Variable geometry exhaust turbocharger

A variable geometry exhaust turbocharger, comprising:

• a turbine housing to which exhaust gas from an internal combustion engine is introduced;
• a turbine rotor which is arranged in the turbine housing and is rotated by the exhaust gas;
• a turbine shaft whose one end is inserted in the turbine housing and is attached to the turbine rotor;
• a bearing which supports the turbine shaft;
• a bearing housing which is connected to the turbine housing and houses the bearing;
• and
• a variable nozzle mechanism which is fixed to the bearing housing and adjusts a flow of the exhaust gas to the turbine rotor,
• wherein the variable nozzle mechanism includes a nozzle, a nozzle mount which supports the nozzle, a lever plate which engages with the nozzle and a drive ring which engages with the lever plate,
• the turbine housing is a double cylindrical structure having an inner cylindrical portion and an outer cylindrical portion,
• a nozzle plate of a annular shape which comes in contact with a tip of the nozzle is provided in the inner cylindrical portion of the turbine housing,
• a through-hole and a screw through-hole are respectively provided in the nozzle mount and the nozzle plate,
• a sleeve member is arranged coaxially with the through-hole and the screw through-hole between the nozzle mount and the nozzle plate,
• the nozzle mount and the nozzle plate are connected by a fastening bolt which is inserted in the through-hole, the sleeve member and the screw through-hole in this order,
• the sleeve member is formed such that a portion which is in contact with the nozzle mount and the nozzle plate has a thickness greater than that of a middle portion, and
• the sleeve member is made of a material which has a lower rigidity than the nozzle mount, the nozzle plate and the fastening bolt.

A variable geometry exhaust turbocharger, comprising:

• a turbine housing to which exhaust gas from an internal combustion engine is introduced;
• a turbine rotor which is arranged in the turbine housing and is rotated by the exhaust gas;
• a turbine shaft whose one end is inserted in the turbine housing and is attached to the turbine rotor;
• a bearing which supports the turbine shaft;
• a bearing housing which is connected to the turbine housing and houses the bearing;
• and
• a variable nozzle mechanism which is fixed to the bearing housing and adjusts a flow of the exhaust gas to the turbine rotor,
• wherein the variable nozzle mechanism includes a nozzle, a nozzle mount which supports the nozzle, a lever plate which engages with the nozzle and a drive ring which engages with the lever plate,
• the turbine housing is a double cylindrical structure having an inner cylindrical portion and an outer cylindrical portion,
• a nozzle plate of an annular shape which comes in contact with a tip of the nozzle is provided in the inner cylindrical portion of the turbine housing,
• a through-hole and a screw through-hole are respectively provided in the nozzle mount and the nozzle plate,
• a sleeve member is arranged coaxially with the through-hole and the screw through-hole between the nozzle mount and the nozzle plate,
• the nozzle mount and the nozzle plate are connected by a fastening bolt which is inserted in the through-hole, the sleeve member and the screw through-hole in this order,
• the sleeve member is formed such that a portion which is in contact with the nozzle mount and the nozzle plate has a thickness greater than that of a middle portion, and
• the sleeve member is made of a material which has a lower coefficient of linear thermal expansion than the fastening bolt.