The invention relates to an adjustable guide vane mechanism for a turbine, a turbine for an exhaust gas turbocharger as well as to an exhaust gas turbocharger for an internal combustion engine.
Patent specification EP 1 227 221 B1 discloses an, adjustable guide vane mechanism for a turbine. By means of the adjustable guide vane mechanism, the incoming flow of the exhaust gases discharged from a combustion engine into the turbine wheel can be conditioned. For this purpose, the guide mechanism comprises a number of adjustable guide vanes which are positioned in a nozzle duct in the exhaust gas guide portion, upstream of a wheel chamber in which the turbine wheel is rotatably mounted. The guide mechanism comprises a bearing ring with a plurality of guide vanes, with the guide vanes being rotatably supported on the bearing ring via guide vane shafts. Actuating levers are principally allocated to the guide vane shafts, which are formed to be engageable with a rotating ring. The rotating ring comprises recesses for accommodating the actuating levers.
The rotating ring is formed as an annular disk and is radially and axially supported. The axial and radial support is effected by means of a bearing ring. For friction reduction, the rotating ring comprises recesses at its bearing face opposite the bearing ring. Thereby, a surface contact between the rotating ring and the bearing ring and consequently the friction losses due to surface friction are reduced.
It is the principal object of the present invention to provide an adjustable guide vane mechanism with further reduced friction losses. It is another object of the invention to provide a turbine which has a higher operational reliability as well as to configure an exhaust gas turbocharger with improved efficiency.