Magnetic levitation type pump

Abstract

To provide a magnetic levitation type pump capable of suppressing an impeller from moving in an axial direction.SOLUTION: A volute part of a casing in a magnetic levitation type pump includes: a toric top wall arranged on one side in an axial direction than an impeller; a bottom wall arranged on the other side in the axial direction than the impeller; and a cylindrical peripheral wall arranged on the outer side in a radial direction than the impeller and having both end parts in the axial direction connected to the top wall and the bottom wall. The top wall has: a radial inner wall part arranged with an interval on the one side in the axial direction relative to the impeller; and a radial outer wall part arranged on the outer side in the radial direction than the impeller. A volute flow path in which transfer fluid flowing out from an outlet of the impeller flows is formed between the impeller and the peripheral wall and between the radial outer wall part and the bottom wall in the volute part so as to be communicated with the interval, and at least a part of the radial outer wall part extends from an outer end in the radial direction of the radial inner wall part to the one side in the axial direction.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to magnetically levitated pumps. [Background technology]

[0002] A centrifugal pump described in Patent Document 1 is known as a magnetically levitated pump in which a rotating shaft is magnetically levitated and supported without contact with a casing. The magnetically levitated pump described in Patent Document 1 includes a casing, a rotating shaft, a motor, and a magnetic bearing. The rotating shaft is supported rotatably in a radial direction without contact with the casing by magnetism generated by the magnetic bearing, and is rotationally driven by the motor.

[0003] The magnetic levitation pump further includes an impeller that rotates together with the rotary shaft within the casing. The impeller has a main plate and a plurality of blades provided on the main plate. When the impeller rotates together with the rotary shaft, a transfer fluid is sucked into the casing through a suction port formed on one axial side of the casing. The transfer fluid sucked into the casing is discharged by the plurality of blades of the impeller out of the casing through a discharge port formed on the outer periphery of the casing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-046860 Summary of the Invention [Problem to be solved by the invention]

[0005] In the magnetically levitated pump, the pressure of the fluid being transferred decreases near the suction port of the casing due to the structure of the centrifugal pump, which causes a pressure difference in the fluid being transferred in the axial direction inside the casing. When this pressure difference increases, the thrust force pressing the impeller toward one side in the axial direction (the suction port side) increases, and the impeller, which is supported only by magnetism, moves toward one side in the axial direction due to this thrust force, and there is a risk of it coming into contact with the casing and being damaged.

[0006] The present disclosure has been made in consideration of the above circumstances, and aims to provide a magnetic levitation pump that can suppress axial movement of the impeller. [Means for solving the problem]

[0007] (1) A magnetic levitation pump according to the present disclosure includes a rotating shaft rotatable about its axis, a motor that drives the rotating shaft, a magnetic bearing unit that supports the rotating shaft in a non-contact manner, a casing having a volute unit with a suction port for a transfer fluid formed on one axial side, and an impeller that is disposed within the volute unit and is rotatable integrally with the rotating shaft, and has an outlet for a transfer fluid formed on its outer periphery, and the volute unit has an annular top wall disposed on one axial side of the impeller, a bottom wall disposed on the other axial side of the impeller, and a casing having a volute unit with a suction port for a transfer fluid formed on the outer periphery of the impeller. and a cylindrical peripheral wall having both axial ends connected to the top wall and the bottom wall, respectively, the top wall having a radial inner wall portion disposed on one axial side of the impeller with a gap therebetween, and a radial outer wall portion disposed radially outward of the impeller, a volute flow path through which the transport fluid flowing out from the outlet flows is formed between the impeller and the peripheral wall and between the radial outer wall portion and the bottom wall in the volute portion so as to communicate with the gap, and at least a portion of the radial outer wall portion extends from a radial outer end of the radial inner wall portion to the one axial side.

[0008] According to the magnetic levitation pump of the present disclosure, the volute flow passage radially outward of the impeller within the volute section is formed by the radial outer wall portion of the top wall such that the flow passage cross-sectional area expands from the radial outer end of the gap between the radial inner wall portion of the top wall and the impeller toward one axial side (the suction port side). Because this expansion region is formed away from the impeller toward one axial side, the velocity of the transfer fluid flowing through the expansion region decreases, and the pressure of the transfer fluid within the expansion region increases. As a result, the increased pressure in the expansion region propagates to the gap, increasing the pressure of the transfer fluid within the gap, thereby increasing the thrust force pressing the impeller toward the other axial side. This makes it possible to suppress the impeller from moving toward one axial side due to a decrease in transfer fluid pressure near the suction port of the volute section, as in the prior art.

[0009] (2) In the magnetic levitation pump of (1), it is preferable that at least a portion of the radially outer wall portion extends obliquely from a radially outer end of the radially inner wall portion toward one axial side and radially outward. In this case, the transfer fluid in the expansion region of the volute flow path flows smoothly along the obliquely extending radial outer wall, which prevents the transfer fluid from stagnating in the expansion region, thereby preventing a decrease in the transfer performance of the magnetic levitation pump.

[0010] (3) In the magnetic levitation pump of (2), it is preferable that the radially outer wall portion extends obliquely toward one axial side and radially outward from the radially outer end of the radially inner wall portion to the peripheral wall. In this case, the transport fluid in the expanded region of the volute flow path flows more smoothly along the obliquely extending radial outer wall portion, thereby further preventing a decrease in the transport performance of the transport fluid of the magnetic levitation pump. [Effects of the Invention]

[0011] According to the magnetic levitation pump of the present disclosure, axial movement of the impeller can be suppressed. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic cross-sectional view showing a magnetic levitation pump according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a perspective view of the impeller as viewed from the axially lower side. [Figure 3] FIG. 2 is a cross-sectional view showing the inside of the impeller. [Figure 4] FIG. 2 is an enlarged cross-sectional view showing a main part of the volute portion. [Figure 5] 10 is a graph showing test results of the pressure of the transfer fluid in the first gap. [Figure 6] 10 is a graph showing test results of axial thrust force acting on an impeller. [Figure 7] 10 is a graph showing test results of the pump head. [Figure 8] FIG. 10 is an enlarged cross-sectional view showing a main part of a volute portion of a pump according to a second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0013] Next, preferred embodiments will be described with reference to the accompanying drawings. First Embodiment [Overall configuration] FIG. 1 is a schematic cross-sectional view showing a magnetically levitated pump 1 according to a first embodiment of the present disclosure. In FIG. 1, the magnetically levitated pump 1 of this embodiment (hereinafter also simply referred to as "pump 1") is a centrifugal pump. The pump 1 includes a casing 2, a rotating shaft 3, a motor 4, a pair of magnetic bearing units 5, and an impeller 6. Note that the pump 1 is arranged with its axis C oriented vertically, but it may also be arranged so that the axis C is horizontal.

[0014] Hereinafter, in this disclosure, the direction along the axis C of the pump 1 is the axial direction of the pump 1, and will be simply referred to as the "axial direction." Furthermore, the upper side (one axial side) of FIG. 1 will be referred to as the "axial upper side," and the lower side (the other axial side) of FIG. 1 will be referred to as the "axial lower side." The direction perpendicular to the axis C is the radial direction of the pump 1, and will be simply referred to as the "radial direction." The direction rotating around the axis C is the circumferential direction of the pump 1, and will be simply referred to as the "circumferential direction."

[0015] The casing 2 includes a housing portion 10 that houses the rotating shaft 3, and a volute portion 20 provided axially above the housing portion 10. The housing portion 10 has a cylindrical wall 11 and a disk wall 12 provided axially below the cylindrical wall 11. The cylindrical wall 11 is formed in a cylindrical shape centered on the axis C. The disk wall 12 is formed in a disk shape and closes an opening on the axially lower side of the cylindrical wall 11.

[0016] The rotating shaft 3 is disposed in the accommodation portion 10 so as to be rotatable about an axis C. The rotating shaft 3 is formed, for example, in a cylindrical shape. An upper end portion of the rotating shaft 3 in the axial direction is inserted into the volute portion 20.

[0017] The motor 4 drives the rotating shaft 3 to rotate. The motor 4 has a stator 41 provided in the housing 10 and a rotor 42 provided on the rotating shaft 3. The stator 41 is fixed to the axial center of the outer circumferential surface of the cylindrical wall 11. The rotor 42 is fixed to the inner circumferential surface of the rotating shaft 3 at a position radially opposite the stator 41. When a current is applied to the stator 41, a rotating magnetic field is generated, causing the rotor 42 to rotate together with the rotating shaft 3 around the axis C.

[0018] The pair of magnetic bearing units 5 support the rotating shaft 3 in a non-contact manner. Each magnetic bearing unit 5 has a magnetic field generating unit 51 provided in the housing unit 10 and a magnetic body 52 provided on the rotating shaft 3. The magnetic field generating units 51 are arranged on both axial sides of the stator 41 and are fixed to the outer circumferential surface of the cylindrical wall 11. The magnetic body 52 is fixed to the inner circumferential surface of the rotating shaft 3 in a position radially opposite the magnetic field generating unit 51. The rotating shaft 3 is supported in a non-contact manner by the magnetism generated by the magnetic field generating units 51 and the magnetic bodies 52.

[0019] The impeller 6 is disposed within the volute portion 20. The impeller 6 is provided axially above the rotary shaft 3 and is rotatable integrally with the rotary shaft 3 around the axis C. The impeller 6 is a closed impeller.

[0020] Fig. 2 is a perspective view of the impeller 6 as seen from below in the axial direction. Fig. 3 is a cross-sectional view showing the inside of the impeller 6. In Figs. 2 and 3, the impeller 6 includes a main plate 61, a plurality of blades 62, and a side plate (shroud) 63. The main plate 61 is formed in a disk shape centered on the axis C. The outer diameter of the main plate 61 is larger than the outer diameter of the rotary shaft 3. The upper end of the rotary shaft 3 in the axial direction is fixed to an outer surface 61a on the axial lower side of the main plate 61.

[0021] The plurality of blades 62 are provided at equal intervals in the circumferential direction on the inner surface 61b on the axially upper side of the main plate 61. Each blade 62 is formed, for example, in the shape of an arc plate. The impeller 6 of this embodiment has four blades 62. Note that the plate thickness, shape, and number of the blades 62 are not limited to those of this embodiment.

[0022] The side plate 63 is provided axially above the multiple blades 62. The side plate 63 is formed in an annular shape centered on the axis C. The side plate 63 of this embodiment extends obliquely axially downward and radially outward from its radially inner end to its radially outer end. The outer diameter of the side plate 63 is the same as the outer diameter of the main plate 61. The inner peripheral hole of the side plate 63 serves as an inlet 64 through which the transfer fluid flows into the impeller 6. The inlet 64 is formed radially inward of the multiple blades 62.

[0023] Between the main plate 61 and the side plate 63, between adjacent blades 62 in the circumferential direction, flow paths 65 are formed through which the transfer fluid that has flowed into the impeller 6 from the inlet 64 flows from the radially inner side to the radially outer side. The radially outer opening of each flow path 65 serves as an outlet 66 through which the transfer fluid flows out of the impeller 6. Therefore, a plurality of outlets 66 through which the transfer fluid flows out of the impeller 6 are formed on the outer periphery of the impeller 6.

[0024] [Volute section] 1 , the volute portion 20 has a top wall 21 and a bottom wall 22 formed in an annular shape centered on the axis C, and a peripheral wall 23 formed in a cylindrical shape centered on the axis C. The peripheral wall 23 is disposed radially outward of the impeller 6. An axially lower end of the peripheral wall 23 is connected to the radially outer end of the bottom wall 22. An axially upper end of the peripheral wall 23 is connected to the radially outer end of the top wall 21.

[0025] 4 is an enlarged cross-sectional view showing a main part of the volute portion 20. In FIGS. 1 and 4, the top wall 21 is disposed axially above the impeller 6. The top wall 21 has an annular radial inner wall portion 211 disposed radially inside and an annular radial outer wall portion 212 disposed radially outside. The radial inner wall portion 211 is disposed axially above the impeller 6 with a first gap (gap) S1 therebetween. The radial inner wall portion 211 is inclined parallel to the side plate 63 of the impeller 6. In other words, the radial inner wall portion 211 extends obliquely axially downward and radially outward from its radial inner end to its radial outer end.

[0026] The radially outer wall portion 212 is disposed radially outward of the impeller 6. A radially inner end of the radially outer wall portion 212 is connected to a radially outer end of the radially inner wall portion 211. A radially outer end of the radially outer wall portion 212 is connected to an axially upper end of the peripheral wall 23. The radially outer wall portion 212 extends obliquely axially upward and radially outward from the radially outer end of the radially inner wall portion 211 to the peripheral wall 23.

[0027] The bottom wall 22 is disposed axially below the impeller 6. In this embodiment, the bottom wall 22 is disposed axially below the impeller 6 with a second gap S2 therebetween. The bottom wall 22 extends straight radially outward in parallel with the outer surface 61a of the main plate 61. The inner peripheral edge of the bottom wall 22 is connected to the axially upper opening edge of the cylindrical wall 11 of the accommodating section 10. This allows the internal space of the volute section 20 to communicate with the internal space of the accommodating section 10.

[0028] Volute section 20 further has a cylindrical suction section 25 and a cylindrical discharge section 26. Suction section 25 is provided so as to protrude axially upward from the inner peripheral edge of radially inner wall section 211 of top wall 21. Suction section 25 has a suction port 25a that draws the transferred fluid into volute section 20. Therefore, suction port 25a for the transferred fluid is formed on the axially upper side of volute section 20. Discharge section 26 is provided at a predetermined position on the outer periphery of peripheral wall 23. Discharge section 26 has a discharge port 26a that discharges the transferred fluid out of volute section 20.

[0029] A substantially annular volute passage 24 is formed inside the volute portion 20, through which the transport fluid flowing out from the outlet 66 of the impeller 6 flows. The volute passage 24 is formed between the impeller 6 and the peripheral wall 23, and between the radially outer wall portion 212 of the top wall 21 and the bottom wall 22. The volute passage 24 is in communication with the first gap S1 and the second gap S2. The volute passage 24 has a substantially annular expansion region 24a formed on the axially upper side. The expansion region 24a is formed so that the flow path cross-sectional area of ​​the volute passage 24 expands obliquely from the radially outer end of the first gap S1 toward the axially upper side and radially outward.

[0030] [Transport fluid flow] 1 to 4 , when the rotating shaft 3 is driven to rotate by the motor 4, the impeller 6 rotates together with the rotating shaft 3 around the axis C, and the transfer fluid is sucked into the volute section 20 from the suction port 25a of the suction section 25. The transfer fluid sucked into the volute section 20 flows into the impeller 6 from the inlet 64 of the impeller 6 and flows radially from the radially inner side to the radially outer side of the impeller 6 due to the centrifugal force generated by the rotation of the impeller 6. As a result, the transfer fluid passes through the flow passages 65 between adjacent blades 62 and flows out into the volute passage 24 from each outlet 66 on the outer periphery of the impeller 6. Most of the transfer fluid that flows out into the volute passage 24 flows circumferentially within the volute passage 24, flows into the discharge section 26, and is discharged from the discharge port 26a to the outside of the volute section 20. The remaining part of the transfer fluid that flows out into the volute flow path 24 flows into the first gap S1 and the second gap S2.

[0031] The velocity of the transfer fluid flowing circumferentially within the volute channel 24 gradually decreases as the fluid moves axially upward and radially outward from the rotating impeller 6. In contrast, the flow path cross-sectional area of ​​the expansion region 24a of the volute channel 24 expands axially upward and radially outward. Therefore, the velocity of the transfer fluid flowing through the expansion region 24a is lower than the velocity of the transfer fluid flowing through other regions of the volute channel 24.

[0032] When the velocity of the transfer fluid in the expansion region 24a decreases, the pressure of the transfer fluid in the expansion region 24a increases. As a result, the increased pressure in the expansion region 24a is transmitted to the first gap S1, and the pressure of the transfer fluid in the first gap S1 increases. This increase in pressure increases the thrust force that presses the impeller 6 axially downward.

[0033] [Effectiveness verification test] A test was conducted to confirm the operational effects of the pump 1 of this embodiment. In this test, the pressure of the transported fluid in the first gap S1, the axial thrust force, and the head during operation were calculated using fluid analysis software for a conventional pump and the pump 1 of this embodiment.

[0034] Fig. 5 is a graph showing test results for the pressure of the transferred fluid in the first gap S1. As shown in Fig. 5, it was confirmed that the pump 1 of this embodiment has a higher transferred fluid pressure in the range from the radial middle to the outer end of the first gap S1 than the conventional pump. It can be seen that the increased pressure of the transferred fluid in the first gap S1 increases the thrust force that presses the impeller 6 axially downward.

[0035] FIG. 6 is a graph showing test results of the axial thrust force acting on the impeller 6. Here, the axial thrust force acting on the impeller 6 is the difference between the thrust force pressing the impeller 6 axially upward (positive side) and the thrust force pressing the impeller 6 axially downward (negative side). Therefore, the smaller the axial thrust force, the more the axial movement of the impeller 6 is suppressed. As shown in FIG. 6, it was confirmed that the axial thrust force on the positive side of the pump 1 of this embodiment is significantly lower than that of the conventional pump, and therefore the axial movement of the impeller 6 is suppressed.

[0036] Fig. 7 is a graph showing test results for the head of pump 1. Generally, when the axial thrust force acting on impeller 6 is significantly reduced, the head of pump 1 also significantly reduces accordingly. However, as shown in Figs. 6 and 7, it was confirmed that, in pump 1 of this embodiment, the degree of reduction in head is suppressed compared to conventional pump 1, even when the axial thrust force is significantly reduced.

[0037] [Action and effect] In the magnetic levitation pump 1 of the first embodiment, the top wall 21 of the volute section 20 has a radially inner wall section 211 disposed axially upward (toward the suction port 25a) with respect to the impeller 6 with a first gap S1 therebetween, and a radially outer wall section 212 extending obliquely axially upward and radially outward from the radially outer end of the radially inner wall section 211. As a result, an expansion region 24a is formed in the volute flow path 24 within the volute section 20 such that the flow path cross-sectional area expands obliquely from the radially outer end of the first gap S1 axially upward and radially outward. Because the expansion region 24a is formed axially upward and away from the impeller 6, the speed of the transport fluid flowing through the expansion region 24a decreases, and the pressure of the transport fluid within the expansion region 24a increases. As a result, the pressure increased in the expansion region 24a is transmitted to the first gap S1, and the pressure of the transferred fluid in the first gap S1 increases, thereby increasing the thrust force pressing the impeller 6 downward in the axial direction. This makes it possible to prevent the impeller 6 from moving upward in the axial direction due to a decrease in the pressure of the transferred fluid near the suction port 25a of the volute portion 20, as in the conventional case.

[0038] Furthermore, the transfer fluid in the expansion region 24a flows smoothly along the obliquely extending radial outer wall portion 212 of the top wall 21, which prevents the transfer fluid from accumulating in the expansion region 24a. As a result, the transfer performance of the pump 1 for the transfer fluid can be prevented from decreasing.

[0039] Second Embodiment 8 is an enlarged cross-sectional view showing a main portion of the volute portion 20 of a magnetically levitated pump 1 according to a second embodiment of the present disclosure. In this embodiment, the shape of the radially outer wall portion 212 of the top wall 21 in the volute portion 20 differs from that of the first embodiment. The radially outer wall portion 212 of the top wall 21 in this embodiment has a first wall portion 213 located radially inside the volute passage 24 and a second wall portion 214 located radially outside the volute passage 24.

[0040] The radially inner end of the first wall portion 213 is connected to the radially outer end of the radially inner wall portion 211. The first wall portion 213 extends obliquely axially upward and radially outward from the radially outer end of the radially inner wall portion 211. The radially inner end of the second wall portion 214 is connected to the radially outer end of the first wall portion 213. The second wall portion 214 extends straight radially outward from the radially outer end of the first wall portion 213 in parallel to the bottom wall 22. The radially outer end of the second wall portion 214 is connected to the axially upper end of the peripheral wall 23. Since other configurations of this embodiment are similar to those of the first embodiment, the same reference numerals are used and descriptions thereof will be omitted.

[0041] According to this embodiment, the flow path cross-sectional area of ​​the expansion region 24a of the volute flow path 24 is formed larger radially outward than in the first embodiment (see FIG. 4). Therefore, the speed of the transfer fluid flowing through the expansion region 24a further decreases, and the pressure of the transfer fluid in the expansion region 24a further increases. As a result, the pressure of the transfer fluid in the first gap S1 further increases, and the thrust force pressing the impeller 6 axially downward further increases. This effectively prevents the impeller 6 from moving axially upward due to a decrease in the pressure of the transfer fluid near the suction port 25a of the volute portion 20, as in the conventional case.

[0042] Furthermore, the transfer fluid in the expansion region 24a flows smoothly along the slope of the first wall portion 213, which is part of the radially outer wall portion 212, and therefore, the transfer fluid is prevented from accumulating in the expansion region 24a. As a result, the transfer performance of the pump 1 for the transfer fluid is prevented from decreasing.

[0043] <Other> The first wall portion 213 of the top wall 21 in the second embodiment extends obliquely axially upward and radially outward from the radial outer end of the radial inner wall portion 211, but may extend straight axially upward from the radial outer end of the radial inner wall portion 211. Furthermore, the second wall portion 214 of the top wall 21 in the second embodiment extends straight radially outward from the radial outer end of the first wall portion 213, but may extend obliquely axially downward and radially outward from the radial outer end of the first wall portion 213.

[0044] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above meaning, and is intended to include any modifications within the scope of the claims and meaning equivalent to the claims. [Explanation of symbols]

[0045] 1. Magnetic levitation pump 2 Casing 3 Rotation Axis 4 motors 5 Magnetic bearing section 6 impeller 20 Volute section 21 Ceiling wall 22 Bottom wall 23 Peripheral wall 24 Volute passage 25a Intake port 66 Exit 211 Inner wall of diameter 212 diameter outer wall C axis S1 First gap (gap)

Claims

1. A rotation shaft that is rotatable around an axis line; a motor that rotates the rotary shaft; a magnetic bearing portion that supports the rotating shaft in a non-contact manner; a casing having a volute portion on one axial side of which is formed a suction port for a fluid to be transferred; an impeller disposed within the volute portion and rotatable integrally with the rotary shaft, the impeller having an outlet for the transported fluid formed on its outer periphery, The volute portion is an annular top wall disposed on one side of the impeller in the axial direction; a bottom wall disposed on the other axial side of the impeller; a cylindrical peripheral wall disposed radially outward of the impeller, the peripheral wall having opposite axial ends connected to the top wall and the bottom wall, the top wall has a radially inner wall portion disposed on one axial side of the impeller with a gap therebetween, and a radially outer wall portion disposed radially outward of the impeller, a volute flow path through which a transfer fluid flowing out from the outlet flows is formed between the impeller and the peripheral wall and between the radially outer wall portion and the bottom wall in the volute portion, the volute flow path communicating with the gap; At least a portion of the radially outer wall portion extends from a radially outer end of the radially inner wall portion to one side in the axial direction.

2. 2. The magnetic levitation pump according to claim 1, wherein at least a portion of the radially outer wall portion extends obliquely from a radially outer end of the radially inner wall portion toward one axial side and radially outward.

3. 3. The magnetic levitation pump according to claim 2, wherein the radially outer wall portion extends obliquely toward one axial side and radially outward from a radially outer end of the radially inner wall portion to the circumferential wall.

Images