A variable geometry turbine has a gas inlet chamber and a gas flow inlet passage downstream of the inlet chamber and upstream of said turbine wheel. The inlet passage is defined between a moveable first wall and a second wall and an actuator is operable to control displacement of the first wall in o
A variable geometry turbine has a gas inlet chamber and a gas flow inlet passage downstream of the inlet chamber and upstream of said turbine wheel. The inlet passage is defined between a moveable first wall and a second wall and an actuator is operable to control displacement of the first wall in order to vary the size of the gas flow inlet passage. A piston member defining the first wall or being connected to it is received in a piston chamber and serves to move the first wall as a result of displacement of the piston member in the piston chamber. A bypass passage defined in the housing and extends between the piston chamber and a location in the turbine upstream of the inlet passage for delivering gas to the piston chamber. The bypass passage is disposed such that gas introduced through the bypass passage pressurizes the chamber and applies a force to displace the piston member in a direction that causes the first wall to move towards the second wall. The gas, which may be the exhaust gas from an engine, thus serves to assist the operation of the actuator.
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1. A variable geometry turbine comprising a turbine wheel mounted within a housing for rotation about a turbine axis, a gas inlet chamber, a gas flow inlet passage downstream of the inlet chamber and upstream of said turbine wheel, the inlet passage being defined between a moveable first wall and a
1. A variable geometry turbine comprising a turbine wheel mounted within a housing for rotation about a turbine axis, a gas inlet chamber, a gas flow inlet passage downstream of the inlet chamber and upstream of said turbine wheel, the inlet passage being defined between a moveable first wall and a second wall, an actuator operable to control displacement of the first wall in order to vary the size of the gas flow inlet passage, a piston member associated with the first wall and received in a piston chamber defined by a piston chamber wall, the first wall being moveable as a result of displacement of the piston member in the piston chamber, a bypass passage defined in the housing and extending from a location in the turbine upstream of the inlet passage to the piston chamber where it penetrates the piston chamber wall, so that gas in the bypass passage is directed through the piston chamber wall into the piston chamber thus bypassing the inlet passage, the bypass passage being disposed such that gas introduced through the bypass passage pressurises the chamber so as to apply a force that urges the piston member in a direction that causes the first wall to move towards the second wall. 2. A variable geometry turbine according to claim 1, wherein the bypass passage extends from the gas inlet chamber to the piston chamber. 3. A variable geometry turbine according to claim 1, wherein a control valve is provided to control the flow of gas in the bypass passage. 4. A variable geometry turbine according to claim 3, wherein the control valve is situated in, or adjacent to, the bypass passage. 5. A variable geometry turbine according to claim 3, wherein the control valve is situated in, or adjacent, to an outlet passage downstream of the piston chamber. 6. A variable geometry turbine according claim 3, wherein the control valve also controls the opening and closing of a wastegate passage. 7. A variable geometry turbine according to claim 3, wherein the control valve is configured to be operable in response to control signals received from a control system of the turbine. 8. A variable geometry turbine according to claim 1, wherein the piston member defines the first wall. 9. A variable geometry turbine according to claim 1, wherein the piston member is connected directly or indirectly to the first wall. 10. A variable geometry turbine according to claim 3, wherein the piston chamber is divided into two chamber sections by the piston member, the bypass passage being selectively connected for fluid communication with each chamber section. 11. A variable geometry turbine according to claim 10, wherein the selective connection is provided by the control valve. 12. A variable geometry turbine according to claim 11, wherein each chamber section is selectively connectable to a vent in the housing through which gas may be delivered to atmosphere. 13. A variable geometry turbine according to claim 12, wherein the control valve is operable between a first position in which a first of the chamber sections is in fluid communication with the gas inlet chamber and a second of the chamber sections is in fluid communication with the vent and a second position in which the first of the chamber sections is in fluid communication with the vent and the second of the chamber sections is in fluid communication with the gas inlet chamber. 14. A variable geometry turbine according to claim 1, wherein the piston member is mounted on at least one guide member that is translatable in a direction substantially parallel to the turbine axis in response to operation of the actuator. 15. A variable geometry turbine according to claim 1, wherein the first wall supports an array of vanes that extend towards the second wall. 16. A turbomachine comprising a variable geometry turbine as defined in claim 1 and a compressor drivable by the variable geometry turbine. 17. A method for operating a turbocharger having a variable geometry turbine comprising a turbine wheel mounted within a housing for rotation about a turbine axis, an exhaust gas flow inlet passage upstream of said turbine wheel, the inlet passage being defined between a moveable first wall and a second wall, the first wall being moveable as a result of displacement of a piston member in a piston chamber, the piston member being associated with the first wall such that the first wall is moveable as a result of displacement of the piston member in the piston chamber, the method comprising delivering internal combustion engine exhaust gas in a first flow path through the gas flow inlet passage towards the turbine, and directing exhaust gas in a second flow path that bypasses the gas flow inlet passage, passes through a wall of the piston chamber and enters the piston chamber, whereby the gas pressurises the piston chamber on one side of the piston member so as to urge displacement of the first wall towards the second wall. 18. A method according to claim 17, wherein the exhaust gas is directed into the second flow path from an inlet chamber of the variable geometry turbine. 19. A method according to claim 17, wherein the flow of exhaust gas in the second flow path is controlled by means of a control device. 20. A method according to claim 19, wherein the control device is controlled in response to operating parameters of a turbocharger or an engine to which it is connected. 21. A method according to claim 19, wherein the control device is controlled in response to the sensed position of the first wall. 22. A method according to claim 19, wherein the control device is controlled in response to a signal representative of at least one of the force applied by an actuator of the piston member, the power consumed by the actuator or the distance travelled by the actuator or piston member. 23. A method according to claim 17, wherein the second flow path is defined by a bypass passage extending between the inlet chamber and the piston chamber. 24. An internal combustion engine having an air inlet flow path and an exhaust gas outlet flow path and a turbocharger comprising a compressor in said inlet flow path and a variable geometry turbine in said exhaust flow path, the variable geometry turbine comprising a turbine wheel mounted within a housing for rotation about a turbine axis, an inlet chamber, a gas flow inlet passage downstream of the inlet chamber and upstream of said turbine wheel, the inlet passage being defined between a moveable first wall and a second wall, an actuator operable to control displacement of the first wall in order to vary the size of the gas flow inlet passage, a gas flow control mechanism comprising a piston member received in a piston chamber defined by a piston chamber wall in the housing, the first wall being moveable as a result of displacement of the piston member in the piston chamber, a bypass passage defined in the housing and extending from a location in the turbine upstream of the inlet passage to the piston chamber where it penetrates the piston chamber wall, so that gas in the bypass passage is directed through the piston chamber wall into the piston chamber thus bypassing the inlet passage, the bypass passage being disposed such that exhaust gas introduced through the bypass passage pressurises the chamber so as to apply a force that urges the piston member in a direction that causes the first wall to move towards the second wall.
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이 특허에 인용된 특허 (23)
Arnold Steven Don, Actuating mechanism for sliding vane variable geometry turbine.
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