WO2014054554A1

WO2014054554A1 - Water supply device

Info

Publication number: WO2014054554A1
Application number: PCT/JP2013/076476
Authority: WO
Inventors: 正禎池田; 手嶋　友治; 宏則二ノ宮; 木下　昇; 博之田村; 立石　和文; 中島　薫
Original assignee: 株式会社荏原製作所
Priority date: 2012-10-04
Filing date: 2013-09-30
Publication date: 2014-04-10
Also published as: EP2910787B1; CN104704242B; CN104704242A; JP6186366B2; EP2910787A1; JPWO2014054554A1; ES2686333T3; EP2910787A4

Abstract

The present invention pertains to a water supply device that pressurizes water from a water main and supplies this water to a building such as a housing complex or a commercial building. This water supply device is equipped with a control unit (10) that detects a low-water-amount state on the basis of a decrease in the rotational speed of a pump (1). The control unit (10) stores a first lower limit value (L1), which is higher than a closed-state rotational speed (N0) required to achieve a target pressure (PA) when the pump is closed off, and a second lower limit value (L2), which is lower than the closed-state rotational speed (N0). The control unit (10) switches the lower limit value for the rotational speed of the pump (1) from the first lower limit value (L1) to the second lower limit value (L2), and when the rotational speed of the pump (1) reaches or falls below the closed-state rotational speed (N0) within a prescribed detection period, the control unit determines that the pump (1) is in a low-water-amount state.

Description

Water supply device

The present invention relates to a water supply apparatus that pressurizes water from a water main to supply water to a building such as an apartment house or a commercial building.

FIG. 7 is a schematic view showing a conventional water supply apparatus. As shown in FIG. 7, the water supply apparatus includes a pump 1 for pressurizing water, a motor 2 for rotating the pump 1, an inverter 3 for applying a variable frequency voltage to the motor 2, and a discharge side pressure of the pump 1 The operation of the pump 1 is controlled via the inverter 3 and the motor 2 so that the discharge side pressure sensor 16 to be measured and the discharge side pressure measured by the pressure sensor 16 are maintained at a preset target pressure. And a control unit 5.

A check valve 15 is disposed on the discharge side of the pump 1. A flow switch 19 is disposed on the discharge side of the check valve 15, and a pressure sensor 16 and a pressure tank 18 are disposed on the discharge side. The check valve 15 is a valve for preventing backflow of water when the pump 1 is stopped. The flow switch 19 is a flow detector that detects that the discharge flow rate from the pump 1 has decreased to a predetermined value. The pressure tank 18 is a pressure holder for holding the discharge pressure while the pump 1 is stopped. The flow switch 19 and the pressure sensor 16 are connected to the control unit 5 via a signal line.

FIG. 8 is a performance curve diagram of a conventional water supply system. The vertical axis in FIG. 8 represents the discharge side pressure [Pa], and the horizontal axis represents the flow rate [L / min] of water discharged from the pump 1. The rotational speed of the pump 1 changes according to the flow rate (N4 → N0) so that the pressure on the discharge side is maintained at the predetermined target pressure PA. The operating condition when the flow rate is zero is called a so-called shut-off operation. In this cut-off operation, the target pressure PA and the current discharge pressure are in the same equilibrium state, and the control is normal. However, since water does not flow from the pump 1, the operation is wasteful. Therefore, when the flow switch 19 detects that the flow rate of water has decreased to a predetermined value (hereinafter referred to as a small water amount state), the water supply device is configured to perform a small water amount stop operation. Specifically, the operation speed of the pump 1 is temporarily increased, the discharge side pressure is increased to a predetermined stop pressure, and then the operation of the pump 1 is stopped. The pressure on the discharge side is held by the pressure tank 18 and the check valve 15.

When the discharge side pressure decreases to a predetermined start pressure, the control unit 5 starts the operation of the pump 1. The pump 1 is driven at variable speed based on the output signal of the pressure sensor 16. Generally, the pump is maintained so that the pressure signal measured by the pressure sensor 16 (that is, the discharge pressure of the pump 1) is maintained at a predetermined constant target pressure regardless of the flow rate of water discharged from the pump The constant discharge pressure control for controlling the operation speed of 1 and the estimated constant terminal pressure control for constant control of the water pressure supplied to the end faucet by changing the target pressure according to the pipeline resistance are performed.

Although the flow switch 19 has the merit of being able to detect the low water quantity state simply by the detection signal, it is generally expensive, and if the detection float inside is worn due to repeated operations, it may cause an operation failure such as sticking. In addition, the flow switch may cause malfunction due to foreign matter biting. In these malfunctioning states, the water supply device erroneously determines that it is a small amount of water state even though it is not actually a small amount of water state, and the stop operation is performed, causing a drop in discharge pressure or conversely a small amount of water There is an adverse effect that the shut-off operation is continued to overheat the pump 1 to apply mechanical stress or waste energy because the stop operation is not performed because it is misjudged that there is not a low water quantity state.

Therefore, as disclosed in Patent Document 1, a water supply apparatus capable of detecting a low water quantity state without using a flow switch has been proposed. The conventional flow switchless water supply apparatus switches the control mode of the pump from feedback control such as constant discharge pressure control to fixed rotational speed control, rotates the pump at a rotational speed lower than the rotational speed corresponding to the shutoff pressure, and discharges it. By detecting whether or not the side pressure decreases, the low water quantity state is detected.

However, in such a conventional method, it is necessary to switch the control mode of the pump from feedback control to fixed rotational speed control in order to detect a low water quantity state. Such switching of control modes can cause rapid fluctuations in the pressure of the expelled water. In particular, when returning from fixed rotational speed control to feedback control, the rotational speed of the pump may rapidly increase.

JP 2002-130141 A JP 2002-54577 A

The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a water supply device capable of detecting a low water quantity state while performing feedback control such as discharge pressure constant control.

In order to achieve the above-mentioned object, one aspect of the present invention measures a pump, a motor for rotating the pump, an inverter for applying a variable frequency voltage to the motor, and a discharge side pressure of the pump The pump and the pump via the motor and the inverter such that the discharge side pressure of the pump is maintained at a predetermined target pressure based on the discharge side pressure sensor and the measured value of the discharge side pressure. A controller for feedback controlling the rotational speed of the motor, wherein the controller is a first lower limit of a rotational speed higher than a cutoff rotational speed required to achieve the target pressure in a cutoff state. Value and a second lower limit of the rotational speed lower than the shutoff rotational speed are stored, and the control unit stores the lower limit of the rotational speed of the pump from the first lower limit to the second lower limit. Switched to limited values, when the rotational speed of the pump within a predetermined detection time is equal to or less than the deadline rotational speed, the pump is characterized in that it is determined that it falls low water conditions.

In a preferred aspect of the present invention, the control unit sets the lower limit value of the rotational speed of the pump to the first lower value when the state where the rotational speed of the pump is less than the first lower limit continues for a predetermined confirmation time. Switching from the lower limit value to the second lower limit value is characterized.
In a preferred aspect of the present invention, the control unit continues the predetermined confirmation time in a state where the rotational speed of the pump is equal to or less than the first lower limit and the discharge pressure is higher than a predetermined control value. And switching the lower limit value of the rotational speed of the pump from the first lower limit value to the second lower limit value.
A preferred embodiment of the present invention is characterized in that the control value is the same as the target pressure at the time of the shutoff operation.

In a preferred aspect of the present invention, the control unit is configured such that the rotational speed of the pump is less than the shutoff rotational speed within the predetermined detection time, and the rotational speed of the pump is less than the shutoff rotational speed. And the pump is determined to be in a low water state.
A preferred embodiment of the present invention is characterized in that the target pressure is constant regardless of the flow rate of water discharged from the pump.
A preferred embodiment of the present invention is characterized in that the target pressure changes in accordance with the flow rate of water expelled from the pump.

When the pump is in a low flow condition or shutoff condition, the operating point of the pump is on the pump performance curve which represents the first lower limit. In this state, when the first lower limit value is switched to the second lower limit value, the rotational speed of the pump is rapidly reduced based on feedback control. Therefore, the control unit can detect the low water quantity state from the decrease in the rotational speed of the pump.

It is a figure showing one embodiment of a water supply device concerning the present invention. It is a figure which shows the pump performance curve of the water supply apparatus which concerns on this invention. It is a flowchart of a small water quantity detection operation. It is a pump performance curve figure which shows presumed terminal pressure fixed control. It is a schematic diagram which shows a direct connection type water supply apparatus. FIG. 2 shows an embodiment of a water supply system with two sets of pumps, a motor and an inverter. It is a schematic diagram which shows the conventional water supply apparatus. It is a performance curve figure of the conventional water supply apparatus.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a view showing an embodiment of a water supply apparatus according to the present invention. The same elements as the elements shown in FIG. 7 are indicated by the same reference numerals and the description thereof will be omitted.

The basic configuration of the water supply apparatus of the present embodiment is the same as the water supply apparatus shown in FIG. 7, but differs from the water supply apparatus shown in FIG. 7 in that the flow switch is not provided. The water supply apparatus of the present embodiment includes a control unit 10 that controls the rotational speed of the pump 1 via the motor 2 and the inverter 3 based on the discharge side pressure measured by the pressure sensor 16. More specifically, the control unit 10 controls the rotational speed of the pump 1 based on the discharge side pressure measured by the pressure sensor 16 so that the discharge side pressure of the pump 1 becomes a preset target pressure. Perform feedback control to control the

As an example of feedback control, discharge pressure constant control that controls the operating speed of the pump 1 so as to maintain the discharge side pressure at a constant target pressure regardless of the water discharge flow rate, The estimated terminal pressure constant control which maintains the supply water pressure in the end faucet constant by changing accordingly is mentioned.

The control unit 10 transmits to the inverter 3 a command value of the rotational speed of the pump 1 for eliminating the difference between the current discharge pressure measured by the pressure sensor 16 and the preset target pressure. There is. The inverter 3 drives the motor 2 in accordance with the command value of the rotational speed, whereby the pump 1 rotates at the commanded rotational speed. The control unit 10 further has a function of detecting a state in which the flow rate of water discharged from the pump 1 has reached a predetermined lower limit value (that is, a small water amount state) based on the above-described feedback control.

FIG. 2 is a diagram showing a pump performance curve of the water supply device according to the present invention. FIG. 2 shows an example of constant discharge pressure control in which the target pressure is constant regardless of the flow rate. The control unit 10 stores a first lower limit L1 and a second lower limit L2, which are lower limits of the rotational speed of the pump 1. The first lower limit L1 is set to a value higher than the rotational speed N0 of the pump 1 corresponding to the target pressure PA during shutoff operation (hereinafter referred to as shutoff rotation speed N0), and the second lower limit L2 is , Is set to a value lower than the cutoff rotational speed N0. Specifically, the first lower limit L1 is a value (N0 × 1.05) of 105% of the shutoff rotational speed N0, and is a value slightly higher than the shutoff rotational speed N0. The second lower limit L2 is a 95% value (N0 × 0.95) of the shutoff rotational speed N0, and is a value slightly lower than the shutoff rotational speed N0. These coefficients 105% and 95% are exemplifications, and the present invention is not limited to these numerical values, and can be changed in a range where there is no problem in operation such as not being too long for the determination of the low water quantity state. The cut-off rotational speed N0 is the rotational speed of the pump 1 necessary for the pump 1 to achieve the predetermined target pressure PA when the pump 1 is at cut-off operation, that is, when the flow rate is zero. The cutoff rotational speed N0 is stored in advance in the control unit 10.

The control unit 10 has a function of switching the lower limit value of the rotational speed of the pump 1 between the first lower limit value L1 and the second lower limit value L2 while the pump 1 is in operation. In normal pump operation, the lower limit value of the rotational speed of the pump 1 is set to the first lower limit value L1, and the pump 1 is feedback-controlled within the speed range equal to or higher than the first lower limit value L1. That is, the control unit 10 controls the rotational speed of the pump 1 so that the discharge side pressure of the pump 1 is maintained at the preset target pressure PA.

The pump 1 is operated at an operating point indicated by a black circle in FIG. When the flow rate decreases, the rotational speed of the pump 1 also decreases and eventually reaches the first lower limit L1. When the flow rate further decreases, the operating point of the pump 1 rides on the pump performance curve showing the first lower limit L1, as shown in FIG. In the low water state, particularly in the closed state (flow rate is 0), the current discharge pressure measured by the pressure sensor 16 is necessarily higher than the target pressure PA. The control unit 10 transmits a rotational speed command value equal to or less than the shutoff rotational speed N0 to the inverter 3 in order to eliminate the difference between the current discharge side pressure and the target pressure PA. Therefore, when the lower limit value of the rotational speed of the pump 1 is switched from the first lower limit value L1 to the second lower limit value L2, the rotational speed of the pump 1 rapidly decreases and becomes equal to or less than the cutoff rotational speed N0. Such a decrease in the rotational speed of the pump 1 is expressed as a decrease in the command value of the rotational speed of the pump 1. The control unit 10 can detect the decrease in the rotational speed of the pump 1 from the command value of the rotational speed generated by itself.

As described above, when the lower limit value of the rotational speed of the pump 1 is switched from the first lower limit value L1 to the second lower limit value L2 in the small water amount state (and the shutoff state), feedback to maintain the target pressure PA The rotational speed of the pump 1 is rapidly reduced based on the control. Therefore, the control unit 10 can detect the low water quantity state from such a decrease in the rotational speed of the pump 1.

In the conventional low water content detection method, the control mode is switched from feedback control to fixed rotation speed control. On the other hand, the control unit 10 of the present invention performs feedback control to maintain the target pressure PA even when the small amount of water is detected. That is, when the operation of the water supply apparatus is switched from the normal water supply operation to the low water amount detection operation, and also when the low water amount detection operation is returned to the normal water supply operation, the rotational speed of the pump 1 is controlled according to feedback control. Therefore, the rotational speed of the pump 1 does not change suddenly, and a smooth water supply operation can be realized.

Next, the details of the small amount of water detection operation will be described with reference to FIG. FIG. 3 is a flowchart of the small amount of water detection operation. As shown in FIG. 3, the control unit 10 determines whether or not the command value of the rotational speed of the pump 1 is a value equal to or less than the first lower limit L1 (step 1). When the command value of the rotational speed of the pump 1 is a value equal to or less than the first lower limit value L1, the control unit 10 compares the current discharge pressure obtained from the pressure sensor 16 with a predetermined control value, It is determined whether or not the discharge side pressure is higher than this control value (step 2). This control value is the same value as the target pressure PA at the time of shutoff operation.

When the command value of the rotational speed of the pump 1 is a value equal to or less than the first lower limit L1 and the current discharge side pressure is a value higher than a predetermined control value, the control unit 10 sets in advance. The

steps

1 and 2 are repeated (step 3) until a verification time (e.g. 10 seconds) has elapsed. When the command value of the rotational speed of the pump 1 is equal to or less than the first lower limit L1 and the current discharge pressure is higher than the predetermined control value during the above confirmation time, The control unit 10 switches the lower limit value of the rotational speed of the pump 1 from the first lower limit value L1 to the second lower limit value L2 (step 4). Then, the control unit 10 determines whether or not the command value of the rotational speed of the pump 1 is a value equal to or less than the shutoff rotational speed N0 (step 5). Control unit 10 further determines whether the command value of the rotational speed of pump 1 has decreased to a value equal to or less than cut-off rotational speed N0 within a predetermined detection time (for example, 2 seconds) (step 6). Even after switching from the first lower limit L1 to the second lower limit L2, when the water is discharged to some extent, the rotational speed of the pump 1 is slow (for example, a time longer than 2 seconds Over time). Therefore, in such a case, it is not judged that the low water quantity state.

If the command value of the rotational speed of the pump 1 falls to a value less than or equal to the shutoff rotational speed N0 within the detection time, the control unit 10 proceeds to step 5 until the preset monitoring time (for example, 2 seconds) elapses. And repeat step 6 (step 7). When the pump 1 is in the low water state or in the shutoff state, the discharge side pressure is held by the check valve 15, so the difference between the current discharge side pressure and the target pressure PA does not disappear. The control unit 10 generates a command value of the rotational speed of the pump 1 for reducing the current discharge side pressure to the target pressure PA. As a result, the rotational speed of the pump 1 becomes equal to or less than the shutoff rotational speed N0. And when the command value of the rotational speed of the pump 1 continues the state of the value of the cut-off rotational speed N0 or less for the predetermined monitoring time, the control unit 10 determines the low water quantity state (step 8). After the determination of the low water quantity state, the control unit 10 temporarily accelerates the pump 1 to perform pressure accumulation operation to increase the pressure in the pressure tank 18 (step 9), and then stops the pump 1 (step 10) .

The small water amount detection operation of the control unit 10 described above can be applied not only to the discharge pressure constant control but also to the estimated terminal pressure constant control. FIG. 4 is a pump performance curve diagram showing estimated end pressure constant control. The estimated terminal pressure constant control is a control method that controls the water pressure supplied to the terminal water tap at a constant level by changing the target pressure according to the pipeline resistance. The curve R shown in FIG. 4 shows the target pressure which changes according to the pipeline resistance. The pipeline resistance increases with the flow rate. The target pressure at the maximum rotational speed N3 of the pump 1 is PA, and the target pressure during shutoff operation is PB. The target pressure gradually increases from PB to PA according to the flow rate.

Also in this example, the first lower limit value L1 of the rotational speed of the pump 1 is set to a value slightly higher than the cutoff rotational speed N0 required to achieve the target pressure PB during the shutoff operation. The lower limit L2 is set to a value slightly lower than the cutoff rotational speed N0. For example, the first lower limit L1 is set to 105% of the shutoff rotational speed N0, and the second lower limit L2 is set to 95% of the shutoff rotational speed N0.

When the flow rate decreases, the rotational speed of the pump 1 also decreases and eventually reaches the first lower limit L1. When the flow rate further decreases, the operating point of the pump 1 rides on the pump performance curve showing the first lower limit L1, as shown in FIG. In the low water state, particularly in the closed state (flow rate is 0), the current discharge side pressure measured by the pressure sensor 16 is always higher than the target pressure corresponding to the flow rate. The control unit 10 transmits a rotational speed command value equal to or less than the shutoff rotational speed N0 to the inverter 3 in order to eliminate the difference between the current discharge side pressure and the target pressure. Therefore, when the lower limit value of the rotational speed of the pump 1 is switched from the first lower limit value L1 to the second lower limit value L2, the rotational speed of the pump 1 rapidly decreases and becomes equal to or less than the shutoff rotational speed N0. The control unit 10 detects the state of the small amount of water from such a decrease in the rotational speed of the pump 1.

The water supply apparatus shown in FIG. 1 is a water supply apparatus for suctioning water in a water receiving tank, but the present invention can be applied to a so-called direct connection type water supply apparatus directly connected to a water main. FIG. 5 is a schematic view showing a direct connection type water supply apparatus. The basic configuration of the direct connection type water supply device is the same as the water supply device shown in FIG. 1, but the suction side pressure sensor 20 for measuring the suction side pressure is provided on the suction side of the pump 1 and It differs in that a backflow prevention device 21 for preventing backflow of water to the main pipe is provided. The suction side pressure sensor 20 is connected to the control unit 10, and a measurement value of the suction side pressure is sent to the control unit 10. The control unit 10 detects the low water quantity state according to the method described above.

The present invention can also be applied to a water supply apparatus provided with a plurality of pumps. FIG. 6 shows an embodiment of a water supply system with a plurality of pumps, motors and inverters. The water supply apparatus includes two

pumps

1 and 1 connected in parallel to each other,

motors

2 and 2 for rotating the

pumps

1 and 1, and

inverters

3 and 3 for applying a voltage of variable frequency to the

motors

2 and 2. And have. The

inverters

3 and 3 are connected to the control unit 10. Check

valves

15, 15 are respectively installed on the discharge side of the

pumps

1, 1, and a pressure sensor 16 and a pressure tank 18 are installed on the discharge sides of the

check valves

15, 15. The control unit 10 detects the low water quantity state of each pump according to the method described above.

Although FIG. 6 is a water supply apparatus for sucking water in a water receiving tank, the present invention is also applicable to a direct connection type water supply apparatus provided with a plurality of pumps. In this case, the suction side pressure sensor 20 and the backflow prevention device 21 shown in FIG. 5 are installed on the upstream side of the

pumps

1 and 1.

Furthermore, the present invention can be applied to a so-called flow switchless water supply device that does not have a flow switch, and can also be applied to a water supply device that has a flow switch when the flow switch malfunctions. In such a case, the small amount of water may be detected by the present invention without removing the detection signal from the flow switch without removing the flow switch causing the malfunction. After that, even when the flow switch becomes normal due to repair or the like, it is possible to appropriately select the flow switch or the detection of the low water quantity state according to the present invention to operate the water supply device.

The embodiments described above are described for the purpose of enabling one skilled in the art to which the present invention belongs to to practice the present invention. Various modifications of the above-described embodiment can naturally be made by those skilled in the art, and the technical idea of the present invention can be applied to other embodiments. Accordingly, the present invention is not limited to the described embodiments, but is to be construed in the broadest scope in accordance with the technical concept defined by the claims.

INDUSTRIAL APPLICABILITY The present invention is applicable to a water supply apparatus that pressurizes water from a water main to supply water to a building such as an apartment house or a commercial building.

Reference Signs List 1 pump 2 motor 3

inverter

5, 10 control unit 15 check valve 16 discharge side pressure sensor 18 pressure tank 19 flow switch 20 suction side pressure sensor 21 backflow prevention device

Claims

With the pump,
A motor for rotating the pump;
An inverter for applying a variable frequency voltage to the motor;
A discharge side pressure sensor that measures a discharge side pressure of the pump;
The rotational speed of the pump is feedback controlled via the motor and the inverter so that the discharge side pressure of the pump is maintained at a predetermined target pressure based on the measured value of the discharge side pressure. A water supply apparatus having a control unit,
The control unit is configured to: a first lower limit value of rotational speed higher than a cutoff rotational speed required to achieve the target pressure in a cutoff state; and a second lower limit value of rotational speed lower than the cutoff rotational speed Remember
The control unit
Switching the lower limit value of the rotational speed of the pump from the first lower limit value to the second lower limit value;
It is judged that the pump is in a low water quantity state when the rotational speed of the pump becomes equal to or less than the shutoff rotational speed within a predetermined detection time.
The control unit is configured to set the lower limit value of the rotational speed of the pump from the first lower limit value to the second limit value when the state where the rotational speed of the pump is less than the first lower limit continues for a predetermined confirmation time. The water supply apparatus according to claim 1, wherein the lower limit value is switched.
When the rotational speed of the pump is equal to or less than the first lower limit value and the discharge pressure is higher than a predetermined control value, the control unit controls the pump for the predetermined confirmation time. The water supply apparatus according to claim 2, wherein the lower limit value of the rotational speed is switched from the first lower limit value to the second lower limit value.
The water supply apparatus according to claim 3, wherein the control value is the same as the target pressure at the time of a shutoff operation.
The control unit continues the state in which the rotational speed of the pump is less than or equal to the shutoff rotational speed within the predetermined detection time and the rotational speed of the pump is less than or equal to the shutoff rotational speed for a predetermined monitoring time. The water supply apparatus according to any one of claims 1 to 4, wherein it is determined that the pump is in a small amount of water state in the case where the water supply amount is low.
The water supply device according to any one of claims 1 to 5, wherein the target pressure is constant regardless of the flow rate of water discharged from the pump.
The water supply device according to any one of claims 1 to 5, wherein the target pressure changes in accordance with a flow rate of water discharged from the pump.