Variable geometry system turbocharger
A variable geometry system turbocharger includes an annular heat shield plate which shields heat from a turbine wheel side. The heat shield plate is integrally provided at a central part of a side surface of a bearing housing opposed to a back surface of a turbine disk. A first seal ring is provided between an inner peripheral surface of a first nozzle ring and an outer peripheral surface of the heat shield plate. A second seal ring is provided between an inner peripheral surface of a second nozzle ring and an outer peripheral surface of a protrusion of a turbine housing.
1. A variable geometry system turbocharger comprising:
a variable nozzle unit disposed between a turbine scroll passage and a turbine wheel in a turbine housing adjacent to a bearing housing, the variable nozzle unit being configured to adjust a passage area for exhaust gas to be supplied to the turbine wheel, and
a support ring including an outer peripheral edge sandwiched between the bearing housing and the turbine housing, configured to support the variable nozzle unit,
wherein the variable nozzle unit includes:
a first nozzle ring disposed in the turbine housing, including an inner peripheral surface facing radially inward;
a second nozzle ring opposed to the first nozzle ring in an axial direction;
a plurality of variable nozzles disposed at intervals in a circumferential direction between the first nozzle ring and the second nozzle ring, and rotatably provided around nozzle axes thereof parallel to the axial direction;
a link configured to rotate the plurality of variable nozzles synchronously;
an annular heat shield plate provided between the bearing housing and the turbine wheel, configured to shield heat from a turbine wheel side of the turbine housing toward the bearing housing, the annular heat shield plate including an outer peripheral surface facing radially outward and opposed to the inner peripheral surface of the first nozzle ring; and
a first seal member provided between the inner peripheral surface of the first nozzle ring and the outer peripheral surface of the heat shield plate.
2. The variable geometry system turbocharger according to claim 1 , wherein the heat shield plate is fastened to the bearing housing with an attachment bolt.
3. The variable geometry system turbocharger according to claim 2 , wherein a fastened portion between the bearing housing and the heat shield plate is an annular sealing portion configured to suppress a leakage of the exhaust gas from a back surface side of the heat shield plate to a back surface side of the turbine wheel.
4. The variable geometry system turbocharger according to claim 1 , further comprising
a second seal member, wherein
the second nozzle ring includes an inner peripheral surface facing radially inward and surrounding an annular portion of the turbine housing, the annular portion being integrally formed with the turbine housing and located between the turbine scroll passage and the turbine wheel, and
the second seal member is provided between the inner peripheral surface of the second nozzle ring and an outer peripheral surface of the annular portion of the turbine housing.
5. The variable geometry system turbocharger according to claim 4 , wherein
the first seal member and the second seal member are seal rings.
6. The variable geometry system turbocharger according to claim 1 , wherein
the first nozzle ring is provided with a plurality of first support through holes formed in the first nozzle ring at intervals in the circumferential direction,
the second nozzle ring is provided with a plurality of second support blind holes formed in the second nozzle ring and aligned with the plurality of first support through holes,
each of the plurality of variable nozzles includes: a first side surface facing the first nozzle ring, a second side surface facing the second nozzle ring, a first nozzle shaft integrally provided with the first side surface, and a second nozzle shaft integrally provided with the second first side surface, the first nozzle shaft being rotatably supported by a corresponding one of the plurality of the first support through holes in the first nozzle ring, and the second nozzle shaft being rotatably supported by a corresponding one of the plurality of the second support blind holes in the second nozzle ring, and
the turbine scroll passage communicates with a link chamber in which the link is accommodated and end surfaces of the first nozzle shafts of the plurality of variable nozzles are exposed, the communication between the turbine scroll passage and the link chamber allowing airflow therebetween.
7. The variable geometry system turbocharger according to claim 1 , wherein the heat shield plate includes a surface opposed to the turbine wheel, the surface is provided with an annular housing recess to house part of the turbine wheel, and the annular housing recess recedes toward the bearing housing.
8. The variable geometry system turbocharger according to claim 1 , wherein an inner diameter of the first nozzle ring and an inner diameter of the second nozzle ring are set to an equal dimension, and an outer diameter of the first nozzle ring and an outer diameter of the second nozzle ring are set to an equal dimension.