Turbocharger

1. A turbocharger comprising:

a rotating shaft extending along an axis;

a turbine wheel disposed on a first end portion side of the rotating shaft;

a compressor wheel disposed on a second end portion side of the rotating shaft;

a turbine housing accommodating the turbine wheel;

a scroll flowpath formed in the turbine housing, continuing in a circumferential direction on a radially outer side of the turbine wheel, and guiding gas to the turbine wheel;

a nozzle flowpath guiding the gas radially inwards from the scroll flowpath and supplying the gas to the turbine wheel;

a vane disposed in the nozzle flowpath and adjusting an amount of the gas introduced in the nozzle flowpath;

a bearing housing rotatably supporting the rotating shaft; and

a nozzle mount disposed on a bearing housing side with respect to the nozzle flowpath and having an outer circumferential end portion sandwiched and held between the bearing housing and a mount fixing portion formed in the turbine housing, and directly supporting the vane,

wherein the scroll flowpath is formed such that an inner circumferential inside wall surface on a side close to the turbine wheel is gradually displaced radially outwards downstream in the circumferential direction in which the gas flows and the cross-sectional area of the flowpath gradually decreases and the scroll flowpath is formed such that an offset dimension of a cross-sectional center position of the scroll flowpath with respect to a radially outer position of the nozzle flowpath in a direction along the axis gradually decreases as the cross-sectional area of the flowpath gradually decreases along the flow direction of the gas, and

wherein the turbine housing includes a cover portion extending radially inwards from the mount fixing portion toward the nozzle flowpath and covering at least a part of the nozzle mount, and

wherein a space is formed between the cover portion and the nozzle mount.

2. The turbocharger according to claim 1 , wherein the scroll flowpath is formed such that an outer circumferential wall surface on the radially outer side along the flow direction of the gas has a constant radial position with respect to the axis.

3. The turbocharger according to claim 1 , further comprising:

an exhaust section formed in the turbine housing for the gas sent out by the turbine wheel; and

a heat insulating portion suppressing heat escape from the scroll flowpath to the exhaust section.

4. The turbocharger according to claim 3 , wherein the heat insulating portion includes a gap formed in a shroud portion partitioning the scroll flowpath and the exhaust section from each other in the turbine housing.

5. The turbocharger according to claim 4 , wherein the gap is filled with a heat insulating material.

6. The turbocharger according to claim 3 , further comprising:

a nozzle plate disposed on a side opposite to the bearing housing with respect to the nozzle flowpath,

wherein the heat insulating portion includes a heat insulating material sandwiched between the nozzle plate and a shroud portion partitioning the exhaust section and the scroll flowpath from each other in the turbine housing.

7. The turbocharger according to claim 3 , further comprising:

a nozzle plate disposed on a side opposite to the bearing housing with respect to the nozzle flowpath,

wherein the heat insulating portion includes a coating layer formed on a surface of the nozzle plate and including a heat insulating material.

8. The turbocharger according to claim 2 , further comprising:

an exhaust section formed in the turbine housing for the gas sent out by the turbine wheel; and

a heat insulating portion suppressing heat escape from the scroll flowpath to the exhaust section.