Abstract: A turbocharger includes a compressor housing having an accommodation depression, a return passage, a ring member, and a covering member mounted to the compressor housing. The return passage has an inlet, an outlet, and a communication passage through which the inlet is connected to the outlet. A bottom surface of the accommodation depression has an inlet forming surface that cooperates with the ring member to form the inlet. The communication passage is formed between an inner peripheral surface of the accommodation depression and an outer peripheral surface of the ring member. The covering member has a falling prevention portion and an outlet forming surface. The outlet forming surface cooperates with the ring member to form the outlet. The falling prevention portion is located between the ring member and the outlet forming surface, and contacts the ring member to prevent the ring member from falling off the accommodation depression.

Abstract: A turbocharger impeller is provided with a hub portion with a plurality of vane portions extending outwardly thereof. The hub portion is substantially shaped as a truncated cone with a diameter that gradually increases along a rotation axis. The vane portions are formed on a surface of the hub portion and guide a fluid flowing along the rotation axis radially outward relative to the hub portion. Grooves are formed in and/or on surfaces of the vane portions along a direction of the fluid flowing radially outward during rotation of the impeller. Protruding crest portions are formed between adjacent grooves. Crest portions in a central region near the rotation axis are lower in height than crest portions in an outer region further away from the rotation axis.

Abstract: A turbocharger impeller is provided with a hub portion with a plurality of vane portions extending outwardly thereof. The hub portion is substantially shaped as a truncated cone with a diameter that gradually increases along a rotation axis. The vane portions are formed on a surface of the hub portion and guide a fluid flowing along the rotation axis radially outward relative to the hub portion. Grooves are formed in and/or on surfaces of the vane portions along a direction of the fluid flowing radially outward during rotation of the impeller. Protruding crest portions are formed between adjacent grooves. Crest portions in a central region near the rotation axis are lower in height than crest portions in an outer region further away from the rotation axis.