JPH0652080B2 - Predictive end pressure constant controller for water supply system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a water supply apparatus for supplying water by operating a pump at a variable speed so that the pressure at the water supply end becomes constant along the resistance curve of the water supply pipe. The present invention relates to a predictive end pressure constant control device for controlling the rotation speed of a pump.

[Background of the Invention]

In the water supply device, a control system of a pump is often adopted due to the development of electronics and the improvement of cost performance of electronic parts. Regarding the conventional control method, various ones have been proposed and put into practical use, but as the discharge pressure control, the discharge pressure constant control,
There is a predicted end pressure constant control.

The former is intended to keep the discharge pressure constant by changing the number of revolutions of the pump according to the fluctuation of the amount of water used, which is relatively inexpensive and easy to control. Since the speed change range is narrow and the number of times the pump is started increases, the power saving effect is small.

On the other hand, the latter is for keeping the discharge pressure at the water supply end constant, and its conventional example is shown in FIG. In the figure, 1 is a water receiving tank, 3 is a pump, 2 is a suction pipe that connects the suction side of the pump 3 and the water receiving tank, and 6 is a discharge side of the pump 3 via a check valve 4 and a sluice valve 5. It is a connected water supply pipe. Reference numeral 7 is a pressure sensor which is installed at an intermediate position of the water supply pipe 6 and emits an electric signal proportional to the discharge pressure, 8 is a flow sensor which is installed at an intermediate position of the water supply pipe and emits an electric signal proportional to the discharge flow rate, and 9 is a pump 3 is a shift motor that drives the No. 3 motor.

X is a function calculator for converting the target pressure by substituting the function formula Ha + aQ ⁿ to read and later the detection signal from the flow sensor 8, C is had it occurred detecting the target pressure H ₀ and a pressure sensor 7 that is converted A comparator that compares the discharge pressure H and amplifies the deviation (H ₀ −H) thereof, and Y is a proportional that issues a speed command signal according to the set gain and integration time of the output signal of the comparator C. The integrator and Z are speed control means for controlling the rotation of the shift motor 9 based on the output signal of the proportional integrator Y.

In FIG. 2, the horizontal axis indicates the discharge flow rate Q and the vertical axis indicates the discharge pressure H.
It is an operating characteristic curve figure of the pump which carried out. A shows the Q-H performance curve of the pump 3 when the speed change motor 9 is operating at the rotation speed Nmax, and the same applies to B, C, D and E hereinafter.
Shows Q-H performance curves of the pump 3 when operating at rotational speeds of N ₁ , N ₂ , N ₃ and N ₄ , respectively. Further, Ha represents the pressure obtained by adding the required pressure at the end to the actual head of the pump 3, and F represents the resistance curve of the water supply line. Although H _a is a value obtained by adding the required end pressure when opening highest faucet to actual head up highest faucet from the water supply position, in the present application embodiment, as described later, The characteristics shown in FIG. 5 were replaced by the characteristics shown in FIG. 6 by experiment, and K ₁ and K obtained there were obtained.
_{Since 2} is stored in the memory and used for the calculation, H _a itself is not used for the calculation in the embodiment described later. Thus, setting of the terminal discharge pressure H _a is not particularly necessary. The resistance curve F is determined by constants such as the pipe material used, the diameter, and the shape. Accordance connexion, the actual resistance of the case where the predicted beforehand resistance curve F is given by aQ ^n. Note that a
Is the pipeline system number, and n is a constant and is generally 2.

That is, the conduit resistance increases as the discharge flow rate Q increases. For example, the line resistance at the discharge flow rate Q ₀ point is H
t-Ha, which is 0 when the ejection amount becomes 0. From this, the target pressure H ₀ is given by Ha + aQ ⁿ .

Now, the amount of water used is Q ₀ , and the rotation speed of the speed change motor 9 is Nm.
It is assumed that the Q-H performance curve of the ax and the pump 3 is A and the pump is operating at the point a. From this state, when the amount of water used becomes Q ₁ ,
Since the discharge pressure of the pump 3 rises along the Q-H performance curve A, it becomes the rising pressure H _{1 and} becomes the point a ′. The pressure sensor 7 detects this rising pressure H ₁ , and the flow rate sensor 8 detects the discharge flow rate Q ₁ . Then, the function calculator X reads the detection signal from the flow rate sensor 8 and substitutes it into the above equation to obtain the target pressure H ₀ (= Ha + aQ ⁿ ), and the comparator C outputs the target pressure H ₀ and the pressure sensor 7. Pressure H
₁ and a deviation _H 0 -H ₁ of, by comparing the integrator Y is commanded speed to the speed control means Z on the basis of the deviation _H 0 -H _1, next to the rotational speed _{N 1} of the shift Motoru 9, Moreover, the Q-H performance curve of the pump becomes B, and the point moves from the operating point a'to the point b. Therefore, when the amount of water used changes, the conduit resistance changes with the change in flow rate. Therefore, by controlling the rotation speed of the shift motor 9 along the resistance curve F, the discharge pressure at the end of the conduit is controlled. Can be kept constant. Since the resistance of the water supply pipe decreases as the flow rate decreases, the target pressure H ₀ also decreases as the discharge flow rate decreases,
Since the rotation speed of the shift motor 9 decreases accordingly,
That is advantageous in terms of power saving.

However, the predicted end pressure constant control device shown above,
Equipment such as the function calculator X, the comparator C, and the proportional integrator Y are required, and the control is complicated, so that there is a problem that the equipment cost is high.

[Object of the Invention]

In view of the above circumstances, the present invention provides a terminal pressure constant control device for a water supply device, which is inexpensive and has a simple structure, which can maintain a constant terminal discharge pressure in a certain initial state using a microcomputer. It is in.

[Outline of Invention]

In order to achieve the above object, in the present invention, a reference numeral is added to the pump that is variably operated according to the change in the amount of water used, in order to make a certain rotation speed N _i (hereinafter, referred to as an embodiment to be described later). ) And a hypothetical pipeline resistance curve F (H ₀ = H _a + aQ _i ⁿ ) of the water supply route when operating at the discharge flow rate Q _i
The target pressure, which is the pump discharge pressure H ₀ , and the rotation speed N _i remain unchanged, and the pump discharge flow rate Q _i is Q
flow rate Q _i at the time of the previous sampling when changing to _i ′
From the pressure value H ₀ stored as the current target pressure obtained based on the pipe resistance curve F from the above, and the pressure value H actually detected at the time of this sampling when the flow rate changes to Q _i ″. Discharge pressure difference Δh (= H−
H ₀ ), and the number of revolutions N _i does not change, and the discharge flow rate Q _i of the pump changes to Q _i ′, it is obtained from the conduit resistance curve F based on the flow rate Q _i at the previous sampling. Also, the pressure value H ₀ stored as the current target pressure and the flow rate change to Q _i ′, and the pump discharge pressure H ₀ ′ obtained from the pipe resistance curve F at the time of this sampling is obtained.
The pressure at the water supply end of the water supply pipe is predicted from the parameter such as the target pressure difference which is the difference ΔH (= H ₀ ′ −H ₀ ), and the rotational speed of the pump is controlled so that this pressure becomes constant. In a predictive terminal pressure constant control device for a water supply device, a variable speed drive unit for controlling the rotation speed of a variable speed motor for driving the pump and a discharge side of the pump are installed, and discharge pressure from the pump can be detected. A pressure sensor and a detection signal of the pressure sensor are read, and a relationship between the discharge pressure difference and the target pressure difference and a relationship between the discharge pressure difference and a command speed difference are respectively obtained, and the discharge pressure difference is further calculated. And the above two relations, a current command speed difference and a current target pressure difference are obtained, a command speed to be sent to the variable speed drive unit is calculated based on the current command speed difference, and a speed signal is sent to the variable speed drive unit. Send And characterized in that it includes a microcomputer to successively set the next target pressure value based on the current target pressure difference.

Example of Invention

An example of the embodiment of the present invention will be described below with reference to FIGS.

This water supply system, as shown in FIG.
The water in the water tank 1 is sucked into the suction side of the pump 3 through the suction pipe 2 by driving the pump 3 with the check valve 4 and the sluice valve 5 from the discharge side of the pump 3.
Through the water supply pipe 6 to be supplied to the water supply terminal. In that case, the rotational speed of the shift motor 9 is controlled according to the change in the amount of water used, so that the pump 3 can be variably moved.

Therefore, the predictive terminal pressure constant control device of the present embodiment is installed on the discharge side of the pump 3 and the variable speed drive unit 10 that controls the rotation speed of the speed change motor 9 in general.
From a pressure sensor 7 capable of detecting the discharge pressure from the pressure sensor 7 and a micro computer (hereinafter, abbreviated as microcomputer) 20 which reads a detection signal from the pressure sensor 7 and sends a speed signal to the variable speed drive unit 10. I'm running.

FIG. 4 shows a circuit diagram of the constant predictive end pressure controller. In the figure, a power source 30 is connected via a wiring breaker 31, a make contact 32a of an electromagnetic switch 32, a variable frequency inverter forming a variable speed drive unit 10 and a thermal relay 33 so as to drive a shift motor 9. There is.

A circuit 40 for switching the make contact 32a is connected between the make contact 32a and the wiring breaker 32. The circuit 40 includes a microcomputer 20 described later.
NPN transistor 42 whose base is connected to the output port 20e of the transistor via a resistor 41, and an electromagnetic relay 44 connected to the collector of the transistor 42 via a resistor 43.
And a relay switch 47 to which the make contact 44a of the electromagnetic relay 44, the electromagnetic switch 32, and the thermal relay 33 are connected in series on one side, and the transformer 45 and the stabilizing power source 46 are connected to the other side. In the circuit 40, when the signal that the NPN transistor 42 is turned on is input from the microcomputer 20 when the relay switch 47 is closed, the electromagnetic relay 44 is excited and its make contact 44.
When a is closed, the electromagnetic switch 32 is excited and its make contact 32a is closed, thereby driving the shift motor 9 via the variable frequency inverter 10.
When a signal for turning off the NPN transistor 42 is input from the microcomputer 20, the electromagnetic relay 44 is demagnetized to open its make contact 44a and the electromagnetic switch 32.
Is demagnetized and its make contact 32a is opened, so that the speed change motor 9 is transmitted via the variable frequency inverter 10.
Stop driving.

The microcomputer 20 connects the pressure sensor 7 with the interface 5
1, an input port 20a connected through 1, a memory 20b for writing and reading data, and the memory 20b
A central processing unit 20c which takes in necessary data from the input port 20a in accordance with the above-mentioned program and transfers data to and from the memory 20b for processing, and a central processing unit 20c which processes the data. It comprises a first output port 20d for outputting data to the variable frequency inverter 10 via the interface 52 and a second output port 20e for outputting it to the NPN transistor 42. When the relay switch 47 is closed, the microcomputer 20 is powered on via the transformer 45 and the stabilizing power supply 46.

Before explaining the control operation of the predictive constant terminal pressure controller of the present embodiment, the principle of the present invention will be described with reference to FIGS. 5 and 6. As shown in FIG. 5, it is assumed that the amount of water used is Qi, the operating speed of the speed change motor 9 is Ni, the QH performance curve of the pump 3 is I, and the pump is operating at the intersection Oi on the resistance curve F. To do. In this state, when the amount of water used increases to Qi ′, the discharge pressure decreases by 4h ₁ and the operating point becomes Oi.
Changes to Oi ₁ .

However, in order to control the pressure along the resistance curve F, the operating point must reach Oi _2, and therefore, the rotation speed of the shift motor 9 is increased by 4N ₁ and the target pressure is increased by 4H ₁ from the current target pressure. It needs to be high.

Further, when the amount of water used is reduced to Qi ″, the discharge pressure increases by 4 h ₂ and the operating point changes from Oi to Oi _3. Therefore, in order to control the pressure along the resistance curve F, the operating point is Oi. ₄ and therefore shift motor 9
It is necessary to lower the rotation speed of 4 N _{2 and} lower the target pressure by 4 H ₂ .

When the relationship between the change of the discharge pressure and the change of the target pressure, and the relationship between the change of the discharge pressure and the change of the rotation speed are plotted and shown in a graph, as shown in FIGS. 6 (a) and 6 (b). As shown in. This relationship is given by the following equation.

ΔN = -K ₁ · Δh (1) ΔH = -K ₂ · Δh (2) where Δh is the discharge pressure difference, which is the deviation between the discharge pressure from the pressure sensor 7 and the target pressure. , ΔN is a command speed difference, which is a deviation between the current rotation speed of the shift motor obtained based on the discharge pressure difference and the rotation speed to be changed, and ΔH is a target pressure difference and the discharge pressure to be changed. It is the deviation from the pressure.

It should be noted that K ₁ and K ₂ are proportional constants, and since the slope of the resistance curve F of the water supply line varies depending on the water supply system, it can be appropriately changed according to the change.

The above equations (1) and (2) are obtained based on FIG. And FIG. 6 is calculated | required based on FIG. First, a method for obtaining FIGS. 5 to 6 will be described.
FIG. 6 (a) shows the relationship between the discharge pressure change Δh and the target pressure difference change ΔH under the condition that the pump rotation speed N _i is constant.

Consider a case where the flow rate Q changes under the condition that the pump rotation speed N _i is constant, and the pressure H changes along the characteristic curve I of FIG.

(A) When there is no change in the flow rate Q at the previous and current samplings Since the characteristic curve I and the pipeline resistance curve F (H ₀ = Ha + aQ ⁿ ) intersect at O _i when the flow rate Q _i , each curve Pressures are the same, that is, target value H of discharge pressure
₀ (the value obtained by the conduit resistance curve F) and the actual discharge pressure H (the value obtained by the characteristic curve I) match, and the discharge pressure Δh = 0. If there is no change in the flow rate Q between the previous sampling and the current sampling (Qi
= Qi ′), the target pressure H ₀ does not change (H ₀ =
H ₀ ′), and therefore the target pressure difference ΔH = 0.

That is, Δh = 0, ΔH = 0, and in this case, the origin (0, 0) in FIG. 6A is obtained.

(B) When the flow rate Q at this time of sampling is increased from the time of the last time of sampling: Since the characteristic curve I is a characteristic curve descending to the right, if the flow rate Q _i increases like Q _i ′ as shown in FIG. The discharge pressure actually detected is the target pressure H at the time of the previous sampling.
_With respect to ₀ , it decreases by Δh ₁ along the characteristic curve I, so that the discharge pressure difference Δh becomes a negative value.

In contrast, since the pipeline resistance curve _{F (H 0 = Ha + aQ} n) is a characteristic upward curves, the flow rate _{Q i} against _{H 0} when flow rate _{Q i} is increased as _{Q i} ', target pressure pipe resistance curve _{H 0} ', and the pressure _{H 0} in this case' shifts to O _i2 along the F difference between the pressure _{H 0} when the flow rate _{Q i,}
That is, the target pressure difference ΔH = H ₀ −H ₀ ′ has a positive value like ΔH ₁ .

In this way, when the flow rate Q _i increases under the condition that the pump rotation speed is constant, ΔH becomes a function of Δh descending to the right (using the flow rate Q _i as a parameter) (in the case of Δh <0 in FIG. 6 (a)). region).

(C) When the flow rate Q increases at the current sampling time compared to the previous sampling time Since the characteristic curve I is a characteristic curve that rises to the right, it is actually detected that the flow rate Q _i decreases like Q _i ″ as shown in FIG. The discharge pressure to be generated is the target pressure H ₀ at the time of the previous sampling.
It increased by Delta] h ₂ along the characteristic curve relative, thus discharging the pressure difference Delta] h is a positive value.

On the other hand, since the conduit resistance curve F (H ₀ = Ha + aQ ⁿ ) is a characteristic curve that rises to the right, the pressure H _{0 at the} flow rate Q _i is
, The target pressure difference ΔH becomes a positive value like ΔH ₁ , and when the flow rate Q _i decreases like Q _i ″, the target pressure reaches the point of O _i4 along the conduit resistance curve F. The pressure H ₀ ′ at this time is ΔH ₂ from the pressure H _{0 at the} flow rate Q _i.
The target pressure difference ΔH = H ₀ ′ −H ₀ becomes a negative value.

Thus, when the relationship between ΔH and Δh is calculated under the condition that the pump rotation speed is constant, ΔH is (using the flow rate Q _i as a parameter).
It becomes a function of Δh that descends to the right (Δh> 0 in FIG. 6 (a))
Area).

(D) When the flow rate changes slightly around the flow rate Q _{i Based} on the above (a), (b), and (c), when the flow rate Q increases or decreases at the time of this sampling compared to the time of the previous sampling, Considering the range in which the change width of the flow rate Q _i is small, the relationship between ΔH and Δh can be approximated by a linear function.
When this function is graphed, Δh = 0 (origin) can be drawn corresponding to the point of the flow rate Q _i in FIG. 5, and is as shown in FIG. 6 (a).

When this relationship is expressed by an equation, it becomes like the equation (2). In the equation (2), K ₂ is a value obtained by experiment. That is, the characteristic shown in FIG. 6A is obtained by an experiment, and K ₂ is obtained from the slope of the characteristic curve.

Similarly, the relationship between the command speed difference ΔN and Δh can also be graphed as shown in FIG. 6 (b). This will be described next.

FIG. 6 (b) shows the relationship between the change Δh in the discharge pressure and the change ΔN in the command speed difference under the condition that the rotational speed of the pump is constant. When the pump speed is constant, the flow rate Q
When H changes, the pressure H changes.

(A) When there is no change in the flow rate Q during the previous and current samplings Since the characteristic curve I and the pipeline resistance curve F (H ₀ = Ha + aQ ⁿ ) intersect at the point O _i when the flow rate Q _i , the The pressures of the curves are the same, that is, the target value of discharge pressure H ₀
(The value obtained by the conduit resistance curve F) and the actual discharge pressure H (the value obtained by the characteristic curve I) match, and the discharge pressure Δh = 0. If there is no change in the flow rate Q between the previous sampling and the current sampling (Qi
= Qi ′), the command speed N ₀ does not change, and therefore the command speed difference ΔN = 0.

That is, Δh = 0 and ΔN = 0, and in this case, the origin (0, 0) in FIG. 6B is obtained.

(B) When the flow rate Q at this time of sampling is increased from the time of the last time of sampling: Since the characteristic curve I is a characteristic curve descending to the right, if the flow rate Q _i increases like Q _i ′ as shown in FIG. The discharge pressure actually detected is the target pressure H at the time of the previous sampling.
_With respect to ₀ , it decreases by Δh ₁ along the characteristic curve I, so that the discharge pressure difference Δh becomes a negative value.

In contrast, the command speed when the flow rate Q _i is N _{i, 'when} increases as the command speed moves to O _i2 is N _i along the pipeline resistance curve _F' flow Q _i is Q _i becomes . Therefore, the difference .DELTA.N ₌ N i '-N _i of' command speed _{N i} when the 'command speed _{N i} and the flow rate _{Q i} when the flow _{Q i} is a positive value .DELTA.N
Becomes ₁ .

In this way, when the flow rate Q _i increases under the condition that the pump rotational speed is constant, ΔN becomes a function of Δh which is decreasing to the right with the flow rate Q _i as a parameter (the region of Δh <0 in FIG. 6 (b)). .

(C) When the flow rate Q has increased at the time of this sampling relative to the time of the previous sampling Since the characteristic curve I is a characteristic curve descending to the right, it is actually detected that the flow rate Q _i decreases as Q _i ″ as shown in FIG. The discharge pressure to be generated is the target pressure H ₀ at the time of the previous sampling.
It increased by Delta] h ₂ along the characteristic curve relative, thus discharging the pressure difference Delta] h is a positive value.

In contrast, the command speed when the flow rate Q _i is N _i, the flow rate Q _i is Q _{i "Decreasing} as, moves to O _i4 points along the pipeline resistance curve F, the command speed is N _2" Becomes Thus negative value difference .DELTA.N ₌ N 2 "-N _i of" command speed _{N 2} when the "command speed _{N i} and the flow rate _{Q i} when the flow _{Q i} .DELTA.N
It becomes ₂ .

Thus, when the flow rate Q _i decreases under the condition that the pump rotation speed is constant, ΔN becomes a function of Δh which is decreasing to the right (using the flow rate Q _i as a parameter) (Δh> 0 in FIG. 6A). region).

(D) When the flow rate changes slightly around the flow rate Q _{i Based} on the above (a), (b), and (c), when the flow rate Q increases or decreases at the time of this sampling compared to the time of the previous sampling, Considering a range in which the change width of the flow rate Q _i is small, the relationship between ΔN and Δh can be approximated by a linear function.
When this function is graphed, Δh = 0 (origin) can be drawn corresponding to the point of the flow rate Q _i in FIG. 5, and is as shown in FIG. 6 (b).

When this relationship is expressed by an expression, it becomes as shown in expression (1). In the formula (1), K ₁ is a value obtained by experiment. That is, the characteristic of FIG. 6 (b) is obtained by an experiment, and K ₁ is obtained from the slope of the characteristic curve.

That is, the discharge pressure difference Δh is measured, and the discharge pressure difference Δh is measured.
Based on the above equation (1), the speed difference ΔN is added or subtracted from the speed at which the vehicle is currently operating. Similarly, based on the discharge pressure difference Δh measured by the above equation (2), By adding or subtracting the target pressure difference ΔH to the target pressure of, the predicted end pressure constant control can be performed so that the desired operating point of the pump 3 comes on the resistance curve F.

Therefore, when the amount of water used fluctuates, the microcomputer 20 compares the current discharge pressure H with the target pressure H ₀ to obtain the discharge pressure difference Δh, and the discharge pressure difference Δh is calculated as described above.
The command speed difference ΔH and the target pressure difference ΔH are obtained by substituting the equations (1) and (2). Then, the operation speed of the pump 3 is changed to a desired speed by obtaining the command speed to be sent to the variable frequency inverter 10 based on the command speed difference ΔN.
Moreover, the next target pressure can be set based on the target pressure difference ΔH. Therefore, the microcomputer 20 has a calculation unit for obtaining the discharge pressure difference Δh, a calculation unit for obtaining the command speed difference ΔN and the target pressure difference ΔH, and an instruction speed and a target pressure based on the command speed difference ΔN and the target pressure difference ΔH. And an arithmetic unit for obtaining

Next, the operation of the predicted constant end pressure control device will be described in detail with reference to FIG. In this case, it is assumed that the microcomputer 20 is programmed in advance so that it can be controlled according to the flow chart.

In order to simplify the explanation, as shown in FIG. 5, the amount of water used is Qi, the operating speed of the shift motor 9 is Ni, and the pump 3 is
The Q-H performance curve of 1 is I, and the vehicle is operating at the intersection point Oi on the resistance curve F.

In FIG. 7, the operations in the initial setting and the current operating state are not related to the gist of the present invention, so that the description thereof will be omitted and the operation will be described from step 101.

The initial target pressure H ₀ is set in step 101, the water supply pressure H is detected by the pressure sensor 7 in step 102, and the initial target pressure H ₀ and the water supply pressure H are compared in step 103. For example, when water consumption has decreased to and Qi "decreases, since the water supply pressure H is increased to ₃ Oi, the initial target pressure H ₀ is greater than the pressure. In addition, the initial target pressure H _0, the pump starts early It is stored in advance in a memory as a value corresponding to the operating speed, and is read from the memory and set at the time of startup.

As a result, in step 104, the initial target pressure H ₀ is subtracted from the water supply pressure H to obtain the water supply pressure difference Δh.
In step 5, the specified speed difference ΔN is obtained from the equation (1) based on the water supply pressure difference Δh. Then, in step 106, the command speed difference ΔN is added to the current rotation speed (N) of the variable motor 9 to obtain the command speed N, and the command speed N is the first output port of the microcomputer 20 shown in FIG. 20d outputs it to the variable frequency inverter 10 through the interface 52.
In this case, Δh = H−H ₀ > 0. As a result, the variable frequency inverter 10 reduces the rotation speed of the shift motor 9 to the command speed N.

Thereafter, in step 107, the target pressure difference ΔH is obtained from the equation (2) based on the water supply pressure difference Δh, and step 108
In step 101, the target pressure difference ΔH is added to the initial target pressure H ₀ obtained in step 101 to set the next target pressure H ₀ . In this case, since Δh = H−H ₀ > 0, ΔH <0, and the target pressure H ₀ is reduced by | Δh |. Then
After waiting for the time Δt required for the shift motor 9 to reach the command speed N in step 114, the processing in step 102 and subsequent steps is executed.

As a result of comparison between the target pressure H ₀ and the water supply pressure H in step 103, if they are equal, the current command speed N and the target pressure H ₀ are maintained.

On the other hand, in step 103, the initial target pressure H ₀ and the water supply pressure H ₀
As a result of the comparison with the water supply pressure H
Is smaller than the initial target pressure H ₀ , step 10
9 to 113 are executed. That is, the speed currently in operation
The command speed difference ΔN controls the shift Motoru 9 at a rotational speed N obtained by adding the (N), and the current target pressure H ₀ by adding the desired pressure difference ΔH update the following target pressure H _0.

Therefore, even if the water supply pressure changes according to the change in the amount of water used,
Since the pump can be controlled at a position where the resistance curve F and the Q-H performance curve of the pump 3 coincide with each other, the pressure at the water supply end can be made substantially constant. In addition, the microcomputer 2
By using 0, the conventional function calculator X,
Not only the devices such as the comparator C and the proportional integrator Y become unnecessary, but also the flow rate sensor 8 becomes unnecessary, so that the constituent devices of the control device can be simplified.

〔The invention's effect〕

As described above, according to the present invention, the microcomputer is used and the pressure on the pump discharge side is controlled by the differential value so that it is on the conduit resistance curve which is the target value. Therefore, the terminal pressure in a certain initial state is constant. In addition to being able to hold it with high accuracy, the constituent devices of the control device can be simplified, so that it is possible to provide a constant terminal pressure control device for a water supply device that is inexpensive and has a simple structure.

[Brief description of drawings]

FIG. 1 is a block diagram showing a control device of a conventional water supply device,
FIG. 2 is an operation characteristic diagram for explaining the operation of the water supply device,
FIG. 3 is a block diagram showing an embodiment of the predictive constant end pressure controller for a water supply device according to the present invention, FIG. 4 is a circuit diagram of the predictive constant end pressure controller, and FIG. Explanatory drawing showing the operating characteristics of the pump, FIG. 6
(a) is an explanatory view showing the relationship between the discharge pressure difference and the target pressure difference, (b) is an explanatory view showing the relationship between the discharge pressure difference and the indicated speed difference, and FIG. 7 is the procedure of the control operation. Is a flow chart. 1 ... Water tank, 2 ... Suction pipe, 3 ... Pump, 6 ... Water supply pipe, 7 ... Pressure sensor, 9 ... Shift motor, 10 ...
... Variable speed drive unit (variable frequency inverter), 20 ... Microcomputer, Δh ... Discharge pressure difference, ΔH ... Target pressure difference, ΔN ... Indicated speed difference, F ... Water supply line resistance curve

Claims (1)

[Claims] 1. A target pressure, which is a pump discharge pressure obtained from a virtual conduit resistance curve of a water supply path when the pump is operated at a certain rotation speed and a discharge flow rate, and the pump speed is unchanged. When the discharge flow rate changes, the pressure value stored as the current target pressure obtained from the flow rate at the previous sampling based on the pipe resistance curve and the flow rate changed are actually detected at the time of this sampling. The discharge pressure difference which is the difference between the pressure value and the current value obtained from the pipe resistance curve based on the flow rate at the previous sampling when the discharge flow rate of the pump changed without changing the rotation speed. The pressure value stored as the target pressure and the flow rate are changed. Predicts the pressure at the feed water end of the conduit,
A predictive terminal pressure constant control device for a water supply device that variably operates a pump so that this pressure is constant, in a variable speed drive unit that controls the rotation speed of a speed change motor that drives the pump, and is installed on the discharge side of the pump. The pressure sensor capable of detecting the discharge pressure from the pump, the detection signal of the pressure sensor, and the relationship between the discharge pressure difference and the target pressure difference, and the discharge pressure difference and the command speed difference. And the target pressure difference at present from the discharge pressure difference and the two relations, and send them to the variable speed drive unit based on the present command speed difference. A microcomputer for obtaining a command speed, sending a speed signal to the variable speed drive unit, and successively setting a next target pressure value based on the current target pressure difference. A predictive terminal pressure constant control device for a water supply device, characterized by: