JPH0688594A - Feed water supply system - Google Patents

Abstract

PURPOSE:To control a terminal pressure to be constant even under such a condition that pressure at the suction side varies by installing a compensating means for compensating the discharge pressure of a pump at a time when the suction side pressure detected by a first pressure sensor is out of the specified range. CONSTITUTION:Pumps 210, 211 are directly connected to a water main 201, pumping up water in this water main 201 and feeding it to a deman terminal. Differently, they pump up another water in a receiving tank, feeding it to the demand terminal as well, otherwise. A first pressure sensor 207 is set up in space between an inlet port of the pump and a water pipe emitting a pressure signal according to pressure at the water feed side. A second pressure sensor 218 is connected to a discharge port of the pump, emitting the pressure signal likewise according to pressure at the demand side. On the other hand, driving means 212, 213 of the pump drive the pump so as to pump up the water. A control means 222 controls these driving means so as to make the pump perform its prediction terminal pressure control. A compensation means compensates the discharge pressure of the pump at a time when the suction side pressure detected by the first pressure sensor is out of the specified ranged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water supply device which detects the pressure on the suction side and corrects the pressure on the discharge side.

[0002]

2. Description of the Related Art A system as shown in FIG. 17 has been studied as a water supply device for controlling a constant end pressure using an inverter. However, in order to make the end pressure constant, the pressure on the suction side has conventionally been constant. As a premise, the following control was performed.

As described in JP-A-60-142097 as a control method (1),

[0004]

[Equation 1]

Utilizing the similarity rule of, the rotational speed of the pump and the discharge pressure have a one-to-one correspondence, so the rotational speed is set in advance for the target pressure, or the rotational speed is calculated. There is one in which the terminal pressure is controlled to be constant by setting it.

As shown in FIG. 18, the vertical axis is H and the horizontal axis is Q, and the conduit resistance curve is F. In the case of the control method (1), when the terminal pressure constant control is performed on the water supply amount Q1, the target pressure is Ho, the pump speed is N1, and the pump is operated at N1. Is a point. Here, if the rotational speed of the pump is maintained at N1 when the demand water amount decreases from Q1 and changes to Q2, performance curve A
The driving point becomes the point B along.

The pressure H1 at point B is the pressure sensor 318 of FIG.
Is detected and compared with the target pressure Ho. If Ho <H1, it is considered that the demand water amount has decreased, and the discharge pressure is Ho.
Lower the pump speed until Discharge pressure is H
o, If the number of rotations of the pump when the operating point becomes C point is N2, the target pressure is reset to the pressure H2 set to N2. Also, the rotation speed is reduced to the target pressure.

These operations are repeated at a pump rotation speed N3 to control the discharge pressure to H3 and the operating point to the E point to keep the terminal pressure constant. When the water demand increases, the operation opposite to this may be performed.

Further, in the control method (2) (see Japanese Patent Application Laid-Open No. 61-11497), the rotational speed of the pump is changed bit by bit so that the discharge pressure becomes the target pressure Ho, and it is set per bit. The discharge pressure is changed by the changed width of the generated pressure. The system configuration of hardware is the same as that of the control method (1). As shown in FIG. 19, the vertical axis is H and the horizontal axis is Q, and the conduit resistance curve is F. When the constant end pressure control is performed for the water supply amount Q1, the target pressure is Ho, the pump is operated at N1 and the pump performance curve is A, then the operating point is point A. Here, if the rotational speed of the pump is maintained at N1 when the demanded water amount decreases from Q1 and changes to Q2, the operating point becomes a point B along the performance curve A.

The pressure H1 at point B is detected by the pressure sensor 318 and compared with the target pressure Ho. If Ho <H1, it is considered that the water demand has decreased. Up to this point, the control method is the same as in the control method (1), but the pump rotation speed is reduced by 1 bit so that the discharge pressure becomes Ho. If the discharge pressure is still higher than Ho when the a-bit is lowered, the target pressure is lowered by 1 bit from Ho and reset to H2. The change width per bit is determined by the equation (2).

[0011]

[Equation 2]

The maximum water supply amount Qmax is determined as the water supply device, and the minimum rotation speed Nmin and the maximum rotation speed Nmax of the pump are stored in memory as initial values depending on the performance of the pump. (2)
The formula calculates the difference between the maximum rotation speed Nmax and the minimum rotation speed Nmin,
The maximum pressure Hma is determined by the ratio of the rotation speed increment ΔN to this difference.
It is obtained by multiplying the difference between x and the minimum pressure Hmin to obtain the pressure increase ΔH.

By repeating this, the operating point is set to point C and the terminal pressure is controlled to be constant. When the water demand increases, the reverse operation may be performed.

[0014]

In the above-mentioned prior art, consider a case where the suction pressure fluctuates, for example, a direct connection to a water main. As shown in FIG. 20, assuming that the pump performance curve is A and the pipe resistance curve has an operating point at point A on F, the water supply amount is Q1 and the suction side pressure, that is, the main side pressure is HB If it rises, the performance of the pump will look like a B curve and the operating point will also be a B point.

However, here, the pressure H1 at point B is detected by the pressure sensor (318 in FIG. 17), and since Ho <H1, it is judged that the demand water amount has decreased and the same control as described above is started. However, since the demand water amount is still Q1, only the pressure on the discharge side is detected, so that the operating point will eventually become a point in both control methods (1) and (2). Control is performed, and the operating point comes below the pipeline resistance curve F.

Similarly, when the pressure on the suction side, that is, the pressure in the main pipe, drops, the operating point comes to the point above the pipe line resistance curve F on the contrary. Further, in the case of the control method (2), the minimum rotation speed Nmin of the pump is predetermined, so that the water supply amount is 0.
It becomes impossible to control in the vicinity.

In this case, there is no operating point on the conduit resistance curve F, which is also a feature of the terminal pressure constant control, and the terminal pressure constant control is not performed. That is, since the conventional expected constant end pressure control device performs control on the assumption that the suction side of the pump is constant, sufficient control cannot be performed when the suction side pressure fluctuates.

Therefore, it is an object of the present invention to similarly perform a constant end pressure control even when the suction side pressure fluctuates.

[0019]

In order to solve the above-mentioned problems, the present invention provides a water supply device, a pump having a suction port directly connected to a water pipe, and a first water pump disposed between the suction port and the water pipe. A pressure sensor, a pressure tank and a second pressure sensor connected to the discharge port of the pump, a drive means for the pump, a control means for controlling the drive means so that the pump performs the predicted end pressure control, and When the pressure on the suction side detected by the pressure sensor is outside a predetermined range, it has a correction means for correcting the discharge pressure of the pump.

[0020]

[Operation] The pump is directly connected to the water main to pump water from the water main and send it to the demand end, or pump water from the receiving tank to send it to the demand end. The first pressure sensor is arranged between the suction port of the pump and the water pipe and emits a pressure signal according to the pressure on the water supply side. The second pressure sensor is connected to the discharge port of the pump and emits a pressure signal according to the pressure at the demand end. The drive means of the pump drives the pump to pump water. The control means controls the drive means such that the pump performs the predicted end pressure control. The correction means corrects the discharge pressure of the pump when the pressure on the suction side detected by the first pressure sensor is outside the predetermined range. By doing so, the terminal pressure can be controlled to be constant even if the pressure on the suction side fluctuates.

[0021]

Embodiments of the present invention will be described below with reference to FIGS.

Recently, as shown in FIG. 16, a system in which a pump is directly connected to a water mains to pressurize is being studied. Therefore, in this embodiment, the expected end pressure can be controlled to be constant even if the suction side pressure fluctuates as follows.

That is, in this embodiment, a pressure sensor is provided also on the upstream side (suction side) of the pump, and the pressure on the suction side is read in first and stored in memory to discharge the discharge pressure fluctuation during pump operation. When the pressure sensor on the suction side detects, the pressure on the suction side is read and the target pressure on the discharge side is corrected by the pressure fluctuation on the suction side. Specifically, when there is no pressure fluctuation on the suction side, the conventional end pressure constant control is performed, and when the pressure on the suction side fluctuates, the target pressure is set to the pressure obtained by subtracting the pressure difference from the target pressure. After that, the discharge pressure is controlled by a control method similar to the conventional one.

For the speed control, a transmission such as an inverter is provided, and the control means gives a speed command to give an operation command as follows.

(1) The pressure signal on the suction side is read, and the pressure on the suction side is stored in memory. When the pressure signal on the discharge side is sequentially caught and the pressure on the discharge side fluctuates, the pressure signal on the suction side is read again. Read and compare with the pressure stored in memory.

(2) If the suction pressure does not fluctuate, the normal end pressure constant control is performed while monitoring the suction pressure.

(3) If the suction pressure fluctuates, or if the suction pressure fluctuates while the terminal pressure constant control is being performed, the following (4) or (5) is sequentially performed and then the terminal pressure. Perform constant control.

(4) When the suction pressure decreases, the pressure difference is subtracted from the target pressure.

(5) When the suction pressure increases, the pressure difference is added to the target pressure.

By doing so, even if the pressure on the suction side fluctuates, the fluctuation amount is corrected to correct the target pressure on the discharge side, so that the terminal pressure can be controlled to be constant.

Next, FIG. 1 shows the structure of the water supply system of this embodiment. A water supply device is connected from a water main 201 to a pipe 202 via a check valve 206. A pressure sensor 207 as a first pressure sensor that emits a pressure signal according to the pressure here is connected upstream of the water supply device.

The water supply system includes a pipe 210 in which a pump 210 connected to a sluice valve 208 and driven by an electric motor 212 as a driving means, a check valve 214 connected downstream of the pump, and a sluice valve 216 are connected in series. , A pump 211 connected to a sluice valve 209 connected in series and driven by an electric motor 213 as driving means, and a check valve 215 and a sluice valve 217 connected downstream of the pump are connected in series. Pipe lines are connected in parallel so that they merge at the downstream side, respectively, a water supply pipe 220 connected to this merged portion, a pressure tank 219 connected to this water supply pipe 220, and a pressure signal according to the pressure here. It has a pressure sensor 218 as a second pressure sensor that emits and a control device 222 for the pumps 210 and 211, and is connected downstream of the pressure sensor 207. Pressure tank 219
May be a pressure tank having an air reservoir inside or a diaphragm tank.

The control device 222 as the control means is the pump 21.
A control circuit including an inverter (not shown) that drives the electric motors 212 and 213 of 0 and 211 at a variable speed and a microcomputer (not shown) that controls the inverter is built in. As the hardware configuration of this control circuit, for example, the configuration shown in FIG. 6 of Japanese Patent Application No. 4-42820 is used. Further, the microcomputer has a function as a correction means as described later.

The operation of the apparatus configured as described above is shown in FIG.
Starting from FIG. FIG. 13 to FIG. 15 show a divided flow of a series of operations of the microcomputer in this embodiment.

As an initial value, it is assumed that the water supply amount is Qn with the water tap at the demand end (not shown) being open. This is because the mains of the water supply has some pressure, so the faucet at the demand end is not always closed when the pump is started. Here, the control system stores all the initial value data in the memory. The initial target discharge pressure Ha is also set therein (step 901).

From step 902, the suction pressure HBN is detected and the value is stored in HB. In step 903, the pump is started at the rotation speed Nmin. Discharge pressure H in step 904
out is detected by the pressure sensor 218 on the discharge side in FIG.
If Hout is larger than + HBN, the speed is reduced in step 905, and if Hout is small, the speed is increased in step 906. With this, until Hout becomes equal to Ha + HBN (discharge pressure is constant)
Steps 904 and below are repeated (step 907).

After Hout becomes equal to Ha + HBN, Nn is detected as the number of revolutions of the pump at that time, and the current water supply amount Qn is obtained from the equations (3) and (4) (step 908).

[0038]

[Equation 3]

[0039]

[Equation 4]

[0040]

[Equation 5]

Qmax is the maximum water supply of the system, Nc
Is the rotational speed of the pump such that the discharge pressure becomes Ha when the suction pressure is 0 and the water supply amount is Qmax. Hb is the pump speed Nm when the suction pressure is 0 and the water supply is Qmax.
It is the discharge pressure when operating at ax (Fig. 12).

The target pressure Ho is determined by using (5) from Qn (step 909). In step 910, it is determined whether Hout is Ho. If Hout is large, deceleration is performed, and if Hout is small, acceleration is performed (steps 911 to 913), and step 910 and subsequent steps are repeated until Hout = Ho. The terminal pressure at is kept constant.

When the terminal pressure becomes constant, the suction pressure HBN is read and the value is stored in HB (step 91).
Four).

In step 917, the discharge pressure is detected again and compared with the target pressure. Further, in step 918, suction pressure HB
Detect N and compare with the suction pressure HB detected previously.
Steps 917 and below (subroutine) are repeated until both are equal.

The combination of the pressure fluctuation on the suction side and the fluctuation of the water supply amount will be described below with reference to FIGS. 2 to 11. Figure 2
Therefore, in FIG. 11, the water supply amount Q is initially set at the point a by the control system in which the target pressure is Ho and the terminal pressure is controlled to be constant at the end pressure and the pump rotational speed is Nn. The first value when the control system resets the target pressure is Hof. In addition, FIG. 13 to FIG.
In the deceleration / acceleration routine, the letters a to j in the figure correspond to the states shown in FIGS. 2 to 11, respectively.

If Hout and Ho are equal in step 917, the process proceeds to step 918, and if they are not equal, the process proceeds to step 926. If HB and HBN are not equal in step 918, the process proceeds to step 919, and if HB and HBN are equal, the process returns to step 916. If Hs <0 from the equation (6) in step 919 (when the demand water amount decreases and the suction side pressure decreases and the discharge pressure does not change as shown in FIG. 2), the process proceeds to step 920 and Hs> If 0 (as shown in FIG. 3, the demand water amount increases, the suction side pressure increases, and the discharge pressure does not change) Step
Continue to 923. S and C in equations (8) and (9) are constants for each water supply device, and are stored in memory as initial values in advance.

[0047]

[Equation 6]

[0048]

[Equation 7]

[0049]

[Equation 8]

[0050]

[Equation 9]

In step 920, based on the differential pressure Hs between HB and HBN, assuming that normal end pressure constant control is performed, and the reduction range of the pump rotational speed when lowering the discharge pressure Hs is Ns, this Ns is Ns. = Calculated from Hs / C. Then, the target pressure decrease width NsS is obtained based on the Ns, and Ho (Hof) is reset to the pressure subtracted from Ho (step 921).

Since Hs <0, the pump is decelerated (step 922) and the operating point is controlled from point B to point 2 (FIG. 2).
Similarly, in steps 923 to 925, since Hs> 0, the pump is accelerated to control the operating point from point B to point D (FIG. 3).

Here, step 921 and step 924 are the same because Hs is determined by the equation (6), so if HB> HBN, Hs>
This is because 0, and if HB <HBN, then Hs <0.

Next, if Hout and Ho are not equal in step 917 and HB and HBN are equal in step 926, the process proceeds to step 927, and if HB and HBN are not equal, the process proceeds to step 930.

In step 927, the discharge pressure Hout and the target pressure Ho are compared, and if Hout is large (as shown in FIG. 4, the discharge side pressure remains unchanged and the discharge pressure rises because the demand water amount decreases). Slow down the pump (step 928)
The operating point is controlled from point B to point C. If Ho is large (as shown in Fig. 5, the pressure on the suction side does not change and the discharge pressure rises due to an increase in the demand water volume), the pump is accelerated (step 929), and the operating point changes from point B to point C. And control. After this, the process returns to step 917 again.

If Hout and Ho are equal in step 917 and HB and HBN are not equal in step 926, the process proceeds to step 930. When HBN is larger than HB in step 930 (Hs <0), the process proceeds to step 931 and when HBN is smaller than HB (Hs> 0)
Go to step 942.

In step 931, the differential pressure Hs of the suction pressure and the differential pressure Ht of the discharge pressure are compared, and if Hs and Ht are equal (the demand water amount does not change and the pressure on the suction side rises as shown in FIG. If the pressure increases, the process proceeds to step 932, and if they are not equal, the process proceeds to step 935.

In step 932, Ns is obtained from the suction pressure differential pressure Hs in the same manner as described above. Since Ht> 0, (Hs <
0. Hs = Ht. ∴Ht> 0) Pressure Ho with NsS added Ho
Ho is reset to f (step 933), and since Ht> 0, deceleration is performed (step 934), and the operating point is controlled from the low point to the high point. Then, the process returns to step 917.

Similarly, Ns is obtained in step 935, and Hof is obtained from Ns (step 936). Hof and H in step 937
Compare out, and if Hof> Hout, set the target pressure Ho to Hof again to decelerate, and control the operating point from the low point to the high point (the demand water amount increases and the suction side pressure as shown in FIG. 7). Rises and the discharge pressure rises). If Hof> Hout, the target pressure Ho is reset to Hof to accelerate the speed, and the operating point is controlled from the low point to the second point (the demand water amount increases and the suction side pressure increases as shown in FIG. 8). When the discharge pressure rises). Then, the process returns to step 917.

After step 942, the same as step 931 and thereafter, the deceleration of step 934 becomes the acceleration of step 945 (the demand water amount does not change and the discharge side pressure decreases because the suction side pressure decreases as shown in FIG. 9). if you did this).

Since steps 935 to 941 and steps 946 to 952 are the same, they may be one subroutine, but here, for the sake of explanation, if steps Ho
946 to 952 are cases where Ho> Hout. Further, FIG. 10 shows a case where the demand water amount is decreased and the suction side pressure is lowered and the discharge pressure is lowered, and FIG. 11 is a case where the demand water amount is unchanged and the suction side pressure is lowered so that the discharge pressure is lowered. is there. Then, FIG. 10 shows deceleration (step 949), and FIG. 11 shows acceleration (step 951).

That is, the microcomputer serving as the correction means performs step 935 when the pressure on the suction side detected by the first pressure sensor 207 is out of the predetermined range.
~ 941 and steps 946-952 correct the pump discharge pressure. By doing so, the terminal pressure can be controlled to be constant even if the pressure on the suction side fluctuates.

As described above, in this embodiment, the number of revolutions with respect to the target pressure is obtained by calculation. However, when the memory capacity has a margin, the conventional control method (1) is used to set the suction pressure to some extent as shown in Table 1. It is also possible to use a simple method in which the number of revolutions corresponding to the target pressure is stored in advance in the memory in accordance with the division with a width.

[0064]

[Table 1]

In this embodiment, the pump is directly connected to the water main to pump water from the water main and send it to the demand end. However, the water in the water receiving tank is pumped and sent to the demand end. The present invention may be applied to.

[0066]

According to the present invention, the pressure on the suction side is detected by the pressure sensor to correct the target pressure, so that the terminal pressure can be controlled to be constant even under conditions where the pressure on the suction side fluctuates. Can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a water supply device according to an embodiment of the present invention,

FIG. 2 is a driving characteristic diagram of the present embodiment,

FIG. 3 is a driving characteristic diagram of the present embodiment,

FIG. 4 is a driving characteristic diagram of the present embodiment,

FIG. 5 is a driving characteristic diagram of the present embodiment,

FIG. 6 is a driving characteristic diagram of the present embodiment,

FIG. 7 is a driving characteristic diagram of the present embodiment,

FIG. 8 is a driving characteristic diagram of the present embodiment,

FIG. 9 is a driving characteristic diagram of the present embodiment,

FIG. 10 is a driving characteristic diagram of the present embodiment,

FIG. 11 is a driving characteristic diagram of the present embodiment,

FIG. 12 is a driving characteristic diagram of the present embodiment,

FIG. 13 is a flowchart showing the operation procedure of the present embodiment,

FIG. 14 is a flowchart showing the operation procedure of the present embodiment,

FIG. 15 is a flowchart showing the operation procedure of the present embodiment,

FIG. 16 is a conventional water supply system,

FIG. 17 is a configuration diagram of a conventional water supply device,

FIG. 18 is an operation characteristic diagram of the conventional control method (1),

FIG. 19 is an operation characteristic diagram of the conventional control method (2),

FIG. 20 is an explanatory diagram of a malfunction operation of a conventional control device,

Claims (1)

[Claims] 1. A pump having a suction port directly connected to a water pipe, a first pressure sensor arranged between the suction port and the water pipe, and a pressure tank connected to a discharge port of the pump. And a second pressure sensor, a drive means for the pump, a control means for controlling the drive means so that the pump performs predicted end pressure control, and a suction side pressure detected by the first pressure sensor. A water supply device having a correction means for correcting the discharge pressure of the pump when it is outside a predetermined range.