Patent ID: 12188475

DETAILED DESCRIPTION OF THE EMBODIMENTS

At first, with reference to the sectional view inFIG.1, an embodiment of a centrifugal pump is explained, which comprises an electromagnetic rotary drive which is designed as a bearingless motor. Of course, this embodiment can be designed according to the invention.

The centrifugal pump is indicated as a whole with the reference sign1. The centrifugal pump1for conveying a fluid comprises a pump housing2with an inlet21and an outlet22for the fluid to be conveyed. A rotor3is arranged in the pump housing2, which, together with a stator4arranged outside the pump housing2, forms an electromagnetic rotary drive with which the rotor3can be driven to rotate about an axial direction A.

The electromagnetic rotary drive is designed as an internal rotor, i.e. the rotor3is arranged inside the stator4, so that the stator4surrounds the rotor3. The rotor3is magnetically levitated without contact with respect to the stator4. Furthermore, the rotor3can be magnetically driven without contact to rotate around a desired axis of rotation by the stator4. The desired axis of rotation is that axis around which the rotor3rotates in the operating state, when the rotor3is in a centered and non-tilted position with respect to the stator4. This desired axis of rotation defines an axial direction A. Usually, the desired axis of rotation defining the axial direction A coincides with the central axis of the stator4.

In the following, a radial direction is referred to as a direction that is perpendicular to the axial direction A.

The rotor3comprises a magnetically effective core31, which is designed in the form of a circular disk, or a circular cylinder, or annular. The “magnetically effective core31” refers to that region of the rotor3which interacts with the stator4for torque generation and the generation of magnetic bearing forces. Depending on the design, the magnetically effective core31can comprise one or a plurality of permanent magnets. Alternatively, it is also possible to design the magnetically effective core31without permanent magnets, for example as a reluctance rotor. The magnetically effective core31includes, at least partially, a ferromagnetic material, for example iron.

The magnetically effective core31preferably includes a jacket35, which completely encapsulates the magnetically effective core31, so that the magnetically effective core31does not contact the fluid to be conveyed. The jacket35is preferably made of a plastic but can also be made of a metallic material.

The rotor3further comprises an impeller32having a plurality of vanes33for conveying the fluid from the inlet21to the outlet22. The impeller32is arranged on the jacket35. The impeller32with the vanes33is preferably made of plastic and can, for example, be designed in one piece with the jacket35. Of course, it is also possible to manufacture the individual vanes33or the entirety of vanes33in a separate production process and then connect them to the jacket35, for example by a welding process. Of course, it is also possible to manufacture the impeller from a metallic material.

The impeller32is preferably designed as a radial impeller, which gets a flow of fluid in the axial direction A and then deflects the fluid in a radial direction.

The rotary drive with the stator4and the rotor3is designed, for example, as a so-called temple motor.

The characteristic feature of a design as a temple motor is that the stator4comprises a plurality of separate coil cores41—for example six coil cores41—each of which comprises a bar-shaped longitudinal leg42, which extends from a first end in the axial direction A to a second end, wherein all first ends—these are the lower ends according to the representation inFIG.1—are connected to each other by a reflux45. Each coil core41further comprises a transverse leg43, which is arranged on the second end of the respective longitudinal leg42, and which extends in the radial direction, i.e. perpendicular to the axial direction A and thus perpendicular to the respective longitudinal leg42. Each transverse leg43extends to the radial direction towards inside, i.e. towards the rotor3. Thus, each coil core41has an L-shaped design, wherein the longitudinal legs42each form the long leg of the L extending in the axial direction A, and the transverse legs43extending perpendicular to the longitudinal legs42in the radial direction towards the rotor3each form the short leg of the L.

The radially inward ends of the transverse legs43each form a stator pole46. The stator poles46are arranged annularly around the pump housing2with the rotor3arranged therein. The pump housing2is designed in such a way that it can be inserted into the stator4, more precisely between the stator poles46, so that the stator poles46surround the magnetically effective core31of the rotor3. In the operating state, the stator poles46and the magnetically effective core31of the rotor3are located at the same level with respect to the axial direction A, if the rotor3is not deflected from its desired position. In the operating state, the rotor3is thus magnetically levitated without contact between the stator poles46.

The reflux45and the coil cores41are each made of a soft magnetic material because they serve as flux guiding elements for guiding the magnetic flux. Suitable soft magnetic materials are, for example, ferromagnetic or ferrimagnetic materials, i.e. in particular iron, nickel-iron or silicon-iron.

The parallel longitudinal legs42of the coil cores41, which all extend parallel to the axial direction A, and which surround the rotor3, are the ones that gave the temple motor its name, because these parallel longitudinal legs41resemble the columns of a temple.

The stator4further comprises a plurality of windings6for generating electromagnetic rotating fields, with which the rotor3can be magnetically driven without contact and can be magnetically levitated without contact with respect to the stator4. The windings6are designed for example as six individual coils, wherein one coil is provided at each of the longitudinal leg42in each case. Each coil is arranged around the respective longitudinal leg42, so that the coil axis is parallel to the axial direction A in each case. For example, each longitudinal leg42supports exactly one coil61. Of course, such embodiments are also possible in which each longitudinal leg42supports more than one coil.

That plane, where the rotor3is levitated in the operating state, is also called the radial plane. The radial plane defines the x-y-plane of a Cartesian coordinate system whose z-axis extends in the axial direction A.

In a preferred embodiment, the electromagnetic rotary drive designed as a temple motor is designed according to the principle of a bearingless motor. This means that during the operation of the centrifugal pump1, the magnetically effective core31of the rotor3interacts with the stator poles46of the stator4according to the principle of the bearingless motor described above, in which the rotor3can be magnetically driven without contact and magnetically levitated without contact with respect to the stator4.

The principle of the bearingless motor has become sufficiently well known to the person skilled in the art in the meantime, so that a detailed description of the function is no longer necessary. The principle of the bearingless motor means that the rotor3is magnetically levitated, wherein the stator4is designed as a bearing and drive stator, which is both the stator of the electric drive and the stator of the magnetic levitation. For this purpose, the stator4comprises the windings6with which both the drive function and the levitation function is realized. An electromagnetic rotating field can be generated by the windings6, which on the one hand exerts a torque on the magnetically effective core31of the rotor3, which causes its rotation about the axial direction A, and which on the other hand exerts an arbitrarily settable shear force on the magnetically effective core31of the rotor3, so that its radial position—i.e. its position in the radial plane—can be actively controlled or regulated. In the case of a bearingless motor, in contrast to classical magnetic bearings, the magnetic levitation and the drive of the motor is realized by electromagnetic rotating fields, which exert a torque and a sellable shear force on the magnetically effective core31of the rotor3. The rotating fields required for this can either be generated with different coils, or the rotating fields can be generated by mathematical superposition of the required fluxes and then with the aid of a single coil system, in this case the windings6. In the case of a bearingless motor, it is therefore not possible to divide the electromagnetic flux generated by the windings6of the stator2into an electromagnetic flux, which only provides the drive of the rotor3and an electromagnetic flux which only realizes the magnetic levitation of the rotor3.

According to the principle of the bearingless motor, at least three degrees of freedom of the rotor3can be actively regulated, namely its position in the radial plane and its rotation about the axial direction A. With respect to its axial deflection in the axial direction A, the magnetically effective core31of the rotor3is passively magnetically stabilized by reluctance forces, i.e. it cannot be controlled. With respect to the remaining two degrees of freedom, namely tilting with respect to the radial plane perpendicular to the desired axis of rotation, the magnetically effective core31of the rotor3is also passively magnetically stabilized. This means that the rotor3is passively magnetically levitated or passively magnetically stabilized by the interaction of the magnetically effective core31with the stator poles46in the axial direction A and against tilting (three degrees of freedom in total) and actively magnetically levitated in the radial plane (two degrees of freedom).

As is common practice, within the framework of this invention, an active magnetic levitation refers to one that can be actively controlled or regulated, for example by the electromagnetic rotating fields generated by the windings6. A passive magnetic levitation or a passive magnetic stabilization is one that cannot be controlled or regulated. The passive magnetic levitation or stabilization is based, for example, on reluctance forces which bring the rotor3back into its equilibrium position when it is deflected from its equilibrium position, e.g. when it is displaced in the axial direction A or when it is tilted.

The magnetically effective core31of the rotor3has a diameter d, wherein the diameter d means the outer diameter of the magnetically effective core31. The magnetically effective core31further has a height HR, wherein the height HR is the extension in the axial direction A. It is particularly advantageous for the passive magnetic stabilization of the rotor3, if the diameter d of the magnetically effective core31of the rotor3is greater than 2.6 times the height HR of the magnetically effective core31of the rotor3, i.e. if the geometric condition d>2.6*HR is fulfilled.

FIG.2shows in a schematic sectional view an embodiment of a centrifugal pump1according to the invention, which is designed according to the embodiment explained with reference toFIG.1. As it is sufficient for the understanding, inFIG.2the stator4is only indicated by the stator poles46. The stator4and the rotor3are again designed in such a way that they interact according to the principle of the bearingless motor, as explained in connection withFIG.1.

The pump housing2comprises a housing part26and a cover25, wherein the cover25is arranged on the housing part26to close the pump housing2. The housing part26and the cover25preferably include a plastic and are firmly and sealingly connected to each other, for example welded. In other embodiments, the housing part26and/or the cover26are made of a metallic material.

For a better understanding,FIG.4shows a sectional view of the cover25in a section in the axial direction A, andFIG.5a plan view on the cover25seen from the housing part26. Furthermore,FIG.6shows a sectional view of the housing part26in a section in the axial direction, andFIG.7shows a plan view on the housing part26seen from the cover25.

The housing part26comprises a lower cylindrical portion261and an upper cylindrical portion262which are arranged coaxially and one behind the other with respect to the axial direction A, wherein the upper cylindrical portion262has a larger diameter than the lower cylindrical portion261. The lower cylindrical portion261of the housing part26comprises a bottom27, which forms the lower end of the pump housing2according to the representation, and which is arranged perpendicular to the axial direction A.

The cover25rests on the upper end, according to the representation, of the upper cylindrical portion262and is firmly connected to it. The inlet21for the fluid to be conveyed is disposed on the cover25. The inlet21is designed as inlet connection, which is preferably manufactured in one piece with the cover25. The inlet21designed as an inlet connection extends in the axial direction A, so that the fluid can flow into the pump housing2in the axial direction. The inlet connection21preferably has an inlet surface211, through which the fluid enters the inlet connection21, and an outlet surface212, through which the fluid leaves the inlet connection21and flows to the impeller32. Preferably, the inlet surface211is larger than or equal to the outlet surface212. The outlet22for the fluid to be conveyed is provided on the upper cylindrical portion262. Here, the outlet22is designed as an outlet connection22, which is preferably manufactured in one piece with the housing part26. The outlet22designed as an outlet connection extends parallel to the radial plane, i.e. perpendicular to the inlet21, so that the fluid flows out of the pump housing2in a radial direction. The outlet connection22has an inlet surface221, through which the fluid enters the outlet connection22, and an outlet surface222, through which the fluid leaves the outlet connection22. Preferably, the inlet surface221is smaller than the outlet surface222, as also represented inFIG.2. The outlet connection22is preferably designed cylindrically with regard to its outer shape. In order that the inlet surface221of the outlet connection is nevertheless smaller than the outlet surface222of the outlet connection21, a tapering area can be provided in the wall of the outlet connection22where the thickness of the wall changes so that the inner diameter of the outlet connection22changes. Due to this, the flow cross-section for the fluid also changes, which means the surface perpendicular to the central axis M of the outlet connection22through which the fluid flows. Such an embodiment is shown in more detail inFIG.8, for example.

For the cylindrical design of the outlet connection22it is preferred that the outlet connection22is arranged with respect to the axial direction A in such a way that the central axis M of the outlet connection22is closer to the magnetically effective core31of the rotor3than to the cover25of the pump housing2. This means that the outlet connection22is not arranged centrally in the upper cylindrical portion262of the housing part26with respect to the axial direction A but is displaced in direction of the bottom27—i.e. downwards according to the representation.

The rotor3, which comprises the magnetically effective core31, the jacket35and the impeller32, is arranged in the pump housing2between the bottom27and the cover25of the pump housing2, wherein the magnetically effective core31with the optional jacket35is arranged below the impeller32according to the representation. The magnetically effective core31including the jacket35is preferably designed cylindrically.

The pump housing2is inserted into the stator4—as can also be seen inFIG.1—so that the upper cylindrical portion262rests on the stator4and the lower cylindrical portion261of the pump housing2is arranged in the stator4, more precisely between the stator poles46. The pump housing2can be fixed to the stator4, for example by screws (not shown).

The rotor3is designed and arranged in such a way that in the operating state the magnetically effective core31of the rotor3is surrounded by the stator poles46and can be centered in the radial plane between the stator poles46by the electromagnetic fields generated by the windings6and can be driven to rotate about the axial direction A. If the rotor3is centered and not deflected with respect to the axial direction A, the magnetically effective core31is located centrally between the stator poles46.

The rotor3has an outer diameter D, which is the diameter D of the magnetically effective core31including the jacket35. If the jacket35is provided, the outer diameter D of the rotor3is larger than the diameter d (FIG.1) of the magnetically effective core31of the rotor3.

The impeller32is preferably designed as a radial impeller32so that the vanes33deflect the fluid flowing in the axial direction A through the inlet21in a radial direction and convey it to the outlet22.

According to the invention, at least one indentation is disposed in the bottom27and/or in the cover25, which indentation is designed to generate a local turbulence. In the embodiment described here, a total of eight indentations9are provided, four of which are arranged in the cover25and four in the bottom27.

In other embodiments, indentations9can also be disposed only in the cover or only in the bottom. The number of indentations9is also to be understood as an example. There can be only one indentation, or two or three indentations, or more than eight or significantly more than eight indentations, for example more than fifty. In principle, there is no upper limit to the number of indentations9. The number and arrangement of the indentations can be adapted to the respective application, so that the desired reduction of the forces acting on the rotor3, in particular the hydrodynamic forces, is achieved.

The indentation9or the indentations9represent a geometrical influence on the flow conditions inside the pump housing2whose purpose is to reduce the forces acting on the impeller32or on the rotor3, respectively, in particular the forces acting in the axial direction A, as well as the moments which try to tilt the rotor3against the radial plane. Thus, the indentations9improve the stabilization of the rotor3with respect to all those degrees of freedom—here three—with respect to which the rotor is passively magnetically levitated or stabilized. The indentations9arranged in the bottom27or in the cover25thus change the flow behavior in such a way that the position of the rotor3can be set with less effort and travel.

The reduction of the forces, in particular the hydrodynamic forces, is based on the flow turbulence or the creation of turbulences caused by the indentations9, which represent a local change of shape of the pump housing2.

The embodiment according to the invention with the at least one indentation9can thus in principle take place without geometric barriers to reduce flow velocities, and without pressure-compensating bores through the rotor, as well as without narrow, wedge-shaped fluid gaps which, as for example in classical hydrodynamic bearings, cause a local increase in pressure. Rather, the indentations9lead to local turbulences and flow separation, which reduce the force effects of laminar or turbulent flow on the surfaces of the rotor3exposed to the flow. These turbulences or flow separations reduce the dynamic lift acting on the rotor3and thus the forces acting on the rotor3.

Naturally, embodiments of the invention are also possible in which, for example, pressure-equalizing bores are additionally provided through the rotor3. Such an embodiment is explained further on with reference to the second embodiment.

Each indentation9can be designed as a dimple, depression, countersink, bore or similar to locally swirl the flow. For example, the indentations9can be spherical or cylindrical. They can have a square or rectangular profile. The indentations can also be designed pyramid-shaped, cone-shaped, truncated cone-shaped, annular or with a free-form geometry. For manufacturing reasons, however, such geometries are preferred for the indentations9that can be generated with drilling or milling tools. For this reason, those designs of the indentation9are preferred in which each indentation9has a circular profile perpendicular to the axial direction A, i.e. is designed spherically or cylindrically.

InFIG.3, one of the indentations9is represented in a sectional view with an exemplary nature, which in this case is designed as a blind hole in the bottom27of the pump housing2.

Usually, each indentation9has an extension E in the radial direction, which means the maximum width of the indentation9with respect to the radial direction, and a depth T, which means the maximum extension of the indentation with respect to the axial direction A.

In the case of the design as a blind hole shown inFIG.3, the extension E is the diameter E of the hole in the radial direction, and the depth T is the length of the hole in the axial direction A.

In practice, it has proven to be advantageous if for each indentation9the respective extension E in the radial direction is at least one fiftieth of the outer diameter D of the rotor3, i.e. E is greater than or equal to 0.02 D. It is also advantageous if for each indentation9the respective extension E in the radial direction is at most half of the outer diameter D of the rotor3, i.e. E is smaller or equal to 0.5 D.

With respect to the axial direction A, it has proven to be advantageous if for each indentation9the respective depth T in the axial direction A is at least one hundred and fiftieth of the outer diameter D of the rotor3, i.e. is greater than or equal to 0.015 D. It is particularly preferred if the respective depth T in the axial direction A is at least one hundredth of the outer diameter D of the rotor3, i.e. if T is greater than or equal to 0.01 D.

Furthermore, with respect to the axial direction A, it is preferred if for each indentation9the respective depth T in the axial direction A is at most one tenth of the outer diameter D of the rotor3, i.e. T is smaller than or equal to 0.1 D.

With respect to the position of the indentation9or the indentations9, it is preferred that the indentation9or the indentations9is/are arranged in a radially outer edge area of the bottom27and/or the cover25. As represented inFIG.2,4,5,6, this means in particular, that the indentation(s)9in the cover25of the pump housing2is/are located closer to the radially outer edge of the cover25than to the center of the cover25, and that the indentation(s)9in the circular bottom27of the pump housing2is/are located closer to the radially outer edge of the bottom27than to the center of the bottom27.

In preferred embodiments of the invention, the pump housing2and/or the impeller32and/or the jacket35of the rotor3are made of a plastic. Preferably, the pump housing2and the impeller32and the jacket35of the rotor3are made of a plastic. The pump housing2and the impeller3and the jacket35can all be made of the same plastic or at least two different plastics.

The selection of suitable plastics naturally depends on the respective application. Suitable plastics are, for example: polyethylenes (PE), polypropylenes (PP), low density polyethylenes (LDPE), ultra-low density polyethylenes (ULDPE), ethylene vinyl acetates (EVA), polyethylene terephthalates (PET), polyvinylchloride (PVC), polyvinylidene fluorides (PVDF), acrylonitrile buta diene styrenes (ABS), polyacrylics, polycarbonates.

In other likewise preferred embodiments of the invention, the pump housing2and/or the impeller32and/or the jacket35of the rotor3are made of one metallic material or of several different metallic materials. Examples of preferred metallic materials are titanium or stainless steels.

FIG.8shows in a schematic sectional view a second embodiment of a centrifugal pump1according to the invention. For a better understanding,FIG.9still shows a plan view on the rotor of the second embodiment, seen from the bottom of the pump housing. Furthermore, the section line VIII-VIII, along which the section shown inFIG.8was made, is shown inFIG.9.

In the following, only the differences to the first embodiment described above will be discussed. In particular, the reference signs have the same meaning as already explained in connection with the first embodiment. It is understood that all previous explanations apply in the same way or in the analogously same way to the second embodiment.

In the second embodiment, further measures are still realized, which, depending on the application, can further improve the stabilization of the rotor3with respect to the axial direction A and with respect to tilts against the radial plane, i.e. with respect to the three passively magnetically stabilized degrees of freedom. It is understood that all these measures can all be realized, but not all of them need to be realized. This means that such embodiments are also possible in which, for example, one or more of the measures described with reference to the second embodiment are combined with the first embodiment.

In the second embodiment of the centrifugal pump1according to the invention represented inFIG.8andFIG.9, the inlet21of the pump housing2designed as an inlet connection has a constriction area213in which the flow cross-section perpendicular to the axial direction A is smaller than the inlet surface211and smaller than the outlet surface212of the inlet connection21. In addition, the inlet surface211of the inlet connection21is larger than its outlet surface212. Comparing the respective surfaces, the inlet surface211is larger than the outlet surface212, and the outlet surface212is larger than the flow cross-section in the constriction area213.

The outlet22of the pump housing2is designed in the analogously same way as explained for the first embodiment, i.e. in such a way that the inlet surface221of the outlet connection22is smaller than the outlet surface222of the outlet connection22, and that the outlet connection22is arranged with respect to the axial direction A in such a way that the central axis M is closer to the annular magnetically effective core31of the rotor3than to the cover25of the pump housing2. With reference to the dotted lines in the outlet22, it is represented inFIG.8how the inside of the outlet connection22is designed, so that the outlet surface222of the outlet connection22is larger than the inlet surface221of the outlet connection21.

The size of the outlet surface222of the outlet connection22and the size of the inlet surface211of the inlet connection21, including the respective surrounding wall, are usually predefined by standards. The outer diameter of both the inlet connection21at the inlet surface211and the outer diameter of the outlet connection22at the outlet surface222is dimensioned such that the centrifugal pump1can be connected to normal pipes or tubes in a flow system.

Furthermore, the rotor3has a cover plate36which is designed like an annular disk and which covers the vanes33of the impeller32at their edge facing the inlet21or the cover25, wherein a centrally arranged opening361is provided in the cover plate36through which the fluid can flow to the impeller32.

Optionally, the magnetically effective core31of the rotor3can have a central bore37which extends in the axial direction A completely through the magnetically effective core31and the optional jacket35.

Alternatively, or in addition, the rotor3can comprise a balancing hole38or a plurality of balancing holes38, wherein each balancing hole38extents in the axial direction A completely through the magnetically effective core31of the rotor3and the optional jacket35. Each balancing hole38preferably is arranged decentral, i.e. not in the center of the rotor3.

In the second embodiment, a plurality of balancing holes38is provided, namely eight balancing holes38.

The balancing holes38are preferably arranged on a circular line, wherein the center of the circle is located in the center of the rotor3. This means, if the central bore37is disposed in the rotor3, the balancing holes38are arranged in a circle around the central bore37. Preferably, at most or exactly eight balancing holes38are provided, which are preferably arranged equidistantly around the central bore37of the rotor3or around the center of the rotor3.

Each balancing hole38has a diameter in each case, which is smaller than the diameter of the central bore37.

A plurality of rear vanes39is provided on the axial end face of the rotor3facing away from the cover25and facing the bottom27. In the operating state, these rear vanes39are opposite the bottom27of the pump housing2. In the second embodiment, a total of eight rear vanes39is provided.

The rear vanes39can be realized, for example, by providing recesses in the jacket35of the rotor3, so that the rear vanes39are each formed between two adjacent recesses.

Furthermore, it is of course also possible to design the rear vanes39as elevations. For this purpose, for example, a structure similar to an impeller can be generated, which is then attached to the axial end face of the rotor3, so that the rear vanes39are opposite the bottom27of the pump housing2. Of course, the rear vanes38can also be manufactured individually and then be attached to the axial end face of the rotor3.

Preferably, each rear vane39starts at the radial outer edge of the axial end face of the rotor3and extends from there radially inwards. Each rear vane39can extend to the center of the axial end face or to the central bore37, or each rear vane39, as shown inFIG.9, has a length in the radial direction which is smaller than the radius of the axial end face, e.g. half as large. In other embodiments, the rear vanes39can also be designed in a curved manner.

In the second embodiment, an annular or circular disk-shaped pressure plate321is disposed on the impeller32, which is aligned perpendicular to axial direction A. The pressure plate321is arranged, with respect to the axial direction A, between the magnetically effective core and the end of the impeller32facing the cover25of the pump housing2, for example halfway up the vanes33of the impeller32. The pressure plate321extends between the vanes of the impeller32. If the rotor3has a cover plate36, the pressure plate321is arranged, with respect to the axial direction A, between the magnetically effective core31and the cover plate36and parallel to the cover plate36. The pressure plate321extends between all vanes33. With respect to the radial direction, the pressure plate321is arranged centered with respect to the rotor3and extends in the radial direction at least so far that it covers all balancing holes38at an axial distance. In the embodiment represented inFIG.8, the diameter of the pressure plate321is significantly smaller than the diameter of the impeller32, which is measured at the vanes33.

FIG.10shows in a schematic sectional view a variant for the rotor3, which differs from the rotor3represented inFIG.8in that the pressure plate321has a larger diameter. In the variant shown inFIG.10, the pressure plate321extends in the radial direction approximately to the radially outer end of the vanes33of the impeller32.