Impeller and magnetically levitated pump

Abstract

To provide an art which enables low-cost manufacturing of an impeller on which a position restoring force in an axial direction acts.SOLUTION: An impeller of the disclosure is disposed rotatably around an axis in a housing having an inflow port and an outflow port of a transferred fluid and includes: a columnar impeller body in which a balance hole penetrating in an axial direction is formed at the radial inner side; a discoid partition plate which faces an opening at one axial side, which is the side close to the inflow port, in the balance hole while forming a space at the one axial side; and a plurality of blades arranged along a circumferential direction of the partition plate at the radial outer side relative to the partition plate. The plurality of blades are disposed spaced apart from an outer peripheral surface of the partition plate in a radially outward direction.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] In a magnetic levitation pump, an impeller is levitated magnetically with respect to a housing and rotated while being supported in a non-contact manner. When the impeller moves axially during its rotation, there is a risk of contacting the housing and being damaged. For this reason, the impeller of a magnetic levitation pump requires a mechanism for applying a position restoring force for pushing it back to the other axial side when it moves to one axial side (see, for example, FIG. 2 of Patent Document 1).

[0003] The impeller (rotor) of the magnetic levitation pump described in Patent Document 1 includes an impeller body having a plurality of balance holes (relief bore), a disk-shaped partition element (partition element), and a plurality of blades fixed to the outer periphery of the partition element. Each blade has a first blade portion (first vanes) above the partition plate and a second blade portion (second vanes) below the partition plate.

[0004] The first blade portion generates a flow of transfer fluid (main flow) from the inlet to the outlet of the housing due to the centrifugal force accompanying the rotation of the impeller above the partition plate. Due to this main flow, a load that pulls the impeller upward in the axial direction acts on the impeller. The second blade portion generates a flow (circulation flow) in which the transfer fluid circulates between the inner peripheral side (balance hole) and the outer peripheral side of the impeller body below the partition plate. Due to this circulation flow, a reverse load that pulls the impeller downward in the axial direction acts on the impeller.

[0005] During the operation of the magnetic levitation pump, the impeller is held at a predetermined axial position by the balance between the load acting upward in the axial direction and the reverse load acting downward in the axial direction. When the impeller moves downward in the axial direction due to an external force from this state, the flow rate of the circulating flow decreases and the reverse load acting downward in the axial direction becomes smaller. As a result, the load acting upward in the axial direction acts predominantly on the impeller as a position restoring force. Conversely, when the impeller moves upward in the axial direction due to an external force, the flow rate of the circulating flow increases and the reverse load acting downward in the axial direction becomes larger. As a result, the reverse load acts predominantly on the impeller as a position restoring force. These position restoring forces restrict the movement of the impeller in both axial directions from the predetermined position.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] When manufacturing the impeller of the above magnetic levitation pump, for example, when fixing the blades to the outer periphery of the partition plate by welding, it is necessary to weld each of the plurality of blades to the partition plate. For this reason, there is a problem that the man-hours required for manufacturing the impeller increase and the manufacturing cost increases.

[0008] The present disclosure has been made in view of such circumstances, and an object thereof is to provide a technique capable of manufacturing an impeller on which an axial position restoring force acts at low cost.

Means for Solving the Problems

[0009] (1) The disclosed impeller is an impeller rotatably arranged around an axis in a housing having an inlet and an outlet for a transfer fluid, and includes a columnar impeller body in which a balance hole penetrating axially is formed on the radially inner side, a disc-shaped partition plate spaced apart in the one axial direction from an opening on one axial side close to the inlet in the balance hole, and a plurality of blades arranged along the circumferential direction of the partition plate on the radially outer side of the partition plate. The plurality of blades are each arranged with a gap on the radially outer side with respect to the outer peripheral surface of the partition plate.

[0010] In order to apply an axial position restoring force to the impeller, it is generally considered that the main flow and the circulating flow generated on both axial sides of the partition plate should be completely separated. In order to completely separate the main flow and the circulating flow, it is necessary to fix and integrate a plurality of blades to the outer periphery of the partition plate. On the contrary, as a result of intensive research, the inventor of the present application has found that, contrary to the above general idea, even when a plurality of blades are separated from the partition plate, an axial position restoring force acts on the impeller. As a result, the invention according to the above (1) was obtained.

[0011] According to the impeller of the present disclosure, the plurality of blades are arranged with a gap on the radially outer side with respect to the outer peripheral surface of the partition plate. Therefore, it is not necessary to fix each of the plurality of blades to the partition plate by welding or the like, so that the man-hours required for manufacturing the impeller can be significantly reduced. Further, even if the plurality of blades are not fixed to the partition plate as described above, an axial position restoring force acts on the impeller. Therefore, an impeller on which an axial position restoring force acts can be manufactured at low cost.

[0012] (2) In the impeller of (1) above, when the outer diameter of the partition plate is A and the diameter of the virtual circumscribed circle circumscribing the closest end of each of the plurality of blades to the partition plate is B, it is preferable to satisfy the relationship of 0.89 ≦ A / B < 1.00. As a result of further intensive research, the inventor of the present application has found that when the ratio (A / B) of the outer diameter A of the partition plate to the diameter B of the virtual circumscribed circle of the plurality of blades is within a predetermined range, an axial position restoring force acts appropriately on the impeller. Based on such findings, the invention according to the above (2) has been completed. According to the invention according to the above (2), since an axial position restoring force can act appropriately on the impeller, it is possible to effectively suppress the impeller from coming into contact with the housing and being damaged.

[0013] (3) In the impeller according to the above (1) or (2), when the axial dimension of the interval is C and the minimum axial dimension of the blade is D, it is preferable to satisfy the relationship of 0.2 ≤ C / D ≤ 0.6. As a result of further intensive research, the inventor of the present application has found that when the ratio (C / D) of the axial interval C between the opening on one axial side of the balance hole and the partition plate to the minimum axial dimension D of the blade is within a predetermined range, it is possible to suppress a reduction in fluid transfer characteristics (the differential pressure between the inlet and outlet of the housing). Based on such findings, the invention according to the above (3) has been completed. According to the invention according to the above (3), it is possible to suppress a reduction in the fluid transfer characteristics of the magnetic levitation pump.

[0014] (4) The magnetic levitation pump of the present disclosure includes a housing having an inlet and an outlet for the transfer fluid, an impeller according to any one of the above (1) to (3) disposed in the housing, a motor for rotationally driving the impeller, and a magnetic bearing portion for supporting the rotating impeller in a non-contact manner. According to the above magnetic levitation pump, the same operational effects as those of the above impeller are achieved.

Effects of the Invention

[0015] According to the present disclosure, an impeller on which an axial position restoring force acts can be manufactured at low cost.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0017] Next, preferred embodiments will be described with reference to the accompanying drawings. [Overall Configuration] FIG. 1 is a schematic cross-sectional view showing a magnetic levitation pump 1 according to an embodiment of the present disclosure. In FIG. 1, the magnetic levitation pump 1 (hereinafter, also simply referred to as "pump 1") of the present embodiment is a centrifugal pump. The pump 1 includes a housing 2, an impeller 3, a motor 4, and a magnetic bearing portion 5.

[0018] Hereinafter, in the present disclosure, the direction along the axis X of the pump 1 is the axial direction of the pump 1, and is simply referred to as the "axial direction". Further, the direction orthogonal to the axis X is the radial direction of the pump 1, and is simply referred to as the "radial direction". The direction of rotation about the axis X is the circumferential direction of the pump 1, and is simply referred to as the "circumferential direction".

[0019] The housing 2 has a cylindrical housing main body 21, a top wall 22 provided on the upper side in the axial direction of the housing main body 21, and a bottom wall 23 provided on the lower side in the axial direction of the housing main body 21. The housing main body 21 is formed in a cylindrical shape about the axis X. The top wall 22 is formed in a substantially conical plate shape and closes the opening on the upper side in the axial direction of the housing main body 21. The bottom wall 23 is formed in a disc shape and closes the opening on the lower side in the axial direction of the housing main body 21.

[0020] The housing 2 further has an inlet 24 into which the transfer fluid flows and an outlet 25 from which the transfer fluid flows out. The inlet 24 is formed at the center of the top wall 22. The outlet 25 is formed on the upper side in the axial direction of the outer periphery of the housing body 21.

[0021] The impeller 3 is disposed rotatably about the axis X within the housing 2. When the impeller 3 rotates, the transfer fluid flows into the housing 2 from the inlet 24 and flows out of the housing 2 from the outlet 25 by centrifugal force. Details of the impeller 3 will be described later.

[0022] The motor 4 rotationally drives the impeller 3. The motor 4 has a stator 11 disposed outside the housing 2 and a rotor 12 provided on the impeller 3. The stator 11 has a fixed magnetic portion 11a made of a magnetic material such as iron and a winding 11b wound around the fixed magnetic portion 11a. The rotor 12 has a permanent magnet 12a provided within the impeller 3. When operating the pump 1, an electric current is applied to the winding 11b of the stator 11. Thereby, a rotating magnetic field is generated, and the rotor 12 rotates about the axis X together with the impeller 3.

[0023] The magnetic bearing portion 5 supports the rotating impeller 3 in a non-contact manner. The magnetic bearing portion 5 has a magnetic generation portion 5a disposed outside the housing 2 and a rotating-side magnetic body 5b provided on the impeller 3. In the present embodiment, the motor 4 also serves as the magnetic bearing portion 5. Specifically, the stator 11 of the motor 4 also serves as the magnetic generation portion 5a, and the rotor 12 of the motor 4 also serves as the rotating-side magnetic body 5b. Due to the magnetism generated by the magnetic generation portion 5a and the rotating-side magnetic body 5b, the impeller 3 rotates while being supported in a non-contact manner.

[0024] [Impeller] FIG. 2 is an enlarged cross-sectional view showing the impeller 3. In FIG. 2, the illustration of the rotor 12 of the motor 4 is omitted. FIG. 3 is a cross-sectional view taken along the line I-I of FIG. 1. In FIGS. 2 and 3, the impeller 3 has an impeller body 31, a partition plate 32, a plurality of blades 33, and a cover plate 34.

[0025] The impeller main body 31 is formed in a columnar shape centered on the axis X. With the impeller 3 being supported in a non-contact manner by the magnetic bearing portion 5, an annular first space S1 is formed between the outer peripheral surface 31a of the impeller main body 31 and the inner peripheral surface 21a of the housing main body 21. Also, with the impeller 3 being supported in a non-contact manner, a second space S2 is formed between the end surface 31b on the lower side in the axial direction of the impeller main body 31 and the bottom wall 23.

[0026] A plurality of balance holes 35 penetrating in the axial direction are formed on the inner side in the radial direction of the impeller main body 31. In the impeller main body 31 of the present embodiment, eight balance holes 35 are formed in the circumferential direction centered on the axis X. Each balance hole 35 is, for example, circular in cross section. A part of the transfer fluid passes through each balance hole 35. In the impeller main body 31, the permanent magnet 12a is provided on the outer side in the radial direction than the plurality of balance holes 35 (see FIG. 1).

[0027] The partition plate 32 is formed in a disk shape centered on the axis X. The partition plate 32 has a thick portion 321 with a relatively large axial thickness and a thin portion 322 with a relatively small axial thickness. The thick portion 321 protrudes downward in the axial direction more than the thin portion 322. The thick portion 321 is fixed by welding or the like at a position on the upper end surface 31c in the axial direction of the impeller main body 31, on the inner side in the radial direction than the plurality of balance holes 35. The thin portion 322 is formed in an annular shape on the outer side in the radial direction of the thick portion 321. The thin portion 322 faces the opening on the upper side in the axial direction (one side in the axial direction) closer to the inlet 24 in each balance hole 35, with a gap E1 therebetween in the axial direction.

[0028] The plurality of blades 33 are arranged at equal intervals along the circumferential direction of the partition plate 32 on the radially outer side of the partition plate 32. The plurality of blades 33 are each arranged with a gap E2 on the radially outer side with respect to the outer peripheral surface 32a of the partition plate 32. This gap E2 is the radial gap between the closest end 33d (described later) of each blade 33 and the outer peripheral surface 32a of the partition plate 32. Each blade 33 is fixed in a state of being placed on the end surface 31c on the upper side in the axial direction of the impeller body 31.

[0029] Each blade 33 is formed in a substantially triangular shape in a plan view, for example. Each blade 33 has a first side surface 33a, a second side surface 33b, and an outer surface 33c. The first side surface 33a and the second side surface 33b of each blade 33 are surfaces perpendicular to the end surface 31c of the impeller body 31, and extend while curving from the center side of the impeller body 31 toward the radially outer side. The curved length of the second side surface 33b is longer than the curved length of the first side surface 33a.

[0030] Each blade 33 has a closest end 33d that is closest to the outer peripheral surface 32a of the partition plate 32. The closest end 33d of each blade 33 in the present embodiment is the connection end between the first side surface 33a and the second side surface 33b. The outer surface 33c of each blade 33 is an arc surface having the same radius of curvature as the outer peripheral surface 31a of the impeller body 31. Note that the shape of each blade 33 is not limited to the shape of the present embodiment.

[0031] The cover plate 34 is formed in an annular shape centered on the axis X. The cover plate 34 is fixed to the end surface on the upper side in the axial direction of each blade 33. The inner peripheral hole of the cover plate 34 is an introduction hole 36 through which the transfer fluid is introduced into the impeller 3. Between the impeller body 31 and the cover plate 34, a flow path 37 is formed between the blades 33 adjacent to each other in the circumferential direction, through which the transfer fluid in the impeller 3 flows from the radially inner side toward the radially outer side.

[0032] When the pump 1 is operated and the impeller 3 rotates around the axis X, the transfer fluid is introduced into the impeller 3 from the inlet 24 of the housing 2 through the introduction hole 36. The transfer fluid introduced into the impeller 3 radially flows outward in the radial direction along the surface on the upper side in the axial direction of the partition plate 32 due to the centrifugal force associated with the rotation of the impeller 3, passes through the flow path 37 between adjacent blades 33, and is sent out of the impeller 3. Most of the transfer fluid sent out of the impeller 3 flows out of the housing 2 from the outlet 25 of the housing 2. Therefore, in the rotating impeller 3, a flow of the transfer fluid from the inlet 24 to the outlet 25 of the housing 2 occurs on the upper side in the axial direction rather than the partition plate 32. Hereinafter, this flow is referred to as the "main flow".

[0033] A remaining part of the transfer fluid sent out of the impeller 3 passes through the first space S1 and the second space S2 in this order, and flows into the balance hole 35 from the lower side in the axial direction of the impeller body 31. The transfer fluid flowing into the balance hole 35 flows into the interval E1 between the end face 31c of the impeller body 31 and the thin portion 322 of the partition plate 32 from the opening on the upper side in the axial direction in the balance hole 35. The transfer fluid flowing into the interval E1 radially flows outward due to the centrifugal force, passes through the flow path 37 between adjacent blades 33, and is sent out of the impeller 3 again. Therefore, in the rotating impeller 3, a flow in which the transfer fluid circulates between the inner side in the radial direction (balance hole 35) and the outer side in the radial direction (first space S1) of the impeller body 31 occurs on the lower side in the axial direction rather than the partition plate 32 (thin portion 322). Hereinafter, this flow is referred to as the "circulation flow". [Position restoring force]

[0034] A load F1 that pulls upward in the axial direction acts on the impeller 3 due to the main flow. Specifically, in the middle of the main flow, a negative pressure is generated at the center of the partition plate 32 because the transfer fluid flows from the inner side in the radial direction to the outer side in the radial direction along the above surface of the partition plate 32. Due to this negative pressure, a load F1 in the upward direction in the axial direction acts on the impeller 3. Hereinafter, this load F1 is also referred to as the "upward load F1".

[0035] On the impeller 3, a load F2 that is pulled downward in the axial direction acts due to the circulation flow. Specifically, in the middle of the circulation flow, the transfer fluid flows into a plurality of balance holes 35 from the lower side in the axial direction (second space S2) of the impeller main body 31, generating a negative pressure at the center of the end face 31b of the impeller main body 31. Due to this negative pressure, a load F2 acting downward in the axial direction on the impeller 3 is generated. Hereinafter, this load F2 is also referred to as the "downward load F2".

[0036] During the operation of the pump 1, the impeller 3 is held at a predetermined position in the axial direction (the position shown in FIG. 2) by the balance between the upward load F1 and the downward load F2. In the pump 1 of this embodiment, due to the structure of the centrifugal pump, the downward load F2 is larger than the upward load F1, so that the two loads F1 and F2 are balanced. When the impeller 3 moves downward in the axial direction by an external force from this balanced state, the second space S2 becomes narrower, reducing the flow rate of the circulation flow. As a result, the downward load F2 becomes smaller, so that the upward load F1 acts more dominantly on the impeller 3 than the downward load F2. Therefore, the impeller 3 that has moved downward in the axial direction is pushed back upward in the axial direction toward the predetermined position by the upward load F1 acting as a position restoring force.

[0037] On the other hand, when the impeller 3 moves upward in the axial direction by an external force from the balanced state of the loads F1 and F2, the second space S2 becomes wider, increasing the flow rate of the circulation flow. As a result, the downward load F2 becomes larger, so that the downward load F2 acts more dominantly on the impeller 3 than the upward load F1. Therefore, the impeller 3 that has moved upward in the axial direction is pushed back downward in the axial direction toward the predetermined position by the downward load F2 acting as a position restoring force. From the above, either the upward load F1 or the downward load F2 acts on the impeller 3 as a position restoring force in the axial direction.

[0038] In FIG. 3, in order to appropriately apply an axial position restoring force to the impeller 3, it is preferable that the partition plate 32 and the plurality of blades 33 satisfy the relationship of the following formula (1). A / B in this embodiment is, for example, 0.95. 0.89 ≤ A / B < 1.00 ···(1) A is the outer diameter of the partition plate 32. B is the diameter of the virtual circumscribed circle (the circle shown by the two-dot chain line in FIG. 3) that circumscribes the closest end 33d to the partition plate 32 in each of the plurality of blades 33. Note that the gap E2 between the closest end 33d of each blade 33 and the outer peripheral surface 32a of the partition plate 32 is (B - A) / 2.

[0039] In FIG. 1, in order to suppress the reduction of the fluid transfer characteristic (the differential pressure between the inlet 24 and the outlet 25 of the housing 2) of the pump 1, it is preferable that the partition plate 32 and the plurality of blades 33 further satisfy the following relationship of formula (2). C / D in the present embodiment is, for example, 0.43. 0.2 ≤ C / D ≤ 0.6 ···(2) C is the axial dimension of the distance E1 between the end face 31c of the impeller main body 31 and the thin portion 322 of the partition plate 32. D is the minimum axial dimension of the blade 33.

[0040] [Verification Test 1] Regarding the pump 1 of the present embodiment, a verification test 1 was conducted on whether an axial position restoring force acts appropriately on the impeller 3. FIG. 4 is an explanatory diagram of the verification test 1. In FIG. 4, in the verification test 1, when the impeller 3 is moved and rotated in the Y direction (axial direction) from a state where the upward load F1 and the downward load F2 are balanced, the load (position restoring force) in the Y direction acting on the impeller 3 was calculated by fluid analysis software. The origin in the Y direction was set as the position on the upper end face 31c in the axial direction of the impeller main body 31 in a state where both loads F1 and F2 are balanced.

[0041] FIG. 5 is a table showing the results of the verification test 1. As shown in FIG. 5, when the impeller 3 is rotated in a state of being moved from the origin (Y = 0 mm) to the upper limit position on the positive side in the Y direction (Y = +2 mm), it was confirmed that the load (downward load F2) acting on the negative side in the Y direction increases. That is, it was confirmed that when the impeller 3 moves to the positive side in the Y direction, the downward load F2 on the negative side in the Y direction acts more predominantly than the upward load F1 on the positive side in the Y direction.

[0042] On the other hand, it was confirmed that as the impeller 3 is moved from the origin (Y = 0 mm) to the lower limit position on the negative Y side (Y = -3 mm), the load acting on the positive Y side (upward load F1) gradually increases. That is, it was confirmed that when the impeller 3 moves to the negative Y side, the upward load F1 on the positive Y side acts more dominantly than the downward load F2 on the negative Y side.

[0043] [Verification Test 2] Next, a verification test 2 was conducted to determine whether an axial position restoring force acts appropriately on the impeller 3 when the partition plate 32 and the plurality of blades 33 satisfy the relationship of the above formula (1). In verification test 2, with the impeller 3 fixed at the upper limit position (Y = +2 mm) in FIG. 4, when the value of A / B was changed, the load (position restoring force) in the Y direction acting on the impeller 3 was calculated using fluid analysis software. In changing the value of A / B, the diameter B of the virtual circumscribed circle was set as a constant value (26.4 mm), and the outer diameter A of the partition plate 32 was gradually changed from 17.4 mm to 25.4 mm.

[0044] FIG. 6 is a table showing the results of verification test 2. In verification test 2, the position restoring force acting on the impeller 3 at the upper limit position is the downward load F2 (see FIG. 4). Therefore, if the load in the Y direction shown in FIG. 6 is a negative value, it can be considered that the axial position restoring force acts appropriately on the impeller 3. In the test results of FIG. 6, the minimum value of A / B when the load in the Y direction becomes a negative value was confirmed to be 0.89, which is the same as the lower limit value of the above formula (1).

[0045] [Function and Effect] According to the magnetic levitation pump 1 and the impeller 3 of this embodiment, a plurality of blades 33 are arranged with a clearance E2 on the outer peripheral surface 32a of the partition plate 32 in the radially outer direction. For this reason, since it is not necessary to fix each of the plurality of blades 33 to the partition plate 32 by welding or the like, the man-hours required for manufacturing the impeller 3 can be significantly reduced. Further, even if the plurality of blades 33 are not fixed to the partition plate 32, an axial position restoring force acts on the impeller 3. Therefore, the impeller 3 on which the axial position restoring force acts can be manufactured at low cost.

[0046] The outer diameter A of the partition plate 32 and the diameter B of the virtual circumscribed circle circumscribing the closest ends 33d of the plurality of blades 33 satisfy the relationship of the above formula (1). Thereby, since an axial position restoring force can be appropriately applied to the impeller 3, it is possible to effectively suppress the impeller 3 from coming into contact with the housing 2 and being damaged.

[0047] The axial dimension C of the interval E1 between the end face 31c of the impeller body 31 and the thin portion 322 of the partition plate 32, and the minimum axial dimension D of the blade 33 satisfy the relationship of the above formula (2). Thereby, it is possible to suppress a reduction in the fluid transfer characteristics of the magnetic levitation pump 1.

[0048] [Others] In the magnetic levitation pump 1 of this embodiment, the motor 4 also serves as the magnetic bearing portion 5, but a fixed magnetic portion 11a may be provided separately from the motor 4. If an axial position restoring force acts on the impeller 3, it does not have to satisfy the relationship of the above formula (1), nor does it have to satisfy the relationship of the above formula (2). The number of balance holes 35 is not limited to this embodiment.

[0049] The embodiments disclosed this time should be considered to be 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 is intended to include meanings equivalent to the claims and all modifications within the scope.

Explanation of Reference Numerals

[0050] 1 Magnetic levitation pump 2 Housing 3 Impeller 4 Motor 5 Magnetic bearing section 24 Inlet 25 Outlet 31 Impeller body 32 Partition plate 32a Outer peripheral surface 33 Blade 33d Nearest end 35 Balance hole E1 Spacing E2 Gap X Axis

Claims

1. An impeller rotatably disposed about an axis within a housing having an inlet and an outlet for a fluid to be transferred, the impeller comprising: A cylindrical impeller body having a balance hole axially penetrating therethrough and formed radially inward; A disk-shaped partition plate spaced axially from one axial side of an opening on one axial side closer to the inlet in the balance hole; A plurality of blades disposed along the circumferential direction of the partition plate on the radially outer side of the partition plate; The plurality of blades are each disposed with a gap on the radially outer side with respect to the outer peripheral surface of the partition plate.

2. The impeller according to claim 1, wherein when the outer diameter of the partition plate is A and the diameter of a virtual circumscribed circle circumscribing the closest end of each of the plurality of blades to the partition plate is B, the relationship 0.89 ≦ A / B < 1.00 is satisfied.

3. The impeller according to claim 1 or claim 2, wherein when the axial dimension of the gap is C and the minimum axial dimension of the blade is D, the relationship 0.2 ≦ C / D ≦ 0.6 is satisfied.

4. A housing having an inlet and an outlet for a fluid to be transferred; The impeller according to claim 1 or claim 2 disposed within the housing; A motor for rotationally driving the impeller; A magnetic bearing unit for non-contact support of the rotating impeller. A magnetic levitation pump comprising.

Images