Variable nozzle mechanism and variable displacement type exhaust turbocharger

A variable-geometry type exhaust turbocharger, comprising:

• a turbine part configured to be driven by exhaust gas introduced from an internal combustion engine;
• a compressor part configured to compress and send external air to the internal combustion engine along with the turbine part;
• and
• a variable nozzle mechanism disposed in a turbine housing into which the exhaust gas is introduced at the turbine part,
• wherein the variable nozzle mechanism includes,
• a nozzle mount having an annular shape;
• a plurality of nozzle vanes supported rotatably at a plurality of respective locations along a circumferential direction of the nozzle mount;
• and
• a drive ring disposed rotatably with respect to the nozzle mount, the drive ring being configured to transmit a driving force to the nozzle vanes so that a vane angle of the nozzle vanes is variable and to rotate the nozzle vanes, the drive ring having a plurality of recessed portions with which a lever plate for transmitting the driving force to the nozzle vanes are engaged,
• wherein the drive ring includes:
• a plurality of lower-rigidity regions;
• and
• a plurality of higher-rigidity regions including an uneven portion in a thickness direction of the drive ring, and having a greater cross-sectional secondary moment than the plurality of lower-rigidity regions in a radial cross section and about a radial direction of the drive ring,
• wherein each of the plurality of lower-rigidity regions includes an undercut which is different from the plurality of recessed portions,
• wherein each of the plurality of lower-rigidity regions and each of the plurality of higher-rigidity regions are disposed alternately in the circumferential direction,
• wherein the number of the plurality of lower-rigidity regions and the number of the plurality of higher-rigidity regions are odd numbers, or the plurality of lower-rigidity regions and the plurality of higher-rigidity regions are disposed at an irregular pitch in the circumferential direction,
• wherein the uneven portion of the plurality of higher-rigidity regions is formed by a rib extending along the circumferential direction at an inner peripheral side of the drive ring, and
• wherein the rib forming the uneven portion is disposed selectively in the plurality of higher-rigidity regions.