Turbocharger

Abstract

This turbocharger (10) is provided with: a turbine wheel (26); a turbine housing (14); a plurality of variable nozzles (33); an annular first plate and second plate that are disposed so as to sandwich the variable nozzles (33); and a disc spring (50) that biases the second plate toward the first plate. The turbine housing (14) includes an opposing wall portion (18) that faces the second plate. A gap positioned between the opposing wall portion (18) and the second plate communicates with a turbine chamber (15). The disc spring (50) is disposed such that the inner end portion (51) is positioned on the opposing wall portion (18) side and the outer end portion (52) is positioned on the second plate side. A scroll chamber (16) includes, in the circumferential direction, a first region (R1) configured only by a first portion (161) and a second region (R2) including the first portion (161) and the second portion (162).

Description

turbocharger

[0001] The present disclosure relates to turbochargers.

[0002] As a conventional turbocharger, Japanese Patent Application Laid-Open No. 2013-104414 (Patent Document 1) discloses a configuration in which a shroud plate is arranged to face the inner wall surface of a turbine housing in which a spiral scroll chamber is provided around a turbine chamber, and an annular sealing member (disc spring) is arranged in the gap between the shroud plate and the turbine housing.

[0003] JP 2013-104414 A

[0004] In the turbocharger described in Patent Document 1, the scroll chamber is positioned outward from the peripheral end surface of the shroud plate over the entire circumferential direction, which reduces the cross-sectional area of ​​the scroll chamber through which exhaust gas passes, resulting in increased pressure loss at high flow rates.

[0005] One way to reduce pressure loss is to increase the cross-sectional area of ​​the scroll chamber around the entire circumference so that the disc spring is exposed to the scroll chamber. However, this exposes the disc spring to high-temperature exhaust gases. In this case, the disc springs may be thermally deformed, reducing their sealing ability and causing the exhaust gas inside the scroll chamber to leak into the turbine chamber.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and an object of the present disclosure is to provide a turbocharger that can suppress thermal deformation of the disc spring caused by high-temperature exhaust gas while suppressing a decrease in turbo efficiency.

[0007] A turbocharger according to the present disclosure includes a turbine housing including a turbine wheel, a turbine chamber that accommodates the turbine wheel, and a scroll chamber that is disposed around the turbine chamber and through which exhaust gas from an engine flows, a plurality of variable nozzles that are rotatable about a rotation axis and that adjust the flow velocity of the exhaust gas flowing toward the turbine wheel, annular first and second plates that are disposed on either side of the variable nozzle in an extension direction of the rotation axis and that define a communication passage that connects the scroll chamber and the turbine chamber, and a disc spring that biases the second plate toward the first plate. The turbine housing includes an opposing wall that faces the second plate at a distance from a side of the second plate opposite to a side on which the first plate is located in a first direction parallel to the extension direction. A gap between the opposing wall and the second plate communicates with the turbine chamber. The disc spring is arranged such that, when viewed from a direction parallel to the extension direction, its inner edge portion located on the inner periphery is located on the opposing wall portion side and its outer edge portion located on the outer periphery is located on the second plate side. The second plate has an outer periphery end face located on the outer periphery in the radial direction of the second plate. The scroll chamber includes a first region and a second region in the circumferential direction. The first region is composed of only a first portion located outward from the outer periphery end face in the radial direction. The second region includes the first portion and a second portion located on the opposite side of the second plate from the side on which the first plate is located in the direction parallel to the extension direction and located more inward than the outer periphery end face.

[0008] In the turbocharger according to the present disclosure, the turbine housing may include an introduction portion provided with an introduction passage for introducing the exhaust gas into the scroll chamber. At an angular position of the scroll chamber centered on an axis of the turbine housing, when viewed from the axial direction, the first region may be located such that the angular position is in a range of −90° to 90°, where a direction passing through the axis and parallel to an inlet opening face of the introduction portion when viewed from the axial direction, a direction toward the inlet opening face, is defined as 0°, and a winding direction of the scroll chamber from the direction toward the inlet opening face is defined as positive.

[0009] In the turbocharger according to the present disclosure, each of the first region and the second region may include a region in which a cross-sectional area perpendicular to the winding direction gradually decreases along the winding direction, and in this case, a rate of decrease in the cross-sectional area in the first region may be smaller than a rate of decrease in the cross-sectional area in the second region.

[0010] In the turbocharger according to the present disclosure, the angular positions may be such that a first angle, a second angle, and a third angle are located in this order between 0° and 360°. In a temperature distribution of the disc spring corresponding to the angular positions of the scroll chamber from 0° to 360°, in a region corresponding to 0° to the first angle, the temperature may increase as the angle of the angular position increases. In a region corresponding to the first angle to the second angle, the temperature may decrease as the angle of the angular position increases. In a region corresponding to the second angle to the third angle, the temperature may increase as the angle of the angular position increases. In a region corresponding to the third angle to 360°, the temperature may decrease as the angle of the angular position increases.

[0011] The turbocharger according to the present disclosure may further include a shielding member that shields the disc spring from the exhaust gas. The shielding member may be disposed so as to sandwich the disc spring between the shielding member and the second plate in the extension direction.

[0012] According to the present disclosure, it is possible to provide a turbocharger that can suppress the thermal deformation of the disc spring caused by high-temperature exhaust gas while suppressing a decrease in turbo efficiency.

[0013] It is a partial cross-sectional view showing a schematic configuration of a turbocharger according to an embodiment. It is a schematic configuration diagram showing a configuration of a turbine housing according to an embodiment. It is a diagram showing a change in cross-sectional area of ​​a scroll chamber according to an embodiment. It is a diagram showing a circumferential temperature distribution of a disc spring measured in a verification experiment. It is a diagram showing conditions of the verification experiment.

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the embodiments described below, the same or common parts are denoted by the same reference numerals in the drawings, and the description thereof will not be repeated.

[0015] FIG. 1 is a partial cross-sectional view showing the schematic configuration of a turbocharger according to an embodiment. In this embodiment, the turbocharger 10 is mounted on a vehicle. The vehicle is equipped with an engine. The engine combusts a mixture of air drawn into a combustion chamber through an intake passage and fuel supplied to the combustion chamber. The engine is provided with the turbocharger 10 shown in FIG. 1.

[0016] The turbocharger 10 includes a turbine shaft 11 and a bearing housing 12. The bearing housing 12 accommodates a bearing 13. The turbine shaft 11 is rotatably supported in the bearing housing 12 by the bearing 13.

[0017] The turbocharger 10 includes a turbine housing 14 and a compressor housing (not shown). The turbine housing 14 is disposed adjacent to one side (right side in FIG. 1) of the bearing housing 12 in the direction along the axis L1 of the turbine shaft 11 (left-right direction in FIG. 1; hereinafter referred to as the "axial direction"). The compressor housing, which is made up of multiple members, is disposed adjacent to the other side (left side in FIG. 1) of the bearing housing 12 in the axial direction.

[0018] The turbine housing 14 and the compressor housing are each fastened and fixed to the bearing housing 12. The bearing housing 12, the turbine housing 14, and the compressor housing form the housing of the turbocharger 10.

[0019] A cylindrical turbine chamber 15 extending in the axial direction is formed in the center of the turbine housing 14. A scroll chamber 16 is formed around the turbine chamber 15 within the turbine housing 14. The scroll chamber 16 is formed in a spiral shape. Exhaust gas E from the engine flows through the scroll chamber 16. The scroll chamber 16 is formed on the outer side of the turbine chamber 15 in the radial direction of the turbine shaft 11. The turbine chamber 15 and the scroll chamber 16 are connected to each other via a communication passage 17. The communication passage 17 is defined by a nozzle plate 31 serving as a first plate and a shroud plate 41 serving as a second plate, which are disposed opposite each other in a direction parallel to the axial direction, as will be described later. The shroud plate 41 has an outer peripheral end surface 41c in the radial direction.

[0020] A turbine wheel 26 is fixed to the end of the turbine shaft 11 located on one side in the axial direction. The turbine wheel 26 rotates within the turbine chamber 15. A compressor wheel (not shown) is fixed to the end of the turbine shaft 11 located on the other side in the axial direction. The compressor wheel rotates within a compressor housing.

[0021] The turbocharger 10 is equipped with a variable nozzle mechanism 30. The variable nozzle mechanism 30 can change the flow speed of the exhaust gas E blown onto the turbine wheel 26 by changing the exhaust flow area of ​​the communication passage 17. This adjusts the rotation speed of the turbocharger 10 and the amount of air forcibly sent into the combustion chamber.

[0022] The variable nozzle mechanism 30 includes a nozzle plate 31 and a unison ring 35. The nozzle plate 31 and the unison ring 35 have an annular shape centered on the axis L1.

[0023] In the nozzle plate 31, a plurality of shafts 32 are arranged at approximately equal angular intervals on a circle centered on the axis L1. Each shaft 32 extends parallel to the axis L1 and is inserted through the nozzle plate 31 so as to be rotatable.

[0024] Each shaft 32 extends in a direction parallel to the axial direction. A variable nozzle (nozzle vane) 33 is fixed to each shaft 32. Specifically, the variable nozzle 33 is fixed to one side of the shaft 32 in the direction parallel to the axial direction. This one side of the shaft 32 is exposed from the nozzle plate 31. The base end of an arm 34 is fixed to the other side of the shaft 32 in the direction parallel to the axial direction. The tip end of the arm 34 is fixed to the inner circumferential surface of the unison ring 35.

[0025] The unison ring 35 is rotated from outside the turbocharger 10 via a link mechanism or the like. When the unison ring 35 is rotated around the axis L1 from outside the turbocharger 10 using a link mechanism or the like, the arms 34 engaged with the unison ring 35 are rotated (opened and closed) in synchronization with each other around the shaft 32.

[0026] As each shaft 32 rotates, the variable nozzle 33 rotates about the shaft 32. The shaft 32 functions as a rotation axis. The variable nozzle 33 is disposed in the communication passage 17 located between the nozzle plate 31 and the shroud plate 41. The rotation of the variable nozzle 33 changes the opening of the variable nozzle 33, thereby changing the exhaust flow area of ​​the communication passage 17. The flow velocity of the exhaust E blown onto the turbine wheel 26 through the space between adjacent variable nozzles 33 is adjusted.

[0027] The turbine housing 14 has an opposing wall 18. The opposing wall 18 faces the shroud plate 41 at a distance in a direction parallel to the axial direction. More specifically, the opposing wall 18 faces the shroud plate 41 from the side opposite to the side on which the nozzle plate 31 is located. Note that the direction parallel to the axial direction is parallel to the extension direction of a rotation shaft of a variable nozzle 33, which will be described later.

[0028] The opposing wall portion 18 has an annular shape. A portion of the opposing wall portion 18 in the circumferential direction faces the entire shroud plate 41 along the radial direction, and the other portion of the opposing wall portion 18 in the circumferential direction faces a portion of the shroud plate 41 (a portion located on the inner circumferential side) along the radial direction.

[0029] A gap is formed between the opposing wall portion 18 and the shroud plate 41 , and the gap is connected to the turbine chamber 15 .

[0030] The turbocharger 10 includes a disc spring 50 and a shielding member 60. The disc spring 50 biases the shroud plate 41 toward the nozzle plate 31. The disc spring 50 is formed into an annular shape from an elastic body such as a metal plate. The disc spring 50 is formed to be elastically deformable in the axial direction.

[0031] The disc spring 50 is disposed around the axis L1. The disc spring 50 is disposed around the turbine wheel 26. The disc spring 50 is formed in a conical (tapered) shape that approaches the inner wall surface of the turbine housing 14 as it approaches the center.

[0032] When viewed in a direction parallel to the extension direction of the shaft 32, the disc spring 50 has an inner peripheral edge portion 51 located on the inner peripheral side and an outer peripheral edge portion 52 located on the outer peripheral side. The disc spring 50 is disposed so that the inner peripheral edge portion 51 is located on the opposing wall portion 18 side and the outer peripheral edge portion 52 is located on the shroud plate 41 side.

[0033] The shielding member 60 is formed in an annular shape from an elastic body such as a metal plate. The shielding member 60 is disposed about the axis L1. The shielding member 60 is disposed around the turbine wheel 26. The shielding member 60 is configured as a separate member from the shroud plate 41.

[0034] A disc spring 50 is sandwiched between the shroud plate 41 and the shielding member 60 in a direction parallel to the extension direction of the shaft 32. The shielding member 60, together with the shroud plate 41, surrounds the disc spring 50. The shielding member 60 is disposed to cover the disc spring 50. The shielding member 60 has an annular plate portion 61 and a cylindrical portion 62. The cylindrical portion 62 extends from the outer peripheral end of the plate portion 61 toward the other side in a direction parallel to the axial direction.

[0035] An outer peripheral edge 52 of the disc spring 50 contacts the shroud plate 41, and an inner peripheral edge 51 contacts a portion of the shielding member 60 located on the opposing wall portion 18 (a portion of the plate portion 61 that abuts against the opposing wall portion 18). As a result, the disc spring 50 and the shielding member 60 partition the gap between the shroud plate 41 and the turbine housing 14. This restricts the flow of exhaust gas E passing through the gap between the shroud plate 41 and the turbine housing 14, and prevents the exhaust gas E from bypassing the communication passage 17 and leaking into the turbine chamber 15.

[0036] The shielding member 60 may be omitted. In this case, the inner peripheral edge 51 contacts the opposing wall 18.

[0037] 2 is a schematic diagram showing the configuration of the turbine housing according to the embodiment. The turbine housing 14 will be described in detail with reference to FIGS.

[0038] 1 and 2 , the scroll chamber 16 in the turbine housing 14 has a first region R1 and a second region R2 in the circumferential direction. The first region R1 is formed only by a first portion 161 located radially outward from the outer peripheral end surface 41 c of the shroud plate 41.

[0039] On the first region R1 side, the open end of the gap between the opposing wall portion 18 and the shroud plate 41, which is located on the first region R1 side, is closed by the wall portion of the turbine housing 14 that defines the first portion 161. At least a part of the portion of the shielding member 60 that is located on the outer peripheral end surface 41 c of the shroud plate 41 is exposed to the scroll chamber 16.

[0040] The second region R2 includes the first portion 161 and the second portion 162. The second portion 162 is located on the opposite side of the shroud plate 41 from the side on which the nozzle plate 31 is located in the direction parallel to the extending direction, and is located radially inward of the outer peripheral end surface 41 c.

[0041] In the second region R2, the portion of the disc spring 50 located on the radially outer side does not face the opposing wall portion 18, but is arranged alongside the second portion 162 in a direction parallel to the extending direction. The disc spring 50 is covered with a shielding member 60. The portion of the shielding member 60 that does not face the opposing wall portion 18 is exposed to the scroll chamber 16.

[0042] 2, the turbine housing 14 includes an introduction section 80 provided with an introduction passage for introducing the exhaust gas E into the scroll chamber 16. The introduction passage connects an inlet opening surface 80h of the introduction section 80 and the scroll chamber 16.

[0043] In the angular position of the scroll chamber 16 centered around the axis L of the turbine housing 14, if the direction passing through the axis L and parallel to the inlet opening surface 80h of the introducing portion 80 as viewed from the direction of the axis L is defined as 0 degrees (the direction toward the inlet opening surface 80h), and the winding direction of the scroll chamber from the direction toward the inlet opening surface 80h is defined as positive, in this embodiment, the first region R1 is located in an angular position range of -45° to 45°. The second region R2 is located in an angular position range of greater than 45° and less than 315°. The winding direction is clockwise, and the axis L coincides with the axis L1 of the turbine shaft 11.

[0044] The ranges of the first region R1 and the second region R2 are not limited to those described above. The range of the first region R1 may be located in an angular position range of -90° to 90°. The range of the second region R2 may be located in an angular position range of more than 90° to less than 270°.

[0045] 3 is a diagram showing the change in the cross-sectional area of ​​the scroll chamber according to the embodiment. The cross-sectional area of ​​the scroll chamber 16 perpendicular to the winding direction gradually decreases toward the downstream side of the winding direction. Note that the cross-sectional area is substantially constant within the range of angular positions from 315° to 360°.

[0046] Each of the first region R1 and the second region R2 includes a region in which the cross-sectional area perpendicular to the winding direction gradually decreases along the winding direction, and the rate of decrease in the cross-sectional area in the first region R1 is smaller than the rate of decrease in the cross-sectional area in the second region R2. This prevents the turbine housing 14 from becoming larger in the portion that defines the first region R1, and prevents the turbocharger 10 from becoming larger in size.

[0047] As described above, in turbocharger 10 according to the present embodiment, an annular disc spring 50 is provided that is located on the side of shroud plate 41 opposite to the side on which nozzle plate 31 is located, and that urges shroud plate 41 toward nozzle plate 31. Disc spring 50 has an inner peripheral edge portion 51 located on the opposing wall portion 18 side and an outer peripheral edge portion 52 located on the shroud plate 41 side, thereby preventing exhaust gas E from bypassing communicating passage 17 and heading from scroll chamber 16 to turbine chamber 15.

[0048] Here, the scroll chamber 16 includes, in the circumferential direction, a first region constituted only by a first portion 161 located radially outward from the outer peripheral end face 41c of the shroud plate 41, and a second region having the first portion 161 and a second portion 162 located radially inward from the outer peripheral end face 41c.

[0049] As described above, on the first region R1 side, the open end of the gap between the opposing wall portion 18 and the shroud plate 41, which is located on the first region R1 side, is blocked by the wall portion of the turbine housing 14 that defines the first portion 161. This significantly reduces the intrusion of the exhaust gas E from the first portion 161 into the gap between the opposing wall portion 18 and the shroud plate 41. In addition, the portion of the shielding member 60 exposed to the scroll chamber 16 is also the portion located on the outer peripheral end surface 41 c of the shroud plate 41. This reduces the transfer of heat from the exhaust gas E to the disc springs 50 via the shielding member 60 on the first region R1 side. As a result, thermal deformation of the disc springs 50 can be reduced.

[0050] On the other hand, since the second region R2 includes the second portion 162, the cross-sectional area of ​​the scroll chamber 16 can be increased compared to when the scroll chamber 16 is configured with the first region R1 over the entire circumferential direction, thereby suppressing pressure loss of the exhaust gas E passing through the scroll chamber 16 and suppressing a decrease in turbo efficiency.

[0051] In this way, in the turbocharger 10 according to this embodiment, by providing the first region R1 and the second region R2 in the winding direction of the scroll chamber 16, it is possible to suppress a decrease in turbo efficiency while suppressing thermal deformation of the disc spring due to high-temperature exhaust gas.

[0052] Furthermore, when the angular position is in the range of -45° or more and 45° or less, the exhaust gas E introduced from the inlet opening surface 80h is likely to directly hit the inlet opening surface 80h, making it more likely that the temperature will become high. By positioning the first region R1 in this range, heat transfer to the disc spring 50 in the region where the temperature is likely to become high is suppressed, and thermal deformation of the disc spring 50 can be effectively suppressed. Note that even when the first region R1 is positioned in the range of -90° or more and 90° or less, heat transfer to the disc spring 50 in the region where the temperature is likely to become high can be suppressed. However, when the first region R1 is positioned in the range of -45° or more and 45° or less, heat transfer to the disc spring 50 can be more effectively suppressed, and thermal deformation of the disc spring 50 can be suppressed.

[0053] Fig. 4 is a diagram showing the circumferential temperature distribution of the disc spring measured in the verification experiment. Fig. 5 is a diagram showing the conditions of the verification experiment. The results of the verification experiment will be explained using Fig. 4 and Fig. 5. In Fig. 4 and Fig. 5, the temperature distribution of the disc spring according to Example 1 is shown by a solid line, the temperature distribution of the disc spring according to Comparative Example 1 is shown by a dashed line, and the temperature distribution of the disc spring according to Comparative Example 2 is shown by a two-dot chain line.

[0054] As shown in Fig. 4, turbochargers according to Example 1 and Comparative Examples 1 and 2 were prepared, and the temperature distribution of the disc springs in the circumferential direction was measured. Temperature sensors such as thermocouples were arranged on the disc springs at approximately equal intervals in the circumferential direction, and measurements were made using these temperature sensors.

[0055] The turbocharger according to Example 1 was the turbocharger according to Embodiment 1. The turbocharger according to Comparative Example 1 was one in which the scroll chamber 16 was in the second region R2 over the entire circumferential direction. The turbocharger according to Comparative Example 2 was one in which the scroll chamber 16 was in the first region R1 over the entire circumferential direction. Comparative Examples 1 and 2 differ from Example 1 in the configuration of the scroll chamber 16, but the other configurations are substantially similar to Example 1.

[0056] As shown in Fig. 5, in Comparative Examples 1 and 2, the rate of reduction in the cross-sectional area of ​​the scroll chamber 16 was approximately constant in the range where the angular position was greater than 45° and less than 315°. The rate of reduction in the cross-sectional area in Comparative Example 2 was smaller than the rate of reduction in the cross-sectional area in Comparative Example 1. The rate of reduction in the cross-sectional area in the second region R2 in Example 1 was approximately the same as the rate of reduction in the cross-sectional area in Comparative Example 1. The rate of reduction in the cross-sectional area in the first region R1 in Example 1 was smaller than the rates of reduction in the cross-sectional area in Comparative Examples 1 and 2. Note that in both Comparative Examples 1 and 2 and Example 1, the cross-sectional area of ​​the scroll chamber 16 was approximately constant in the range where the angular position was greater than or equal to 315° and less than 360°.

[0057] 4, in the temperature distribution of the disc spring in Comparative Example 1 corresponding to the angular positions of the scroll chamber from 0° to 360°, in the region corresponding to 0° to 180°, the temperature decreased as the angle of the angular position increased. In the temperature distribution, in the region corresponding to 180° to 360°, the temperature increased as the angle of the angular position increased.

[0058] Regarding the temperature distribution of the disc spring in Comparative Example 2 corresponding to the angular positions of the scroll chamber from 0° to 360°, in the region corresponding to 0° to 180°, the temperature decreased as the angle of the angular position increased. In the temperature distribution, in the region corresponding to 180° to 360°, the temperature increased as the angle of the angular position increased.

[0059] Regarding the temperature distribution of the disc spring in Example 1 corresponding to the angular positions of the scroll chamber from 0° to 360°, in the region corresponding to 0° to the first angle, the temperature increased as the angle of the angular position increased. Regarding the temperature distribution, in the region corresponding to the first angle to the second angle, the temperature decreased as the angle of the angular position increased. Regarding the temperature distribution, in the region corresponding to the third angle to 360°, the temperature decreased as the angle of the angular position increased.

[0060] The predetermined first, second, and third angles were located in this order between 0° and 360° in terms of angle position, with the first angle being located near 90°, the second angle being located near 180°, and the third angle being located near 270°, for example.

[0061] In the region corresponding to the angular positions from the first angle to the third angle, the temperature distribution of the disc spring of Example 1 was almost the same as that of Comparative Example 1.

[0062] As described above, when the results of Comparative Example 1 and Comparative Example 2 are compared, the temperature of the disc spring in Comparative Example 2 was lower in all regions corresponding to angular positions from 0° to 360° than the temperature of the disc spring in Comparative Example 1. This confirmed that, as in Comparative Example 2, the temperature of the disc spring can be reduced by blocking the open end located on the first region R1 side of the gap between the opposing wall portion 18 and the shroud plate 41 over the entire circumference with the wall portion of the turbine housing 14 that defines the first portion 161.

[0063] By comparing Example 1 with Comparative Examples 1 and 2, it was confirmed that by making the shape of the scroll chamber 16 in the first region R1 closer to that of Comparative Example 2, it was possible to reduce the temperature of the disc spring corresponding to the first region R1 compared to Comparative Example 1. In particular, it was confirmed that it was possible to reduce the temperature of the disc spring in the region where the exhaust gas E introduced from the inlet opening surface 80h is likely to directly hit and where the temperature is likely to become high.

[0064] The embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims, and includes all modifications within the meaning and scope of the claims.

[0065] 10 turbocharger, 11 turbine shaft, 12 bearing housing, 13 bearing, 14 turbine housing, 15 turbine chamber, 16 scroll chamber, 17 communicating passage, 18 opposing wall portion, 26 turbine wheel, 30 variable nozzle mechanism, 31 nozzle plate, 32 shaft, 33 variable nozzle, 34 arm, 35 unison ring, 41 shroud plate, 41c outer peripheral end surface, 50 disc spring, 51 inner peripheral edge portion, 52 outer peripheral edge portion, 60 shielding member, 61 plate portion, 62 cylindrical portion, 80 introduction portion, 80h inlet opening surface, 161 first portion, 162 second portion, E exhaust, L, L1 axis, R1 first region, R2 second region.

Claims

1. A turbine housing comprising: a turbine wheel; a turbine chamber that accommodates the turbine wheel; and a scroll chamber that is disposed around the turbine chamber and through which exhaust gas from an engine flows; a plurality of variable nozzles that are rotatable about a rotation axis and that adjust the flow rate of the exhaust gas toward the turbine wheel; annular first and second plates that are arranged on either side of the variable nozzle in the direction of extension of the rotation axis and that define a communication passage that connects the scroll chamber and the turbine chamber; and a disc spring that urges the second plate toward the first plate, wherein the turbine housing includes an opposing wall portion that faces the second plate at a distance from the side opposite to the side on which the first plate is located with respect to the second plate in a direction parallel to the direction of extension, and a gap located between the opposing wall portion and the second plate is connected to the turbine chamber, a turbocharger in which, when viewed from a direction parallel to the extension direction, the disc spring is arranged such that an inner peripheral edge portion located on the inner periphery side is located on the opposing wall portion side and an outer peripheral edge portion located on the outer periphery side is located on the second plate side; the second plate has an outer peripheral end face located on the outer periphery in the radial direction of the second plate; the scroll chamber includes a first region and a second region in the circumferential direction, the first region being constituted by only a first portion located outward from the outer peripheral end face in the radial direction; and the second region including the first portion and a second portion located on the opposite side of the second plate from the side on which the first plate is located in the direction parallel to the extension direction and located more inward than the outer peripheral end face.

2. A turbocharger according to claim 1, wherein the turbine housing includes an introduction section provided with an introduction passage for introducing the exhaust gas into the scroll chamber, and at an angular position of the scroll chamber centered on the axis of the turbine housing, when viewed from the axial direction, the direction toward the inlet opening surface of the introduction section that passes through the axis and is parallel to the inlet opening surface is defined as 0 degrees, and the winding direction of the scroll chamber from the direction toward the inlet opening surface is defined as positive, the first region is located at an angular position in the range of -90° to 90°.

3. A turbocharger according to claim 2, wherein each of the first region and the second region includes a region in which a cross-sectional area perpendicular to the winding direction gradually decreases along the winding direction, and the rate of decrease in the cross-sectional area in the first region is smaller than the rate of decrease in the cross-sectional area in the second region.

4. A turbocharger according to claim 2 or 3, wherein a first angle, a second angle, and a third angle are located in this order between 0° and 360° at the angular positions, and wherein in a temperature distribution of the disc spring corresponding to the angular positions of the scroll chamber from 0° to 360°, in a region corresponding to 0° to the first angle, the temperature increases as the angle of the angular position increases, in a region corresponding to the first angle to the second angle, the temperature decreases as the angle of the angular position increases, in a region corresponding to the second angle to the third angle, the temperature increases as the angle of the angular position increases, and in a region corresponding to the third angle to 360°, the temperature decreases as the angle of the angular position increases.

5. A turbocharger as claimed in any one of claims 1 to 3, further comprising a shielding member that shields the disc spring from the exhaust gas, the shielding member being arranged so as to sandwich the disc spring between itself and the second plate in the extension direction.

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