Turbocharger having a meridionally divided turbine housing and a variable turbine nozzle
A turbocharger has a meridionally divided turbine housing defining a first scroll and a first nozzle, and a second scroll and a second nozzle. The first and second nozzles are divided from each other by a shroud plate mounted within the nozzle, for isolating the exhaust gas streams flowing through the two nozzles from each other. A plurality of first vanes are disposed in the first nozzle, and plurality of second vanes are disposed in the second nozzle. A nozzle ring rotatably supports a plurality of vane shafts that extend across the first and second nozzles, passing through openings in the shroud plate. A first vane and a second vane are affixed to each vane shaft. Rotation of the vane shafts causes the first vanes and the second vanes to pivot for regulating the two streams of exhaust gas flowing through the first and second nozzles.
1. A turbocharger having a meridionally divided variable-nozzle turbine, comprising:
a turbine comprising a turbine housing and a turbine wheel mounted in the turbine housing and connected to a rotatable shaft for rotation therewith, the turbine housing defining a meridionally divided scroll extending circumferentially and surrounding the turbine wheel, the meridionally divided scroll defining a first scroll extending substantially fully about the turbine wheel and a separate second scroll extending substantially fully about the turbine wheel;
the turbine housing defining a separate inlet for each of the first and second scrolls through which separate first and second exhaust gas streams are received;
a nozzle leading from the meridionally divided scroll generally radially inwardly to the turbine wheel;
a compressor comprising a compressor housing and a compressor wheel mounted in the compressor housing and connected to the rotatable shaft for rotation therewith;
a center housing connected between the compressor housing and the turbine housing and containing bearings for the shaft;
a generally annular nozzle ring having a first face that comprises one wall of the nozzle and that is axially spaced from an opposite wall of the nozzle;
a shroud plate mounted within the nozzle, the shroud plate meridionally dividing the nozzle into a first nozzle and a second nozzle, the first nozzle receiving the first exhaust gas stream from the first scroll, the second nozzle receiving the second exhaust gas stream from the second scroll; and
a plurality of circumferentially spaced first vanes disposed in the first nozzle and a plurality of circumferentially spaced second vanes disposed in the second nozzle, the first and second vanes being rotatably mounted to the nozzle ring so as to be variable in setting angle for regulating exhaust gas flow to the turbine wheel.
2. The turbocharger of claim 1 , wherein the meridionally divided scroll of the turbine housing defines a divider wall that provides separation between the first exhaust gas stream in the first scroll from the second exhaust gas stream in the second scroll, and wherein a radially innermost edge of the divider wall is proximate a radially outer edge of the shroud plate, such that the shroud plate continues the separation between the first and second exhaust gas streams through the nozzle.
3. The turbocharger of claim 1 , wherein the nozzle ring defines a plurality of circumferentially spaced bearing holes, and further comprising a plurality of vane shafts respectively disposed in the bearing holes and rotatable within the bearing holes about respective axes of the vane shafts, each of the vane shafts having a first shaft portion affixed to one of the first vanes in the first nozzle and having a second shaft portion extending through an opening in the shroud plate and affixed to one of the second vanes in the second nozzle, such that rotation of the vane shafts about the respective axes thereof causes the first vanes to pivot within the first nozzle and causes the second vanes to pivot within the second nozzle.
4. The turbocharger of claim 3 , wherein the second shaft portions of the vane shafts project axially beyond the second vanes and extend into blind shaft receptacles defined in the opposite wall of the nozzle.
5. The turbocharger of claim 4 , wherein the blind shaft receptacles are defined in an annular insert that is formed separately from the turbine housing and is disposed in an annular recess defined in the turbine housing.
6. The turbocharger of claim 1 , further comprising a plurality of first spacers disposed between the nozzle ring and the shroud plate to govern a first axial spacing between the first face of the nozzle ring and the shroud plate, and a plurality of second spacers disposed between the shroud plate and the opposite wall of the nozzle to govern a second axial spacing between the shroud plate and the opposite wall of the nozzle.
7. The turbocharger of claim 6 , wherein each of the first spacers includes a pin of smaller diameter than the first spacer, the pin having a first portion that projects axially from one side of the first spacer toward the nozzle ring, and wherein the nozzle ring defines a plurality of first receiving holes that respectively receive the first portions of the pins of the first spacers.
8. The turbocharger of claim 7 , wherein each pin also includes a second portion that projects axially from an opposite side of the first spacer toward the opposite wall of the nozzle, the second portions of the pins passing through pin-receiving holes in the shroud plate, and wherein the opposite wall of the nozzle defines a plurality of second receiving holes that respectively receive ends of the second portions of the pins of the first spacers.
9. The turbocharger of claim 8 , wherein the second spacers comprise sleeves of greater diameter than the pins of the first spacers, each of the sleeves defining a central bore through which a respective one of the pins of the first spacers passes.
10. The turbocharger of claim 8 , wherein the opposite wall of the nozzle is defined by an annular insert and the turbine housing defines an annular recess in which the annular insert is disposed, and wherein the annular insert defines the second receiving holes for the pins.
11. The turbocharger of claim 10 , wherein the second receiving holes pass entirely through an axial thickness of the annular insert and wherein the turbine housing defines a plurality of blind holes that align with the second receiving holes and that receive terminal ends of the second portions of the pins.