TWO-STAGE SUPERCHARGING SYSTEM FOR INTERNAL COMBUSTION ENGINE

摘要

A sequential-type, two-stage supercharging system (1) having a high-pressure-stage turbocharger (6) and a low-pressure-stage turbocharger (5), in which high-pressure-stage exhaust gas bypass channels (6d, 6e) for bypassing a high-pressure-stage turbine (6t) is formed by both the first bypass channel (6d) having a small-diameter valve (6f) and the second bypass channel (6e) having a large-diameter valve (6g) with a diameter greater than that of the small-diameter valve (6f). The effective valve area of the small-diameter valve (6f) is set to 9.5% - 26.5% of the channel cross-sectional area required when exhaust gas is at its maximum total flow rate. This allows, in medium speed/medium load operation, fine EGR rate control and air-fuel ratio control.