Intravascular blood pump

Abstract

To further reduce the package size of an intravascular blood pump and increase the service life of the blood pump.SOLUTION: The present invention relates to an intravascular blood pump including: a drive section (11); a catheter (14) fastened to the proximal side of the drive section; and a pump section (12) fastened distally of the drive section. The intravascular blood pump has an electric motor (21), of which motor shaft (25) is mounted in the drive section (11) with two radial sliding bearings (27, 31) and an axial sliding bearing (40). During operation, a rinsing fluid is conveyed through the bearing gap of the axial sliding bearing (40) and further through the radial sliding bearing (31) at the distal end of the drive section (11). The rinsing fluid is highly viscous, for example 20% glucose solution.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an intravascular blood pump for use in a human body, or optionally in an animal body, for assisting blood circulation, which is inserted, for example, in the femoral artery and guided through the vascular system of the body, for example to assist or replace the beating of the heart. The present invention also relates to a system including such an intravascular blood pump. [Background technology]

[0002] The requirements that such blood pumps must meet in terms of service life and miniaturization are increasing day by day. The smallest pumps of this type have an outer diameter of about 4 mm. Further reduction in the outer diameter is limited, in particular by the unavailability of the mechanical elements used in the pumps in the desired small size. Furthermore, the mechanical elements are subjected to high loads, since these pumps operate at high rotational speeds of tens of thousands of revolutions per minute, depending on the package size and the high blood flow rates that they carry in the human blood circulation. Although blood pumps of this type were originally intended for short-term cardiac support, they are increasingly being used for long-term treatments lasting several days or weeks.

[0003] From EP 0961621 B1 an intravascular blood pump is known which comprises a drive part, a catheter attached to the proximal end of the drive part and having lines extending therethrough for powering the drive part, and a pump part fixed to the distal end of the drive part. The drive part comprises a motor housing in which an electric motor is arranged, the motor shaft of which projects distally from the drive part into the pump part. The pump part itself comprises a tubular pump housing, which has an impeller which is installed at the end of the motor shaft projecting from the motor housing and rotates therein. The motor shaft is mounted in the motor housing on exactly two bearings which are maximally spaced apart from one another in order to ensure that the impeller is guided in the pump housing in an actual and exact central position. As bearings at the proximal end of the motor housing, radial ball bearings are actually used, while the bearings on the impeller side are additionally configured as shaft seals, preventing the ingress of blood into the motor housing. In practice, to further resist blood ingress into the motor housing, the purge fluid is forced past the motor housing and the impeller-side bearing configured as a shaft seal, at a purge fluid pressure higher than the prevailing blood pressure.

[0004] Intravascular blood pumps typically pump blood from the pump housing through the motor housing from distal to proximal; the reverse pumping direction is also possible. In either case, the impeller generates an axial force as it pumps blood, which is transmitted through the motor shaft to the bearings and received by the radial ball bearings. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] European Patent No. 0961621B1 Summary of the Invention [Problem to be solved by the invention]

[0006] Starting from this prior art, it is an object of the present invention to provide a method as to how to further reduce the package size of such an intravascular blood pump and extend its useful life. [Means for solving the problem]

[0007] This object is achieved by an intravascular blood pump having the features of patent claim 1. The dependent claims describe advantageous developments and embodiments of the invention, in each of which the blood circulation is assisted using an intravascular blood pump.

[0008] The blood pump according to the invention is characterized in that it is axially mounted in the motor housing by an axial bearing, which is an axial plain bearing or a radial-axial plain bearing. Therefore, the axial force of the motor shaft does not have to be supported by a radial ball bearing arranged at the proximal end of the motor housing. The radial ball bearing can therefore be correspondingly miniaturized or can be replaced by another compact radial bearing, in particular a radial plain bearing. This in turn makes it possible to develop blood pumps with even smaller outer diameters.

[0009] At the same time, this method results in a longer service life for the blood pump, since the radial bearings are less strained by the reduced axial forces that they were never intended to bear, thereby reducing the wear that they experience.

[0010] Alternatively, the present invention can be incorporated into current package sizes, resulting in longer usable life and less complexity.

[0011] The axial force acting on the motor shaft is opposite to the transport direction. When the blood pump is arranged to transport alternately in the proximal and distal directions, the axial force acts on the motor shaft, in one case in the distal direction and in the other in the proximal direction. In such blood pumps, therefore, two axial plain bearings or axial-radial plain bearings are installed in the motor housing for axial mounting of the motor shaft. An axial plain bearing can be simply formed by a disk mounted on the motor shaft and supported on a circumferential shoulder of the motor housing. In the case of an axial-radial plain bearing, the disk has a convex or concave, in particular spherical, bearing surface. Hereinafter, the term "axial plain bearing" is used synonymously for both types of axial plain bearings and radial-axial plain bearings.

[0012] The motor housing itself is filled with a fluid suitable for forming a lubricating film in the bearing gap of the axial plain bearing. Alternatively, the purge fluid supplied through the purge fluid supply line and flowing through the radial bearing installed at the distal end of the motor housing can be used to flow into the bearing gap of the axial plain bearing and form a lubricating film therein. In order to ensure that the purge fluid reaches the distal radial bearing at a pressure higher than the current blood pressure in this case, at least one of the surfaces forming the bearing gap of the axial plain bearing can be provided with a path passing through the bearing gap from the radial outside to the radial inside, through which the purge fluid flows to the distal radial bearing. This path does not necessarily have to be in the bearing gap surface, but can be realized as a separate path or as a hole. However, providing the path on one of the bearing gap surfaces has the advantage that the lubricating film in the bearing gap does not become too hot, since part of the lubricating film is always replaced by the purge fluid that flows afterwards. Preferably, the path is located on a stationary surface of the bearing gap, thereby minimizing the radial transport capacity.

[0013] Preferably, the axial plain bearing is configured as a hydrodynamic plain bearing. In contrast to radial plain bearings, hydrodynamic plain bearings generate pressure in the lubricating film through the pumping action of two surfaces that are moved relative to one another. For this purpose, according to a preferred embodiment. The bearing gap can be configured as a converging gap in a region in the circumferential direction of the axial plain bearing. In this connection, the moving surface is preferably flat, i.e. the opposite stationary surface of the bearing gap has an inclined portion that converges towards the moving surface in the direction of rotation of the moving surface. Thus, a wedge is formed in the bearing gap, into which the lubricating fluid is conveyed, as a result of which pressure is generated, which causes the moving surface to move against the stationary surface. In this state, sliding friction occurs on the fluid film, which friction practically does not cause wear. Since blood pumps usually transport at constantly high rotational speeds, they are particularly low-wear and therefore suitable for long-term use.

[0014] In the simplest embodiment, the moving disc can be configured as a wobble disc and simply through the ramps the converging gaps or wedges can be formed.

[0015] Instead of a bearing gap with converging surface areas, one of the surfaces forming the bearing gap can be provided with one or more spirally arranged grooves. In this case, the lubricating fluid is pumped along the grooves through the relative movement of the two surfaces towards the centre of the bearing, where pressure is generated which in turn moves the two surfaces against each other. In the embodiment of the bearing with spiral grooves, it is preferred to provide the moving surface with spirally arranged grooves, as this allows the lubricating fluid to be transported more effectively into the grooves.

[0016] For design reasons, the axial force of the pump unit (F ex rotor When the axial force F ) becomes larger than the load carrying capacity of the axial plain bearing, the axial force of the pump device can be partially compensated by a suitable axial arrangement of the rotary magnet in the motor. According to the invention, the rotary magnet acts like a solenoid and is forced to be centered in the motor stationary part by the magnetic force. When it is pulled out of this rest position, the magnetic force moves in the opposite direction (Fax magnet ) This force is generated in the direction of the axial force (F ax rotor ) to further stabilize it in the axial direction or in the opposite direction to unload the axial plain bearing. Furthermore, the resulting force on the axial bearing can be adjusted by varying the pressure of the purge fluid (see Figure 2).

[0017] It is further preferred that the surfaces forming the bearing gap of the axial plain bearing are made of ceramic, preferably zirconium oxide. Ceramic surfaces have high strength and low wear. In particular, the entire distal end of the motor housing, including the surfaces for the axial plain bearing, can simply be manufactured from one ceramic part, thereby reducing the overall manufacturing costs of the blood pump.

[0018] The lead wires of the electric motor received in the motor housing are usually wound around the outside of the proximal radial bearing and are conductively connected to the power supply wires running into the catheter. According to a preferred embodiment of the invention, the lead wires of the electric motor are then guided through the outer ring of the radial bearing or, advantageously, through one or more radially outward slots in the outer ring. This results in an overall radial space saving, which in turn is beneficial for the development of blood pumps with small outer diameters. It is thus possible to reserve space, for example, for pressure measurement, which can be carried out at the proximal end of the motor.

[0019] The lead wires can be advantageously soldered to the power supply wires proximal to the proximally located radial bearing of the motor housing. This is advantageous because direct electrical connection of the lead wires of an electric motor to the power supply wires can be difficult due to the thin lead wires and relatively thick power supply wires. If the relevant surfaces of the electric motor are made of plastic or ceramic, the solder location areas can be conductively coated, for example with copper, as described below, and then soldered, with the lead wires and supply wires being separately soldered in this area.

[0020] Preferably, the relevant parts of the motor housing are then potted in plastic and the solder locations and preferably also the motor windings are potted, whereby the solder locations are electrically insulated on the one hand and mechanically protected on the other hand.

[0021] According to a preferred development of the invention, the radial bearings for the motor shaft are also configured as plain bearings at the proximal and distal ends of the motor housing, respectively. These radial bearings can be configured as simple plain bearings, since they essentially only serve to guide the shaft exactly in the middle and are therefore only subjected to small radial forces. The overall radial space required for radial plain bearings is significantly smaller than that of rolling element bearings with their inner and outer rings. This also has an advantageous effect on the ability to manufacture blood pumps with small outer diameters.

[0022] In particular, the radial plain bearing is preferably arranged at the proximal end of the ceramic motor housing, so that the ceramic bearing bears directly against the circumferential surface of the motor shaft. The radial bearing installed at the distal end of the motor housing can also be configured in a corresponding manner. The surface of the motor shaft facing the ceramic surface, which together with the ceramic surface forms the bearing gap of the radial plain bearing, is preferably coated with an amorphous carbon coating (DLC = diamond-like carbon or diamond-like coating). DLC layers are particularly resistant to wear and have low friction. They are only a few micrometers thick and can be produced, for example, by chemical vapour deposition (CVD) or physical vapour deposition (PVD). Alternatively, the shaft can be made of a fracture-resistant ceramic.

[0023] In operation, the blood pump is attached to a purge fluid source and fluid is fed into the motor housing through a purge fluid line. The purge fluid then flows through the axial plain bearing and further distal radial bearing. In the axial plain bearing, it forms a lubricating film in the bearing gap. However, the pressure with which the purge fluid flows through the motor housing has a detrimental effect on the width of the bearing gap, because the higher the purge fluid pressure, the smaller the width of the bearing gap and the thinner the lubricating film between the sliding surfaces. The thinner the lubricating film, the higher the motor current required to drive the electric motor, which in turn overcomes the frictional forces. This is detrimental to the control of the blood pump, because the current transport quantity is usually determined by a stored characteristic curve based only on the motor current and the rotational speed, both of which are known quantities. If the pressure of the purge fluid also affects the motor current, the extent of other influences would have to be taken into account. In view of the fact that the same type of blood pump can be used for various applications where the pressure of the purge fluid varies between 300 and 1400 mmHg, it is important to avoid a dependency of the motor current on the purge fluid pressure.

[0024] This is achieved in practice when choosing as purge fluid a fluid with a viscosity much higher than that of water (η = 0.75 mPa·s at 37 °C). In the case of a highly viscous purge fluid, the fluid film is maintained even at high pressures and therefore the friction of the axial plain bearing is not dominated by the pressure of the purge fluid. It turns out that if the viscosity of the purge fluid is around 1.2 mPa·s at 37 °C or higher, the axial plain bearing can be configured as a simple plain bearing and does not have to be configured as a hydrodynamic plain bearing. For example, good results were obtained when using a glucose solution with a concentration of 20% or more between ceramic surfaces made of zirconium oxide.

[0025] One embodiment of the present invention is a drive (11) having a motor housing (20) having a proximal end and a distal end, and an electric motor (21) disposed within the motor housing, the electric motor having a motor shaft (25) having one end protruding from the distal end of the motor housing (20) and mounted radially (27, 31) within the motor housing at both the proximal and distal ends of the motor housing, and a wire (23) connected to the proximal end of the motor housing (20) and extending therealong for powering the electric motor. In an intravascular blood pump (10) including a pump section (12) having a catheter (14) extending therefrom, a tubular pump housing (32) fixed to the distal end of a motor housing (20), and an impeller (34) protruding from the distal end of the motor housing and seated on the end of a motor shaft (25) rotatable within the pump housing (32), the motor shaft (25) is axially mounted within the motor housing (20) by at least one axial plain bearing (40) or radial-axial plain bearing (46).

[0026] Desirably, the axial plain bearing (40) or radial-axial plain bearing (46) is mounted on the motor shaft (25) and comprises a disk (44) supported on a circumferential shoulder of the motor housing (20).

[0027] Desirably, a purge fluid line (29) is included, which is arranged so that fluid supplied through the purge fluid line flows through the bearing gaps of the axial plain bearing (40) and the radial bearing (31) located at the distal end of the motor housing, or the bearing gaps of the radial-axial plain bearing (46).

[0028] Desirably, at least one of the surfaces (41, 42) forming the bearing gap of the axial plain bearing (40) or the radial-axial plain bearing (46) has a passage (43) passing through the bearing gap from the radial outside to the radial inside.

[0029] In an intravascular blood pump, preferably, the bearing clearance of the axial plain bearing (40) or the radial-axial plain bearing (46) is configured as a clearance that converges in a certain region in the circumferential direction.

[0030] Desirably, of the surfaces (42, 41) which form the bearing gap of the axial plain bearing (40) or the radial-axial plain bearing (46), the moving surface (42) is flat.

[0031] Desirably, at least one of the surfaces (41, 42) forming the bearing gap of the axial plain bearing (40) or the radial-axial plain bearing (46) has one or more grooves (45) arranged in a spiral manner.

[0032] Desirably, the moving surface (42) of the surfaces (41, 42) forming the bearing gap of the axial plain bearing (40) or the radial-axial plain bearing (46) has grooves arranged in a spiral manner.

[0033] Preferably, the surfaces (41, 42) forming the bearing gap of the axial plain bearing (40) or the radial-axial plain bearing (46) are made of ceramic.

[0034] Preferably, the radial bearing (27) mounted at the proximal end of the motor housing (20) has an outer ring, and the lead wires (51) of the electric motor (21) extend through the outer ring or within slots (50) located radially outward of the outer ring.

[0035] Desirably, the lead wires (51) of the electric motor (21) and the wires (23) extending along the catheter (14) are conductively connected onto a surface (52) located proximally of the radial bearing (27) at the proximal end of the motor housing.

[0036] Preferably, the motor housing is at least partially a cast plastic housing, and the soldered portions (52) are also cast.

[0037] Desirably, at least one of the radial bearings (27, 31) of the motor shaft (25) is configured as a radial plain bearing at the proximal and distal ends of the motor housing (20).

[0038] Preferably, in at least one radial plain bearing, one of the surfaces forming the bearing gap is a ceramic surface and the corresponding other of the surfaces forming the bearing gap is an amorphous carbon coating (DLC).

[0039] Desirably, the system includes an intravascular blood pump and a purge fluid source for supplying a fluid having a viscosity of 1.2 mPa·s or greater at 37° C. to the purge fluid line.

[0040] A related art method of the present invention is a method of assisting blood circulation using an intravascular blood pump, in which the viscosity of the fluid supplied to the purge fluid line is 1.2 mPa·s or more at 37°C.

[0041] Desirably, the purge fluid is a 20% or greater glucose solution.

[0042] The invention will now be described, by way of example only, with reference to the accompanying drawings in which: [Brief description of the drawings]

[0043] [Figure 1] FIG. 1 is a schematic diagram of a blood pump inserted anteriorly into the left ventricle and its blood removal cannula positioned within the left ventricle. [Diagram 2] 1 is a schematic longitudinal cross-sectional view of an exemplary embodiment of a blood pump. [Diagram 3] FIG. 3 is an enlarged view of detail III of FIG. 2; [Figure 4] FIG. 4 is a modified version of detail III from FIG. 3 . [Diagram 5] FIG. 3 is an enlarged view of detail IV of FIG. 2. [Figure 6A] 1 shows a plan view and development of an axial plain bearing surface according to a first exemplary embodiment; [Figure 6B] 1 shows a plan view and development of an axial plain bearing surface according to a first exemplary embodiment; [Figure 7] FIG. 4 is a cross-sectional view of an axial plain bearing according to a second exemplary embodiment. [Figure 8] FIG. 13 is a plan view of an axial plain bearing surface according to a third exemplary embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] FIG. 1 shows the use of a blood pump 10 to assist the left ventricle. The blood pump includes a motor section 11 and a pump section 12, which are arranged axially one behind the other, resulting in a rod-like configuration. The pump section is extended by a flexible suction hose 13, which has openings at its end and / or its side wall through which blood can enter the pump. The end of the blood pump 10 facing away from the suction hose 13 is connected to a catheter 14, which is inserted into the aortic arch 15a and the aorta 16. The blood pump 10 is placed so that it is primarily in the ascending aorta 15b, and the pump section 12 together with the suction hose 13 is substantially in the left ventricle 17. When the aortic valve 18 is closed, it is in contact with the pump housing or the outside of the suction hose 13. The blood pump 10 with the suction hose 13 at its front is advanced to the position shown by advancing the catheter 14, optionally using a guidewire. While doing so, the suction hose 13 passes in the reverse direction through the aortic valve 18, whereby blood is sucked into the suction hose 13 and pumped into the aorta 16. Up to this point, the blood pump corresponds to the blood pump known from EP 0 961 621 B1.

[0045] The use of the blood pump is not limited to the application shown in Figure 1, which is merely an example of a general application, therefore the pump can also be inserted into other peripheral blood vessels, for example the subclavian artery, or placed in the right heart.

[0046] FIG. 2 shows a preferred exemplary embodiment of a blood pump having a motor section 11 and a pump section 12 firmly connected thereto. The motor section 11 has an elongated housing 20 in which an electric motor 21 is housed. The stator 24 of the electric motor 21 has, in the usual way, a number of circumferentially distributed windings and a longitudinal magnetic return path 28. This is firmly connected to the motor housing. The stator 24 surrounds a rotor 26 consisting of an active magnetized permanent magnet connected to a motor shaft 25. The motor shaft 25 extends the entire length of the motor housing 20 and projects distally therefrom. It then carries an impeller 34 having blades 36 or pump vanes projecting therefrom which rotate within a tubular pump housing 32, which itself is firmly connected to the motor housing 20.

[0047] The proximal end of the motor housing 20 has a flexible catheter 14 hermetically attached thereto. An electric cable 23 for powering and controlling the electric motor 21 extends through the catheter 14. A purge fluid line 29 also extends through the catheter 14, which passes through the proximal end wall 22 of the motor housing 20. Purge fluid is supplied from the purge fluid line 29 to the interior of the motor housing 20 and exits at an end face 30 at the distal end of the motor housing. The purging pressure is selected such that it is higher than the prevailing blood pressure, thereby preventing the ingress of blood into the motor housing, which may be between 300 and 1400 mmHg depending on the particular application.

[0048] When the impeller 34 rotates, blood is sucked into the end suction opening 37 of the pump housing 32 and is transported axially backwards in the pump housing 32. Through the outlet 38 of the pump housing 32, the blood leaves the pump section 12 and flows further along the motor housing 20. This ensures that heat generated in the drive section is removed. It is also possible to operate the pump section in the opposite transport direction, whereby blood is sucked along the motor housing 20 and leaves through the opening 37.

[0049] The motor shaft 25 is mounted in radial bearings 27 and 31 at the proximal end of the motor housing on the one hand and at the distal end of the motor housing on the other hand. The radial bearings are each configured as simple plain bearings in this exemplary embodiment. Furthermore, the motor shaft 25 is also mounted axially in the motor housing 20. The axial bearing 40 is likewise configured as a plain bearing. The axial bearing 40 will be described in more detail below with respect to FIG. 3. It serves to take up the axial force of the motor shaft 25 acting in the distal direction when the impeller 34 is conveyed from the distal side to the proximal side. If the blood pump is used to transport blood in the reverse direction as well or only in the reverse direction, a corresponding axial plain bearing 40 (also / only) is installed in a corresponding manner at the proximal end of the motor housing 20.

[0050] The blood pump according to Fig. 2 can alternatively be used for short periods of a few hours without purge fluid, by providing a one-time supply of lubricant to the plain bearings and further providing a radial lip seal at the distal plain bearing 31 to prevent blood ingress. Advantageously, the purge fluid line can then be omitted altogether.

[0051] Figure 3 shows detail III of figure 2 in more detail. In particular, the radial plain bearing 31 and the axial plain bearing 40 can be seen. The bearing gap of the radial plain bearing 31 is formed on the one hand by the circumferential surface of the DLC-coated motor shaft 25 and on the other hand by the through-bore surface of the distal end wall 30 of the motor housing 20, which is manufactured as a ceramic part, for example from zirconium oxide.

[0052] The bearing gap of the axial plain bearing 40 is formed on the one hand by the axial inner surface 41 of the end wall 30 and on the other hand by the opposing surface 42. This opposing surface 42 is part of a ceramic disk 44, which is mounted on the motor shaft 25, distal to the rotor 26, and rotates with it. A channel 43 in the bearing gap surface 41 of the end wall 30 allows the purge fluid to pass between the bearing gap surfaces 41 and 42 of the axial plain bearing 40, to the radial plain bearing 31 and to exit distally from the motor housing 20. The purge fluid is selected to have a viscosity of at least 1.2 mPa·s at 37° C. A suitable fluid has been found to be, for example, a 20% glucose solution. The axial plain bearing 40 shown in FIG. 3 is a normal plain bearing. A variant of a hydrostatic plain bearing will be described below with reference to FIGS. 6A / B, 7, 8. In contrast to the figures, the axial gap of the axial plain bearing 40 is very small, amounting to a few μm.

[0053] Instead of the axial plain bearing 40 and the radial plain bearing 31, a combined radial-axial plain bearing 46 can be realized, which has a concave bearing shell, in which the convex surface moves. Such a variant is shown in FIG. 4 by a spherical plain bearing 46. The bearing gap surface 41 is of spherical concave design, and the opposing bearing gap surface 42 is of corresponding spherical convex design. The channel 43 is again in this case in the stationary bearing gap surface 41 of the end wall 30. Alternatively, the stationary bearing gap surface 41 of the end wall 30 can be convex, and the opposing bearing gap surface 42 can be concave. The surfaces 42, 43 can also be conical, rather than spherical. Preferably, corresponding radial-axial plain bearings are installed on both sides of the motor housing 20, so that no radial displacement occurs when the shaft 25 moves axially. The advantage of a combined axial-radial plain bearing is a higher load capacity. However, the disadvantage is a larger friction diameter.

[0054] 5 shows a radial bearing 27 at the distal end of the motor housing 20. The motor shaft 25 again runs in a bearing bush which is covered with a DLC coating and which forms an integral part of the proximal end wall 22, again made of ceramic, of the motor housing 20. Up to this point, the radial plain bearing 27 corresponds to the radial plain bearing 31.

[0055] The end wall 22 is provided with three axially extending slots 50 spaced 120° apart around its circumference, only one of which is visible in FIG. 5. Thin lead wires 51 run through these slots 50 to the windings of the stator 24. The lead wires 51 are soldered to the proximal side of the end wall 20 at solder locations 52 which have previously been made conductive by a local copper coating. At the same solder locations 52, the ends of the power supply wires 23 are also soldered. The connection of the wires of the stator windings to the power supply wires can be performed by any conventional joining method (soldering, welding, clamping, laser welding, gap welding, contact bonding, etc.). The end wall 22 including the lead wires 51 and the solder locations 52 is then encapsulated in a plastic material, and the motor windings of the stator are also encapsulated at the same time. This can be done, for example, by vacuum casting.

[0056] The blood pump described above does not require a radial ball bearing for mounting the motor shaft 25, which is difficult to mount and has a size of at least 3 mm. As a result, a smaller pump can be manufactured, for example with an outer diameter of only 3 mm. Furthermore, the service life of this blood pump is significantly longer compared to one with a radial ball bearing, due to the reduced wear. Hence, an operating time of more than 30 days can be achieved with little wear. The latter is crucial, since the mounting and correct operation of the impeller is important to limit hemolysis.

[0057] FIG. 6A shows in plan view the surface 41 of the distal end wall 30 of the motor housing 20 according to an alternative exemplary embodiment. FIG. 6B shows a development of the surface 41 of FIG. 6A. The surface 41 itself is stationary. The direction indicated by the arrow indicates the direction in which the opposing surface 42 of the plain bearing 40 moves. This also corresponds to the direction in which the lubricant film moves in the bearing gap relative to the stationary surface 41. The surface 41 thus has inclined portions arranged behind each other, which together with the opposing flat moving surface 42 form a converging gap. As a result, hydrodynamic pressure is generated in the lubricant film, which keeps the surfaces forming the bearing gap apart.

[0058] The configuration of the rotating surface with a ramp-like structure according to figures 6A and 6B is advantageous for the efficiency of the axial plain bearing, but leads to a large radial transport effect in the bearing gap, which opposes the transport direction of the purge fluid. Figure 7 shows the simplest configuration for the realization of the convergent gap with a ramp in the form of a wobble disk. Here, the disk 44 is simply placed on a ramp or is slightly inclined. The amount of inclination is typically 1-5 μm.

[0059] Figure 8 shows another variant of the hydrodynamically acting surface of an axial plain bearing 40. This involves a bearing with so-called spiral grooves, which are preferably formed in the moving surface of the bearing gap, and thus in the surface 42 of the ceramic disc 44. In this case, several grooves 45 are arranged spirally in the surface 42. The grooves 45 are only shown diagrammatically in Figure 8. When the ceramic disc 44 rotates in the direction indicated by the arrow in Figure 8, the lubricant film is carried radially inwards along the grooves 45 and generates a pressure there, which keeps the surfaces forming the bearing gap apart.

Claims

1. An intravascular blood pump (10), comprising: a drive (11) having a motor housing (20) having a proximal end and a distal end, and an electric motor (21) disposed within the motor housing, the electric motor having a motor shaft (25) having one end protruding from the distal end of the motor housing (20) and radially (27, 31) mounted within the motor housing at both the proximal and distal ends of the motor housing, one or both of a radial bearing (27) at the proximal end of the motor shaft (25) and a radial bearing (31) at the distal end of the motor housing (20) being a radial plain bearing, the motor shaft (25) being axially mounted within the motor housing (20) by at least one axial plain bearing (40) or radial-axial plain bearing (46); a catheter (14) connected to a proximal end of said motor housing (20) and having wires (23) extending along it for powering said electric motor; a pump section (12) having a tubular pump housing (32) fixed to a distal end of the motor housing (20) and an impeller (34) projecting from the distal end of the motor housing and seated on an end of the motor shaft (25) rotatable within the pump housing (32); In an intravascular blood pump (10), one or more surfaces forming a bearing gap of said axial plain bearing (40) or said radial-axial plain bearing (46) are made of ceramic; An intravascular blood pump, wherein in at least one of the radial plain bearings (27, 31), one of the surfaces forming the bearing gap is a ceramic surface and the corresponding other of the surfaces forming the bearing gap is an amorphous carbon coating (DLC), or both.

2. 2. The intravascular blood pump according to claim 1, The axial plain bearing (40) or the radial-axial plain bearing (46) comprises a disk (44) mounted on the motor shaft (25) and supported on a circumferential shoulder of the motor housing (20).

3. 3. The intravascular blood pump according to claim 2, The disk (44) is a ceramic disk.

4. The intravascular blood pump according to any one of claims 1 to 3, An intravascular blood pump including a purge fluid line (29) arranged such that fluid supplied through the purge fluid line flows through the bearing gaps of the axial plain bearing (40) and the radial bearing (31) located at the distal end of the motor housing, or through the bearing gaps of the radial-axial plain bearing (46).

5. The intravascular blood pump according to any one of claims 1 to 4, At least one of the surfaces (41, 42) forming a bearing gap of the axial plain bearing (40) or the radial-axial plain bearing (46) has a passage (43) penetrating the bearing gap from the radial outside to the radial inside.

6. The intravascular blood pump according to any one of claims 1 to 5, An intravascular blood pump, wherein the bearing clearance of the axial plain bearing (40) or the radial-axial plain bearing (46) is configured as a clearance that converges in a certain region in the circumferential direction.

7. 7. The intravascular blood pump according to claim 6, An intravascular blood pump, wherein the moving surface (42) of the surfaces (42, 41) forming the bearing gap of the axial plain bearing (40) or the radial-axial plain bearing (46) is flat.

8. The intravascular blood pump according to any one of claims 1 to 5, At least one of the surfaces (41, 42) forming a bearing gap of the axial plain bearing (40) or the radial-axial plain bearing (46) has one or more grooves (45) arranged in a spiral manner.

9. 9. The intravascular blood pump according to claim 8, An intravascular blood pump, wherein a moving surface (42) of the surfaces (41, 42) forming a bearing gap of the axial plain bearing (40) or the radial-axial plain bearing (46) has one or more grooves arranged in a spiral.

10. The intravascular blood pump according to any one of claims 1 to 9, The intravascular blood pump, wherein the ceramic is zirconium oxide.

11. The intravascular blood pump according to any one of claims 1 to 10, An intravascular blood pump, wherein the radial bearing (27) at the proximal end of the motor housing (20) has an outer ring, and lead wires (51) of the electric motor (21) extend through the outer ring or in slots (50) located radially outward of the outer ring.

12. 12. The intravascular blood pump according to claim 11, An intravascular blood pump, wherein the lead wires (51) of the electric motor (21) and the wires (23) extending along the catheter (14) are conductively connected onto a surface positioned proximally of the radial bearing (27) at the proximal end of the motor housing.

13. 13. The intravascular blood pump of claim 12, An intravascular blood pump, wherein the motor housing is at least partially a cast plastic housing, and the conductive connection (52) between the lead wire (51) and the wire (23) extending along the catheter (14) is cast onto a surface positioned proximally of the radial bearing (27) at the proximal end of the motor housing (20).

14. The intravascular blood pump according to any one of claims 1 to 13, An intravascular blood pump, wherein the entire distal end of the motor housing (20), including the surfaces of at least one of the axial plain bearing (40) and the radial-axial plain bearing (46), is manufactured from a single ceramic component.

15. The intravascular blood pump according to any one of claims 1 to 14, At least one of the axial plain bearing (40) and the radial-axial plain bearing (46) is formed from an axial inner surface (41) of an end wall (30) of the motor housing (20) and a facing surface (42) consisting of a ceramic disc (44) that seats on the motor shaft (25) distal to the rotor (26) and rotates with the rotor (26).

16. The intravascular blood pump according to any one of claims 1 to 15, an end wall (30) of the motor housing (20) and a corresponding other of the surfaces forming the bearing gap of the at least one radial plain bearing (27, 31) which is formed by a circumferential surface of the motor shaft (25) having a DLC coating;

17. The intravascular blood pump according to any one of claims 1 to 15, The motor shaft (25) is made of ceramic, and in the at least one radial plain bearing (27, 31), one of the surfaces forming the bearing gap is a ceramic surface, and the other of the surfaces forming the bearing gap corresponding to this is formed by the ceramic motor shaft (25).

18. 18. The intravascular blood pump according to claim 16 or 17, The ceramic surface is formed by a through hole in a distal end wall of the motor housing.

19. 18. The intravascular blood pump according to claim 16 or 17, The ceramic surface is defined by a bearing bushing that forms an integral part of a proximal end wall of the motor housing.

20. 5. A system comprising the intravascular blood pump of claim 4 and a purge fluid source for supplying to said purge fluid line a fluid having a viscosity of 1.2 mPa·s or greater at 37°C.

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