Variable capacity turbocharger

Abstract

Variable capacity turbocharger (1) comprising the following: a turbine impeller (6); a housing (8) that contains the turbine impeller (6); and a variable nozzle unit (25) which is housed in the casing (8), wherein the variable nozzle unit (25) has a nozzle vane (23) arranged at a passage of a gas introduced into the turbine impeller (6), a nozzle ring (31) rotatably supporting the nozzle vane (23), and a drive unit (26) arranged opposite to the nozzle vane (23), wherein the nozzle ring (31) is arranged between the drive unit (26) and the nozzle vane (23), and which rotates the nozzle vane (23), the housing (8) has a drive chamber (40) which houses the drive unit (26) and a fluid passage (44) which is connected to the drive chamber (40), the drive chamber (40) has an inner circumferential surface (42) facing an outer circumferential section (27a) of the drive unit (26), and a surface roughness of a passage surface (44a) of the liquid passage (44) is greater than a surface roughness of at least one region of the facing inner circumferential surface (42), wherein the region is connected to the liquid passage (44).

Description

Technical field

[0001] The present disclosure relates to a variable-capacity turbocharger. State of the art

[0002] A variable-capacity turbocharger with a variable nozzle unit is known. The variable nozzle unit has nozzle vanes that regulate the flow of a gas passing through a turbine impeller, and a drive unit that drives the nozzle vanes. The nozzle vanes are rotatably mounted on a nozzle ring via nozzle shafts, and the drive unit drives the nozzle vanes by rotating the nozzle shafts. The housing of the variable-capacity turbocharger includes a drive chamber that houses the drive unit. In a case, for example, where the variable-capacity turbocharger is used in a cold region, there is a possibility that if moisture in the gas inside the drive chamber stagnates and freezes, the movement of the drive unit will be impeded. Therefore, a variable-capacity turbocharger is known in which a drain hole, etc., is provided.a variable-capacity turbocharger is provided in a lower section of a drive chamber (see JP 2006 - 177 318 A, JP 2009 - 74 492 A, JP 2009 - 228 450 A, JP 2012 - 102 660 A and JP 2015 - 63 944 A). Another variable-capacity turbocharger is known from JP 2005 - 331 410 A. However, the cited prior art does not disclose the feature of claim 1, namely that the surface roughness of a fluid passage area is greater than the surface roughness of at least one region of the facing inner circumferential surface, wherein the region is connected to the fluid passage. Summary of the invention: Technical problem

[0003] However, the hole, etc., provided in the drive chamber may easily become a narrow region due to its relationship with other structural components, and in such a case there is a possibility that the effect of sufficient fluid discharge cannot be achieved and the movement of the drive unit may be hindered by the freezing of moisture.

[0004] The present disclosure provides for a variable-capacity turbocharger that can improve the discharge behavior of liquid, such as water, inside a drive chamber. Solution to the problem

[0005] According to one aspect of the present disclosure, a variable-capacity turbocharger is provided, comprising: a turbine impeller; a housing that accommodates the turbine impeller; and a variable nozzle assembly housed within the housing. The variable nozzle assembly has a nozzle vane arranged at a passage for gas introduced into the turbine impeller, a nozzle ring that rotatably supports the nozzle vane, and a drive unit arranged opposite the nozzle vane, with the nozzle ring positioned between the drive unit and the nozzle vane, and which rotates the nozzle vane. The housing has a drive chamber that accommodates the drive unit and a fluid passage that communicates with the drive chamber.The drive chamber has an inner circumferential surface facing an outer circumferential section of the drive unit, and a surface roughness of a passage surface of the fluid passage is greater than a surface roughness of at least one region of the inner circumferential surface facing it, wherein the region is connected to the fluid passage.

[0006] The variable-capacity turbocharger has a drive chamber that houses the actuator, and the drive chamber has an inner circumferential surface facing the outer circumferential section of the actuator. Fluid, such as water, contained in the gas inside the drive chamber is likely to stagnate on this inner circumferential surface. The housing is provided with a fluid passage that connects to the drive chamber to discharge the fluid. Therefore, by mounting the variable-capacity turbocharger in a vehicle, etc., such that the region of the inner circumferential surface becomes a lower section in a vertical direction, with this region connected to the fluid passage, the fluid generated inside the drive chamber can be discharged through this passage.Furthermore, the surface roughness of the fluid passage area is greater than the surface roughness of the region of the facing inner circumferential surface connected to the fluid passage. The housing of the variable-capacity turbocharger is made of metal, and one surface of the housing, at least the facing inner circumferential surface of the drive chamber and the fluid passage area, essentially form hydrophilic surfaces. In the case of a hydrophilic surface, the greater the surface roughness, the smaller the contact angle of a water droplet becomes, and the more easily the water droplet passes through narrow gaps. Even if the fluid stagnates at the facing inner circumferential surface, it is easily diverted to a fluid passage side with a high surface roughness, and the fluid discharge behavior can be improved.

[0007] In some aspects, at least part of the fluid passage area can be flush with the facing inner circumferential surface. If sections are provided that are flush with each other without a step between the fluid passage area and the facing inner circumferential surface, it is less likely that an incident will occur where the fluid remains due to a step, and the fluid discharge behavior can be improved.

[0008] In some aspects, the housing may have a screw passage formed around the turbine impeller. The fluid passage may be designed to allow a connection between the screw passage and the drive chamber. Since the fluid delivered to the screw passage quickly evaporates and disappears due to the driving of the turbine impeller, the fluid delivery behavior can be improved.

[0009] In some aspects, the housing may have an inner wall section located between the drive chamber and the screw passage, overlapping an outer circumferential section of the nozzle ring. This outer circumferential section of the nozzle ring may be provided with a pressure relief port to reduce the pressure differential between the drive chamber and the screw passage. The fluid passage in the inner wall section may be configured such that at least a portion of it overlaps the pressure relief port. By ensuring that at least a portion of the fluid passage overlaps the pressure relief port, it becomes easier to widen the region where the fluid passage communicates with the drive chamber while avoiding the nozzle ring, and the fluid dispensing characteristics can be improved.

[0010] In some aspects, the fluid passages can be provided at least at two points in a circumferential direction along one direction of rotation of the turbine impeller, and a phase angle between one fluid passage and the other fluid passage can be between 8° and 23°. Even if, for example, a vehicle, etc., in which the variable-capacity turbocharger is mounted, is stopped on an incline, the fluid that stagnates inside the drive chamber is easily discharged from one of the fluid passages, and the discharge characteristics of the fluid can be improved.

[0011] In some aspects, the passage surface of the liquid and the facing inner circumferential surface can be hydrophilic surfaces.

[0012] In some aspects, the compensating holes can be provided at a multitude of locations in a circumferential direction of the nozzle ring, and the multitude of compensating holes can be provided at equal intervals in the circumferential direction of the nozzle ring.

[0013] In some aspects, the cross-sectional area of ​​the liquid passage can be designed such that the entire width of the cross-sectional area of ​​the liquid passage fits into a cross-sectional area of ​​the compensating hole in a circumferential direction of the nozzle ring. Advantageous effects of the invention

[0014] According to the present invention, the dispensing behavior of the liquid inside the drive chamber can be improved. Brief description of the drawings Fig. Figure 1 is a cross-sectional view showing an example of a variable capacity turbocharger according to an embodiment. Fig. 2 is an enlarged view of a region, which is identified by reference sign A in Fig. is marked with 1. Fig. 3 is a cross-sectional view along a line III-III in Fig. 2. Fig. 4 is a cross-sectional view along a line IV-IV in Fig. 3. Fig. Figure 5 is a descriptive view that schematically shows the contact angle of a water droplet and the shape of the water droplet, where Fig. 5(a) is a view that schematically shows a relationship between the water droplet on a flat surface and the contact angle, Fig. 5(b) is a view to describe a relationship between the contact angle and the shape of the water droplet in the case of a hydrophilic surface, and Fig. 5(c) is a view to describe a relationship between the contact angle and the shape of the water droplet in the case of a hydrophobic surface. Fig. Figure 6 schematically shows a relationship between the inclination of a vehicle, etc., in which the variable capacity turbocharger is mounted, and the positions of the exhaust ports, wherein Fig. 6(a) is a descriptive view showing the arrangement of the derivative passage according to the embodiment, and Fig. 6(b) is a descriptive view showing the arrangement of the derivation passes according to a comparative embodiment. Description of exemplary implementations

[0015] An example of an embodiment of the present disclosure is described below with reference to the drawings. It should be noted that in the description of the drawings, the same reference numerals are assigned to the same elements, and duplicate descriptions have been omitted.

[0016] A variable-capacity turbocharger 1 according to an exemplary embodiment (see Fig. 1) is applied, for example, to internal combustion engines for ships or vehicles. As in Fig. As shown in Figure 1, the variable-capacity turbocharger 1 has a turbine 2 and a compressor 3. The turbine 2 has a turbine housing 4 and a turbine impeller 6, which is housed in the turbine housing 4. The turbine housing 4 has a worm gear passage 16 that extends circumferentially around the turbine impeller 6 (direction of rotation of the turbine impeller 6). The compressor 3 has a compressor housing 5 and a compressor impeller 7, which is housed in the compressor housing 5. The compressor housing 5 has a worm gear passage 17 that extends circumferentially around the compressor impeller 7 (direction of rotation of the compressor impeller 7).

[0017] The turbine impeller 6 is provided at one end of a rotating shaft 14, and the compressor impeller 7 is provided at the other end of the rotating shaft 14. A bearing housing 13 is provided between the turbine housing 4 and the compressor housing 5. The rotating shaft 14 is rotatably supported by a bearing 15 through the bearing housing 13, and the rotating shaft 14, the turbine impeller 6, and the compressor impeller 7 rotate about an axis of rotation H as a single, rotatable body 12. A housing 8 of the variable-capacity turbocharger 1 according to the present embodiment comprises the turbine housing 4, the bearing housing 13, and the compressor housing 5.

[0018] The turbine housing 4 is provided with an exhaust gas inlet (not shown) and an exhaust gas outlet 10. Exhaust gas emitted by an internal combustion engine (not shown) flows into the turbine housing 4 through the exhaust gas inlet, flows into the turbine impeller 6 through the screw passage 16, and rotates the turbine impeller 6. The exhaust gas then flows out to the outside of the turbine housing 4 through the exhaust gas outlet 10.

[0019] The compressor housing 5 is provided with an intake port 9 and a discharge port (not shown). When the turbine impeller 6 rotates as described above, the compressor impeller 7 rotates via the drive shaft 14. The rotating compressor impeller 7 draws in ambient air through the intake port 9, compresses the intake air, and discharges the compressed air from the discharge port through the screw passage 17. The compressed air discharged from the discharge port is supplied to the internal combustion engine described above.

[0020] Turbine 2 is described. Turbine 2 is a variable-capacity turbine and has a gas inlet passage 21 that connects the screw passage 16 and the turbine runner 6. The gas inlet passage 21 is a passage for the exhaust gas that is introduced into the turbine runner 6. A plurality of movable nozzle vanes 23 are arranged at the gas inlet passage 21. The plurality of nozzle vanes 23 are arranged around a circumference with the axis of rotation H as its center, and each nozzle vane 23 rotates about an axis parallel to the axis of rotation H. By rotating the nozzle vanes 23, the cross-sectional area of ​​the gas passage is optimally adjusted according to the flow rate of the exhaust gas that is introduced into Turbine 2. Turbine 2 has a variable nozzle assembly 25 as a drive mechanism for rotating the nozzle vanes 23.

[0021] The variable nozzle unit 25 is housed in the casing 8. Specifically, the variable nozzle unit 25 is fitted into the interior of the turbine casing 4 in a position where it is adjacent to the turbine impeller 6 and is sandwiched between the turbine casing 4 and the bearing casing 13 and fixed in place.

[0022] The variable nozzle unit 25 has the plurality of nozzle vanes 23 described above, and a first nozzle ring 31 (an example of a nozzle ring) and a second nozzle ring 32, between which the nozzle vanes 23 are arranged in one direction of the axis of rotation H. Each of the first nozzle ring 31 and the second nozzle ring 32 has an annular shape with the axis of rotation H as its center and is arranged to surround the turbine impeller 6 in the circumferential direction (direction of rotation of the turbine impeller 6). The first nozzle ring 31 and the second nozzle ring 32 are arranged to face each other with a predetermined gap held by a connecting pin 35. A region formed between the first nozzle ring 31 and the second nozzle ring 32 serves as the gas inlet passage 21. The second nozzle ring 32 is the screw passage 16 (see Fig. 1) facing the screw passage 16, and the second nozzle ring 32 forms part of an inner wall of the screw passage 16. A rotating shaft 23a from each of the nozzle vanes 23 passes through the first nozzle ring 31, and the first nozzle ring 31 supports each of the nozzle vanes 23 in a cantilevered manner. The nozzle vanes 23 according to the present embodiment are arranged at equal intervals around a circumference, but they can be arranged at unequal intervals. The first nozzle ring 31 is an example of a nozzle ring that rotatably supports the nozzle vanes 23.

[0023] The variable nozzle unit 25 has a drive unit 26 that rotates the nozzle vanes 23. The drive unit 26 is arranged opposite the nozzle vanes 23, with the first nozzle ring 31 positioned between them. The drive unit 26 has a drive ring 27, a plurality of nozzle connecting element plates 28, and a drive connecting element plate 29. The drive ring 27 is a component that transmits a force applied from the outside to the nozzle vanes 23 as a driving force to rotate the nozzle vanes 23. The drive ring 27 has an annular shape extending around a circumference with the axis of rotation H as its center. The drive ring 27 is attached to a support component that is fixed to the housing 8 and is supported by the support component to be rotatable about the axis of rotation H.

[0024] The plurality of nozzle connecting plates 28 are attached to the rotating shafts 23a of the respective nozzle vanes 23. The plurality of nozzle connecting plates 28 are arranged at equal intervals around a circumference inside the drive ring 37. The drive connecting plate 29 is arranged to be aligned with the nozzle connecting plates 28. The drive connecting plate 29 tilts (rotates) by receiving a driving force from the outside, and the drive ring 27 is rotated by the tilting. The plurality of nozzle connecting plates 28 rotate while following the rotation of the drive ring 27 and rotate the nozzle vanes 23 via the respective rotating shafts 23a. The drive connecting plate 29 and the drive ring 27 work together to rotate the nozzle connecting plates 28, and the nozzle connecting plates 28 are rotated by the rotation.

[0025] As in Fig. As shown in Figure 2, the housing 8 has a drive chamber 40 that contains the drive unit 26. The drive chamber 40 is located at the point of connection between the turbine housing 4 and the bearing housing 13 and has an inner wall surface 41 that surrounds the drive unit 26. The drive unit 26 has an outer circumferential section 27a. The outer circumferential section 27a is a section outside the rotating turbine impeller 6 in a centrifugal (radial) direction Da. For example, an outer circumferential end face of the drive ring 27 forms at least part of the outer circumferential section 27a. A region of the inner wall surface 41 that faces the outer circumferential section 27a of the drive unit 26 is an facing inner circumferential surface 42.For example, the facing inner circumferential surface 42 is an area of ​​a region where a fluid L, such as water, can stagnate when it is generated inside the drive chamber 40 in a state in which the variable capacity turbocharger 1 is installed such that the axis of rotation H of the turbine impeller 6 is horizontal.

[0026] The housing 8 has an inner wall section 43 located between the drive chamber 40 and the screw passage 16. The inner wall section 43 separates the drive chamber 40 and the screw passage 16 from each other in conjunction with the first nozzle ring 31. For example, the inner wall section 43 is located inside the turbine housing 4 and is designed to project inwards (in a direction opposite to the centrifugal direction Da) from the inner circumferential surface 42 facing the drive chamber 40. For example, the inner wall section 43 is a wall that is provided in an annular shape along the entire circumference of an outer circumferential section 31b of the first nozzle ring 31.

[0027] Here, a relationship between the outer circumferential section 31b of the first nozzle ring 31 and the inner wall section 43 is described. The first nozzle ring 31 has a main body section 31a that rotatably supports the nozzle vanes 23 (see Fig. 1), and the outer circumferential section 31b, which has a thin wall and extends outwards (in the centrifugal direction Da) from the main body section 31a in a flange shape. A stepped section 31c is formed between the main body section 31a and the outer circumferential section 31b. It should be noted that, for example, the stepped section 31c need not be provided, and the main body section 31a and the outer circumferential section 31b may be essentially continuous with each other with the same plate thickness.

[0028] The outer circumferential section 31b of the first nozzle ring 31 has a first side surface 43a on one side of the screw passage 16 and a second side surface 43b on one side of the drive chamber 40. The inner wall section 43 overlaps the first side surface 43a. At least part of the inner wall section 43 is arranged to fit into a gap formed by the step section 31c.

[0029] As in Fig. 2, Fig. 3 and Fig. As shown in Figure 4, the inner wall section 43 is provided with a drain passage 44 (an example of a liquid passage) that connects the drive chamber 40 to the screw passage 16. The drive passage 44 serves to discharge the liquid L, such as water, contained in the gas when the liquid L stagnates inside the drive chamber 40. The drain passage 44 can, for example, be designed to extend in the direction of the axis of rotation H. Designing the drain passage 44 to extend in the direction of the axis of rotation H simplifies manufacturing. Furthermore, the drain passage 44 can, for example, be designed to extend in a direction inclined relative to the direction of the axis of rotation H. Designing the drain passage 44 to be inclined relative to the direction of the axis of rotation H improves the discharge characteristics.For example, the drainage passage 44 can be inclined such that the other end section of the drainage passage 44 near the screw passage 16 is lower than an end section of this near the drive chamber 40.

[0030] For example, the derivation passage 44 is a groove, and a passage cross-section has a shape in which part of an outer edge is open, for example a semicircular shape or a U-shape.

[0031] For example, the derivation passage 44 is a through hole, and a through cross-section can have a shape in which the entirety of an outer edge is closed, and can be a circular shape, an elliptical shape, or any other shape.

[0032] For example, a portion of the passage area 44a of the drain passage 44 is flush with the facing inner circumferential surface 42 of the drive chamber 40. By providing the passage area 44a to be flush with the facing inner circumferential surface 42 of the drive chamber 40, the fluid L, which stagnates at the facing inner circumferential surface 42, is easily discharged through the drain passage 44. The passage area 44a of the drain passage 44 can, for example, be designed so as not to include a section that is flush with the facing inner circumferential surface 42.In this setup, a step is created between the passage surface 44a of the drainage passage 44 and the facing inner circumferential surface 42; however, if the liquid level of the liquid L (height from a lowest surface to the liquid level of the liquid L), which stagnates at the facing inner circumferential surface 42, rises and at least exceeds the step, the liquid L can be drained through the drainage passage 44.

[0033] A surface roughness of the passage surface 44a of the derivation passage 44 is greater than a surface roughness of at least one region 42a of the facing inner circumferential surface 42, wherein the region 42a is connected to the derivation passage 44 (see Fig. 4) It should be noted that in Fig. 4. The surface roughness is represented by points, with denser points indicating greater surface roughness. Furthermore, region 42a of the facing inner circumferential surface 42 refers to a region where an extension region of the drainage passage 44 overlaps the facing inner circumferential surface 42, with region 42a being connected to the drainage passage 44 and extending to one side of the facing inner circumferential surface 42. By setting the surface roughness of the passage area 44a of the drainage passage 44 to be greater than the surface roughness of the facing inner circumferential surface 42, the discharge behavior of the liquid L, which stagnates at the facing inner circumferential surface 42, can be improved. The discharge function is described in detail.

[0034] Fig. 5 is a view that shows a relationship between properties of a surface in contact with a water droplet La and a contact angle, where Fig. 5(a) is a view to describe the contact angle of the water droplet La on a flat (smooth) surface Sf. Furthermore, Fig. 5(b) a view which schematically shows a relationship between the contact angle and the shape of the water droplet La when a surface is a hydrophilic surface, and Fig. 5(c) is a view that schematically shows a relationship between the contact angle and the shape of the water droplet La when a surface is a hydrophobic surface. Fig. 5 denotes θ as a contact angle on the flat surface Sf and θw as a contact angle on a rough surface Sg, which has a greater surface roughness than the flat surface Sf. The contact angle θw of the rough surface Sg can be obtained by the following Wenzel equation (1). Here, r denotes a ratio of an actual area to an apparent area, “r = 1” refers to the flat surface Sf and “r > 1” means that the surface roughness is greater than that of the flat surface Sf. cosθw=rcosθ

[0035] As in Fig. As shown in Figure 5, in the case of a hydrophilic surface, the contact angle θ on the flat surface Sf is less than 90°, and the greater the surface roughness relative to the flat surface Sf, the smaller the contact angle θw becomes. Conversely, in the case of a hydrophobic surface, the contact angle θ on the flat surface Sf is greater than 90°, and the greater the surface roughness relative to the flat surface Sf, the larger the contact angle θw becomes. Here, the smaller the contact angle θw, the more easily the water droplet La penetrates narrow gaps, and the more the release behavior improves.

[0036] The variable-capacity turbocharger 1 is verified based on the preceding information. First, the housing 8 of the variable-capacity turbocharger 1 is made of metal, and one surface of the housing 8 forms a hydrophilic surface. Specifically, the greater the surface roughness, the smaller the contact angle, and the more easily the water droplet La penetrates narrow gaps. In the case of the variable-capacity turbocharger 1, the surface roughness of the through-surface 44a of the discharge passage 44 is greater than the surface roughness of region 42a of the facing inner circumferential surface 42, where region 42a is connected to the discharge passage 44.As a consequence, for example, the liquid L, which stagnates on the facing inner circumferential surface 42, is drawn in to move into the passage surface 44a of the drainage passage 44 and is discharged through the drainage passage 44 to the screw passage 16.

[0037] Next, a method for manufacturing the variable-capacity turbocharger 1 is described, in particular a method for forming the exhaust port 44 in the turbine housing 4. The turbine housing 4 can be made of, for example, ductile cast iron, Ni-Resist cast iron, a cast steel-based material, etc., depending on the exhaust gas temperature, and can be manufactured by applying a precision casting process such as a shell molding process or a cold-box process. The exhaust port 44 is formed, for example, by applying a cutting (drilling) process, etc., to the turbine housing 4, which has been manufactured by the above method.During cutting, the surface roughness of the passage surface 44a of the discharge passage 44 is adjusted to be greater than the surface roughness of the inner wall surface 41 of the drive chamber 40 of the turbine housing 4, in particular the surface roughness of the facing inner circumferential surface 42. Furthermore, after cutting has been carried out on the discharge passage 44, post-processing can also be performed to increase the surface roughness of the passage surface 44a of the discharge passage 44 relative to the surface roughness.

[0038] Furthermore, the entire turbine housing 4, including the discharge passage 44, can also be manufactured using a conventional casting process, etc. In this case, the surface roughness of the turbine housing 4 will be greater compared to the precision casting process. Therefore, machining or polishing can also be performed on the facing inner circumferential surface 42, while the passage surface 44a of the discharge passage 44 is left in its cast state. In fact, the machining or polishing can also be carried out in such a way that the surface roughness of the passage surface 44a of the discharge passage 44 is greater than the surface roughness of the facing inner circumferential surface 42.

[0039] Next, a compensating hole 33, which is formed in the first nozzle ring 31, is described with reference to Fig. 2 and Fig. The compensating hole 33 is a groove or through-hole that connects the drive chamber 40 and the screw passage 16. The compensating hole 33 serves to reduce the pressure differential that arises between the drive chamber 40 and the screw passage 16. Its function is described in more detail below.

[0040] The first nozzle ring 31 (see Fig. 1) is pressed against the bearing housing 13 via a disc spring 30a, a heat shield 30b, etc., and is held in a predetermined position. In this state, if the pressure inside the screw passage 16 becomes greater than the pressure inside the drive chamber 40 and the state is maintained, there is a possibility that the contact load of the disc spring 30a, which supports the first nozzle ring 31, becomes greater than necessary, and creep occurs in the disc spring 30a. Furthermore, there is a possibility that the nozzle vanes 23 displace in one direction towards the first nozzle ring 31. According to the inventors' empirical knowledge, the fluid behavior is better when the nozzle vanes 23 are arranged closer to the second nozzle ring 32 than to the first nozzle ring 31.Therefore, if the distance between the nozzle vanes 23 and the second nozzle ring 32 is greater than the distance between the nozzle vanes 23 and the first nozzle ring 31, there is a possibility that the performance will deteriorate. Here, by providing the compensating hole 33, the pressure difference generated between the drive chamber 40 and the screw passage 16 can be reduced, and as a result, both the occurrence of creep and the deterioration of performance can be suppressed.

[0041] The compensating holes 33 are provided, for example, at a plurality of locations arranged at equal intervals (the same phases) in the circumferential direction of the first nozzle ring 31. Specifically, the plurality of compensating holes 33 are provided at three locations with a phase of 120°. It should be noted that one compensating hole 33 may be provided, or the compensating holes 33 may be provided at a plurality of locations arranged at unequal intervals in the circumferential direction.

[0042] At least part of the drainage passage 44, which is provided in the inner wall section 43, is arranged to overlap the compensating hole 33 from the perspective in the direction of the axis of rotation H (see Fig. 3) For example, the cross-sectional area of ​​the discharge passage 44 has a semicircular shape with the arc located on a lower side, and the compensating hole 33 has a semicircular shape with the arc located on an upper side. For example, the discharge passage 44 overlaps the compensating hole 33 such that substantially the entire cross-sectional area of ​​the discharge passage 44 fits into the cross-sectional area of ​​the outlet hole 33, except for a portion of its lower section. Specifically, the discharge passage 44 overlaps the compensating hole 33 such that the entire width of the cross-sectional area of ​​the discharge passage 44, in the circumferential direction of the first nozzle ring 31, fits into the cross-sectional area of ​​the compensating hole 33.It should be noted that the meaning that at least part of the discharge passage 44 overlaps the compensating hole 33 can also be described as a state in which phases of the discharge passage 44 and the compensating hole 33 overlap with each other from the perspective of the direction of rotation of the turbine impeller 6. For example, a region of the cross-section of the compensating hole 33 is larger than a region of the through-cross-section of the discharge passage 44. For example, the region of the cross-section of the compensating hole 33 and the region of the through-cross-section of the discharge passage 44 may be the same, or the region of the through-cross-section of the discharge passage 44 may be larger than the region of the cross-section of the compensating hole 33.

[0043] Next, the arrangement of the discharge passage 44 around the axis of rotation H of the turbine impeller 6 is described with reference to Fig. 6 described. Fig. Figure 6(a) shows an example of arranging the derivative passage 44 according to the present embodiment. Fig. Figure 6(b) shows an example of the arrangement of the derivative passes 44A and 44B according to a modification embodiment.

[0044] A discharge passage 44 of the variable-capacity turbocharger 1 can be provided. If a vehicle, etc., in which the variable-capacity turbocharger 1 is installed, is tilted and stopped, as shown in Fig.As shown in Figure 6(a), the discharge port 44 is located at a position offset from a vertical axis. In this case, an alignment deviation of the discharge port 44 with respect to a lower endpoint Pa on the vertical axis can be represented, for example, by a rotation angle (phase angle) α1 about the axis of rotation H. The fluid L, which stagnates inside the drive chamber 40, is discharged from the discharge port 44 when a fluid level (depth height) h of the fluid L from the lower endpoint Pa reaches the discharge port 44. Here, if the distance from the axis of rotation H to the discharge port 44 is defined as r, the fluid level h at which the fluid L is discharged from the discharge port 44 is expressed by the following equation (2). h=r−rcosα1

[0045] Next, the derivation passes 44A and 44B are described according to the modification example. In the modification example, the derivation passes 44A and 44B are provided at a plurality of locations along the circumferential direction of the inner wall section 43. For example, in the modification example, the derivation passes 44A and 44B are provided at two locations. A vehicle, etc., in which the variable-capacity turbocharger 1 is mounted, is not limited to always stopping at a location without an incline, and there is a possibility that the vehicle, etc., will stop on a slope with a minimum gradient of approximately 15°. In this case, by providing the plurality of derivation passes 44A and 44B, one of the derivation passes 44A and 44B is brought closer to the lower endpoint Pa of the vertical axis.As a consequence, the stagnant fluid L can be discharged at a position where the fluid level h is as low as possible.

[0046] Furthermore, a relative positional relationship between the multiple derivative passes 44A and 44B can, for example, be represented by a rotation angle (phase angle) α2 about the axis of rotation H. Specifically, a first straight line Lx, formed by the axis of rotation H and one derivative pass 44A, and a second straight line Ly, formed by the axis of rotation H and the other derivative pass 44B, are assumed. Here, the angle formed by the first straight line Lx and the second straight line Ly, intersecting at the axis of rotation H, is the rotation angle α2 about the axis of rotation H. The rotation angle α2 can be set between 8° and 23°. Moreover, as described above, if one assumes the possibility of a vehicle coming to a stop on a slope with an incline of approximately 15°, it is desirable for the rotation angle α2 to be between 14° and 17°.

[0047] Next, the operating modes and effects of the variable-capacity turbocharger 1 are described. The variable-capacity turbocharger 1 has a drive chamber 40, which houses the drive unit 26, and the drive chamber 40 has an inner circumferential surface 42 facing the outer circumferential section 27a of the drive unit 26. The fluid L, such as water, contained in the gas inside the drive chamber 40, is likely to stagnate on the inner circumferential surface 42. The inner wall section 43 of the housing 8 is provided with a drain passage 44, which is connected to the drive chamber 40, to drain the fluid L. Therefore, by mounting the variable-capacity turbocharger 1 in a vehicle, etc.such that the region 42a of the facing inner circumferential surface 42 becomes a low section in a vertical direction, wherein the region 42a is connected to the drainage passage 44, the fluid L which is generated inside the drive chamber 40 is discharged from the drainage passage 44.

[0048] Furthermore, the surface roughness of the passage surface 44a of the drainage passage 44 is greater than the surface roughness of region 42a of the facing inner circumferential surface 42, where region 42a is connected to the drainage passage 44. The housing 8 is made of metal, and the facing inner circumferential surface 42 and the passage surface 44a of the drainage passage 44 essentially form hydrophilic surfaces. In the case of a hydrophilic surface, the greater the surface roughness, the smaller the contact angle of a water droplet becomes, and the more easily the water droplet passes through narrow gaps. Even if the liquid L stagnates at the facing inner circumferential surface 42, the liquid L is drawn in and easily discharged to one side of the drainage passage 44 with a high surface roughness, thus improving the discharge behavior of the liquid L.

[0049] By improving the discharge behavior of the fluid L, which stagnates inside the drive chamber 40, the fluid level of the fluid L can be lowered, even if the fluid L is stagnant. As a consequence, even if, for example, a vehicle etc. in which the variable-capacity turbocharger 1 is installed is stopped in a cold region and the fluid L inside the drive chamber 40 freezes, it is possible to reduce the risk of freezing hindering the operation of the drive unit 26, especially during start-up of the drive unit 26.

[0050] Furthermore, at least a portion of the passage area 44a of the drainage passage 44 is flush with the adjacent inner circumferential surface 42. Specifically, sections are provided that are flush with each other without a step between the passage area 44a of the drainage passage 44 and the adjacent inner circumferential surface 42, and the liquid L is easily drained through these sections. As a consequence, an incident where the liquid L remains due to a step is less likely to occur, and the discharge behavior of the liquid L can be improved.

[0051] Furthermore, the discharge passage 44 is designed to allow a connection between the screw passage 16 and the drive chamber 40, and the liquid L that has passed through the discharge passage 44 is discharged to the screw passage 16. The liquid L discharged to the screw passage 16 evaporates rapidly and disappears due to the driving of the turbine impeller 6. As a result, the discharge characteristics of the liquid L can be improved.

[0052] Furthermore, the variable-capacity turbocharger 1 has the balancing holes 33 provided in the first nozzle ring 31. At least part of the discharge passage 44 is designed to overlap the balancing hole 33. As a result, widening of the region where the discharge passage 44 connects to the drive chamber 40, while avoiding the first nozzle ring 31, is facilitated, and the delivery characteristics of the fluid L can be improved.

[0053] Furthermore, the compensating holes 33 serve to reduce the pressure differential between the drive chamber 40 and the screw passage 16. However, if the area of ​​the compensating holes 33 is increased, there is a possibility that maintaining pressure inside the screw passage 16 will become unstable. Therefore, it is important to design the compensating holes 33 with suitable dimensions. Here, if the drain passage 44 is provided to allow a connection between the screw passage 16 and the drive chamber 40, the design of the compensating holes 33 must be carefully considered, also taking into account the influence of the drain passage 44. However, in the variable-capacity turbocharger 1, at least part of the drain passage 44 is arranged to overlap the compensating hole 33.Therefore, in comparison to a design in which the drainage passage 44 is formed independently of the compensating holes 33, the influence of the drainage passage 44 is also smaller, and the suitable formation of the compensating holes 33 becomes easier.

[0054] Furthermore, the variable-capacity turbocharger 1, according to the modification example, has two discharge ports 44A and 44B, and the rotation angle (phase angle) α2 between one discharge port 44A and the other discharge port 44B is between 8° and 23°. As a consequence, even if, for example, a vehicle, etc., in which the variable-capacity turbocharger 1 is mounted, is stopped on an incline, the fluid L, such as water, which stagnates inside the drive chamber 40, is easily discharged from one of the discharge ports 44A, 44B, and the discharge behavior of the fluid L can be improved.

[0055] The designs of the exemplary embodiments can be combined and used within the scope of the patent claims as is appropriate. Reference symbol list 1 variable capacity turbocharger 8 cases 6 Turbine wheel 16 snail passages 21 Gas inlet passage 23 nozzle blades 25 variable nozzle unit 26 Drive unit 27 Drive ring 27a Outer circumferential section 31 first nozzle ring (nozzle ring) 33 Compensation hole 40 Drive chamber 42 facing inner circumferential surface 43 inner wall section 44. Derivative pass (liquid pass) 44a Passage area 42a Region, which is connected to the drainage passage 44A Derivative passage 44B Derivative passage H axis of rotation L liquid

Claims

[1] Variable capacity turbocharger (1) comprising the following: a turbine impeller (6); a housing (8) that contains the turbine impeller (6); and a variable nozzle unit (25) which is housed in the casing (8), wherein the variable nozzle unit (25) has a nozzle vane (23) arranged at a passage of a gas introduced into the turbine impeller (6), a nozzle ring (31) rotatably supporting the nozzle vane (23), and a drive unit (26) arranged opposite to the nozzle vane (23), wherein the nozzle ring (31) is arranged between the drive unit (26) and the nozzle vane (23), and which rotates the nozzle vane (23), the housing (8) has a drive chamber (40) which houses the drive unit (26) and a fluid passage (44) which is connected to the drive chamber (40), the drive chamber (40) has an inner circumferential surface (42) facing an outer circumferential section (27a) of the drive unit (26), and a surface roughness of a passage surface (44a) of the liquid passage (44) is greater than a surface roughness of at least one region of the facing inner circumferential surface (42), wherein the region is connected to the liquid passage (44). [2] Turbocharger (1) with variable capacity according to claim 1, wherein at least a part of the passage area (44a) of the fluid passage (44) is continued flush with the facing inner circumferential surface (42). [3] Turbocharger (1) with variable capacity according to claim 1 or 2, wherein the housing (8) further has a screw passage (16) which is formed around the turbine impeller (6), and the liquid passage (44) is designed to allow a connection between the screw passage (16) and the drive chamber (40). [4] Turbocharger (1) with variable capacity according to claim 3, wherein the housing (8) has an inner wall section (43) which is provided between the drive chamber (40) and the screw passage (16) and overlaps an outer circumferential section (31b) of the nozzle ring (31), the outer circumferential section (31b) of the nozzle ring (31) is provided with a compensating hole (33) which reduces a pressure difference between the drive chamber (40) and the screw passage (16), and the liquid passage (44) in the inner wall section (43) is provided such that at least part of the liquid passage (44) overlaps the equalization hole (33). [5] Turbocharger (1) with variable capacity according to any one of claims 1 to 4, wherein the fluid passages (44) are provided at least at two points in a circumferential direction along a direction of rotation of the turbine impeller (6), and a phase angle between one liquid passage (44) and the other liquid passage (44) is between 8° and 23°. [6] Turbocharger (1) with variable capacity according to any one of claims 1 to 5, wherein the passage area (44a) of the fluid passage (44) and the facing inner circumferential surface (42) are hydrophilic surfaces. [7] Turbocharger (1) with variable capacity according to claim 4, wherein the compensating holes (33) are provided at a plurality of locations in a circumferential direction of the nozzle ring (31). [8] Turbocharger (1) with variable capacity according to claim 7, wherein the plurality of compensating holes (33) are provided at equal intervals in the circumferential direction of the nozzle ring (31). [9] Turbocharger (1) with variable capacity according to claim 4, wherein a flow cross-section of the fluid passage (44) is provided such that an entire width of the flow cross-section of the fluid passage (44) in a circumferential direction of the nozzle ring (31) fits into a flow cross-section of the compensating hole (33). [10] Turbocharger (1) with variable capacity according to one of claims 1 to 9, wherein the fluid passage (44) extends in a rotational axis direction of the turbine impeller (6). [11] Turbocharger (1) with variable capacity according to one of claims 1 to 4, wherein the fluid passages (44) are provided at least at two points in a circumferential direction along a direction of rotation of the turbine impeller (6), and wherein both fluid passages (44) extend in a direction of rotation of the turbine impeller (6). [12] Turbocharger (1) with variable capacity according to any one of claims 1 to 4, wherein the fluid passages (44) are provided at least at two locations in a circumferential direction along a direction of rotation of the turbine impeller (6), and wherein a phase angle between one fluid passage (44) and the other fluid passage (44) is between 14° and 17°.

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