阅读说明：本技术 血泵 (Blood pump ) 是由 M·格劳温克尔 W·克尔霍夫斯 于 2020-03-16 设计创作，主要内容包括：本发明涉及用于经皮插入患者的血管中的血管内血泵(1)。血泵(1)包括具有血流入口(21)和血流出口(22)的泵壳体(2)、布置在所述泵壳体(2)中以绕旋转轴线(10)可旋转的叶轮(3)。叶轮(3)具有大小为且成形为用于将血液从血流入口(21)输送到血流出口(22)的叶片(31)。血泵(1)包括用于使叶轮(3)旋转的驱动单元(4),驱动单元(4)包括磁芯(400),磁芯(400)包括绕旋转轴线(10)布置的多个柱体(40)以及连接柱体(40)并在中间区域(59)中在柱体(40)间延伸的背板(50)。线圈绕组(44)围绕柱体(40)中的每个设置。线圈绕组(44)能够被控制以创建旋转磁场,其中叶轮(3)包括布置成与旋转磁场相互作用以引起叶轮(3)旋转的磁性结构(32)。柱体(40)中的至少一个的至少一部分的材料与背板(50)的中间区域(59)的材料为一体。此外,本发明涉及一种制造磁芯(400)的方法和一种制造血管内血泵(1)的方法。(The present invention relates to an intravascular blood pump (1) for percutaneous insertion into a blood vessel of a patient. The blood pump (1) comprises a pump housing (2) having a blood flow inlet (21) and a blood flow outlet (22), an impeller (3) arranged in the pump housing (2) so as to be rotatable about a rotational axis (10). The impeller (3) has blades (31) sized and shaped for conveying blood from the blood flow inlet (21) to the blood flow outlet (22). The blood pump (1) comprises a drive unit (4) for rotating the impeller (3), the drive unit (4) comprising a magnetic core (400), the magnetic core (400) comprising a plurality of columns (40) arranged around the rotation axis (10) and a back plate (50) connecting the columns (40) and extending between the columns (40) in an intermediate region (59). Coil windings (44) are disposed around each of the columns (40). The coil windings (44) are controllable to create a rotating magnetic field, wherein the impeller (3) comprises a magnetic structure (32) arranged to interact with the rotating magnetic field to cause rotation of the impeller (3). The material of at least a portion of at least one of the posts (40) is integral with the material of the middle region (59) of the backplate (50). Furthermore, the invention relates to a method for producing a magnetic core (400) and to a method for producing an intravascular blood pump (1).)

1. An intravascular blood pump (1) for percutaneous insertion into a blood vessel of a patient, the intravascular blood pump (1) comprising:

a pump housing (2), the pump housing (2) having a blood flow inlet (21) and a blood flow outlet (22),

an impeller (3), the impeller (3) being arranged in the pump housing (2) to be rotatable about an axis of rotation (10), the impeller (3) having blades (31) sized and shaped for conveying blood from the blood flow inlet (21) to the blood flow outlet (22),

a drive unit (4), the drive unit (4) being for rotating the impeller (3), the drive unit (4) comprising a magnetic core (400), the magnetic core (400) comprising a plurality of columns (40) arranged around the rotation axis (10) and a back plate (50) connecting the columns (40) and extending between the columns (40) in an intermediate region (59), and

a coil winding (44), the coil winding (44) disposed around each of the columns (40), the coil winding (44) controllable to create a rotating magnetic field,

wherein the impeller (3) comprises a magnetic structure (32) arranged to interact with the rotating magnetic field to cause rotation of the impeller (3),

characterized in that the material of at least a portion of at least one of said columns (40) is integral with the material of said intermediate region (59) of said backplate (50).

2. The intravascular blood pump (1) according to claim 1, wherein the magnetic core (400) comprises or consists of a soft magnetic material that is discontinuous in electrical conductivity in a cross section transverse to the axis of rotation (10).

3. The intravascular blood pump (1) according to claim 2, wherein the soft magnetic material comprises a laminated sheet (85) of soft magnetic material.

4. The intravascular blood pump (1) according to claim 2 or 3, wherein the sheet (85) of soft magnetic material is oriented parallel to the axis of rotation (10).

5. The intravascular blood pump (1) according to any one of claims 2 to 4, comprising at least one weld (82, 83, 86), the at least one weld (82, 83, 86) joining a discontinuity in the soft magnetic material in terms of electrical conductivity.

6. The intravascular blood pump (1) according to claim 5, wherein at least one of the at least one weld (82, 83, 86) is arranged on a surface of the back plate (50) opposite to the cylinder (40).

7. The intravascular blood pump (1) according to claim 5 or 6, wherein at least one of the at least one weld is arranged at an end surface of the cylinder (40) opposite to the back plate (50).

8. A method of manufacturing a magnetic core (400) for a drive unit (4) of an intravascular blood pump (1), the magnetic core (400) having a rotational axis (10) and comprising a plurality of columns (40) arranged around the rotational axis (10) and a back plate (50) connecting the columns (40), the method comprising the steps of: -providing a unitary piece (9) of magnetically conductive material and cutting slits in the unitary piece (9) to construct the cylinder (40) and the backplate (50) such that the cylinder (40) is arranged about the axis of rotation (10) and such that the backplate (50) and the cylinder (40) are formed as one unitary piece.

9. The method of claim 8, wherein at least one of the slits (49) is cut through the axis of rotation (10).

10. Method according to claim 8 or 9, wherein the slits (49) are cut so that the cylinders (40) all have equal length.

11. The method according to any one of claims 8 to 10, wherein the slit (49) is cut such that the back plate (50) has a thickness smaller than a maximum cross-sectional dimension of the cylinder (40) transverse to its Longitudinal Axis (LA).

12. The method according to any of claims 8 to 11, wherein the slits (49) are cut using electrical discharge machining.

13. The method of claim 12, wherein the slits are cut using wire cutting by electrical discharge machining.

14. A method according to any one of claims 8 to 11, wherein the slits are cut using electrochemical machining.

15. A method of manufacturing an intravascular blood pump (1), the intravascular blood pump (1) having a drive unit (4), the drive unit (4) having a magnetic core (400), wherein the magnetic core (400) is manufactured according to any one of claims 8 to 14.

Technical Field

The present invention relates to a blood pump, in particular an intravascular blood pump, for percutaneous insertion into a blood vessel of a patient to support blood flow in the blood vessel of the patient. The blood pump has an improved drive unit.

Background

Different types of blood pumps are known, such as axial blood pumps, centrifugal (i.e. radial) blood pumps or hybrid blood pumps where the blood flow is caused by both axial and radial forces. Intravascular blood pumps are inserted into a patient's blood vessel, such as the aorta, by means of a catheter. Blood pumps generally include a pump housing having a blood flow inlet and a blood flow outlet connected by a passageway. In order to induce a flow of blood along the pathway from the blood flow inlet to the blood flow outlet, an impeller or rotor is rotatably supported within the pump housing, wherein the impeller is provided with vanes for conveying the blood.

The blood pump is typically driven by a drive unit, which may be an electric motor. For example, US 2011/0238172 a1 discloses an extracorporeal blood pump having an impeller that may be magnetically coupled to an electric motor. The impeller includes a magnet disposed adjacent to a magnet in the electric motor. The rotation of the motor is transmitted to the impeller due to the attractive force between the magnets in the impeller and in the motor. In order to reduce the number of rotating parts, it is also known from US 2011/0238172 a1 to utilize a rotating magnetic field, wherein the drive unit has a plurality of stator cylinders arranged around the axis of rotation, each cylinder carrying a coil winding and acting as a magnetic core. The control unit sequentially supplies voltages to the coil windings to create a rotating magnetic field. In order to provide a sufficiently strong magnetic coupling, the magnetic force must be sufficiently high, which can be achieved by supplying a sufficiently high current to the drive unit or by providing a large magnet, which however results in a large overall diameter of the blood pump.

EP 3222301B 1 discloses a blood pump, in particular an intravascular blood pump, with a magnetic coupling between the drive unit and the impeller, wherein the blood pump has a compact design, in particular a high ratio of pumping power to pump size, resulting in an outer dimension that is small enough to allow the blood pump to be inserted transvascularly, transvenously, transarterially, or transvalveally, or even smaller for reasons of ease of operation.

More specifically, the blood pump in EP 3222301B 1 comprises a pump housing having a blood flow inlet and a blood flow outlet, an impeller, and a drive unit for rotating the impeller. By rotation of the impeller within the pump housing about the axis of rotation, blood can be conveyed from the blood flow inlet to the blood flow outlet by the blades of the impeller. The driving unit includes a magnetic core including a plurality of, preferably six, legs and a back plate connecting rear ends of the legs to serve as a yoke. The cylinders are arranged circularly around the axis of rotation, when seen in a plane perpendicular to the axis of rotation, wherein each cylinder has a longitudinal axis, which is preferably parallel to said axis of rotation. The back plate has through openings in each of which a rear end of the post is snugly received such that an end surface of the rear end of each post is flush with the rear surface of the back plate. In this way, a magnetic connection between the cylinder and the back plate is created between the circumference of the cylinder and the inner contour of the opening of the back plate. The posts each have a coil winding disposed around the post. To generate a rotating magnetic field to drive the impeller, the coil windings may be controlled in a coordinated manner. The impeller comprises a magnetic structure in the form of a magnet arranged to interact with the rotating magnetic field such that the impeller follows its rotation.

It is an object of the present invention to increase the magnetic flux in a magnetic core.

Disclosure of Invention

The blood pump of the present invention corresponds to the blood pump described above. Hereby, it may be an axial blood pump or a diagonal blood pump pumping partly axially and partly radially (the diameter of a pure centrifugal blood pump is typically too large for intravascular applications). However, according to one aspect of the invention, the material of at least a portion of at least one of the legs of the magnetic core is integral with the material of a middle region of the back plate of the magnetic core, wherein the middle region of the back plate is the region of the back plate between the legs. Preferably, all the columns are integrally connected to the back plate in this way. In other words, the at least one column and the back plate, preferably the entire magnetic core, may be made of a single piece of material, hereinafter also referred to as a monolithic (monoblock). One advantage of such a core is that: the reluctance at the transition between the post and the back plate is minimized and thus the magnetic flux is increased. Furthermore, a good mechanical stiffness at the transition between the cylinder and the back plate can be achieved.

Each of the cylinders has a longitudinal axis that may be parallel to the axis of rotation. Preferably, the magnetic core comprises a discontinuous soft magnetic material. More preferably, the soft magnetic material of the core is discontinuous in a cross-section transverse, preferably perpendicular, to the longitudinal axis of the cylinder. In other words, the soft magnetic material of the cylinder is discontinuous in a cross section transverse, preferably perpendicular, to the direction of the magnetic flux caused by the respective coil windings in the cylinder. By separating or interrupting the soft magnetic material in the cross section, eddy currents in the cylinder can be reduced or avoided, so that heat generation and energy consumption can be reduced. Reducing power consumption is particularly useful for long-term applications of the blood pump where it is desirable that the blood pump be battery powered to provide mobility to the patient. Furthermore, in long-term use, the blood pump can be operated without emptying, which is only possible if the heat generation is low.

"discontinuous" in the sense of the present document means that the soft magnetic material, seen in any cross section transverse to the longitudinal axis of e.g. a cylinder, is interrupted, divided, truncated, etc. by insulating or other material or gap to form strictly separated regions of soft magnetic material or regions that are interrupted but connected at different locations.

Providing discontinuous soft magnetic material in a cross-sectional plane transverse to the direction of magnetic flux reduces eddy currents and thus reduces heat generation and power consumption, as described above. In order not to substantially reduce the magnetic field compared to a continuous or full (i.e., solid) soft magnetic material, the total amount of soft magnetic material is maximized while minimizing the continuous regions of soft magnetic material. This may be achieved, for example, by providing the soft magnetic material in the form of a plurality of sheets of soft magnetic material, such as electrical steel. In particular, the sheets may form a stack of sheets. The sheets are preferably electrically insulated from each other, for example by providing an adhesive, lacquer, porcelain or the like between adjacent ones of the sheets. This arrangement may be called "slotted". The amount of soft magnetic material is only reduced a little compared to the full body soft magnetic material and the amount of insulating material is kept small so that the magnetic field caused by the slotted cylinder is substantially the same as the magnetic field caused by the solid cylinder. In other words, while heat generation and power consumption can be significantly reduced, the loss of the magnetic field caused by the insulating material is insignificant.

The sheets preferably extend substantially parallel to the longitudinal axis of the respective cylinder. In other words, the sheet may extend substantially parallel to the magnetic flux direction such that the columns are discontinuous in a cross-section transverse or perpendicular to the magnetic flux direction. It will be appreciated that the sheets may extend at an angle relative to the longitudinal axis of the respective cylinder, as long as the soft magnetic material is discontinuous in a cross-section transverse to the longitudinal axis. The sheet preferably has a thickness in the range 25 μm to 1mm, more preferably 50 μm to about 450 μm, for example 200 μm.

In particular, a certain type of material region, such as a sheet of soft magnetic material, may extend in both the cylinder and the back plate. Although the material is discontinuous, the core may be made from a single piece of such material. The extension of this certain type of material region is not interrupted by the transition between the posts and the back plate, but is integrally continuous from the posts to the middle region of the back plate located between the posts.

It is known to provide a slotted soft magnetic material, such as electrical steel, in an electric motor to avoid or reduce eddy currents. However, this technique has been applied in the past to large-scale equipment where the sheet typically has a thickness in the range of about 500 μm or more. In small applications, such as in a blood pump of the present invention where one of the cylinders typically has a diameter of the order of magnitude and the power input is relatively low (e.g., up to 20 watts (W)), no eddy currents and associated problems are expected. Surprisingly, although the diameter of the cylinder is small, eddy currents and thus heat generation and energy consumption can be reduced by providing a slotted cylinder. This is advantageous for the operation of blood pumps, which can be operated at high speeds up to 50,000rpm (revolutions per minute).

It will be appreciated that other arrangements than the slotted arrangement described above may be used to provide discontinuous soft magnetic material in the cylinder. For example, instead of a plurality of sheets, a plurality of wires, fibers, cylinders or other elongated elements may be provided to form each cylinder of the drive unit. The wires or the like may be provided in the form of a bundle, wherein the wires are electrically insulated from each other, for example by means of a coating surrounding each wire or an insulating matrix in which the wires are embedded, and may have various cross-sectional shapes such as circular, rounded, rectangular, square, polygonal, and the like. Similarly, particles, wire wool or other spongy or porous structures of soft magnetic material may be provided, wherein the spaces between the areas of soft magnetic material comprise an electrically insulating material, such as a binder, lacquer, polymer matrix or the like. The porous and thus discontinuous structure of the soft magnetic material may also be formed by sintered or pressed material. In this structure, the additional insulating material can be omitted because the insulating layer can be automatically formed by the oxidation of the soft magnetic material due to exposure to air.

Although the sheets or other structures of soft magnetic material may be formed uniformly, i.e. the sheets within one or all of the columns may have the same thickness or the wires may have the same diameter, non-uniform arrangements may also be provided. For example, the sheets may have different thicknesses or the wires may have different diameters. More specifically, particularly for a stack of sheets, one or more central sheets may have a greater thickness, while adjacent sheets towards the ends of the stack may have a smaller thickness, i.e. the thickness of the sheets decreases from the centre towards the ends of the stack, i.e. towards the outermost sheets in the stack. Similarly, one or more central wires in a bundle of wires may have a larger diameter, while wires at the edges of the cylinder may have a smaller diameter, i.e. the diameter of the wires may decrease from the centre towards the edges of the bundle, i.e. towards the outermost wires in the bundle. Providing a larger continuous area of soft magnetic material in the centre of the columns with respect to a cross-section transverse to their longitudinal axis, i.e. providing a relatively thick sheet or wire in the centre, may be advantageous as this may enhance the magnetic flux passing through the centre along the longitudinal axis of each column, and eddy currents in the centre are less relevant than eddy currents at the sides of the columns. In other words, such an arrangement may be advantageous, as eddy currents in the side regions of the column are more critical and may be reduced by the thin sheet or wire of the side regions.

The diameter of the back plate may be in the range of 3mm to 9mm, such as 5mm or 6mm to 7 mm. The thickness of the backing plate may be in the range 0.5mm to 2.5mm, such as 1.5 mm. The outer diameter of the blood pump may be in the range 4mm to 10mm, preferably 7 mm. The outer diameter of the arrangement of the plurality of pillars may be in the range 3mm to 8mm, such as 4mm to 7.5mm, preferably 6.5 mm.

As described above, the cylinder is made of a soft magnetic material such as electrical steel (magnetic steel). The post and the backplate may be made of the same material. Preferably, the drive unit including the column and the back plate is made of cobalt steel. The use of cobalt steel helps to reduce the size, particularly the diameter, of the pump. With the highest permeability and highest saturation flux density among all magnetic steels, cobalt steels produce the most flux for the same amount of material used.

The dimensions of the column, particularly the length and cross-sectional area, may vary depending on various factors. In contrast to the size of the blood pump, e.g. the outer diameter, depending on the application of the blood pump, the size of the cylinder is determined by the electromagnetic properties and is adjusted to achieve the desired performance of the drive unit. One of the factors is the magnetic flux density through the minimum cross-sectional area of the column to be achieved. The smaller the cross-sectional area, the higher the current necessary to achieve the desired magnetic flux. However, the higher the current, the more heat is generated in the wire of the coil due to the resistance. This means that although a "thin" cylinder is preferred to reduce the overall size, this would require high currents and therefore cause undesirable heat. The amount of heat generated in the wire is also dependent on the length and diameter of the wire used for the coil winding. Short wire lengths and large wire diameters are preferred to minimize winding losses (referred to as "copper losses" or "copper energy losses" if copper wires are used, as is often the case). In other words, if the wire diameter is small, more heat is generated than a thicker wire at the same current, so that the preferred wire diameter is, for example, 0.05mm to 0.2mm, such as 0.1 mm. Further factors affecting the cylinder size and the performance of the drive unit are the number of windings of the coil and the outer diameter of the windings, i.e. the cylinder comprising the windings. The large number of windings may be arranged in more than one layer around each cylinder, for example two or three layers may be provided. However, the higher the number of layers, the more heat is generated due to the increased length of wire in the outer layers having the larger winding diameter. The increased length of the wire may generate more heat due to the higher resistance of the long wire as compared to the shorter wire. Therefore, a single layer winding with a small winding diameter would be preferred. The general number of windings, in turn, may be about 50 to about 150, such as 56 or 132, depending on the length of the column. Independently of the number of windings, the coil windings are made of an electrically conductive material, in particular a metal, such as copper or silver. Silver may be preferred over copper because silver has a resistance of about 5% less than that of copper.

Preferably, the magnetic core comprises one or more welds. The weld may be arranged on the outer surface of the magnetic core, which is particularly accessible for e.g. laser welding. The weld joins the discontinuity in electrical conductivity in the soft magnetic material and thus electrically connects at least two sheets of soft magnetic material. The weld also adds mechanical stability to the discontinuous soft magnetic material.

One or more welds may be disposed on a surface of the backplate opposite the post. They can be produced by laser welding. In the case of using a material made of laminated sheets, the weld preferably joins adjacent soft magnetic sheets obliquely or laterally.

In a further aspect of the invention, a method of manufacturing a magnetic core for a drive unit of an intravascular blood pump is presented. The magnetic core has an axis of rotation and includes a plurality of posts arranged about the axis of rotation and a back plate connecting the posts. The method comprises the following steps: providing a unitary piece of magnetically permeable material and cutting the unitary piece into a gap to construct the cylinder and the backplate such that the cylinder is disposed about the axis of rotation and such that the backplate and the cylinder are formed as a unitary piece. As noted above, one advantage of such fabrication is the production of a magnetic core with reduced reluctance.

At least one slit, preferably all slits, which are opposite to each other with respect to the rotational axis can be produced by cutting through the rotational axis of the magnetic core. An even distribution of the cylinders about the axis of rotation can then easily be achieved. Preferably, the slits are cut so that the cylinders all have equal lengths. The slit is particularly cut such that the back plate has a thickness smaller than the largest cross-sectional dimension of the cylinder transverse to its longitudinal axis.

It is preferable to cut the slit using electric discharge machining, particularly wire electric discharge machining, or using electrochemical machining. These methods exert only a small force on the material to be processed and are therefore particularly advantageous for processing discontinuous materials.

In a further aspect of the invention, a method of manufacturing a blood pump is presented. The blood pump comprises a drive unit with a magnetic core, wherein the magnetic core is manufactured in the manner described hereinbefore.

Drawings

The foregoing summary, as well as the following detailed description of preferred embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, reference is made to the accompanying drawings. The scope of the disclosure is not limited to the specific embodiments disclosed in the drawings. In the drawings:

figure 1 shows a cross-sectional view of a blood pump;

FIG. 2 shows a cross-sectional view of a preferred embodiment of a drive unit-impeller arrangement;

fig. 3A to 3C show steps of manufacturing an integrated magnetic core for the drive unit according to fig. 2;

fig. 4A to 4C show a soldering part on the integrated magnetic core as manufactured according to fig. 3A to 3C; and

fig. 5A-5J illustrate cross-sections through a cylinder according to various embodiments.

Detailed Description

Referring to fig. 1, a cross-sectional view of a blood pump 1 is illustrated. The blood pump 1 comprises a pump housing 2 having a blood flow inlet 21 and a blood flow outlet 22. The blood pump 1 is designed as an intravascular pump, also called catheter pump, and is placed in the blood vessel of the patient by means of a catheter 25. During use, the blood flow inlet 21 is at the end of a flexible sleeve 23 that can be placed through a heart valve, such as an aortic valve. The blood flow outlet 22 is located in a side surface of the pump housing 2 and may be placed in a cardiac vessel, such as the aorta. The blood pump 1 is electrically connected with an electrical line 26 extending through the conduit 25 to supply electrical power to the blood pump 1 to drive the pump 1 by means of the drive unit 4, as described in more detail below.

If the blood pump 1 is intended for long-term use, i.e. in case the blood pump 1 is implanted in a patient for weeks or even months, the power is preferably supplied by a battery. This allows the patient to move because the patient is not connected to the base station by a cable. The battery may be carried by the patient and may supply electrical energy to the blood pump 1, e.g. wirelessly.

Blood is transported along a path 24 connecting the blood flow inlet 21 and the blood flow outlet 22 (the arrows indicate the blood flow). The impeller 3 is provided for conveying blood along the passage 24 and is mounted so as to be rotatable about the axis of rotation 10 within the pump housing 2 by means of the first bearing 11 and the second bearing 12. The axis of rotation 10 is preferably the longitudinal axis of the impeller 3. In this embodiment, both bearings 11, 12 are contact type bearings. However, at least one of the bearings 11, 12 may be a non-contact type bearing, such as a magnetic or hydrodynamic bearing. The first bearing 11 is a pivot bearing with a spherical bearing surface allowing rotational movement as well as some degree of pivoting movement. A pin 15 is provided to form one of the bearing surfaces. The second bearing 12 is arranged in a support member 13 to stabilize the rotation of the impeller 3, the support member 13 having at least one opening 14 for the flow of blood. Vanes 31 are provided on the impeller 3 for conveying blood once the impeller 3 rotates. The rotation 3 of the impeller is caused by the drive unit 4 being magnetically coupled to the magnet 32 at an end portion of the impeller 3. The illustrated blood pump 1 is a hybrid blood pump, the main flow direction of which is axial. It will be appreciated that the blood pump 1 may also be a pure axial blood pump, depending on the arrangement of the impeller 3, in particular the blades 31.

The blood pump 1 comprises an impeller 3 and a drive unit 4. The drive unit 4 comprises a plurality of cylinders 40, such as six cylinders 40, only two of which are visible in the sectional view of fig. 1. The cylinders 40 are arranged parallel to the rotation axis 10, more specifically, the longitudinal axis of each of the cylinders 40 is parallel to the rotation axis 10. One end of the cylinder 42 is disposed adjacent the impeller. Coil windings 44 are disposed about the post 40. The coil windings 44 are sequentially controlled by the controller to create a rotating magnetic field. Part of the control unit is a printed circuit board 6 connected to the electrical lines 26. The impeller has a magnet 32, the magnet 32 being formed in this embodiment as a multi-piece magnet. The magnet 32 is arranged 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 the impeller 3 to rotate about the axis of rotation 10.

To close the flux path, a back plate 50 is located at the end of the post 40 opposite the impeller side of the post. The cylinder 40 acts as a magnetic core and is made of a suitable material, in particular a soft magnetic material, such as steel or a suitable alloy, in particular cobalt steel. Similarly, the backplate 50 is made of a suitable soft magnetic material, such as cobalt steel. The back plate 50 enhances the magnetic flux, which allows the overall diameter of the blood pump 1 to be reduced, which is important for intravascular blood pumps. 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 has in this embodiment a conical shape to guide the blood flow along the impeller 3. The yoke 37 may also be made of cobalt steel. One or more flushing passages extending towards the central bearing 11 may be formed in the yoke 37 or the magnet 32.

Fig. 2 shows a sectional view of a preferred embodiment of a drive unit-impeller arrangement for the blood pump according to fig. 1. As shown in fig. 2, the impeller-side end 420 of the cylinder 40 does not extend radially beyond the windings 44. Rather, the cross-section of the cylinder 40 is constant in the direction of the longitudinal axis LA of the cylinder 40. It is thus avoided that the cylinders 40 are close to each other, since this would cause local magnetic short-circuits, with a consequent reduction in the power of the electric motor of the blood pump.

The drive unit according to fig. 2 may comprise at least two, at least three, at least four, at least five or preferably six cylinders 40. A greater number of posts 40, such as nine or twelve, are possible. Only two of the cylinders 40 are visible due to the cross-sectional view. The cylinder 40 and the back plate 50 form a magnetic core 400 of the drive unit 4, which may have a diameter of less than 10 mm.

The magnetic core 400 comprises the magnetic components of the drive unit 4 as one single piece or piece, the magnetic components being the column 40 and the back plate 50. The whole piece is made of a discontinuous soft magnetic material that is discontinuous in electrical conductivity. The discontinuous soft magnetic material includes a plurality of sheets 85 made of a ferromagnetic material and laminated to each other. The stacking direction is arranged in the direction of the longitudinal axis LA of the cylinder 40 and is indicated by the arrow DL. As shown, the cylinder 40 is arranged parallel to the rotation axis 10.

The coil windings 44 extend up to the impeller side end 420 of the cylinder 40. This has the advantage that a magnetomotive force can be generated along the complete cylinder 40. The magnetic core 400 includes a protrusion 401 protruding radially from the cylinder 40 at the rear end 450 of the cylinder 40. This protrusion 401 may be the end of the coil winding 44 towards the back plate 50. Because the integrated magnetic core 400 has high rigidity between the back plate 50 and the column 40, the spacer between the columns 40 at the impeller-side ends 420 of the columns may be omitted. The integrated magnetic core 400 provides the advantage that an optimal magnetic connection between the post 40 and the back plate 50 can be achieved. The magnetic core 400 may have a diameter of less than 10 mm.

Fig. 3A to 3C show steps of manufacturing the magnetic core 400 of the drive unit 4 for the drive unit-impeller arrangement shown in fig. 2. Fig. 3A shows in perspective a cuboid-shaped whole piece 9, which forms the workpiece for manufacturing the magnetic core 400. The whole piece 9 is made of a discontinuous soft magnetic material discontinuous in electrical conductivity. It comprises a sheet 85 oriented in a stacking direction DL extending along a main plane of the sheet 85. The sheets 85 are each bonded to their respective adjacent sheets by a bonding layer of non-conductive material, which is not explicitly shown in fig. 3A to 3C.

Fig. 3B shows the magnetic core 400 in a semi-manufactured state that has been processed, e.g. transformed from a cubic whole 9 into a substantially cylindrical body 94. In this processing step, the protrusion 401 is manufactured. The reduced diameter section 404 of the body 94 forms an outer peripheral surface of the post 40 of the magnetic core 400 that is manufactured to have a diameter corresponding to the outer diameter of the outermost convex side surface 842 of the post 40.

The body 94 may then be further manufactured to produce the magnetic core 400 shown in fig. 3C. For this production step, electrical discharge machining may be used. In particular, electrical discharge machining by wire cutting can be applied to produce the slits 49 separating the cylinders 40 from one another. Inside the slot, space is provided for the coil winding 44. At the bottom of the slot 49, a middle region 59 of the integral backplate 50 extends between the rear ends of the posts 40. The intermediate region is integral with the post 40 and with the backplate 50. The entire core is thus formed by the whole piece 9.

The lamination direction DL in the magnetic core 400 is such that: which is parallel to the axis of rotation 10. It is acceptable that the lamination direction DL in the base plate 50 is not parallel with respect to the magnetic flow between the columns 40 in the base plate 50. The core 400 may also be made from a wound soft magnetic sheet material separated by non-conductive layers. Then, the lamination direction DL in the bottom plate 50 is always in the circumferential direction, which is advantageous for avoiding eddy current of the magnetic flux in the bottom plate 50.

Fig. 4A to 4C illustrate how one or more welds may be provided on the surface of a unitary magnetic core as manufactured according to fig. 3A to 3C. Accordingly, in the embodiment shown, three weld seams 82, 83 are provided on one side of the cuboid monolith 9. The welds 82, 83 are welded at a distance from each other and across the section of the body 94 to be cut from the whole piece 9. The welds 82, 83 extend perpendicular to the stacking direction DL of the sheets 85. In this way, the sheets of discontinuous soft magnetic material are connected to each other. Instead of three welds, more welds or a single wide weld may be provided. Otherwise, a similar weld may be provided on the opposite side of the unitary piece 9 (not shown). Instead of or in addition to the welds being on opposite sides, one or more welds may be provided on the side surface of the whole 9 at the level of the back plate 50 to completely or at least partially surround the back plate 50. The sheets 85 have a better mechanical connection to each other due to the welds 82 and 83, but are also electrically connected. The latter has the advantages that: current may flow from any location of the discontinuous soft magnetic material to a location of the body 94 that may be each electrical connection required for, for example, electrical discharge machining. Thus, electric discharge machining is significantly facilitated. Moreover, higher processing reliability is achieved because the back plate-cylinder units to be cut out of the body 94 are not frayed by the delamination. Preferably, laser welding is applied. It may be advantageous to apply two or more welding powers to the same weld.

Fig. 5A-5J illustrate various embodiments of the cylinder as seen in cross-section. Fig. 5A to 5D show an embodiment in which the cylinder is slotted, i.e. formed by a plurality of sheets 171 insulated from each other by an insulating layer 172. The insulating layer 172 may include an adhesive, lacquer, porcelain, or the like. Fig. 5A and 5B illustrate an embodiment in which the thickness of the sheet 171 is uniform. The thickness may be in the range of 25 μm to 450 μm. The sheet 171 shown in fig. 5A has a greater thickness than the sheet 171 shown in fig. 5B. The sheets in fig. 5C have different thicknesses, with the center sheet having the largest thickness and the outermost sheet having the smallest thickness. This may be advantageous because eddy currents in the lateral regions of the pillars are more critical and may be reduced by thin sheets. Eddy currents in the central region are less critical and the relatively thick central sheet can help to improve the magnetic flux. The orientation of the sheets 171 may be different as exemplarily shown in fig. 5D as long as the soft magnetic material in the illustrated cross section, i.e., in a cross section transverse to the direction of the magnetic flux, is discontinuous or interrupted.

Fig. 5E and 5F show embodiments in which the cylinder 141 is formed from a bundle of wires 181 insulated from each other by an insulating material 182. The insulating material 182 may be present as a coating of each of the wires 181 or may be a matrix in which the wires 181 are embedded. In the embodiment of fig. 5E, all wires have the same diameter, while in the embodiment of fig. 5F, the center wire has the largest diameter and the outer wires have smaller diameters, similar to the embodiment shown in fig. 5C with sheets of varying thickness. As shown in fig. 5G, wires 181 of different diameters may be mixed, which may increase the overall cross-sectional area of the soft magnetic material compared to an embodiment where all wires have the same diameter. Alternatively still, to further minimize the insulating layer 184 between the wires 183, the wires 183 may have a polygonal cross-sectional area, such as rectangular, square, or the like.

Alternatively, the discontinuous cross-section of the pillars 141 can be created by metal particles 185 embedded in a polymer matrix 186 as shown in fig. 5I, or by steel wool or other porous structure throughout the insulating matrix. The porous and thus discontinuous structure of the soft magnetic material can also be produced by a sintering process or a high-pressure molding process, wherein the insulating matrix can be omitted, since the insulating layer is automatically formed by the oxidation of the soft magnetic material by exposure to air. Still alternatively, the cylinder 141 may be formed from a rolled sheet 187 of soft magnetic material, with the layers of the rolled sheet 187 separated by an insulating layer 188, as shown in fig. 5J. This also provides a discontinuous cross-section in the sense of the present invention which reduces eddy currents in pillars 141 or pillars 40.