TURBINE FOR SUPERCHARGER AND METHOD FOR ASSEMBLING SUPERCHARGER

A purpose of the invention is to reduce size and weight and to make assembly easier while maintaining high response performance or the like required for a turbocharger for an automobile. A rotor blade upstream flow channel space s2 of a cylindrical portion 22 is gradually reduced from an upstream side toward a downstream side in a swirling direction of exhaust gas e in accordance with a reduction in volume of a scroll chamber s1. That is, a back plate 24 is formed so as to swell out to a rotor blade side gradually from the upstream side toward the downstream side in the swirling direction of the exhaust gas e in accordance with the reduction in volume of the scroll chamber s1. The swelling amount of the back plate 24 approaches a rotor blade 16 beyond a communication portion d, and reaches a position adjacent to a leading edge 16a of the rotor blade 16 at a termination end thereof. Therefore, the flow channel space s2 disappears substantially at this termination end.