Centrifugal pump apparatus

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

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

a fluid outlet port for allowing said fluid to flow to the outside of said housing from an opening provided in a sidewall of said first chamber, wherein

during rotation of said impeller, a first attractive force acting between said first and second magnetic elements and a second attractive force acting between said third magnetic element and said drive unit are 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 is formed in the 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 is formed in the other surface of said impeller or in said dividing wall facing the other surface,

at least one of said first and second magnetic elements is formed annularly around a rotation centerline of said impeller, and

the first attractive force on an opening side of said sidewall is set to be different from the first attractive on an opposite side from said opening side of said sidewall such that said impeller becomes parallel to said dividing wall during rotation of said impeller.

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

the first attractive force on said opening side is set to be smaller than the first attractive force on the opposite side of said opening.

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

said second magnetic element is a permanent magnet formed annularly around the rotation centerline of said impeller, and

a thickness of said second magnetic element on said opening side is smaller than a thickness of said second magnetic element on the opposite side from said opening.

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

said second magnetic element is a permanent magnet formed annularly around the rotation centerline of said impeller, and

a facing area of said first and second magnetic elements on said opening side is smaller than a facing area of said first and second magnetic elements on the opposite side from said opening.

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

said second magnetic element is a permanent magnet formed annularly around the rotation centerline of said impeller, and

a notch is provided in said second magnetic element on said opening side.

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

said first magnetic element includes a plurality of first permanent magnets that are different in diameter from each other and are each formed annularly, and

said second magnetic element includes a plurality of second permanent magnets that are different in diameter from each other and are each formed annularly.

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

first magnetic poles of said plurality of second permanent magnets are all oriented in a direction of said impeller, and second magnetic poles of said plurality of second permanent magnets are all oriented in an opposite direction of said impeller, and second magnetic poles of said plurality of first permanent magnets are provided to face the first magnetic poles of said plurality of second permanent magnets, respectively,

the centrifugal pump apparatus further comprising:

a fourth magnetic element attracted to a predetermined region on said opening side, of the second magnetic poles of said plurality of second permanent magnets.

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

a first magnetic pole of one of two adjacent second permanent magnets is oriented in a direction of said impeller, and a second magnetic pole of the other second permanent magnet is oriented in the direction of said impeller, and magnetic poles of said plurality of first permanent magnets are arranged to attract magnetic poles of said plurality of second permanent magnets, respectively,

the centrifugal pump apparatus further comprising:

a fourth magnetic element attracted to a predetermined region on the opposite side of said opening, of the magnetic poles of said plurality of second permanent magnets on an opposite side of said impeller.

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

a sidewall of said first chamber facing a side surface of said impeller is formed cylindrically, and assuming that a direction of an end of said opening on an upstream side when viewed from a centerline of the sidewall of said first chamber is 0 degree and an opposite side thereof is 180 degrees, said opening side is said 0-degree direction side when viewed from the centerline of the sidewall of said first chamber, and the opposite side of said opening is said 180-degree direction side when viewed from the centerline of the sidewall of said first chamber, and

an attractive force between said first and second magnetic elements within a range of 0 degree through A degree, where the A degree is an angle that is larger than 0 degree and smaller than 180 degrees, when viewed from the centerline of the sidewall of said first chamber is smaller than an attractive force between said first and second magnetic elements outside the range.

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

said drive unit includes a plurality of stator coils arranged annularly to face said third magnetic element of said impeller, for generating a rotating magnetic field and rotating said impeller, and

a centerline of the rotating magnetic field generated by said plurality of stator coils matches a centerline of the sidewall of said first chamber.

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

said drive unit includes:

a plurality of fifth magnetic elements arranged annularly to face said third magnetic element of said impeller; and

a plurality of stator coils wound around said plurality of fifth magnetic elements respectively, for generating a rotating magnetic field and rotating said impeller, and

a centerline of the rotating magnetic field generated by said plurality of stator coils matches a centerline of the sidewall of said first chamber.

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

said drive unit includes:

a rotor rotatably provided along said dividing wall in said second chamber;

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

13. A centrifugal pump apparatus including a housing having first and second chambers partitioned from each other by a dividing wall, an impeller rotatably provided in said first chamber along said dividing wall, for delivering fluid by centrifugal force during rotation, and a drive unit provided in said second chamber, for driving said impeller to rotate with said dividing wall being interposed, the centrifugal pump apparatus 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;

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

a fluid outlet port for allowing said fluid to flow to the outside of said housing from an opening provided in a sidewall of said first chamber, wherein

during rotation of said impeller, a first attractive force acting between said first and second magnetic elements and a second attractive force acting between said third magnetic element and said drive unit are 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 is formed in the 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 is formed in the other surface of said impeller or in said dividing wall facing the other surface,

each of the first and second magnetic elements is formed annularly around a rotation centerline of said impeller, and

a corner of an end surface of said first or second magnetic element is chamfered such that the first attractive force on said opening side becomes smaller than the first attractive force on an opposite side of said opening when said impeller becomes eccentric toward said opening side due to hydrodynamic force.

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

an outer-circumferential-side corner of the end surface of said second magnetic element is chamfered.

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

an inner-circumferential-side corner of the end surface of said first magnetic element is chamfered.

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

said drive unit includes a plurality of stator coils arranged annularly to face said third magnetic element of said impeller, for generating a rotating magnetic field and rotating said impeller, and

a centerline of the rotating magnetic field generated by said plurality of stator coils matches a centerline of the sidewall of said first chamber.

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

said drive unit includes:

a plurality of fourth magnetic elements arranged annularly to face said third magnetic element of said impeller; and

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

a centerline of the rotating magnetic field generated by said plurality of stator coils matches a centerline of the sidewall of said first chamber.

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

said drive unit includes:

a rotor rotatably provided along said dividing wall 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 rotation centerline of said rotor matches a centerline of the sidewall of said first chamber.

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

a centerline of said second magnetic element is arranged at a position different from that of a 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.

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

said fluid is blood, and

said centrifugal pump apparatus is used for circulating said blood.