Turbines and turbochargers

Abstract

The present invention comprises a turbine housing in which a scroll flow passage and a tongue part of the scroll flow passage are formed, and a variable nozzle unit arranged inside the turbine housing and having a plurality of nozzle vanes arranged in a gas inflow passage into which gas flows from the scroll flow passage, wherein at least the nozzle vane among the nozzle vanes which is arranged at a position closest to the tongue part is a special vane different from the other nozzle vanes, and the width of the special vane in the rotational axis direction is smaller than the width of the other nozzle vanes.

Description

[Technical field]

[0001] The present disclosure relates to turbines and superchargers. [Background technology]

[0002] Conventionally, as techniques in this field, turbochargers described in Patent Document 1 (JP Patent Publication 10-141074 A) and Patent Document 2 (JP Patent Publication 2007-309140 A) are known. These are variable displacement turbochargers, and have a plurality of nozzle vanes for adjusting the inflow of exhaust gas into the turbine wheel. In a gas inlet passage connecting the scroll passage and the turbine wheel, the nozzle vanes are arranged at equal intervals around the turbine wheel. The nozzle vanes rotate synchronously in the gas inlet passage, thereby changing the flow passage cross-sectional area and adjusting the flow velocity of the exhaust gas. The rotational speed of the turbine wheel and the compressor wheel is adjusted by adjusting the flow velocity of the exhaust gas, and the pressure of the compressed air delivered to the internal combustion engine is appropriately adjusted. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-141074 [Patent Document 2] JP 2007-309140 A Summary of the Invention [Problem to be solved by the invention]

[0004] In this type of variable geometry turbine, a fluid force acts on each nozzle vane due to the flow field of the fluid in the connecting passage. Among these, the fluid force acting on the nozzle vanes located near the tongue of the scroll passage is particularly large. The large fluid force acting on the nozzle vanes can cause wear, sticking, and galling of the nozzle vanes, so the nozzle vanes near the tongue are less reliable than the other nozzle vanes. In view of such problems, the present disclosure has an object to provide a turbine and a turbocharger that can ensure the reliability of the nozzle vanes near the tongue. [Means for solving the problem]

[0005] The turbine disclosed herein comprises a turbine housing in which a scroll passage and a tongue of the scroll passage are formed, and a variable nozzle unit disposed within the turbine housing and having a plurality of nozzle vanes arranged in a gas inlet passage into which gas flows from the scroll passage, at least the nozzle vane arranged closest to the tongue among the nozzle vanes is a special vane different from the other nozzle vanes, and the width of the special vane in the direction of rotation axis is smaller than the width of the other nozzle vanes.

[0006] The rotation shaft of the special vane may be thicker than the rotation shafts of the other nozzle vanes. The special vane may be configured to be unable to rotate when the nozzle in the variable nozzle unit is in a fully closed position. The special vane may be positioned in the gas inlet passage toward the fluid discharge direction of the turbine wheel. The turbine of the present disclosure may have a biasing mechanism that biases the special vane in the fluid discharge direction. The turbine of the present disclosure may include a plurality of scroll flow paths. The turbocharger of the present disclosure is a turbocharger including any of the turbines described above. Effect of the Invention

[0007] According to the present disclosure, it is possible to provide a turbine and a turbocharger that can ensure the reliability of the nozzle vanes near the tongue portion. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view showing a turbocharger according to a first embodiment. [Diagram 2] FIG. 2 is an exploded perspective view of the variable nozzle unit. [Diagram 3] FIG. 3 is a cross-sectional view of the turbine as seen in the axial direction. [Figure 4] FIG. 4 is a cross-sectional view showing the special vane and other nozzle vanes. [Diagram 5] FIG. 5 is an enlarged cross-sectional view showing a main part of the variable nozzle unit. [Figure 6] FIG. 6 is an enlarged cross-sectional view showing a main part of another embodiment of the variable nozzle unit. [Figure 7] FIG. 7 is a cross-sectional view of the turbine according to the second embodiment as viewed in the axial direction. [Figure 8] 8(a) and (b) are contour diagrams showing the pressure distribution inside the turbine. [Figure 9] FIG. 9(a) to (f) are graphs showing fluid forces acting on a vane. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] First, each example of the present disclosure will be described. A turbine according to a first example of the present disclosure includes a turbine housing in which a scroll passage and a tongue of the scroll passage are formed, and a variable nozzle unit disposed in the turbine housing, the variable nozzle unit having a plurality of nozzle vanes disposed in a gas inlet passage into which gas from the scroll passage flows in. At least one of the nozzle vanes disposed closest to the tongue is a special vane different from the other nozzle vanes, and the width of the special vane in the rotation axis direction is smaller than the width of the other nozzle vanes.

[0010] The second example is the turbine according to the first example, where the rotation shaft of the special vane is thicker than the rotation shafts of the other nozzle vanes.

[0011] A third example is a turbine according to the first or second example, in which the special vane is configured not to be rotatable at a nozzle fully closed position in the variable nozzle unit.

[0012] A fourth example is a turbine according to any one of the first to third examples, in which the special vane is positioned in the gas inlet passage toward the fluid discharge direction of the turbine wheel.

[0013] A fifth example is a turbine according to the fourth example, and includes a biasing mechanism that biases the special vane in the fluid discharge direction.

[0014] A sixth example is a turbine according to any one of the first to fifth examples, and includes a plurality of scroll passages.

[0015] The turbine according to the seventh example includes a turbine housing in which a scroll passage and a tongue of the scroll passage are formed, a turbine wheel housed in the turbine housing, a gas inlet passage connecting the scroll passage and the turbine wheel, and a plurality of nozzle vanes arranged in the gas inlet passage on a circumference centered on the rotation axis of the turbine wheel. At least the width in the rotation axis direction of the nozzle vane adjacent to the tongue among the plurality of nozzle vanes is smaller than the width in the rotation axis direction of the other nozzle vanes having a different shape from the nozzle vane adjacent to the tongue. Note that in the turbine according to the seventh example, the rotation axis of the nozzle vane adjacent to the tongue may be thicker than the rotation axis of the other nozzle vanes. Note that the configuration according to any one of the second to sixth examples may be applied to the turbine according to the seventh example.

[0016] The eighth example is a turbine related to the seventh example, and is provided with a first scroll passage and a second scroll passage arranged at positions that are rotationally symmetrical about the rotation axis, the first scroll passage has a first tongue portion, and the second scroll passage has a second tongue portion, and the width in the rotational axis direction of the nozzle vane adjacent to the first tongue portion and the width in the rotational axis direction of the nozzle vane adjacent to the second tongue portion are smaller than the widths of the other nozzle vanes.

[0017] The ninth example is a turbocharger including the turbine according to the first to eighth examples.

[0018] Next, an embodiment of the turbine and a turbocharger including the turbine according to the present disclosure will be described with reference to the drawings. Note that in each drawing, the features of the components may be exaggerated, and the dimensional ratios of the various parts in the drawings do not necessarily correspond to the actual ones. Components that are the same or equivalent to each other are given the same reference numerals in the drawings, and duplicated explanations will be omitted.

[0019] (First embodiment) A variable geometry turbocharger 1 of this embodiment shown in Fig. 1 is applied to an internal combustion engine of a ship or vehicle, for example. As shown in Fig. 1, the variable geometry turbocharger 1 includes a turbine 2 and a compressor 3. The turbine 2 includes a turbine housing 4 and a turbine wheel 6 housed in the turbine housing 4. The turbine housing 4 has a scroll passage 16 extending in the circumferential direction around the turbine wheel 6. The compressor 3 includes a compressor housing 5 and a compressor wheel 7 housed in the compressor housing 5. The compressor housing 5 has a scroll passage 17 extending in the circumferential direction around the compressor wheel 7.

[0020] The turbine wheel 6 is provided at one end of a rotating shaft 14, and the compressor wheel 7 is provided at the other end of the rotating shaft 14. A bearing housing 13 is provided between the turbine housing 4 and the compressor housing 5. The rotating shaft 14 is rotatably supported by the bearing housing 13 via a bearing 15, and the rotating shaft 14, the turbine wheel 6, and the compressor wheel 7 rotate around the rotation axis H as an integrated rotating body.

[0021] The turbine housing 4 is provided with an exhaust gas inlet 8 and an exhaust gas outlet 10. Exhaust gas discharged from an internal combustion engine (not shown) flows into the turbine housing 4 through the exhaust gas inlet 8, and flows into the turbine wheel 6 through a scroll passage 16, causing the turbine wheel 6 to rotate. The exhaust gas then flows out of the turbine housing 4 through the exhaust gas outlet 10.

[0022] The compressor housing 5 is provided with an intake port 9 and a discharge port 11. When the turbine wheel 6 rotates as described above, the compressor wheel 7 rotates via the rotary shaft 14. The rotating compressor wheel 7 draws in external air through the intake port 9. This air passes through the compressor wheel 7 and the scroll passage 17, is compressed, and is discharged from the discharge port 11. The compressed air discharged from the discharge port 11 is supplied to the internal combustion engine described above.

[0023] Next, the turbine 2 will be described in more detail. In the following description, when the terms "axial direction", "radial direction", "circumferential direction", etc. are used simply, they mean the direction of the rotation axis H of the turbine wheel 6, the rotation radial direction, and the rotation circumferential direction, respectively. Furthermore, when the terms "upstream", "downstream", etc. are used, they mean the upstream and downstream of the exhaust gas in the turbine 2. Furthermore, in the direction of the rotation axis H, the side closer to the turbine 2 (the left side in Figs. 1 and 2) may be simply referred to as the "turbine side", and the side closer to the compressor 3 (the right side in Figs. 1 and 2) may be simply referred to as the "compressor side".

[0024] The exhaust gas from the scroll passage 16 flows into the turbine wheel 6 of the turbine 2 through the gas inlet passage 21 in a direction perpendicular to the rotation axis H. Then, the exhaust gas is discharged from the turbine wheel 6 in the direction of the rotation axis H toward the exhaust gas outlet 10. The gas inlet passage 21 connecting the scroll passage 16 and the turbine wheel 6 is provided with a movable nozzle vane 23. A plurality of nozzle vanes 23 are arranged on a circumference centered on the rotation axis H, and each nozzle vane 23 rotates around an axis NX parallel to the rotation axis H. By rotating the nozzle vane 23 as described above, the cross-sectional area of ​​the gas passage is optimally adjusted according to the flow rate of the exhaust gas introduced into the turbine 2. The turbine 2 is provided with a variable nozzle unit 25 as a drive mechanism for rotating the nozzle vane 23 as described above. The variable nozzle unit 25 is fitted inside the turbine housing 4 and is fixed by being sandwiched between the turbine housing 4 and the bearing housing 13.

[0025] The variable nozzle unit 25 will be described in more detail below with reference to Figs. 1 and 2. The variable nozzle unit 25 has the above-mentioned multiple (ten in the illustrated example) nozzle vanes 23. The variable nozzle unit 25 further has a nozzle ring 31 that axially sandwiches the nozzle vanes 23, and a clearance control plate (hereinafter referred to as a "CC plate") 32. The nozzle ring 31 and the CC plate 32 each have a ring shape centered on the rotation axis H, and are arranged to surround the turbine impeller 6 in the circumferential direction. The area sandwiched between the nozzle ring 31 and the CC plate 32 constitutes the gas inlet passage 21 described above. The nozzle ring 31 and the CC plate 32 are connected via multiple (three in the illustrated example) connecting pins 35, and the dimensions of the connecting pins 35 are manufactured with high precision, thereby ensuring the axial dimensional precision of the gas inlet passage 21.

[0026] The rotating shafts 23a of the nozzle vanes 23 are rotatably inserted into the bearing holes 31a of the nozzle ring 31, and the nozzle ring 31 supports each of the nozzle vanes 23 in a cantilever manner. In the example shown in the figure, the nozzle vanes 23 are arranged at equal intervals on the circumference, but it is not essential that the nozzle vanes 23 be arranged at equal intervals.

[0027] A drive ring 28 is installed on the compressor side of the nozzle ring 31, and is supported by a ring support portion (not shown) so as to be rotatable about the rotation axis H. The drive ring 28 is a member that transmits a driving force input from the outside to the nozzle vanes 23, and is formed as a single member, for example, from a metal material. The drive ring 28 is in the shape of a ring extending on a circumference centered on the rotation axis H, and rotates about the rotation axis H when receiving a driving force from the outside.

[0028] The levers 29 are attached to the rotating shafts 23a of the nozzle vanes 23, respectively, and are arranged at equal intervals on the circumference inside the drive ring 28. The drive ring 28 has grooves 28a formed at equal intervals at positions corresponding to the levers 29. The outer peripheral end of each lever 29 meshes with the corresponding groove 28a of the drive ring 28. The rotating shafts 23a of each nozzle vane 23 pass through the bearing holes 31a and are fixed to the inner peripheral end of each lever 29. In addition to the groove 28a, the drive ring 28 has one input groove 28b formed therein. The outer peripheral end of an input lever 30 meshes with the input groove 28b, and the inner peripheral end of the input lever 30 is connected to a drive mechanism (not shown).

[0029] When a driving force from outside the turbine 2 is input to the input lever 30 through the drive mechanism, the input lever 30 rotates around an axis parallel to the rotation axis H. Then, the outer peripheral end of the input lever 30 presses the input groove 28b in the circumferential direction, and the drive ring 28 rotates around the rotation axis H. As the drive ring 28 rotates, each lever 29 meshing with the groove 28a rotates around the axis NX, and further each nozzle vane 23 rotates in synchronization in the gas inlet passage 21 via each rotation shaft 23a.

[0030] FIG. 3 is a cross-sectional view of the turbine 2 as seen from the axial direction. As shown in FIG. 3, the tongue portion 41 of the scroll passage 16 is formed in the turbine housing 4. The tongue portion 41 is a portion that radially separates the start and end of the spirally wound scroll passage 16. In the gas inlet passage 21, the nozzle vanes 23 are installed at equal intervals around the turbine impeller 6. In the turbine 2, a fluid force acts on each nozzle vane 23 due to the flow field of the fluid in the gas inlet passage 21. Among them, the fluid force acting on the nozzle vane 23 in the vicinity of the tongue portion 41 is particularly large. In addition, in a state where the nozzle of the variable nozzle unit 25 is fully open, the nozzle vane 23 in the vicinity of the tongue portion 41 is easily subjected to a circumferential pressure difference and is subjected to a force due to this pressure difference.

[0031] Therefore, a special nozzle vane (special vane) different from the others is adopted for one nozzle vane 23 located closest to the tongue portion 41. Hereinafter, the one nozzle vane 23 located closest to the tongue portion 41 is called the "nearest vane" and is marked with the symbol "23T". "Closest to the tongue portion 41" means that the distance between the tip of the tongue portion 41 and the rotation axis NX of the nozzle vane 23 is the shortest. Also, the nozzle vane 23T is a nozzle vane adjacent to the tongue portion 41. In order to avoid complicating the drawings, the special structure of the nearest vane 23T is not shown in Figs. 1 to 3. Note that each nozzle vane except for such a special nozzle vane has the same configuration as each other. In addition, for example, the special nozzle vane is a first nozzle vane, and the nozzle vane having a shape different from the first nozzle vane is a second nozzle vane.

[0032] The nearest vane 23T has at least one of the following features 1 to 4. Note that FIG. 4 illustrates the nearest vane 23T having all of the features 1, 2, and 4. [Feature 1]: As shown in FIG. 4, the width D1 of the nearest vane 23T in the direction of the axis NX is narrower than the width D2 of the other nozzle vanes 23 in the direction of the axis NX. 4, the rotation shaft 23Ta of the nearest vane 23T is thicker (has a larger diameter) than the rotation shaft 23a of the other nozzle vanes 23. Due to the difference in diameter between the rotation shafts 23Ta, 23a, the bearing hole 31Ta into which the rotation shaft 23Ta of the nearest vane 23T is inserted is formed with a larger diameter than the bearing hole 31a into which the rotation shaft 23a of the other nozzle vanes 23 is inserted.

[0033] [Feature 3]: As shown in Fig. 3, nearest vane 23T is configured so as not to be able to rotate at the fully closed nozzle position in variable nozzle unit 25. Note that 23T' shown by a dashed line in Fig. 3 indicates the fully open nozzle position in variable nozzle unit 25. As a specific configuration for achieving this feature 3, for example, rotating shaft 23Ta may be joined to the inner circumferential surface of bearing hole 31Ta. [Feature 4]: As shown in FIG. 4, the nearest vane 23T is located in the gas inlet passage 21 closer to the exhaust gas discharge direction of the turbine impeller 6 (the direction from the turbine impeller 6 toward the exhaust gas outlet 10). That is, the nearest vane 23T is located in the gas inlet passage 21 closer to the shroud surface 21a. Therefore, the gap Gk between the nearest vane 23T and the nozzle ring 31 is larger than the gap Gj between the nearest vane 23T and the CC plate 32. Note that the nearest vane 23T may abut against the shroud surface 21a, and the gap Gj may become zero. In order to realize this feature 4, the turbine 2 has a biasing mechanism that biases the nearest vane 23T toward the shroud surface 21a. The biasing mechanism means an elastic structure, for example, a compression spring. A specific configuration showing an example of this biasing mechanism is shown in FIG. 5 and FIG. 6. The biasing mechanism is not limited to the coil spring 43 or the disc spring 45 described below, but may be a leaf spring.

[0034] 5, the compressor side end of the rotation shaft 23Ta of the nearest vane 23T is joined to the inner peripheral end of the lever 29 by crimping or the like. At the joint between the rotation shaft 23Ta and the lever 29, a coil spring 43 is compressed and sandwiched between the variable nozzle unit 25 and the bearing housing 13. The coil spring 43 is disposed coaxially with the rotation shaft 23Ta and biases the joint between the rotation shaft 23Ta and the lever 29 toward the turbine. As a result, the lever 29 and the nearest vane 23T are pressed toward the turbine, and the nearest vane 23T is positioned closer to the CC plate 32 within the gas inlet passage 21.

[0035] "The nearest vane 23T is located closer to the CC plate 32 in the gas inlet passage 21" means that the gap between the nearest vane 23T and the CC plate 32 is narrower than the gap Gk between the nearest vane 23T and the nozzle ring 31. Note that the coil springs 43 may be provided not only for the nearest vane 23T but also for all other nozzle vanes 23. In this case, all nozzle vanes 23 including the nearest vane 23T are located closer to the CC plate 32 in the gas inlet passage 21.

[0036] 6, a disc spring 45 may be provided instead of the coil spring 43. As shown by the two-dot chain line in FIG. 2, the disc spring 45 has a substantially conical shape with the rotation axis H as the conical axis, and is compressed and sandwiched between the variable nozzle unit 25 and the bearing housing 13. One end 45a of the disc spring 45 in the conical axis direction contacts the lever 29, and the other end 45b contacts the bearing housing 13, and the disc spring 45 biases the lever 29 toward the turbine. As a result, the lever 29 and the nearest vane 23T are pressed toward the turbine, and the nearest vane 23T is positioned closer to the CC plate 32 in the gas inlet passage 21. In the embodiment of FIG. 6, all the levers 29 of the variable nozzle unit 25 are biased toward the turbine by the disc spring 45. Therefore, not only the nearest vane 23T but also all the other nozzle vanes 23 are positioned closer to the CC plate 32 in the gas inlet passage 21.

[0037] Next, the operation and effects of the turbine 2 and the supercharger 1 including the same will be described. As described above, in the turbine 2, the fluid force acting on the nozzle vane 23 tends to be relatively strong in the vicinity of the tongue portion 41, and the fluid force acts particularly strongly on the nearest vane 23T.

[0038] According to the above-described feature 1, as shown in FIG. 4, the axial width D1 of the nearest vane 23T is smaller than the axial width D2 of the other nozzle vanes 23 (D1 < D2). Further, the nearest vane 23T is positioned in the gas inlet passage 21 with a relatively large gap (Gj + Gk) in the axial direction as compared with the other nozzle vanes 23. Therefore, the fluid force acting on the nearest vane 23T due to the gas flow field is reduced because the area of the vane is small and a part of the exhaust gas leaks from the gaps Gj and Gk. Therefore, abrasion, roughness, and galling generated in the nearest vane 23T can be suppressed, and as a result, the reliability of the nearest vane 23T can be ensured.

[0039] Further, according to the above-described feature 2, as shown in FIG. 4, the nearest vane 23T has a rotation shaft 23Ta with a larger diameter as compared with the other nozzle vanes 23. Thereby, the nearest vane 23T has higher rigidity than the other nozzle vanes 23, and rattling of the nearest vane 23T in the exhaust gas flow field is also suppressed to be small. Therefore, the degree of abrasion, roughness, and galling generated in the nearest vane 23T can be suppressed, and as a result, the reliability of the nearest vane 23T can be ensured.

[0040] According to the above-mentioned feature 3, the nearest vane 23T is configured to be unable to rotate at the nozzle fully closed position in the variable nozzle unit 25. If the nearest vane 23T is at the fully open position 23T' as shown by the broken line in FIG. 3, the high-pressure exhaust gas flowing in from the exhaust gas inlet 8 is present on the left side of the nearest vane 23T, and the low-pressure exhaust gas that has traveled almost one revolution around the scroll passage 16 and reached the vicinity of the tongue portion 41 is present on the right side of the nearest vane 23T. A relatively strong fluid force due to the pressure difference between the left and right sides acts on the nearest vane 23T. On the other hand, in the turbine 2, the nearest vane 23T is fixed at the fully closed position, so that the exhaust gas is likely to flow in the circumferential direction beyond the position of the nearest vane 23T. Therefore, the above-mentioned strong fluid force is unlikely to act on the nearest vane 23T. Therefore, wear, stiction, galling, etc. occurring on the nearest vane 23T can be suppressed, and as a result, the reliability of the nearest vane 23T can be ensured.

[0041] Furthermore, when the width D1 of the nearest vane 23T is reduced as in the above-mentioned feature 1, leakage flow from the nearest vane 23T in the gas inlet passage 21 increases, and the turbulence of the gas flow increases. In particular, turbulence of the flow on the shroud surface 21a side significantly affects the performance of the turbine 2, so it is desirable to reduce the leakage flow from the nozzle vanes, especially on the shroud surface 21a side. In contrast, according to the above-mentioned feature 4, the nearest vane 23T is positioned closer to the shroud surface 21a side in the gas inlet passage 21, so that the leakage flow from the nearest vane 23T on the shroud surface 21a side can be reduced. As a result, it is possible to suppress deterioration of the performance of the turbine 2 due to the leakage flow from the nearest vane 23T caused by feature 1.

[0042] The nearest vane 23T may have all of Features 1 to 4, or any two or three of Features 1 to 4. The special nozzle vane configuration having such features may be applied not only to the nearest vane 23T, but also to several nozzle vanes 23 located relatively close to the tongue portion 41. For example, the special nozzle vane configuration may be applied to three nozzle vanes 23 including the nearest vane 23T and the nozzle vanes 23 on both sides of the nearest vane 23T.

[0043] Second embodiment Next, a second embodiment of the turbine of the present disclosure and a turbocharger including the same will be described. A turbocharger 201 of this embodiment includes a turbine 202 shown in FIG. 7 instead of the turbine 2 of the first embodiment. The turbine 202 is a multi-scroll turbine and includes two scroll passages 16A and 16B. The scroll passage 16A (first scroll passage) and the scroll passage 16B (second scroll passage) have the same shape and are provided at rotationally symmetric positions with respect to the rotation axis H. The turbine 202 includes two tongue portions 41A (first tongue portion) and 41B (second tongue portion). In addition, a variable nozzle unit 225 of the turbine 202 includes thirteen nozzle vanes N1 to N13. The nozzle vanes are numbered N1 to N13 in ascending order counterclockwise as shown in Fig. 7, and among them, nozzle vane N4 is the nozzle vane closest to tongue portion 41B, and nozzle vane N10 is the nozzle vane closest to tongue portion 41A. Additionally, nozzle vane N4 is the nozzle vane adjacent to tongue portion 41B, and nozzle vane N10 is the nozzle vane adjacent to tongue portion 41A.

[0044] In this turbine 202, there exists a state in which exhaust gas flows in from only one of the two scroll passages 16A, 16B (here, scroll passage 16A) (hereinafter referred to as "single-port inflow state"). Figure 8 is a contour diagram showing the pressure distribution in the turbine 202 in the single-port inflow state, which is based on a simulation by the present inventors. Figure 8(a) shows the state in which the nozzle is fully closed, and Figure 8(b) shows the state in which the nozzle is fully open.

[0045] 9(a) to 9(f) are graphs showing the fluid forces acting on the nozzle vanes N1 to N13, which are based on the simulations of the present inventors. FIG. 9(a) to (c) show a single-port inflow state, with FIG. 9(a) showing the nozzle fully open, FIG. 9(b) showing the nozzle half open, and FIG. 9(c) showing the nozzle fully closed. For comparison, FIG. 9(d) to (f) show a double-port inflow state (a state in which exhaust gas flows in from both of the two scroll passages 16A and 16B), with FIG. 9(d) showing the nozzle fully open, FIG. 9(e) showing the nozzle half open, and FIG. 9(f) showing the nozzle fully closed. In both of FIG. 9(a) to FIG. 9(f), the case where the pressure ratio is 3.0 is shown by a solid line graph, and the case where the pressure ratio is 1.8 is shown by a dashed line graph. The above pressure ratio is the ratio of the pressure at the outlet to the pressure at the inlet of the turbine 202. In addition, in all of Figures 9(a) to 9(f), the vertical axis represents the normalised magnitude of aerodynamic force.

[0046] Referring to FIG. 8, it can be seen that in the single-port inflow state, a pressure difference occurs in the circumferential direction near the tongues 41A and 41B. In particular, when the nozzle is fully open (FIG. 8(b)), the pressure difference is remarkable, and it can be seen that a large pressure difference occurs in the circumferential direction across the vanes in the nozzle vane N4 closest to the tongue 41B and the nozzle vane N10 closest to the tongue 41A. In other words, it can be seen that a large fluid force acts on the nozzle vanes N4 and N10 due to the large pressure difference in the circumferential direction across the vanes. Furthermore, referring to FIG. 9(a) to FIG. 9(c), it can be seen that a large fluid force acts on the nozzle vanes N4 and N10 compared to the other nozzle vanes. Also, comparing FIG. 9(a) to FIG. 9(c) with FIG. 9(d) to FIG. 9(f), it can be seen that the bias of the fluid force on the nozzle vanes N4 and N10 is more remarkable in the single-port inflow state than in the double-port inflow state.

[0047] Therefore, in the turbine 202 of this embodiment, a special configuration different from the other nozzle vanes is applied to the nozzle vanes N4 and N10 located closest to the tongues 41A and 41B, respectively. Specifically, like the nearest vane 23T of the first embodiment, the nozzle vanes N4 and N10 have at least one of the above-mentioned features 1 to 4. The nozzle vanes N4 and N10 may have all of the features 1 to 4, or may have any two or three of the features 1 to 4. The special nozzle vane configuration having such features may be applied not only to the nozzle vanes N4 and N10, but also to some nozzle vanes located relatively close to the tongues 41A and 41B, respectively. For example, the above-mentioned special nozzle vane configuration may be applied to a total of four vanes, namely the nozzle vanes N4, N5, and the nozzle vanes N10 and N11.

[0048] According to the turbine 202 of this embodiment and the turbocharger 201 including the same, the same effects as those of the turbine 2 and the turbocharger 1 of the first embodiment described above can be obtained.

[0049] The present disclosure can be embodied in various forms including the above-mentioned embodiment and various modifications and improvements based on the knowledge of a person skilled in the art. In addition, it is also possible to configure modified examples by utilizing the technical matters described in the above-mentioned embodiment. The configurations of the respective embodiments may be used in appropriate combination. For example, in the embodiment, the nozzle vanes 23, 23T, N1 to N13 are cantilevered by the nozzle ring 31, but these nozzle vanes may be supported by both the nozzle ring 31 and the CC plate 32. [Explanation of symbols]

[0050] 1,201 Variable Geometry Turbocharger 2,202 Turbines 4 Turbine housing 6 Turbine wheel 16, 16A, 16B Scroll passage 21 Gas inlet 23, 23T, N1~N13 Nozzle vanes 25,225 Variable nozzle unit 23a, 23Ta Rotating shaft 41,41A,41B Tongue 43 Coil spring (biasing mechanism) 45 Disc spring (biasing mechanism)

Claims

1. a turbine housing in which a scroll passage and a tongue portion of the scroll passage are formed; a variable nozzle unit disposed in the turbine housing, the variable nozzle unit having a plurality of nozzle vanes disposed in a gas inlet passage into which gas from the scroll passage flows, the variable nozzle unit includes a nozzle ring that rotatably supports a rotation shaft of the nozzle vane, At least one of the nozzle vanes arranged closest to the tongue portion is a special vane different from the other nozzle vanes, The width of the special vane in the rotation axis direction is smaller than the width of the other nozzle vanes, A turbine, wherein the special vane is positioned within the gas inlet passage, closer to the fluid discharge direction of the turbine wheel than the other nozzle vanes, and the distance between the special vane and the nozzle ring is greater than the distance between the other nozzle vanes and the nozzle ring.

2. The turbine according to claim 1 , wherein a rotation shaft of the special vane is thicker than rotation shafts of the other nozzle vanes.

3. a turbine housing in which a scroll passage and a tongue portion of the scroll passage are formed; a variable nozzle unit disposed in the turbine housing, the variable nozzle unit having a plurality of nozzle vanes disposed in a gas inlet passage into which gas from the scroll passage flows, At least one of the nozzle vanes arranged closest to the tongue portion is a special vane different from the other nozzle vanes, The width of the special vane in the rotation axis direction is smaller than the width of the other nozzle vanes, A turbine, wherein the special vane is configured so as not to be rotatable when the nozzle of the variable nozzle unit is in a fully closed position.

4. The turbine according to claim 1 , further comprising a biasing mechanism for biasing the special vane in the fluid discharge direction.

5. The turbine of claim 1 comprising a plurality of said scroll passages.

6. a turbine housing in which a scroll passage and a tongue portion of the scroll passage are formed; A turbine wheel accommodated in the turbine housing; a gas inlet passage connecting the scroll passage and the turbine wheel; a plurality of nozzle vanes arranged in the gas inlet passage on a circumference centered on a rotation axis of the turbine wheel; a nozzle ring that rotatably supports a rotation shaft of the nozzle vane, a width in the rotation axis direction of at least one of the nozzle vanes adjacent to the tongue portion is smaller than a width in the rotation axis direction of the other nozzle vanes having a shape different from that of the nozzle vane adjacent to the tongue portion, A turbine, wherein the nozzle vane adjacent to the tongue portion is positioned within the gas inlet passage closer to the fluid discharge direction of the turbine wheel than the other nozzle vanes, and the distance between the nozzle vane adjacent to the tongue portion and the nozzle ring is greater than the distance between the other nozzle vanes and the nozzle ring.

7. The scroll flow passage includes a first scroll flow passage and a second scroll flow passage that are provided at positions that are rotationally symmetrical about the rotation axis, the first scroll passage includes a first tongue; the second scroll flow passage includes a second tongue; The turbine according to claim 6 , wherein a width in the rotation axis direction of the nozzle vane adjacent to the first tongue portion and a width in the rotation axis direction of the nozzle vane adjacent to the second tongue portion are smaller than a width in the rotation axis direction of the other nozzle vanes.

8. A turbocharger comprising the turbine according to claim 1.

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