Impeller and magnetic levitation type pump

Abstract

To provide a technique that can improve the pump head of a magnetic levitation type pump while restraining movement of an impeller in an axial direction.SOLUTION: An impeller according to the present disclosure is arranged in a housing comprising an inflow port and an outflow port for transferred fluid in a magnetic levitation type pump, and capable of rotating around an axis, and comprises an impeller body having an outside shape formed in a circular shape around the axis, and a plurality of blades provided on the impeller body, and arranged at intervals in a circumferential direction of the outside shape. The blades each comprises a main blade part provided in the range of the outside shape of the impeller body in a planar view from a direction of the axis, and an auxiliary blade part provided on the main blade part, and protruding outward in a radial direction from the outside shape of the impeller body.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] As a magnetic levitation pump that magnetically levitates a rotating shaft with respect to a housing 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 housing, a rotating shaft, a motor, and a magnetic bearing. The magnetic bearing rotatably supports the rotating shaft with respect to the housing in a non-contact manner, and by driving the motor, the rotating shaft rotates with respect to the housing.

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

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the above-described magnetic levitation pump, in order to improve the head, it is necessary to increase the rotational speed of the impeller or increase the outer diameter of the impeller. However, no matter which of these is adopted, since there is a low-pressure region at the suction port, a pressure difference is generated in the axial direction. As a result, in the housing, a vortex of secondary flow is generated. When the flow rate of the transferred fluid decreases, this vortex becomes stronger and the axial pressure difference expands. Thus, when the axial pressure difference increases, the axial thrust force acting on the impeller increases. Therefore, the impeller may move axially due to the thrust force and come into contact with the housing and be damaged.

[0006] The present disclosure has been made in view of such circumstances, and an object thereof is to provide a technique capable of improving the head of a magnetic levitation pump while suppressing the axial movement of the impeller.

Means for Solving the Problems

[0007] (1) The impeller of the present disclosure is an impeller that is disposed in a housing having an inlet and an outlet for a transferred fluid in a magnetic levitation pump and is rotatable about an axis. The impeller has an impeller body having an outer shape formed in a circular shape centered on the axis, and a plurality of blades provided on the impeller body and arranged at intervals in the circumferential direction of the outer shape. The blades have a main blade portion provided within the range of the outer shape of the impeller body in a plan view seen from the axial direction, and an auxiliary blade portion provided on the main blade portion and protruding radially outward from the outer shape of the impeller body.

[0008] According to the impeller of the present disclosure, an auxiliary blade portion that protrudes radially outward from the outer shape of the impeller body is provided on the main blade portion provided within the range of the outer shape of the impeller body. By this auxiliary blade portion, the centrifugal force accompanying the rotation of the impeller can be increased. As a result, since the energy imparted to the transfer fluid discharged from the outlet of the housing increases, the head of the magnetic levitation pump can be improved. Further, outside the impeller in the radial direction within the housing, the auxiliary blade portion is arranged so as to axially divide the vortex of the secondary flow. Thereby, since the axial pressure difference within the housing is suppressed, the axial thrust force acting on the impeller can be reduced. As a result, the axial movement of the impeller caused by the thrust force can be suppressed.

[0009] (2) In the impeller of (1) above, it is preferable that the auxiliary blade portion is inclined with respect to a virtual plane orthogonal to the axial direction. In this case, since the axial thrust force acting on the impeller can be further reduced, the axial movement of the impeller caused by the thrust force can be further suppressed.

[0010] (3) In the impeller of (1) or (2) above, it is preferable that the axial thickness of the auxiliary blade portion is smaller than the axial thickness of the main blade portion. In this case, since the resistance of the auxiliary blade portion during the rotation of the impeller can be reduced, the rotational torque of the magnetic levitation pump can be reduced.

[0011] (4) The magnetic levitation pump of the present disclosure includes a housing having an inlet and an outlet for a transfer fluid, a rotating shaft disposed within the housing and 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, and the impeller according to any one of (1) to (3) above that is disposed within the housing and is integrally rotatable with the rotating shaft. According to the above magnetic levitation pump, the same operational effects as those of the above impeller are achieved.

Advantages of the Invention

[0012] According to the present disclosure, it is possible to improve the head of the magnetic levitation pump while suppressing the axial movement of the impeller.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0014] 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 a first embodiment of the present disclosure. In FIG. 1, 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 10. 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.

[0015] Hereinafter, in the present disclosure, the direction along the axis C of the pump 1 is the axial direction of the pump 1, 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, simply referred to as the "radial direction". The direction of rotation about the axis C is the circumferential direction of the pump 1, simply referred to as the "circumferential direction".

[0016] The housing 2 includes a first housing portion 21 that houses the rotating shaft 3 and a second housing portion 22 that houses the impeller 10. The first housing portion 21 has a cylindrical wall 211 and a bottom wall 212 provided on the lower side in the axial direction of the cylindrical wall 211. The cylindrical wall 211 is formed in a cylindrical shape about the axis C. The bottom wall 212 is formed in a disc shape and closes the opening on the lower side in the axial direction of the cylindrical wall 211.

[0017] The second housing portion 22 is provided on the upper side in the axial direction of the first housing portion 21. The second housing portion 22 has a cylindrical wall 221, a bottom wall 222 provided on the lower side in the axial direction of the cylindrical wall 221, and a top wall 223 provided on the upper side in the axial direction of the cylindrical wall 221. The cylindrical wall 221 is formed in a cylindrical shape about the axis C. The outer diameter of the cylindrical wall 221 is larger than the outer diameter of the cylindrical wall 211 of the first housing portion 21.

[0018] The top wall 223 of the second housing portion 22 is formed in a substantially conical plate shape. The outer peripheral edge of the top wall 223 is connected to the opening edge on the upper side in the axial direction of the cylindrical wall 221. The bottom wall 222 of the second housing portion 22 is formed in an annular plate shape. The outer peripheral edge of the bottom wall 222 is connected to the opening edge on the lower side in the axial direction of the cylindrical wall 221. The inner peripheral edge of the bottom wall 222 is connected to the opening edge on the upper side in the axial direction of the cylindrical wall 211 of the first housing portion 21. Thereby, the internal space of the second housing portion 22 communicates with the internal space of the first housing portion 21.

[0019] The second housing portion 22 further has an inlet 23 through which the transfer fluid flows in and an outlet 24 through which the transfer fluid flows out. The inlet 23 is formed at the center of the top wall 223. The outlet 24 is formed at a predetermined position on the outer periphery of the cylindrical wall 221.

[0020] The rotating shaft 3 is rotatably arranged about the axis C within the first housing portion 21. 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 housing portion 22.

[0021] The motor 4 rotationally drives the rotating shaft 3. The motor 4 has a stator 41 provided in the first housing portion 21 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 211. 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.

[0022] The pair of magnetic bearing portions 5 supports the rotating shaft 3 in a non-contact manner. Each magnetic bearing portion 5 has a magnetic generation portion 51 provided in the first housing portion 21 and a magnetic body 52 provided on the rotating shaft 3. The magnetic generation portion 51 is arranged on both axial sides of the stator 41 and is fixed to the outer peripheral surface of the cylindrical wall 211. The magnetic body 52 is fixed at a position radially opposed to the magnetic generation 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 generation portion 51 and the magnetic body 52.

[0023] [Impeller] FIG. 2 is a perspective view showing the rotating shaft 3 and the impeller 10. In FIGS. 1 and 2, the impeller 10 is arranged within the second housing portion 22. The impeller 10 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. In a state where the rotating shaft 3 is supported in a non-contact manner by the magnetic bearing portions 5, an annular space S is formed between the impeller 10 and the cylindrical wall 221 in the second housing portion 22.

[0024] Figure 3 is a plan view of the impeller 10 as viewed from the upper axial direction. Figure 4 is a side view showing the impeller 10. In FIGS. 2 to 4, the impeller 10 of the present embodiment is, for example, a closed impeller. The impeller 10 includes an impeller main body 11 and a plurality of blades 15.

[0025] The impeller main body 11 has an outer shape formed in a circular shape around the axis C in a plan view. The impeller main body 11 has a base portion 12 and a cover portion (shroud) 13 disposed axially above the base portion 12. The base portion 12 is formed, for example, in a disk shape. The outer diameter of the base portion 12 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 outer surface 12a on the lower side in the axial direction of the base portion 12.

[0026] The cover portion 13 is disposed at a distance from the inner surface 12b on the upper side in the axial direction of the base portion 12. The cover portion 13 is formed in an annular plate shape. The outer diameter of the cover portion 13 is the same as the outer diameter of the base portion 12, and the inner surface 13b on the lower side in the axial direction of the cover portion 13 is disposed to face the inner surface 12b of the base portion 12. In the present embodiment, the outer shape of the cover portion 13 in a plan view is the outer shape of the base portion 12 or the outer shape of the cover portion 13.

[0027] The outer surface 13a on the upper side in the axial direction of the cover portion 13 is inclined so as to gradually project upward in the axial direction from the outer peripheral edge toward the inner peripheral edge. An inlet 11a for introducing the transfer fluid into the impeller main body 11 is formed on the inner peripheral side of the outer surface 13a. The inlet 11a communicates with the inlet 23 of the second housing portion 22 (see FIG. 1).

[0028] [Blades] The plurality of blades 15 are provided between the base portion 12 and the cover portion 13 of the impeller main body 11. The plurality of blades 15 are arranged at equal intervals in the circumferential direction of the impeller main body 11. The impeller 10 of the present embodiment includes four blades 15.

[0029] Each blade 15 has a main blade portion 16 provided on the impeller main body 11 and an auxiliary blade portion 17 provided on the main blade portion 16. The main blade portion 16 is provided within the range of the outer shape of the impeller main body 11 in a plan view (see FIG. 3) when viewed from the axial direction (axis C direction). That is, the main blade portion 16 is provided on the impeller main body 11 so as not to protrude radially outward of the impeller main body 11 in a plan view. The main blade portion 16 of the present embodiment is fixed to the inner surface 12b of the base portion 12. A cover portion 13 is fixed to the upper end surface in the axial direction of the main blade portion 16.

[0030] The main blade portion 16 is formed, for example, in a substantially triangular shape in a plan view. The main blade portion 16 has a first side surface 16a, a second side surface 16b, and an outer side surface 16c. The first side surface 16a and the second side surface 16b are surfaces perpendicular to the inner surface 12b of the base portion 12. The first side surface 16a and the second side surface 16b extend while curving from the center side of the base portion 12 toward the radially outer side in a plan view. The outer side surface 16c of the main blade portion 16 is an arc surface having the same radius of curvature as the outer peripheral surface of the base portion 12 (cover portion 13).

[0031] A flow path 18 is formed between adjacent main blade portions 16 in the circumferential direction and between the base portion 12 and the cover portion 13. Each flow path 18 is a flow path through which the transfer fluid introduced into the impeller main body 11 from the inlet 11a flows from the radially inner side toward the radially outer side. The radially outer opening of each flow path 18 is taken as an outlet 11b through which the transfer fluid is sent out of the impeller main body 11. Therefore, a plurality of outlets 11b through which the transfer fluid is sent out of the impeller main body 11 are formed on the outer periphery of the impeller main body 11.

[0032] The auxiliary blade portion 17 is mainly fixed to the outer side surface 16c of each main blade portion 16. The auxiliary blade portion 17 protrudes radially outward of the outer shape of the impeller main body 11. The auxiliary blade portion 17 of the present embodiment is formed so as to taper while curving toward one side in the circumferential direction (counterclockwise direction side in FIG. 3) from the base end portion on the main blade portion 16 side toward the protruding end portion in a plan view.

[0033] The auxiliary blade part 17 has a first outer surface 17a and a second outer surface 17b. The radially inner end of the first outer surface 17a of the auxiliary blade part 17 is connected to the first side surface 16a of the main blade part 16. The first outer surface 17a is curved so as to extend radially outward along the curvature of the first side surface 16a in plan view.

[0034] The radially inner end of the second outer surface 17b of the auxiliary blade part 17 is connected to the second side surface 16b of the main blade part 16. The second outer surface 17b is curved so as to extend radially outward along the curvature of the second side surface 16b in plan view. The radially outer ends of the first outer surface 17a and the second outer surface 17b of the auxiliary blade part 17 are connected to each other.

[0035] As shown in FIG. 4, the first outer surface 17a and the second outer surface 17b of the auxiliary blade part 17 are curved so as to be convex surfaces radially outward in side view. The axial thickness t2 of the auxiliary blade part 17 is smaller than the axial thickness t1 of the main blade part 16. The auxiliary blade part 17 is inclined with respect to a virtual plane K orthogonal to the axial direction. The auxiliary blade part 17 of the present embodiment is gradually inclined upward in the axial direction from one circumferential end to the other circumferential end (from the left end to the right end in FIG. 4).

[0036] In FIGS. 1 and 2, when the rotary shaft 3 is rotationally driven by the motor 4, the impeller 10 rotates about the axis C together with the rotary shaft 3. Then, the transfer fluid is sucked into the housing 2 from the inlet 23, and further introduced into the impeller main body 11 from the inlet 11a. The transfer fluid introduced into the impeller main body 11 flows radially outward in a radial direction due to the centrifugal force accompanying the rotation of the plurality of blades 15. At this time, the transfer fluid passes through the flow path 18 between the adjacent blades 15 and is sent out of the impeller main body 11. Most of the transfer fluid sent out of the impeller main body 11 is discharged out of the housing 2 from the outlet 24 of the housing 2.

[0037] [Thrust force] When rotating the impeller 10 to discharge the transfer fluid as described above, in the housing 2, an axial thrust force is generated on the impeller 10 due to the secondary flow. FIG. 5 is an explanatory diagram of the action of increasing the thrust force on the impeller 10 due to the secondary flow. In FIG. 5, the illustration of the auxiliary blade portion 17 of the impeller 10 is omitted. As shown in FIG. 5, when rotating the impeller 10 to discharge the transfer fluid, in the space S in the second housing portion 22, a secondary flow vortex 70 is generated by a part of the transfer fluid sent out of the impeller main body 11. The vortex 70 is generated in the space S so as to rotate in the counterclockwise direction in FIG. 5.

[0038] When the vortex 70 rotating as described above is generated, among the transfer fluid sent out of the impeller main body 11, the velocity of the transfer fluid 81 flowing upward in the axial direction of the space S increases, and the velocity of the transfer fluid 82 flowing downward in the axial direction of the space S decreases. As a result, the upper side in the axial direction of the space S is depressurized, and the lower side in the axial direction of the space S is pressurized. As a result, the axial pressure difference in the second housing portion 22 becomes large, and an axial thrust force (here, the upper side in the axial direction) is generated on the impeller 10.

[0039] However, in the present embodiment, as shown in FIGS. 1 and 2, a plurality of auxiliary blade portions 17 are arranged in the space S in the second housing portion 22. Therefore, the plurality of auxiliary blade portions 17 can divide the vortex 70 generated in the space S in the axial direction. As a result, the axial pressure difference in the second housing portion 22 is suppressed, so that the axial thrust force acting on the impeller 10 can be reduced. Further, in the present embodiment, the centrifugal force accompanying the rotation of the impeller 10 can be increased by the auxiliary blade portion 17. As a result, the energy imparted to the transfer fluid discharged from the outlet 24 of the housing 2 becomes large, so that the head of the pump 1 can be improved.

[0040] <Second Embodiment> FIG. 6 is a side view showing the impeller 10 of the pump 1 according to the second embodiment of the present disclosure. In the impeller 10 of the present embodiment, the shape of the auxiliary blade portion 17 is different from that of the first embodiment. Each auxiliary blade portion 17 in the present embodiment is formed in parallel with the virtual plane K so as not to be inclined with respect to the virtual plane K orthogonal to the axial direction. The first outer surface 17a and the second outer surface 17b of each auxiliary blade portion 17 are formed flat over the entire thickness (the entire axial direction) of the auxiliary blade portion 17 in a side view. 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.

[0041] <Effect Confirmation Test> A test was conducted to confirm the effects of the pump 1 of the present disclosure. In this test, for the following three types of pumps a), b), and c), the head and the axial thrust force during operation were calculated by fluid analysis software, respectively. a) A conventional pump equipped with an impeller having no auxiliary blade portion b) The pump 1 of the first embodiment equipped with the impeller 10 having the inclined auxiliary blade portion 17 c) The pump 1 of the second embodiment equipped with the impeller 10 having the non-inclined auxiliary blade portion 17

[0042] FIG. 7 is a graph showing the test results of the head. As shown in FIG. 7, it was confirmed that the head of the pumps 1 of the first embodiment and the second embodiment is improved compared with the conventional pump. Also, it was confirmed that the head of the pump 1 of the first embodiment in which the auxiliary blade portion 17 is inclined is slightly improved compared with the pump 1 of the second embodiment in which the auxiliary blade portion 17 is not inclined.

[0043] FIG. 8 is a graph showing the test results of the thrust force. As shown in FIG. 8, it was confirmed that the thrust force of the pumps 1 of the first embodiment and the second embodiment is reduced compared with the conventional pump. Also, it was confirmed that the thrust force of the pump 1 of the first embodiment in which the auxiliary blade portion 17 is inclined is significantly reduced compared with the pump 1 of the second embodiment in which the auxiliary blade portion 17 is not inclined.

[0044] <Function and Effect> According to the magnetic levitation pump 1 of the first and second embodiments, an auxiliary blade portion 17 that protrudes radially outward from the outer shape of the impeller body 11 is provided on the main blade portion 16 provided within the range of the outer shape of the impeller body 11. By this auxiliary blade portion 17, the centrifugal force associated with the rotation of the impeller 10 can be increased. As a result, since the energy imparted to the transfer fluid discharged from the outlet 24 of the housing 2 becomes larger, the head of the magnetic levitation pump 1 can be improved.

[0045] Also, outside the impeller 10 in the radial direction within the housing 2, the auxiliary blade portion 17 is arranged so as to axially divide the secondary flow vortex 70. Thereby, since the axial pressure difference within the housing 2 is suppressed, the axial thrust force acting on the impeller 10 can be reduced. As a result, the axial movement of the impeller 10 due to the thrust force can be suppressed, and thus the impeller 10 coming into contact with the housing 2 and being damaged can be suppressed.

[0046] The auxiliary blade portion 17 is inclined with respect to a virtual plane K orthogonal to the axial direction. Thereby, since the axial thrust force acting on the impeller 10 can be further reduced, the axial movement of the impeller 10 due to the thrust force can be further suppressed. Also, the head of the magnetic levitation pump 1 can be further improved.

[0047] The axial thickness t2 of the auxiliary blade portion 17 is smaller than the axial thickness t1 of the main blade portion 16. Thereby, since the resistance of the auxiliary blade portion 17 during the rotation of the impeller 10 can be reduced, the rotational torque of the magnetic levitation pump 1 can be reduced.

[0048] <Others> The impeller 10 of the present disclosure is a closed impeller having a cover portion 13, but may also be an open impeller without a cover portion 13. The respective numbers of the main blade portions 16 and the auxiliary blade portions 17 in the impeller 10 of the present disclosure are not limited to the present embodiment. The auxiliary blade portions 17 of the present disclosure are provided on all the main blade portions 16, but may be provided on only some of the main blade portions 16. The axial thickness t2 of the auxiliary blade portions 17 may be equal to or greater than the axial thickness t1 of the main blade portions 16.

[0049] The main blade portions 16 and the auxiliary blade portions 17 are not limited to the shapes of the present embodiment. For example, for example, the auxiliary blade portions 17 may have a blade shape. In that case, the blade shape of the auxiliary blade portions 17 may be formed such that the upper side in the axial direction is at a high pressure and the lower side in the axial direction is at a low pressure in the space S of the second housing portion 22. Thereby, the axial pressure difference (see FIG. 5) caused by the vortex 70 generated in the space S is offset by the axial pressure difference generated by the auxiliary blade portions 17, so that the axial thrust force acting on the impeller 10 can be reduced.

[0050] 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 scope of claims, and it is intended that all modifications within the meaning and scope equivalent to the scope of claims are included.

Explanation of Reference Numerals

[0051] 1 Magnetic Levitation Pump 2 Housing 3 Rotating Shaft 4 Motor 5 Magnetic Bearing Portion 10 Impeller 11 Impeller Body 15 Blade 16 Main Blade Portion 17 Auxiliary Blade Portion 24 Inlet 25 Outlet C Axis K Virtual Plane t1 Thickness of Main Blade Portion Thickness of the t2 auxiliary blade root

Claims

1. An impeller disposed in a housing having an inlet and an outlet for a transfer fluid and rotatable about an axis in a magnetic levitation pump, an impeller body having an outer shape formed in a circular shape about the axis, a plurality of blades provided on the impeller body and arranged at intervals in the circumferential direction of the outer shape, and the blades are a main blade portion provided within the range of the outer shape of the impeller body in a plan view seen from the axial direction, an auxiliary blade portion provided on the main blade portion and protruding radially outward from the outer shape of the impeller body.

2. The impeller according to claim 1, wherein the auxiliary blade portion is inclined with respect to a virtual plane orthogonal to the axial direction.

3. The impeller according to claim 1 or claim 2, wherein the axial thickness of the auxiliary blade portion is smaller than the axial thickness of the main blade portion.

4. A housing having an inlet and an outlet for a transfer fluid, a rotating shaft disposed in the housing and 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, and a magnetic levitation pump comprising the impeller according to claim 1 or claim 2 disposed in the housing and integrally rotatably provided on the rotating shaft.

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