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)包括绕旋转轴线(10)布置的多个柱体(40)以及连接该部件的后端部的背板,柱体和背板共同形成驱动单元的磁芯。线圈绕组(47)围绕柱体中的每个(40)设置。线圈绕组(82,83,86)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)。磁芯(400)或其一部分包括在截面中在导电性方面不连续的不连续软磁性材料,其中至少一个焊接部(82,83,86)设置在不连续软磁性材料的表面(811)。焊接部(82,83,86)衔接不连续软磁性材料中的导电性方面的至少一个不连续。此外,本发明涉及一种制造磁芯(400)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 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 plurality of columns (40) arranged around the axis of rotation (10) and a back plate connecting the rear ends of the components, the columns and the back plate together forming a magnetic core of the drive unit. Coil windings (47) are disposed around each of the columns (40). The coil windings (82, 83, 86) 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 magnetic core (400) or a part thereof comprises a discontinuous soft magnetic material which is discontinuous in electrical conductivity in cross section, wherein at least one weld (82, 83, 86) is provided on a surface (811) of the discontinuous soft magnetic material. The weld (82, 83, 86) joins at least one discontinuity in electrical conductivity in the discontinuous soft magnetic material. Furthermore, the invention relates to a method of manufacturing a magnetic core (400).)

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) for rotating the impeller (3), the drive unit (4) comprising a plurality of columns (40) arranged around the rotation axis (10) and a back plate (50) connecting rear ends (450) of the columns (40), wherein the columns (40) and the back plate (50) form a magnetic core (400) of the drive unit (4), 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), and

characterized in that the core (400) or a part thereof comprises or consists of a discontinuous soft magnetic material which is discontinuous in electrical conductivity in cross section, wherein at least one weld (82, 83, 86) is provided on a surface (811) of the discontinuous soft magnetic material, the weld (82, 83, 86) joining at least one discontinuity in electrical conductivity in the discontinuous soft magnetic material.

2. The intravascular blood pump (1) according to claim 1, wherein at least one of the at least one weld (82, 83, 86) is arranged at a rear end surface (45) of the cylinder.

3. The intravascular blood pump (1) according to claim 1, wherein at least one of the at least one weld (82, 83, 86) is arranged at an impeller-side end surface of the cylinder (40).

4. The intravascular blood pump (1) according to claim 1, wherein at least one of the at least one weld (82, 83, 86) is arranged at an impeller-side end surface of the cylinder (40) and at least one further weld (82, 83, 86) is arranged at the rear end surface (45) of the cylinder (40).

5. The intravascular blood pump (1) according to any of the preceding claims, wherein two of the at least one welds (82, 83, 86) are arranged at one end of the cylinder (40) spaced apart from each other.

6. The intravascular blood pump (1) according to any of the preceding claims, wherein at least one of the at least one weld (82, 83, 86) extends on a side surface of the cylinder (40), preferably at least partially encircling at least one of the cylinders (40).

7. The intravascular blood pump (1) according to any of the preceding claims, wherein more than one of the at least one welds (82, 83, 86) are arranged on the same surface side of the cylinder (40).

8. The intravascular blood pump (1) according to any of the preceding claims, wherein the at least one weld (82, 83, 86) comprises the at least one discontinuous weld seam joining an electrically conductive aspect in the discontinuous soft magnetic material.

9. The intravascular blood pump (1) according to any one of the preceding claims, wherein at least one of the columns (40) comprises a stack of soft magnetic material and soft magnetic sheets (85) are oriented parallel to a Longitudinal Axis (LA) of the column (40).

10. The intravascular blood pump (1) according to claim 9, wherein said at least one of the columns (40) has a triangular cross-section (84) in a direction transverse to the rotation axis (10) and the soft magnetic sheet (85) of soft magnetic material is oriented in or parallel to a plane passing through a bisector (B) of the triangular cross-section (84).

11. A method of manufacturing a magnetic core (400) or a part of a magnetic core (400) for a drive unit (4) of an intravascular blood pump (1), in particular for an intravascular blood pump (1) according to any one of claims 1 to 10, characterized by the steps of:

-providing a piece (8, 81) of discontinuous soft magnetic material, which piece (8, 81) is discontinuous in terms of electrical conductivity in a cross section of the piece (8, 81) and from which the magnetic core (400) or a part of the magnetic core (400) is to be manufactured, and

-providing a weld (82, 83, 86) at a surface (811) of the work piece (8, 81) such that the weld (82, 83, 86) engages at least one discontinuity in electrical conductivity in the discontinuous soft magnetic material of the work piece (8, 81).

12. The method of claim 11, wherein the magnetic core (400) or a portion of the magnetic core (400) is separated out of the work piece (8, 81) after the weld is provided.

13. The method of claim 12, wherein at least a portion of the weld (82, 83, 86) remains at the magnetic core (400) or a portion of the magnetic core (400) after separating the magnetic core (400) or a portion of the magnetic core (400) from the workpiece (8, 81).

14. The method of claim 12 or 13, wherein the step of separating the magnetic core (400) or a portion of the magnetic core (400) out of the workpiece (8, 81) comprises separating at least one of the columns (40) out of the workpiece (8, 81) by electrical discharge machining.

15. Method according to any one of claims 12 to 14, wherein the at least one weld (82, 83, 86) is produced by laser welding or by double application of a welding laser, in particular double laser welding.

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 transvascular, transvenous, transarterial, or transvalveal insertion of the blood pump, 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 plurality of, preferably six columns, and a back plate connecting rear ends of the columns to serve as a yoke. The column and the back plate form a magnetic core of the driving unit. 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 cylinders each have a coil winding disposed around each cylinder. 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.

In unpublished european patent application No. 17191940.0, discontinuous soft magnetic material can be used for the magnetic components of the drive unit, in particular for the cylinder, in order to keep eddy current losses low. The discontinuous material may be, for example, a laminate material comprising soft magnetic sheets. However, the magnetic components of the drive unit made of such materials are prone to disintegration and fraying at delamination between the sheets. Another problem is related to the possibility of manufacturing such components by electrical discharge machining. When such a workpiece is contacted for electrical discharge machining at a certain location, not all other locations of the material are in electrical contact with the contacted location. This complicates the electric discharge machining.

It is an object of the invention to facilitate the manufacture of a drive unit for an intravascular blood pump.

Disclosure of Invention

The blood pump of the present invention corresponds to the blood pump described above in EP 3222301B 1. 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 magnetic core or at least one of its parts, in particular the columns, comprises, or consists of, a discontinuous soft magnetic material which is discontinuous with respect to its electrical conductivity in a cross section transverse to the longitudinal axis of the respective column. At least one weld is provided on the surface of the discontinuous soft magnetic material, in particular on at least one of the columns. The weld joins the discontinuities in the electrical conductivity of the discontinuous soft magnetic material.

Each of the cylinders has a longitudinal axis. Preferably, the longitudinal axis of each cylinder is parallel to the axis of rotation. The columns each comprise a soft magnetic material that is discontinuous in a cross section transverse, preferably perpendicular, to the longitudinal axis of the respective column. 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 cleaning (purge), 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, 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 450 μm, for example 200 μm.

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 configuration, the additional insulating material may be omitted, since the insulating layer may be automatically formed by an oxide layer caused by the oxidation of the soft magnetic material upon 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 weld enables easy manufacture of the magnetic core made of discontinuous soft magnetic material or a part thereof. That is, when separating the magnetic core or the pillar of the magnetic core from a larger workpiece made of discontinuous soft magnetic material, the discontinuous soft magnetic material may delaminate or lose its integrity due to the processing forces exerted on the workpiece during the separation process. This is particularly critical due to the extremely small dimensions of the magnetic core, in particular its cylinder, and can even occur when electrical discharge machining, in particular electrical discharge machining by wire cutting, is used to separate the magnetic core or its cylinder out of the workpiece. By virtue of the weld applied on the work piece before the separation step, the mechanical stability of the discontinuous material is improved. In the case of electrical discharge machining for cutting a magnetic core or a cylindrical body into a workpiece, the flow of current to the cutting site is also improved. The weld or welds may later form part of a magnetic core or cylinder.

In particular, the impeller-side end surface of the cylinder oriented transverse to the axis of rotation is exposed to the discontinuous material. Accordingly, the weld or welds may be arranged on the surface of the impeller side of the cylinder. Alternatively or additionally, the weld or welds may be disposed at the rear end surface of the column, or, if the magnetic core including the back plate serving as the yoke is integrated with the workpiece (monoblock), another weld or welds may be disposed at the rear end surface of the back plate.

Preferably, the rear end surface of at least one of the cylinders, preferably all of the cylinders, is arranged substantially perpendicular to the longitudinal axis of at least one of the cylinders. At least one of the cylinders, preferably all of the cylinders, may further comprise a circumferential/peripheral surface disposed about and extending along a longitudinal axis of the cylinder, wherein the trailing end surface is disposed at a longitudinal trailing end of the circumferential surface and faces away from the impeller. Preferably, the rear end surface is substantially perpendicular to the circumferential surface.

Preferably, the entire surface of the core or its pillars may be covered by a weld to join all soft magnetic components, such as sheets of discontinuous material present at that surface. Most preferably, all of the discrete material components are joined. By joining as many soft magnetic parts of discontinuous material as possible, an optimal manufacturing can be achieved.

Preferably, two welds are arranged spaced apart from each other at one end of at least one cylinder. These welds are preferably welds. Such welds are preferably arranged parallel to each other. In particular, the spaced apart seams may be welded to the surface of an unprocessed material or workpiece from which the cylinder should be cut after welding.

Alternatively or additionally, the weld or welds may extend over the side surface of the post. This alternative may cause less eddy currents because the weld plane is not transverse to the magnetic flux as compared to the end surface of the weld cylinder.

More than one of the at least one weld may be disposed on the same surface side of at least one of the columns, which may be a side surface or an end surface or both. Further in the alternative, the weld may at least partially surround a side surface of the cylinder.

Preferably, the weld or welds are provided as welds. The slots may have a smaller cross-section than a weld covering the entire surface so that the slots may induce less additional eddy currents.

As with the cylinder, the backplate may comprise discontinuous soft magnetic material. Since the magnetic flux in the back plate is substantially transverse or perpendicular to the axis of rotation, the soft magnetic material of the back plate is preferably discontinuous in a cross section parallel to the axis of rotation. This case may be exceptional: the post and the backplate are manufactured as one piece. In addition to this, substantially all of the functions and explanations mentioned above with respect to the discontinuous material of the pillars are also valid for the back plate. For example, as with the cylinder, the back plate may be slotted, i.e., may be formed from a plurality of stacked sheets, and the sheets of the back plate are preferably electrically insulated from each other. The sheet of the back plate may extend substantially perpendicular to the sheet of the columns. As described above, eddy currents and thus heat generation and power consumption can be reduced. However, the back plate may alternatively be formed of a continuous, i.e. solid, soft magnetic material.

The back plate, like the cylinder, is preferably made of a soft magnetic material, such as electrical steel (magnetic steel) or other material suitable for closing the magnetic flux circuit, preferably cobalt steel. 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, the size of the cylinder is determined by the electromagnetic properties, depending on the application of the blood pump, 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 cylinder has a triangular cross-section transverse to the axis of rotation and the soft magnetic sheet of soft magnetic material is preferably oriented in or parallel to a plane passing through a bisector of the triangular cross-section. This orientation has the advantage that the longest soft magnetic sheet is arranged in the middle of the cylinder. In the mounted state of the cylinder, the bisector may extend through the radially innermost angle of the triangular cross-section and preferably further through the axis of rotation.

In a further aspect of the invention, a method of manufacturing a magnetic core, or a part of a magnetic core, for a drive unit of an intravascular blood pump is proposed. Which comprises the following steps carried out in sequence: providing a work piece comprising, or consisting of, a discontinuous soft magnetic material, the soft magnetic material being discontinuous in electrical conductivity in a cross section of the work piece and a magnetic core or a part of a magnetic core to be manufactured therefrom, providing a weld on a surface of the work piece such that the weld engages at least one discontinuity in electrical conductivity in the discontinuous soft magnetic material of the work piece, and separating the magnetic core or the part of the magnetic core from the work piece after the weld is provided.

At least a portion of the weld may remain at the post after separating the magnetic core or a portion of the magnetic core from the workpiece. Then, for example, sheets of laminated soft magnetic material may be firmly held together by the welding portion.

According to a preferred embodiment, the step of separating the magnetic core or a part of the magnetic core out of the workpiece comprises separating at least one of the cylinders out of the workpiece by Electrical Discharge Machining (EDM), in particular by wire cutting. Preferably, one dimension of the workpiece is pre-cut to the length of the cylinder before the cylinder is machined from the workpiece of soft magnetic material such that the pre-cut workpiece has an outer dimension equal to the length of the cylinder. At the end surfaces defining the length of the cylinder, welds may be provided before the cylinder is cut. For example, one or preferably two welds may be arranged spaced along each surface of the pre-cut workpiece that will later form the cross-sectional end surface of the cylinder to be cut from the workpiece. Preferably, all soft magnetic pieces of discontinuous soft magnetic material of the cylinder to be cut are electrically connected by the weld. The weld may extend over more than one cylinder cross-section to be cut from the workpiece. In particular, the weld seam preferably extends from one edge of the pre-cut workpiece to the opposite edge of the pre-cut workpiece, wherein it also extends through at least one section of the cylinder to be cut. More than one cylinder may be machined from a pre-cut workpiece. The section of the cylinder to be cut can be suitably distributed in the pre-cut material to utilize a high percentage of the material. As described above, the discontinuous soft magnetic material of the workpiece may be a laminate material comprising a stack of soft magnetic sheets. For example, the triangular cross-sections of two cylinders to be cut from a workpiece may be oriented: the bisectors of the angles in each triangular section are aligned with the stack plane of the soft magnetic material, wherein the bisectors are at a distance from each other and the angles of the triangular sections with the bisectors point in opposite directions. The above measures contribute to an efficient production of the cylinder from the workpiece.

Preferably, for a triangular column, the weld or welds may be arranged along one triangular side of the triangular cross-section of the column. The column can then be mechanically stabilized by this side. In this way, the laminated sheets of soft magnetic material may be electrically connected by the weld, preferably all of the sheets of the column.

Preferably, the at least one weld is produced by laser welding. Double laser welding may also be applied, whereby the weld is welded at least once more at the location of the weld. This may, for example, help to bridge the gap between two adjacent sheets of laminated soft magnetic material.

The cut-out magnetic core or a part of the magnetic core, in particular the cut-out cylinder, may be deburred at the at least one weld after separating the magnetic core or the part of the magnetic core out of the workpiece. The burrs may pierce the electrical insulation.

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 shows a spacer in a perspective view for the drive unit-impeller arrangement according to fig. 2;

FIG. 3B shows a front view of the spacer of FIG. 3A;

FIG. 3C shows a side view of the spacer of FIGS. 3A and 3B;

fig. 4A shows a perspective view of a first layer of a back plate with openings for the cylinders of the drive unit of the arrangement according to fig. 2;

fig. 4B shows a perspective view of a second layer of the back plate without openings for the cylinders of the drive unit of the arrangement according to fig. 2;

FIG. 4C shows a cross-sectional view of an assembled backplane comprising the first and second layers of FIGS. 4A and 4B;

fig. 5A to 5D show stages of manufacturing an intermediate product for further manufacturing the column of the drive unit according to the arrangement of fig. 2;

6A-6C illustrate welds on an intermediate product according to FIG. 5C;

fig. 7 shows a perspective view of a column separated from an intermediate product as prepared according to fig. 5A to 6C;

FIG. 8 shows a front view in plan of the intermediate product of FIG. 6A, with two welds and two sections of a cylinder to be cut from the intermediate product;

FIG. 9 shows a front view of an end surface of a cylinder with a weld;

figure 10 shows a cross-sectional view of a second embodiment of a drive unit-impeller arrangement;

fig. 11A to 11C show steps of manufacturing an integrated magnetic core for the drive unit according to fig. 10;

fig. 12A to 12C illustrate soldering portions on the integrated magnetic core manufactured according to fig. 11A to 11C; and

fig. 13A-13J 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, and the flexible sleeve 23 may 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, for example in wireless form.

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 having a spherical bearing surface allowing rotational as well as pivoting movement to a certain extent. 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 of the impeller 3 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.

As shown, the pillars 40 may be constructed of 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 spacer 7 is disposed around the column 40. It is made of a nonmagnetic material in order to maintain the distance between the columns 40 constant at the impeller-side end 420 of the columns 40. The spacer 7 will be described in more detail with respect to fig. 3A to 3C. The impeller-side end 424 of the coil winding 44 extends up to the spacer 7. A back plate 50 is provided at the other end of the column 40. According to the embodiment shown in fig. 2, the back plate 50 has a recess for receiving the post 40 therein. More specifically, it comprises a first layer 51 having an opening 511 for the rear end 450 of the cylinder 40. The back plate 50 will be described in more detail with respect to fig. 4A to 4C.

Embodiments of the blood pump 1 with any combination of the above features are conceivable: the wheel-side ends 424 of the columns do not extend radially beyond the wheel-side ends of the windings 44, nonmagnetic spacers 7 are provided between the columns 40, and the back plate 50 has a recess for receiving the rear end 450 of the column 40.

Fig. 3A to 3C show a perspective view, a front view, and a side view of the spacer 7, respectively. The spacer 7 has overall the form of a disc or wheel with a through hole 75 in the middle. The spacer 7 includes an opening 71 for each of the columns. For an embodiment having six columns 40, six openings 71 are present as shown. Between the openings 71, spacing spokes 72 are arranged. Spacing spokes 72 maintain the distance between posts 40 constant when posts 40 are inserted into openings 71. Further, spacer 7 includes an outer race 73 and an inner race 74 that connect adjacent spaced spokes 72 and stabilize the spacer. The spacer 7 is made of titanium, which is a paramagnetic material, avoiding magnetic short circuits when arranged between the impeller-side ends 420 of the cylinder 40. Titanium provides high mechanical strength so as to allow the spacer 7 to be manufactured with a small thickness. This is advantageous in view of the construction space occupied.

Fig. 4A shows a perspective view of the first layer 51 of the back sheet 50. The first layer 51 is generally disk or wheel shaped with a central aperture 515. The first layer 51 includes an opening 511 into which the rear end 450 of the post 40 is to be disposed. The first layer 51 includes spaced spokes 512 disposed between the openings 511. One purpose of spacing the spokes 512 is to keep the distance between the rear ends 450 of the posts 40 constant from each other. Further, the first layer 51 includes an outer ring 513 and an inner ring 514 connecting the spaced spokes 512 at a radially outer end and a radially inner end of the opening 511, respectively. The first layer 51 may be made of a discontinuous soft magnetic material discontinuous in electrical conductivity. It may be composed of several ferromagnetic sheets 85, in particular three sheets, as shown in fig. 4A. The sheet 85 is laminated with a non-conductive material to form a discontinuous soft magnetic material. The stacking direction DL is generally parallel to the sheets 85 and the main extension direction of the sheets defines a stacking plane. Within the back plate 50, the sheet 85 is perpendicular to the axis of rotation 10. In the middle of the first layer 51, an aperture 515 is arranged. The effect of this may be to ease the assembly of the first layer 51 with the second layer 52, e.g. to center the first layer 51 and the second layer 52.

In fig. 4B, a perspective view of the second layer 52 of the back plate 50 is shown. The second layer 52 has substantially the form of a disc with holes 525 in the middle corresponding to the holes 515 in the first layer 51. Second layer 52 does not have any openings for the rear ends of pillars 40. Instead, the second layer 52 has a contact flat 526 facing the rear end 450 of the post 40. The rear end 450 of the post is in contact with the contact plane 526 of the second layer 52 of the back plate 50 in the assembled state of the drive unit to transfer magnetic flux between the rear end 450 of the post 40 and the back plate 50. When all of the rear ends 450 of the pillars 40 are in contact with the contact plane 526, magnetic flux may be exchanged between the pillars 40, and a magnetic zero may be formed in the second layer 52. To enable this, the second layer 52 is made of a soft magnetic material. The soft magnetic material may be a discontinuous soft magnetic material that is discontinuous in electrical conductivity and may include sheets 85 laminated together, similar to the structure described above with respect to the first layer 51. As one example, three sheets 85 as shown in fig. 4B may constitute the second layer 52. In the second layer 52, the lamination direction DL is perpendicular to the rotation axis 10. The sheets 85 are ferromagnetic and electrically conductive, while the intervening layers (not explicitly shown) between the sheets 85 are non-ferromagnetic and electrically non-conductive. This type of discontinuous soft magnetic material reduces eddy currents that would otherwise be generated in greater amounts by the change in magnetic flux. The hole 525 in the middle of the second layer 52 may have the effect of facilitating the assembly of the first layer 51 with the second layer 52, e.g. centering the first layer 51 and the second layer 52.

Fig. 4C shows a cross section of the back plate 50. It consists of a first layer 51 and a second layer 52 bonded to each other at the major surface with the greatest extension. The bond between the first layer 51 and the second layer 52 of the backsheet 50 may be established in the same manner as between the sheets 85 of the first layer 51 and the second layer 52. The through-holes 515 of the first layer 51 and the through-holes 525 of the second layer 52 are aligned with each other to center the first layer 51 and the second layer 52. By stacking the first layer 51 and the second layer 52, the opening 511 is closed at one end by the second layer 52 such that a recess 501 is formed to accommodate the rear end 450 of the cylinder 40. On the bottom surface of the recess 501, a contact plane 526 is formed. When the cylinder 40 is inserted into the recess 501, its rear end 450 contacts the contact plane 526. Also, the position of cylinder 40 is fixed by spacing spokes 512 and outer and inner rings 513, 514, with spacing spokes 512, 513 and 514 surrounding each of cylinders 40 together. In this way, a magnetic connection is established between the second layer 52 and the rear end surface 45 of the pillar 40 at the contact plane 526, and additionally, a second magnetic connection is established between the pillar 40 and the surrounding portion of the above-mentioned first layer 51. However, most of the magnetic flux is transferred via the contact plane 526. Preferably, the surface at the rear end 450 of the cylinder 40 has a predefined flatness and the contact plane 526 also has a predefined flatness. In this way, the gap between the surface 45 at the rear end 450 of the post 40 and the contact plane 526 can be maintained below a certain size, preferably less than 10 μm. This improves the transfer of magnetic flux between the post 40 and the backplate 50. Preferably, there is no additional material between the surface 45 at the rear end 450 of the cylinder 40 and the contact plane 526. In this embodiment of the invention, the transfer of magnetic flux through the surface 45 and the backplate 50 is independent of the manner in which the posts 40 are secured to the backplate 50.

Fig. 5A to 5D show the preparatory steps for producing the column 40. Fig. 5A shows a perspective view of a plate 8 of discontinuous soft magnetic material, which is discontinuous in terms of electrical conductivity, also referred to as workpiece in the following.

In fig. 5A, the plate member 8 is indicated by a width W for cutting the workpiece bar 81 from the plate member 8. The width W of the work piece stem 81 is equal to the length of the cylinder 40 to be manufactured from the work piece stem 81. An enlarged view of the portion indicated by the rectangle R in fig. 5A is shown in fig. 5B. Here, the stacked discrete sheets 85 of soft magnetic material can be seen. The lamination direction DL extends along the main plane of the plate member 8 and thus forms a lamination plane.

Fig. 5C shows the workpiece bar 81 cut from the plate 8 as a single discrete piece of material. An enlarged view of the portion indicated by the rectangle R in fig. 5C is shown in fig. 5D. The sheet 85 of the workpiece bar 81 is visible in this enlarged view.

Fig. 6A shows the workpiece stem 81 of fig. 5C and 5D, which forms the basis of a welding step in preparation for cutting the cylinder 40 from the stem 81. On the side plane of the bar 81 directed to the left in fig. 6A, a plurality of sections 84 of the column 40 to be produced from the bar 81 are drawn. The cylinder 40 is manufactured by cutting these sections 84 out of the rod 81. Since the width W of the lever 81 corresponds to the length of the cylinder 40, the side surfaces 811 and 812 of the lever 81 become end surfaces at the rear end 450 and the impeller-side end 420 of the cylinder 40.

Fig. 6B shows the next pre-preparation step before cutting out the cylinder 40. Two welding seams 82 and 83 are welded at a distance from each other on the face 811 of the rod 81 and pass through each of the sections 84 of the cylinder 40 to be cut. The welds 82 and 83 extend perpendicular to the stacking direction DL of the sheets 85. In this way, the sheets of discontinuous material are connected to each other. Instead of two welds, a single weld may be provided. Otherwise, similar welds may be provided on the opposite side 812 of the stem 81. The sheets 85 have a better mechanical connection to each other due to the welds 82 and 83, but also by an electrical connection. The latter has the advantages that: the current may flow from any location where discontinuous soft magnetic material is desired to be the pillar 40 to a location of the stem 81 where each electrical connection may be required, for example, for electrical discharge machining. Thus, electric discharge machining is significantly facilitated. Also, higher processing reliability is achieved because the cut cylinder 40 is not frayed by delamination. Preferably, laser welding is applied. It may be advantageous to apply two or more welding powers to the same weld. The portion of the rod 81 indicated by the rectangle R is shown enlarged in fig. 6C.

Thus, fig. 6C shows a plurality of sections 84 of cylinder 40 to be cut from rod 81. The cross-section 84 has a substantially triangular shape. As shown, the corners may be rounded. The triangular convex side 842 shown on the left side of the cross-section 84 in fig. 6C has a convex form. This type of cross section 84 is advantageous in order to make full use of the available construction space inside the cylindrical pump housing 2. The bisector of angle 841 of section 84 opposite convex side 842 of section 84 is aligned with stacking direction DL. In this way, the sheet 85 extends symmetrically across the cross-section 84.

Fig. 7 shows cylinder 40 having been cut from rod 81. As can be seen at the surface 45 at the rear end 450 of the rod 81, the welds 82 and 83 are still present at this surface. The cylinder 40 has a constant cross-section 84 along its entire length. Welds 82 and 83 are deburred after cylinder 40 is cut.

Fig. 8 shows a further arrangement of two cross sections 84 on the side 811 of the workpiece bar 81. In contrast to the workpiece bar 81 shown in fig. 6A to 6C, the side surface 811 of the workpiece bar 81 of fig. 8 has a size that allows two cross sections 84 disposed beside each other in a direction perpendicular to the stacking direction DL. The sections 84 are oriented relative to the stacking direction DL such that a bisector B of an angle of each section 84 opposite its respective convex side 842 is aligned with the stacking direction DL. By providing the cross-section 84 along the rod 81 in this way, material can be saved. Less waste material is produced. It is contemplated that even more sections 84 of columns 40 are stacked in a direction perpendicular to stacking direction DL depending on the thickness of rods 81 and the desired cross-sectional dimensions of columns 40. Welds 82 and 83 each extend through each of sections 84. The weld seams 82, 83 also extend through the entire side 811 of the bar 81 in a direction perpendicular to the stacking direction DL. In this way, all the sheets 85 of discontinuous soft magnetic material of the rod 81 are connected to each other.

Fig. 9 shows a front view of one example of a cylinder 40 cut from a welded rod 81, i.e. one of the end surfaces of the cylinder 40. As shown in FIG. 9, a single weld 86 of substantial width may cover more than about one-third of the height of the triangular cross-section 84, which extends along the convex side 842 of the cross-section 84. The weld 86 extends perpendicular to the lamination direction DL to connect all its sheets. The bisector B of the angle 841 opposite the convex side 842 is again aligned with the stacking direction DL.

Fig. 10 shows a second embodiment of a drive unit-impeller arrangement for the blood pump 1 according to fig. 1. Similar to the first embodiment 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. 10 may comprise at least two, at least three, at least four, at least five or preferably six cylinders 40. A greater number of columns 40, such as eight, ten, 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.

This embodiment differs from the first embodiment shown in fig. 2 in the different structure of the magnetic core. Here, the magnetic core 400 comprises the magnetic components of the drive unit 4, which are the column 40 and the back plate 50, as one piece or unitary. The whole is composed of a discontinuous soft magnetic material. The discontinuous soft magnetic material is discontinuous in electrical conductivity. As shown, it comprises a plurality of sheets 85 of ferromagnetic material, the sheets 85 being laminated to each other to form an integral body 9 as shown in fig. 11C. The stacking direction DL is 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 a stop for the coil winding 44 towards the back plate 50. Because the integral 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 unitary 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. 11A to 11C show steps of manufacturing the magnetic core 400 of the drive unit 4 for the drive unit-impeller arrangement shown in fig. 10. Fig. 11A shows in perspective view a cuboid-shaped whole 9 which forms a workpiece for manufacturing the magnetic core 400. The whole 9 is composed 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. 11A-11C.

Fig. 11B shows the magnetic core 400 in a semi-manufactured state that has been processed, e.g. transformed from the cubic whole 9 into the 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. 11C. 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 central 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 backing plate 50. The entire magnetic core is thus formed by the whole 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. 12A to 12C show how one or more soldering portions may be provided on the surface of an integrated magnetic core as manufactured according to fig. 11A to 11C. Accordingly, in the embodiment shown, three welds 82, 83 are provided on one side of the cuboid entirety 9. The welds 82, 83 are welded at a distance from each other and through a section of the body 94 to be cut from the whole 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 whole 9 (not shown). Instead of or in addition to welds 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 also by an electrical connection. 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. 13A-13J illustrate various embodiments of the cylinder as seen in cross-section. Fig. 13A-13D illustrate an embodiment in which the cylinder is slotted, i.e., formed from a plurality of sheets 171 that are insulated from each other by an insulating layer 172. The insulating layer 172 may include an adhesive, lacquer, porcelain, or the like. Fig. 13A and 13B 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. 13A has a larger thickness than the sheet 171 shown in fig. 13B. The sheets in fig. 13C 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 improve the magnetic flux. The orientation of the sheet 171 may be different as exemplarily shown in fig. 13D as long as the soft magnetic material in the illustrated cross section, i.e., in a cross section transverse to the magnetic flux direction, is discontinuous or interrupted.

Fig. 13E and 13F show an embodiment 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. 13E, all wires have the same diameter, while in the embodiment of fig. 13F, the center wire has the largest diameter and the outer wires have smaller diameters, similar to the embodiment shown in fig. 13C with sheets of varying thickness. As shown in fig. 13G, 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. 13I, 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. 13J. This also provides a discontinuous cross-section in the sense of the present invention which reduces eddy currents in pillars 141 or pillars 40.