Centrifugal pumps and pump housings

Abstract

To provide a centrifugal pump which is improved in passive magnetic stabilization with respect to, in particular, a displacement in an axial direction.SOLUTION: There is provided a fluid-transporting centrifugal pump having a pump housing (2) arranged with a rotor (3) therein for transporting fluid, and a stator (4) forming an electromagnetic rotation drive unit for rotating the rotor (3) around an axial direction (A) together with the rotor (3). The stator (4) is designed as a bearing / drive stator which can magnetically drive the rotor (3) in a non-contact manner, and can magnetically float the rotor (3) with respect to the stator (4) in a non-contact manner. The rotor (3) is passively magnetically floated in the axial direction (A), and actively magnetically floated within a plane in a radial direction vertical to the axial direction (A).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a centrifugal pump and a pump housing for conveying a fluid as defined in the preambles of the independent patent claims in the respective categories. [Background technology]

[0002] Centrifugal pumps are known with an electromagnetic rotary drive designed and operated according to the principle of a bearingless motor. Here, the term "bearingless motor" refers to an electromagnetic rotary drive in which the rotor is fully magnetically levitated relative to the stator, and in which no separate magnetic bearings are provided. For this reason, the stator is designed as a bearing and drive stator, both for the electric drive and for the magnetic levitation. The electrical windings of the stator make it possible to generate a rotating magnetic field which exerts a freely settable shear force on the rotor, so that a torque is exerted on the rotor which causes it to rotate, while the radial position of the rotor can be actively controlled or adjusted. In this way, three degrees of freedom of the rotor can be actively adjusted, in particular its rotation and radial position (two degrees of freedom). With respect to three further degrees of freedom, in particular its axial position and its tilt with respect to a radial plane perpendicular to the desired axis of rotation (two degrees of freedom), the rotor is passively magnetically levitated or stabilized by magnetic resistance forces, i.e. cannot be controlled. The bearingless motor gets its name from the fact that the rotor is completely magnetically levitated without the need for a separate magnetic bearing.

[0003] Bearingless motors are now well known to those skilled in the art and are used in many different applications, for example US Pat. No. 5,399,433 and US Pat. No. 5,499,463 provide a basic description. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] European Patent Publication No. 0860046 [Patent Document 2] European Patent Publication No. 0819330 Summary of the Invention [Problem to be solved by the invention]

[0005] Centrifugal pumps, designed based on the principle of bearingless motors, demonstrate their capabilities in a wide range of applications.

[0006] Due to the absence of mechanical bearings, centrifugal pumps with bearingless motors are particularly suitable for applications conveying very sensitive substances, such as blood pumps, or applications requiring very high purity, such as in the pharmaceutical and biotechnology industries, or for conveying abrasive or corrosive substances that would destroy mechanical bearings in a very short time, such as pumps for slurries or acidic fluids in the semiconductor industry.

[0007] The bearingless motor principle has further advantages due to the rotor design, which is an integrated rotor, both the rotor of the electromagnetic drive and the rotor of the centrifugal pump: in addition to contactless magnetic levitation, this advantage is a very compact and space-saving construction.

[0008] In addition, the bearingless motor principle allows the design of centrifugal pumps in which the rotor or the pump housing in which the rotor is arranged can be very easily separated from the stator. This is a great advantage, since the pump housing can be designed as a disposable part, for example in disposable applications. Today, such disposable applications often replace processes in which, due to very high purity requirements, all parts that come into contact with the handled fluid during the process had to be cleaned and disinfected in complex ways, for example by steam disinfection. In the case of a disposable design, the parts that come into contact with the handled fluid are used only once and are then replaced by new, i.e. unused, disposable parts for the next application.

[0009] In all these applications where bearingless motors have been successfully applied in centrifugal pumps, it is basically possible to design the bearingless motor as an inner rotor, i.e. a rotor arranged inside and a stator arranged around it, or as an outer rotor, i.e. a stator arranged inside and a rotor arranged around it. However, in both designs, it has been found that in some applications the passive magnetic stabilization of the rotor against axial displacements and tilts relative to the radial plane reaches its limits and is not sufficient to guarantee a safe and problem-free operation of the centrifugal pump.

[0010] The invention therefore aims to propose a centrifugal pump having an electromagnetic rotary drive with a contact-free magnetically drivable and contact-free magnetically levitable rotor, with improved passive magnetic stabilization of the rotor, in particular against axial displacements, in accordance with the state of the art, and a pump housing for such a centrifugal pump.

[0011] The object of the invention to solve the above problems is characterized by the features of the independent claims in the respective categories. [Means for solving the problem]

[0012] Thus, according to the invention, a centrifugal pump for conveying a fluid is proposed, which has a pump housing in which a rotor is provided for conveying a fluid and a stator which together with the rotor forms an electromagnetic rotary drive for rotating the rotor in an axial direction, the stator being designed as a bearing and drive stator capable of magnetically driving the rotor without contact and of magnetically levitating the rotor without contact relative to the stator, the rotor being passively magnetically levitated in the axial direction and actively magnetically levitated in a radial plane perpendicular to the axial direction, the pump housing comprising a bottom and a cover, the rotor being arranged in the pump housing between the bottom and the cover in the axial direction, the bottom and / or the cover being provided with at least one recess which is designed to generate local turbulence.

[0013] The invention is based on the finding that at least one recess in the pump housing can influence the flow conditions in the pump housing, in particular in such a way that the forces acting on the rotor in the axial direction can be reduced. This reduction leads to a reduction in the magnetic levitation of the rotor in the axial direction, which leads to a significant improvement in the passive magnetic stabilization of the rotor. It was also found that the at least one recess significantly improves the passive magnetic stabilization against the tilt of the rotor relative to a radial plane perpendicular to the axial direction. The generation of local turbulence leads to an intended change in the flow behavior around the rotor, which reduces the forces acting on the rotor, in particular the forces acting in the axial direction.

[0014] In the present invention, there is essentially no need for geometrical barriers to reduce the backflow from the pressure side to the suction side or to reduce the speed of this backflow, or for relief holes extending completely through the rotor in the axial direction for pressure compensation. The at least one recess provides local turbulence and / or flow separation, which reduces the flow forces on the rotor surfaces surrounded by the flow. For example, the forces acting on the rotor are reduced due to the reduction in dynamic lift caused by the flow separation caused by the recess.

[0015] According to a preferred embodiment, the rotor comprises a ring-shaped or disk-shaped magnetically active core and a multi-bladed impeller for conveying the fluid, whereby the magnetic core interacts with the stator to drive the rotor and levitate it without contact while the bladed impeller conveys the fluid.

[0016] The centrifugal pump is preferably designed with a radial impeller. A fluid inlet is provided on the cover of the pump housing, designed to allow the fluid to flow axially into the pump housing. Furthermore, the pump housing comprises a fluid outlet, designed to allow the fluid to flow radially out of the pump housing. This means that the impeller receives the axial flow and conveys the fluid perpendicular to it. In other embodiments, the impeller can also be designed as a semi-axial impeller.

[0017] Furthermore, the rotary drive of the centrifugal pump is preferably designed according to the inner rotor principle, for which the stator has, for example, a number of stator poles arranged in an annular manner, and the pump housing, inside which the rotor is arranged, is designed so that it can be inserted between the stator poles in such a way that the magnetically effective core of the rotor is surrounded by the stator poles of the stator.

[0018] In practice, it has proven advantageous if the rotor has an outer diameter and if each recess has a dimension in the radial direction which is at least 1 / 50th of the outer diameter of the rotor.

[0019] It is furthermore advantageous if the rotor has an outer diameter and if each recess has a radial dimension which is at most half the outer diameter of the rotor.

[0020] In a further preferred measure, the rotor has an outer diameter and each recess has a depth in the axial direction which is at least 150 times smaller, preferably at least 100 times smaller, of the outer diameter of the rotor.

[0021] Preferably, the rotor has an outer diameter and each recess has a depth in the axial direction that is at most one tenth of the outer diameter of the rotor.

[0022] There are several factors that can be optimized for an application that can influence the required reduction of the forces and tilting moments acting on the rotor. These factors include in particular the number of recesses, their location and their geometric dimensions, i.e. in particular their radial and axial dimensions. If the cover and / or bottom have several recesses, it is of course not necessary that they all have the same dimensions. They can quite possibly have different dimensions and / or geometries.

[0023] The specific shape of the recesses does not have a significant effect. Each recess can be designed, for example, to have a square or rectangular outline. Each recess can be designed to be pyramidal, conical, truncated conical, annular, or of a free geometric shape. The recess or recesses may be designed so that the surface condition is locally changed at the location of the recess or recesses so that the fluid flow becomes a vortex.

[0024] However, for manufacturing reasons, it is preferred that each recess has a circular contour perpendicular to the axial direction, in which case, for example, each recess is designed as a blind hole whose diameter is the radial dimension of the recess and whose length is the axial depth of the recess.

[0025] In a preferred embodiment, at least one recess is provided in both the cover and the bottom of the pump housing.

[0026] As a further preferred measure, the recesses are arranged in the radially outer edge region of the pump housing, which in particular means that the recesses in the cover of the pump housing are closer to the radially outer edge of the cover than to the center of the cover, and the recesses in the base of the pump housing are closer to the radially outer edge of the base than to the center of the base.

[0027] The pump housing is preferably constructed from a plastic or metal material.

[0028] The impeller is also preferably constructed from a plastic or metal material.

[0029] As a further advantageous measure, the rotor has a jacket which completely encases the magnetically active core of the rotor such that the magnetically active core does not come into contact with the fluid, the jacket being preferably constructed from plastic, although it could also be constructed from a metallic material.

[0030] The pump housing, impeller and jacket can be made of the same or different plastic or metal materials, or of a combination of plastic and metal materials, e.g., the rotor jacket can be made of plastic and the pump housing can be made of metal.

[0031] Further measures are possible to further mitigate the passive magnetic stabilization or levitation of the rotor in the three degrees of freedom (axial displacement, tilt relative to the radial plane) and to further improve the stabilization of the rotor in these three degrees of freedom. These include, but are not exhaustive:

[0032] The rotor may have a cover plate covering the side of the impeller blades opposite the inlet, the cover plate having a centrally located opening through which fluid can flow into the impeller.

[0033] The magnetically active core of the rotor may have a central bore extending axially completely through the magnetically active core and any jacket.

[0034] The rotor may include one balance hole or multiple balance holes, each extending axially completely through the rotor's magnetically active core and any jacket, and preferably the balance holes are distributed, i.e. located other than at the center of the rotor.

[0035] If more than one balance hole is provided, the balance holes are preferably arranged in a circular line around the central hole or around the center of the rotor. Preferably, there are a maximum of or exactly eight balance holes, which are preferably equidistantly arranged around the central hole or around the center of the rotor.

[0036] Each balance hole preferably has a diameter smaller than the diameter of the central hole.

[0037] The axial end face of the rotor facing away from the inlet may be provided with a number of trailing vanes which, in operating condition, face the bottom of the pump housing.

[0038] The trailing blades can be realized, for example, by providing recesses in the rotor jacket and forming each trailing blade between two adjacent recesses.

[0039] Furthermore, it is possible to design the rear vanes as ridges, for example by making an impeller-like structure and attaching it to the axial end of the rotor, so that the rear vanes face the bottom of the pump housing. Of course, it is also possible to manufacture each rear vane separately and attach it to the axial end of the rotor.

[0040] Each trailing vane preferably extends radially. Preferably, each trailing vane extends radially inward from a radially outer edge of the axial end face of the rotor. Each trailing vane can extend to the center or central hole of the axial end face, or each trailing vane has a radial length that is less than the radius of the axial end face, for example half of it.

[0041] The outlet is preferably designed as an outlet connection, which preferably extends perpendicular to the axial direction. The outlet connection preferably has an inlet face, through which the fluid enters the outlet connection, and an outlet face, through which the fluid leaves the outlet connection. The inlet face is preferably smaller than the outlet face.

[0042] The outlet connection is preferably designed cylindrically on its outer diameter, with the outlet connection preferably having a central axis and being axially arranged such that the central axis is closer to the magnetically effective core of the rotor than to the cover of the pump housing.

[0043] It is also possible to design the inlet of the pump housing as an inlet connection, which preferably extends in the axial direction. The inlet connection preferably has an inlet surface, through which the fluid enters the inlet connection, and an outlet surface, through which the fluid leaves the inlet connection and flows towards the impeller. The inlet surface is preferably larger than the outlet surface. Furthermore, the inlet connection preferably has a constriction region, the flow cross section perpendicular to the axial direction of which is smaller than that of the inlet surface and smaller than that of the outlet surface.

[0044] As another advantageous measure, an annular or disk-shaped pressure plate is provided on the impeller and is arranged perpendicular to the axial direction. The pressure plate is arranged in the axial direction between the magnetically effective core and the end of the impeller facing the cover of the pump housing and extends between the vanes of the impeller. If the rotor has a cover plate, the pressure plate is arranged in the axial direction between the magnetically effective core and the cover plate. The pressure plate extends between all the vanes.

[0045] The pressure plate is radially centered on the rotor and preferably extends radially up to the radially outer edge of each blade, but it can also be designed radially such that its diameter is significantly smaller than the diameter of the impeller.

[0046] If the rotor has one balance hole or multiple balance holes, the pressure plate is preferably radially sized to cover at least all of the balance holes.

[0047] For passive magnetic stabilization of the rotor, it is particularly advantageous if the diameter of the rotor's magnetically effective core is greater than 2.6 times its axial dimension, the height of the rotor's magnetically effective core. Thus, where d is the diameter of the rotor's magnetically effective core and HR is its axial height, it is advantageous to satisfy the condition d>2.6×HR.

[0048] The above-mentioned means can be provided, for example, individually, or a plurality of means can be combined, for example, all of the means can be combined.

[0049] Furthermore, the invention proposes a pump housing, inside which a rotor is provided for conveying a fluid, which is designed for a centrifugal pump according to the invention.

[0050] The pump housing according to the invention can in particular also be designed as a disposable part for single use, whereas the stator of the centrifugal pump according to the invention is preferably designed as a reusable device for multiple uses.

[0051] Further advantageous measures and embodiments of the invention emerge from the dependent claims.

[0052] The invention will now be explained in more detail on the basis of embodiments and with reference to the drawings, in which: FIG. [Brief description of the drawings]

[0053] [Figure 1] 1 is a schematic cross-sectional view of an embodiment of a centrifugal pump with an electromagnetic rotary drive designed as a bearingless motor; [Diagram 2] 1 is a schematic cross-sectional view of a first embodiment of a centrifugal pump according to the present invention. [Diagram 3] FIG. [Figure 4] FIG. 3 is a cross-sectional view of the cover of the first embodiment in FIG. 2. [Diagram 5]5 is a plan view of the cover in FIG. 4 as viewed from the bottom of the pump housing. [Figure 6] FIG. 3 is a cross-sectional view of the housing portion of the first embodiment in FIG. 2. [Figure 7] 7 is a plan view of the accommodation portion in FIG. 6 as viewed from the cover of the pump housing. [Figure 8] FIG. 2 is a schematic cross-sectional view of a second embodiment of a centrifugal pump according to the present invention. [Figure 9] FIG. 11 is a plan view of a rotor according to a second embodiment, as viewed from the bottom of a pump housing. [Figure 10] FIG. 11 is a schematic cross-sectional view of a modified example of the rotor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054] First, an embodiment of a centrifugal pump with an electromagnetic rotary drive designed as a bearingless motor will be described with reference to the cross-sectional view of Figure 1. Of course, this embodiment can be designed according to the invention.

[0055] The centrifugal pump is designated as a whole by the reference symbol 1. The centrifugal pump 1 for conveying a fluid comprises a pump housing 2 having an inlet 21 and an outlet 22 for the fluid to be conveyed. A rotor 3 is arranged within the pump housing 2 and, together with a stator 4 arranged outside the pump housing 2, constitutes an electromagnetic rotary drive capable of driving the rotor 3 in rotation about an axial direction A.

[0056] The electromagnetic rotary drive is designed as an inner rotor, i.e. the rotor 3 is arranged inside the stator 4, which surrounds the rotor 3. The rotor 3 is magnetically levitated without contact with respect to the stator 4. Furthermore, the rotor 3 can be magnetically driven without contact by the stator 4 to rotate about a desired axis of rotation. The desired axis of rotation is the axis about which the rotor 3 rotates in an operating state in which the rotor 3 is in a centered and non-tilted position with respect to the stator 4. 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 stator 4.

[0057] In the following, the radial direction is defined as a direction perpendicular to the axial direction A.

[0058] The rotor 3 comprises a magnetically active core 31, which is designed in the shape of a disk, a cylinder or an annulus. The term "magnetically active core 31" refers to the part of the rotor 3 which interacts with the stator 4 to generate torque and generate magnetic bearing forces. Depending on the design, the magnetically active core 31 may comprise one or more permanent magnets. It is also possible for the magnetically active core 31 to be designed without permanent magnets, for example as a reluctance motor. The magnetically active core 31 consists at least partially of a ferromagnetic material, for example iron.

[0059] The magnetically effective core 31 is preferably provided with a jacket 35 which completely encases the magnetically effective core 31 so as to prevent contact with the fluid being conveyed by the magnetically effective core 31. The jacket 35 is preferably constructed from a plastic, although it may be constructed from a metallic material.

[0060] The rotor 3 further comprises an impeller 32 with a number of blades 33 for conveying the fluid from the inlet 21 to the outlet 22. The impeller 32 is arranged on a jacket 35. The impeller 32 with the blades 33 is preferably made of plastic and can for example be designed integrally with the jacket 35. Of course, it is also possible to manufacture each blade 33 or all the blades 33 in a separate manufacturing process and then connect them to the jacket 35, for example by a welding process. It is also of course possible to manufacture the impeller from a metallic material.

[0061] The impeller 32 is preferably designed as a radial impeller that receives a fluid flow from the axial direction A and then deflects the fluid radially.

[0062] The rotary drive with the stator 4 and the rotor 3 is designed, for example, as a so-called temple motor.

[0063] As a design feature of the temple motor, the stator 4 comprises a number of separate coil cores 41, for example six coil cores 41, each with a rod-shaped longitudinal leg 42. The longitudinal legs 42 extend along the axial direction A from a first end to a second end, the first ends of each of which, in the illustrated example in FIG. 1, are connected to one another by a reflux 45. Each coil core 41 further comprises a transverse leg 43. The transverse leg 43 is arranged at the second end of the corresponding longitudinal leg 42 and extends radially, i.e. perpendicular to the axial direction A and thus perpendicular to the corresponding longitudinal leg 42. Each transverse leg 43 extends radially inwards, i.e. towards the rotor 3. Thus, each coil core 41 has an L-shaped design, with each longitudinal leg 42 forming a long line of L extending in the axial direction A and each transverse leg 43 extending radially perpendicular to the longitudinal leg 42 towards the rotor 3 forming a short line of L.

[0064] The radially inner ends of each lateral leg 43 form a stator pole 46. The stator poles 46 are arranged in an annular manner around the pump housing 2 in which the rotor 3 is arranged. The pump housing 2 is designed to be insertable into the stator 4, more specifically between the stator poles 46. The stator poles 46 thus surround the magnetically effective core 31 of the rotor 3. In the operating state, when the rotor 3 is not displaced from its desired position, each stator pole 46 and the magnetically effective core 31 of the rotor 3 are located at the same height in the axial direction A. In the operating state, the rotor 3 is therefore magnetically levitated in a contactless manner between the stator poles 46.

[0065] The reflux 45 and the coil core 41 function as flux guide elements for guiding the magnetic flux and are therefore made of a soft magnetic material, such as ferromagnetic or ferrimagnetic materials, particularly iron, nickel-iron, silicon-iron, etc.

[0066] The parallel longitudinal legs 42 of the coil core 41, all of which extend parallel to the axial direction A and surround the rotor 3, resemble the columns of a temple, hence the name temple motor.

[0067] The stator 4 further comprises a number of windings 6 for generating a rotating electromagnetic field, by means of which the rotor 3 can be magnetically driven without contact and magnetically levitated with respect to the stator 4 without contact. The windings 6 are designed, for example, as six individual coils, one for each longitudinal leg 42. Each coil is arranged around the corresponding longitudinal leg 42, so that the respective coil axis is parallel to the axial direction A. For example, each longitudinal leg 43 supports only one coil 61. Of course, embodiments in which each longitudinal leg 42 supports several coils are also possible.

[0068] The plane in which the rotor 3 flies in the operating state is also called the radial plane, which defines the xy plane of a Cartesian coordinate system whose z axis extends in the axial direction A.

[0069] In a preferred embodiment, the electromagnetic rotary drive designed as a temple motor is designed according to the bearingless motor principle, which means that during operation of the centrifugal pump 1, the magnetically active core 31 of the rotor 3 interacts with the stator poles 46 of the stator 4 according to the above-mentioned bearingless motor principle, in which the rotor 3 can be magnetically driven without contact and can be magnetically levitated without contact with respect to the stator 4.

[0070] The principle of a bearingless motor is now sufficiently well known to the person skilled in the art that it is not necessary to explain its function in detail. The principle of a bearingless motor means that the rotor 3 is magnetically levitated and the stator 4 is designed as a bearing and driving stator, both as a stator for electric drive and as a stator for magnetic levitation. To this end, the stator 4 is provided with windings 6 which realize both the drive and the levitation functions. By means of the windings 6 a rotating electromagnetic field can be generated, which exerts a torque on the magnetically effective core 31 of the rotor 3, causing it to rotate about the axial direction A, while exerting a freely settable shear force on the magnetically effective core 31 of the rotor 3, allowing its radial position, i.e. its position in the radial plane, to be actively controlled or adjusted. In the case of a bearingless motor, in contrast to conventional magnetic bearings, the magnetic levitation and the drive of the motor are realized by a rotating electromagnetic field which exerts a torque and a settable shear force on the magnetically effective core 31 of the rotor 3. The rotating field required for this can be generated by using different coils, but also by mathematically superposing the required fluxes, using a single coil system, here the winding 6. Therefore, in the case of a bearingless motor, it is not possible to separate the electromagnetic flux generated by the winding 6 of the stator 2 into an electromagnetic flux that only drives the rotor 3 and an electromagnetic flux that only ensures magnetic levitation of the rotor 3.

[0071] The principle of the bearingless motor allows for active adjustment of at least three degrees of freedom of the rotor 3, namely its position in the radial plane and its rotation about the axial direction A. The magnetically effective core 31 of the rotor 3 is passively magnetically stabilized by reluctance forces with respect to axial misalignment in the axial direction A, i.e. cannot be controlled. With respect to the remaining two degrees of freedom, i.e. tilt with respect to a radial plane perpendicular to the desired axis of rotation, the magnetically effective core 31 of the rotor 3 is also passively magnetically stabilized. This means that the rotor 3 is passively magnetically levitated or passively magnetically stabilized with respect to the axial direction A and tilt (three degrees of freedom in total) and actively magnetically levitated in the radial plane (two degrees of freedom) by the interaction of the magnetically effective core 31 with the stator poles 46.

[0072] As is common practice, within the scope of the present invention, active magnetic levitation refers to one that can be actively controlled or regulated, for example by a rotating electromagnetic field generated by the windings 6. Passive magnetic levitation or passive magnetic stabilization is one that cannot be controlled or regulated. Passive magnetic levitation or stabilization is based on magnetic reluctance forces that return the rotor 3 to its equilibrium position when it is deviated from this position, for example when it is displaced or tilted in the axial direction A.

[0073] The magnetically effective core 31 of the rotor 3 has a diameter d, which refers to the outer diameter of the magnetically effective core 31. Furthermore, the magnetically effective core 31 has a height HR, which is a dimension in the axial direction A. It is particularly advantageous for passive magnetic stabilization of the rotor 3 if the diameter d of the magnetically effective core 31 of the rotor 3 is greater than 2.6 times the height HR of the magnetically effective core 31 of the rotor 3, i.e., if the geometric condition d>2.6*HR is satisfied.

[0074] Figure 2 shows a schematic cross-sectional view of an embodiment of a centrifugal pump 1 according to the invention, designed according to the embodiment described with reference to Figure 1. In Figure 2, only the stator poles 46 are shown as the stator 4, as this is sufficient for understanding. Again, the stator 4 and the rotor 3 are designed to interact with each other according to the principle of a bearingless motor, as described in relation to Figure 1.

[0075] The pump housing 2 comprises a receiving portion 26 and a cover 25, which is arranged on the receiving portion 26 to close the pump housing 2. The receiving portion 26 and the cover 25 preferably consist of plastic and are rigidly and hermetically connected to one another, for example by welding. In another embodiment, the receiving portion 26 and / or the cover 26 consist of a metallic material.

[0076] For a deeper understanding, Fig. 4 shows a cross-sectional view of the cover 25 taken along the axial direction A, and Fig. 5 shows a plan view of the cover 25 seen from the housing portion 26. Furthermore, Fig. 6 shows a cross-sectional view of the housing portion 26 taken along the axial direction, and Fig. 7 shows a plan view of the housing portion 26 seen from the cover 25.

[0077] The accommodating portion 26 includes a lower cylindrical portion 261 and an upper cylindrical portion 262 arranged coaxially in front-to-back relation along the axial direction A, and the upper cylindrical portion 262 has a larger diameter than the lower cylindrical portion 261. The lower cylindrical portion 261 of the accommodating portion 26 forms the lower end of the pump housing 2 in the figure, and includes a bottom portion 27 arranged perpendicular to the axial direction A.

[0078] The cover 25 is placed on the upper end of the upper cylindrical part 262 in the figure and is firmly connected thereto. An inlet 21 for the fluid to be conveyed is provided on the cover 25. The inlet 21 is designed as an inlet connection and is preferably manufactured integrally with the cover 25. The inlet 21 designed as an inlet connection extends in the axial direction A, whereby the fluid can flow axially into the pump housing 2. The inlet connection 21 preferably has an inlet face 211, through which the fluid enters the inlet connection 21, and an outlet face 212, through which the fluid leaves the inlet connection 21 and flows to the impeller 32. The inlet face 211 is preferably equal to or larger than the outlet face 212. An outlet 22 for the fluid to be conveyed is provided on the upper cylindrical part 262. The outlet 22 is here designed as an outlet connection 22 and is preferably manufactured integrally with the receiving part 26. The outlet 22 designed as an outlet connection extends parallel to the radial plane, i.e. perpendicular to the inlet 21. The fluid thus leaves the pump housing 2 in a radial direction. The outlet connection 22 has an inlet face 221, through which the fluid enters the outlet connection 22, and an outlet face 222, through which the fluid leaves the outlet connection 22. As also shown in FIG. 2, the inlet face 221 is preferably smaller than the outlet face 222. The outlet connection 22 is preferably designed cylindrically in its outer shape. In order to make the inlet face 221 of the outlet connection smaller than the outlet face 222 of the outlet connection 21, the wall of the outlet connection 22 can be provided with a tapered region, in which the thickness of the wall changes so that the inner diameter of the outlet connection 22 changes. This also changes the cross section of the flow of the fluid, which is a plane perpendicular to the central axis M of the outlet connection 22, through which the fluid flows. Such an embodiment is shown in more detail, for example, in FIG. 8.

[0079] With regard to the cylindrical design of the outlet connection 22, it is preferred that the outlet connection 22 is arranged in the axial direction A in such a way that its central axis M is closer to the magnetically active core 31 of the rotor 3 than to the cover 25 of the pump housing 2. This means that the outlet connection 22 is not arranged in the middle in the axial direction A in the upper cylindrical part 262 of the accommodation part 26, but is offset towards the bottom 27, i.e. downwards in the figure.

[0080] The rotor 3 with the magnetically active core 31, the jacket 35 and the impeller 32 is arranged in the pump housing 2 between the bottom 27 of the pump housing 2 and the cover 25, the magnetically active core 31 with the optional jacket 35 being arranged below the impeller 32 in the figure. The magnetically active core 31 including the jacket 35 is preferably of cylindrical design.

[0081] 1, the pump housing 2 is inserted into the stator 4 such that the upper cylindrical portion 262 is placed on the stator 4, while the lower cylindrical portion 261 of the pump housing 2 is disposed within the stator 4, more specifically between the stator poles 46. The pump housing 2 can be fixed to the stator 4, for example, by using screws (not shown).

[0082] The rotor 3 is designed and arranged such that, in an operating condition, the magnetically effective core 31 of the rotor 3 is surrounded by the stator poles 46 and is centered between the stator poles 46 in a radial plane and can be driven to rotate about the axial direction A by the electromagnetic fields generated by the windings 6. When the rotor 3 is centered and not offset from the axial direction A, the magnetically effective core 31 is centered between the stator poles 46.

[0083] The rotor 3 has an outer diameter D, which is the diameter D of the magnetically effective core 31 including the jacket 35. When the jacket 35 is provided, the outer diameter D of the rotor 3 is greater than the diameter d (FIG. 1) of the magnetically effective core 31 of the rotor 3.

[0084] The impeller 32 is preferably designed as a radial impeller 32 such that the blades 33 radially deflect the fluid flowing in the axial direction A through the inlet 21 and convey it to the outlet 22 .

[0085] According to the invention, the bottom 27 and / or the cover 25 are provided with at least one recess, which is designed to generate localized turbulence. In the embodiment described here, a total of eight recesses 9 are provided, four in the cover 25 and four in the bottom 27.

[0086] In other embodiments, the recesses 9 may be provided only in the cover or only in the bottom. The number of recesses 9 should also be understood as an example. Only one recess may be provided, two or three recesses may be provided, or nine or more recesses or a number significantly greater than nine recesses, for example, more than 50 recesses may be provided. Basically, there is no upper limit to the number of recesses 9. By setting the number and arrangement of recesses according to the application, the force acting on the rotor 3, specifically the fluid force, can be reduced as required.

[0087] Said recess 9 or recesses 9 represent a geometrical influence on the flow conditions in the pump housing 2 aimed at reducing the forces acting on the impeller 32 or rotor 3, respectively, in particular the forces acting in the axial direction A and the moments tending to tilt the rotor 3 with respect to the radial plane. The recesses 9 thus improve the stabilization of the rotor 3 for all (here three) degrees of freedom in which the rotor 3 is passively magnetically levitated or stabilized. The recesses 9 arranged in the bottom 27 or in the cover 25 thus modify the flow behavior in such a way that the rotor 3 can be positioned with less effort and movement.

[0088] The reduction of forces, in particular fluid forces, is based on turbulence or the creation of turbulence by recesses 9 which are local changes in the geometry of the pump housing 2 .

[0089] Thus, an embodiment according to the invention having at least one recess 9 can be realized essentially without geometrical barriers to reduce the flow velocity, without pressure compensating holes through the rotor, and without narrow wedge-shaped fluid gaps that locally increase pressure, as in, for example, conventional hydrodynamic bearings. The recess 9 thus creates local turbulence and flow separation, reducing the flow force effect on the surfaces of the rotor 3 exposed to laminar and turbulent flow. This turbulence or flow separation reduces the dynamic lift acting on the rotor 3, and thus the forces acting on the rotor 3.

[0090] Of course, it is possible for embodiments of the invention to provide further pressure equalisation holes, for example through the rotor 3. Such an embodiment is described below with reference to the second embodiment.

[0091] Each recess 9 can be designed as a dimple, depression, countersink or bore, etc., to locally induce vortices in the flow. For example, the recess 9 can be spherical or cylindrical. It can also have a square or rectangular contour. The recess can be designed as a pyramid, cone, truncated cone, ring or free geometric shape. However, for manufacturing reasons, a geometric shape that can be produced by a drilling or milling tool is preferred for the recess 9. For this reason, the design of the recess 9 is preferably such that each recess 9 has a circular contour perpendicular to the axial direction A. That is to say, it is preferably designed as a sphere or cylinder.

[0092] In FIG. 3, one of the recesses 9 is shown in cross section with an exemplary feature, in this example designed as a blind hole in the bottom 27 of the pump housing 2 .

[0093] Typically, each recess 9 has a radial dimension E, which means the maximum width of the recess 9 in the radial direction, and a depth T, which means the maximum dimension of the recess in the width direction A.

[0094] For the blind hole design shown in FIG. 3, dimension E is the diameter E of the hole in the radial direction and depth T is the length of the hole in the axial direction A.

[0095] In practice, it has proven to be advantageous if the radial dimension E of each recess 9 is at least 1 / 50 of the outer diameter D of the rotor 3, i.e. E is ≥ 0.02D. It is also advantageous if the radial dimension E of each recess 9 is at most half the outer diameter D of the rotor 3, i.e. E is ≤ 0.5D.

[0096] It has proven advantageous if the depth T of each recess 9 in the axial direction A is at least 1 / 150 of the outer diameter D of the rotor 3, i.e. T is 0.015D or more. It is particularly preferred if the depth T of each recess 9 in the axial direction A is at least 1 / 100 of the outer diameter D of the rotor 3, i.e. T is 0.01D or more.

[0097] Furthermore, with respect to the axial direction A, it is preferable that the depth T in the axial direction A of each recess 9 is at most one tenth of the outer diameter D of the rotor 3, that is, T is 0.1D or less.

[0098] Regarding the position of the one or more recesses 9, the one or more recesses 9 are preferably disposed in a radially outer edge region of the bottom 27 and / or the cover 25. This specifically means that, as shown in Figures 2, 4, 5, and 6, the recess 9 in the cover 25 of the pump housing 2 is located closer to the radially outer edge of the cover 25 than to the center of the cover 25, and the recess 9 in the circular bottom 27 of the pump housing 2 is located closer to the radially outer edge of the bottom 27 than to the center of the bottom 27.

[0099] In a preferred embodiment of the invention, the pump housing 2, and / or the impeller 32, and / or the jacket 35 of the rotor 3 are constructed from plastic. It is preferred that the pump housing 2, and the impeller 32, and the jacket 35 of the rotor 3 are constructed from plastic. The pump housing 2, the impeller 3, and the jacket 35 can all be constructed from the same plastic, or can be constructed from at least two different plastics.

[0100] Of course, depending on the application, a suitable plastic is selected, for example, polyethylene (PE), polypropylene (PP), low density polyethylene (LDPE), ultra low density polyethylene (ULDPE), ethylene vinyl acetate (EVA), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), acrylonitrile butadiene styrene (ABS), polyacrylic, polycarbonate.

[0101] In another preferred embodiment of the present invention, the pump housing 2, and / or the impeller 32, and / or the jacket 35 of the rotor 3 are made of a single metal material or several different metal materials. Preferred metal materials include, for example, titanium and stainless steel.

[0102] Fig. 8 shows a schematic cross-sectional view of a second embodiment of a centrifugal pump 1 according to the invention. For a better understanding, Fig. 9 also shows a top view of the rotor of the second embodiment from the bottom of the pump housing. Furthermore, Fig. 9 shows the section line VIII-VIII, along which the section shown in Fig. 8 was obtained.

[0103] In the following, only the differences from the first embodiment described above will be described. In particular, the reference numerals have the same meaning as already explained in relation to the first embodiment. It should be understood that all the above explanations are the same or equivalent for the second embodiment.

[0104] In the second embodiment, several further measures are realised that, depending on the application, can further improve the tilt of the rotor 3 with respect to the axial direction A and the radial plane, i.e. the three degrees of freedom that are passively magnetically stabilized. It is to be understood that these measures can be realised in their entirety, but do not have to be. This means, for example, that embodiments are also possible in which one or more of the measures described with reference to the second embodiment are combined with the first embodiment.

[0105] In a second embodiment of a centrifugal pump 1 according to the invention, shown in figures 8 and 9, the inlet 21 of the pump housing 2, designed as an inlet connection, has a constriction region 213, whose flow cross section perpendicular to the axial direction A is smaller than the inlet face 211 and smaller than the outlet face 212 of the inlet connection 21. The inlet face 211 of the inlet connection 21 is also larger than its outlet face 212. Comparing the faces, the inlet face 211 is larger than the outlet face 212, which is larger than the flow cross section at the constriction region 213.

[0106] The outlet 22 of the pump housing 2 is designed in a manner equivalent to that described in the first embodiment, i.e. the inlet face 221 of the outlet connection 22 is smaller than the outlet face 222 of the outlet connection 22 and the outlet connection 22 is arranged with respect to the axial direction A in such a way that the central axis M is closer to the annular magnetic effective core 31 of the rotor 3 than to the cover 25 of the pump housing 2. With reference to the dotted line in the outlet 22, FIG. 8 shows how the inside of the outlet connection 22 is designed, in which the outlet face 222 of the outlet connection 22 is larger than the inlet face 221 of the outlet connection 21.

[0107] Usually, the size including the peripheral wall of the outlet face 222 of the outlet connection part 22 and the inlet face 211 of the inlet connection part 21 are preset based on a standard. The outer diameter of the inlet face 211 of the inlet connection part 21 and the outer diameter of the outlet face 222 of the outlet connection part 22 are dimensions that allow the centrifugal pump 1 to be connected to general piping or tubes in a flow system.

[0108] Furthermore, the rotor 3 is designed like an annular disk and has a cover plate 36 which covers the edges of the blades 33 of the impeller 32 facing the inlet 21 or the cover 25. The cover plate 36 is provided with a centrally located opening 361 through which the fluid can flow into the impeller 32.

[0109] The magnetically active core 31 of the rotor 3 may optionally have a central bore 37 that extends in the axial direction A completely through the magnetically active core 31 and any jacket 35 .

[0110] Alternatively or additionally, the rotor 3 may include one balance hole 38 or multiple balance holes 38, each extending completely through the magnetically active core 31 and optional jacket 35 of the rotor 3 in the axial direction A. The balance holes 38 are preferably distributed, i.e. located other than at the center of the rotor 3.

[0111] In the second embodiment, a plurality of balance holes 38, specifically, eight balance holes 38, are provided.

[0112] The balance holes 38 are preferably arranged on a circular line, the centre of the circle being located at the centre of the rotor 3. This means that, if the rotor 3 is provided with a central hole 37, the balance holes 38 are arranged in a circle around the central hole 37. Preferably, a maximum or just eight balance holes 38 are provided, which are preferably equidistantly arranged around the central hole 37 of the rotor 3 or around the centre of the rotor 3.

[0113] Each balance hole 38 has a diameter smaller than the diameter of the central hole 37 .

[0114] A plurality of rear vanes 39 are provided on the axial end face of the rotor 3 facing away from the cover 25 and facing the bottom 27. In the operating state, these rear vanes 39 face the bottom 27 of the pump housing 2. In the second embodiment, a total of eight rear vanes 39 are provided.

[0115] The rear vanes 39 can be realized, for example, by providing recesses in the jacket 35 of the rotor 3 and forming each rear vane 39 between two adjacent recesses.

[0116] Furthermore, it is of course possible to design the rear vanes 39 as protuberances. In this case, for example, an impeller-like structure is produced and attached to the axial end face of the rotor 3, so that the rear vanes 39 face the bottom 27 of the pump housing 2. Of course, it is also possible to produce each rear vane 38 separately and attach it to the axial end face of the rotor 3.

[0117] Preferably, each trailing vane 39 extends radially inward from the radially outer edge of the axial end face of the rotor 3. Each trailing vane 39 can extend to the center or central hole 37 of the axial end face, or each trailing vane 39 has a radial length that is smaller than the radius of the axial end face, for example half of it, as shown in Figure 9. In other embodiments, the trailing vanes 39 can also be designed to be curved.

[0118] In the second embodiment, an annular or disk-shaped pressure plate 321 is provided on the impeller 32 and is arranged perpendicular to the axial direction A. The pressure plate 321 is arranged in the axial direction A between the magnetically effective core and the end of the impeller 32 facing the cover 25 of the pump housing 2, for example, at a position corresponding to the middle of each vane 33 of the impeller 32. The pressure plate 321 extends between the vanes of the impeller 32. If the rotor 3 has a cover plate 36, the pressure plate 321 is arranged between the magnetically effective core 31 and the cover plate 36 in the axial direction A and is parallel to the cover plate 36. The pressure plate 321 extends between all the vanes. The pressure plate 321 is arranged radially at the center of the rotor 3 and extends radially at least a distance from a predetermined axial distance to cover all the balance holes 38. In the embodiment shown in FIG. 8, the diameter of the pressure plate 321 is significantly smaller than the diameter of the impeller 32 measured at the vane 33.

[0119] Fig. 10 shows in a schematic cross-sectional view a modified rotor 3. This rotor 3 differs from the rotor 3 shown in Fig. 8 in that the pressure plate 321 has a larger diameter. In the modified example shown in Fig. 10, the pressure plate 321 extends radially almost to the radially outer end of the blades 33 of the impeller 32.

Claims

1. A centrifugal pump for conveying a fluid, comprising a pump housing (2) in which a rotor (3) is arranged for conveying said fluid, and a stator (4) which, together with the rotor (3), forms an electromagnetic rotary drive for rotating the rotor (3) about an axial direction (A), the stator (4) being designed as a bearing and drive stator capable of magnetically driving the rotor (3) without contact and capable of magnetically levitating the rotor (3) without contact relative to the stator (4), the rotor (3) being passively supported in the axial direction (A).

1. A centrifugal pump comprising a rotor (3) arranged in the pump housing (2) between the bottom (27) and the cover (25) in the axial direction (A), the rotor (3) being magnetically levitated and actively magnetically levitated in a radial plane perpendicular to the axial direction (A), the pump housing (2) having a bottom (27) and a cover (25), the rotor (3) being arranged in the pump housing (2) between the bottom (27) and the cover (25) in the axial direction (A), characterized in that the bottom (27) and / or the cover (25) are provided with at least one recess (9), the recess (9) being designed to generate localized turbulence.

2. 2. The centrifugal pump of claim 1, wherein the rotor (3) comprises an annular or disc-shaped magnetically effective core (31) and an impeller (32) having a plurality of blades (33) for conveying the fluid.

3. 3. The centrifugal pump according to claim 1 or 2, wherein an inlet (21) for the fluid designed to allow the fluid to flow into the pump housing (2) in the axial direction (A) is provided on the cover (25) of the pump housing (2), and the pump housing (2) has an outlet (22) for the fluid designed to allow the fluid to flow out of the pump housing (2) in the radial direction.

4. 4. A centrifugal pump according to claim 2 or claim 3 dependent on claim 2, wherein the stator (4) has a plurality of stator poles (46) arranged in an annular manner, and the pump housing (2) in which the rotor (3) is arranged is designed so that it can be inserted between the stator poles (46) such that the magnetically effective core (31) of the rotor (3) is surrounded by the stator poles (46) of the stator (4).

5. 5. The centrifugal pump according to claim 1, wherein the rotor (3) has an outer diameter (D) and each recess (9) has a dimension (E) in the radial direction that is at least 1 / 50 of the outer diameter (D) of the rotor (3).

6. 6. The centrifugal pump according to claim 1, wherein the rotor (3) has an outer diameter (D) and each recess (9) has a dimension (E) in the radial direction that is at most half the outer diameter (D) of the rotor (3).

7. 7. The centrifugal pump according to claim 1, wherein the rotor (3) has an outer diameter (D) and each recess (9) has a depth (T) in the axial direction (A) that is at least 1 / 150 of the outer diameter (D) of the rotor (3).

8. A centrifugal pump as described in claim 7, wherein the depth (T) is at least 1 / 100 of the outer diameter (D) of the rotor (3).

9. 9. The centrifugal pump according to claim 1, wherein the rotor (3) has an outer diameter (D) and each recess (9) has a depth (T) in the axial direction (A) that is at most one tenth of the outer diameter (D) of the rotor (3).

10. A centrifugal pump according to any one of the preceding claims, wherein each recess (9) has a circular contour perpendicular to said axial direction (A).

11. Centrifugal pump according to any one of the preceding claims, wherein at least one recess (9) is provided in both the cover (25) and the bottom (27) of the pump housing (2).

12. Centrifugal pump according to any one of the preceding claims, wherein each recess (9) is arranged in the radially outer edge region of the pump housing (2).

13. Centrifugal pump according to any one of the preceding claims, wherein the pump housing (2) is made of plastic.

14. 5. The centrifugal pump of claim 2 or 4, wherein the impeller (32) is made of plastic.

15. 5. A centrifugal pump as claimed in claim 2 or 4, wherein the rotor (3) has a jacket (35) which completely encases the magnetically active core (31) of the rotor and is made of plastic.

16. A pump housing (2) having a rotor (3) therein for conveying a fluid, characterized in that the pump housing is designed for a centrifugal pump (1) designed according to any one of claims 1 to 15.

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