Turbocharger

Abstract

A turbocharger includes: a turbine wheel; a turbine housing; a bearing housing; a shroud having a facing surface which faces a tip of a blade of the turbine wheel and being configured to surround the turbine wheel, the shroud comprising a separate member from the turbine housing and being disposed inside the turbine housing via a gap with respect to the turbine housing; a mount supported to at least one of the turbine housing or the bearing housing, at a position closer to the bearing housing than a scroll flow path in an axial direction of the turbine wheel; and at least one connection part connecting the mount and the shroud.

Claims

1. A turbocharger, comprising: a turbine wheel configured to be rotated by exhaust gas of an engine; a turbine housing which accommodates the turbine wheel and forms at least a part of a scroll flow path through which exhaust gas to be supplied to the turbine wheel flows; a bearing housing which accommodates a bearing supporting a shaft of the turbine wheel rotatably, the bearing housing being coupled to the turbine housing; a shroud having a facing surface which faces a tip of a blade of the turbine wheel and being configured to surround the turbine wheel, the shroud comprising a separate member from the turbine housing and being disposed inside the turbine housing via a gap with respect to the turbine housing; a mount supported to at least one of the turbine housing or the bearing housing, at a position closer to the bearing housing than the scroll flow path in an axial direction of the turbine wheel; and at least one connection part connecting the mount and the shroud, wherein the turbine housing includes a first housing formed of sheet metal, the first housing accommodating the turbine wheel and forming at least a part of the scroll flow path, and wherein the shroud is disposed inside the first housing via the gap with respect to the first housing, and wherein the turbocharger further comprises: an outlet guide tube configured to guide exhaust gas having passed through the turbine wheel, the outlet guide tube being disposed on a downstream side in the axial direction of the turbine wheel with respect to the shroud; the facing surface comprises a first wall which extends in a radial direction from the axial direction of the turbine wheel and a second wall which extends in the axial direction of the turbine wheel, wherein the second wall is spaced apart from the outlet guide tube, and a piston ring which seals a gap between the first housing and the outlet guide tube, the piston ring being sliding the first housing on to the outlet guide tube in the axial direction of the turbine wheel.

2. The turbocharger according to claim 1, wherein each of the at least one connection part has a blade shape in a cross section perpendicular to an axis of the turbine wheel.

3. The turbocharger according to claim 1, further comprising a seal ring which seals the gap between the shroud and the turbine housing.

4. The turbocharger according to claim 1, wherein the mount is held between the turbine housing and the bearing housing.

5. The turbocharger according to claim 4, wherein the mount is an annular plate, and wherein an outer peripheral portion of the mount is held between the turbine housing and the bearing housing.

6. The turbocharger according to claim 5, further comprising a bolt fastening the turbine housing and the bearing housing, wherein the outer peripheral portion of the mount is held between the turbine housing and the bearing housing by an axial force of the bolt.

7. The turbocharger according to claim 4, wherein the mount includes a tube-shaped portion extending in the axial direction of the turbine wheel and a protruding portion protruding toward an outer peripheral side of the tube- shaped portion from the tube-shaped portion, and wherein the protruding portion of the mount is held between the turbine housing and the bearing housing.

8. The turbocharger according to claim 7, further comprising a nipping member which nips and couples a flange disposed on the turbine housing and a flange disposed on the bearing housing, wherein the protruding portion of the mount is nipped between the turbine housing and the bearing housing by a nipping force of the nipping member.

9. The turbocharger according to claim 1, wherein the mount is an annular member and includes an engagement portion engaged with an annular step portion formed on the bearing housing by spigot-and-socket fitting.

10. The turbocharger according to claim 9, wherein the turbine housing has a double-layer structure including a second housing formed of sheet metal, the second housing accommodating the first housing.

11. The turbocharger according to claim 10, wherein the outlet guide tube is configured integrally with the second housing by an outlet flange joined to the second housing.

12. The turbocharger according to claim 9, wherein the turbine housing has a single-layer structure, and a thickness of the shroud is greater than a thickness of the first housing.

13. The turbocharger according to claim 12, wherein the thickness of the shroud is not less than twice the thickness of the first housing.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic configuration diagram of a cross section of a turbocharger 100A according to an embodiment.

(2) FIG. 2 is a schematic configuration diagram of a cross section of a turbocharger 100B according to an embodiment.

(3) FIG. 3 is a schematic configuration diagram of a cross section of a turbocharger 100C according to an embodiment.

(4) FIG. 4 is a schematic configuration diagram of a cross section of a turbocharger 100D according to an embodiment.

(5) FIG. 5 is a diagram showing an example of a cross-sectional shape perpendicular to the axis O1 of the turbine wheel 2 in the connection part 12 shown in FIGS. 1 to 4.

(6) FIG. 6 is a diagram showing an example of a cross-sectional shape perpendicular to the axis O1 of the turbine wheel 2 in the connection part 12 shown in FIGS. 1 to 4.

(7) FIG. 7 is a schematic configuration diagram of a cross section of a turbocharger according to a reference example.

(8) FIG. 8 is a diagram showing a temperature distribution of the inner casing 030 during operation of the turbocharger shown in FIG. 7.

(9) FIG. 9 is a schematic diagram of a cross-sectional configuration perpendicular to the axis of the turbine housing 004 shown in FIG. 7.

DETAILED DESCRIPTION

(10) Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It is intended, however, that unless particularly specified, dimensions, materials, shapes, relative positions and the like of components described in the embodiments shall be interpreted as illustrative only and not intended to limit the scope of the present invention.

(11) For instance, an expression of relative or absolute arrangement such as in a direction, along a direction, parallel, orthogonal, centered, concentric and coaxial shall not be construed as indicating only the arrangement in a strict literal sense, but also includes a state where the arrangement is relatively displaced by a tolerance, or by an angle or a distance whereby it is possible to achieve the same function.

(12) For instance, an expression of an equal state such as same equal and uniform shall not be construed as indicating only the state in which the feature is strictly equal, but also includes a state in which there is a tolerance or a difference that can still achieve the same function.

(13) Further, for instance, an expression of a shape such as a rectangular shape or a cylindrical shape shall not be construed as only the geometrically strict shape, but also includes a shape with unevenness or chamfered corners within the range in which the same effect can be achieved.

(14) On the other hand, an expression such as comprise, include, have, contain and constitute are not intended to be exclusive of other components.

(15) FIG. 1 is a schematic configuration diagram of a cross section of a turbocharger 100A according to an embodiment. FIG. 2 is a schematic configuration diagram of a cross section of a turbocharger 100B according to an embodiment. FIG. 3 is a schematic configuration diagram of a cross section of a turbocharger 100C according to an embodiment. FIG. 4 is a schematic configuration diagram of a cross section of a turbocharger 100D according to an embodiment.

(16) In some embodiments, as shown in FIGS. 1 to 4 for example, the turbocharger 100 (100A to 100D) includes a turbine wheel 2, a turbine housing 4, a bearing housing 6, a shroud 8, a mount 10, and at least one connection part 12.

(17) In the turbocharger 100 (100A to 100D) shown in FIGS. 1 to 4, the turbine wheel 2 is configured to be rotated by exhaust gas of an engine (not shown). The turbine housing 4 houses the turbine wheel 2, and forms at least a part of a scroll flow path 14 through which exhaust gas to be supplied to the turbine wheel 2 flows. The bearing housing 6 accommodates a bearing 18 that supports a shaft 16 of the turbine wheel 2 rotatably, and is coupled to the turbine housing 4. The shroud 8 has a facing surface 8a facing an end 20a of a blade 20 of the turbine wheel 2, and is configured to surround the turbine wheel 2. Further, the shroud 8 is formed by a member separate from the turbine housing 4, and is disposed inside the turbine housing 4 via a gap 22 with respect to the turbine housing 4. The mount 10 is supported on at least one of the turbine housing 4 or the bearing housing 6, at a position closer to the bearing housing 6 than the scroll flow path 14 in the axial direction of the turbine wheel 2. Each of the at least one connection part 12 (a plurality of connection parts 12 in the embodiment shown in FIGS. 1 to 4) is configured to connect the mount 10 and the shroud 8.

(18) As described above with the turbocharger 100 (100A to 100D), even if a temperature variation is generated in the turbine housing 4 by the exhaust gas flowing through the scroll flow path 14 to cause bending deformation (thermal deformation) of the turbine housing 4, the shroud 8 is formed by a member separate from the turbine housing 4 and is disposed via the gap 22 with respect to the turbine housing 4, and thus the tip clearance (clearance between the facing surface 8a and the tip 20a) between the shroud 8 and the turbine wheel 2 is not basically affected by the above bending deformation of the turbine housing 4. Thus, even if the tip clearance is small between the shroud 8 and the turbine wheel 2, it is possible to avoid contact between the shroud 8 and the turbine wheel 2 due to the above bending deformation of the turbine housing 4. Thus, it is possible to achieve a high turbine efficiency while avoiding contact between the turbine wheel 2 and the shroud 8.

(19) In some embodiments, as shown in FIGS. 1 to 4, the turbine housing 4 includes the first housing 30 made of sheet metal, accommodating the turbine wheel 2 and forming at least a part of the scroll flow path 14, and the shroud 8 is disposed inside the first housing 30, via the gap 22 with respect to the first housing 30.

(20) In such configuration, as compared to a case in which the turbine housing 4 including the first housing 30 is entirely formed of cast, the first housing 30 is formed of sheet metal and thus considerable bending deformation (thermal deformation) is likely to occur in the first housing 30 due to exhaust gas flowing through the scroll flow path 14. Also in this case, the shroud 8 is disposed inside the first housing 30 formed of sheet metal via the gap 22 with respect to the first housing 30, and thus it is possible to achieve a high turbine efficiency while avoiding contact between the turbine wheel 2 and the shroud 8, as described above.

(21) In some embodiments, as shown in FIGS. 1 and 2 for instance, the turbine housing 4 is a double-layer structure housing further including the second housing 32 formed of sheet metal and accommodating the first housing 30.

(22) In the above configuration, the turbine housing is a double-layer structure housing, and thus it is possible to prevent fragments of the turbine wheel 2 from scattering outside the turbine housing 4 reliably as compared to a case of a single-layer structure, in case the turbine wheel 2 breaks in fragments and scatters for some reason.

(23) In some embodiments, as shown in FIGS. 1 and 2 for instance, the turbocharger 100 (100A, 100B) further includes an outlet guide tube 34 and a piston ring 36. The outlet guide tube 34 is configured to guide exhaust gas having passed through the turbine wheel 2, and is joined to the outlet flange 35 of the turbine housing 4. The outlet flange 35 is joined to the second housing 32 by welding, for instance, and the second housing 32 and the outlet guide tube 34 are formed integrally with the outlet flange 35. The piston ring 36 is configured to seal the gap 38 between the first housing 30 and the outlet guide tube 34 so that the first housing 30 is slidable with respect to the outlet guide tube 34 in the axial direction of the turbine wheel 2.

(24) In a case where the turbine housing 4 is a double-layer structure housing including the first housing 30 and the second housing 32 as shown in FIGS. 1 and 2, the first housing 30 forming at least a part of the scroll flow path 14 has a relatively high temperature and a great thermal expansion amount, compared to the second housing 32. Thus, unless some measure is provided, stress may concentrate on the connection part between the first housing 30 and the second housing 32 to cause breakage. In this regard, as described above, the turbocharger 100 (100A, 100B) shown in FIGS. 1 and 2 is provided with the piston ring 36 for sealing the gap 38 between the first housing 30 and the outlet guide tube 34, so that the first housing 30 is slidable in the axial direction with respect to the outlet guide tube 34 formed integrally with the second housing 32. Accordingly, it is possible to avoid breakage due to a difference in the thermal expansion amount of the first housing 30 and the second housing 32, while suppressing a leakage of exhaust gas from the gap 38 between the first housing 30 and the outlet guide tube 34.

(25) In some embodiments, as shown in FIGS. 3 and 4 for instance, the turbine housing 4 is a single-layer structure housing, and the thickness of the shroud 8 is greater than the thickness of the first housing 30.

(26) Even if the turbine housing 4 is a single-structure housing as described above, the thickness of the shroud 8 is greater than the thickness of the first housing 30, and thereby it is possible to receive fragments of the turbine wheel 2 effectively with less material in case of breakage of the turbine wheel 2, compared to a case in which the thickness of the first housing 30 is greater than the thickness of the shroud 8. The thickness of the shroud 8 is desirably not less than twice the thickness of the first housing 30.

(27) In some embodiments, as shown in FIGS. 1 to 4 for instance, the turbine housing 4 has an annular structural part 33 disposed on a portion of the turbine housing 4 adjacent to the bearing housing 6, and the mount 10 is held between the structural part 33 of the turbine housing 4 and the bearing housing 6. In the turbine housing 4 having a double-layer structure shown in FIGS. 1 and 2, the annular structural part 33 is a cast, for instance, and may be joined by welding or the like to the first housing 30 formed of sheet metal and the second housing 32 formed of sheet metal. Furthermore, in the turbine housing 4 having a single-layer structure shown in FIGS. 3 and 4, the annular structural part 33 is a cast, for instance, and may be joined by welding or the like to the first housing 30.

(28) As described above, in the turbocharger 100 (100A to 100D) shown in FIGS. 1 to 4, the mount 10 is held by the turbine housing 4 and the bearing housing 6 that a turbocharger is originally equipped with, and thereby the mount 10 can be fixed with a simple configuration.

(29) In some embodiments, in the turbocharger 100 (100A, 100C) shown in FIGS. 1 and 3 for instance, the mount 10 is an annular plate, and an outer peripheral portion 10a of the mount 10 is held between the turbine housing 4 and the bearing housing 6.

(30) In this case, the thickness of the annular plate is set appropriately, and thereby it is possible to form a part of the scroll flow path 14 by utilizing a side surface 10f of the mount 10 while ensuring the rigidity of the mount 10 for supporting the shroud 8 via the connection part 12. Furthermore, even in a case where the side surface 10f of the mount 10 is utilized to form a part of the scroll flow path 14, if the thickness direction of the mount 10 and the axial direction of the turbine wheel 2 are the same, it is possible to reduce the thermal expansion amount of the mount 10 in the axial direction of the turbine wheel 2, and thus it is possible to suppress fluctuation of the tip clearance between the turbine wheel 2 and the shroud 8.

(31) In some embodiments, as shown in FIGS. 1 and 3 for instance, the turbocharger 100 (100A, 100C) further includes a bolt 26 fastening the structural part 33 of the turbine housing 4 and the bearing housing 6. In this case, the outer peripheral portion 10a of the mount 10 is held between the structural part 33 of the turbine housing 4 and the bearing housing 6 by an axial force of the bolt 26.

(32) As described above, the mount 10 is mounted to the turbine housing 4 and the bearing housing 6 by fastening the turbine housing 4 and the bearing housing 6 with the bolt 26, and thereby it is possible to fix the mount 10 to the turbine housing 4 and the bearing housing 6 with a simple configuration by setting the fastening force of the bolt 26 appropriately.

(33) In some embodiments, as shown in FIGS. 2 and 4 for instance, the mount 10 includes a tube-shaped portion 10b extending in the axial direction of the turbine wheel 2, and a protruding portion 10c having an annular shape and protruding toward the outer peripheral side of the tube-shaped portion 10b from the tube-shaped portion 10b. In this case, the protruding portion 10c of the mount 10 is held between the turbine housing 4 and the bearing housing 6. Accordingly, the mount 10 can be held between the turbine housing 4 and the bearing housing 6 at a position corresponding to the axial directional length of the tube-shaped portion 10b.

(34) In some embodiments, as shown in FIGS. 2 and 4 for instance, the turbocharger 100 (100B, 100D) further includes a nipping member 28 nipping and coupling a flange 40 disposed on the structural part 33 of the turbine housing 4 and a flange 42 disposed on the bearing housing 6. In this case, the protruding portion 10c of the mount 10 is held between the structural part 33 of the turbine housing 4 and the bearing housing 6 by the nipping force of the nipping member 28. Furthermore, the nipping member 28 may be a C ring having a C-shape cross section.

(35) As described above, the mount 10 is mounted to the turbine housing 4 and the bearing housing 6 by fastening the flange of the turbine housing 4 and the flange of the bearing housing 6 with the nipping member 28, and thereby it is possible to fix the mount 10 to the turbine housing 4 and the bearing housing 6 with a simple configuration by setting the nipping force of the bolt 28 appropriately.

(36) In some embodiments, as shown in FIGS. 1 to 4, the mount 10 is an annular member, and has an engagement portion 10d engaged with an annular step portion 6a formed on the bearing housing 6, by socket-and-spigot fitting. Accordingly, it is possible to make the axial center O2 of the shroud 8 supported on the mount 10 via the connection part 12 and the axial center O1 of the shaft 16 supported on the bearing 18 coincide with each other with a simple configuration.

(37) In some embodiments, as shown in FIGS. 1 to 4 for instance, the turbocharger 100 (100A to 100D) further includes a back plate 23. The back plate 23 is provided to seal exhaust gas leaking from the inlet of the turbine wheel 5 and flowing toward the back surface of the turbine wheel 5, and insulate the bearing side from heat. The outer peripheral end of the back plate 23 is supported by an annular step portion 10e disposed on the inner peripheral surface of the mount 10, and the inner peripheral end of the back plate is supported by the annular step portion 6b of the bearing housing 6. Furthermore, the annular step portion 6b is disposed on the inner peripheral side of the annular step portion 6a.

(38) In some embodiments, as shown in FIGS. 1 and 4 for instance, the turbocharger 100 (100A to 100D) further includes a seal ring 24 that seals the gap 22 between the shroud 8 and the first housing 30. It is desirable for the seal ring 24 to have such an elasticity that can maintain the seal of the gap between the shroud 8 and the first housing 30 even in case of thermal deformation of the first housing 30, and for instance, the seal ring 24 may have a C-shaped cross section as shown in FIGS. 1 to 4, may be an O-ring, or may have another shape.

(39) Accordingly, it is possible to suppress leakage of exhaust gas from the gap 22 between the shroud 8 and the first housing 30 with the seal ring 24. Thus, it is possible to suppress a decrease in the turbine efficiency due to leakage of exhaust gas from the gap 22, and to achieve an even higher turbine efficiency.

(40) FIG. 5 is a diagram showing an example of a cross-sectional shape perpendicular to the axis O1 of the turbine wheel 2 in the connection part 12 shown in FIGS. 1 to 4. FIG. 6 is a diagram showing another example of a cross-sectional shape perpendicular to the axis O1 of the turbine wheel 2 in the connection part 12 shown in FIGS. 1 to 4.

(41) In some embodiments, as shown in FIG. 5, each of the connection parts 12 has a blade-shape cross section perpendicular to the axis of the turbine wheel 2. In the depicted embodiment, the leading edge portion of the blade shape (upstream side of exhaust gas flow) is positioned outside, in the radial direction, of the trailing edge portion (downstream side of exhaust gas flow), along the flow direction of exhaust gas flowing through the scroll flow path 14 into the turbine wheel 2. Accordingly, the connection part 12 having a blade-shape cross section in a direction perpendicular to the axis O1 of the turbine wheel 2 rectifies the flow of exhaust gas flowing between the shroud 8 and the mount 10, and thereby it is possible to achieve an even higher turbine efficiency.

(42) In some embodiments, as shown in FIG. 6, each of the connection parts 12 has a circular cross section in a direction perpendicular to the axis of the turbine wheel 2. Accordingly, it is possible to connect the shroud 8 and the mount 10 with a simple configuration.

(43) Embodiments of the present invention were described in detail above, but the present invention is not limited thereto, and various amendments and modifications may be implemented.

DESCRIPTION OF REFERENCE NUMERALS

(44) 2 Turbine wheel 4 Turbine housing 6 Bearing housing 6a Step portion 6b Step portion 8 Shroud 8a Facing surface 10 Mount 10a Outer peripheral portion 10b Tube-shaped portion 10c Protruding portion 10d Engagement portion 10e Step portion 10f Side surface 12 Connection part 14 Scroll flow path 16 Shaft 18 Bearing 20 Blade 20a Tip 22 Gap 23 Back plate 24 Seal ring 26 Bolt 28 Nipping member 30 First housing 32 Second housing 33 Structural part 34 Outlet guide tube 35 Outlet flange 36 Piston ring 38 Gap 40 Flange 42 Flange 100 (100A, 100B, 100C, 100D) Turbocharger