JP4245399B2 - Variable speed water supply device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a variable speed water supply apparatus including a cascade pump, a pressure sensor provided on the discharge side of the cascade pump, a motor for driving the cascade pump, and a controller for controlling the rotational speed of the pump.
[0002]
[Prior art]
Conventionally, in order to supply water to a home, an automatic water supply apparatus using a cascade pump is often used to supply water stored in a water receiving tank and well water. The reason for using the cascade pump is preferable in terms of energy saving and low noise. Such a conventional automatic water supply apparatus is equipped with an inverter and performs constant discharge pressure control (see, for example, Patent Document 1).
[0003]
Further, in order to respond to a request to obtain a predetermined pressure and water amount at a household at the end of a pipe, estimated terminal pressure constant control is known (for example, see Patent Documents 2, 3 and 4).
[0004]
Patent Document 1 Japanese Patent Application Laid-Open No. 10-288185 Patent Document 2 Japanese Patent Application Laid-Open No. 60-142097 Patent Document 3 Japanese Patent Application Laid-Open No. 60-156995 Japanese Patent Application Laid-Open No. 60-189519
However, as a result of various studies, the present inventor has found that there are further points to be improved. In particular, in the past, the control of the estimated terminal pressure was insufficient with respect to the setting of the maximum rotation speed and the water level in the case of a well.
[0006]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a variable speed water supply apparatus that can perform estimated terminal pressure control more accurately using a cascade pump.
[0007]
Another object of the present invention is to provide a variable speed water supply apparatus that can be controlled correctly in accordance with a change in the maximum rotation speed of a cascade pump or a change in the water level of a well.
[0008]
[Means for Solving the Problems]
According to the present invention, in a variable speed water supply apparatus comprising a cascade pump, a pressure sensor provided on the discharge side of the cascade pump, a motor for driving the cascade pump, and a controller for controlling the rotational speed of the motor, The controller includes a storage unit for storing pump characteristics, and the discharge side pressure when the operation frequency of the cascade pump reaches the minimum frequency, or the discharge side pressure reaches the minimum pressure for the estimated terminal pressure constant control. Based on the operating frequency of the cascade pump at this time, it has a function of performing a correction by determining an increase or a decrease in the water level on the suction side and performing an estimated terminal pressure constant control.
[0009]
According to the present invention, the controller increases the water level on the suction side depending on whether the pressure on the discharge side when the operating frequency of the cascade pump reaches the minimum frequency has decreased to the minimum pressure of the estimated terminal pressure constant control. In addition, the lowering of the water level on the suction side is determined depending on whether the operation frequency of the cascade pump has decreased to the lowest frequency when the pressure on the discharge side has reached the lowest pressure of the estimated terminal pressure constant control. Yes.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
1 and 2 show a front view and a top view of an automatic water supply apparatus A equipped with a cascade pump according to the present invention, and a cascade pump 2 driven by a motor 4 is installed on a unit base 1 having a piping function. The unit base 1 is covered with a unit cover 3. A suction pipe 5 and a discharge pipe 6 are fixed to the unit base 1 in the unit cover 3.
[0011]
Along with the rotation of the pump 2, the water flows through the suction pipe 5, a check valve 7 for preventing a reverse flow from the discharge side to the suction side when the pump is stopped, and a flow for detecting the amount of water for stopping the pump It is sucked into the pump 2 through the switch 8. And the discharge water from the pump 2 flows into the pressure tank 9 provided on the discharge side. This pressure tank 9 is for storing water when the pump 2 is stopped. A pressure sensor 10 for detecting the pressure on the discharge side is further provided on the discharge side of the pump 2, a discharge pipe 6 is provided on the downstream side of the pressure sensor 10, and the discharge water from the pump 2 is As described above, the liquid is guided to the discharge pipe 6. In the figure, 11 is a controller for starting and stopping the pump.
[0012]
FIG. 3 is an explanatory diagram of a variable speed water supply apparatus embodying the present invention. In FIG. 3, water W is accumulated up to level L in the well 12 dug from the ground S. The automatic water supply apparatus A is installed on the ground S close to the well 12.
[0013]
As illustrated, the suction pipe 5 is provided with a check valve 7 and a flow switch 8. The discharge pipe 6 of the cascade pump 2 is provided with a pressure sensor 10 and a pressure tank 9. A signal from the pressure sensor 10 is sent to the control unit 11a of the controller 11, and a frequency command from the control unit 11a is sent to the inverter 11b to control the motor 4 as will be described later. In the figure, M denotes a storage unit, which will be described later.
[0014]
FIG. 4 is a diagram for explaining that the estimated terminal pressure constant control is more efficient and so-called energy saving than the constant discharge pressure control according to the present invention. The horizontal axis represents the water amount Q and the vertical axis represents the lower side consumed. Electric power L, the upper side shows pressure H, and the rotation speed is shown as a parameter. In the figure, u represents a curve of 100%, v represents 90%, and w represents 80%. In the above figure, the horizontal straight line x is the case where the discharge is performed at the pressure H0 and the constant pressure control is performed, and the curve y is the characteristic when the estimated terminal pressure constant control is performed according to the present invention.
[0015]
Referring to the upper and lower diagrams of FIG. 4, in the case of constant discharge pressure control, the intersections H0, H2, and H1 between the line x and the lines u, v, and w are the rotation speeds of 100%, 90%, and 80%, respectively. Similarly, the water amounts Q0, Q2, and Q1 at% are shown. Similarly, in the case of the estimated terminal pressure constant control, the water amounts at the intersections H0, H4, and H3 are Q0, Q4, and Q3. The points corresponding to each water amount in the rotation speed curve in the figure below are L0, L2, and L1 in the discharge pressure constant control, and the line x connecting them is the characteristic of the power consumption L in the discharge and pressure constant control. A line y connecting points L0, L4, and L3 to the estimated terminal pressure constant control characteristic.
As can be seen from a comparison between the line x and the line y, it can be understood that the power consumption is small and efficient at any speed other than 100%.
[0016]
The memory | storage part M of FIG. 3 has memorize | stored beforehand the relationship between the rotational speed of a pump, and the internal pressure of piping of the discharge side in one Example.
In addition, the relationship between a plurality of predetermined rotation speeds and the pressure in the feed water pipe is stored in another embodiment.
By having such a storage unit, the estimated terminal pressure can be suitably obtained.
[0017]
According to still another embodiment, the storage unit stores the maximum rotation during variable speed operation. In this way, when a normal rotational speed exceeding the maximum rotational speed is input to the control unit, the maximum rotational speed value is set so that the control target pressure for each pump rotational speed can be reset. Further preferred.
[0018]
As can be seen from the description of FIG. 4, it is necessary to set the point of water quantity Q0, that is, the maximum number of rotations used. However, according to the present invention, it is possible to perform constant control of the estimated terminal pressure without setting the maximum number of rotations to be used.
[0019]
In FIG. 5, the pressure H on the vertical axis and the water amount Q on the horizontal axis are shown. FIG. 6 shows a flowchart. Curves a, b, and c in FIG. 5 are characteristic curves of the cascade pump as in FIG. 4, and the rotation speed of the cascade pump is larger than b and larger than b.
[0020]
A mode of control will be described with reference to FIGS. 5 and 6. When there is no data on the maximum number of rotations used, a reference pressure PA is set, and discharge is performed at the reference pressure, and constant pressure control is performed (step S1). At that time, the cascade pump performs the operation indicated by the straight line d. As the rotational speed of the cascade pump 2 increases, it is assumed that the maximum rotational speed is reached at the point e (step S2). That is, the rotational speed of the curve a is the first maximum rotational speed. Therefore, the controller 11 sets the rotation speed at this point e as the maximum rotation speed, and performs the estimated terminal pressure constant control (step S3). The operation of the cascade pump 2 at that time is as shown by the curve f.
[0021]
In the subsequent operation, when the engine 11 is operated at a rotational speed greater than the first maximum rotational speed a, for example, the rotational speed b (step S4), the controller 11 estimates the point g on the subsequent maximum rotational speed b as a new maximum rotational speed. Terminal pressure constant control is performed (step S5). The characteristics of the cascade pump 2 at that time are as shown by the curve h.
[0022]
Further, when changing the setting of the reference pressure PA, the above operation may be performed again after canceling the maximum number of rotations used.
If the map of the reference pressure and the maximum rotational speed is stored in this way, it is convenient for pipe changes and the like.
[0023]
In addition, when an appropriate maximum rotational speed cannot be obtained, it is preferable to set the pressure based on a predetermined temporary maximum rotational speed.
[0024]
Next, when the water level L in the well 12 changes, there is no problem in the constant discharge pressure control, but the constant end pressure constant control changes the cascade pump performance curve, so it is necessary to correct it according to the water level. .
First, this point will be described with reference to FIG. FIG. 7 is substantially the same as FIG.
[0025]
In FIG. 7, the vertical axis indicates the pressure H, the horizontal axis indicates the water amount Q, and the line u is the performance curve of the cascade pump when the rotation speed is 100%, that is, the maximum rotation speed (maximum frequency). As described above, in the estimated terminal pressure constant control, as shown by the curve y, the pressure is started at the pressure PB when the water amount is zero, and the discharge pressure of the cascade pump is controlled according to the water amount so as to become the pressure PA at the maximum water amount. The pressure PB is the pressure at the time of closing, and the operation frequency of the cascade pump at that time is shown by a curve HzB. In terms of control, the operation frequency is controlled so that this value HzB is the minimum operation frequency and does not drop below this value.
[0026]
Now, when the water level L of the well 12 rises, the suction pressure changes as the water level L rises. Therefore, as shown in FIG. 8, the performance curve of the cascade pump is a curve ua shown by a broken line outside the curve u. To change. At this time, naturally, the estimated terminal pressure constant control also changes as shown by the curve ya. However, if the control is performed with the curve ya, the portion with a small amount of water from the intersection A between the curve HzB and the curve ya is operated with the curve portion yb along the curve with the minimum operation frequency HzB, so the cutoff pressure becomes PBa, and the above-described cutoff pressure PB Since it is higher, it must be operated at a frequency HzBa lower than the lowest operating frequency HzB.
[0027]
FIG. 9 shows an aspect of the estimated terminal pressure constant control of the cascade pump when the water level L is lowered.
Contrary to the case of FIG. 8, in this case, the characteristic of the cascade pump becomes the curve Ub inside the curve U, and as a result, the estimated terminal pressure constant control changes according to the curve yc. The operation frequency of the lowest pressure PB at this time is operated at a frequency HzBb higher than the lowest operation frequency HzB.
[0028]
The water level can be detected by using a water level gauge as well as the water level of the well. If the characteristic curve of the pump is known, it can be calculated from the suction pressure and the discharge pressure using, for example, a map.
However, since the characteristic curve of the cascade pump is stored in the controller based on FIGS. 8 and 9, if this is used, the estimated end pressure due to the rise and fall of the water level of the well can be detected without detecting the water level gauge or the suction pressure. Constant control can be performed.
[0029]
FIG. 10 shows a flowchart of correction according to a change in the water level. First, the process is started, and it is determined whether or not a predetermined time has passed as a correction timing (step S11). As step S11, any timing such as a start time or a stop time can be used in addition to a predetermined time. Therefore, for example, when the timing is the start time, “within a predetermined time” in the following steps is replaced with “start time”.
[0030]
Then, the controller 11 determines whether or not the pressure has decreased to PB when the lowest frequency HzB in FIG. 7 is reached within a predetermined time (step S12). If it is not lowered, that is, if NO, the state is as shown in FIG. 8, so it is determined that the water level has risen (step S13). In this case, as can be seen from FIG. 8, since the pressure PBa is present at the frequency HzB, the pressure PB is corrected to the minimum frequency HzBa (step S14).
[0031]
This correction can be suitably grasped because the degree of well water level rise is unknown.
That is, if the frequency is lowered only to a predetermined value, the discharge pressure at that time is captured, the lowest frequency is finally reduced so that the pressure drops to PB, and when the pressure reaches PB, the new lowest frequency HzBa is set. Thereafter, only the difference between the frequencies HzB and HzBa is corrected, and the estimated terminal pressure constant control is performed.
[0032]
When step S12 is YES, the controller 11 determines whether or not the pressure has decreased to the lowest frequency HzB when the pressure reaches PB within a predetermined time (step S15). If YES, it is determined that there is no change in the water level and no correction is made.
[0033]
However, if step S15 is NO, it is determined that the water level has fallen (step S16), and since the pressure PB is currently at the frequency HzBb, correction is performed assuming that the water level has fallen by the difference between the frequencies HzB and HzBb (step S17).
[0034]
Assuming that this correction was made until the deadline, the well water level was lowered by the difference between the lowest operating frequency HzBb within the predetermined time and the initial operating frequency, and the estimated end pressure constant control was performed. .
[0035]
【The invention's effect】
As described above, according to the present invention, the following excellent effects can be obtained.
(A) Cascade pumps can be operated with less noise because operation with a large amount of water has less noise than operation with a small amount of water.
(B) Even if there is a change in the water level on the suction side, correct constant control of the estimated terminal pressure can be performed.
[Brief description of the drawings]
FIG. 1 is a front view of a variable speed water supply apparatus for carrying out the present invention.
FIG. 2 is a top view of FIG.
FIG. 3 is an explanatory diagram showing an embodiment of the present invention.
FIG. 4 is a diagram for explaining that power consumption is saved when constant estimated terminal pressure control is performed using a cascade pump.
FIG. 5 is a diagram for explaining that the estimated terminal pressure constant control is automatically performed without setting the maximum number of rotations used.
FIG. 6 is a flowchart for performing estimated terminal pressure constant control according to FIG. 5;
FIG. 7 is a basic diagram for explaining a change in estimated terminal pressure constant control by raising and lowering the water level on the suction side.
FIG. 8 is a diagram for explaining a change in estimated terminal pressure constant control due to an increase in water level;
FIG. 9 is a diagram for explaining a change in estimated terminal pressure constant control due to a drop in water level;
FIG. 10 is a flowchart showing an aspect of detection of upper and lower water levels prior to operation.
[Explanation of symbols]
2 ... Cascade pump 4 ... Motor 6 ... Discharge pipe 7 ... Check valve 8 ... Flow switch 9 ... Pressure tank 10 ... Pressure sensor 11 ... Controller 11a ..Control unit 11b ... Inverter 12 ... Well M ... Storage unit L ... Water level

Claims (2)

In a variable speed water supply apparatus comprising a cascade pump, a pressure sensor provided on the discharge side of the cascade pump, a motor for driving the cascade pump, and a controller for controlling the rotational speed of the motor, the controller stores the pump characteristics. The storage pump, and the cascade pump when the operation frequency of the cascade pump reaches the lowest frequency, or when the discharge side pressure reaches the lowest pressure of the estimated terminal pressure constant control A variable-speed water supply apparatus having a function of performing a correction by determining an increase or a decrease in the water level on the suction side based on the operating frequency, and performing an estimated terminal pressure constant control. The controller determines whether the water level on the suction side has risen depending on whether the pressure on the discharge side when the operation frequency of the cascade pump has reached the minimum frequency has decreased to the minimum pressure for the estimated terminal pressure constant control. 2. The lowering of the water level on the suction side is determined based on whether the operation frequency of the cascade pump has decreased to the minimum frequency when the pressure on the side reaches the minimum pressure of the estimated terminal pressure constant control. Variable speed water supply device.

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