Variable displacement supercharger

Abstract

A variable capacity type supercharger includes a turbine wheel, a housing that houses the turbine wheel, and a variable nozzle unit that is housed in the housing, the variable nozzle unit including nozzle vanes that are disposed on a flow path of gas that is introduced to the turbine wheel, a nozzle ring that supports the nozzle vanes so as to be rotatable, and a drive section that is disposed on an opposite side from the nozzle vanes via the nozzle ring and rotates the nozzle vanes, the housing including a drive chamber that houses the drive section and a liquid flow path that is in communication with the drive chamber, the drive chamber including an inner peripheral opposing surface that opposes an outer peripheral portion of the drive section, and a surface roughness of a flow path surface of the liquid flow path is greater than a surface roughness of at least a region of the inner peripheral opposing surface that is connected to the liquid flow path.

Description

Technical Field

[0001] This disclosure relates to variable capacity turbochargers. Background Technology

[0002] A variable-capacity turbocharger with a variable nozzle unit is known. The variable nozzle unit includes: nozzle blades that adjust the flow of gas through a turbine impeller; and a drive unit that drives the nozzle blades. The nozzle blades are rotatably mounted on a nozzle ring via a nozzle shaft, and the drive unit drives the nozzle blades by rotating the nozzle shaft. A drive chamber for housing the drive unit is provided in the housing of the variable-capacity turbocharger. For example, when using a variable-capacity turbocharger in a cold region, if moisture in the gas inside the drive chamber becomes trapped and freezes, it may hinder the operation of the drive unit. Therefore, a variable-capacity turbocharger with a drainage hole or the like provided in the lower part of the drive chamber is known (see Japanese Patent Application Publication Nos. 2006-177318, 2009-74492, 2009-228450, 2012-102660, and 2015-63944).

[0003] Patent Document 1: Japanese Patent Application Publication No. 2006-177318

[0004] Patent Document 2: Japanese Patent Application Publication No. 2009-74492

[0005] Patent Document 3: Japanese Patent Application Publication No. 2009-228450

[0006] Patent Document 4: Japanese Patent Application Publication No. 2012-102660

[0007] Patent Document 5: Japanese Patent Application Publication No. 2015-63944

[0008] However, the holes and other openings in the drive chamber can easily become narrow areas due to their relationship with other structural components. In such cases, the liquid cannot be adequately drained, and the operation of the drive unit may be hindered by the freezing of water. Summary of the Invention

[0009] This disclosure provides a variable capacity booster that can improve the discharge of liquids such as water from the drive chamber.

[0010] One aspect of the variable capacity turbocharger disclosed herein includes: a turbine impeller; a housing housing the turbine impeller; and a variable nozzle unit housed within the housing. The variable nozzle unit includes: nozzle blades disposed in a flow path of gas introduced into the turbine impeller; a nozzle ring supporting the nozzle blades for rotation; and a drive unit disposed across the nozzle ring on the side opposite to the nozzle blades, causing the nozzle blades to rotate. The housing includes: a drive chamber housing the drive unit, and a liquid flow path communicating with the drive chamber. The drive chamber has an inner peripheral opposing surface opposite to the outer periphery of the drive unit, the surface roughness of the liquid flow path being greater than the surface roughness of at least the area of ​​the inner peripheral opposing surface connected to the liquid flow path.

[0011] The aforementioned variable capacity turbocharger includes a drive chamber housing the drive unit, and the drive chamber has an inner peripheral opposing surface opposite the outer periphery of the drive unit. Liquids such as water contained in the gas inside the drive chamber tend to accumulate on the inner peripheral opposing surface. A liquid flow path communicating with the drive chamber is provided in the housing to discharge this liquid. Therefore, by mounting the variable capacity turbocharger in a vehicle or the like with the area in the inner peripheral opposing surface connected to the liquid flow path being the lower part in the vertical direction, liquid generated in the drive chamber can be discharged from the liquid flow path. Furthermore, the surface roughness of the flow path of the liquid flow path is greater than the surface roughness of the area in the inner peripheral opposing surface connected to the liquid flow path. The housing of the variable capacity turbocharger is made of metal, and the surface of the housing, at least the inner peripheral opposing surface of the drive chamber and the flow path of the liquid flow path, substantially form a hydrophilic surface. In the case of a hydrophilic surface, the contact angle of water droplets decreases due to the large surface roughness, making it easier for water droplets to pass through narrow gaps. That is, even if the liquid remains on the inner circumferential opposing surface, the liquid can easily be discharged to the liquid flow path side with a larger surface roughness, which can improve the discharge performance of the liquid.

[0012] In some embodiments, at least a portion of the flow path of the liquid flow path may be flush and continuous with the inner circumferential opposing surface. If a continuous, flush portion without any step difference is provided between the flow path of the liquid flow path and the inner circumferential opposing surface, it is difficult to generate liquid residue caused by step difference, thereby improving liquid discharge performance.

[0013] In some embodiments, the casing may have a vortex flow path formed around the turbine impeller. Alternatively, the liquid flow path may be configured to connect the vortex flow path to the drive chamber. Liquid discharged into the vortex flow path is rapidly evaporated or eliminated by the drive of the turbine impeller, thus improving liquid discharge performance.

[0014] In some embodiments, the housing may have an inner wall portion disposed between the drive chamber and the vortex flow path and overlapping the outer periphery of the nozzle ring. Alternatively, a balancing hole may be provided on the outer periphery of the nozzle ring to reduce the pressure difference between the drive chamber and the vortex flow path. Alternatively, a liquid flow path may be provided on the inner wall portion, at least partially overlapping the balancing hole. If at least a portion of the liquid flow path overlaps with the balancing hole, the liquid flow path can avoid the nozzle ring and easily expand the area communicating with the drive chamber, thus improving liquid discharge performance.

[0015] In some embodiments, the liquid flow path may be provided at at least two locations circumferentially along the rotation direction of the turbine impeller, with a phase angle between one liquid flow path and the other liquid flow path being 8° or more and 23° or less. Even when a vehicle equipped with a variable capacity turbocharger is parked, for example, on a sloped surface, the liquid retained in the drive chamber can be easily discharged from either liquid flow path, thereby improving liquid discharge performance.

[0016] In some configurations, the flow path and the inner circumferential opposing surface of the liquid flow path can be hydrophilic.

[0017] In some embodiments, the balancing holes may be located at multiple positions around the nozzle ring, or multiple balancing holes may be arranged at equal intervals around the nozzle ring.

[0018] In some embodiments, the flow path cross-section of the liquid flow path can be set such that the entire area of ​​the circumferential width of the nozzle ring is contained within the flow path cross-section of the balancing orifice.

[0019] According to the present invention, the drainage of liquid in the drive chamber can be improved. Attached Figure Description

[0020] Figure 1 This is a cross-sectional view showing an example of a variable capacity turbocharger implemented in this way.

[0021] Figure 2 It is Figure 1 An enlarged view of the area indicated by reference numeral A in the attached figure.

[0022] Figure 3 It is along Figure 2 A cross-sectional view along line III-III.

[0023] Figure 4 It is along Figure 3 The attached diagram for the IV-IV line.

[0024] Figure 5These are schematic diagrams illustrating the contact angle and shape of a water droplet. (a) is a schematic diagram illustrating the relationship between the contact angle and the water droplet on a flat surface. (b) is a diagram illustrating the relationship between the contact angle and the shape of the water droplet on a hydrophilic surface. (c) is a diagram illustrating the relationship between the contact angle and the shape of the water droplet on a hydrophobic surface.

[0025] Figure 6 The diagrams schematically illustrate the relationship between the tilt of a vehicle equipped with a variable capacity turbocharger and the position of the drainage path. Figure (a) is an explanatory diagram showing the configuration of the drainage path in the embodiment, and Figure (b) is an explanatory diagram showing the configuration of the drainage path in the comparative embodiment. Detailed Implementation

[0026] Hereinafter, an example of an embodiment of the present disclosure will be described with reference to the accompanying drawings. Furthermore, in the description of the drawings, the same elements are labeled with the same reference numerals, and repeated descriptions are omitted.

[0027] Variable capacity turbocharger 1 of the embodiment (refer to) Figure 1 For example, internal combustion engines used in ships and vehicles. Figure 1 As shown, the variable capacity turbocharger 1 includes a turbine 2 and a compressor 3. The turbine 2 includes a turbine housing 4 and a turbine impeller 6 housed within the turbine housing 4. The turbine housing 4 has a vortex flow path 16 extending circumferentially (in the direction of rotation of the turbine impeller 6) around the turbine impeller 6. The compressor 3 includes a compressor housing 5 and a compressor impeller 7 housed within the compressor housing 5. The compressor housing 5 has a vortex flow path 17 extending circumferentially (in the direction of rotation of the compressor impeller 7) around the compressor impeller 7.

[0028] A turbine impeller 6 is disposed at one end of the rotating shaft 14, and a compressor impeller 7 is disposed at the other end of the rotating shaft 14. A bearing housing 13 is disposed between the turbine housing 4 and the compressor housing 5. The rotating shaft 14 is rotatably supported on the bearing housing 13 via a bearing 15, and the rotating shaft 14, turbine impeller 6, and compressor impeller 7 rotate as a single rotating body 12 about the rotation axis H. The housing 8 of the variable capacity turbocharger 1 in this embodiment is configured to include a turbine housing 4, a bearing housing 13, and a compressor housing 5.

[0029] The turbine housing 4 is provided with an exhaust gas inlet (not shown) and an exhaust gas outlet 10. The exhaust gas discharged from the internal combustion engine (not shown) flows into the turbine housing 4 through the exhaust gas inlet, and then flows into the turbine impeller 6 through the vortex flow path 16, thereby causing the turbine impeller 6 to rotate. Afterwards, the exhaust gas flows out of the turbine housing 4 through the exhaust gas outlet 10.

[0030] The compressor housing 5 is provided with an intake port 9 and an outlet port (not shown). As described above, when the turbine impeller 6 rotates, the compressor impeller 7 rotates via the rotating shaft 14. The rotating compressor impeller 7 draws in external air through the intake port 9, compresses it, and discharges it through the vortex flow path 17 from the outlet port. The compressed air discharged from the outlet port is supplied to the aforementioned internal combustion engine.

[0031] The turbine 2 is described below. The turbine 2 is a variable-capacity turbine, equipped with a gas inlet passage 21 connecting the vortex flow path 16 to the turbine impeller 6. The gas inlet passage 21 is the flow path for the exhaust gas introduced into the turbine impeller 6. Multiple movable nozzle blades 23 are arranged on the gas inlet passage 21. The multiple nozzle blades 23 are arranged on a circumference centered on the rotation axis H, and each nozzle blade 23 rotates about an axis parallel to the rotation axis H. By rotating the nozzle blades 23, the cross-sectional area of ​​the gas flow path is optimally adjusted according to the flow rate of the exhaust gas introduced into the turbine 2. The turbine 2 is equipped with a variable nozzle unit 25 as the drive mechanism for rotating the nozzle blades 23.

[0032] The variable nozzle unit 25 is housed within the housing 8. Specifically, the variable nozzle unit 25 is embedded inside the turbine housing 4 in a state adjacent to the turbine impeller 6, and is fixed by being clamped between the turbine housing 4 and the bearing housing 13.

[0033] The variable nozzle unit 25 includes: the aforementioned plurality of nozzle blades 23, and a first nozzle ring 31 (an example of a nozzle ring) and a second nozzle ring 32 spaced apart from the nozzle blades 23 in the direction of the rotation axis H. The first nozzle ring 31 and the second nozzle ring 32 are each annular about the rotation axis H and are configured to surround the turbine impeller 6 circumferentially (in the direction of rotation of the turbine impeller 6). The first nozzle ring 31 and the second nozzle ring 32 are arranged opposite each other with a predetermined gap separated by a connecting pin 35. The region formed between the first nozzle ring 31 and the second nozzle ring 32 forms the aforementioned gas inflow path 21. The second nozzle ring 32 faces the vortex flow path 16 (see reference). Figure 1 The second nozzle ring 32 forms part of the inner wall of the vortex flow path 16. The rotation axis 23a of each nozzle blade 23 passes through the first nozzle ring 31, which supports each nozzle blade 23 in a single-support manner. In this embodiment, the nozzle blades 23 are arranged at equal intervals on the circumference, but they can also be arranged at non-equal intervals. The first nozzle ring 31 is an example of a nozzle ring that supports the nozzle blades 23 so that they can rotate.

[0034] The variable nozzle unit 25 includes a drive unit 26 for rotating the nozzle blade 23. The drive unit 26 is disposed on the side opposite to the nozzle blade 23, separated by a first nozzle ring 31. The drive unit 26 includes a drive ring 27, a plurality of nozzle connecting rod plates 28, and a drive connecting rod plate 29. The drive ring 27 is a component that transmits externally input forces to the nozzle blade 23 as a driving force for rotating the nozzle blade 23. The drive ring 27 is annular, extending around a circumference centered on the rotation axis H. The drive ring 27 is mounted on a support member fixed to the housing 8 and is supported by the support member so that it can rotate about the rotation axis H.

[0035] Multiple nozzle connecting rod plates 28 are respectively mounted on the rotation shaft 23a of each nozzle blade 23. The multiple nozzle connecting rod plates 28 are arranged at equal intervals on the circumference inside the drive ring 27. A drive connecting rod plate 29 is arranged side-by-side with the nozzle connecting rod plates 28. The drive connecting rod plate 29 tilts (rotates) under external driving force, and this tilting causes the drive ring 27 to rotate. The multiple nozzle connecting rod plates 28 rotate in accordance with the rotation of the drive ring 27, and each causes the nozzle blade 23 to rotate via the rotation shaft 23a. That is, the drive connecting rod plate 29 and the drive ring 27 cooperate to rotate the nozzle connecting rod plate 28, and this rotation causes the nozzle connecting rod plate 28 to rotate.

[0036] like Figure 2 As shown, the housing 8 includes a drive chamber 40 for housing the drive unit 26. The drive chamber 40 is located at the connection between the turbine housing 4 and the bearing housing 13, and has an inner wall surface 41 surrounding the drive unit 26. The drive unit 26 includes an outer peripheral portion 27a. The outer peripheral portion 27a is the portion outside the centrifugal direction (radial) Da of the rotating turbine impeller 6. For example, the outer peripheral end face of the drive ring 27 is at least a part of the outer peripheral portion 27a. The area in the inner wall surface 41 opposite to the outer peripheral portion 27a of the drive unit 26 is an inner peripheral opposing surface 42. For example, when the inner peripheral opposing surface 42 is set in a state where the rotation axis H of the turbine impeller 6 is horizontal, it is the surface of the area where liquid L such as water may stagnate in the drive chamber 40.

[0037] The housing 8 has an inner wall portion 43 disposed between the drive chamber 40 and the vortex flow path 16. The inner wall portion 43 cooperates with the first nozzle ring 31 to separate the drive chamber 40 from the vortex flow path 16. For example, the inner wall portion 43 is disposed within the turbine housing 4 and is erected in a manner that protrudes inward from the inner peripheral opposing surface 42 of the drive chamber 40 (in the direction opposite to the centrifugal direction Da). For example, the inner wall portion 43 is provided as an annular wall along the entire circumference of the outer peripheral portion 31b of the first nozzle ring 31.

[0038] The relationship between the outer peripheral portion 31b and the inner wall portion 43 of the first nozzle ring 31 will be explained here. The first nozzle ring 31 includes a nozzle blade 23 that can be rotatably supported (see reference). Figure 1 The plate has a main body portion 31a and a thin-walled outer peripheral portion 31b extending outward (in the centrifugal direction Da) from the main body portion 31a. A stepped portion 31c is formed between the main body portion 31a and the outer peripheral portion 31b. Alternatively, for example, the stepped portion 31c may be omitted, so that the main body portion 31a and the outer peripheral portion 31b are substantially continuous with the same plate thickness.

[0039] The outer periphery 31b of the first nozzle ring 31 has a first side surface 43a on the side of the vortex flow path 16 and a second side surface 43b on the side of the drive chamber 40. The inner wall portion 43 overlaps with the first side surface 43a. At least a portion of the inner wall portion 43 is configured to be received within a gap formed by the stepped difference portion 31c.

[0040] like Figure 2 , Figure 3 as well as Figure 4 As shown, a drain passage 44 (an example of a liquid flow path) is provided in the inner wall portion 43, connecting the drive chamber 40 and the vortex flow path 16. The drain passage 44 has the function of draining liquid L, such as water contained in the gas, if retained within the drive chamber 40. The drain passage 44 can, for example, be configured to extend along the rotation axis H. By configuring the drain passage 44 to extend along the rotation axis H, manufacturing becomes easier. Furthermore, the drain passage 44 can, for example, be configured to extend in a direction inclined relative to the rotation axis H. By configuring the drain passage 44 to be inclined relative to the rotation axis H, drainage performance is improved. For example, the drain passage 44 can also be inclined such that the end closer to the vortex flow path 16 is lower than the end closer to the drive chamber 40.

[0041] For example, the drainage path 44 can be a groove, with a cross-section that is partially open at the outer edge, such as a semi-circle or a U-shape. Alternatively, the drainage path 44 can be a through hole, with a cross-section that closes the entire circumference of the outer edge, such as a circle, an ellipse, or any other arbitrary shape.

[0042] For example, a portion of the flow surface 44a of the drainage path 44 is flush with and continuous with the inner peripheral opposing surface 42 of the drive chamber 40. By having a flow surface 44a that is flush with and continuous with the inner peripheral opposing surface 42 of the drive chamber 40, the liquid L retained on the inner peripheral opposing surface 42 is easily discharged through the drainage path 44. The flow surface 44a of the drainage path 44 may also be configured without a portion that is flush with and continuous with the inner peripheral opposing surface 42. In the case of this configuration, although a step difference is created between the flow surface 44a of the drainage path 44 and the inner peripheral opposing surface 42, the liquid L can be discharged through the drainage path 44 at least when the water level of the liquid L retained on the inner peripheral opposing surface 42 (the height from the bottom of the liquid L to the water surface) is higher than the step difference.

[0043] The surface roughness of the flow surface 44a of the drainage flow path 44 is greater than the surface roughness of at least the region 42a connected to the drainage flow path 44 in the inner peripheral opposing surface 42 (refer to...). Figure 4 Additionally, in Figure 4 Surface roughness is represented by dots, with a higher density of dots indicating greater surface roughness. Furthermore, the region 42a in the inner circumferential opposing surface 42 that connects to the drainage path 44 signifies the area overlapping the extended region formed by extending the drainage path 44 towards the inner circumferential opposing surface 42. By making the surface roughness of the flow path 44a of the drainage path 44 greater than the surface roughness of the inner circumferential opposing surface 42, the drainage performance of liquid L retained on the inner circumferential opposing surface 42 can be improved. This drainage function will be explained in further detail.

[0044] Figure 5 These are graphs showing the relationship between the properties of the surface contacted by a water droplet La and the contact angle. Graph (a) illustrates the contact angle of a water droplet La on a flat (smooth) surface Sf. Graph (b) schematically shows the relationship between the contact angle and the shape of the water droplet La when the surface is hydrophilic, and graph (c) schematically shows the relationship between the contact angle and the shape of the water droplet La when the surface is hydrophobic. Figure 5 In this context, θ represents the contact angle on the flat surface Sf, and θw represents the contact angle on the rough surface Sg, which has a larger surface roughness than the flat surface Sf. The contact angle θw of the rough surface Sg can be calculated using Wenzel's formula (1) below. Here, r represents the ratio of the actual surface area to the apparent surface area, "r = 1" means the flat surface Sf, and "r > 1" means the surface roughness is larger than the flat surface Sf.

[0045] cosθw=r cosθ (1)

[0046] like Figure 5 As shown, in the case of a hydrophilic surface, the contact angle θ on the flat surface Sf is less than 90°. Taking the flat surface Sf as a reference, the greater the surface roughness, the smaller the contact angle θw. Conversely, in the case of a hydrophobic surface, the contact angle θ on the flat surface Sf is greater than 90°. Taking the flat surface Sf as a reference, the greater the surface roughness, the larger the contact angle θw. Here, a smaller contact angle θw makes it easier for the gap to penetrate a narrow gap, thus improving discharge performance.

[0047] Based on the above insights, the variable capacity turbocharger 1 described above is verified. First, the housing 8 of the variable capacity turbocharger 1 is basically made of metal, and the surface of the housing 8 forms a hydrophilic surface. That is, the greater the surface roughness, the smaller the contact angle, and the easier it is to penetrate narrow gaps. In the case of the variable capacity turbocharger 1, the surface roughness of the flow path 44a of the drain flow path 44 is greater than the surface roughness of the region 42a of the inner peripheral opposing surface 42 that connects to the drain flow path 44. As a result, the liquid L retained on the inner peripheral opposing surface 42 moves within the flow path 44a of the drain flow path 44, for example, by being drawn in, thereby being discharged to the vortex flow path 16 via the drain flow path 44.

[0048] Next, in the manufacturing method of the variable capacity turbocharger 1, the method of forming the drainage flow path 44 in the turbine housing 4 will be specifically described. The turbine housing 4 can be made of materials such as ductile iron, corrosion-resistant high-nickel cast iron, or cast steel, depending on the exhaust gas temperature, and can be manufactured using precision casting methods such as the shell mold method or the cold box method. The drainage flow path 44 is formed, for example, by machining (drilling) the turbine housing 4 manufactured by the above method. During this machining, the surface roughness of the flow path 44a of the drainage flow path 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, and particularly greater than the surface roughness of the inner circumferential opposing surface 42. Furthermore, after machining the drainage flow path 44, the surface roughness of the flow path 44a of the drainage flow path 44 can be subsequently increased.

[0049] Alternatively, the turbine housing 4, including the drainage flow path 44, can be manufactured as a whole using conventional casting methods. In this case, the surface roughness of the turbine housing 4 increases compared to precision casting. Therefore, for the flow surface 44a of the drainage flow path 44, the surface condition of the casting can be maintained, while the inner peripheral opposing surface 42 can be machined and polished. That is, machining and polishing can be performed to make the surface roughness of the flow surface 44a of the drainage flow path 44 greater than the surface roughness of the inner peripheral opposing surface 42.

[0050] Next, refer to Figure 2 as well as Figure 3 The balancing hole 33 formed in the first nozzle ring 31 will be described below. The balancing hole 33 is a groove or through hole that connects the drive chamber 40 and the vortex flow path 16. The balancing hole 33 has the function of reducing the pressure difference generated between the drive chamber 40 and the vortex flow path 16. This function will be explained in further detail.

[0051] First nozzle ring 31 (reference) Figure 1The nozzle 31 is pressed against the bearing housing 13 by a disc spring 30a, a heat shield 30b, etc., and held in a predetermined position. In this state, the pressure in the vortex flow path 16 is greater than the pressure in the drive chamber 40. If this state is maintained, the contact load of the disc spring 30a supporting the first nozzle ring 31 will be greater than required, and the disc spring 30a may creep. In addition, the nozzle blade 23 may shift in the direction close to the first nozzle ring 31. According to the inventor's empirical insight, the fluid performance is good when the nozzle blade 23 is positioned closer to the second nozzle ring 32 than the first nozzle ring 31. Therefore, if the distance between the nozzle blade 23 and the second nozzle ring 32 is greater than the distance between the nozzle blade 23 and the first nozzle ring 31, the performance may be degraded. Here, by providing a balance hole 33, the pressure difference generated between the drive chamber 40 and the vortex flow path 16 can be reduced, and as a result, both creep suppression and performance degradation can be suppressed.

[0052] The balancing holes 33 are, for example, disposed at multiple equally spaced (in phase) locations along the circumference of the first nozzle ring 31. Specifically, the multiple balancing holes 33 are disposed at three locations with a phase of 120°. Alternatively, the balancing holes 33 may be a single hole or disposed at multiple locations with unequal intervals along the circumference.

[0053] At least a portion of the drainage path 44 provided on the inner wall portion 43 is configured to overlap with the balance hole 33 when viewed from the direction of the rotation axis H (see reference). Figure 3 For example, the flow path cross-section of the drainage flow path 44 is a semi-circular shape with the lower side of the arc, and the balance hole 33 is a semi-circular shape with the upper side of the arc. For example, the flow path cross-section of the drainage flow path 44 overlaps with the flow path cross-section of the balance hole 33 in a manner that, except for a portion at the bottom, the entire area is contained within the flow path cross-section of the first nozzle ring 31. That is, the flow path cross-section of the drainage flow path 44 overlaps with the flow path cross-section of the balance hole 33 in a manner that the entire area of ​​the circumferential width of the first nozzle ring 31 is contained within the flow path cross-section of the balance hole 33. In addition, the overlap of at least a portion of the drainage flow path 44 with the balance hole 33 can also be described as a state in which the drainage flow path 44 and the balance hole 33 are phase-overlapping when the rotation direction of the turbine impeller 6 is taken as a reference. For example, the area of ​​the cross-section of the balance hole 33 is larger than the area of ​​the flow path cross-section of the drainage flow path 44. For example, the area of ​​the cross-section of the balance hole 33 and the area of ​​the flow path cross-section of the drainage flow path 44 may be the same, or the area of ​​the flow path cross-section of the drainage flow path 44 may be larger than the area of ​​the cross-section of the balance hole 33.

[0054] Next, refer to Figure 6 The case where a drainage flow path 44 is configured around the rotation axis H of the turbine impeller 6 will be explained. Figure 6 The diagram in (a) shows an example of the configuration of the drainage path 44 in this embodiment. Figure 6Figure (b) shows an example of the configuration of the modified drainage paths 44A and 44B.

[0055] The drain path 44 of the variable capacity turbocharger 1 is provided as a single unit. If a vehicle equipped with the variable capacity turbocharger 1 stops at an angle, then... Figure 6 As shown in Figure (a), the drainage path 44 is located offset from the vertical axis. In this case, for example, the positional offset of the drainage path 44 relative to the lower endpoint Pa on the vertical axis can be represented by the rotation angle (phase angle) α1 about the rotation axis H. If the liquid L retained in the drive chamber 40 reaches the drainage path 44 at a water level (draft) h from the lower endpoint Pa, the liquid L is discharged from the drainage path 44. Here, if the distance from the rotation axis H to the drainage path 44 is set as r, the water level h used to discharge the liquid L from the drainage path 44 becomes the following formula (2).

[0056] h = "-rCOSα1(2)"

[0057] Next, the drainage channels 44A and 44B in the modified example will be described. In the modified example, drainage channels 44A and 44B are provided at multiple locations along the circumference of the inner wall portion 43. In the modified example, for example, drainage channels 44A and 44B are provided at two locations. Vehicles equipped with variable capacity turbochargers 1 are not limited to parking in places without slope, but may be parked on inclines with a minimum slope of about 15°. In this case, by providing multiple drainage channels 44A and 44B, each drainage channel 44A and 44B is located close to the lower end point Pa of the vertical axis. As a result, the water level h of the retained liquid L can be discharged at the lowest possible position.

[0058] Furthermore, for example, the relative positional relationship of the multiple drainage paths 44A and 44B can be represented by the rotation angle (phase angle) α2 about the rotation axis H. Specifically, assume a first straight line Lx formed by the rotation axis H and one of the drainage paths 44A, and a second straight line Ly formed by the rotation axis H and the other drainage path 44B. Here, the angle formed by the first straight line Lx and the second straight line Ly intersecting the rotation axis H is the rotation angle α2 about the rotation axis H. The rotation angle α2 can be set to 8° or more and 23° or less. In addition, as mentioned above, if it is assumed that parking is possible on an inclined surface with a slope of about 15°, the rotation angle α2 is preferably 14° or more, and preferably 17° or less.

[0059] Next, the function and effect of the variable capacity turbocharger 1 described above will be explained. The variable capacity turbocharger 1 includes a drive chamber 40 that houses the drive unit 26, and the drive chamber 40 has an inner peripheral opposing surface 42 that faces the outer peripheral portion 27a of the drive unit 26. Liquids such as water contained in the gas inside the drive chamber 40 tend to accumulate on the inner peripheral opposing surface 42. A drain passage 44 communicating with the drive chamber 40 is provided on the inner wall portion 43 of the housing 8 to drain the liquid L. Therefore, by mounting the variable capacity turbocharger 1 in a vehicle or the like such with the region 42a of the inner peripheral opposing surface 42 that connects to the drain passage 44 being the lower part in the vertical direction, the liquid L generated inside the drive chamber 40 can be discharged from the drain passage 44.

[0060] Furthermore, the surface roughness of the flow path 44a of the drainage path 44 is greater than the surface roughness of the region 42a in the inner peripheral opposing surface 42 that connects to the drainage path 44. The housing 8 is made of metal, and the inner peripheral opposing surface 42 and the flow path 44a of the drainage path 44 essentially form a hydrophilic surface. In the case of a hydrophilic surface, the contact angle of water droplets decreases due to the larger surface roughness, making it easier for them to pass through narrow gaps. That is, even if liquid L remains on the inner peripheral opposing surface 42, the liquid L will be attracted to the side of the drainage path 44 with its larger surface roughness and will be easily discharged, thus improving the dischargeability of liquid L.

[0061] By improving the drainage of the liquid L retained in the drive chamber 40, the level of the liquid L can be reduced even if it remains. As a result, for example, even if a vehicle equipped with a variable capacity turbocharger 1 is parked in a cold region and the liquid L in the drive chamber 40 freezes, the possibility of this freezing causing obstruction to the operation of the drive unit 26, especially during the start-up of the drive unit 26, can be reduced.

[0062] Furthermore, at least a portion of the flow surface 44a of the drainage path 44 is flush with and continuous with the inner peripheral opposing surface 42. That is, by providing a flush and continuous portion without any step difference between the flow surface 44a and the inner peripheral opposing surface 42 of the drainage path 44, liquid L can be easily discharged through this portion. As a result, it is difficult for liquid L to remain due to step differences, and the dischargeability of liquid L can be improved.

[0063] Furthermore, the drainage path 44 is configured to connect the vortex flow path 16 to the drive chamber 40, allowing the liquid L following the drainage path 44 to be discharged into the vortex flow path 16. The liquid L discharged into the vortex flow path 16 is rapidly evaporated or disappears due to the drive of the turbine impeller 6. As a result, the discharge efficiency of the liquid L is improved.

[0064] Furthermore, the variable capacity booster 1 includes a balance hole 33 disposed on the first nozzle ring 31. At least a portion of the drain flow path 44 is configured to overlap with the balance hole 33. As a result, the first nozzle ring 31 can be bypassed and the area communicating between the drain flow path 44 and the drive chamber 40 can be easily expanded, thereby improving the discharge performance of the liquid L.

[0065] Furthermore, although the balancing hole 33 functions to reduce the pressure difference between the drive chamber 40 and the vortex flow path 16, increasing the area of ​​the balancing hole 33 may cause the pressure within the vortex flow path 16 to remain unstable. Therefore, it is important to form the balancing hole 33 with appropriate dimensions. Here, when the drain flow path 44 is arranged in a manner that allows communication between the vortex flow path 16 and the drive chamber 40, the formation of the balancing hole 33 needs to be carefully considered in light of the influence of the drain flow path 44. However, in the variable capacity type booster 1, at least a portion of the drain flow path 44 is configured to overlap with the balancing hole 33. Therefore, compared to a configuration where the drain flow path 44 is formed independently of the balancing hole 33, the influence of the drain flow path 44 is reduced, making it easier to form the balancing hole 33 appropriately.

[0066] Furthermore, in the variable capacity turbocharger 1 of the above-described modified example, two drainage channels 44A and 44B are provided, and the rotation angle (phase angle) α2 between one drainage channel 44A and the other drainage channel 44B is 8° or more and 23° or less. As a result, even if a vehicle equipped with the variable capacity turbocharger 1 is parked on a sloped surface, liquids such as water retained in the drive chamber 40 can be easily discharged from either drainage channel 44A or 44B, thereby improving the discharge performance of liquid L.

[0067] This invention can be implemented in various ways with various modifications and improvements based on the knowledge of those skilled in the art, as exemplified by the embodiments described above. Furthermore, variations can be constructed using the technical aspects described in the embodiments above. The structures of each embodiment can also be appropriately combined.

[0068] Explanation of reference numerals in the attached figures

[0069] 1... Variable capacity turbocharger; 8... Housing; 6... Turbine impeller; 16... Vortex flow path; 21... Gas inlet path; 23... Nozzle blade; 25... Variable nozzle unit; 26... Drive unit; 27... Drive ring; 27a... Outer periphery; 31... First nozzle ring (nozzle ring); 33... Balance hole; 40... Drive chamber; 42... Inner periphery opposing surface; 43... Inner wall; 44... Drainage flow path (liquid flow path); 44a... Flow surface; 42a... Area connected to drainage flow path; 44A... Drainage flow path; 44B... Drainage flow path; H... Rotation axis; L... Liquid.

Claims

1. A variable capacity turbocharger, characterized in that, have: Turbine impeller; Housing that houses the turbine impeller; and A variable nozzle unit, housed within the housing. The variable nozzle unit includes: nozzle blades disposed in the flow path of the gas introduced into the turbine impeller; A nozzle ring that supports the nozzle blades for rotation; and a drive unit disposed on the opposite side of the nozzle blades via the nozzle ring, which rotates the nozzle blades. The housing includes: a drive chamber for housing the drive unit, and a liquid flow path communicating with the drive chamber. The drive chamber has an inner peripheral opposing surface that faces the outer peripheral portion of the drive unit. The surface roughness of the liquid flow path is greater than the surface roughness of at least the region of the inner circumferential opposing surface connected to the liquid flow path.

2. The variable capacity turbocharger according to claim 1, characterized in that, At least a portion of the flow path of the liquid flow path is flush with and continuous with the inner peripheral opposing surface.

3. The variable capacity turbocharger according to claim 1 or 2, characterized in that, The housing also has a vortex flow path formed around the turbine impeller. The liquid flow path is configured to connect the vortex flow path to the drive chamber.

4. The variable capacity turbocharger according to claim 3, characterized in that, The housing has an inner wall portion disposed between the drive chamber and the vortex flow path and overlapping with the outer periphery of the nozzle ring. A balancing hole is provided on the outer periphery of the nozzle ring to reduce the pressure difference between the drive chamber and the vortex flow path. The liquid flow path is provided on the inner wall in such a way that at least a portion overlaps with the balance hole.

5. The variable capacity turbocharger according to any one of claims 1 to 4, characterized in that, The liquid flow path is provided at at least two locations circumferentially along the rotation direction of the turbine impeller. The phase angle between the liquid flow path of one party and the liquid flow path of the other party is greater than 8° and less than 23°.

6. The variable capacity turbocharger according to any one of claims 1 to 5, characterized in that, The flow surface and the inner circumferential opposing surface of the liquid flow path are hydrophilic surfaces.

7. The variable capacity turbocharger according to claim 4, characterized in that, The balancing holes are located at multiple positions around the nozzle ring.

8. The variable capacity turbocharger according to claim 7, characterized in that, The plurality of balancing holes are arranged at equal intervals in the circumferential direction of the nozzle ring.

9. The variable capacity turbocharger according to claim 4, characterized in that, The flow path cross section of the liquid flow path is configured such that the entire area of ​​the circumferential width of the nozzle ring is contained within the flow path cross section of the balance hole.

10. The variable capacity turbocharger according to any one of claims 1 to 9, characterized in that, The liquid flow path extends along the rotation axis of the turbine impeller.

11. The variable capacity turbocharger according to any one of claims 1 to 9, characterized in that, The liquid flow path is provided at at least two locations circumferentially along the rotation direction of the turbine impeller. The liquid flow paths at both locations extend along the rotation axis of the turbine impeller.

12. The variable capacity turbocharger according to any one of claims 1 to 4, characterized in that, The liquid flow path is provided at at least two locations circumferentially along the rotation direction of the turbine impeller. The phase angle between the liquid flow path of one party and the liquid flow path of the other party is greater than 14° and less than 17°.

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