Turbine and supercharger

Abstract

A turbine T comprises: a turbine wheel; a plurality of nozzle vanes 113 that are disposed farther outward in a radial direction than the turbine wheel and separated from each other in the circumferential direction of the turbine wheel, the nozzle vanes 113 being provided so as to be capable of rotating about a rotation shaft following the axial direction of the turbine wheel; blade shafts 113a that protrude in the axial direction from the nozzle vanes 113 and are provided so as to be capable of rotating integrally with the nozzle vanes 113; an annular member (shroud ring 101) that extends in the circumferential direction and faces the plurality of nozzle vanes 113 in the axial direction; a plurality of blade shaft holes 101c that open on a first surface 101d of the annular member facing the plurality of nozzle vanes 113, the blade shaft holes 101c being disposed separated from each other in the circumferential direction, having the blade shafts 113a inserted thereinto, and each having a bottom surface 101c1; and an annular protrusion 101f that is provided on the inner-peripheral side of a second surface 101e of the annular member on the side opposite from the first surface 101d, the annular protrusion 101f extending in the circumferential direction and protruding in the axial direction.

Description

Turbines and turbochargers

[0001] This application claims the benefit of priority from Japanese Patent Application No. 2023-148583, filed on September 13, 2023, the contents of which are incorporated herein by reference.

[0002] Turbines used in turbochargers and the like are sometimes provided with nozzle vanes for adjusting the flow velocity of exhaust gas. For example, as disclosed in Patent Document 1, multiple nozzle vanes are arranged radially outward of the turbine wheel and spaced apart in the circumferential direction of the turbine wheel. As each nozzle vane rotates, the cross-sectional area of ​​the flow passage formed between adjacent nozzle vanes changes, thereby changing the flow velocity of exhaust gas flowing between adjacent nozzle vanes.

[0003] Japanese Patent Application Laid-Open No. 2004-116313

[0004] The nozzle vanes rotate integrally with blade shafts that protrude from the nozzle vanes in the axial direction of the turbine wheel. The blade shafts are supported by a circular member that faces the nozzle vanes in the axial direction of the turbine wheel. When the blade shafts are inserted into through-holes provided in the circular member and supported, a leakage flow occurs, in which exhaust gas leaks through the through-holes. The leakage flow of exhaust gas can be a factor that reduces turbine efficiency.

[0005] An object of the present disclosure is to provide a turbine and a turbocharger that are capable of suppressing the leakage flow of exhaust gas.

[0006] In order to solve the above problems, the turbine of the present disclosure includes a turbine wheel, a plurality of nozzle vanes arranged radially outward of the turbine wheel and spaced apart in the circumferential direction of the turbine wheel and rotatable about a rotation axis along the axial direction of the turbine wheel, a blade shaft protruding axially from the nozzle vane and arranged rotatable integrally with the nozzle vane, a circular member extending circumferentially and facing the plurality of nozzle vanes in the axial direction, a plurality of blade shaft holes having bottom surfaces, opening on a first surface of the circular member facing the plurality of nozzle vanes, arranged spaced apart in the circumferential direction, and through which the blade shafts are inserted, and a circular protrusion arranged on the inner peripheral side of a second surface of the circular member opposite the first surface, extending circumferentially and protruding in the axial direction.

[0007] The entire area of ​​the bottom surface of each of the plurality of blade shaft holes may face the annular protrusion in the axial direction.

[0008] The thickness of a portion of the annular member radially outward from the annular protruding portion may be equal to or less than the depth of the blade shaft hole.

[0009] In order to solve the above problem, a turbocharger according to the present disclosure includes the above turbine.

[0010] According to the present disclosure, it is possible to suppress the leakage flow of exhaust gas.

[0011] Fig. 1 is a schematic cross-sectional view of a turbocharger according to this embodiment. Fig. 2 is a diagram in which a first region of Fig. 1 is extracted. Fig. 3 is a diagram in which a drive ring according to this embodiment is viewed from the bearing housing side. Fig. 4 is a diagram in which a second region of Fig. 1 is extracted. Fig. 5 is a diagram for explaining thermal deformation of a shroud ring and a nozzle ring.

[0012] An embodiment of the present disclosure will be described below with reference to the accompanying drawings. The dimensions, materials, and other specific values ​​shown in the embodiment are merely examples for ease of understanding and do not limit the present disclosure unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present disclosure are not shown.

[0013] Fig. 1 is a schematic cross-sectional view of a turbocharger TC according to this embodiment. In the following description, the direction of arrow L shown in Fig. 1 will be referred to as the left side of the turbocharger TC. The direction of arrow R shown in Fig. 1 will be referred to as the right side of the turbocharger TC. As shown in Fig. 1, the turbocharger TC includes a turbocharger main body 1. The turbocharger main body 1 includes a bearing housing 3, a turbine housing 5, and a compressor housing 7.

[0014] A turbine housing 5 is connected to the left side of the bearing housing 3 by a fastening bolt 9. A compressor housing 7 is connected to the right side of the bearing housing 3 by a fastening bolt 11. The turbocharger TC includes a turbine T and a centrifugal compressor C. The turbine T includes a bearing housing 3 and a turbine housing 5. The centrifugal compressor C includes the bearing housing 3 and a compressor housing 7.

[0015] A bearing hole 3a is formed in the bearing housing 3. The bearing hole 3a penetrates the bearing housing 3 in the left-right direction of the turbocharger TC. A bearing 13 is disposed in the bearing hole 3a. In FIG. 1 , a semi-floating bearing is shown as an example of the bearing 13. However, the bearing 13 may be another type of bearing, such as a full-floating bearing or a rolling bearing. The bearing 13 rotatably supports a shaft 15. A turbine wheel 17 is provided at the left end of the shaft 15. The turbine wheel 17 is rotatably housed in the turbine housing 5. A compressor wheel 19 is provided at the right end of the shaft 15. The compressor wheel 19 is rotatably housed in the compressor housing 7. The turbine wheel 17 and the compressor wheel 19 rotate integrally with the shaft 15.

[0016] Hereinafter, the axial direction, radial direction, and circumferential direction of the turbocharger TC will also be simply referred to as the axial direction, radial direction, and circumferential direction, respectively. The axial direction of the turbocharger TC coincides with the axial direction of the shaft 15, the axial direction of the turbine wheel 17, and the axial direction of the compressor wheel 19. The radial direction of the turbocharger TC coincides with the radial direction of the shaft 15, the radial direction of the turbine wheel 17, and the radial direction of the compressor wheel 19. The circumferential direction of the turbocharger TC coincides with the circumferential direction of the shaft 15, the circumferential direction of the turbine wheel 17, and the circumferential direction of the compressor wheel 19.

[0017] An intake port 21 is formed in the compressor housing 7. The intake port 21 opens to the right side of the turbocharger TC. The intake port 21 is connected to an air cleaner (not shown). A diffuser passage 23 is formed between the bearing housing 3 and the compressor housing 7. The diffuser passage 23 pressurizes the air. The diffuser passage 23 extends in the circumferential direction and is formed in an annular shape. The diffuser passage 23 communicates with the intake port 21 on the radially inner side via a space in which the compressor impeller 19 is disposed.

[0018] A compressor scroll passage 25 is formed in the compressor housing 7. The compressor scroll passage 25 extends in the circumferential direction and is formed in an annular shape. The compressor scroll passage 25 is located, for example, radially outward of the compressor impeller 19. The compressor scroll passage 25 communicates with an intake port of the engine (not shown) and the diffuser passage 23.

[0019] When the compressor impeller 19 rotates, air is drawn into the compressor housing 7 through the intake port 21. The drawn air is pressurized and accelerated as it flows between the blades of the compressor impeller 19. The compressed and accelerated air is then pressurized in the diffuser passage 23 and the compressor scroll passage 25. The pressurized air flows out from a discharge port (not shown) and is led to the intake port of the engine.

[0020] An exhaust port 27 is formed in the turbine housing 5. The exhaust port 27 opens to the left side of the turbocharger TC. The exhaust port 27 is connected to an exhaust gas purification device (not shown). A gap 29 is formed between the bearing housing 3 and the turbine housing 5. A flow passage 31 through which exhaust gas flows is formed in the gap 29. The flow passage 31 extends in the circumferential direction and is formed in an annular shape.

[0021] A turbine scroll passage 33 is formed in the turbine housing 5. The turbine scroll passage 33 is located, for example, radially outward of the turbine wheel 17. The flow passage 31 is located between the turbine wheel 17 and the turbine scroll passage 33. The flow passage 31 communicates the turbine scroll passage 33 with the exhaust port 27 via the space in which the turbine wheel 17 is disposed.

[0022] The turbine scroll passage 33 communicates with a gas inlet (not shown). Exhaust gas discharged from an exhaust manifold (not shown) of the engine is introduced to the gas inlet. The exhaust gas introduced from the gas inlet to the turbine scroll passage 33 is introduced to the exhaust port 27 via the flow passage 31 and between the blades of the turbine wheel 17. The exhaust gas introduced to the exhaust port 27 rotates the turbine wheel 17 during its flow process.

[0023] The rotational force of the turbine wheel 17 is transmitted to the compressor impeller 19 via the shaft 15. As described above, the air is pressurized by the rotational force of the compressor impeller 19 and is led to the intake port of the engine.

[0024] When the flow rate of exhaust gas introduced into the turbine housing 5 decreases, the rotation amount of the turbine wheel 17 decreases. When the rotation amount of the turbine wheel 17 decreases, the rotation amount of the compressor wheel 19 also decreases. When the rotation amount of the compressor wheel 19 decreases, it may not be possible to sufficiently increase the pressure of the air supplied to the intake port of the engine.

[0025] A variable capacity mechanism 100 is provided in the gap 29 in the turbine housing 5. The variable capacity mechanism 100 changes the flow path cross-sectional area of ​​the flow path 31 in accordance with the flow rate of the exhaust gas. For example, when the engine speed is low and the flow rate of the exhaust gas is small, the variable capacity mechanism 100 reduces the flow path cross-sectional area of ​​the flow path 31.

[0026] When the flow path cross-sectional area of ​​the flow path 31 is reduced, the flow velocity of the exhaust gas passing through the flow path 31 becomes faster compared to when the flow path cross-sectional area of ​​the flow path 31 is large. When the flow velocity of the exhaust gas increases, the amount of rotation of the turbine wheel 17 increases. When the amount of rotation of the turbine wheel 17 increases, the amount of rotation of the compressor wheel 19 also increases. When the amount of rotation of the compressor wheel 19 increases, the pressure of the air supplied to the intake port of the engine can be sufficiently increased. In this way, the variable capacity mechanism 100 can increase the amount of rotation of the turbine wheel 17 and the compressor wheel 19 when the flow rate of the exhaust gas is small. The variable capacity mechanism 100 will be described in detail below.

[0027] The variable displacement mechanism 100 includes a shroud ring 101, a nozzle ring 103, a retaining member 105, a drive ring 107, a transmission link 109, a link plate 111, a plurality of nozzle vanes 113, a drive mechanism 115, and an actuator 117. The shroud ring 101 corresponds to an example of an annular member that faces the plurality of nozzle vanes 113 in the axial direction.

[0028] The shroud ring 101 is disposed in the gap 29 on the side farther from the bearing housing 3. The nozzle ring 103 is disposed in the gap 29 on the side closer to the bearing housing 3. The shroud ring 101 is disposed opposite the nozzle ring 103 in the axial direction. The shroud ring 101 is disposed spaced apart from the nozzle ring 103 in the axial direction. A flow passage 31 is formed between the shroud ring 101 and the nozzle ring 103.

[0029] The shroud ring 101 has an annular shape extending in the circumferential direction. The shroud ring 101 is disposed coaxially with the turbine wheel 17. The shroud ring 101 has a thin ring-shaped main body portion 101a. The nozzle ring 103 has an annular shape extending in the circumferential direction. The nozzle ring 103 is disposed coaxially with the turbine wheel 17. The nozzle ring 103 has a thin ring-shaped main body portion 103a.

[0030] The outer diameter of the main body 103a of the nozzle ring 103 is approximately equal to the outer diameter of the main body 101a of the shroud ring 101. However, the outer diameter of the main body 103a of the nozzle ring 103 may be larger or smaller than the outer diameter of the main body 101a of the shroud ring 101. The inner diameter of the main body 103a of the nozzle ring 103 is larger than the inner diameter of the main body 101a of the shroud ring 101. However, the inner diameter of the main body 103a of the nozzle ring 103 may be equal to the inner diameter of the main body 101a of the shroud ring 101 or may be smaller than the inner diameter of the main body 101a of the shroud ring 101.

[0031] Fig. 2 is a diagram illustrating the first region R1 of Fig. 1. As shown in Fig. 2, a plurality of pin shaft holes 101b are formed in the main body portion 101a of the shroud ring 101. Each pin shaft hole 101b passes through the main body portion 101a in the axial direction. The plurality of pin shaft holes 101b are arranged spaced apart from one another in the circumferential direction. For example, the plurality of pin shaft holes 101b are arranged at equal intervals in the circumferential direction. However, the plurality of pin shaft holes 101b may also be arranged at unequal intervals in the circumferential direction.

[0032] A plurality of pin shaft holes 103b are formed in the main body portion 103a of the nozzle ring 103. Each pin shaft hole 103b passes through the main body portion 103a in the axial direction. The plurality of pin shaft holes 103b are arranged spaced apart from one another in the circumferential direction. For example, the plurality of pin shaft holes 103b are arranged at equal intervals in the circumferential direction. However, the plurality of pin shaft holes 103b may also be arranged at unequal intervals in the circumferential direction.

[0033] The number of pin shaft holes 101b matches the number of pin shaft holes 103b. Each pin shaft hole 101b faces each pin shaft hole 103b in the axial direction. That is, each pin shaft hole 101b is arranged coaxially with each pin shaft hole 103b. Connecting pins 119 are inserted through the pin shaft holes 101b and 103b. The shroud ring 101 is connected to the nozzle ring 103 by the connecting pins 119. The distance between the shroud ring 101 and the nozzle ring 103 is basically kept constant by the connecting pins 119. However, as will be described later, the shroud ring 101 and the nozzle ring 103 may deform due to temperature changes caused by heat.

[0034] The holding member 105 is disposed between the nozzle ring 103 and the bearing housing 3. The holding member 105 is connected to the nozzle ring 103 by a connecting pin 119. In the example shown in Fig. 2, the holding member 105 is made up of two ring-shaped thin plates joined together. However, the holding member 105 may be made up of a single ring-shaped thin plate, or may be made up of three or more ring-shaped thin plates joined together.

[0035] The outer peripheral edge of the retaining member 105 is clamped between the turbine housing 5 and the bearing housing 3. The retaining member 105 is held non-rotatably between the turbine housing 5 and the bearing housing 3. The retaining member 105 holds the shroud ring 101 and the nozzle ring 103 non-rotatably. A drive ring 107 is disposed between the nozzle ring 103 and the bearing housing 3. The retaining member 105 holds the drive ring 107 so that it can rotate relative to the nozzle ring 103.

[0036] The drive ring 107 has an annular shape extending in the circumferential direction. The drive ring 107 is disposed coaxially with the turbine wheel 17. The drive ring 107 is provided on the opposite side of the nozzle ring 103 to the plurality of nozzle vanes 113. As will be described later, the drive ring 107 is provided to be rotatable in conjunction with the plurality of nozzle vanes 113.

[0037] Figure 3 is a view of the drive ring 107 as seen from the bearing housing 3 side. As shown in Figure 3, the drive ring 107 has a thin ring-shaped main body portion 107a. The inner circumferential surface of the main body portion 107a engages with the engaging claws 105a of the holding member 105, thereby holding the main body portion 107a so that it can rotate freely relative to the holding member 105. The main body portion 107a is formed with a plurality of transmission link engaging portions 107b and link plate engaging portions 107c.

[0038] The transmission link engaging portion 107b is a portion of the main body portion 107a that is cut out radially outward from the inner circumferential surface of the main body portion 107a. The multiple transmission link engaging portions 107b are arranged at equal intervals in the circumferential direction of the main body portion 107a. The transmission link engaging portion 107b engages with an engaging end 109a of the transmission link 109.

[0039] The link plate engaging portion 107c is a portion of the main body portion 107a that is cut out radially outward from the inner circumferential surface of the main body portion 107a. There is one link plate engaging portion 107c. The link plate engaging portion 107c is formed between two circumferentially adjacent transmission link engaging portions 107b. The link plate engaging portion 107c engages with the engaging end 111a of the link plate 111.

[0040] An insertion hole 109b is formed in the transmission link 109. The insertion hole 109b is formed on the side of the transmission link 109 opposite the engagement end 109a. As shown in FIG. 3 and FIG. 4 described below, a blade shaft 113a of a nozzle vane 113 is inserted into the insertion hole 109b. The transmission link 109 is crimped with the blade shaft 113a of the nozzle vane 113 inserted into the insertion hole 109b. The transmission link 109 and the nozzle vane 113 rotate integrally with the blade shaft 113a.

[0041] An insertion hole 111b is formed in the link plate 111. The insertion hole 111b is formed on the side of the link plate 111 opposite the engagement end 111a. As shown in FIGS. 2 and 3 , a rotation shaft RA of the drive mechanism 115 is inserted into the insertion hole 111b. The link plate 111 is crimped with the rotation shaft RA of the drive mechanism 115 inserted into the insertion hole 111b. The link plate 111 rotates integrally with the rotation shaft RA of the drive mechanism 115. However, the rotation shaft RA of the drive mechanism 115 may be welded to the insertion hole 111b of the link plate 111.

[0042] FIG. 4 is a diagram illustrating the second region R2 of FIG. 1 . As shown in FIG. 4 , a plurality of blade shaft holes 101c are formed in the main body portion 101a of the shroud ring 101. Each blade shaft hole 101c is disposed radially inward of the pin shaft hole 101b in the main body portion 101a. Each blade shaft hole 101c opens to a first surface 101d of the shroud ring 101 that faces the plurality of nozzle vanes 113, and has a bottom surface 101c1. The first surface 101d is the right surface of the main body portion 101a. Each blade shaft hole 101c has a cylindrical shape and extends in the axial direction. The plurality of blade shaft holes 101c are disposed circumferentially spaced apart from one another. Specifically, the plurality of blade shaft holes 101c are disposed at equal intervals in the circumferential direction.

[0043] A plurality of through holes 103c are formed in the main body portion 103a of the nozzle ring 103. Each through hole 103c is disposed radially inward of the pin shaft hole 103b in the main body portion 103a. Each through hole 103c passes through the main body portion 103a in the axial direction. The plurality of through holes 103c are disposed circumferentially spaced apart from one another. Specifically, the plurality of through holes 103c are disposed at equal intervals in the circumferential direction.

[0044] The number of through holes 103c matches the number of blade shaft holes 101c. Each through hole 103c faces a corresponding blade shaft hole 101c in the axial direction. That is, each through hole 103c is arranged coaxially with its corresponding blade shaft hole 101c. Blade shafts 113a protrude axially from both axially opposite surfaces of each nozzle vane 113. The left blade shaft 113a and the right blade shaft 113a provided for each nozzle vane 113 are arranged coaxially with each other. Each blade shaft 113a has a cylindrical shape. Each blade shaft 113a is inserted through the blade shaft hole 101c and the through hole 103c, respectively. Each blade shaft 113a is rotatably supported by the blade shaft hole 101c and the through hole 103c, respectively.

[0045] The multiple nozzle vanes 113 are arranged in the flow passage 31 at intervals from one another in the circumferential direction. That is, the multiple nozzle vanes 113 are arranged radially outward of the turbine wheel 17 at intervals from one another in the circumferential direction. Specifically, the multiple nozzle vanes 113 are arranged at equal intervals in the circumferential direction. Each nozzle vane 113 is provided integrally with the blade shaft 113a so as to be rotatable about the central axis of the blade shaft 113a. That is, each nozzle vane 113 is provided so as to be rotatable about a rotation axis that extends along the axial direction of the turbine wheel 17.

[0046] A seal ring SE is fitted between the inner periphery of the shroud ring 101 and the turbine housing 5. The seal ring SE has an annular shape extending in the circumferential direction. The seal ring SE is arranged coaxially with the turbine impeller 17. The seal ring SE closes the gap between the inner periphery of the shroud ring 101 and the turbine housing 5. The seal ring SE prevents exhaust gas from leaking from the flow passage 31 through the gap between the inner periphery of the shroud ring 101 and the turbine housing 5. In the example of FIG. 4 , there is one seal ring SE. However, multiple seal rings SE may be stacked.

[0047] 1, the actuator 117 is disposed outside the turbine housing 5, the bearing housing 3, and the compressor housing 7. The actuator 117 is, for example, a solenoid. The actuator 117 is connected to a drive mechanism 115. The drive mechanism 115 converts the linear motion of the actuator 117 into rotational motion about a rotation axis RA.

[0048] When the actuator 117 is driven, the rotation axis RA of the drive mechanism 115 rotates. When the rotation axis RA rotates, the link plate 111 rotates integrally with the rotation axis RA around the central axis of the rotation axis RA. When the link plate 111 rotates, the link plate engaging portion 107c is pressed in the circumferential direction of the link plate 111, causing the drive ring 107 to rotate around the central axis of the drive ring 107. When the drive ring 107 rotates, the transfer link 109 is pressed in the circumferential direction by the transfer link engaging portion 107b, causing the transfer link 109 to rotate around the central axis of the insertion hole 109b. When the transfer link 109 rotates, the blade shaft 113a rotates integrally with the transfer link 109. When the blade shaft 113a rotates, the nozzle vane 113 rotates integrally with the blade shaft 113a.

[0049] When each nozzle vane 113 rotates, the distance between two circumferentially adjacent nozzle vanes 113 changes. When the distance between two circumferentially adjacent nozzle vanes 113 changes, the flow path cross-sectional area of ​​the flow passage 31 changes. When the flow path cross-sectional area of ​​the flow passage 31 changes, the flow velocity of the exhaust gas flowing through the flow passage 31 changes.

[0050] The variable displacement mechanism 100 rotates the multiple nozzle vanes 113 in accordance with the flow rate of exhaust gas, thereby changing the distance between two circumferentially adjacent nozzle vanes 113. This changes the opening degree of the nozzle vanes 113. The closer the extension direction of the nozzle vanes 113 is to the circumferential direction of the turbine wheel 17, the narrower the distance between two circumferentially adjacent nozzle vanes 113, and the smaller the opening degree of the nozzle vanes 113. On the other hand, the larger the angle formed between the extension direction of the nozzle vanes 113 and the circumferential direction of the turbine wheel 17, the wider the distance between two circumferentially adjacent nozzle vanes 113, and the larger the opening degree of the nozzle vanes 113.

[0051] The opening degree of the nozzle vanes 113 is adjustable within a range having upper and lower limits. When the nozzle vanes 113 are fully closed, the extension direction of the nozzle vanes 113 is closest to the circumferential direction of the turbine wheel 17, and the opening degree of the nozzle vanes 113 is minimum. On the other hand, when the nozzle vanes 113 are fully open, the angle formed between the extension direction of the nozzle vanes 113 and the circumferential direction of the turbine wheel 17 is maximum, and the opening degree of the nozzle vanes 113 is maximum. The smaller the opening degree of the nozzle vanes 113, the smaller the flow path cross-sectional area of ​​the flow passage 31.

[0052] For example, when the flow rate of exhaust gas is small, the variable capacity mechanism 100 reduces the opening of the nozzle vanes 113 to increase the flow velocity of the exhaust gas. This allows the variable capacity mechanism 100 to increase the rotation amount of the turbine wheel 17 even when the flow rate of exhaust gas is small. As a result, the variable capacity mechanism 100 can increase the rotation amount of the compressor impeller 19 even when the flow rate of exhaust gas is small.

[0053] As shown in FIG. 4 , in the variable displacement mechanism 100, the multiple nozzle vanes 113 are sandwiched between the shroud ring 101 and the nozzle ring 103 on both sides in the axial direction. As described above, the first surface 101d on the right side of the shroud ring 101 faces the multiple nozzle vanes 113. The first surface 101d has an annular shape. A blade shaft 113a protruding to the left from each nozzle vane 113 is inserted and supported in a blade shaft hole 101c opening in the first surface 101d of the shroud ring 101. A left surface 103d of the nozzle ring 103 faces the multiple nozzle vanes 113. The surface 103d has an annular shape. The blade shaft 113a protruding to the right from each nozzle vane 113 is inserted and supported in a through-hole 103c opening in the surface 103d of the nozzle ring 103.

[0054] As described above, in this embodiment, in the shroud ring 101, which is a circular member, the blade shaft hole 101c, through which the blade shaft 113a is inserted, has a bottom surface 101c1. If a through hole axially penetrating the main body 101a is provided in the shroud ring 101 and the blade shaft 113a is inserted and supported in the through hole, a leakage flow occurs, in which exhaust gas leaks through the through hole. Such a leakage flow of exhaust gas can be a factor in reducing the efficiency of the turbine T. On the other hand, in this embodiment, the blade shaft hole 101c, through which the blade shaft 113a is inserted, has the bottom surface 101c1, so that such a leakage flow of exhaust gas can be suppressed. As a result, a reduction in the efficiency of the turbine T can be suppressed.

[0055] To suppress the leakage of exhaust gas, for example, when the blade shaft 113a is inserted and supported through a through-hole that penetrates the main body 101a in the axial direction, it is conceivable to add a member that blocks the opening on the left side of the through-hole. For example, it is conceivable to block the opening on the left side of the through-hole with a thin ring-shaped member that is arranged coaxially with the shroud ring 101. In this case, costs increase due to an increase in the number of parts of the variable displacement mechanism 100 and an increase in the number of steps in the assembly process. Furthermore, it is necessary to manage the gap between the member that blocks the opening on the left side of the through-hole and the shroud ring 101. However, the present embodiment can suppress such increases in costs and labor.

[0056] Furthermore, in this embodiment, measures are taken to suppress thermal deformation of the shroud ring 101 and the nozzle ring 103. Thermal deformation refers to deformation caused by temperature changes due to heat. As described above, the gap between the shroud ring 101 and the nozzle ring 103 is basically kept constant by the connecting pin 119. However, if thermal deformation occurs in the shroud ring 101 and the nozzle ring 103, the gap between the shroud ring 101 and the nozzle ring 103 may become locally narrow, which may hinder smooth operation of the nozzle vanes 113. Below, measures taken to suppress thermal deformation of the shroud ring 101 and the nozzle ring 103 are described.

[0057] Fig. 5 is a diagram for explaining thermal deformation of the shroud ring 101 and the nozzle ring 103. For ease of understanding, Fig. 5 shows the shapes of the shroud ring 101 and the nozzle ring 103 in a simplified manner. In Fig. 5, the shroud ring 101 and the nozzle ring 103 before thermal deformation are shown by solid lines, and the shroud ring 101 and the nozzle ring 103 after thermal deformation are shown by two-dot chain lines.

[0058] When the turbocharger TC is in operation, high-temperature exhaust gas flows between the shroud ring 101 and the nozzle ring 103. As a result, the surfaces of the shroud ring 101 and the nozzle ring 103 that come into contact with the exhaust gas are heated by the heat of the exhaust gas. Therefore, the temperatures of the surfaces of the shroud ring 101 and the nozzle ring 103 that come into contact with the exhaust gas are higher than the temperatures of other portions. For example, the temperature of a first surface 101 d on the right side of the shroud ring 101 is higher than the temperature of a second surface 101 e on the left side of the shroud ring 101. For example, the temperature of a left surface 103 d of the nozzle ring 103 is higher than the temperature of a right surface 103 e of the nozzle ring 103.

[0059] As described above, when the turbocharger TC is in operation, the surfaces of the shroud ring 101 and the nozzle ring 103 that come into contact with the exhaust gas are heated, causing thermal deformation as indicated by the two-dot chain line in Fig. 5. Specifically, as indicated by the two-dot chain line in Fig. 5, the shroud ring 101 and the nozzle ring 103 are warped toward each other on their radially inner sides. Such thermal deformation can be a factor that hinders smooth operation of the nozzle vanes 113.

[0060] 4, in this embodiment, in order to suppress the above-described thermal deformation, an annular protrusion 101f is provided on the shroud ring 101. The annular protrusion 101f is provided on the inner peripheral side of a second surface 101e of the shroud ring 101, which is opposite the first surface 101d. The second surface 101e has an annular shape, similar to the first surface 101d.

[0061] When viewed in the axial direction, the first surface 101d and the second surface 101e overlap each other. That is, the inner diameter of the second surface 101e is the same as the inner diameter of the first surface 101d. However, the inner diameter of the second surface 101e does not strictly match the inner diameter of the first surface 101d and may differ to some extent. The outer diameter of the second surface 101e is the same as the outer diameter of the first surface 101d. However, the outer diameter of the second surface 101e is not strictly matched to the outer diameter of the first surface 101d and may differ to some extent.

[0062] The annular protrusion 101f has an annular shape extending in the circumferential direction. The annular protrusion 101f protrudes in the axial direction. Specifically, the annular protrusion 101f protrudes to the left from the second surface 101e. The axial thickness of the annular protrusion 101f is greater than the axial thickness of other portions of the shroud ring 101. The annular protrusion 101f is disposed coaxially with the turbine wheel 17.

[0063] In the example of Fig. 4, the annular protrusion 101f is provided in a range from the inner peripheral edge to the radial center of the second surface 101e. However, the range in which the annular protrusion 101f is provided on the second surface 101e is not limited to the example of Fig. 4. Providing the annular protrusion 101f on the inner peripheral side of the second surface 101e means, for example, that the radial center of the annular protrusion 101f is located radially inward of the radial center of the second surface 101e.

[0064] For example, in the example of FIG. 4 , the inner peripheral edge of the annular protrusion 101f is continuous with the inner peripheral edge of the second surface 101e. However, the inner peripheral edge of the annular protrusion 101f does not have to be continuous with the inner peripheral edge of the second surface 101e. In this case, for example, a seal member may be provided between the turbine housing 5 and a portion of the second surface 101e that is radially inward of the annular protrusion 101f. Also, a protrusion that protrudes radially inward from the inner peripheral surface of the shroud ring 101 and extends circumferentially may be provided. In this case, a seal member may be provided between the protrusion and the turbine housing 5.

[0065] 4, the outer peripheral edge of the annular protrusion 101f is located near the radial center of the second surface 101e. However, the outer peripheral edge of the annular protrusion 101f may be located radially outward or radially inward from the radial center of the second surface 101e.

[0066] 2, the pin shaft hole 101b is provided radially outward of the annular protrusion 101f. In other words, the outer peripheral edge of the annular protrusion 101f is located radially inward of the pin shaft hole 101b. However, the outer peripheral edge of the annular protrusion 101f may also be located radially outward of the pin shaft hole 101b.

[0067] As described above, in the turbine T, the annular protrusion 101f extending circumferentially and protruding axially is provided on the inner peripheral side of the second surface 101e of the shroud ring 101, which is an annular member and is opposite the first surface 101d. This increases the rigidity of the inner peripheral side of the shroud ring 101. Therefore, thermal deformation, in which the shroud ring 101 and the nozzle ring 103 warp toward each other on the radially inner side, as indicated by the two-dot chain line in FIG. 5, can be suppressed. This prevents the smooth operation of the nozzle vanes 113 from being hindered by thermal deformation of the shroud ring 101 and the nozzle ring 103.

[0068] From the viewpoint of effectively increasing the rigidity of the inner peripheral side of the shroud ring 101, it is preferable that the radial position of the annular protrusion 101f be as close to the inner peripheral edge of the second surface 101e as possible. For example, it is preferable that the inner peripheral edge of the annular protrusion 101f be continuous with the inner peripheral edge of the second surface 101e. For example, it is preferable that the outer peripheral edge of the annular protrusion 101f be located radially inward from the radial center of the second surface 101e. For example, it is preferable that the outer peripheral edge of the annular protrusion 101f be located radially inward from the pin shaft hole 101b.

[0069] When the radial width of the annular protrusion 101 f is constant, the closer the radial position of the annular protrusion 101 f is to the outer peripheral edge of the second surface 101 e, the larger the volume of the annular protrusion 101 f. Therefore, from the viewpoint of preventing the volume of the annular protrusion 101 f from increasing and the size of the shroud ring 101 from increasing, it is preferable that the radial position of the annular protrusion 101 f be as close to the inner peripheral edge of the second surface 101 e as possible.

[0070] In particular, as shown in FIG. 4 , in the turbine T, the entire bottom surface 101c1 of each of the plurality of blade shaft holes 101c faces the annular protrusion 101f in the axial direction. That is, when viewed in the axial direction, the entire bottom surface 101c1 of each blade shaft hole 101c overlaps with the annular protrusion 101f. This allows the annular protrusion 101f to ensure the thickness of the shroud ring 101 near the bottom surface 101c1 of each blade shaft hole 101c. Therefore, compared to a case in which a portion protruding to the left from the second surface 101e is provided separately from the annular protrusion 101f to ensure the thickness near the bottom surface 101c1 of each blade shaft hole 101c, it is possible to prevent the shroud ring 101 from becoming larger.

[0071] However, at least a portion of the bottom surface 101c1 of each blade shaft hole 101c does not have to face the annular protrusion 101f in the axial direction. For example, while a portion of the bottom surface 101c1 of each blade shaft hole 101c faces the annular protrusion 101f in the axial direction, another portion of the bottom surface 101c1 of each blade shaft hole 101c does not have to face the annular protrusion 101f in the axial direction. For example, the entire bottom surface 101c1 of each blade shaft hole 101c does not have to face the annular protrusion 101f in the axial direction.

[0072] In particular, as shown in FIG. 4 , in the turbine T, the thickness D1 of the shroud ring 101, which is an annular member, at a portion radially outward from the annular protrusion 101f is equal to or less than the depth D2 of the blade shaft hole 101c. For example, in the example of FIG. 4 , the thickness D1 of the shroud ring 101 at a portion radially outward from the annular protrusion 101f is equal to the depth D2 of the blade shaft hole 101c. Therefore, the increase in the volume of the shroud ring 101 resulting from forming the bottom surface 101c1 of the blade shaft hole 101c with the annular protrusion 101f can be suppressed to approximately the volume of the annular protrusion 101f. For example, compared to an example in which a through hole through which the blade shaft 113a is inserted is formed in an annular member having a constant thickness and the opening on the left side of the through hole is blocked by another member, the increase in the volume of the shroud ring 101 can be suppressed. In other words, it is possible to prevent the thickness D1 of the portion of the shroud ring 101 radially outward from the annular protruding portion 101f from becoming unnecessarily thick, thereby preventing the shroud ring 101 from becoming large.

[0073] However, the thickness D1 of the portion of the shroud ring 101 radially outward from the annular protruding portion 101f may be longer than the depth D2 of the blade shaft hole 101c.

[0074] Although the embodiments of the present disclosure have been described above with reference to the accompanying drawings, it goes without saying that the present disclosure is not limited to such embodiments. It is clear that a person skilled in the art can conceive of various modifications and alterations within the scope of the claims, and it is understood that such modifications and alterations also fall within the technical scope of the present disclosure.

[0075] In the above description, an example has been described in which the turbine T is mounted on the turbocharger TC. However, the device on which the turbine T is mounted may be a device other than the turbocharger TC.

[0076] 17: Turbine impeller 101: Shroud ring (annular member) 101c: Blade shaft hole 101c1: Bottom surface 101d: First surface 101e: Second surface 101f: Annular protrusion 113: Nozzle vane 113a: Blade shaft T: Turbine TC: Supercharger

Claims

1. A turbine comprising: a turbine wheel; a plurality of nozzle vanes arranged radially outwardly of the turbine wheel and spaced apart from one another in the circumferential direction of the turbine wheel, the nozzle vanes being rotatable about a rotation axis along the axial direction of the turbine wheel; a blade shaft protruding from the nozzle vanes in the axial direction and arranged rotatable integrally with the nozzle vanes; a ring member extending in the circumferential direction and facing the nozzle vanes in the axial direction; a plurality of blade shaft holes having bottom surfaces, the blade shafts being arranged spaced apart from one another in the circumferential direction and through which the blade shafts are inserted, the blade shaft holes opening on a first surface of the ring member facing the nozzle vanes, the blade shafts being inserted 2. The turbine according to claim 1, wherein the entire area of ​​the bottom surface of each of the plurality of blade shaft holes faces the annular protrusion in the axial direction.

3. The turbine according to claim 1, wherein the thickness of the portion of the annular member radially outward from the annular protruding portion is equal to or less than the depth of the blade shaft hole.

4. A turbocharger comprising a turbine according to any one of claims 1 to 3.

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