JP2022030979A - Two-stage centrifugal pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-stage centrifugal pump capable of improving the durability of a slide bearing by suppressing the thrust force acting on a rotor shaft to a small size without causing the structure to become complicated or large.
SOLUTION: Two first and second impellers 4 and 5 are attached to a rotor shaft 3 along an axial direction, and a first impeller 4 and a first impeller 4 and a second are attached to two pump chambers R1 and R2 defined in a pump case 3. The two-stage centrifugal pump 1 configured to accommodate each of the two impellers 5 is provided with a first labyrinth seal portion L1 between the front shroud 4a of the first impeller 4 and the inner surface of the pump case 2 facing the shroud 4a. A second labyrinth seal portion L2 is provided between the rear shroud 5b of the second impeller 5 and the inner surface of the pump case 2 facing the rear shroud 5b, and the first labyrinth seal portion L2 on the axial center side of the first labyrinth seal portion L1 in the pump case 2 is provided. A communication passage 3a configured by communicating the space S1 and the second space S2 on the axial center side of the second labyrinth seal portion L2 with each other is provided.
[Selection diagram] Fig. 3

Description

The present invention relates to a two-stage centrifugal pump provided with a thrust balance mechanism.

In a two-stage centrifugal pump as a form of a fluid machine, two first and second impellers are attached along the axial direction to a rotor shaft that is rotationally driven by a drive source such as an electric motor, and a partition wall is provided inside the pump case. There is a pump chamber configured by accommodating the first impeller and the second impeller, respectively (see, for example, Patent Document 1).

By the way, in a centrifugal pump, the pressure of the handling fluid is generally low on the axial front side, which is the suction side of the impeller, and the pressure of the handling fluid is high on the centrifugal direction, which is the discharge side of the impeller. Therefore, a pressure difference (suction side <discharge side) always occurs during the rotation of the impeller between the front side of the impeller facing the suction side of the impeller and the back surface of the impeller surrounded by the discharge side of the impeller. It is known that this pressure difference becomes a source of the thrust force pushing toward the suction side of the impeller. If this thrust force is excessive, problems such as wear of the slide bearing that rotatably supports the impeller via the rotor shaft and deterioration of its durability occur.

Therefore, various thrust balance mechanisms for reducing the thrust force have been proposed so far.

For example, in Patent Documents 2 and 3, a thrust balance chamber is formed on the back side of the back shroud of the impeller with a pump case, and a thrust balance chamber is provided through a balance hole formed in the back shroud of the impeller. It communicates with the suction side of the impeller (front side of the rear shroud) to reduce the pressure difference acting between the front and back of the back shroud of the impeller, thereby reducing the thrust force in the suction direction acting on the rotor shaft. A thrust balance mechanism has been proposed.

Further, Patent Document 4 proposes a configuration in which a thrust balance disk is attached to a rotor shaft to reduce the thrust force acting on the rotor shaft.

Japanese Patent No. 5599463 Jitsukaisho 58-08434A Japanese Unexamined Patent Publication No. 9-042190 Jikkai Sho 54-002204 Gazette

However, although the thrust balance mechanism proposed in Patent Documents 2 and 3 is effective for a single-stage centrifugal pump, it is not effective for a multi-stage centrifugal pump. In other words, in a multi-stage centrifugal pump, the discharge pressure of the impeller of the previous stage acts on the front side of the impeller of the second and subsequent stages, so it is possible to properly adjust the thrust balance of the entire pump simply by forming a balance hole in the impeller. Have difficulty.

Further, in the configuration proposed in Patent Document 4, since the thrust balance disk is attached to the rotor shaft of the multi-stage centrifugal pump separately from the plurality of impellers, the structure is complicated and the axial length of the entire multi-stage centrifugal pump is increased. There is a problem that the pump itself becomes long and large.

The present invention has been made in view of the above problems, and an object thereof is to improve the durability of a slide bearing by suppressing the thrust force acting on the rotor shaft to a small size without causing the structure to become complicated or large. It is to provide a two-stage centrifugal pump capable of.

In order to achieve the above object, the invention according to claim 1 has a support shaft, a hollow rotor shaft rotatably held by the support shaft, and a cylindrical shape fixed to the outer periphery of an end portion of the rotor shaft. Rotor, a stator arranged on the outer peripheral side of the rotor and generating a rotational magnetic field for rotating the rotor, a cover member having a suction port, a cylindrical tubular portion having a partition wall, and the suction port. It has a bottomed cylindrical portion that opens to the side and houses the rotor, includes a case member that separates the rotor from the stator, and has two first and second impellers axially on the rotor shaft. In two pump chambers defined by the partition in a pump case configured by connecting and integrating the cover member and the case member into two openings in the axial direction of the cylindrical portion. A two-stage centrifugal pump configured by accommodating the first impeller and the second impeller, respectively, in the front shroud between the cover member and the front shroud of the first impeller facing the cover member. A first labyrinth seal portion located on the peripheral portion is provided, and a second labyrinth seal portion located on the outer peripheral portion of the rear shroud is provided between the case member and the back shroud of the second impeller facing the case member. The first space in the cover member facing the suction port on the axial side of the first labyrinth seal portion and the second space facing the bottomed cylindrical portion on the axial side of the second labyrinth seal portion. The first feature is that the rotor shaft is formed with a communication passage that allows the first space and the second space to communicate with each other.

In the invention according to claim 2, in addition to the first feature, a third labyrinth seal portion is provided between the front shroud of the second impeller and the partition wall facing the shroud, and the third labyrinth seal portion is provided in the pump case. The second feature is that the third space is formed on the axis side of the third labyrinth seal portion.

The third feature of the invention according to claim 3 is that, in addition to the second feature, the partition wall is integrally resin-molded together with the tubular portion.

The invention according to claim 4 comprises, in addition to the above-mentioned first to third features, a reservoir chamber having an internal volume of 80% or more of the volume of the rotor in the bottomed cylindrical portion. Is the fourth feature.

According to the first aspect of the invention, there is a first space facing the front side in the axial direction, which is the suction side of the first impeller on the front stage side, and a second space facing the back side in the axial direction of the second impeller on the next stage side. Since they communicate with each other, the pressures in the first space and the second space are balanced and both pressures are substantially equal. On the other hand, the pressure of the liquid boosted by the first impeller acts on the third space facing the axial back side of the first impeller and the axial front side of the second impeller, respectively. In this case, the pressure of the boosted liquid flowing into the third space is higher than the suction pressure acting on the first and second spaces. Therefore, the pressure difference generated during the rotation of the impeller between the front and back surfaces of the first impeller (front side of the first impeller <back side of the first impeller) and the rotation of the impeller between the front and back sides of the second impeller. The pressure difference generated inside (front side of the second impeller> back side of the second impeller) antagonizes. That is, the thrust force acting on the first impeller in the suction direction and the thrust force acting on the second impeller in the anti-suction direction become substantially equal, and the thrust force acting on the rotor shaft is substantially offset. Therefore, the load received by the slide bearing from the rotor shaft is reduced, the wear of the slide bearing is suppressed, and the durability of the slide bearing is enhanced. Since such an effect can be obtained without providing a thrust balance disk on the rotor shaft, the structure of the two-stage centrifugal pump does not become complicated or large.

Further, since the wraparound of the fluid sent from the first impeller into the first space is suppressed by the first labyrinth seal portion, the discharge flow rate of the fluid is increased and the pump efficiency is improved.

According to the second aspect of the present invention, in the second impeller, the front and back surfaces of the front shroud are provided by providing a third labyrinth seal portion between the front shroud of the second impeller and the partition wall facing the front shroud. The pressure of the third space acts on both sides. As a result, the thrust forces in the front shroud of the second impeller almost cancel each other out, so that the thrust force in the anti-suction port direction is suppressed to be smaller than the pressure of the second pump chamber acting on the front surface of the front shroud. Therefore, the thrust force in the anti-suction port direction transmitted from the second impeller to the rotor shaft can be calibrated and appropriately balanced with the thrust force in the suction port direction transmitted from the first impeller to the rotor shaft. Therefore, the thrust force in the suction direction acting on the first impeller and the force in the anti-suction direction acting on the second impeller properly cancel each other out, and the difference between the two thrust forces acting as the thrust force from the rotor shaft to the slide bearing is large. It can be kept as small as possible. As a result, the load received by the slide bearing from the rotor shaft is reduced, and the wear of the slide bearing is suppressed.

Further, since the wraparound of the fluid boosted by the second impeller to the second and third spaces is suppressed by the second labyrinth seal portion and the third labyrinth seal portion, the discharge flow rate of the fluid is increased and the pump efficiency is improved.

According to the third aspect of the present invention, the partition wall of the pump case, which faces the front shroud of the second impeller and constitutes the third labyrinth seal portion, is integrally resin-molded together with the tubular portion, thereby simplifying the structure. It is possible to realize cost reduction.

According to the invention of claim 4, since the volume of the second space into which the relatively high-pressure fluid flows is expanded by the bottomed cylindrical portion that functions as the reservoir chamber, the second space due to the load fluctuation of the two-stage centrifugal pump Fluctuations in the internal pressure are suppressed, and the pressures in the second space and the first space are properly balanced, and the thrust force acting on the rotor shaft is suppressed to be small.

It is a vertical sectional view of the two-stage centrifugal pump which concerns on this invention. It is a figure which shows the guide vane member of the two-stage centrifugal pump which concerns on this invention, (a) is a plan view, (b) is a side view, (c) is a bottom view. A schematic cross-sectional view showing the basic configuration of the thrust balance mechanism portion of the two-stage centrifugal pump according to the present invention, (b) compares the thrust force acting on the first impeller and the second impeller of the two-stage centrifugal pump with the conventional ones. It is a figure shown in.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a vertical sectional view of the two-stage centrifugal pump according to the present invention, FIG. 2 is a view showing a guide blade member of the two-stage centrifugal pump, FIG. 1A is a plan view, and FIG. 2B is a side view. c) is a bottom view.

The two-stage centrifugal pump 1 shown in FIG. 1 is a canned motor pump, and the pump unit P arranged vertically (in the axial direction) in FIG. 1 and the motor unit M as a drive source are connected along the same central axis. It is integrally configured, and on its central axis, a support shaft 6 and a hollow shape that is rotatably held by the support shaft 6 and for transmitting the rotational power exerted by the motor unit M to the pump unit P. A rotor shaft 3 is accommodated, and slide bearings 7 and 8 are interposed between the rotor shaft 3 and the support shaft 6. The two-stage centrifugal pump 1 according to the present embodiment is used in a state where the pump unit P and the motor unit M are arranged vertically, that is, in a vertical installation state, but the pump unit P and the motor unit M are left and right. It can also be used in a horizontal position facing the direction.

The pump portion P is the first stage of the first stage, which is attached to the upper and lower first pump chambers R1 and the second pump chamber R2 formed in the pump case 2 side by side in the upper half of the rotor shaft 3. The impeller 4, the second impeller 5 in the second stage, and the guide blade member 10 provided so as to be inserted between the first and second impellers 4 and 5, are accommodated and configured, respectively. In the present embodiment, the pump case 2, the first and second impellers 4 and 5, and the guide blade member 10 are all made of resin.

The pump case 2 is configured by connecting and integrating a cylindrical tubular portion 21 and a cover member 22 and a case member 23 that cover the two upper and lower openings of the tubular portion 21, respectively, in the axial direction. Here, the internal space of the tubular portion 21 is vertically drawn from the axially intermediate portion of the inner peripheral wall of the tubular portion 21 in the shape of a ring disk and extending along the cross section of the tubular portion 21. The partition wall 21A to be formed is integrally provided, and thus the first pump chamber R1 and the second pump chamber R2 are defined by the partition wall 21A in the pump case 2. A cylindrical discharge pipe (not shown) communicating with the second pump chamber R2 extends in the tangential direction from the outer periphery of the tubular portion 21. A circular hole 21a communicating between the first pump chamber R1 and the second pump chamber R2 is formed on the central axis of the partition wall 21A, and the circular hole 21a, the first pump chamber R1 and the second pump chamber R2 are formed. The rotor shaft 3 is inserted through the rotor shaft 3. Further, a guide blade member 10 is placed on the first pump chamber R1 side of the partition wall 21A, and the guide blade member 10 is formed with a central hole 10a coaxial with the circular hole 21a. The rotor shaft 3 and the support shaft 6 are inserted through the circular hole 21a, the center hole 10a, the first pump chamber R1 and the second pump chamber R2.

In the cover member 22, a cylindrical suction pipe 22A is integrally erected at a portion corresponding to the central axis, and the upper end of the suction pipe 22A opens upward as a suction port 22a. A rectifying cone 22B is integrally formed in the center of the base end portion of the suction pipe 22A in the cover member 22, and a plurality of rectifying cones (two in the illustrated example) are rectified around the rectifying cone 22B. The plate 22b is formed. The outer periphery of the first impeller 4 is surrounded by the guide blade member 10, and the suction side thereof faces the base end portion of the suction pipe 22A, and the first pump chamber R1 on the upper side of the tubular portion 21 is in a posture. It is housed inside and fixed to the rotor shaft 3. Further, the second impeller 5 is housed in the second pump chamber R2 on the lower side of the tubular portion 21 with the suction side facing the circular hole 21a on the lower surface side of the partition wall 21A, and is fixed to the rotor shaft 3. Has been done.

The case member 23 is provided with a cup-shaped bottomed cylindrical portion 23A at the center thereof, and a flange portion 23B is integrally formed from the upper end of the bottomed cylindrical portion 23A toward the outside in the radial direction. .. A columnar boss portion 23a is integrally erected upward at the center of the bottom of the bottomed cylindrical portion 23A of the case member 23, and is formed on the boss portion 23a and the cover member 22. Both ends of the support shaft 6 are fitted to each center of the rectifying cone 22B.

Further, the thrust washer 9 is held in a non-rotatable manner by the support shaft 6 between the rectifying cone 22B of the cover member 22 and the upper sliding bearing 7.

The motor portion M, which is a drive source, includes a motor case 11 connected from below the case member 23, and the motor case 11 has a cylindrical outer shell portion 11A and a lower surface opening of the outer shell portion 11A. It is configured by connecting and integrating a bottomed cylindrical cover member 11B that covers from below in the vertical direction. Here, the outer shell portion 11A is liquidtly connected to the lower surface of the flange portion 23B of the case member 23 via a ring-shaped seal member 12. Further, the upper end surface of the cover member 11B is liquidtly connected to the lower side of the outer shell portion 11A via the ring-shaped sealing member 13.

The motor portion M includes a cylindrical rotor 14 fixed to the lower half side of the rotor shaft 3 and a stator 15 arranged to face the rotor 14 via the bottomed cylindrical portion 23A of the case member 23. .. Here, the rotor 14 is housed inside the bottomed cylindrical portion 23A provided in the case member 23 of the pump case 2, and is fixed to the outer periphery of the lower end portion of the rotor shaft 3. The rotor 14 is composed of a permanent magnet.

The stator 15 is formed by winding a three-phase coil 18 around a stator core 16 via an insulator 17, and the stator core 16 is formed by, for example, a yoke 16a formed in a cylindrical shape and an inner circumference of the yoke 16a. It integrally has T-shaped teeth 16b protruding inward in the radial direction from a plurality of locations evenly spaced in the circumferential direction.

The insulator 17 covers the stator core 16 while exposing the inner peripheral end portion of the teeth 16b so as to face the outside of the bottomed cylindrical portion 23A. On the other hand, in this embodiment, the outer shell portion 11A of the motor case 11 is formed of an electrically insulating resin material into which the insulator 17 is inserted, whereby at least a part of the stator 15 is wrapped in the outer shell portion 11A. It is fixed and fixed. The three-phase coil 18 is electrically connected to a control circuit formed on the control board 19 described later.

By the way, the support legs 11a extend integrally from the lower surface of the outer shell portion 11A of the motor case 11 toward the inside of the cover member 11B, and the lower end of the support legs 11a is energized to each of the three-phase coils 18 of the stator 15. The control board 19 for controlling the above is engaged and supported by the snap-fit claws 11a1 formed at the lower ends of the support legs 11a.

Next, the details of the configuration of the guide blade member 10 will be described below with reference to FIG.

As described above, a central hole 10a is formed in the central portion of the guide blade member 10 mounted on the first pump chamber R1 side of the partition wall 21A, and the rotor shaft 3 is inserted through the central hole 10a. ing. Then, as shown in FIG. 2A, six diffuser vanes (blade rows) 31 having a triangular shape in a plan view are placed on the outer peripheral portion of the upper surface of the guide blade member 10 so as to face the rotating peripheral surface of the first impeller 4. Are integrally projected at equal pitches (60 degree intervals) in the circumferential direction, and the passage area is gradually increasing outward in the radial direction between the two diffuser vanes 31 adjacent to each other in the circumferential direction. Groove-shaped diffuser passages 32 curved in the circumferential direction (rotational direction of the first impeller) are formed. That is, on the outer peripheral portion of the upper surface of the guide blade member 10, six diffuser passages 32 having the same number as the diffuser vanes 31 are arranged at equal angles in the circumferential direction (60 degree intervals in the present embodiment) and the outer peripheral end thereof is the guide blade member. It is partitioned into a shape that gradually approaches the inner wall surface of the tubular portion 21 shown as the circumscribed circle C of 10, and the groove bottom of each diffuser passage 32 gradually approaches the inner wall surface of the tubular portion 21. It is formed in a chord winding shape with a low height (the bottom of the groove approaches the partition wall 21A).

On the other hand, on the lower surface of the guide vane member 10 facing the partition wall 21A, as shown in FIG. (Blade row) 33 are integrally projected in the circumferential direction at equal angle pitches (60 degree intervals). Six return passages 34, which are the same number as the return guide vanes 33, are partitioned between the two return guide vanes 33 adjacent to each other in the circumferential direction.

Here, each of the six diffuser passages 32 and the return passage 34 are connected (communicated) in the first pump chamber R1, and the outer peripheral end of each return passage 34 is in a posture of crossing the diffuser passage 32 in a three-dimensional manner. It is partitioned so as to have a rectangular inflow port 34a that opens below 31, and moreover, an outflow port 32a that is an outer peripheral end of each diffuser passage 32 opens adjacent to the inflow port 34a of each return passage 34. ing. Therefore, each diffuser passage 32 and each return passage 34 communicate with each other via the outlet 32a and the inlet 34a.

By the way, the two-stage centrifugal pump 1 according to the present embodiment is provided with a thrust balance mechanism for reducing the thrust force acting on the rotor shaft 3. Hereinafter, the configuration of this thrust balance mechanism will be described with reference to FIGS. 1 and 3.

A ring-shaped first labyrinth seal portion L1 is provided between the inner peripheral portion of the front shroud 4a of the first impeller 4 on the front stage side and the inner surface of the cover member 22 facing the inner peripheral portion, and is inside the pump case 2. The first space S1 is formed on the rotor shaft 3 side (axis center side) of the first labyrinth seal portion L1.

Further, a ring-shaped second labyrinth seal portion L2 is provided between the outer peripheral portion of the back shroud 5b of the second impeller 5 on the next stage side and the flange portion 23B of the case member 23 facing the outer peripheral portion. In the pump case 2, a second space S2 is formed on the rotor shaft 3 side (axis center side) of the second labyrinth seal portion L2 and on the back surface side of the second impeller 5. Here, the second space S2 includes a bottomed cylindrical portion 23A of the case member 23, a second impeller 5 that substantially covers the upper opening thereof via the second labyrinth seal portion L2, and a bottomed cylinder. A cylindrical space surrounded by the rotor 14 housed on the bottom side of the portion 23A, and in this embodiment, as a reservoir chamber having an internal volume of at least 80% or more of the volume of the rotor 14. It is configured.

Further, a ring-shaped third labyrinth seal portion L3 is provided between the outer peripheral portion of the front shroud 5a of the second impeller 5 and the partition wall 21A facing the outer peripheral portion. Here, the third labyrinth seal portion L3 is a diaphragm piece L3a that projects from the front shroud 5a toward the partition wall 21A and a diaphragm that is recessed in the partition wall 21A and surrounds the peripheral surface of the diaphragm change L3a. It is composed of a portion L3b, and a third space S3 is formed in the pump case 2 on the rotor shaft 3 side (axis center side) of the third labyrinth seal portion L3.

Then, in the present embodiment, as shown in FIG. 1, the communication passage 3a is in the axial direction (vertical direction) of the rotor shaft 3 between the peripheral surface of the rotor shaft 3 and the first impeller 4 and the second impeller 5. The upper end of the communication passage 3a is formed, and the upper end of the communication passage 3a is open to the first space S1, and the lower end of the communication passage 3a communicates with the second space S2. Therefore, the first space S1 and the second space S2 communicate with each other via the communication passage 3a.

Thus, the thrust balance mechanism includes the first labyrinth seal portion L1, the first space S1 formed inside the first labyrinth seal portion L1, the second labyrinth seal L2, the second space S2 formed inside the second labyrinth seal portion L1, and the third labyrinth seal. A third space S3 formed inside the portion L3 is provided, and the first space S1 and the second space S2 are communicated with each other by a communication passage 3a formed in the rotor shaft 3.

Next, the operation of the two-stage centrifugal pump 1 configured as described above will be described.

Under the energization control of each of the three-phase coils 18 of the stator 15, the rotor 14 and the rotor shaft 3 holding the rotor 14 are rotationally driven at a desired speed around the support shaft 6 by the magnetic field generated by the stator 15. To.

In the pump unit P, the first impeller 4 and the second impeller 5 attached to the rotor shaft 3 rotate in the first pump chamber R1 and the second pump chamber R2 in the pump case 2, respectively. Then, a negative pressure is generated in the suction pipe 22A formed in the cover member 22 of the pump case 2 due to the rotation of the first impeller 4, and the liquid to be handled (cooling water) is attracted by this negative pressure as shown by the arrow in FIG. As shown in the above, the suction is sucked into the suction pipe 22A from the suction port 22a of the suction pipe 22A. Then, the liquid sucked into the suction pipe 22A flows downward in the suction pipe 22A and is sucked into the first-stage first impeller 4.

The liquid sucked by the first impeller 4 flows outward in the radial direction while being boosted by kinetic energy given by the rotating first impeller 4, and flows from the outer peripheral end of the first impeller 4 to the first pump chamber R1. And leak. Then, the diffuser passages 32 partitioned by the plurality of (six in the present embodiment) diffuser vanes 31 formed on the upper surface of the guide blade member 10 in the first pump chamber R1 are shown by arrows in FIG. 2A. As shown, they flow outward in the radial direction and proceed to the outlet 32a which opens at the outer peripheral end of each diffuser passage 32. The liquid is decelerated in the process of flowing through each diffuser passage 32 that curves while gradually increasing the passage cross-sectional area toward the radial outer side of the guide blade member 10, and the pressure is further increased.

Thus, the liquid flowing out from the outflow port 32a opening at the outer peripheral opening end surface of each diffuser passage 32 is divided into six sections on the lower surface of the guide blade member 10 from the inflow port 34a opening adjacent to the outflow port 32a. It flows into each return passage 34.

After that, the liquid flowing into each return passage 34 travels inward in each return passage 34 as shown by an arrow in FIG. 2 (c), and as shown by an arrow in FIG. It is guided to the suction side of the second impeller 5 of the second stage facing the circular hole 21a through the circular hole 21a formed in the central portion of the partition wall 21A. Then, the liquid guided to the suction side of the second impeller flows outward in the radial direction while being given kinetic energy by the rotation of the second impeller 5, and the second pump is pumped from the outer peripheral end of the second impeller 5. At the same time as flowing out to the chamber R2, the pressure is further increased while being decelerated in the process of flowing through the volute portion formed in the second pump chamber S2. The liquid pressurized through the first impeller 4 and the second impeller 5 flows tangentially from the second pump chamber R2 into a discharge pipe (not shown), and is discharged from this discharge pipe to the outside of the pump case 2. To.

Next, the operation of the thrust balance mechanism will be described below with reference to FIG.

As described above, from the inside of the first space S1 to the back surface of the front shroud 4a (that is, the inside of the first impeller 4), there is a liquid before pressurization sucked into the suction pipe 22A. Further, since the first space S1 and the second space S2 communicate with each other via the communication passage 3a formed in the rotor shaft 3, the second space S2 also has a pressure before being sucked into the suction pipe 22A. Liquid is present.

Then, the liquid accelerated by the first impeller 4 and flowing out to the first pump chamber R1 is introduced into the suction side (third space S3) of the second impeller 5 while being boosted by the guide blade member 10. A part of this pressurized liquid also enters the upper gap (front surface of the front shroud 4a) in FIG. 3 (a) of the front shroud 4a. Since the first labyrinth seal portion L1 formed between the inner peripheral portion of the front shroud 4a and the inner surface of the cover member 22 facing the inner peripheral portion thereof is dammed, a part of the boosted liquid is removed. Almost stays on the upper surface of the front shroud 4a.

The liquid introduced into the third space S3 travels from there into the second impeller 5, and is led out to the second pump chamber R2 while being reaccelerated by the second impeller 5, but this liquid is second. Since it is blocked by the labyrinth seal portion L2 and the third labyrinth seal portion L3, the liquid is prevented from entering the gap above the front shroud 5a and below the rear shroud 5b from the second pump chamber R2. Therefore, the liquid introduced into the third space S3 is substantially retained in the gap above the front shroud 5a, and the liquid introduced into the second space S2 is substantially retained in the gap below the back shroud 5b. do.

Here, in the first impeller 4, the liquid pressure p3 of the third space S3 boosted by the guide blade member 10 acts on the front surface (upper surface) of the front shroud 4a, and the back surface of the front shroud 4a (first impeller 4). The liquid pressure p1 before the pressurization of the first space S1 acts on the inside). Further, the liquid pressure p1 of the first space S1 acts on the front surface (upper surface) of the back shroud 4b facing the first space S1, and the third space S3 is placed on the back surface (lower surface) of the back shroud 4b facing the third space S3. Liquid pressure p3 acts. Here, since the liquid pressure p3 in the third space S3 is higher than the liquid pressure p1 in the first space S1 (p3> p1), in the conventional two-stage centrifugal pump not provided with the thrust balance mechanism, FIG. 3 ( As shown in the left column of b), a relatively large upward (suction port direction) thrust force F1'acts on the first impeller 4 in FIG. On the other hand, in the two-stage centrifugal pump 1 according to the present invention provided with the thrust balance mechanism, the downward (anti-suction port direction) thrust force F1down acts on the front shroud 4a and the rear surface. In the shroud 4b, the upward thrust force F1up (in the direction of the suction port) acts in FIG. Then, as shown in the right column of FIG. 3B, the thrust force F1 (<F1') in the suction port direction acts on the first impeller 4 as a whole for the thrust forces F1up and F1down whose action directions are opposite to each other. do. In other words, in the two-stage centrifugal pump 1 according to the present invention, in the first impeller 4, the thrust force F1'in the suction port direction, which has been conventionally generated on the back surface of the rear shroud 4b, is the thrust balance mechanism of the first labyrinth seal portion. It is offset by the downward thrust force F1down generated on the front surface of the front shroud 4a to which L1 is added, and is reduced to F1 (<F1').

On the other hand, in the second impeller 5, in the two-stage centrifugal pump not provided with the thrust balance mechanism, on the back surface of the rear shroud 5b of the second impeller 5, the volute of the second pump chamber R2 from the outer peripheral end of the second impeller 5 The liquid pressure p4 (not shown) flowing out to the portion acts, but as described above, the liquid pressure p4 boosted by the volute portion is the pressure p2 in the second space S2 and the pressure in the third space S3 before the pumping. Since it is even higher than p3 (p4> p3> p2), as shown in the left column of FIG. 3 (b), a relatively large upward (suction port direction) thrust force F2'acts in FIG. On the other hand, in the two-stage centrifugal pump 1 according to the present invention provided with the second labyrinth seal portion L2, the third labyrinth seal portion L3, and the communication passage 3a, which are thrust balance mechanisms, the front surface of the front shroud 5a ( The liquid pressure p3 of the third space S3 acts on the back surface of the front surface shroud 5a and the front surface of the back surface shroud 5b (that is, the inside of the second impeller 5), and the lower surface of the back surface shroud 5b (second impeller 5). The liquid pressure p2 of the second space S2 acts on the outer side and the lower surface of the space S2. As described above, since the liquid pressure p3 in the third space S3 boosted by the guide blade member 10 is higher than the pressure p2 in the second space S2 before boosting (p3> p2), the front surface of the second impeller 5 The thrust force in the shroud 5a is almost offset on the front and back sides, and the thrust force F2 in the anti-suction port direction (downward in FIG. 3) acts on the back shroud 5b.

Therefore, the contradictory thrust forces F1 and F2 act together on the rotor shaft 3 of the two-stage centrifugal pump 1 according to the present embodiment. In other words, in the two-stage centrifugal pump 1 according to the present invention, in the rotor shaft 3, the thrust force F1 in the direction of the suction port remaining in the first impeller 4 is offset by the downward thrust force F2 generated in the second impeller 5. Has been done. Therefore, the load received by the slide bearings 7 and 8 from the rotor shaft 3 is reduced, the wear of the slide bearings 7 and 8 is suppressed, and the durability of these slide bearings 7 and 8 is enhanced. Since such an effect can be obtained without providing the thrust balance disk on the rotor shaft 3, the structure of the two-stage centrifugal pump 1 does not become complicated or large.

Further, the wraparound of the fluid boosted by the first impeller 4 to the first space S1 is suppressed by the first labyrinth seal portion L1, and the fluid boosted by the second impeller 5 is suppressed in the second space S2 and the third space S3. Since the second labyrinth seal portion L2 and the third labyrinth seal portion L3 suppress the wraparound to the liquid, the discharge flow rate of the liquid is increased and the pump efficiency of the two-stage pump 1 is improved.

Further, in the present embodiment, the first space S1 and the second space S2 can be communicated with each other by a simple configuration in which an axial communication passage 3a is formed in the rotor shaft 3 without requiring additional parts. Therefore, the structure of the two-stage centrifugal pump 1 can be simplified and the cost can be reduced.

Further, in the two-stage centrifugal pump 1 according to the present embodiment, the volume of the second space S2 into which the relatively high-pressure fluid flows is set to be relatively large, and the second space S2 functions as a reservoir chamber. That is, in the reservoir chamber in which the volume is set to be relatively large while communicating with the suction port 22a, the liquid pressurized by the second impeller 5 leaks to the second space S2 beyond the second labyrinth seal portion L2. Since the accompanying pressure change is small, the fluctuation of the liquid pressure p2 in the second space S2 can be suppressed, and the effect that the thrust force F2 related to the liquid pressure p2 can be smoothly acted can be obtained.

In the above embodiment, an example in which the present invention is applied to a two-stage water pump using a coolant as a handling liquid has been described, but in the present invention, any liquid other than the coolant is used as the handling liquid. The same applies to the two-stage centrifugal pump used.

Further, in the embodiment, an example in which the third labyrinth seal portion L3 is formed on the outer peripheral portion of the front shroud 5a of the second impeller 5 has been described, but the present invention is not limited thereto. For example, the third labyrinth seal portion L3 can be formed on the radial intermediate portion of the front shroud 5a of the second impeller 5 or on the inner peripheral portion of the front shroud 5a. As a result, the magnitude of the thrust force F2 acting in the direction of the anti-suction port can be adjusted, so that the thrust force F1 of the first impeller 4 and the thrust force F2 of the second impeller 5 are appropriately offset and the slide bearing. The thrust force acting on 7 can be suppressed as small as possible.

In addition, the present invention is not limited to the embodiments described above, and various modifications can be made within the scope of claims and the technical ideas described in the specification and drawings. Of course.

1 Two-stage centrifugal pump 2 Pump case 21 Cylindrical part 21A Partition 22 Cover member 22a Suction port 23 Case member 23A Bottomed cylindrical part (reservoir chamber)
3 Rotor shaft 3a Rotor shaft communication passage 4 1st impeller 4a Front shroud of 1st impeller 5 2nd impeller 5a Front shroud of 2nd impeller 5b Back shroud of 2nd impeller 6 Support shaft 10 Guide blade member 14 Rotor 15 stator L1 1st labyrinth seal part L2 2nd labyrinth seal part L3 3rd labyrinth seal part M motor part (drive source)
P Pump section R1 1st pump room R2 2nd pump room S1 1st space S2 2nd space S3 3rd space

Claims (4)

Support axis (6) and
A hollow rotor shaft (3) rotatably held by the support shaft (6), and
A cylindrical rotor (14) fixed to the outer periphery of the end of the rotor shaft (3), and
A stator (15) arranged on the outer peripheral side of the rotor (14) and generating a rotating magnetic field for rotating the rotor (14), and a stator (15).
A cover member (22) having a suction port (22a) and
A cylindrical tubular portion (21) having a partition wall (21A),
A case member (23) having a bottomed cylindrical portion (23A) that opens to the suction port (22a) side and houses the rotor (14), and partitions the rotor (14) and the stator (15). ) And
Two first and second impellers (4, 5) are attached to the rotor shaft (3) along the axial direction, and the cover member (22) is provided in the two openings in the axial direction of the tubular portion (21). The first impeller (4) is placed in two pump chambers (R1, R2) defined by the partition wall (21A) in a pump case (2) configured by connecting and integrating the case member (23). ) And the second impeller (5) are housed in the two-stage centrifugal pump (1).
The first labyrinth seal portion (L1) located on the inner peripheral portion of the front shroud (4a) between the cover member (22) and the front shroud (4a) of the first impeller (4) facing the cover member (22). And at the same time
A second labyrinth seal portion (L2) located on the outer peripheral portion of the back shroud (5b) is provided between the case member (23) and the back shroud (5b) of the second impeller (5) facing the case member (23). Provided,
The first space (S1) facing the suction port (22a) on the axial side of the first labyrinth seal portion (L1) in the cover member (22) and the second labyrinth seal portion (L2). A communication passage (S2) that forms a second space (S2) facing the bottomed cylindrical portion (23A) on the axial center side and communicates with each other between the first space (S1) and the second space (S2). A two-stage centrifugal pump characterized in that 3a) is formed on the rotor shaft (3). A third labyrinth seal portion (L3) is provided between the front shroud (5a) of the second impeller (5) and the partition wall (21A) facing the shroud (5a), and the third labyrinth in the pump case (2) is provided. The two-stage centrifugal pump according to claim 1, wherein a third space (S3) is formed on the axial center side of the seal portion (L3). The two-stage centrifugal pump according to claim 2, wherein the partition wall (21A) is integrally resin-molded together with the cylindrical portion (21). The two-stage centrifugation according to any one of claims 1 to 3, wherein a reservoir chamber having an internal volume of 80% or more of the volume of the rotor (14) is configured in the bottomed cylindrical portion (23A). pump.

Images