Blood pump

Abstract

The present invention relates to an intravascular blood pump for percutaneous insertion into a patient's blood vessels. The blood pump comprises a pump casing 2 having a blood inlet 21 and a blood outlet 22, and an impeller 3 rotatably disposed within the pump casing 2 about a rotation axis 10. The impeller 3 has blades 31 sized and shaped to transport blood from the blood inlet 21 to the blood outlet 22. The blood pump also comprises a drive unit 4 for rotating the impeller 3, the drive unit 4 including a plurality of posts 40 disposed about the rotation axis 10. Each of the posts 40 has an impeller end 420 facing the impeller 3, with a front surface 42 facing the impeller 3. A coil winding 44 is disposed around each of the pillars 40 to create magnetic field lines 500 extending through the front face 42 of each of the pillars 40 and is controllable to create a rotating magnetic field, and the impeller 3 includes a magnet structure 32 positioned to interact with the rotating magnetic field to cause rotation of the impeller 3. The front face 42 of at least one of the pillars 40 includes a recess sloping downwardly toward a central region of the front face 42 such that the front face 42 focuses at least a portion of the magnetic field lines 500 extending through the front face 42.

Description

Technical Field

[0001] The present invention relates to an intravascular blood pump for assisting blood flow in a patient's blood vessel, particularly an intravascular blood pump for percutaneous insertion into a patient's blood vessel. The blood pump has an improved drive unit.

Background Art

[0002] Different types of blood pumps are known, such as axial flow blood pumps, centrifugal (i.e., radial) blood pumps, or hybrid blood pumps in which blood flow is caused by both axial and radial forces. An intravascular blood pump is inserted into a patient's blood vessel, such as the aorta, using a catheter. The blood pump typically comprises a pump casing having a blood flow inlet and a blood flow outlet connected by a passage. An impeller or rotor is rotatably supported within the pump casing to create blood flow along the passage from the blood flow inlet to the blood flow outlet, and the impeller is provided with blades for transporting blood.

[0003] The blood pump is typically driven by a drive unit, which can be an electric motor. For example, International Publication No. WO 2017 / 162619 (A1) discloses an intravascular blood pump having an impeller magnetically coupled to an electric motor. The impeller includes magnets disposed adjacent to an electrically magnetized zone within the electric motor. Due to the attractive force between the electrically magnetized zones within the impeller and within the motor, the rotation of the motor is transmitted to the impeller. That is, the drive unit has a plurality of fixed posts disposed around the axis of rotation of the impeller, each post holding a wire coil winding and serving as a magnetic core. A control unit sequentially supplies voltage to the coil windings to create a rotating magnetic field that rotates the magnetically coupled impeller.

[0004] More specifically, the intravascular blood pump in International Publication No. 2017 / 162619 (A1) includes a pump casing having a blood flow inlet and a blood flow outlet, an impeller, and a drive unit for rotating the impeller. By the rotation of the impeller inside the pump casing around the rotation axis, blood can be transported from the blood flow inlet to the blood flow outlet by the blades of the impeller. The drive unit includes six columns and a back plate that connects the rear ends of the columns and serves as a yoke. The columns are circularly arranged around the rotation axis when viewed in a plane perpendicular to the rotation axis, and each of the columns has a longitudinal axis that is parallel to the aforementioned rotation axis. Each column has a shaft and an inclined head portion at the impeller-side end of the shaft facing the impeller, and the head portion forms a shoulder that can serve as an axial stopper for the coil winding disposed around each column and extends radially beyond the shaft. The control unit sequentially supplies voltage to the coil windings to create a rotating magnetic field. The impeller includes a magnet structure arranged such that the impeller follows its rotation by interacting with the rotating magnetic field.

[0005] During operation, adjacent columns may have different magnetizations. As a result, the magnetic flux extending through the columns tends to flow between those adjacent columns, avoiding the impeller. Such magnetic flux is a loss for torque generation. The disadvantage of the prior art is that the head portions that extend radially beyond the shaft have a significantly small distance from each other. Therefore, there is a significant parasitic magnetic flux between the head portions that is a loss for torque generation. Such parasitic magnetic flux can be offset by disposing a magnetic insulating material, such as a magnet, between the head portions, but the available space is extremely limited, and in order to achieve appropriate insulation, the polarization of the magnet would have to change periodically, which is difficult. The present invention aims to improve the drive unit in this regard.

Summary of the Invention

Means for Solving the Problems

[0006] The blood pump of the present invention can correspond to the above-described blood pump. Therefore, it can be an axial flow blood pump or a mixed flow blood pump that pumps partially axially and partially radially (the diameter of a pure centrifugal blood pump is usually too large for intravascular applications). However, according to one aspect of the present invention, the front surface of at least one of the columns - preferably each of the columns - on the impeller side has a recess in which the front surface is inclined downward toward the central area of the front surface so as to converge at least a portion of the magnetic field lines extending through the front surface.

[0007] The magnetic field lines of the magnetic flux emerging from and entering the surface of a component made of a magnetic material extend perpendicular to the surface. That is, they enter and exit vertically to the surface plane. By providing a recess on the front surface of the column, i.e., a concave area in which the front surface is inclined downward toward the center of the front surface, the magnetic field lines extending into and out of the column through the front surface are forced to extend closer to the central axis of the column. As a result, since the magnetic field lines never cross each other, they are focused in front of the impeller side end of the column and directed as a bundle toward the impeller. Thereby, the parasitic magnetic flux between adjacent columns is reduced.

[0008] The inclination of the recess is less than 90° with respect to the surface plane, preferably 0° to 30°.

[0009] Preferably, the recess extends to the periphery of the front surface. In other words, the recess can start from the outer edge of the front surface. This also has the effect that the outermost magnetic field lines are also affected by the inclination of the recess. The outermost magnetic field lines have the greatest tendency to bridge to adjacent columns. Therefore, the recess is most effective when it extends to the periphery of the front surface of the column.

[0010] It may be sufficient if the recess extends up to the periphery of the front face of the column at at least two, preferably exactly two, opposite sides of the front face, i.e., at those sides closest to the adjacent columns. This can be particularly advantageous when the column is, for example, cylindrical and thus has a circular cross-section. That is, the risk of magnetic field lines bridging to adjacent columns is greatest where the columns are at a small distance from each other. Therefore, the recess is sufficiently effective if it extends up to the periphery of the front face of the column only at the two sides positioned closest to each adjacent column.

[0011] Nevertheless, it is preferable that the periphery of the recess coincides with the periphery of the front face. In this way, due to the inclination of the recess, the outermost magnetic field lines are directed towards the center of the front face along the entire periphery of the front face. As described above, the outermost magnetic field lines have the greatest tendency to turn away from the impeller. Therefore, the recess is most effective when its periphery coincides with the periphery of the front face.

[0012] Since it may be sufficient to direct the outermost magnetic field lines towards the center, the recess may have a flat bottom. Therefore, at least the area around the recess slopes downwards. In this case, the recess may have straight inclined side walls when viewed in a cross-sectional plane extending vertically through the front face, or it may have curved inclined side walls when viewed in a cross-sectional plane extending vertically through the front face. Curved inclined side walls with an increasing inclination towards the periphery of the recess have the effect of maximizing the focusing effect on the outermost magnetic field lines.

[0013] Alternatively, the recess may have a curved cross-section with a curved bottom rather than a flat bottom when viewed in a cross-sectional plane extending vertically through the front face. In this way, the centering effect on the magnetic field lines gradually decreases from the periphery of the recess towards its center.

[0014] Alternatively, the recess may have a triangular cross-section when viewed in a cross-sectional plane extending vertically through the front face. By doing so, the maximum depth of the recess can be increased. The deeper the recess, the greater the distance between each portion of the front face of the column and the magnet structure of the impeller, resulting in a reduction of the axial magnetic force generated between the column and the impeller. In particular, by reducing the axial magnetic force, the ratio of magnetic torque to axial magnetic force can be increased, and the aforementioned ratio is an important figure for the development of a magnetically driven intravascular blood pump. The magnetic flux that can be generated is generally limited, and thus, it is desirable to use as much of it as possible for torque generation, making the aforementioned ratio important. The technical effect of the recess is a reduction of the axial force acting axially on the rotor without motor power loss, or alternatively, an increase in motor power at the same total magnetic flux.

[0015] According to a preferred embodiment of the present invention, this ratio can be further increased by the downward inclination of the front face within the recess in the radially outer direction (in addition to being inclined downward toward its central region). Therefore, with respect to the rotation axis, the radially inner region of the front face within the recess protrudes axially more than the radially outer region of the front face within the recess. Also in this case, as before, the result is that the maximum depth of the recess is increased. As described above, the deeper the recess, the greater the distance between each portion of the front face of the column and the magnet structure of the impeller, resulting in a reduction of the axial magnetic force generated between the column and the impeller. Therefore, the ratio of magnetic torque to axial magnetic force can be further increased by the downward inclination of the front face within the recess in the radially outer direction.

[0016] Another important effect achieved by the downward slope of the front surface in the radially outward direction is that the bundle of converged magnetic field lines is directed radially outward, and therefore, it also hits the magnet structure of the impeller radially outward as compared to a flat front surface. This has a positive effect on the achievable magnetic torque. Also in this case, as before, this results in an improvement in the ratio of magnetic torque to axial magnetic force. Therefore, the positive effect of the downward slope of the front surface within the recess in the radially outward direction on the ratio of magnetic torque to axial magnetic force is twofold.

[0017] According to a preferred embodiment of the present invention, the combination of the slopes of the front surface within the recess in both the central direction and the radially outward direction results in a recess that opens towards the side surface of the column, i.e., towards the side surface that is located radially outward with respect to the rotation axis. Preferably, the column has a triangular cross-section with three side surfaces, and one of the three side surfaces is located radially outward with respect to the rotation axis as compared to the other two side surfaces. In such a case, the recess opens towards one of the three side surfaces located radially outside the column.

[0018] In all of the above-described variations, the recess may preferably have a maximum depth of 0.05 mm to 0.3 mm.

[0019] According to another aspect of the present invention, the column does not radially extend beyond the impeller-side end portions of the respective coil windings disposed around the column at its impeller-side end. Here, the term "radially" relates to a direction that crosses, preferably is perpendicular to, the longitudinal axis of each column. In other words, the column does not have a special head portion. Instead, the column preferably has a constant cross-section, at least in those impeller-side end regions, and more preferably along their entire length.

[0020] The advantage of a column without a head portion is that magnetic losses due to parasitic magnetic flux between adjacent columns are reduced by the greater distance between the columns. The result, as in the previous case, is that the ratio of achievable magnetic torque to the magnetic axial force between the drive unit and the impeller is increased compared to the pump described in International Publication No. WO 2017 / 162619 (A1), in which the columns extend in such a way that their impeller-side ends extend radially beyond the impeller-side ends of the respective coil windings.

[0021] According to a further aspect of the invention, the columns may each include a soft magnetic material that is discontinuous in a cross-section preferably transverse, and more preferably perpendicular, to the longitudinal axis of each column, which axis is preferably parallel to the axis of rotation as described in more detail in International Publication No. WO 2019 / 057636 (A1). "Discontinuous" in the context of the present invention means that the soft magnetic material is separated, segmented, or otherwise configured with an insulating material, other material, or gap in any cross-section taken transverse to the longitudinal axis such that it forms strictly separated regions of the soft magnetic material or regions that are segmented but connected at different locations. In other words, the soft magnetic material of the columns is discontinuous in a cross-section preferably transverse, and more preferably perpendicular, to the direction of the magnetic flux generated by each coil winding within the column. Providing a soft magnetic material that is discontinuous in the cross-sectional plane transverse to the direction of the magnetic flux reduces eddy currents. This further enhances the effectiveness of the intravascular blood pump.

[0022] Preferably, at least one weld is provided on the surface (811) of the discontinuous soft magnetic material, and the weld bridges at least one discontinuity regarding the electrical conductivity within the discontinuous soft magnetic material. The weld enables easy fabrication of a core or a part thereof from the discontinuous soft magnetic material. That is, when separating a core or a column for the core from a larger workpiece of the discontinuous soft magnetic material, the discontinuous soft magnetic material may delaminate or otherwise lose its integrity due to the processing forces applied to the workpiece during the separation process. This is particularly critical due to the very small dimensions of the core and especially its columns, and can occur even when electrical discharge machining, in particular wire cut electrical discharge machining, is used to separate the core or its columns from the workpiece. By using the weld, which is applied to the workpiece prior to the separation step, the mechanical stability of the discontinuous material is improved. When electrical discharge machining is used to cut out the core or columns from the workpiece, the flow of current to the cutting location is also improved. The weld or group of welds may later form part of the core or columns. Specifically, the impeller side end face of the column oriented across the axis of rotation exposes the discontinuous material. Thus, the weld or group of welds may be disposed on the impeller side surface of the column.

[0023] The drive unit may include a backplate connecting the rear ends of the columns. Similar to the columns, the backplate may include a discontinuous soft magnetic material. Since the magnetic flux within the backplate is substantially across or perpendicular to the axis of rotation, the soft magnetic material of the backplate may be fabricated discontinuously in a cross-section parallel to the axis of rotation. Alternatively, the columns and the backplate may be fabricated from a monoblock of the discontinuous soft magnetic material such that the soft magnetic material of the backplate and the discontinuous soft magnetic material of the columns are discontinuous in the same direction, preferably discontinuous in a cross-section perpendicular to the axis of rotation. Except for that, substantially all of the features and descriptions mentioned above regarding the discontinuous material of the columns also apply to the backplate. However, the backplate may alternatively be formed of a continuous, i.e., solid, soft magnetic material.

[0024] According to one preferred embodiment of the drive unit including a back plate that connects the rear ends of the columns, at least one of the columns is integrally formed with the material of the intermediate region of the back plate. Here, the intermediate region of the back plate is the region of the back plate disposed between the columns. Preferably, all the columns are integrally connected to the back plate in this way. In other words, at least one column and the back plate of the drive unit, preferably the entire magnetic core, can be made of a single material block, which can also be referred to as a monoblock. The advantage of such a magnetic core is that the magnetic resistance at the transition between the column and the back plate is minimized, and thus the magnetic flux is improved. Furthermore, good mechanical rigidity of the transition between the column and the back plate can be achieved.

[0025] According to another preferred embodiment of the drive unit including a back plate that connects the rear ends of the columns, at least one, and preferably all, of the columns contact the back plate with the rear end faces of the respective columns. This provides the advantage that the quality of the magnetic connection between the column and the back plate can be made independent of the quality of the mechanical fixation of the column to the back plate. For example, the column can be mechanically fixed to the back plate within a corresponding recess in the back plate or using an adhesive provided around the rear end of the column. Therefore, a good magnetic connection, and thus a good magnetic flux, can be achieved directly through the rear end face of the column into the back plate without being forced to accept constraints regarding the mechanical properties of the mechanical connection between the column and the back plate. Furthermore, when the rear end of the column is received within a properly sized recess in the back plate, a magnetic path for the transmission of the magnetic flux is established in addition to the circumferential transmission of the magnetic flux.

[0026] Therefore, in this case, the pillar can be magnetically connected to the back plate on the corresponding contact plane of the back plate. The contact plane is preferably arranged parallel to the rear end face of the pillar. Preferably, it is arranged perpendicular to the rotation axis. Preferably, the entire surface area of the rear end face of the pillar is in contact with the back plate. This greatly reduces the magnetic resistance of the connection between the pillar and the back plate. The non-flatness of the rear end face and the contact plane of the back plate is preferably such that the resulting gap is 10 μm or less.

[0027] The back plate, like the pillar, is preferably made of electrical steel (magnetic steel), or other materials suitable for closing the magnetic flux circuit, preferably soft magnetic materials such as cobalt steel. The diameter of the back plate can be in the range of 3 mm to 9 mm, for example, 5 mm or in the range of 6 mm to 7 mm. The thickness of the back plate can be in the range of 0.5 mm to 2.5 mm, for example, 1.5 mm. The outer diameter of the blood pump can be in the range of 4 mm to 10 mm, preferably 7 mm. The outer diameter of the configuration of multiple pillars can be in the range of 3 mm to 8 mm, for example, in the range of 4 mm to 7.5 mm, preferably 6.5 mm.

[0028] As described above, the pillar is made of a soft magnetic material such as electrical steel (magnetic steel). The pillar and the back plate can be made of the same material. Preferably, the magnetic core of the drive unit, including the pillar and the back plate, is made of cobalt steel. The use of cobalt steel contributes to the reduction of the pump size, especially the diameter. Since it has the highest magnetic permeability and the highest saturation magnetic flux density among all magnetic steels, cobalt steel generates the maximum amount of magnetic flux for the same amount of material used.

[0029] The dimensions of the column, particularly the length and cross-sectional area, can vary and may depend on various factors. In contrast to the dimensions of the blood pump, such as the outer diameter, which depend on the application of the blood pump, the dimensions of the column are determined by electromagnetic characteristics that are adjusted to achieve the desired performance of the drive unit. One of the factors is the magnetic flux density to be achieved through the minimum cross-sectional area of the column. The smaller the cross-sectional area, the higher the current required to achieve the desired magnetic flux. However, the higher the current, the more heat is generated in the wire of the coil due to electrical resistance. Even more importantly, if the cross-section of the column is too small, the stator material will rapidly magnetically saturate. This means that while "thin" columns are preferred to reduce the overall size, this will require a high current and will therefore generate undesirable heat. The heat generated in the wire also depends on the length and diameter of the wire used for the coil winding. To minimize winding losses (referred to as "copper loss" or "copper power loss" when copper wire is used, as is usually the case), a short wire length and a large wire diameter are preferred. In other words, when the wire diameter is small, more heat is generated at the same current compared to a thicker wire. The preferred wire diameter is 0.05 mm to 0.2 mm, for example, 0.1 mm, etc. Further factors that affect the dimensions of the column and the performance of the drive unit are the number of turns of the coil and the outer diameter of the winding, i.e., the column including the winding. Multiple turns can be arranged in more than one layer around each column, for example, two or three layers can be provided. However, the more layers there are, the more heat will be generated due to the increased length of the wire in the outer layer having a larger winding diameter. The increased length of the wire can generate more heat due to the higher resistance of the longer wire compared to a shorter one. Therefore, a single layer of windings with a small winding diameter would be preferred, but usually more than one winding is provided due to the power required.

[0030] Typical number of windings, which is next dependent on the length of the column, can be from about 50 to about 150, for example, 56 or 132. Regardless of the number of windings, the coil winding is made of an electrically conductive material, particularly a metal such as copper or silver. Silver can be preferred over copper because it has an electrical resistance that is about 5% lower than that of copper.

[0031] Preferably, there is at least one column, and more preferably, each column has a triangular cross-section across the longitudinal axis of the column. Preferably, the cross-section of the column is triangular over its entire length. Such columns can be packed densely around the axis of rotation, so the triangular columns can utilize a high percentage of the available space inside the pump housing. Preferably, one side of the triangle faces outward as seen from the axis of rotation and is curved. The curvature is curved around the axis of rotation. The radius of curvature preferably corresponds to the radius of the outer diameter defined by a plurality of columns arranged around the axis of rotation. Such curvature can achieve a further expansion of the utilization of the space inside the cylindrical pump housing.

[0032] The above summary and the following detailed description of the preferred embodiments will be better understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the present disclosure, reference is made to the drawings. However, the scope of the present disclosure is not limited to the specific embodiments disclosed in the drawings.

Brief Description of the Drawings

[0033]

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DETAILED DESCRIPTION OF THE INVENTION

[0034] Referring to FIG. 1, a cross-sectional view of a blood pump 1 is shown. The blood pump 1 includes a pump casing 2 having a blood flow inlet 21 and a blood flow outlet 22. The blood pump 1 is designed as an intravascular blood pump, also called a catheter pump, and is deployed into a patient's blood vessel using a catheter 25. The blood flow inlet 21 is, in use, at the end of a flexible cannula 23 that can be disposed through a heart valve such as the aortic valve. The blood flow outlet 22 is located within the side surface of the pump casing 2 and can be disposed within a cardiovascular vessel such as the aorta. The blood pump 1 is electrically connected to an electrical wire 26 that extends through a catheter 25 for supplying power to the blood pump 1 to drive the pump 1 using a drive unit 4, as will be described in more detail below.

[0035] When the blood pump 1 is intended to be used within an implant for an extended period of time, i.e., in a situation where the blood pump 1 is implanted in a patient for several weeks or even several months, the power is preferably supplied using a battery. Since the patient is not connected to a base point by a cable, this allows the patient to move. The battery can be carried by the patient and supply electrical energy to the blood pump 1, for example, wirelessly.

[0036] Blood is conveyed along a passage 24 connecting a blood flow inlet 21 and a blood flow outlet 22 (the blood flow is indicated by the arrow). An impeller 3 is provided to convey the blood along the passage 24 and is mounted within the pump casing 2 using a first bearing 11 and a second bearing 12 to be rotatable about a rotating shaft 10. The rotating shaft 10 is preferably the longitudinal axis of the impeller 3. Both bearings 11 and 12 are contact bearings in this embodiment. However, at least one of the bearings 11 and 12 could be a non-contact bearing, such as a magnetic or hydrodynamic bearing. The first bearing 11 is a pivot bearing having a spherical bearing surface that allows rotational movement and a certain degree of pivoting movement. A pin 15 that forms one of the bearing surfaces is provided. The second bearing 12 is disposed within a support member 13 for stabilizing the rotation of the impeller 3, and the support member 13 has at least one opening 14 for blood flow. When the impeller 3 rotates, blades 31 for conveying the blood are provided on the impeller 3. The rotation of the impeller 3 is caused by a drive unit 4 magnetically coupled to a magnet 32 at an end portion of the impeller 3. The illustrated blood pump 1 is a hybrid blood pump, and the main direction of the flow is axial. It will be understood that the blood pump 1 could also be a purely axial blood pump depending on the configuration of the impeller 3, particularly the blades 31.

[0037] The blood pump 1 includes an impeller 3 and a drive unit 4. The drive unit 4 includes a plurality of posts 40, such as six posts 40, only two of which are visible in the cross-sectional view of FIG. 1. The posts 40 are arranged parallel to the rotation axis 10. More specifically, the longitudinal axis of each of the posts 40 is parallel to the rotation axis 10. One end 420 of the post 40 is disposed adjacent to the impeller. A coil winding 44 is disposed around the post 40. The coil winding 44 is sequentially controlled by control to create a rotating magnetic field. The control unit part is a printed wiring board 6 connected to the electric wire 26. The impeller has magnets 32, which are formed as multi-piece magnets in this embodiment. The magnets 32 are disposed at the end of the impeller 3 facing the drive unit 4. The magnets 32 are arranged to interact with the rotating magnetic field to cause rotation of the impeller 3 around the rotation axis 10.

[0038] To close the magnetic flux path, a back plate 50 is disposed at the end of the post 40 opposite to the impeller side of the post. The post 40 serves as a magnetic core and is made of a suitable material, particularly a soft magnetic material such as steel or a suitable alloy, particularly cobalt steel. Similarly, the back plate 50 is made of a suitable soft magnetic material such as cobalt steel. The back plate 50 enhances the magnetic flux, which enables reduction of the overall diameter of the blood pump 1, which is important for an intravascular blood pump. For the same purpose, a yoke 37, i.e., an additional impeller back plate, is provided in the impeller 3 on the side of the magnet 32 facing away from the drive unit 4. The yoke 37 in this embodiment has a conical shape to guide the blood flow along the impeller 3. The yoke 37 can also be made of cobalt steel. One or more washout channels extending towards the central bearing 11 can be formed in the yoke 37 or the magnet 32.

[0039] Figure 2 shows a cross-sectional view of a first preferred embodiment of a drive unit-impeller configuration for the blood pump according to FIG. 1. As can be seen in FIG. 2, the impeller-side end portion 420 of the column 40 does not radially extend beyond the winding 44. Rather, the cross-section of the column 40 is constant in the direction of the longitudinal axis LA of the column 40. Thus, the columns 40 are prevented from approaching each other. This is because this can cause a partial magnetic short circuit, resulting in a reduction in the power of the electric motor of the blood pump.

[0040] The drive unit according to FIG. 2 may include at least two columns 40. The number of columns is preferably a multiple of 3 and can therefore be 3, 9, or 12. Alternatively, the number of columns 40 can be a multiple of 2, such as 2, 4, 6, 8, 10, or 12. A greater number of columns 40 can also be possible. A number of 6 columns 40 is preferred. Only two columns 40 are visible due to the cross-sectional view. The columns 40 and the back plate 50 form the magnetic core 400 of the drive unit 4, which may have a diameter of less than 10 mm.

[0041] The column 40 can be made of a discontinuous soft magnetic material that is discontinuous with respect to electrical conductivity, as shown. The discontinuous soft magnetic material is made of a ferromagnetic material and includes a plurality of sheets 85 laminated to each other. The lamination direction is arranged in the direction of the longitudinal axis LA of the column 40 and is labeled by the arrow DL. As shown, the column 40 is arranged parallel to the rotation axis 10.

[0042] The spacer 7 is disposed around the column 40. It is made of a magnetically inert material and has the purpose of keeping the distance of the column 40 at their impeller-side ends 420 constant. The spacer 7 will be described in more detail with respect to FIGS. 6A-6C. The impeller-side end 424 of the coil winding 44 extends up to the spacer 7. On the other end of the column 40, a back plate 50 is provided. According to the embodiment shown in FIG. 2, the back plate 50 has a recess for receiving the column 40 therein. More specifically, it includes a first layer 51 having an opening 511 for the rear end 450 of the column 40. The back plate 50 will be described in more detail with respect to FIGS. 7A-7C.

[0043] It is conceivable to implement an embodiment of the blood pump 1 having any combination of the three above-described features: that the impeller-side end 424 of the column does not radially extend beyond the impeller-side end of the winding 44, providing a magnetically inert spacer 7 between the columns 40, and a back plate 50 having a recess for receiving the rear end 450 of the column 40.

[0044] FIGS. 3A and 3B show a side view and a perspective view of the magnetic core 400 of the drive unit 4 of the drive unit-impeller configuration according to FIGS. 1 and 2. The column 40 and the back plate 50 of the magnetic core 400 are shown to have a distance to the magnet structure 32 of the impeller 3. As can be seen from the figure, each front surface 42 of the impeller-side end 420 of the column 40 is provided with a recess. In this particular embodiment, and in all embodiments described below, the recess extends across the entire front surface 42 such that the perimeter of the recess coincides with the perimeter of the front surface 42.

[0045] Therefore, the depression extends around the front surface 42. The depression has a triangular cross-section when viewed in a cross-sectional plane extending vertically through the front surface 42, and the plane is perpendicular to the longitudinal axis of each column 40 in the illustrated embodiment. This would be different in an embodiment where each front surface 42 of the column 40 is inclined so as to together form the conical front side of the magnetic core 400, as described in International Publication No. WO 2017 / 162619 (A1). That is, in International Publication No. WO 2017 / 162619 (A1), the column has a shaft and an inclined head portion at the impeller-side end of the shaft, respectively. Also, although the front surfaces of those head portions are inclined, the front surface is inclined downward toward the central area of the front surface, and the above-described depression having a triangular cross-section can be provided when viewed in a cross-sectional plane extending vertically through the front surface.

[0046] The inclination of the front surface 42 in the downward depression toward the central area of the front surface converges the magnetic field lines extending through the front surface, and thus serves to bundle them, as will be described below with respect to FIG. 4. However, inside the depression, the front surface 42 is not only inclined downward toward the central area of the front surface 42, but also further inclined downward in the radially outward direction with respect to the rotation axis 10. In other words, the radially inner region of the front surface 42 within the depression protrudes axially more than the radially outer region of the front surface 42 within the depression. The purpose of the downward inclination outward in the radial direction is to direct the magnetic field lines toward the outer peripheral edge of the magnet structure 32 of the impeller, thereby increasing the lever arm by which the impeller 3 is rotated, and thus including the purpose of increasing the torque. Therefore, the fact that the depression is inclined toward the center of the front surface 42 and also outward in the radial direction results in the depression opening toward the side surface of the column 40 located radially outward with respect to the rotation axis for the column 40 having a triangular cross-section. Therefore, the point of the maximum depth of the front surface 42 is located on the outer periphery of each column 40 and can range from 0.05 mm to 0.3 mm, preferably from 0.1 mm to 0.2 mm, and most preferably about 0.2 mm.

[0047] Figure 4 schematically shows the unwrapping of the windings of six poles 40a, 40b of the magnetic core 400, such as the magnetic core 400 shown in FIGS. 3A and 3B. To create a rotating magnetic field, two planes are important. First, some of the poles must be magnetized in the positive direction, while others are magnetized in the negative direction. Therefore, the magnetic flux lines of the magnetic fluid enter the negatively magnetized pole from the positive by the magnetized pole, pass through the magnet structure of the impeller 32, and further extend back into the positively magnetized pole through the back plate 50, thereby creating a closed magnetic field. Second, the magnetization direction of the poles must be sequentially changed from pole to pole in the circumferential direction to rotationally pull the magnet structure 32 of the impeller 3 around the rotation axis 10. To achieve this, adjacent poles are magnetized in opposite directions by appropriately directed currents flowing through the coil windings 44 provided around each of the poles 40. For example, the first pole can be magnetized positively, the second adjacent pole negatively, the third adjacent pole positively, the fourth adjacent pole negatively again, and so on. However, in a preferred embodiment, there are always two adjacent poles magnetized in one direction to pull the magnet structure 32 of the impeller 3, and only one of the next subsequent poles is magnetized in the opposite direction. In the case of six poles, as indicated in FIG. 4, which schematically shows the unwrapping of the windings of the six poles, four poles 40b are magnetized in one direction and two poles 40a are magnetized in the opposite direction. As can be further seen from FIG. 4, the magnetic field lines 500 extending through the recessed front surface 42 are focused by the inclined surface within the recess so that the magnetic field lines form a bundle. Therefore, the risk of a short circuit in the sense that the magnetic field lines 500 bridge between adjacent poles 40a and 40b is minimized.

[0048] Figures 5A-5D each show side views on the impeller side end 420 of a column according to four different embodiments. The embodiment shown in Figure 5A corresponds to the above-described embodiment having a recess with two inclined side walls 42a that have a perimeter that matches the perimeter of the front face and that slope downward toward the central region of the front face 42 and also slope radially outward with respect to the axis of rotation. As a result, the recess has a triangular cross-section when viewed in any cross-sectional plane that extends vertically through the front face 42 and is open on the radially outer side of the column.

[0049] The embodiment shown in Figure 5B corresponds substantially to the embodiment of Figure 5A, except that it has a flat bottom 42b. Therefore, the triangular cross-section of the recess is limited to the radially inner side of the column with respect to the axis of rotation. Further radially outward, the cross-section is trapezoidal. Therefore, the bottom 42b is flat and parallel to the general plane of the front face 42, while the side walls 42a are straight side walls with oppositely oriented slopes.

[0050] In the embodiment shown in Figure 5C, the recess has curved inclined side walls 42a such that the inclination of the recess is maximized at the perimeter of the front face 42.

[0051] The embodiment shown in Figure 5D is a combination of the embodiments shown in Figures 5B and 5C. That is, the recess has a flat bottom 42b and curved inclined side walls 42a.

[0052] Figures 6A to 6C respectively show a perspective view, a front view, and a side view of the spacer 7. The spacer 7 generally has the form of a disk or a wheel with a through hole 75 in the center. The spacer 7 includes openings 71 for each of the columns. For an embodiment having six columns 40, as shown, there are six openings 71. Discrete spokes 72 are arranged between the openings 71. When the column 40 is inserted into the opening 71, the discrete spokes 72 keep the distance between the columns 40 constant. Further, the spacer 7 includes an outer rim 73 and an inner rim 74 that connect adjacent discrete spokes 72 and stabilize the spacer. The spacer 7 is made of titanium, a paramagnetic material that avoids magnetic short - circuit when placed between the impeller - side ends 420 of the columns 40. Titanium provides high mechanical strength, which enables the production of the spacer 7 with a small thickness. This is advantageous in terms of construction space consumption. Also, titanium has a low electrical conductivity so that eddy - current losses are minimized, and titanium is easy to machine. However, any other non - magnetic material can be used as well, provided that it is stable, machinable with high precision, and does not conduct electricity easily. Also, the use of a diamagnetic material is possible because it cancels out the external magnetic field.

[0053] FIG. 7A shows a perspective view of the first layer 51 of the backplate 50. The first layer 51 has the overall shape of a disc or wheel with a central hole 515. The first layer 52 includes an opening 511 in which the rear end portion 450 of the post 40 will be disposed. The first layer 51 includes spaced spokes 512 between the openings 511. One purpose of the spaced spokes 512 is to keep the distance between the rear end portions 450 of the posts 40 constant. Further, the first layer 51 includes an outer rim 513 and an inner rim 514 that connect the spaced spokes 512 at the outer and inner radial ends of the opening 511, respectively. The first layer 51 may be made of a discontinuous soft magnetic material that is discontinuous with respect to electrical conductivity. It may include several ferromagnetic sheets 85, particularly, as shown in FIG. 7A, three sheets. The sheets 85 are laminated to each other using an electrically non-conductive material to form a discontinuous soft magnetic material. The lamination direction DL is generally parallel to the sheets 85, and the main spreading direction of the sheets defines the lamination plane. Within the backplate 50, the sheets 85 are perpendicular to the rotation axis 10. At the center of the first layer 51, a hole 515 is disposed. It has the purpose of facilitating the assembly of the first layer 51 and the second layer 52. For example, it may serve to align the first and second layers 51, 52.

[0054] Figure 7B shows a perspective view of the second layer 52 of the backplate 50. The second layer 52 substantially has the form of a disc having a hole 525 at the center corresponding to the hole 515 in the first layer 51. The second layer 52 has no opening for the rear end portion of the pillar 40. Instead, the second layer 52 provides a contact plane 526 facing the rear end portion 450 of the pillar 40. The rear end portion 450 of the pillar is in contact with the contact plane 526 of the second layer 52 of the backplate 50 in the assembled state of the drive unit, and transmits magnetic flux between the rear end portion 450 of the pillar 40 and the backplate 50. Since all of the rear end portion 450 of the pillar 40 is in contact with the contact plane 526, magnetic flux can be exchanged between the pillars 40, and a magnetic zero point can occur within the second layer 52. To enable this, the second layer 52 is made of a soft magnetic material. The soft magnetic material can be a discontinuous soft magnetic material that is discontinuous with respect to electrical conductivity, and can include sheets 85 laminated on each other having the same structure as described above with respect to the first layer 51. As an example, three sheets 85 as shown in FIG. 7B can form the second layer 52. Within the second layer 52, the lamination direction D is perpendicular to the rotation axis 10. The sheet 85 is ferromagnetic and electrically conductive, while the intermediate layer between the sheets 85, not explicitly shown, is non-ferromagnetic and electrically non-conductive. This type of discontinuous soft magnetic material reduces eddy currents that would otherwise be generated in larger amounts due to changes in magnetic flux. The hole 525 at the center of the second layer 52 has the purpose of facilitating the assembly of the first layer 51 and the second layer 52. For example, it can serve to align the first and second layers 51, 52.

[0055] FIG. 7C shows a cross-section of the backplate 50. It is composed of a first layer 51 and a second layer 52 joined to each other on their main surfaces having the largest spread. The joining between the first layer 51 and the second layer 52 of the backplate 50 can be established in the same way as between the sheets 85 of the first and second layers 51, 52. The through-holes 515 and 525 of the first layer 51 and the second layer 52 are aligned with each other to align the first and second layers 51, 52. By stacking the first and second layers 51, 52, the opening 511 is closed at one end by the second layer 52, whereby the recess 501 is formed for accommodating the rear end portion 450 of the column 40. The bottom of the recess 501 forms a contact plane 526. When the column 40 is inserted into the recess 501, its rear end portion 450 contacts the contact plane 526. Further, the position of the column 40 is fixed by spaced spokes 512 surrounding each of the columns 40 together, as well as by outer and inner rims 513, 514. Thus, a magnetic connection is established between the second layer 52 and the rear end surface 45 of the column 40 at the contact plane 526, and in addition, a second magnetic connection is established between the column 40 and the above-described surrounding portion of the first layer 51. However, the main part of the magnetic flux is transmitted through the contact plane 526. Preferably, both the surface at the rear end portion 450 of the column 40 and the contact plane 526 have a predetermined flatness. Thus, the gap between the surface 45 at the rear end portion 450 of the column 40 and the contact plane 526 can preferably be maintained less than a specific value of less than 10 μm. This improves the transmission of magnetic flux between the column 40 and the backplate 50. Preferably, there is no additional material between the surface 45 at the rear end portion 450 of the column 40 and the contact plane 526. In this embodiment of the present invention, the transmission of magnetic flux through the surface 45 and the backplate 50 is independent of the way of fixing the column 40 to the backplate 50.

[0056] FIGS. 8A to 8D show the preparation steps for the generation of the column 40. FIG. 8A shows a perspective view of a plate 8 made of a discontinuous soft magnetic material that is discontinuous with respect to electrical conductivity and is also referred to as a workpiece hereinafter.

[0057] In FIG. 8A, a width W for cutting a workpiece bar 81 from a plate 8 is marked on the plate 8. The width W of the workpiece bar 81 is the same as the length of the column 40 to be fabricated from the workpiece bar 81. FIG. 8B shows an enlarged view of the portion marked by the rectangle R in FIG. 8A. Here, a stack of discontinuous soft magnetic material sheets 85 can be visually recognized. The stacking direction DL extends along the main plane of the plate 8 and thus forms a stacking plane.

[0058] FIG. 8C shows the workpiece bar 81 cut out as individual pieces of discontinuous material from the plate 8. FIG. 8D shows an enlarged view of the portion marked by the rectangle R in FIG. 8C. The sheet 85 of the workpiece bar 81 can be visually recognized in this figure.

[0059] FIG. 9A shows the workpiece bar 81 of FIGS. 8C and 8D that forms a base for a welding step for cutting out the column 40 from the bar 81. A plurality of cross-sections 84 of the column 40 to be fabricated from the bar 81 are shown on the side surface of the bar 81 facing left in FIG. 9A. The column 40 is fabricated by cutting out these cross-sections 84 from the bar 81. Since the width W of the bar 81 corresponds to the length of the column 40, the side surfaces 811 and 812 of the bar 81 become the end faces at the impeller side end 420 and the rear end 450 of the column 40.

[0060] Figure 9B shows the next preparatory step before cutting out the column 40. Two weld seams 82 and 83 are welded on the surface 811 of the bar 81 at a distance from each other and across each of the cross-sections 84 of the column 40 to be cut out. The weld seams 82 and 83 extend perpendicular to the lamination direction DL of the sheet 85. In this way, sheets of discontinuous material are connected to each other. Instead of two weld seams, a single weld seam may be provided. In addition, similar weld seams may be provided on the opposite side surface 812 of the bar 81. The sheet 85 has a better mechanical connection to each other due to the weld seams 82 and 83 and is further electrically connected. The latter has the advantage that current can flow from any position of the discontinuous soft magnetic material intended to become the column 40, for example, to each position of the electrical connection of the bar 81, which may be required for electrical discharge machining. In this way, electrical discharge machining is greatly facilitated. Furthermore, since the cut-out column 40 cannot delaminate, a higher process reliability is achieved. Preferably, laser welding is applied. It may be advantageous to apply the welding power to the same weld area two or more times. In Figure 9C, the portion of the bar 81 labeled by the rectangle R is shown enlarged.

[0061] Therefore, Figure 9C shows a plurality of cross-sections 84 of the column 40 to be cut out from the bar 81. The cross-sections 84 have a substantially triangular shape. As shown, the corners may have rounded edges. The convex side 842 of the triangle shown on the left side of the cross-section 84 in Figure 9C has a convex shape. This type of cross-section 84 is advantageous for making full use of the available construction space inside the cylindrical pump housing 2. The bisector of the corner 841 of the cross-section 84 on the side opposite to the convex side 842 of the cross-section 84 is aligned with the lamination direction DL. In this way, the sheet 85 extends symmetrically through the cross-section 84.

[0062] Figure 10 shows the column 40 cut out from the bar 81. As can be seen from the figure, the weld seams 82 and 83 still exist on the surface 45 at the rear end portion 450 of the bar 81. The column 40 has a constant cross-section 84 along its entire length. If required, the weld seams 82 and 83 can have the burrs removed after the column 40 is cut out. Simultaneously, or in a subsequent step, a recess having a structure as shown in any of FIGS. 5A to 5D, or a different structure, is cut into the surface at the opposite end of the column 40, and this surface will later form the front surface 42 of the impeller side end portion 420 of the column 40. Alternatively, the recess can be formed before cutting the column 40 from the bar 81, such as by providing a weld and using wire electrical discharge machining.

[0063] Figure 11 shows another configuration of two cross-sections 84 on the side surface 811 of the workpiece bar 81. In contrast to the workpiece bar 81 shown in FIGS. 9A to 9C, the side surface 811 of the workpiece bar 81 in FIG. 11 has a size that enables the two cross-sections 84 to be arranged adjacent to each other in a direction perpendicular to the lamination direction DL. The cross-sections 84 are oriented such that, with respect to the lamination direction DL, the bisector B of the corner on the side opposite the respective convex sides 842 of each of the cross-sections 84 is aligned with the lamination direction DL. Arranging the cross-sections 84 along the bar 81 in this way saves material. The resulting waste material is reduced. Depending on the thickness of the bar 81 and the required cross-sectional dimensions of the column 40, it is conceivable to stack even more cross-sections 84 of the column 40 in a direction perpendicular to the lamination direction DL.

[0064] Each of the weld seams 82 and 83 extends across each of the cross-sections 84. The weld seams 82, 83 extend across the entire side surface 811 of the bar 81 in a direction perpendicular to the lamination direction DL. In this way, all the sheets 85 of the discontinuous soft magnetic material of the bar 81 are connected to each other.

[0065] FIG. 12 shows an example of the column 40 cut out from the welded bar 81, that is, a front view on the rear end face 45 of the column 40. As shown in FIG. 12, a single weld seam 86 of a considerable width that can cover more than about one-third of the height of the triangular cross-section 84 extends along the convex side 842 of the cross-section 84. The weld seam 86 extends perpendicular to the lamination direction DL so as to connect all of its sheets. However, two weld seams as shown in FIG. 11 are more preferable than a single seam. Also in this case, the bisector B of the corner 841 on the side opposite to the convex side 842 is aligned with the lamination direction DL, as in the previous case.

[0066] FIG. 13 shows a second embodiment of the drive unit-impeller configuration for the blood pump 1 according to FIG. 1. Similar to the first embodiment shown in FIG. 2, the front surface 42 of the impeller-side end 420 has a recess that tapers away from the magnet structure 32 of the impeller 3 in the radially outward direction. In addition, the impeller-side end 420 of the column 40 does not extend radially beyond the winding 44. Rather, the cross-section of the column 40 is constant in the direction of the longitudinal axis LA of the column 40. Thus, the columns 40 are prevented from approaching each other. This is because this can cause a partial magnetic short circuit and thus reduce the power of the electric motor of the blood pump.

[0067] Also in this case, the drive unit according to FIG. 13 may include at least two columns 40. The number of columns is preferably a multiple of 3 and can therefore be 3, 9, or 12. Alternatively, the number of columns can be a multiple of 2, such as 2, 4, 6, 8, 10, or 12. A larger number of columns 40 may also be possible. A number of 6 columns 40 is preferred. Only two columns 40 are visible due to the cross-sectional view. The columns 40 and the back plate 50 form the magnetic core 400 of the drive unit 4 that can have a diameter of less than 10 mm.

[0068] This second embodiment is different from the first embodiment shown in FIG. 2 due to the different structure of the magnetic core. Here, the magnetic core 400 includes the magnet components of the drive unit 4, which are the column 40 and the back plate 50, as one single part or monoblock. The monoblock is made of a discontinuous soft magnetic material. The discontinuous soft magnetic material is discontinuous with respect to electrical conductivity. As shown in the figure, it includes a plurality of sheets 85 of ferromagnetic material that are laminated on top of each other to form a monoblock 9 as shown in FIG. 14C. The lamination direction DL is parallel to the rotation axis 10.

[0069] The coil winding 44 extends to the impeller side end 420 of the column 40. This has the advantage that the magnetomotive force can be generated along the entire column 40. The magnetic core 400 includes a protrusion 401 at the rear end 450 of the column 40 that protrudes radially away from the column 40. This protrusion 401 forms a stopper for the coil winding 44 towards the back plate 50. Since the integrated magnetic core 400 connects the back plate 50 and the column 40 with high rigidity, the spacer between the columns 40 at the impeller side end 420 of the column can be omitted. The integrated magnetic core 400 brings the advantage that an optimal magnetic connection between the column 40 and the back plate 50 is achieved. The magnetic core 400 can have a diameter of less than 10 mm.

[0070] FIGS. 14A - 14C show the steps of manufacturing the magnetic core 400 for the drive unit 4 of the drive unit - impeller configuration as shown in FIG. 13. FIG. 14A shows a perspective view of a cubic monoblock 9 that forms the workpiece for manufacturing the magnetic core 400. The monoblock 9 is made of a discontinuous soft magnetic material that is discontinuous with respect to electrical conductivity. It includes sheets 85 that are oriented in the lamination direction DL that extends along the main plane of the sheets 85. Each of the sheets 85 is joined to its respective adjacent sheet by a bonding layer of an electrically non - conductive material that is not explicitly shown in FIGS. 14A - 14C.

[0071] FIG. 14B shows the magnetic core 400 in a semi-finished state, as it is machined from the cubic monoblock 9 into a substantially cylindrical body 94. In this machining step, the protrusion 401 is produced. The reduced-diameter section 404 of the body 94 that forms the peripheral surface of the column 40 of the magnetic core 400 is produced to have a diameter corresponding to the outer radius of the outermost convex side surface 842 of the column 40.

[0072] Next, the body 94 is further fabricated to produce the magnetic core 400 as shown in FIG. 14C. For this production step, electrical discharge machining can be used. For example, wire-cut electrical discharge machining can be applied to produce the slot holes 49 that separate the columns 40 from each other. A space for the coil winding 44 is provided inside the slot holes. At the bottom of the slot holes 49, the intermediate area 59 of the integral backplate 50 extends between the rear ends of the columns 40. The intermediate area 59 is integral with the columns 40 and the backplate 50. Therefore, the entire magnetic core is formed by the monoblock 9.

[0073] The lamination direction DL within the magnetic core 400 is such that it is parallel to the rotation axis 10. It is acceptable that the lamination direction DL within the base plate 50 is not parallel to the magnetic flux between the columns 40 within the base plate 50. It is also possible to produce the magnetic core 400 from coil-shaped soft magnetic sheet materials separated by electrically non-conductive layers. In this case, the lamination direction DL within the base plate 50 is always in the circumferential direction, which is advantageous for avoiding eddy currents within the magnetic flux within the base plate 50.

[0074] Figures 15A - 15C show how one or more welds can be provided on the surface of an integrated core as fabricated according to Figures 14A - 14C. Thus, in the illustrated embodiment, three weld seams 82, 83 are provided on one side surface of a cubic monoblock 9. The weld seams 82, 83 are welded at a distance from each other and across the cross-section of the body 94 to be cut out from the monoblock 9. The weld seams 82, 83 extend perpendicular to the lamination direction DL of the sheet 85. In this way, sheets of discontinuous soft magnetic material are connected to each other. Instead of three weld seams, more weld seams or a single wider weld may be provided. Additionally, similar weld seams may be provided on the opposite side of the monoblock 9 (not shown). As an alternative to, or in addition to, the welds on the opposite side surface, one or more weld seams may be provided on the side surface of the monoblock 9 at the level of the backplate 50 so as to completely or at least partially surround the backplate 50. The sheet 85 has a better mechanical connection to each other due to the weld seams 82, 83 and is further electrically connected. The latter has the advantage that current can flow from any position of the discontinuous soft magnetic material to each position of the electrical connection within the body 94 that may be required, for example, for electrical discharge machining. In this way, electrical discharge machining is significantly facilitated. Furthermore, a higher process reliability is achieved because the backplate - post unit cut out from the body 94 cannot delaminate. Preferably, laser welding is applied. It may be advantageous to apply the welding power to the same weld twice or even a greater number of times.

[0075] Thereafter, the body 94 is machined to form a core 400 as shown in Figure 15C. In this second embodiment, the recess in the front surface 42 of the post 40 has, not two, but three inclined side walls, all having a downward slope towards the center of the front surface. The outer periphery of the recess coincides with the outer periphery of the front surface 42 of the post 40. However, the recess does not open to any side surface of the post 40. In particular, the embodiment as shown in Figure 14C having only two inclined side walls is more effective and thus preferred.

Claims

1. An intravascular blood pump (1) for percutaneous insertion into a patient's blood vessel, comprising: a pump casing (2) having a blood flow inlet (21) and a blood flow outlet (22); an impeller (3) disposed within the pump casing (2) so as to be rotatable about a rotation axis (10), the impeller (3) having blades (31) sized and shaped to transport blood from the blood flow inlet (21) to the blood flow outlet (22); a drive unit (4) for rotating the impeller (3), the drive unit (4) including a plurality of posts (40) disposed around the rotation axis (10), each of the posts (40) having a front surface (42) facing the impeller (3) and an impeller-side end (420) facing the impeller (3); a coil winding (44) disposed around each of the posts (40) for creating magnetic field lines (500) extending through the front surface (42) of each of the posts (40) and controllable to create a rotating magnetic field; and the impeller (3) includes a magnet structure (32) arranged to interact with the rotating magnetic field to cause rotation of the impeller (3); at least one of the front surfaces (42) of the posts (40) includes a recess in which the front surface (42) slopes downward, i.e., away from the impeller (3); wherein (a) the front surface (42) slopes downward toward a central region of the front surface (42) so as to focus at least a portion of the magnetic field lines (500) extending through the front surface (42), and (b) the front surface (42) slopes downward radially outward with respect to the rotation axis (10) such that a radially inner region of the front surface (42) within the recess projects axially, i.e., toward the impeller (3), beyond a radially outer region of the front surface (42) within the recess; characterized in that the intravascular blood pump (1).

2. The intravascular blood pump (1) according to claim 1, characterized in that the recess extends to the periphery of the front surface (42).

3. The intravascular blood pump (1) according to claim 2, wherein the recess extends at least to the periphery of the front surface (42), or exactly at two sides of the front surface closest to adjacent ones of the plurality of pillars (40). The intravascular blood pump (1) is characterized in that.

4. The intravascular blood pump (1) according to claim 2 or 3, wherein the periphery of the recess coincides with the periphery of the front surface (42). The intravascular blood pump (1) is characterized in that.

5. The intravascular blood pump (1) according to any one of claims 1 to 4, wherein the recess has a flat bottom (42b). The intravascular blood pump (1) is characterized in that.

6. The intravascular blood pump (1) according to claim 5, wherein the recess has a linear inclined side wall (42a) when viewed in a cross-sectional plane extending vertically through the front surface (42). The intravascular blood pump (1) is characterized in that.

7. The intravascular blood pump (1) according to claim 5, wherein the recess has a curved inclined side wall (42a) when viewed in a cross-sectional plane extending vertically through the front surface (42). The intravascular blood pump (1) is characterized in that.

8. The intravascular blood pump (1) according to any one of claims 1 to 4, wherein the recess has a curved cross-section with a curved bottom when viewed in a cross-sectional plane extending vertically through the front surface (42). The intravascular blood pump (1) is characterized in that.

9. The intravascular blood pump (1) according to any one of claims 1 to 4, wherein the recess has a triangular cross-section when viewed in a cross-sectional plane extending vertically through the front surface (42). The intravascular blood pump (1) is characterized in that.

10. The intravascular blood pump (1) according to any one of claims 1 to 9, wherein the recess has no wall at the end, and thus the recess has an opening on the side of at least one first side of the pillar (40), and the first side is located radially outward with respect to the rotation axis (10). The intravascular blood pump (1) is characterized in that.

11. The intravascular blood pump (1) according to claim 10, wherein at least one of the columns (40) has a triangular cross-section having three side surfaces including the first side surface, and the first side surface is located radially outward with respect to the rotation axis (10) compared to the other two of the three side surfaces. Intravascular blood pump (1).

12. The intravascular blood pump (1) according to any one of claims 1 to 11, wherein the depression has a maximum depth of 0.05 mm to 0.3 mm. Intravascular blood pump (1).

13. The intravascular blood pump (1) according to any one of claims 1 to 12, wherein at least one of the columns (40) has a longitudinal axis (LA), and its impeller-side end (420) is arranged around at least one of the columns (40). It does not extend radially beyond the impeller-side end (424) of the coil winding (44), where the term "radially" relates to a direction transverse to the longitudinal axis (LA). Intravascular blood pump (1).

14. The intravascular blood pump (1) according to any one of claims 1 to 13, wherein at least one of the columns comprises or consists of a discontinuous soft magnetic material that is discontinuous with respect to electrical conductivity in a cross-section transverse to the longitudinal axis (LA) of each column (40). Intravascular blood pump (1).

15. The intravascular blood pump (1) according to claim 14, wherein at least one welding part (82, 83, 86) is provided on the surface (811) of the discontinuous soft magnetic material, and the welding part (82, 83, 86) bridges at least one discontinuity with respect to electrical conductivity in the discontinuous soft magnetic material. Intravascular blood pump (1).

16. The intravascular blood pump (1) according to any one of claims 1 to 15, wherein each of the columns (40) has a rear end portion (450), and the drive unit (4) connects the rear end portions (450) of the columns (40). And includes a back plate (50) that extends between the columns (40) within the intermediate region (59), and the material of at least one of the columns (40) is integrated with the material of the intermediate region (59) of the back plate (50). Intravascular blood pump (1).

17. An intravascular blood pump (1) according to any one of claims 1 to 15, wherein each of the columns (40) has a rear end portion (450), the drive unit (4) includes a back plate (50) connecting the rear end portions (450) of the columns (40), and at least one of the rear end portions (450) of the columns (40) has a rear end face (45) in contact with the back plate (50).

Images