JPS59200094A - Liquid supply system - Google Patents

Abstract

PURPOSE:To make it possible to control operation of a pump, by conducting a probing operation when a pump operational speed reaches a predetermined low speed, and stopping operation of the pump when a pump discharge pressure is changed to a specific relation in an area of too little amount of water in the pump, then detecting the two little amount of water. CONSTITUTION:Normally, a variable speed operation of a pump 4 is conducted under a known feed-back control. When a demand amount of water is decreased at night for example, and an operational speed of the pump 4 reaches a low speed in the range of the variable speed operation, the operational speed of the pump 4 is experimentally accelerated or decelerated to a minute extent to conduct a probing operation. When a pressure change at start of the probing operation is in a specific relation in an area of too little amount of water of the pump, that is, difference between a target pressure H0 and a pressure H in a water feed pipe 10 is zero, the demand amount of water is judged to be too little, and an operation stop signal is outputted to stop the operation of the pump 4. After stoppage of the pump 4, when the pressure in the water feed pipe 10 is decreased to a pump start pressure, the pump is restarted. Thusly, a stable operation of the pump may be controlled.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a liquid supply device using a variable speed pump, and is particularly effective when switching from pump speed control operation to intermittent operation at night when the amount of water used is small. The present invention relates to a liquid supply device equipped with a control device.

[Background of the invention]

Conventionally, in order to reduce operating power costs and save energy, the operating speed of the pump and motor is changed according to the amount of water used to control the pump discharge pressure at a constant level. When this occurs, the pump speed control operation is switched to intermittent operation, and the pump is stopped when it is not needed. This method will be explained with reference to FIGS. 1 and 2. Figure 1 is a configuration diagram of the pump device.
1 is a water tank, 2 is a suction pipe, 31.32 is a gate valve, 4 is a pump, 5 is a motor that drives the pump 4, 6 is a check valve, 7 is a pressure tank, 8 is a water supply pipe with a pressure of 1° A pressure sensor detects the pressure and generates an electric signal in accordance with the pressure sensor, 9 is a flow rate switch disposed on the water supply pipe 1o, and 11 is a water faucet at the end.

FIG. 2 is a diagram showing the operating characteristics of the primary pump device, with the water amount Q being plotted on the horizontal axis and the pressure H being plotted on the vertical axis. In the same figure, Ho
is the discharge target pressure of the pump, which is set by the control device (not shown). Qmin is the insufficient amount of water to stop the pump, generally 10j/mn
That's about it. In addition, curve a shows the Q-H performance when the pump operating speed is the maximum speed Nmx, and the following surfaces s'b and c
, a, and e are stepless continuous control, but the pump operating speed is changed to intermediate stages Nho, N2, N, and 8.
The Q-H performance when taken into mouth is shown. Further, the curve f shows the QH performance when the pump is stopped by detecting insufficient water iQ. The flow rate sensor 9 shown in FIG. 1 emits a signal when it detects an insufficient amount of water Q= as shown in FIG.
- In FIG. 2, the water supply is sent to the water faucet 11 at the end via the water supply pipe 10 by the operation of the pump 4. At this time, a control device (not shown) changes the operating speeds of the pump motors 4 and 5 in response to fluctuations in the amount of water used, and continues operation while keeping the discharge pressure of the pump 4 constant. That is, the water supply pipe 10
The pressure H is detected by a pressure sensor and compared with a predetermined target pressure H6, and the operating speed of the pump motor 4ψ5 is controlled so that the difference matches.

For example, if the amount of water used decreases from Q to Qro, the operating speed will decrease from Nmax to 8, and the insufficient water amount QII
When the flow rate reaches Im, the flow rate sensor 9 detects this and stops the pump motor A5. In addition, pump/motor 4/5
The restart occurs when the pressure sensor 8 detects a pressure a,7 slightly lower than the target pressure H8.

However, the above conventional techniques have the following problems. In other words, if the flow rate sensor 9 is clogged with water scale or the output part is rusted due to moisture, etc., an extremely serious problem arises in that the insufficient water amount Qim cannot be detected, the pump motor does not stop, and power is wasted. There is a possibility that this may occur. Furthermore, if the pump is not stopped when the amount of water used is low, the pump will run in a closed state, resulting in overheating inside the pump and the risk of damaging the casing.

As a method of solving these problems, it is possible to stop the pump motor when the operating speed of the pump motor reaches the minimum speed IJm without using a flow rate sensor that is not reliable enough. However, with this method, if the water absorption level of the water receiving tank 1 decreases or the characteristics of the KJ:repump deteriorate, such as by wear of the sliding parts of the pump, the minimum Q-H performance will decrease as shown by the curve G shown in Figure 3. When constant discharge pressure control is performed, the actual operating speed does not fall below 1irnix, making it impossible to detect the lowest speed N=, which again causes the same problem as the pump motor not stopping. remain.

[Purpose of the invention]

The purpose of the present invention is to have a self-judgment function that always determines the appropriate minimum speed of 1L without using the flow rate sensor signal when the amount of water used is low, such as at night, and stops the pump motor extremely reliably. It is an object of the present invention to provide a liquid supply device equipped with an operation control device for a variable speed pump that can be operated at different speeds.

[Summary of the invention]

That is, the present invention includes a pump, variable speed drive means for driving the pump, a liquid supply pipe connected to the discharge side of the pump, and a pressure sensor connected to the liquid supply pipe, and Controls the variable speed operation of the variable speed drive means to maintain the pressure at the target pressure. By performing a search operation that changes the operating speed, and by providing a control device that stops the pump operation when the change in discharge pressure due to the search operation shows characteristics peculiar to the pump's low water flow region,
The present invention aims to provide a liquid supply device that allows the necessary pump operation to proceed without the need for a flow rate sensor.

[Embodiments of the invention]

The present invention will be explained in detail below. FIG. 4 shows the basic process flow of the embodiment, and normally the pump is operated at a variable speed by controlling the discharge pressure to be constant or by controlling the end pressure to be constant by conventionally known feedback control. If the water demand decreases at night, etc., and the pump operating speed remains at a low speed within the town speed volatile range, the pump operating speed will be slightly accelerated or decelerated on a trial basis to perform a search operation. When the pressure changes before and after the start of operation are in a relationship specific to the pump's low water volume region, it is determined that the required water volume is very small, and an operation stop signal is output to stop the pump's operation. Of course, after the pump is stopped, when the pressure in the water supply pipe drops to the pump starting pressure, the pump is started again and variable speed operation is performed.

Here, the pressure change specific to the low water flow area is a phenomenon in which the width of the pressure change or the rate of pressure change becomes less than a predetermined value when the pump operating speed is increased or decreased due to search operation, or If the pipeline system is equipped with a check valve and a pressure tank, the determination is made by detecting the phenomenon in which the pressure does not drop when the pump operating speed is reduced or stopped through search operation.

Next, specific examples will be explained with reference to FIGS. 1, 3, 5 to 8. Since the overall configuration of the pump device is the same as that already explained in FIG. 1, the explanation will be omitted here. FIG. 5 shows the control device of the embodiment, where MOB is the breaker for the main circuit, MO is the coil of the electromagnetic contactor, MCa is the contact point, and MV is the variable for changing the rotation speed of the variable speed mode 9. Frequency inverter device (Although an inverter device is used in this embodiment, primary voltage control, eddy current coupling, or other variable speed control devices may be used as a means for changing the rotational speed of the drive mode of the pump 4). TH is a thermal relay for overload prevention, and μcon is a central processing unit. PU (hereinafter referred to as AU
, abbreviated),)-ey □)
A microcomputer consisting of M, power supply terminal E, input/output boat P Aa@P Equation At) P Equation AC8P Equation Ad, FI is equipped with an A/D converter and inputs the signal detected by the pressure sensor 8. An interface for reading the speed command signal from the microcomputer to the input terminal of the inverter NV, DS is an interface for reading it into the microcomputer μcon through the output port P, There is a DIP switch that sets the speed, and from here the same minimum speed is set by the microcomputer μ via the input/output boat P.
Load it into con. Y is transformer T, power supply unit z,
Start, stop switch SB, magnetic contactor MO.

This is a control circuit consisting of a transistor Tr and a relay X. The base of the transistor Tr is connected to the input/output board PIAc (8b) of the microcomputer μcon.
For example, it is connected by the nuo bit and the signal ff1JA of it), and when the -40 bit becomes 1,
The transistor Tr becomes conductive and the relay X is energized. Further, FIG. 6 is a diagram explaining in detail the relationship between the dip switch DB and the input/output port PIAd, and rO to r7 are resistors. In the figure, each bit b of the dip switch Ds. By arbitrarily setting ~b, it is possible to set the lowest speed data (converted to binary numbers and coded). Then, this data is read into the microcomputer μQOn. In the control circuit Y, turn on the breaker MOB and turn on the start/stop switch S.
When S is closed, stable rectified and smoothed power is supplied to the microcomputer μ from the power supply unit z via the transformer T.
The signal is sent to the power terminal E of the con, and the preparation for operation is completed.

FIGS. 7 and 8 are flowcharts showing the control procedure of the operation control device.

To explain in more detail with reference to these drawings, the memory M of the microcomputer μcon is shown in FIG.

A program is included so that the pump device can be operated according to the flowchart shown in FIG. That is, these initial values are set in one step as follows.

Memo IJMO (ROM): Inputs the data of the low speed Ns for starting the search operation for determining insufficient water volume.

Memo+)M, (RAIA)...Secure the data area for the initial speed N1n when starting the pump.

Memo IJM, (RAM)...Secures a data area for the minimum speed N during normal variable speed operation of the pump.

Memory M, (RoM) --- Maximum pump speed N
Store rmx data.

Memory M4 (R?5 M)...stores the data of speed Nst when the pump/motor is stopped O Memory M, (RAM)...--Secures the data area for the pump operation command speed Nx .

Memo IJM, (RUM)...Inputs data in order of lower limit value NL of the speed change range of the speed change control means.

Memory M. (RmM)...--Store the data of target pressure H8.

Memory M,, (RnM)... Pressure at restart H7
Store data.

Memory M+t (ROM)...Stores the ON data of the magnetic contactor MO (01 (16).

Note that the relationship between each set operating speed is selected as follows.

N L=riN=<NS(:N 1nfiN stAlso,
A small water flow area QB is set with some margin given to the detected low water flow area q.

Low water flow area q Low water flow area Qe<Normal operation area Furthermore,
After loading the initial pump speed Nin data into the secured memory M1, set the delay switch D in a few steps.
Read the data of the minimum speed H= set by S,
Secured memory M.

Write to (RAM). Then, in step 4.5, data O' (+a) is output from input/output boat P,
The transistor Tr and the relay X are energized to turn on the electromagnetic contactor MO. Next, 6.7
,.

In the step, the data of the initial speed Nin stored in the memory M1 is sent from the input/output boat P to the speed input terminal of the inverter device NV via the ink face F. Thus, the pump motor 4.5 has an initial speed Nin
Start driving. Next, the microcomputer μcan
stores the initial velocity N in in the memory M8 in 8 steps, and then executes the next 9-step instruction. That is, the pressure signal detected by the pressure sensor 8 is transferred to the interface F1.
and loads it into the A register. Also, 10
In the step, the target pressure H8 stored in the memory MIO is
The data is transferred to the B register, and the data in both registers are compared in step 11. As a result of the comparison, if the two are equal, the pressure in the water supply pipe 10 is at the target pressure H6, so the process proceeds to step 12 without performing the speed change process. However, if the pressure signal detected by the pressure sensor 8 is greater than the target pressure H8, the speed must be reduced, so the process proceeds to steps 16 and onward, and in steps 16 to 15, the current operating speed is set to the lower limit of the shift range. pLm
Determine whether the speed has reached m, and if the speed has not reached st, execute the 16th to 18th step command and subtract the operating speed width equivalent to 1 bit of the resolution of the control system from the current operating speed. 〇Specifically, pump/motor 4/5
The binary speed data of M! is decremented once and used as new speed data, and this driving speed data is stored in memory M! Store in. After this, in step 20, a waiting time t corresponding to the delay time necessary for the pump motors 4 and 5 to complete the speed change operation is executed based on the new speed command, and the process returns to step 9 again, where the pressure sensor 8 This loop process for deceleration is performed until the detected pressure H matches the target pressure H6. As a result of the 15-step determination, if the operating speed has reached the lower limit value NL= of the shift range, the system jumps 20 steps and performs the subsequent processing. If, on the other hand, it is determined in step 11 that the pressure detected by pressure sensor 8 is lower than the target pressure H6, the process proceeds to step 19, where the deceleration process described above is performed in exactly the opposite way, and the pump is turned off. The speed increases by an operating speed width corresponding to 1 bit of resolution of the control system.

As the amount of water used decreases, the deceleration process continues and the next 21
．． In step 22, it is determined whether the current operating speed has reached the speed Ns corresponding to the small water flow range QB shown in Fig. 3. If the speed has not been reached yet, the process returns to step 9 and the subsequent processing is repeated. Continue, and if it is judged that the target pressure H8 and water supply pipe 1 have been reached, in steps 23 to 27,
Find the difference H6-H between the pressure H within 0 and determine whether this difference is 0. If the result of the determination is not 0, the process returns to step 9 and the subsequent processing continues. 28-33 if 0
Execute the step command and perform search operation. That is,
Decrement the binary data of the current operating speed 6 to 5 times. Try to reduce the operating speed of the pump 4 by a small amount. Therefore, N for 28 steps should be approximately 6 to 5 times. It is determined in the next 34 steps whether the pressure relationship before and after the start of the search operation in steps 28 to 33 is unique to the low water flow region of the pump. In the embodiment, since the check valve 6 is connected to the water supply pipe 10 between the pressure tank 7 and the pump 4, the pressure in the pipe downstream of the check valve 6 is maintained by the action K of the pressure tank 7. Even if the operating speed of the pump is reduced, if the pump is operated in the insufficient water flow region q, the pressure inside the pipe will not decrease. Further, even if there is a decrease, it is extremely small and can be easily distinguished from the normal operating range. That is, if the difference between the target pressure H8 and the pressure H in the water supply pipe 10 is 0 in step 34, it can be determined that the pump 4 is operating in the insufficient water flow region q.

Furthermore, in steps '55 to 59, once again the pressure difference H8
It is determined whether -H is 0, and if it is not 0, the process returns to step 9 again and the subsequent processing instructions are executed. If it is 0, it is determined that the amount of water used is stable and in the insufficient water amount area as described above, so take the memo 'JM' in the next 40 steps.
The speed Hz before the search operation, which is stored in 11, is transferred to the memory M2 as the true minimum speed Nm and updated, and after driving for a certain period of time t at this true minimum speed Nm1x,
In steps 45 to 45, the operating speed is increased by the stop speed NθtJ, the discharge pressure is increased to the restart pressure H1 or higher, water is stored in the pressure tank 7, and steps 47 to 48 are executed. The pump moders 4 and 5 are stopped by outputting an operation stop signal through the machine AC.

After pump 4 is stopped, execute the following 49 steps and record the discharge pressure H detected by the pressure sensor and a memo')
The restart pressure H7 stored in Mu is constantly compared, and when it is determined that the discharge pressure H has fallen below the restart pressure H7, the process from step 4 onwards is performed again, and the pump 4 is returned to the initial speed. It will be restarted at Nin.

In addition, in the embodiment, the pressure difference between the target pressure H8 and the pressure H in the water supply pipe was calculated in steps 35 to 39 as one criterion for stopping the pump 4;
By checking whether the pressure H within 0 has reached the target pressure H8, it can be determined that the operation is in a stable low water amount region q.

According to such a water supply device, an insufficient amount of water can be detected and the busy pump can be reliably stopped without using a flow rate sensor.

In the above example, when the operating speed of the pump became lower than the predetermined low speed N8, a search operation was performed to determine whether there was an insufficient amount of water. Since it is necessary to set the low speed N8, some effort is required for the initial setting. Further, after installing the water supply device, if there is a change in the water supply system or a change in the water suction conditions of the pump, it is necessary to set the low speed NO again to continue proper pump operation. FIG. 9 shows an improved embodiment that solves these difficulties. This embodiment is an improvement of 27 steps from the 23 steps of the embodiment explained in FIGS. 7 and 8, and is a low speed No.
The variable speed operation of the pump is continued even when the operating speed is below, and when the operating speed of the pump stops changing, the system is configured to shift to search operation. This example will be explained in detail below. First, after clearing the D register in step 100, data of current discharge pressure H1 and target pressure H8 are read into registers A and B in step IQ1 and 102, and both data are compared in step 103. If it is determined from this comparison that the discharge pressure H exceeds the target pressure Ho, steps 104 to 109 are performed, and the pump is decelerated in the same manner as described in steps 13 to 18 in FIG. 7.

Conversely, if the discharge pressure H is less than the target pressure H8, 11
After processing one step or less, the speed of the pump is increased. After this speed increase processing, in steps 112 and 113, the data of the low speed N days is loaded into the B register, and compared with the new operating speed after the speed increase processing in the A register, it is determined that the new operating speed is the low speed N.
If the EI is exceeded, follow the steps 9 already explained in Figure 7.
Continue processing below the step. Also, 103
When it is determined that the measured pressures H6 and H are equal in the step, and the value T or more corresponds to a predetermined time (approximately several minutes), the process of 28 steps or less as explained in FIG. 8 is performed and a search operation is performed. . In addition, after performing increase/decrease processing,
11Q, 11! Clear the D register to 0 in step,
Also, if the number T has not been reached in 116 steps,
After executing the waiting time t in the next 117 steps, IQ1
Execute the following process again.

In this way, the pump speed is balanced in the low demand water area (
By detecting the lowest speed (no longer changing), if you set the low speed N8 as a tentative guide to detecting the possibility of insufficient water flow, it will not be affected by changes in the water supply system or changes in discharge pressure. , the pump can always be run to its lowest speed. Also, after configuring like this,
By recording the state of change in the minimum speed Nm, the operating state of the pump can be grasped to some extent. In other words, if the minimum speed increases, the water level on the suction side of the pump will drop, the pump will deteriorate, or there will be water leakage in the pipe system, and if the minimum speed decreases, the water level on the suction side will rise. therefore,
By detecting such changes, it is possible to issue alarms for maintenance and inspection of the water supply system.

Now, in the above-mentioned embodiment, the search operation for detecting an insufficient amount of water was carried out by lowering the operating speed of the pump by a certain amount, but the present invention is also capable of increasing or decreasing the operating speed of the pump, or An example can be considered in which the operation of the vehicle is stopped.

In other words, as can be seen from the pump load curve, the pressure change on the discharge side of the pump due to a change in pump operating speed increases as the discharge flow rate increases. A memory device is installed to store the relationship between the change in discharge pressure and the change in discharge pressure, which is obtained by actual measurement or calculation in advance, and a search operation is performed when the pump operating speed falls below a predetermined low speed N8. The water supply device can be configured to compare the pressure change with a value stored in advance in the storage device, and when the pressure change is less than this value, it is determined that the pump is being operated with an insufficient amount of water, and the pump is stopped. In this embodiment, when the search operation is performed by reducing the operating speed of the pump, a check valve provided in the pipeline system to prevent backflow is preferably provided on the upstream side of the pump.

Also, if the pump is operating in the small water flow area Q, s,
Since the pressure drop on the discharge side is gradual even when the pump is stopped, this characteristic can be used to calculate the degree of pressure drop when the pump is operated to the low water flow region q and then stopped, or the pressure drop within a certain range. Prepare a memory device that measures and stores the time required for the pump to wake up in advance, perform a search operation in which the pump is stopped when the operating speed of the pump falls below a predetermined low speed N8, and measure the pressure drop caused by this search operation. The degree of pressure drop or the time until a certain range of pressure drop occurs is measured, and these values are compared with pre-stored memorized values to determine whether the amount of water is too low. Based on this result, the pump can be stopped or The water supply device may also be configured to select restart.

Now, in the embodiment already explained, after comparing the target pressure and discharge pressure, the pump operating speed is increased or decreased by the speed corresponding to the minimum resolution of the control system. Of course, it is also possible to directly change the speed by a speed width corresponding to the difference between the two. With such a configuration, the responsiveness of the control system to sudden changes in the amount of water demand improves.

Further, in the embodiment, a pressure sensor that can obtain a variable output according to pressure changes has been described, but the present invention
It can also be realized by a combination of pressure switches from which the 'N-0FF signal can be obtained. Furthermore, in the example, the minimum speed was determined based on the same operating speed continuing for a certain period of time below the low speed Ns. can also be detected.

〔Effect of the invention〕

As is clear from the above description, the present invention is a liquid supply device equipped with a variable speed pump, and when the operating speed of the pump reaches a predetermined low speed, the operating speed of the pump is varied to perform a search operation. According to the present invention, there is provided a liquid supply device that is equipped with a control device that stops operation of the pump when the change in discharge pressure due to this search operation becomes a change specific to the low water flow region of the pump. The amount of water can be detected reliably and the operation of the pump can be controlled.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the configuration of a liquid supply device, FIG. 2 is an operating characteristic diagram for explaining a conventional liquid supply device, and FIG. 3 is a diagram for explaining one embodiment of the present invention. FIG. 4 is a flowchart for explaining the basic control operation of the present invention, FIGS. 5 and 5 are block diagrams for explaining the configuration of the control device of the embodiment, and FIG. 7 and 8 are flowcharts for explaining the control operation of the embodiment, and FIG. 9 is a flowchart for explaining the control operation of the further improved embodiment. . 4...Pump, 6...Check valve, 7...Pressure tank, 8...Pressure sensor, 10...Liquid supply pipe, Nθ・
...Low speed, Ho...Target pressure, q...Insufficient water flow area □□-1] =565 1°'' Fig. 4

Claims (1)

[Scope of Claims] 1. A pump, a variable speed drive means for driving the pump, a liquid supply pipe connected to the discharge side of the pump, and a pressure sensor connected to the liquid supply pipe, When the operating speed of the pump decreases to a predetermined speed while the liquid supply device controls the operation of the variable speed drive means to maintain the discharge pressure of the pump at the target pressure, the operating speed of the pump is changed. A control device is provided that outputs an operation stop signal to stop the operation of the pump when a change in discharge pressure due to the search operation becomes a characteristic relationship in an insufficient water flow region of the pump. liquid supply device. 2. In claim 1, the pressure sensor is attached to the liquid supply pipe which is sequentially provided with a pressure tank and a check valve upstream from the position, and the discharge pressure does not change due to the search operation. A liquid supply device including the control device that outputs an operation stop signal to stop operation of the pump when the pump reaches a relationship specific to an insufficient water flow region. 3. In claim 1, when the search operation causes the discharge pressure to fall below a predetermined pressure change width specific to the low water flow region of the pump, the operation of the pump is stopped. A liquid supply device including the control device that outputs a signal.