Pump unit for centrifugal pump, and centrifugal pump

Abstract

To provide a pump unit for a centrifugal pump, which includes the pump unit and a stator extending in an axial direction from a first axial end to a second axial end.SOLUTION: A pump unit includes a pump housing and a rotor that has vanes for conveying a fluid. The pump housing has a cover part and a bottom part. The bottom part has a cylindrical cup to receive the rotor. The cylindrical cup can be inserted into a cup-shaped recess of a stator. An inlet has a lip which forms one axial end of the inlet such that the lip projects into a pump chamber and, when viewed in the flow direction, ends in front of an end face of the rotor when the rotor is disposed at the center with respect to the axial direction in the operating state.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a pump unit for a centrifugal pump according to the preamble of the independent claim. The invention further relates to a centrifugal pump comprising such a pump unit. [Background technology]

[0002] Centrifugal pumps are known that include a pump unit and a stator designed as a drive unit for the rotor of the pump unit, where the rotor of the pump unit forms the centrifugal wheel of the centrifugal pump. The rotor can be magnetically supported without contact and can be driven by the stator in the pump unit to rotate about its axial axis without contact. Such centrifugal pumps are, for example, commercially available from the applicant under the trade name Levitronix® BPS Pump.

[0003] The stator and rotor form an electromagnetic rotary drive. For example, in the Levitronix® BPS pump, the electromagnetic rotary drive is designed according to the bearingless motor principle. The term bearingless motor refers to an electromagnetic rotary drive in which the rotor can be fully magnetically supported relative to the stator, without the provision of a separate magnetic bearing. For this purpose, the stator is designed as a bearing and drive stator, serving both as the stator of the electric drive and as the stator of the magnetic bearing. The stator's electrical windings can be used to generate a magnetic rotating field that exerts a torque on the rotor that, on the one hand, realizes its rotation about a desired axis of rotation defined by the axial direction, and, on the other hand, exerts a transverse force on the rotor that can be optionally adjusted to allow its radial position to be actively controlled or adjusted. Thus, three degrees of freedom of the rotor can be actively adjusted: its rotational position and its radial position (two degrees of freedom). With regard to the other three degrees of freedom, namely its position in the axial direction and its tilt relative to the radial plane perpendicular to the desired axis of rotation (two degrees of freedom), the rotor is passively magnetically supported or stabilized by reluctance forces, i.e., the rotor cannot be controlled. The absence of a separate magnetic bearing with a complete magnetic bearing of the rotor is the characteristic that gives bearingless motors their name. In a bearing-drive stator, the bearing function cannot be separated from the drive function.

[0004] Of course, other centrifugal pump designs are also known in which the rotor is magnetically supported without contact, for example, by providing a separate magnetic bearing for the rotor, thereby separating the magnetic bearing function from the drive function. For example, a separate coil is provided for this purpose, and this separate coil is used to provide only the bearing force for the rotor, but does not contribute to the drive of the rotor. For example, such a centrifugal pump is disclosed in WO 2022 / 004144.

[0005] Centrifugal pumps with contactless, magnetically supported and driven rotors, for example rotors designed and operating according to the principle of bearingless motors, have found numerous applications. The absence of mechanical bearings makes such centrifugal pumps suitable for applications where very delicate substances are conveyed, such as blood pumps, or where the demands on purity are very high, for example in the semiconductor, pharmaceutical, or biotechnology industries, or for conveying abrasive or corrosive substances that would cause mechanical bearings to fail very quickly, such as pumps for slurries, sulfuric acid, phosphoric acid, or other chemicals in the semiconductor industry.

[0006] Figure 1 shows a representation of a centrifugal pump known from the state of the art, designed according to the bearingless motor principle, such as the Levitronix® BPS pump. To allow a better understanding, a portion of the centrifugal pump is cut away in Figure 1 to make the interior visible.

[0007] The centrifugal pump 200' comprises a stator 100' and a pump unit 1'. For a better understanding, Fig. 2 shows a top view of the pump unit 1' from the axial direction A, and Fig. 3 shows the pump unit 1' in a cross-sectional view along line III-III in Fig. 2.

[0008] 1, 2 and 3 are devices from the state of the art, the respective reference numerals being here prefixed with inverted commas or dashes. The centrifugal pump is designated in its entirety by the reference numeral 200'.

[0009] A rotor 10' forming a centrifugal wheel or impeller is arranged in the pump unit 1', by means of which the fluid is conveyed. A stator 100' has a stator housing 130' and extends in the axial direction A from a first axial end 110' to a second axial end 120', in which a cup-shaped recess 121' is provided at the first axial end 110', into which the pump unit 1' can be inserted. The stator 100' together with the rotor 10' form an electromagnetic rotary drive for rotating the rotor 10' about the axial direction A. The stator 100' is designed for contactless magnetic bearing of the rotor 10' according to the bearingless motor principle. For this purpose, the stator 100' is designed as a bearing-drive stator, by means of which the rotor 10' can be contactlessly magnetically driven for rotation about the axial direction A and can also be contactlessly magnetically supported relative to the stator 100', in which the rotor 10' is passively magnetically stabilized in the axial direction A and actively magnetically supported in a radial plane perpendicular to the axial direction A, which radial plane is indicated in Figure 1 by the line E.

[0010] The electromagnetic rotary drive having the stator 100' and the rotor 10' is designed as a so-called temple motor. The stator 100' comprises a plurality of coil cores 125', here eight coil cores 125', each of which comprises a longitudinal leg 126' extending in the axial direction A from a first end, which is the lower end according to the representation in FIG. 1, to a second end, and a transverse leg 127' arranged at the second end of the longitudinal leg 126' in a radial plane E. Each transverse leg 127' extends radially from the associated longitudinal leg 126' towards the rotor 10' and is bounded by an end face located radially inside. The coil core 126' is circumferentially arranged around the cup-shaped recess 121' and thus around the rotor 10', so that the rotor 10' is positioned between the radially inner end faces of the lateral legs 127' of the coil core 126'.

[0011] The first ends of all of the transverse legs 126' are connected to one another by a back iron 122' for conducting magnetic flux. At least one concentrated winding 160', 161' is provided on each longitudinal leg 126' and surrounds the respective longitudinal leg 126'. Regarding the number and arrangement of the concentrated windings 160', 161', many variations are known that will not be described in detail here. For example, there is a winding 160' that is wound around exactly one longitudinal leg 126' and a winding 161' that is wound around exactly two longitudinal legs 126'.

[0012] These multiple longitudinal legs 126', which extend in the axial direction A and are reminiscent of the columns of a temple, are what give the temple motor its name.

[0013] The pump unit 1' (FIGS. 2 and 3) comprises a pump housing 2' having an inlet 21' and an outlet 22' for the fluid to be pumped, and a rotor 10' arranged in the pump housing 2' for pumping the fluid, the rotor being rotatable about an axial direction A. The pump housing 2' defines a pump chamber 23'. The rotor 10' comprises a magnetically effective core 101' which magnetically cooperates with a stator 100' to generate torque and to generate a magnetic bearing force. For example, the magnetically effective core 101' is a permanent magnet ring or a permanent magnet disk.

[0014] In operation, the desired position of the rotor 10' is centered relative to the axial direction A and centered in the radial plane E between the coil core 125', and here between the lateral legs 127' of the coil core 125'. Centered relative to the axial direction A means that the rotor's magnetically active core 101' is aligned with the lateral legs 127' of the coil core 125'. Thus, the magnetic center plane of the rotor 10' (typically the geometric center plane of the magnetically active core 101') is located in the radial plane E. This provides a magnetic restoring force that moves the rotor 10' back to its desired position if the rotor 10' is axially displaced from this desired central position or tilted relative to the axial direction A.

[0015] It is also possible to design the magnetic core 101' in a permanent magnet-free manner, i.e., without permanent magnets. In this case, the rotor 10' is designed, for example, as a reluctance rotor. In this case, the magnetic core 101' of the rotor 10' is made, for example, of a soft magnetic material. Suitable soft magnetic materials for the magnetic core 101' are, for example, ferromagnetic or ferrimagnetic materials, such as iron, nickel-iron, cobalt-iron, silicon-iron, mu-metal, and the like.

[0016] Furthermore, the magnetically effective core 101' of the rotor 10' can be designed to include both ferromagnetic and permanent magnet materials. For example, the permanent magnets can be disposed or embedded in a ferromagnetic substrate. Such a design is advantageous, for example, when it is desired to conserve permanent magnet material and reduce the cost of large rotors.

[0017] Typically, the magnetic core 101' is completely covered by plastic. In other designs, the magnetic core 101' is completely surrounded by a sheath made of a ceramic material or a metallic material, such as stainless steel or titanium or tantalum.

[0018] Additionally, the rotor 10' includes a plurality of vanes 103' for conveying the fluid from the inlet 21' to the outlet 22'.

[0019] The pump housing 2' comprises a bottom part 3' and a cover part 4' for closing the bottom part 3', wherein a sealing element 90' (Figure 1), such as an O-ring or a flat seal, is provided between the bottom part 3' and the cover part 4' to prevent leakage of fluid to the environment.

[0020] The inlet 21' of the pump housing 2' is arranged in the cover part 4' and is designed so that the fluid to be conveyed flows in the axial direction A towards the rotor 10'. The outlet 22' extends parallel to the radial plane E, i.e. substantially perpendicular to the inlet 21'. Typically, the inlet 21' is designed to form a curved transition to the pump chamber 23'.

[0021] The bottom 3' of the pump housing 2' has a cylindrical cup 31' for receiving the rotor 10'. The cup 31' is inserted into a recess 121' in the stator housing 130', so that the rotor 10', or more precisely the magnetically effective core 101' of the rotor 10', is positioned between the lateral legs 127' of the coil core 126'.

[0022] For example, the pump unit 1' is attached to the stator housing 130' by mounting elements 11', such as a plurality of screws 11'. The screws 11' are disposed in the bottom portion 3' and secure the bottom portion 3' to the first axial end 110' of the stator 100'. Typically, the cover portion 4' is connected to the bottom portion 3' via a press fit. Additionally, the cover portion 4' is secured to the bottom portion 3' by a plurality of mounting screws 13' that engage through the cover portion 4' in the axial direction A and within the bottom portion 3'.

[0023] In many applications, such as those in the semiconductor industry, the pump unit 1', except for the magnetically effective core 101', is made of plastic, such as perfluoroalkoxy polymer (PFA) or polytetrafluoroethylene (PTFE), because these are plastics with very high chemical resistance. These plastics are essentially inert materials, such as those frequently used in the semiconductor industry, which cannot be attacked even by highly corrosive chemicals. In addition, PFA and PTFE are very pure plastics because they contain no additives and their molecular complexes are at least approximately inert. PFA is often preferred because it can be processed in injection molding processes.

[0024] Although this type of pump unit 1' and centrifugal pump 200' has proven to be very successful in practice, there is still room for improvement, especially when these centrifugal pumps 200' are designed for very high power outputs. At particularly high hydraulic outputs, a large leakage flow occurs from the trailing edge of the vanes 103' toward the inlet 21'. The leakage flow is indicated by an arrow without a reference number in FIG. 3 . This leakage flow reduces the efficiency of the centrifugal pump and, consequently, its energy efficiency. Additionally, the leakage flow generates a tear-off effect, especially in the inlet region, which can lead to cavitation and a further decrease in efficiency. [Prior art documents] [Patent documents]

[0025] [Patent Document 1] WO2022 / 004144 Summary of the Invention [Problem to be solved by the invention]

[0026] Starting from this state of the art, it is therefore an object of the present invention to propose a pump unit for a centrifugal pump, which has a rotor that can be magnetically levitated without contact, which allows a very high efficiency of the centrifugal pump, particularly but not exclusively at high hydraulic outputs, and also to propose a centrifugal pump having such a pump unit. [Means for solving the problem]

[0027] The subject matter of the invention which meets this object is characterized by the features of the independent claims.

[0028] Therefore, according to the present invention, a pump unit for a centrifugal pump is proposed, comprising a pump unit and a stator extending axially from a first axial end to a second axial end, wherein a cup-shaped recess is provided at the first axial end, wherein the pump unit can be inserted into the cup-shaped recess, wherein the pump unit has a pump housing with an inlet and an outlet for the fluid to be conveyed, and a rotor arranged in the pump housing with a plurality of vanes for conveying the fluid, each vane extending axially to an end face of the rotor facing towards the inlet, wherein the pump housing defines a pump chamber, wherein the rotor can be rotated about the axial direction, wherein the pump unit is designed for contactless magnetic levitation of the rotor and for contactless magnetic driving of the rotor by the stator, wherein the pump housing has a cover part and a bottom, wherein the bottom has a cylindrical cup for receiving the rotor, wherein the cylindrical cup can be inserted into the cup-shaped recess of the stator. The inlet has a lip forming one axial end of the inlet which projects into the pump chamber when the rotor is axially centered in the operating condition and terminates forward of the end face of the rotor when viewed in the direction of flow.

[0029] Therefore, when the rotor is in its desired position in operation, i.e., axially centered, the lip is at a distance from the end face of the rotor such that it does not protrude into the rotor in the axial direction. Of course, magnetic levitation of the rotor allows the entire rotor to be displaced in the axial direction in operation. Such displacement of the rotor in the axial direction can cause the lip to penetrate axially into the rotor in operation, depending on the lip design. Therefore, the expression that the lip terminates axially in front of the end face of the rotor when viewed in the flow direction refers to an operating state in which the rotor is axially centered, i.e., in its desired position.

[0030] The lip forming one axial end of the inlet and projecting into the pump chamber significantly reduces leakage flow from the trailing edge of the vane in the direction of the inlet 21 because its projection into the pump chamber reduces the free flow cross-section for leakage flow. Alternatively, the lip allows for a more sophisticated design of the pump chamber in the axial direction without increasing the free flow cross-section for leakage flow. Furthermore, the lip forms a clearly defined separation edge for the fluid flowing through the inlet. This defined separation edge determines where flow separation occurs at the inlet, regardless of specific fluid properties, such as fluid viscosity, and regardless of specific flow conditions, such as flow rate. The significant reduction in leakage flow from the trailing edge of the vane to the inlet of the pump housing improves the efficiency of the centrifugal pump. Furthermore, separation effects caused by leakage flow, which can lead to cavitation, are at least significantly reduced.

[0031] By reducing the leakage flow, the perturbation forces acting on the rotor in the radial direction are also significantly reduced, which in turn reduces the current required for effective magnetic radial levitation of the rotor, thereby improving the efficiency and energy efficiency of the centrifugal pump.

[0032] Another advantage of the lip acting as a release edge is that it minimizes the suction effect on the cover of the pump housing, thereby reducing the static and dynamic axial forces on the rotor.

[0033] The inlet lip protrudes into the pump chamber, creating an inlet valve effect as well, which is beneficial for axial stabilization of the rotor, both with respect to rotor tilt and rotor axial displacement.

[0034] Preferably, the lip is designed to be ring-shaped and extend circumferentially along the entire circumference of the inlet. However, embodiments are also possible in which the lip has one or more gaps when viewed circumferentially. For example, the lip may be designed to have a notch. Thus, the lip may be designed to have a circumferential discontinuity.

[0035] According to a preferred embodiment, the rotor blades are arranged around a central inlet region that extends axially to the end face of the rotor and has one diameter. The central inlet region of the rotor has no blades. Each blade extends from a leading edge located radially inward to a trailing edge located radially outward. The leading edges of the blades are located on a line, preferably a circular line, that has a non-zero distance from the central axis of the rotor. The diameter of the central inlet region is determined by the distance of the leading edges of the blades from the central axis of the rotor. This diameter of the central inlet region is equal to twice the distance of the leading edges of the blades from the central axis of the rotor.

[0036] Furthermore, the rotor preferably has at least one relief opening extending axially through the rotor from the central inlet region, which may reduce axial thrust acting on the rotor.

[0037] According to a preferred embodiment, the inlet lip has an outer diameter that is larger than the diameter of the central inlet region. However, embodiments are also possible in which the outer diameter of the lip is smaller than the inner diameter of the central inlet region. Thus, in these embodiments, axial displacement of the rotor allows the lip to enter the central inlet region of the rotor in operating conditions.

[0038] According to a preferred embodiment, the lip has a substantially triangular profile, the apex of which faces the end face of the rotor. As a result, the end of the inlet facing the rotor is designed as a narrow edge, which is advantageous for its function as a cutting edge. It will be understood that in the case of a substantially triangular profile, the apex is not designed as a sharp edge, i.e., not in the sense of a blade, but as an edge with a finite width.

[0039] Furthermore, it is a preferred measure that the lip diverges when viewed in the flow direction, thus increasing the cross-sectional area of ​​the lip when viewed in the flow direction. For example, the lip can be designed to diverge conically in the axial direction.

[0040] An embodiment is also possible in which the lip is designed to curve outwards.

[0041] In another possible embodiment, the lip is designed as a cylindrical pipe section.

[0042] According to another embodiment, the cover part of the pump housing is designed to be angled such that the cover part surrounds the inlet at an angle greater than 90° to the axial direction.

[0043] According to another preferred embodiment, the outlet has an immersion surface through which fluid can flow from the pump chamber into the outlet, where the immersion surface of the outlet has a profile different from a circular surface. This embodiment of the immersion surface of the outlet can significantly reduce the distance between the immersion surface and the vane measured in the axial direction without having to reduce the cross-sectional area of ​​the immersion surface. Because the profile of the immersion surface of the outlet is different from a circular surface, the immersion surface can be positioned closer to the vane in the axial direction than in the case of a circular immersion surface profile, without reducing the cross-sectional area of ​​the immersion surface.

[0044] For example, when comparing an immersion surface having a circular profile with a predetermined diameter to an immersion surface having a non-circular profile, the immersion surface having a non-circular profile can be designed to have a larger cross-sectional area than the immersion surface having a circular profile without the maximum extension of the immersion surface having a non-circular profile being greater than the predetermined diameter of the immersion surface having a circular profile.

[0045] Conversely, this means that an immersion surface with a non-circular profile can be designed to have the same cross-sectional area as an immersion surface with a circular profile, and yet have a smaller extension, particularly in the axial direction, compared to an immersion surface with a circular profile. Thus, the immersion surface with a non-circular profile can be arranged axially closer to the blades or with a greater overlap with the blades. This has a particularly advantageous effect for the contactless magnetic levitation of the rotor, since the static and dynamic axial and tilting forces on the rotor, as well as the radial perturbation forces acting on the rotor, are significantly reduced.

[0046] According to a preferred embodiment, the profile of the immersion surface is designed to be substantially rectangular.

[0047] Furthermore, in a preferred embodiment, particularly for reasons of production technology, the profile of the penetration surface is designed to have rounded corners.

[0048] According to a preferred embodiment, the profile of the immersion surface has an axial profile height and a radial profile width perpendicular to the axial direction, wherein the profile width is greater than the profile height.

[0049] Furthermore, the present invention proposes a centrifugal pump for conveying a fluid, having a pump unit designed according to the present invention, with a stator extending axially from a first axial end to a second axial end, wherein a cup-shaped recess is provided at the first axial end, and a cylindrical cup of the pump unit can be inserted into the cup-shaped recess, wherein the stator together with the rotor forms an electromagnetic rotary drive for rotating the rotor about the axial direction, wherein the stator is designed as a bearing-drive stator, and the rotor can be magnetically driven without contact by the stator and magnetically levitated relative to the stator without contact, wherein the rotor is passively magnetically stabilized in the axial direction and actively magnetically levitated in a radial plane perpendicular to the axial direction.

[0050] Particularly preferably, the electromagnetic rotary drive is designed as a temple motor, the stator having a plurality of coil cores, each of which has a longitudinal leg extending axially from a first end to a second end, as well as a transverse leg arranged at the second end of the longitudinal leg in a radial plane, the transverse leg extending radially from the longitudinal leg, the coil cores being arranged circumferentially around the rotor, so that the rotor is arranged between the transverse legs of the coil core, and at least one concentrated winding is provided on each longitudinal leg, at least one concentrated winding surrounding each longitudinal leg.

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

[0052] In the following, the invention will be explained in more detail with reference to embodiments and with reference to the drawings. [Brief explanation of the drawings]

[0053] [Figure 1] 1 is a perspective view of a centrifugal pump according to the state of the art; FIG. [Figure 2] FIG. 2 is a top view of the pump unit from the axial direction A. [Figure 3] 3 is a cross-sectional view of the pump unit from FIG. 2 taken along the section line III-III in FIG. 2. [Figure 4] 1 is a cross-sectional view showing a first embodiment of a pump unit according to the present invention along the axial direction. [Figure 5] 5 is a cross-sectional view showing a variation for the first embodiment, corresponding to the cross-sectional view of FIG. 4; FIG. [Figure 6] 5 is a cross-sectional view showing a variation for the first embodiment, corresponding to the cross-sectional view of FIG. 4; FIG. [Figure 7] 5 is a cross-sectional view showing a variation for the first embodiment, corresponding to the cross-sectional view of FIG. 4; FIG. [Figure 8] 5 is a cross-sectional view showing a variation for the first embodiment, corresponding to the cross-sectional view of FIG. 4; FIG. [Figure 8A] 5 is a cross-sectional view showing a variation for the first embodiment, corresponding to the cross-sectional view of FIG. 4; FIG. [Figure 9] FIG. 2 is a cross-sectional view showing a second embodiment of a pump unit according to the present invention along the axial direction. [Figure 10] FIG. 10 shows a first variant for the profile of the intrusion surface of the outlet. [Figure 11] FIG. 10 shows a second variant for the profile of the intrusion surface of the outlet. [Figure 12] 1 is a schematic cross-sectional view showing an embodiment of a centrifugal pump according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0054] As already explained above, Fig. 1 shows a centrifugal pump 200' having a contactless magnetically supported and contactless magnetically driven rotor 10' known from the state of the art. Figs. 2 and 3 show a pump unit 1' of this centrifugal pump 200' in top view and cross-sectional view, respectively.

[0055] In a cross-sectional view corresponding to FIG. 3, FIG. 4 shows a first embodiment of a pump unit according to the invention, designated in its entirety by the reference number 1.

[0056] The pump unit 1 is designed for a centrifugal pump 200 (see FIG. 12) for conveying a fluid and comprises a pump housing 2 having an inlet 21 and an outlet 22 for the fluid. A rotor 10 for conveying the fluid is arranged in the pump housing 2, the rotor forming a centrifugal wheel or impeller of the pump unit 1 and thus of the centrifugal pump 200. The rotor 10 can be rotated about a desired axis of rotation that defines an axial direction A. This desired axis of rotation is the central axis M of the rotor 10.

[0057] In the axial direction A, the rotor 10 extends from an end face 107 facing towards the inlet 21 to a rear side facing away from the inlet 21 .

[0058] The direction perpendicular to the axial direction A is designated as the radial direction. In the following, the term "axial" is used in the commonly accepted sense of "axially" or "in the axial direction." The term "radial" is used in the commonly accepted sense of "radially" or "in the radial direction."

[0059] The pump unit 1 is designed for contactless magnetic levitation of the rotor 10 and for contactless magnetic actuation of the rotor 10. This can be achieved in a manner similar to that described with reference to FIGS. 1 to 3. The pump unit 1 according to the present invention can therefore be designed in a manner similar to that of the pump unit 1' of FIG. 3 with respect to magnetic levitation and magnetic actuation. For this purpose, the rotor 10 of the pump unit 1 comprises a magnetically effective core 101, for example, designed as a permanent magnet ring or disk, surrounded by a sheath 102. The sheath 102 is preferably designed as a plastic sheath. The sheath 102 is made of, for example, PTFE or PFA. The magnetically effective core 101 is enclosed within the sheath 102, i.e., the sheath 102 completely, preferably hermetically, surrounds the magnetically effective core 101. As a result, the magnetically effective core 101 is protected from the fluid. The sheath 102 can be made, for example, by spraying plastic around the magnetically effective core 101 .

[0060] The magnetically effective core 101 of the rotor 10 is the component of the rotor 10 that magnetically cooperates with the stator 100 to generate torque and to generate magnetic levitation forces.

[0061] Furthermore, the rotor 10 comprises a plurality of vanes 103 for conveying the fluid from the inlet 21 to the outlet 22. The vanes 103 are arranged on a sheath 102 of the magnetically effective core 101. The vanes 103 are preferably made of plastic and can, for example, be designed as a single piece together with the sheath 102. Of course, it is also possible to produce the individual vanes 103 or the entire vane 103 in a separate manufacturing process and connect the vanes 103 to the sheath 102 of the magnetically effective core 101 by means of, for example, a welding process.

[0062] The impeller with the blades 103 formed by the rotor 10 is preferably designed as a radial impeller which is approached in the axial direction A by the fluid from the inlet 21 and redirects the fluid radially.

[0063] The pump housing 2 comprises a cover part 4 and a bottom part 3, which are hermetically connected to one another and which are not shown in more detail in Figure 4 as this is not necessary for understanding the invention. The bottom part 3 comprises a cylindrical cup 31 for receiving the rotor 10. The cup 31 is preferably designed and arranged so that it can be inserted into a cup-shaped recess in the stator 100, as shown diagrammatically in Figure 12.

[0064] The stator 100 (FIG. 12) extends in the axial direction A from the first axial end 110 to the second axial end 120 and has a stator housing (not shown in FIG. 12) that is substantially designed to be cylindrical. The cup-shaped recess is arranged at the first axial end 110 of the stator 100, preferably centrally located in the end face that forms the first axial end 110 of the stator 100. The design of the stator housing with the cup-shaped recess can be realized in a manner similar to that described with reference to FIG. 1 for the stator housing 130′ and the cup-shaped recess 121′. Thus, the cup 31 is arranged and designed so that it can be inserted into the recess 121′ (FIG. 1) in the first axial end 110′ of the stator 100′, and the magnetically effective core 101 is arranged between the lateral legs 127′ of the coil core 125′.

[0065] 4, according to this representation there is a pump chamber 23 above the cup 31, the pump chamber 23 being bounded by the pump housing 2, in which the vanes 103 of the rotor 10 are arranged. The pump chamber 23 is designed to be at least substantially cylindrical, the diameter of which is greater than the inner diameter of the cup 31. Consequently, the pump housing 2 has a flange-like protrusion 24 which, according to this representation, bounds the pump chamber 23 downwards with respect to the axial direction A.

[0066] The inlet 21 is centrally located within the cover part 3 of the pump housing 2 so that fluid can flow in the axial direction A towards the rotor 10 .

[0067] Each vane 103 extends from a radially inwardly disposed leading edge 109 to a radially outwardly disposed trailing edge 108. In the embodiment described herein, the vanes 103 are designed with exemplary properties, such as extending radially in a straight line from the leading edge 109 to the trailing edge 108 and having a constant height throughout their extent. Here, height refers to the extent of the vane 103 in the axial direction A. As previously mentioned, it will be understood that this design is to be considered exemplary. In other embodiments, the vanes 103 are designed, for example, to be curved relative to the radial direction and / or to have a height in the axial direction A that varies from the leading edge 109 to the trailing edge 108. For example, FIG. 12 illustrates an embodiment in which the vane 103 has a greater height at its leading edge 109 compared to its trailing edge 108.

[0068] Furthermore, a ring-shaped cover plate 8 is optionally provided, which is arranged on the upper edges of the blades 103 facing towards the inlet 21. The cover plate 8 covers all of the blades 103. In the radial direction, the ring-shaped cover plate 8 extends from the leading edge 109 to the trailing edge 108 of the blades 103. The cover plate 8 here forms the end face 107 of the rotor 10. If the rotor 10 is designed without a cover plate 8, the upper edges of the blades 103 facing towards the inlet form the end face of the rotor 10.

[0069] The blades 103 of the rotor 10 are arranged around a central inlet region 25 that does not have any blades 103. The leading edges 109 of the blades 103 are located on a line, here a circular line, that has a non-zero distance from the central axis M of the rotor 10. A diameter D1 of the central inlet region 25 is determined by the distance of the leading edges 109 of the blades 103 from the central axis M of the rotor 10. This diameter D1 of the central inlet region 25 is equal to twice the distance of the leading edges 109 of the blades 103 from the central axis M of the rotor 10. In the embodiment described here, the diameter D1 of the central inlet region 25 is the same size as the inner diameter of the ring-shaped cover plate 8. With respect to the axial direction A, the central inlet region 25 extends along the leading edges 109 of the blades 103 to the end face 107 of the rotor 10.

[0070] The leading edges 109 of the vanes do not extend parallel to the axial direction A but are inclined relative to the axial direction A, and for example, the diameter D1 of the central inlet region 25 is determined by the distance of the leading edges 109 at the upper edges of the vanes 103 facing towards the inlet 21.

[0071] Furthermore, the rotor 10 includes a relief opening 104 that is designed to be cylindrical and extends in the axial direction A. The relief opening 104 is centrally located within the rotor 10, so that the axis of the relief opening 104 coincides with the central axis M of the rotor 10. The relief opening 104 extends in the axial direction A from the central inlet region 25 through the rotor 10 to the aft side of the rotor 10.

[0072] The outlet 22 has an intrusion surface 221, through which fluid can flow from the pump chamber 23 into the outlet 22, and an outflow surface (not visible in FIG. 4), through which fluid leaves the outlet 22. As is generally the case, the profile of the intrusion area 221 refers to the cross-sectional area that is perpendicular to the primary direction of fluid flow within the outlet 22. As shown in FIG. 4, the profile of the intrusion surface 221 is a circular surface. The profile of the intrusion surface 221 is the perpendicular projection of the intrusion surface 221 onto a plane that is perpendicular to the direction of fluid flow within the outlet 22.

[0073] According to the invention, the inlet 21 comprises a lip 28 forming one axial end of the inlet 21, wherein in the operating state, when the rotor 10 is centered with respect to the axial direction A, the lip 28 projects into the pump chamber 23 and is spaced apart from the end face 107 of the rotor 10 in the axial direction A. When viewed in the direction of fluid flow, the lip 28 terminates in front of the end face 107 of the rotor 10. The lip 28 is preferably designed to be ring-shaped.

[0074] The magnetic levitation of the rotor 10, of course, allows the entire rotor to be displaced axially in operation. In this case, it is entirely possible for the rotor 10 to be displaced in the axial direction A so as to zero the distance of the lip 28 from the end face 107, or even so as to cause the lip 28 to penetrate into the central inlet region 25 of the rotor 10. The feature of the lip 28 terminating at a fixed distance from the end face 107 therefore means that the rotor 10 is in its desired position in the axial direction A, so that the rotor 10 is centered relative to the stator 100 in the axial direction A. In the drawings, the rotor 10 is always shown in this centered position in the axial direction A.

[0075] The distance of the lip 28 from the end face 107 of the rotor 10 in the axial direction is hereinafter referred to as the lip distance DL. Thus, the lip distance DL refers to the operating condition when the rotor 10 is centered with respect to the axial direction A.

[0076] The lip 28 acts as a break-off edge for the fluid flowing into the pump chamber 23. The lip 28 provides a well-defined location where fluid break-off occurs. In this way, negative break-off effects that lead to cavitation and reduced efficiency may be at least significantly reduced. It will be appreciated that the lip 28 need not be designed to be continuous in the circumferential direction, but may also be designed to have discontinuities.

[0077] Another effect of the lip 28 protruding into the pump chamber 23 is that it significantly reduces the leakage flow from the trailing edge 108 of the vane in the direction of the inlet 21. The lip 28 reduces the free flow cross section between the trailing edge 108 of the vane and the inlet 21. This reduction in the cross section through which the leakage flow can flow also reduces the leakage flow, and as a result, less fluid flows per unit time from the trailing edge 108 of the vane 103 back to the inlet. The reduced leakage flow improves the efficiency of the centrifugal pump 200, and therefore its energy efficiency.

[0078] In a first embodiment shown in Figure 4, the lip 28 has a triangular profile, with the apex of the triangular profile pointing towards the end face 107 of the rotor 10. The lip 28 has a depth T in the axial direction A, which indicates the extent to which the lip 28 protrudes from the cover part 4 of the pump housing 2 into the pump chamber 23. The design of the lip 28 with a triangular profile is advantageous for its function as a release edge. Preferably, the lip 28 with a triangular profile is not designed as a sharp edge, but rather is designed so that the apex of the substantially triangular profile has a finite width in the radial direction that is not zero.

[0079] The lip 28 has an outer diameter D2, which means the outer diameter D2 of the lip 28 at its axial end point facing the rotor 10. In the first embodiment shown in Figure 4, the outer diameter D2 of the lip 28 is smaller than the diameter D1 of the central inlet region 25 of the rotor 10. Therefore, the lip 28 can penetrate into the central inlet region 25 when the rotor 10 is displaced upward in the axial direction A in the operating state according to the present indication.

[0080] 4, the lip 28 is preferably designed to widen in the flow direction. In particular, in the first embodiment, the lip 28 is designed to widen conically, so that the interior space of the lip 28 has the shape of a truncated cone.

[0081] Various variants for the first embodiment of the pump unit 1 are shown in Figures 5 to 8, where each representation corresponds to the representation in Figure 4. Figures 5 to 8 are therefore each a cross-sectional view, where the cross-section is made along the axial direction A.

[0082] 5, the lip 28 has a smaller depth T, i.e. the lip 28 projects less into the pump chamber 23 in the axial direction A. Furthermore, the outer diameter D2 of the lip 28 at its axial end facing the rotor 10 is greater than the diameter D1 of the central inlet region 25 of the rotor 10. Therefore, the lip 28 cannot penetrate into the central inlet region 25.

[0083] In the variant shown in FIG. 6, the lip 28 is curved outward so that the lip 28 also widens in the flow direction, but has walls designed to curve in the axial direction A.

[0084] In the variant shown in Figure 7, the lip 28 is designed as a cylindrical pipe section, i.e. has a constant inner diameter in the axial direction A. Here, it is possible to design the lip 28 to be an integral part of the cover part 4, as shown in Figure 7. In other embodiments, the lip 28 can also be designed as a separate component, for example as a hollow cylindrical pipe section that is mounted in or at the inlet 21.

[0085] In the variant shown in Figure 8, the cover part 4 of the pump housing 2 is designed to be angled so that the cover part 4 surrounds the inlet 21 at an angle greater than 90° to the axial direction. The area of ​​the cover part 4 adjacent to the inlet 21 is therefore not parallel to the bottom of the pump housing 2 but rises towards the inlet 21.

[0086] 8A shows a variant in which the end of the lip 28 pointing towards the end face 107 of the rotor 10 is designed to be strongly flattened. This variant is particularly advantageous from a manufacturing point of view.

[0087] FIG. 9 shows a second embodiment of a pump unit 1 according to the invention in a cross-sectional view, where the cross-section is taken along the axial direction.

[0088] In the following, only the differences with respect to the first embodiment will be considered. Parts that are the same or equivalent in function with respect to the second embodiment are designated with the same reference signs as in the first embodiment. In particular, the reference signs have the same meaning as already explained in connection with the first embodiment. It will be understood that all the above descriptions of the first embodiment and all its variants apply in the same way or analogously in the same way to the second embodiment.

[0089] The second embodiment differs from the first embodiment in the design of the inlet surface 221 of the outlet 22, through which the fluid flows out of the pump chamber and into the outlet 22.

[0090] While in the first embodiment (see, for example, Figure 4) the profile of the intrusion surface 221 of the outlet 22 is designed as a circular surface, a second embodiment of the pump unit 1 according to the present invention has an intrusion surface 221 of the outlet 22 that is different from a circular surface.

[0091] The outlet 22 further has a percolation surface 222 (also see FIG. 2) through which the fluid leaves the outlet 22. As shown in FIG. 9, the profile of the percolation surface 222 of the outlet 22 is a circular surface, in particular a circular surface having a larger cross-sectional area than the profile of the infiltration surface. Thus, the outlet 22 is designed to diverge when viewed in the flow direction and to change its cross-sectional area from the non-circular infiltration surface 221 to the circular percolation surface.

[0092] In the embodiment shown in Fig. 9, the intrusion surface 221 of the outlet 22 is designed to have a plurality of straight edges 225. Here, the intrusion surface 221 is designed to be substantially rectangular, in particular substantially square. Furthermore, it is preferable that the profile of the intrusion surface 221 is designed to have rounded corners, as shown in Fig. 9. Designing the intrusion surface 221 to have a non-circular profile, for example having a plurality of edges 225, has the advantage that the cross-sectional area of ​​the intrusion surface 221 can be made larger compared to a circular profile, without the need to increase the extension range in the axial direction A, or that the intrusion surface 221 of the outlet 22 can be positioned closer to the vanes 103 or can be positioned to have a greater overlap with the vanes 103 in the axial direction A.

[0093] In the following, the maximum extent of the profile of the immersion surface 221 in the axial direction A is referred to as the profile height H1, and its maximum extent in the radial direction perpendicular thereto is referred to as the profile width B1.

[0094] Furthermore, such an embodiment of the profile of the immersion surface 221 of the outlet 22 is also suitable, in which the profile height H1 is smaller than the profile width B1. For example, the profile of the immersion surface can be designed to be rectangular, in which the profile width B1 is greater than the profile height H1. This design allows the center of the profile to extend deeper compared to a circular profile of the same surface. Therefore, in such an embodiment, the profile has exactly four straight edges 225, in which the radially extending edges 225 are longer than the edges 225 extending in the axial direction A. The corners connecting two adjacent straight edges 225 can be rounded in a manner similar to that shown in FIG. 9 for the square profile of the immersion surface 221.

[0095] In the following, two further variants for the profile of the intrusion surface 221 of the outlet 22 are described on the basis of Figures 10 and 11, in which the intrusion surface 221 has a profile different from a circular surface. In particular, designs are possible in which the profile is designed to be more rounded or even to have no straight edges at all.

[0096] In Fig. 10, a first variant for the profile of the immersion surface 221 is shown. The profile is designated with the reference character P. In this first variant, the profile height H1 is the same size as the profile width B1. For example, compared to the substantially square design of the profile shown in Fig. 9, the profile P according to Fig. 10 is designed to be significantly more rounded.

[0097] For comparison, a circular surface K is also depicted in Figure 10, the diameter of which is the same size as the profile height H1 and the profile width B1. It can be clearly seen that the cross-sectional area of ​​the profile P is larger than the surface of the circle K.

[0098] Due to the profile P of the intrusion surface 221 deviating from a circular surface, it is possible to design the profile P of the intrusion surface 221 of the outlet 22 with a larger cross-sectional area compared to a circular design of the profile (see, for example, FIG. 4 ), without having to change the geometric dimensions of the pump housing 2. The larger cross-sectional area of ​​the profile P of the intrusion surface 221 of the outlet 22 has the advantage in terms of the efficiency of the pump unit 1 that the pressure drop across the outlet 22, which is substantially bounded by this cross-sectional area, can be reduced. The reduced pressure drop across the outlet 22 increases the efficiency of the centrifugal pump 200.

[0099] In Figure 11, a second variant is shown for the profile P of the immersion surface 221. In the second variant shown in Figure 11, the profile width B1 is greater than the profile height H1. This design of the profile P causes the center Z of the profile P, or in the more general case of asymmetric profiles, the center of gravity of the profile P, according to this indication, to be shifted further downwards in the axial direction A compared to a circular profile of the same cross-sectional area. In this design, in which the profile width B1 is greater than the profile height H1, the center Z or the center of gravity of the profile P is closer to the plane that divides the trailing edge 108 of the blade 103 into two sections of equal height in the axial direction A.

[0100] Various designs of the profile P are also possible, in which the profile width B1 is greater than the profile height H1. For example, a design as a more strongly rounded rectangle is shown in FIG. 11. The rounding of the rectangle can be so strong that the profile does not have any straight edges in the strict sense. It is also possible to design the profile to be elliptical. Such a design is usually preferred in the second variant, in which there is at least a second direction B in which the profile P has a maximum extent greater than the profile height H1, i.e., the maximum extent of the profile in the axial direction A, and in which the second direction B encompasses a non-zero angle β with the axial direction A. In the representation of FIG. 11, the second direction B has, by way of example, an angle β of 45° with the axial direction A.

[0101] Furthermore, the invention proposes a centrifugal pump 200 for conveying a fluid by means of a pump unit 1, wherein the pump unit 1 is designed according to the invention. Fig. 12 shows, as a schematic cross-section, an embodiment of the centrifugal pump 200 according to the invention. The centrifugal pump 200 comprises a stator 100 extending in the axial direction A from a first axial end 110 to a second axial end 120, wherein a cup-shaped recess 121 (not shown in Fig. 12) is provided at the first axial end 110, into which a cylindrical cup 31 of the pump unit 1 can be inserted. The stator 100, together with the rotor 10, forms an electromagnetic rotary drive for rotating the rotor 10 about the axial direction A, where the stator 100 is designed as a bearing-drive stator, and where the rotor 10 can be magnetically driven without contact by the stator 100 and magnetically levitated relative to the stator 100 without contact, where the rotor 10 is passively magnetically stabilized in the axial direction A and actively magnetically levitated in a radial plane E perpendicular to the axial direction A.

[0102] The stator 100 comprises a stator housing, which is not shown in Fig. 12 for a better overview, but the stator 100 may be designed in a similar manner to the stator 100' having a stator housing 130' shown in Fig. 1, for example, in which a recess 121' is provided in the stator housing 130' and the cylindrical cup 31 of the bottom 3 of the pump housing 1 is inserted into the recess 121'.

[0103] Particularly preferably, the electromagnetic rotary drive comprising the rotor 10 and the stator 100 is designed as a temple motor, in which the stator 100 has a plurality of coil cores 125, each of which has a longitudinal leg 126 extending in the axial direction A from a first end to a second end thereof and a transverse leg 127 arranged at the second end of the longitudinal leg 126 in the radial plane E. The transverse leg 127 extends radially inward from the longitudinal leg 126 towards the rotor 10.

[0104] The first ends, or lower ends according to the present designation, of all of the longitudinal legs 126 are connected to one another by a back iron 122 for conducting magnetic flux.

[0105] The coil core 125 is disposed circumferentially around the rotor 10 such that the rotor 10 is disposed between the lateral legs 127 of the coil core 125. At least one concentrated winding 160 is provided on each longitudinal leg 126, such that the concentrated winding 160 surrounds each longitudinal leg 126.

[0106] The concentrated windings 160 generate the electromagnetic fields necessary for magnetically driving and levitating the rotor 10. Using these concentrated windings 160, such fields are thus generated in operation to exert a torque on the rotor 10 in a manner known per se, and such rotating electromagnetic fields can also be used to exert an optionally adjustable transverse force radially on the rotor 10, thereby actively controlling or adjusting the radial position of the rotor 10, i.e., its position in the radial plane E perpendicular to the axial direction A. With regard to the other three degrees of freedom, namely its position in the axial direction A and its tilt with respect to the radial plane E perpendicular to the desired axis of rotation (two degrees of freedom), the rotor 10 is passively magnetically levitated or stabilized by reluctance forces, i.e., the rotor 10 cannot be controlled.

Claims

1. A pump unit for a centrifugal pump, comprising a pump unit and a stator (100) extending in an axial direction (A) from a first axial end (110) to a second axial end (120), wherein a cup-shaped recess is provided at the first axial end (110), and the pump unit (1) can be inserted into the cup-shaped recess, the pump unit (1) having a pump housing (2) with an inlet (21) and an outlet (22) for a fluid to be conveyed, and a rotor (10) arranged in the pump housing (2) with a plurality of vanes (103) for conveying the fluid, each vane (103) extending in the axial direction to an end face (107) of the rotor (10) facing towards the inlet, the pump housing (2) defining a boundary of a pump chamber (23), and the rotor (10) can be rotated about the axial direction (A).

1. A pump unit, comprising: a pump unit (1) designed for contactless magnetic levitation of the rotor (10) and for contactless magnetic driving of the rotor (10) by the stator (100); a pump housing (2) having a cover part (4) and a bottom part (3), the bottom part (3) having a cylindrical cup (31) for receiving the rotor (10), the cylindrical cup (31) being insertable into the cup-shaped recess of the stator (100); and wherein the inlet (21) has a lip (28) forming one axial end of the inlet (21), the lip (28) protruding into the pump chamber (23) when the rotor (10) is centered with respect to the axial direction (A) in an operating state, and terminating forward of the end face (107) of the rotor (10) when viewed in the flow direction.

2. 2. The pump unit of claim 1, wherein the vanes (103) of the rotor (10) are arranged around a central inlet region (25) having a diameter (D1) and extending in the axial direction (A) to the end face (107) of the rotor (10).

3. 3. The pump unit of claim 2, wherein the rotor (10) has at least one relief opening (104) extending through the rotor (10) in the axial direction (A) from the central inlet region (25).

4. 4. A pump unit according to any one of claims 2 to 3, wherein the lip (28) of the inlet (21) has an outer diameter (D2) that is greater than the diameter (D1) of the central inlet region (25).

5. 5. A pump unit according to claim 1, wherein the lip (28) has a substantially triangular profile, the apex of the substantially triangular profile pointing towards the end face (107) of the rotor (10).

6. 6. A pump unit according to any one of claims 1 to 5, wherein the lip (28) diverges when viewed in the flow direction.

7. 7. Pump unit according to any one of the preceding claims, wherein the lip (28) is designed to be curved outwards.

8. 6. Pump unit according to any one of claims 1 to 5, wherein the lip (28) is designed as a cylindrical pipe section.

9. 9. A pump unit according to any one of claims 1 to 8, wherein the cover part (4) of the pump housing (2) is designed to be oblique in relation to the axial direction (A) at an angle (α) greater than 90° so that the cover part (4) surrounds the inlet (21).

10. 10. The pump unit of claim 1, wherein the outlet (22) has an entry surface (221) through which the fluid can flow from the pump chamber (23) into the outlet (22), and wherein the entry surface (221) of the outlet (22) has a profile different from a circular surface.

11. 11. Pump unit according to claim 10, wherein the profile (P) of the penetration surface (221) is designed to be substantially rectangular.

12. Pump unit according to any one of claims 10 to 11, wherein the profile (P) of the entry surface (221) is designed with rounded corners.

13. 13. A pump unit according to any one of claims 10 to 12, wherein the profile (P) of the immersion surface (221) has a profile height (H1) in the axial direction (A) and a profile width (B1) in a radial direction perpendicular to the axial direction (A), the profile width (B1) being greater than the profile height (H1).

14. A centrifugal pump for conveying a fluid, comprising a pump unit designed according to any one of claims 1 to 13, and a stator (100) extending in an axial direction (A) from a first axial end (110) to a second axial end (120), wherein a cup-shaped recess is provided at the first axial end (110), into which a cylindrical cup (31) of the pump unit (1) can be inserted, and wherein the stator (100) and a rotor (10) are arranged in the axial direction (A). a rotor (10) configured to rotate in a radial plane (E) perpendicular to the axial direction (A), the rotor (10) being passively magnetically stabilized in the axial direction (A) and actively magnetically levitated in a radial plane (E) perpendicular to the axial direction (A), the rotor (10) being configured to rotate in a radial plane (E) perpendicular to the axial direction (A), the rotor (10) being configured to rotate in a radial plane (E) perpendicular to the axial direction (A), the rotor (10) being configured to rotate in a radial plane (E) perpendicular to the axial direction (A), the rotor (10) being configured to rotate in a radial plane (E) perpendicular to the axial direction (A), the rotor (10) being passively magnetically stabilized in the axial direction (A), and the rotor (10) being actively magnetically levitated ...

15. The electromagnetic rotary drive device is designed as a temple motor, and the stator (100) has a plurality of coil cores (125), each of which has a longitudinal leg (126) extending in the axial direction (A) from a first end to a second end, and a transverse leg (127) arranged at the second end of the longitudinal leg (126) in the radial plane and extending radially from the longitudinal leg (126).

15. The centrifugal pump of claim 14, wherein the coil core is circumferentially disposed around the rotor such that the rotor is disposed between the lateral legs of the coil core, and at least one concentrated winding is provided on each longitudinal leg, the at least one concentrated winding surrounding each longitudinal leg.

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