Variable capacity turbine and turbocharger equipped with the same

Abstract

Provided are a variable geometry turbine and a turbocharger with the same. The variable geometry turbine is provided with a turbine impeller, a housing, a plurality of nozzle vanes, and a link mechanism. Inside the housing, a link compartment in which the link mechanism is accommodated is formed, the link compartment being separated from a nozzle flow path by a hub-side member having a hub side surface defining the nozzle flow path. The link mechanism and each of the plurality of nozzle vanes are coupled together via a nozzle shaft penetrating through the hub-side member. The hub-side member has at least one communication hole providing communication between the nozzle flow path and the link compartment. When each of the plurality of nozzle vanes is fully opened, the opening of the at least one communication hole on the nozzle flow path side is formed on the inner side radially of the turbine impeller than the leading edge of each of the plurality of nozzle vanes.

Description

Technical Field

[0001] The present disclosure relates to a variable-capacity turbine including a plurality of nozzle vanes and a link mechanism for rotating each of the plurality of nozzle vanes, and a turbocharger including the same.

Background Art

[0002] A variable geometry turbocharger is used in engines that require operation over a wide range of engine speeds or boost at low engine speeds. A variable-capacity turbine, which is one of the main components of a variable geometry turbocharger, includes a scroll that defines a scroll flow path through which exhaust gas discharged from the engine flows into the turbine, a nozzle assembly that controls the flow velocity and the incident angle at the turbine rotor inlet by nozzle vanes, a turbine rotor, and a diffuser that pushes the exhaust gas to the outside. In recent years, due to the application of the Miller cycle to gasoline vehicle engines, the demand for variable geometry turbochargers has been increasing not only for conventional diesel vehicle engines but also for gasoline vehicle engines. However, in a variable geometry turbocharger, the exhaust gas becomes hot to enable such engine operation, or the number of moving parts of the variable-capacity turbine increases, resulting in a major reliability problem. [[ID=!16]]

[0003] Patent Document 1 discloses an example of the invention related to the variable-capacity turbocharger described above. The invention according to this Patent Document 1 aims to solve the problem that unburned gas contained in the exhaust gas flowing through the scroll passage leaks into the link chamber through clearances such as those between the nozzle vane and the nozzle mount due to the pressure difference between the scroll passage and the link chamber, and accumulates on the movable parts in the link chamber, thereby inhibiting the movement of the movable parts. Therefore, in the invention according to Patent Document 1, by providing a through-hole in the nozzle mount that allows the inflow of exhaust gas from the scroll passage into the link chamber, the pressure difference between the scroll passage and the link chamber is reduced, thereby reducing the leakage of exhaust gas and the accumulation of deposits on the movable parts. Further, in Patent Document 1, by allowing the high-temperature exhaust gas flowing through the scroll passage to flow into the link chamber, the heat of the exhaust gas acts to vaporize and eliminate the deposits adhering and accumulating on the movable parts, so that it is disclosed that the movement of the movable parts can be kept good over a long period of time.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, since the nozzle vane is a movable member, clearances are provided between the nozzle shaft passing through the nozzle mount (hub-side member) and the nozzle mount, between the nozzle vane and the nozzle mount, and between the nozzle vane and the nozzle plate. And the inventors have found that when external forces such as gravity and engine vibration are applied to the variable-capacity turbine during its operation, the nozzle vane may repeatedly make unnecessary movements in the extending direction (axial direction) of the nozzle shaft, and the nozzle vane may be worn.

[0006] In view of the above problems, at least one embodiment of the present invention aims to provide a variable-capacity turbine capable of suppressing repeated unnecessary movement of a nozzle vane and suppressing the progress of wear of the nozzle vane, and a turbocharger including the same.

Means for Solving the Problems

[0007] To achieve the above object, a variable-capacity turbine according to one aspect includes a turbine impeller, a housing that houses the turbine impeller, a plurality of nozzle vanes disposed in a nozzle flow path formed inside the housing, and a link mechanism for rotating each of the plurality of nozzle vanes. Inside the housing, there is a link chamber that houses the link mechanism, and the link chamber is partitioned from the nozzle flow path by a hub side member having a hub side surface that defines the nozzle flow path. The link mechanism and each of the plurality of nozzle vanes are connected via a nozzle shaft that penetrates the hub side member. At least one communication hole that communicates the nozzle flow path and the link chamber is formed in the hub side member. The opening on the nozzle flow path side of the at least one communication hole is formed radially inward of the front edge of each of the plurality of nozzle vanes when each of the plurality of nozzle vanes is in a fully open state.

Advantages of the Invention

[0008] According to an embodiment of the present disclosure, it is possible to provide a variable-capacity turbine capable of suppressing unnecessary movement of the nozzle vane and suppressing the progress of wear of the nozzle vane by increasing the pressure difference between the nozzle flow path and the link chamber and increasing the axial force acting on the nozzle vane, and a turbocharger including the same.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7A

Figure 7B

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0010] Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying 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 present disclosure, but are merely illustrative examples. For example, expressions representing relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial" not only strictly represent such arrangements, but also represent states where there are tolerances, or relative displacements with angles and distances that can achieve the same function. For example, expressions representing that things such as "identical", "equal", and "homogeneous" are in an equal state not only strictly represent an equal state, but also represent states where there are tolerances, or differences that can achieve the same function. For example, expressions representing shapes such as a square shape or a cylindrical shape not only represent shapes such as a square shape or a cylindrical shape in a geometrically strict sense, but also represent shapes including concave and convex portions, chamfered portions, etc. within a range where the same effect can be obtained. On the other hand, the expressions "comprising", "including", or "having" for a component are not exclusive expressions that exclude the existence of other components. Note that the same reference numerals may be given to the same configurations and the description may be omitted.

[0011] (Overall configuration of the turbocharger) FIG. 1 is a schematic diagram showing the configuration of a turbocharger (supercharger) according to an embodiment.

[0012] As shown in FIG. 1, the turbocharger 1 includes a variable geometry turbine 2, a compressor 3, and a rotating shaft 5 (turbine shaft). The variable geometry turbine 2 is disposed on the exhaust side of an engine 100 having a piston 101 and a cylinder (not shown), and is rotationally driven by using the exhaust energy from the engine 100. The variable geometry turbine 2 includes a nozzle vane 27 described later and is connected to one end of the rotating shaft 5. The compressor 3 is disposed on the intake side of the engine 100 and is connected to the other end of the rotating shaft 5, and is coaxially and rotatably connected to the variable geometry turbine 2 via the rotating shaft 5. When the variable geometry turbine 2 is rotated using the exhaust of the engine 100 as a working fluid, the compressor 3 is rotated using the rotational force, and intake air (supercharged air) is supplied into the engine 100.

[0013] (Overall configuration of variable geometry turbine) FIG. 2 is a schematic partial cross-sectional view showing a variable geometry turbine according to an embodiment.

[0014] As shown in FIG. 2, the variable geometry turbine 2 includes a turbine impeller 21, a housing 23 that houses the turbine impeller 21, a plurality of nozzle vanes 27 disposed in a nozzle flow path 25 formed inside the housing 23, and a link mechanism 60 that changes the blade angle of each of the plurality of nozzle vanes 27 by rotating each of the plurality of nozzle vanes 27.

[0015] The turbine impeller 21 includes a hub 21A connected to the rotating shaft 5 and a plurality of moving blades 21B arranged in the circumferential direction on the outer peripheral surface of the hub 21A. The exhaust flowing through the nozzle flow path 25 acts on the moving blades 21B, so that the turbine impeller 21 and the rotating shaft 5 connected thereto are configured to rotate.

[0016] The housing 23 is configured to rotatably accommodate the turbine impeller 21. Inside the housing 23, there are defined a scroll flow path 26 that is located on the outer peripheral side of the turbine impeller 21 and is defined by the inner peripheral wall portion 23A, a nozzle flow path 25 for introducing the exhaust gas that has flowed through the scroll flow path 26 into the turbine impeller 21, an outlet side flow path 50 for discharging the exhaust gas that has passed through the turbine impeller 21 to the outside, and a link chamber 28 (to be described later). The arrows in the figure indicate the flow direction of the exhaust gas.

[0017] In the illustrated embodiment, the housing 23 includes a turbine housing 22 that defines the scroll flow path 26 and the outlet side flow path 50 inside and houses the turbine impeller 21 therein, and a bearing housing 24 that houses a bearing (not shown) for rotatably supporting the rotating shaft 5. Also, in an embodiment not shown, the housing 23 may be composed of a single housing member in which the turbine housing 22 and the bearing housing 24 are integrally formed.

[0018] Each of the plurality of nozzle vanes 27 is arranged at intervals along the circumferential direction of the turbine impeller 21 in the nozzle flow path 25. Each of the plurality of nozzle vanes 27 is connected to one end side in the axial direction of the nozzle shaft 30, and the other end side in the axial direction of the nozzle shaft 30 is connected to a link mechanism 60 (to be described later). Each of the plurality of nozzle vanes 27 can have its opening degree adjusted between a fully closed state and a fully open state by the link mechanism 60 via the nozzle shaft 30.

[0019] (Link mechanism) The link mechanism 60 includes a plurality of lever plates 61 and a single drive ring 62 to which each of the plurality of lever plates 61 is connected. Each of the plurality of nozzle vanes 27 is connected to one end side (radially inner side) of the lever plate 61 via the nozzle shaft 30. Also, the other end side (radially outer side) of the lever plate 61 is connected to the disk-shaped drive ring 62. The drive ring 62 is driven by an actuator (not shown) and is rotatable about the rotation axis 5. When the drive ring 62 rotates, each lever plate 61 rotates, and accordingly, the nozzle shaft 30 rotates about the axis 30L along the axial direction. Then, the opening degree (blade angle) of the nozzle vane 27 changes via the nozzle shaft 30.

[0020] Inside the housing 23, a link chamber 28 for accommodating the link mechanism 60 is formed. The link chamber 28 is partitioned from the nozzle flow path 25 by a hub side member 40 having a hub side surface 40A that defines the nozzle flow path 25, specifically, the other surface 40B of the hub side member 40. The nozzle flow path 25 is defined by the hub side surface 40A of the hub side member 40 and the shroud side surface 29A of a shroud side member 29 provided on one side of the rotation axis 5 (the side away from the compressor 3) with respect to the hub side member 40. Each of the link mechanism 60 and the plurality of nozzle vanes 27 is connected via a nozzle shaft 30 that penetrates the hub side member 40. Specifically, the hub side member 40 has a through hole 41 through which the nozzle shaft 30 penetrates, and the nozzle shaft 30 is rotatably supported by penetrating the through hole 41 of the hub side member 40.

[0021] (Configuration of communication hole) FIG. 3 is an enlarged cross-sectional view of the main part (A) of FIG. 2. FIG. 4 is a diagram for explaining the positional relationship between the nozzle vane and the communication hole in the variable-capacity turbine according to an embodiment. In FIG. 4, the turbine housing 22 and the shroud side member 29 are not shown, and the variable-capacity turbine 2 in which each of the plurality of nozzle vanes 27 is in the fully open state is viewed from the front side (from one side of the rotation axis 5 toward the other side).

[0022] As shown in FIG. 3, at least one communication hole 70 that communicates the nozzle flow path 25 and the link chamber 28 is formed in the hub side member 40. Different from the above-described through hole 41, the communication hole 70 is a hole through which the nozzle shaft 30 is not inserted. Then, as shown in FIG. 4, the opening 70A on the nozzle flow path 25 side of at least one communication hole 70 (the opening 70A of the communication hole 70 provided on the hub side surface 40A of the hub side member 40) is formed radially inward of the front edge 27a of each of the plurality of nozzle vanes 27 when each of the plurality of nozzle vanes 27 is in the fully open state.

[0023] The hole shape of the communication hole 70 only needs to allow the exhaust gas to communicate, and is not particularly limited. In the illustrated embodiment, the hole shape of the communication hole 70 is circular.

[0024] (Description of FIGS. 5 to 7) FIG. 5 is a diagram for explaining the acting direction of the axial force (Z-direction force) acting on each of the plurality of nozzle vanes in a variable capacity turbine according to an embodiment. FIG. 5(a) is a schematic view showing a state in which each of the plurality of nozzle vanes 27 is arranged on a plane orthogonal to the axis L of the rotating shaft 5. In FIG. 5(a), the Y direction indicates the radial direction of the turbine impeller 21, and the X direction indicates a direction orthogonal to the Y direction. FIG. 5(b) is a schematic view of each of the plurality of nozzle vanes 27 viewed from the side. In FIG. 5(b), the Z direction indicates a direction orthogonal to the X direction and the Y direction, and is parallel to the axis L of the rotating shaft 5.

[0025] In the embodiment shown in FIG. 5, nine nozzle vanes 27 (271 to 279) are arranged at intervals along the circumferential direction of the turbine impeller 21. The reference numeral of the nozzle vane 27 closest to the tongue portion 80 (FIG. 8) that partitions the start and end of the scroll flow path 26 and arranged at the start (upstream side) of the scroll flow path 26 shown in FIG. 8 described later is 271, and nozzle vanes 272 to 279 are arranged in order (counterclockwise in FIG. 8) toward the downstream side in the exhaust flow direction.

[0026] FIG. 6 is a graph showing the analysis result of the axial force (Z-direction force) acting on each of the plurality of nozzle vanes in a variable capacity turbine according to an embodiment. In FIG. 6, the horizontal axis of the graph indicates the reference numerals (271 to 279) of the nozzle vanes 27, and the vertical axis of the graph indicates the magnitude of the Z-direction force. The Z-direction force acting on the nozzle vane 27 is shown with the force direction from the nozzle flow path 25 toward the link chamber 28 along the axis L of the rotating shaft 5 being positive (+), and the force direction from the link chamber 28 toward the nozzle flow path 25 being negative (-). Also, in FIG. 6, the symbol E indicates the analysis result (example) in the variable-capacity turbine 2 according to one embodiment in which the communication hole 70 is formed, and the symbol R indicates the analysis result (comparative example) in the conventional variable-capacity turbine in which the communication hole 70 is not formed.

[0027] As shown in FIG. 6, in the comparative example, the Z-direction forces are small (close to 0) in the nozzle vanes 274, 276, and 279. On the other hand, in the example, the value of the Z-direction force is positively larger compared to the comparative example. Therefore, in the example, the nozzle vanes 274, 276, and 279, in which the Z-direction force is small (close to 0) in the comparative example, have an increase in the Z-direction force and a large Z-direction force acts thereon.

[0028] FIGS. 7A and 7B are diagrams showing the pressure distributions in the nozzle flow path and the link chamber in the variable-capacity turbine according to one embodiment. FIG. 7A shows the analysis result (comparative example) in the conventional variable-capacity turbine in which the communication hole 70 is not formed, and FIG. 7B shows the analysis result (example) in the variable-capacity turbine 2 according to one embodiment in which the communication hole 70 is formed. Also, in FIGS. 7A and 7B, the magnitude of the pressure obtained by numerical analysis is represented by the shade of color. It shows that the lighter the color, the lower the pressure, and the darker the color, the higher the pressure.

[0029] In the embodiment of FIG. 7B in which the communication hole 70 is formed, the pressure in the link chamber 28 is lower than that in the comparative example of FIG. 7A. In the nozzle flow path 25, there is no significant change in the magnitude of the pressure between the comparative example of FIG. 7A and the embodiment of FIG. 7B. That is, due to the decrease in the pressure in the link chamber 28, in the embodiment of FIG. 7B in which the communication hole 70 is formed, the difference in pressure between the pressure in the link chamber 28 and the pressure at the radial position near the nozzle shaft 30 of the nozzle flow path 25 is larger than that in the comparative example of FIG. 7A.

[0030] (Function and effect) As described with reference to FIG. 5, in each of the plurality of nozzle vanes 27, a force in the axial direction (Z direction) acts in addition to the circumferential direction (X direction) and the radial direction (Y direction). This Z-direction force is a force generated by the pressure difference between the nozzle flow path 25 and the link chamber 28, and the greater the pressure difference between the nozzle flow path 25 (high-pressure side) and the link chamber 28 (low-pressure side), the greater the force generated.

[0031] As shown in FIG. 6, according to the study by the present inventors, it has been clarified that there are nozzle vanes 27 (274, 276, 279) in which the Z-direction force is small (close to 0) among the plurality of nozzle vanes 27. In the nozzle vane 27 with a small Z-direction force, since it is likely to move in the Z direction due to the influence of an external force, the unnecessary movement of the nozzle vane 27 described above is more likely to occur, and there is a risk that the wear of the nozzle vane 27 will progress.

[0032] The exhaust gas flowing through the nozzle flow path 25 has its pressure reduced by controlling the flow velocity and flow direction by the nozzle vane 27. Therefore, the pressure of the exhaust gas flowing radially inside the leading edge 27a of each of the plurality of nozzle vanes 27 is lower than the pressure of the exhaust gas flowing radially outside the leading edge 27a of each.

[0033] According to the variable capacity turbine 2 according to the present disclosure, the opening 70A on the nozzle flow path 25 side of at least one communication hole 70 is formed radially inside the leading edge 27a of each of the plurality of nozzle vanes 27 when each of the plurality of nozzle vanes 27 is in the fully open state. Therefore, as shown in FIGS. 7A and 7B, the exhaust gas filling the link chamber 28 flows out from the communication hole 70 into the nozzle flow path 25, so that the pressure in the link chamber 28 can be reduced. Thereby, by increasing the pressure difference between the nozzle flow path 25 and the inside of the link chamber 28 and increasing the Z-direction force acting on some of the nozzle vanes 27, unnecessary movement of the nozzle vanes 27 described above can be suppressed, and the progress of wear of the nozzle vanes 27 can be suppressed.

[0034] In some embodiments, as shown in FIG. 2, the hub side member 40 is formed as a nozzle mount 44 separate from the turbine housing 22 and the bearing housing 24. The nozzle mount 44 is an annular plate-like member extending in the circumferential direction on the outer peripheral side of the turbine impeller 21. The nozzle mount 44 is supported in the housing 23 by the outer peripheral edge portion of the nozzle mount 44 being sandwiched between the turbine housing 22 and the bearing housing 24.

[0035] The link chamber 28 described above is defined by the bearing housing 24 and the other surface 44B of the nozzle mount 44.

[0036] According to such a configuration, since the communication hole 70 may be formed in the nozzle mount 44 which is an annular member, the manufacturing cost can be suppressed as compared with forming the communication hole 70 in the bearing housing 24 or the turbine housing 22 having a complicated shape.

[0037] In an embodiment not shown, the hub side member 40 may be formed integrally with the turbine housing 22 or the bearing housing 24.

[0038] In some embodiments, as shown in FIG. 2, the shroud side member 29 is formed as a nozzle plate 33 separate from the turbine housing 22. The nozzle plate 33 is supported within the housing 23 by fixing the shroud side surface 33A of the nozzle plate 33 to the other end side of a nozzle support (not shown) whose one end side is fixed to the hub side surface 44A of the nozzle mount 44. The nozzle flow path 25 described above is defined by the hub side surface 44A of the nozzle mount 44 and the shroud side surface 33A of the nozzle plate 33.

[0039] Also, in an embodiment not shown, the shroud side member 29 may be formed integrally with the turbine housing 22.

[0040] (Description of FIG. 8) FIG. 8 is a diagram showing the pressure distribution of the nozzle flow path in a variable capacity turbine according to an embodiment. In FIG. 8, the nozzle flow path 25 is viewed along the axis L of the rotation shaft 5. In FIG. 8, the magnitude of the pressure obtained by numerical analysis is represented by the shade of color. It is shown that the lighter the color, the lower the pressure, and the darker the color, the higher the pressure. Although the opening 70A on the nozzle flow path 25 side of the communication hole 70 is not shown in FIG. 8, the opening 70A is arranged at the same position as in FIG. 10 described later.

[0041] As shown in FIG. 8, the pressure of the exhaust gas in the nozzle flow path 25 starts to decrease from the vicinity upstream of the leading edge 27a of the nozzle vane 27 and gradually decreases toward the radially inner side.

[0042] In some embodiments, as shown in FIG. 4, the opening 70A on the nozzle flow path 25 side of the communication hole 70 is formed radially inside the nozzle shaft 30. That is, the center (centroid) of the opening 70A is located radially inside the axis 30L of the nozzle shaft 30.

[0043] In the illustrated embodiment, the opening 70A has an area smaller than that of the through hole 41.

[0044] According to such a configuration, since the pressure in the nozzle flow path 25 becomes lower toward the radially inner side, by forming the opening 70A on the nozzle flow path 25 side of the communication hole 70 that penetrates the nozzle flow path 25 and the link chamber 28 to be radially inner than the nozzle shaft 30, the pressure in the link chamber 28 can be reduced more efficiently.

[0045] In some embodiments, as shown in FIG. 4, the opening 70A on the nozzle flow path 25 side of the communication hole 70 is formed at a position overlapping with the concentric circle 90 passing through the trailing edge 27b of each of the plurality of nozzle vanes 27 when each of the plurality of nozzle vanes 27 is in the fully open state. That is, when each of the plurality of nozzle vanes 27 is in the fully open state, among the openings 70A on the nozzle flow path 25 side of the communication hole 70, the opening portion 70a closest to the radially inner side is formed so as to be in contact with the line segment of the concentric circle 90 or to be radially inner than the line segment of the concentric circle 90 (see the enlarged view of part B). Also, the opening 70A on the nozzle flow path 25 side of the communication hole 70 may be formed radially inner than the concentric circle 90. That is, the center (center of the circle) of the opening 70A is located radially inner than the line segment of the concentric circle 90.

[0046] As shown in FIG. 8, the pressure of the exhaust gas in the nozzle flow path 25 is lower toward the radially inner side, and when each of the plurality of nozzle vanes 27 is in the fully open state, the position overlapping with the concentric circle 90 and the position radially inner than the concentric circle 90 are the regions where the pressure is the lowest.

[0047] According to such a configuration, since the pressure in the nozzle flow path 25 becomes lower toward the radially inner side, by forming the opening 70A on the nozzle flow path 25 side of the communication hole 70 that penetrates the nozzle flow path 25 and the link chamber 28 at a position overlapping with the concentric circle 90 or radially inner than the concentric circle 90, the pressure in the link chamber 28 can be reduced more efficiently.

[0048] FIG. 9 is a cross-sectional view of the main part (A) of FIG. 2 in another embodiment different from FIG. 3, with the main part enlarged.

[0049] In some embodiments, as shown in FIG. 9, the opening 70A on the nozzle flow path 25 side of at least one communication hole 70 and the opening 70B on the link chamber 28 side of at least one communication hole 70 are formed such that their positions in the radial direction are different.

[0050] According to such a configuration, it is not necessary to align the opening 70A on the nozzle flow path 25 side of the communication hole 70 and the opening 70B on the link chamber 28 side of the communication hole 70 in the radial direction. Therefore, the degree of freedom in layout for providing the opening 70B on the link chamber 28 side of the communication hole 70 can be increased within the link chamber 28 where space is limited.

[0051] Also, in some embodiments, the opening 70A on the nozzle flow path 25 side of at least one communication hole 70 and the opening 70B on the link chamber 28 side of at least one communication hole 70 may be formed such that their positions in the circumferential direction are different. According to such a configuration, it is not necessary to align the opening 70A on the nozzle flow path 25 side of the communication hole 70 and the opening 70B on the link chamber 28 side of the communication hole 70 in the circumferential direction. Therefore, the degree of freedom in layout for providing the opening 70B on the link chamber 28 side of the communication hole 70 can be increased within the link chamber 28 where space is limited.

[0052] In some embodiments, as shown in FIG. 9, the opening 70A on the nozzle flow path 25 side of at least one communication hole 70 is formed radially inward of the opening 70B on the link chamber 28 side of at least one communication hole 70.

[0053] According to such a configuration, no matter where the opening 70B on the link chamber 28 side of the communication hole 70 is located in the radial direction, the opening 70A on the nozzle flow path 25 side can be formed on the inner side in the radial direction. Since the pressure in the nozzle flow path 25 becomes lower toward the inner side in the radial direction, by forming the opening 70A on the nozzle flow path 25 side more toward the inner side in the radial direction, the pressure in the link chamber 28 can be reduced more efficiently.

[0054] Also, in some embodiments, the opening 70A on the nozzle flow path 25 side of at least one communication hole 70 may be formed on the upstream side in the flow direction of the exhaust gas in the circumferential direction with respect to the opening 70B on the link chamber 28 side of at least one communication hole 70. According to such a configuration, since the exhaust gas easily flows from the opening 70A to the opening 70B, the pressure in the link chamber 28 can be reduced more efficiently.

[0055] FIG. 10 is a diagram for explaining the positional relationship between the nozzle vane and the communication hole in a variable capacity turbine according to an embodiment. In FIG. 10, the turbine housing 22 and the shroud side member 29 are not shown, and a plurality of nozzle vanes 27 in the fully open state and a nozzle vane 27 in the fully closed state are visually recognized from the front side (from one side of the rotation axis 5 toward the other side). Note that the nozzle vanes 27 in the fully open state are shown by solid lines, and the nozzle vanes 27 in the fully closed state are shown by two-dot chain lines.

[0056] In some embodiments, as shown in FIG. 10, the opening 70A on the nozzle flow path 25 side of at least one communication hole 70 is formed so as not to overlap each of the plurality of nozzle vanes 27 in any opening state from fully open to fully closed of each of the plurality of nozzle vanes 27. That is, although the opening state of the nozzle vane 27 changes in the range from fully open to fully open, if the region where the nozzle vane 27 can be located when the nozzle vane 27 moves from fully open to fully closed is defined as the movable region B as shown in FIG. 10, the opening 70A on the nozzle flow path 25 side of the communication hole 70 is formed at a position that does not overlap the movable region B.

[0057] According to such a configuration, even when the nozzle vane 27 is in any opening state from fully open to fully closed, the nozzle vane 27 does not block the communication hole 70 that communicates the nozzle flow path 25 and the link chamber 28. Therefore, the communication hole 70 can always maintain a state of communicating the nozzle flow path 25 and the link chamber 28. Further, since the nozzle vane 27 does not block a part of the communication hole 70, the communication hole 70 can always keep the opening as it is even while the variable capacity turbine 2 is operating. Therefore, the pressure in the link chamber 28 can be reduced.

[0058] The present disclosure is not limited to the above-described embodiments, and includes forms obtained by modifying the above-described embodiments and forms obtained by appropriately combining these forms.

[0059] The contents described in some of the above embodiments can be understood as follows, for example.

[0060] 1) The variable capacity turbine (2) according to one aspect includes a turbine impeller (21), a housing (23) that houses the turbine impeller, a plurality of nozzle vanes (27) arranged in a nozzle flow path (25) formed inside the housing (23), and a link mechanism (60) that changes the blade angle of each of the plurality of nozzle vanes by rotating each of the plurality of nozzle vanes (27). Inside the housing (23), there is a link chamber (28) that houses the link mechanism (60), and the link chamber (28) is partitioned from the nozzle flow path (25) by a hub side member (40) having a hub side surface that defines the nozzle flow path (25). Each of the link mechanism (60) and the plurality of nozzle vanes (27) is connected via a nozzle shaft (30) that penetrates the hub side member (40). The hub side member (40) is formed with at least one communication hole (70) that communicates the nozzle flow path (25) and the link chamber (28). The opening on the nozzle flow path side of at least one communication hole (70) is formed radially inside the diameter of the turbine impeller (21) than the front edge of each of the plurality of nozzle vanes (27) when each of the plurality of nozzle vanes (27) is in the fully open state.

[0061] For each of the plurality of nozzle vanes, a force in the axial direction (Z direction) acts in addition to the circumferential direction (X direction) and the radial direction (Y direction). This Z-direction force is a force generated by the pressure difference between the nozzle flow path and the link chamber, and the greater the pressure difference between the nozzle flow path (high pressure side) and the link chamber (low pressure side), the greater the force generated.

[0062] According to the study by the present inventors, it has become clear that there are nozzle vanes 274, 276, 279 in which the Z-direction force is small (close to 0) among some of the plurality of nozzle vanes. In the nozzle vanes with a small Z-direction force, since they are likely to move in the Z direction due to the influence of external force, the above-mentioned unnecessary movement of the nozzle vanes is more likely to occur, and there is a risk that the wear of the nozzle vanes will progress more easily.

[0063] The exhaust gas flowing through the nozzle flow path has its pressure reduced by controlling the flow velocity and flow direction by the nozzle vanes. Therefore, the pressure of the exhaust gas flowing radially inside the front edge of each of the plurality of nozzle vanes is lower than the pressure of the exhaust gas flowing radially outside the front edge of each.

[0064] According to the variable-capacity turbine according to the present disclosure, the opening on the nozzle flow path side of at least one communication hole is formed radially inside the diameter of the turbine impeller than the front edge of each of the plurality of nozzle vanes when each of the plurality of nozzle vanes is in the fully open state. Therefore, the low-pressure exhaust gas flowing through the nozzle flow path can flow from the communication hole into the link chamber and reduce the pressure in the link chamber. Thereby, by increasing the pressure difference between the nozzle flow path and the link chamber and increasing the Z-direction force acting on some of the nozzle vanes, the above-mentioned unnecessary movement of the nozzle vanes can be suppressed, and the progress of wear of the nozzle vanes can be suppressed.

[0065] 2) The variable capacity turbine (2) according to another aspect is the variable capacity turbine (2) described in 1), wherein the opening (70A) on the nozzle flow path (25) side of the communication hole is formed radially inward of the nozzle shaft (30).

[0066] According to such a configuration, since the pressure in the nozzle flow path becomes lower as it goes radially inward, by forming the opening on the nozzle flow path side of the communication hole that penetrates the nozzle flow path and the link chamber radially inward of the nozzle shaft, the pressure in the link chamber can be reduced more efficiently.

[0067] 3) The variable capacity turbine (2) according to another aspect is the variable capacity turbine (2) described in 1) or 2), wherein the opening (70A) on the nozzle flow path (25) side of the communication hole (70) is formed at a position overlapping a concentric circle (90) passing through the trailing edge of each of the plurality of nozzle vanes (27) when each of the plurality of nozzle vanes (27) is in the fully open state, or is formed radially inward of the concentric circle (90).

[0068] According to such a configuration, since the pressure in the nozzle flow path becomes lower as it goes radially inward, by forming the opening on the nozzle flow path side of the communication hole that penetrates the nozzle flow path and the link chamber at a position overlapping the concentric circle or radially inward of the concentric circle, the pressure in the link chamber can be reduced more efficiently.

[0069] 4) The variable capacity turbine (2) according to another aspect is the variable capacity turbine (2) described in 1) to 3), wherein the opening (70A) on the nozzle flow path (25) side of at least one communication hole (70) and the opening (70B) on the link chamber side (28) of the at least one communication hole are formed so that their positions in the radial direction are different.

[0070] According to such a configuration, it is not necessary to align the opening on the nozzle flow path side of the communication hole and the opening on the link chamber side of the communication hole in the radial direction. Therefore, in the link chamber where space is limited, the degree of freedom in layout for providing the opening on the link chamber side of the communication hole can be increased.

[0071] 5) The variable capacity turbine (2) according to another aspect is the variable capacity turbine (2) described in 4), wherein the opening (70A) on the nozzle flow path (25) side of at least one communication hole (70) is formed radially inward of the opening (70B) on the link chamber (28) side of at least one communication hole (70).

[0072] According to such a configuration, regardless of the position of the opening on the link chamber side of the communication hole in the radial direction, the opening on the nozzle flow path side can be formed radially inward. Since the pressure in the nozzle flow path becomes lower as it goes radially inward, by forming the opening on the nozzle flow path side more radially inward, the pressure in the link chamber can be reduced more efficiently.

[0073] 6) The variable capacity turbine (2) according to another aspect is the variable capacity turbine (2) described in 1) to 5), wherein the opening (70A) on the nozzle flow path (25) side of at least one communication hole (70) is formed so as not to overlap with each of the plurality of nozzle vanes (27) in any opening degree state from fully open to fully closed of each of the plurality of nozzle vanes (27).

[0074] According to such a configuration, in any opening degree state of the nozzle vane from fully open to fully closed, the nozzle vane does not block the communication hole that communicates the nozzle flow path and the link chamber. Therefore, the communication hole can always maintain a state of communicating the nozzle flow path and the link chamber. Also, since the nozzle vane does not block a part of the communication hole, the communication hole can always keep the opening as it is while the variable capacity turbine is operating. Therefore, the pressure in the link chamber can be reduced.

[0075] 7) The variable-capacity turbine (2) according to another aspect is the variable-capacity turbine (2) described in 1) to 6), wherein the hub-side member (40) is formed by a nozzle mount (44) of an annular member supported by the housing (23).

[0076] According to such a configuration, since it is only necessary to form a communication hole in the nozzle mount which is an annular member, the manufacturing cost can be suppressed as compared with forming a communication hole in a bearing housing or a turbine housing having a complicated shape.

[0077] 8) The turbocharger (1) according to one aspect is the variable-capacity turbine (2) described in the above 1) to 7), and a compressor (3) driven by the variable-capacity turbine (2).

[0078] According to such a configuration, in a turbocharger provided with a compressor driven by a variable-capacity turbine, the effects described in any one of the above 1) to 7) can be enjoyed.

Explanation of Reference Numerals

[0079] 1 Turbocharger 2 Variable-capacity turbine 3 Compressor 5 Rotating shaft 21 Turbine impeller <^ 21A Hub 21B Moving blade 22 Turbine housing 23 Housing 23A Inner peripheral wall portion 24 Bearing housing 25 Nozzle flow path 26 Scroll flow path 27(271 to 279) Nozzle vane 27a Leading edge 27b Trailing edge 28 Link chamber <^ 29 Shroud-side member 29A, 33A Shroud side surface 30 Nozzle Shaft 30L (Axis of the nozzle shaft) 33 Nozzle Plate 40 Hub Side Member 40A, 44A Hub Side Surface 40B, 44B Other Surface 41 Through-Hole 44 Nozzle Mount 50 Outlet Side Flow Path 60 Link Mechanism 61 Lever Plate 62 Drive Ring 70 Communication Hole 70A Opening on the Nozzle Flow Path Side 70B Opening on the Link Chamber Side 70a Opening Portion Nearest to the Innermost in the Radial Direction 80 Tongue Portion 90 Concentric Circles 100 Engine 101 Piston B Movable Region L Axis

Claims

1. A turbine impeller, a housing that houses the turbine impeller, a plurality of nozzle vanes disposed in a nozzle flow path formed inside the housing, and a link mechanism that changes the blade angle of each of the plurality of nozzle vanes by rotating each of the plurality of nozzle vanes, inside the housing, there is a link chamber that houses the link mechanism, and the link chamber is partitioned from the nozzle flow path by a hub side member having a hub side surface that defines the nozzle flow path, each of the link mechanism and the plurality of nozzle vanes is connected via a nozzle shaft that penetrates the hub side member, at least one communication hole that communicates the nozzle flow path and the link chamber is formed in the hub side member, the opening on the nozzle flow path side of the at least one communication hole is formed radially inward of the turbine impeller from the front edge of each of the plurality of nozzle vanes when each of the plurality of nozzle vanes is in the fully open state, the opening on the nozzle flow path side of the at least one communication hole is formed radially inward of each of the plurality of nozzle shafts, a variable displacement turbine.

2. A turbine impeller, a housing that houses the turbine impeller, a plurality of nozzle vanes disposed in a nozzle flow path formed inside the housing, and a link mechanism that changes the blade angle of each of the plurality of nozzle vanes by rotating each of the plurality of nozzle vanes, inside the housing, there is a link chamber that houses the link mechanism, and the link chamber is partitioned from the nozzle flow path by a hub side member having a hub side surface that defines the nozzle flow path, each of the link mechanism and the plurality of nozzle vanes is connected via a nozzle shaft that penetrates the hub side member, at least one communication hole that communicates the nozzle flow path and the link chamber is formed in the hub side member, the opening on the nozzle flow path side of the at least one communication hole is formed radially inward of the turbine impeller from the front edge of each of the plurality of nozzle vanes when each of the plurality of nozzle vanes is in the fully open state, The opening on the nozzle flow path side of the at least one communication hole is formed at a position overlapping a concentric circle passing through the trailing edge of each of the plurality of nozzle vanes when each of the plurality of nozzle vanes is in a fully open state, or is formed inside the concentric circle in the radial direction. Variable displacement turbine.

3. A turbine impeller, A housing that houses the turbine impeller, A plurality of nozzle vanes arranged in a nozzle flow path formed inside the housing, A link mechanism that changes the blade angle of each of the plurality of nozzle vanes by rotating each of the plurality of nozzle vanes, Inside the housing, there is a link chamber that houses the link mechanism, and a link chamber is formed that is partitioned from the nozzle flow path by a hub side member having a hub side surface that defines the nozzle flow path. Each of the link mechanism and the plurality of nozzle vanes is connected via a nozzle shaft that penetrates the hub side member. The hub side member is formed with at least one communication hole that communicates the nozzle flow path and the link chamber. The opening on the nozzle flow path side of the at least one communication hole is formed inside the radial direction of the turbine impeller rather than the leading edge of each of the plurality of nozzle vanes when each of the plurality of nozzle vanes is in a fully open state. The opening on the nozzle flow path side of the at least one communication hole is formed so as not to overlap each of the plurality of nozzle vanes in any opening state from fully open to fully closed of each of the plurality of nozzle vanes. Variable displacement turbine.

4. The opening on the nozzle flow path side of the at least one communication hole and the opening on the link chamber side of the at least one communication hole are formed so that their positions in the radial direction are different. The variable displacement turbine according to any one of claims 1 to 3.

5. The opening on the nozzle flow path side of the at least one communication hole is formed inside the radial direction rather than the opening on the link chamber side of the at least one communication hole. The variable displacement turbine according to claim 4.

6. The hub side member is formed by a nozzle mount of an annular member supported by the housing. The variable displacement turbine according to any one of claims 1 to 5.

7. The variable displacement turbine according to any one of claims 1 to 6, A compressor driven by the variable displacement turbine, A turbocharger equipped with

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