supercharger

Abstract

A supercharger TC1 is provided with: a housing 1 including a turbine impeller 3, a compressor impeller 4, a bearing B, a first space S1 accommodating the turbine impeller 3, a second space S2 accommodating the compressor impeller 4, and a bearing hole 51 separated from the first space S1 and the second space S2 and accommodating the bearing B; a shaft 2 arranged inside the housing 1 and rotatably supported by the bearing B; and first sleeves 21, 82 arranged around the shaft 2 inside the bearing hole 51, with at least the surfaces of the first sleeves 21, 82 being formed from a material having higher resistance to hydrogen embrittlement than the material of the shaft 2.

Description

turbocharger

[0001] This application claims the benefit of priority from Japanese Patent Application No. 2024-069211, filed on April 22, 2024, the contents of which are incorporated herein by reference.

[0002] For example, a supercharger may be connected to the engine. For example, Patent Document 1 discloses a hydrogen engine equipped with a supercharger.

[0003] WO 2023 / 228570

[0004] Turbochargers connected to hydrogen engines can be exposed to hydrogen through various routes, which can cause hydrogen embrittlement in the turbocharger components.

[0005] An object of the present disclosure is to provide a turbocharger that can suppress hydrogen embrittlement.

[0006] In order to solve the above problems, a turbocharger according to one aspect of the present disclosure includes a housing including a turbine impeller, a compressor impeller, a bearing, a first space that accommodates the turbine impeller, a second space that accommodates the compressor impeller, and a bearing hole that is separated from the first space and the second space and accommodates the bearing; a shaft that is disposed inside the housing and rotatably supported by the bearing; and a first sleeve that is disposed around the shaft inside the bearing hole, wherein at least a surface of the first sleeve is formed from a material that has higher resistance to hydrogen embrittlement than a material of the shaft.

[0007] The first sleeve may include a shaft sleeve disposed between the shaft and the bearing.

[0008] The first sleeve may include a thrust collar that receives a load in the axial direction of the shaft.

[0009] The turbocharger may include a second sleeve disposed inside the bearing hole between the inner peripheral surface of the bearing hole and the bearing, at least the surface of the second sleeve being formed from a material that has higher resistance to hydrogen embrittlement than the material of the housing.

[0010] The bearing may be a plain bearing.

[0011] According to the present disclosure, hydrogen embrittlement can be suppressed.

[0012] Fig. 1 is a schematic cross-sectional view of a turbocharger according to a first embodiment. Fig. 2 is a schematic enlarged cross-sectional view of a portion A in Fig. 1. Fig. 3 is a schematic enlarged cross-sectional view of a turbocharger according to a second embodiment. Fig. 4 is a schematic enlarged cross-sectional view of a turbocharger according to a third embodiment.

[0013] An embodiment of the present disclosure will be described below with reference to the accompanying drawings. Specific dimensions, materials, numerical values, etc. 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.

[0014] 1 is a schematic cross-sectional view of a turbocharger TC1 according to a first embodiment. The turbocharger TC1 is applied to a hydrogen engine (not shown). For example, the turbocharger TC1 includes a housing 1, a shaft 2, a turbine impeller 3, and a compressor impeller 4.

[0015] As will be described later, the turbine impeller 3 and the compressor impeller 4 rotate integrally with the shaft 2. Therefore, in the present disclosure, the axial direction, radial direction, and circumferential direction of the shaft 2, the turbine impeller 3, and the compressor impeller 4 may be simply referred to as the "axial direction," the "radial direction," and the "circumferential direction," respectively, unless otherwise specified. Also, in the present disclosure, the axis of the shaft 2, the turbine impeller 3, and the compressor impeller 4 may be simply referred to as the "axis" unless otherwise specified.

[0016] The housing 1 includes a bearing housing 5, a turbine housing 6, and a compressor housing 7. One end of the bearing housing 5 in the axial direction is connected to the turbine housing 6. The other end of the bearing housing 5 in the axial direction is connected to the compressor housing 7.

[0017] The bearing housing 5 includes a bearing hole 51. The bearing hole 51 extends in the axial direction within the bearing housing 5. The bearing hole 51 accommodates a bearing B. The bearing B rotatably supports the shaft 2. The shaft 2 passes through the bearing hole 51. The shaft 2 and the bearing B will be described in detail later.

[0018] A turbine impeller 3 is provided at a first end of the shaft 2 in the axial direction. The turbine impeller 3 rotates integrally with the shaft 2. The turbine housing 6 defines a first space S1 that houses the turbine impeller 3.

[0019] A compressor impeller 4 is provided at a second end of the shaft 2 opposite the first end in the axial direction. The compressor impeller 4 rotates integrally with the shaft 2. The compressor housing 7 defines a second space S2 that houses the compressor impeller 4.

[0020] The compressor housing 7 includes an air intake port 71 at an end opposite to the bearing housing 5 in the axial direction. The air intake port 71 is connected to an air cleaner (not shown).

[0021] The bearing housing 5 and the compressor housing 7 define a diffuser passage 72 therebetween. The diffuser passage 72 has an annular shape. The diffuser passage 72 is located radially outward from the compressor impeller 4. The diffuser passage 72 is in fluid communication with the intake port 71 via the compressor impeller 4.

[0022] The compressor housing 7 includes a compressor scroll passage 73. The compressor scroll passage 73 is located radially outward of the diffuser passage 72. The compressor scroll passage 73 is connected to the diffuser passage 72. The compressor scroll passage 73 is also in fluid communication with an intake port of a hydrogen engine (not shown).

[0023] When the compressor impeller 4 rotates, air is drawn into the compressor housing 7 through the intake port 71. The air is accelerated and pressurized by centrifugal force while passing through the compressor impeller 4. The air is further pressurized as it passes through the diffuser passage 72 and flows into the compressor scroll passage 73. The compressed air flows out from a discharge port (not shown) and is led to the intake port of the hydrogen engine. In the turbocharger TC1, the portion including the compressor impeller 4 and the compressor housing 7 functions as a centrifugal compressor C.

[0024] The turbine housing 6 includes a discharge port 61 at an end opposite to the bearing housing 5 in the axial direction. The discharge port 61 is connected to an exhaust gas purification device (not shown).

[0025] The turbine housing 6 includes a connecting passage 62. The connecting passage 62 has an annular shape. The connecting passage 62 is located radially outward from the turbine impeller 3. The connecting passage 62 is in fluid communication with the discharge port 61 via the turbine impeller 3.

[0026] The turbine housing 6 includes a turbine scroll passage 63. The turbine scroll passage 63 is located radially outward of the connecting passage 62. The turbine scroll passage 63 is connected to the connecting passage 62. The turbine scroll passage 63 is also in fluid communication with a gas inlet (not shown). The gas inlet receives exhaust gas discharged from an exhaust manifold of the hydrogen engine.

[0027] Exhaust gas is guided from the gas inlet to the turbine scroll passage 63, and then through the connecting passage 62 and the turbine impeller 3 to the discharge port 61. The exhaust gas rotates the turbine impeller 3 as it passes through it. The rotational force of the turbine impeller 3 is transmitted to the compressor impeller 4 via the shaft 2. When the compressor impeller 4 rotates, the air is compressed as described above. The compressed air is then guided to the intake port of the hydrogen engine. In the turbocharger TC1, a portion including the turbine impeller 3 and the turbine housing 6 functions as the turbine T.

[0028] Next, the shaft 2 and the bearing B will be described in detail.

[0029] FIG. 2 is a schematic enlarged cross-sectional view of part A in FIG.

[0030] In this embodiment, a plain bearing is used as bearing B. Specifically, in this embodiment, a full-floating bearing is used as bearing B. In other embodiments, for example, a semi-floating bearing may be used as bearing B.

[0031] In this embodiment, the bearing B includes a first bearing B1 and a second bearing B2. The number of bearings B is not limited to two, and may be one, or three or more. For example, in other embodiments, an integrated plain bearing may be used as the bearing B.

[0032] The first bearing B1 is disposed closer to the turbine impeller 3 than the second bearing B2. The second bearing B2 is disposed closer to the compressor impeller 4 than the first bearing B1. The first bearing B1 and the second bearing B2 are spaced apart from each other in the axial direction.

[0033] In this embodiment, the first bearing B1 is supported in the axial direction by a pair of positioning rings R1 fitted into grooves formed in a housing sleeve 56, which will be described later. In this embodiment, the second bearing B2 is supported in the axial direction by a positioning ring R2 fitted into a groove formed in the housing sleeve 56, and a thrust bearing 81, which will be described later. In other embodiments, instead of the positioning rings R1 and R2, a sleeve may be disposed between the first bearing B1 and the second bearing B2.

[0034] The first bearing B1 and the second bearing B2 are supported in the radial direction by the inner circumferential surface of the bearing hole 51 via the housing sleeve 56. In this embodiment, the first bearing B1 and the second bearing B2 are plain bearings, and therefore the first bearing B1 and the second bearing B2 can slide in the circumferential direction relative to the inner circumferential surfaces of the housing sleeve 56 and the bearing hole 51. For example, the first bearing B1 and the second bearing B2 are made of a copper material such as brass.

[0035] The bearing housing 5 includes a main oil passage 52. The main oil passage 52 extends in the axial direction. The main oil passage 52 extends parallel to the bearing hole 51. The main oil passage 52 is located above the bearing hole 51.

[0036] The bearing hole 51 and the main oil passage 52 open into a wall inside the bearing housing 5. A bearing retainer 83 (described later) is attached to the wall, and the opening of the main oil passage 52 is closed by the bearing retainer 83.

[0037] The main oil passage 52 communicates with a through hole 53. The through hole 53 is formed in the bearing housing 5. The through hole 53 extends from the outer wall of the bearing housing 5 to the main oil passage 52. Oil used in the hydrogen engine is supplied to the main oil passage 52 from an oil pump (not shown) via the through hole 53.

[0038] The bearing housing 5 includes a first oil passage 54 and a second oil passage 55. The first oil passage 54 and the second oil passage 55 each open to the main oil passage 52. Furthermore, the first oil passage 54 and the second oil passage 55 each open to the bearing hole 51. The first oil passage 54 and the second oil passage 55 each connect the main oil passage 52 and the bearing hole 51. The first oil passage 54 is provided at a position corresponding to the first bearing B1 and opens toward the first bearing B1. The second oil passage 55 is provided at a position corresponding to the second bearing B2 and opens toward the second bearing B2. Therefore, the first bearing B1 and the second bearing B2 are supplied with oil used in the hydrogen engine.

[0039] The bearing hole 51 is fluidly separated from the first space S1 that houses the turbine impeller 3 by a seal Se1. The seal Se1 is arranged between the bearing hole 51 and the first space S1 in the axial direction. The seal Se1 is arranged between the shaft 2 and the wall of the bearing housing 5 in the radial direction. The seal Se1 blocks the bearing hole 51 from exhaust gas flowing through the first space S1.

[0040] The bearing hole 51 is fluidly separated from the second space S2, which houses the compressor impeller 4, by a seal Se2. The seal Se2 is disposed axially between the bearing hole 51 and the second space S2. The seal Se2 is disposed radially between an oil thrower 84 disposed around the shaft 2 and the wall of the bearing housing 5. The seal Se2 blocks the bearing hole 51 from air flowing through the second space S2.

[0041] The shaft 2 includes a medium diameter portion 2a, a large diameter portion 2b, and a small diameter portion 2c.

[0042] In the axial direction, the medium diameter portion 2a extends in a region radially opposed to the bearing hole 51. In the axial direction, the medium diameter portion 2a is located between the large diameter portion 2b and the small diameter portion 2c. The medium diameter portion 2a has a cylindrical shape. The medium diameter portion 2a is inserted into the first bearing B1 and the second bearing B2 via a shaft sleeve 21, which will be described later. The medium diameter portion 2a is radially supported by the first bearing B1 and the second bearing B2 via the shaft sleeve 21. The medium diameter portion 2a is rotatably supported by the first bearing B1 and the second bearing B2 via the shaft sleeve 21. In this embodiment, the medium diameter portion 2a has a constant outer diameter. In other embodiments, the outer diameter of the medium diameter portion 2a does not have to be constant.

[0043] In the axial direction, the large diameter portion 2b extends from a first end (the end closest to the turbine impeller 3) of the medium diameter portion 2a toward the first space S1. For example, the large diameter portion 2b has a generally annular shape. The outer diameter of the large diameter portion 2b is larger than the outer diameter of the medium diameter portion 2a. For example, the outer diameter of the large diameter portion 2b is larger than the inner diameter of the bearing hole 51. For example, the large diameter portion 2b faces the wall of the bearing housing 5 that defines the bearing hole 51 in the axial direction.

[0044] In the axial direction, the small diameter portion 2c extends from the second end portion (the end portion closer to the compressor impeller 4) of the medium diameter portion 2a toward the second space S2. The small diameter portion 2c has a cylindrical shape. The outer diameter of the small diameter portion 2c is smaller than the outer diameter of the medium diameter portion 2a. The small diameter portion 2c has a constant outer diameter. However, the outer diameter of the small diameter portion 2c does not have to be constant.

[0045] A thrust bearing 81, a thrust collar (first sleeve) 82, a bearing retainer 83, and an oil thrower 84 are provided on the shaft 2 in the axial direction between the second bearing B2 and the compressor impeller 4, in that order from closest to the second bearing B2. The shaft 2 is inserted into the thrust bearing 81, the thrust collar 82, and the oil thrower 84.

[0046] The thrust bearing 81 is disposed adjacent to the second bearing B2 in the axial direction. The thrust bearing 81 also faces the wall of the bearing housing 5 that defines the bearing hole 51 in the axial direction. The thrust bearing 81 is disposed around the medium diameter portion 2a. The thrust bearing 81 has an annular shape. In this embodiment, a plain bearing is used as the thrust bearing 81. Therefore, the thrust bearing 81 is capable of sliding in the circumferential direction relative to the wall of the bearing housing 5. For example, the thrust bearing 81 is made of a copper material such as brass.

[0047] The thrust collar 82 is disposed adjacent to the thrust bearing 81 in the axial direction. The thrust collar 82 is also disposed adjacent to the step between the medium diameter portion 2a and the small diameter portion 2c in the axial direction. The thrust collar 82 is also in contact with the shaft sleeve 21 in the axial direction. The thrust collar 82 is disposed around the small diameter portion 2c. The thrust collar 82 has an annular shape. In this embodiment, the thrust collar 82 functions as a first sleeve together with the shaft sleeve 21, which will be described later.

[0048] The bearing retainer 83 is disposed adjacent to the thrust collar 82 in the axial direction. The bearing retainer 83 is disposed around the oil thrower 84. The bearing retainer 83 is also fixed to the bearing housing 5. Therefore, the thrust bearing 81 and the thrust collar 82 are supported in the axial direction by the second bearing B2 and the bearing retainer 83. The bearing retainer 83 has an annular shape. The bearing retainer 83 includes an oil passage for guiding a portion of the oil flowing through the main oil passage 52 to the thrust collar 82.

[0049] The oil thrower 84 contacts the thrust collar 82 in the axial direction. One end of the oil thrower 84 is disposed inside the bearing retainer 83. The other end of the oil thrower 84 is disposed inside the seal Se2. The other end of the oil thrower 84 also contacts the compressor impeller 4 in the axial direction. The oil thrower 84 has a generally cylindrical shape. The oil thrower 84 also includes a generally annular projection that protrudes radially.

[0050] 1 and 2 , for example, the shaft sleeve 21, the thrust collar 82, the oil thrower 84, and the compressor impeller 4 may be pressed against the step between the large diameter portion 2 b and the medium diameter portion 2 a by bolts. In this manner, the shaft sleeve 21, the thrust collar 82, the oil thrower 84, and the compressor impeller 4 are fixed to the shaft 2 and rotate integrally with the shaft 2. Alternatively, for example, the thrust collar 82, the oil thrower 84, and the compressor impeller 4 may be pressed against the step between the medium diameter portion 2 a and the small diameter portion 2 c by bolts. In this manner, the thrust collar 82, the oil thrower 84, and the compressor impeller 4 are fixed to the shaft 2 and rotate integrally with the shaft 2.

[0051] 2, when the shaft 2 moves axially toward the first space S1, the load in the axial direction is supported by the oil film pressure between the thrust bearing 81 and the thrust collar 82. When the shaft 2 moves axially toward the second space S2, the load in the axial direction is supported by the oil film pressure between the thrust collar 82 and the bearing retainer 83.

[0052] 1, as described above, the turbocharger TC1 is applied to a hydrogen engine, and therefore the turbocharger TC1 may be exposed to hydrogen through various routes.

[0053] For example, turbine T receives exhaust gas from a hydrogen engine. Therefore, components in turbine T may be exposed to unburned hydrogen in the exhaust gas. However, hydrogen engines typically operate primarily with lean burn. Therefore, most of the hydrogen is burned in the hydrogen engine, and the concentration of hydrogen in the exhaust gas is expected to be low.

[0054] In contrast, for example, the bearing bore 51 receives oil used in a hydrogen engine. In a hydrogen engine, the oil is exposed to blow-by gas leaking between the piston and the cylinder. The blow-by gas may contain pre-combustion hydrogen. Therefore, in a hydrogen engine, it is presumed that the oil absorbs the hydrogen in the blow-by gas. In this case, the components in the bearing bore 51 may be exposed to the oil containing hydrogen. Therefore, the components in the bearing bore 51 may suffer from aqueous embrittlement.

[0055] 2 , in this embodiment, as described above, the first bearing B1, the second bearing B2, and the thrust bearing 81 are plain bearings. Therefore, the bearings B1, B2, and 81 can slide relative to the surrounding components. Therefore, in this embodiment, it is presumed that hydrogen embrittlement may occur on the sliding surfaces between the bearings B1, B2, and 81 and the surrounding components.

[0056] As described above, in this embodiment, the first bearing B1, the second bearing B2, and the thrust bearing 81 are made of a copper material such as brass. In contrast, the components surrounding the bearings B1, B2, and 81 are made of steel. Although certain copper materials such as tough pitch copper can cause hydrogen embrittlement, steel is generally considered to be more susceptible to hydrogen embrittlement than copper materials such as brass. Therefore, in this embodiment, among the components within the bearing hole 51, hydrogen embrittlement is considered to be more likely to occur in the components surrounding the bearings B1, B2, and 81. In particular, the shaft 2 may rotate at high speeds. Therefore, it is assumed that hydrogen embrittlement is more likely to occur on the surface of the shaft 2.

[0057] To address this problem, in this embodiment, a shaft sleeve (first sleeve) 21 is disposed around the shaft 2 .

[0058] The shaft sleeve 21 is disposed inside the bearing hole 51 between the medium diameter portion 2 a of the shaft 2 and the bearing B. The shaft sleeve 21 includes contact surfaces with the first bearing B1 and the second bearing B2. The shaft sleeve 21 has a cylindrical shape. In this embodiment, the shaft sleeve 21 covers the medium diameter portion 2 a. The shaft sleeve 21 is fixed to the shaft 2 and rotates integrally with the shaft 2. For example, the shaft sleeve 21 may be fixed to the shaft 2 together with the thrust collar 82, the oil thrower 84, and the compressor impeller 4 by bolts, as described above. Alternatively, the shaft sleeve 21 may be fixed to the shaft 2 by welding, for example. In this embodiment, the first bearing B1 and the second bearing B2 are plain bearings, and therefore the shaft sleeve 21 is slidable in the circumferential direction relative to the first bearing B1 and the second bearing B2.

[0059] At least the surface of the shaft sleeve 21 is formed of a material that has higher resistance to hydrogen embrittlement than the material of the shaft 2. For example, the shaft sleeve 21 may be formed of a material that suppresses hydrogen embrittlement. For example, such a material may be SUS316L. The material that suppresses hydrogen embrittlement is not limited to this. Alternatively, for example, the shaft sleeve 21 may be coated with a Co coating to suppress hydrogen embrittlement. For example, such a Co coating may be a known coating including ceramic. The Co coating is not limited to this.

[0060] In this embodiment, a housing sleeve (second sleeve) 56 is disposed between the inner peripheral surface of the bearing hole 51 and the bearing B.

[0061] The housing sleeve 56 covers the inner circumferential surface of the bearing hole 51. The housing sleeve 56 includes through holes for oil at positions corresponding to the first oil passage 54 and the second oil passage 55. The housing sleeve 56 includes contact surfaces with the first bearing B1 and the second bearing B2. The housing sleeve 56 has a cylindrical shape. The housing sleeve 56 is fixed to the bearing housing 5. For example, the housing sleeve 56 may be fixed to the bearing housing 5 by fitting. Alternatively, for example, the housing sleeve 56 may be fixed to the bearing housing 5 by welding. In this embodiment, the first bearing B1 and the second bearing B2 are plain bearings, and therefore the first bearing B1 and the second bearing B2 are slidable in the circumferential direction relative to the housing sleeve 56.

[0062] Similar to the shaft sleeve 21, at least the surface of the housing sleeve 56 is formed of a material that is more resistant to hydrogen embrittlement than the material of the bearing housing 5. For example, the housing sleeve 56 may be formed of a material that suppresses the above-mentioned hydrogen embrittlement. Alternatively, for example, the housing sleeve 56 may be coated with Co to suppress the above-mentioned hydrogen embrittlement.

[0063] As described above, the thrust collar 82 rotates integrally with the shaft 2. In this embodiment, at least the end surface of the thrust collar 82 that comes into contact with the thrust bearing 81 may include a coating Co for suppressing the above-described hydrogen embrittlement, similar to the shaft sleeve 21. Alternatively, the entire thrust collar 82 may be formed from a material that suppresses the above-described hydrogen embrittlement.

[0064] As described above, the turbocharger TC1 according to this embodiment includes a housing 1 including a turbine impeller 3, a compressor impeller 4, a bearing B, a first space S1 that accommodates the turbine impeller 3, a second space S2 that accommodates the compressor impeller 4, and a bearing hole 51 that is separated from the first space S1 and the second space S2 and accommodates the bearing B; a shaft 2 that is disposed within the housing 1 and rotatably supported by the bearing B; and a first sleeve 21, 82 that is disposed around the shaft 2 within the bearing hole 51. At least the surface of the first sleeve 21, 82 is formed of a material that is more resistant to hydrogen embrittlement than the material of the shaft 2. As described above, in the turbocharger TC1 applied to a hydrogen engine, it is presumed that components in the bearing hole 51 will suffer hydrogen embrittlement due to oil that has absorbed hydrogen in the blow-by gas. According to the above configuration, the portion of the shaft 2 that is disposed within the bearing hole 51 is protected by the first sleeve 21, 82, which has high resistance to hydrogen embrittlement. Therefore, the above-mentioned hydrogen embrittlement can be suppressed.

[0065] Furthermore, in the turbocharger TC1, the first sleeve includes a shaft sleeve 21 disposed between the shaft 2 and the bearing B. The shaft 2 may slide against the bearing B at high speed. Therefore, it is presumed that hydrogen embrittlement is more likely to occur on the surface of the shaft 2. According to the above configuration, the portion of the shaft 2 that comes into contact with the bearing B can be protected from hydrogen embrittlement by the shaft sleeve 21.

[0066] Furthermore, in the turbocharger TC1, the first sleeve includes the thrust collar 82 that receives a load in the axial direction of the shaft 2. As described above, the thrust collar 82 may slide at high speed against the thrust bearing 81 together with the shaft 2. Therefore, it is presumed that hydrogen embrittlement is more likely to occur on the surface of the thrust collar 82. With the above configuration, the thrust collar 82 can be protected from hydrogen embrittlement.

[0067] The turbocharger TC1 also includes a housing sleeve 56 disposed inside the bearing hole 51 between the inner circumferential surface of the bearing hole 51 and the bearing B. At least the surface of the housing sleeve 56 is formed of a material that has higher resistance to hydrogen embrittlement than the material of the bearing housing 5. As described above, the bearing B is slidable relative to the inner circumferential surface of the bearing hole 51. Therefore, hydrogen embrittlement may occur on the inner circumferential surface of the bearing hole 51. With the above configuration, the inner circumferential surface of the bearing hole 51 can be protected from hydrogen embrittlement by the housing sleeve 56.

[0068] In the turbocharger TC1, the bearing B is a plain bearing. Hydrogen embrittlement occurs on the surfaces where components slide against each other. Therefore, with the above configuration, it is possible to suppress hydrogen embrittlement of the components that slide against the plain bearing.

[0069] Next, other embodiments will be described.

[0070] Fig. 3 is a schematic enlarged cross-sectional view of a turbocharger TC2 according to the second embodiment. Fig. 3 shows a region of the turbocharger TC2 according to the second embodiment, which corresponds to part A in Fig. 1. The turbocharger TC2 differs from the turbocharger TC1 according to the first embodiment in that a step 2d is provided in the center of the medium diameter portion 2a of the shaft 2 in the axial direction, and that the shaft sleeve is divided into a first shaft sleeve 21a and a second shaft sleeve 21b in the axial direction, with the step 2d sandwiched between them. The other configurations of the turbocharger TC2 may be the same as those of the turbocharger TC1.

[0071] The step portion 2d protrudes radially outward from the medium diameter portion 2a and has an annular shape.

[0072] The first shaft sleeve 21a is provided between the large diameter portion 2b and the step portion 2d in the axial direction. The first shaft sleeve 21a includes a region that contacts the first bearing B1. Like the shaft sleeve 21 of the first embodiment, the first shaft sleeve 21a may be formed of a material that has higher resistance to hydrogen embrittlement than the material of the shaft 2, or may include a coating to suppress hydrogen embrittlement.

[0073] For example, the first shaft sleeve 21 a may be interference-fitted to the medium diameter portion 2 a. In this case, for example, the large diameter portion 2 b and the medium diameter portion 2 a may be formed separately from each other, and may be connected to each other by welding or the like after the first shaft sleeve 21 a is interference-fitted to the medium diameter portion 2 a.

[0074] The second shaft sleeve 21b is provided between the step portion 2d and the thrust collar 82 in the axial direction. The second shaft sleeve 21b includes a region that comes into contact with the second bearing B2. Like the shaft sleeve 21 of the first embodiment, the second shaft sleeve 21b may be made of a material that has higher resistance to hydrogen embrittlement than the material of the shaft 2, or may include a coating to suppress hydrogen embrittlement.

[0075] For example, the second shaft sleeve 21b may be tightly fitted to the medium diameter portion 2a.

[0076] Such a turbocharger TC2 has the same effects as the turbocharger TC1 according to the first embodiment.

[0077] Next, still another embodiment will be described.

[0078] Fig. 4 is a schematic enlarged cross-sectional view of a turbocharger TC3 according to a third embodiment. Fig. 4 shows a region of the turbocharger TC3 according to the third embodiment, which corresponds to part A in Fig. 1. The turbocharger TC3 differs from the turbocharger TC1 according to the first embodiment in that the inner diameter of the shaft sleeve 21 is reduced in stages from the first end (left end) to the second end (right end), and in that the medium diameter portion 2a includes a plurality of step portions 2e, 2f, 2g corresponding to the plurality of inner diameters of the shaft sleeve 21. The other configurations of the turbocharger TC3 may be the same as those of the turbocharger TC1.

[0079] The first step portion 2e is adjacent to the large diameter portion 2b in the axial direction. The first step portion 2e protrudes radially outward from the medium diameter portion 2a. The first step portion 2e has an annular shape. The diameter of the first step portion 2e and the inner diameter of the shaft sleeve 21 corresponding to the first step portion 2e may be determined such that the first step portion 2e and the shaft sleeve 21 are tightly fitted together.

[0080] The second step 2f is located at the center of the medium diameter portion 2a in the axial direction. The second step 2f protrudes radially outward from the medium diameter portion 2a. The second step 2f has an annular shape. The diameter of the second step 2f is smaller than the diameter of the first step 2e. The diameter of the second step 2f and the inner diameter of the shaft sleeve 21 corresponding to the second step 2f may be determined so that the second step 2f and the shaft sleeve 21 are transition-fitted to each other.

[0081] The third step 2g is adjacent to the small diameter portion 2c in the axial direction. The third step 2g protrudes radially outward from the medium diameter portion 2a. The third step 2g has an annular shape. The diameter of the third step 2g is smaller than the diameter of the second step 2f. The diameter of the third step 2g and the inner diameter of the shaft sleeve 21 corresponding to the third step 2g may be determined so that the third step 2g and the shaft sleeve 21 are tightly fitted together.

[0082] Such a turbocharger TC3 has the same effects as the turbocharger TC1 according to the first embodiment. Furthermore, in the turbocharger TC3, the shaft sleeve 21 can be easily assembled to the shaft 2.

[0083] While one embodiment of the present disclosure has been described above with reference to the accompanying drawings, it goes without saying that the present disclosure is not limited to such an embodiment. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that such modifications also fall within the technical scope of the present disclosure.

[0084] For example, in the first embodiment, the shaft sleeve 21 and the thrust collar 82 are separate components. In other embodiments, the shaft sleeve 21 and the thrust collar 82 may be integrally formed with each other and function as a single, integral first sleeve.

[0085] Also, for example, in the above embodiment, the housing sleeve 56 is provided. In other embodiments, the housing sleeve 56 may not be provided, and the bearing B may be in direct contact with the inner circumferential surface of the bearing hole 51.

[0086] The present disclosure provides ２ It can promote the use of hydrogen, which leads to reduced emissions, thereby contributing, for example, to Sustainable Development Goal (SDG) 7 "Ensure access to affordable, reliable, sustainable and modern energy" and SDG 13 "Take urgent action to combat climate change and its impacts."

[0087] REFERENCE SIGNS LIST 1 Housing 2 Shaft 3 Turbine impeller 4 Compressor impeller 21 Shaft sleeve (first sleeve) 51 Bearing hole 56 Housing sleeve (second sleeve) 82 Thrust collar (first sleeve) B Bearing B1 First bearing B2 Second bearing Co Coating (material highly resistant to hydrogen embrittlement) S1 First space S2 Second space TC1 Turbocharger TC2 Turbocharger TC3 Turbocharger

Claims

1. A turbocharger comprising: a turbine impeller; a compressor impeller; a bearing; a housing including a first space that accommodates the turbine impeller, a second space that accommodates the compressor impeller, and a bearing hole that is separated from the first space and the second space and accommodates the bearing; a shaft that is disposed inside the housing and rotatably supported by the bearing; and a first sleeve that is disposed around the shaft inside the bearing hole, wherein at least a surface of the first sleeve is formed from a material that has higher resistance to hydrogen embrittlement than a material of the shaft.

2. The turbocharger according to claim 1, wherein the first sleeve includes a shaft sleeve disposed between the shaft and the bearing.

3. A turbocharger according to claim 1 or 2, wherein the first sleeve includes a thrust collar that receives a load in the axial direction of the shaft.

4. A turbocharger according to claim 1 or 2, further comprising a second sleeve disposed inside the bearing hole between the inner peripheral surface of the bearing hole and the bearing, at least the surface of the second sleeve being formed from a material that has higher resistance to hydrogen embrittlement than the material of the housing.

5. The turbocharger according to claim 1 or 2, wherein the bearing is a plain bearing.

Images