US20090022607A1

US20090022607A1 - Arrangement for delivering fluids

Info

Publication number: US20090022607A1
Application number: US11/576,688
Authority: US
Inventors: Alexander Jordan; Michael Burgert
Original assignee: Ebm Papst St Georgen GmbH and Co KG
Current assignee: Ebm Papst St Georgen GmbH and Co KG
Priority date: 2004-10-06
Filing date: 2005-08-10
Publication date: 2009-01-22
Also published as: EP1797330B1; EP1797330A1; WO2006037396A1; DE502005006436D1; ATE420292T1

Abstract

An arrangement for delivering fluids has a fluid pump having a pump wheel (90), which wheel is joined to a first permanent magnet (92). The pump wheel (90) is rotatably arranged inside a liquid-tight pump housing (80, 82, 84, 86, 88). This housing is shaped, near the first permanent magnet (92), as a partitioning can (80, 82). The arrangement also has an electronically commutated electric motor (20) having a stator (22) and a rotor (26) arranged rotatably relative thereto, which rotor comprises a second permanent magnet (67) that coacts with the first permanent magnet (92) to act as a magnetic coupling (94). Arranged in the space between the second permanent magnet (67) and partitioning can (80, 82) is a plurality of soft ferromagnetic magnetic flux conductors (150).

Description

CROSS-REFERENCE

This application is a section 371 of PCT/EP05/08668, filed 10 Aug. 2005 and published 13 Apr. 2006 as WO 2006-37396-A.

FIELD OF THE INVENTION

The invention relates to an arrangement for pumping fluids. As fluids, liquid and/or gaseous media can be pumped.

BACKGROUND

In computers, components having high heat flux densities (e.g. 60 W/cm²) are in use today. The heat from these components must first be transferred into a liquid circulation system, and from that circulation system the heat must be discharged to the ambient air via a liquid/air heat exchanger.
Dissipation of heat from components having a high heat flux density is accomplished by means of so-called heat absorbers or cold plates. In these, heat is transferred to a cooling liquid, and the latter is usually caused to circulate in a circulation system.
In this context, the cooling liquid flows not only through the heat absorber but also through a liquid pump that produces the forced circulation and produces an appropriate pressure buildup and appropriate volumetric flow through the heat absorber and an associated heat exchanger, so that the heat transfer coefficients relevant to these heat-transfer elements become large and the temperature gradients necessary for heat transfer become small.
A fan is usually arranged near the heat exchanger, which fan produces, on the air side of the heat exchanger, a forced convection of the cooling air as well as good transfer coefficients.
In cooling arrangements of this kind, the fan and the liquid pump are driven separately, and these components are also often physically separate from one another. Two drives are therefore required, which in most cases operate rotationally. These drives require energy and also a fairly large installation space, both of which are undesirable.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to make available a novel arrangement for delivering fluids.
According to the invention, this object is achieved by using soft ferromagnetic flux conductors to assist in magnetically coupling an electric motor to a pump rotor across a partitioning can which separates them.
A very compact arrangement with good efficiency is thereby obtained, in which context the soft ferromagnetic magnetic flux conductors bridge the space between the partitioning can and the second permanent magnet and thereby make possible a greater distance between the first permanent magnet and second permanent magnet of the magnetic coupling.

BRIEF FIGURE DESCRIPTION

Further details and advantageous refinements of the invention will be evident from the exemplifying embodiments, in no way to be understood as a limitation of the invention, that are described below and depicted in the drawings.

FIG. 1 is a longitudinal section through a preferred embodiment of the invention, looking along line I-I of FIG. 5;

FIGS. 2 and 3 are exploded views of the arrangement according to FIG. 1;

FIG. 4 is a schematic view to explain the invention;

FIG. 5 is a section looking along line V-V of FIG. 1;

FIG. 6 is a three-dimensional view of an arrangement having flux-conducting plates, according to a variant of the invention;

FIG. 7 is an enlarged view of a portion of FIG. 6, showing projections that are deformed upon ultrasonic welding and thereby create a local welded join;

FIG. 8 is a plan view from below of the arrangement of FIG. 6, looking in the direction of arrow VIII of FIG. 6;

FIG. 9 is a plan view from above of the arrangement of FIG. 6, looking in the direction of arrow IX of FIG. 6;

FIG. 10 schematically depicts how the arrangement according to FIG. 6 is mounted by being pressed on and ultrasonically welded;

FIG. 11 is an enlargement of a detail;

FIG. 12 shows the arrangement according to FIG. 10 after its assembly;

FIG. 13 is a three-dimensional view of an arrangement having flux-conducting plates, according to a further variant of the invention;

FIG. 14 is an enlarged view of a portion of FIG. 13;

FIG. 15 is a horizontal section through the arrangement according to FIG. 13;

FIG. 16 shows a detail of FIG. 15;

FIG. 17 is a section through a flux-conducting plate of FIG. 13; and

FIGS. 18 and 19 are two schematic views to explain assembly of the rotor and its bearings in the context of the arrangement according to FIGS. 1 to 3.

DETAILED DESCRIPTION

In the description that follows, the terms “left,” “right,” “top,” and “bottom” refer to the respective Figure of the drawings. Identical or identically functioning parts are labeled in the various Figures with the same reference characters, with an apostrophe added if applicable, e.g. 150 and 150′.
FIG. 1 is an enlarged depiction of an arrangement having an electronically commutated external-rotor motor 20. The latter has an internal stator 22 of conventional design as depicted by way of example in section in FIG. 2, e.g. a stator having salient poles or a claw pole stator, and the latter is separated by a substantially cylindrical air gap 24 from a permanent-magnet external rotor 26 whose construction is likewise particularly easy to see in FIG. 2. External rotor 26 rotates around internal stator 22 during operation, and such motors 20 are therefore referred to as external-rotor motors.
Internal stator 22 is mounted, usually by being pressed on, on a bearing tube 30 made of a suitable plastic. The shape of bearing tube 30 is particularly clearly evident from FIGS. 2 and 3. Located to the right of internal stator 22 in FIG. 1 is a circuit board 32. Located on the latter are, for example, electronic components (not depicted here) that are necessary for electronic commutation of motor 20, as well as a rotor position sensor 34 that is controlled by a permanent ring magnet 36 of external rotor 26. Ring magnet 36 is radially magnetized and preferably has four rotor poles. Its magnetization, i.e. the distribution of its magnetic flux density, can be e.g. rectangular or trapezoidal. Sensor 34 is controlled by a leakage field of ring magnet 36, enabling non-contact sensing of the position of rotor 26.
External rotor 26 has a design with a so-called rotor cup 40, which is implemented here as a deep-drawn cup-shaped sheet-metal part made of soft ferromagnetic material. Ring magnet 36 is mounted in this sheet-metal part 40 so that the latter forms a magnetic yoke for rotor magnet 36.
Sheet-metal part 40 is mounted on a hub 44 in which a shaft 46 is mounted in the manner depicted. Shaft 46 is journaled in two ball bearings 48, 50 whose outer rings are held at a distance from one another by a spacing element 52 (cf. the schematic depictions in FIGS. 18 and 19). Upon assembly, these ball bearings 48, 50, together with shaft 46, are pressed from the left in FIG. 1 into bearing tube 30 and are retained there by a latching member 54 (cf. FIGS. 18 and 19). An axial projection 56 of flange part 44 serves for pressing in latching member 54. Located between said flange part and the inner ring of rolling bearing 48 is a compression spring 58 that, after installation, presses rotor 26 to the left (with reference to FIG. 1) until a snap ring 59 mounted at the right end of shaft 46 abuts against the inner ring of rolling bearing 50. With this assembly procedure, shaft 46 is therefore displaceable in the inner rings of the two rolling bearings 48, 50. This assembly procedure of course represents only one preferred embodiment. Many other procedures are possible.
This assembly procedure makes it possible, in the context of FIG. 1, to install rotor 26, together with its already pre-installed bearings 48, 50, into bearing tube 30 from the left, so that the right end 60 (in FIG. 1) of the internal opening of bearing tube 30 can be closed off in liquid-tight fashion as depicted. This assembly procedure will be explained in further detail with reference to FIGS. 18 and 19 below.
The outer side of sheet-metal part 40 is surrounded by a plastic part 63 in which fan blades 64 are formed, in the manner depicted, by plastic injection molding. These blades rotate, during operation, in an opening 66 of a fan housing 68 (cf. FIG. 3). Fan housing 68 preferably has the usual square outline of an equipment fan, and has an attachment hole 70 at each of its corners. Plastic part 63 has, at the right in FIG. 1, a continuation part 65 in which is mounted a permanent magnet 67 that is part of a magnetic coupling.
Bearing tube 30 transitions to the right in FIG. 1 into a flange-like portion 80, which proceeds perpendicular to rotation axis 81 of rotor 26 and transitions at its periphery into a cylindrical portion 82 that here has the function of a so-called partitioning can and is therefore referred to hereinafter as partitioning tube 82. The latter transitions via a shoulder 84 into a cylindrical portion 86 whose free end, as depicted, serves for mounting of a cover 88, for example by laser welding. An inflow fitting 96 for cooling liquid is provided on cover 88. A pump wheel 90 is rotatably arranged in the housing part that is closed off by cover 88. Bearing tube 83 is, as depicted, preferably manufactured integrally with parts 82, 84, 86 from a magnetically transparent plastic.
Pump wheel 90 is preferably implemented integrally with a permanent-magnet rotor 92 that, with permanent magnet 67, forms a magnetic coupling 94; i.e., when permanent magnet 67 rotates, permanent magnet 92 also rotates and thereby drives delivery wheel 90, with the result that the latter draws in liquid via inlet 96 and pumps it out via an outlet 98, as indicated by arrows. Any desired other hydraulic machine, e.g. a compressor for a refrigerant, can of course also be provided instead of a spiral pump.
As is apparent from the drawings, the distance from permanent magnet 67 to permanent magnet 92 is large, so that a direct transfer of torque between these two magnets would not be possible. For this reason, a plurality of magnetic flux conductors in the form of flux-conducting elements 150 is arranged between magnets 67, 92, which elements map the magnetic field of the rotating permanent magnet 67 onto partitioning tube 82 and thereby produce a rotation of permanent magnet 92.
FIG. 2 is a perspective depiction of approximately half of the flux-conducting elements 150, and FIG. 4 explains their manner of operation. Flux-conducting elements 150 have, in FIGS. 1 and 2, the shape of pentagonal panels made of dynamo sheet, i.e. soft ferromagnetic material. In the exemplifying embodiment according to FIGS. 1 to 5, they are embedded with their radially inner ends in partitioning tube 82 (cf. FIG. 5), and proceeding from there they become wider in the radially outward direction. They are arranged in a star shape, e.g. in the shape according to FIG. 5. Their outer ends 152 are separated from permanent magnet 67 by a magnetic air gap 154. (“Magnetic air gap” is an electrical-engineering term. A plastic that is magnetically transparent can also form an “air gap” of this kind, i.e. in magnetic terms it acts like air.)
FIG. 4 shows an instantaneous rotational position of magnet 67, which is depicted as having four poles, as is magnet 92. The latter is depicted in simplified fashion. In this position, a pole boundary 156 located between two adjacent poles of magnet 67 is shown at approximately the 12:30 position with reference to a clock dial. To the left of boundary 156, flux-conducting elements 150 are located opposite south poles S; to the right of boundary 156, however, they are located opposite north poles N. Flux-conducting elements 150 each extend here in radial planes and at a distance from one another, with the result that they are magnetically insulated from one another. They are preferably distributed regularly over the circumference, in order to prevent the creation of reluctance torques and preferred magnetic positions.
Accordingly, south poles S are also constituted at the inner end (viewed radially) of flux-conducting elements 150 to the left of pole boundary 156, which poles attract the north pole N of permanent magnet 92.
To the right of pole boundary 156, flux-conducting elements 150 are located opposite north poles N, and north poles N that attract a south pole of permanent magnet 92 are accordingly located at the radially inner ends of flux-conducting elements 150 there.
When external magnet 67 rotates clockwise, as depicted in FIG. 5, the poles on the inner ends of flux-conducting elements 150 thus also move and consequently produce a rotation of the inner permanent magnet 92 at the same speed. The arrangement according to FIG. 4 thus works on the principle of a synchronous motor. (Alternatively, in special cases, operation with slippage is also not precluded; this requires the use of particular materials in magnetic coupling 94, as known to one skilled in the art.)
Flux-conducting elements 150 therefore bridge the distance between magnets 67 and 92, so that magnet 92 can have a small diameter. This is important because magnet 92 rotates in the cooling liquid, and consequently, if the diameter of magnet 92 is small, the frictional losses produced in that cooling liquid are low. This contributes to good efficiency for the arrangement.
Permanent magnet 92 of the fluid pump is rotatably journaled by means of a plain bearing 100 on a stationary shaft 106 that is mounted in liquid-tight fashion, in the manner depicted, in a rightward-protruding projection 107 of portion 80. A snap ring (not depicted) can be provided at the right end of shaft 106. Magnet 92 is attracted by the adjacent flux-conducting elements 150 and retained in the axial position depicted.
For the mounting procedure depicted for bearings 48, 50, an open space 109 is required between the right end (in FIG. 1) of shaft 46 and the bottom of opening 60. Despite this open space 109, the configuration with projection 107 enables an axially compact design.
Cylindrical portion 86 is joined via radially extending struts 114 to fan housing 68, so that the latter, with partitioning tube 82, portion 80, and bearing tube 30, forms a one-piece plastic part; this simplifies assembly of the arrangement, minimizes the number of parts, and reliably separates from one another the units being used, so that liquid cannot travel from hydraulic machine 90 to electric motor 20 and damage it. Stationary shaft 106 likewise forms a constituent of this injection-molded part, since it is anchored therein during manufacture, and therefore likewise contributes to the compact design.

Manner of Operation

In operation, external-rotor motor 20 drives external rotor 26 so that fan blades 64 rotate in housing 68 and thereby generate an air flow therein. Alternatively, the fan can also be implemented as a diagonal or radial fan. An axial fan is depicted.
At the same time, ring magnet 67 drives rotor magnet 92 via flux-conducting elements 150 and through partitioning tube 82, thus rotating pump wheel 90 so that the latter draws in liquid through inlet 96 and pumps it out through outlet 98. A pump of this kind can be used, for example, in a fountain in order to draw in water and pump it out, or to pump blood in a heart-lung machine, or to transport cooling liquid in a closed cooling circuit, in which case pump wheel 90 then has the function of a circulating pump.
Because cover 88 is joined in liquid-tight fashion to cylindrical part 86, e.g. by laser welding, no liquid can escape to the outside from housing 88. Contributing to this is the fact that portion 80 and its projection 107 are free of any kind of orifices. This is possible because rotor 26 is very easy to install, for example, in the manner described below in the context of FIGS. 18 and 19, and it is not necessary to have access to the right end (in FIG. 1) of shaft 46 during installation. Pump wheel 90 of the centrifugal pump with its plain bearing 100 can likewise be installed from the right in FIG. 1 onto stationary shaft 106 before cover 88 is mounted. The result of flux-conducting elements 150 is that rotor 26, including its axial extension 65 and permanent magnet 67, can very easily be pushed during installation by way of said flux-conducting elements 150, without requiring any complex installation operations for the purpose. The entire remaining portion of the arrangement can be preassembled prior to the installation of rotor 26, since because of flux-conducting elements 150 it is possible to make the outside diameter in the region of these elements 150 larger than the outside diameter of internal stator 22 and circuit board 32.
As an alternative to FIG. 1, it is possible to provide for the journaling of pump wheel 90 a rotating shaft that is journaled, just like shaft 46 of motor 20, in a bearing tube (not depicted) that, like bearing tube 30, is then implemented integrally with portion 80 and protrudes therefrom to the right, i.e. in mirror-image fashion to bearing tube 30.
According to FIG. 18, which differs slightly from what is depicted in FIGS. 1 to 5, various components are preinstalled on shaft 46 before motor 20 is assembled.
Beginning at projection 56, the first is compression spring 58, whose larger-diameter end rests in a depression 39. This spring is followed by the annular retaining member in the form of retaining washer 54. Spring 58 does not abut against retaining member 54.
Retaining member 54 is followed by rolling bearing 48, with its outer ring 48 e and its inner ring 48 i. The latter is displaceable in an axial direction on shaft 46. The lower end of spring 58 abuts against the upper end of inner ring 48 i. Rolling bearing 48 is followed by spacing element 52, which is guided displaceably on shaft 46 by means of a radially inwardly protruding projection 53, and whose upper end, as depicted, abuts against the lower end of outer ring 48 e.
Spacing element 52 is followed by lower rolling bearing 50, with its outer ring 50 e that abuts with its upper end against spacing element 52, and with its inner ring 50 i that is axially displaceable on shaft 46 and abuts with its lower end against snap ring 59 when the assembling of motor 20 is finished.
As is readily apparent, it is possible, by pushing upward on lower rolling bearing 50 with a force F, to compress spring 58 and thereby to displace the two bearings 48, 50, spacing element 52, and retaining washer 54 upward on shaft 46, so that inner ring 50 i no longer abuts against snap ring 59 but instead ends up at a distance therefrom. In this case projection 56 of rotor 22 comes into contact against retaining washer 54 and makes it possible, by way thereof, to transfer an axial force to retaining washer 54, outer ring 48 e, spacing element 52, and outer ring 50 e when rotor 26 is pressed downward with a force K during assembly.
FIG. 19 shows a “snapshot” during the “mating” operation in which shaft 46 of rotor 26, with rolling bearings 48, 50 present thereon, is introduced into internal opening 77 of bearing tube 30.
In this context, a force K is applied to rotor 26 in the axial direction; and because outer rings 48 e, 50 e of rolling bearings 48, 50 are pressed with a press fit into bearing tube 30, spring 58 is compressed by force K so that shaft 46 is displaced in ball bearings 48, 50, and projection 56 acts via retaining washer 54 on outer ring 48 e of ball bearing 48 and also via spacing element 52 on outer ring 50 e of ball bearing 50, and thus presses the two ball bearings 48, 50 into bearing tube 30.
Pressing-in continues until outer ring 50 e of the lower ball bearing 50 abuts against the upper end of ribs 83 that are provided in bearing tube 30 at its inner end 60.
According to FIG. 19, in this context retaining member 54 is displaced in bearing tube 30 and digs into its plastic material, so that the entire bearing arrangement latches into bearing tube 30.
Force K is removed after pressing-in is complete, and what then results is the situation according to FIG. 1, i.e. spring 58 now once again pushes shaft 46 until snap ring 59 abuts against inner ring 50 i of rolling bearing 50. Spring 58 now clamps the two inner rings 48 i, 50 i against one another, which is necessary for quiet running of motor 20.
FIGS. 6 to 12 show a first variant for the mounting of flux-conducting elements 150′ on a plastic ring 160. The latter has a cylindrical opening 162 with which, according to FIGS. 10 and 12, it is slid onto partitioning tube 82. On its outer side it has projections 164 in which flux-conducting elements 150′ are anchored in the manner depicted.
Ring 160 is provided, on its lower side (in FIGS. 6, 7, and 10 to 12), with projections 168 that are approximately wedge-shaped. The result of impingement with an ultrasonic transducer in the direction of arrows 170 in FIG. 10 is that these projections 168 dig into shoulder 84 and become welded to it.
Partitioning tube 82 can have a thinner wall thickness in this case.
FIGS. 13 and 14 show a similar embodiment, except that a wedge-like edge 174 is provided that extends continuously. The mounting operation is the same as depicted in FIGS. 10 to 12.
FIG. 15 shows a section through a ring 160 and through flux-conducting elements 150″ anchored therein. FIG. 16 shows, in an enlarged depiction, that flux-conducting elements 150″ in this variant are thickened in wedge-shaped fashion at the radially inner end in order to effect secure anchoring. Flux-conducting element 150″ also, according to FIG. 17, has a hook-like enlargement 180 at the radially inner end.
As is clearly apparent to one skilled in the art from FIG. 1, flux-conducting elements 150 also act as flux concentrators, since in their radially outer region they have approximately the same length as magnet 67, whereas in their radially inner region they have approximately the (shorter) length of magnet 92, so that the flux of magnet 67 becomes concentrated. This also takes into account the circumstance that magnets 67 and 92 are of different lengths, and improves the torque that can be transferred by the magnetic coupling.
Numerous variants and modifications are of course possible within the scope of the present invention.

Claims

1. An arrangement for pumping fluids, which comprises:

a fluid pump having a pump wheel (90), which wheel is joined to a first permanent magnet (92), which pump wheel (90) is rotatably arranged inside a liquid-tight pump housing (80, 82, 84, 86, 88), which housing (80, 82, 84, 86, 88) is implemented, adjacent said first permanent magnet (92), as a partitioning can (80, 82);

an electronically commutated electric motor (20) having a stator (22) and a rotor (26) arranged rotatably relative thereto, which rotor comprises a second permanent magnet (67) that coacts with the first permanent magnet (92) to act as a magnetic coupling (94);

and a plurality of soft ferromagnetic magnetic flux conductors (150; 150′; 150″) arranged in the space between the second permanent magnet (67) and the partitioning can (80, 82), which conductors are arranged at a distance from one another in such a way that they map the magnetic field of the second permanent magnet (67), which field is effective at their end facing away from the partitioning can (80, 82), onto a region of the partitioning can (80, 82) associated with the first permanent magnet (92).

2. The arrangement according to claim 1, wherein

the soft ferromagnetic magnetic flux conductors (150; 150′; 150″) are implemented as elements made of soft ferromagnetic material, which are arranged in a star configuration around the partitioning can (80, 82).

3. The arrangement according to claim 2, wherein

the elements (150; 150′; 150″) are implemented in substantially plate-shaped fashion from soft ferromagnetic material.

4. The arrangement according to claim 1,

wherein

the soft ferromagnetic magnetic flux conductors (150; 150′; 150″) are implemented in the manner of flux concentrators.

5. The arrangement according to claim 1, wherein

the electronically commutated electric motor is implemented as an external-rotor motor (20) having a rotor cup (63), inside which cup are arranged the rotor magnet (36) of the motor (20) and the second permanent magnet (67).

6. The arrangement according to claim 1, wherein

a bearing element (106) for the pump wheel (90) is arranged inside the partitioning can (80, 82) on the latter, and

a bearing element (30) for the rotor (26) of the electronically commutated electric motor (20) is arranged outside the partitioning can (80, 82) on the latter.

7. The arrangement according to claim 6, wherein

the bearing element for the rotor (26) of the electric motor (20) comprises a bearing tube (30) that is fixedly connected to the partitioning can (80, 82).

8. The arrangement according to claim 7, wherein

the bearing tube (30) is integrally formed with the partitioning can (80, 82).

9. The arrangement according to claim 1, wherein fan blades (64) are joined to the rotor (26) of the electric motor (20).

10. The arrangement according to claim 9, wherein

the permanent magnet of the rotor comprises a yoke that is implemented as a cup-like part (40), and the fan blades (64) are arranged on this cup-like part (40).

11. The arrangement according to claim 9, wherein the fan blades (64) are implemented as part of an axial fan wheel.

12. The arrangement according to claim 9, wherein

the fan blades are implemented as part of a diagonal fan wheel.

13. The arrangement according to claim 9, wherein

the fan blades are implemented as part of a radial fan wheel.

14. The arrangement according to claim 1, further comprising

an air-directing housing (68) is joined to the partitioning can (80, 82).

15. The arrangement according to claim 14, wherein

the air-directing housing (68) is implemented as a plastic part integral with the partitioning can (80, 82).

16. The arrangement according to claim 15, wherein

the partitioning can (80, 82) is joined to the air-directing housing (68) via at least one strut (114).

17. The arrangement according to claim 7, wherein

the electric motor is implemented as an external-rotor motor (20); and

the internal stator (92) of said motor is mounted on the bearing tube (30), which tube serves for journaling of the rotor (26).

18. The arrangement according to claim 1, wherein

the soft ferromagnetic magnetic flux conductors (150; 150′; 150″) are joined at their radially inner end regions to a support part (160) made of non-ferromagnetic material.

19. The arrangement according to claim 18, wherein the support part (160) is arranged on the partitioning can (80, 82).

20. The arrangement according to claim 19, wherein

the partitioning can (80, 82) has an approximately cylindrical periphery; and

the support part (160) is arranged on said periphery.

21. The arrangement according to claim 18, wherein

the support part (160) is formed of plastic material, and is equipped with axial projections (168; 174) that are joined by means of a welding operation to an adjacent plastic part of the arrangement.

22. The arrangement according to claim 21, wherein

the welded join is implemented by ultrasonic welding (170) at one axial end of the support part (160).

23. The arrangement according to claim 1,

wherein

the cross section of soft ferromagnetic magnetic flux conductors (150″) inside the support part (160) is enlarged (180), at least locally, in order to produce good anchoring of said conductors (150″) in the support part.