Pump head of magnetic suspension blood pump

Abstract

The utility model discloses a pump head of a magnetic suspension blood pump, which relates to the technical field of medical instruments and comprises a pump casing and a rotor in the pump casing, a blood inlet is arranged at the center of the pump casing, an outlet pipe communicated with the inside of the pump casing is fixedly mounted on the side wall of the pump casing, the rotor and the blood inlet are coaxially arranged, and a permanent magnet is arranged in the rotor. An impeller is fixedly installed on the rotor, and the ratio of the diameter of the outer contour circle of blades of the impeller to the maximum diameter of the transverse cutting circle of the pump ranges from 0.7 to 0.9. The ratio range of the outer contour circle diameter of the impeller blades to the inscribed circle diameter of the pump shell is set to be 0.7-0.9, the hydraulic performance of the blood pump is guaranteed, and meanwhile damage to blood can be reduced as much as possible.

Description

Technical Field

[0001] This utility model relates to the field of medical device technology, and in particular to a magnetic levitation blood pump head. Background Technology

[0002] Currently, extracorporeal membrane oxygenation (ECMO) is a medical emergency device used to provide extracorporeal breathing and circulation for patients during cardiopulmonary surgery, such as in cases of severe cardiopulmonary failure or heart transplantation. In addition to temporarily replacing the patient's cardiopulmonary function and reducing the burden on the patient's heart and lungs, it can also buy more time for medical personnel to provide treatment.

[0003] As the power source for extracorporeal membrane oxygenation (ECMO) devices, the centrifugal pump's main function is to continuously draw venous blood from patients and pump it into the external circulation system using centrifugal force. As a type of centrifugal pump, the magnetic levitation blood pump includes a magnetic drive unit and a pump head. The pump head contains a rotor with an impeller. During operation, power is supplied to the magnetic drive unit, causing the rotor inside the pump head to rotate at high speed. The kinetic energy of the rotating impeller is transferred to the fluid, creating a high-pressure zone on the inner wall of the pump and a low-pressure zone in the center. The center of the magnetic levitation blood pump is the inlet, and the periphery is the outlet. Under the influence of this pressure difference, the liquid moves unidirectionally from the center to the periphery.

[0004] However, the flow gap between the outer contour circle of the impeller blades and the inner tangent circle of the pump head in a magnetic levitation blood pump can affect the hydraulic performance of the centrifugal pump and blood compatibility. When the flow gap is too large, the hemolytic activity will be better, but the hydraulic performance of the magnetic levitation blood pump will be compromised. When the flow gap is too small, the hydraulic performance of the magnetic levitation blood pump will be better, but the fluid velocity gradient will be large, resulting in a large shear force on the blood cells, which will damage the blood. Utility Model Content

[0005] The purpose of this invention is to provide a magnetic levitation blood pump head that can minimize damage to the blood while ensuring the hydraulic performance of the magnetic levitation blood pump.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a magnetic levitation blood pump head, comprising a pump housing and a rotor disposed within the pump housing, wherein a blood inlet is opened at the center of the pump housing, an outlet pipe communicating with the inside of the pump housing is fixedly installed on the side wall of the pump housing, the rotor is coaxially arranged with the blood inlet, a permanent magnet is disposed inside the rotor, and an impeller is fixedly installed on the rotor, wherein the ratio of the outer contour circle diameter of the impeller blades to the maximum diameter of the transverse circle of the pump housing is between 0.7 and 0.9.

[0007] The technical principle of this utility model is as follows: Based on the indicators of blood damage, the volume percentage of the scalar shear stress below 200Pa within the pump's flow range is higher than 99%, and the surface area percentage of the wall shear stress below 200Pa on all blood contact surfaces is about 90%. By setting the ratio of the outer contour circle diameter of the impeller blade to the maximum diameter of the cross-sectional circle of the pump casing between 0.7 and 0.9, the damage to the blood is minimal.

[0008] Furthermore, the blades in the impeller have a backward-curving blade shape.

[0009] Furthermore, the blade profile in the impeller is a binomial curve or a circular line. At the blade inlet position, the angle between the fluid velocity relative to the impeller and the circumferential velocity in the opposite direction is the blade inlet installation angle β1. At the blade outlet position, the angle between the fluid velocity relative to the impeller and the circumferential velocity in the opposite direction is the blade outlet installation angle β2. The values ​​of β1 and β2 are both in the range of 0-90°.

[0010] Furthermore, a top cover is fixedly installed on the side of the impeller away from the permanent magnet, and a gap is left between the top cover and the inner wall of the pump casing.

[0011] Furthermore, a protrusion that cooperates with the magnetic drive device is fixedly installed on the outer wall of the pump casing.

[0012] The beneficial effects of this utility model are as follows:

[0013] 1. Set the ratio of the outer diameter of the impeller blade to the maximum diameter of the cross-sectional circle of the pump casing between 0.7 and 0.9. This will ensure the hydraulic performance of the blood pump while minimizing damage to the blood.

[0014] 2. By setting the blade's backward blade shape and the settings of β1 and β2, the blade is made more in line with fluid dynamics, thereby further reducing damage to the blood.

[0015] 3. By designing the impeller as a closed impeller through the top cover, the upward axial force on the closed impeller is smaller, resulting in a smaller axial displacement of the impeller caused by hydraulic forces. Therefore, the axial position of the closed impeller is more stable and will not float significantly as the rotational speed increases. Within the same flow channel height, the height of the closed impeller can be appropriately higher than that of the open impeller, thereby achieving higher hydraulic performance. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of this utility model;

[0017] Figure 2 This is a cross-sectional view of the present invention;

[0018] Figure 3This is a schematic diagram of the rotor structure in this utility model.

[0019] Figure 4 This is a top view of the impeller in this utility model.

[0020] In the above attached figures:

[0021] 1. Pump housing; 101. Blood inlet; 102. Outlet pipe; 103. Protrusion; 2. Rotor; 3. Permanent magnet; 4. Blade; 5. Top cover. Detailed Implementation

[0022] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments; the structures described in various embodiments can be freely combined without conflict in terms of structure or principle.

[0023] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0024] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this utility model is in use. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0025] The following description, in conjunction with the accompanying drawings, describes some embodiments of the present invention:

[0026] like Figures 1-4As shown, this utility model proposes a magnetic levitation blood pump head, which includes a pump housing 1 and a rotor 2 disposed inside the pump housing 1. A blood inlet 101 is opened at the center of the pump housing 1. An outlet pipe 102 communicating with the inside of the pump housing 1 is fixedly installed on the side wall of the pump housing 1. The rotor 2 is coaxially arranged with the blood inlet 101. A permanent magnet 3 is disposed inside the rotor 2. An impeller 4 is fixedly installed on the rotor 2. The ratio of the outer contour circle diameter of the impeller 4 blades to the maximum diameter of the transverse circle of the pump housing 1 is between 0.7 and 0.9. An upper cover 5 is fixedly installed on the upper side of the impeller 4, and a gap is left between the upper cover 5 and the inner wall of the pump housing 1.

[0027] In this device, the diameter of the outer contour circle of the impeller 4 blades is D1, the maximum diameter of the transverse circle of the pump casing 1 is D2, the value of D1 ranges from 40-50 mm, the value of D2 ranges from 50-60 mm, the final distance between the blades and the inner wall of the pump casing 1 is between 0.45-0.65 mm, the distance between the upper cover 5 and the inner wall of the pump casing 1 is between 1.5-4 mm, and the distance between the bottom of the rotor 2 and the inner wall of the pump casing 1 is between 1.2-2 mm. According to the relevant calculation indicators of blood damage, the volume percentage of the pump's internal flow area with a scalar shear stress below 200 Pa is higher than 99%, and the surface area percentage of all blood contact surfaces with a wall shear stress below 200 Pa is approximately 90%.

[0028] This blood pump technology controls the ratio of the outer diameter of the impeller blades (4) to the maximum diameter of the transverse circle of the pump casing (1) within the range of 0.7-0.9. This meets the relevant calculation indicators for blood damage and ensures the hydraulic performance of the blood pump. Under normal clinical operating conditions, this blood pump causes minimal blood damage. When the ratio is less than 0.7, it indicates a smaller outer diameter of the blades. In this case, the blood pump causes less damage to the blood, but its hydraulic performance is insufficient. When the ratio is greater than 0.9, it indicates a larger outer diameter of the blades, ensuring the hydraulic performance of the blood pump. However, in this case, the gap between the blades and the pump casing is extremely small, which can cause greater damage to the blood. The formula required for this calculation process is existing technology and will not be elaborated here.

[0029] This device is suitable for use as an external ventricular assist system and can provide temporary hemodynamic support for patients with low cardiac output after cardiac surgery and patients with acute heart failure.

[0030] By configuring the top cover 5, the impeller 4 is designed as a closed impeller. At a rotational speed of 4000 rpm, a typical flow rate of 4 L / min is selected, which can meet most of the clinical needs for the indication. Using existing computational fluid dynamics simulation software, simulation calculations are performed on the structures of the closed and semi-open impellers:

[0031] 1. Semi-open impeller (the upper part of the impeller is open, and the lower part is connected to an annular plastic structure that accommodates the permanent magnet 3, hence it is a semi-open impeller);

[0032] 2. Closed impeller (the impeller has a top cover, and all blades are located between the top cover and the annular plastic structure that houses the permanent magnet 3, hence it is a closed impeller).

[0033] The two models are identical in pump body structure except for the impeller structure. Simulations compared the axial force on the impeller and the pump head in both models. The semi-open impeller in Model 1 experienced an axial force of 3.6 N (Y+ direction), while the closed impeller in Model 2 experienced an axial force of 1.2 N (Y+ direction), which is one-third the magnitude of the axial force on the impeller in Model 1. The axial force on the closed impeller is much smaller than that on the semi-open impeller. The full magnetic levitation technology used in this invention passively controls the axial position of the impeller. Axial fluid force causes the impeller to float. After balancing the axial fluid force, magnetic pull, and the gravity of rotor 2, rotor 2 will stabilize at a higher axial position. To prevent high shear forces near the upper surface of the impeller from damaging the blood, the distance between the upper surface of the impeller and the inner wall of the pump casing 1 must be greater than 1 mm. Therefore, within the same pump internal space, the blade height of the closed impeller can be higher without worrying about excessive upward displacement of rotor 2 leading to a gap of less than 1 mm between it and the pump casing 1.

[0034] The increased blade height and larger working area of ​​a single blade in a closed impeller improve the overall hydraulic performance of the impeller. This means that under the same rotational speed and flow rate conditions, a closed impeller pump will generate a higher head (pressure after pump - pressure before pump).

[0035] Simulation results show that the head of Model 1 is 346 mmHg, and the head of Model 2 is 364 mmHg. Because the closed impeller has taller blades and a larger working area, it generates a head approximately 18 mmHg higher than the open impeller. Therefore, the typical operating point of this blood pump is 4000 rpm, a flow rate of 4 L / min, and a head of 364 mmHg. Based on clinical experience, this can meet the requirements for extracorporeal blood circulation flow rate and head (used to resist the flow resistance of the extracorporeal circulation tubing, specifically determined by the cannula and tubing dimensions and the cannula insertion route).

[0036] Closed impellers experience less upward axial force, resulting in less axial displacement due to hydraulic forces. Consequently, the axial position of a closed impeller is more stable and does not exhibit significant upward movement as the rotational speed increases. Within the same flow channel height, the height of a closed impeller can be appropriately higher than that of an open impeller, thus achieving superior hydraulic performance.

[0037] The number of blades can be 4, 5, 6, 7, 8, 9, or 10. Increasing the number of blades improves hydraulic performance, but it also increases the blood contact area, potentially causing more severe blood damage. To ensure the hydraulic performance of the magnetic levitation blood pump while minimizing damage to the blood, 8 blades are preferred.

[0038] Unlike existing blood pumps, the blood pump in this technology does not have a flow guide cone structure, which has the following advantages:

[0039] 1. The secondary flow from the top cover 5 and the bottom surface of the rotor 2 returns to the wide central hole channel of the impeller 4 under the drive of the pressure difference. Here, the flow velocity decreases, but there is no stagnation zone. Compared to flow channels with guide cone structures, the risk of blood damage is lower.

[0040] 2. During the suspension and rotation of the impeller 4, the axial position will be offset. Since the guide cone structure is fixedly installed inside the pump casing 1, when the impeller 4 is lifted by hydraulic force, the relative position of the impeller 4 and the guide cone will change, deviating from the initial design. This may cause flow separation and small vortices, resulting in a loss of hydraulic efficiency and additional blood damage.

[0041] The pump housing 1 is a semi-circular ring formed by rotating a volute. The outer volute is concentric with the rotor 2. The outlet pipe 102 is tangent to the inner contour circle of the volute (i.e., the largest transverse circle of the pump housing 1). The diameter of the semi-circular volute is equal to the inner diameter of the outlet pipe 102. Therefore, there is no step at the junction of the volute and the outlet pipe 102, ensuring that blood flows smoothly from the volute into the outlet pipe 102. The inner side is a tongue-like part, which separates the fluid flowing inside the pump from the fluid about to flow out from the outlet.

[0042] Furthermore, such as Figure 3 and Figure 4 As shown, the blades in impeller 4 have a backward-curved blade profile, and the blade profile is a binomial curve or a circular line. At the blade inlet position, the angle between the fluid velocity relative to impeller 4 and the circumferential velocity in the opposite direction is the blade inlet installation angle β1, and at the blade outlet position, the angle between the fluid velocity relative to impeller 4 and the circumferential velocity in the opposite direction is the blade outlet installation angle β2. The values ​​of β1 and β2 are both in the range of 0-90°.

[0043] When β1 = β2 = 90°, the blade is a straight blade. The blade profile can be considered as a binomial curve with a quadratic coefficient of 0, or as a circular curve with an infinite diameter. This is a critical special case and can be considered a design choice. To minimize damage to the blood, the blade inlet installation angle β1 ranges from 45° to 65°, and the blade outlet installation angle β2 ranges from 60° to 80°. By setting the backward airfoil profile and the values ​​of β1 and β2, the blade is made more conform to fluid dynamics, thereby further reducing damage to the blood.

[0044] Furthermore, such as Figure 1 As shown, a protrusion 103 that cooperates with the magnetic drive device is fixedly installed on the outer side wall of the pump casing 1.

[0045] By setting the protrusion 103, the pump housing 1 can be fixedly installed on the magnetic drive device, thereby facilitating the rotation of the rotor 2 inside the pump housing 1.

Claims

1. A magnetically levitated blood pump head, characterized in that: The pump includes a pump housing (1) and a rotor (2) disposed inside the pump housing (1). A blood inlet (101) is opened at the center of the pump housing (1). An outlet pipe (102) communicating with the inside of the pump housing (1) is fixedly installed on the side wall of the pump housing (1). The rotor (2) is coaxially arranged with the blood inlet (101). A permanent magnet (3) is disposed inside the rotor (2). An impeller (4) is fixedly installed on the rotor (2). The ratio of the outer contour circle diameter of the impeller (4) blade to the maximum diameter of the transverse circle of the pump housing (1) is between 0.7 and 0.

9.

2. The magnetic levitation blood pump head according to claim 1, characterized in that, The blades in the impeller (4) have a backward-curving blade shape.

3. A magnetically levitated blood pump head according to claim 1 or 2, characterized in that, The blade profile in the impeller (4) is a binomial curve or a circular line. The angle between the velocity of the fluid relative to the impeller (4) and the circumferential velocity at the blade inlet position is the blade inlet installation angle β1. The angle between the velocity of the fluid relative to the impeller (4) and the circumferential velocity at the blade outlet position is the blade outlet installation angle β2. The values ​​of β1 and β2 are both in the range of 0-90°.

4. A magnetically levitated blood pump head according to claim 1 or 2, characterized in that, A top cover (5) is fixedly installed on the side of the impeller (4) away from the permanent magnet (3), and a gap is left between the top cover (5) and the inner wall of the pump casing (1).

5. A magnetically levitated blood pump head according to claim 3, characterized in that, A top cover (5) is fixedly installed on the side of the impeller (4) away from the permanent magnet (3), and a gap is left between the top cover (5) and the inner wall of the pump casing (1).

6. A magnetically levitated blood pump head according to claim 1, 2, or 5, characterized in that, A protrusion (103) that is designed to cooperate with the magnetic drive device is fixedly installed on the outer side wall of the pump casing (1).

7. A magnetically levitated blood pump head according to claim 3, characterized in that, A protrusion (103) that is designed to cooperate with the magnetic drive device is fixedly installed on the outer side wall of the pump casing (1).

8. A magnetically levitated blood pump head according to claim 4, characterized in that, A protrusion (103) that is designed to cooperate with the magnetic drive device is fixedly installed on the outer side wall of the pump casing (1).

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