JPS5931724B2 - Pump operation number control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for controlling the number of pumps in operation, which controls the increase or decrease in the number of pumps in operation.

Conventionally, there has been a device of this type as shown in FIG.

FIG. 1 is a block diagram showing a case where five pumps are controlled. 1 is a liquid tank, 2a to 2e are pumps, 3a to 3e are discharge valves of each pump 2a to 2e, and each pump 2a is a corresponding one.
~2e is open during operation.

Reference numeral 4 denotes a pipe for introducing the liquid discharged by each of the pumps 2a to 2e, and 5 is a storage tank which temporarily stores the liquid discharged by the pumps 2a to 2e and has a function of adjusting the flow rate of the liquid to be delivered. have

6 is a pipe for distributing the liquid in the storage tank 5 to a demand destination, □ is a flow rate detector installed in the pipe 6 and detects the flow rate Q10 of the liquid distributed via this pipe 6, 8 is the above-mentioned storage A liquid level detector that detects the liquid level H in the tank 5; 9 a first ratio setter that multiplies the detected value H of the liquid level detector by 1 to a first correction ratio; 10 a flow rate detector T; A computation that compares the detected value Q of , and the value obtained by multiplying the correction ratio in the detected 15 value H of the liquid level detector 8 supplied from the ratio setting device 9 by 1 with H, and generates a signal corresponding to this value. The circuit 11 is a flow rate setting circuit that sets a target flow rate based on the output of this arithmetic circuit, and the reference numeral 12 is an operation command circuit that operates or stops the pumps 2a to 2e according to the set value of the flow rate setting circuit 11.

Next, the operation will be explained.

Generally, when controlling the number of a plurality of pumps, the amount is increased or decreased depending on the delivered flow rate.

25 That is, the ratio setting device 9 inputs the liquid level H in the storage tank 5 detected by the liquid level detector 8, and calculates -KIH if this is above the set liquid level, and H if it is below the set liquid level. circuit 1
Supply to 0.

The arithmetic circuit 10 receives the value -KIH supplied from the ratio setter 9.
Alternatively, the KIH 30 and the delivery flow rate Q of the storage tank 5 supplied from the flow rate detector 7 are input, and (Q-, H) or (Q+, H) is calculated. This calculated value is supplied to the flow rate setting circuit 11, whereby the flow rate setting circuit 11 sets a target flow rate and outputs it to the operation command circuit 12 (35). Further, the operation command ◆ circuit 12 controls the number of operating pumps 2a to 2e to increase or decrease according to the target flow rate of the flow rate setting circuit 11. Here, although the flow rate of the liquid delivered through the pipe 6 changes continuously, the discharge flow rate of the pumps 2a to 2e may change in stages due to the number control, or due to detection errors of the flow rate detector 7, etc. Therefore, the liquid level in the storage tank 5 fluctuates constantly.

However, as a function of the storage tank 5, it is desirable to always maintain a liquid level above a certain level, and overflow is also undesirable from the standpoint of effective use of the liquid. Therefore, as an example of maintaining the liquid level in the storage tank 5 within a predetermined range, in the case of FIG. If KlH is below the set liquid level, KlH is supplied to the arithmetic circuit 10, and further by the arithmetic circuit 10,
The above-mentioned -KlH or Kl is applied to the detected value Q of the flow rate detector 7.
By supplying the value in which H is added to the flow rate setting circuit 11, the liquid level H in the storage tank 5 can be added to the control signal based on the simple delivery flow rate Q.
The number of operating pumps 2a to 2e is controlled by the signal corrected by . In other words, if the liquid level H in the storage tank 5 is equal to or higher than the set liquid level, the output from the calculation circuit 1c (Q-KlH)
is smaller than the detection value Q of the flow rate detector 7, so the discharge flow rate of the liquid discharged from the pumps 2a to 2e is smaller than the delivery flow rate Q of the storage tank 5. Therefore, the liquid level in the storage tank 5 gradually decreases. Conversely, if the liquid level H in the storage tank 5 is below the set liquid level, the output from the arithmetic circuit 10 (Q+KlH)
is larger than the detected value Q of the flow rate detector 7, so the pump 2
The discharge flow rate of the liquid discharged from a to 2e is greater than the discharge flow rate Q of the storage tank 5.

Therefore, the liquid level in the storage tank 5 gradually rises. However, if the liquid level correction ratio K1 is made large, a hunting phenomenon will occur in which the liquid level oscillates around the 5-set liquid level, so it cannot be made very large.

Now, FIG. 2 is a diagram for explaining the case where the pumps 2a to 2e are controlled according to the delivery flow rate Q of the storage tank 5. An explanation will be added regarding the operation of the conventional device.

Now, while one pump is in operation, the delivered flow rate Q of the storage tank 5 increases, and the calculated value (Q-K,H) or (Q+KlH) of the arithmetic circuit 10 output to the flow rate setting circuit 11 becomes Qlll (Q
-KlH) or Qllk 4・(Q+KlH), the flow rate setting circuit 11 goes to the operation command circuit 12.
A setting signal for starting the second pump is output, and in response to this, the second pump is operated by the operation command circuit 12.

Accordingly, when the delivery flow rate Q of the storage tank 5 increases and the calculated value of the arithmetic circuit 10 increases to Q2l, the third pump is operated, and the calculated values of the arithmetic circuit 10 increase to Q3l, Q.
When the number increases to 4, the fourth and fifth pumps are operated.

Conversely, the delivered flow rate decreases and the calculated value of the calculation circuit 10 becomes Q4.
When the calculated value decreases from 1 to Q42, the operation command circuit 12 stops the 5th pump and changes the operation from 5 pumps to 4 pumps. When the calculated value decreases to Q32, the pumps 2a to 2a start operating 3 pumps, and so on. The number of 2e vehicles in operation will be reduced.

In this case, in order to prevent hunting when increasing or decreasing the number of operating pumps 2a to 2e, flow rate setting Ql for operation and stop is necessary.
1 to Q4l and Q2l to Q4l have hysteresis.

As described above, the number of pumps 2a to 2e in operation is controlled according to the distribution amount Q, but the above-mentioned conventional device has the following drawbacks.

That is, when the pumps 2a to 2e become inoperable due to a power outage, or when an abnormality occurs such as a failure of the pumps 2a to 2e, the liquid level in the storage tank 5 may drop abnormally.

When such an abnormality is restored, it is desirable to immediately raise the liquid level in the storage tank 5 to the set liquid level. However, in the conventional device described above, the correction ratio K1 based on the liquid level is kept small to prevent hunting, and as a result, it takes a long time to restore the liquid level in the storage tank 5 to the set level after an abnormality recovery. It had a drawback that made it expensive. This invention was made in view of the above-mentioned drawbacks of the conventional ones, and by detecting an abnormal drop in the liquid level in the storage tank 5 and increasing the correction ratio at this time, it is possible to improve the storage level after the abnormality is restored. The purpose is to quickly return the liquid level in the tank 5 to the set liquid level. FIG. 3 is a block diagram showing one embodiment of the present invention, and numerals 1 to 12 are similar to the conventional one shown in FIG.

In FIG. 3, reference numeral 13 inputs the liquid level H in the storage tank 5 detected by the liquid level detector 8, and the liquid level setting circuit 13b, which operates when the abnormal liquid level is below Ls (H<Ls), controls this liquid level. 13a is a normally-open contact that opens when the liquid level setting circuit 13 operates; 91 inputs the detected value H of the liquid level detector 8 by closing this contact 13a; A ratio setter that supplies K2H to the arithmetic circuit 10,
The correction ratio K2 of the ratio setter 91 is K1<K2 with respect to the first correction ratio K1 of the ratio setter 9.

In other words, the liquid level H in the storage tank 5 is higher than the abnormal liquid level Ls! In the above normal state, the liquid level setting circuit 13 does not operate and the contact 13b is closed. Therefore, the detected value of the liquid level detector 8 is supplied to the arithmetic circuit 10 via the ratio setting device 9, so that the pumps 2a to 2e are controlled in the same manner as the conventional device described above. Next, assume that an abnormality such as a power outage occurs while the pumps 2a to 2e are in operation, and the liquid level in the storage tank 5 falls below the abnormal liquid level Ls.

In this state, when the power outage is restored, the liquid level setting circuit 13
responds to the fact that the detected value H of the liquid level detector 8 is below the abnormal liquid level Ls, and opens the contact 13b and closes the circuit 13a.

Therefore, the detected value H of the liquid level detector 8 is input to the ratio setter 91, and K2H is supplied to the arithmetic circuit 10. Therefore, the calculation circuit 10 calculates (Q+K2H), and the flow rate setting circuit 11
Output to. Here, since the correction ratio K2 of the ratio setter 91 is considerably larger than the correction ratio K1 of the other ratio setters 9, the pumps 2a to 2e controlled by the output (Q+K2H) of the arithmetic circuit 10 The discharge flow rate is considerably higher than the delivery flow rate of the storage tank 5.

Therefore, the liquid level in the storage tank 5 will rise rapidly. Note that once the liquid level setting circuit 13 operates, it is effective to have a hysteresis characteristic that maintains the operating state until the liquid level in the storage tank 5 returns to a predetermined level without worrying about hunting or the like. .

In addition, in the above embodiment, when the liquid level in the storage tank 5 abnormally decreases, the liquid level correction ratio is changed to a large value, but the correction ratio of 3 or more is changed depending on the degree of abnormal decrease in the liquid level. It may be changed sequentially.

In addition, in the description of the above embodiment, the case where the liquid level in the storage tank 5 decreased to the abnormal liquid level Ls due to a power outage was explained.
For example, the liquid level is abnormal due to a failure of the pumps 2a to 2e.
Similar control can be expected when an abnormality occurs, such as when the value drops to s.

Furthermore, in the above embodiment, the case where five pumps are controlled is explained as an example, but it goes without saying that 2 to 4 pumps or 6 pumps are controlled.
It may be more than one.

As described above, according to the present invention, there is provided a flow rate detector that detects the delivered flow rate of a storage tank that temporarily stores liquid discharged from a plurality of pumps, and a detection value of the flow rate detector and a flow rate of the liquid in the storage tank. an arithmetic circuit that inputs a value obtained by multiplying the first correction ratio by a first correction ratio, and outputs a signal obtained by comparing these values; When the liquid level in the storage tank falls abnormally, a value obtained by multiplying the liquid level in the storage tank by a second correction ratio, which is considerably larger than the first correction ratio, is input to the calculation circuit. Therefore, even if the liquid level in the storage tank drops abnormally due to an abnormality such as a power outage, the liquid level in the storage tank can be quickly restored after the abnormality such as a power outage is restored.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional pump operation number control device, Fig. 2 is a diagram illustrating a case where the number of pumps is controlled, and Fig. 3 is a block diagram showing an embodiment of the present invention. 2a to 2e are pumps, 5 is a storage tank, 7 is a flow rate detector, 8 is a liquid level detector, 9 and 91 are ratio setters,
10 is a computing unit, 11 is a flow rate setting circuit, 12 is an operation command circuit, and 13 is a liquid level setting circuit.

Claims (1)

[Claims] 1. A flow rate detector that detects the delivered flow rate of a storage tank that temporarily stores liquid discharged from multiple pumps, and the detection value of this flow rate detector and the liquid level of the storage tank are multiplied by a first correction ratio. In a device for controlling the number of pumps in operation, the device includes an arithmetic circuit that inputs a value and outputs a signal obtained by comparing these values, and controls the number of the plurality of pumps in operation according to the output of the arithmetic circuit. , when the liquid level in the storage tank abnormally decreases, a value obtained by multiplying the liquid level in the storage tank by a second correction ratio is supplied to the calculation circuit, and the calculation circuit outputs the detected value of the flow rate detector; A device for controlling the number of pumps in operation, characterized in that a signal obtained by comparing the liquid level of the storage tank multiplied by a second correction ratio is output.