Actuation assembly for variable geometry turbochargers

Abstract

Improved actuation assemblies are used with variable geometry turbochargers comprising a plurality of movable aerodynamic vanes attached to a movable unison ring that is coupled to an actuator. The actuation assembly includes a crank arm that is attached at a first end to the actuator, and at a second end to the unison ring. A first gear member is attached to the crank arm second end and includes teeth. The unison ring includes a second gear member attached thereto that also comprises teeth. The teeth of the first and second gear-members are cooperatively engaged with one another. The second gear member is movably attached to the unison ring to maintain predetermined distance between the first and second gear members during operation of the turbocharger and related thermal movement of the unison ring.

Description

FIELD OF INVENTION [0001] This invention relates generally to the field of turbochargers and, more particularly, to variable geometry turbochargers having a plurality of movable aerodynamic vanes, and an actuation assembly for more efficiently and dependably moving the vanes within the turbocharger. BACKGROUND OF THE INVENTION [0002] Turbochargers for gasoline and diesel internal combustion engines are devices known in the art that are used for pressurizing or boosting the intake air stream, routed to a combustion chamber of the engine, by using the heat and volumetric flow of exhaust gas exiting the engine. Specifically, the exhaust gas exiting the engine is routed into a turbine housing of a turbocharger in a manner that causes an exhaust gas-driven turbine to spin within the housing. [0003] The exhaust gas-driven turbine is mounted onto one end of a shaft that is common to a radial air compressor mounted onto an opposite end of the shaft and housed in a compressor housing. Thus, ...

AI Technical Summary

Benefits of technology

[0013] Improved actuation assemblies of this invention operate to minimize or eliminate potential impairments to proper vane actuation caused either by unwanted sliding friction or thermal expansion / contraction binding between coupled actuating members.

Problems solved by technology

Thus, rotary action of the turbine causes the air compressor to spin within the compressor housing.

It is known that VGTs comprising such a crank arm-unison ring arrangement can be prone to suffer from two types of issues.

A first issue involves sliding friction and the fact that the crank arm pin that engages the unison ring is know to incur a severe amount of sliding friction, which can cause the pin and / or unison ring slot to wear in an aggressive manner.

Such wear can impact the desired interplay of the crank arm and unison ring by not providing the full range of desired movement, or ultimately can cause the crank arm pin to break, thereby prohibiting desired unison ring movement.

A second issue involves the high and cyclic temperatures that the VGT turbine housing and all parts disposed therein are subjected to.

Such different thermal expansion and contraction characteristics can cause the crank arm pin to bind within the unison ring slot, thereby impairing efficient and dependable unison ring actuation.

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