Simplified variable geometry turbocharger with variable flow volumes

A turbocharger for an internal combustion engine comprising:

• a turbine housing (2) including an inlet at a turbine housing foot (51) for receiving exhaust gas;
• a turbine wheel rotatably mounted in said housing;
• a volute for directing exhaust gases from said inlet onto said turbine wheel, said volute including a radially outer wall, said radially outer wall constituted by
• a fixed radially outer wall segment of the turbine housing terminating in a tongue, and
• a flexible radially outer wall having an upstream end anchored to the turbine housing (2) upstream of the tongue and a curved downstream end, said flexible radially outer wall moveable from a retracted position further from the turbine wheel to an extended position nearer the turbine wheel;
• and
• a control device configured to control movement of the flexible radially outer wall downstream end from said retracted position to the extended position,
• wherein the flexible radially outer wall includes a reinforcing rib that protrudes from a radially outward-facing side of the flexible radially outer wall, is elongated in a direction corresponding to a direction of exhaust gas flow through the turbine housing, and together with the flexible radially outer wall is movable relative to the fixed radially outer wall segment.

A turbocharger for an internal combustion engine comprising:

• a turbine housing (2) including an inlet at a turbine housing foot (51) for receiving exhaust gas, said turbine housing including a volute with a radially outer wall (74) having a constant radius;
• a turbine wheel rotatably mounted in said housing;
• a rotating curved wedge segment (72) defined by a radially outer wall flush with said turbine housing wall (74) of constant radius, and a radially inner wall of constantly decreasing radius in the downstream direction, said curved wedge segment thus having a tapered upstream end and a wide downstream end, said rotating curved wedge segment mounted for rotating between a lower effective flow volume position and a higher effective flow volume position;
• a fixed curved wedge part (73) including a chamber for receiving the rotating curved wedge segment thick end when the rotating curved wedge segment (72) is rotated to a high effective flow volume position, and having an exterior defining a continuation of the rotating curved wedge segment when the rotating curved wedge segment is pivoted to the low effective flow volume position.

A method for controlling backpressure in a turbocharger for an internal combustion engine, the turbocharger comprising:

• a turbine housing (2) including an inlet at a turbine housing foot (51) for receiving exhaust gas;
• a turbine wheel rotatably mounted in said housing;
• a volute for directing exhaust gases from said inlet onto said turbine wheel, said volute including a radially outer wall, said radially outer wall constituted by
• a fixed radially outer wall segment of the turbine housing terminating in a tongue, and
• a pivotable radially outer wall (33) having an upstream end pivotably mounted to the turbine housing (2) upstream of the tongue and a curved downstream end, said pivotable radially outer wall pivotable from a retracted position further from the turbine wheel to an extended position nearer the turbine wheel;
• and
• a control device configured to control movement of the pivotable radially outer wall downstream end from said retracted position to the extended position
• said method comprising:
• pivoting said pivotable wall (33) to the extended position such that the upstream part of the pivotable wall cooperates with the tongue to form a smaller constriction for accelerating exhaust gas flow, and a curved terminal part of the pivotable wall directs gas flow closer to the turbine wheel, thereby reducing the effective flow volume of the volute to increase turbine backpressure, enhancing the ability of the system to drive EGR flow from the exhaust side of the engine to the inlet side of the engine, and
• pivoting said pivotable wall (33) to the retracted position such that the upstream part of the pivotable wall moves away from tongue to form a less restricted flow, and such that the curved terminal part of the pivotable wall directs gas flow further from to the turbine wheel, thereby increasing the effective volume of the volute to decrease turbine backpressure.