Seal structure for supercharger

Abstract

This seal structure for a supercharger comprises: a rotary member including a rotary shaft of the supercharger and a rotary wheel provided on one end side of the rotary shaft; a stationary member including a housing that stores the rotary member; a bearing that rotatably supports the rotary shaft; and a seal member provided in a seal gap that is formed between the rotary member and the stationary member to provide communication between a first space in which the rotary wheel is stored and a second space in which the bearing is stored. The stationary member includes a stationary-side inner peripheral surface defining the seal gap, and a stationary-side end surface extending from an edge of the stationary-side inner peripheral surface on the second space side along a radial direction of the rotary shaft. The stationary member has an oil discharge groove provided on the stationary-side end surface below an axis of the rotary shaft and extending downward along a vertical direction from the edge of the stationary-side inner peripheral surface on the second space side.

Description

Turbocharger seal structure

[0001] The present disclosure relates to a seal structure for a supercharger.

[0002] A turbocharger includes a rotor (rotating body) including a rotating shaft, a turbine impeller attached to one side of the rotating shaft, and a compressor impeller attached to the other side of the rotating shaft; bearings that rotatably support the rotating shaft between the turbine impeller and the compressor impeller; and a casing that houses the rotor and the bearings. Since the bearings of a turbocharger support the rotating shaft that rotates at high speed, they are prone to become hot, and insufficient lubrication can lead to seizure. For this reason, the bearings are lubricated and cooled by supplying lubricating oil to the bearings. Some turbochargers include a seal ring that seals between the outer surface of a rotating body such as the rotor and the inner surface of a stationary body such as a casing to prevent leakage of lubricating oil supplied to the bearings to the compressor side or the turbine side (see, for example, Patent Document 1).

[0003] JP 2008-232124 A

[0004] In a turbocharger equipped with a sealing mechanism using a seal ring, there is a risk of lubricating oil leakage. Specifically, lubricating oil may accumulate in the space between the outer surface of the rotating body to which the seal ring is attached and the inner surface of the stationary body, and the lubricating oil accumulated in the space may leak into the space on the opposite side of the seal ring.

[0005] In view of the above circumstances, at least one embodiment of the present invention has an object to provide a seal structure for a turbocharger that can suppress leakage of lubricating oil.

[0006] a seal structure for a turbocharger according to at least one embodiment of the present invention, comprising: a rotating member including at least a rotating shaft of the turbocharger and a rotating wheel provided on one end side of the rotating shaft; a stationary member including at least a housing that accommodates the rotating member; a bearing that rotatably supports the rotating shaft; and a seal member provided in a seal gap formed between the rotating member and the stationary member, the seal gap communicating between a first space that accommodates the rotating wheel and a second space that accommodates the bearing; wherein the rotating member includes at least a rotating-side outer peripheral surface that defines the seal gap; and the stationary member includes a stationary-side inner peripheral surface that defines the seal gap, and a stationary-side end face that extends from an edge of the stationary-side inner peripheral surface on the second space side along a radial direction of the rotating shaft; and the stationary member has an oil drain groove provided in the stationary-side end face below the axis of the rotating shaft, the oil drain groove extending vertically downward from the edge of the stationary-side inner peripheral surface on the second space side.

[0007] According to at least one embodiment of the present invention, there is provided a seal structure for a turbocharger that can suppress leakage of lubricating oil.

[0008] Fig. 1 is a schematic cross-sectional view showing a cross section along the axis of a turbocharger including a sealing structure for a turbocharger according to one embodiment; Fig. 2 is a schematic cross-sectional view showing a cross section along the axis of the sealing structure for a turbocharger according to one embodiment; Fig. 3 is a schematic view showing the sealing structure for a turbocharger according to one embodiment as viewed from the second space side; Fig. 4 is a schematic view showing the sealing structure for a turbocharger according to one embodiment as viewed from the second space side; Fig. 5 is a schematic view showing the vicinity of an oil drain groove in the sealing structure for a turbocharger according to one embodiment as viewed from above; Fig. 6 is a schematic cross-sectional view showing a cross section along the axis of the sealing structure for a turbocharger according to one embodiment;

[0009] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention.

[0010] (Turbocharger) Fig. 1 is a schematic cross-sectional view showing a cross section along an axis of a turbocharger including a seal structure for a turbocharger according to one embodiment. As shown in Fig. 1, the turbocharger 1 includes a rotating shaft 11, a compressor wheel 12A provided on one end of the rotating shaft 11, a turbine wheel 12B provided on the other end of the rotating shaft 11, a bearing 13 that rotatably supports the rotating shaft 11, and a housing 14 that accommodates the rotating shaft 11, the compressor wheel 12A, the turbine wheel 12B, and the bearing 13.

[0011] The bearing 13 is supported by a housing 14. The rotating shaft 11 is supported by the bearing 13 between the compressor wheel 12A and the turbine wheel 12B, and is thereby rotatable about an axis LA of the rotating shaft 11.

[0012] Hereinafter, the direction in which the axis LA of the rotating shaft 11 extends is defined as the axial direction of the rotating shaft 11 (turbocharger 1), and the direction perpendicular to the axis LA is defined as the radial direction of the rotating shaft 11 (turbocharger 1). In the axial direction of the rotating shaft 11 (turbocharger 1), the side where the compressor wheel 12A is located relative to the turbine wheel 12B is defined as the compressor side, and the side where the turbine wheel 12B is located relative to the compressor wheel 12A is defined as the turbine side.

[0013] The turbine wheel 12B is configured to rotate by the energy of exhaust gas discharged from the engine and guided to the turbine wheel 12B. The compressor wheel 12A rotates together with the rotary shaft 11 in conjunction with the rotation of the turbine wheel 12B. The turbocharger 1 is configured to compress gas (e.g., air) guided to the compressor wheel 12A by the rotation of the compressor wheel 12A, increase the density of the gas, and send the gas to a supply destination (e.g., the engine).

[0014] (Sealing structure of turbocharger) Fig. 2 is a schematic cross-sectional view showing a cross section along an axis of the sealing structure of a turbocharger according to one embodiment. Fig. 2 shows an area surrounded by a two-dot chain line in Fig. 1. Figs. 3 and 4 are each a schematic view showing the sealing structure of a turbocharger according to one embodiment as viewed from the second space side. Fig. 5 is a schematic view showing the vicinity of the oil drain groove in the sealing structure of a turbocharger according to one embodiment as viewed from above. A sealing structure 2 of a turbocharger according to some embodiments is a sealing structure provided in a turbocharger 1 for suppressing leakage of lubricating oil in the turbocharger 1. As shown in Fig. 1, the sealing structure 2 of a turbocharger includes a rotating member 3, a stationary member 4 that houses the rotating member 3, a seal member 5 provided in a seal gap 20 formed between the rotating member 3 and the stationary member 4, and the bearing 13 described above.

[0015] (Rotating member, stationary member) The rotating member 3 is configured to rotate when the turbocharger 1 is driven. The rotating member 3 includes at least a rotating shaft 11 and a rotating wheel 12 provided on one end side of the rotating shaft 11. The stationary member 4 is configured to remain stationary (does not rotate) even when the rotating member 3 rotates when the turbocharger 1 is driven. The stationary member 4 includes at least a housing 14.

[0016] The stationary member 4 (housing 14) accommodates the rotating member 3 and the bearing 13. Inside the stationary member 4 (housing 14), the above-mentioned seal gap 20, a first space 21 that accommodates the rotating wheel 12, and a second space 22 that accommodates the bearing 13 are formed. The seal gap 20 is provided between the first space 21 and the second space 22 in the axial direction of the rotating shaft 11, and connects the first space 21 and the second space 22.

[0017] The rotating member 3 has a rotating-side outer peripheral surface 31 that defines the seal gap 20. The stationary member 4 has a stationary-side inner peripheral surface 41 that defines the seal gap 20. The stationary-side inner peripheral surface 41 is provided further outward in the radial direction of the rotating shaft 11 than the rotating-side outer peripheral surface 31, and faces the rotating-side outer peripheral surface 31 across the annular seal gap 20.

[0018] As shown in Fig. 2, the stationary member 4 has a stationary-side end face 43 that extends from an edge 42 of the stationary-side inner peripheral surface 41 on the second space 22 side toward the outside in the radial direction of the rotating shaft 11. The rotating member 3 may have a rotating-side end face 33 that extends from an edge 32 of the rotating-side outer peripheral surface 31 on the second space 22 side toward the inside in the radial direction of the rotating shaft 11.

[0019] (Sealing Member) The sealing member 5 is configured to seal the gap between the stationary-side inner peripheral surface 41 and the rotating-side outer peripheral surface 31. In the illustrated embodiment, as shown in Fig. 2, the sealing member (seal ring) 5 is disposed in a compressed state between the stationary-side inner peripheral surface 41 and the rotating-side outer peripheral surface 31, with its outer peripheral surface abutting against the stationary-side inner peripheral surface 41 and its inner peripheral surface abutting against the rotating-side outer peripheral surface 31. As shown in Figs. 1 and 2, at least one of the stationary-side inner peripheral surface 41 and the rotating-side outer peripheral surface 31 may be provided with an annular groove extending along the circumferential direction of the rotating shaft 11, into which a portion of the sealing member 5 is fitted.

[0020] (Lubricant Oil System) The turbocharger 1 is configured so that lubricant oil flows into the bearing 13 and the second space 22 in which the bearing 13 is housed. In the embodiment shown in Fig. 1, the housing 14 is formed with a lubricant oil inlet 23 for introducing lubricant oil into the interior thereof, a lubricant oil supply path 24 for guiding the lubricant oil from the lubricant oil inlet 23 to the bearing 13, and a lubricant oil outlet 25 for discharging the lubricant oil to the outside of the housing 14. The lubricant oil supply path 24 is formed with a flow path defined by the inner wall surface of the housing 14, which connects the lubricant oil inlet 23 and the second space 22. The lubricant oil outlet 25 is provided below the second space 22 and communicates with a lower part of the second space 22.

[0021] The lubricating oil introduced into the housing 14 through the lubricating oil inlet 23 is guided to the bearing 13 through the lubricating oil supply passage 24. Most of the lubricating oil guided to the bearing 13 flows downward in the second space 22 and is discharged to the outside of the housing 14 through the lubricating oil outlet 25. Some of the lubricating oil guided to the bearing 13 may flow into the seal gap 20.

[0022] A seal structure 2 for a turbocharger 1 according to some embodiments includes the rotating member 3 described above, the stationary member 4 described above, the bearing 13 described above, and the seal member 5 provided in the seal gap 20 described above. The stationary member 4 includes the stationary-side inner circumferential surface 41 described above and the stationary-side end face 43 described above. As shown in FIGS. 2 to 4 , the stationary-side end face 43 has an oil drain groove 6 provided on the stationary-side end face 43 below the axis LA of the rotating shaft 11. The oil drain groove 6 extends downward along the vertical direction from an edge 42 of the stationary-side inner circumferential surface 41 on the second space 22 side. Hereinafter, the direction perpendicular to the extension direction of the oil drain groove 6 will be referred to as the width direction of the oil drain groove 6. The width direction of the oil drain groove 6 extends along a horizontal direction perpendicular to the axis LA of the rotating shaft 11.

[0023] 2 to 5, the stationary-side end face 43 further has a flat surface 43A provided in a region other than the region where the oil drain groove 6 is formed. The flat surface 43A extends from an edge 42 of the stationary-side inner circumferential surface 41 on the second space 22 side toward the outside in the radial direction of the rotating shaft 11. As shown in FIG. 5, of the edge 42 on the second space 22 side of the stationary-side inner circumferential surface 41, the oil drain groove side edge 42A (the upper edge of the oil drain groove 6) that is continuous with the oil drain groove 6 has a concave shape (in the illustrated example, a U-shape with sharp corners) that is recessed more toward the first space 21 in the axial direction of the rotating shaft 11 than a flat surface side edge 42B (the inner circumferential edge of the flat surface 43A that is continuous with the stationary-side inner circumferential surface 41) that is continuous with the flat surface 43A.

[0024] The lubricating oil that has flowed into the seal gap 20 accumulates in the lower part of the seal gap 20. At least a part of the lubricating oil that accumulates in the lower part of the seal gap 20 flows down along the oil drain groove 6 and is discharged into the second space 22.

[0025] According to the above configuration, the oil drain groove 6 provided on the stationary side end face 43 below the axis LA of the rotating shaft 11 allows the lubricating oil to be discharged from the lower part of the seal gap 20, thereby preventing the lubricating oil from accumulating in the lower part of the seal gap 20. By preventing the lubricating oil from accumulating in the lower part of the seal gap 20, the seal structure 2 for the turbocharger can prevent the lubricating oil from leaking beyond the seal member 5 provided in the seal gap 20 to the first space 21 side (the side where the rotating wheel 12 is located).

[0026] In some embodiments, as shown in Fig. 1, the seal structure 2A(2) for a turbocharger is intended to suppress leakage of lubricating oil from the second space 22 to the first space 21A(21) in which the compressor wheel 12A is housed. The rotating wheel 12 of the seal structure 2A for a turbocharger is made up of the compressor wheel 12A described above. As shown in Fig. 1, the first space 21A, which is the space in which the compressor wheel 12A is housed, and the seal gap 20A(20) are provided on the compressor side in the axial direction of the rotating shaft 11 relative to the second space 22 in which the bearing 13 is housed.

[0027] The rotating-side outer peripheral surface 31A (31) may be, for example, the outer peripheral surface of an annular sleeve 15 included in the turbocharger 1 as shown in Fig. 1. The sleeve 15 is attached to the rotating shaft 11 between a compressor wheel 12A (rotating wheel 12) and a bearing 13 in the axial direction of the rotating shaft 11 so as to cover the outer periphery of the rotating shaft 11. The rotating member 3 may further include the sleeve 15. The stationary-side inner peripheral surface 41A (41) may be an inner wall surface of the housing 14 that faces the outer peripheral surface of the sleeve 15 across the seal gap 20B.

[0028] In some embodiments, as shown in Fig. 1, the seal structure 2B(2) for a turbocharger is intended to suppress leakage of lubricating oil from the second space 22 to the first space 21B(21) in which the turbine wheel 12B is housed. The rotating wheel 12 of the seal structure 2B for a turbocharger is formed of the turbine wheel 12B described above. As shown in Fig. 1, the first space 21B, which is the space in which the turbine wheel 12B is housed, and the seal gap 20B(20) are provided closer to the turbine in the axial direction of the rotating shaft 11 than the second space 22 in which the bearing 13 is housed.

[0029] The rotating-side outer peripheral surface 31B (31) may be, for example, the outer peripheral surface of a boss portion protruding from the back surface of the turbine wheel 12B as shown in Fig. 1. The stationary-side inner peripheral surface 41B (41) may be the inner wall surface of the housing 14 that faces the outer peripheral surface of the boss portion of the turbine wheel 12B across the seal gap 20B. The rotating-side outer peripheral surface 31 may also be the outer peripheral surface of the rotating shaft 11.

[0030] The turbocharger 1 may be provided with both the turbocharger seal structures 2A and 2B. That is, the end face of the stationary-side inner circumferential surface 41A that is continuous with the turbine side and the end face of the stationary-side inner circumferential surface 41B that is continuous with the compressor side may each be the stationary-side end face 43 that includes the oil drain groove 6 described above.

[0031] 3 and 4 , the angle θ is defined such that the angle vertically below the axis LA of the rotating shaft 11 is 0°, and the angle increases in the rotation direction of the rotating shaft 11. In some embodiments, the oil drain groove 6 has a pair of groove wall surfaces 62, 63 that face each other across a gap in the width direction of the oil drain groove 6. One groove wall surface 62 of the pair of groove wall surfaces 62, 63 is preferably provided with an upper end 64 that connects to the stationary-side inner circumferential surface 41 when the angular position θ is in the range of +45° to +95°. The other groove wall surface 63 of the pair of groove wall surfaces 62, 63 is preferably provided with an upper end 65 that connects to the stationary-side inner circumferential surface 41 when the angular position θ is in the range of -95° to -45°.

[0032] In the embodiment shown in Figure 3, the upper end 64 of one groove wall surface 62 is located at an angular position θ of +45°, and the upper end 65 of the other groove wall surface 63 is located at an angular position θ of -45°.

[0033] According to the above configuration, by providing the upper end 64 of one groove wall surface 62 in the angular position θ range of +45° to +95° and providing the upper end 65 of the other groove wall surface 63 in the angular position θ range of −95° to −45°, it is possible to reduce the inclination angle of the stationary-side inner circumferential surface 41 with respect to the vertical at the connection position between the one groove wall surface 62 and the other groove wall surface 63, and therefore it is possible to guide the lubricating oil flowing down the stationary-side inner circumferential surface 41 into the oil drain groove, thereby preventing the lubricating oil from accumulating on the stationary-side inner circumferential surface 41. Furthermore, according to the above configuration, the length of the oil drain groove 6 in the width direction is large, which promotes the flow of lubricating oil from the lower part of the seal gap 20 into the oil drain groove 6.

[0034] In the illustrated embodiment, the oil drain groove 6 further has a groove bottom surface 61 connecting the ends of the pair of groove wall surfaces 62, 63 on the first space 21 side. The groove bottom surface 61 of the oil drain groove 6 is formed so that it includes the position where the angular position θ is 0°. By forming the oil drain groove 6 so that it includes the position where the angular position θ is 0°, the lubricating oil can be directly discharged into the oil drain groove 6 from the lower part of the seal gap 20 where the lubricating oil accumulates.

[0035] As shown in Fig. 4, it is more preferable that the upper end 64 of the one groove wall surface 62 is provided at a position where the angular position θ is equal to or greater than +85° and equal to or less than +95°. It is more preferable that the upper end 65 of the other groove wall surface 63 is provided at a position where the angular position θ is equal to or greater than -95° and equal to or less than -85°. In the embodiment shown in Fig. 4, the upper end 64 of the one groove wall surface 62 is provided at a position where the angular position θ is +90°, and the upper end 65 of the other groove wall surface 63 is provided at a position where the angular position θ is -90°.

[0036] According to the above configuration, by arranging the upper end 64 of one groove wall surface 62 in the range of angular position θ of +85° or more and +95° or less, and by arranging the upper end 65 of the other groove wall surface 63 in the range of angular position θ of -95° or more and -85° or less, the inclination angle of the stationary side inner circumferential surface 41 relative to the vertical at the connection position with each of the one groove wall surface 62 and the other groove wall surface 63 can be reduced, so that the lubricating oil flowing down the stationary side inner circumferential surface 41 can be effectively guided to the oil drain groove 6, and the accumulation of lubricating oil on the stationary side inner circumferential surface 41 can be effectively prevented.

[0037] 4 , when the length of the oil drain groove 6 in the width direction is L1 and the diameter of the stationary-side inner circumferential surface 41 is L2, the oil drain groove 6 satisfies the condition 0.95×L2≦L1≦1.05×L2. In the illustrated embodiment, the length L1 of the oil drain groove 6 in the width direction is constant. However, in other embodiments, the oil drain groove 6 may be configured so that its length in the width direction increases or decreases as it extends downward. Note that if the length of the oil drain groove 6 in the width direction is not constant, the length L1 may be the length in the width direction of the upper edge of the oil drain groove 6 (the edge connected to the oil drain groove side edge 42A).

[0038] According to the above configuration, by making the length L1 in the width direction of the oil drain groove 6 the same as the diameter L2 of the stationary-side inner circumferential surface 41, the lubricating oil that flows down along the stationary-side inner circumferential surface 41 can be effectively guided into the oil drain groove 6, and the accumulation of the lubricating oil on the stationary-side inner circumferential surface 41 can be effectively prevented. Furthermore, by making the length L1 in the width direction of the oil drain groove 6 the same as the diameter L2 of the stationary-side inner circumferential surface 41, the lubricating oil can be efficiently discharged from the oil drain groove 6.

[0039] In some embodiments, as shown in Figure 2, the above-mentioned groove bottom surface 61 is located below the axis LA of the rotating shaft 11 and closer to the first space 21 than the edge 32 on the rotating side outer peripheral surface 31 that faces the second space 22.

[0040] According to the above configuration, the groove bottom surface 61 is located below the axis LA of the rotating shaft 11 and closer to the first space 21 than the edge 32 of the rotation-side outer peripheral surface 31 that faces the second space 22. In this case, the shape of the groove makes it difficult for the lubricating oil that flows down the rotation-side end face 33 to enter the seal gap 20, so that the inflow of the lubricating oil into the seal gap 20 can be suppressed, and ultimately the accumulation of the lubricating oil in the lower part of the seal gap 20 can be suppressed.

[0041] FIG. 6 is a schematic cross-sectional view showing a cross section along the axis of a seal structure for a turbocharger according to one embodiment. FIG. 6 illustrates the area surrounded by the two-dot chain line in FIG. 1 . In some embodiments, as shown in FIG. 6 , the stationary-side end face 43 has the oil drain groove 6 and a flat surface 43B provided outside the area where the oil drain groove 6 is formed. Like the flat surface 43A, the flat surface 43B extends radially outward from the edge 42 of the stationary-side inner circumferential surface 41 on the second space 22 side along the radial direction of the rotating shaft 11. Below the axis LA of the rotating shaft 11, the flat surface 43B is located closer to the first space 21 than the edge 32 of the rotating-side outer circumferential surface 31 on the second space 22 side. In this case, the shape of the rotation-side end face 33 makes it difficult for lubricating oil flowing down the rotation-side end face 33 to enter the seal gap 20. This makes it possible to suppress the inflow of lubricating oil into the seal gap 20, thereby suppressing the accumulation of lubricating oil in the lower part of the seal gap 20.

[0042] A protruding member (not shown) may be provided on the stationary-side inner circumferential surface 41 to suppress the inflow of lubricating oil from the second space 22 into the seal gap 20. The protruding member protrudes from the stationary-side inner circumferential surface 41 toward the inside in the radial direction of the rotating shaft 11 and extends along the circumferential direction of the rotating shaft 11.

[0043] In this specification, expressions expressing relative or absolute arrangements, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such arrangements, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions expressing that things are in an equal state, such as "identical," "equal," and "homogeneous," not only express a state in which there is a strict equivalence, but also express a state in which there is a tolerance or a difference to the extent that the same function is obtained. Furthermore, in this specification, expressions expressing shapes such as a rectangular shape or a cylindrical shape not only express shapes such as a rectangular shape or a cylindrical shape in the strict geometric sense, but also express shapes including concave and convex portions, chamfered portions, etc., to the extent that the same effect is obtained. Furthermore, in this specification, the expressions "comprise," "include," or "have" a component are not exclusive expressions that exclude the presence of other components.

[0044] The present disclosure is not limited to the above-described embodiments, but also includes modifications to the above-described embodiments and appropriate combinations of these modifications.

[0045] The contents of the above-described embodiments can be understood, for example, as follows.

[0046] 1) A seal structure (2) for a turbocharger according to at least one embodiment of the present disclosure is a seal structure for a turbocharger (1), comprising: a rotating member (3) including at least a rotating shaft (11) of the turbocharger (1) and a rotating wheel (12) provided on one end side of the rotating shaft (11); a stationary member (4) including at least a housing (14) that accommodates the rotating member (3); a bearing (13) that rotatably supports the rotating shaft (11); and a seal member (5) provided in a seal gap (20) formed between the rotating member (3) and the stationary member (4), the seal gap (20) communicating between a first space (21) in which the rotating wheel (12) is accommodated and a second space (22) in which the bearing (13) is accommodated, wherein the rotating member (3) includes at least a rotating-side outer peripheral surface (31) that defines the seal gap (20), The stationary member (4) includes a stationary-side inner peripheral surface (41) that defines the seal gap (20), and a stationary-side end face (43) that extends from an edge (42) of the stationary-side inner peripheral surface (41) on the second space (22) side along the radial direction of the rotating shaft (11), and the stationary-side end face (43) has an oil drain groove (6) that is provided on the stationary-side end face (43) below the axis (LA) of the rotating shaft (11), and that extends downward along the vertical direction from the edge (42) of the stationary-side inner peripheral surface (41) on the second space (22) side.

[0047] According to the configuration of 1) above, the oil drain groove (6) provided on the stationary side end face (43) below the axis (LA) of the rotating shaft (11) allows the lubricating oil to be discharged from the lower part of the seal gap (20), thereby preventing the lubricating oil from accumulating in the lower part of the seal gap (20). The seal structure (2) for the turbocharger described in 1) above prevents the lubricating oil from accumulating in the lower part of the seal gap (20), thereby preventing the lubricating oil from leaking beyond the seal member (5) provided in the seal gap (20) to the first space (21) side (the side where the rotating wheel 12 is located).

[0048] 2) In some embodiments, in the seal structure (6) for a turbocharger described in 1) above, the oil drain groove (6) has a pair of groove wall surfaces (62, 63) that face each other across a gap in a width direction of the oil drain groove (6), and when an angular position (θ) is defined such that a vertically downward direction with respect to the axis line (LA) of the rotating shaft (11) is set to 0° and the angle increases toward the rotation direction of the rotating shaft (11), one groove wall surface (62) of the pair of groove wall surfaces (62, 63) has an upper end (64) in a range where the angular position (θ) is equal to or greater than +45° and equal to or less than +95°, and the other groove wall surface (63) of the pair of groove wall surfaces (62, 63) has an upper end (65) in a range where the angular position (θ) is equal to or greater than −95° and equal to or less than −45°.

[0049] According to the configuration 2), by providing the upper end (64) of one groove wall surface (62) in an angular position (θ) in the range of +45° or more and +95° or less and providing the upper end (65) of the other groove wall surface (63) in an angular position (θ) in the range of −95° or more and −45° or less, it is possible to reduce the inclination angle of the stationary-side inner circumferential surface (41) with respect to the vertical direction at the connection position with each of the one groove wall surface (62) and the other groove wall surface (63). This makes it possible to guide the lubricating oil flowing down the stationary-side inner circumferential surface (41) to the oil drain groove, thereby making it possible to prevent the lubricating oil from accumulating on the stationary-side inner circumferential surface (41).

[0050] 3) In some embodiments, in the seal structure (2) for a turbocharger described in 2) above, the upper end (64) of the one groove wall surface (62) is provided at a position where the angular position (θ) is equal to or greater than +85° and equal to or less than +95°, and the upper end (65) of the other groove wall surface (63) is provided at a position where the angular position (θ) is equal to or greater than -95° and equal to or less than -85°.

[0051] According to the configuration of 3), by setting the upper end (64) of one groove wall surface (62) in the angular position in the range of +85° or more and +95° or less and by setting the upper end (65) of the other groove wall surface (63) in the angular position (θ) in the range of -95° or more and -85° or less, the inclination angle of the stationary-side inner circumferential surface (41) with respect to the vertical direction at the connection position can be reduced, and therefore the lubricating oil flowing down the stationary-side inner circumferential surface (41) can be effectively guided to the oil drain groove (6), and the accumulation of lubricating oil on the stationary-side inner circumferential surface (41) can be effectively suppressed.

[0052] 4) In some embodiments, in the seal structure (2) for a turbocharger described in 3) above, when the length of the oil drain groove (6) in the width direction is L1 and the diameter of the stationary-side inner circumferential surface (41) of the stationary member (4) is L2, the oil drain groove (6) satisfies the condition 0.95 × L2 ≦ L1 ≦ 1.05 × L2.

[0053] According to the configuration of 4) above, by making the length L1 of the oil drain groove (6) in the width direction the same as the diameter L2 of the stationary-side inner peripheral surface (41), it is possible to effectively guide the lubricating oil flowing down the stationary-side inner peripheral surface (41) into the oil drain groove (6), and to effectively prevent the lubricating oil from accumulating on the stationary-side inner peripheral surface (41). Furthermore, by making the length L1 of the oil drain groove (6) the same as the diameter L2 of the stationary-side inner peripheral surface (41), it is possible to improve the dischargeability of the lubricating oil in the oil drain groove (6).

[0054] 5) In some embodiments, in the seal structure (2) for a turbocharger described in any one of 2) to 4) above, the oil drain groove (6) further has a groove bottom surface (61) connecting edges of the pair of groove wall surfaces (62, 63) on the first space (21) side, and the groove bottom surface (61) is located below the axis (LA) of the rotating shaft (11) and closer to the first space (21) than the edge (32) on the second space (22) side of the rotating-side outer peripheral surface (31).

[0055] According to the configuration of 5) above, the groove bottom surface (61) is located below the axis (LA) of the rotating shaft (11) and closer to the first space (21) than the edge (32) of the rotation-side outer peripheral surface (31) on the second space (22) side. In this case, the shape makes it difficult for the lubricating oil flowing down the rotation-side end face (33) to enter the seal gap (20), so that the inflow of the lubricating oil into the seal gap (20) can be suppressed, and therefore, the accumulation of the lubricating oil in the lower part of the seal gap (20) can be suppressed.

[0056] REFERENCE SIGNS LIST 1 Turbocharger 2, 2A, 2B Seal structure 3 Rotating member 4 Stationary member 5 Seal member 6 Oil drain groove 11 Rotating shaft 12 Rotating wheel 12A Compressor wheel 12B Turbine wheel 13 Bearing 14 Housing 15 Sleeve 20, 20A, 20B Seal gap 21, 21A, 21B First space 22 Second space 23 Lubricating oil inlet 24 Lubricating oil supply path 25 Lubricating oil outlet 31, 31A, 31B Rotating side outer peripheral surface 32 Edge 33 Rotating side end face 41, 41A, 41B Stationary side inner peripheral surface 42 Edge 42A Oil drain groove side edge 42B Flat surface side edge 43 Stationary side end face 43A, 43B Flat surface 44 Lower end edge 61 Groove bottom surface 62, 63 Groove wall surface 64, 65 Upper end LA Axis θ Angular position

Claims

1. A seal structure for a turbocharger comprising: a rotating member including at least a rotating shaft of the turbocharger and a rotating wheel provided on one end side of the rotating shaft; a stationary member including at least a housing that accommodates the rotating member; a bearing that rotatably supports the rotating shaft; and a seal member provided in a seal gap formed between the rotating member and the stationary member, the seal gap communicating a first space in which the rotating wheel is accommodated and a second space in which the bearing is accommodated; the rotating member includes at least a rotating side outer peripheral surface that defines the seal gap, the stationary member includes a stationary side inner peripheral surface that defines the seal gap, and a stationary side end face extending from an edge of the stationary side inner peripheral surface on the second space side along the radial direction of the rotating shaft, and the stationary member has an oil drain groove provided in the stationary side end face below the axis of the rotating shaft, the oil drain groove extending vertically downward from the edge of the stationary side inner peripheral surface on the second space side.

2. A sealing structure for a turbocharger as set forth in claim 1, wherein the oil drain groove has a pair of groove wall surfaces facing each other with a gap between them in a width direction of the oil drain groove, and when an angular position is defined such that a position vertically below the axis of the rotating shaft is 0° and the angle increases in the rotational direction of the rotating shaft, one of the pair of groove wall surfaces has an upper end in the angular position range of +45° or more and +95° or less, and the other of the pair of groove wall surfaces has an upper end in the angular position range of -95° or more and -45° or less.

3. A sealing structure for a turbocharger as set forth in claim 2, wherein the upper end of the one groove wall surface is provided at a position where the angular position is equal to or greater than +85° and equal to or less than +95°, and the upper end of the other groove wall surface is provided at a position where the angular position is equal to or greater than -95° and equal to or less than -85°.

4. A sealing structure for a turbocharger as set forth in claim 3, wherein, when the length of the oil drain groove in the width direction is L1 and the diameter of the stationary side inner circumferential surface of the stationary member is L2, the oil drain groove satisfies the condition 0.95 x L2 ≦ L1 ≦ 1.05 x L2.

5. A sealing structure for a turbocharger as described in any one of claims 2 to 4, wherein the oil drain groove further has a groove bottom surface connecting the edges of each of the pair of groove wall surfaces on the first space side, and the groove bottom surface is located below the axis of the rotating shaft and closer to the first space than the edge of the rotating side outer peripheral surface on the second space side.

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