Variable-geometry turbocharger
Patent Information
- Application Number
- PCT/JP2025/015212
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-04-18
- Publication Date
- 2026-10-22
Smart Images
Figure JP2025015212_22102026_PF_FP_ABST
Abstract
Description
Variable capacity turbocharger
[0001] The present disclosure relates to a variable capacity turbocharger.
[0002] A variable capacity turbocharger includes a turbine wheel, a casing that houses the turbine wheel, nozzle vanes capable of adjusting the flow rate of exhaust gas flowing into the turbine wheel, and a link mechanism for driving the nozzle vanes. Inside the casing, a nozzle flow path in which the nozzle vanes are disposed and a link chamber in which the link mechanism is disposed are formed, and the casing includes a partition wall portion that separates the nozzle flow path and the link chamber. The partition wall portion is formed with an insertion hole into which the shaft portion of the nozzle vane is inserted.
[0003] In the partition wall portion of the variable capacity turbocharger described in Patent Document 1, a communication hole that connects the nozzle flow path and the link chamber is formed at a position radially outward of the insertion hole in the radial direction of the turbine wheel. It is described that by providing this communication hole, part of the high-temperature exhaust gas in the scroll flow path flows into the link chamber through this communication hole, and deposits adhering to the link mechanism in the link chamber are removed by the exhaust gas, whereby malfunction of the link mechanism caused by the deposits can be suppressed.
[0004] Japanese Unexamined Patent Publication No. 2013-96355
[0005] According to the findings of the inventor of the present application, when a communication hole is provided in the partition wall portion as described above to guide the exhaust gas in the scroll flow path to the link chamber, the internal pressure of the link chamber rises to create a pressure difference between the link chamber and the inlet of the turbine wheel, and a flow directed from the link chamber side toward the nozzle flow path side is generated in the gap between the outer peripheral surface of the shaft portion of the nozzle vane and the inner peripheral surface of the insertion hole. Further, as a result of studies by the inventor of the present application, it has been found that when the flow velocity of the flow in this gap is low, fuel and soot mixed into the link chamber are not sufficiently discharged to the nozzle flow path side and accumulate in the gap, causing sticking of the nozzle vanes.
[0006] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide a variable capacity turbocharger capable of suppressing the occurrence of sticking of nozzle vanes.
[0007] To achieve the above objective, a variable displacement turbocharger according to at least one embodiment of the present disclosure comprises: a turbine wheel; a casing housing the turbine wheel; a first nozzle vane capable of adjusting the flow rate of exhaust gas flowing into the turbine wheel; and a link mechanism for driving the first nozzle vane, wherein the first nozzle vane includes a vane portion and a shaft portion connected to the vane portion; the casing has a nozzle passage where the vane portion is arranged and a link chamber where the link mechanism is arranged; the casing includes a partition wall portion separating the nozzle passage and the link chamber; the partition wall portion has a first insertion hole into which the shaft portion is inserted; the partition wall portion has a communication hole connecting the nozzle passage and the link chamber at a position outside the first insertion hole in the radial direction of the turbine wheel; the surface of the partition wall portion includes a nozzle passage side wall surface facing the nozzle passage side and a convex curved surface connecting the nozzle passage side wall surface and the inner circumferential surface of the first insertion hole. The surface of the first nozzle vane includes a vane end face facing the nozzle flow path side wall surface of the partition wall, and a concave curved surface that connects the vane end face and the outer circumferential surface of the shaft and faces the convex curved surface.
[0008] According to at least one embodiment of the present disclosure, a variable displacement turbocharger capable of suppressing nozzle vane sticking is provided.
[0009] This is a cross-sectional view showing the schematic configuration of a turbocharger 2 according to one embodiment of the present disclosure. This is an enlarged cross-sectional view of the vicinity of the nozzle vane 8 in the nozzle flow path 18 of Figure 1. This is an enlarged cross-sectional view of section A in Figure 2. This is a cross-sectional view showing the exhaust gas flow in the range corresponding to Figure 3 in the first comparative embodiment. This is a cross-sectional view showing the exhaust gas flow in the range corresponding to Figure 3 in the second comparative embodiment. This is a diagram for explaining the exhaust gas flow in the cross-section shown in Figure 3. This is a diagram showing the relationship between the ratio of r to d, r / d, and the pressure loss coefficient ζ of the gap between the shaft portion 46 and the insertion hole 40, where d is the size of the gap between the shaft portion 46 and the insertion hole 40 in the radial direction of the shaft portion 46, and r is the radius of curvature of the convex curved surface 72 in the cross-section along the rotation axis C of the shaft portion 46. This is a diagram showing an example of the arrangement of the turbine housing 30 and a plurality of nozzle vanes 8 in a cross-section perpendicular to the axial direction. This is a contour diagram showing the distribution of static pressure on the nozzle flow path side wall surface 70 of the partition wall member 26. This is a cross-sectional view showing a modified example of the nozzle vane 8.
[0010] Hereinafter, several embodiments of this disclosure will be described with reference to the attached drawings. However, the dimensions, materials, shapes, relative arrangements, etc., of the components described as embodiments or shown in the drawings are not intended to limit the scope of the invention, but are merely illustrative examples. For example, expressions describing relative or absolute arrangements such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" should not only strictly represent such arrangements, but also represent states where there is a tolerance, or a relative displacement of an angle or distance sufficient to achieve the same function. For example, expressions describing things as being in an equal state such as "identical," "equal," and "homogeneous" should not only strictly represent states of equality, but also represent states where there is a tolerance, or a difference sufficient to achieve the same function. For example, expressions describing shapes such as a square shape or a cylindrical shape should not only represent geometrically precise shapes such as square shapes or cylindrical shapes, but also represent shapes including concave and concave parts, chamfered parts, etc., to the extent that the same effect can be achieved. On the other hand, expressions such as "to possess," "to be equipped with," "to have," "to include," or "to have" a single component are not exclusive expressions that exclude the existence of other components.
[0011] Figure 1 is a cross-sectional view showing the schematic configuration of a turbocharger 2 according to one embodiment. As shown in Figure 1, the turbocharger 2 is a variable displacement turbocharger comprising a turbine wheel 4, a bearing device 6 that rotatably supports the turbine wheel 4, a plurality of nozzle vanes 8 for adjusting the flow rate of exhaust gas flowing into the turbine wheel 4, a link mechanism 9 for driving the plurality of nozzle vanes 8, and a casing 10.
[0012] The turbine wheel 4 is connected to a compressor impeller (not shown) via a rotating shaft 12 and rotates integrally with the compressor impeller. The bearing device 6 rotatably supports the rotating shaft 12. In the following description, "radial direction" means the radial direction of the turbine wheel 4 unless otherwise specified, "axial direction" means the axial direction of the turbine wheel 4 unless otherwise specified, and "circumferential direction" means the circumferential direction of the turbine wheel 4 unless otherwise specified.
[0013] Multiple nozzle vanes 8 are arranged circumferentially at intervals in the nozzle flow path 18, which will be described later. The link mechanism 9 rotates each of the multiple nozzle vanes 8 by transmitting the driving force of an actuator (not shown) to the multiple nozzle vanes 8, thereby adjusting the flow rate of exhaust gas flowing into the turbine wheel 4.
[0014] The casing 10 houses the turbine wheel 4, bearing device 6, multiple nozzle vanes 8, link mechanism 9, and a compressor impeller (not shown). Inside the casing 10, a scroll channel 16, nozzle channel 18, and link chamber 24 are formed.
[0015] The scroll channel 16 is a vortex-shaped channel formed on the outer circumference of the turbine wheel 4. The nozzle channel 18 is configured to guide the exhaust gas (exhaust gas discharged from an engine, not shown) flowing through the scroll channel 16 to the turbine wheel 4. The nozzle channel 18 is formed in an annular shape, with an annular inlet formed on the outer circumference of the nozzle channel 18 and an annular outlet formed on the inner circumference of the nozzle channel 18. The exhaust gas flowing through the scroll channel 16 flows into the nozzle channel 18 from the annular inlet, flows radially inward through the nozzle channel 18, exits the annular outlet of the nozzle channel 18 and flows into the turbine wheel 4. A link mechanism 9 is arranged in the link chamber 24.
[0016] The casing 10 includes a partition member 26 (partition) that separates the nozzle passage 18 from the link chamber 24. The casing 10 may be composed of multiple parts. In the illustrated exemplary embodiment, the casing 10 includes a turbine housing 30 that houses the turbine wheel 4 and forms the scroll passage 16, and a bearing housing 32 that houses the bearing device 6. The partition member 26 is an annular plate configured as a separate part from the turbine housing 30 and the bearing housing 32. The link chamber 24 is defined between the bearing housing 32 and the partition member 26.
[0017] In the illustrated exemplary embodiment, the casing 10 includes a partition member 28 (partition) that separates the nozzle flow path 18 from the scroll flow path 16. The partition member 28 is an annular plate configured as a separate component from the partition member 26, the turbine housing 30, and the bearing housing 32. The partition member 26 and the partition member 28 are arranged to face each other, and the nozzle flow path 18 is defined between the partition member 26 and the partition member 28. In the illustrated exemplary embodiment, the inner circumference of the partition member 28 includes a shroud portion 29 that surrounds the blade tip of the turbine wheel 4. In addition, in the illustrated exemplary embodiment, the partition member 26 and the partition member 28 are connected by a plurality of nozzle supports 33 that are spaced apart in the circumferential direction.
[0018] The partition member 26 has a plurality of insertion holes 40 and a plurality of communication holes 42. The plurality of insertion holes 40 are spaced apart in the circumferential direction, and each insertion hole 40 corresponds one-to-one with each nozzle vane 8. Each of the insertion holes 40 penetrates the partition member 26 in the axial direction to connect the nozzle flow path 18 and the link chamber 24.
[0019] The multiple communication holes 42 are located outside the multiple insertion holes 40 in the radial direction and are spaced apart in the circumferential direction. Each of the communication holes 42 penetrates the partition member 26 in the axial direction to connect the nozzle flow path 18 and the link chamber 24.
[0020] Figure 2 is an enlarged cross-sectional view of the vicinity of the nozzle vane 8 in the nozzle flow path 18 of Figure 1. As shown in at least one of Figures 1 and 2, each of the nozzle vane 8 includes a vane portion 44 positioned in the nozzle flow path 18 and a cylindrical shaft portion 46 that penetrates the partition member 26 and connects to the vane portion 44. The shaft portion 46 is inserted into the insertion hole 40, and the end of the shaft portion 46 opposite to the vane portion 44 is connected to a link mechanism 9. When the link mechanism 9 rotates the shaft portion 46 by a driving force transmitted from an actuator (not shown), the nozzle vane 8 rotates around the rotation axis of the shaft portion 46, thereby adjusting the flow area of the nozzle flow path 18 and adjusting the flow rate of exhaust gas flowing into the turbine wheel 4.
[0021] In the exemplary embodiment shown in Figure 2, the vane portion 44 includes an airfoil-shaped portion 50 having an airfoil shape, and a disc-shaped flange portion 52 formed on the base end side (shaft portion 46 side) of the airfoil-shaped portion 50 and projecting radially outward from the shaft portion 46. The diameter of the flange portion 52 is greater than the diameter of the shaft portion 46 and greater than the diameter of the insertion hole 40.
[0022] Figure 3 is an enlarged cross-sectional view of section A in Figure 2. As shown in Figure 3, the surface 26s of the partition member 26 includes a nozzle channel side wall surface 70 facing the nozzle channel 18 side (partition member 28 side) and a convex curved surface 72 connecting the nozzle channel side wall surface 70 and the inner circumferential surface 40i of the insertion hole 40. That is, the edge portion 73 on the nozzle channel 18 side of the insertion hole 40 has a rounded shape (a shape with rounded corners). The convex curved surface 72 is provided for each insertion hole 40 and connects the nozzle channel side wall surface 70 and the inner circumferential surface 40i of the insertion hole 40 for each insertion hole 40. The nozzle channel side wall surface 70 is a plane perpendicular to the axial direction. In a cross-section along the rotation axis C of the shaft portion 46 (see Figure 2), the convex curved surface 72 is a circular arc (convex curve) that extends radially outward from the shaft portion 46 and axially toward the partition wall member 28 as it moves from the inner circumferential surface 40i of the insertion hole 40 toward the nozzle flow path side wall surface 70.
[0023] Furthermore, in each of the multiple nozzle vanes 8, the surface 8s of the nozzle vane 8 (in the illustrated example, the surface of the flange portion 52 of the vane portion 44) includes the vane portion end face 60 facing the nozzle flow path side wall surface 70 of the partition wall member 26, the outer circumferential surface 64 of the shaft portion 46 facing the inner circumferential surface 40i of the insertion hole 40, and the concave curved surface 66 that connects the vane portion end face 60 and the outer circumferential surface 64 of the shaft portion 46 and faces the convex curved surface 72. That is, the corner portion 75 where the vane portion end face 60 and the outer circumferential surface 64 of the shaft portion 46 connect has a rounded shape. In the illustrated exemplary embodiment, the vane portion end face 60 is the surface of the flange portion 52 facing the link chamber 24 side and is a plane perpendicular to the axial direction. In a cross-section along the rotation axis C of the shaft portion 46 (see Figure 2), the concave curved surface 66 is an arc (concave curve) that extends radially outward from the shaft portion 46 and toward the axial partition wall member 28 as it moves from the outer peripheral surface 64 of the shaft portion 46 toward the vane end face 60.
[0024] Here, the effects of the turbocharger 2 described above will be explained in comparison with the two comparative configurations shown in Figures 4 and 5. Figure 4 is a cross-sectional view showing the exhaust gas flow in the range corresponding to Figure 3 in the first comparative configuration. Figure 5 is a cross-sectional view showing the exhaust gas flow in the range corresponding to Figure 3 in the second comparative configuration. The first comparative configuration shown in Figure 4 is a configuration in which the nozzle flow path side wall surface 70 and the inner circumferential surface 40i of the insertion hole 40 are connected at a right angle, and the vane end surface 60 and the outer circumferential surface 64 of the shaft portion 46 are connected at a right angle (a right-angle corner is formed at the end edge 73 on the nozzle flow path 18 side of the insertion hole 40, and the vane end surface 60 and the outer circumferential surface 64 of the shaft portion 46 are connected via a right-angle corner 75). The second comparative configuration shown in Figure 5 is one in which a chamfered portion 82 is formed at the boundary between the nozzle flow path side wall surface 70 and the inner circumferential surface 40i of the insertion hole 40, and the vane end face 60 and the outer circumferential surface 64 of the shaft portion 46 are connected at a right angle (a chamfered portion 82 is formed on the end edge 73 on the nozzle flow path 18 side of the insertion hole 40, and the vane end face 60 and the outer circumferential surface 64 of the shaft portion 46 are connected via a right-angle corner 75).
[0025] As shown in Figures 4 and 5, in the first and second comparative configurations, when the exhaust gas in the link chamber 24 flows out into the nozzle flow path 18 through the gap between the outer circumferential surface 64 of the shaft portion 46 and the inner circumferential surface 40i of the insertion hole 40, as shown by arrows f1 and f2, separation and recirculation of the exhaust gas flow occur at the edge 73 of the insertion hole 40 and the corner 75 of the nozzle vane 8, increasing energy loss. As a result, the flow velocity of the exhaust gas in the gap between the outer circumferential surface 64 of the shaft portion 46 and the inner circumferential surface 40i of the insertion hole 40 decreases, and fuel and soot tend to accumulate in the gap, making it easy for the nozzle vane 8 to stick.
[0026] In contrast, as shown in Figure 6, in the above embodiment, when the exhaust gas in the link chamber 24 (exhaust gas supplied to the link chamber 24 from the nozzle passage 18 through the communication hole 42 as shown by arrow f in Figure 1) flows out into the nozzle passage 18 through the gap between the outer circumferential surface 64 of the shaft portion 46 and the inner circumferential surface 40i of the insertion hole 40, the flow of the exhaust gas is smoothly redirected through the gap between the convex curved surface 72 and the concave curved surface 66 and discharged into the nozzle passage 18. Therefore, separation and recirculation of the exhaust gas flow in the gap can be suppressed, and energy loss can be reduced. As a result, a decrease in the flow velocity of the exhaust gas passing through the gap can be suppressed, and the accumulation of fuel and soot mixed into the link chamber 24 through the communication hole 42 (see Figure 1) in the gap can be suppressed. Therefore, the occurrence of sticking of the nozzle vane 8 can be suppressed.
[0027] Figure 7 shows the relationship between the ratio of r to d, r / d, and the pressure loss coefficient ζ of the gap between the shaft portion 46 and the insertion hole 40, where d is the size of the gap between the shaft portion 46 and the insertion hole 40 in the radial direction of the shaft portion 46 (see Figure 3), and r is the radius of curvature of the convex curved surface 72 in the cross section along the rotation axis of the shaft portion 46 (see Figure 3). In Figure 7, the solid line graph corresponds to the above embodiment, and the dashed line straight line corresponds to the above first comparison form. r / d is a shape variable related to the curvature of the flow path (gap) and the total pressure loss, and the total pressure loss of the flow occurring in the flow path can be estimated based on r / d.
[0028] In some embodiments, as shown in Figure 7, the nozzle vane 8 and the partition member 26 may be configured to satisfy 0.9 ≤ r / d ≤ 9.3, and more preferably, the nozzle vane 8 and the partition member 26 may be configured to satisfy 2.9 ≤ r / d ≤ 9.3. By satisfying 0.9 ≤ r / d ≤ 9.3, the pressure loss coefficient ζ of the gap between the shaft portion 46 and the insertion hole 40 can be reduced, and the decrease in the flow velocity of the exhaust gas in the gap can be suppressed. Furthermore, although there may be processing constraints on the radius of curvature r, by satisfying 2.9 ≤ r / d ≤ 9.3, it is possible to achieve both the ease of processing the convex curved surface 72 and the reduction of the pressure loss coefficient ζ of the gap.
[0029] This disclosure is not limited to the embodiments described above, but also includes modified forms of the embodiments described above, as well as forms that combine these forms as appropriate.
[0030] For example, in the embodiment described above, a concave curved surface 66 connecting the vane end face 60 and the outer peripheral surface 64 of the shaft portion 46 is formed on each of the nozzle vanes 8 of the turbocharger 2, and a convex curved surface 72 connecting the nozzle flow path side wall surface 70 and the inner peripheral surface 40i of the insertion hole 40 is formed on each of the insertion holes 40 of the turbocharger 2. However, the concave curved surface 66 and the convex curved surface 72 may be formed on only some of the nozzle vanes 8 and some of the insertion holes 40 of the turbocharger 2.
[0031] For example, as shown in Figure 8, if we define the angular position α such that the angular position of the tongue portion 80 of the scroll flow path 16 is 0° and the angle gradually increases from the tongue portion 80 toward the downstream side of the scroll flow path 16, and define each of the multiple nozzle vanes 8 located within the range satisfying 90° ≤ α ≤ 270° as a tongue-far nozzle vane 8A, and define each of the multiple nozzle vanes 8 located within the range satisfying -90° < α < 90° as a tongue-near nozzle vane 8B, then the shape of the nozzle vane 8 and insertion hole 40 described using Figure 3 applies to at least one tongue-far nozzle vane 8A and at least one insertion hole 40 corresponding to that at least one tongue-far nozzle vane 8A, but does not have to apply to the other nozzle vanes 8 and insertion holes 40. Furthermore, "angular position of the tongue portion 80" refers to the position P0 on the inner surface of the turbine housing 30 where the starting and ending portions of the scroll flow path 16 connect (the position of the tip of the tongue-shaped projection formed by the inner surface of the turbine housing 30).
[0032] For example, in each of the far-side nozzle vanes 8A located within the range satisfying 90° ≤ α ≤ 270°, a concave curved surface 66 is formed connecting the vane end face 60 and the outer circumferential surface 64 of the shaft portion 46, as explained with reference to Figure 3. In each of the insertion holes 40 located within the range satisfying 90° ≤ α ≤ 270°, a convex curved surface 72 is formed connecting the nozzle flow path side wall surface 70 and the inner circumferential surface 40i of the insertion hole 40, as explained with reference to Figure 3. In this case, in each of the near-side nozzle vanes 8B located within the range satisfying -90° < α < 90°, the vane end face 60 and the outer circumferential surface 64 of the shaft portion 46 may be connected at a right angle, as shown in Figure 5. In this case, in the insertion holes 40 corresponding to each of the near-side nozzle vanes 8B, a chamfered portion 82 may be formed at the boundary between the nozzle flow path side wall surface 70 of the partition member 26 and the inner circumferential surface 40i of the insertion hole 40. The C-chamfered portion 82 is a conical surface formed to surround the end of the shaft portion 46 (the end on the vane portion 44 side), and in a cross-section along the rotation axis of the shaft portion 46, the C-chamfered portion 82 extends in a straight line toward the radially outward side of the shaft portion 46 and toward the axial partition member 28 side as it moves from the inner circumferential surface 40i of the insertion hole 40 toward the nozzle flow path side wall surface 70 side. In another embodiment, in the insertion hole 40 corresponding to each of the nozzle vanes 8B near the tongue portion, a right-angle corner portion may be formed at the boundary between the nozzle flow path side wall surface 70 of the partition member 26 and the inner circumferential surface 40i of the insertion hole 40 (a corner portion where the nozzle flow path side wall surface 70 of the partition member 26 and the inner circumferential surface 40i of the insertion hole 40 are connected at a right angle, as shown in the edge portion 73 in Figure 4).
[0033] As shown in Figure 9, the static pressure of the main exhaust gas flow in the nozzle passage 18 tends to decrease as it moves away from the tongue portion 80 in the circumferential direction. The static pressure of the main exhaust gas flow in the nozzle passage 18 in the range satisfying 90° ≤ α ≤ 270° tends to be lower than the static pressure of the main exhaust gas flow in the nozzle passage 18 in other ranges (-90° < α < 90°). For this reason, in the range satisfying 90° ≤ α ≤ 270°, the flow of exhaust gas from the nearby communication hole 42 toward the link chamber 24 tends to weaken, and without any countermeasures, nozzle vane 8 is more likely to stick compared to other ranges (-90° < α < 90°).
[0034] Therefore, as described above, by applying the shapes of the nozzle vane 8 and insertion hole 40 described with reference to Figure 3 to the tongue-shaped far nozzle vane 8A located in the range satisfying 90° ≤ α ≤ 270° and the insertion hole 40 corresponding to the tongue-shaped far nozzle vane 8A, it is possible to suppress the decrease in exhaust gas flow velocity in the gap between the shaft portion 46 of the tongue-shaped far nozzle vane 8A, which is prone to sticking, and the insertion hole 40, thereby effectively suppressing the sticking of the tongue-shaped far nozzle vane 8A.
[0035] In some embodiments, as shown in Figure 10, the nozzle vane 8 does not need to have a flange portion 52. Even in this case, if the vane portion 44 of the nozzle vane 8 has a vane end face 60 that faces the nozzle flow path side wall surface 70 of the partition member 26, the configuration described with reference to Figure 3 (a configuration including a concave curved surface 66 connecting the vane end face 60 and the outer peripheral surface 64 of the shaft portion 46, and a convex curved surface 72 connecting the nozzle flow path side wall surface 70 and the inner peripheral surface 40i of the insertion hole 40) can be similarly applied.
[0036] The contents described in each of the above embodiments can be understood, for example, as follows:
[0037] [1] A variable displacement turbocharger according to at least one embodiment of the present disclosure (for example, the turbocharger 2 described above) comprises: a turbine wheel (for example, the turbine wheel 4 described above); a casing (for example, the casing 10 described above) housing the turbine wheel; a first nozzle vane (for example, the nozzle vane 8 described above) capable of adjusting the flow rate of exhaust gas flowing into the turbine wheel; and a link mechanism (for example, the link mechanism 9 described above) for driving the first nozzle vane, wherein the first nozzle vane includes a vane portion (for example, the vane portion 44 described above) and a shaft portion (for example, the shaft portion 46 described above) connected to the vane portion; the casing has a nozzle passage (for example, the nozzle passage 18 described above) in which the vane portion is arranged and a link chamber (for example, the link chamber 24 described above) in which the link mechanism is arranged; the casing includes a partition wall portion (for example, the partition wall member 26 described above) separating the nozzle passage and the link chamber; and the partition wall portion has a first insertion hole (for example, the insertion hole 40 described above) into which the shaft portion is inserted. The partition wall portion has a communication hole (for example, the communication hole 42 described above) that connects the nozzle flow path and the link chamber at a position outside the first insertion hole in the radial direction of the turbine wheel. The surface of the partition wall portion includes a nozzle flow path side wall surface (for example, the nozzle flow path side wall surface 70 described above) facing the nozzle flow path side, and a convex curved surface (for example, the convex curved surface 72 described above) that connects the nozzle flow path side wall surface and the inner circumferential surface of the first insertion hole. The surface of the first nozzle vane includes a vane end surface (for example, the vane end surface 60 described above) facing the nozzle flow path side wall surface of the partition wall portion, and a concave curved surface (for example, the concave curved surface 66 described above) that connects the vane end surface and the outer circumferential surface of the shaft portion and faces the convex curved surface.
[0038] According to the variable displacement turbocharger described in [1] above, when exhaust gas supplied from the nozzle passage through the communication hole to the link chamber flows out into the nozzle passage through the gap between the outer surface of the shaft and the inner surface of the first insertion hole, the flow of exhaust gas is smoothly redirected between the convex and concave curved surfaces and discharged into the nozzle passage. Therefore, compared to cases where the nozzle passage side wall and the inner surface of the first insertion hole are connected at a right angle (see, for example, Figure 4) or where a chamfered portion is formed at the boundary between the nozzle passage side wall and the inner surface of the first insertion hole (see, for example, Figure 5), when exhaust gas in the link chamber flows out into the nozzle passage through the gap between the outer surface of the shaft and the inner surface of the first insertion hole, separation and recirculation of the exhaust gas flow can be suppressed, thereby reducing energy loss. As a result, a decrease in the flow velocity of the exhaust gas passing through the gap can be suppressed, and the accumulation of fuel and soot mixed into the link chamber through the communication hole can be suppressed in the gap, thereby suppressing the occurrence of sticking of the first nozzle vane.
[0039] [2] In some embodiments, in the variable displacement turbocharger described in [1] above, if d is the size of the gap between the shaft portion and the first insertion hole in the radial direction of the shaft portion, and r is the radius of curvature of the convex curved surface in a cross section along the rotation axis of the shaft portion, then the condition 0.9 ≤ r / d ≤ 9.3 is satisfied.
[0040] According to the variable displacement turbocharger described in [2] above, the pressure loss coefficient of the gap between the shaft portion of the first nozzle vane and the insertion hole can be reduced compared to the case where the nozzle flow path side wall surface and the inner circumferential surface of the first insertion hole are connected at a right angle (see, for example, Figure 4). This suppresses a decrease in the flow velocity of exhaust gas passing through the gap and prevents fuel and soot mixed into the link chamber through the communication hole from accumulating in the gap, thereby suppressing the occurrence of sticking of the first nozzle vane.
[0041] [3] In some embodiments, the variable displacement turbocharger described in [2] above satisfies 2.9 ≤ r / d ≤ 9.3.
[0042] According to the variable capacity turbocharger described in the above [3], it is possible to achieve both ease of machining of the convex curved surface and reduction of the pressure loss coefficient.
[0043] [4] In some embodiments, in the variable capacity turbocharger according to any one of the above [1] to [3], the variable capacity turbocharger includes a plurality of nozzle vanes (for example, the plurality of nozzle vanes 8 described above) arranged in the nozzle flow path, the first nozzle vane is one of the plurality of nozzle vanes (for example, the tongue distant nozzle vane 8A described above), and regarding the angular position around the rotational axis of the turbine wheel, when the angular position of the tongue portion of the scroll flow path inside the casing is defined as 0°, and the angular position α is defined such that the angle gradually increases from the tongue portion toward the downstream side of the scroll flow path, the first nozzle vane is located within a range that satisfies 90° ≤ α ≤ 270°.
[0044] The static pressure of the main flow of exhaust gas in the nozzle flow path tends to decrease as the distance from the tongue portion increases in the circumferential direction. For this reason, the static pressure of the main flow of exhaust gas in the nozzle flow path in the range satisfying 90° ≤ α ≤ 270° tends to be lower than the static pressure of the main flow of exhaust gas in the nozzle flow path in the other range (the range of -90° < α < 90°). Therefore, in the range satisfying 90° ≤ α ≤ 270°, the flow of exhaust gas heading from the adjacent communication hole toward the link chamber tends to be weak, and if no measures are taken, seizure of the nozzle vanes is more likely to occur compared with the other range (the range of -90° < α < 90°). In this regard, as described in the above [4], it is possible to suppress the decrease in the flow velocity of the exhaust gas in the gap between the shaft portion of the first nozzle vane, which is prone to seizure, and the insertion hole, thereby effectively suppressing the seizure of the first nozzle vane.
[0045] [5] In some embodiments, in the variable displacement turbocharger described in [4] above, the plurality of nozzle vanes include a second nozzle vane (for example, the tongue-near nozzle vane 8B described above) located within the range satisfying -90° < α < 90°, the second nozzle vane includes a vane portion (for example, the vane portion 44 described above) and a shaft portion (for example, the shaft portion 46 described above) connected to the vane portion, the partition wall portion has a second insertion hole (for example, the insertion hole 40 described above) into which the shaft portion of the second nozzle vane is inserted, and a C-chamfered portion (for example, the C-chamfered portion 82 described above) or a right-angled corner portion (for example, the right-angled corner portion formed on the edge portion 73 described above) is formed at the boundary between the nozzle flow path side wall surface and the inner circumferential surface of the second insertion hole in the partition wall portion.
[0046] For ranges where nozzle vane adhesion is less likely to occur (-90° < α < 90°), a chamfered portion may be provided as described in [5] above by deburring the end of the second insertion hole in the partition wall.
[0047] 2: Turbocharger 4: Turbine wheel 6: Bearing device 8: Nozzle vane 8A: Nozzle vane far from the tongue 8B: Nozzle vane near the tongue 8s: Surface 9: Link mechanism 10: Casing 12: Rotating shaft 16: Scroll flow path 18: Nozzle flow path 24: Link chamber 26: Partition wall 26s: Surface 28: Partition wall 29: Shroud section 30: Turbine housing 32: Bearing housing 33: Nozzle support 40: Insertion hole 40i: Inner circumferential surface 42: Communication hole 44: Vane section 46: Shaft section 50: Wing-shaped section 52: Flange section 60: Vane section end face 64: Outer circumferential surface 66: Concave curved surface 70: Nozzle flow path side wall surface 72: Convex curved surface 73: Edge portion 75: Corner portion 80: Tongue portion 82: Chamfered portion
Claims
1. A turbine wheel, a casing housing the turbine wheel, a first nozzle vane capable of adjusting the flow rate of exhaust gas flowing into the turbine wheel, and a link mechanism for driving the first nozzle vane, wherein the first nozzle vane includes a vane portion and a shaft portion connected to the vane portion, the casing has a nozzle passage where the vane portion is arranged and a link chamber where the link mechanism is arranged, the casing includes a partition wall separating the nozzle passage and the link chamber, the partition wall has a first insertion hole into which the shaft portion is inserted, the partition wall has a communication hole connecting the nozzle passage and the link chamber at a position outside the first insertion hole in the radial direction of the turbine wheel, the surface of the partition wall includes a nozzle passage side wall surface facing the nozzle passage side and a convex curved surface connecting the nozzle passage side wall surface and the inner circumferential surface of the first insertion hole. A variable displacement turbocharger wherein the surface of the first nozzle vane includes a vane end face facing the nozzle flow path side wall surface of the partition wall, and a concave curved surface that connects the vane end face and the outer circumferential surface of the shaft and faces the convex curved surface.
2. A variable displacement turbocharger according to claim 1, wherein d is the size of the gap between the shaft portion and the first insertion hole in the radial direction of the shaft portion, and r is the radius of curvature of the convex curved surface in a cross-section along the rotation axis of the shaft portion, satisfying 0.9 ≤ r / d ≤ 9.
3.
3. A variable displacement turbocharger according to claim 2, satisfying 2.9 ≤ r / d ≤ 9.
3.
4. A variable displacement turbocharger according to claim 1, comprising a plurality of nozzle vanes arranged in the nozzle flow path, wherein the first nozzle vane is one of the plurality of nozzle vanes, and with respect to the angular position around the rotation axis of the turbine wheel, the angular position α is defined such that the angular position of the tongue portion of the scroll flow path inside the casing is 0°, and the angle gradually increases from the tongue portion toward the downstream side of the scroll flow path, the first nozzle vane is located within the range satisfying 90° ≤ α ≤ 270°.
5. The variable displacement turbocharger according to claim 4, wherein the plurality of nozzle vanes include a second nozzle vane located within the range satisfying -90° < α < 90°, the second nozzle vane includes a vane portion and a shaft portion connected to the vane portion, the partition wall portion has a second insertion hole into which the shaft portion of the second nozzle vane is inserted, and a chamfered portion or a right-angled corner portion is formed at the boundary between the nozzle flow path side wall surface and the inner circumferential surface of the second insertion hole in the partition wall portion.