Variable nozzle mechanism and variable geometry turbocharger

A variable nozzle mechanism for a variable geometry turbocharger, comprising:

• a first annular member;
• a second annular member disposed so as to face the first annular member and forming an exhaust gas flow passage having an annular shape between the first annular member and the second annular member, for guiding exhaust gas to a turbine rotor of the turbo charger from a scroll flow passage formed on a radially outer side of the turbine rotor;
• and
• a plurality of nozzle vanes supported rotatably on the first annular member and configured to be capable of adjusting a flow passage area of the exhaust gas flow passage,
• wherein the first annular member has a plurality of support holes for supporting the plurality of nozzle vanes rotatably, the support holes being disposed at intervals in a circumferential direction of the turbine rotor,
• wherein an inner peripheral edge of the first annular member includes a first inner peripheral edge having a first inner diameter that engages a casing of the variable geometry turbocharger and a second inner peripheral edge having a second inner diameter smaller than the first inner diameter, and the second inner peripheral edge includes a plurality of first inner edge portions belonging to an angular range in which the support holes exist in the circumferential direction of the turbine rotor and a plurality of second inner edge portions belonging to an angular range in which the support holes do not exist in the circumferential direction of the turbine rotor, and
• wherein at least one second inner edge portion of the plurality of second inner edge portions comprises a recess portion recessed outward in a radial direction of the turbine rotor, the recess portion extending in an axial direction of the turbine rotor from the side of the exhaust gas flow passage.