Patent ID: 8118543

Claim:
A centrifugal compressor for compressing gas, comprising: a casing; a rotary shaft supported by the casing; an impeller rotatably fixed to the rotary shaft, wherein the impeller sends the gas radially outward to a flow path downstream thereof; a diffuser formed around the impeller and defined by a pair of diffuser walls having the diffuser therebetween; a first scroll formed around the diffuser; a second scroll formed between the diffuser and the impeller; a first passage formed from the impeller to the first scroll through the diffuser; a second passage formed from the impeller to the second scroll; and a switching member for switching the flow path between the first passage and the second passage by opening and closing the diffuser, wherein the switching member includes a movable diffuser wall which is at least one of the pair of the diffuser walls, wherein the movable diffuser wall is moved closer to and away from the other of the pair of the diffuser walls so as to switch the flow path between the first passage and the second passage, wherein a wall surface of the movable diffuser wall facing the diffuser includes a diffuser wall surface and a scroll wall forming surface, wherein the scroll wall forming surface forms part of an inner surface of the second scroll.