JP4938304B2 - Pump control method and water supply device - Google Patents

Description

  The present invention relates to a pump control method and a water supply device, and more particularly, to a pump control method and a water supply device capable of performing constant estimated terminal pressure control even when there is a fluctuation in suction pressure.

  In order to supply water in a receiving tank or well water to a place where water is used, such as a home, a water supply device that performs constant control of the estimated end pressure using a variable speed pump is often used. The estimated terminal pressure constant control is to control the discharge pressure of the variable speed pump so that the discharge pressure of water in the terminal water supply device becomes constant even if the discharge water amount of the variable speed pump varies. In general, the resistance of the pipe line connecting the variable speed pump and the terminal water supply device increases in proportion to the square of the amount of water flowing in the pipe line. Since the pipe resistance causes pressure loss in the pipe, the pressure considering the pressure loss due to the pipe resistance at the discharge water volume is used as the discharge pressure of the variable speed pump, so that the end of the pipe resistance regardless of the fluctuation of the discharge water volume of the variable speed pump. The discharge pressure of water in the water supply equipment is kept constant.

By the way, if the suction pressure of the variable speed pump fluctuates, it is difficult to perform constant control of the estimated terminal pressure due to the influence of the back pressure. The inflow water pressure is detected by a pressure sensor provided on the inflow side of the pump. By adjusting the control calculation formula one by one with the value, such as a variable speed water supply device that can control the pressure on the outflow side of the pump to be constant terminal pressure even if the pressure on the primary side of the pump changes depending on the use state of water, There is known a water supply device that detects the pressure on the suction side and corrects the suction pressure that is a reference for the estimated terminal pressure constant control (see, for example, Patent Document 1).
JP 2003-120580 A

  However, in the above water supply apparatus that provides a pressure sensor on the suction side, while fluctuations in the suction pressure can be directly grasped, the number of parts of the water supply apparatus increases and the probability that a failure will occur increases. Cost will be high.

  In view of the above-described problems, the present invention provides a pump control method capable of performing constant control of the terminal pressure even when there is a change in the suction pressure without providing a pressure sensor on the suction side, and a terminal pressure without increasing the number of parts. It aims at providing the water supply apparatus which can perform constant control.

  In order to achieve the above object, the pump control method according to the first aspect of the present invention includes a step (S2) of detecting the discharge pressure of the pump 21 that discharges the liquid w, for example, as shown in FIGS. , S5); from the discharge pressure and rotation speed of the pump 21 when the suction pressure of the pump 21 is the first suction pressure, and the discharge pressure and rotation speed when the maximum flow rate of the liquid w is discharged. A step (S1) of setting an operation curve for the pump 21 to perform constant estimated terminal pressure control; a step (S2) of operating the pump 21 according to the operation curve; and a change in the discharge pressure of the pump 21 over a predetermined time A step (S2, S5) of correcting the suction pressure of the pump 21 for obtaining a reference for setting the operation curve when the width is within a predetermined range.

  If comprised in this way, since it has the process of correct | amending the suction pressure of the pump for calculating | requiring the reference | standard which sets an operation curve, when the fluctuation range of the discharge pressure of a pump over a predetermined time is in a predetermined range, The suction pressure of the pump is corrected in a state where the discharge pressure is stable, so that accurate correction can be made, and even if the suction pressure of the pump fluctuates, the estimated terminal pressure constant control can be performed.

The control method of the pump according to the first aspect of the present invention, for example as shown in FIG. 1 and FIG. 3, the step of correcting the suction pressure of the pump 21 (S5) is a first rotation of the pump 21 The first discharge pressure of the pump 21 at the speed and the first rotation speed, the second rotation speed of the pump 21 different from the first rotation speed, and the second discharge pressure of the pump 21 at the second rotation speed , A second suction pressure of the pump 21 is calculated based on the first rotation speed and the first discharge pressure, the second rotation speed and the second discharge pressure, and the second suction pressure Ru and a step of the suction pressure after corrected. Moreover, the pump control method according to the invention described in claim 2 is a step of setting an operation curve (S1) in the control method of the pump 21 described in claim 1, for example, as shown in FIGS. Is based on the relationship between the suction pressure of the pump 21 and the rotation speed that gives the discharge pressure during the shut-off operation, and the rotation that gives the discharge pressure during the shut-off operation of the pump 21 corresponding to the second suction pressure. A new speed for the pump 21 to perform the constant control of the estimated end pressure under the second suction pressure using the rotational speed that obtains the speed and gives the discharge pressure during the shutoff operation of the pump 21 corresponding to the second suction pressure. It is configured to set a proper driving curve.

If comprised in this way, the 2nd suction pressure of a pump will be calculated based on the 1st rotation speed and the 1st discharge pressure, the 2nd rotation speed, and the 2nd discharge pressure, and the 2nd suction pressure will be calculated. because comprising the step of the suction pressure after the correction, Ru can be obtained from the relationship between the rotational speed and the pressure in the similarity law of the pump easily second suction pressure. In addition , a new operation curve for the pump to perform the estimated terminal pressure constant control under the second suction pressure using the rotational speed at the time of the shutoff operation of the pump corresponding to the second suction pressure related in advance. Therefore, even if the suction pressure of the pump changes to the second suction pressure, the estimated terminal pressure constant control can be performed.

Further, the pump control method according to the invention described in claim 3 is, for example, as shown in FIGS. 1 and 3, the pump 21 suction pressure of the pump 21 in the control method of the pump 21 according to claim 1 or 2. When the flow rate of the pump 21 is less than or equal to a predetermined underflow instead of when the fluctuation range of the discharge pressure of the pump 21 is within a predetermined range over the predetermined time (S6) The first discharge pressure is set to the discharge pressure when the pump 21 is shut off, and the second discharge pressure is the target discharge pressure when the pump 21 is stopped. Is set to The amount of liquid fed from the pump is equal to or less than a predetermined underflow rate is typically a flow rate that triggers the pump to stop. Also, setting the discharge pressure at the time of the shutoff operation of the pump is typically realized by setting the rotation speed to give the discharge pressure at the time of the shutoff operation.

  With this configuration, it is possible to calculate the second suction pressure by detecting the first rotation speed, the first discharge pressure, the second rotation speed, and the second discharge pressure in the pump stop control process. Even if the suction pressure of the pump fluctuates to the second suction pressure, the estimated terminal pressure constant control can be performed.

  In order to achieve the above object, a water supply apparatus according to the invention described in claim 4 is a water supply system for supplying water w to a terminal water supply device 42 (see FIG. 1B), for example, as shown in FIG. 4. A pump 21; a prime mover 22 that drives the feed water pump 21; a controller 31 that controls the rotational speed of the prime mover 22; a pressure sensor 28 that detects the discharge pressure of the feed water pump 21; The control apparatus 30 which controls the feed water pump 21 using the pump control method of 1 item | term is provided.

  If comprised in this way, since a feed water pump is controlled using the above-mentioned pump control method, even if the suction pressure of a pump fluctuates, it becomes a water supply apparatus which can perform estimated terminal pressure constant control.

  Moreover, the water supply apparatus which concerns on invention of Claim 5 is shown in Fig.1 (a), for example, in water supply apparatus 20 of Claim 4, the amount of water discharged from the water supply pump 21 is predetermined | prescribed underwater quantity. A flow switch 27 for detecting that the following has occurred; when the flow switch 27 detects that the amount of water discharged from the water supply pump 21 has fallen below a predetermined amount of underwater, the control device 30 claims The feed water pump 21 is controlled using the described pump control method.

  With this configuration, when the flow switch detects that the amount of water discharged from the water supply pump is equal to or less than a predetermined excessive water amount, the control device uses the pump control method according to claim 3 to use the water supply pump. Therefore, the suction pressure that fluctuates in the process of pump stop control is calculated, and the water supply device that can perform the estimated terminal pressure constant control based on the fluctuating suction pressure.

  According to the present invention, when the fluctuation range of the discharge pressure of the pump is within a predetermined range over a predetermined time, the pump suction pressure for correcting the pump for obtaining a reference for setting the operation curve is provided. The suction pressure of the pump is corrected in a state where the discharge pressure is stable, so that accurate correction can be made, and even if the suction pressure of the pump fluctuates, the estimated terminal pressure constant control can be performed.

  In addition, the step of correcting the suction pressure of the pump is replaced when the fluctuation range of the discharge pressure of the pump is within a predetermined range over a predetermined time, and the amount of liquid fed from the pump becomes equal to or less than a predetermined underflow rate. When the pump suction pressure is corrected, the first rotation speed, the first discharge pressure, the second rotation speed, and the second discharge pressure are detected in the pump stop control process. Thus, the second suction pressure can be calculated, and the estimated terminal pressure constant control can be performed even if the suction pressure of the pump fluctuates.

  Embodiments of the present invention will be described below with reference to the drawings. In each drawing, the same or corresponding members are denoted by the same or similar reference numerals, and redundant description is omitted.

  First, with reference to FIG. 1, the structure of the water supply apparatus 20 which concerns on embodiment of this invention is demonstrated. FIG. 1 is a diagram illustrating the configuration and installation status of a water supply device 20, (a) is a schematic configuration diagram, and (b) is a system diagram of a shallow well water supply system 11 having a water supply device 20. The water supply device 20 constituting the shallow well water supply system 11 includes a water supply pump 21 that sends the water w of the shallow well SW to a water supply device 42 (for example, a faucet) as a terminal water supply device, an electric motor 22 that drives the water supply pump 21, A flow switch 27 for detecting the discharge water w from the water supply pump 21, a pressure sensor 28 for detecting the discharge pressure when water w is supplied from the water supply pump 21, a pressure tank 29 for storing the discharge pressure of the water supply pump 21, A controller 31 that controls the rotational speed of the shaft of the prime mover 22 and a controller 30 that performs constant control of the estimated terminal pressure of the feed water pump 21 are provided.

  In the shallow well water supply system 11, the water supply device 20 is installed on the ground, a suction pipe 44 is connected to the suction side of the water supply device 20, and a delivery pipe 45 is connected to the discharge side of the water supply device 20. The suction pipe 44 is immersed in the ground water w in the shallow well SW at the end opposite to that connected to the water supply device 20. The delivery pipe 45 is connected to the water supply device 42. Hereinafter, the detail of the water supply apparatus 20 is demonstrated.

  The feed water pump 21 is typically a cascade pump. The cascade pump is also called a friction pump, and has an impeller formed as a disk having a large number of grooves on the periphery. Although this pump is small in size, a single impeller can obtain a lift comparable to several stages of centrifugal pumps, and is suitable for the purpose of a small capacity and high lift. Moreover, since it has a self-absorbing property, it is suitable for supplying water or well water stored in a water receiving tank to supply water to the home. The impeller is housed in a pump casing having a removable casing cover. The casing cover is attached to the pump casing with bolts, and when the casing cover is removed, the impeller can be accessed so that maintenance and inspection can be easily performed. Further, the water supply pump 21 is provided with a thermistor 23 that detects the temperature rise of the water w in the water supply pump 21 in order to prevent the electric motor 22 from burning out.

  The prime mover 22 is typically a direct current brushless motor (hereinafter referred to as “DCBL motor”). Since the DCBL motor works by inputting DC power, the rotational speed of the shaft can be easily changed. The electric motor 22 is provided with an impeller of a water supply pump 21 on its shaft, and variable speed operation for changing the rotational speed of the impeller of the water supply pump 21 and the discharge pressure of the water supply pump 21 by changing the rotational speed of the shaft. It is configured to be able to. The electric motor 22 may be an AC electric motor connected to an inverter device.

  A discharge pipe 25 is disposed on the discharge side of the water supply pump 21. The discharge pipe 25 is connected to a delivery pipe 45 outside the water supply apparatus 20. In the discharge pipe 25, a flow switch 27, a pressure tank 29, and a pressure sensor 28 are arranged in this order from upstream to downstream. The flow switch 27 detects that the discharge water amount of the water supply pump 21 has become equal to or less than a predetermined excessive water amount, and transmits the detection result to the control device 30 to cause the water supply pump 21 to stop. The pressure sensor 28 detects the pressure in the discharge pipe 25 (including the discharge pressure of the water supply pump 21), and transmits the detection result to the control device 30. The pressure tank 29 has a rubber bladder built in the pressure vessel, and when the pressure on the discharge side rises, the air outside the bladder is compressed and water w is stored in a pressurized state. Further, as the pressure on the discharge side decreases, the compressed air expands and pushes the stored water w to the discharge pipe 25. In this way, even if the water supply pump 21 is stopped, the water w is supplied from the pressure tank 29 to the discharge pipe 25 for a while. Since the flow switch 27 is installed on the upstream side of the pressure tank 29, the flow switch 27 does not detect the water flow supplied from the pressure tank 29 when the water supply pump 21 is stopped.

  A suction pipe 24 is disposed on the suction side of the water supply pump 21. The suction pipe 24 is connected to a suction pipe 44 outside the water supply apparatus 20. A check valve 26 is disposed in the suction pipe 24. The check valve 26 is a check valve that prevents the water w from flowing back into the shallow well SW when the water supply pump 21 is stopped. In the present embodiment, since the feed water pump 21 is a cascade pump, even if there is air in the suction pipe 24 when the feed water pump 21 is started, the air can be discharged and the water w can be sucked up. Therefore, it is not necessary to expel air every time the water supply pump 21 starts and stops. From the viewpoint of maintaining the pressure on the discharge side, the check valve 26 is not limited to the suction pipe 24 and may be located upstream of the position where the pressure tank 29 is attached to the discharge pipe 25. However, it is preferable to provide the suction pipe 24 on the suction side of the feed water pump 21 from the viewpoint of holding the expiration water.

  The controller 31 has a rectifier, converts AC power input from the AC power supply 41 into DC power, adjusts the magnitude of the DC power, and outputs the DC power to the DCBL motor 22 that is an electric motor. The controller 31 is configured to control the rotational speed of the DCBL motor 22 by controlling the magnitude of the DC power to be output. The controller 31 is merely distinguished from the control device 30 in terms of concept, and may constitute a part of the control device 30 without being physically distinguished.

  The control device 30 receives a detection result equal to or less than a predetermined underwater amount detected by the flow switch 27 and receives a detection result of the discharge pressure of the water supply pump 21 detected by the pressure sensor 28. In addition, the control device 30 can detect the rotation speed of the water supply pump 21 from the value of the DC power output from the controller 31. Moreover, the control apparatus 30 has CPU, the suction pressure of the water supply pump 21 and the rotational speed at the time of a cutoff operation are linked | related previously, and are memorize | stored in CPU as a table or a function.

  In FIG. 2, the table of the rotational speed at the time of a cutoff operation in each suction pressure of the feed water pump 21 is illustrated. The discharge pressure of the water supply pump 21 during the shut-off operation is a constant value Pb determined by the actual lift from the water supply pump 21 to the terminal water supply device 42 and the required discharge pressure in the water supply device 42. The actual head is the actual pumping height. The suction pressure PsX is positive when the water source water level is higher than the discharge port of the water supply pump 21, and is negative when the water source water level is lower than the discharge port of the water supply pump 21. In the case of the present embodiment, the suction pressure PsX is negative because the water surface of the shallow well SW that is the water source is at a position lower than the discharge port of the water supply pump 21. As apparent from FIG. 2, the higher the suction pressure PsX is, the lower the discharge pressure Pb is, and the lower the suction pressure PsX is, the higher the rotation speed is.

  The control device 30 is a quadratic curve having a correlation with the pipe friction loss head from the discharge pressure at the shutoff operation of the feed water pump 21 and the discharge pressure at the maximum flow rate. The operation curve is calculated, and the output power of the controller 31 can be controlled so that the feed water pump 21 operates with the calculated operation curve.

  Hereinafter, with reference to FIG.1 and FIG.3, the control method of the water supply pump 21 is demonstrated with the effect | action of the water supply apparatus 20. FIG. FIG. 3 is a flowchart illustrating a method for controlling the water supply pump 21. The water supply device 20 detects the pressure in the discharge pipe 25 by the pressure sensor 28 while the water supply pump 21 is stopped, and transmits it to the control device 30. If there is running water from the water supply device 42 such as a faucet while the water supply pump 21 is stopped, the pressure in the discharge pipe 25 decreases, and the water supply pump 21 is activated when the pressure detected by the pressure sensor 28 becomes lower than a predetermined pressure. . Here, the “predetermined pressure” is typically a lower limit pressure at which water w can be discharged from the water supply device 42 at a necessary pressure. In addition, when the water supply pump 21 is stopped, the water w is discharged from the water supply device 42 at a necessary pressure by the pressure stored in the pressure tank 29.

When the feed water pump 21 is activated, the control device 30 sets an operation curve for the feed water pump 21 to perform the constant estimated terminal pressure control (S1). Here, the operation curve will be described with reference to FIG.
FIG. 4 is a diagram for explaining an operation curve R1 of the water supply pump 21 at the suction pressure Ps1 as the first suction pressure. FIG. 4A shows the discharge water amount Q on the horizontal axis and the discharge pressure P on the vertical axis. QP diagram, (b) is an NP diagram with the horizontal axis representing the rotational speed N and the vertical axis representing the discharge pressure P. In FIG. 4A, the rotation speed of the feed water pump 21 is used as a parameter. In the water supply apparatus 20, a discharge pressure Pb (deadline pressure Pb) of the water supply pump 21 when the water amount is zero and a discharge pressure Pa of the water supply pump 21 when the maximum flow rate Qm1 is set in advance. The operation curve R1 is set from the discharge pressure Pb when the water supply pump 21 is closed and the discharge pressure Pa when the water w having the maximum flow rate Qm1 is discharged. Here, the discharge pressure Pb during the shut-off operation is a pressure obtained by adding the required discharge pressure of the water supply device 42 and the actual head when the amount of water is zero. The discharge pressure Pa at the maximum flow rate Qm1 is a pressure obtained by adding the discharge pressure Pb of the terminal water supply device 42 to the pressure of the loss in the discharge pipe 25 and the delivery pipe 45 when the planned maximum water usage amount Qm1 flows. . In FIG. 4, the rotational speed of the water supply pump 21 at the discharge pressure Pb at the suction pressure Ps1 is represented as Nb1. Further, the rotation speed of the feed water pump 21 at the discharge pressure Pa at the suction pressure Ps1 is represented as Nm1.

  In FIG. 4A, the operation curve R1 when the feed water pump 21 performs the estimated terminal pressure constant control at the suction pressure Ps1 is the point Xb1 of the discharge pressure Pb when the water amount is zero and the terminal pressure at the maximum flow rate Qm1. It is represented by a quadratic curve connecting the point Xa1 of the discharge pressure Pa necessary for maintaining at Pb. The estimated terminal pressure constant control is calculated by the Darcy-Weissbach equation in order to set the discharge pressure of the feed water pump 21 as a discharge pressure of the water supply pump 21 in consideration of the pressure loss due to the pipe resistance when the flow rate Q changes. There is a correlation with a resistance curve in which the pipe friction loss head P is a function of the discharge water amount Q.

  In FIG. 4B, a quadratic curve Cs1 is a cutoff operation curve showing the relationship between the rotational speed N and the discharge pressure P during the cutoff operation of the feed water pump 21 at the suction pressure Ps1. In FIG. 4B, the operation curve R1 is represented by a line connecting the point Yb1 of the rotational speed Nb1 that gives the discharge pressure Pb on the cutoff operation curve Cs1 and the point Ya1 of the rotational speed Nm1 at the discharge pressure Pa. The In FIG. 4B, the operation curve R1 is a substantially straight line.

  3 will be mainly referred to again, and the description of the control method of the water supply pump 21 will be continued with reference to FIGS. 1 and 4 as appropriate. When the operation curve R1 is set (S1), the target discharge pressure TPc at the current rotational speed Nc1 is calculated from the operation curve R1, and compared with the actual pressure Pc detected by the pressure sensor 28, the target discharge pressure TPc and actual The rotational speed Nc1 of the water supply pump 21 is adjusted so that the difference from the pressure Pc of the water becomes zero (S2). For example, when the actual pressure Pc when operating the feed pump 21 at the rotational speed Nc1 is lower than the target discharge pressure TPc determined from the operation curve R1, the rotational speed is increased, and conversely, higher than the target discharge pressure TPc. Decreases the rotational speed. Thus, the rotation speed Nc1 of the feed water pump 21 is adjusted, and when the target discharge pressure TPc becomes equal to the actual pressure Pc, the operation of stable estimated terminal pressure constant control can be performed.

Now, in the shallow well water supply system 11, the suction pressure of the feed water pump 21 is fluctuate | varied with the fluctuation | variation of the water level of the shallow well SW.
FIG. 5 is an NP diagram illustrating a change in the cutoff operation curve (Cs1 → Cs2) when the suction pressure fluctuates. As shown in FIG. 5, when the water supply pump 21 operating at the suction pressure Ps1 is changed to the suction pressure Ps2, which is the second suction pressure, due to the change in the water level of the shallow well SW, the discharge pressure during the shut-off operation The rotational speed of the feed water pump 21 that supplies Pb changes from Nb1 to Nb2. In other words, the discharge pressure Pz during the shut-off operation at the rotational speed Nb1 when the suction pressure Ps1 is changed to the suction pressure Ps2 is higher than the pressure Pb. In the case of the present embodiment, this means that the discharge pressure Pb can be set at a rotational speed Nb2 that is lower than the rotational speed Nb1 due to fluctuations in the suction pressure. Therefore, in order to perform the estimated terminal pressure constant control when the suction pressure is changed from Ps1 to Ps2, the rotation speed Nb2 that gives the operation curve R1 at the suction pressure Ps1 and the discharge pressure Pb at the shutoff operation time at the suction pressure Ps2. It is necessary to replace it with a new operation curve R2 starting from the point Yb2. This replacement should be performed by the control device 30. If the operating curve is not updated even if the suction pressure changes due to the fluctuation of the water level of the shallow well SW, the estimated terminal pressure constant control cannot be performed as described below.

  FIG. 6 is a QP diagram for explaining an actual operation state of the pump in the case of following the operation curve before update with respect to the fluctuation of the suction pressure. As described above, when the suction pressure Ps1 is changed to the suction pressure Ps2, the discharge pressure Pb can be set at the rotational speed Nb2 smaller than the rotational speed Nb1. However, if the operation curve is not updated with the fluctuation of the suction pressure, the control device 30 still recognizes that the minimum rotation speed that gives the discharge pressure Pb is the rotation speed Nb1, so the rotation speed Nb1 is set to the lower limit. Will drive. Then, even when the discharge water amount becomes smaller than the discharge water amount Qb1 at the rotation speed Nb1 as the discharge pressure Pb, the rotation speed Nb1 is maintained, and the discharge pressure increases as the discharge water amount approaches zero. As a result, when the operation curve is not updated with respect to fluctuations in the suction pressure, the actual water supply pump 21 operates on the curve Rr connected by the points Xz1, Xb1, and Xa1. This is clearly different from the operation curve R2 of the estimated terminal pressure constant control at the suction pressure Ps2.

  Therefore, the suction pressure required in the step (S1) of setting the operation curve shown in FIG. 3 is reviewed according to the following procedure. When the rotational speed Nc1 of the water supply pump 21 is adjusted so that the difference between the target discharge pressure TPc and the actual pressure Pc becomes zero (S2), it is determined whether or not the flow switch 27 is OFF (S3). The flow switch 27 is OFF in a state where the amount of water discharged from the water supply pump 21 is equal to or less than a predetermined amount of excessive water. The predetermined underwater amount is typically a flow rate at which the discharge water amount is substantially zero.

  When the flow switch 27 is not OFF, it is determined whether or not the fluctuation range of the discharge pressure of the water supply pump 21 is within a predetermined range over a predetermined time (S4). The predetermined time is a time for obtaining a stable discharge pressure necessary for calculating an accurate suction pressure. For example, an appropriate time within one minute may be set. Further, the predetermined range is a fluctuation range of the discharge pressure that does not interfere with the accurate calculation of the suction pressure, and may be 1 m (0.01 MPa), for example. An example of a state in which the discharge pressure is stable includes a state in which when the water supply device 42 is a faucet, a necessary amount of water is obtained and the opening degree of the faucet does not need to be changed.

  When the fluctuation range of the discharge pressure of the water supply pump 21 is not within the predetermined range over a predetermined time, in other words, when the discharge pressure fluctuation exceeds the predetermined range within the predetermined time, the target discharge pressure The process returns to the step (S2) of adjusting the rotational speed Nc1 of the water supply pump 21 so that the difference between TPc and the actual pressure Pc becomes zero. On the other hand, when the fluctuation range of the discharge pressure of the water supply pump 21 is within a predetermined range over a predetermined time, the first rotation speed of the water supply pump 21 at the first point and the water supply at that time are two different points. The first discharge pressure of the pump 21, the second rotation speed of the feed water pump 21 at the second point, and the second discharge pressure of the feed water pump 21 at that time are detected, and the detected first rotation speed and first Based on the first discharge pressure, the second rotation speed, and the second discharge pressure, the second suction pressure of the water supply pump 21 is calculated (S5). At this time, the first and second rotation speeds are determined from the current rotation speeds during operation of the feed water pump 21, and the first and second discharge pressures are determined by detecting the discharge pressures when operating at those rotation speeds. The first and second rotation speeds may be detected by determining the first and second discharge pressures from the current discharge pressure and controlling the rotation speed of the feed water pump 21 so as to be the discharge pressures. May be detected.

  FIG. 7 is an NP diagram illustrating detection of two different rotational speeds and discharge pressures. The NP diagram of FIG. 7 assumes the suction pressure Ps1. Assuming that the current operating point of the water supply pump 21 is the discharge pressure Pc and the point Yc of the rotational speed Nc1, any operating point having a higher discharge pressure and higher rotational speed than the current operating point Yc is set to the discharge pressure Pd, It is represented by a point Yd of the rotation speed Nd1, and an arbitrary operation point having a lower discharge pressure and lower rotation speed than the current operation point Yc is represented by a point Ye of the discharge pressure Pe and the rotation speed Ne1. Two different points for calculating the second suction pressure described above may be selected from any two points among the operating points Yc, Yd, and Ye. Here, in order to increase the calculation accuracy of the second suction pressure, the width of the two different points is preferably large, and in order to reduce the flow fluctuation and the suction pressure fluctuation width, the width of the two different points is preferably small. . Therefore, in order to reduce the flow fluctuation and the suction pressure fluctuation range while maintaining a certain degree of accuracy, in order to make the width of the two points as large as possible without greatly leaving the current operating point Yc, two points above and below the point Yc are used. The points Yd and Ye are preferably set to the two different points.

上記（１）式を吸込圧力Ｐｓ２で解くと下記の（２）式となる。

上記（２）式に、検出した、点Ｙｄにおける吐出圧力Ｐｄ、回転速度Ｎｄ１、点Ｙｅにおける吐出圧力Ｐｅ、回転速度Ｎｅ１を代入することで、吸込圧力Ｐｓ２を求めることができる。なお、算出の結果吸込圧力の変動がない場合、第２の吸込圧力Ｐｓ２は第１の吸込圧力Ｐｓ１と等しいこととなる。 When the first and second discharge pressures and the rotation speed are detected, the second suction pressure Ps2 is calculated based on the detected values. The suction pressure Ps2 can be obtained from the following equation representing the pump similarity law that the pump head is proportional to the square of the rotational speed. In the following formula, a case where two different points are the point Yd and the point Ye is shown.

When the above equation (1) is solved by the suction pressure Ps2, the following equation (2) is obtained.

The suction pressure Ps2 can be obtained by substituting the detected discharge pressure Pd at the point Yd, the rotational speed Nd1, the discharge pressure Pe at the point Ye, and the rotational speed Ne1 into the equation (2). When there is no fluctuation in the suction pressure as a result of the calculation, the second suction pressure Ps2 is equal to the first suction pressure Ps1.

  The description will be continued with reference to FIG. When the suction pressure Ps2 is obtained by the above equation (2), the process returns to the step (S1) for setting the operation curve for the feed water pump 21 to perform the constant control of the estimated terminal pressure, and at the time of the shut-off operation that becomes a reference for setting the operation curve. The operating curve is corrected with the suction pressure required to determine the rotation speed of the feed water pump 21 giving the discharge pressure Pb as the newly calculated suction pressure Ps2. After updating to the new operation curve, the estimated terminal pressure constant control of the feed water pump 21 is performed, and the rotational speed Nc1 of the feed water pump 21 is adjusted so that the difference between the target discharge pressure TPc and the actual pressure Pc becomes zero ( S2) The above flow is repeated.

  On the other hand, in the step of determining whether or not the flow switch 27 is OFF (S3), if the flow switch 27 is OFF, the control device 30 enters control for stopping the water supply pump 21. As described above, when the flow switch 27 is OFF, the discharge water amount of the water supply pump 21 is equal to or less than a predetermined excessive water amount (the operation point at this time is referred to as a “stop command point”, and the discharge of the stop command point is performed). The pressure is called “stop command discharge pressure” and the rotation speed is called “stop command rotation speed”). When entering the stop control, the feed water pump 21 stops after performing an operation in which the discharge pressure is increased to a preset pump stop pressure. The pump stop pressure is the discharge pressure Pa at the maximum discharge water amount Qm1 in the estimated terminal pressure constant control operation that is typically performed until the pump stops. The stop command discharge pressure is typically the discharge pressure of the water supply pump 21 when the amount of water is zero. As described above, when the operation of increasing the discharge pressure immediately before stopping the water supply pump 21 is performed, the pressure is stored in the pressure tank 29, and the pressure stored in the pressure tank 29 is stored without starting the water supply pump 21. The water w can be discharged from the water supply device 42 at a required pressure until the pressure disappears. Such a pressure accumulating operation can reduce the frequency of starting and stopping the water supply pump 21 and extend the life of the water supply pump 21.

  Note that the stop command rotation speed changes with a change in the actual suction pressure. This will be described with reference to FIG. FIG. 6 is based on the rotational speed that gives the discharge pressure during the shutoff operation when the set operation curve is the first suction pressure Ps1, but the suction pressure is Ps2 due to the rise in the water level of the shallow well SW. However, if the driving curve is not updated, the driving is actually performed according to the driving curve Rr. In this case, the flow rate of Qb1 is still flowing even when the rotational speed Nb1 giving the discharge pressure Pb at the set deadline operation is reached. In order to turn off the flow switch 27, the flow rate needs to be further reduced. However, when the operation is performed according to the operation curve Rr, the discharge pressure increases as the flow rate decreases. Therefore, when the discharge pressure rises even though the rotation speed of the water supply pump 21 remains Nb1, the control device 30 actually indicates that the discharge water amount is small under a situation where the suction pressure is fluctuating. The control is switched to control that decreases the rotational speed so as to maintain the discharge pressure Pb. The discharge water amount decreases with the discharge pressure Pb kept constant, and the rotation speed of the water supply pump 21 is detected when the flow switch 27 is eventually turned off. Thus, the rotation speed detected when the flow switch 27 is turned OFF becomes the stop command rotation speed. Conversely, when the water level of the shallow well SW decreases, not only the stop command rotation speed but also the stop command discharge pressure changes. When the water level of the shallow well SW is lowered, the flow switch 27 is turned off before the discharge pressure is lowered to Pb and before the rotational speed is lowered to Nb1. In this case, the rotation speed detected when the flow switch 27 is turned off is the stop command rotation speed, and the detected discharge pressure is the stop command discharge pressure.

  When the flow switch 27 is OFF and the control for stopping the feed water pump 21 is started, the stop command discharge pressure and stop command rotation speed, the pump stop pressure and the rotation speed at this time are detected, and these discharges are detected. The second suction pressure Ps2 is calculated from the above-described equation (2) using the discharge pressure and the rotation speed at two points with different pressures and rotation speeds (S6). When the suction pressure Ps2 is calculated from the stop command discharge pressure and the stop command rotation speed, the pump stop pressure, and the rotation speed at this time, the suction pressure Ps2 is stored in the control device 30, and the feed water pump 21 is stopped. Next time, when the water supply pump 21 is started and the operation curve for setting the estimated terminal pressure constant control is reached (S1), the discharge pressure Pb at the closing operation at the suction pressure calculated before the stop is used as a reference. Set the driving curve as.

In the above description, it has been described that the water supply device 20 is provided in the shallow well water supply system 11, but the present invention can also be applied to other water supply systems.
FIG. 8 is a system diagram of a water receiving tank water supply system 18 having the water supply apparatus 20 according to the embodiment of the present invention. The water receiving tank water supply system 18 includes a water supplying device 20, a water receiving tank TL installed higher than the water supplying device 20, and a suction pipe 44. In the water receiving tank water supply system 18, a delivery pipe 45 is connected to the discharge side of the water supply device 20, and a water supply device 42 (for example, a faucet) as a terminal water supply device is provided at the end of the delivery pipe 45. . The structure and operation of the water supply device 20 are the same as those of the water supply device 20 of the shallow well water supply system 11 (see FIG. 1). In the water receiving tank water supply system 18, the suction pressure of the water supply pump 21 fluctuates due to the fluctuation of the water level in the water receiving tank TL. In the water receiving tank water supply system 18, the above-described control for setting the operation curve according to the fluctuation of the suction pressure is performed. I do. Thereby, even if the suction pressure fluctuates, it is possible to perform constant control of the estimated end pressure. In addition, it can apply similarly as an intermediate water tank provided in the middle floor of a high-rise building instead of the water receiving tank TL.

  FIG. 9 is a diagram for explaining the configuration and installation status of a water supply apparatus 90 according to another embodiment of the present invention, where (a) is a schematic configuration diagram, and (b) is a deep well water supply system having the water supply apparatus 90. FIG. 19 is a system diagram of nineteen. In the water supply apparatus 90, a submersible pump 91 is disposed in the deep well DW instead of the water supply pump 21 (see FIG. 1) in the water supply apparatus 20. The submersible pump 91 incorporates a prime mover 92, and the shaft of the prime mover 92 is connected to the impeller of the submersible pump 91. The submersible pump 91 is connected via an in-unit pipe 95 and a suction pipe 94 in the ground unit. In the ground unit, a control device 30 having a flow switch 27, a pressure sensor 28, a pressure tank 29, and a controller 31 is disposed in addition to the in-unit piping 95. The flow switch 27, the pressure sensor 28, and the pressure tank 29 have the same configuration as that of the water supply device 20 (see FIG. 1), and are arranged in this order from the upstream to the downstream in the unit pipe 95. ing. A delivery pipe 45 provided with a water supply device 42 (for example, a faucet) as a terminal water supply device is connected to the end of the in-unit pipe 95 opposite to the end where the suction pipe 94 is connected. In the deep well water supply system 19, the suction pressure of the submersible pump 91 fluctuates due to the fluctuation of the water level in the deep well DW. In the deep well water supply system 19, the above-described control for setting the operation curve according to the fluctuation of the suction pressure is performed. I do. Thereby, even if the suction pressure fluctuates, it is possible to perform constant control of the estimated end pressure.

It is a figure explaining the structure and installation condition of the water supply apparatus which concerns on embodiment of this invention. (A) is a schematic block diagram, (b) is a systematic diagram of the shallow well water supply system which has a water supply apparatus. It is a figure of the table of the rotational speed at the time of a cutoff operation in each suction pressure of a pump. It is a flowchart explaining the control method of a water supply pump. It is a figure explaining the operation curve R1 of a water supply pump at the time of 1st suction pressure. (A) is a QP diagram, (b) is an NP diagram. It is a NP diagram explaining the change of the cutoff operation curve at the time of suction pressure fluctuation. It is a QP diagram explaining the actual operation state of the pump in the case of following the operation curve before update with respect to the fluctuation of the suction pressure. It is a NP diagram explaining the detection of two different rotational speeds and discharge pressures. It is a systematic diagram of the receiving tank water supply system which has the water supply apparatus which concerns on embodiment of this invention. It is a figure explaining the structure and installation condition of the water supply apparatus which concerns on another embodiment of this invention. (A) is a schematic block diagram, (b) is a systematic diagram of the deep well water supply system which has a water supply apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Shallow well water supply system 18 Receiving tank water supply system 19 Deep well water supply system 20 Water supply apparatus 21 Water supply pump 22 Engine 27 Flow switch 28 Pressure sensor 30 Control apparatus 31 Controller 42 Terminal water supply equipment w Water DW Deep well SW Shallow well TL Receiving tank

Claims (5)

Detecting the discharge pressure of a pump for discharging liquid;
When the suction pressure of the pump is the first suction pressure, the pump determines the estimated end pressure from the discharge pressure and rotation speed during the shutoff operation and the discharge pressure and rotation speed when the maximum flow rate of liquid is discharged. Setting an operation curve for constant control;
Operating the pump according to the operating curve;
When the variation range of the discharge pressure of the pump over a predetermined time is within a predetermined range, Bei example and a step of correcting the suction pressure of the pump to determine the criteria for setting the operating curve;
Correcting the suction pressure of the pump,
The first rotation speed of the pump and the first discharge pressure of the pump at the first rotation speed, and the second rotation speed and the second rotation speed of the pump different from the first rotation speed. Detecting a second discharge pressure of the pump in
A second suction pressure of the pump is calculated based on the first rotation speed, the first discharge pressure, the second rotation speed, and the second discharge pressure, and the second suction pressure is corrected. A subsequent suction pressure step;
How to control the pump. Step of setting the previous Symbol operation curve,
Based on the relation between the suction pressure of the pump and the rotation speed that gives the discharge pressure during the shut-off operation, the rotation speed that gives the discharge pressure during the shut-off operation of the pump corresponding to the second suction pressure. And the pump performs the estimated terminal pressure constant control under the second suction pressure using the rotation speed that gives the discharge pressure during the shutoff operation of the pump corresponding to the second suction pressure. Configured to set a new driving curve;
The pump control method according to claim 1. The step of correcting the suction pressure of the pump is replaced when the fluctuation range of the discharge pressure of the pump is within a predetermined range over a predetermined time, and the amount of liquid fed from the pump becomes a predetermined underflow or less. Configured to correct the suction pressure of the pump when
The first discharge pressure is set to a discharge pressure when the pump is closed and the second discharge pressure is set to a target discharge pressure when the pump is stopped;
The pump control method according to claim 1 or 2. A feed pump that feeds water to the terminal water supply equipment;
A prime mover driving the feed pump;
A controller for controlling the rotational speed of the prime mover;
A pressure sensor for detecting a discharge pressure of the feed water pump;
A control device that controls the feed water pump using the pump control method according to any one of claims 1 to 3;
Water supply device. A flow switch for detecting that the amount of water discharged from the water supply pump has become equal to or less than a predetermined underwater amount;
4. When the flow switch detects that the amount of water discharged from the water supply pump is equal to or less than the predetermined underwater amount, the control device controls the water supply pump using the pump control method according to claim 3. Configured to control;
The water supply apparatus of Claim 4.

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