in the case, and the pump is switched at a high speed when no abnormality occurs continuously for a predetermined number of times.