JP2013212218A - Centrifugal blood pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shape of a kinetic pressure groove of a highly precise radial kinetic pressure bearing, which is used as a kinetic pressure groove of a radial kinetic pressure bearing of a centrifugal blood pump and used as an alternative to an existing spiral groove, can be easily machined or stamped in injection molding, and is manufactured while saving a manufacturing cost and time.SOLUTION: A centrifugal blood pump includes a casing equipped with an inflow port and an outflow port, and a vaned wheel for sending a liquid from the inflow port to the outflow port by rotation in the casing. In the pump, a kinetic pressure groove which is a radial kinetic pressure bearing for generating a kinetic pressure between the static shaft of the inner cylinder of the casing and the inner circumference of the rotating vane has a multirobe shape of the rotating surface shape, and the shaft direction shape is such that the groove portion is parallel to the rotating shaft.

Description

  The present invention relates to a centrifugal blood pump for artificial heart, auxiliary circulation, and cardiac surgery, and has a feature in the structure of a bearing. Further, it can be used as a medical pump, a biological pump, an industrial pump, or the like other than those for artificial heart, auxiliary circulation and cardiac surgery.

In recent years, with the advancement of medical technology and the like, centrifugal blood pumps have been used as pumps for artificial heart, auxiliary circulation, and heart surgery.
For example, in the centrifugal blood pump described in Patent Document 1, the contact bearing is devised to be supported by a single spherical contact bearing in order to reduce that the contact bearing becomes an obstacle to blood and the flow is delayed and a thrombus is generated. Is given.
However, in the case of contact bearings, the flow of blood is inevitably stagnated in that part, and it is not possible to generate thrombus. Many centrifugal blood pumps used have been proposed, for example, as in Patent Documents 2-6.
In Patent Document 2, a hydrodynamic hydrodynamic bearing which is a non-contact bearing is adopted as a thrust direction (axial direction) bearing and a radial direction (radial direction) bearing, and the hydrodynamic bearing is spiral in both the thrust direction and the radial direction. A groove is used.
In Patent Document 3, a hydrodynamic thrust bearing, which is a non-contact bearing, is used as the thrust direction bearing, and in the radial direction, the magnetic interaction between the motor stator and the magnetic region of the impeller is a radial impeller. This is done by creating rigidity and corresponds to a magnetic bearing which is a so-called non-contact bearing. In addition, it does not have a rotation fixed shaft inside the casing.
In Patent Document 4, the non-contact bearing in the thrust direction is a combination of a hydrodynamic thrust bearing with a dynamic pressure groove and the attractive force of a plurality of permanent magnets, and the non-contact bearing in the radial direction is permanent as in Patent Document 3 above. This is realized by increasing the support rigidity by the magnetic attraction force of the magnet (it hits a so-called magnetic bearing).
Patent Document 5 was filed earlier by the present applicant and the like, and employs hydrodynamic hydrodynamic bearings that are non-contact bearings for thrust direction bearings and radial direction bearings. It is a spiral groove shape.
Patent Document 6 was filed earlier by the present applicant and employs hydrodynamic hydrodynamic bearings that are non-contact bearings for thrust direction bearings and radial direction bearings. The groove shape.

JP 2004-144070 A JP 2005-61543 A Special table 2010-525871 gazette JP 2010-209691 A JP 2004-245303 A JP 2009-254436 A

As described above, in order to realize long-term use of a centrifugal blood pump, a centrifugal blood pump using a magnetic bearing and a dynamic pressure bearing that are non-contact bearings has been developed. However, a pump using a magnetic bearing requires a displacement sensor for impeller levitation and a complicated electric circuit for feedback, which not only complicates the system but also reduces long-term reliability. . On the other hand, since the pump using a dynamic pressure bearing employs a passive bearing, a displacement sensor and an electric circuit for impeller levitation are not required, and the safety and long-term reliability are high. Moreover, since the number of strands of the electric cable connecting the motor and the driver is small, there is little risk of disconnection.
Conventionally, when a dynamic pressure bearing is provided to stabilize the centrifugal blood pump in the radial direction, a herringbone dynamic pressure bearing having a spiral groove shape has been mainly used. However, in the spiral groove shape, it is necessary to form a dynamic pressure groove on the side surface of the bearing, and in the case of cutting, it is necessary to perform cutting from the side surface of the bearing. In the case of injection molding using a mold, it is necessary to pull out the product while rotating the mold in the same direction as the spiral groove. Therefore, the increase in manufacturing cost, the deterioration of the groove shape accuracy, and the increase in manufacturing time are problems. In addition, in order to increase the force generated by the dynamic pressure groove, the bearing gap between the fixed shaft and the rotary shaft is narrowed, or the edge and groove portion of the dynamic pressure groove are sharpened. There is a way to increase the local pressure. Generally, in an industrial dynamic pressure bearing such as a hard disk, the bearing gap is about several μm. However, in centrifugal blood pumps that use blood as the working fluid, erythrocyte blood cell destruction and thrombus formation due to high shear stress in narrow bearing gaps and sharp edges and grooves, such as industrial dynamic pressure bearings, are major problems. ing.

In order to solve the above problems, the present invention provides a casing having an inlet and a radially outer outlet in the center, an impeller rotatably accommodated in the casing, and a casing lower center in the casing inward. The inner cylinder has a recessed inner cylinder, and the inner cylinder supports a rotating impeller as a fixed shaft, and is built in the impeller and a permanent magnet that is rotated by a motor in a space surrounded by the inner cylinder of the casing. A rotary drive device in which a magnetic coupling is formed through a partition wall of an inner cylinder of a casing with a permanent magnet, a vane that is provided at the top of the impeller and sends out liquid from the inlet toward the outlet by rotation of the impeller; A centrifugal blood pump comprising a thrust dynamic pressure bearing composed of an impeller upper and lower surface and a casing inner surface facing the impeller, and a radial dynamic pressure bearing composed of an inner cylinder and an inner peripheral surface of the impeller facing the inner cylinder. The upper portion of the impeller projects into the upper space of the inner cylinder end surface of the casing, and the radial dynamic pressure bearing is formed on either the outer peripheral surface of the cylinder or the inner peripheral surface of the impeller facing the cylindrical outer peripheral surface. The dynamic pressure groove is characterized in that the in-plane shape is a multi-arc shape, and the axial shape is such that the groove portion is parallel to the rotation axis.
In the centrifugal blood pump, the present invention is characterized in that blood compatibility is improved by setting a minimum bearing clearance of the radial dynamic pressure bearing to 10 μm or more.
In the centrifugal blood pump, the present invention is characterized in that at least one of the multi-arc-shaped edge portion and the groove portion of the dynamic pressure groove is subjected to R processing or chamfering processing.
In the centrifugal blood pump, the present invention is characterized in that a metal or a polymer material is used as a material of a portion forming the dynamic pressure groove of the radial dynamic pressure bearing.

ADVANTAGE OF THE INVENTION According to this invention, the displacement blood sensor and electric circuit for impeller levitation | floating are unnecessary, and the centrifugal blood pump with high safety | security and high long-term reliability can be provided. As for the production surface of the blood pump, compared with a centrifugal blood pump having a radial dynamic pressure groove with a conventional spiral groove, in the present invention, the radial in-plane shape of the radial bearing is a multi-arc shape, and the axial direction Since the groove part is parallel to the rotation axis, it is easy to cut only in the bottom direction or die-cut at the time of injection molding with a mold, so a highly accurate bearing shape can be achieved while reducing production cost and production time. Can be provided.
Further, by expanding the bearing gap between the fixed shaft and the rotating shaft to 10 μm or more, preferably 50 μm or more, it is possible to solve blood compatibility problems such as hemolysis and thrombus formation.
Furthermore, by carrying out R machining or chamfering on the edge or groove of the bearing, a bearing without a sharp corner or groove can be formed, so that hemolysis due to high shear sites and thrombus formation in the groove can be suppressed.
In addition, according to the centrifugal blood pump of the radial dynamic pressure bearing type of the present invention, the dynamic pressure bearing (non-contact bearing) is more effective than the circular journal bearing (non-contact bearing) used in other artificial hearts. ) Is large, stable driving can be realized.

Sectional drawing of one Example of the centrifugal blood pump of this invention. It is a figure explaining a multi-arc-shaped dynamic pressure radial bearing, Comprising: The bottom view of the 4 arc bearing added to the fixed shaft (Left: inner peripheral side is fixed axis, right: outer peripheral side is fixed shaft). It is a figure explaining a multi-arc-shaped dynamic pressure radial bearing, Comprising: The bottom view of the 4 arc bearing added to the rotating shaft (Left: inner peripheral side is fixed axis, right: outer peripheral side is fixed axis). It is a figure explaining a multi-arc-shaped dynamic pressure radial bearing, Comprising: The bottom view of the 4-arc bearing by which R process was given to the edge added to the fixed shaft. It is a figure explaining the dynamic pressure radial bearing of a multi-arc shape, Comprising: The bottom view of the 4-arc bearing which gave R process to the groove part added to the fixed shaft. The comparative example by the numerical fluid analysis of the radial bearing rigidity of the perfect circular radial bearing (what is called journal bearing) added to the conventional fixed shaft and the multi-arc shape dynamic pressure radial bearing (in the case of 4 arcs) of the present invention. The comparative example of the hemolytic index which shows the bearing clearance gap and the amount of hemolysis in a centrifugal blood pump (pump types AF).

The present invention includes a permanent magnet that rotatably accommodates an impeller in a casing having an inlet and a radially outer outlet in the center, and is driven to rotate by a motor in a space surrounded by an inner cylinder of the casing; It has a permanent magnet built in the impeller, and the impeller is driven to rotate by magnetic coupling through the partition of the inner cylinder of the casing, and the liquid from the inlet is made into the outlet by the vane provided in the upper part of the impeller. The centrifugal blood pump uses a hydrodynamic bearing for the thrust direction bearing and radial direction bearing of the impeller, and the upper part of the impeller projects into the upper space of the inner cylinder end surface of the casing and moves in the radial direction. As a pressure bearing, the in-plane shape of the rotation surface is a multi-arc shape, and the axial shape is characterized in that the groove portion is parallel to the rotation axis.
Since the groove portion of the radial dynamic pressure bearing is parallel to the rotation axis, the radial dynamic pressure bearing can be easily manufactured by cutting only the axial direction of the cylindrical surface or die-cutting during injection molding with a mold (while rotating Therefore, it is possible to provide a highly accurate bearing shape while reducing the manufacturing cost and time, and the generated force of the hydrodynamic bearing is large. The thrust dynamic pressure bearing on the upper surface of the impeller can be expanded to extend toward the top of the impeller, and the generated force of the dynamic pressure bearing is large. Less stable rotation can be obtained.
In addition, blood compatibility is improved by setting the minimum gap between the fixed shaft and the rotating shaft in the multi-arc radial radial dynamic pressure bearing portion to 10 μm or more, preferably 50 μm or more. If R processing or chamfering is applied to at least one of the multi-arc shaped edge or groove, blood compatibility can be further improved.

A cross-sectional view of one embodiment of the centrifugal blood pump of the present invention is shown in FIG. The casing has an inflow port at the center and an outflow port on the radially outer side, and rotatably accommodates the impeller inside the casing. An inner cylinder recessed inward of the casing is provided at the center of the casing lower part, and the inner cylinder supports a rotating impeller as a fixed shaft. The rotational driving of the impeller is performed by the inner cylinder of a permanent magnet (driving magnet) that is rotationally driven by a motor in a space surrounded by the inner cylinder of the casing and a permanent magnet (driven magnet) built in the impeller. This is performed by magnetic coupling through a partition wall. When the impeller rotates, blood from the inflow port is sent out toward the outflow port by a vane provided at the upper part of the impeller. Both the thrust direction bearing and the radial direction bearing of the impeller are non-contact bearings using dynamic pressure bearings. The configuration described so far is the same as the above-mentioned Patent Document 6 filed by the applicant. In order to make the explanation easy to understand, the upper direction is expressed as “up” and the lower direction is expressed as “lower” in FIG. 1. For example, in the case of a centrifugal blood pump for an artificial heart, the posture of the human body changes. Therefore, “upper” and “lower” are used for convenience.
The characteristic configuration of the present invention is in the structure of the radial dynamic pressure bearing, and the dynamic pressure groove provided on the outer peripheral surface of the inner cylinder of the casing that is the fixed shaft of the impeller has a multi-circular shape in the rotational surface. The axial shape is characterized in that the groove portion is parallel to the rotation axis. In other words, it can be said that the outer peripheral surface shape of the cylinder is formed in a spline shaft shape having grooves parallel to the axial direction, and the cross section of the spline shaft has a multi-arc shape. For this reason, radial dynamic pressure bearings can be manufactured by cutting only in the axial direction of the cylindrical surface, or can be easily removed during injection molding with a mold, reducing production costs and production time. The bearing shape can be provided, and the generated force of the hydrodynamic bearing is large. Although FIG. 1 shows the case where the dynamic pressure groove is formed on the inner cylinder side of the casing, the same applies when the dynamic pressure groove is formed on the inner peripheral surface on the impeller side. The multi-arc radial dynamic pressure bearing will be described in detail in the description of FIGS.
Another characteristic configuration of the present invention is that the upper part of the impeller protrudes into the upper space of the inner cylinder end face of the casing as shown in FIG. 1, and for this reason, the thrust dynamic pressure formed on the upper face of the impeller The dynamic pressure groove of the bearing can be formed in a large area, and the generated force is large. Also, since there is an overhanging portion, stable rotation can be obtained with little shaft runout during rotation. It is also advantageous that the vane can be taken longer by the amount of overhang. The thrust dynamic pressure bearing formed on the upper and lower surfaces of the impeller has no problem even if a conventional dynamic pressure groove is used. For example, the same spiral shape as in Patent Document 6 may be used. In FIG. 1, the dynamic pressure grooves of the thrust dynamic pressure bearing are formed on the upper and lower surfaces of the impeller, but may be formed on the inner surfaces of the opposing casings.

2 and 3 are diagrams for explaining a radial dynamic pressure bearing having a multi-arc shape (four arc shapes in the figure) according to the present invention, both of which show the shape of the shaft and the hole in the rotation surface. Although not shown, it is needless to say that the axial shape is such that the groove portion is parallel to the rotation axis. 2 and 3 show an example of a four-arc bearing, but the same is true when the number of arcs of the arc-bearing is changed to two arcs, three arcs, and five arcs.
Fig. 2 shows an example in which a dynamic pressure groove is provided on the fixed side. The left figure shows the case where the shaft is fixed and the hole rotates (counterclockwise in the figure). The right figure shows the case where the hole is fixed and the shaft is fixed. The case of rotation (clockwise in the figure) is shown, and what is shown in FIG. 1 of the present invention corresponds to the left figure.
FIG. 3 is an example in which a dynamic pressure groove is provided on the rotation side, the left figure shows a case where the hole is fixed and the shaft rotates (clockwise in the figure), and the right figure shows a case where the shaft is fixed and the hole ( The case of rotating counterclockwise in the figure is shown.

FIG. 4 is a view in which R processing is applied to the edge portion of the multi-arc shape (4 arc shape in the figure) of the present invention, and FIG. It is the figure which gave the process.
Moreover, it may replace with R process of FIG.4 and FIG.5, and a chamfering process may be given.

  FIG. 6 shows a numerical fluid analysis of the bearing rigidity in the radial direction of a conventional radial bearing (so-called journal bearing) added to a fixed shaft and a multi-arc dynamic pressure radial bearing (in the case of four arcs) according to the present invention. The vertical axis represents normalized radial force, the horizontal axis represents the revolution radius, ● represents the four-arc shape of the present invention, and ◆ represents a conventional journal bearing. From the figure, it can be seen that the generated force by the multi-arc shaped dynamic pressure groove of the present invention is larger in the four-arc shaped dynamic pressure bearing of the present invention than the conventional bearing.

  FIG. 7 is a diagram showing a comparison of the hemolytic index indicating the bearing clearance and the amount of hemolysis in the centrifugal blood pump (pump types A to F) according to the present invention. / 100L) is indicated by a broken line, but there is no problem if it is practically about 0.05 (g / 100L) or less. The bearing gap is represented by the minimum bearing gap. For each pump model A to F, the hemolysis index (g / 100 L) is indicated by a shaded bar graph, and the bearing clearance (μm) is indicated by a black bar graph. In FIG. 7, the bearing gap increases in order from A to F. As the bearing gap increases, the hemolysis index decreases, and from the figure, it is 0.01 (g / 100 L) or less, which is no problem as a blood pump. It is understood that a bearing clearance of about 50 μm or more between E type and F type may be formed. It should be noted that when it is 0.05 (g / 100 L) or less, which has no practical problem, it is sufficient to form a bearing clearance of approximately 10 μm or more between the B type and the C type.

  The centrifugal blood pump of the present invention is used for artificial heart, auxiliary circulation, and cardiac surgery, but other medical pumps, biological pumps for culturing and transporting chemicals, do not generate wear. It can also be used as an industrial pump.

Claims (4)

A casing having an inlet at the center and an outlet at the radially outer side, an impeller rotatably accommodated inside the casing, an inner cylinder recessed inward of the casing at the center of the casing, As a fixed shaft, a permanent magnet that supports a rotating impeller and is driven to rotate by a motor in a space surrounded by the inner cylinder of the casing, and a permanent magnet built in the impeller, over the partition of the inner cylinder of the casing A rotary drive device having a magnetic coupling formed thereon, a vane provided at the top of the impeller for sending liquid from the inlet toward the outlet by rotation of the impeller, an upper and lower surfaces of the impeller, and an inner surface of the casing facing the vane A centrifugal blood pump comprising a configured thrust dynamic pressure bearing, and a radial dynamic pressure bearing composed of an inner cylinder and an inner peripheral surface of an impeller facing the inner cylinder,
The impeller upper part protrudes into the upper space of the inner cylinder end surface of the casing,
The radial dynamic pressure bearing is composed of a dynamic pressure groove formed on one of a cylindrical outer peripheral surface and an inner peripheral surface of an impeller opposed to the cylindrical outer peripheral surface. A centrifugal blood pump characterized in that an axial shape is such that a groove portion is parallel to a rotation axis.   The centrifugal blood pump according to claim 1, wherein blood compatibility is improved by setting a minimum bearing clearance of the radial dynamic pressure bearing to 10 µm or more.   3. The centrifugal blood pump according to claim 2, wherein at least one of the multi-arc-shaped edge portion and the groove portion of the dynamic pressure groove is subjected to R processing or chamfering processing.   The centrifugal blood pump according to claim 3, wherein a metal or a polymer material is used as a material of a portion forming the dynamic pressure groove of the radial dynamic pressure bearing.