Abstract: A variable-vane assembly for a variable nozzle turbine comprises a nozzle ring supporting a plurality of vanes affixed to vane arms that are engaged in recesses in the inner edge of a unison ring. The unison ring is rotatable about the axis of the nozzle ring so as to pivot the vane arms, thereby pivoting the vanes in unison. The unison ring is radially restrained by a combination of radial guide rollers and fixed axial-radial guide pins secured to the nozzle ring, and is axially restrained by one or more axial stops affixed to the nozzle ring.

Abstract: A turbocharger assembly comprises a variable-vane assembly. The variable-vane assembly includes a unison ring with vane arms and/or a main-arm which adjust the setting angle of vanes. Vane arm-engaging elements and main-arm-engaging elements in the unison ring engage ends of the vane arms and the main-arm, respectively. Each vane arm-engaging element comprises an inner contact surface that engages an outer contact surface of the respective vane arm. The main-arm-engaging element comprises an inner actuation surface that engages an outer actuation surface of the main-arm. The inner contact surface and the outer contact surface and/or the inner actuation surface and the outer actuation surface may comprise conjugate curve profiles, such as involute curve profiles based on the involute of a circle. Use of conjugate curve profiles may result in rolling movement between the unison ring and vane arms and/or main arm, which may reduce friction occurring during pivoting of the vanes.