JP7480934B2 - Submersible pumps and their equipment - Google Patents

Description

The present invention relates to a submersible pump and its equipment. More specifically, it relates to a submersible pump that is fixed to the gate body of a water gate installed across a river or the like, and that 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 drainage is possible, thereby making it possible to suppress repeated starting and stopping of the pump and its equipment.

When the water level on the suction side of a submersible pump drops below a certain level, air is sucked into the pump casing from the suction, causing a mixed air-water operation, which reduces the amount of discharge and increases vibration and noise. For this reason, when the water level on the suction side drops below a certain level, the pump is temporarily stopped, and then the pump is restarted when the inflow rate increases and the water level on the suction side rises. In this way, frequent on-off switching of the pump depending on the water level on the suction side makes operation management cumbersome, and the pump starts up more frequently, which is undesirable as it places a heavy burden on the submersible motor and starter.

The submersible pump described in Patent Document 1 has a suction cover with a straightening effect installed above the suction port of the submersible pump, which suppresses the generation of air suction vortices and underwater vortices and allows it to operate at lower water levels. In addition, the submersible pump in Patent Document 2 sucks in air through the notch in the suction cover or the suction pipe when the water level on the suction port side drops, and performs air-water mixing operation to reduce the amount of drainage. Even if the water level on the suction port side is below the water level during full drainage operation, it maintains operation at the rated speed and suppresses repeated on-off of the pump. However, the submersible pump described in Patent Document 2 generates large vibrations and noise during air-water mixing operation and also reduces the amount of drainage. In addition, if the water level drops further, if it is operated at the rated speed while the amount of drainage is lost, it will switch to air standby operation, but it is better to keep the air-water mixing operation as short as possible or to not have it at all.

JP 2003-3450 A WO2016/178387

The present invention was invented against the above background, and achieves the following objectives. The objective of the present invention is to provide a submersible pump and its equipment that 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 drainage is possible, and that makes it possible to suppress repeated starting and stopping of the pump.

In order to solve the above problems, the present invention takes the following measures.
That is, the submersible pump 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 the electric motor;
an impeller connected to an output shaft of the electric motor and driven to rotate;
a suction cover having one end fixed to the suction port and the other end formed with an opening for sucking water,
The suction cover is
In order to enable full drainage operation even if the water level at the suction port becomes lower than the lower end position (Y3) of the impeller, the lower end position (Y3) of the impeller is disposed at a position higher than the upper edge position (Y1) of the opening .
When the water level rises, the operation is instantly switched from the air standby operation to the total discharge operation, and when the water level falls, the operation is instantly switched from the total discharge operation to the air standby operation.
The submersible pump is an axial flow pump or a mixed flow pump,
The axis of the output shaft of the electric motor is arranged horizontally or inclined at a predetermined angle from the horizontal so that the suction port is lower than the exhaust port.

The underwater pump of the present invention 2 is characterized in that, in the present invention 1, the axial flow pump or the mixed flow pump has guide vanes fixed to the casing, and the axial flow pump is arranged in the order of the guide vanes and the impeller from the suction port side, and the mixed flow pump is arranged in the order of the impeller and the guide vanes from the suction port side.
The underwater pump of the third invention is characterized in that, in the first or second invention, the opening is formed so that the lower edge of the opening is formed downstream of the upper edge of the opening, and the lower edge is positioned lower than the upper edge.

The underwater pump of the fourth aspect of the present invention is characterized in that, in the first or second aspect of the present invention, the opening is formed in a straight line at a predetermined angle from the horizontal so that the lower edge of the opening is formed downstream of the upper edge of the opening and the lower edge is located at a lower position than the upper edge.
The submersible pump equipment of the present invention 5 is an equipment using a submersible pump described in any one of claims 1 to 4 selected from the present inventions 1 to 4, characterized in that the submersible pump is mounted on a sluice gate or culvert that crosses a river or waterway.

The submersible pump and its equipment of the present invention instantly switch from full-flow drainage operation to air standby operation when the water level on the suction port side falls below the minimum water level at which full-flow drainage operation is possible, and instantly switch from air standby operation to full-flow drainage operation if the water level on the suction port side rises during air standby operation. Therefore, since there is no air-water mixing operation or it ends in a short time, it is possible to reduce vibration and noise, maintain operation at the rated speed, and suppress repeated starting and stopping of the pump.

FIG. 1 is a vertical cross-sectional view showing a submersible pump according to a first embodiment of the present invention, illustrating a state in which the water level on the suction port side is sufficient for full drainage operation. FIG. 2 is a vertical cross-sectional view showing a submersible pump according to a first embodiment of the present invention, illustrating the state where the water level on the suction port side is the lowest water level at which full drainage operation is possible when the water level is dropping. FIG. 3 is a vertical cross-sectional view showing the submersible pump of the first embodiment of the present invention, showing the state immediately after water falls when the water level on the suction port side has dropped below the vicinity of the upper edge of the opening. FIG. 4 is a perspective view of the suction cover according to the first embodiment of the present invention. FIG. 5 is a graph showing the current and vibration of a conventional submersible pump when the water level on the suction port side is increased or decreased. FIG. 6 is a graph showing the current and vibration of the submersible pump of the first embodiment of the present invention when the water level on the suction port side is increased and decreased. FIG. 7 is a graph showing the flow rate and noise on the discharge side of a conventional submersible pump and the submersible pump of the first embodiment of the present invention when the water level on the suction port side is increased and decreased. FIG. 8 is a vertical cross-sectional view showing a submersible pump according to a second embodiment of the present invention, illustrating the state where the water level on the suction port side is the lowest water level at which full drainage operation is possible when the water level is dropping. FIG. 9 is a vertical sectional view showing another embodiment of the suction cover. FIG. 10 is a vertical sectional view showing still another embodiment of the suction cover. FIG. 11 is a front view and a left side view showing still another embodiment of the suction cover. FIG. 12 is a vertical cross-sectional view showing a submersible pump according to a third embodiment of the present invention. FIG. 13 is a vertical cross-sectional view showing a submersible pump according to a fourth embodiment of the present invention.

[First embodiment of the submersible pump]
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 pump according to the first embodiment of the present invention, showing a state in which the water level on the suction port side is sufficient for full-volume drainage operation. FIG. 2 is a vertical cross-sectional view of a submersible pump according to the first embodiment of the present invention, showing a state in which the water level on the suction port side is at the lowest water level at which full-volume drainage operation is possible when the water level on the suction port side is dropping. FIG. 3 is a vertical cross-sectional view of a submersible pump according to the first embodiment of the present invention, showing a state immediately after the water falls when the water level on the suction port side drops below the vicinity of the upper edge of the opening. FIG. 4 is a perspective view of a suction cover according to the first embodiment of the present invention. As shown in FIGS. 1 to 4, the submersible pump 1 according to the first embodiment of the present invention is fixed to a gate body 100 of a sluice gate or a culvert that is installed across a river, a waterway, a sewer channel, or the like, via a bracket 101. It is also possible to fix the flange portion of the casing 2 directly to the gate body 100 of the sluice gate or the culvert. This is an integrated gate equipped with an underwater pump, and is called a gate pump (Japanese Trademark Registration No. 2585973, commonly known as a "pump gate").

The submersible pump 1, which is called an axial flow pump in this example, has a casing 2 with an inlet 21 on one side (the left side in Figs. 1 to 3) and an outlet 22 on the other side (the right side in Figs. 1 to 3). An electric motor 3 for rotating is fixed inside the casing 2. An output shaft 31 is attached to the electric motor 3 on the outlet 22 side, and an impeller 32 is fixed to the output shaft 31, so that 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.

The casing 2 is fitted with a flap valve 4 supported so as to be openable and closable on the side of the discharge port 22. When the discharge pressure of the water from the discharge port 22 is low, the flap valve 4 closes under its own weight, and when the discharge pressure of the water is high, it opens around a fulcrum 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. 4, the suction cover 5 is formed of one upper plate 51 and two side plates 52, 52. The upper plate 51 is arranged at a predetermined angle from the horizontal so that the left side in FIGS. 1 to 4 is lower, and a horizontal suction guide plate 511 is formed at the left end in FIGS. 1 to 4. The side plates 52, 52 are formed on both sides of the upper plate 51, facing downward from the upper plate 51, parallel to the paper plane of FIGS. 1 to 3. The lower edges 521, 521 of the side plates 52, 52 are formed in a straight line at a predetermined angle from the horizontal so that the right side in Figs. 1 to 4 is lower. As shown in the modified example of the suction cover below, the shape of the lower edges 521, 521 of the side plates 52, 52 is not limited to a straight line. The suction cover 5 has an opening 53 on the lower surface surrounded by the upper plate 51, the side plates 52, 52, and the suction guide plate 511, and water is sucked in through this opening 53.

As shown in Figures 1 to 3, the axis 311 of the output shaft 31 of the submersible pump 1 is inclined at a predetermined angle from the horizontal so that the suction port 21 side is lower than the discharge port 22 side. In Figure 2, 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 is Y1 and the height from the bottom surface 102 of the waterway to the lower end of the impeller 32 is Y3, the inclination angle is set so that Y3 is located at a position higher than Y1. In the example of a submersible pump 1 with a pump diameter (diameter of the discharge port) of 300 mm (mm), Y1 is set to 300 mm and Y3 is set to 340 mm. As shown in Figure 1, when the water level on the suction port side is sufficiently higher than Y1, if the motor 3 is driven at the rated speed, the submersible pump 1 does not suck in air from the opening 53, so a full discharge operation is performed and the flap valve 4 opens.

Even if the water level on the suction port side drops during full drain operation, as shown in FIG. 2, if the water level on the suction port side is about 10 mm or more higher than Y1, air is not sucked in from the opening 53, so the inside of the suction cover 5 and the inside of the casing 2 are filled with water. Therefore, the submersible pump 1 continues to perform full drain operation at the rated speed. That is, taking into account the capacity of the submersible pump, Y1 is determined so that the flow rate of water near the suction guide plate 511 is 1 m/s or less. The lower sides 521, 521 of the side plates 52, 52 are formed in a straight line inclined at a predetermined angle from the horizontal, and are formed in a straight line that continuously connects the upper edge 531 of the opening 53 and the lower edge 532 of the opening 53. The lower edge 532 of the opening 53 is formed on the suction port 21 side (downstream side) than the upper edge 531 of the opening 53. Therefore, there is no air being sucked in from the side, and full drain operation is possible at the rated speed even if the water level on the suction port side becomes lower than the lower end of the impeller 32. In the example of a submersible pump 1 with a pump diameter of 300 mm, the height Y2 from the bottom surface 102 of the waterway to the lower edge 532 of the opening 53 is set to 150 mm.

When the water level on the suction side falls below the water level in FIG. 2, air is sucked in through the opening 53. As a result, as shown in FIG. 3, the water in the suction cover 5 and the casing 2 of the submersible pump 1 instantly falls, the flap valve 4 closes under its own weight, and the impeller 32 is exposed to the air and enters standby operation (the motor 3 continues to rotate at the rated speed). Therefore, noise and vibration are small, and the burden on the motor 3 is small. The mechanism of this water fall is as follows. (1) When the water level on the suction side falls, air is sucked in intermittently through the opening 53. (2) The submersible pump 1 that has sucked in air fluctuates greatly in its discharge volume. (3) The large fluctuation in the discharge volume of the submersible pump 1 causes the water level on the suction side to ripple up and down. (4) When the water level on the suction side falls significantly, a large amount of air is sucked in through the opening 53 that has expanded to the side. (5) The large amount of air sucked in causes water to fall in the submersible pump 1 (water falls after several air sucks in). Even if the water level on the suction port side falls further than the water level in Figure 3 (for example, measured with a water level gauge not shown), as long as it is within a set time (for example, set with a timer not shown), air standby operation will continue. Therefore, since there is no air-water mixing operation, there is less noise and vibration.

When the water level on the suction port side rises from the state shown in FIG. 3, the lower end of the impeller 32 passes under the water surface, stirring the water. However, since no new air is sucked into the casing 2 through the opening 53, and the impeller 32 is not submerged to the extent that it pumps out water, air-water mixing operation is not performed, and noise and vibration are small. When the water level on the suction port side rises further and reaches the water level Y4 in FIG. 3 (the water level at which the impeller 32 is submerged by about 60%), full-volume drainage operation begins again, and the flap valve 4 opens. In the example of a submersible pump 1 with a pump diameter of 300 mm, the water level Y4 at which full-volume drainage begins when the water level rises is 490 mm. The submersible pump 1 of the first embodiment of the present invention instantly switches from full-volume drainage operation to air-standby operation when the water level on the suction port side falls below the minimum water level at which full-volume drainage operation is possible, and instantly switches from air-standby operation to full-volume drainage operation when the water level on the suction port side rises during air-standby operation. This means there is no air-water mixing, vibration and noise are reduced, operation is maintained at the rated speed, and repeated starting and stopping of the pump is suppressed.

Figures 5 to 7 are graphs showing the current, vibration, discharge flow rate and noise when the motor is continuously driven at the rated speed and the water level on the suction port side is raised and lowered. Figure 5 is a graph showing the motor current (A) and vibration (μm) in the X, Y and Z directions of a conventional submersible pump (pump diameter 300 mm). In Figure 5, the water level on the suction port side is raised from 200 mm to 540 mm, and then lowered to 200 mm. The conventional submersible pump is a type of submersible pump described in Patent Document 2 in which the axis of the output shaft of the motor is arranged horizontally. As shown in Figure 5, air-water mixed operation occurs at two water levels, when the water level reaches 380 mm and when the water level drops to 380 mm, so the fluctuations in the current (A) and the fluctuations in the vibration (μm) in the X, Y and Z directions become large.

Figure 6 is a graph showing the current (A) and vibration (μm) in the X, Y, and Z directions of the motor 3 of the submersible pump (pump bore 300 mm) 1 of the first embodiment of the present invention. In Figure 6, 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 6, when the water level rises, the operation shifts instantly from air standby to full drain operation, and when the water level falls, the operation shifts instantly from full drain operation to air standby operation, and no air-water mixing operation occurs, so the fluctuations in the current (A) and the fluctuations in the vibration (μm) in the X, Y, and Z directions are small.

FIG. 7 is a graph showing the discharge flow rate (m ³ /min) and noise (dB) of a conventional submersible pump (pump bore 300 mm) and a submersible pump 1 according to the first embodiment of the present invention (pump bore 300 mm). In FIG. 7, the motor is continuously driven at the rated speed, and the water level on the suction port side rises and falls in the same manner as in FIG. 5 and FIG. 6. As shown in FIG. 7, the conventional submersible pump draws in air and causes air-water mixed operation, so it takes time to switch from air standby operation to full drainage operation and from full drainage operation to air standby operation, and the noise is large. In contrast, the submersible pump 1 according to the first embodiment of the present invention does not cause air-water mixed operation, so the switch from air standby operation to full drainage operation and from full drainage operation to air standby operation is instantaneous, and the noise is small.

Second embodiment of the submersible pump
A second embodiment of the present invention will be described below with reference to the drawings. FIG. 8 is a vertical cross-sectional view of a submersible pump 10 according to a second embodiment of the present invention, showing the lowest water level at which the suction port side water level is capable of performing a full-volume drainage operation when the water level is lowered. The submersible pump 10 according to the second embodiment is an example in which the axis 311 of the output shaft 31 is arranged horizontally. In the following description, the same parts as those of the submersible pump 1 according to the first embodiment are given the same numbers, and duplicated descriptions are omitted. The electric motor 3 of the submersible pump 10 is provided with a horizontal output shaft 31 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.

A suction cover 5A is fixed to the suction port 21 of the casing 2 to smoothly guide water to the suction port 21. As shown in FIG. 8, the suction cover 5A is formed of one upper plate 51A and two side plates 52A, 52A. The upper plate 51A is formed by bending in two stages so that the left side of FIG. 8 is lower, and a horizontal suction guide plate 511A is formed at the left end of FIG. 8. The upper plate 51A of the submersible pump 10 of the second embodiment may be formed in a straight line inclined at a predetermined angle, as in the submersible pump 1 of the first embodiment. In this case, the side plates 52A, 52A of the upper plate 51 are formed on both sides of the upper plate 51A, downward from the upper plate 51A, parallel to the paper surface of FIG. 8. The lower sides 521A, 521A of the side plates 52A, 52A are formed in a straight line inclined at a predetermined angle from the horizontal so that the right side of FIG. 8 is lower. The suction cover 5A has an opening 53A on the underside surrounded by the upper plate 51A, side plates 52A, 52A, and suction guide plate 511A, and water is sucked in through this opening 53A.

As shown in FIG. 8, if the height from the bottom surface 102 of the waterway to the upper edge (the lower surface of the suction guide plate 511A) 531A of the opening 53A is Y1, and the height from the bottom surface 102 of the waterway to the lower end of the impeller 32 is Y3, the shape of the suction cover 5A is set so that Y3 is located at a position higher than Y1. When the water level on the suction port side is sufficiently higher than Y1, if the motor 3 is driven at the rated speed, the submersible pump 10 will not suck in air from the opening 53A, so a full drain operation will be performed and the flap valve 4 will open.

Even if the water level on the suction port side drops during full-volume drainage operation, as shown in FIG. 8, if the water level on the suction port side is about 10 mm or more higher than Y1, air is not sucked in from the opening 53A, so the suction cover 5A and the casing 2 are filled with water. Therefore, the submersible pump 10 continues full-volume drainage operation at the rated speed. The lower sides 521A, 521A of the side plates 52A, 52A are formed in a straight line inclined at a predetermined angle from the horizontal, and are formed in a straight line that continuously connects the upper edge 531A of the opening 53A and the lower edge 532A of the opening 53A. Therefore, the height Y2 from the bottom surface 102 of the waterway to the lower edge 532A of the opening 53A is set at a position lower than the height Y1 from the bottom surface 102 of the waterway to the upper edge 531A of the opening 53A. In addition, the lower edge 532A of the opening 53A is formed closer to the suction port 21 side (downstream side) than the upper edge 531A of the opening 53A. Therefore, there is no air intake from the side, and even if the water level on the suction port side becomes lower than the bottom end of the impeller 32, full drainage operation is possible at the rated speed.

When the water level on the suction port side falls below the water level in FIG. 8, air is sucked in through the opening 53A. As a result, although not shown, the water in the suction cover 5A and the casing 2 of the submersible pump 10 instantly falls, the flap valve 4 closes under its own weight, and the impeller 32 is exposed to the air and enters air standby operation (the motor 3 continues to rotate at the rated speed), resulting in less noise and vibration and less strain on the motor 3. 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 pump 10 of the second embodiment does not have air-water mixed operation, so there is less noise and vibration. The submersible pump 10 of the second embodiment of the present invention instantly switches from full-volume drainage operation to air standby operation when the water level on the suction port side falls below the minimum water level that allows full-volume drainage operation, and instantly switches from air standby operation to full-volume drainage operation if the water level on the suction port side rises during air standby operation. As a result, there is no air-water mixing operation, vibration and noise are reduced, operation can be maintained at the rated speed, and repeated starting and stopping of the pump can be suppressed.

[Another embodiment of the suction cover]
FIG. 9 is a vertical cross-sectional view showing another embodiment of the suction cover, which is a modified example of the suction cover 5 of the submersible pump 1 of the first embodiment, and is a modified example of the side plate 52 and the lower edge 521. The lower edges 521B, 521B of the side plates 52B, 52B of the suction cover 5B in FIG. 9(a) are formed by bending in two stages so that the right side is lower, and are formed in a broken line connecting the upper edge 531B of the opening 53B and the lower edge 532B of the opening 53B. The lower edges 521C, 521C of the side plates 52C, 52C of the suction cover 5C in FIG. 9(b) are formed in a smooth curved shape so that the right side is lower, and are formed by connecting the upper edge 531C of the opening 53C and the lower edge 532C of the opening 53C. The lower edges 521D, 521D of the side plates 52D, 52D of the suction cover 5D in Fig. 9(c) are formed in a straight line inclined at a predetermined angle from the horizontal, and are formed in a straight line, bent and curved shape that continuously connects the upper edge 531D of the opening 53D and a position away from the lower edge 532D of the opening 53D to the upper side. The modified examples of the side plates 52 and the lower edge 521 described in Figs. 9(a), (b) and (c) can also be applied to the suction cover 5A of the submersible pump 10 of the second embodiment.

Figure 10(a) is a vertical cross-sectional view showing yet another embodiment of the suction cover, which is a modified version of the suction cover 5 of the submersible pump 1 of the first embodiment. As shown in Figure 10(a), the upper plate 51E of the suction cover 5E is bent in two stages so that the left side in Figure 10(a) is lower, and a horizontal suction guide plate 511E is formed at the left end of Figure 10(a). Figure 10(b) is a vertical cross-sectional view showing yet another embodiment of the suction cover, which is a modified version of the suction cover 5A of the submersible pump 10 of the second embodiment. As shown in Figure 10(b), the upper plate 51F of the suction cover 5F is arranged at a predetermined angle from the horizontal so that the left side in Figure 10(b) is lower, and a motor storage section 54F for accommodating the electric motor 3 is formed in the upper plate 51F by protruding upward. The motor storage section 54F described in FIG. 10(b) can also be applied to the suction covers 5, 5B, 5C, 5D, and 5E of the submersible pump 1 of the first embodiment.

Figure 11 is a vertical cross-sectional view showing yet another embodiment of the suction cover, which can be applied to the submersible pump 1 of the first embodiment and the submersible pump 10 of the second embodiment. Figure 11(a) is a front view (right side of Figure 11) and a left side view (left side of Figure 11) of the suction cover 5 of the submersible pump 1 of the first embodiment. As described above, the suction cover 5 is formed of one upper plate 51 and two side plates 52, 52. The upper plate 51 is flat and is arranged at a predetermined angle from the horizontal so that the left side of the front view of Figure 11(a) is lower, and a horizontal suction guide plate 511 is formed at the left end of the front view of Figure 11(a). The side plates 52, 52 are also flat and are formed on both side surfaces of the upper plate 51, parallel to each other, from the upper plate 51 downward. The suction cover 5 has an opening 53 on the underside surrounded by the upper plate 51, side plates 52, 52, and suction guide plate 511, and water is sucked in through this opening 53.

In the suction cover 5G of FIG. 11(b), planar side plates 52G, 52G are formed on both sides of the upper plate 51G so that the distance between them narrows from the upper plate 51G downward. As a modification of FIG. 11(b), the planar side plates 52G, 52G may be formed so that the distance between them widens from the upper plate 51G downward. The side plates 52G, 52G may also be curved. In the suction cover 5H of FIG. 11(c), after an inclined surface 55H is formed from the upper plate 51H on both sides of the upper plate 51H, planar side plates 52H, 52H are formed parallel to each other downward. In the suction cover 5J of FIG. 11(d), after the upper parts of the upper plate and the side plates are formed with a smooth curved surface 56J, planar side plates 52J, 52J are formed parallel to each other downward on both sides of the curved surface 56J. Additionally, the side plates of the suction cover 5H in FIG. 11(c) and the suction cover 5J in FIG. 11(d) may be formed so that the distance between them narrows or widens, like the side plates in FIG. 11(b).

[Third embodiment of the submersible pump]
Figure 12 is a vertical cross-sectional view showing a submersible pump according to a third embodiment of the present invention. The submersible pumps of the first and second embodiments described above are axial flow pumps, but the submersible pump of the third embodiment is a mixed flow pump. That is, an axial flow pump uses an impeller to send fluid in the axial direction, while a mixed flow pump uses an impeller to send fluid in a diagonal direction relative to the axis. The water level shown in Figure 12 indicates the lowest water level at which full drainage operation is possible when the water level on the suction port side is dropping.

As shown in FIG. 12, the axis 311' of the output shaft 31' of the submersible pump 1', which is a mixed flow pump, is inclined at a predetermined angle from the horizontal so that the suction port 21' side is lower than the discharge port 22' side. In FIG. 12, if the height from the bottom surface 102' of the waterway to the upper edge (the bottom surface of the suction guide plate 511') 531' of the opening 53' is Y1, and the height from the bottom surface 102' of the waterway to the lower end of the impeller 32' is Y3, the inclination angle is set so that Y3 is located at a position higher than Y1. In this example of a submersible pump 1' with a pump diameter of 300 mm, Y1 is set to 300 mm and Y3 is set to 340 mm. When the water level on the suction port side is sufficiently higher than Y1, if the motor 3' is driven at the rated speed, the submersible pump 1' will not suck in air from the opening 53', so a full discharge operation will be performed and the flap valve 4' will open.

Even if the water level on the suction port side drops during full drain operation, as shown in FIG. 12, if the water level on the suction port side is about 20 mm or more higher than Y1 (320 mm in this example), air is not sucked in from the opening 53', so the inside of the suction cover 5' and the inside of the casing 2' are filled with water. Therefore, the submersible pump 1' continues to perform full drain operation at the rated speed. The height Y2 from the bottom surface 102' of the waterway to the lower edge 532' of the opening 53' is set at a position lower than the height Y1 from the bottom surface 102' of the waterway to the upper edge 531' of the opening 53'. In addition, the lower edge 532' of the opening 53' is formed on the suction port 21' side (downstream side) than the upper edge 531' of the opening 53'. Therefore, there is no air being sucked in from the side, and full drain operation is possible at the rated speed even if the water level on the suction port side becomes lower than the lower end (Y3) of the impeller 32'.

When the water level on the suction port side falls below the water level shown in FIG. 12, air is sucked in through the opening 53'. As a result, the water in the suction cover 5' and the casing 2' of the submersible pump 1' instantly falls, the flap valve 4' closes under its own weight, and the impeller 32' is exposed to the air and enters air standby operation (the motor 3' continues to rotate at the rated speed). 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, noise and vibration are small, and the burden on the motor 3' is small. The mechanism of this water fall is the same as that of the submersible pumps of the first and second embodiments described above, so its description is omitted.

[Fourth embodiment of the submersible pump]
FIG. 13 is a vertical cross-sectional view showing a submersible pump 10' according to a fourth embodiment of the present invention. The submersible pump 10' according to the fourth embodiment is a mixed flow pump similar to that of the third embodiment. The water level on the suction port side shown in FIG. 13 indicates the lowest water level state at which full discharge operation is possible when the water level drops. The mixed flow submersible pump 10' according to the fourth embodiment is an example in which the axis 311' of the output shaft 31' is arranged horizontally. In the following description, the same parts as those of the submersible pump 1' according to the third embodiment are given the same numbers, and duplicated descriptions are omitted. The electric motor 3' of the submersible pump 10' has a horizontal output shaft 31' attached to the suction port 21' side, an impeller 32' is fixed to the output shaft 31', and the rotation of the electric motor 3' is transmitted to the impeller 32'. The guide vanes 33' guide the water pumped up by the impeller 32'.

The suction cover 5' is fixed to the suction port 21' of the casing 2' to smoothly guide water to the suction port 21'. The suction cover 5' has an opening 53' that opens downward, and water is sucked in from this opening 53'. As shown in FIG. 13, if the height from the bottom surface 102' of the waterway to the upper edge (the bottom surface of the suction guide plate 511') 531' of the opening 53' is Y1, and the height from the bottom surface 102' of the waterway to the lower end of the impeller 32' is Y3 (343 mm in this example), the shape of the suction cover 5' is set so that Y3 is located at a position higher than Y1. When the water level on the suction port side is sufficiently higher than Y1, if the motor 3' is driven at the rated speed, the submersible pump 10' does not suck in air from the opening 53', so a full discharge operation is performed and the flap valve 4' opens.

Even if the water level on the suction port side drops during full drain operation, as shown in FIG. 13, if the water level on the suction port side is about 20 mm or more higher than Y1 (320 mm in this example), air is not sucked in from the opening 53', so the inside of the suction cover 5' and the inside of the casing 2' are filled with water. Therefore, the submersible pump 10' continues to perform full drain operation at the rated speed. The height Y2 from the bottom surface 102' of the waterway to the lower edge 532' of the opening 53' is set at a position lower than the height Y1 from the bottom surface 102' of the waterway to the upper edge 531' of the opening 53'. In addition, the lower edge 532' of the opening 53' is formed on the suction port 21' side (downstream side) than the upper edge 531' of the opening 53'. Therefore, there is no air being sucked in from the side, and full drain operation is possible at the rated speed even if the water level on the suction port side becomes lower than the lower end (Y3) of the impeller 32'.

When the water level on the suction port side falls below the water level shown in FIG. 13, air is sucked in through the opening 53'. As a result, the water in the suction cover 5' and the casing 2' of the submersible pump 10' instantly falls, the flap valve 4' closes under its own weight, and the impeller 32' is exposed to the air and enters the air standby operation (the motor 3' continues to rotate at the rated speed), so noise and vibration are 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, noise and vibration are small and the burden on the motor 3' is small. The mechanism of this water fall is the same as that of the submersible pump of the above-mentioned embodiment 1, and therefore its description is omitted.
[Other embodiments]
Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. The suction cover 5, 5A in the above-mentioned embodiment is described as being composed of one upper plate and two side plates, but this is not intended to be a combination of multiple plate materials joined by welding, and may be a pressed product or a cast product that is integrally formed. Therefore, the one upper plate and two side plates described above do not necessarily mean that they are separate members.

100...door body 101...bracket 102...bottom surface of waterway 1, 10, 1', 10'...underwater pump 2, 2'...casing 21, 21'...suction port 22, 22'...discharge port 3, 3'...motor 31, 31'...output shaft 311, 311'...axis 32, 32'...impeller 33, 33'...guide vane 34, 34'...oil chamber 4, 4'...flap valve 5, 5', 5A, 5B, 5C, 5D, 5E, 5F, 5G, 5H, 5J...suction cover 51, 51A, 51B, 51C, 51D, 51E, 51F, 51G, 51H...upper plate 511, 511', 511A, 511B, 511C, 511D, 511E, 511F, 5 11G, 511H, 511J... Suction guide plate 52, 52A, 52B, 52C, 52D, 52E, 52F, 52G, 52H, 52J... Side plate 521, 521A, 521B, 521C, 521D, 521E, 521F... Lower side 53, 53', 53A, 53B, 53C, 53D, 53E, 53F, 53G, 53H, 53J... Opening 531, 531', 531A, 531B, 531C, 531D, 531E, 531F... Upper edge of opening 532, 532', 532A, 532B, 532C, 532D, 532E, 532F... Lower edge of opening 54F... Motor storage section 55H... Inclined surface 56J... Curved surface

Claims (5)

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 the electric motor;
an impeller connected to an output shaft of the electric motor and rotated;
a suction cover having one end fixed to the suction port and the other end formed with an opening for sucking water,
The suction cover is
In order to enable full drainage operation even if the water level at the suction port becomes lower than the lower end position (Y3) of the impeller, the lower end position (Y3) of the impeller is disposed at a position higher than the upper edge position (Y1) of the opening .
When the water level rises, the operation is instantly switched from the air standby operation to the total discharge operation, and when the water level falls, the operation is instantly switched from the total discharge operation to the air standby operation.
The submersible pump is an axial flow pump or a mixed flow pump,
An underwater pump, characterized in that an axis of the output shaft of the electric motor is inclined at a predetermined angle from the horizontal so that the suction port is lower than the discharge port , or is arranged horizontally. 2. The submersible pump according to claim 1 ,
The axial flow pump or the mixed flow pump has guide vanes fixed to the casing,
The axial flow pump is arranged in the order of the guide vane and the impeller from the suction port side,
The mixed flow pump is characterized in that the impeller and the guide vanes are arranged in this order from the suction port side. 3. The submersible pump according to claim 1,
The opening is formed so that a lower edge of the opening is formed downstream of an upper edge of the opening, and the lower edge is positioned lower than the upper edge. 3. The submersible pump according to claim 1,
An underwater pump characterized in that the opening is formed in a straight line at a predetermined angle from the horizontal so that the lower edge of the opening is formed downstream of the upper edge of the opening and the lower edge is located at a lower position than the upper edge. An underwater pump installation using the underwater pump according to any one of claims 1 to 4 ,
The submersible pump facility is characterized in that the submersible pump is mounted on a sluice gate or a culvert that crosses a river or a waterway.

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