Patent ID: 8186158

Claim:
A variable geometry turbocharger, comprising: exhaust inlet walls provided at a nozzle at an outer side of a turbine wheel and facing each other; a plurality of nozzle vanes disposed between the exhaust inlet walls with a predetermined interval along a circumferential direction of the turbine wheel; a slide mechanism that advances and retreats one of the exhaust inlet walls in a facing direction relative to the other of the exhaust inlet walls; and a hydraulic servo drive device that drives the slide mechanism, wherein: the hydraulic servo drive device includes a housing that has an opening at a portion thereof, a servo piston slidably housed in the housing and connected to the slide mechanism via the opening, and a pilot spool that is housed in a center hole of the servo piston and slides by pilot pressure, the housing includes a first hydraulic chamber at a first end of the servo piston and a second hydraulic chamber at a second end of the servo piston, pressure oil being flown into and out of the first hydraulic chamber and the second hydraulic chamber, the servo piston separately includes a pressure port for introducing the pressure oil from an outside into the center hole, a first piston port for intercommunicating the center hole and the first hydraulic chamber, a second piston port for intercommunicating the center hole and the second hydraulic chamber, and a return port for flowing out the pressure oil of the first and second hydraulic chambers to the outside, the pilot spool includes a switch that switches an intercommunicating state of the ports, the slide mechanism includes a first converter that converts rotary movement of a rotatable driveshaft into advancing and retreating movement of the one of the exhaust inlet walls, the driveshaft and the servo piston are connected via a second converter that converts the advancing and retreating movement of the servo piston into rotary movement of the driveshaft, and the second converter includes a slide groove formed perpendicular to the axial direction on an outer circumference of the servo piston, a slider that slidably engages in the slide groove, and an arm having a first end rotatable engaged to the slider and a second end connected to the driveshaft.