CN114060285B

CN114060285B - Two-stage centrifugal pump

Info

Publication number: CN114060285B
Application number: CN202110890193.2A
Authority: CN
Inventors: 伊香德人
Original assignee: Hitachi Astemo Ltd
Current assignee: Hitachi Astemo Ltd
Priority date: 2020-08-07
Filing date: 2021-08-04
Publication date: 2023-08-25
Anticipated expiration: 2041-08-04
Also published as: JP7469990B2; JP2022030980A; CN114060285A

Abstract

The invention provides a two-stage centrifugal pump, which can restrain the flow loss (energy loss) of liquid flowing through a guide vane component to be small, thereby preventing the reduction of pump efficiency. The multistage centrifugal pump has 2 impellers mounted on a rotor shaft in an axial direction, each impeller is accommodated in 2 pump chambers divided by a partition wall in a pump housing, a guide vane member is interposed between the impellers adjacent in the axial direction, a diffusion passage divided by a plurality of diffusion vanes is formed in a surface of the guide vane member facing a front surface of a base portion thereof, a return passage divided by a plurality of return guide vanes is formed in a rear surface of the base portion facing the partition wall, a plurality of interpolation portions are provided so as to protrude in a circumferential direction in a surface of the partition wall facing the guide vane member, and the plurality of interpolation portions are used for filling a step (delta) formed between a surface of the partition wall facing the guide vane member and an outer peripheral opening end of each diffusion passage of the guide vane member.

Description

Two-stage centrifugal pump

Technical Field

The present invention relates to a two-stage centrifugal pump having a guide vane member for guiding fluid discharged from a front stage impeller to a suction side of a secondary stage impeller.

Background

As one embodiment of the fluid machine, a multistage centrifugal pump has the following structure as disclosed in patent documents 1 and 2: a plurality of impellers are mounted on a rotor shaft which is rotationally driven by a drive source such as an electric motor in the axial direction, the impellers are accommodated in a plurality of pump chambers which are partitioned by a partition wall in a pump housing, and guide vane members are interposed between 2 impellers which are adjacent to each other in the axial direction through the partition wall in the pump housing. Here, the guide vane member has: a base portion having a center hole through which the rotor shaft is inserted; a function (diffusion function) formed on the front surface of the base portion and configured to convert (boost) kinetic energy applied to the processing fluid by the impeller on the front stage side of the 2 impellers into static pressure; and a function (guiding function) of changing the flow angle of the processing fluid subjected to the pressure increase and guiding the processing fluid to the secondary impeller, wherein a plurality of diffusing passages are formed as diffusing functions based on diffusing blades (blade rows) protruding from the outer peripheral surface of the impeller on the front stage side of the base portion, and a plurality of return passages are formed as guiding functions based on a plurality of guiding blades protruding from the rear surface of the base portion.

In such a multistage centrifugal pump, the liquid accelerated by the impeller on the front stage side is decelerated and the pressure is increased (boosted) while flowing radially outward along the diffuser passage of the guide vane member. When the liquid is delivered from the diffusion passage to the return passage, the liquid flows radially inward along the return passage and is guided to the suction side of the secondary impeller, and is accelerated again by the secondary impeller. The re-accelerated liquid is decelerated and pressurized while flowing through the scroll portion in the pump chamber formed radially outside the secondary impeller, and is finally discharged to the outside from the discharge port of the pump housing.

Further, although a part of the internal structure of the conventional two-stage centrifugal pump that functions as described above is shown in the partially cut-away perspective view of fig. 6, as shown in the figure, a steep step δ may occur between the partition wall 121A of the pump housing 102 and the outflow port 132a that opens at the outer peripheral ends of the plurality of diffusion passages 132 formed in the guide vane member 110 that is placed on the partition wall 121A. Therefore, the flow direction of the liquid flowing in the direction of the arrow shown in the drawing in each of the diffusion passages 132 changes abruptly at the step δ, and the liquid cannot smoothly flow into each of the return passages 134, and as a result, the flow loss (energy loss) of the liquid increases, and the pump efficiency often decreases.

Accordingly, patent document 1 proposes a multistage centrifugal pump having a cast (metal) guide vane member configured such that rear ends of a plurality of intersecting vanes, which are divided at once from a front surface to a rear surface of the guide vane member, are inclined in a circumferential direction so as to communicate a diffuser passage, a curved passage, and a return passage, which are disposed downstream of an impeller. By adopting such a structure, peeling of the liquid flow in the return passage can be suppressed, and a decrease in pump efficiency can be prevented.

Patent document 2 discloses a multistage centrifugal pump having the following structure: the pump housings accommodating the respective impellers are provided for each stage, and a plurality of pump housings are stacked in the axial direction to be integrated.

Prior art literature

Patent document 1: japanese patent laid-open No. 2020-060114

Patent document 2: patent publication No. 5599463

Disclosure of Invention

Problems to be solved by the invention

However, in the multistage centrifugal pump proposed in patent document 1, since the curved passage and the guide vane member are integrated together in addition to the diffuser passage and the return passage, it is necessary to gently curve the curved passage by increasing the thickness along the peripheral edge portion of the base portion of the curved passage in order to control the separation of the fluid by the guide vane member. Therefore, the base portion is solid and thick, and thus, there is a problem that the centrifugal pump using the base portion is heavy and large.

The present invention has been made in view of the above-described problems, and an object thereof is to provide a two-stage centrifugal pump capable of suppressing a flow loss (energy loss) of a liquid flowing through a guide vane member to a small level while suppressing a heavy and large size, and preventing a decrease in pump efficiency.

However, in the multistage centrifugal pump disclosed in patent document 1, since the rear ends of the blade rows of the plurality of intersecting blades are inclined in the circumferential direction, there is a problem that the plurality of intersecting blades form undercuts in shape, and demolding after molding cannot be performed. Further, for example, when a lost foam casting method in which a casting mold is lost every time a casting is produced is used as a molding method, a plurality of intersecting blades can be integrally molded with a base portion, but there is a problem in that the production process is complicated, the number of production per hour is reduced, and the production cost is increased.

Further, in the two-stage centrifugal pump disclosed in patent document 2, since a plurality of pump housings provided for each stage of impeller are stacked and integrated in the axial direction, there is a problem in that the number of components increases, which results in a complicated structure, and in that the number of assembly steps increases, which results in an increase in cost.

Accordingly, another object of the present invention is to provide a two-stage centrifugal pump that can reduce the number of components and assembly man-hours, thereby simplifying the structure and reducing the cost.

Means for solving the problems

In order to achieve the above object, the invention described in claim 1 is a two-stage centrifugal pump comprising: a pump housing configured to include a cylindrical portion, a cover portion and a housing member each covering an axial opening of the cylindrical portion; a partition wall having a circular hole through which a rotor shaft rotatably driven by a driving source is inserted, and partitioning a space in the pump housing; and a guide vane member that is placed on a front surface of the partition wall so that a center hole formed in a disk-shaped base portion is coaxial with the circular hole, wherein the secondary centrifugal pump is configured such that 2 impellers held by the rotor shaft are respectively housed in 2 pump chambers partitioned by the partition wall in the pump housing, the partition wall and the guide vane member are interposed between the 2 impellers adjacent to each other in an axial direction, and wherein a plurality of diffusion passages 32 surrounding an impeller on a front stage side of the 2 impellers on a front surface side of the base portion and a plurality of return passages facing the partition wall on a rear surface side of the base portion are formed in the guide vane member, and wherein a plurality of interpolation portions for filling a step difference generated between the front surface of the partition wall and the outer peripheral opening portion into a smooth slope shape are projected along an outer peripheral opening portion of each of the diffusion passages on the front surface side of the partition wall.

In the invention according to claim 2, in addition to the first feature, a second feature is that a radially outer contour of the guide vane member along the outer peripheral opening end face of each of the diffuser passages and the inflow port of each of the return passages is formed in a notch shape bent in a V shape toward a radially inner side than a circumscribed circle of the guide vane member.

In the invention according to claim 3, in addition to the first or second feature, the partition wall and the plurality of interpolation portions are integrally formed with the cylindrical portion by resin molding.

Effects of the invention

According to the invention of claim 1, since the step between the peripheral opening of each diffusion passage of the guide vane member and the partition wall of the pump casing is buried by the interpolation portion of the partition wall, the liquid does not smoothly flow from each diffusion passage to each return passage with an abrupt change in the flow direction in the guide vane member. Therefore, the flow loss (energy loss) of the liquid at the guide vane member is suppressed low, thereby preventing a decrease in pump efficiency.

According to the invention of claim 2, since the radially outer contour of the guide vane member along the outer peripheral opening end surface of each diffuser passage and the inflow port of each return passage is formed in a notch shape curved in a V shape toward the radially inner side than the circumscribed circle of the guide vane member, a space having a fan shape as viewed in the axial direction is formed between the guide vane member and the inner peripheral wall of the pump housing, and the interpolation portion is provided so as to protrude in the partition wall of the pump housing to fill the space. Therefore, a plurality of (the same number as the diffusion passages) protruding interpolation portions are provided protruding in the circumferential direction on the outer peripheral portion of the partition wall of the pump housing, and the step between the outer peripheral opening portion of each diffusion passage and the partition wall is filled by these interpolation portions. As a result, the diffusion passages and the return passages in the guide vane member are smoothly connected, and the fluid flowing through the diffusion passages smoothly flows into the return passages, thereby preventing abrupt changes in the flow direction of the fluid and reducing the flow loss (energy loss). Further, since the interpolation portion is fitted in the space formed between the outer peripheral opening end face of each diffusion passage of the guide vane member and the inner peripheral wall of the pump casing, the guide vane member and the pump casing are positioned with high accuracy and reliability by the fitting, and no special positioning means is required.

According to the invention of claim 3, the partition wall and the plurality of interpolation portions of the pump housing are integrally formed with the cylindrical portion by resin molding, so that the pump chambers can be formed on both sides in the axial direction of the partition wall, respectively. Therefore, compared with a conventional multistage centrifugal pump having a structure in which a plurality of pump housings provided for each stage of impeller are stacked and integrated in the axial direction, the number of components and the number of assembly steps can be reduced, and simplification of the structure and cost reduction can be achieved.

Drawings

Fig. 1 is a longitudinal sectional view of a two-stage centrifugal pump of the present invention.

Fig. 2 is a view showing a guide vane member of the secondary centrifugal pump according to the present invention, (a) is a top view, (b) is a side view, and (c) is a bottom view.

Fig. 3 is a perspective view of a pump casing (cylindrical portion) of the secondary centrifugal pump of the present invention.

Fig. 4 is a plan view showing a state in which a guide vane member is incorporated in a pump casing (cylindrical portion) of the secondary centrifugal pump of the present invention.

Fig. 5 is a partially cut-away perspective view showing a part of the internal structure of the pump casing of the secondary centrifugal pump of the present invention.

Fig. 6 is a partially cut-away perspective view showing a part of the internal structure of a pump casing of a conventional two-stage centrifugal pump.

Description of the reference numerals

1: a secondary centrifugal pump;

2: a pump housing;

21: a cylindrical portion of the pump housing;

21A: a partition wall of the pump housing;

21a: round holes of the partition wall;

21b: an interpolation section of the partition wall;

22: a cover member of the pump housing;

23: a housing component of the pump housing;

3: a rotor shaft;

4: a first impeller;

5: a second impeller;

6: a support shaft;

10: a guide vane member;

10a: a central bore for guiding the vane member;

31: a diffuser blade guiding the blade member;

32: a diffusion path;

32a: outflow openings (outer peripheral openings) of the diffusion passages;

32b: an outer peripheral open end face of the diffusion passage;

33: a return guide vane of the guide vane member;

34: a return path;

34a: an inflow port of the return passage;

34b: an outer peripheral open end of the return passage;

c: a circumscribed circle of the guide vane member;

m: a motor unit (drive source);

p: a pump section;

s1: a first pump chamber;

s2: a second pump chamber;

delta: step difference.

Detailed Description

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

Fig. 1 is a longitudinal sectional view of a secondary centrifugal pump according to the present invention, fig. 2 is a view showing a guide vane member of the secondary centrifugal pump, (a) is a plan view, (b) is a side view, (c) is a bottom view, fig. 3 is a perspective view of a pump housing (cylindrical portion) of the secondary centrifugal pump, fig. 4 is a plan view showing a state in which the guide vane member is incorporated in the pump housing (cylindrical portion), and fig. 5 is a partially cut-away perspective view showing a part of an internal structure of the pump housing.

A two-stage centrifugal pump (hereinafter simply referred to as "pump") 1 shown in fig. 1 is a motor pump, and is configured such that a pump portion P arranged vertically (in the axial direction) in fig. 1 and a motor portion M serving as a driving source are integrally connected along the same central axis, a support shaft 6 is housed in the central axis thereof, and a hollow rotor shaft 3 for transmitting rotational power generated by the motor portion M rotatably held by the support shaft 6 to the pump portion P is interposed between the rotor shaft 3 and the support shaft 6, with slide bearings 7 and 8 interposed therebetween. The pump 1 of the present embodiment is used in a state where the pump portion P and the motor portion M are arranged vertically, that is, in a vertically arranged state, but may be used in a horizontally arranged state where the pump portion P and the motor portion M are arranged horizontally.

The pump section P is configured such that a first impeller 4 of a first stage and a second impeller 5 of a second stage, which are mounted in a vertically aligned manner on an upper half of the rotor shaft 3, and a guide vane member 10 provided so as to be interposed between the first and second impellers 4, 5 are housed in a first pump chamber S1 and a second pump chamber S2, which are formed in a top and bottom of the pump housing 2, respectively. In the present embodiment, the pump casing 2, the first and second impellers 4 and 5, and the guide vane member 10 are made of resin.

The pump housing 2 is configured such that a cylindrical portion 21, and a cover member 22 and a housing member 23 that cover upper and lower openings of the cylindrical portion 21 are integrally coupled in the axial direction. Here, a partition wall 21A is integrally provided in an annular circular plate shape from a substantially middle position in an axial direction of an inner peripheral wall of the tubular portion 21, and the partition wall 21A extends in a direction along a cross section of the tubular portion 21 and vertically divides an inner space of the tubular portion 21, and a first pump chamber S1 and a second pump chamber S2 are divided by the partition wall 21A in the pump housing 2. A cylindrical discharge pipe 21B communicating with the second pump chamber S2 extends in a tangential direction from a lower side of an outer periphery of the cylindrical portion 21 (see fig. 3 and 4). A circular hole 21A is formed in the central axis of the partition wall 21A to communicate between the first pump chamber S1 and the second pump chamber S2. A guide vane member 10 is mounted on the first pump chamber S1 side of the partition wall 21A, and a center hole 10a coaxial with the circular hole 21A is formed in the guide vane member 10. The rotor shaft 3 and the support shaft 6 are inserted into the circular hole 21a, the center hole 10a, the first pump chamber S1, and the second pump chamber S2.

The cover member 22 is provided with a cylindrical suction pipe 22A integrally standing at a position corresponding to the central axis, and an upper end of the suction pipe 22A is opened 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 (3 in the example of the drawing) rectifying plates 22B are formed around the rectifying cone 22B.

The first impeller 4 is housed in the first pump chamber S1 above the cylindrical portion 21 in a state in which its outer periphery is surrounded by the guide vane member 10 and its suction side faces the base end portion of the suction pipe 22A, and is fixed to the rotor shaft 3. The second impeller 5 is housed in the second pump chamber S2 below the cylindrical portion 21 on the lower surface side of the partition wall 21A with its suction side facing the circular hole 21A, and is fixed to the rotor shaft 3.

The case member 23 includes a cup-shaped bottomed cylindrical portion 23A at a center portion thereof, and a flange portion 23B is integrally formed from an upper end of the bottomed cylindrical portion 23A toward a radial outside. A cylindrical boss portion 23A is integrally provided to the bottom center portion of the bottomed cylindrical portion 23A of the case member 23 so as to stand upward, and the upper and lower ends of the support shaft 6 are fitted to the boss portion 23A and the center portions of the rectifying cones 22B formed in the cover member 22.

Further, the thrust washer 9 is held so as not to rotate with the support shaft 6 between the cone 22B of the cover member 22 and the upper slide bearing 7.

The motor unit M includes a motor case 11 connected from below the case member 23, and the motor case 11 is configured such that a cylindrical outer shell 11A and a bottomed cylindrical cover member 11B covering a lower surface opening of the outer shell 11A from below are vertically connected to each other to form a single body. Here, the outer peripheral portion 11A is connected to the lower surface of the flange portion 23B of the case member 23 in a fluid-tight manner with the annular seal member 12 interposed therebetween. The upper end surface of the cover member 11B is connected to the lower side of the outer peripheral portion 11A in a fluid-tight manner via an annular seal member 13.

The motor unit M includes a cylindrical rotor 14 fixedly attached to the lower side of the rotor shaft 3, and a stator 15 disposed opposite to the rotor 14 via a bottomed cylindrical portion 23A of the housing member 23. Here, the rotor 14 is accommodated in a bottomed cylindrical portion 23A provided in a housing member 23 of the pump housing 2, and is fixedly attached to the outer periphery of the lower end portion of the rotor shaft 3. The rotor 14 is composed of permanent magnets.

The stator 15 is formed by winding and mounting three-phase coils 18 on a stator core 16 via an insulator 17, and the stator core 16 integrally includes a yoke 16a formed in a tubular shape, for example, and T-shaped teeth 16b protruding radially inward from a plurality of portions of the inner periphery of the yoke 16a at equal intervals in the circumferential direction.

The insulator 17 covers the stator core 16 so that the inner peripheral side end portions of the teeth 16b are exposed so as to face the outside of the bottomed cylindrical portion 23A. On the other hand, in the present embodiment, the outer peripheral portion 11A of the motor housing 11 is molded from an electrically insulating resin material in which the insulator 17 is an insert, and thereby the stator 15 is fixed so that at least a part thereof is surrounded by the outer peripheral portion 11A. The three-phase coils 18 are electrically connected to control circuits formed on a control board 19 described later.

The support leg 11A integrally extends from the lower surface of the outer contour portion 11A of the motor housing 11 into the cover member 11B, and the control board 19 for controlling the energization of the three-phase coils 18 of the stator 15 is engaged with and supported by the lower end of the support leg 11A by the engagement claw 11A1 formed at the lower end of the support leg 11A.

Next, the details of the structure of the guide vane member 10 will be described with reference to fig. 2 and 5.

As described above, the center hole 10a is formed in the center portion of the guide vane member 10 on the first pump chamber R1 side of the partition wall 21A, and the rotor shaft 3 penetrates the center hole 10a. As shown in fig. 2a, 6 diffusion blades (blade rows) 31 each having a triangular shape as viewed in the axial direction facing the posture of the rotation peripheral surface of the first impeller 4 are integrally provided on the outer peripheral portion of the upper surface of the guide blade member 10 at equal angular intervals (60-degree intervals) in the circumferential direction, and groove-shaped diffusion passages 32 each having a passage area gradually increasing toward the radial outside and curved in the circumferential direction (the rotation direction of the first impeller) are formed between 2 diffusion blades 31 adjacent in the circumferential direction. That is, 6 diffusion passages 32, which are the same in number as the diffusion blades 31, are divided in the circumferential direction into shapes in which the outer peripheral ends gradually approach the inner wall surface of the cylindrical portion 21 shown as the circumscribed circle C of the guide blade member 10 at 60 degree intervals on the outer peripheral portion of the upper surface of the guide blade member 10, and the diffusion passages 32 are formed radially at equal angular intervals (60 degree intervals).

On the other hand, as shown in fig. 2 c, 6 return guide vanes (vane rows) 33 extending in a spiral shape while being bent from the radially outer side toward the center hole 10a are integrally provided on the lower surface of the guide vane member 10 facing the partition wall 21A of the pump housing 2 at 60-degree intervals in the circumferential direction. Further, 6 return passages 34 of the same number as the return guide vanes 33 are respectively divided between 2 return guide vanes 33 adjacent in the circumferential direction.

Here, the 6 diffuser passages 32 and the return passages 34 are connected (communicate) in the first pump chamber R1, that is, as shown in fig. 5, the outer peripheral ends of the return passages 34 are divided into rectangular inflow ports 34a that open below the diffuser vanes 31 in a posture that intersects the diffuser passages 32 three-dimensionally, and outflow ports 32a that are the outer peripheral ends of the diffuser passages 32 are opened adjacent to the inflow ports 34a of the return passages 34. Accordingly, the diffusion passages 32 and the return passages 34 communicate with each other via the outflow port 32a and the inflow port 34 a.

Here, as shown in fig. 2 (a), the outer peripheral opening end surface (end surface where the outflow port 32a opens) 32b of each diffusion passage 32 is inclined radially inward from the circumscribed circle C of the guide vane member 10. In addition, similarly to the outer peripheral opening end portion (end surface of the inlet 34a opening) 34b of the inlet 34a of each return passage 34 adjacent thereto, the outer contour of the guide vane member 10 is formed with 6 notch portions bent (recessed) in a V-shape toward the radial inner side when viewed in the axial direction by being inclined toward the radial inner side as compared with the circumscribed circle C of the guide vane member 10. Therefore, a space S in a fan shape as viewed in the axial direction surrounded by the cutout portion and the cylindrical portion 21 is formed in the first pump chamber S1.

As described above, the guide vane member 10 configured as described above is housed in the first pump chamber S1 partitioned by the partition wall 21A in the cylindrical portion 21 of the pump casing 2, whereas in the conventional centrifugal pump, as shown in fig. 6, the upper surface of the partition wall 121A in the cylindrical portion is configured as a flat plane, and therefore, a step δ is formed between the outflow port 132a of the outer peripheral end surface opening of the diffuser passageway 132 and the upper surface of the partition wall 121A, and this step δ causes a sudden change in the flow direction of the liquid, and as a result, the pump efficiency of the pump is reduced.

Therefore, in the present embodiment, a total of 6 interpolation portions 21b for filling the step δ formed between the outflow port 32a of each diffusion passage 32 of the guide vane member 10 and the upper surface of the partition wall 21A are integrally projected at 60-degree intervals in the circumferential direction on the upper surface of the partition wall 21A of the cylindrical portion 21 provided in the pump housing 2.

Here, as described above, 6 spaces S in a total of a fan shape in an axial direction (in plan view) are formed between the outer peripheral opening end face 32b and the outer peripheral opening end portion 34b of the guide vane member 10 and the inner peripheral wall of the pump casing 2 (the cylindrical portion 21), and the interpolation portion 21b is projected from the partition wall 21A of the pump casing 2 so as to fill the spaces S. Further, since the interpolation sections 21b are formed in a downward slope shape toward the radial direction inside of the inflow port 34a of the return passage 34, the diffusion passages 32 and the return passages 34 in the guide vane member 10 are smoothly connected to each other by the interpolation sections 21b. In this case, since the interpolation portion 21b is fitted in the space S formed between the outer peripheral opening end face 32b of each diffusion passage 32 of the guide vane member 10 and the inner peripheral wall of the pump casing 2 (the cylindrical portion 21), the guide vane member 10 and the pump casing 2 are positioned in the circumferential direction by fitting the interpolation portion 21b in the space S, and thus the guide vane member 10 and the pump casing 2 can be positioned in the circumferential direction with high accuracy and reliability without requiring a special positioning means.

Next, the operation of the pump 1 configured as described above will be described.

By the magnetic field generated by the stator 15 under the energization control of the three-phase coils 18 of the stator 15 from the control board 19, the rotor 14 and the rotor shaft 3 holding the rotor 14 are driven to rotate at a desired speed around the support shaft 6.

In the pump portion P, the first impeller 4 and the second impeller 5 mounted on the rotor shaft 3 rotate in the first pump chamber S1 and the second pump chamber S2, respectively, in the pump housing 2. Then, by the rotation of the first impeller 4, a negative pressure is generated in the suction pipe 22A of the cover member 22 formed in the pump housing 2, and the treatment liquid (cooling water) is sucked by the negative pressure and is sucked into the suction pipe 22A from the suction port 22A as indicated by an arrow in fig. 1. The liquid sucked into the suction pipe 22A flows downward in the suction pipe 22A, and is sucked into the first impeller 4 of the first stage.

The liquid sucked to the first impeller 4 flows radially outward while kinetic energy is imparted from the rotating first impeller 4, flows radially outward from the outer peripheral end of the first impeller 4 as indicated by arrows (a) of fig. 2 in the plurality of (6 in the present embodiment) diffusing passages 32 formed in the upper surface of the guide vane member 10, and then proceeds to the outflow openings 32a opened at the outer peripheral ends of the diffusing passages 32 as indicated by arrows of fig. 5. The liquid is decelerated and the pressure increases in the course of flowing through each of the diffuser passages 32, which gradually increases in the passage cross-sectional area toward the radially outer side of the guide vane member 10 and is curved.

The liquid flowing out from the outflow port 32a opened at the outer peripheral opening end face of each diffusion passage 32 flows into each of the 6 return passages 34 partitioned on the lower surface of the guide vane member 10 from the inflow port 34a opened adjacent to the outflow port 32a. In this case, as described above, since the diffusion passages 32 and the return passages 34 in the guide vane member 10 are smoothly connected by the interpolation portions 21b provided so as to protrude from the partition wall 21A, the flow direction of the liquid flowing through the diffusion passages 32 does not suddenly change immediately after the liquid flows out from the outflow openings 32a of the diffusion passages 32. Therefore, the flow loss (energy loss) of the liquid when the liquid is intersected from each diffusion passage 32 to each return passage 34 is suppressed to be small.

Thereafter, as indicated by the arrow in fig. 2 (c), the liquid flowing into each return passage 34 travels radially inward in each return passage 34, and is guided to the suction side of the second impeller 5 facing the second stage of the round hole 21A by the round hole 21A formed in the center portion of the partition wall 21A as indicated by the arrow in fig. 1. The liquid introduced to the suction side of the second impeller is in the following state: the kinetic energy is imparted by the rotation of the second impeller 5, and the fluid flows radially outward, flows out from the outer peripheral end of the second impeller 5 into the second pump chamber S2, and decelerates and increases the pressure further while flowing through the scroll portion formed in the second pump chamber S2. In this way, the liquid pressurized by the first impeller 4 and the second impeller 5 flows into the discharge pipe 21B in the tangential direction from the second pump chamber S2, and is discharged to the outside from the discharge pipe 21B.

That is, in the pump 1 of the present embodiment, as shown in fig. 2 (a), by inclining the outer peripheral opening end surfaces 32b and the outer peripheral opening end portions 34b of the diffusion passages 32 of the guide vane member 10, a total of 6 notch portions which are bent in a V-shape inward in the radial direction from the circumscribed circle C of the guide vane member 10 are formed in the outer peripheral outline of the guide vane member 10, a total of 6 spaces S which are fan-shaped as viewed in the axial direction are formed between the notch portions and the inner peripheral wall of the pump housing 2, and 6 interpolation portions 21b are projected from the partition wall 21A of the pump housing 2 so as to fill the spaces S. More specifically, as shown in fig. 3 and 4, 6 (the same number as the diffusion passages 32) protruding interpolation portions 21b are provided on the upper surface of the partition wall 21A of the pump housing 2 so as to protrude at equal angular intervals (60 degree intervals) in the circumferential direction, and the step δ between the outflow port 32a and the partition wall 21A, which are open at the outer peripheral end of each diffusion passage 32, is buried by these interpolation portions 21b.

As described above, in the pump (2-stage centrifugal water pump) 1 of the present embodiment, the step δ between the outflow port 32a opened at the outer peripheral end of each diffusion passage 32 of the guide vane member 10 and the partition wall 21A of the pump housing 2 is filled with a total of 6 interpolation sections 21b provided so as to protrude from the partition wall 21A, and therefore, the liquid smoothly flows from each diffusion passage 32 to each return passage 34 without accompanying abrupt changes in the flow direction. Therefore, the following effects can be obtained: the flow loss (energy loss) of the liquid accompanying the abrupt change in the flow direction of the liquid is suppressed to be small, thereby preventing the pump efficiency of the pump 1 from being lowered.

Since the interpolation portions 21b are fitted in the spaces S formed between the guide vane members 10 and the inner peripheral wall of the pump casing 2, the guide vane members 10 and the pump casing 2 can be positioned with high accuracy and reliability by the fitting, and no special positioning means is required.

In the pump 1 of the present embodiment, 1 partition wall 21A is integrally molded with the tubular portion 21 of the pump housing 2 from the inner peripheral wall of the tubular portion 21 toward the radial direction inside, whereby the first pump chamber S1 and the second pump chamber S2 can be formed at one time in the upper and lower (both axial sides) directions of the partition wall 21A. Therefore, compared to a conventional two-stage centrifugal pump (see patent document 2) having a structure in which a plurality of pump housings provided for each stage of impeller are stacked and integrated in the axial direction, the number of components and assembly man-hours can be reduced, and thus the following effects can be obtained: the construction of the pump 1 can be simplified and cost reduced.

In the above embodiments, the description has been given of the example in which the present invention is applied to the electric water pump using the coolant as the processing fluid, but the present invention can be similarly applied to a two-stage centrifugal pump using any liquid other than the coolant (for example, oil) as the processing fluid.

The present invention is not limited to the embodiments described above, and can be modified in various ways within the scope of the technical ideas described in the claims, the specification, and the drawings.

Claims

1. A two-stage centrifugal pump, having:

a pump housing (2) configured to include a cylindrical portion (21), and a cover member (22) and a housing member (23) each covering an axial opening of the cylindrical portion (21);

a partition wall (21A) which has a circular hole (21A) through which a rotor shaft (3) rotationally driven by a drive source (M) is inserted, and which partitions a space in the pump housing (2); and

a guide vane member (10) which is placed on the front surface of the partition wall (21A) so that a center hole (10 a) formed in a disk-shaped base portion is coaxial with the circular hole (21A),

the two-stage centrifugal pump is configured such that 2 impellers (4, 5) held by the rotor shaft (3) are respectively accommodated in 2 pump chambers (S1, S2) defined in the pump housing (2) by the partition wall (21A), the partition wall (21A) and the guide vane member (10) are interposed between the 2 impellers (4, 5) adjacent to each other in the axial direction,

a plurality of diffuser passages (32) surrounding the impeller (4) on the front stage side of the 2 impellers (4, 5) on the front surface side of the base part, and a plurality of return passages (34) facing the partition wall (21A) on the back surface side of the base part are formed on the guide vane member (10),

it is characterized in that the method comprises the steps of,

a plurality of interpolation parts (21 b) are projected along the peripheral opening (32 a) of each diffusion path (32) on the front surface side of the partition wall (21A), and the plurality of interpolation parts (21 b) are used for filling a step (delta) generated between the front surface of the partition wall (21A) and the peripheral opening (32 a) so as to enable the step (delta) to be formed into a slope shape in a part smoothly.

2. The two-stage centrifugal pump according to claim 1, wherein,

the radially outer contour of the guide vane member (10) along the outer peripheral opening (32 a) of each diffusion passage (32) and the inflow port (34 a) of each return passage (34) is formed in a notch shape bent in a V shape toward the radially inner side than the circumscribed circle (C) of the guide vane member (10).

3. A two-stage centrifugal pump according to claim 1 or 2, wherein,

the partition wall (21A) and the plurality of interpolation sections (21 b) are integrally formed together with the cylindrical section (21) by resin molding.