Submerged Pump

Abstract

A submerged pump capable of removing liquefied gas remaining in a motor chamber. [Solution] The submerged pump (1) according to the present invention has a housing that houses a rotating shaft and an impeller. The housing includes a motor chamber (21), a pump chamber (20), a recess (24) disposed in the motor chamber, a first flow path (23, 52, 7) disposed below the motor and communicating between the motor chamber and the pump chamber, a second flow path disposed above the motor and communicating between the motor chamber and the exterior of the housing, and a third flow path (26) communicating between the recess and the exterior. The third flow path opens to a portion (24a) of the inner surface of the recess that is disposed at the lowest position. When the submerged pump discharges pumped fluid, a portion of the pumped fluid discharged from the impeller passes through the first flow path and is introduced from the pump chamber to the motor chamber. The pumped fluid introduced into the motor chamber passes through the motor, the second flow path, and the third flow path before being discharged from the motor chamber to the exterior.

Description

[Technical Field]

[0001] The present invention relates to a submerged pump. [Background technology]

[0002] Submerged pumps are used to extract liquefied gas (e.g., liquefied natural gas) from a storage tank in which the gas is stored (see, for example, Patent Document 1). The submerged pump is immersed in the liquefied gas stored in the storage tank. The submerged pump includes a pump chamber that houses an impeller and a motor chamber that houses a motor. The impeller draws and discharges pumped liquid from an inlet port located at the bottom end of the pump chamber. A portion of the pumped liquid discharged from the impeller is used to lubricate and cool bearings, and is also used to cool the motor by passing through an introduction path (e.g., a bearing) and being introduced into the motor chamber.

[0003] The submerged pump is removed from the storage tank for maintenance, for example. When the submerged pump stops operating, the interior of the submerged pump is filled with residual liquefied gas. When the submerged pump is raised above the liquid level, the liquefied gas remaining in the pump chamber is discharged from the suction port, and the liquefied gas remaining in the motor chamber passes through the introduction path and the pump chamber and is discharged from the suction port. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-83172 Summary of the Invention [Problem to be solved by the invention]

[0005] A portion of the housing defining the motor chamber functions as a bearing bracket that holds the bearing. The bearing bracket is formed, for example, in a cylindrical shape to hold the outer ring and holder of the bearing. The housing also has a structure that allows accessories (e.g., a bearing vibration sensor) to be attached to the motor chamber. As such, the housing defining the motor chamber has recesses and projections. As a result, some of the liquefied gas remaining in the motor chamber remains in recesses formed by the recesses and projections. In this state, liquefied gas and vaporized gas leak to the outside during maintenance of the submerged pump. Much of the residual gas is flammable and toxic. Therefore, when the submerged pump is raised above the liquid surface, it is necessary to remove the liquefied gas remaining in the motor chamber (recess).

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide a submerged pump capable of removing liquefied gas remaining in a motor chamber. [Means for solving the problem]

[0007] A submerged pump in one embodiment of the present invention is a submerged pump that is immersed in a pumped liquid, and includes a motor, a rotating shaft attached to the motor, an impeller attached to the rotating shaft, and a housing that houses the rotating shaft and the impeller, wherein the housing includes a motor chamber that houses the motor, a pump chamber that is arranged below the motor chamber and houses the impeller, a recess that is arranged in the motor chamber and recessed downward, a first flow path that is arranged below the motor and communicates with the motor chamber and the pump chamber, a second flow path that is arranged above the motor and communicates with the motor chamber and an external space of the housing, and a third flow path that communicates with the recess and the external space, wherein the third flow path opens to a portion of the inner surface of the recess that is arranged at the lowest position, The flow rate of the third flow path is smaller than the flow rate of the second flow path,When the submerged pump is discharging the pumped fluid, a portion of the pumped fluid discharged from the impeller passes through the first flow path and is introduced from the pump chamber into the motor chamber, and the pumped fluid introduced into the motor chamber passes through the motor, the second flow path, and the third flow path, and is discharged from the motor chamber to the external space. [Effects of the Invention]

[0008] The present invention can provide a submerged pump that can remove liquefied gas remaining in the motor chamber. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view showing a state in which a submerged pump according to the present invention is used. [Figure 2] FIG. 2 is a cross-sectional view of the submerged pump of FIG. 1. [Figure 3] FIG. 3 is a partially enlarged cross-sectional view of part A in FIG. 2. [Figure 4] 2 is a schematic diagram showing the flow of pumped fluid when the submerged pump of FIG. 1 is discharging the pumped fluid. FIG. [Figure 5] 2 is a partially enlarged schematic cross-sectional view of the submerged pump of FIG. 1, illustrating a flow of a portion of the pumped fluid when the submerged pump is discharging the pumped fluid. FIG. [Figure 6] 2 is a schematic diagram showing the flow of pumped liquid when the submerged pump of FIG. 1 is pulled up above the liquid surface. FIG. [Figure 7] 2 is a partially enlarged schematic cross-sectional view of the submerged pump of FIG. 1, showing a flow of a portion of the pumped liquid when the submerged pump is pulled up above the liquid surface. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of a submerged pump according to the present invention will be described below. In the following description, reference will be made to the drawings as appropriate. In the drawings, the same members and elements are designated by the same reference numerals, and duplicated descriptions will be omitted. Furthermore, the dimensional proportions of the elements may be exaggerated for the sake of convenience, and are not limited to the proportions shown in the drawings.

[0011] ●Submerged pump● ●Configuration of submerged pump FIG. 1 is a schematic cross-sectional view showing a submerged pump according to the present invention in use.

[0012] The submerged pump 1 (hereinafter referred to as "this pump 1") is disposed inside a storage tank T in which the pumped liquid is stored, and pumps the pumped liquid from the storage tank T to the outside. This pump 1 is immersed in the pumped liquid.

[0013] The "handled liquid" is a liquid that is handled (transported) by the pump 1. The handled liquid is, for example, a liquefied gas such as liquefied natural gas or liquefied ammonia.

[0014] FIG. 2 is a cross-sectional view of the pump 1. In the following description, FIG. 1 will be referred to together with FIG. 2 as appropriate.

[0015] The pump 1 includes a housing 2, a motor 3, a rotating shaft 4, a bearing 5, an impeller 6, and a thrust balance mechanism 7.

[0016] In the following description, the term "radial direction" refers to the radial direction of the rotating shaft 4. The term "circumferential direction" refers to the circumferential direction of the rotating shaft 4.

[0017] Housing 2 houses motor 3, rotating shaft 4, bearing 5, impeller 6, and thrust balance mechanism 7. Housing 2 is shaped like a cylinder extending in the vertical direction. Housing 2 includes a peripheral wall 2a, an upper wall 2b, a lower wall 2c, a partition wall 2d, a pump chamber 20, a motor chamber 21, two bearing brackets 22 and 23, a recess 24, an outlet hole 25, a drain hole 26, an orifice member 27, a suction port 28, a discharge flow path 29, and a discharge port (not shown; the same applies below).

[0018] In the following description, the “upstream side” refers to the upstream side of the flow of treated fluid flowing inside the casing 2 , and the “downstream side” refers to the downstream side of the flow of treated fluid flowing inside the casing 2 .

[0019] The peripheral wall 2a is a substantially cylindrical wall that separates the internal space of the housing 2 (the pump chamber 20 and the motor chamber 21) from an external space S of the housing 2.

[0020] The "external space S" is the space outside (surrounding) the housing 2 (the pump 1). In this embodiment, the external space S is the internal space of the storage tank T. When the pump 1 is operating, at least the portion of the external space S surrounding the pump 1 is filled with the treated liquid.

[0021] The upper wall portion 2b is a wall disposed above the peripheral wall portion 2a. The upper wall portion 2b defines a motor chamber 21 and is disposed above the motor 3.

[0022] The lower wall portion 2c is a wall disposed below the partition wall portion 2d. The lower wall portion 2c defines a pump chamber 20.

[0023] The partition wall portion 2d is a wall located below the peripheral wall portion 2a, between the pump chamber 20 and the motor chamber 21. The partition wall portion 2d separates the pump chamber 20 from the motor chamber 21. The partition wall portion 2d is located below the motor 3. The partition wall portion 2d has an upper surface 2e and a retaining hole 2f (see FIG. 3 for both; the same applies below). The retaining hole 2f is located in the center of the partition wall portion 2d, and is a through-hole that passes through the partition wall portion 2d in the vertical direction. The partition wall portion 2d is an example of a partition wall according to the present invention.

[0024] The pump chamber 20 accommodates the impeller 6. The pump chamber 20 is disposed in the lower half of the housing 2.

[0025] The motor chamber 21 accommodates the motor 3. The motor chamber 21 is disposed in the upper half of the housing 2. That is, the motor chamber 21 is disposed above the pump chamber 20.

[0026] A part of the upper wall portion 2b protrudes downward in a cylindrical shape to form a bearing bracket 22. The bearing bracket 22 holds a bearing 51 (described later).

[0027] The bearing bracket 23 holds a bearing 52 (described later). The bearing bracket 23 has a two-stage cylindrical shape. The bearing bracket 23 has an upper part 23a and a lower part 23b (see FIG. 3 for both; the same applies below). The inner diameter of the upper part 23a is smaller than the inner diameter of the lower part 23b. The bearing bracket 23 is held by the partition wall part 2d (retaining hole 2f). The bearing bracket 23 is positioned below the motor 3. The upper part 23a protrudes upward beyond the partition wall part 2d.

[0028] In the radial direction, a recess 24 is defined by the housing 2 (partition wall portion 2d, upper portion 23a, and peripheral wall portion 2a) outward from the bearing bracket 23. The recess 24 is shaped like a ring groove that is concave downward. When viewed from the up-down direction, the recess 24 is ring-shaped. That is, the recess 24 is open only upward and has a shape that allows liquid to remain. In other words, a part of the housing 2 (near the partition wall portion 2d) is concave downward to form the recess 24. The recess 24 is located in the motor chamber 21, radially outward from the bearing bracket 23 and below the motor 3. The recess 24 has a bottom surface 24a.

[0029] The bottom surface 24a has a flat shape parallel to the horizontal direction. The bottom surface 24a is disposed at the lowest position of the recess 24. The bottom surface 24a is formed by the upper surface 2e of the partition wall portion 2d.

[0030] The outlet hole 25 is a through-hole that penetrates the peripheral wall portion 2a in the radial direction. The outlet hole 25 communicates with the motor chamber 21 and the external space S of the housing 2. The outlet hole 25 is disposed in the upper part of the peripheral wall portion 2a. In the up-down direction, the outlet hole 25 is disposed above the motor 3. The outlet hole 25 is an example of a second flow path in the present invention.

[0031] FIG. 3 is a partially enlarged schematic cross-sectional view of part A in FIG. In the following description, FIGS. 1 and 2 will be referred to together with FIG. 3 as appropriate.

[0032] The drain hole 26 is a through-hole that penetrates the partition wall portion 2d. The drain hole 26 opens to the upper surface 2e of the partition wall portion 2d (the bottom surface 24a of the recess 24) and the outer peripheral surface 2g of the partition wall portion 2d. That is, the drain hole 26 is disposed in the partition wall portion 2d and communicates with the recess 24 (the motor chamber 21) and the external space S. When viewed in the radial direction, the drain hole 26 has a substantially "L" shape. The drain hole 26 includes a first drain hole 26a, a second drain hole 26b, and two openings 26c and 26d. The cross-sectional area "A1" of the drain hole 26 is smaller than the cross-sectional area "A2" of the outlet hole 25. The "cross-sectional area" refers to the area of ​​a virtual cross section (transverse cross section) perpendicular to the direction of flow of the treated fluid inside each hole. The drain hole 26 is an example of a third flow path according to the present invention.

[0033] The first drain hole 26a is a portion of the drain hole 26 that extends in the up-down direction. The second drain hole 26b is a portion of the drain hole 26 that extends in the radial direction (horizontal direction). The second drain hole 26b is disposed adjacent to the first drain hole 26a on the downstream side (lower end side) of the first drain hole 26a. The opening 26c opens to the bottom surface 24a and is disposed at the upstream end (upper end) of the first drain hole 26a. The opening 26d opens to the peripheral wall portion 2a and is disposed at the downstream end (radially outward end) of the second drain hole 26b.

[0034] The orifice member 27 throttles the flow rate of the pumped fluid flowing through the drain hole 26. The orifice member 27 is, for example, a plug that is screwed into the drain hole 26 (first drain hole 26a). The orifice member 27 has, for example, a cylindrical shape. The orifice member 27 has a throttle hole 27a. The orifice member 27 throttles the flow rate of the pumped fluid flowing through the drain hole 26. opening It is detachably attached to the end on the 26c side.

[0035] The throttle hole 27a is a through-hole that passes through the orifice member 27 in the vertical direction. The throttle hole 27a communicates with the recess 24 (motor chamber 21) and a portion of the drain hole 26 that is downstream of the throttle hole 27a. The cross-sectional area "A3" of the throttle hole 27a is smaller than the cross-sectional area "A1" of the drain hole 26. Here, the ratio (A3 / A2) of the cross-sectional area "A3" of the throttle hole 27a to the cross-sectional area "A2" of the outlet hole 25 is preferably designed to be 0.3 or less, and more preferably 0.1 or less. The throttle hole 27a is an example of a communication passage in the present invention.

[0036] In the following description, the drawing to which reference will be made primarily will be Figure 2. The lower portion of the lower wall portion 2c has a reduced diameter to form an intake port 28. That is, the intake port 28 is disposed at the lower end portion of the housing 2.

[0037] The discharge flow path 29 is a flow path through which the handled fluid flows after being discharged from the impeller 6. The discharge flow path 29 is disposed inside the peripheral wall portion 2a and the partition wall portion 2d.

[0038] The motor 3 is driven under predetermined operating conditions to rotate the impeller 6. The motor 3 is a known motor that includes a rotor 31 and a stator 32.

[0039] The rotating shaft 4 rotates due to the rotation of the motor 3 and transmits rotational power to the impeller 6. The rotating shaft 4 has a cylindrical shape extending in the vertical direction. The rotating shaft 4 is attached to the rotor 31. A lower half 4a of the rotating shaft 4 extends downward from the motor 3 toward the inside of the pump chamber 20.

[0040] The bearing 5 rotatably supports the rotating shaft 4. The bearing 5 is, for example, a rolling bearing. The bearing 5 includes bearings 51 and 52. The bearing 51 is held by the bearing bracket 22. The bearing 52 is held by the upper portion 23a of the bearing bracket 23.

[0041] The impeller 6 is attached to the lower half 4a of the rotary shaft 4 and discharges the pumped fluid drawn in from below radially outward. The impeller 6 is housed in the pump chamber 20 and is disposed above the suction port 28 in the vertical direction.

[0042] The thrust balance mechanism 7 reduces the thrust force (the force pushing the impeller 6 downward) generated by the pressure difference between the downward and upward sides of the impeller 6. The thrust balance mechanism 7 is a known thrust balance mechanism used in known pumps. The thrust balance mechanism 7 is attached to the rotating shaft 4 and housed in the lower part 23b of the bearing bracket 23.

[0043] ●Flow of liquid handled by submerged pump Next, the flow of pumped liquid in the pump 1 when the pump 1 is discharging the pumped liquid (when the pump 1 is operating) and when the pump 1 is pulled up above the liquid surface will be described below. In the following description, Figures 1 to 3 will be referred to as appropriate.

[0044] ●Flow of the liquid when the submerged pump is discharging the liquid FIG. 4 is a schematic diagram showing the flow of pumped fluid when the pump 1 is discharging the pumped fluid. FIG. 5 is a partially enlarged schematic cross-sectional view of the pump 1, showing the flow of part of the pumped fluid when the pump 1 is discharging the pumped fluid.

[0045] When the pump 1 is discharging the pumped liquid (when the pump 1 is operating), the pumped liquid in the external space S (the internal space of the storage tank T) is sucked into the pump 1 through the suction port 28 (flow F1). The pumped liquid sucked into the suction port 28 is sucked into the impeller 6 and discharged into the pump chamber 20 on the downstream side of the impeller 6. Most of the pumped liquid discharged from the impeller 6 is discharged from the discharge port via the discharge flow path 29 to a liquid destination (not shown) (flow F2).

[0046] A portion of the pumped fluid discharged from the impeller 6 passes through the thrust balance mechanism 7 and the bearing 52 inside the bearing bracket 23 and is introduced into the motor chamber 21 (flow F3). In other words, the bearing bracket 23, the thrust balance mechanism 7, and the bearing 52 form a flow path that introduces a portion of the pumped fluid discharged from the impeller 6 from the pump chamber 20 to the motor chamber 21. The bearing bracket 23, the thrust balance mechanism 7, and the bearing 52 are an example of the first flow path in the present invention. At this time, the pumped fluid functions as a lubricant and a coolant for the bearing 52.

[0047] Most of the pumped fluid introduced into the pump chamber 20 passes through the motor 3 and is introduced upward of the motor 3 (flow F4). At this time, the pumped fluid functions as a coolant for the motor 3. The pumped fluid that has passed through the motor 3 passes through the outlet hole 25 and is discharged to the external space S (flow F5).

[0048] A portion of the pumped fluid introduced into the pump chamber 20 passes through the recess 24, the throttle hole 27a of the orifice member 27, and the drain hole 26, and is discharged into the external space S (flow F6).

[0049] A part of the pumped fluid that has flowed through the discharge flow path 29 passes through the bearing 51 and is introduced into the motor chamber 21 (flow F7). At this time, the pumped fluid functions as a lubricating fluid and a coolant for the bearing 51.

[0050] In this way, flows F1, F3, F4, and F5 form a circulation flow Fc that lubricates and cools the bearing 52 and cools the motor 3. On the other hand, flow F6 does not contribute to cooling the motor 3 and is a flow that does not occur in a conventional pump (hereinafter referred to as a "conventional pump") that does not have a drain hole 26. If the flow rate of flow F6 increases and flow F6 obstructs or significantly disturbs the circulation flow Fc, the performance of the present pump 1 will deteriorate. Therefore, flow F6 is essentially an unnecessary flow. For this reason, the flow rate of flow F6 (in other words, the flow rate "Q1" of the treated fluid flowing through the drain hole 26 throttled by the throttle hole 27a) is designed to be sufficiently smaller than the flow rate of the circulation flow Fc (in other words, the flow rate "Q2" of flow F5).

[0051] As described above, the cross-sectional area "A3" of the throttle hole 27a is smaller than the cross-sectional area "A1" of the drain hole 26 and the cross-sectional area "A2" of the lead-out hole 25. The cross-sectional area "A1" of the drain hole 26 is smaller than the cross-sectional area "A2" of the lead-out hole 25. Therefore, the internal resistance of the throttle hole 27a (drain hole 26) is greater than the internal resistance of the lead-out hole 25. As a result, the flow rate "Q1" of the handled fluid (flow F6) flowing through the drain hole 26 throttled by the throttle hole 27a is smaller than the flow rate "Q2" of the handled fluid (flow F5) flowing through the lead-out hole 25. The pump 1 utilizes this difference in the internal resistance of the pipes to limit the flow rate "Q1." Specifically, the difference in the resistance within the pipe is designed so that the ratio (Q1 / Q2) of the flow rate "Q1" to the flow rate "Q2" is preferably 0.1 or less (for example, 0.01 to 0.05). As a result, in this pump 1, the flow rate "Q1" is kept within an allowable range in which the performance of this pump 1 does not deteriorate. Therefore, even if flow F6 occurs during operation of this pump 1, the performance of this pump 1 does not deteriorate (even if performance deteriorates, the deterioration is kept within an allowable range).

[0052] ●Flow of liquid handled when the submerged pump is pulled up above the liquid surface FIG. 6 is a schematic diagram showing the flow of the pumped liquid when the pump 1 is pulled up above the liquid surface. FIG. 7 is a partially enlarged schematic cross-sectional view of the pump 1, showing the flow of part of the pumped liquid when the pump 1 is pulled up above the liquid surface.

[0053] The pump 1 is removed from the storage tank T, for example, for maintenance. At this time, the operation of the pump 1 is stopped. When the operation of the pump 1 is stopped, the interior of the pump 1 is filled with residual pumped liquid. When the pump 1 is raised above the liquid level, the pumped liquid remaining in the pump chamber 20 is discharged downward (to the external space S) from the suction port 28 (flow F11). In addition, the pumped liquid remaining in the motor chamber 21 passes through the bearing bracket 23, the bearing 52, and the thrust balance mechanism 7 and is discharged into the pump chamber 20 (flow F12), and then passes through the pump chamber 20 and is discharged downward (to the external space S) from the suction port 28 (flow F11).

[0054] As described above, the recess 24 is recessed downward. Therefore, a portion of the pumped fluid remaining in the motor chamber 21 remains in the recess 24. The pumped fluid remaining in the recess 24 passes through the throttle hole 27a and the drain hole 26 and is discharged to the external space S (flow F13). In this way, when the pump 1 is raised above the liquid level, the pumped fluid remaining in the motor chamber 21 (recess 24) is removed. Therefore, the pumped fluid and its vaporized gas do not leak outside the pump 1 during maintenance of the pump 1.

[0055] As described above, the pump 1 does not include an opening / closing mechanism that closes the drain hole 26 while the pump 1 is operating and opens the drain hole 26 only when the pumped fluid remaining in the recess 24 is being discharged. That is, in the pump 1, the drain hole 26 is constantly connected to the recess 24 and the external space S. Most of the pumped fluid in the pump 1 is cryogenic liquefied gas. While the pump 1 is operating, the pressure of the pumped fluid introduced into the motor chamber 21 is increased by the impeller 6. Therefore, if an opening / closing mechanism for opening and closing the drain hole 26 is to be attached to the pump 1, the opening / closing mechanism must be liquid-tight to prevent the cryogenic, high-pressure pumped fluid from leaking into the external space S, and must be able to open and close normally and reliably even at cryogenic temperatures. Therefore, manufacturing such an opening / closing mechanism is not easy, and additional labor and processing are required to attach the opening / closing mechanism to the pump 1, resulting in high manufacturing costs. In the present pump 1, the pumped fluid remaining in the recess 24 can be discharged simply by forming a through-hole in the housing 2 (partition wall portion 2d) that communicates with the recess 24. Therefore, in the present pump 1, the man-hours and processing required for attaching an opening and closing mechanism are not required. As a result, in the present pump 1, the flow rate "Q1" of the flow F6 when the present pump 1 is operating is limited, so that the performance of the present pump 1 is not reduced, and the pumped fluid remaining in the motor chamber 21 is easily discharged to the external space S without the need for the aforementioned opening and closing mechanism.

[0056] Furthermore, the orifice member 27 is detachable from the drain hole 26. Therefore, the internal resistance of the throttle hole 27a (drain hole 26) (the flow rate "Q1" of the flow F6) can be easily adjusted simply by replacing the orifice member 27 with one having a throttle hole 27a of a different size.

[0057] Summary According to the embodiment described above, the pump 1 includes the bearing bracket 23, the recess 24, the outlet hole 25, the drain hole 26, the bearing 52, and the thrust balance mechanism 7. The recess 24 is disposed in the motor chamber 21. The recess 24 is shaped like a ring groove that is concave downward. The bearing bracket 23, the bearing 52, and the thrust balance mechanism 7 are disposed below the motor 3 and function as a first flow path connecting the motor chamber 21 and the pump chamber 20. The outlet hole 25 is disposed above the motor 3 and functions as a second flow path connecting the motor chamber 21 and the external space S. The drain hole 26 functions as a third flow path connecting the recess 24 and the external space S. The drain hole 26 opens to the bottom surface 24a, which is the lowest part of the inner surface of the recess 24. When the pump 1 is discharging pumped fluid (operating), a portion of the pumped fluid discharged from the impeller 6 passes through the thrust balance mechanism 7 and the bearing 52 (first flow path) inside the bearing bracket 23 and is introduced into the motor chamber 21. The pumped fluid introduced into the motor chamber 21 passes through the motor 3, the outlet hole 25, and the drain hole 26, and is then discharged from the motor chamber 21 to the external space S. With this configuration, the drain hole 26 is constantly in communication with the recess 24 and the external space S. When the pump 1 is operating, at least the flow F5 through the outlet hole 25 is ensured, and the circulation flow Fc is also ensured. Furthermore, when the pump 1 is raised above the liquid level, the pumped fluid remaining in the motor chamber 21 (recess 24) is removed. Therefore, during maintenance of the pump 1, the pumped fluid and its vaporized gas do not leak outside the pump 1.

[0058] Furthermore, according to the embodiment described above, the flow rate Q1 of the flow F6 is smaller than the flow rate Q2 of the flow F5. This configuration makes it easy to ensure the circulation flow Fc, and reduces the degradation of the performance of the pump 1.

[0059] Furthermore, according to the embodiment described above, the ratio (Q1 / Q2) of the flow rate "Q1" of flow F6 to the flow rate "Q2" of flow F5 is designed to be equal to or less than "0.1." With this configuration, the flow rate "Q1" is kept within an allowable range that does not degrade the performance of the pump 1. Therefore, even if flow F6 occurs during operation of the pump 1, the performance of the pump 1 will not degrade (even if performance does degrade, the degradation will be kept within an allowable range).

[0060] Furthermore, according to the embodiment described above, the housing 2 includes the orifice member 27. The orifice member 27 is detachably attached to the drain hole 26 and throttles the flow rate of the drain hole 26. With this configuration, the internal resistance of the drain hole 26 (the flow rate "Q1" of the flow F6) can be easily adjusted by attaching and detaching the orifice member 27.

[0061] Furthermore, according to the embodiment described above, the orifice member 27 is provided with a throttle hole 27a that communicates with the pump chamber 20 and the drain hole 26. The cross-sectional area of ​​the throttle hole 27a is smaller than the cross-sectional area of ​​the drain hole 26. With this configuration, the internal pipe resistance of the throttle hole 27a (drain hole 26) (the flow rate "Q1" of flow F6) can be easily adjusted simply by replacing the orifice member 27 with one having a throttle hole 27a of a different size.

[0062] Furthermore, according to the embodiment described above, the housing 2 includes a partition wall 2d that separates the pump chamber 20 from the motor chamber 21. The recess 24 and the drain hole 26 are disposed in the partition wall 2d. With this configuration, the drain hole 26 can be formed simply by forming a through-hole in the partition wall 2d. In other words, the formation of the drain hole 26 does not require the attachment of an opening / closing mechanism or complicated processing.

[0063] Other embodiments In the present invention, the pump 1 may be housed in a cylindrical pump column disposed in the internal space of the storage tank T.

[0064] Furthermore, in the present invention, the configuration of the first flow path (bearing bracket 23, bearing 52, and thrust balance mechanism 7) is not limited to this embodiment.

[0065] Furthermore, in the present invention, the number of recesses 24 is not limited to "1." In this case, the housing 2 may be provided with a drain hole 26 for each recess 24.

[0066] Furthermore, in the present invention, the position of the recess 24 is not limited to the radially outward direction of the bearing bracket 23 .

[0067] Furthermore, in the present invention, the housing 2 may be provided with a flow path (outlet flow path) arranged inside the housing 2 instead of the outlet hole 25. In this case, the outlet flow path communicates with the motor chamber 21 and the external space S. The outlet flow path is an example of the second flow path in the present invention.

[0068] Furthermore, in the present invention, the number of the outlet hole 25 is not limited to "1".

[0069] Furthermore, in the present invention, the number of drain holes 26 is not limited to "1".

[0070] Furthermore, the shape of drain hole 26 as viewed in the radial direction is not limited to an "L" shape. That is, for example, second drain hole 26b does not have to be arranged along the radial direction. That is, for example, second drain hole 26b may be arranged at an angle with respect to the radial direction so that opening 26d is at the lowest end of drain hole 26.

[0071] Furthermore, in the present invention, the throttle hole 27a is not limited to a through hole. That is, for example, the throttle hole 27a may be configured as a groove disposed on the outer peripheral surface of the orifice member 27.

[0072] Furthermore, in the present invention, if the pipeline resistance of the drain hole 26 exceeds a required value, the housing 2 does not need to include the orifice member 27.

[0073] Furthermore, in the present invention, the orifice member 27 may be attached to the end of the drain hole 26 on the opening 26d side.

[0074] Furthermore, in the present invention, the ratio of the flow rate "Q1" to the flow rate "Q2" is not limited to "0.1" or less, provided that the flow F6 does not significantly disturb the circulation flow Fc (provided that the degradation in performance of the pump 1 is suppressed within an acceptable range).

[0075] Furthermore, in the present invention, the number of impellers 6 is not limited to "1".

[0076] ●Embodiments of the present invention● Next, embodiments of the present invention that can be understood from the above-described embodiments will be described below, using the terms and symbols described in the embodiments.

[0077] A first embodiment of the present invention is a submerged pump (for example, submerged pump 1) immersed in a treated liquid, and includes a motor (for example, motor 3), a rotating shaft (for example, rotating shaft 4) attached to the motor, an impeller (for example, impeller 6) attached to the rotating shaft, and a housing (for example, housing 2) that accommodates the rotating shaft and the impeller. The housing includes a motor chamber (for example, motor chamber 21) in which the motor is accommodated, a pump chamber (for example, pump chamber 20) arranged below the motor chamber and accommodating the impeller, a recess (for example, recess 24) arranged in the motor chamber and recessed downward, and a first flow path (for example, bearing bracket 23, bearing 52) arranged below the motor and communicating with the motor chamber and the pump chamber. , and thrust balance mechanism 7), a second flow path (e.g., a discharge hole 25) that is arranged above the motor and communicates with the motor chamber and an external space of the housing (e.g., external space S), and a third flow path (e.g., a drain hole 26) that communicates with the recess and the external space, the third flow path opening to a portion of the inner surface of the recess that is arranged lowest (e.g., a bottom surface 24a), and when the submerged pump is discharging the pumped fluid, a portion of the pumped fluid discharged from the impeller passes through the first flow path and is introduced from the pump chamber to the motor chamber, and the pumped fluid introduced into the motor chamber passes through the motor, the second flow path, and the third flow path, and is introduced from the motor chamber to the external space. According to this configuration, when the pump is raised above the liquid surface, the pumped liquid remaining in the motor chamber (recess) is removed.

[0078] A second embodiment of the present invention is a submerged pump in which, in the first embodiment, the flow rate of the third flow path (e.g., flow rate "Q1") is smaller than the flow rate of the second flow path (e.g., flow rate "Q2"). This configuration makes it easy to ensure a circulating flow, and reduces the deterioration of the performance of the pump.

[0079] A third embodiment of the present invention is the submerged pump of the second embodiment, wherein the ratio of the flow rate of the third flow path to the flow rate of the second flow path is "0.1" or less. With this arrangement, even if a flow occurs during operation of the pump, the performance of the pump is not degraded.

[0080] A fourth embodiment of the present invention is a submerged pump in which, in the second embodiment, the housing is provided with an orifice member (e.g., orifice member 27) that is detachably attached to the third flow path and restricts the flow rate of the third flow path. According to this configuration, the resistance inside the pipe of the drain hole can be easily adjusted by attaching and detaching the orifice member.

[0081] A fifth embodiment of the present invention is a submerged pump in which, in the fourth embodiment, the orifice member has a communication passage (e.g., a throttling hole 27a) that communicates with the pump chamber and the third flow path, and the cross-sectional area of ​​the communication passage (e.g., cross-sectional area "A3") is smaller than the cross-sectional area of ​​the third flow path (e.g., cross-sectional area "A1"). According to this configuration, the internal resistance of the throttle hole (drain hole) can be easily adjusted simply by replacing the orifice member with one having a different throttle hole size.

[0082] A sixth embodiment of the present invention is a submerged pump in which, in the first embodiment, the housing has a partition wall (e.g., partition wall portion 2d) that separates the pump chamber and the motor chamber, and the recess and the third flow path are arranged in the partition wall. According to this configuration, the drain hole can be formed simply by forming a through hole in the partition wall portion. [Explanation of symbols]

[0083] 1 Submerged Pump 2. Case 2d Partition wall (partition wall) 20 Pump Room 21 Motor Room 23 Bearing bracket (first flow path) 24 recess 24a Bottom (part) 25 Outlet hole (second flow path) 26 Drain hole (third flow path) 27 Orifice member 27a Throttle hole (communicating passage) 3 motors 4 rotation axes 52 Bearing (first flow path) 6 impeller 7 Thrust balance mechanism (first flow path) S External space

Claims

1. A submerged pump that is immersed in the pumped liquid, A motor; a rotating shaft attached to the motor; an impeller attached to the rotary shaft; a housing that houses the rotary shaft and the impeller; and The housing includes: a motor chamber in which the motor is housed; a pump chamber disposed below the motor chamber and accommodating the impeller; a recessed portion disposed in the motor chamber and recessed downward; a first flow path disposed below the motor and communicating with the motor chamber and the pump chamber; a second flow path disposed above the motor and communicating with the motor chamber and an external space of the housing; a third flow path communicating with the recess and the external space; With The third flow path opens to a portion of the inner surface of the recess that is located at the lowest position, a flow rate of the third flow path is smaller than a flow rate of the second flow path; When the submerged pump is discharging the pumped liquid, A portion of the pumped fluid discharged from the impeller passes through the first flow path and is introduced from the pump chamber into the motor chamber, The pumped fluid introduced into the motor chamber passes through the motor, the second flow path, and the third flow path, and is then discharged from the motor chamber to the external space. Submerged pump.

2. The ratio of the flow rate of the third flow path to the flow rate of the second flow path is 0.1 or less.

2. The submerged pump according to claim 1.

3. The housing includes: an orifice member detachably attached to the third flow path and throttling a flow rate of the third flow path; Equipped with 2. The submerged pump according to claim 1.

4. The orifice member is a communication passage communicating with the motor chamber and the third flow path; With The cross-sectional area of ​​the communication passage is smaller than the cross-sectional area of ​​the third flow passage.

4. The submerged pump according to claim 3.

5. The housing includes: a partition wall that separates the pump chamber from the motor chamber; With the recess and the third flow path are disposed in the partition wall.

2. The submerged pump according to claim 1.

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