Structure of scroll of variable-throat exhaust turbocharger and method for manufacturing the turbocharger

A method of manufacturing a variable-throat exhaust turbocharger equipped with a nozzle throat area varying mechanism for varying the blade angle of a plurality of nozzle vanes arranged in an annular flow passage formed in the inner side of a scroll chamber of a turbine casing whereby engine exhaust gas is introduced to the scroll chamber to pass through the annular flow passage to flow into a radial flow type turbine, comprising:

• a step of manufacturing a cartridge-like nozzle assembly unit which is composed such that a plurality of nozzle vanes are supported rotatably by an annular nozzle mount and an annular nozzle plate is connected to said nozzle mount by means of a plurality of nozzle supports to sandwich said nozzle vanes;
• a step of fitting a seal member for sealing against gas leakage between the scroll chamber and the downstream side of said annular flow passage to a supporting portion of the turbine casing where the inner surface of the annular nozzle plate is to be fitted;
• and
• a step of attaching the cartridge-like nozzle assembly unit to the turbine casing so that said nozzle plate forms part of the inside side wall face of the scroll chamber and a wall face of the annular flow passage.