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 via said diaphragm, comprising:

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

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

a plurality of third magnetic materials provided in the other surface of said impeller, and arranged along a single circle such that adjacent magnetic polarities thereof are different from each other, wherein

said drive unit includes

a plurality of fourth magnetic materials arranged to face said plurality of third magnetic materials, and

a plurality of coils provided correspondingly to said plurality of fourth magnetic materials, respectively, each being wound around a corresponding one of the fourth magnetic materials for generating a rotating magnetic field, and wherein

during rotation of said impeller, a first attractive force between said first and second magnetic materials and a second attractive force between said plurality of third magnetic materials and said plurality of fourth magnetic materials are balanced with each other substantially in a center of a movable range of said impeller in said first chamber;

a control unit that causes said impeller to contact said diaphragm prior to activation of said impeller to rotate, by causing a current to flow through said plurality of coils such that said second attractive force becomes higher than said first attractive force; and

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

wherein each of said first to third magnetic materials is a permanent magnet.

2. The centrifugal pump apparatus according to claim 1 , wherein a sum of an absolute value of a negative axial supporting rigidity value of said impeller which is constituted of said first and second attractive forces and an absolute value of a positive radial rigidity value of said impeller is smaller than an absolute value of a positive rigidity value obtained by said first and second grooves in a normal rotation speed range where said impeller rotates.

3. The centrifugal pump apparatus according to claim 1 , wherein a hydrodynamic pressure generated by said first grooves is different from a hydrodynamic pressure generated by said second grooves.

4. The centrifugal pump apparatus according to claim 1 , wherein at least one of said first and second grooves is an inward spiral groove.

5. The centrifugal pump apparatus according to claim 1 , wherein said fourth magnetic materials are made of a soft magnetic material.

6. The centrifugal pump apparatus according to claim 1 , wherein said control unit causes said impeller to contact said diaphragm when said impeller is activated to rotate, by causing a first current to flow through said plurality of coils, and then causes said impeller to rotate by causing a second current smaller than said first current to flow through said plurality of coils.

7. The centrifugal pump apparatus according to claim 1 , wherein a diamond-like carbon coating for reducing frictional force is formed on at least one of a surface of said impeller and the inner wall of said first chamber.

8. The centrifugal pump apparatus according to claim 1 , wherein surfaces facing each other of every two adjacent fourth magnetic materials are provided substantially parallel to each other.

9. The centrifugal pump apparatus according to claim 8 , further comprising a fifth magnetic material provided correspondingly to each of the fourth magnetic materials, on a tip surface of a corresponding one of the fourth magnetic materials facing one of said third magnetic materials, wherein

a surface of said fifth magnetic material facing said third magnetic material has an area larger than an area of the tip surface of said fourth magnetic material.

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

each of the fourth magnetic materials includes a plurality of steel plates stacked in a rotation direction of said impeller.

11. The centrifugal pump apparatus according to claim 1 , further comprising:

a magnetic sensor provided in said second chamber to face a path through which said plurality of third magnetic materials pass, for detecting variation in magnetic field associated with rotation and change of position of said impeller; and

a control unit for causing a current to flow through said plurality of coils based on a detection result from said magnetic sensor, to generate a rotating magnetic field to drive said impeller to rotate.

12. The centrifugal pump apparatus according to claim 11 , further comprising a first operation unit for determining an axial position of said impeller in said first chamber based on the detection result from said magnetic sensor.

13. The centrifugal pump apparatus according to claim 12 , wherein said first operation unit outputs information indicating the axial position of said impeller to outside.

14. The centrifugal pump apparatus according to claim 12 , further comprising a determination unit for determining whether or not the axial position of said impeller determined by said first operation unit is within a normal range, and outputting a signal indicating a determination result.

15. The centrifugal pump apparatus according to claim 1 , further comprising:

a first detection unit for detecting a voltage applied to each of the coils;

a second detection unit for detecting a current flowing through each of the coils; and

an operation unit for determining an axial position of said impeller in said first chamber based on detection results from said first and second detection units and information indicating a rotation speed of said impeller.

16. The centrifugal pump apparatus according to claim 15 , further comprising a determination unit for determining whether or not the axial position of said impeller determined by said operation unit is within a normal range, and outputting a signal indicating a determination result.

17. The centrifugal pump apparatus according to claim 15 , further comprising a determination unit for determining whether or not an axial position of said impeller is within a normal range based on the axial position of said impeller determined by said operation unit and the information indicating a rotation speed of said impeller, and outputting a signal indicating a determination result.

18. The centrifugal pump apparatus according to claim 15 , further comprising a determination unit for determining whether or not an axial position of said impeller is within a normal range based on the axial position of said impeller determined by said operation unit, the information indicating a rotation speed of said impeller, and viscosity information on said liquid, and outputting a signal indicating a determination result.

19. The centrifugal pump apparatus according to claim 1 , wherein said liquid is blood, and

said centrifugal pump apparatus is used for circulating said blood.

20. 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 via said diaphragm, comprising:

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

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

a plurality of third magnetic materials provided in the other surface of said impeller, and arranged along a single circle such that adjacent magnetic polarities thereof are different from each other, wherein

said drive unit includes

a plurality of fourth magnetic materials each stationary during rotation of said impeller and arranged to magnetically couple with said plurality of third magnetic materials, and

a plurality of coils provided correspondingly to said plurality of fourth magnetic materials, respectively, each being wound around a corresponding one of the fourth magnetic materials for generating a rotating magnetic field, and wherein

during rotation of said impeller, a first attractive force between said first and second magnetic materials and a second attractive force between said plurality of third magnetic materials and said plurality of fourth magnetic materials are balanced with each other substantially in a center of a movable range of said impeller in said first chamber;

a control unit that causes said impeller to contact said diaphragm prior to activation of said impeller to rotate, by causing a current to flow through said plurality of coils such that said second attractive force becomes higher than said first attractive force; and

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

wherein each of said first to third magnetic materials is a permanent magnet.

21. 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 via said diaphragm, comprising:

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

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

a plurality of third magnetic materials provided in the other surface of said impeller, and arranged such that adjacent magnetic polarities thereof are different from each other, wherein

said drive unit includes

a plurality of fourth magnetic materials arranged to face said plurality of third magnetic materials, and

a plurality of coils provided correspondingly to said plurality of fourth magnetic materials, respectively, each being wound around a corresponding one of the fourth magnetic materials for generating a rotating magnetic field, and wherein

during rotation of said impeller, a first attractive force between said first and second magnetic materials and a second attractive force between said plurality of third magnetic materials and said plurality of fourth magnetic materials are balanced with each other substantially in a center of a movable range of said impeller in said first chamber; and

a control unit that causes said impeller to contact said diaphragm prior to activation of said impeller to rotate, by causing a current to flow through said plurality of coils such that said second attractive force becomes greater than said first attractive force.