EP2503152A2

EP2503152A2 - Centrifugal pump

Info

Publication number: EP2503152A2
Application number: EP12158756A
Authority: EP
Inventors: Toshitaka Ishibashi
Original assignee: Panasonic Corp
Current assignee: Panasonic Corp
Priority date: 2011-03-25
Filing date: 2012-03-09
Publication date: 2012-09-26
Also published as: JP2012202320A

Abstract

A centrifugal pump comprises an impeller provided in the rear of its rear shroud with a magnetic follower, a housing storing said impeller, and a magnetic actuator located in said housing so as to surround said magnetic follower of said impeller and magnetically driving to rotate said magnetic follower. Then, said housing comprises a plastic recess for storing said magnetic follower, and said recess is provided in its inner surface with a nonmagnetic metallic plate which is harder than iron.

Description

TECHNICAL FIELD

The invention relates generally to centrifugal pumps.

BACKGROUND ART

Japanese Patent Application Laid-Open No. 9-49496 discloses a magnetic coupling pump, which comprises an impeller having a rotor magnet and a stator rotating the impeller by means of exerting a magnetic attractive force to the rotor magnet.
Incidentally, in regard to the pump described in the above document, sometimes fluid discharged from the impeller to the impeller's circumference comes around behind the impeller. Then, sometimes the fluid includes ferromagnetic materials as foreign materials. The ferromagnetic materials are, for example, iron powders. The foreign materials are affected by a magnetic force produced in the rotor magnet and a magnetic field produced in the stator, and thus may be absorbed onto an outer periphery of the rotor magnet and an inner surface of a housing facing said outer periphery. Then, when the impeller rotates while the foreign materials are absorbed onto the outer periphery of the rotor magnet and the inner surface of the housing, the absorbed foreign materials may damage to the inner surface of the housing. In some cases, fluid may leak from the damaged area of the inner surface to the outside.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a centrifugal pump, which can prevent that foreign materials, such as iron powders, included in fluid damage to an inner surface of a housing.
A centrifugal pump of the present invention comprises an impeller provided in the rear of its rear shroud with a magnetic follower, a housing storing said impeller, and a magnetic actuator located in said housing so as to surround said magnetic follower of said impeller and magnetically driving to rotate said magnetic follower. Then, said housing comprises a plastic recess for storing said magnetic follower, and then said recess is provided in its inner surface with a nonmagnetic metallic plate which is harder than iron.
In this configuration, the centrifugal pump can prevent that foreign materials, such as iron powders, included in fluid damage to an inner surface of a housing.
Then, preferably, said metallic plate is located only in a position of said inner surface of said recess corresponding to a rear end portion of said magnetic follower.
Then, preferably, said recess and said metallic plate are integrally molded.
Then, preferably, said recess is provided in a position of its inner surface corresponding to a front end portion of said magnetic follower with a projection as said metallic plate.
Then, preferably, said housing further comprises a plastic division plate. Then, said division plate has said recess which is formed into closed bottom tubular-shape and of which the front is opened and the rear is closed as the bottom, and a flange projecting outward along a radial direction from a front edge of said recess. Then, said projection comprises a plate-shaped member located over a range of an inner periphery of said recess to a front surface of said flange along said division plate.
Then, another centrifugal pump of the present invention comprises an impeller provided in the rear of its rear shroud covering the rears of a plurality of vanes with a magnetic follower, a housing storing said impeller, and a magnetic actuator located in said housing so as to surround said magnetic follower of said impeller and magnetically driving to rotate said magnetic follower. Then, said housing comprises a plastic recess for storing said magnetic follower, and then said magnetic follower is provided with a plurality of second vanes for sending fluid existing around the circumference of said magnetic follower in the inside of said recess forward.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described in further details. Other features and advantages of the present invention will become better understood with regard to the following detailed description and accompanying drawings where:

Fig. 1 is a cross-sectional view showing a centrifugal pump in accordance with a first embodiment of the present invention;
Fig. 2 is a cross-sectional view showing a centrifugal pump in accordance with a second embodiment of the present invention;
Fig. 3 is a cross-sectional view showing a centrifugal pump in accordance with a third embodiment of the present invention;
Fig. 4 is a cross-sectional view showing a centrifugal pump in accordance with a fourth embodiment of the present invention;
Fig. 5 is a cross-sectional view showing a centrifugal pump in accordance with a fifth embodiment of the present invention; and
Fig. 6 is a cross-sectional view showing a centrifugal pump in accordance with a sixth embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a centrifugal pump of the present invention is explained referring to attached figures. In addition, in the following explanation, a direction of a rotating axis of an impeller 2 is defined as a front-back direction, and the side of an inlet 11 is defined as the front side with respect to the direction of said rotating axis.

(First Embodiment)

As shown in Fig. 1, a centrifugal pump 1 of first embodiment comprises a housing 3 which is an outer fence, and an impeller 2 stored in the housing 3. The impeller 2 is provided in its front with a pump section 4, and is provided in its rear with a magnetic follower 6.
The housing 3 comprises a drive block 9 formed with a rotor chamber 7 of which the front is opened, and a casing 8 formed with a pump chamber 5 of which the rear is opened.
The drive block 9 is located in the rear of the casing 8. The rotor chamber 7 of the drive block 9 leads to the pump chamber 5 of the casing 8, and then the pump and rotor chambers 5, 7 constitute a storage chamber 18 for storing the whole impeller 2.
The drive block 9 comprises a division plate 24, a magnetic actuator 25, a controller 33, and a resin molding member 34 which is an outer fence.
The division plate 24 is constructed of plastics material and, for example, is formed of polyphenylene sulfide (PPS) resin. The division plate 24 is formed into container-shape and its front is opened. The division plate 24 comprises a recess 26 which is formed into bottomed cylindrical-shape and of which the front is opened and the rear is closed as the bottom 50, and a flange 27 which projects outward along a radial direction from a front edge of the recess 26. The inside of the recess 26 is the rotor chamber 7. A rear corner 39 is located in the point of demarcation between a peripheral wall 28 and the bottom 50 of the recess 26, and its cross-section is formed into arc-shape so as to project to the outside. The flange 27 is formed along the entire length of a circumferential direction of the peripheral wall 28. Then, a front corner 49 is located in the point of demarcation between the peripheral wall 28 and the flange 27 of the recess 26, and its cross-section is formed into arc-shape so as to project to the inside.
The recess 26 is formed in the center of the bottom 50 with a rear fixed part 35 projecting forward. A ceramic shaft 23 supports the impeller 2 rotatably, and a rear end portion of the shaft 23 is fixed to the rear fixed part 35.
The magnetic actuator 25 is a stator, and comprises a stator core 31 formed of magnetic steel, and a coil 32 wound on the stator core 31 while being electrically insulated. The magnetic actuator 25 is located around the peripheral wall 28 of the recess 26.
The controller 33 comprises a control board and is configured to control the magnetic actuator 25. The control board is located in the rear of the division plate 24 and the magnetic actuator 25. The controller 33 is electrically connected to the coil 32 of the magnetic actuator 25. When a current is applied to the coil 32 of the magnetic actuator 25 by the control of the controller 33, the magnetic actuator 25 produces a magnetic field for rotating the magnetic follower 6 of the impeller 2.
The resin molding member 34 is formed of unsaturated polyester resin, and is located in the outside of the division plate 24, and integrally contains the division plate 24, the magnetic actuator 25 and the controller 33.
In regard to the impeller 2, the magnetic follower 6 is stored in the rotor chamber 7, and the pump section 4 is stored in the pump chamber 5. Then, the magnetic follower 6 comprises a plastic rotor 20, a magnet 19 located in the circumference of the rotor 20, and a shaft bearing 21 located in the center of the rotor 20. The rotor 20 is constructed of polyphonylene ether (PPE) resin, and the magnet 19 is constructed of ferrite, and the shaft bearing 21 is constructed of carbon.
The rotor 20 comprises a tubular bearing fixed part 22 having a through-hole extending in the front-back direction, and a magnet fixed part 36 located around the bearing fixed part 22.
Then, the bearing fixed part 22 is provided in its rear with a small diameter section 45 and in its front with a large diameter section 46. The small diameter section 45 has a smaller diameter than the large diameter section 46, and then the shaft bearing 21 is inserted and secured to the inside of the small diameter section 45. Then, the shaft 23 is inserted into the shaft bearing 21. Then, the shaft 23 supports the impeller 2 rotatably and, that is, the impeller 2 can rotate around an axis of the shaft 23 extending in the front-back direction.
The magnet fixed part 36 is formed into cylindrical shape, and then a front edge of its inner periphery is integrally connected to the large diameter section 46 of the bearing fixed part 22. The magnet fixed part 36 is formed in its outer periphery with a storage groove 40. The magnet 19 is covered with a magnet cover 38 formed of nonmagnetic stainless, and is stored and secured in the storage groove 40. Then, an outer periphery of the magnet cover 38 is set so as to be flush with outer peripheries in both ends of the front-back direction of the magnet fixed part 36. The magnet 19 is located in a periphery of the rotor 20 and in the inside of the magnetic actuator 25, and then the peripheral wall 28 of the recess 26 of the division plate 24 is located between the magnet 19 and the magnetic actuator 25. Then, the magnet cover 38 is optional.
The pump section 4 is located in the front of the magnetic follower 6, and then comprises a plurality of vanes 13 arranged in a circumferential direction of the impeller 2, a rear shroud 15 for covering the rear of each vane 13 and a front shroud 14 for covering the front of each vane 13.
The rear shroud 15 is formed into disc-shape, and is formed in its center with a through-hole 41 extending in the front-back direction. Then, a circumference of the through-hole 41 of the rear shroud 15 is integrally connected to a front edge of the large diameter section 46 of the bearing fixed part 22. The rear shroud 15 and the rotor 20 are integrally molded, after the magnet 19, the magnet cover 38 and the shaft bearing 21 are inserted. In addition, the magnet fixed part 36 is located in the rear of the rear shroud 15 through a clearance in the figure. However, a front end of the magnet fixed part 36 may be coupled with the rear shroud 15 without such a clearance.
The front shroud 14 is formed into disc-shape, and is formed in its center with an inlet section 16 having a through-hole extending in the front-back direction. An outer circumference location of the front shroud 14 is set so as to be corresponding to that of the rear shroud 15 with respect to a radial direction of the impeller 2. Then, a clearance is formed between the outer circumferences of the front and rear shrouds 14, 15. The clearance leads to the inlet section 16 through a flow channel 52 which is formed between adjacent vanes 13, 13 and between the front and rear shrouds 14, 15. The clearance constitutes an outlet section 17 of the pump section 4.
A front end of each vane 13 is integrally coupled with a rear surface of the front shroud 14, and each vane 13 and the front shroud 14 are integrally molded. Then, a rear end of each vane 13 is attached to a front surface of the rear shroud 15.
Each vane 13 applies pressure in the radial direction to fluid (liquid in the present embodiment) flowing to the flow channel 52 through the inlet section 16 when the impeller 2 rotates. Thereby, fluid provided from the inlet section 16 to the flow channel 52 is sent to the circumference of the impeller 2, and is discharged from the outlet section 17 to the circumference of the pump section 4.
The casing 8 is constructed of plastics material and, for example, is formed of polyphenylene sulfide (PPS) resin. As shown in Fig. 1, the casing 8 is formed into container-shape and its rear is opened. The casing 8 has an outer peripheral wall 43 constituting an inner periphery of the pump chamber 5. Then, the outer peripheral wall 43 is formed in its rear edge with a flange section 30 projecting in its radial direction along the entire length of its circumferential direction. The flange section 30 has contact with an outer peripheral edge of a front face of the flange 27. Then, the front of the rotor chamber 7 is covered with the casing 8. The flange section 30 of the casing 8 is attached to an outer periphery of the drive block 9 including the flange 27 by means of using a plurality of screws. Then, the casing 8 is provided with a front fixed part 42, which is located in the center of the storage chamber 18, and a front end portion of the shaft 23 is secured to the front fixed part 42. In addition, signs 59, 60 shown in Fig.1 mean bearing plates for bearing a load applied to the shaft bearing 21 in a thrust direction.
The casing 8 is formed in its center with an inlet 11, which projects forward and is formed into tubular-shape. Then, the inlet 11 faces the inlet section 16 of the impeller 2. Then, the casing 8 is formed in its outer peripheral wall 43 with an outlet 12, which projects outward and is formed into tubular-shape. The outlet 12 leads to a part of the outer periphery of the pump chamber 5.
The controller 33 controls to apply a current to the coil 32, and thereby the centrifugal pump 1 is operated. When a current flows to the coil 32, a magnetic field is produced by the magnetic actuator 25. Then, the magnet 19 of the impeller 2 repels/attracts the magnetic actuator 25, and then the magnetic follower 6 rotates around the shaft 23, and thereby the pump section 4 rotates around an axis of the front-back direction. Then, when the pump section 4 rotates, fluid flows from the inlet 11 to the flow channel 52 of the pump section 4 through the inlet section 16, and then is discharged from the outlet section 17 to the circumference of the pump section 4, and then is discharged to the outside of the centrifugal pump 1 through the outlet 12.
The outer peripheral wall 43 of the casing 8 is located in the outside of the peripheral wall 28 of the division plate 24, and thus the pump chamber 5 bulges more than the rotor chamber 7 with respect to a radial direction. The bulging are faces an inner part of a front surface of the flange 27 of the division plate 24. Then, an outer peripheral edge of the pump section 4 is located in the bulging are, and projects more than the magnetic follower 6 along a radial direction. Then, a rear surface of the outer peripheral edge (that is, a rear surface of the rear shroud 15) is located near the inner part of the front surface of the flange 27. Therefore, when the centrifugal pump 1 is operated, fluid discharged from the outlet section 17 of the pump section 4 hardly comes around behind the rear shroud 15, and then most of the fluid is discharged from the outlet 12.
Then, a small clearance 44 is formed between the outer peripheral edge of the rear shroud 15 and the front corner 49 of the division plate 24 in order to permit rotation of the pump section 4. Thus, when the centrifugal pump 1 is operated, a part of fluid discharged from the outlet section 17 of the pump section 4 hits against the outer peripheral wall 43 of the casing 8, and then reaches the clearance 44, and then flows behind the rear shroud 15 in the pump chamber 5 through the clearance 44. Then, the part of the fluid comes around behind the magnetic follower 6, and then reaches between the shaft bearing 21 and the shaft 23, and then returns to the flow channel 52 of the pump section 4. As described above, the centrifugal pump 1 is configured so that a part of fluid discharged from the outlet section 17 reaches between the shaft bearing 21 and the shaft 23. Thus, the centrifugal pump 1 can lubricate rotation of the shaft 23.
Incidentally, if fluid provided to the rotor chamber 7 includes foreign materials being ferromagnetic materials, such as iron powders, there is a possibility that such foreign materials damages to the recess 26 of the division plate 24 constituting the rotor chamber 7. In order to improve this problem, as shown in Fig. 1, the recess 26 of the present embodiment is provided in its inner surface with a nonmagnetic metallic plate 48 which is harder than iron.
The metallic plate 48 is formed of nonmagnetic stainless into about container-shape along the inner surface of the recess 26, and then has a bottomed cylindrical part 61 of which the front is opened and a flange part 56 projecting outward from a front edge of the cylindrical part 61. A corner 63 is located in the point of demarcation between the cylindrical part 61 and the flange part 56, and its cross-section is formed into arc-shape. Then, the cylindrical part 61 is formed in the center of its bottom with a through-hole 62.
The metallic plate 48 is attached to the division plate 24 while the rear fixed part 35 is inserted into the through-hole 62 and the cylindrical part 61 is fitted to the inner surface of the recess 26 and the flange part 56 is fitted to the front surface of the flange 27 and the corner 63 is fitted to the front corner 49.
As described above, the recess 26 is provided in its inner surface with the metallic plate 48 which is harder than iron, and thus the metallic plate 48 can protect the inner surface of the recess 26. Therefore, even if a part of fluid discharged from the outlet section 17 of the pump section 4 includes iron powders etc. and reaches the rotor chamber 7 through the clearance 44, the centrifugal pump 1 can prevent that foreign materials, such as iron powders, included in the part of the fluid damages to the inner surface of the recess 26. Then, since the metallic plate 48 is nonmagnetic, the metallic plate 48 hardly has an influence on a magnetic field produced by the magnetic actuator 25. Thus, the centrifugal pump 1 can operate the magnetic follower 6 efficiently. In addition, the metallic plate 48 having container-shape is fitted to the division plate 24 having container-shape, and thus the metallic plate 48 can be easily located.
In addition, as described above, the centrifugal pump 1 of the present embodiment is configured so that a part of fluid discharged from the outlet section 17 returns to the pump section 4 through a small gap between the shaft bearing 21 and the shaft 23. However, there is no need that the part of the fluid discharged from the outlet section 17 is aggressively sent to the rotor chamber 7.

(Second Embodiment)

Then, a centrifugal pump 1 of second embodiment is explained below. In the following second embodiment, the same composition elements as the first embodiment are denoted by the same signs, and explanations thereof are omitted for clarity.
As shown in Fig. 2, in a centrifugal pump 1 of the present embodiment, a metallic plate 48 is located only in a position of an inner surface of a recess 26 corresponding to a rear end portion of a magnetic follower 6.
The metallic plate 48 has a cylindrical part 61 of which the front and rear are opened and an inward flange 64 projecting inward from a rear edge of the cylindrical part 61. A corner 65 is located in the point of demarcation between the cylindrical part 61 and the inward flange 64, and its cross-section is formed into arc-shape.
The metallic plate 48 is attached to the division plate 24 while the cylindrical part 61 is fitted to the inner periphery of the peripheral wall 28 and the inward flange 64 is fitted to the bottom 50 of the division plate 24 and the corner 65 is fitted to the rear corner 39.
As described above, because the metallic plate 48 is located only in the position of the inner surface of the recess 26 corresponding to the rear end portion of the magnetic follower 6, the centrifugal pump 1 can prevent that an eddy current is produced in the metallic plate 48 due to the influence of the magnetic field produced by the magnetic actuator 25. Thus, the centrifugal pump 1 can operate the magnetic follower 6 efficiently.
Then, it can be said that in the rotor chamber 7, especially the above position corresponding to the rear end portion of the magnetic follower 6 is a place where fluid flowing from the clearance 44 to the pump chamber 5 flows inward by hitting against the bottom 50 of the recess 26, and a place where foreign materials, such as iron powders, included in fluid are easily collected. Thus, it can be said that the foreign materials easily damages to the above position of the inner surface of the recess 26 corresponding to the rear end portion of the magnetic follower 6. However, in the present embodiment, the metallic plate 48 protects the above position of the inner surface of the recess 26 corresponding to the rear end portion of the magnetic follower 6, and thus the centrifugal pump 1 can properly prevent that the foreign materials damages to the above position.

(Third Embodiment)

Then, a centrifugal pump 1 of third embodiment is explained below. In the following third embodiment, the same composition elements as the first embodiment are denoted by the same signs, and explanations thereof are omitted for clarity.
As shown in Fig. 3, in a centrifugal pump 1 of the present embodiment, a metallic plate 48 and a division plate 24 having a recess 26 are integrally molded.
The metallic plate 48 of the present embodiment is formed into cylindrical-shape, and is located only in a peripheral wall 28 which is a position of the division plate 24 corresponding to a magnet 19 of a magnetic follower 6.
Then, the metallic plate 48 is inserted into a metal mold for molding the division plate 24, and then is integrally molded with the division plate 24. That is, the metallic plate 48 and the division plate 24 are an inset molding product. Then, an inner periphery of the metallic plate 48 is exposed to the rotor chamber 7, and is located in the division plate 24 so as to be flush with an inner periphery of the peripheral wall 28. Thus, a metal mold for molding the inner periphery of the peripheral wall 28 can be pull forward without any difficulty.
In the present embodiment, the recess 26 is integrally molded with the metallic plate 48. Thus, the metallic plate 48 faces pressure from the contracting division plate 24 formed of plastics material along a direction in which the metallic plate 48 is narrowed when being molded. Thereby, the metallic plate 48 can be attached tightly to an inner surface of the rotor chamber 7.
Then, in the present embodiment, the metallic plate 48 is located only in the peripheral wall 28 of the division plate 24. However, location of the metallic plate 48 is not limited to this. For example, the metallic plate 48 may be located over the entire of an inner surface of the division plate 24, like the first embodiment, or may be located only in a position corresponding to a rear end portion of the magnetic follower 6, like the second embodiment, or may be located only in a position of an inner surface of the recess 26 corresponding to a front end portion of the magnetic follower 6, like fourth embodiment described below, or may be located over a range of a front end portion of the peripheral wall 28 to the flange 27 via the front corner 49, like fifth embodiment described below.

(Fourth Embodiment)

Then, a centrifugal pump 1 of fourth embodiment is explained below. In the following fourth embodiment, the same composition elements as the first embodiment are denoted by the same signs, and explanations thereof are omitted for clarity.
As shown in Fig. 4, in a centrifugal pump 1 of the present embodiment, a metallic plate 48 is located only in a position of an inner surface of a recess 26 corresponding to a front end portion of a magnetic follower 6.
The metallic plate 48 is formed into cylindrical-shape and is attached to an inner periphery of a peripheral wall 28 of a division plate 24. The metallic plate 48 projects inward from the inner periphery of the peripheral wall 28 by its thickness, and then constitutes a projection 53.
As described above, the metallic plate 48 of the present embodiment is located in the position of the inner surface of the recess 26 corresponding to the front end portion of the magnetic follower 6, that is, corresponding to a front end portion of the magnet 19 and a front end portion of the magnet fixed part 36, and constitutes the projection 53 projecting from an inner surface of the recess 26. For this configuration, a clearance 54 is formed between the metallic plate 48 and an outer periphery of the magnetic follower 6 facing the metallic plate 48, and is smaller than a clearance formed between an inner periphery of the peripheral wall 28 and the outer periphery of the magnetic follower 6. Thus, the metallic plate 48 can prevent that fluid discharged from the outlet section 17 of the pump section 4 flows to the side of the pump chamber 5, and thereby the centrifugal pump 1 can prevent that foreign materials, such as iron powders, included in fluid damages to the inner surface of the recess 26. In addition, in the present embodiment, the projection 53 is the metallic plate 48 which is harder than iron, and thus the projection 53 can prevent that the foreign materials included in the fluid damages to the position of the inner surface of the recess 26 corresponding to the front end portion of the magnetic follower 6 when the fluid comes around to the rotor chamber 7. Then, since the metallic plate 48 is nonmagnetic, the metallic plate 48 hardly has an influence on a magnetic field produced by the magnetic actuator 25. Therefore, the centrifugal pump 1 can operate the magnetic follower 6 efficiently.

(Fifth Embodiment)

Then, a centrifugal pump 1 of fifth embodiment is explained below. In the following fifth embodiment, the same composition elements as the fourth embodiment are denoted by the same signs, and explanations thereof are omitted for clarity.
As shown in Fig. 5, in a centrifugal pump 1 of the present embodiment, a metallic plate 48 is located over a range of a front end portion of a peripheral wall 28 of a division plate 24 to a flange 27 via a front corner 49. The metallic plate 48 has a cylindrical part 55 and a flange part 56 projecting outward from a front edge of the cylindrical part 55. A corner 57 is located in the point of demarcation between the cylindrical part 55 and the flange part 56, and its cross-section is formed into arc-shape.
The metallic plate 48 is attached to the division plate 24 while the cylindrical part 55 is fitted to a front end portion of an inner periphery of the peripheral wall 28 and the corner 57 is fitted to an inner surface of the front corner 49 and the flange part 56 is fitted to a front surface of the flange 27. A projection 53 projecting from the division plate 24 comprises the metallic plate 48 attached in this way.
As described above, the projection 53 comprises the metallic plate 48 which is formed into plate-shape and is located over a range of a front end portion of the peripheral wall 28 of the division plate 24, that is, the inner surface of the recess 26 to the front surface of the flange 27, and thereby the metallic plate 48 is attached easily to the division plate 24. Then, the flange part 56 of the metallic plate 48 can protect the flange 27 of the division plate 24.
In addition, in the present embodiment and the fourth embodiment, the projection 53 comprises the metallic plate 48. However, the projection 53 may comprise another plate-shaped member. For example, the projection 53 and the division plate 24 may be integrally formed.

(Sixth Embodiment)

Then, a centrifugal pump 1 of sixth embodiment is explained below. In the following sixth embodiment, the same composition elements as the first embodiment are denoted by the same signs, and explanations thereof are omitted for clarity.
A centrifugal pump 1 of the present embodiment does not comprise a metallic plate 48. Instead, the centrifugal pump 1 comprises an impeller 2 shown in Fig. 6. A magnetic follower 6 of this impeller 2 is provided with a plurality of second vanes 67 for sending fluid existing around the circumference of the magnetic follower 6 in the inside of a recess 26 forward.
Then, in the magnetic follower 6 provided with the plurality of second vanes 67, a front edge of a cylindrical-shaped magnet fixed part 36 of a rotor 20 is connected to a rear shroud 15. The magnet fixed part 36 is formed in its inner periphery with a bearing fixed part 69 having a through-hole extending in a front-back direction as substitute for a bearing fixed part 22. Although not shown in the figure, a shaft 23 is inserted and secured to the through-hole of the bearing fixed part 69.
Then, a space 70 is formed in a front part of the inside of the magnet fixed part 36, and then leads to a flow channel 52 of a pump section 4 via a through-hole 75 formed in the center of the rear shroud 15. Then, a space 71 is formed in a rear part of the inside of the magnet fixed part 36, and then is located in the rear of the space 70 via the bearing fixed part 69. The space 71 is communicated with the space 70 through a first continuous hole 72 formed in the magnet fixed part 36. Then, the magnet fixed part 36 is formed in its front end portion with a second continuous hole 74, and thereby the space 71 leads to a space 73 formed in the circumference of the magnet fixed part 36.
The plurality of second vanes 67 are formed in a rear end face of the magnet fixed part 36 along a circumferential direction. The plurality of second vanes 67 sends fluid existing in the space 70 to the space 71 through the first continuous hole 72, when the impeller 2 rotates. Then, the fluid is discharged into the circumference of the plurality of second vanes 67, and then passes through a space which is formed between an inner periphery of the peripheral wall 28 and the magnetic follower 6 facing the inner periphery, and then passes through the space 73, and then passes through the second continuous hole 74, and then returns to the space 70.
In addition, although the space 70 leads to the flow channel 52 of the pump section 4, the second continuous hole 74 is formed in the magnet fixed part 36 and thus a negative pressure is hardly produced near the through-hole 75 of the rear shroud 15. Therefore, fluid including iron powders etc. is also hardly provided to the space 70, and thus the centrifugal pump 1 can prevent that most of fluid including iron powders etc. is provided from the through-hole 75 of the rear shroud 15 to the rotor chamber 7 through the space 70.
In the present embodiment, the magnetic follower 6 is provided with the plurality of second vanes 67 for producing circulating flow as described above. Thus, the plurality of second vanes 67 can send fluid existing in the circumference of the magnetic follower 6 of the rotor chamber 7 forward. Then, the fluid flows in a direction opposite to fluid flowing from the outlet section 17 to the rotor chamber 7 through the clearance 44. Therefore, the centrifugal pump 1 can prevent that fluid flows from the outlet section 17 to the pump chamber 5 through the clearance 44, and prevent that foreign materials, such as iron powders, damage to an inner surface of the rotor chamber 7.
Although the present invention has been described with reference to certain preferred embodiments, numerous modifications and variations can be made by those skilled in the art without departing from the true spirit and scope of this invention, namely claims.

Claims

A centrifugal pump (1) comprising:
an impeller (2) provided in the rear of its rear shroud (15) with a magnetic follower (6);

a housing (3) storing said impeller (2); and

a magnetic actuator (25) located in said housing (3) so as to surround said magnetic follower (6) of said impeller (2), and magnetically driving to rotate said magnetic follower (6),
characterized in that:
said housing (3) comprises a plastic recess (26) for storing said magnetic follower (6),
wherein said recess (26) is provided in its inner surface with a nonmagnetic metallic plate (48) which is harder than iron.
The centrifugal pump (1) as claimed in claim 1
wherein said metallic plate (48) is located only in a position of said inner surface of said recess (26) corresponding to a rear end portion of said magnetic follower (6).
The centrifugal pump (1) as claimed in claim 1 or 2
wherein said recess (26) and said metallic plate (48) are integrally molded.
The centrifugal pump (1) as claimed in claim 1
wherein said recess (26) is provided in a position of its inner surface corresponding to a front end portion of said magnetic follower (6) with a projection (53) as said metallic plate (48).
The centrifugal pump (1) as claimed in claim 4
wherein said housing (3) further comprises a plastic division plate (24),
wherein said division plate (24) has said recess (26) which is formed into closed bottom tubular-shape and of which the front is opened and the rear is closed as the bottom, and a flange (27) projecting outward along a radial direction from a front edge of said recess (26),
wherein said projection (53) comprises a plate-shaped member located over a range of an inner periphery of said recess (26) to a front surface of said flange (27) along said division plate (24).
A centrifugal pump (1) comprising:
an impeller (2) provided in the rear of its rear shroud (15) covering the rears of a plurality of vanes (13) with a magnetic follower (6);

a housing (3) storing said impeller (2); and

a magnetic actuator (25) located in said housing (3) so as to surround said magnetic follower (6) of said impeller (2), and magnetically driving to rotate said magnetic follower (6),
characterized in that:
said housing (3) comprises a plastic recess (26) for storing said magnetic follower (6),
wherein said magnetic follower (6) is provided with a plurality of second vanes (67) for sending fluid existing around the circumference of said magnetic follower (6) in the inside of said recess (26) forward.