Submersible pump with air pipe and its equipment

Abstract

To make it possible to maintain an operation at a rated speed and inhibit repeated starts and stops of a pump even if the suction port side water level is equal to or less than a lowest water level allowing an all-volume pumping-out operation.SOLUTION: A horizontal-shaft submersible mixed flow pump 1 has a discharge port 65 disposed to face an impeller 32, and inspired air is supplied from the discharge port 65 formed in a suction cover 5. When the water level decreases, air is supplied from the discharge port 65 at a time right before entry to an air-water mixing discharge operation. Water in a casing 2 of the submersible mixed flow pump 1 instantaneously drops so that the impeller 32 stops causing discharge of water, and thus the intra-pump pressure drops and a flap valve 4 is closed by its own weight and the external water pressure, so as to start an aerial stand-by operation in which the impeller 32 is exposed into air (a motor 3 maintains a rotary drive state at a rated speed). The oscillation is small and the burden on the motor 3 is small. If the water level increases during the aerial stand-by operation, then the air from the discharge port 65 is blocked to cause an instantaneous transition to an all-volume pumping-out operation.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a submersible pump with an air pipe and its installation, and more particularly to a submersible pump fixed to the gate of a water gate installed across a river or the like, which maintains operation at the rated speed even when the water level on the suction port side is below the minimum water level at which full discharge can be performed, and which makes it possible to suppress repeated starting and stopping of the pump, and its installation. [Background technology]

[0002] In a submersible pump, when the water level on the suction side falls below a certain level, air is sucked into the pump casing from the suction side, resulting in mixed air-water operation, which reduces the amount of discharge and increases vibration and noise. Therefore, when the water level on the suction side falls below a certain level, the pump operation is temporarily stopped, and then the pump is restarted when the inflow rate increases and the water level on the suction side rises. In such a case, if the pump is frequently turned on and off depending on the water level on the suction side, operation management becomes complicated, the frequency of starting and stopping the pump becomes complicated, and the burden on the submersible motor and starter becomes large, which is not desirable.

[0003] The pump gate described in Patent Document 1 is provided with a suction cover with a flow straightening effect on the top of the pump suction port, which suppresses the occurrence of air suction vortices and underwater vortices, allowing the pump to operate at a lower water level. The advance standby operation pump described in Patent Document 2 is provided with a compressed air supply passage in the main shaft of the pump, which is a vertical shaft, to prevent abnormal vibrations and noise when switching from drainage operation to water retention operation. This compressed air supply passage discharges compressed air from the inlet side of the impeller, and the remaining water in the discharge pipe is quickly dropped into the water supply well, shortening the water retention operation that allows full speed operation regardless of the water level of the pump well. Furthermore, the underwater pump described in Patent Document 3 draws air from a notch provided in the suction cover or from the intake pipe when the water level on the suction port side drops, and performs air-water mixing operation to reduce the amount of water discharged, and maintains operation at the rated speed even if the water level on the suction port side is below the water level during full water drainage operation, suppressing repeated on-off switching of the pump. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-3450 A [Patent Document 2] Japanese Patent Application Publication No. 8-312580 [Patent Document 3] WO2016 / 178387 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the pump described in Patent Document 1 prevents the continuous generation of air suction vortexes and prevents vibration noise that occurs when air is sucked in, but it repeatedly turns the pump on and off depending on the water level on the suction port side, and does not allow operation at the rated speed even when the water level is below the minimum water level. The pump in the advance standby operation described in Patent Document 2 is a pump with a vertical impeller drive shaft, and is not designed to be horizontal or inclined. The submersible pump described in Patent Document 3 is a horizontal shaft, and introduces air when the water level falls below a certain level, but vibrations and noise increase during air-water mixed operation, and the discharge volume also decreases. Furthermore, if the water level further decreases, if the pump is operated at the rated speed while the discharge volume is lost, it will switch from air-water mixed operation to air standby operation, but it is better to keep this air-water mixed operation as short as possible, or to not actually operate at all. The present invention has been made against the above background and has the following objectives. An object of the present invention is to provide an air pipe-equipped submersible pump and its equipment that uses an air on-off valve to prevent air-water mixed operation. Another object of the present invention is to provide an underwater pump with an air pipe and its equipment which maintains operation at the rated speed even when the water level on the suction side is below the minimum water level at which full drainage is possible, thereby suppressing repeated starting and stopping of the pump. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention takes the following measures. That is, the submersible pump with air pipe of the present invention 1 is as follows: a casing having a suction port on one side and a discharge port on the other side; an electric motor fixed within the casing for rotating and driving the device; an impeller coupled to the output shaft of the electric motor, the output shaft being disposed in a lateral direction in which the axis of the output shaft is horizontal, or the axis of the output shaft being inclined at a predetermined angle from the horizontal, and being rotated; a suction cover fixed to the casing and having an opening for sucking in a fluid; In a submersible pump comprising: an air pipe for drawing air into the submersible pump from a discharge port disposed upstream of the impeller and within the submersible pump; an air on-off valve for supplying or cutting off air to the air pipe; 、 A water level meter that detects the water level on the suction port side; an on-off valve control means for controlling the opening and closing of the air on-off valve based on the water level detection value of the water level meter; 、 The air pipe The discharge port faces the impeller, and the central axis of the discharge port is arranged parallel to the axis. And, The central axis of the discharge port is disposed at a position lower than the axis of the output shaft. It is characterized by:

[0007] The submersible pump with an air pipe of the present invention 2 is characterized in that, in the submersible pump with an air pipe of the present invention 1, the submersible pump with an air pipe is a submersible mixed flow pump in which the flow path of the fluid driven by the impeller is inclined with respect to the axis, or a submersible axial flow pump in which the flow path of the fluid is in the direction of the axis. The submersible pump with air pipe of the present invention 3 is 1 or 2 In the submersible pump with an air pipe, the on-off valve control means controls the water level when opening and closing the air on-off valve differently when the water level is rising and when the water level is falling.

[0008] The submersible pump with air pipe of the present invention 4 is 1 or 2 In the submersible pump with air pipe, the air pipe is connected to the suction cover or the casing. The submersible pump equipment with an air pipe of the present invention 5 is the same as the submersible pump equipment of the present invention 1 to of 4 A submersible pump facility using a submersible pump with an air pipe, characterized in that the submersible pump with an air pipe is mounted on a sluice gate or a culvert that crosses a river or waterway. Effect of the Invention

[0010] The submersible pump with air pipe and its equipment of the present invention supplies air from the air pipe when the water level on the suction side falls below the minimum water level required for full-flow drainage operation, allowing instantaneous transition from full-flow drainage operation to air-standby operation. If the water level on the suction side rises during air-standby operation, the air is cut off, allowing instantaneous transition from air-standby operation to full-flow drainage operation. As a result, air-water mixing operation is terminated in a short time or is eliminated entirely, making it possible to maintain operation at the rated speed while reducing vibration and suppressing repeated starting and stopping of the pump. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a vertical cross-sectional view showing a submersible mixed-flow pump 1 equipped with an air supply circuit 60 according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is an explanatory diagram showing an overview of an air supply circuit 60 for supplying or blocking air to the submersible mixed-flow pump 1 according to the first embodiment of the present invention. [Diagram 3] FIG. 3 is a flow chart showing an example of the operation of the motor-operated valve control circuit 71 for supplying or cutting off air to the submersible mixed-flow pump 1 according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a graph showing the current and vibration of the submersible mixed-flow pump 1 according to the first embodiment of the present invention when the water level on the suction port side is increased and decreased. [Diagram 5] FIG. 5 is a graph showing the current and vibration of a conventional submersible mixed-flow pump when the water level on the suction port side is raised and lowered. [Figure 6] FIG. 6 is a vertical cross-sectional view showing a submersible axial flow pump 10 equipped with an air supply circuit 60 according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] [Submersible mixed-flow pump 1 according to the first embodiment] A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical cross-sectional view of a submersible mixed-flow pump 1 according to the first embodiment of the present invention. As shown in FIG. 1, the submersible mixed-flow pump 1 according to the first embodiment of the present invention is fixed by bolts or the like via a bracket 101 or the like to a gate body 100 of a water gate or a culvert installed across a river, a waterway, a sewerage channel, or the like. Note that a structure in which a flange portion of a casing 2 of the submersible mixed-flow pump 1 is directly fixed to the gate body 100 of the water gate or the culvert may also be used. These structures are structures in which a submersible pump is mounted on a water gate (gate) to integrate the two, and are called a gate pump (trademark registration No. 2585973, commonly known as a "pump gate").

[0013] The submersible mixed-flow pump 1 of this embodiment is called a mixed-flow pump in which the flow of fluid discharged from the impeller is diagonal to the center line of the output shaft 31. The submersible mixed-flow pump 1 has a casing 2 having a suction port 21 on one side (left side of FIG. 1) and a discharge port 22 on the other side (right side of FIG. 1). An electric motor 3 for rotating an impeller 32 is fixed inside the casing 2. An output shaft 31 is attached to the electric motor 3 of the submersible mixed-flow pump 1 on the suction port 21 side, and the impeller 32 is fixed to the output shaft 31, and the rotational torque of the electric motor 3 is transmitted to the impeller 32. A guide vane 33 is fixed adjacent to the downstream side of the impeller 32 and between the inner circumference of the casing 2 and the outer circumference of the oil chamber 34. The guide vane 33 guides the water pumped up by the impeller 32.

[0014] A flap valve 4 that is supported so as to be able to open and close is disposed on the discharge port 22 side of the casing 2. This flap valve 4 is attached so as to be able to swing about a fulcrum 4a disposed at the top of the casing 2. When the water discharge pressure from the discharge port 22 is low, the flap valve 4 closes under its own weight, and when the water discharge pressure becomes high, it opens about the fulcrum 4a at the top, allowing water to be discharged from the discharge port 22. A suction cover 5 is fixed to the suction port 21 of the casing 2 for smoothly guiding water to the suction port 21. An opening 53 at the tip of the suction cover 5 faces diagonally downward from the horizontal (angle of attack θ), and upstream river water is sucked in from this opening 53.

[0015] As shown in FIG. 1, the submersible mixed-flow pump 1 has the axis 311 of the output shaft 31 arranged horizontally. If the height from the bottom surface 102 of the waterway to the upper edge (the lower surface of the suction guide plate 511) 531 of the opening 53 of the suction cover 5 is Y1, and the height from the bottom surface 102 of the waterway to the lower end of the impeller 32 is Y3, then Y1 is arranged at a position higher than Y3. The upper edge 531 of the opening 53 of the suction cover 5 is arranged at a position lower than the axis 311 of the output shaft 31 of the motor 3. The lower edge 532 of the opening 53 is at a height Y2 from the bottom surface 102 of the waterway. When the water level is equal to or lower than the water level Y2 of the lower edge 532 of the opening 53, the position is lower than the height Y3 to the lower end of the impeller 32, so the submersible mixed-flow pump 1 does not suck in river water. The water level shown on the left of Figure 1 indicates the boundary between the water level at which full drainage operation is possible when the water level is falling or rising, and the standby operation water level (air standby operation) when operating the submersible mixed-flow pump 1 of the first embodiment of the present invention.

[0016] Air supply circuit 60 FIG. 2 is a block diagram showing an outline of an air supply circuit 60 for supplying or cutting off air to the submersible mixed-flow pump 1. The air supply circuit 60 includes a water level gauge 70, an electric valve control circuit 71, an electric air valve 63, an air pipe 64, and an outlet 65. Air, which is the atmosphere, passes through the electric air valve 63 and the air pipe 64 and is sucked into the casing 2 from the outlet 65 by the suction force (negative pressure) during operation of the submersible mixed-flow pump 1. The outlet 65 is piped to an air pipe 64 attached to the suction cover 5. The electric air valve 63 is stored in a watertight sealed storage chamber 66 so as not to get wet (see FIG. 1). The central axis of the outlet 65, which is a pipe, is arranged parallel to the axis 311 of the output shaft 31 of the submersible mixed-flow pump 1. More precisely, the central axis of the outlet 65 is arranged at a position lower than the axis 311 of the output shaft 31. That is, the discharge port 65 is disposed opposite the impeller 32 and at a position lower than the axis 311 .

[0017] For this reason, the air sucked in from the discharge port 65 is sucked in toward the center of the impeller 32 and above and below the impeller 32 almost uniformly while moving slightly upward due to the buoyancy of the air. The timing of opening and closing the motorized air valve 63 is controlled by the motorized valve control circuit 71. The water level gauge 70 constantly measures the water level of the upstream river, measuring the water level by water pressure or the like. This structure and function are well known technologies and will not be described here. The motorized valve control circuit 71 controls the opening and closing of the motorized air valve 63 while watching the water level of the water level gauge 70 when the submersible mixed-flow pump 1 is operating. The opening and closing control of the motorized air valve 63 is performed according to the water level detected by the water level gauge 70. In FIG. 1, the leftmost part shows the water level at which the motorized air valve 63 is opened when switching from full discharge operation to air standby operation when the water level is falling. To the right of this, the water level at which the motorized air valve 63 is closed when switching from air standby operation to full discharge operation when the water level is rising is shown.

[0018] The reason why the water level positions for opening and closing the motorized air valve 63 are different when the water level is falling and rising is as follows. That is, in order to avoid air-water mixed operation when the water level is rising and falling, "when the water level is falling, if the water level is near the upper edge 531 of the opening 53 of the suction cover 5, the casing 2 is full of water and a total amount of water is discharged, and when the water level falls below the upper edge 531, air is sucked in from the suction cover 5. The motorized air valve 63 is opened at the "air valve opening water level" (in this embodiment, a water level about 10 mm higher than the upper edge 531) which is the water level near the upper edge 531, air is sucked into the casing 2 from the air pipe 64, the water in the casing 2 is drained at once, and the operation is instantly switched from the total amount of water discharge operation to the air standby operation." Also, "when the water level is rising, when the water level reaches 60% or more of the height of the impeller 32, the impeller 32 can discharge the water in the casing 2 by itself. In order to reliably avoid air-water mixed operation at this water level when the water level is rising, the motorized air valve 63 is closed at the "air valve closing water level" (in this embodiment, a water level that is about 55% of the impeller 32), which is a water level slightly lower than that water level, and air from the air pipe 64 is cut off, and when the water level reaches a water level at which full drain operation is possible (a water level that is about 60% of the impeller 32), the operation instantly shifts from air standby operation to full drain operation. For the above reasons, the water level positions at which the motorized air valve 63 opens and closes are different when the water level is falling and when the water level is rising.

[0019] Operation of the air supply circuit 60 FIG. 3 is a flow diagram showing an example of the operation of the motor-operated valve control circuit 71 of the air supply circuit 60. This flow diagram is a control example when the "air valve opening water level" and "air valve closing water level" of the motor-operated air valve 63 are set to the positions shown in FIG. 1. The power supply to the motor 3 (FIG. 1) is turned on (S1). The timer counter that sets the operation time of the motor 3 is set to zero, and the valve of the motor-operated air valve 63, which is in a state where air is cut off, is closed (S2, S3). When the operation of this control device starts, the control is in a full-volume drainage operation state. Next, the water level gauge 70 measures the water level on the intake side to obtain water level data (S4). It is determined whether this water level data is "above the air valve closing water level" (see FIG. 1) or not (S5).

[0020] In S3, the motorized air valve 63 is closed, and in this S5, if the water level is "above the air valve closing water level" (YES), that is, this water level is not in the air standby operation but is in the water level in the full-flow drain operation region (see FIG. 1). In this case (YES), it is determined whether "motorized air valve 63: closed?" (S12). If the motorized air valve 63 is closed (YES), the full-flow drain operation is possible, the timer counter is set to zero (S14), and the process returns to "water level measurement" (S4) to continue the full-flow drain operation. If the motorized air valve 63 is not closed (NO), the motorized air valve 63 is closed (S13), the timer counter is set to zero (S14), and the process similarly returns to "water level measurement" (S4) to continue the full-flow drain operation.

[0021] In S5, if the water level is not "above the air valve closing water level?" (NO), it is further determined whether the water level is "below the air valve opening water level?" (S6). In S6, if the water level is "below the air valve opening water level" (YES), the water level at this time means that the water level is in the air standby operation region regardless of whether the water level is "falling" or "rising" (see FIG. 1). If it is determined to be in this air standby operation region (YES), the motorized air valve 63 must be open, so the process proceeds to the next step S7 for confirmation, and it is determined whether "motorized air valve 63: open?" (S7). If the motorized air valve 63 is already open (YES), the process proceeds to step S9. If the motorized air valve 63 is closed (NO), it is in the air standby operation region, so the motorized air valve 63 is opened, and the operation time for air standby operation of the electric motor 3 is set (S8, S9). This operating time setting is for setting the operating time of the motor 3 since the water level is in a low range and there is no need to continue air standby operation any longer than necessary. In S10, it is determined whether the time since the transition to air standby operation is "longer than the operating time?"

[0022] If the operation time of the motor 3 is not equal to or longer than the set time (NO), the process returns to step S4, i.e., the air standby operation is continued. If the operation time of the motor 3 is equal to or longer than the set time (YES), the power supply to the motor 3 is turned off (step S11). That is, the operation of the submersible mixed-flow pump 1 is stopped because the set operation time has reached the set time. On the other hand, if the water level is not "air valve opening water level or lower?" in S6 (NO), the process proceeds to S15. The water level at this time is neither "air valve closing water level or higher?" (S5) nor "air valve opening water level or lower?" (S6), so the water level at this time means an intermediate water level between the "air valve opening water level" and the "air valve closing water level" (see FIG. 1). This intermediate water level is a setting region in which the motor air valve 63 is opened when the water level rises and closed when the water level falls.

[0023] In this step S15, if the motorized air valve 63 is open (YES), it means that the water level is rising. In the step S15, the water level region that is the intermediate water level is the air standby operation region. The motorized air valve 63 is left open, and the process jumps to S9 to continue the air standby operation until the set time. That is, at this intermediate water level, the fact that the motorized air valve 63 is already open usually means that the water level is rising, and at this water level, it means that the water level is the air standby operation water level. For this reason, the motorized air valve 63 remains open. Then, the process jumps to S4 to continue the operation of the electric motor 3. In this step S15, if the motorized air valve 63 is not open (NO), it means that the water level is falling. The process jumps to S4 to continue the operation of the electric motor 3. In other words, at this intermediate water level, the fact that the electric air valve 63 is not open means that the water level is falling, which is the "water level falling" range, and that the area is in the full-flow drainage operation range. With the electric air valve 63 closed, the timer counter is set to zero (S16), and the system returns to the "water level meter side" (S4) and continues the full-flow drainage operation.

[0024] The above operations can be generally controlled as follows. For example, when an operator turns on the switch (not shown) of the electric motor 3 of the submersible mixed flow pump 1, the electric motor 3 starts rotating, pumping up river water from the upstream side and discharging it downstream. The electric valve control circuit 71 judges the current water level from the water level signal from the water level gauge 70, controls the opening and closing of the electric air valve 63, and selects full discharge operation or air standby operation. Then, the timing of opening and closing the electric air valve 63 is changed depending on whether the water level is rising or falling. Even if the water level on the suction port side drops during full discharge operation while the water level is falling, as shown in FIG. 1, if the water level on the suction port side is higher than the "air valve opening water level", air is not sucked in from the opening 53, and the inside of the suction cover 5 and the inside of the casing 2 are filled with water. Therefore, the submersible mixed flow pump 1 continues full discharge operation at the rated speed. When the water level drops from the full discharge operation water level, the motor-operated valve control circuit 71 opens the motor-operated air valve 63 when it reaches the "air valve open water level" position, and supplies air to the submersible mixed-flow pump 1 via the air pipe 64. This supply of air causes the submersible mixed-flow pump 1 to immediately enter the air standby operation mode.

[0025] When the water level rises from the air standby operation, the motor-operated valve control circuit 71 closes the motor-operated air valve 63 when it reaches the position of the "air valve closing water level" to cut off the air to the submersible mixed flow pump 1 through the air pipe 64. In this embodiment, when the water level reaches 60% or more of the impeller 32, the impeller is in a state where it can discharge the water in the casing 2 by itself, so the submersible mixed flow pump 1 goes from the air standby operation mode to the total discharge operation mode in one go. Also, even if the water level on the suction port side drops during the total discharge operation while the water level is rising, as shown in FIG. 1, the motor-operated air valve 63 is closed because the water level on the suction port side is at the "air valve closing water level", so if the water level is higher than this water level, air is not sucked in from the opening 53, and the inside of the suction cover 5 and the inside of the casing 2 are filled with water. Therefore, the submersible mixed flow pump 1 continues the total discharge operation at the rated speed. The "air valve opening water level" and "air valve closing water level" will differ depending on the natural conditions, or more precisely, the on-site conditions, where the pump (submersible mixed flow pump 1) is installed, so it is a good idea to operate the pump in the river where it will actually be installed and determine the optimal water level based on the results.

[0026] When the water level on the suction port side falls below the "air valve opening water level" in FIG. 1, air is sucked in from the opening 53. Before air is sucked in from this opening 53, the electric air valve 63 is opened and air is supplied through the air pipe 64. As a result, the water in the suction cover 5 and the casing 2 of the submersible mixed flow pump 1 instantly falls, and the impeller 32 does not discharge water, so the pressure inside the pump drops, the flap valve 4 closes due to its own weight and the pressure of the outside water, and the impeller 32 is exposed to the air and goes into air standby operation (the motor 3 continues to rotate at the rated speed), so vibration is small and the burden on the motor 3 is small. Even if the water level on the suction port side falls further, the air standby operation continues within a set time (for example, set by a timer not shown). Therefore, the submersible mixed flow pump 1 of the first embodiment of the present invention does not have an air-water mixing operation, so vibration is small. The submersible mixed-flow pump 1 of this embodiment instantly switches from full-discharge operation to air standby operation when the water level on the suction port side falls below the minimum water level at which full-discharge operation is possible, and instantly switches from air standby operation to full-discharge operation if the water level on the suction port side rises during air standby operation and reaches the water level at which full-discharge operation is possible (approximately 60% water level of the impeller 32).As a result, there is no air-water mixing operation, vibration is reduced, and operation at the rated speed can be maintained.

[0027] When the water level is below the water level Y2 at the lower edge 532 of the opening 53 of the suction cover 5, river water cannot be physically sucked in, so there is no need to suck air into the casing 2 from the discharge port 65 of the air pipe 64. However, at the water level for air standby operation (see FIG. 1), the air standby operation continues within a set time (set by a timer, not shown) with the electric air valve 63 open. This control makes it possible to suppress repeated starting and stopping of the submersible mixed-flow pump 1. FIG. 4 is a graph showing the current (A) and vibration (note: composite vibration in the X, Y, and Z directions) (μm) of the motor 3 of the submersible mixed-flow pump (pump diameter 300 mm) 1 of this embodiment of the present invention. In FIG. 4, the water level on the suction port side is raised from 200 mm to 600 mm, and then lowered to 200 mm. As shown in Figure 4, when the water level rises, the system instantly switches from air standby operation to full drain operation, and when the water level falls, the system instantly switches from full drain operation to air standby operation. Since no air-water mixing operation occurs, fluctuations in current (A) and vibration (μm) are reduced.

[0028] Fig. 5 is a graph showing the current (A) and vibration (note: composite vibration in the X, Y, and Z directions) (μm) of the motor 3 of a conventional submersible mixed flow pump (pump diameter 300 mm) that does not have an air pipe. As shown in Fig. 5, the conventional submersible mixed flow pump draws in air from the upper edge 531 of the opening 53, causing air-water mixed operation, so it takes time to switch from air standby operation to total discharge operation and from total discharge operation to air standby operation, and the vibration is large. In contrast, the submersible mixed flow pump 1 of the first embodiment of the present invention does not cause air-water mixed operation as shown in Fig. 4, so the switch from air standby operation to total discharge operation and from total discharge operation to air standby operation is instantaneous and the vibration is small.

[0029] [Submersible axial flow pump 10 according to the second embodiment] The submersible axial flow pump 10 of the second embodiment shown in FIG. 6 has a different structure from that of the first embodiment. The submersible axial flow pump 10 is a pump that sends a fluid in the direction of the axis 311 of an output shaft 31, and has a casing 2 having a suction port 21 on one side (left side in FIG. 6) and a discharge port 22 on the other side (right side in FIG. 6). An electric motor 3 for rotational drive is fixed inside the casing 2. An output shaft 31 is attached to the electric motor 3 on the discharge port 22 side, and an impeller 32 is fixed to the output shaft 31, and the rotation of the electric motor 3 is transmitted to the impeller 32. A guide vane 33 is fixed between the inner circumference of the casing 2 and the outer circumference of the oil chamber 34 on the suction port 21 side (upstream side) of the impeller 32. The guide vane 33 guides the water pumped up by the impeller 32.

[0030] A flap valve 4 is attached to the casing 2 on the discharge port 22 side so as to be openable and closable. When the discharge pressure of water from the discharge port 22 is low, the flap valve 4 closes by its own weight, and when the discharge pressure of water increases, it opens around a fulcrum 4a at the top, allowing water to be discharged from the discharge port 22. A suction cover 5 is fixed to the suction port 21 of the casing 2 to smoothly guide water to the suction port 21. As shown in FIG. 6, the suction cover 5 is formed of one or more plates such as an upper plate and a side plate. The submersible axial flow pump 10 of the second embodiment is provided with an air supply circuit 60 that operates on the same principle as that of the first embodiment described above. It is composed of a water level gauge 70, an electric valve control circuit 71, an electric air valve 63, an air pipe 64, a discharge port 65, and the like.

[0031] The suction force of the submersible axial flow pump 10 during operation causes an air pipe 64 connected to an electric air valve 63 to branch into two, and the air, which is the atmosphere, is sucked into the casing 2 from two outlet ports 65 of each branch pipe (not shown). The two outlet ports 65 are arranged on the left and right sides of the outer periphery of the electric motor 3, i.e., in the suction cover 5 on either side of the electric motor 3. The outlet ports 65 are piped to an air pipe 64 fixed to the suction cover 5. The central axis of the outlet port 65 is arranged parallel to the axis 311 of the output shaft 31 of the submersible axial flow pump 10. To be precise, the central axis of the outlet port 65 is arranged slightly lower than the axis 311 of the output shaft 31. In other words, the outlet port 65 is arranged lower than the axis 311 so as to face the front of the impeller 32. The water level gauge, control circuit, etc. for operating the motorized air valve 63 of the submersible axial flow pump 10 of the second embodiment are substantially the same as those of the submersible mixed flow pump 1 of the first embodiment, and a description thereof will be omitted. As shown in the leftmost part of Fig. 6, the reason why the water level positions for opening and closing the motorized air valve 63 differ when the water level is falling and when the water level is rising is as follows. That is, in order to avoid air-water mixed operation when the water level is rising and falling, "when the water level is falling, if the water level is close to the upper edge 531 of the opening 53 of the suction cover 5, the casing 2 is filled with water and a total drain operation is performed, and when the water level falls below the upper edge 531, air is sucked in from the suction cover 5.

[0032] The motorized air valve 63 opens at the "air valve opening level" (in this embodiment, a water level about 10 mm higher than the upper edge 531), which is the water level near the upper edge 531, and air is sucked into the casing 2 from the air pipe 64, causing the water in the casing 2 to drain all at once, and instantly shifting from full-discharge operation to air-standby operation.' Also, 'When the water level rises, when the water level reaches 60% or more of the height of the impeller 32, the impeller 32 can discharge the water in the casing 2 by itself. In order to reliably avoid air-water mixed operation at a water level in this vicinity when the water level rises, the motorized air valve 63 closes at the "air valve closing level" (in this embodiment, a water level about 55% of the impeller 32), which is a water level slightly lower than that water level, and air from the air pipe 64 is cut off, and when the water level reaches a water level that allows full-discharge operation (about 60% of the impeller 32), the operation instantly shifts from air-standby operation to full-discharge operation. For the above reasons, the water level positions at which the motor-operated air valve 63 opens and closes differ when the water level is falling and when the water level is rising.

[0033] [Other embodiments] Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment. For example, the electric air valve 63 in the above-mentioned embodiment is a valve driven by an actuator using a motor (electric motor), but it may be an electromagnetic valve using a solenoid electromagnet. In addition, in the above-mentioned submersible mixed flow pump 1 and the submersible axial flow pump 10, the output shaft 31 of the electric motor 3 and the axis of the impeller 32 connected thereto are both arranged horizontally. However, this axis may be inclined from the horizontal. In addition, the air supplied to the air pipe to avoid air-water mixed operation is atmospheric air, but pressurized air may be supplied by a blower or compressor to actively drain the water in the pump casing. Furthermore, the shape of the suction cover 5 of the above-mentioned submersible mixed flow pump 1 and the submersible axial flow pump 10 differs depending on the structure of the submersible pump. Therefore, the suction cover 5 in the present invention is not limited to the cover on the suction side of the pump body, but is a concept that includes the main body part. [Explanation of symbols]

[0034] 1...Submersible mixed flow pump 10...Submersible axial flow pump 100…Door body 101…Bracket 102...Bottom of the waterway 2…Casing 21…Suction port 22…Discharge port 3...Electric motor 31…Output shaft 311…Axis center 32...Impeller 33...Guide vane 34…Oil chamber 4...Flap valve 5…Suction cover 60...Air supply circuit 63...Motor-operated air valve

Claims

1. a casing having a suction port on one side and a discharge port on the other side; an electric motor fixed within the casing for rotating and driving the device; an impeller coupled to the output shaft of the electric motor, the output shaft being disposed in a lateral direction in which the axis of the output shaft is horizontal, or the axis of the output shaft being inclined at a predetermined angle from the horizontal, and being rotated; a suction cover fixed to the casing and having an opening for sucking in a fluid; In a submersible pump comprising: an air pipe for drawing air into the submersible pump from a discharge port disposed upstream of the impeller and within the submersible pump; an air on-off valve for supplying or blocking air to the air pipe; A water level meter that detects the water level on the suction port side; an on-off valve control means for controlling the opening and closing of the air on-off valve based on a water level detection value of the water level gauge; The discharge port of the air pipe is disposed opposite the impeller, and a central axis of the discharge port is parallel to the axis of the impeller. The central axis of the discharge port is disposed at a position lower than the axis of the output shaft. A submersible pump with an air pipe.

2. 2. The submersible pump with air tube according to claim 1, The submersible pump with an air pipe is a submersible mixed flow pump in which the flow path of the fluid driven by the impeller is inclined with respect to the axis, or a submersible axial flow pump in which the flow path of the fluid is in the axial direction. A submersible pump with an air pipe.

3. 3. The submersible pump with air pipe according to claim 1, The on-off valve control means controls the air on-off valve so that the water level when the air on-off valve is opened or closed is different when the water level is rising and when the water level is falling. A submersible pump with an air pipe.

4. 3. The submersible pump with air pipe according to claim 1, The air pipe is connected to the suction cover or the casing. A submersible pump with an air pipe.

5. A submersible pump system using the submersible pump with an air pipe according to any one of claims 1 to 4, The submersible pump with air pipe is mounted on a sluice or culvert that crosses a river or waterway.

2. A submersible pump system with an air pipe.

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