Magnetic levitation pump

Abstract

To provide a magnetic levitation pump that can keep an impeller from shifting in a radial direction during rotation with a simple structure.SOLUTION: A casing of a magnetic levitation pump includes: a volute part having a single volute flow passage formed in the inside so that a transfer fluid flows around an impeller; and a discharge part connected to the volute part, and having a discharge flow passage formed in the inside to discharge a transfer fluid from the volute flow passage. The volute part has: a tongue end serving as a winding starting end of the volute flow passage; and a bulged part bulged such that the volume flow passage expands partially in a predetermined range including a first opposing position of 180° around the rotational center of the impeller relative to the tongue end. The bulged part is bulged so that an area where the pressure of a transfer fluid lowers due to connection between the volute part and the discharge part and an area where the pressure of a transfer fluid lowers due to the bulged part can easily form in the volute flow passage in point symmetry to the rotational center.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a magnetic levitation pump.

Background Art

[0002] As a magnetic levitation pump that magnetically levitates a rotating shaft with respect to a casing and supports it in a non-contact manner, the one described in Patent Document 1 is known. The magnetic levitation pump described in Patent Document 1 includes a casing, a rotating shaft, a motor, and a magnetic bearing. The rotating shaft is rotatably supported in a non-contact manner in the radial direction with respect to the casing by the magnetism generated from the magnetic bearing, and is rotationally driven by a motor.

[0003] The magnetic levitation pump further includes an impeller that rotates together with the rotating shaft inside the casing. When the impeller rotates together with the rotating shaft, the transfer fluid is sucked into the casing from the suction port formed in the casing. The transfer fluid sucked into the casing is discharged outside the casing from the discharge port formed on the outer periphery of the casing by the impeller.

[0004] The impeller is supported in a non-contact manner in the radial direction together with the rotating shaft by a magnetic bearing. For this reason, if the radial fluid force (radial force) acting on the rotating impeller becomes non-uniform in the circumferential direction due to the transfer fluid, the impeller may shift in the radial direction, and there is a risk that the impeller will contact the casing and be damaged. Therefore, in order to suppress the radial displacement of the impeller, it is conceivable to adopt a double volute structure (double spiral structure) used in general pumps (see, for example, FIG. 2 of Patent Document 2).

[0005] In the casing of the pump described in Patent Document 2, a partition wall (stator vane) is provided radially outward of the impeller, and two volute channels are formed with the partition wall in between. The tongue end (starting end) of the partition wall is arranged at a position 180° opposite to the tongue end formed near the discharge port of the casing. Due to these two tongue ends, the pressure distribution of the fluid being transferred in the casing occurs point-symmetrically with respect to the center of the impeller. As a result, the radial force acting on the impeller at an arbitrary position in the circumferential direction and the radial force acting on the impeller at a position 180° opposite to the arbitrary position cancel each other out, so that it is possible to suppress the radial displacement of the impeller during rotation.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] When the above double volute structure is adopted, a partition wall for forming two volute channels in the casing is separately required, and a structure for attaching the partition wall to the casing is also required. For this reason, there is a problem that the number of parts increases and the structure becomes complicated.

[0008] The present disclosure has been made in view of such circumstances, and an object thereof is to provide a magnetic levitation pump that can suppress the radial displacement of the impeller during rotation with a simple configuration.

Means for Solving the Problems

[0009] (1) The magnetic levitation pump of the present disclosure includes a rotating shaft rotatable about an axis, a motor that rotationally drives the rotating shaft, a magnetic bearing portion that supports the rotating shaft in a non-contact manner, an impeller provided integrally rotatably with the rotating shaft, and a casing that houses the impeller. The casing includes a volute portion in which a single volute flow path is formed so that a transfer fluid flows around the impeller, and a discharge portion connected to the volute portion and having a discharge flow path formed therein for discharging the transfer fluid from the volute flow path. The volute portion has a tongue end that is the start end of the volute flow path, and a bulging portion that bulges so that the volute flow path partially expands in a predetermined range including a first opposing position of 180° centered on the rotation center of the impeller with respect to the tongue end. The bulging portion bulges so that in the volute flow path, a region where the pressure of the transfer fluid decreases due to the connection between the volute portion and the discharge portion and a region where the pressure of the transfer fluid decreases due to the bulging portion are likely to occur point-symmetrically with respect to the rotation center.

[0010] According to the magnetic levitation pump of the present disclosure, the volute portion in which a single volute flow path is formed therein has a bulging portion that bulges so as to partially expand the volute flow path in a predetermined range including a first opposing position of 180° centered on the rotation center of the impeller with respect to the tongue end. Due to this bulging portion, in the volute flow path, a region where the pressure of the transfer fluid decreases due to the connection between the volute portion and the discharge portion and a region where the pressure of the transfer fluid decreases due to the bulging portion are likely to occur point-symmetrically with respect to the rotation center. As a result, in both regions where the pressure decreases, the radial forces acting on the impeller cancel each other out. Therefore, it is possible to suppress the radial displacement of the impeller during rotation with a simple configuration without using a partition wall as in the prior art.

[0011] (2) In the magnetic levitation pump according to (1) above, the volute part has the tongue end, and includes a first peripheral wall part formed from the tongue end to the bulging part, and a second peripheral wall part having the winding end of the volute flow path and formed from the bulging part to the winding end. It is preferable that both the first peripheral wall part and the second peripheral wall part have an inner surface in the shape of an arc with the same radius of curvature in a cross-sectional view perpendicular to the axial direction. In this case, since the inner surfaces of the first peripheral wall part and the second peripheral wall part of the volute part are both formed in the shape of an arc with the same radius of curvature, it is easier for both regions where the pressure drops to occur point-symmetrically with respect to the rotation center of the impeller. As a result, it is possible to further suppress the radial displacement of the impeller during rotation.

[0012] (3) In the magnetic levitation pump according to (2) above, the predetermined range in which the bulging part bulges is preferably an angular range from a position 45° away from the first opposing position on the first peripheral wall part side with respect to the rotation center to a position 45° away from the first opposing position on the second peripheral wall part side with respect to the rotation center, with the rotation center as the center. In this case, it is easier for both regions where the pressure drops to occur point-symmetrically with respect to the rotation center of the impeller. As a result, it is possible to further suppress the radial displacement of the impeller during rotation.

[0013] (4) In the magnetic levitation pump according to (2) or (3) above, the bulging start position where the bulging part starts to bulge from the first peripheral wall part is preferably located at a second opposing position of 180° with respect to the winding end, with the rotation center as the center. In this case, it is easier for both regions where the pressure drops to occur point-symmetrically with respect to the rotation center of the impeller. As a result, it is possible to further suppress the radial displacement of the impeller during rotation.

[0014] (5) In the magnetic levitation pump according to any one of (2) to (4) above, the bulging part preferably has a first end part formed to bulge smoothly from the first peripheral wall part and a second end part formed to bulge smoothly from the second peripheral wall part. In this case, since the first end portion and the second end portion of the bulging portion bulge smoothly from the first peripheral wall portion and the second peripheral wall portion respectively, even if the volute flow path is partially expanded by the bulging portion, the pressure loss of the transferred fluid associated with the expansion can be reduced.

[0015] (6) In the magnetic levitation pump according to any one of (1) to (5) above, the bulging portion has an inner surface facing the volute flow path, and the inner surface of the bulging portion is preferably formed in an arc shape in a cross-sectional view in the axial direction. In this case, since the inner surface of the bulging portion facing the volute flow path is formed in an arc shape in a cross-sectional view, even if the volute flow path is partially expanded by the bulging portion, the generation of a secondary flow (eddy) of the transferred fluid in the expanded portion can be suppressed. Thereby, the pressure loss of the transferred fluid associated with the expansion of the volute flow path can be further reduced.

Advantages of the Invention

[0016] According to the present disclosure, with a simple configuration, it is possible to suppress the radial displacement of the impeller during rotation.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0018] 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 magnetic levitation pump 1 according to the first embodiment of the present disclosure. FIG. 2 is a cross-sectional view taken along the line I-I of FIG. 1. In FIGS. 1 and 2, the magnetic levitation pump 1 of the present embodiment (hereinafter, also simply referred to as "pump 1") is a centrifugal pump. The pump 1 includes a housing 2, a rotating shaft 3, a motor 4, a pair of magnetic bearing portions 5, and an impeller 6. Note that the pump 1 is arranged with its axis C in the vertical direction, but it may be arranged such that the axis C is in the horizontal direction.

[0019] Hereinafter, in the present disclosure, the direction along the axis C of the pump 1 is the axial direction of the pump 1, and is simply referred to as the "axial direction". Also, the upper side of FIG. 1 is referred to as the "upper side in the axial direction" of the pump 1, and the lower side of FIG. 1 is referred to as the "lower side in the axial direction" of the pump 1. The direction orthogonal to the axis C is the radial direction of the pump 1, and is simply referred to as the "radial direction". The direction of rotation about the axis C is the circumferential direction of the pump 1, and is simply referred to as the "circumferential direction".

[0020] The housing 2 includes a first casing 10 that houses the rotating shaft 3 and a second casing (casing) 20 that houses the impeller 6. The first casing 10 has a cylindrical wall 11 and a bottom wall 12 provided on the lower side in the axial direction of the cylindrical wall 11. The cylindrical wall 11 is formed in a cylindrical shape centered on the axis C. The bottom wall 12 is formed in a disc shape and closes the opening on the lower side in the axial direction of the cylindrical wall 11.

[0021] The second casing 20 is provided on the upper side in the axial direction of the first casing 10. The second casing 20 includes a volute portion 21. The outer shape of the volute portion 21 (excluding the bulging portion 33 described later) is formed in a circular shape in a plan view seen from the axial direction. A single volute structure is adopted inside the volute portion 21. That is, a single volute flow path 21a is formed inside the volute portion 21. The volute flow path 21a is formed in a substantially annular shape so that the transfer fluid flows around the impeller 6.

[0022] The volute portion 21 has a peripheral wall 22 formed in a cylindrical shape, a top wall 23 provided on the upper side in the axial direction of the peripheral wall 22, and a bottom wall 24 provided on the lower side in the axial direction of the peripheral wall 22. The peripheral wall 22 has a first peripheral wall portion 31, a second peripheral wall portion 32, and a bulging portion 33. The first peripheral wall portion 31 is formed from the tongue end 31a (described later) to the connection end P2 (described later) of the bulging portion 33. The first peripheral wall portion 31 has an inner surface 31b facing the volute flow path 21a. The inner surface 31b is formed in an arc shape centered on the axis C in a cross-sectional view perpendicular to the axial direction (Figure 2). The inner surface 31b of the first peripheral wall portion 31 is formed in a flat shape that extends straight in the axial direction, similar to the inner surface 33a (see Figure 3) of the bulging portion 33 described later, in a cross-sectional view in the axial direction.

[0023] The second circumferential wall portion 32 is formed from the connection end P3 (described later) of the bulging portion 33 to the winding end 32a (described later). The second circumferential wall portion 32 has an inner surface 32b facing the volute flow path 21a. The inner surface 32b is formed in an arc shape with the same radius of curvature as the inner surface 31b of the first circumferential wall portion 31 around the axis C in a cross-sectional view perpendicular to the axial direction (FIG. 2). The inner surface 32b of the second circumferential wall portion 32 is formed in a flat shape that extends straight in the axial direction, similar to the inner surface 31b of the first circumferential wall portion 31, in a cross-sectional view in the axial direction. Details of the bulging portion 33 will be described later.

[0024] The top wall 23 of the volute portion 21 is formed in a substantially conical plate shape. The outer peripheral edge of the top wall 23 is connected to the opening edge on the upper side in the axial direction of the circumferential wall 22. The bottom wall 24 of the volute portion 21 is formed in a substantially annular shape. The outer peripheral edge of the bottom wall 24 is connected to the opening edge on the lower side in the axial direction of the circumferential wall 22. The inner peripheral edge of the bottom wall 24 is connected to the opening edge on the upper side in the axial direction of the cylindrical wall 11 of the first casing 10. Thereby, the internal space of the second casing 20 communicates with the internal space of the first casing 10.

[0025] The second casing 20 further has a suction portion 25 and a discharge portion 26. The suction portion 25 is provided so as to protrude upward in the axial direction at the central portion of the top wall 23 of the volute portion 21. The suction portion 25 is formed in a cylindrical shape around the axis C. Inside the suction portion 25, a suction flow path 25a for sucking the transfer fluid into the volute portion 21 is formed. The opening on the upper side in the axial direction of the suction portion 25 serves as a suction port 25b for the transfer fluid.

[0026] The discharge portion 26 is connected to the circumferential wall 22 of the volute portion 21. The discharge portion 26 of the present embodiment is provided between the first circumferential wall portion 31 and the second circumferential wall portion 32. The discharge portion 26 protrudes from the circumferential wall 22 so as to extend in the tangential direction of the second circumferential wall portion 32. Inside the discharge portion 26, a discharge flow path 26a for discharging the transfer fluid from the volute flow path 21a to the outside of the second casing 20 is formed. The opening on the protruding end side of the discharge portion 26 serves as a discharge port 26b for the transfer fluid.

[0027] The connecting portion of the first peripheral wall portion 31 with the discharge portion 26 is formed to taper toward the inside of the second casing 20. The tip of the connecting portion serves as the starting end of the volute flow path 21a. That is, the first peripheral wall portion 31 has a tongue end 31a that serves as the starting end of the volute flow path 21a. The second peripheral wall portion 32 has an ending end 32a of the volute flow path 21a. The ending end 32a is the connection end of the second peripheral wall portion 32 with the discharge portion 26.

[0028] The rotating shaft 3 is rotatably arranged within the first casing 10 about the axis C. The rotating shaft 3 is formed, for example, in a cylindrical shape. The upper end portion in the axial direction of the rotating shaft 3 extends into the second casing 20.

[0029] The motor 4 rotationally drives the rotating shaft 3. The motor 4 has a stator 41 provided on the first casing 10 and a rotor 42 provided on the rotating shaft 3. The stator 41 is fixed to the central portion in the axial direction of the outer peripheral surface of the cylindrical wall 11. The rotor 42 is fixed at a position radially opposed to the stator 41 on the inner peripheral surface of the rotating shaft 3. When an electric current is applied to the stator 41, a rotating magnetic field is generated, causing the rotor 42 to rotate about the axis C together with the rotating shaft 3.

[0030] A pair of magnetic bearing portions 5 supports the rotating shaft 3 in a non-contact manner. Each magnetic bearing portion 5 has a magnetic generating portion 51 provided on the first casing 10 and a magnetic body 52 provided on the rotating shaft 3. The magnetic generating portion 51 is arranged on both axial sides of the stator 41 and fixed to the outer peripheral surface of the cylindrical wall 11. The magnetic body 52 is fixed at a position radially opposed to the magnetic generating portion 51 on the inner peripheral surface of the rotating shaft 3. The rotating shaft 3 is supported in a non-contact manner by the magnetism generated by the magnetic generating portion 51 and the magnetic body 52.

[0031] The impeller 6 is arranged within the second casing 20. The impeller 6 is provided on the upper side in the axial direction of the rotating shaft 3 and is integrally rotatable about the axis C together with the rotating shaft 3. The rotation direction of the rotating shaft 3 and the impeller 6 in the present embodiment is the clockwise direction in FIG. 2. The impeller 6 includes a base portion 61 and a plurality of blades 62.

[0032] The base portion 61 is formed, for example, in a disc shape. The outer diameter of the base portion 61 is larger than the outer diameter of the rotating shaft 3. The upper end in the axial direction of the rotating shaft 3 is fixed to the end surface on the lower side in the axial direction of the base portion 61. The plurality of blades 62 are fixed to the end surface on the upper side in the axial direction of the base portion 61. The plurality of blades 62 are arranged at equal intervals in the circumferential direction of the base portion 61. The impeller 6 of the present embodiment includes five blades 62.

[0033] When the rotating shaft 3 is rotationally driven by the motor 4, the impeller 6 rotates about the axis C together with the rotating shaft 3, and the transfer fluid is sucked from the suction port 25b of the suction portion 25 through the suction flow path 25a into the central portion in the volute portion 21. The transfer fluid sucked into the volute portion 21 flows radially outward from the central portion of the impeller 6 due to the centrifugal force accompanying the rotation of the impeller 6. Thereby, the transfer fluid passes between adjacent blades 62 and flows into the volute flow path 21a. The transfer fluid that has flowed into the volute flow path 21a flows from the end 32a where the volute flow path 21a ends into the discharge flow path 26a of the discharge portion 26 and is discharged outside the second casing 20 from the discharge port 26b.

[0034] [Bulging portion] The bulging portion 33 of the volute portion 21 is provided between the first peripheral wall portion 31 and the second peripheral wall portion 32. The bulging portion 33 bulges radially outward from the virtual arc K so that the volute flow path 21a expands partially. The virtual arc K is an arc having the same radius of curvature as the inner surfaces 31b and 32b of the first peripheral wall portion 31 and the second peripheral wall portion 32. The bulging portion 33 bulges in a predetermined range including the first opposing position P1. The first opposing position P1 is an opposing position rotated 180° from the tongue end 31a of the first peripheral wall portion 31 about the rotation center (axis C) of the impeller 6. Hereinafter, the rotation center of the impeller 6 is also referred to as the rotation center C.

[0035] In the present embodiment, the predetermined range in which the bulging portion 33 bulges in the volute portion 21 is an angular range of ±45° with respect to the first opposing position P1. That is, the predetermined range is an angular range from a position P2 that is 45° away from the first opposing position P1 toward the first peripheral wall portion 31 side around the rotation center C of the impeller 6 to a position P3 that is 45° away from the first opposing position P1 toward the second peripheral wall portion 32 side. The position P2 is the connection end of the bulging portion 33 with the first peripheral wall portion 31. The position P3 is the connection end of the bulging portion 33 with the second peripheral wall portion 32. Hereinafter, the connection end of the bulging portion 33 with the first peripheral wall portion 31 and the connection end with the second peripheral wall portion 32 are also referred to as the connection end P2 and the connection end P3, respectively.

[0036] The position P2 is the bulging start position where the bulging portion 33 starts to bulge from the first peripheral wall portion 31 and is located at the second opposing position. The second opposing position is an opposing position rotated 180° from the winding end 32a of the volute flow path 21a around the rotation center C of the impeller 6. Hereinafter, the second opposing position is also referred to as the second opposing position P2.

[0037] The bulging portion 33 has a first end portion 331 having a connection end P2 with the first peripheral wall portion 31, a second end portion 332 having a connection end P3 with the second peripheral wall portion 32, and an intermediate portion 333 connecting the first end portion 331 and the second end portion 332.

[0038] The first end portion 331 is formed so as to bulge smoothly from the first peripheral wall portion 31. In the cross-sectional view of FIG. 2, the first end portion 331 of the present embodiment extends straight in the tangential direction of the first peripheral wall portion 31 from the connection end P2 with the first peripheral wall portion 31. Specifically, the first end portion 331 extends parallel and in the opposite direction (the downward direction in FIG. 2) to the direction in which the discharge portion 26 extends (the upward direction in FIG. 2).

[0039] The second end portion 332 is formed so as to bulge smoothly from the second peripheral wall portion 32. In the cross-sectional view of FIG. 2, the second end portion 332 of the present embodiment is formed in a concave curved shape so as to extend in a substantially tangential direction of the second peripheral wall portion 32 from the connection end P3 with the second peripheral wall portion 32.

[0040] The middle portion 333 is smoothly connected to the first end portion 331 and the second end portion 332. In the cross-sectional view of FIG. 2, the middle portion 333 of the present embodiment is formed in a concave curved shape with a curvature smaller than that of the second peripheral wall portion 32. The middle portion 333 is formed such that the first opposing position P1 becomes the maximum bulging position. The maximum bulging position is the position where the bulging portion 33 bulges most radially outward with respect to the virtual circular arc K.

[0041] FIG. 3 is a cross-sectional view taken along the line II-II of FIG. 2 at the first opposing position P1 of the volute portion 21. In FIG. 3, the cross-sectional view of the impeller 6 is omitted. In FIG. 3, the bulging portion 33 has an inner surface 33a facing the volute flow path 21a. Both axial ends of the inner surface 33a are connected to the top wall 23 and the bottom wall 24. Both circumferential ends of the inner surface 33a of the bulging portion 33 are connected to the inner surfaces 31b and 32b of the first peripheral wall portion 31 and the second peripheral wall portion 32, respectively (see FIG. 2).

[0042] The inner surface 33a of the bulging portion 33 of the present embodiment is formed in a flat shape that extends straight in the axial direction in the cross-sectional view in the axial direction (FIG. 3). The flat shape of the inner surface 33a is formed over the entire circumferential direction of the bulging portion 33. That is, the flat shape of the inner surface 33a is formed from the first end portion 331 through the middle portion 333 to the second end portion 332.

[0043] [Mechanism for the impeller to shift radially] FIG. 4 is a diagram for explaining the direction in which the transfer fluid flows at the end 32a of the winding end and the second opposing position P2 in the volute portion 21 when the volute portion 21 does not have the bulging portion 33. As shown in FIG. 4, at the end 32a of the winding end of the volute portion 21 that does not have the bulging portion 33, the direction of the main flow F1 in which the transfer fluid mainly flows in the volute flow path 21a is the direction guided by the tongue end 31a to the discharge flow path 26a. That is, the direction of the main flow F1 is the direction that extends straight in the tangential direction of the second peripheral wall portion 32. On the other hand, at the end 32a of the winding end, the direction of the outflow flow F2 in which the transfer fluid flows out from the outer periphery of the rotating impeller 6 into the volute flow path 21a is the direction of the combined velocity of the rotational direction flow f21 and the radial direction flow f22.

[0044] On the other hand, at the second opposing position P2 in FIG. 4, the direction of the main flow F3 in which the transfer fluid in the volute flow path 21a mainly flows is the rotational direction along the volute flow path 21a. In contrast, at the second opposing position P2 in FIG. 4, the direction of the outflow flow F4 in which the transfer fluid flows out from the outer periphery of the rotating impeller 6 into the volute flow path 21a is the direction of the combined velocity of the velocity of the rotational direction flow f41 and the velocity of the radial direction flow f42.

[0045] As described above, when the volute portion 21 does not have the bulging portion 33, the angular difference α1 between the direction of the main flow F1 and the direction of the outflow flow F2 at the winding end 32a is relatively small. In contrast, the angular difference α2 between the direction of the main flow F3 and the direction of the outflow flow F4 at the second opposing position P2 is relatively large.

[0046] FIG. 5 is a diagram showing the pressure distribution of the transfer fluid in the volute flow path 21a and the discharge flow path 25a in the volute portion 21 of FIG. 4. In FIG. 5, the closer the hatching interval is, the higher the pressure of the transfer fluid is (the same applies to FIG. 7). In FIGS. 4 and 5, when the angular difference α1 becomes small as described above, in the region R1 slightly downstream of the winding end 32a in the volute flow path 21a, due to the connection between the volute portion 21 and the discharge portion 26, the flow velocity of the transfer fluid increases and the pressure of the transfer fluid decreases.

[0047] On the other hand, when the angular difference α2 becomes large as described above, in the region R2 slightly downstream of the second opposing position P2 in the volute flow path 21a, the flow velocity of the transfer fluid decreases and the pressure of the transfer fluid increases. As a result, the radial force acting on the impeller 6 in the region R2 is larger than the radial force acting on the impeller 6 in the region R1. The region R2 is located at the 180° opposing position with respect to the region R1 with the rotation center C of the impeller 6 as the center. Therefore, when the volute portion 21 does not have the bulging portion 33, the impeller 6 supported non - contact by the magnetic bearing portion 5 is likely to shift in the radial direction (the direction of the arrow in FIG. 5) during rotation.

[0048] [Mechanism for Suppressing Radial Displacement of Impeller] FIG. 6 is a diagram for explaining the direction in which the transfer fluid flows in the volute portion 21 having the bulging portion 33 of the present embodiment at the end 32a of winding and the second facing position P2. Since the directions of the main flow and the discharge flow of the transfer fluid at the end 32a of winding in FIG. 6 are the same as the directions of the main flow F1 and the outflow flow F2 of the transfer fluid at the end 32a of winding in FIG. 4, the same reference numerals are given and the description thereof is omitted.

[0049] At the second facing position P2 in FIG. 6, the direction of the main flow F5 in which the transfer fluid mainly flows in the volute flow path 21a is the direction of flowing along the first end portion 331 by the bulging portion 33, that is, the direction extending straight in the tangential direction of the first peripheral wall portion 31. On the other hand, at the second facing position P2 in FIG. 6, the direction of the outflow flow F6 in which the transfer fluid flows out from the outer periphery of the rotating impeller 6 to the volute flow path 21a is the direction of the combined velocity of the velocity of the rotational direction flow f61 and the velocity of the radial direction flow f62.

[0050] As described above, when the volute portion 21 has the bulging portion 33, the angle difference α3 between the direction of the main flow F5 and the direction of the outflow flow F6 at the second facing position P2 becomes relatively small, similar to the angle difference α1 between the direction of the main flow F1 and the direction of the outflow flow F2 at the end 32a of winding. Thereby, the angle difference α1 and the angle difference α3 can be approximated.

[0051] FIG. 7 is a diagram showing the pressure distribution of the transfer fluid in the volute flow path 21a and the discharge flow path 25a in the volute portion 21 of FIG. 6. In FIGS. 6 and 7, when the angle difference α1 becomes small as described above, in the region R3 slightly downstream of the end 32a in the volute flow path 21a, the flow velocity of the transfer fluid increases and the pressure of the transfer fluid decreases. When the angle difference α3 becomes small as described above, in the region R4 slightly downstream of the second facing position P2 in the volute flow path 21a, due to the bulging portion 33, the flow velocity of the transfer fluid increases and the pressure of the transfer fluid decreases. The region R4 is located at a position 180° opposite to the region R3 with respect to the rotation center C of the impeller 6.

[0052] Therefore, in the volute flow path 21a, the region R3 where the pressure of the transfer fluid decreases due to the tongue tip 31a and the region R4 where the pressure of the transfer fluid decreases due to the bulging portion 33 are likely to occur point-symmetrically with respect to the rotation center C of the impeller 6. As a result, the radial force acting on the impeller 6 in the region R3 and the radial force acting on the impeller 6 in the region R4 cancel each other out (see the arrows in FIG. 7), so that the impeller 6 can be suppressed from shifting radially during rotation.

[0053] [Effect confirmation test] A test was conducted to confirm the effect of the pump 1 of the present embodiment. In this test, for the two types of pumps 1 described in a) and b) below, the head during operation and the radial force acting on the impeller 6 in the regions R2 and R4 (see FIGS. 5 and 7) were calculated by fluid analysis software, respectively. a) Pump 1 without the bulging portion 33 (see FIG. 4) b) Pump 1 with the bulging portion 33 (see FIG. 3)

[0054] FIG. 8 is a graph showing the test results of the radial force acting on the impeller 6 in the regions R2 and R4. As shown in FIG. 8, it was confirmed that the radial force acting on the impeller 6 in the region R4 of the pump 1 having the bulging portion 33 is significantly smaller than the radial force acting on the impeller 6 in the region R2 of the pump 1 without the bulging portion 33.

[0055] FIG. 9 is a graph showing the test results of the head of the pump 1. Generally, when the radial force acting on the impeller 6 is significantly reduced, the head of the pump 1 also decreases significantly accordingly. However, as shown in FIGS. 8 and 9, it was confirmed that in the pump 1 having the bulging portion 33, even when the radial force is significantly reduced compared to the pump 1 without the bulging portion 33, the degree of head reduction can be suppressed.

[0056] [Function and effect] According to the magnetic levitation pump 1 of the first embodiment, the volute portion 21 in which a single volute flow path 21a is formed inside has a bulging portion 33 that bulges so as to partially expand the volute flow path 21a in a predetermined range including a first opposed position P1 of 180° around the rotation center C of the impeller 6 with respect to the tongue end 31a. Due to this bulging portion 33, in the volute flow path 21a, a region R3 where the pressure of the transferred fluid decreases due to the connection between the volute portion 21 and the discharge portion 26, and a region R4 where the pressure of the transferred fluid decreases due to the bulging portion 33 are likely to occur point-symmetrically with respect to the rotation center C. As a result, in both regions R3 and R4 where the pressure decreases, the radial forces acting on the impeller 6 cancel each other out. Therefore, it is possible to suppress the radial displacement of the impeller 6 during rotation with a simple configuration without using a partition wall as in the prior art.

[0057] Also, since the radial displacement of the impeller 6 is suppressed by the pressure change of the transferred fluid in the volute flow path 21a as described above, even if the magnetic generation portion 51 generates a weak magnetic field, the radial displacement of the impeller 6 can be suppressed. Therefore, the manufacturing cost of the magnetic levitation pump 1 can be reduced.

[0058] The inner surfaces 31b and 32b of the first peripheral wall portion 31 and the second peripheral wall portion 32 of the volute portion 21 are both formed in an arc shape with the same radius of curvature. As a result, both regions R3 and R4 where the pressure decreases are more likely to occur point-symmetrically with respect to the rotation center C of the impeller 6. As a result, it is possible to further suppress the radial displacement of the impeller 6 during rotation.

[0059] The predetermined range in which the bulging portion 33 bulges is an angular range from a position P2 that is 45° away from the first opposed position P1 toward the first peripheral wall portion 31 side around the rotation center C of the impeller 6 to a position that is 45° away from the first opposed position P1 toward the second peripheral wall portion 32 side. As a result, both regions R3 and R4 where the force decreases are more likely to occur point-symmetrically with respect to the rotation center C of the impeller 6. As a result, it is possible to further suppress the radial displacement of the impeller 6 during rotation.

[0060] The bulging start position where the bulging part 33 starts to bulge from the first peripheral wall part 31 is located at the second opposing position P2 of 180° centered on the rotation center C of the impeller 6 with respect to the winding end 32a. Thereby, the two regions R3 and R4 where the pressure force decreases are more likely to occur point-symmetrically with respect to the rotation center C of the impeller 6. As a result, it is possible to further suppress the radial displacement of the impeller 6 during rotation.

[0061] The first end 331 and the second end 332 of the bulging part 33 bulge smoothly from the first peripheral wall part 31 and the second peripheral wall part 32, respectively. Therefore, even if the volute flow path 21a is partially expanded by the bulging part 33, the pressure loss of the transferred fluid accompanying the expansion can be reduced.

[0062] <Second Embodiment> FIG. 10 is a cross-sectional view corresponding to FIG. 3 showing the volute part 21 of the magnetic levitation pump 1 according to the second embodiment of the present disclosure. In the present embodiment, the shape of the inner surface 33a of the bulging part 33 of the volute part 21 is different from that of the first embodiment. The inner surface 33a of the bulging part 33 in the present embodiment is formed in an arc shape over the entire axial direction in a cross-sectional view in the axial direction (FIG. 10). The arc shape of the inner surface 33a is formed over the entire circumferential direction of the bulging part 33. That is, the arc shape of the inner surface 33a is formed from the first end 331 through the intermediate part 333 to the second end 332 (see FIG. 2). Since other configurations of the present embodiment are the same as those of the first embodiment, the same reference numerals are given and the description thereof is omitted.

[0063] In the magnetic levitation pump 1 of the second embodiment, the same effects as those of the first embodiment are also achieved. Further, the inner surface 33a of the bulge portion 33 facing the volute flow path 21a is formed in an arc shape in a cross-sectional view in the axial direction. Thereby, it is possible to suppress the generation of a secondary flow (vortex) of the transfer fluid in the vicinity of the connection portion between the bulge portion 33 (inner surface 33a) and the top wall 23 and in the vicinity of the connection portion between the bulge portion 33 (inner surface 33a) and the bottom wall 24 in the volute flow path 21a. Therefore, even if the volute flow path 21a is partially expanded by the bulge portion 33, it is possible to suppress the generation of a secondary flow (vortex) of the transfer fluid in the expanded portion. As a result, it is possible to further reduce the pressure loss of the transfer fluid accompanying the expansion of the volute flow path 21a.

[0064] <Others> The outer shape of the volute portion 21 in the present disclosure excluding the bulge portion 33 is formed in a circular shape, but it may be formed in a spiral shape (see FIG. 2 of Patent Document 2 above). The shape of the bulge portion 33 is not limited to the shape of the present disclosure as long as the pressure-reducing regions R3 and R4 are likely to be point-symmetrical.

[0065] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above meaning but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0066] 1 Magnetic levitation pump 3 Rotating shaft 4 Motor 5 Magnetic bearing portion 6 Impeller 20 Second casing (casing) 21 Volute portion 21a Volute flow path 26 Discharge portion 26a Discharge flow path 31 First peripheral wall portion 31a Tongue end 31b Inner surface 32 Second peripheral wall portion 32a End of winding 32b Inner surface 33 Bulging portion 33a Inner surface 331 First end 332 Second end C Axis P1 First opposing position P2 Second opposing position R3, R4 Regions where pressure decreases

Claims

1. a rotating shaft rotatable about an axis, a motor for rotationally driving the rotating shaft, a magnetic bearing portion for supporting the rotating shaft in a non-contact manner, an impeller provided integrally rotatably with the rotating shaft, a casing housing the impeller, and comprising: the casing includes a volute portion in which a single volute flow path is formed inside so that a transfer fluid flows around the impeller, a discharge portion connected to the volute portion and having a discharge flow path formed inside for discharging the transfer fluid from the volute flow path, the volute portion a tongue end that is a starting end of the volute flow path, a bulging portion that bulges so that the volute flow path partially expands in a predetermined range including a first opposing position that is 180° around the rotation center of the impeller with respect to the tongue end, the bulging portion bulges in the volute flow path such that a region where the pressure of the transfer fluid decreases due to the connection between the volute portion and the discharge portion and a region where the pressure of the transfer fluid decreases due to the bulging portion are likely to occur point-symmetrically with respect to the rotation center, a magnetic levitation pump.

2. the volute portion has the tongue end and a first peripheral wall portion formed from the tongue end to the bulging portion, has an end of the volute flow path and a second peripheral wall portion formed from the bulging portion to the end of the volute flow path, the first peripheral wall portion and the second peripheral wall portion each have an inner surface in an arc shape with the same radius of curvature in a cross-sectional view perpendicular to the axial direction, the magnetic levitation pump according to claim 1.

3. the predetermined range in which the bulging portion bulges is an angular range from a position 45° away from the first opposing position toward the first peripheral wall portion around the rotation center to a position 45° away from the first opposing position toward the second peripheral wall portion around the rotation center, the magnetic levitation pump according to claim 2.

4. a bulging start position where the bulging portion starts to bulge from the first peripheral wall portion is located at a second opposing position that is 180° around the rotation center with respect to the end of the volute flow path, the magnetic levitation pump according to claim 2 or claim 3.

5. the bulging portion has a first end portion formed to bulge smoothly from the first peripheral wall portion and a second end portion formed to bulge smoothly from the second peripheral wall portion, the magnetic levitation pump according to claim 2 or claim 3.

6. the bulging portion has an inner surface facing the volute flow path, The inner surface of the bulging portion is formed in an arc shape in a cross-sectional view in the axial direction, the magnetic levitation pump according to claim 1 or claim 2.

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