Shaft for a supercharger and supercharger

Abstract

The shaft (2) for the turbocharger (TC) has a first part (21) disposed inside the bearing bore (51) of the housing (1), the bearing bore (51) being separated from a first space (S1) housing the turbine impeller (3) and a second space (S2) housing the compressor impeller (4), the first part (21) having a coating (Co) on the contact surface with the bearing (B) disposed inside the bearing bore (51) to inhibit hydrogen embrittlement.

Description

Technical Field

[0001] This disclosure relates to a shaft for a turbocharger and a turbocharger. This application claims the benefit of priority based on Japanese Patent Application No. 2024-069210, filed April 22, 2024, the contents of which are incorporated herein by reference. Background Technology

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

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2023 / 228570 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] The turbocharger connected to a hydrogen engine may be exposed to hydrogen through various pathways. Hydrogen may cause hydrogen embrittlement of the turbocharger's components.

[0008] The purpose of this disclosure is to provide a shaft for a turbocharger and a turbocharger capable of suppressing hydrogen embrittlement.

[0009] Solution for solving the problem

[0010] To address the aforementioned issues, one embodiment of the present disclosure provides a shaft for a turbocharger that includes a first portion disposed inside a bearing bore in a housing. The bearing bore is separated from a first space for housing a turbine impeller and a second space for housing a compressor impeller. The first portion has a coating on its contact surface with the bearing disposed inside the bearing bore that inhibits hydrogen embrittlement.

[0011] The shaft may also have a second part that is welded to the turbine impeller and has no coating.

[0012] The shaft may also have a third part that fits into the center hole of the compressor impeller and is uncoated.

[0013] Another aspect of this disclosure is a turbocharger comprising: a turbine impeller; a compressor impeller; a bearing; a housing including a first space for receiving the turbine impeller, a second space for receiving the compressor impeller, and a bearing bore spaced apart from the first and second spaces and for receiving the bearing; and a shaft disposed inside the housing and supported by the bearing for rotation, the shaft being disposed inside the bearing bore and having a first portion containing a coating for inhibiting hydrogen embrittlement on its contact surface with the bearing.

[0014] The shaft may also include a second part welded to the turbine impeller and without coating.

[0015] The shaft may also include a third part that fits into the center bore of the compressor impeller and is uncoated.

[0016] Bearings can also be sliding bearings.

[0017] The turbocharger may also have a thrust ring disposed around the shaft and bearing the load in the axial direction of the shaft. The surface of the thrust ring bearing the load in the axial direction may also contain a material that inhibits hydrogen embrittlement.

[0018] Invention Effects

[0019] According to this disclosure, hydrogen embrittlement can be suppressed. Attached Figure Description

[0020] Figure 1 This is a schematic cross-sectional view of the turbocharger.

[0021] Figure 2 yes Figure 1 A schematic enlarged sectional view of part A in the diagram. Detailed Implementation

[0022] Hereinafter, an embodiment of the present disclosure will be described with reference to the accompanying drawings. The specific dimensions, materials, and values ​​shown in the embodiment are merely illustrative for ease of understanding and do not limit the present disclosure unless specifically stated otherwise. Furthermore, in this specification and the accompanying drawings, elements with substantially the same function or structure are omitted from repeated description by using the same symbols; additionally, elements not directly related to the present disclosure are omitted from illustration.

[0023] Figure 1 This is a schematic cross-sectional view of the turbocharger TC. The turbocharger TC is used in a hydrogen engine (not shown). For example, the turbocharger TC includes a housing 1, a shaft 2, a turbine impeller 3, and a compressor impeller 4.

[0024] As described below, the turbine impeller 3 and the compressor impeller 4 rotate integrally with the shaft 2. Therefore, in this disclosure, the axial direction, radial direction, and circumferential direction of the shaft 2, turbine impeller 3, and compressor impeller 4 can be simply referred to as "axial direction," "radial direction," and "circumferential direction," respectively, unless otherwise indicated. Furthermore, in this disclosure, the axis of the shaft 2, turbine impeller 3, and compressor impeller 4 can be simply referred to as "axis," unless otherwise indicated.

[0025] Housing 1 includes a bearing housing 5, a turbine housing 6, and a compressor housing 7. In the axial direction, one end of the bearing housing 5 is connected to the turbine housing 6. In the axial direction, the other end of the bearing housing 5 is connected to the compressor housing 7.

[0026] The bearing housing 5 includes a bearing bore 51. The bearing bore 51 extends axially within the bearing housing 5. The bearing bore 51 houses a bearing B. The bearing B supports the shaft 2 for rotation. The shaft 2 passes through the bearing bore 51. The shaft 2 and the bearing B will be described in detail later.

[0027] A turbine impeller 3 is provided at the first end of the shaft 2 along the axial direction. The turbine impeller 3 rotates integrally with the shaft 2. The turbine housing 6 defines a first space S1 for accommodating the turbine impeller 3.

[0028] A compressor impeller 4 is provided at the second end of the shaft 2 on the side opposite to 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 for housing the compressor impeller 4.

[0029] The compressor housing 7 includes an intake port 71 at its end on the side opposite to the bearing housing 5 in the axial direction. The intake port 71 is connected to an air filter (not shown).

[0030] A diffuser flow path 72 is defined between the bearing housing 5 and the compressor housing 7. The diffuser flow path 72 has an annular shape. The diffuser flow path 72 is located radially outward relative to the compressor impeller 4. The diffuser flow path 72 is in fluid communication with the intake port 71 via the compressor impeller 4.

[0031] The compressor housing 7 includes a compressor vortex flow path 73. The compressor vortex flow path 73 is located radially outward relative to the diffuser flow path 72. The compressor vortex flow path 73 is connected to the diffuser flow path 72. In addition, the compressor vortex flow path 73 is in fluid communication with the intake port of a hydrogen engine (not shown).

[0032] When the compressor impeller 4 rotates, air is drawn into the compressor housing 7 from the intake port 71. The air is accelerated and pressurized by centrifugal force as it passes through the compressor impeller 4. The air is further pressurized as it passes through the diffuser flow path 72 and flows into the compressor vortex flow path 73. The pressurized air flows out from the discharge port (not shown) and is guided to the intake port of the hydrogen engine. The portion of the supercharger TC including the compressor impeller 4 and the compressor housing 7 functions as a centrifugal compressor C.

[0033] The turbine housing 6 has an outlet 61 at its end on the side opposite to the bearing housing 5 in the axial direction. The outlet 61 is connected to an exhaust gas purification device (not shown).

[0034] The turbine casing 6 includes a connecting flow path 62. The connecting flow path 62 has an annular shape. The connecting flow path 62 is located radially outward relative to the turbine impeller 3. The connecting flow path 62 is in fluid communication with the discharge port 61 via the turbine impeller 3.

[0035] The turbine housing 6 includes a turbine vortex flow path 63. The turbine vortex flow path 63 is located radially outward relative to the connecting flow path 62. The turbine vortex flow path 63 is connected to the connecting flow path 62. Additionally, the turbine vortex flow path 63 is in fluid communication with a gas inlet (not shown). The gas inlet receives exhaust gas from the exhaust manifold of the hydrogen engine.

[0036] Exhaust gas is guided from the gas inlet to the turbine vortex flow path 63, and further guided to the outlet 61 via the connecting flow path 62 and the turbine impeller 3. The exhaust gas causes the turbine impeller 3 to rotate during its passage. 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 pressurized as described above. Thus, the pressurized air is guided to the intake of the hydrogen engine. The portion of the turbocharger TC including the turbine impeller 3 and the turbine housing 6 functions as the turbine T.

[0037] Next, a detailed description of shaft 2 and bearing B will be provided.

[0038] Figure 2 yes Figure 1 A simplified enlarged sectional view of part A in the diagram.

[0039] In this embodiment, a sliding bearing is used as bearing B. Specifically, in this embodiment, a fully floating bearing is used as bearing B. In other embodiments, for example, a semi-floating bearing may also be used as bearing B.

[0040] In this embodiment, bearing B includes a first bearing B1 and a second bearing B2. The number of bearings B is not limited to two; it can be one or more. For example, in other embodiments, an integral sliding bearing can also be used as bearing B.

[0041] The first bearing B1 is positioned near the turbine impeller 3 relative to the second bearing B2. The second bearing B2 is positioned near the compressor impeller 4 relative to the first bearing B1. The first bearing B1 and the second bearing B2 are separated from each other in the axial direction.

[0042] In this embodiment, the first bearing B1 is supported axially by a pair of locating rings R1 that engage with grooves formed on the inner circumferential surface of the bearing bore 51. In this embodiment, the second bearing B2 is supported axially by a locating ring R2 that engages with grooves formed on the inner circumferential surface of the bearing bore 51 and a thrust bearing 81 (described later). In other embodiments, a sleeve may be provided between the first bearing B1 and the second bearing B2 instead of the locating rings R1 and R2.

[0043] The first bearing B1 and the second bearing B2 are radially supported by the inner circumferential surface of the bearing bore 51. In this embodiment, the first bearing B1 and the second bearing B2 are sliding bearings, and therefore the first bearing B1 and the second bearing B2 can slide circumferentially relative to the inner circumferential surface of the bearing bore 51. For example, the first bearing B1 and the second bearing B2 are made of copper material such as brass.

[0044] The bearing housing 5 includes a main oil passage 52. The main oil passage 52 extends along the axial direction. The main oil passage 52 extends parallel to the bearing bore 51. The main oil passage 52 is located above the bearing bore 51.

[0045] The bearing bore 51 and the main oil passage 52 are opened in the wall inside the bearing housing 5. A bearing retainer 83, described later, is installed on the wall, and the opening of the main oil passage 52 is closed by the bearing retainer 83.

[0046] The main oil passage 52 is connected to the 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. The oil used in the hydrogen engine is supplied to the main oil passage 52 via the through hole 53 by an oil pump (not shown).

[0047] The bearing housing 5 includes a first oil passage 54 and a second oil passage 55. Both the first oil passage 54 and the second oil passage 55 open into the main oil passage 52. Additionally, both the first oil passage 54 and the second oil passage 55 open into the bearing bore 51. The first oil passage 54 and the second oil passage 55 connect the main oil passage 52 and the bearing bore 51. The first oil passage 54 is located at a position corresponding to the first bearing B1 and opens towards the first bearing B1. The second oil passage 55 is located at a position corresponding to the second bearing B2 and opens towards the second bearing B2. Therefore, oil used in the hydrogen engine is supplied to both the first bearing B1 and the second bearing B2.

[0048] The bearing bore 51 is fluidly isolated from the first space S1 housing the turbine impeller 3 by a seal Se1. The seal Se1 is disposed axially between the bearing bore 51 and the first space S1. The seal Se1 is disposed radially between the shaft 2 and the wall of the bearing housing 5. The bearing bore 51 is isolated from the exhaust gas flowing in the first space S1 by the seal Se1.

[0049] The bearing bore 51 is fluidly isolated from the second space S2 housing the compressor impeller 4 by a seal Se2. The seal Se2 is axially disposed between the bearing bore 51 and the second space S2. The seal Se2 is radially disposed between an oil baffle ring 84 and the wall of the bearing housing 5, the oil baffle ring 84 being disposed around the shaft 2. The bearing bore 51 is isolated from the air flowing in the second space S2 by the seal Se2.

[0050] Shaft 2 includes a middle diameter section 2a, a large diameter section 2b, and a small diameter section 2c.

[0051] In the axial direction, the intermediate diameter portion 2a extends in the region radially opposite to the bearing bore 51. In the axial direction, the intermediate diameter portion 2a is located between the large diameter portion 2b and the small diameter portion 2c. The intermediate diameter portion 2a has a cylindrical shape. The intermediate diameter portion 2a is inserted into the first bearing B1 and the second bearing B2. The intermediate diameter portion 2a is radially supported by the first bearing B1 and the second bearing B2. The intermediate diameter portion 2a is supported by the first bearing B1 and the second bearing B2 to be rotatable. In this embodiment, the first bearing B1 and the second bearing B2 are sliding bearings, therefore the intermediate diameter portion 2a can slide circumferentially relative to the first bearing B1 and the second bearing B2. The intermediate diameter portion 2a has a constant outer diameter. However, the outer diameter of the intermediate diameter portion 2a may not be constant.

[0052] In the axial direction, the large-diameter portion 2b extends from the first end of the intermediate-diameter portion 2a (near the end of the turbine impeller 3) 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 intermediate-diameter portion 2a. For example, the outer diameter of the large-diameter portion 2b is larger than the inner diameter of the bearing bore 51. For example, the large-diameter portion 2b is axially opposed to the wall of the bearing housing 5 that defines the bearing bore 51.

[0053] In the axial direction, the small-diameter portion 2c extends from the second end of the intermediate-diameter portion 2a (the end near the compressor impeller 4) 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 intermediate-diameter portion 2a. The small-diameter portion 2c has a constant outer diameter. However, the outer diameter of the small-diameter portion 2c may not be constant.

[0054] On shaft 2, in the axial direction, between the second bearing B2 and the compressor impeller 4, a thrust bearing 81, a thrust ring 82, a bearing restraint 83, and an oil baffle ring 84 are arranged in order of proximity to the second bearing B2. Shaft 2 is inserted into the thrust bearing 81, the thrust ring 82, and the oil baffle ring 84.

[0055] The thrust bearing 81 is disposed adjacent to and in contact with the second bearing B2 in the axial direction. Furthermore, the thrust bearing 81 is in contact with the wall of the bearing housing 5 that defines the bearing bore 51 in the axial direction. The thrust bearing 81 is disposed around the intermediate diameter portion 2a. The thrust bearing 81 has an annular shape. In this embodiment, a sliding bearing is used as the thrust bearing 81. Therefore, the thrust bearing 81 can slide circumferentially relative to the wall of the bearing housing 5. For example, the thrust bearing 81 is made of a copper material such as brass.

[0056] The thrust ring 82 is disposed adjacent to and in contact with the thrust bearing 81 in the axial direction. Additionally, the thrust ring 82 contacts the stepped portion between the intermediate diameter portion 2a and the minor diameter portion 2c in the axial direction. The thrust ring 82 is disposed around the minor diameter portion 2c. The thrust ring 82 has an annular shape.

[0057] The bearing restraint 83 is disposed adjacent to and in contact with the thrust ring 82 in the axial direction. The bearing restraint 83 is positioned around the oil retainer ring 84. Furthermore, the bearing restraint 83 is fixed to the bearing housing 5. Therefore, the thrust bearing 81 and the thrust ring 82 are supported in the axial direction by the second bearing B2 and the bearing restraint 83. The bearing restraint 83 has an annular shape. The bearing restraint 83 includes an oil passage for guiding a portion of the oil flowing in the main oil passage 52 to the thrust ring 82.

[0058] An oil baffle ring 84 is disposed adjacent to and in contact with a thrust ring 82 in the axial direction. One end of the oil baffle ring 84 is disposed inside the bearing restraint member 83. The other end of the oil baffle ring 84 is disposed inside the seal Se2. Additionally, the other end of the oil baffle ring 84 contacts the compressor impeller 4 in the axial direction. The oil baffle ring 84 has a generally cylindrical shape. Furthermore, the oil baffle ring 84 includes radially projecting, generally annular protrusions.

[0059] Reference Figure 1 as well as Figure 2 The thrust ring 82, oil baffle ring 84, and compressor impeller 4 on the small diameter portion 2c are bolted to the stepped portion between the intermediate diameter portion 2a and the small diameter portion 2c. In this way, the thrust ring 82, oil baffle ring 84, and compressor impeller 4 are fixed relative to the shaft 2 and rotate integrally with the shaft 2.

[0060] Reference Figure 2 When shaft 2 moves along the axial direction 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 ring 82. When shaft 2 moves along the axial direction toward the second space S2, the load in the axial direction is supported by the oil film pressure between the thrust ring 82 and the bearing restraint 83.

[0061] Reference Figure 1 As mentioned above, the turbocharger TC is used in hydrogen engines. Therefore, the turbocharger TC may be exposed to hydrogen through various pathways.

[0062] 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 combustion. Therefore, it is assumed that most of the hydrogen is burned within the hydrogen engine, resulting in a low concentration of hydrogen in the exhaust gas.

[0063] Conversely, for example, bearing bore 51 receives oil used in a hydrogen engine. In a hydrogen engine, the oil is exposed to leaking gas from between the piston and cylinder. This leaking gas may contain hydrogen before combustion. Therefore, it is presumed that in a hydrogen engine, the oil absorbs hydrogen from the leaking gas. In this case, components in bearing bore 51 may be exposed to oil containing hydrogen. Therefore, components in bearing bore 51 may cause hydrogen embrittlement.

[0064] Reference Figure 2 In particular, in this embodiment, as described above, the first bearing B1, the second bearing B2, and the thrust bearing 81 are sliding bearings. Therefore, bearings B1, B2, and 81 are capable of sliding relative to surrounding components. Thus, in this embodiment, it is presumed that hydrogen embrittlement may occur at the sliding surfaces between bearings B1, B2, and 81 and surrounding components.

[0065] As described above, in this embodiment, the first bearing B1, the second bearing B2, and the thrust bearing 81 are made of copper materials such as brass. In contrast, the components surrounding bearings B1, B2, and 81 are made of steel. While certain copper raw materials such as brass can cause hydrogen embrittlement, steel is generally considered to cause hydrogen embrittlement more than copper raw materials such as brass. Therefore, in this embodiment, it is believed that the components surrounding bearings B1, B2, and 81 within the bearing bore 51 are more likely to cause hydrogen embrittlement. In particular, the shaft 2 sometimes rotates at high speeds. Therefore, it is speculated that hydrogen embrittlement is more likely to occur on the surface of the shaft 2.

[0066] To address this problem, in this embodiment, shaft 2 includes a first portion 21.

[0067] The first portion 21 is located inside the bearing bore 51. The first portion 21 includes contact surfaces that contact the first bearing B1 and the second bearing B2. In this embodiment, the first portion 21 includes the surface of the middle diameter portion 2a. The first portion 21 is coated with a coating Co to suppress hydrogen embrittlement. For example, such a coating Co can also be a known coating including ceramics. The coating Co is not limited thereto.

[0068] Shaft 2 includes a second portion 22. The second portion 22 includes a region connected to the turbine impeller 3. In this embodiment, shaft 2 is connected to the turbine impeller 3 by welding. Therefore, the second portion 22 includes a region welded to the turbine impeller 3. In this embodiment, the second portion 22 includes an end face in the axial direction of the large-diameter portion 2b. For example, the welding may also be electron beam welding. For example, the aforementioned coating, including ceramic, is sometimes non-conductive. If the second portion 22 includes such a coating, shaft 2 may not be able to be welded to the turbine impeller 3. Therefore, the second portion 22 does not contain the coating Co.

[0069] Shaft 2 includes a third portion 23. The third portion 23 includes a region connected to the compressor impeller 4. In this embodiment, shaft 2 is connected to the center hole of the compressor impeller 4 by fitting. Therefore, the third portion 23 includes a region that fits into the center hole of the compressor impeller 4. In this embodiment, the third portion 23 includes the circumferential surface of the small diameter portion 2c. Specifically, in this embodiment, the third portion 23 includes a region in the small diameter portion 2c where the thrust ring 82, the oil baffle ring 84, and the compressor impeller 4 are inserted. For example, if the above-described coating is applied to the third portion 23, the dimensional accuracy may be reduced, and the shaft 2 may not be able to insert the thrust ring 82, the oil baffle ring 84, and the compressor impeller 4. Therefore, the third portion 23 does not contain the coating Co.

[0070] For example, shaft 2 can also be manufactured by the following method. First, shaft 2 is formed from steel. For example, shaft 2 can also be formed by machining or other removal processes. Next, a coating Co is applied to the entire shaft 2. Then, the coating Co is removed from the second part 22 and the third part 23 by grinding or other removal processes.

[0071] Alternatively, shaft 2 can also be manufactured by the following method. First, shaft 2 is formed from steel. For example, shaft 2 can also be formed by machining or other removal processes. Next, the second part 22 and the third part 23 are covered with a mask. Next, a coating Co is applied to the entire shaft 2, including the mask. Next, the mask is removed from the second part 22 and the third part 23.

[0072] Additionally, as described above, the thrust ring 82 rotates integrally with the shaft 2. In this embodiment, at least the end face of the thrust ring 82 that contacts the thrust bearing 81 may also include a coating Co for suppressing hydrogen embrittlement, similar to the first portion 21. Alternatively, the thrust ring 82 may be entirely formed of a material that suppresses hydrogen embrittlement. For example, such a material could be SUS316L. The material for suppressing hydrogen embrittlement is not limited to this.

[0073] As described above, the shaft 2 for the turbocharger TC in this embodiment includes a first portion 21 disposed inside the bearing bore 51 of the housing 1. The bearing bore 51 is separated from the first space S1 housing the turbine impeller 3 and the second space S2 housing the compressor impeller 4. The first portion 21 includes a coating Co to suppress hydrogen embrittlement on its contact surface with the bearing B disposed inside the bearing bore 51. As described above, in the turbocharger TC applied to a hydrogen engine, it is presumed that the components in the bearing bore 51 may cause hydrogen embrittlement due to the absorption of hydrogen from leaking oil. According to the above structure, the first portion 21 disposed inside the bearing bore 51 of the shaft 2 includes a coating Co to suppress hydrogen embrittlement. Therefore, hydrogen embrittlement as described above can be suppressed.

[0074] Furthermore, the shaft 2 includes a second portion 22 welded to the turbine impeller 3 and excluding the coating Co. As mentioned above, the coating Co is sometimes non-conductive. However, according to the above structure, the second portion 22 welded to the turbine impeller 3 does not include the coating Co, thus ensuring electrical connection between the turbine impeller 3 and the second portion 22 during welding.

[0075] Furthermore, the shaft 2 has a third portion 23 that fits into the center hole of the compressor impeller 4 and does not include the coating Co. As mentioned above, the coating Co may reduce dimensional accuracy. However, according to the structure described above, the third portion 23 that fits into the center hole of the compressor impeller 4 does not include the coating Co, so the third portion 23 can be easily inserted into the center hole of the compressor impeller 4 during assembly.

[0076] Furthermore, the turbocharger TC of this embodiment includes: a turbine impeller 3; a compressor impeller 4; a bearing B; a housing 1, which includes a first space S1 for housing the turbine impeller 3, a second space S2 for housing the compressor impeller 4, and a bearing bore 51 separated from the first space S1 and the second space S2 and housing the bearing B; and a shaft 2, which is disposed inside the housing 1 and supported by the bearing B to be rotatable. The shaft 2 is disposed inside the bearing bore 51 and includes a first portion 21 on the contact surface with the bearing B, the first portion 21 including a coating Co to suppress hydrogen embrittlement. According to this structure, as described above, hydrogen embrittlement of the first portion 21 of the shaft 2 disposed inside the bearing bore 51 can be suppressed.

[0077] Furthermore, in the turbocharger TC, bearing B is a sliding bearing. Hydrogen embrittlement is more likely to occur at the surfaces where the constituent elements slide against each other. Therefore, according to the structure described above, hydrogen embrittlement of shaft 2, which slides relative to the sliding bearing, can be suppressed.

[0078] Additionally, the turbocharger TC includes a thrust ring 82 disposed around the shaft 2 and bearing loads in the axial direction of the shaft 2. The surface of the thrust ring 82 bearing the axial loads includes a material that inhibits hydrogen embrittlement (coated Co or the entire thrust ring 82). With this structure, hydrogen embrittlement of the thrust ring 82 can be suppressed.

[0079] The present disclosure has been described above with reference to the accompanying drawings, but the present disclosure is not limited to this embodiment. Obviously, those skilled in the art will be able to conceive of various modifications or alterations within the scope of the claims, and these should be understood to fall within the technical scope of the present disclosure as well.

[0080] For example, in the above embodiment, neither the second portion 22 nor the third portion 23 of shaft 2 includes the coating Co. However, in other embodiments, at least one of the second portion 22 and the third portion 23 may include the coating Co. For example, the coating Co may remain on the third portion 23 if the reduction in dimensional accuracy caused by the coating Co is not a problem.

[0081] This disclosure can promote the use of hydrogen associated with the reduction of CO2 emissions, and thus, for example, contribute to Sustainable Development Goals (SDGs) Goal 7, “Ensuring access to affordable, reliable and sustainable modern energy for all”, and Goal 13, “Taking urgent action to address climate change and its effects.”

[0082] Symbol Explanation

[0083] 1—Housing, 2—Shaft, 3—Turbine impeller, 4—Compressor impeller, 21—First part, 22—Second part, 23—Third part, 51—Bearing bore, 82—Thrust ring, B—Bearing, B1—First bearing, B2—Second bearing, Co—Coating, S1—First space, S2—Second space, TC—Intensifier.

Claims

1. A shaft for a turbocharger, characterized in that, The housing includes a first portion disposed inside a bearing bore, the bearing bore being separated from a first space for housing a turbine impeller and a second space for housing a compressor impeller, and the first portion having a coating on its contact surface with the bearing disposed inside the bearing bore to inhibit hydrogen embrittlement.

2. The shaft for a turbocharger according to claim 1, characterized in that, The shaft has a second portion that is welded to the turbine impeller and does not contain the coating.

3. The shaft for a turbocharger according to claim 1 or 2, characterized in that, The shaft has a third portion that fits into the central hole of the compressor impeller and does not contain the coating.

4. A booster, characterized in that, have: Turbine impeller; Compressor impeller; Bearings; A housing, comprising a first space for receiving the turbine impeller, a second space for receiving the compressor impeller, and a bearing bore spaced apart from the first space and the second space and for receiving the bearing; and A shaft, disposed inside the housing and supported by the bearing to be rotatable, is disposed inside the bearing bore and includes a first portion containing a coating that inhibits hydrogen embrittlement on its contact surface with the bearing.

5. The booster according to claim 4, characterized in that, The shaft includes a second portion welded to the turbine impeller and without the coating.

6. The booster according to claim 4 or 5, characterized in that, The shaft includes a third portion that fits into the central bore of the compressor impeller and does not contain the coating.

7. The booster according to claim 4 or 5, characterized in that, The bearing is a sliding bearing.

8. The booster according to claim 4 or 5, characterized in that, The supercharger includes a thrust ring disposed around the shaft and bearing loads in the axial direction of the shaft. The surface of the thrust ring that bears the load in the axial direction contains a material that inhibits hydrogen embrittlement.

Images