Turbocharger having by-pass valve operable to promote rapid catalytic converter light off

Abstract

A turbocharger assembly has a housing (1) in which is formed a turbine volute inlet duct (4) having a butterfly valve (8) disposed therein and a bypass duct (6) which contains a swing valve (15), the valves being operable to control the flow of exhaust gas through each duct. A link member (30) is mounted for rotation about the pivot axis (21) of the swing valve (15) and has an opening in which an actuating pin (20) engages with a tolerance fit so as to non-rotatably connect the swing valve (15) to the link plate (30). The link plate also has an elongated channel (34) along which an actuating pin (13) of the butterfly valve travels upon rotation of the link plate (30) about the pivot axis (21). The elongated channel has a first portion (34a) which extends along an arc centred on the axis of rotation (21) and a second portion (34b) which extends along an arc whose centre is offset from said axis (21). In this way, during a first range of movement of the link plate (30) the actuating pin (13) of the butterfly valve moves along the first portion (34a) and no operative movement of the valve (8) is effected, whilst during a second range of movement of the link plate (30), a camming action is applied to the actuating pin (13) causing it to rotate about the axis of the butterfly valve (8) and close it. The link plate (30) is thereby able to provide normal wastegate relief to the turbocharger during the first range of movement by operation of the swing valve only, and is also able to provide cold start bypass of the turbocharger in the second range of movement, during which the butterfly valve (8) is closed and the swing valve (15) fully opened so that all the exhaust gas bypasses the turbocharger and reaches the catalytic converter with minimum heat loss. Rapid light-off of the catalytic converter during cold start conditions is thereby ensured.

Dependencies are inferred from the claim text.