Abstract:
An arrangement for dissipating heat from components producing high heat flux densities, such as computers, features a combination fan and fluid pump with a magnetic coupling ( 93 ) which acts across a fluid-tight partitioning can ( 52 ). The pump has a pump wheel ( 90 ) connected to a first permanent magnet ( 92 ), and an electronically commutated internal-rotor motor (ECM  70 ) to drive it. The motor has a stator ( 68 ) inside which is rotatably arranged a rotor ( 60 ) equipped with a second permanent magnet ( 64 ). Interaction between the first and second permanent magnets creates the magnetic coupling ( 93 ). The stator ( 68 ) of the internal-rotor motor ( 70 ) is arranged radially outside the magnetic coupling ( 93 ). A first shaft ( 54 ), arranged on the outer side of the can ( 52 ), serves for rotatable journaling of the rotor ( 60 ) of the internal-rotor motor ( 70 ) and a second shaft ( 50 ) inside the can serves for journaling the pump rotor.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a section 371 of International Application PCT/EP08/00617 filed 26 Jan. 2008 and published as WO-2008-119404-A. 
     FIELD OF THE INVENTION 
     The present invention relates to an arrangement for delivering fluids. Liquid and/or gaseous media can be delivered as fluids. 
     BACKGROUND 
     Components having high heat flux densities, for example 60 W/cm 2 , are used today especially in computers. Heat from these components must first be transferred into a liquid circulation system, and from there it is discharged to the ambient air via a liquid-air heat exchanger. The dissipation of heat from components having a high heat flux density is accomplished by means of heat absorbers or so-called “cold plates.” In these, heat is transferred to a cooling liquid, and the latter usually is caused to circulate in forced fashion in a circulation system. 
     In this context, the cooling liquid flows not only through the heat exchanger but also through a liquid pump, which produces the forced circulation and produces an appropriate pressure buildup and an appropriate volumetric flow rate through the heat absorber and an associated heat exchanger, so that the pertinent heat transfer coefficients become high, and the temperature gradients necessary for heat transfer become low. 
     A fan is usually arranged at the heat exchanger and produces, on the air side of the heat exchanger, forced convection of the cooling air and good transfer coefficients. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to make available a novel compact arrangement for delivering fluids. 
     According to the invention, this object is achieved by using a partitioning can to hermetically separate a fluid pump from a concentrically surrounding fan motor, which transfers power to it across a magnetic coupling between a first permanent magnet forming part of the fan and a second permanent magnet forming part of the pump. A compact arrangement with good efficiency is thereby obtained. 
    
    
     
       BRIEF FIGURE DESCRIPTION 
       Further details and advantageous refinements of the invention are 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 an arrangement according to the present invention; 
         FIG. 2  is an enlarged portion of  FIG. 1 ; 
         FIG. 3  shows a variant of  FIGS. 1 and 2 ; 
         FIG. 4  is a perspective depiction of a claw washer  120 ; and 
         FIG. 5  shows claw washer  120  of  FIG. 4  at approximately 1:1 scale. 
     
    
    
     DETAILED DESCRIPTION 
     In the description that follows, the terms “upper,” “lower,” “left,” and “right” refer to the particular figure. Identical or identically functioning parts are labeled with the same reference characters whenever possible, and are described only once. 
       FIG. 1  is a longitudinal section through an exemplifying embodiment of an arrangement  20  according to the present invention. The latter has externally an approximately cylindrical fan housing  22 . This is connected, via obliquely extending struts or spokes  32 , to cylindrical part  36  of a pump housing that, in the completed state, is closed off by a cover  38  on which is located an inlet tube  40 . Cover  38  can be connected to part  36  in liquid-tight fashion, for example by way of an adhesive join, by plastic welding, by means of an O-ring seal, etc. 
     Part  36  transitions on its left side (in  FIG. 1 ) into a portion  44  that proceeds perpendicular to a rotation axis  42  and transitions on its radially inner side into a cylindrical partitioning tube  46 . At its left end (in  FIG. 1 ) partitioning tube  46  is closed off by a portion  48 , on which is mounted in suitable fashion a shaft  50  that is made of a ceramic material and projects to the right, in the direction defined by rotation axis  42 . Partitioning tube  46  and portion  48  together form a so-called partitioning can  52 . The latter can also have a geometrical shape other than the one depicted in  FIG. 1 . 
     A partitioning tube or partitioning can is understood in electrical engineering as a component, made of a nonmagnetic material such as plastic or stainless steel, that extends at least in part through the air gap of a magnetic circuit and forms there a fluid barrier that does not, or does not substantially, impede the magnetic flux in the air gap. The term “canned motor” is often used. 
     Adjoining portion  48  on the left is a non-rotating shaft  54 . The latter has an outer corrosion-inhibiting layer  49  that is formed by a plastic, normally the plastic of partitioning can  52  with which said layer  49  is usually integrally configured. Located inside layer  49  is ceramic shaft  50 , which therefore in this case has the function, together with plastic layer  49 , of forming and stiffening second shaft  54 . Journaled on it by means of a left rolling bearing  55  and a right rolling bearing  56  is a sleeve  57  ( FIG. 2 ), made of soft ferromagnetic material, that is part of a rotor  60  whose rotor magnet is labeled  64 . The outer corrosion-inhibiting layer  49  also produces hermetic sealing of the region through which a liquid flows, which region is depicted on the right in  FIG. 1 . The risk of leaks thereby becomes particularly low. 
     Layer  49 , applied by injection molding, also ensures that the straightness and running tolerance of shaft  54 , relative to shaft  50  and relative to an opening  72  described below, are further improved, resulting in an even lower level of solid-borne sound for the entire unit. 
     Sleeve  57  made of ferromagnetic material has a dual function: 
     It forms a magnetic yoke for rotor magnet  64 , which latter is depicted particularly clearly in  FIG. 2  and is implemented as a cylindrical ring made of magnetic material that, as depicted, is preferably magnetized radially, e.g. with four poles that are indicated partly in  FIG. 2 . Sleeve  57  is connected for this purpose, at a lower (in  FIG. 2 ) region  58 , to the inner side of rotor magnet  64 , for example by adhesive bonding or by being pressed on. 
     It forms the hub of a fan wheel  80  of any design, which wheel will be described below with reference to an example and rotates during operation about non-rotating shaft  54 , being driven by rotor  60 . 
     As  FIG. 1  shows, ring magnet  64  is separated by an air gap  66  from stator  68  of an electronically commutated internal-rotor motor (ECM)  70 . As  FIG. 1  shows, stator  68  is mounted in the cylindrical opening  72  of a carrier part  74  that preferably is implemented integrally with portion  44 . During operation, ring magnet  64  rotates around partitioning can  52 . 
     Fan wheel  80 , which can be implemented e.g. as an axial, diagonal, or radial fan wheel, is mounted on sleeve  57 . Said fan wheel has an approximately cylindrical outer part  81  whose outside diameter corresponds to that of the carrier part, and fan blades  82  are arranged, in the manner depicted in  FIG. 1 , on said part  81 . During operation, blades  82  rotate within fan housing  22  and deliver air through it. Fan wheel  80  is preferably injection-mounted onto sleeve  57  by plastic injection molding. For that purpose, sleeve  57  is placed into the injection mold before the injection operation. Alternatively, fan wheel  80  can also be manufactured as an individual part, and then pressed or adhesively bonded onto sleeve  57 . 
     Pump wheel  90  of a centrifugal pump or other fluid kinetic machine  91  is rotatably journaled on shaft  50  by means of a plain bearing  89 , said pump wheel preferably being implemented integrally with a plastic-matrix first permanent magnet  92 . The latter preferably has the same number of magnet poles as ring magnet  76  (which hereinafter will also be referred to as the second permanent magnet), and forms therewith a magnetic coupling  93  that transfers to pump wheel  90 , through partitioning can  92 , the torque generated by motor  70 , and thereby drives said wheel at the rotation speed of rotor  60 . 
     The result is that during operation, liquid is drawn in through connecting pipe  40  in the direction of an arrow  94 , and delivered outward through an outlet connecting pipe (not depicted). 
     Rotor  60  therefore drives not only fan wheel  80  by way of a direct mechanical coupling, but also pump wheel  90  via magnetic coupling  93 . 
     It is space-saving and therefore very advantageous that motor  70  and magnetic coupling  93  are nested into one another, magnet  92  of pump wheel  90  being the innermost rotating element. This enables the diameter of magnet  92  to be made as small as is tolerable, given the torque to be transferred. 
     Because magnet  92  rotates directly in the pumped fluid, the fluid immediately adjacent to it adheres directly to it, and moves at the same circumferential speed. 
     This fluid also adheres at the interface to the stationary partitioning can  52 , with the result that it is at a standstill there. A monotonic velocity gradient exists between these two extreme values. The fluid in the gap between first magnet  90  and housing  52  is thus exposed to shear stresses, and frictional losses occur because of the viscosity of the fluid. A critical factor for these losses is the diameter of the rotating surfaces, the square of which diameter enters into the equation for the frictional torque. The frictional power dissipation thus increases as the cube of the diameter (D 3 ) of the rotating surfaces, and can consequently be minimized in the context of the present invention. 
     The design that has been depicted and described allows very high efficiency for a pump of this kind that is driven via a magnetic coupling  93 , since the rotating surfaces on first magnet  92  can be implemented to be small. As already stated, the smallest possible diameter is determined by the torque that must be transferred by magnetic coupling  93 . If the diameter were made even smaller, this would result in a decrease in pump output, i.e. with the arrangement described, the magnetic coupling can be designed so that good efficiency is obtained at the working point. 
     Further optimization is possible by using particularly high-grade magnetic materials for permanent magnets  64  and  92 . This allows a further reduction in the diameters of the rotating surfaces, which yields particularly high efficiency, but it increases cost. 
     As  FIG. 1  and  FIG. 2  show, in this embodiment the sleeve  57  has a radially inwardly protruding projection  100  that, in  FIG. 2 , separates a short lower cylindrical portion  102  from a long upper cylindrical portion  104  of the same diameter. 
     Outer ring  105  of rolling bearing  56  is placed into portion  102 , and the lower (in  FIG. 2 ) shoulder  106  forms a stop for the upper shoulder of outer ring  105 . Inner ring  108  of rolling bearing  56  is slid onto shaft  54 . 
     Projection  100  has an upper (in  FIG. 2 ) shoulder  110  that serves as an abutment for the lower end of a compression spring  112  whose upper end bears against the lower shoulder of outer ring  114  of upper abutment  55 . The latter has an inner ring  116  whose upper shoulder abuts against a retaining member  120  such as a snap ring or a claw washer. An example of a claw washer  120  is depicted in  FIGS. 4 and 5 . 
     As depicted, a snap ring is mounted in an annular groove of shaft  54 , and claw washer  120  can be directly pressed, to the correct dimension, onto shaft  54  into the desired position. A claw washer  120  can be particularly advantageous for leak-prevention reasons.  FIGS. 4 and 5  show a typical claw washer  120  at enlarged scale. It has claws  121  that protrude radially inward from an outer ring  123  and, upon assembly, dig into plastic layer  49  of shaft  54  and thereby retain the inner ring of rolling bearing  56  in its position.  FIG. 5  shows claw washer  120  at approximately actual size, i.e. at 1:1 scale. 
     Under load, compression spring  112  presses outer ring  114  of rolling bearing  55  upward, and thereby biases outer ring  114  with respect to inner ring  116 ; this produces quiet running. 
     Assembly 
     Stator  74 , on which are arranged left-hand (in  FIG. 1 ) shaft  54  and right-hand shaft  50 , is installed first. 
     Rolling bearing  56  is then slid, pressed, or adhesively bonded onto shaft  54 . Rotor  60  is then inserted so that shoulder  106  of projection  100  abuts against outer ring  105  of rolling bearing  56 . 
     Alternatively, rolling bearing  56  can also be first slid, pressed, or adhesively bonded into sleeve  57  and into portion  102 , and rotor  60  together with rolling bearing  56  is then slid or pressed onto shaft  54 . 
     Compression spring  112  is then inserted so that its lower end abuts against shoulder  110 , and rolling bearing  55  is then brought into the position shown in  FIGS. 1 and 2 , spring  112  being loaded and rolling bearing  55  being retained in this position by snap ring  120 . A cover is then inserted into an opening  124  provided therefor, in order to protect rolling bearings  55  and  56  from contamination. One such cover  230  is depicted and described in  FIG. 3 . 
     Rolling bearings  55  and  56  journal sleeve  57  and, with it, fan wheel  80  and ring magnet  64 , which in turn is driven by internal-rotor motor  70  during operation. Pump  91  is driven via magnetic coupling  93 , ring magnet  64  of internal-rotor motor  70  interacting with ring magnet  92  of pump wheel  90  as magnetic coupling  93 . 
       FIG. 3  shows a variant of the first exemplifying embodiment according to  FIGS. 1 and 2 . This variant is identical to  FIGS. 1 and 2  with regard to pump  91 , internal-rotor motor  70 , and shafts  50  and  54 , and differs in terms of the manner of journaling; for that reason, only the differing parts are depicted in order to avoid unnecessary length. 
     In  FIG. 3  as well, a sleeve  157  made of soft ferromagnetic material is used; onto its outer side, at  58 , rotor magnet  64  is adhesively bonded or pressed on so that sleeve  157  serves as a soft ferromagnetic yoke for ring magnet  64 , which is implemented identically to rotor magnet  64  according to  FIGS. 1 and 2 . 
     Sleeve  157  also serves as a carrier for fan wheel  80 . The sleeve has at its right end (in  FIG. 3 ) an inwardly projecting shoulder  160  that serves as a stop for a right rolling bearing  156  that is introduced with its outer ring  205  into sleeve  157  and is applied with its inner ring  208  onto shaft  54 ; both operations are possible by sliding on, pressing on, or adhesive bonding. 
     A left rolling bearing  155  is also slid with its outer ring  214  into sleeve  157  and is supported there by means of a snap ring  220  that is inserted into an annular groove  222  on inner side  224  of sleeve  157 . Alternatively, retaining member  220  can also be embodied as a claw washer that is pressed to the correct dimension, i.e. as far as the desired position, into sleeve  157 . 
     Inner ring  216  of rolling bearing  155  is arranged on shaft  54  with a slight clearance, in order to enable bracing by a compression spring  212  that is arranged on shaft  54  between the two inner rings  208 ,  216 . The two rolling bearings  155 ,  156  are reciprocally biased with respect to one another by it, resulting in particularly quiet running of arrangement  20 . 
     The advantage that results, as compared with  FIG. 2 , is that spring  112  can be smaller and thus more economical, and that it is easier to manufacture a permanent annular groove  222  in metal part  157 . 
     Assembly 
     Assembly is similar to what was described with reference to  FIGS. 1 and 2 . Firstly, stator  68  is installed, usually together with pump  91 . The latter can, of course, also be installed later. 
     The rotor with ring magnet  64 , and sleeve  157  with rolling bearing  156  arranged therein, are then installed on shaft  54 . These are followed by bracing spring  212 , left rolling bearing  155 , and lastly retaining member  220 , e.g. a snap ring or a claw washer. 
     Lastly, a cover  230 , that protects bearings  155 ,  156  from contamination, is installed. 
     Numerous variants and modifications are of course possible within the scope of the present invention.