Patent ID: 8033108

Claim:
A two-stage supercharging system for an internal combustion engine comprising: a low-pressure-stage compressor of a low-pressure-stage turbocharger and a high-pressure-stage compressor of a high-pressure-stage turbocharger are provided from an upstream of an intake air passage of the internal combustion engine in order, and at the same time, a high-pressure-stage turbine of the high-pressure-stage turbocharger and a low-pressure-stage turbine of the low-pressure-stage turbocharger are provided from the upstream of an exhaust passage in order, a high-pressure-stage intake air bypass passage bypassing the high-pressure-stage compressor and a high-pressure-stage exhaust bypass passage bypassing the high-pressure-stage turbine are provided, and in the two-stage supercharging system for the internal combustion engine, the high-pressure-stage exhaust bypass passage being composed of a first bypass passage provided with a small-diameter valve and a second bypass passage provided with a large-diameter valve larger than the small-diameter valve, wherein, a valve effective area of the small-diameter valve is configured to be in a range of 9.5% to 26.5% of a necessary passage cross sectional area at the time of a maximum total flow rate of the exhaust gas.