Patent ID: 7748964

Claim:
A centrifugal blood pump apparatus comprising: a housing having a blood inlet port and a blood outlet port; a centrifugal pump section including an impeller having a magnetic material and rotating inside said housing to feed a fluid by a centrifugal force generated during a rotation thereof; an impeller rotational torque generation section for attracting thereto said impeller of said centrifugal pump section and rotating said impeller; and a portion, in which a groove for hydrodynamic bearing is formed, provided on an inner surface of said housing at a side of said impeller rotational torque generation section or a surface of said impeller at said side of said impeller rotational torque generation section, said impeller being rotated without contacting said housing, wherein a plurality of grooves for hydrodynamic bearing are formed on said portion in which a groove for hydrodynamic bearing is formed; each of said grooves for hydrodynamic bearing has a first side and a second side both extending from a periphery of said portion in which a groove for hydrodynamic bearing is formed toward a central side thereof and opposed to each other, a third side connecting one end of said first side and one end of said second side to each other, and a fourth side connecting said other end of said first side and said other end of said second side to each other; said first side and said second side are formed as a circular arc respectively in such a way that centers of said circular arcs are different from each other; a value relating to a groove depth ratio a (a=h 1 /h 2 ) computed from a distance h 1 between said impeller and said housing in said groove for hydrodynamic bearing of said portion in which a groove for hydrodynamic bearing is formed during a rotation of said impeller and from a distance h 2 between said impeller and said housing in a hydrodynamic bearing groove-non-present portion of said portion in which a groove for hydrodynamic bearing is formed during said rotation of said impeller is in a range of 1.5 to 2.5; and a value relating to a groove width ratio s (s=B 0 /B) computed from a width B 0 of a peripheral portion of each groove for hydrodynamic bearing and a sum B (B=B 0 +B 1 ) of said width B 0 and a width B 1 of a hydrodynamic bearing groove-non-present portion between peripheral portions of adjacent grooves for hydrodynamic bearing is in a range of 0.6 to 0.8.