JP4668403B2 - Water supply equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a variable speed water supply apparatus that supplies water using a variable speed pump, and more particularly to operation control of a pump when the amount of water is small.
[0002]
[Prior art]
For example, when supplying tap water to an apartment house, etc., the water supplied from the water main is once received in a water receiving tank, pressurized using a pump, and supplied to the terminal taps of each house of the apartment house. As a water supply apparatus for such a use, what is shown in FIG. 7 is known. This water supply device temporarily stores water in a water receiving tank (not shown) connected to the water main, and uses the two pumps P1 and P2 to connect the discharge consumer pipe 12 from the discharge collecting pipe 12 to the end customer. Water is supplied to a water tap (not shown). Here, at least one pump changes its rotational speed by variable speed operation, the pressure on the pump discharge side is constant, or the pressure is constant on the customer side, including the pipe loss to the end customer. Variable speed operation is performed to obtain such a pump discharge pressure. Two pumps are arranged in parallel when one pump is supplied when the amount of load water is small, and two pumps are arranged in parallel when the amount of load water increases and one pump is insufficient. This is because it is necessary to drive.
[0003]
In the water supply apparatus shown in FIG. 7, a plurality of pumps P1 and P2 that do not fail even if a certain shut-off operation is performed, a pressure tank 13, and a pressure sensor 14 that detects the pressure in the discharge collecting pipe 12 on the discharge side of the pump. And a control panel 15 for controlling the operation of the pump. The pressure sensor 14 detects the pump discharge pressure, and performs variable speed operation control to change the rotation speed of the pump so that the pump discharge pressure becomes the target pressure. Such a water supply apparatus is generally provided with a small water amount stop mechanism that automatically stops the pump when water is no longer used on the customer side. This is because when the water is almost unused, the pump is in a deadline operation and the pump overheats. For this reason, it is based on the request | requirement of energy saving which prevents the damage by the overheating of a pump, and prevents consumption of useless energy.
[0004]
As a typical method for stopping the pump operation at such a small amount of water, there is a method using a flow switch. This is provided with a flow switch 16 that operates in the vicinity of a small amount of water in the vicinity of the pump shut-off operation in the discharge collecting pipe 12, and detects the feed water flow rate to the end consumer side. If the water supply flow rate is small, for example, 10 L / min or less by the flow switch, the continuation of the small water amount state for a certain time is confirmed by a timer or the like, and the pump discharge pressure is increased by temporarily increasing the rotational speed of the pump. This is a method of accumulating pressure in a pressure tank and then stopping the pump. Here, as the flow switch, for example, a switch that operates a reed switch by a float with a magnet is used. There is also a method of stopping the pump when a small amount of water is detected without accumulating pressure in the pressure tank 13 and setting the starting pressure of the pump to a pressure lower than the pressure at the time of stopping.
[0005]
Such a small water amount stopping operation of the pump is originally an operation for preventing the pump from shutting down, and it is ideal to stop the pump when the feed water flow rate becomes zero. However, with the above-described flow switch, it is difficult to detect the zero point of the feed water flow rate, and actually, for example, a minimum flow rate of about 10 lit / min is detected. By the way, when the pump is shut off, the pump is in an idle operation state, and the rotational energy of the pump is changed to heat. Therefore, the actual temperature rise of the pump is determined by the balance between the rotational energy of the pump and the heat radiation from the pump casing. come. Therefore, it is known that even if the pump is operated for several minutes depending on the pump, the calorific value is relatively small and there is no problem in actual operation. Especially when the rotation speed of the pump is controlled, the feed water flow rate is generally zero in the small water volume region, the pump rotation speed is smaller than when there is a feed water flow rate, and the calorific value is It tends to be less than during operation when there is a flow rate.
[0006]
According to such a small water amount stop operation of the pump, the pump is stopped by the small water amount stop operation when the water is used below the operating water amount of the flow switch. Since the amount of water is very small, the pressure in the discharge pipe decreases after the pump stops, and the pump restarts immediately after the pressure sensor detects this. If such a state continues, the pump will repeatedly start and stop, causing so-called inching, which in turn causes damage to the pump. Therefore, it can be said that the small water amount stop operation is ideal to stop the pump when the feed water flow rate becomes zero in a range where there is no risk of overheating due to the deadline operation. In addition, the flow switch is generally expensive and has a life because it is a mechanical part, and there is a problem that the detection float is worn by repeated operations.
[0007]
As a means for detecting the shut-off operation state of the pump, there are known a method based on detection of a current value of a motor that drives the pump, a method based on search operation, and the like in addition to the above-described means using the flow switch. In the method based on the detection of the current value, the pump driving current value becomes small because the load on the pump decreases when the amount of water is small. For this reason, it is theoretically possible to detect the small water amount state while viewing the current value. However, since the change in the current value is very small with respect to the change in the flow rate, there are some ideas such as setting an allowable value for determining the current value when determining the small water volume stop operation, and resetting the detected current value every time the operation is performed. There is a problem that control is complicated. The search operation method is a method for confirming the small water amount state by increasing or decreasing the rotation speed of the pump when the pump discharge water amount is close to the small water amount. It is. In addition, there is a problem that the discharge pressure fluctuates and the supply water pressure fluctuates as the rotational speed of the pump increases and decreases. Furthermore, the control program becomes complicated, and a large number of setting values for operation become necessary and complicated.
[0008]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described circumstances, and can enter a small water amount stop operation by reliably detecting a closing operation state of zero water amount by a relatively simple method without using an expensive flow switch. It aims at providing the water supply apparatus which can do.
[0009]
[Means for Solving the Problems]
The water supply apparatus of the present invention comprises a pump, a pressure sensor for detecting the pressure on the discharge side via the check valve of the pump, and means for controlling the rotational speed of the pump in response to the pressure. The control target pressure of the pump is controlled according to the discharge pressure constant control or the estimated terminal pressure constant control, and includes a data table indicating a relationship between the rotation speed of the pump and a shutoff pressure corresponding to the rotation speed, and the pump of at rotational speed is reduced to discharge operation speed corresponding to the control target pressure during discharge operation, until the slightly lower speed than the discharge operation speed corresponding to the control target pressure the rotational speed during the discharge operation of the pump At that time, whether or not the detected pressure of the pressure sensor drops below a predetermined value is monitored for a certain period of time. And, wherein the entering into the small amount of water stop operation of the pump.
[0010]
When the clamping switching operation state, by comparing the deadline pressure corresponding to the detected pressure and the rotation speed of the actual pressure sensor, it is possible to positively detect that water is in a state of zero. That is, the pressure detected by the pressure sensor does not decrease even if the rotational speed of the pump is reduced by the check valve, and becomes higher than the discharge pressure of the pump when the shutoff operation state is entered. For this reason, the rotational speed of the pump is decreased by PI (proportional integral) control. However, even if the discharge pressure of the pump is reduced, the pressure in the discharge collecting pipe is not reduced because the pressure in the discharge collecting pipe is held in the closing operation state where the flow rate is almost zero. For this reason, since the rotational speed of the pump continues to decrease, it is possible to reliably detect the closed state by comparing the cutoff pressure corresponding to the rotational speed with the detected pressure. On the other hand, when there is a load flow rate, the pressure at the discharge port of the pump on the upstream side of the check valve is slightly higher than the detection position of the pressure sensor on the downstream side of the check valve. For this reason, the rotational speed of the pump moves along the load line according to the amount of water, and the cutoff pressure at that rotational speed is always higher than the pressure at the operating point. Therefore, by comparing the deadline pressure corresponding to the rotational speed with the detected pressure, it is possible to reliably detect that there is no deadline state. Thereby, it is possible to reliably and easily detect the closing operation state with almost no water amount without using an expensive flow switch.
[0011]
According to the present invention, the rotational speed of the pump at the decreased discharge operation speed corresponding to the control target pressure during discharge operation, and the rotational speed of the pump corresponding to the control target pressure during the discharge operation the Decreasing to a speed slightly lower than the shut-off operation speed, and monitoring at that time whether or not the pressure detected by the pressure sensor falls below a predetermined value, and if it does not drop, it is determined that it is in the shut-off operation state, By entering the operation for stopping the small amount of water of the pump, it is possible to reliably detect the small amount of water by a relatively simple operation and to enter into the operation for stopping the small amount of water of the pump.
[0012]
Further, in a water supply apparatus comprising a pump, a pressure sensor for detecting a pressure on the discharge side through the check valve of the pump, and a means for controlling the rotational speed of the pump in response to the pressure, Data on the relationship between the rotational speed and the cutoff pressure corresponding to the rotational speed is provided, and it is determined that the system is in the cutoff operation state when the detected pressure of the pressure sensor is larger than the cutoff pressure corresponding to the rotational speed of the pump. And it is preferable to enter into the small water amount stop operation of the pump. Thereby, the small water amount stop operation of the pump can be started in a state where the feed water flow rate is zero.
[0013]
Moreover, it is preferable that the small water amount stop operation | movement of the said pump raises the control target pressure of a pump, operates for a fixed time, and stops a pump after that.
Further, during operation by increasing the control target pressure of the pump to return the pump to normal operation if the pump rotational speed is greater than the discharge operation speed corresponding to the control target pressure, the pump rotational speed is the It is preferable to stop the pump when the operation speed is equal to or lower than the shut-off operation speed corresponding to the control target pressure . As a result, when a water supply flow rate is generated, the normal operation can be immediately resumed.
Further, it is preferable that the pump is started even if it does not decrease to a predetermined starting pressure when the temporal change of the decrease in the pressure detected by the pressure sensor is large after the small amount of water is stopped. As a result, when a change occurs in the feed water flow rate, a quick response is possible.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to FIGS.
[0015]
FIG. 1 shows a water supply apparatus according to an embodiment of the present invention. There are two pumps P1 and P2, and the pipes on the suction side are connected to a water receiving tank (not shown). A discharge side pipe of the pump is connected to a discharge collecting pipe 12 via a check valve 11 and is connected to a water tap of a terminal customer (not shown) via a pipe (not shown). A pressure tank 13 and a pressure sensor 14 are connected to the discharge collecting pipe 12, and the pressure tank 13 accumulates pressurized water by a pump, and when the amount of water is small, the operation of the pump is stopped and energy saving operation can be performed. The pressure sensor 14 detects the discharge pressure of the pump in the discharge collecting pipe 12 and inputs this to the control panel 15 to change the rotation speed of the pump so that the discharge pressure of the pump becomes a predetermined target value. Let That is, the control panel 15 is provided with an inverter device for changing the rotational speed of the pump, and a signal from the pressure sensor 14 is input, and the pump is PI (proportional integral) controlled so that the pump discharge pressure becomes the control target pressure. To do. The control target pressure of the pump is controlled to be constant regardless of the magnitude of the feed water flow rate, or along the general resistance curve corresponding to the flow rate, taking into account the piping resistance to the consumer end depending on the magnitude of the feed water flow rate. It is controlled by a constant control of the estimated end pressure that changes the rotational speed of the pump.
[0016]
FIG. 2 is a block diagram showing an outline of the operation control apparatus of the water supply apparatus according to the embodiment of the present invention. This operation control device (control panel) 15 is provided with a data table 21 for the relationship between the rotational speed of the pump and its cutoff pressure. This is because, for example, in the operation control device for a water supply pump using a microcomputer, the setting mode is set, the valve on the pump discharge side is closed and the shutoff state is closed, and the rotational speed of the pump is gradually increased. The rotation speed and the cutoff pressure detected by the pressure sensor are measured and stored in a storage device such as an E ² PROM attached to the microcomputer. Further, the characteristic curve of the pump used in advance is often known. In this case, a data table of the pump rotation speed and its shut-off pressure may be created from known characteristic data and stored in the storage device of the microcomputer of the operation control device 15. In addition, in the water supply device, in other control items, for example, constant estimated terminal pressure constant control, data on the pump rotation speed and its shut-off pressure are required separately. For this reason, a data table prepared separately may be used.
[0017]
In this operation control device 15, the CPU 23 performs an overall calculation control operation according to the operation control program 22 of the water supply device. That is, the CPU 23 gives a speed command to the inverter device 24 in accordance with the program 22 in accordance with the discharge pressure signal of the pressure sensor 14 so as to perform the variable speed operation of the pump by the constant discharge pressure control or the estimated terminal pressure constant control method.
[0018]
FIG. 3 is a QH diagram showing the principle of detection of the cutoff operation state according to the embodiment of the present invention. It is assumed that the current operation state is a discharge pressure P and a water amount Q. At this time, the rotational speed of the pump is N +, and the cutoff pressure at this rotational speed is P +. Thus, when there is a normal water supply flow rate, the discharge pressure P at the operating point and the cutoff pressure P + corresponding to the rotational speed N + at that time are always
P +> P
It becomes the relationship.
On the other hand, when the discharge pressure P is constant and the water amount Q is almost zero, a so-called shut-off operation is performed, and the check valve is a one-way valve. pressure downstream of the valve is held in the discharge collecting pipe, the pressure may become a control target pressure by remote slightly higher state.
In such a case, since the discharge pressure exceeds the control target pressure, a deceleration command is given to the pump. However, in the cutoff operation state, even if the pump speed decreases, the pressure in the discharge collecting pipe is held by the check valve and does not drop below the discharge pressure P. For this reason, for example, when the rotational speed is reduced to N−, the corresponding cutoff pressure P− at that time is lower than the discharge pressure P. That is,
P> P-
It becomes the relationship. Therefore, it can be determined that the water supply flow rate is a complete deadline operation state.
[0019]
FIG. 4 is a flowchart for detecting the above-described deadline operation state. As shown, the current and the discharge pressure P detected Ri by the pressure sensor, the relationship between the pump shut-off pressure Px corresponding to the current rotational speed N is determined. As shown in FIG. 3, it is assumed that the current water supply flow rate is Q and the discharge pressure is P. For the current rotational speed N +, the corresponding pressure P + at the closing time is greater than the current discharge pressure P. Therefore, in this state, it is determined that the pump is not in the cutoff operation state, and the normal operation is continued. In contrast, water Q becomes zero, when the shut-off operating state, the discharge pressure P by check valve is held in the discharge pipe, not lowered under the control target pressure Chikara以. In this case, a rotational speed reduction command is given to the pump so as to reduce the discharge pressure of the pump. Then, the rotational speed of the pump decreases, and the cutoff pressure Px corresponding to the rotational speed N is
P> Px
It becomes the relationship. Thus, in the state that written pump is determined that the discharge operation state enters the small amount of water stop operation. Actually, the state that written to detect a predetermined time by the timer or the like, so that it is determined that the pump-discharge operation state with that this state continues.
[0020]
FIG. 5 is a QH diagram showing detection of the shutoff operation state of the pump according to another embodiment of the present invention. In this embodiment, when the rotational speed Hz of the pump decreases to a rotational speed HzB corresponding to the control target pressure PB during the cutoff operation, the pump rotational speed is set to the cutoff corresponding to the control target pressure PB during the cutoff operation. The rotational speed is lowered to a slightly lower rotational speed (HzB-1 Hz) than the operating speed HzB. Then, at that time, it is monitored for a certain time whether or not the pressure detected by the pressure sensor falls below a predetermined value (PB-1m). If the detected pressure does not decrease, the detected pressure of the pressure sensor is not changed by the check valve even if the pump rotation speed is decreased, so that it is determined that the engine is in the cutoff operation state. When the pump is operated at a reduced rotation speed and the pressure detected by the pressure sensor decreases, the pump is not in a complete shut-off operation state, and normal operation of the pump is continued. Then, in the operation of stopping the small amount of water of the pump, the rotational speed is increased to HzB 'so that the discharge pressure is, for example, about +3 m with respect to the pressure PB at the time of detecting the cutoff operation, and then the pump is stopped.
[0021]
FIG. 6 shows a flowchart of the operation in this embodiment. Sometimes speed Hz of the pump is reduced to the rotational speed HzB corresponding to the control target pressure PB during discharge operation, rotation is reduced by 1Hz than discharge operation speed HzB corresponding rotational speed Hz of the pump to the control target pressure PB Set to speed (Hz = Hz B -1 Hz). And it is confirmed whether the detection pressure P of the pressure sensor at that time is below a predetermined value (PB-1m). That is, to check whether there is only reduced pressure or 1m from the control eyes Shimegi圧 force PB. Here, the state is observed for a predetermined time, for example, 10 seconds. If the detected pressure of the pressure sensor does not drop below the predetermined value (PB-1m) at this time, “No” is set, and a small water amount stop operation is performed in which the pressure accumulation operation is performed and then the pump is stopped.
[0022]
In the small water amount stop operation, the control target pressure is raised to PB + 3 m and the pressure accumulation operation is performed. If the rotation speed of the pump becomes 1 Hz or more higher than the corresponding shut-off operation speed HzB 'during the pressure accumulation operation, the pump is returned to the normal operation and operated. That is, when the normal pressure accumulation operation is continued, the pump is operated at the control target pressure (PB + 3 m) and the rotation speed HzB ′ corresponding thereto. However, if the water supply flow rate is increased to cancel the shut-off operation state during the pressure accumulation operation, it is considered that the small water amount stop state has been released, and the pump returns to the normal operation. In addition, it is preferable to check the state of decrease in the pressure detected by the pressure sensor after the pump is stopped. When the time change of the decrease in the detected pressure is large, it is judged that the water supply flow rate to the customer side has increased, and the pump is started even if the detected pressure of the pressure sensor does not decrease to the predetermined start pressure. Is preferred. As a result, when the water supply flow rate suddenly increases, it is possible to respond quickly and prevent the water supply pressure from decreasing.
[0023]
In the above embodiment, the example in which the shutoff operation state of the pump is compared with the shutoff operation pressure corresponding to the rotational speed and the detected pressure has been described, but various modifications may be made without departing from the spirit of the present invention. Of course, examples are possible.
[0024]
【The invention's effect】
As described above, according to the present invention, it is possible to enter a small water amount stop operation by detecting a state where the feed water flow rate is zero without using an expensive flow switch. For this reason, since a flow switch becomes unnecessary, a long-life and inexpensive water supply apparatus can be provided. Since the pump can be stopped by entering the pressure accumulating operation when the feed water flow rate is zero, an ideal small water amount stopping operation can be realized. In addition, even when there is a change in the water supply flow rate on the consumer side, the pump can be started quickly, so that a stable water supply operation can be performed without causing a pressure drop or the like.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of a water supply apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram showing an outline of an operation control apparatus for a water supply apparatus according to an embodiment of the present invention.
FIG. 3 is a QH characteristic diagram illustrating detection of a shutoff operation state of the pump according to the embodiment of this invention.
FIG. 4 is a control flow diagram corresponding to FIG. 3;
FIG. 5 is a QH characteristic diagram illustrating detection of a shutoff operation state of a pump according to another embodiment of the present invention.
FIG. 6 is a control flow diagram corresponding to FIG. 5;
FIG. 7 is a diagram showing an outline of a conventional water supply device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Water receiving tank 11 Check valve 12 Discharge collecting pipe 13 Pressure tank 14 Pressure sensor 15 Control panel (operation control apparatus)
21 Table of pump rotation speed and deadline pressure P1, P2 Pump

Claims (3)

In a water supply apparatus comprising a pump, a pressure sensor for detecting a pressure on the discharge side via a check valve of the pump, and a means for controlling the rotational speed of the pump corresponding to the pressure,
The control target pressure of the pump is controlled according to the discharge pressure constant control or the estimated terminal pressure constant control,
A data table showing the relationship between the rotational speed of the pump and the cutoff pressure corresponding to the rotational speed ;
Sometimes the rotational speed of the pump is reduced to discharge operation speed corresponding to the control target pressure during discharge operation, the rotational speed of the pump slightly lower than the discharge operation speed corresponding to the control target pressure during the discharge operation The speed is reduced to a speed, and at that time, it is monitored whether or not the detected pressure of the pressure sensor falls below a predetermined value for a certain period of time. Water supply device characterized by entering. The operation of stopping the small amount of water of the pump is an operation of increasing the control target pressure of the pump and operating the pump for a predetermined time, and then stopping the pump, and during the operation while increasing the control target pressure of the pump, when the pump returns to normal operation, the pump rotational speed is equal to or less than the discharge operation speed corresponding to the control target pressure when it becomes larger than the discharge operation speed corresponding to the control target pressure, stopping the pump The water supply device according to claim 1, wherein   3. The pump according to claim 1, wherein the pump is started even if the pressure does not decrease to a predetermined start pressure when the temporal change of the decrease in the pressure detected by the pressure sensor is large after the stop of the small amount of water. Water supply device.

Images