WO2021199308A1

WO2021199308A1 - Turbocharger

Info

Publication number: WO2021199308A1
Application number: PCT/JP2020/014878
Authority: WO
Inventors: 北村　剛; 直谷口; 雄祐古田
Original assignee: 三菱重工エンジン＆ターボチャージャ株式会社
Priority date: 2020-03-31
Filing date: 2020-03-31
Publication date: 2021-10-07

Abstract

A turbocharger according to one aspect comprises: a turbine wheel mounted on one end side of the rotational shaft; a compressor wheel mounted on the other end side of the rotational shaft; a bearing housing accommodating a bearing part that supports the rotational shaft rotatably; a back plate that partitions, along the axial direction of the rotational shaft, an inner space defined between a turbine housing accommodating the turbine wheel and the bearing housing, and that forms one side space between a back surface of the turbine wheel and the back plate, and forms other side space between the bearing housing and the back plate; and a cooling gas passage that bleeds compressed gas compressed by the compressor wheel, and has an outlet-side opening communicating with the other side space.

Description

Turbocharger

This disclosure relates to a turbocharger.

The exhaust turbocharger supercharges the air supplied to the engine by using the energy of the exhaust gas discharged from the engine. The temperature of the exhaust gas supplied to the turbine housing of the exhaust turbocharger tends to be high in order to improve the thermal cycle efficiency. For example, it is around 800 ° C. for a diesel engine and around 1000 ° C. for a gasoline engine. Therefore, the durability of the member against the high temperature of the exhaust gas has become a problem. As a countermeasure, even if a general heat-resistant material (such as a Ni-based alloy) is used for a member such as a turbine wheel, the life at a high temperature cannot be ensured.

As a measure against high temperature, the exhaust turbocharger disclosed in Patent Document 1 forms a cooling hole in the boss portion and the blade portion of the turbine wheel, and supplies compressed air on the compressor side to the cooling hole to cool the turbine wheel. Is taking.

Japanese Unexamined Patent Publication No. 2004-232622

As described in Patent Document 1, measures for forming cooling holes in the boss portion and the wing portion of the turbine wheel are not easy to process, and particularly in the case of a small turbocharger such as a turbocharger for vehicles. Implementation is difficult in terms of cost and feasibility.

The present disclosure has been made in view of the above-mentioned problems, and an object of the present disclosure is to propose a cooling means that is easy to realize at low cost as a means for cooling a turbine wheel of a turbocharger.

In order to achieve the above object, the turbocharger according to the present disclosure includes a rotating shaft, a turbine wheel provided on one end side of the rotating shaft, a compressor wheel provided on the other end side of the rotating shaft, and the rotation. A back plate that partitions an internal space defined between a bearing housing that accommodates a bearing portion that rotatably supports a shaft and the compressor wheel and the bearing housing along the axial direction of the rotating shaft. A back plate that forms a space on one side with the back surface of the turbine wheel and a space on the other side with the bearing housing, and a compressed gas compressed by the compressor wheel are extracted to create the space on the other side. It is provided with a cooling gas passage having an outlet side opening communicating with the above.

According to the turbocharger according to the present disclosure, the turbine wheel can be cooled by a low-cost and easy-to-realize means, and its life can be suppressed from being shortened.

It is a front view sectional view which shows the whole structure of the turbocharger which concerns on one Embodiment. It is a front view sectional view which enlarged a part of FIG. It is a perspective view of the back plate which concerns on one Embodiment. It is a front view sectional view which shows the whole structure of the turbocharger which concerns on one Embodiment. It is an enlarged front view sectional view of a part of the turbocharger which concerns on one Embodiment. It is an enlarged front view sectional view of a part of the turbocharger which concerns on one Embodiment. It is an enlarged front view sectional view of a part of the turbocharger which concerns on one Embodiment. It is a front view sectional view which shows the diffuser flow path of a compressor part enlarged.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention to this, but are merely explanatory examples. No.
For example, expressions that represent relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" are exact. Not only does it represent such an arrangement, but it also represents a state of relative displacement with tolerances or angles and distances to the extent that the same function can be obtained.
Further, for example, an expression representing a shape such as a quadrangular shape or a cylindrical shape not only represents a shape such as a quadrangular shape or a cylindrical shape in a geometrically strict sense, but also includes a concavo-convex portion or a concavo-convex portion within a range in which the same effect can be obtained. The shape including the chamfered portion and the like shall also be represented.
On the other hand, the expressions "equipped", "equipped", "equipped", "included", or "have" one component are not exclusive expressions that exclude the existence of other components.

1 to 7 are diagrams showing turbochargers according to some embodiments. 1 to 3 relate to the turbocharger 10 (10A) according to one embodiment, FIG. 1 is a front sectional view showing the overall configuration of the turbocharger, and FIG. 2 is a partially enlarged view of FIG. , FIG. 3 is a perspective view of the back plate 40. FIG. 4 is a front view sectional view of the turbocharger 10 (10B) according to another embodiment. 5 to 7 are partially enlarged front view sectional views showing the vicinity of the back plate 40 of the turbocharger according to the different embodiments.

As shown in FIGS. 1 and 4, the turbocharger 10 (10A, 10B) is located at the center of the housing, the rotating shaft 12 is arranged in the lateral direction, and the turbine wheel 14 is provided on one end side of the rotating shaft 12. A compressor wheel 16 is provided on the other end side of the rotating shaft 12. The housing accommodating these members is provided between the turbine housing 20 accommodating the turbine wheel 14, the compressor housing 22 accommodating the compressor wheel 16, and the turbine housing 20 and the compressor housing 22, and the rotating shaft 12 can rotate. It is composed of a bearing housing 24 for accommodating a bearing portion 18 that supports the turbine. The rotating shaft 12, the turbine wheel 14, and the compressor wheel 16 are configured to rotate about the axis CA.

A plurality of blades 28 are provided on the hub surface of the turbine wheel 14, and a plurality of blades 30 are provided on the hub surface of the compressor wheel 16. The turbine wheel 14 is rotated by the exhaust gas e flowing into the turbine wheel 14 from the exhaust gas flow path 26 formed inside the turbine housing 20. As the compressor wheel 16 rotates with the rotation of the turbine wheel 14, the gas to be compressed (for example, air) is sucked into the compressor wheel 16 from the inlet opening 32 formed in the compressor housing 22. A diffuser flow path 34 is formed on the outlet side of the compressor wheel 16, and the kinetic energy of the compressed gas g discharged from the compressor wheel 16 is converted into pressure energy in the diffuser flow path 34. The compressed gas g is supplied to the internal combustion engine via the scroll flow path 36 formed inside the diffuser flow path 34 and the compressor housing 22.

In the turbocharger 10 (10A, 10B), an internal space Si is formed between the turbine wheel 14 and the bearing housing 24, and the back plates 40 (40a, 40b) are arranged in the internal space Si. The back plate 40 is arranged so as to partition the internal space Si along the axial direction of the rotating shaft 12. That is, the space S _{1 (one} side space) is formed between the rear surface 14a of the back plate 40 and the turbine wheel 14, the space S _{2 (the} other side space) between the back plate 40 and the bearing housing 24 is It is formed. Furthermore, it bled compressed gas g, which is compressed by the compressor wheel 16, and a cooling gas passage 42 having an outlet opening 46 communicating with the space _{S 2} (42a, 42b). The outlet side of the compressor wheel 16 (e.g., outlet region or scroll passage 36 of the diffuser flow path 34) the pressure of the compressed gas g in is higher than the pressure in the space S _2, compressed gas bled to the cooling gas passage 42 g is ejected from the outlet opening 46 into the space _{S 2.}

Thus, a portion of the compressed gas g is introduced into the space S _2, further, by flowing from the space S ₂ in the space S _1, it can be cooled turbine wheel 14. Therefore, it is possible to suppress a decrease in life due to thermal deformation, thermal burnout, or the like of the turbine wheel 14. As described above, the pressure of the compressed gas g the discharge side of the compressor wheel 16 is higher than the pressure in the space S _2, a driving means for supplying compressed gas g in the space S ₂ is not required. Incidentally, compressed gas g jetted into the space S ₂ flows from a gap between the turbine wheel 14 and the turbine housing 20 in the exhaust gas line 26, which contributes to the turbine output.

In one embodiment, as shown in FIGS. 1 and 4, the cooling gas passages 42 (42a, 42b) have an inlet side opening 44 that communicates with an outlet side region of the diffuser flow path 34 that houses the compressor wheel 16. Inlet-side opening 44 of the cooling gas passage 42, since the opening on the outlet side region of the diffuser flow path 34 can supply compressed gas g of a high pressure through a diffuser flow path 34 into the space S _2. As described above, the pressure difference between the inlet side opening 44 and the outlet side opening 46 of the cooling gas passage 42 makes it possible to easily supply the _{compressed gas g to the space S 2 without requiring other power.}

FIG. 8 is a front view enlarged cross-sectional view showing the diffuser flow path 34. As shown in FIG. 8, assuming that the inlet of the diffuser flow path 34 is 0% and the outlet is 100%, the "outlet side region of the diffuser flow path 34" referred to in the present specification means that the pressure of the compressed gas g is high. It refers to a region of 50 to 100% and a region facing the scroll flow path 36, and the inlet side opening 44 is preferably opened in this region. Preferably, the inlet side opening 44 is opened in an outlet side region of 80 to 100% of the diffuser flow path 34 or a region facing the scroll flow path 36. However, in the region of the scroll flow path 36 that is distant from the outlet of the diffuser flow path 34, a long cooling gas passage 42 must be formed up to the turbine side, so that the inlet side opening 44 is a scroll near the outlet of the diffuser flow path 34. It is preferable to open the flow path 36.

In one embodiment, as shown in FIGS. 2 and 3, the back plate 40 (40a) has a plurality of discretely arranged first through holes 50. The so-called jet cooling (impingement cooling) is performed by the compressed gas g ejected from the plurality of first through holes 50 toward the back surface 14a of the turbine wheel colliding with the back surface 14a. Thereby, the cooling effect of the turbine wheel 14 can be improved. The mode of distribution of the plurality of first through holes 50 is not limited to a specific mode. The compressed gas g after colliding with the back surface 14a flows out to the exhaust gas flow path 26 from the gap c1 formed between the outer peripheral end of the turbine wheel 14 and the turbine housing 20, and contributes to the turbine output.

In an exemplary embodiment of the back plate 40 (40a) shown in FIG. 3, a plurality of first through holes 50 are arranged in a grid pattern at equal intervals from each other. That is, a virtual quadrangle 52 is defined on one surface of the back plate 40 (40a), and each first through hole 50 is arranged at a corner of the virtual quadrangle 52. The virtual quadrangle may be a square or a rectangle. By appropriately setting the length x1 of one side of the virtual quadrangle 52, the length x2 of the other side, and the diameter D of the first through hole 50, the flow velocity Uj of the compressed gas g ejected from the first through hole 50 is set. .. Further, the distance z between the first through hole 50 and the surface to be cooled 54 (back surface 14a in each embodiment) is set, and the flow velocity Uj of the compressed gas g ejected from the first through hole 50 is set to a set value or more to set the surface to be cooled. By colliding with 54, the cooling effect of jet cooling can be improved. The first through holes 50 may be arranged at appropriate intervals at the corners of the virtual triangle or the outer edge of another figure instead of the virtual quadrangle.

In one embodiment, as shown in FIG. 2, the back plate 40 (40a) is formed in a ring shape, its inner peripheral end is in contact with a corner portion 24a formed in the bearing housing 24, and its outer peripheral end is a turbine. It is arranged so as to be in contact with the corner portion 20a formed in the housing 20. For example, when assembling the turbocharger 10, the inner peripheral end of the back plate 40 (40a) presses the corner portion 24a by utilizing the elasticity of the back plate 40 (40a), and the outer peripheral end of the back plate 40 (40a) is pressed. Assemble so that the corner portion 20a is pressed. As a result, leakage of the compressed gas g at the inner peripheral end and the outer peripheral end of the back plate 40 (40a) can be suppressed.

In one embodiment, as shown in FIG. 1, a second through hole 56 extending along the axial direction of the rotating shaft 12 is formed inside the bearing housing 24. The second through hole 56 forms a part of the cooling gas passage 42 (42a). According to this embodiment, since the second through hole 56 forming a part of the cooling gas passage 42 (42a) is formed inside the bearing housing 24, a space for arranging the cooling gas passage is provided outside the bearing housing 24. Can be reduced. Therefore, the bearing housing 24 can be made compact.

In the exemplary embodiment shown in FIG. 1, almost all of the cooling gas passage 42 (42a) is composed of the second through hole 56. Therefore, since almost all of the cooling gas passage 42 (42a) is arranged inside the bearing housing 24 and there is no portion exposed to the outside of the bearing housing 24, other equipment arranged outside the bearing housing 24. It doesn't get in the way of placement.

In one embodiment, as shown in FIGS. 1 and 4, a cooling water space 48 to which cooling water is supplied is formed inside the bearing housing 24. The bearing housing 24 can be cooled by circulating the cooling water in the cooling water space 48. The cooling effect of the turbine wheel 14 can be improved by combining the cooling by the compressed gas g and the cooling by the cooling water supplied to the cooling water space 48.

In one embodiment, as shown in FIG. 4, the turbocharger 10 (10B) includes an external pipe 60 provided between the compressor housing 22 and the bearing housing 24. The external pipe 60 constitutes a part of the cooling gas passage 42 (42b). According to this embodiment, since the external pipe 60 forms a part of the cooling gas passage 42 (42b), the processing for forming the cooling gas passage inside the bearing housing 24 can be reduced. Therefore, the formation of the cooling gas passage 42 (42b) becomes relatively easy.

In the exemplary embodiment shown in FIG. 4, the cooling gas passage 42 (42b) includes a cooling gas passage 62 formed inside the bearing housing 24 on the upstream side of the external pipe 60, the external pipe 60, and the external pipe 60. It is composed of a cooling gas passage 64 formed inside the bearing housing 24 on the downstream side of the bearing housing 24. By forming a part of the cooling gas passage 42 (42b) with the external pipe 60 in this way, the arrangement of the cooling gas passage 42 (42b) becomes relatively easy.
Further, as shown in FIG. 4, a check valve 66 may be provided to prevent the compressed gas g from flowing back from the internal space Si toward the compressor housing 22 side.

In one embodiment, as shown in FIG. 5, the back plate 40 is composed of a back plate 40 (40b). A gap c2 through which the compressed gas g can flow is formed between the inner peripheral end surface 68 of the back plate 40 (40b) and the bearing housing 24. According to this embodiment, compressed gas g supplied to the space S _2, since the flow from the gap c2 to the space S _1, can be cooled turbine wheel 14.

In the exemplary embodiment shown in FIG. 5, the outer peripheral end 70 of the back plate 40 (40b) is sandwiched and fixed between the bearing housing 24 and the turbine housing 20. Since the back plate 40 (40b) has the outer peripheral end portion 70, the back plate 40 (40b) can be fixed at a predetermined position in the internal space Si. Further, the back plate 40 (40b) has a bent portion 72 on the inner peripheral side of the external pipe 60, and the inner peripheral side portion of the bent portion 72 is located on the turbine wheel 14 side. This is to allow a space S ₁ and S ₂ at an appropriate volume ratio on each side of the inner circumferential side portion.

In one embodiment, the surface 41 of the back plate 40 (40a, 40b) facing the space _{S 2} is configured such that the radiation rate from the back surface 14a of the turbine wheel 14 increases. Here, the "emissivity" is the emissivity of thermal radiation of the entire electromagnetic wave including infrared rays, and is defined by the following equation (1).
Emissivity = Radiant exitance of an object / Radiant exitance of a blackbody at the same temperature ... (1)

When the back plate 40 absorbs thermal radiation, the temperature rises, and when the back plate 40 emits thermal radiation, the temperature decreases. Backplate 40 facing the space S ₂ is cooled by radiant heat transfer and heat conduction from the bearing housing 24. Since the temperature of the back plate 40 is lowered, compressed gas g which passes through the space S ₂ is cooled by contact with the surface 41. By cooling the compressed gas g in this way, the cooling effect of the turbine wheel 14 can be enhanced. As a result, thermal deformation and thermal burnout of the turbine wheel 14 can be suppressed.

As a means for increasing the emissivity of the surface 41 of the back plate 40, for example, surface treatment such as applying black paint to the surface 41, making the surface 41 uneven, or roughening the roughness of the surface 41, etc. There is a means.

In one embodiment, as shown in FIG. 6, a third through hole 80 is formed inside the turbine wheel 14. The inlet side opening 80a of the third through hole 80 is formed on the back surface 14a of the turbine wheel 14, the outlet side opening 80b is formed on the end surface (boss end surface) 74a of the boss portion 74 of the turbine wheel 14, and the third through hole 80 is formed. It extends between these openings inside the turbine wheel 14. Compressed gas g which has flowed into the space S ₂ from the outlet opening 46 flows from the space S ₁ to the inlet side opening 80a, and flows out from the outlet opening 80b through the third through-hole 80. Therefore, the turbine wheel 14 can be effectively cooled. One third through hole 80 or a plurality of third through holes 80 can be formed in the circumferential direction of the turbine wheel 14.

As shown in FIG. 6, assuming that the radial position of the back surface 14a of the turbine wheel 14 corresponding to the outer peripheral surface of the rotating shaft 12 is 0% and the radial position corresponding to the outer peripheral end of the back surface 14a is 100%, the inlet side. It is desirable that the opening 80a is arranged at a position of 0 to 50%. When the inlet side opening 80a is arranged in the range of 50 to 100%, the third through hole 80 needs to be bent in the middle in order to communicate with the outlet side opening 80b that opens to the boss end surface 74a, and is linear as a whole. It is difficult to form the third through hole 80. On the other hand, it is difficult to form a through hole that bends inside the turbine wheel 14, and there is a problem that the pressure loss increases. In the range of 50 to 100%, such a problem disappears. More preferably, the inlet side opening 80a is preferably formed in the range of 0 to 30%. When the inlet side opening 80a is in this range, it is even easier to form a linear third through hole 80 that communicates with the outlet side opening 80b that opens in the boss end surface 74a.

In one embodiment, as shown in FIG. 6, the rotating shaft 12 is formed in a small diameter portion 12a at a joint portion with the back surface 14a of the turbine wheel 14. This makes it easier to form the inlet side opening 80a at a position close to the axis CA.

In one embodiment, as shown in FIG. 7, a fourth through hole 90 is formed inside the turbine wheel 14. The inlet side opening 90a of the fourth through hole 90 is formed on the back surface 14a of the turbine wheel 14, and the outlet side opening 90b is formed on the hub surface 92 of the turbine wheel 14. The fourth through hole 90 extends inside the turbine wheel 14 from the inlet side opening 90a toward the outlet side opening 90b. The compressed gas g that has flowed into the fourth through hole 90 from the inlet side opening 90a flows out from the outlet side opening 90b to the hub surface 92 of the turbine wheel 14. Then, since it flows along the hub surface 92 along with the exhaust gas e flowing toward the turbine outlet side along the hub surface 92, a film-like flow of the compressed gas g can be formed on the hub surface 92. As a result, the hub surface 92 can be film-cooled, so that the cooling effect of the turbine wheel 14 can be enhanced.

In one embodiment, the axis of the fourth through hole 90 extends along the tangential direction of the hub surface 92 at the position where the outlet side opening 90b is formed. As a result, the outlet-side opening 80b of the fourth through hole 90 opens along the tangential direction with respect to the hub surface 92, so that a film-like flow of the compressed gas g can easily be formed on the hub surface 92. Thereby, the cooling effect by cooling the hub surface 92 by the film can be improved.

As shown in FIG. 7, the radial position of the back surface 14a of the turbine wheel 14 corresponding to the outer peripheral surface of the rotating shaft 12 is 0%, and the radial position of the back surface 14a corresponding to the outer peripheral end of the back surface 14a is 100%. .. Further, of the hub surface 92, the outlet end of the exhaust gas e is set to 0%, and the position of the hub surface 92 corresponding to the outer peripheral end of the back surface 14a is set to 100%. The temperature distribution of the exhaust gas e on the surface of the blade 30 is the highest at the inlet end of the blade 30, and the temperature gradually decreases by consuming kinetic energy toward the downstream side. On the other hand, the creep strength of the blade 30 decreases toward the downstream side of the exhaust gas flow due to the shape and structure of the blade 30. Therefore, it is preferable to arrange the outlet side opening 90b so that the film can be cooled at least in the downstream side region of 0 to 50% of the hub surface 92. Further, from the viewpoint of workability and pressure loss, when a condition that the fourth through hole 90 can be formed in a straight line as a whole is added, the inlet side opening 90a of the fourth through hole 90 is 0 to 0 on the back surface 14a. It is preferable to arrange the opening in a region of 50% and the outlet side opening 90b so as to open in a region of 30 to 75% of the hub surface 92. Further, preferably, the downstream side range of the opening position of the outlet side opening 90b is further limited to the upstream side to be a region of 40 to 75% of the hub surface 92.

Note that each of the above embodiments can also be applied to a variable capacity turbocharger having a nozzle vane.

The contents described in each of the above embodiments are grasped as follows, for example.

1) The turbocharger (10 (10A, 10B)) according to one embodiment is provided on a rotating shaft (12), a turbine wheel (14) provided on one end side of the rotating shaft, and on the other end side of the rotating shaft. The provided compressor wheel (16), a bearing housing (24) accommodating a bearing portion (18) that rotatably supports the rotating shaft, a turbine housing (20) accommodating the turbine wheel, and the bearing housing. A back plate that partitions the internal space (Si) defined between the turbine wheels along the axial direction of the rotating shaft, and forms a _{one-sided space (S 1) with the back surface (14a) of the turbine wheel.} _{At the same time, the back plate (40 (40a, 40b)) forming the other side space (S 2} ) with the bearing housing and the compressed gas (g) compressed by the compressor wheel are extracted, and the other side is extracted. A cooling gas passage (42 (42a, 42b)) having an outlet-side opening (46) communicating with the space is provided.

According to such a configuration, the turbine wheel can be cooled and its life can be suppressed by introducing the compressed gas compressed by the compressor wheel into the other side space and flowing it from the other side space into the one side space. .. Due to the pressure difference between the compression side passage of the compressor wheel and the internal space, it is easy to introduce the compressed gas compressed by the compressor wheel into the other space.

2) The turbocharger according to another aspect is the turbocharger according to 1), and the back plate has a plurality of first through holes (50) arranged discretely.

According to such a configuration, the compressed gas ejected from the plurality of first through holes toward the back surface of the turbine wheel collides with the back surface, and so-called jet cooling (impingement cooling) becomes possible. In this way, the cooling effect of the turbine wheel can be improved.

3) The turbocharger according to still another aspect is the turbocharger according to 1) or 2), and the compressed gas can flow between the inner peripheral end surface (68) of the back plate and the bearing housing. A gap (c2) is formed.

According to such a configuration, the compressed gas supplied to the other side space flows into the one side space through the gap formed between the inner peripheral end surface of the back plate and the bearing housing, so that the turbine wheel can be cooled. ..

4) The turbocharger according to still another aspect is the turbocharger according to any one of 1) to 3), and the cooling gas passage is on the outlet side of the diffuser flow path (34) accommodating the compressor wheel. It has an inlet side opening (44) that communicates with the region.

According to such a configuration, since the inlet side opening of the cooling gas passage is opened in the outlet side region of the diffuser flow path, the compressed gas having a high pressure can be supplied to the other side space through the diffuser flow path. .. In this way, due to the pressure difference between the inlet side and the outlet side of the cooling gas passage, the compressed gas can be easily supplied to the internal space on the outlet side without requiring other power.

5) The turbocharger according to still another aspect is the turbocharger according to any one of 1) to 4), and the bearing housing has a second through hole extending along the axial direction of the rotating shaft. The second through hole (56) constitutes a part of the cooling gas passage.

According to such a configuration, a part of the cooling gas passage can be formed inside the bearing housing, so that the space for arranging the cooling gas passage can be reduced outside the bearing housing.

6) The turbocharger according to still another aspect is the turbocharger according to any one of 1) to 4), and includes a compressor housing (22) accommodating the compressor wheel, the compressor housing, and the bearing housing. An external pipe (60) provided between the two is further provided, and the external pipe constitutes a part of the cooling gas passage.

According to such a configuration, since a part of the cooling gas passage can be formed by the external piping, the formation of the cooling gas passage becomes relatively easy.

7) The turbocharger according to still another aspect is the turbocharger according to any one of 1) to 6), and one surface (41) of the back plate facing the other side space is the turbine wheel. It is configured so that the emissivity is higher than that of the back surface.

The temperature of the back plate rises when it absorbs thermal radiation, and decreases when it radiates. According to the above configuration, the surface of the back plate facing the outlet side opening of the cooling gas passage communicating with the internal space has a higher emissivity than the back surface of the turbine wheel, so that one surface of the back plate facing the other side space is The temperature is lower than the back of the turbine wheel. As a result, the cooling effect of the compressed gas in contact with the one surface when passing through the space on the other side can be enhanced, so that the temperature of the turbine wheel can be reduced.

8) The turbocharger according to still another aspect is the turbocharger according to any one of 1) to 7), and the turbine wheel is the turbine from an inlet side opening formed on the back surface of the turbine wheel. It has a third through hole (80) extending into the outlet side opening (80b) formed on the boss surface (74a) of the wheel.

According to such a configuration, the turbine wheel can be effectively cooled by supplying the compressed gas to the third through hole.

9) The turbocharger according to still another aspect is the turbocharger according to any one of 1) to 7), and the turbine wheel is the turbine from an inlet side opening formed on the back surface of the turbine wheel. It has a fourth through hole (90) extending into the outlet side opening (90b) formed on the hub surface (92) of the wheel.

According to such a configuration, the compressed gas supplied to the fourth through hole is ejected from the hub surface of the turbine wheel and flows along the hub surface along with the exhaust gas flowing toward the turbine outlet side. , The hub surface can be film-cooled. This makes it possible to enhance the cooling effect of the turbine wheel.

10 (10a, 10B) Turbocharger 12 Rotating shaft 12a Small diameter 14 Turbine wheel 14a Back surface 16 Compressor wheel 18 Bearing 18a Square 20 Turbine housing 20a Square 22 Compressor housing 24 Bearing housing 24a Corner 26 Exhaust

gas flow path

28, 30 Blade 32 Inlet opening 34 Diffuser flow path 36 Scroll flow path 40 (40a, 40b) Back plate 41 Surface 42 (42a, 42b), 62, 64 Cooling gas passage 44 Inlet side opening 46 Outlet side opening 48 Cooling water space 50 1st Through hole 52 Virtual square 54 Cooled surface 56 Second through hole 60 External piping 66 Check valve 68 Inner peripheral end surface 70 Outer peripheral end 72 Bent 74 Boss 74a Boss end surface 80 Third through hole 80a Inlet side opening 80b Exit side Opening 90 4th through hole 90a Entrance side opening 90b Exit side opening 92 Hub surface CA Axis Si Internal space S ₁ space (one side space)
S ₂ space (space on the other side)
c1, c2 Gap e Exhaust gas g Compressed gas

Claims

Rotation axis and
A turbine wheel provided on one end side of the rotating shaft and
A compressor wheel provided on the other end side of the rotating shaft and
A bearing housing that houses a bearing that rotatably supports the rotating shaft,
A back plate that partitions an internal space defined between a turbine housing accommodating the turbine wheel and the bearing housing along the axial direction of the rotating shaft, and is a one-sided space between the back surface of the turbine wheel. And a back plate that forms a space on the other side with the bearing housing.
A cooling gas passage having an outlet side opening that draws out the compressed gas compressed by the compressor wheel and communicates with the other side space.
To prepare
Turbocharger.
The back plate has a plurality of discretely arranged first through holes.
The turbocharger according to claim 1.
A gap through which the compressed gas can flow is formed between the inner peripheral end surface of the back plate and the bearing housing.
The turbocharger according to claim 1 or 2.
The cooling gas passage has an inlet side opening communicating with an outlet side region of the diffuser flow path accommodating the compressor wheel.
The turbocharger according to any one of claims 1 to 3.
The bearing housing has a second through hole extending along the axial direction of the rotating shaft.
The second through hole constitutes a part of the cooling gas passage.
The turbocharger according to any one of claims 1 to 4.
The compressor housing that houses the compressor wheel and
An external pipe provided between the compressor housing and the bearing housing,
With more
The external pipe constitutes a part of the cooling gas passage.
The turbocharger according to any one of claims 1 to 4.
One surface of the back plate facing the other side space is configured to have a higher emissivity than the back surface of the turbine wheel.
The turbocharger according to any one of claims 1 to 6.
Any of claims 1 to 7, wherein the turbine wheel has a third through hole extending from an inlet side opening formed on the back surface of the turbine wheel to an outlet side opening formed on a boss surface of the turbine wheel. The turbocharger described in item 1.
The turbine wheel has a fourth through hole extending from an inlet side opening formed on the back surface of the turbine wheel to an outlet side opening formed on the hub surface of the turbine wheel.
The turbocharger according to any one of claims 1 to 7.