Abstract: A waste gate structure of a turbocharger includes a turbine housing having a turbine rotor rotated by exhaust gas. An exhaust gas inlet is formed in the turbine housing and communicates with an inlet of the turbine rotor. An exhaust gas outlet is formed in the turbine housing, and can communicate between the exhaust gas inlet and the exhaust gas outlet while bypassing the turbine rotor. A waste gate valve disposed in the bypass passage opens or closes the bypass passage to control the quantity of exhaust gas supplied to the inlet of the turbine rotor. A scroll chamber is formed in the turbine housing in the bypass passage. The scroll chamber opens into the exhaust gas outlet and has a circular opening oriented along the direction of a flow of exhaust gas discharged from the turbine rotor. A spiral groove is formed on an inner surface of a portion of the exhaust gas outlet located more downstream than the circular opening of the scroll chamber.

Abstract: A mechanical supercharger utilized in internal combustion engines includes a housing having an inlet port and an outlet port, and a bypass passage disposed in the housing for connecting the inlet port and the outlet port with each other. A relief valve is disposed in the bypass passage for releasing air pressure from the outlet port to the inlet port.