PURPOSE: To suppress a weight increase and a cost up attaining the saving of space by providing a movable blade in an edge part of a stator impeller and a spring member which inhibits air from its inflow into the stator impeller.
CONSTITUTION: A movable blade 24, rotatably supported in its one end part to a stator blade 30, is provided in an edge part of a stator impeller 21 opposing its blade 30 facing to a rotor impeller 20. A torsional spring 54, which urges this movable blade 24 in such a manner as to prevent working fluid from its inflow into the stator impeller 21 inhibiting air from its inflow into the stator impeller 21, is provided. Thus enabling the saving of space to be attained, a weight increase and also a cost up can be suppressed.