Turbine housing and variable geometry turbocharger

Abstract

To provide a turbine housing capable of improving reliability of a nozzle vane, and a variable-capacity type turbo charger comprising the turbine housing.SOLUTION: A turbine housing comprises a scroll flow path wall surface that connects an outer peripheral end of a scroll flow path and an outer peripheral end of a hub side flow path wall surface. The scroll flow path wall surface includes a first arc part extending from an outer peripheral end connected to the outer peripheral end of the scroll flow path toward an inner side in a radial direction of a turbine rotor in a cross section along an axial line of the turbine rotor passing through a tongue part, and a cliff part that connects an inner peripheral end of the first arc part and the outer peripheral end of the hub side flow path wall surface, the cliff part including a second arc part that is connected to the inner peripheral end of the first arc part and forms an inflection point between the second arc part and the first arc part. The inflection point is positioned to be offset to a tip end side in an axial direction of the turbine rotor with respect to the outer peripheral end of the hub side flow path wall surface and an outside in the radial direction with respect to the outer peripheral end of the hub side flow path wall surface.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a turbine housing and a variable geometry turbocharger including the turbine housing. [Background technology]

[0002] A variable geometry turbocharger equipped with a variable geometry turbine is known as a turbocharger that supercharges the intake air of an engine (internal combustion engine) by utilizing the energy of exhaust gas emitted from the engine (see, for example, Patent Document 1). A variable geometry turbine has a plurality of nozzle vanes arranged circumferentially in a flow path (nozzle flow path) of exhaust gas that sends the exhaust gas from the scroll flow path of the turbine to the turbine rotor, and the blade angle of these nozzle vanes can be changed externally by an actuator to adjust the flow path cross-sectional area of ​​the exhaust gas flow path (flow path between adjacent nozzle vanes). A variable geometry turbine adjusts the flow path cross-sectional area of ​​the exhaust gas flow path to change the flow velocity and pressure of the exhaust gas introduced to the turbine rotor, thereby enhancing the supercharging effect. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-229815 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, engine pulsation causes fluctuations in the pressure ratio of the exhaust gas introduced into the variable geometry turbine, which in turn changes the load (fluid force from the exhaust gas) applied to the nozzle vanes. The load acting on the nozzle vanes can narrow the clearance between the vane shaft fixed to the nozzle vane and other components that support the nozzle vane, causing contact. Frequent contact between the vane shaft and these other components during operation of the variable geometry turbine can cause wear on the vane shaft, which could result in damage.

[0005] If the direction of the load acting on the vane shaft reverses over a short period of time, such as one cycle of engine pulsation, the above-mentioned contact occurs frequently, increasing the risk of wear on the vane shaft and reducing the reliability of the nozzle vanes, so measures must be taken. In particular, nozzle vanes located near the tongue of the scroll passage may experience a reversed direction of the load acting on the vane shaft over a short period of time, such as one cycle of engine pulsation, due to the influence of the swirling flow of exhaust gas and the wake (flow distortion) generated at the tongue during the flow of exhaust gas. Note that Patent Document 1 does not focus on the issues of suppressing vane shaft wear due to pulsation of an internal combustion engine and improving the reliability of nozzle vanes.

[0006] In view of the above circumstances, an object of at least one embodiment of the present invention is to provide a turbine housing capable of improving the reliability of nozzle vanes, and a variable geometry turbocharger including the turbine housing. [Means for solving the problem]

[0007] A turbine housing according to at least one embodiment of the present invention comprises: A turbine housing for accommodating a turbine rotor, comprising: a scroll passage forming portion that forms a scroll passage extending in a circumferential direction about the axis of the turbine rotor; a nozzle flow path forming section that forms a nozzle flow path for guiding exhaust gas from the scroll flow path to the turbine rotor that is disposed on the inner circumferential side of the scroll flow path, the nozzle flow path forming section having a shroud-side flow path wall surface and a hub-side flow path wall surface that define the nozzle flow path; a variable nozzle unit for adjusting the flow of the exhaust gas in the nozzle flow path, the variable nozzle unit including at least one nozzle vane arranged in the nozzle flow path, the scroll passage forming portion includes a scroll passage wall surface connecting an outer circumferential end of the scroll passage and an outer circumferential end of the hub-side passage wall surface, The scroll flow passage wall surface, in a cross section along the axis passing through a tongue portion of the scroll flow passage forming portion, a first arc portion whose outer peripheral end is connected to the outer peripheral end of the scroll passage and extends from the outer peripheral end toward an inner side in a radial direction of the turbine rotor; a cliff portion having one end connected to the inner circumferential end of the first arc portion and the other end connected to the outer circumferential end of the hub-side flow path wall surface, the cliff portion including a second arc portion connected to the inner circumferential end of the first arc portion and forming an inflection point between the first arc portion and the cliff portion, The inflection point is located toward the tip side in the axial direction of the turbine rotor from the outer peripheral end of the hub-side flow path wall surface and offset radially outward from the outer peripheral end of the hub-side flow path wall surface.

[0008] A variable geometry turbocharger according to at least one embodiment of the present invention includes: the turbine housing; a turbine rotor rotatably accommodated in the turbine housing. [Effects of the Invention]

[0009] According to at least one embodiment of the present invention, there are provided a turbine housing capable of improving the reliability of nozzle vanes, and a variable geometry turbocharger including the turbine housing. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view taken along the axis of a variable geometry turbocharger according to an embodiment of the present invention; [Figure 2] 1 is a schematic cross-sectional view perpendicular to the axis of a variable geometry turbocharger according to one embodiment of the present invention; [Figure 3] 1 is a schematic diagram of an internal combustion engine system including a variable geometry turbocharger according to an embodiment; [Figure 4] FIG. 10 is a schematic cross-sectional view taken along an axis passing through a tongue portion of a turbine housing according to a comparative example. [Figure 5] FIG. 10 is an explanatory diagram for explaining the load evaluation results of a nozzle vane located near a tongue portion in a comparative example. [Figure 6] 2 is a schematic cross-sectional view of an embodiment of a turbine housing taken along an axis passing through a tongue; FIG. [Figure 7] 2 is a schematic cross-sectional view of an embodiment of a turbine housing taken along an axis passing through a tongue; FIG. [Figure 8] 10 is an explanatory diagram for explaining the relationship between the axial length X and the radial length Y of a cliff portion and the angular position θ in one embodiment. FIG. [Figure 9] 10 is an explanatory diagram for explaining the relationship between the axial length X and the radial length Y of a cliff portion and the angular position θ in one embodiment. FIG. [Figure 10] 10 is an explanatory diagram for explaining the relationship between the axial length X and the radial length Y of a cliff portion and the angular position θ in one embodiment. FIG. [Figure 11] 3A to 3C are explanatory diagrams illustrating shapes of a scroll flow passage wall surface at a plurality of angular positions in one embodiment. [Figure 12] FIG. 10 is an explanatory diagram illustrating the relationship between the maximum axial length between one end and the other end of the cliff portion in one embodiment and the amount of exhaust gas flowing from the scroll flow path to the nozzle flow path in the circumferential range in which the cliff portion is formed. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention.

[0012] Fig. 1 is a schematic cross-sectional view taken along an axis LA of a variable geometry turbocharger 1 according to one embodiment. Fig. 2 is a schematic cross-sectional view perpendicular to the axis LA of the variable geometry turbocharger 1 according to one embodiment. As shown in Figs. 1 and 2, the variable geometry turbocharger 1 according to some embodiments includes a turbine housing 2 and a turbine rotor 3 rotatably accommodated in the turbine housing 2.

[0013] Hereinafter, the direction in which the axis LA of the turbine rotor 3 extends is defined as the axial direction of the turbine rotor 3, and the side of the axial direction where the blade surface is located relative to the back surface of the turbine rotor 3 is defined as the leading edge side, and the side opposite the leading edge side where the back surface is located relative to the blade surface of the turbine rotor 3 is defined as the trailing edge side. Also, the direction perpendicular to the axis LA of the turbine rotor 3 is defined as the radial direction. Within the radial direction, the outer side in the radial direction is defined as the outer circumferential side, and the inner side in the radial direction is defined as the inner circumferential side.

[0014] (turbine housing) 1 and 2, the turbine housing 2 includes a scroll passage forming section 4 that forms a scroll passage 40, a nozzle passage forming section 5 that forms a nozzle passage 50, and a variable nozzle unit 6 that adjusts the flow of exhaust gas in the nozzle passage 50. The scroll passage 40 and the nozzle passage 50 are each formed inside the turbine housing 2.

[0015] (Scroll flow path) The scroll passage 40 is a spiral passage for guiding exhaust gas introduced from outside the turbine housing 2 to the turbine rotor 3. The scroll passage 40 extends in the circumferential direction around the axis LA of the turbine rotor 3, on the outer circumferential side of the turbine rotor 3.

[0016] (Nozzle flow path) The nozzle flow passage 50 is a flow passage for guiding exhaust gas from the scroll flow passage 40 to the turbine rotor 3, which is arranged on the inner peripheral side of the scroll flow passage 40. The nozzle flow passage 50 is formed between the scroll flow passage 40 and the turbine rotor 3 so as to surround the outer peripheral side of the turbine rotor 3. The exhaust gas introduced into the turbine housing 2 passes through the scroll flow passage 40 and then the nozzle flow passage 50, and is then guided from the outer peripheral side of the turbine rotor 3 to the turbine rotor 3.

[0017] The nozzle flow path forming portion 5 has a shroud-side flow path wall surface 51 and a hub-side flow path wall surface 52 that define the nozzle flow path 50. Each of the shroud-side flow path wall surface 51 and the hub-side flow path wall surface 52 extends in a direction intersecting (for example, perpendicular to) the axis LA in a cross section taken along the axis LA as shown in Fig. 1. The shroud-side flow path wall surface 51 is located closer to the tip end in the axial direction than the hub-side flow path wall surface 52 and faces the shroud-side flow path wall surface 51 with the nozzle flow path 50 interposed therebetween.

[0018] (Nozzle flow path forming part) 1 , the nozzle flow path forming portion 5 includes a nozzle mount 53 and a nozzle plate 54 that is arranged on the axially distal side of the nozzle mount 53. The nozzle flow path forming portion 5 may further include at least one nozzle support 55 (a plurality of nozzle supports in the illustrated example) that supports the nozzle mount 53 and the nozzle plate 54 while spaced apart from each other. The nozzle mount 53, the nozzle plate 54, and each of the plurality of nozzle supports 55 are arranged inside the turbine housing 2 and fixed to the turbine housing 2.

[0019] The nozzle mount 53 includes a first annular plate portion 56 that extends along the circumferential direction of the turbine rotor 3 on the outer circumferential side of the turbine rotor 3. The nozzle mount 53 has a hub-side flow path wall surface 52 that is formed on the tip side of the first annular plate portion 56 in the axial direction.

[0020] The nozzle plate 54 includes a second annular plate portion 57 extending along the circumferential direction of the turbine rotor 3 on the outer circumferential side of the turbine rotor 3 and on the axially leading end side of the first annular plate portion 56. The nozzle plate 54 has a shroud-side flow path wall surface 51 formed on the axially trailing end side of the second annular plate portion 57.

[0021] 1, the nozzle plate 54 may further include a cylindrical portion 58 that protrudes axially from the inner peripheral edge of the second annular plate portion 57 toward the tip end in the axial direction. The nozzle plate 54 has a shroud surface 59 that is continuous with the shroud-side flowpath wall surface 51 and curves convexly. The shroud surface 59 is formed on the inner peripheral edge of the second annular plate portion 57, and a gap (clearance) is formed between the shroud surface 59 and the blade tips of the turbine rotor 3.

[0022] The multiple nozzle supports 55 are arranged at intervals along the circumferential direction of the turbine rotor 3. One end of each of the multiple nozzle supports 55 is fixed to the first annular plate portion 56, and the other end is fixed to the second annular plate portion 57. The nozzle plate 54 is supported by the multiple nozzle supports 55 at a distance from the nozzle mount 53 in the axial direction.

[0023] (Turbine rotor) The turbine rotor 3 is configured to guide exhaust gas introduced from the outer periphery side (outside in the radial direction) of the turbine rotor 3 through the nozzle flow passages 50 to the tip side in the axial direction.

[0024] (Variable nozzle unit) The variable nozzle unit 6 is configured to adjust the flow of exhaust gas in the nozzle flow path 50. The variable nozzle unit 6 includes at least one nozzle vane 61 (in the illustrated example, a plurality of nozzle vanes) arranged in the nozzle flow path 50. As shown in FIG. 2 , the plurality of nozzle vanes 61 are arranged at intervals in the nozzle flow path 50 along the circumferential direction of the turbine rotor 3.

[0025] 1, the variable nozzle unit 6 further includes a rotation mechanism 62 configured to link the multiple nozzle vanes 61 and rotate them around their respective rotation centers RC. The variable nozzle unit 6 can increase or decrease the flow path cross-sectional area of ​​the exhaust gas flow path formed between the nozzle vanes 61 by changing the blade angle of the multiple nozzle vanes 61 using the rotation mechanism 62. The turbine housing 2 can change the flow velocity, pressure, and inflow angle of the exhaust gas guided to the turbine rotor 3 by increasing or decreasing the flow path cross-sectional area of ​​the exhaust gas flow path formed between the nozzle vanes 61 using the variable nozzle unit 6.

[0026] In the embodiment shown in FIG. 1, the rotation mechanism 62 includes an annular drive ring 63 rotatably arranged along the circumferential direction of the turbine rotor 3 relative to the nozzle mount 53, a plurality of vane shafts 64, a plurality of lever plates 65, an actuator 66 configured to rotate the drive ring 63 around the axis LB of the drive ring 63, and a controller (control device) 67 configured to control the driving of the actuator 66.

[0027] The rotation mechanism 62 includes vane shafts 64 and lever plates 65 in the same number as the number of nozzle vanes 61 included in the variable nozzle unit 6. One end of each of the multiple vane shafts 64 is fixed to a different (corresponding) nozzle vane 61, and the other end is mechanically connected to one end of a different (corresponding) lever plate 65. The other end of each of the multiple lever plates 65 is mechanically connected to a drive ring 63. The actuator 66 includes an electric motor, an air cylinder, etc. The actuator 66 is mechanically connected to the drive ring 63.

[0028] The power transmission path from the actuator 66 to the multiple nozzle vanes 61 is configured so that the actuator 66 and the drive ring 63, the drive ring 63 and each lever plate 65, and each lever plate 65 and each vane shaft 64 are connected to one another. When the actuator 66 is driven by the controller 67, the drive ring 63 rotates about the axis LB as a rotation center in accordance with the driving of the actuator 66. When the drive ring 63 rotates, each nozzle vane 61 rotates about its own rotation center RC in conjunction with the rotation of the drive ring 63 via each lever plate 65 and each vane shaft 64, changing its blade angle.

[0029] When the drive ring 63 is rotated in one circumferential direction, the nozzle vanes 61 adjacent to each other in the circumferential direction move away from each other, increasing the flow path cross-sectional area of ​​the exhaust gas flow path between the nozzle vanes 61. When the drive ring 63 is rotated in the other circumferential direction, the nozzle vanes 61 adjacent to each other in the circumferential direction move toward each other, decreasing the flow path cross-sectional area of ​​the exhaust gas flow path between the nozzle vanes 61.

[0030] (Internal combustion engine systems, turbochargers) Fig. 3 is a schematic diagram of an internal combustion engine system 10 including a variable geometry turbocharger 1 according to one embodiment. As shown in Fig. 3, the internal combustion engine system 10 includes the turbocharger 1, an engine (internal combustion engine) 11 having a plurality of cylinders 12 (four cylinders 12A, 12B, 12C, and 12D in the illustrated example), exhaust gas lines 13 (13A, 13B, 13C, and 13D) for guiding exhaust gas discharged from the plurality of cylinders 12 of the engine 11 to the turbocharger 1, and a gas line 14 for guiding gas (e.g., air) compressed in the turbocharger 1 to the plurality of cylinders 12 of the engine 11.

[0031] 1, the turbocharger 1 includes a turbine 15 configured to be driven by the energy of exhaust gas discharged from the engine 11, and a centrifugal compressor 16 configured to be driven in conjunction with the driving of the turbine 15 and to compress gas (e.g., air) sent to the engine 11. The turbine 15 includes the above-mentioned turbine housing 2 and turbine rotor 3. The centrifugal compressor 16 includes a compressor housing 161 and an impeller 162 rotatably housed in the compressor housing 161.

[0032] 3, the turbocharger 1 includes a turbine housing 2, a turbine rotor 3, a compressor housing 161, an impeller 162, a rotating shaft 17 having the turbine rotor 3 on one end and the impeller 162 on the other end, and a bearing 18 disposed between the turbine rotor 3 and the impeller 162 and configured to rotatably support the rotating shaft 17. The impeller 162 is configured to guide gas introduced along the axial direction to the outside in the radial direction of the impeller 162.

[0033] The compressor housing 161 has a gas discharge port 163 for discharging the gas that has passed through the impeller 162 to the outside. The gas line 14 has its upstream end (one end) connected to the gas discharge port 163, and its multiple branched downstream ends (other ends) each connected to a different (corresponding) cylinder 12 (12A, 12B, 12C, 12D). The gas that has been guided into the compressor housing 161 and compressed by the impeller 162 is guided through the gas line 14 to each cylinder 12 of the engine 11 and is used for combustion in each cylinder 12.

[0034] The turbine housing 2 has at least one exhaust gas inlet (gas inlet) 80 for introducing exhaust gas into it. The upstream ends (one ends) of the exhaust gas lines 13 (13A, 13B, 13C, 13D) are connected to different (corresponding) cylinders 12 (12A, 12B, 12C, 12D), and the downstream ends (the other ends) of the exhaust gas lines 13 are connected to at least one exhaust gas inlet 80.

[0035] 3, the at least one exhaust gas inlet 80 includes a first exhaust gas inlet (gas inlet) 81 and a second exhaust gas inlet (gas inlet) 82. The exhaust gas line 13 includes a first junction line 13E where an exhaust gas line 13A, the upstream end of which is connected to the cylinder 12A, and an exhaust gas line 13D, the upstream end of which is connected to the cylinder 12D, join together. In other words, the exhaust gas line 13A shares the first junction line 13E with the exhaust gas line 13D. The downstream end of the first junction line 13E is connected to the first exhaust gas inlet 81.

[0036] The exhaust gas line 13 includes a second junction line 13F where an exhaust gas line 13B, whose upstream end is connected to the cylinder 12B, and an exhaust gas line 13C, whose upstream end is connected to the cylinder 12C, join. In other words, the exhaust gas line 13B shares the second junction line 13F with the exhaust gas line 13C. The downstream end of the second junction line 13F is connected to a second exhaust gas inlet 82. Exhaust gas from the cylinders 12A and 12D is introduced into the turbine housing 2 through a first exhaust gas inlet 81. Exhaust gas from the cylinders 12B and 12C is introduced into the turbine housing 2 through the second exhaust gas inlet 82. The exhaust gas introduced into the turbine housing 2 passes through the scroll passage 40 and the nozzle passage 50 and is introduced to the turbine rotor 3.

[0037] The turbine 15 of the turbocharger 1 is configured to rotate the turbine rotor 3 using the energy of exhaust gas from the engine 11. The impeller 162 is mechanically connected to the turbine rotor 3 via the rotating shaft 17, and therefore rotates in conjunction with the rotation of the turbine rotor 3. The centrifugal compressor 16 of the turbocharger 1 is configured to compress the gas passing through the impeller 162 by the rotation of the impeller 162, increase the density of the gas, and send it to the engine 11.

[0038] (Scroll flow passage forming section) 2, the scroll passage forming portion 4 has a tongue portion 42 that protrudes toward the scroll passage 40 and separates the start and end of the winding of the scroll passage 40 in a cross section perpendicular to the axis LA of the turbine rotor 3. As shown in FIG. 2, the angular position of the tongue portion 42 in the circumferential direction about the axis LA of the turbine housing 2 is defined as 0°, and the angle θ is defined so that the angle gradually increases from the tongue portion 42 toward the downstream side of the scroll passage 40.

[0039] (Nozzle vane near the tongue) In a cross section perpendicular to the axis LA of the turbine rotor 3 as shown in Figure 2, the nozzle vane 61A closest to the tongue portion 42 and the two nozzle vanes 61B and 61C adjacent to the nozzle vane 61A in the circumferential direction of the turbine rotor 3 are defined as the nozzle vanes near the tongue portion.

[0040] (Turbine housing according to a comparative example) Fig. 4 is a schematic cross-sectional view taken along an axis LA passing through the tongue portion 42 (see Fig. 3) of the turbine housing 02 according to the comparative example. Fig. 4 shows a cross section of the turbine housing 02 at an angular position θ of 0°. Note that in the turbine housing 02 according to the comparative example, parts that are common to the turbine housing 2 are given the same reference numerals, and duplicated explanations will be omitted where appropriate.

[0041] The turbine housing 02 according to the comparative example includes a scroll passage wall surface 041 that connects the outer peripheral end 401 of the scroll passage 40 and the outer peripheral end 521 of the hub-side passage wall surface 52. The scroll passage wall surface 041 does not have a cliff portion 72, which will be described later. The scroll passage wall surface 041 has an arc shape that extends from the outer peripheral end 401 of the scroll passage 40 to the outer peripheral end 521 of the hub-side passage wall surface 52, and the distance (radial distance) from the axis LA decreases as the scroll passage wall surface 041 approaches the rear end in the axial direction. The arc shape is a concave curve that is concave toward the rear end in the axial direction. In this case, exhaust gas flowing radially inward along the scroll passage wall surface 041 flows directly into the nozzle passage 50.

[0042] 5 is an explanatory diagram illustrating the results of load evaluation of nozzle vanes 61A, 61B, and 61C located near the tongue portion in a comparative example. A CFD analysis was performed to examine changes in the load acting on nozzle vane 61 under pressure conditions that simulated pulsation conditions from engine 11 and increased or decreased the pressure ratio of exhaust gas introduced into exhaust gas inlet 80 of turbine housing 2 during one cycle of engine 11. As shown in FIG. 5, a load VL1 acting in a certain acting direction (positive direction) and a load VL2 acting in an acting direction opposite to the positive direction (negative direction) may occur on nozzle vanes 61A, 61B, and 61C near the tongue portion during one cycle of engine 11. If the direction of the load acting on the nozzle vane 61 reverses within a short period of time, such as one cycle of the engine 11, the vane shaft 64 fixed to the nozzle vane 61 will collide with other components (nozzle mount 53) more frequently, increasing the risk of wear on the vane shaft 64 and potentially reducing the reliability of the nozzle vane 61. The greater the load amplitude ΔVL, which is the sum of the absolute value of the maximum load VL1max in the positive direction and the absolute value of the maximum load VL2max in the negative direction acting on the nozzle vane 61 during one cycle of the engine 11, the higher the risk of wear on the vane shaft 64 fixed to the nozzle vane 61 and the lower the reliability of the nozzle vane 61.

[0043] 6 and 7 are schematic cross-sectional views along the axis LA passing through a tongue portion of a turbine housing 2 according to one embodiment. FIGS. 6 and 7 show cross sections of the turbine housing 2 at an angular position θ of 0°. As shown in FIGS. 6 and 7 , the turbine housing 2 according to some embodiments includes the scroll passage forming portion 4 described above, the nozzle passage forming portion 5 described above, and the variable nozzle unit 6 described above. The scroll passage forming portion 4 includes a scroll passage wall surface 41 connecting an outer circumferential end 401 of the scroll passage 40 and an outer circumferential end 521 of the hub-side passage wall surface 52. The outer circumferential end 521 is an outer edge, in the radial direction of the turbine rotor 3, of the hub-side passage wall surface 52 that forms the nozzle passage 50 between the hub-side passage wall surface 52 and the shroud-side passage wall surface 51. The scroll passage wall surface 41 includes a first arc portion 71 and a cliff portion 72 in a cross section along the axis LA passing through the tongue portion 42 of the scroll passage forming portion 4, as shown in FIGS. 6 and 7 .

[0044] The first arc portion 71 has an outer circumferential end 711 connected to the outer circumferential end 401 of the scroll passage 40, and extends from the outer circumferential end 711 toward the inside in the radial direction of the turbine rotor 3. The first arc portion 71 has a concave curved shape that is concave toward the rear end in the axial direction so that the distance (radial distance) from the axis LA decreases toward the rear end in the axial direction.

[0045] The cliff portion 72 has an outer circumferential end (one end) 721 connected to the inner circumferential end 712 of the first arc portion 71, and an inner circumferential end (the other end) 722 connected to the outer circumferential end 521 of the hub-side flowpath wall surface 52. The cliff portion 72 includes a second arc portion 73 connected to the inner circumferential end 712 of the first arc portion 71. The second arc portion 73 has a convex curved shape that protrudes toward the front end in the axial direction so that the distance (radial distance) from the axis LA decreases toward the rear end in the axial direction. The second arc portion 73 forms an inflection point P1 with the first arc portion 71.

[0046] The inflection point P1 is located toward the tip side of the turbine rotor 3 in the axial direction of the turbine rotor 3 from the outer peripheral end 521 of the hub side flow path wall surface 52, and offset radially outward from the outer peripheral end 521 of the hub side flow path wall surface 52.

[0047] 2, the cliff portion 72 is located at an angular position where the angular position θ is 0° so that its upstream end 723 is connected to the tongue portion 42. The cliff portion 72 extends from its upstream end 723 toward the downstream side of the scroll passage 40 along the circumferential direction of the turbine rotor 3 over a predetermined circumferential range (90° or more).

[0048] According to the above configuration, by providing the cliff portion 72 in the scroll passage forming portion 4, it is possible to prevent exhaust gas with a high Mach number that flows near the tongue portion 42 of the scroll passage 40 and wake (flow distortion) that occurs at the tongue portion due to the swirling flow of the exhaust gas from flowing into the nozzle passage 50 near the tongue portion 42. In this case, the exhaust gas that has been guided downstream of the scroll passage 40 and has a lower Mach number than near the tongue portion 42 can be guided to the nozzle passage 50, thereby reducing the fluid force from the exhaust gas acting on the nozzle vanes 61. For example, it is possible to prevent the direction of the load acting on the tongue-proximal nozzle vanes 61A, 61B, and 61C from reversing during one cycle of the engine 11, and to reduce the load amplitude ΔVL of the tongue-proximal nozzle vanes 61A, 61B, and 61C during one cycle of the engine 11. By reducing the fluid force from the exhaust gas acting on the nozzle vanes 61, wear on the vane shafts 64 that support the nozzle vanes 61 can be suppressed, and the reliability of the nozzle vanes 61 can be improved.

[0049] In some embodiments, as shown in Fig. 6, the cliff portion 72 described above further includes an inclined portion 74 that extends from an inner circumferential end 731 of the second arc portion 73 toward the rear end in the axial direction and radially inward. The inclined portion 74 is configured so that the distance (radial distance) from the axis LA of the turbine rotor 3 decreases toward the rear end in the axial direction. The inclined portion 74 is formed in a linear shape with a constant inclination in a cross section taken along the axis LA as shown in Fig. 6.

[0050] According to the above configuration, the cliff portion 72 including the inclined portion 74 can effectively prevent exhaust gas with a high Mach number that flows near the tongue portion 42 of the scroll passage 40 and that swirls greatly, and wake (flow distortion) that occurs at the tongue portion 42 due to the swirling flow of the exhaust gas, from flowing into the nozzle passage 50 near the tongue portion 42. Furthermore, the cliff portion 72 including the inclined portion 74 can prevent the exhaust gas that flows toward the nozzle passage 50 along the cliff portion 72 (inclined portion 74) from forming a vortex, and therefore can suppress flow path loss in the scroll passage 40 that faces the cliff portion 72.

[0051] In some embodiments, as shown in FIG. 7, the cliff portion 72 described above further includes an extension portion 75 extending from the inner peripheral end 731 of the second arc portion 73 along the axial direction toward the rear end side of the axial direction, and a third arc portion 76 extending from the rear end side end 751 of the extension portion 75 toward the rear end side of the axial direction and radially inward.

[0052] The third arc portion 76 has a concave curved shape that is concave toward the rear end in the axial direction so that the distance (radial distance) from the axis LA decreases toward the rear end in the axial direction. An inner peripheral end of the third arc portion 76 is connected to the outer peripheral end 521 of the hub-side flow path wall surface 52.

[0053] According to the above configuration, the cliff portion 72 including the extension portion 75 and the third arc portion 76 can effectively prevent exhaust gas with a high Mach number that flows near the tongue portion 42 of the scroll passage 40 and that swirls greatly, and wake (flow distortion) that occurs at the tongue portion due to the swirling flow of the exhaust gas, from flowing into the nozzle passage 50 near the tongue portion 42. Note that the cliff portion 72 including the above-described inclined portion 74 can more effectively prevent exhaust gas that flows along the cliff portion 72 toward the nozzle passage 50 from forming a vortex flow, compared to the cliff portion 72 including the extension portion 75 and the third arc portion 76.

[0054] In some embodiments, as shown in FIG. 2, when the angular position of the tongue portion 42 in the circumferential direction of the turbine housing 2 is defined as 0° and the angular position θ is defined so that the angle gradually increases from the tongue portion 42 toward the downstream side of the scroll flow passage 40, the angular position θmax of the downstream end 724 of the cliff portion 72 satisfies the condition 120°≦θmax≦180°.

[0055] According to the above configuration, the larger the angular position θmax of the cliff portion 72, the more the effect of suppressing the inflow of exhaust gas from the scroll passage 40 to the nozzle passage 50 can be ensured over a wide range extending to the downstream side of the scroll passage 40, and the exhaust gas can be sent all the way to the downstream side of the scroll passage 40. However, it is necessary to ensure the amount of exhaust gas that flows from the scroll passage 40 to the nozzle passage 50 on the downstream side of the scroll passage 40. By setting the angular position θmax of the cliff portion 72 to satisfy the condition 120°≦θmax≦180°, the exhaust gas can be sent all the way to the downstream side of the scroll passage 40, and the amount of exhaust gas that flows from the scroll passage 40 to the nozzle passage 50 on the downstream side of the scroll passage 40 can be made appropriate.

[0056] (Cliff length X, Y) 6 and 7, the axial length between the outer circumferential end (one end) 721 and the inner circumferential end (the other end) 722 of the cliff portion 72 is defined as X, and the radial length between the outer circumferential end (one end) 721 and the inner circumferential end (the other end) 722 of the cliff portion 72 is defined as Y. Furthermore, the maximum value of the length X from the upstream end 723 to the downstream end 724 of the cliff portion 72 is defined as Xmax, and the maximum value of the length Y from the upstream end 723 to the downstream end 724 of the cliff portion 72 is defined as Ymax.

[0057] 8 to 10 are explanatory diagrams illustrating the relationship between the axial length X and the radial length Y of the cliff portion 72 and the angular position θ in one embodiment. FIG. 11 is an explanatory diagram illustrating the shape of the scroll flow passage wall surface 41 at multiple angular positions θ in one embodiment. In some embodiments, as shown in FIGS. 8 to 10, the axial length X of the cliff portion 72 described above is configured to decrease toward the downstream side of the scroll flow passage 40. The length X when the angular position θ is 0° is the maximum value Xmax of the length X, and the length X when the angular position θ is θmax is the minimum value of the length X.

[0058] 11 shows shapes of the scroll passage wall surface 41 at multiple angular positions θ (θ=20°, 80°, 140°) including the cliff portion 72 and shapes of the scroll passage wall surface 41 at multiple angular positions θ (θ=200°, 260°, 320°) not including the cliff portion 72. In the embodiment shown in FIG. 11, the outer peripheral end (one end) 721 of the cliff portion 72 of the scroll passage wall surface 41 moves toward the rear end in the axial direction as it moves toward the downstream side of the scroll passage 40 (as the angular position θ increases) in a circumferential range (0°≦θ≦θmax) in which the cliff portion 72 is formed. Note that the scroll passage wall surface 41 moves radially inward as it moves toward the downstream side of the scroll passage 40 (as the angular position θ increases) in a circumferential range (θmax<θ<360°) in which the cliff portion 72 is not formed.

[0059] According to the above configuration, the longer the length X of the cliff portion 72, the greater the effect of suppressing the inflow of exhaust gas from the scroll passage 40 to the nozzle passage 50. By configuring the length X of the cliff portion 72 to become smaller toward the downstream side of the scroll passage 40, it is possible to suppress the inflow of exhaust gas from the scroll passage 40 to the nozzle passage 50 on the upstream side of the scroll passage 40, such as in the vicinity of the tongue portion 42, while making the amount of exhaust gas that inflows from the scroll passage 40 to the nozzle passage 50 on the downstream side of the scroll passage 40 appropriate.

[0060] 6 and 7, the length in the axial direction of the nozzle flow path 50 at the outer peripheral end 521 of the hub-side flow path wall surface 52 is defined as L. In some embodiments, the maximum value Xmax of the length X in the axial direction of the cliff portion 72 described above satisfies the condition 0.75×L≦Xmax≦1.25×L.

[0061] 12 is an explanatory diagram illustrating the relationship between the maximum value Xmax of the length X in the axial direction between the outer circumferential end (one end) 721 and the inner circumferential end (the other end) 722 of the cliff portion 72 in one embodiment, and the inflow rate F of exhaust gas from the scroll passage 40 to the nozzle passage 50 in the circumferential range (0°≦θ≦θmax) in which the cliff portion 72 is formed. As shown in Fig. 12, in the range in which the maximum value Xmax is equal to or less than the axial length L of the nozzle passage 50, as the maximum value Xmax increases, the inflow rate F decreases and the amount of decrease in the inflow rate F becomes smaller.

[0062] According to the above configuration, if the maximum value Xmax is too small, there is a risk that the effect of suppressing the inflow of exhaust gas from the scroll passage 40 to the nozzle passage 50 will be reduced. On the other hand, if the maximum value Xmax is too large, there is a risk that vortexes will be generated in the scroll passage 40 facing the cliff portion 72, and flow path loss in the scroll passage 40 facing the cliff portion 72 will be large. By setting the maximum value Xmax of the cliff portion 72 to satisfy the condition 0.75×L≦Xmax≦1.25×L, it is possible to suppress the generation of vortexes in the scroll passage 40 facing the cliff portion 72 while ensuring the effect of suppressing the inflow of exhaust gas from the scroll passage 40 to the nozzle passage 50.

[0063] 8, the length Y in the radial direction of the cliff portion 72 described above is configured to decrease toward the downstream side of the scroll flow passage 40. The length Y when the angular position θ is 0° is the maximum value Ymax of the length Y, and the length Y when the angular position θ is θmax is the minimum value of the length Y. In the scroll flow passage wall surface 41, within the circumferential range (0°≦θ≦θmax) in which the cliff portion 72 is formed, the outer circumferential end (one end) 721 of the cliff portion 72 moves radially inward toward the downstream side of the scroll flow passage 40 (as the angular position θ increases).

[0064] According to the above configuration, the smaller the length Y of the cliff portion 72, the smaller the flow path cross-sectional area of ​​the scroll flow path 40 (the flow path communicating with the nozzle flow path 50) located radially inward from the cliff portion 72, and therefore the greater the effect of suppressing the inflow of exhaust gas from the scroll flow path 40 to the nozzle flow path 50. By configuring the length Y of the cliff portion 72 to increase toward the downstream side of the scroll flow path 40, the effect of suppressing the inflow of exhaust gas from the scroll flow path 40 to the nozzle flow path 50 can be ensured over a wide range extending to the downstream side of the scroll flow path 40.

[0065] In some embodiments, as shown in Fig. 9, the radial length Y of the cliff portion 72 described above is configured to be constant within a predetermined circumferential range. In the embodiment shown in Fig. 9, the radial length Y of the cliff portion 72 described above is configured to be constant within the circumferential range (0°≦θ≦θmax) in which the cliff portion 72 is formed, but it may be configured to be constant within a portion of the circumferential range in which the cliff portion 72 is formed.

[0066] According to the above configuration, the effect of suppressing the inflow of exhaust gas from the scroll passage 40 to the nozzle passage 50 within a predetermined circumferential range in which the length Y of the cliff portion 72 is constant is dominated by the length X of the cliff portion 72. Therefore, by adjusting the length X of the cliff portion 72, the effect of suppressing the inflow of exhaust gas from the scroll passage 40 to the nozzle passage 50 can be easily adjusted.

[0067] In some embodiments, as shown in Fig. 10, the length Y of the cliff portion 72 in the radial direction may be configured to increase toward the downstream side of the scroll flow passage 40. As shown in Fig. 10, the length Y when the angular position θ is 0° may be the minimum value of the length Y, and the length Y when the angular position θ is θmax may be the maximum value Ymax of the length Y. Furthermore, as shown in Fig. 11, the scroll flow passage wall surface 41 may be configured such that, within a circumferential range (0°≦θ≦θmax) in which the cliff portion 72 is formed, an outer circumferential end (one end) 721 of the cliff portion 72 moves outward in the radial direction as it moves toward the downstream side of the scroll flow passage 40 (as the angular position θ increases).

[0068] 6 and 7, Dmax is defined as the maximum radial length of the scroll passage 40 in a cross section (cross section at an angular position of 0°) along the axis LA passing through the tongue portion 42 of the scroll passage forming portion 4. In some embodiments, the maximum value Ymax of the radial length Y of the cliff portion 72 described above satisfies the condition 0≦Ymax≦0.7×Dmax.

[0069] According to the above configuration, if the maximum value Ymax is too small, the effect of suppressing the inflow of exhaust gas from the scroll passage 40 to the nozzle passage 50 becomes excessive, increasing the possibility of vortexes occurring in the scroll passage 40 facing the cliff portion 72, and there is a risk of increased flow path loss in the scroll passage 40 facing the cliff portion 72. Furthermore, if the maximum value Ymax is too large, there is a risk of a decrease in the effect of suppressing the inflow of exhaust gas from the scroll passage 40 to the nozzle passage 50. By setting the maximum value Ymax of the cliff portion 72 to satisfy the condition 0≦Ymax≦0.7×Dmax, it is possible to suppress the generation of vortexes in the scroll passage 40 facing the cliff portion 72 while ensuring the effect of suppressing the inflow of exhaust gas from the scroll passage 40 to the nozzle passage 50.

[0070] 2 , the turbine housing 2 further includes a first exhaust gas inlet (gas inlet) 81 for guiding exhaust gas (gas) to the scroll passage 40, a second exhaust gas inlet (gas inlet) 82 for guiding exhaust gas (gas) to the scroll passage 40, the second exhaust gas inlet 82 being provided on the outer side of the first exhaust gas inlet 81 in the radial direction of the turbine rotor 3, and a junction passage forming portion 84 for forming a junction passage 83. The junction passage 83 is configured so that the exhaust gas (gas) guided into the turbine housing 2 by the first exhaust gas inlet 81 and the exhaust gas (gas) guided into the turbine housing 2 by the second exhaust gas inlet 82 are joined together. The junction passage 83 is in communication with the upstream end 402 of the scroll passage 40.

[0071] The exhaust gas introduced into the turbine housing 2 from the first exhaust gas introduction port 81 or the second exhaust gas introduction port 82 passes through the confluence passage 83 and then flows into the scroll passage 40. During one cycle of the engine 11, there are cases where the exhaust gas is mainly introduced from the first exhaust gas introduction port 81, cases where the exhaust gas is mainly introduced from the second exhaust gas introduction port 82, and cases where the exhaust gas is introduced from both the first exhaust gas introduction port 81 and the second exhaust gas introduction port 82.

[0072] According to the above configuration, the inflow angle of the exhaust gas flowing into the scroll passage 40 changes depending on whether the exhaust gas is mainly introduced through the first exhaust gas inlet 81 or the second exhaust gas inlet 82. The inflow angle of the exhaust gas flowing into the nozzle passage 50 also changes depending on whether the exhaust gas is mainly introduced through the first exhaust gas inlet 81 or the second exhaust gas inlet 82. In a configuration such as the above, in which exhaust gas is introduced through both the first exhaust gas inlet 81 and the second exhaust gas inlet 82, the inflow angle of the exhaust gas flowing into the nozzle passage 50 fluctuates more during one cycle of the engine 11 than in a configuration in which exhaust gas is introduced through a single gas inlet. This increases the load amplitude ΔVL acting on the nozzle vane 61, potentially increasing the risk of wear on the vane shaft 64 fixed to the nozzle vane 61. Even in the above configuration, the provision of the cliff portion 72 effectively reduces the fluid force (load amplitude ΔVL) acting on the nozzle vane 61 during one cycle of the engine 11.

[0073] In some embodiments, as shown in FIG. 2, the above-mentioned confluence flow path forming portion 84 includes a constriction portion 85 configured so that the flow path area of ​​the confluence flow path 83 decreases toward the downstream side of the confluence flow path 83.

[0074] 2, the throttle section 85 has an inner wall surface 86 that forms the merging flow passage 83, and an outer wall surface 87 that is formed farther from the axis LA than the inner wall surface 86 and forms the merging flow passage 83 between itself and the inner wall surface 86. The inner wall surface 86 is configured so that the distance from the axis LA increases toward the downstream side of the merging flow passage 83. The outer wall surface 87 is configured so that the distance from the axis LA decreases toward the downstream side of the merging flow passage 83.

[0075] According to the above configuration, by providing the constriction section 85 having the inner wall surface 86 and the outer wall surface 87 in the confluence passage 83, the flow velocity and inflow angle of the exhaust gas flowing from the confluence passage 83 into the scroll passage 40 can be stabilized, and therefore the exhaust gas can be sent to the downstream side of the scroll passage 40 whether the exhaust gas is mainly introduced from the first exhaust gas inlet 81 or the exhaust gas is mainly introduced from the second exhaust gas inlet 82. This makes it possible to effectively prevent exhaust gas with a high Mach number that flows near the tongue portion 42 of the scroll passage 40 and that flows with a large swirl and causes a wake (flow distortion) at the tongue portion due to the swirling flow of the exhaust gas from flowing into the nozzle passage 50 near the tongue portion 42.

[0076] 1, a variable geometry turbocharger 1 according to some embodiments includes the above-described turbine housing 2 and the above-described turbine rotor 3. In this case, by improving the reliability of the nozzle vanes 61 in the turbine housing 2, the reliability of the turbocharger 1 can be improved.

[0077] In this specification, expressions expressing relative or absolute arrangement such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" not only express such an arrangement strictly, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions such as "identical," "equal," and "homogeneous" that indicate that something is in an equal state not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. Furthermore, in this specification, expressions representing shapes such as a rectangular shape or a cylindrical shape not only represent rectangular shapes or cylindrical shapes in the strict geometric sense, but also represent shapes including uneven portions, chamfered portions, etc., to the extent that the same effect can be obtained. Furthermore, in this specification, the expressions "comprise," "include," or "have" a component are not exclusive expressions that exclude the presence of other components.

[0078] The present disclosure is not limited to the above-described embodiments, but also includes modifications to the above-described embodiments and appropriate combinations of these modifications.

[0079] The contents of the above-described embodiments can be understood, for example, as follows.

[0080] 1) A turbine housing (2) according to at least one embodiment of the present disclosure comprises: A turbine housing (2) for accommodating a turbine rotor (3), a scroll passage forming portion (4) that forms a scroll passage (40) extending in a circumferential direction around an axis (LA) of the turbine rotor (3); a nozzle flow path forming section (5) that forms a nozzle flow path (50) for guiding exhaust gas from the scroll flow path (40) to the turbine rotor (3) that is arranged on the inner circumferential side of the scroll flow path (40), the nozzle flow path forming section (5) having a shroud-side flow path wall surface (51) and a hub-side flow path wall surface (52) that define the nozzle flow path (50); a variable nozzle unit (6) for adjusting the flow of the exhaust gas in the nozzle flow path (50), the variable nozzle unit (6) including at least one nozzle vane (61) arranged in the nozzle flow path (50); the scroll passage forming portion (4) includes a scroll passage wall surface (41) connecting an outer circumferential end (401) of the scroll passage (40) and an outer circumferential end (521) of the hub-side passage wall surface (52), The scroll flow passage wall surface (41) has a cross section along the axis (LA) passing through the tongue portion (42) of the scroll flow passage forming portion (4), a first arc portion (71) having an outer circumferential end (711) connected to the outer circumferential end (401) of the scroll passage (40) and extending from the outer circumferential end (711) toward a radially inner side of the turbine rotor (3); a cliff portion (72) having one end (721) connected to the inner circumferential end (712) of the first arc portion (71) and the other end (722) connected to the outer circumferential end (521) of the hub-side flow path wall surface (52), the cliff portion (72) including a second arc portion (73) connected to the inner circumferential end (712) of the first arc portion (71) and forming an inflection point (P1) between the cliff portion (72) and the first arc portion (71); The inflection point (P1) is located closer to the tip end of the turbine rotor (3) in the axial direction than the outer peripheral end (521) of the hub-side flow path wall surface (52), and is offset radially outward from the turbine rotor (3) than the outer peripheral end (521) of the hub-side flow path wall surface (52).

[0081] According to the configuration 1), the cliff portion 72 is provided in the scroll passage-forming portion 4, thereby preventing the exhaust gas with a high Mach number that flows near the tongue portion 42 of the scroll passage 40 and the wake (flow distortion) generated at the tongue portion due to the swirling flow of the exhaust gas from flowing into the nozzle passage 50 near the tongue portion 42. In this case, the exhaust gas that has been guided downstream of the scroll passage 40 and has a lower Mach number than the exhaust gas near the tongue portion 42 can be guided to the nozzle passage 50, thereby reducing the fluid force of the exhaust gas acting on the nozzle vanes 61. The reduction in the fluid force of the exhaust gas acting on the nozzle vanes 61 reduces wear on the vane shafts 64 that support the nozzle vanes 61, thereby improving the reliability of the nozzle vanes 61.

[0082] 2) In some embodiments, the turbine housing (2) according to 1) above, The cliff portion (72) further includes an inclined portion (74) extending from an inner peripheral end (731) of the second arc portion (73) toward a rear end side opposite the tip end side in the axial direction and toward the inside in the radial direction, the inclined portion (74) being configured so that the distance from the axis (LA) of the turbine rotor (3) becomes shorter as it approaches the rear end side in the axial direction.

[0083] According to the configuration 2), the cliff portion (72) including the inclined portion (74) can effectively prevent the exhaust gas with a high Mach number that flows near the tongue portion (42) of the scroll flow path (40) and the wake (flow distortion) that occurs at the tongue portion due to the swirling flow of the exhaust gas from flowing into the nozzle flow path (50) near the tongue portion (42). Furthermore, the cliff portion (72) including the inclined portion (74) can prevent the exhaust gas that flows along the cliff portion (72) toward the nozzle flow path (50) from forming a vortex flow, thereby reducing flow path loss in the scroll flow path (40) facing the cliff portion (72).

[0084] 3) In some embodiments, the turbine housing (2) according to 1) above, The cliff portion (72) is an extension portion (75) extending from an inner peripheral end (731) of the second arc portion (73) along the axial direction toward a rear end side opposite to the front end side in the axial direction; The extension portion (75) further includes a third arc portion (76) extending from the rear end side end (751) of the extension portion (75) toward the rear end side in the axial direction and inward in the radial direction.

[0085] According to the above configuration 3), the cliff portion (72) including the extension portion (75) and the third arc portion (76) can effectively prevent the exhaust gas with a large swirl and a high Mach number flowing near the tongue portion (42) of the scroll flow path (40) and the wake (flow distortion) generated at the tongue portion due to the swirling flow of the exhaust gas from flowing into the nozzle flow path (50) near the tongue portion (42).

[0086] 4) In some embodiments, the turbine housing (2) according to any one of 1) to 3) above, When the length in the axial direction between the one end (721) and the other end (722) of the cliff portion (72) is defined as X, the length X is configured to become smaller toward the downstream side of the scroll flow path (40).

[0087] According to the configuration 4), the longer the length X of the cliff portion (72), the greater the effect of suppressing the inflow of exhaust gas from the scroll flow path (40) to the nozzle flow path (50). By configuring the length X of the cliff portion (72) to decrease toward the downstream side of the scroll flow path (40), it is possible to suppress the inflow of exhaust gas from the scroll flow path (40) to the nozzle flow path (50) on the upstream side of the scroll flow path (40), such as in the vicinity of the tongue portion (42), and to make the amount of exhaust gas that flows from the scroll flow path (40) to the nozzle flow path (50) appropriate on the downstream side of the scroll flow path (40).

[0088] 5) In some embodiments, the turbine housing (2) according to any one of 1) to 4) above, When the length in the axial direction between the one end (721) and the other end (722) of the cliff portion (72) is defined as X, the maximum value of the length X in the cliff portion (72) is defined as Xmax, and the length in the axial direction of the nozzle flow path (50) at the outer circumferential end (521) of the hub-side flow path wall surface (52) is defined as L, the maximum value Xmax satisfies the condition 0.75×L≦Xmax≦1.25×L.

[0089] According to the configuration of 5), if the maximum value Xmax is too small, the effect of suppressing the inflow of exhaust gas from the scroll flow path (40) into the nozzle flow path (50) may be reduced. On the other hand, if the maximum value Xmax is too large, a vortex may be generated in the scroll flow path (40) facing the cliff portion (72), which may increase the flow path loss in the scroll flow path (40) facing the cliff portion (72). By setting the maximum value Xmax of the cliff portion (72) to satisfy the condition 0.75×L≦Xmax≦1.25×L, the effect of suppressing the inflow of exhaust gas from the scroll flow path (40) into the nozzle flow path (50) can be ensured while suppressing the generation of a vortex in the scroll flow path (40) facing the cliff portion (72).

[0090] 6) In some embodiments, the turbine housing (2) according to any one of 1) to 5) above, When the length in the radial direction between the one end (721) and the other end (722) of the cliff portion (72) is defined as Y, the length Y is configured to become smaller toward the downstream side of the scroll flow path (40).

[0091] According to the configuration 6) above, the smaller the length Y of the cliff portion (72), the smaller the cross-sectional area of ​​the scroll flow path (40, flow path communicating with the nozzle flow path 50) located radially inward of the cliff portion (72) in the direction perpendicular to the cliff portion (72), and therefore, the greater the effect of suppressing the inflow of exhaust gas from the scroll flow path (40) to the nozzle flow path (50). By configuring the length Y of the cliff portion (72) to increase toward the downstream side of the scroll flow path (40), the effect of suppressing the inflow of exhaust gas from the scroll flow path (40) to the nozzle flow path (50) can be ensured over a wide range extending to the downstream side of the scroll flow path (40).

[0092] 7) In some embodiments, the turbine housing (2) according to any one of 1) to 6) above, When the radial length between the one end (721) and the other end (722) of the cliff portion (72) is defined as Y, the length Y is configured to be constant within a predetermined circumferential range.

[0093] According to the above configuration 7), the effect of suppressing the inflow of exhaust gas from the scroll flow path (40) to the nozzle flow path (50) in a predetermined circumferential range where the length Y of the cliff portion (72) is constant is dominated by the length X of the cliff portion (72). Therefore, by adjusting the length X of the cliff portion (72), the effect of suppressing the inflow of exhaust gas from the scroll flow path (40) to the nozzle flow path (50) can be easily adjusted.

[0094] 8) In some embodiments, the turbine housing (2) according to any one of 1) to 7) above, When the radial length between the one end (721) and the other end (722) of the cliff portion (72) is defined as Y, the maximum value of the length Y at the cliff portion (72) is defined as Ymax, and the radial maximum length of the scroll flow path (40) in a cross section along the axis (LA) passing through the tongue portion (42) of the scroll flow path forming portion (4) is defined as Dmax, the maximum value Ymax satisfies the condition 0≦Ymax≦0.7×Dmax.

[0095] According to the configuration of 8), if the maximum value Ymax is too small, the effect of suppressing the inflow of exhaust gas from the scroll flow path (40) to the nozzle flow path (50) becomes excessive, which increases the possibility of generating a vortex in the scroll flow path (40) facing the cliff portion (72), and this may increase flow path loss in the scroll flow path (40) facing the cliff portion (72). Furthermore, if the maximum value Ymax is too large, the effect of suppressing the inflow of exhaust gas from the scroll flow path (40) to the nozzle flow path (50) may decrease. By setting the maximum value Ymax of the cliff portion (72) to satisfy the condition 0≦Ymax≦0.7×Dmax, it is possible to suppress the generation of a vortex in the scroll flow path (40) facing the cliff portion (72) and ensure the effect of suppressing the inflow of exhaust gas from the scroll flow path (40) to the nozzle flow path (50).

[0096] 9) In some embodiments, the turbine housing (2) according to any one of 1) to 8) above, When the angular position θ of the tongue portion (42) in the circumferential direction of the turbine housing (2) is defined as 0°, and the angle gradually increases from the tongue portion (42) toward the downstream side of the scroll flow path (40), The angular position θmax of the downstream end 724 of the cliff portion 72 satisfies the condition 120°≦θmax≦180°.

[0097] According to the configuration 9), the larger the angular position θmax of the cliff portion (72), the more the effect of suppressing the inflow of exhaust gas from the scroll flow path (40) to the nozzle flow path (50) can be ensured over a wide range extending to the downstream side of the scroll flow path (40), and the exhaust gas can be sent to the downstream side of the scroll flow path (40). However, it is necessary to ensure the amount of exhaust gas that flows from the scroll flow path (40) to the nozzle flow path (50) at the downstream side of the scroll flow path (40). By setting the angular position θmax of the cliff portion (72) to satisfy the condition 120°≦θmax≦180°, the exhaust gas can be sent to the downstream side of the scroll flow path (40), and the amount of exhaust gas that flows from the scroll flow path (40) to the nozzle flow path (50) at the downstream side of the scroll flow path (40) can be made appropriate.

[0098] 10) In some embodiments, the turbine housing (2) according to any one of 1) to 9) above, a first gas inlet (81) for introducing gas into the scroll flow path (40); a second gas inlet (82) for introducing gas into the scroll flow path (40), the second gas inlet (82) being provided radially outward of the first gas inlet (81); The turbine housing (2) further includes a confluence flow path forming portion (84) that forms a confluence flow path (83) where the gas introduced into the interior of the turbine housing (2) through the first gas introduction port (81) and the gas introduced into the interior of the turbine housing (2) through the second gas introduction port (82) are joined, the confluence flow path (83) communicating with an upstream end (402) of the scroll flow path (40).

[0099] According to the configuration of 10), the inflow angle of the exhaust gas flowing into the scroll flow path (40) changes depending on whether the exhaust gas is mainly introduced through the first gas inlet (81) or the second gas inlet (82). This also changes the inflow angle of the exhaust gas flowing into the nozzle flow path (50). In the configuration of 10), in which the exhaust gas is introduced through each of the first gas inlet (81) and the second gas inlet (82), the inflow angle of the exhaust gas flowing into the nozzle flow path (50) during one cycle of the engine 11 varies more than in the configuration in which the exhaust gas is introduced through one gas inlet. This increases the load amplitude ΔVL acting on the nozzle vane (61), which may increase the risk of wear on the vane shaft (64) fixed to the nozzle vane (61). In the above configuration 10), the provision of the cliff portion (72) also makes it possible to effectively reduce the fluid force (load amplitude ΔVL) acting on the nozzle vane (61) during one cycle of the engine 11.

[0100] 11) In some embodiments, the turbine housing (2) according to 10) above, the converging flow path forming portion (84) includes a throttle portion (85) configured so that the flow path area of ​​the converging flow path (83) decreases toward the downstream side of the converging flow path (83), The throttle portion (85) has, in a cross section perpendicular to the axis (LA), an inner wall surface (86) that forms the junction flow path (83), the inner wall surface (86) having a distance from the axis (LA) that increases toward the downstream side of the junction flow path (83); and an outer wall surface (87) formed on a side farther from the axis (LA) than the inner wall surface (86) and forming the junction flow path (83) between itself and the inner wall surface (86), the outer wall surface (87) having a distance from the axis (LA) decreasing toward the downstream side of the junction flow path (83).

[0101] According to the configuration 11), the constriction portion (85) having the inner wall surface (86) and the outer wall surface (87) is provided in the junction flow path (83), thereby stabilizing the flow velocity and the inflow angle of the exhaust gas flowing from the junction flow path (83) into the scroll flow path (40). Therefore, the exhaust gas can be sent to the downstream side of the scroll flow path (40) whether the exhaust gas is mainly introduced through the first gas inlet (81) or the second gas inlet (82). This effectively prevents the exhaust gas with a large swirl and a high Mach number flowing near the tongue portion (42) of the scroll flow path (40) and the wake (flow distortion) generated at the tongue portion due to the swirling flow of the exhaust gas from flowing into the nozzle flow path (50) near the tongue portion (42).

[0102] 12) A variable geometry turbocharger (1) according to at least one embodiment of the present disclosure includes: A turbine housing (2) according to any one of 1) to 11), and a turbine rotor (3) rotatably accommodated in the turbine housing.

[0103] According to the configuration 12), the reliability of the nozzle vanes (61) in the turbine housing (2) can be improved, thereby improving the reliability of the turbocharger (1). [Explanation of symbols]

[0104] 1 turbocharger 2 Turbine housing 3 Turbine rotor 4. Scroll flow passage forming section 5 Nozzle flow path forming section 6 Variable nozzle unit 10 Internal combustion engine system 11 Engine 12, 12A, 12B, 12C, 12D cylinders 13, 13A, 13B, 13C, 13D Exhaust gas line 13E, 13F merging line 14 Gas Line 15 Turbine 16 Centrifugal compressor 17 Rotating shaft 18 bearings 40 Scroll flow passage 41 Scroll flow passage wall 42 Tongue 50 nozzle flow path 51 Shroud side flow passage wall 52 Hub side flow passage wall 53 Nozzle mount 54 Nozzle plate 55 Nozzle Support 56 First annular plate 57 Second annular plate 58 Cylindrical part 59 Shroud surface 61 Nozzle vane 61A, 61B, 61C Nozzle vane near the tongue 62 Rotation mechanism 63 Drive Ring 64 vane shaft 65 Lever plate 66 Actuator 67 Controller 71 First arc 72 Cliff Club 73 Second arc 74 Slope 75 Extension 76 Third Arc 80 Exhaust gas inlet 81 First exhaust gas inlet 82 Second exhaust gas inlet 83 Confluence 84 Confluence channel forming section 85 Constriction section 86 Inner wall 87 Outside wall 161 Compressor housing 162 Impeller 163 Gas outlet F inflow rate LA axis P1 inflection point VL1max,VL2max Maximum load VL1, VL2 load Xmax,Ymax maximum value

Claims

1. A turbine housing for accommodating a turbine rotor, comprising: a scroll passage forming portion that forms a scroll passage extending in a circumferential direction about the axis of the turbine rotor; a nozzle flow path forming section that forms a nozzle flow path for guiding exhaust gas from the scroll flow path to the turbine rotor that is disposed on the inner circumferential side of the scroll flow path, the nozzle flow path forming section having a shroud-side flow path wall surface and a hub-side flow path wall surface that define the nozzle flow path; a variable nozzle unit for adjusting a flow of the exhaust gas in the nozzle flow path, the variable nozzle unit including at least one nozzle vane disposed in the nozzle flow path, the scroll passage forming portion includes a scroll passage wall surface connecting an outer circumferential end of the scroll passage and an outer circumferential end of the hub-side passage wall surface, The scroll flow passage wall surface, in a cross section along the axis passing through a tongue portion of the scroll flow passage forming portion, a first arc portion having an outer peripheral end connected to the outer peripheral end of the scroll passage and extending from the outer peripheral end toward an inner side in a radial direction of the turbine rotor; a cliff portion having one end connected to an inner circumferential end of the first arc portion and the other end connected to the outer circumferential end of the hub-side flowpath wall surface, the cliff portion including a second arc portion connected to the inner circumferential end of the first arc portion and forming an inflection point between the first arc portion and the cliff portion, the inflection point is located at a position closer to a tip end of the hub-side flow passage wall surface in an axial direction of the turbine rotor than the outer circumferential end of the hub-side flow passage wall surface and offset radially outward of the turbine rotor than the outer circumferential end of the hub-side flow passage wall surface; When a length in the axial direction between the one end and the other end of the cliff portion is defined as X, the length X is configured to become smaller toward the downstream side of the scroll flow path. Turbine housing.

2. the cliff portion further includes an inclined portion extending from an inner circumferential end of the second arc portion toward a rear end side opposite the front end side in the axial direction and toward an inner side in the radial direction, the inclined portion being configured such that a distance from the axis of the turbine rotor decreases toward the rear end side in the axial direction. The turbine housing of claim 1 .

3. The cliff portion is an extension portion that extends from an inner circumferential end of the second arc portion along the axial direction to a rear end side that is opposite to the front end side in the axial direction; a third arc portion extending from the rear end side of the extension portion toward the rear end side in the axial direction and toward the inside in the radial direction, The turbine housing of claim 1 .

4. A turbine housing for accommodating a turbine rotor, comprising: a scroll passage forming portion that forms a scroll passage extending in a circumferential direction about the axis of the turbine rotor; a nozzle flow path forming section that forms a nozzle flow path for guiding exhaust gas from the scroll flow path to the turbine rotor that is disposed on the inner circumferential side of the scroll flow path, the nozzle flow path forming section having a shroud-side flow path wall surface and a hub-side flow path wall surface that define the nozzle flow path; a variable nozzle unit for adjusting a flow of the exhaust gas in the nozzle flow path, the variable nozzle unit including at least one nozzle vane disposed in the nozzle flow path, the scroll passage forming portion includes a scroll passage wall surface connecting an outer circumferential end of the scroll passage and an outer circumferential end of the hub-side passage wall surface, The scroll flow passage wall surface, in a cross section along the axis passing through a tongue portion of the scroll flow passage forming portion, a first arc portion having an outer peripheral end connected to the outer peripheral end of the scroll passage and extending from the outer peripheral end toward an inner side in a radial direction of the turbine rotor; a cliff portion having one end connected to an inner circumferential end of the first arc portion and the other end connected to the outer circumferential end of the hub-side flowpath wall surface, the cliff portion including a second arc portion connected to the inner circumferential end of the first arc portion and forming an inflection point between the first arc portion and the cliff portion, the inflection point is located at a position closer to a tip end of the hub-side flow passage wall surface in an axial direction of the turbine rotor than the outer circumferential end of the hub-side flow passage wall surface and offset radially outward of the turbine rotor than the outer circumferential end of the hub-side flow passage wall surface; When the length in the axial direction between the one end and the other end of the cliff portion is defined as X, the maximum value of the length X in the cliff portion is defined as Xmax, and the length in the axial direction of the nozzle flow path at the outer circumferential end of the hub-side flow path wall surface is defined as L, the maximum value Xmax satisfies the condition 0.75×L≦Xmax≦1.25×L, Turbine housing.

5. A turbine housing for accommodating a turbine rotor, comprising: a scroll passage forming portion that forms a scroll passage extending in a circumferential direction about the axis of the turbine rotor; a nozzle flow path forming section that forms a nozzle flow path for guiding exhaust gas from the scroll flow path to the turbine rotor that is disposed on the inner circumferential side of the scroll flow path, the nozzle flow path forming section having a shroud-side flow path wall surface and a hub-side flow path wall surface that define the nozzle flow path; a variable nozzle unit for adjusting a flow of the exhaust gas in the nozzle flow path, the variable nozzle unit including at least one nozzle vane disposed in the nozzle flow path, the scroll passage forming portion includes a scroll passage wall surface connecting an outer circumferential end of the scroll passage and an outer circumferential end of the hub-side passage wall surface, The scroll flow passage wall surface, in a cross section along the axis passing through a tongue portion of the scroll flow passage forming portion, a first arc portion having an outer peripheral end connected to the outer peripheral end of the scroll passage and extending from the outer peripheral end toward an inner side in a radial direction of the turbine rotor; a cliff portion having one end connected to an inner circumferential end of the first arc portion and the other end connected to the outer circumferential end of the hub-side flowpath wall surface, the cliff portion including a second arc portion connected to the inner circumferential end of the first arc portion and forming an inflection point between the first arc portion and the cliff portion, the inflection point is located at a position closer to a tip end of the hub-side flow passage wall surface in an axial direction of the turbine rotor than the outer circumferential end of the hub-side flow passage wall surface and offset radially outward of the turbine rotor than the outer circumferential end of the hub-side flow passage wall surface; When a length in the radial direction between the one end and the other end of the cliff portion is defined as Y, the length Y is configured to become smaller toward the downstream side of the scroll flow path. Turbine housing.

6. When a length in the radial direction between the one end and the other end of the cliff portion is defined as Y, the length Y is configured to be constant within a predetermined circumferential range. A turbine housing according to any one of claims 1 to 3.

7. A turbine housing for accommodating a turbine rotor, comprising: a scroll passage forming portion that forms a scroll passage extending in a circumferential direction about the axis of the turbine rotor; a nozzle flow path forming section that forms a nozzle flow path for guiding exhaust gas from the scroll flow path to the turbine rotor that is disposed on the inner circumferential side of the scroll flow path, the nozzle flow path forming section having a shroud-side flow path wall surface and a hub-side flow path wall surface that define the nozzle flow path; a variable nozzle unit for adjusting a flow of the exhaust gas in the nozzle flow path, the variable nozzle unit including at least one nozzle vane disposed in the nozzle flow path, the scroll passage forming portion includes a scroll passage wall surface connecting an outer circumferential end of the scroll passage and an outer circumferential end of the hub-side passage wall surface, The scroll flow passage wall surface, in a cross section along the axis passing through a tongue portion of the scroll flow passage forming portion, a first arc portion having an outer peripheral end connected to the outer peripheral end of the scroll passage and extending from the outer peripheral end toward an inner side in a radial direction of the turbine rotor; a cliff portion having one end connected to an inner circumferential end of the first arc portion and the other end connected to the outer circumferential end of the hub-side flowpath wall surface, the cliff portion including a second arc portion connected to the inner circumferential end of the first arc portion and forming an inflection point between the first arc portion and the cliff portion, the inflection point is located at a position closer to a tip end of the hub-side flow passage wall surface in an axial direction of the turbine rotor than the outer circumferential end of the hub-side flow passage wall surface and offset radially outward of the turbine rotor than the outer circumferential end of the hub-side flow passage wall surface; When a length in the radial direction between the one end and the other end of the cliff portion is defined as Y, a maximum value of the length Y in the cliff portion is defined as Ymax, and a maximum length in the radial direction of the scroll passage in a cross section along the axis that passes through the tongue portion of the scroll passage forming portion is defined as Dmax, the maximum value Ymax satisfies the condition of 0≦Ymax≦0.7×Dmax. Turbine housing.

8. A turbine housing for accommodating a turbine rotor, comprising: a scroll passage forming portion that forms a scroll passage extending in a circumferential direction about the axis of the turbine rotor; a nozzle flow path forming section that forms a nozzle flow path for guiding exhaust gas from the scroll flow path to the turbine rotor that is disposed on the inner circumferential side of the scroll flow path, the nozzle flow path forming section having a shroud-side flow path wall surface and a hub-side flow path wall surface that define the nozzle flow path; a variable nozzle unit for adjusting a flow of the exhaust gas in the nozzle flow path, the variable nozzle unit including at least one nozzle vane disposed in the nozzle flow path, the scroll passage forming portion includes a scroll passage wall surface connecting an outer circumferential end of the scroll passage and an outer circumferential end of the hub-side passage wall surface, The scroll flow passage wall surface, in a cross section along the axis passing through a tongue portion of the scroll flow passage forming portion, a first arc portion having an outer peripheral end connected to the outer peripheral end of the scroll passage and extending from the outer peripheral end toward an inner side in a radial direction of the turbine rotor; a cliff portion having one end connected to an inner circumferential end of the first arc portion and the other end connected to the outer circumferential end of the hub-side flowpath wall surface, the cliff portion including a second arc portion connected to the inner circumferential end of the first arc portion and forming an inflection point between the first arc portion and the cliff portion, the inflection point is located at a position closer to a tip end of the hub-side flow passage wall surface in an axial direction of the turbine rotor than the outer circumferential end of the hub-side flow passage wall surface and offset radially outward of the turbine rotor than the outer circumferential end of the hub-side flow passage wall surface; When the angular position of the tongue portion in the circumferential direction of the turbine housing is defined as 0° and the angle θ is defined such that the angle gradually increases from the tongue portion toward the downstream side of the scroll flow path, the angular position θmax of the downstream end of the cliff portion satisfies the condition 120°≦θmax≦180°; Turbine housing.

9. a first gas inlet for introducing gas into the scroll flow path; a second gas inlet for introducing gas into the scroll flow path, the second gas inlet being provided on an outer side in the radial direction than the first gas inlet; a confluence passage forming section that forms a confluence passage in which the gas introduced into the interior of the turbine housing through the first gas introduction port and the gas introduced into the interior of the turbine housing through the second gas introduction port are joined, the confluence passage communicating with an upstream end of the scroll passage, A turbine housing according to any one of claims 1 to 5, 7 and 8.

10. the converging flow path forming portion includes a throttle portion configured such that a flow path area of ​​the converging flow path decreases toward a downstream side of the converging flow path, The throttle portion, in a cross section perpendicular to the axis, an inner wall surface that forms the confluence flow path, the inner wall surface having a distance from the axis that increases toward a downstream side of the confluence flow path; an outer wall surface formed farther from the axis than the inner wall surface and forming the merging flow path between the inner wall surface and the outer wall surface, the distance from the axis decreasing toward the downstream side of the merging flow path; The turbine housing of claim 9 .

11. A turbine housing according to any one of claims 1 to 5, 7, 8 and 10; a turbine rotor rotatably accommodated in the turbine housing, Variable geometry turbocharger.

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