JPH0874781A - Variable speed pump device and control method of variable speed pump device - Google Patents

Abstract

PURPOSE: To control the inferred terminal pressure at a specific value in a simple operation, without storing a curved line necessary to obtain an object pressure, by controlling the rotation frequency of a pump to make the detected discharge pressure of the pump to the calculated object pressure. CONSTITUTION: Detecting signals are inputted to a controller 15 from a flow rate detector 9 and a pressure detector 10, and the rotation frequency of a motor 8 is controlled by the controller 15. In this case, the controller 15 finds the pressure at the intersection of a straight line combining an object pressure at the shutoff flow rate, and an object pressure at a specific flow rate; and a straight line parallel to a straight line passing through the shutoff pressure at a ramdom rotation frequency, and combining the shutoff pressure at a specific rotation frequency, and the object pressure at a specific flow rate; as an object pressure, and controls the rotation frequency of the pump 4 to make the discharge pressure of the pump 4 detected by the pressure detector 10 at an object pressure. Consequently, it is not necessary to provide a function to set a curved line to find the object pressure, and a memory to store the curved line is also not necessary to prepare, so as to realize an inferred terminal pressure constant control at a low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable speed pump device and a method for controlling the variable speed pump device, which are capable of controlling a constant estimated end pressure.

[0002]

2. Description of the Related Art In a water supply system, there is known a variable speed pump device which keeps the pressure at the end of the water supply constant. In such a water supply system, the rotation speed of the variable speed pump is controlled so that the pressure at the end of the water supply is kept constant even if the flow rate varies.

When controlling the rotation speed of the variable speed pump, the pressure near the water tap at the end of the water supply system is directly detected,
If the rotation speed of the variable speed pump is controlled based on this detected pressure (terminal pressure constant control method), it is not necessary to correct the piping resistance between the pump and the water tap, and the pump can be directly pumped based on the above detected pressure. It is possible to control the number of rotations of, and the end pressure can be controlled with high accuracy.

However, in such means, pressure detecting means must be provided near the water tap at the end of the water supply system, and this pressure detecting means must be installed in the pipe at the end of the water supply system, and the detection signal is transmitted. It is not practical because it requires routing wiring for sending, and these works are expensive.

On the other hand, the pressure near the discharge port of the pump is detected, the pipe resistance corresponding to the flow rate is assumed, and the pressure at the end of the water supply system is estimated by the measurement and calculation of these to estimate the rotation speed of the variable speed pump. There is known a method for controlling (a presumed terminal pressure constant control method).

[0006] FIG. 1 shows a conventional constant estimated end pressure system.
It will be described with reference to FIGS. FIG.
In the above, 1 is a water receiving tank. A water absorption pipe 2 is taken out from the water receiving tank 1.

The water suction pipe 2a is connected to the suction side of the pump 4 via the sluice valve 3, and the discharge side of the pump 4 is connected to the water supply pipe 7 via the check valve 5 and the sluice valve 6. Pump 4
Is controlled by the motor 8.

The water supply pipe 7 is provided with a flow rate detector 9 for detecting the amount of water flowing in the pipe on and off, and a pressure detector 10 for detecting the water pressure in the pipe is provided downstream of the flow rate detector 9. Is provided.

Further, a pressure tank 12 is connected downstream of the pressure detector 10 via a gate valve 11. A downstream end of the pressure tank 12 is connected to a terminal water tap 14 via a sluice valve 13.

Detection signals from the flow rate detector 9 and the pressure detector 10 are input to the controller 15. The rotation speed control of the motor 8 described above is performed by the controller 15. The detailed configuration of the controller 15 will be described with reference to FIG. The inverter control circuit 16 of the controller 15 includes a flow rate detection unit 9
Also, the detection signal from the pressure detection unit 10 is input.

The inverter control circuit 16 outputs a speed signal to the inverter 17 based on the input detection signal. The inverter 17 outputs the AC power output from the commercial power supply 19 to the motor 8 through the contact 18s of the electromagnetic switch as an AC signal having a frequency corresponding to the speed signal.

Next, a detailed structure of the inverter control circuit 16 will be described with reference to FIG. In FIG. 3, the pressure signal of the water supply pipe 7 detected by the pressure detection unit 10 is amplified by the amplifier 21, then converted into a digital signal by the A / D converter 22, and the CPU (via the input port 23) Central processing unit) 24.

Further, the detection signal output from the flow rate detecting unit 9 is fetched by the CPU 24 via the input port 23. A memory 25 is connected to the CPU 24.
Further, the input port 23 is connected with a digital switch 26 for setting the target pressure at the shutoff flow rate and a digital switch 27 for setting the target pressure at the maximum flow rate.

Further, an output port 28 is connected to the CPU 24. This output port 28 is a D / A converter 29,
A speed signal is output to the above-mentioned inverter 17 via the amplifier 30.

Further, the output port 28 is connected to the coil 18 of the electromagnetic switch through an amplifier 31 for the electromagnetic switch. FIG. 10 is an HQ characteristic diagram of the pump, in which the vertical axis represents the pressure H and the horizontal axis represents the flow rate Q. The curve indicated by a is a characteristic showing the relationship between the flow rate and the pressure at the preset rated rotation speed No of the pump.

[0016] c is a resistance curve, and friction loss of the pipe occupies most of it, which changes according to the square of the flow rate. That is, the resistance curve c is a function of the flow rate. Assuming that the minimum required pressure at the end of the water supply system is g, the pressure in the vicinity of the discharge port of the pump 4 needs to be controlled along the resistance curve c in consideration of the actual head d and the friction loss e of the pipe. Becomes

That is, during the operation near the deadline operation, if the pressure near the pump discharge port is d + g, the terminal pressure can be g. However, since the pipe resistance e increases as the flow rate increases, the pressure near the discharge port of the pump must be controlled to the level of d + g + e, and the pressure along the so-called resistance curve c must be controlled as the target pressure. There is.

The characteristic of the pump is a function of the flow rate Q, the pressure H, and the rotation speed N, and there is a relation of f (Q, H, N) = constant.

Therefore, if any two of the flow rate Q, the pressure H, and the rotation speed N are determined, the rest are uniquely determined. And between these, a. The flow rate is proportional to the rotation speed.

B. There is a relationship that pressure is proportional to (rotation speed) ² . Using this characteristic, a method of measuring the flow rate from the number of rotations of the pump and the discharge pressure is disclosed in JP-B-53-134.
No. 11 publication. This will be described with reference to FIG.

In the HQ characteristic diagram of FIG. 11, the curve indicated by a is a characteristic showing the relationship between the flow rate and the pressure at the preset rated rotation speed No of the pump. The flow rate and pressure when operating at the rated speed No are: (n / No) times the flow rate and (n / N) when operating at an arbitrary speed n.
o) becomes ^twice, the characteristic is indicated by a curve a '. Therefore, the intersection of the pressure p during operation and the curve a'is the flow rate q at that time.

By estimating the flow rate q in this way, the flow rate can be known without using a particularly expensive flow meter.
Actually, the pressure p during operation is multiplied by (No / n) ² times, the flow rate qo at the rated speed No is obtained from the intersection with the previously measured curve a, and this flow rate qo is multiplied by (n / No), The flow rate q corresponding to the pressure during operation can be obtained, and the flow rate can be obtained only by the curve a without obtaining the curve a ′.

Therefore, based on the flow rate thus obtained, the pressure corresponding to the flow rate can be obtained along the curve c in FIG. 10 and set as the target pressure. The method of measuring the flow rate from the rotation speed of the pump and the discharge pressure and obtaining the target pressure based on the obtained flow rate has been described above. However, as another method, the target pressure may be obtained from the rotation rate of the pump. it can. This will be described with reference to FIG.

In FIG. 12, the vertical axis represents pressure and the horizontal axis represents rotational speed. As described above, the flow rate, the pressure, and the rotation speed of the pump can be naturally known if any two of them are known. Therefore, when operating along the curve c in FIG. 10, since the flow rate and the pressure are known, the rotation speed is naturally determined. FIG. 12 shows the number of rotations in comparison with the pressure. That is, when driving along the curve c in FIG. 10, at the same time, driving along the curve in FIG. Therefore, if the curve of FIG. 12 is set in advance and the operation is performed along the curve of FIG. 12, it is possible to naturally operate along the curve c of FIG.

[0025]

However, in the conventional device, the target pressure could not be obtained unless the curve a in FIG. 11 or the curve in FIG. 12 was set in advance. It required functions to set and memorize, required an expensive microcomputer, and required a large amount of memory for memorizing curves. Therefore, there is a problem that the manufacturing cost of the device is increased.

The present invention has been made in view of the above points, and an object thereof is a variable speed capable of performing constant control of estimated end pressure by a simple calculation without storing a curve necessary for obtaining a target pressure. A pump device and a variable speed pump device control method are provided.

[0027]

A variable speed pump device according to a first aspect of the present invention is a variable speed pump, a rotation speed detecting means for detecting the rotation speed of the pump, and a pressure detecting means for detecting the discharge pressure of the pump. In a variable speed pump device equipped with, a straight line connecting a target pressure at a cutoff flow rate and a target pressure at a predetermined flow rate and a cutoff pressure at an arbitrary rotation speed, and a cutoff pressure at a predetermined rotation speed and a predetermined flow rate. In the target pressure calculation means for calculating the pressure at the intersection of the straight line connecting the target pressure in and the straight line parallel to the target pressure as the target pressure, and the discharge pressure of the pump detected by the discharge pressure detection means by the target pressure calculation means. And a rotation speed control means for controlling the rotation of the pump so that the calculated target pressure is obtained.

A control method for a variable speed pump device according to a second aspect comprises a variable speed pump, a rotation speed detecting means for detecting a rotation speed of the pump, and a pressure detecting means for detecting a discharge pressure of the pump. In the variable speed pump device, the straight line connecting the target pressure at the cutoff flow rate and the target pressure at the predetermined flow rate passes through the cutoff pressure at the arbitrary rotation speed, and the cutoff pressure at the predetermined rotation speed and the target pressure at the predetermined flow rate. It is characterized in that the pressure at the intersection of the straight line connecting with and the parallel line is obtained as the target pressure.

[0029]

According to the present invention, the straight line connecting the target pressure at the cutoff flow rate and the target pressure at the predetermined flow rate and the cutoff pressure at the arbitrary rotation speed are passed, and the cutoff pressure and the predetermined flow rate at the predetermined rotation speed are passed. The pressure at the intersection of the straight line connecting with the target pressure and the parallel line is obtained as the target pressure.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Since the configurations of FIGS. 1 to 3 have already been described, detailed description thereof will be omitted. Here, in FIG. 3, the formula (3) described later is stored in the memory 25.
And the control program for performing the processing shown in the flowcharts of FIGS. 8 and 9 are stored.

Next, how to obtain the target pressure for operating along the curve c in FIG. 10 will be described with reference to FIGS. 4 to 8. In FIG. 4, the vertical axis represents pressure and the horizontal axis represents flow rate. In the figure, Hmin and Hmax are target pressures preset at the shutoff flow rate and the maximum flow rate preset by the above-mentioned digital switch, and Ho is the shutoff pressure when operating at the rated speed No. When the description of the target pressure calculating means of claim 1 is applied to each symbol of FIG. 4 to describe in more detail, it is as follows. That is, “a straight line c ′ connecting the target pressure Hmin at the cutoff flow rate and the target pressure Hmax at the predetermined flow rate Qmax and the cutoff pressure (N / No) ² · Ho at an arbitrary rotation speed N is passed through the predetermined rotation speed. Pressure H at an intersection E between a straight line a ′ connecting the shutoff pressure Ho at a number No and a target pressure Hmax at a predetermined flow rate Qmax and a parallel line b ′.
Is the target pressure. That is, the target pressure for performing the estimated constant end pressure control is obtained as the pressure at the intersection E of the straight line c'and the straight line b '. By controlling the pressure at the intersection E as the target pressure, it is possible to operate along the curve c in FIG.

This will be described in detail with reference to FIG.
5, the same symbols as in FIG. 4 indicate the same contents. Here, a curve a is a pump characteristic at a rated rotation speed No, a curve b is a pump characteristic at an arbitrary rotation speed N, and a curve c indicated by a broken line is a target pressure curve for the estimated constant end pressure control and is a square curve. . This is because the wiring resistance is approximately proportional to the square of the flow rate as shown in FIG. The target pressure during operation at an arbitrary operating point is the pressure at the intersection F between the curve b, which is the pump characteristic at an arbitrary rotational speed N, and the curve c, which is the target pressure curve for the estimated constant end pressure control. Is. However, since the pressure at the intersection F of the curves c and b and the pressure at the intersection E of the straight lines c ′ and b ′ are almost equal, instead of the intersection F, the intersection E
Can be used. This will be described in detail. Curve a
The pump characteristic at the rated speed No shown by is approximated by the following function as H = Ho-k · Q ² (1). The flow rate and pressure of the pump characteristics are proportional to the first and second powers of the rotational speed, respectively. Therefore, at any rotation speed N, H '= (N / No) ² .HQ' = (N / No) .Q. When these are substituted into the above equation (1), the pump characteristic at any rotation speed N H '= (N / No) 2 · Ho -k · Q' is ² ... (2). That is, the equations (1) and (2) are curves parallel to each other, and the curve a of FIG. 5 shown by the equation (1) is shown by the equation (2) when the rotation speed = N, A curve b of 5 is obtained. The curve b is obtained by translating the curve a in the vertical axis direction. That is, the difference between the dead pressure Ho of the curve a and the dead pressure (N / No) ² · Ho of the curve b = Ho − (N
/ No) ² · Ho in parallel with the vertical axis. In such a state, the target pressure when operating at an arbitrary rotation speed is the pressure at the intersection F between the pump characteristic curve b and the target pressure curve c.

However, when the pump characteristic curves a and b and the target pressure curve c are both square curves, the pressure at the intersection E of the straight lines b'and c'instead of the intersection F of the curves b and c. Can be the target pressure. That is, the straight line b ',
When the intersection E of c ′ is the target pressure, the actual operating point is the intersection F of the curves b and c, and the vehicle operates along the square curve c. This is because the intersection E of the straight lines b ′ and c ′ and the intersection F of the curves b and c have the same coordinate in the vertical axis direction. This will be explained.

The curve c in FIG. 5 is a quadratic curve having a point D on the Y axis as its apex. The curve b is also a quadratic curve having a point B on the Y axis as its apex. Therefore, the bow DF-A'-E-D consisting of the curve c and the straight line c'and the bow BF-B'-EB consisting of the curve b and the straight line b'are different in the vertical direction. They are arcuate shapes that are opposite to each other and have different scales in the Y-axis direction. Therefore, if the bow BF-B'-EB consisting of the curve b and the straight line b'is inverted upside down and expanded in the Y-axis direction, the bow D-comprising the curve c and the straight line c '.
It overlaps with F-A'-E-D. Therefore, the curve b and the straight line b '
A horizontal line E-F on the bow B-F-B'-E-B consisting of
Is an arc D-F-A'-E consisting of a curve c and a straight line c '.
It overlaps with the horizontal line EF on -D.

From this, the intersection point F between the curve b and the curve c
And the intersection E of the straight line b ′ and the straight line c ′ have the same coordinate in the vertical axis direction. Therefore, instead of setting the pressure at the intersection F between the curves b and c as the target pressure, the pressure at the intersection E between the straight line b'and the straight line c'can be set as the target pressure.

The method of obtaining the intersection has been described above geometrically. Actually, the intersection can be obtained by replacing the calculation with a microcomputer. Next, a method for obtaining an intersection by calculation will be described.

The following formulas are set in the memory 25 in advance. H = (a-d-b-c) / (a-b-c + d) (3) However, a = (N / No) ² Ho (4) b = (N / No) ² Ho- (Ho-Hmax) (5) c = Hmin (6) d = Hmax (7) Ho is the cutoff pressure at the rated speed No. The above constants, Hmin and Hmax are as described above. , Preset by the digital switches 26 and 27 of FIG. The shutoff pressure Ho at the rated speed No is set by a setting means (not shown).

As described above, the target pressure H for the estimated constant end pressure control can be obtained by the equation (3). The above equation (3) is obtained as follows. The coordinates of the respective points of the straight line b'and the straight line c'in FIG. 4 in the vertical axis direction are simplified like the straight lines b'and c'in FIG. 6 to simplify the calculation. The straight line b'and the straight line c'in FIG. 6 are expressed by the following equations, respectively.

H = a− (ab) · Q / Qmax (8) Straight line b ′ H = c + (dc) · Q / Qmax (9) Straight line c ′ Straight line b ′, Straight line c The pressure at the intersection point of ′, that is, the above equation (3) is obtained by solving Q / Qmax by eliminating the above equations (8) and (9) as simultaneous equations. Then, from the correspondence between FIG. 6 and FIG. 4, equations (4) to (7) are obtained.

The above arithmetic processing is executed along the flowchart shown in FIG. In the above description, the characteristic of the pump is approximated by the equation (1), that is, the curve a of FIG. 5, but the actual characteristic of the pump is slightly different. This will be described with reference to FIG.

In FIG. 7, the same symbols as in FIG. 5 indicate the same contents. The curve a ″ in FIG. 7 is a characteristic of an actual pump. Then, the characteristic at an arbitrary rotation speed becomes a curve b ″, which is not a perfect parallel movement but coincides at the point B and a little at the point B ′. It shifts. The actual operating point is not point F but point F '. Therefore, the vehicle is not driven along the curve c, but is driven along the curve c ″. Therefore, the difference between the curves c and c ″ is an error. Deadline flow rate and maximum flow rate Q
At the two points at both ends of max, this error becomes 0,
Errors occur at intermediate flow rates. However, in comparison with the case where the discharge pressure constant control is performed only with d + g in FIG. 10, the curve c is closer, and the above error is acceptable, and the practical effect is large.

Next, a method for obtaining the shutoff pressure Ho will be described with reference to FIGS. During pump operation,
When the flow rate detecting means 9 in FIG. 1 detects a minimum flow rate below a predetermined level, the pressure H detected by the pressure detection unit 10 at that time and the speed signal from the inverter control circuit 16 to the inverter 17, that is, the rotation speed N. From the above, the deadline pressure Ho at the rated speed No is obtained. Since the pump pressure is proportional to the square of the rotation speed, it can be obtained by the following formula.

Ho = (No / N) ² · H The above processing is executed according to the flowchart shown in FIG. By doing so, Ho is automatically obtained when the flow rate used is below the minimum flow rate. Therefore, simply set the two values Hmin and Hmax described above in advance.
It is convenient because it can control the estimated end pressure.

In the above embodiment, one variable speed pump has been described, but a plurality of pumps may be used. For example,
It is also possible to operate two or three units in parallel.

During parallel operation of the variable speed pump and the constant speed pump,
Although the application of the present application is difficult, the present application can be easily applied particularly when a plurality of inverters are provided and are operated in parallel at the same rotation speed.

The method for detecting the rotation speed may be any method that is related to the rotation speed, such as frequency, current, and power consumption. Further, the pressure is not limited to the discharge pressure, but may be anything such as the total head.

In the embodiment, the intersection is obtained by calculation, but it may be obtained by a method other than calculation such as a graphic processing method. As described above, the estimated end pressure constant control is performed only by finding the intersection of two straight lines that are determined by the preset target pressure at the deadline flow rate and the maximum flowrate and the deadline pressure at the rated rotation speed and the arbitrary rotation speed. The target pressure of can be obtained. Therefore, it is not necessary to previously set the pump characteristic curve or the rotation speed-target pressure curve as in the conventional case, and therefore, the curve setting means is also unnecessary. Therefore, no complicated calculation is required. Therefore, the calculation function and the memory capacity can be extremely small.

Generally, when a one-chip microcomputer is used as the microcomputer shown in FIG. 3, since the arithmetic function and the memory capacity are small, another memory is externally attached to store the conventional curve. Costs have increased due to the need to take measures such as doing so, and the use of large-capacity memory and expensive one-chip microcomputers with advanced arithmetic functions.

According to the present application, since the memory of the curve is not required, the memory capacity is small, and the operation is simple, so that an inexpensive low-function one-chip microcomputer can be used, and the cost can be reduced. Becomes

Further, it is conceivable that the inverter control circuit 16 becomes unnecessary by adding these programs to the microcomputer incorporated in the inverter itself. In such a case, However, the conventional method is difficult to apply due to the limited memory capacity and calculation speed.
Since the present application is small in scale, it is possible to easily deal with such a case.

[0051]

As described above in detail, according to the present invention, the function of setting and storing these curves is not required, and many memories for storing the curves are also unnecessary. Therefore, it is possible to provide the variable speed pump device that can realize the constant estimated end pressure control at low cost.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a variable speed pump device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a detailed configuration of a controller shown in FIG.

FIG. 3 is a block diagram showing a detailed configuration of the inverter control circuit of FIG.

FIG. 4 is a diagram showing pressure-flow rate characteristics.

FIG. 5 is a diagram showing pressure-flow rate characteristics.

FIG. 6 is a diagram showing pressure-flow rate characteristics.

FIG. 7 is a diagram showing pressure-flow rate characteristics.

FIG. 8 is a flowchart for explaining the operation of the embodiment.
To.

FIG. 9 is a flowchart for explaining the operation of one embodiment.
To.

FIG. 10 is a diagram showing pressure-flow rate characteristics.

FIG. 11 is a diagram showing pressure-flow rate characteristics.

FIG. 12 is a diagram showing pressure-flow rate characteristics.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Water tank, 2 ... Water absorption pipe, 3, 6, 11, 13 ... Gate valve, 4 ... Pump, 5 ... Check valve, 7 ... Water supply pipe, 8 ... Mo-
, 9 ... Flow rate detection unit, 10 ... Pressure detection unit, 12 ... Pressure tank, 14 ... End water tap, 15 ... Controller, 16 ... Inverter control circuit, 17 ... Inverter, 19 ... Commercial power source, 2
1 ... Amplifier, 22 ... A / D converter, 23 ... Input port,
24 ... CPU, 25 ... Memory, 26, 27 ... Digital switch, 28 ... Output port, 29 ... D / A converter, 3
0,31 ... Amplifier.

Claims (2)

[Claims] 1. A variable speed pump device comprising a variable speed pump, a rotation speed detection means for detecting the rotation speed of the pump, and a pressure detection means for detecting the discharge pressure of the pump. The intersection of the straight line connecting the pressure and the target pressure at the specified flow rate, and the straight line that passes through the cutoff pressure at the desired rotation speed and is parallel to the straight line connecting the cutoff pressure at the specified rotation speed and the target pressure at the specified flow rate The target pressure calculation means for obtaining the pressure at the target pressure as the target pressure, and the rotation speed of the pump so that the discharge pressure of the pump detected by the discharge pressure detection means becomes the target pressure calculated by the target pressure calculation means. A variable speed pump device comprising: a rotation speed control unit for controlling. 2. A variable speed pump device comprising a variable speed pump, a rotation speed detection means for detecting the rotation speed of the pump, and a pressure detection means for detecting the discharge pressure of the pump. The intersection of the straight line connecting the pressure and the target pressure at the specified flow rate, and the straight line that passes through the cutoff pressure at the desired rotation speed and is parallel to the straight line connecting the cutoff pressure at the specified rotation speed and the target pressure at the specified flow rate A method for controlling a variable speed pump device, characterized in that the pressure at step S1 is obtained as a target pressure.