Centrifugal pump apparatus

1. A centrifugal pump apparatus including a housing having first and second chambers partitioned from each other by a diaphragm, an impeller rotatably provided in said first chamber along said diaphragm, for delivering liquid by centrifugal force during rotation, and a drive unit provided in said second chamber for driving said impeller to rotate with said diaphragm being interposed, comprising:

a first magnetic element provided in one surface of said impeller;

a second magnetic element provided in an inner wall of said first chamber facing the one surface of said impeller, for attracting said first magnetic element; and

a third magnetic element provided in the other surface of said impeller and attracted by said drive unit,

during rotation of said impeller, first attractive force acting on between said first and second magnetic elements and second attractive force acting on between said third magnetic element and said drive unit being balanced with each other substantially in a center of a movable range of said impeller in said first chamber,

a first groove for hydrodynamic bearing being formed in one surface of said impeller or in the inner wall of said first chamber facing the one surface and a second groove for hydrodynamic bearing being formed in the other surface of said impeller or in said diaphragm facing the other surface,

a sidewall of said first chamber facing a side surface of said impeller being formed cylindrically, and

a centerline of said second magnetic element being arranged at a position different from that of a centerline of the sidewall of said first chamber such that a rotation centerline of said impeller matches the centerline of the sidewall of said first chamber during rotation of said impeller.

2. The centrifugal pump apparatus according to claim 1 , wherein

the centerline of said second magnetic element is arranged at a position distant in a prescribed direction by a prescribed distance from the centerline of the sidewall of said first chamber such that the rotation centerline of said impeller matches the centerline of the sidewall of said first chamber during rotation of said impeller, and

said prescribed distance is a distance over which, when the centerline of said second magnetic element is matched with the centerline of the sidewall of said first chamber, the rotation centerline of said impeller moves in a direction opposite to said prescribed direction from the centerline of the sidewall of said first chamber during rotation of said impeller.

3. The centrifugal pump according to claim 1 , further comprising

a cylindrical liquid outlet port provided to extend in a tangential direction of the sidewall of said first chamber, for allowing said liquid to flow outside said housing from an opening provided in the sidewall of said first chamber, wherein

the centerline of said second magnetic element is arranged on a side opposite to said opening when viewed from the centerline of the sidewall of said first chamber, such that the rotation centerline of said impeller matches the centerline of the sidewall of said first chamber during rotation of said impeller, and

if the centerline of said second magnetic element is matched with the centerline of the sidewall of said first chamber, the rotation centerline of said impeller moves in a direction of said opening during rotation of said impeller.

4. The centrifugal pump apparatus according to claim 3 , wherein

assuming that a direction of an end of said opening on an upstream side when viewed from the centerline of the sidewall of said first chamber is defined as 0 degree and an opposite direction is defined as 180 degrees, the centerline of said second magnetic element is arranged within a range of 135 degrees to 225 degrees.

5. The centrifugal pump apparatus according to claim 1 , wherein

said drive unit includes a plurality of coils provided to face said third magnetic element, for generating rotating magnetic field, and

a centerline of said rotating magnetic field matches the centerline of the sidewall of said first chamber.

6. The centrifugal pump apparatus according to claim 1 , wherein

said drive unit includes

a plurality of fourth magnetic elements provided to face said third magnetic element, and

a plurality of coils wound around said plurality of fourth magnetic elements, for generating rotating magnetic field, and

a centerline of said rotating magnetic field matches the centerline of the sidewall of said first chamber.

7. The centrifugal pump apparatus according to claim 1 , wherein

said drive unit includes

a rotor rotatably provided along said diaphragm in said second chamber,

a fourth magnetic element provided in said rotor to face said third magnetic element, for attracting said third magnetic element, and

a motor for rotating said rotor, and

a centerline of said rotor matches the centerline of the sidewall of said first chamber.

8. The centrifugal pump apparatus according to claim 1 , wherein

at least one of said first magnetic element and said second magnetic element includes a plurality of first sub magnetic elements aligned annularly.

9. The centrifugal pump apparatus according to claim 8 , wherein

each of said first and second magnetic elements is a permanent magnet,

each of said plurality of first sub magnetic elements is a permanent magnet, and

N poles of said plurality of first sub magnetic elements are oriented in a same direction.

10. The centrifugal pump apparatus according to claim 1 , wherein

at least one of said first magnetic element and said second magnetic element includes a plurality of annular second sub magnetic elements having diameters different from one another.

11. The centrifugal pump apparatus according to claim 10 , wherein

centerlines of said plurality of second sub magnetic elements match with one another.

12. The centrifugal pump apparatus according to claim 10 , wherein

each of said first and second magnetic elements includes said plurality of second sub magnetic elements,

each of said plurality of second sub magnetic elements is a permanent magnet, and

N poles of the plurality of second sub magnetic elements adjacent in a radial direction of said impeller are oriented in a same direction.

13. The centrifugal pump apparatus according to claim 12 , wherein

a sum of a distance between the centerline of said second magnetic element and the centerline of the sidewall of said first chamber and ½ of a movable distance of said impeller in the radial direction in said first chamber is smaller than ½ of an interval between two adjacent second sub magnetic elements.

14. The centrifugal pump apparatus according to claim 10 , wherein

each of said first and second magnetic elements includes said plurality of second sub magnetic elements,

each of said plurality of second sub magnetic elements is a permanent magnet, and

N poles of two second sub magnetic elements adjacent in a radial direction of said impeller are oriented in different directions.

15. The centrifugal pump apparatus according to claim 14 , wherein

a sum of a distance between the centerline of said second magnetic element and the centerline of the sidewall of said first chamber and ½ of a movable distance of said impeller in the radial direction in said first chamber is smaller than an interval between two adjacent second sub magnetic elements.

16. The centrifugal pump apparatus according to claim 1 , wherein

said liquid is blood, and

said centrifugal pump apparatus is used for circulating said blood.