JPH0263119B2 - - Google Patents

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 maintain a constant pump discharge pressure. When the amount is low, the speed control operation of the pump is switched to intermittent operation, and when it is not needed, the pump is stopped. 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 and 32 are gate valves,
4 is a pump, 5 is a motor that drives pump 4,
6 is a check valve, 7 is a pressure tank, 8 is a water supply pipe 10
9 is a flow rate switch disposed on the water supply pipe 10, and 11 is a faucet at the end.

FIG. 2 is a diagram showing the operating characteristics of the same pump device, with the horizontal axis representing water quantity Q and the vertical axis representing pressure H. In the figure, H ₀ is the target discharge pressure of the pump,
Although not shown, it is set by the control device. Qmin is the amount of water required to stop the pump, and is generally around 10/min. In addition, curve a shows the Q-H performance when the pump operating speed is the maximum speed Nmax, and curves b, c, d, and e below are stepless continuous control, but the pump operating speed is changed in intermediate steps. The Q-H performance is shown when Nho, Nd, Nha, and Nro are set. Furthermore, the curve f shows an insufficient amount of water.
It shows the Q-H performance when the pump stops after detecting Qmin. Incidentally, the flow rate sensor 9 shown in FIG. 1 issues a signal when it detects an insufficient water amount Qmin shown in FIG. 2.

In FIGS. 1 and 2 described above, 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 pressure H in the water supply pipe 10 is detected by the pressure sensor 8, compared with a predetermined target pressure _H0 , and the operating speeds of the pump motors 4 and 5 are controlled so that this difference approaches zero. It is. For example, if the amount of water used decreases from Q to Q, the operating speed will decrease from Nmax to N, and the amount of water used will further decrease until the water amount is too low, Qmin.
When the flow rate reaches this point, the flow rate sensor 9 detects this and stops the pump motors 4 and 5. In addition, when restarting the pump motors 4 and 5, the pressure sensor 8 detects the target pressure.
This is when a pressure H′ slightly lower than H ₀ is detected.

However, the above conventional techniques have the following problems. That is, the flow rate sensor 9
If the output part becomes clogged with limescale, etc., or the output part becomes rusted due to moisture, etc., an extremely serious problem may occur in which the insufficient water amount Qmin cannot be detected, the pump/motor does not stop, and power is wasted. . 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 way to solve these problems, it may be possible to stop the pump/motor when the operating speed of the pump/motor reaches the minimum speed Nmin without using an insufficiently reliable flow rate sensor. However, with this method, the water absorption level of water tank 1 may decrease,
When the characteristics of the pump deteriorate due to wear of the sliding parts of the pump, the minimum Q-H performance decreases as shown by the curve G shown in Figure 3, and when constant discharge pressure control is performed, the actual operating speed is less than Nmin. Therefore, it becomes impossible to detect the minimum speed Nmin, and the same problem as described above remains that the pump motor does not stop.

[Purpose of the invention]

The purpose of the present invention is to have a self-judgment function that always determines the appropriate minimum speed 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, 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, and In a fluid supply system that performs variable speed operation control of a variable speed drive means to maintain pressure at a target pressure, when the pump operating speed decreases to a low speed within a predetermined variable speed range, the pump operating speed is determined in advance. A control device is provided that outputs an operation stop signal and stops the operation of the pump based on detecting that the pressure change on the discharge side of the pump at that time is smaller than a predetermined value. This provides a liquid supply device that can reliably detect that the amount of water is too low without providing a flow rate sensor.

The discharge pressure of the pump is proportional to the square of the speed, so when operating at low speed in the low water flow range,
Compared to high-speed operation, the change in discharge pressure with respect to a change in unit speed is smaller.

[Embodiments of the invention]

Examples of the present invention will be described below. FIG. 4 shows the basic processing flow of the embodiment, and normally the pump is operated at a variable speed by keeping the discharge pressure constant by feedback control or by controlling the end pressure to be constant. If the water demand decreases at night, etc., and the pump operating speed reaches a low speed within the variable speed operating 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 the pump are in a relationship specific to the low water volume region of the pump, it is determined that the water demand is very small, and an operation stop signal is output to stop the pump 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 operating speed of the pump is increased or decreased during 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 are shown in Figures 1, 3, and 5.
This will be explained with reference to FIG. Since the overall configuration of the pump device is the same as that already explained in FIG. 1, the explanation will be omitted here. Figure 5 shows the control device of the embodiment, where the MCB is a main circuit disconnector,
MC is the coil of the magnetic contactor, MCa is its contact,
INV is a variable frequency inverter device for changing the rotation speed of the variable speed motor 5 (an inverter device is used in this embodiment, but primary voltage control, eddy (Current couplings or other speed change control devices may also be used.) TH is a thermal relay for overload prevention,
μcon is the central processing unit CPU (hereinafter abbreviated as CPU), memory M, power supply terminal E, and input/output port.
A microcomputer consisting of PIAa, PIAb, PIAc, and PIAd, _F1 is equipped with an A/D converter, and the signal detected by pressure sensor 8 is sent to the input/output port.
Microcomputer μcon via PIAHa
interface, as well as F ₂
DS is an interface for sending the speed command signal from the microcomputer to the input terminal of the inverter INV, and DS is a deep switch for setting the minimum speed, from which the minimum speed Nmin is sent to the microcomputer via the input/output port PIAd. Load into μcon. Y is a control circuit consisting of a transformer T, a power supply unit Z, a start/stop switch SS, an electromagnetic contactor MC, a transistor Tr, and a relay X. Note that the base of the transistor Tr is connected to b0bit of the input/output port PIAc (8bit) of the microcomputer μcon by signal line A, and when b0 bit becomes 1,
The transistor Tr becomes conductive and the relay X is energized. Also, Figure 6 shows the deep switch DS.
In this figure, r0 to r7 are resistors. In the figure, by arbitrarily setting each bit _b0 to _b7 of the dip switch DS, the lowest speed data (converted into a binary number record) can be set.
This data is then transferred to the microcomputer μcon.
is read internally. In the control circuit Y, when the circuit breaker MCB is turned on and the start/stop switch SS is closed, stable rectified and smoothed power is transferred from the power supply unit Z via the transformer T to the power supply terminal E of the microcomputer μcon. The vehicle is sent to the factory and ready for operation.

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 Figure 7.
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.

Memory M ₀ (ROM)...Inputs the data of the low speed Ns that starts the search operation for determining insufficient water volume.

Memory M ₁ (RAM)...Initial speed when starting the pump
Secure Nin data area.

Memory _M2 (RAM): Secures the data area for the minimum speed Nmin during normal variable speed operation of the pump.

Memory _M3 (ROM)……Maximum pump speed Nmax
Store data.

Memory _M4 (ROM): Stores the data of speed Nst when the pump/motor is stopped.

Memory _M5 (RAM)...Pump operation command speed Nx
Secure a data area.

Memory _M6 (ROM)...Inputs the data of the lower limit value NLmin of the speed change range of the speed change control means.

Memory M ₁₀ (ROM)...Stores the data of target pressure H ₀ .

Memory _M11 (ROM)...Stores pressure H data at restart.

Memory _M12 (ROM)...Stores the ON data 01 (11) of the magnetic contactor MC.

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

NLmin<Nmin<Ns<Nin<Nst In addition, the small water flow region Qs is set with some margin for the detected low water flow region q.

Insufficient water flow area q < Small water flow area Qs < Normal operation area In addition, the initial speed of the pump is set in the secured memory M ₁ .
After loading the Nin data, read the minimum speed Nmin data set by the deep switch DS in a few steps. Reserved memory
Write to M ₂ (RAM). Then, in steps 4 and 5, data 01 to ₁₆ are output from the input/output port PIAc,
Transistor Tr and relay X are energized to turn on the magnetic contactor MC. Next, in steps 6 and 7, the data of the initial speed Nin stored in memory _M1 is interfaced from the input/output port PIAb.
Send it to the speed input terminal of the inverter device INV via _F2 . Thus, the pump motors 4, 5 start operating at the initial speed Nin. Next, the microcomputer μcon stores the initial speed Nin in 8 steps.
After storing to _M5 , execute the next 9-step instruction. That is, the pressure signal detected by the pressure sensor 8 is read through the interface _F1 and loaded into the A register. Further, in the 10th step, the data of the target pressure _H0 stored in the memory _M10 is transferred to the B register, and in the 11th step, the data in both registers are compared. As a result of the comparison, if the two are equal, the pressure inside the water supply pipe 10 is the target pressure.
Since it is in the state of H ₀ , the process proceeds to step 12 without performing the gear change process. However, if the pressure signal detected by the pressure sensor 8 is greater than the target pressure _H0 , it is necessary to decelerate, so the process proceeds to steps 13 and 15. In steps 13 to 15, the current operating speed is set to the lower limit of the shift range. It is determined whether the speed has reached the value Nlmin, and if the speed has not reached Nlmin, the 16th to 18th step commands are executed, and the operating speed width corresponding to 1 bit of the resolution of the control system is subtracted from the current operating speed. Specifically, the pump
The binary speed data of the motors 4 and 5 is decremented once and used as new speed data, and the operating speed data is stored in the memory _M5 . After this, in step 20, the pump motors 4 and 5 execute a waiting time t corresponding to the delay time necessary for completing the speed change operation based on the new speed command, and then return to step 9 again, and press the pressure sensor 8.
This loop process for deceleration is performed until the detected pressure H matches the target pressure H ₀ . Furthermore, as a result of the 15-step judgment, if the operating speed has reached the lower limit value NLmin of the shifting range, 2
Jump to step 0 and perform subsequent processing. If it is determined in step 11 that the pressure detected by the pressure sensor 8 is lower than the target pressure H ₀ , the process proceeds to step 19 and the deceleration process described above is performed in reverse order. , the speed of the pump is increased by an operating speed range corresponding to 1 bit of resolution of the control system.

As the amount of water used decreases, we will continue to slow down the process.
In the next 21st and 22nd steps, judge whether the current operating speed has reached the speed Ns corresponding to the small water flow range Qs shown in Figure 3, and if it has not yet reached it, return to step 9, and from this point onwards. Continue the process again, and if it is determined that it has reached 23
In steps 27 to 27, the difference H ₀ -H between the target pressure H ₀ and the pressure H in the water supply pipe 10 is determined, and it is determined whether this difference is 0 or not. If the result of the determination is not 0, the process returns to step 9 and the subsequent processing continues. If it is 0, the commands in steps 28 to 33 are executed to perform a search operation. In other words, 2 of the speed you are currently driving.
Try to reduce the operating speed of the pump 4 by a small amount by decrementing the forward data 3 to 5 times. Therefore, N for 28 steps should be about 3 to 5 times. This 2
It is determined in the next 34 steps whether the pressure relationship before and after the start of the search operation in steps 8 to 33 is unique to the pump's low water flow region. 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 check valve 6
The pressure inside the pipeline on the downstream side is maintained by the action of the pressure tank 7, and even if the operating speed of the pump is reduced, if this pump is operated in the low water flow region q, the pressure inside the pipeline will remain the same. Does 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 H ₀ 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, 35-39
In step 1, it is determined once again whether the pressure difference is H ₀ -H, and if it is not 0, the process returns to step 9 again to execute subsequent processing instructions. In the case of 0, it is determined that the amount of water used is stable and in the insufficient water amount area as described above, so in the next 40 steps, the speed Nx before the search operation stored in the memory _M5 is set to the true minimum speed Nmin. is transferred to memory _M2 and updated, and after operating for a certain period of time t at this true minimum speed Nmin, the operating speed is increased to the stop speed Nst in steps 44 to 45, and the discharge pressure is restarted. After increasing the pressure to _H2 or more and storing water in the pressure tank 7, execute steps 47 and 48,
The pump motors 4 and 5 are stopped by outputting an operation stop signal through PIAc.

After the pump 4 is stopped, the following 49 steps are executed, and the discharge pressure H detected by the pressure sensor is constantly compared with the restart pressure _H2 stored in the memory _M11 . When it is determined that the pressure has dropped below the current pressure _H2 , the processes from step 4 onwards are performed again, and the pump 4 is restarted at the initial speed Nin.

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

According to such a water supply device, an insufficient amount of water can be detected and the 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 Ns, a search operation was performed to determine whether the water amount was too low. Since the speed Ns must be set, some effort is required for initial setting. Furthermore, after installing the water supply device, if the water supply system is changed or the water suction conditions of the pump change, it is necessary to set the low speed Ns again to continue proper pump operation. FIG. 9 shows an improved embodiment that solves these difficulties. This embodiment is an improvement of 23 steps to 27 steps of the embodiment explained in FIG. 7 and FIG. The system is configured to shift to search operation when the current does not change. This example will be explained in detail below. First, after clearing the D register in step 100, the data of the current discharge pressure H and target pressure _H0 are read into the A and B registers in steps 101 and 102, and both data are compared in step 103. By this comparison, the discharge pressure H becomes the target pressure.
If it is determined that it exceeds H ₀ , 104~
After processing 109 steps, the process shown in FIGS. 7, 13 to 18
Perform the pump deceleration process as explained in step. On the other hand, if the discharge pressure H is less than the target pressure H ₀ , the processing in steps 111 and below is continued and the speed of the pump is increased. After this speed increasing process, 112,
In step 113, the data of the low speed Ns is loaded into the B register and compared with the new operating speed after the speed increase process in the A register.If the new operating speed exceeds the low speed Ns, the data is already explained in Fig. 7. The process continues with the nine steps or less. Also, 1
If it is determined that both pressures H _{0 and} H are equal in step 03, the D register is incremented by soft timer processing in steps 115 and 116, and in relation to the processing in step 117, this is a predetermined time (about several minutes). When the value exceeds the value T corresponding to , the process of 28 steps or less explained in FIG. 8 is performed to perform a search operation. After performing the increase/decrease process, the D register is cleared to 0 in steps 110 and 114, and if the value T has not been reached in step 116, the time t is executed in the next step 117. After that, the processes from 101 onwards are executed again.

In this way, by detecting the minimum speed at which the pump speed is balanced (no longer changes) in the low water demand area, and by setting the low speed Ns as a tentative guideline for detecting insufficient water volume, changes in the water supply system can be made. ,
Alternatively, the pump can always be operated at the lowest speed without being affected by changes in discharge pressure. Also, after configuring like this, the lowest speed
By recording the state of change in Nmin, 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, it is possible to detect such changes and issue an alarm for maintenance and inspection of the water supply system.

Now, in the above-described embodiment, the search operation for detecting an insufficient amount of water was performed 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. Alternatively, an example may be considered in which the operation of the pump 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, and a search operation is performed when the pump operating speed falls below a predetermined low speed Ns. 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 addition, when the pump is operating in the small water flow region Qs, the pressure drop on the discharge side is gradual even when the pump is stopped, so using this characteristic, the pump can be operated until it reaches the low water flow region q and then stopped. Prepare a memory device that measures and stores in advance the degree of pressure drop when the pressure drop occurs or the time required for a certain width of pressure drop to occur, and when the pump operating speed drops below the predetermined low speed Ns. Perform a exploratory operation in which the pump is stopped, measure the degree of pressure drop caused by this exploratory operation, or the time until a certain width of pressure drop occurs, and compare these calculated values with pre-stored memorized values to determine if the amount of water is too low. It is also possible to configure the water supply device to determine whether or not the pump is running, and to select whether to stop or restart the pump based on the result.

Now, in the embodiment already explained, after comparing the target pressure and discharge pressure, the pump operating speed is increased or decreased by a 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. Also,
In the embodiment, a pressure sensor which can obtain a variable speed output according to pressure changes has been described, but the present invention can also be realized by a combination of pressure switches which can obtain ON-OFF signals. 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, but this is because the change in operating speed becomes slow;
In other words, detection can be made even when the width of change becomes smaller.

〔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. It is possible to reliably detect the amount of water and control the operation of the pump.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the configuration of the liquid supply device,
Fig. 2 is an operating characteristic diagram for explaining a conventional liquid supply device, Fig. 3 is an operating characteristic diagram for explaining one embodiment of the present invention, and Fig. 4 is a basic control operation of the present invention. FIG. 5 is a block diagram for explaining the configuration of the control device of the embodiment, FIG. 6 is a diagram for explaining details of the configuration of the control device, and FIGS. FIG. 8 is a flowchart for explaining the control operation of the embodiment, and FIG. 9 is a flowchart for explaining the control operation of a further improved embodiment. 4... Pump, 6... Check valve, 7... Pressure tank, 8... Pressure sensor, 10... Liquid supply pipe,
Ns...Low speed, _H0 ...Target pressure, q...Low water flow area.

Claims (1)

[Claims] 1 comprising 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, and configured to set the discharge pressure of the pump to a target. In a fluid supply device that controls the operation of the variable speed driving means to maintain the pressure, when the operating speed of the pump decreases to a predetermined speed, the operating speed of the pump is increased by a predetermined width. and detecting in relation to the output of the pressure sensor that the pressure change on the discharge side of the pump at that time is smaller than a predetermined value, outputs an operation stop signal and stops the operation of the pump. A liquid supply device characterized by having a control device for stopping the liquid.