Compressor housing

Abstract

The object is to provide a compressor housing which can suppress blowback of oil. A compressor housing (1) is used in a compressor which uses a compressor impeller (5) provided in an intake air flow path more to a downstream side than a blow-by gas inlet. The compressor housing (1) includes an impeller chamber (2), and an intake air duct (6) which extends along an axis line (C). The duct (6) includes an inner-wall face (61). A step part (67) that is arc shaped along a circumferential direction of the impeller (5) and has a distance along the radial direction of the impeller (5) from the axis line (C) that is farther at a downstream side than at an upstream side thereof is formed in the inner-wall face (61) more to an upstream side along the axis line (C) than the intake air inlet (22).

Claims

1. A compressor housing of a compressor that uses an impeller provided in an intake air flow path of an internal combustion engine of a vehicle more to a downstream side than a blow-by gas recirculation part in which blow-by gas of the internal combustion engine recirculates, to pressurize intake air flowing through the intake air flow path, the compressor housing comprising: an impeller chamber that houses the impeller to be rotatable, and an intake air duct that extends along an axis line of the impeller and introduces intake air to the impeller chamber, and a breather duct that extends in the radial direction of the impeller and introduces blow-by gas into the intake air duct, wherein the intake air duct includes an inner-wall face that connects with an intake air inlet formed in the impeller chamber, wherein a step part that is arc shaped along a circumferential direction of the impeller and has a distance along the radial direction of the impeller from the axis line that is farther at a downstream side than at an upstream side thereof is formed in the inner-wall face more to an upstream side along the axis line than the intake air inlet, wherein a blow-by gas inlet connecting an inner circumferential face of the breather duct and the inner-wall face is provided vertically above the intake air inlet in a state where the compressor housing is mounted on the vehicle, and wherein the blow-by gas inlet is provided in the intake air flow path more to a downstream side than the step part.

2. The compressor housing according to claim 1, wherein a connecting face in the inner-wall face that connects the blow-by gas inlet and the intake air inlet is substantially perpendicular relative to the axis line.

3. The compressor housing according to claim 1, wherein a recess is formed in the inner-wall face at a portion between the intake air inlet and the step part of a base serving as a bottom in a state where the compressor housing is mounted on the vehicle, and wherein the step part is formed more to an upstream side along the axis line than the recess.

4. The compressor housing according to claim 1, wherein a recess is formed in the inner-wall face at a portion between the intake air inlet and the step part of a base serving as a bottom in a state where the compressor housing is mounted on the vehicle, and wherein the step part is formed more to an upstream side along the axis line than the recess.

5. The compressor housing according to claim 2, wherein a recess is formed in the inner-wall face at a portion between the intake air inlet and the step part of a base serving as a bottom in a state where the compressor housing is mounted on the vehicle, and wherein the step part is formed more to an upstream side along the axis line than the recess.

6. The compressor housing according to claim 3, wherein the step part is formed in the inner-wall face at a portion other than the base.

7. The compressor housing according to claim 4, wherein the step part is formed in the inner-wall face at a portion other than the base.

8. The compressor housing according to claim 5, wherein the step part is formed in the inner-wall face at a portion other than the base.

9. The compressor housing according to claim 2, wherein the step part extends along the circumferential direction to a side of the blow-by gas inlet from a position, which is higher than a lowest point of the intake air inlet, on the inner-wall face at a lateral part in a state where the compressor housing is mounted on the vehicle.

10. The compressor housing according to claim 5, wherein the step part extends along the circumferential direction to a side of the blow-by gas inlet from a position, which is higher than a lowest point of the intake air inlet, on the inner-wall face at a lateral part in a state where the compressor housing is mounted on the vehicle.

11. The compressor housing according to claim 8, wherein the step part extends along the circumferential direction to a side of the blow-by gas inlet from a position, which is higher than a lowest point of the intake air inlet, on the inner-wall face at a lateral part in a state where the compressor housing is mounted on the vehicle .

12. The compressor housing according to claim 1, further comprising a groove extending along the radial direction of the impeller from a position, which is higher than a lowest point of the intake air inlet, on a circumferential edge of the intake air inlet that in a state where the compressor housing is mounted on the vehicle, is formed in the inner-wall face more to an upstream side along the axis line than the intake air inlet.

13. The compressor housing according to claim 12, further comprising a recirculation duct that extends along a radial direction of the impeller and introduces blow-by gas or exhaust gas into the intake air duct, wherein the groove extends from a circumferential edge of the intake air inlet to a side of an inner circumferential face of the recirculation duct.

14. The compressor housing according to claim 13, wherein a recirculation opening that connects the inner circumferential face of the recirculation duct and the inner-wall face is provided at a position higher than the intake air inlet in a state where the compressor housing is mounted on the vehicle, and wherein the groove extends from a circumferential edge top part of the intake air inlet to a side of the inner circumferential face of the recirculation duct.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a plan view of an engine room of a vehicle to which a compressor housing according to an embodiment of the present invention is applied;

(2) FIG. 2 is a front view of the compressor housing according to the embodiment;

(3) FIG. 3 is a cross-sectional view of the compressor housing according to the embodiment;

(4) FIG. 4 is a cross-sectional view of the compressor housing according to the embodiment;

(5) FIG. 5 is a cross-sectional view of the compressor housing according to the embodiment;

(6) FIG. 6 is a perspective view of the compressor housing according to the embodiment;

(7) FIG. 7 is a cross-sectional view of the compressor housing according to the embodiment;

(8) FIG. 8 is a perspective view of the compressor housing according to the embodiment;

(9) FIG. 9 is a time chart for explaining a problem of the present invention; and

(10) FIG. 10 is a view showing an aspect of the inside of a conventional compressor housing.

DETAILED DESCRIPTION OF THE INVENTION

(11) Hereinafter, an embodiment of the present invention will be explained while referencing the drawings. FIG. 1 is a plan view of an engine room ER of a vehicle equipped with a turbocharging system S of an internal combustion engine (hereinafter referred to as engine). FIG. 1 mainly shows devices constituting the intake air system of the turbocharger system S, among the various devices provided in the engine room ER. In other words, FIG. 1 is a drawing when viewing, from above in the vertical direction, the turbocharger system S in a state equipped at a predetermined equipped orientation in the engine room ER.

(12) The turbocharging system S includes an air-cleaner box 91 that purifies the ambient air; a turbocharger 92 that includes an exhaust turbine which converts the exhaust gas energy into the mechanical energy of a rotating shaft, and a compressor 92C that pressurizes the intake air using a compressor impeller described later, which is coupled to the rotating shaft; intake air plumbing 93 that connects the air-cleaner box 91 and the compressor 92C; an air-flow meter 94 that detects the flowrate of intake air flowing in the intake air plumbing 93; EGR plumbing 95 that connects the compressor 92C and an exhaust flow path of the engine which is not illustrated; and breather plumbing 96 that connects the compressor 92C and the crankcase of the engine which is not illustrated. It should be noted that FIG. 1 shows a state in which the exhaust turbine of the turbocharger 92 is covered by a plate-like cover member 97.

(13) The intake air plumbing 93 extends substantially horizontally at the equipped orientation thereof to connect the air-cleaner box 91 and the intake air duct described later, which is formed at the compressor housing 1 constituting the main body of the compressor 92. Inside of the compressor housing 1, the main flow of intake air purified by the air-cleaner box 91 flows in the direction shown by the arrow 98a in FIG. 1 by way of this intake air plumbing 93. The air-flow meter 94 is provided in the intake air plumbing 93 at a position closer to the air-cleaner box 91 than the compressor housing 1.

(14) The EGR plumbing 95 connects the exhaust flow path (not illustrated) and an EGR duct described later, which is formed at the compressor housing 1. Part of the exhaust gas of the engine (hereinafter referred to as EGR gas) thereby flows inside of the compressor housing 1 in a direction substantially perpendicular to the main flow of intake air shown by the arrow 98a, as shown by the arrow 98b in FIG. 1.

(15) The breather plumbing 96 connects the crankcase (not illustrated) and a breather duct described later, which is formed in the compressor housing 1. Blow-by gas thereby flows inside of the compressor housing 1 in a direction substantially perpendicular to the main flow of intake air shown by the arrow 98a, as shown by the arrow 98c in FIG. 1.

(16) In addition, in the turbocharger system 8, an EGR gas recirculation part (i.e. EGR duct 7 described later) in which EGR gas is recirculated, and a blow-by gas recirculation part (i.e. breather duct 8 described later) in which blow-by gas is recirculated are provided in the intake air flow path constituted by the air-cleaner box 91, intake air plumbing 93 and compressor housing 1, more to a downstream side than the air-flow meter 94.

(17) FIG. 2 is a front view of the compressor housing 1. More specifically, FIG. 2 is a drawing when viewing the compressor housing 1 from an intake air upstream side along the axis line of the compressor impeller, which is provided to be rotatable inside of the impeller chamber 2 described later. FIG. 3 is a cross-sectional view of the compressor housing 1. More specifically, FIG. 3 is a drawing when viewing the cross section of the compressor housing 1 along the line IIa-IIa in FIG. 2 in the direction of the arrow A3. It should be noted that FIG. 2 and FIG. 3 are drawings when viewing the compressor housing 1 at the equipped orientation from the side. In other words, the up/down directions in FIG. 2 and FIG. 3 equal the vertical direction of the compressor housing 1 at the equipped orientation thereof.

(18) The compressor housing 1 includes the impeller chamber 2 which houses the compressor impeller 5 to be rotatable about the rotating shaft R; a diffuser chamber 3; a scroll flow path 4; an intake air duct 6 to which the intake air plumbing 93 (refer to FIG. 1) is connected, and introduces intake air to the impeller chamber 2; the EGR duct 7 to which the EGR plumbing 95 (refer to FIG. 1) is connected, and introduces EGR gas into the intake air duct 6; and the breather duct 8 to which the breather plumbing 96 (refer to FIG. 1) is connected, and introduces breather gas into the intake air duct 6.

(19) The compressor impeller 5 includes a wheel 51 coupled to the rotating shaft R that is rotationally driven by the exhaust turbine, and a plurality of blades provided to a conical hub face of this wheel 51. Each of the blades 52 is provided at equal intervals along the circumferential direction on the hub face of the wheel 51. Each of the blades 52 is a plate shape that extends at a predetermined angular distribution from a leading edge 53, which is the inlet of intake air, towards a trailing edge 54, which is the outlet of intake air. A tip end 55 of each blade 52 is formed along a surface profile of a shroud 21 described later, which opposes the compressor impeller 5 when housed inside of the impeller chamber 2.

(20) The shroud 21, which covers a lateral part of the compressor impeller 5, is formed in the impeller chamber 2. The shroud 21 includes a shroud face of a shape following the tip edges 55 from the leading edge 53 until the trailing edge 54 of the compressor impeller 5, and more specifically, a shroud face of a shape substantially matching the enveloping surface formed by the tip edges 55, when the compressor impeller 5 rotates around the rotating shaft R, and the shroud 21 covers the tip edges 55, which are the lateral part of the compressor impeller 5 by way of this shroud face. A side at the leading edge 53 of this shroud 21 forms an intake air inlet 22 having an inside diameter substantially equal to the outside diameter of this leading edge 53. In addition, a side at the trailing edge 54 of the shroud 21 forms an annular intake air discharge opening having a width substantially equal to the height of this trailing edge 54.

(21) The compressor impeller 5 rotates clockwise when viewing from the intake air upstream side around the rotating shaft R (i.e. clockwise in FIG. 2), for example, when the turbine impeller of the exhaust turbine coupled by the rotating shaft R with this rotates by way of the energy of exhaust gas. When the compressor impeller 5 rotates in a state provided inside the impeller chamber 2, there is influx along the axis line C from the leading edge 53 of each blade 52, which flows between the respective blades 52, and then is discharged from each of the trailing edges 54 towards the outside in the radial direction.

(22) The diffuser chamber 3 is annular, and is formed so as to surround the intake air discharge opening of the impeller chamber 2. A raw of linear vanes provided to stand is formed at predetermined intervals along the circumferential direction of the compressor impeller 5 in the diffuser chamber 3. By the compressor impeller 5 rotating, the intake air discharged from the trailing edge 54 thereof to the outside in the radial direction is decelerated in the course of flowing while expanded along the vane row formed in the diffuser chamber 3.

(23) The scroll flow path 4 is annular, and is formed so as to surround the diffuser chamber 3. The flow path cross-sectional area of the scroll flow path 4 becomes gradually larger along the same direction as the rotational direction of the compressor impeller 5. The intake air discharged from the diffuser chamber 3 to outside in the radial direction, after further decelerated in the course of flowing through the scroll flow path 4, is guided to the combustion chamber of the engine (not illustrated) via the intake air discharge duct 41 (refer to FIG. 2).

(24) The intake air duct 6 is substantially tubular extending along the axis line C of the compressor impeller 5. The intake air duct 6 includes an inner-wall face 61 that connects to the intake air inlet 22 formed at the impeller chamber 2. The intake air introduced by the intake air plumbing 93 in FIG. 1 is introduced into the impeller chamber 2 along the axis line C via the intake air flow path formed by the inner-wall face 61 of this intake air duct 6.

(25) As shown in FIGS. 2 and 3, the inner-wall face 61 of the intake air duct 6 is configured by a substantially cylindrical inner circumferential face 62 having a larger inside diameter than the inside diameter of the intake air inlet 22 of the impeller chamber 2 and extending along the axis line C; and an annular shoulder face 63 that extends along the radial direction of the compressor impeller 5 to connect the inner circumferential face 62 and the intake air inlet 22 having a smaller diameter than this. In addition, as shown in FIG. the center 62C of the inner circumferential face 62 when viewing along the axis line C of the compressor impeller 5 at the equipped orientation is eccentric to somewhat above in the vertical direction relative to the center 22C of the intake air inlet 22 of the impeller chamber 2. It should be noted that the specific configuration of this inner-wall face 61 will be explained in detail while referencing cross-sectional views later.

(26) The EGR duct 7 is a pipe member that communicates a plumbing connection part 71 provided at the outside of the compressor housing 1 and the intake air flow path formed by the inner-wall face 61 on the inside of the intake air duct 6. The aforementioned EGR plumbing 95 (refer to FIG. 1) is connected to this plumbing connection part 71. The EGR gas is thereby recirculated within the intake air duct 6. The inner circumferential face 72 of the EGR duct 7 is substantially cylindrical, and extends along the radial direction of the compressor impeller 5. When defining an opening connecting the inner circumferential face 72 of this EGR duct 7 and the inner-wall face 61 of the intake air duct 6 as an EGR inlet 73, the center of this EGR inlet 73 is provided at a position higher than the center 22C of the intake air inlet 22, at the equipped orientation of the compressor housing 1 as shown in FIG. 2.

(27) The breather duct 8 is a pipe member communicating a plumbing connection part 81 provided outside of the compressor housing 1 and the intake air flow path formed by the inner-wall face 61 at the inside of the intake air duct 6. The aforementioned breather plumbing 96 (refer to FIG. 1) is connected to this plumbing connection part 81. The blow-by gas is thereby recirculated within the intake air duct 6. The inner circumferential face 82 of the breather duct 8 is substantially cylindrical, and extends along the radial direction of the compressor impeller 5. When defining an opening connecting the inner circumferential face 82 of this breather duct 8 and the inner-wall face 61 of the intake air duct 6 as a blow-by gas inlet 83, this blow-by gas inlet 83 is provided above in the vertical direction the intake air inlet 22 at the equipped orientation of the compressor housing 1.

(28) FIG. 4 is a cross-sectional view of the compressor housing 1. More specifically, FIG. 4 is a drawing when viewing the cross section of the compressor housing 1 along the line IIa-IIa in FIG. 2 in the direction of the arrow A4. A connecting face 66 of the shoulder face 63 of the intake air duct 6 connects the intake air inlet 22 and the blow-by gas inlet 83 provided vertically above this. The connecting face 66 is substantially perpendicular to the axis line C as shown in FIG. 4. In other words, irregularities serving as a barrier to oil flowing along the wall face are not provided to the connecting face 66 which connects the blow-by gas inlet 83 and the intake air inlet 22. The distance between the blow-by gas inlet 83 and the intake air inlet 22 can thereby be made as short as possible. In addition, most of the oil in the blow-by gas recirculated within the intake air duct 6 from the blow-by gas inlet 83 can be made to run along the connecting face 66 by its own weight and be aspirated into the intake air inlet 22.

(29) Referring back to FIG. 3, at a portion of the inner circumferential face 62 of the intake air duct 6 adjacent to the intake air inlet 22 of a base 64 serving as the bottom, at the equipped orientation of the compressor housing 1, a recess 65 that is lower than the lowest point 221 of the intake air inlet 22 is formed. As explained by referencing FIGS. 9 and 10, swirl flow in the same direction as the rotational direction of the compressor impeller 5 is produced inside of the intake air duct 6 when performing steady operation of the engine. In addition, when such swirl flow is produced, a part of the oil falling down by running along the connecting face 6 which connects the blow-by gas inlet 83 and the intake air inlet 22 (refer to FIG. 2 or 4) may continue to swirl along the shoulder face 63 around the intake air inlet 22, without being aspirated into the intake air inlet 22. The oil swirling around the intake air inlet 22 during steady operation of the engine in this way collects in the recess 65 by way of its own weight when becoming low load operation and the swirl flow weakens.

(30) FIG. 5 is a cross-sectional view of the compressor housing 1. More specifically, FIG. 5 is a drawing when viewing the cross section of the compressor housing 1 along the line III-III in FIG. 3 in the direction of the arrow A5. FIG. 6 is a perspective view of the compressor housing 1. More specifically, FIG. 6 is a perspective view when viewing a portion on the left side in FIG. 2 of the inner-wall face 61 of the compressor housing 1.

(31) As shown in FIGS. 3, 5 and 6, an arc-shaped step part 67 along the circumferential direction of the compressor impeller 5 is formed in the inner circumferential face 62 more to the upstream side along the axis line C than the recess 65. In addition, the distance along the radial direction of the compressor impeller 5 from the axis line C until the wall face is farther at the downstream side than the upstream side with the step part 67 as the border (refer to FIG. 5). Therefore, this step part 67 serves as a barrier relative to the flow of oil (refer to arrow 5a in FIG. 5) running along the inner circumferential face 62 to the upstream side from the recess 65 provided on the downstream side therefrom. It should be noted that the position at which forming the step part 67 is not limited thereto. However, in order to configure so as not to add to the amount of oil collecting in the recess 65, the step part 67 is preferably formed at a portion other than the base 64 in the inner circumferential face 62.

(32) The step part 67 extends along the circumferential direction of the compressor impeller 5 to a side of the blow-by gas inlet 83 provided above in the vertical direction the intake air inlet 22, from a position, which is higher than the lowest point 221 of the intake air inlet 22, on a lateral part in the equipped orientation of the compressor housing 1 of the inner circumferential face 62 of the intake air duct 6.

(33) The effects of this step part 67 will be explained while referencing FIG. 6. First, as explained by referencing FIGS. 9 and 10, surging occurs when stepping on the accelerator pedal, and a strong swirl flow may be produced from the side of the impeller chamber 2 towards the upstream side inside of the intake air duct 6. On this occasion, if oil is collected in the recess 65, the oil having collected in the recess 65 will run along the inner circumferential face 62 of the intake air duct 6 and flow to the upstream side by way of the strong swirl flow in the reverse direction. However, since the step part 67 serves as a barrier relative to the flow of oil running along the such a wall face, the oil blown back due to the reverse swirl flow from the recess 65 will run up to the side of the blow-by gas inlet 83 along the extending direction of the step part 67 as shown by the arrow 6a in FIG. 6, i.e. circumferential direction of the compressor impeller. In addition, the oil led until the side of the blow-by gas inlet 83 by the step part 67 arrives at the connecting face 66 that is substantially perpendicular to the axis line C connecting the blow-by gas inlet 83 and the intake air inlet 22 (refer to FIG. 4), and runs along the connecting wall 66 to be aspirated into the intake air inlet 22, as shown by the arrow 6b in FIG. 6. According to the step part 67, the blowback to the upstream side of oil collected in the recess 65 is thereby suppressed, and the aspiration of collected oil to the intake air inlet 22 is promoted.

(34) FIG. 7 is a cross-sectional view of the compressor housing 1. More specifically, FIG. 7 is a drawing when viewing the cross section of the compressor housing 1 along the line IIb-IIb in FIG. 2 in the direction of the arrow A7. FIG. 8 is a perspective view of the compressor housing 1. More specifically, FIG. 8 is a perspective view when viewing a portion on the right side in FIG. 2 of the inner-wall face 61 of the compressor housing 1.

(35) As shown in FIGS. 2, 7 and 8, a substantially V-shaped groove 68 in a cross-sectional view extending along the radial direction of the compressor impeller 5 from the circumferential edge of the intake air inlet 22 is formed more to the upstream side along the axis line C than the intake air inlet 22 in the shoulder face 63 inside of the intake air duct 6. The groove 68 extends along the radial direction of the compressor impeller 5 from an apex 222 of the circumferential edge of the intake air inlet 22 in the equipped orientation of the compressor housing 1, and reaches the EGR inlet 73 provided at a position higher than the intake air inlet 22 as mentioned above.

(36) The effects of this groove 68 will be explained while referencing FIG. 8. First, as explained by referencing FIGS. 9 and 10, while performing steady operation of the engine, swirl flow is produced from the upstream side to the side of the impeller chamber 2 inside of the intake air duct 6, and oil in the blow-by gas may continue to swirl around the intake air inlet 22 along the shoulder face 63 due to this, whereby the oil may collect in the recess 65 when releasing the accelerator pedal. The groove 68 extends along the radial direction of the compressor impeller 5, and the groove 68 is substantially perpendicular relative to the flowing direction of oil during steady operation. Therefore, at the shoulder face 63 at the inside of the intake air duct 6, for the oil swirling and moving along the circumferential direction of the impeller around the intake air inlet 22 as shown by the arrow 8a in FIG. 8, at this groove 68, the traveling direction thereof is changed to the extending direction of the groove 68, i.e. radial direction of the compressor impeller 5, and the oil spreads along both wall faces 68a, 68b constituting the groove 68 as shown by the arrow 8b in FIG. 8. Therefore, according to this groove 68, the oil swirling around the intake air inlet 22 during steady operation can be made to temporarily evacuate without allowing to reach the recess 65 below. In addition, the reference point of the groove 68 as mentioned above serves as the apex 222 of the circumferential edge of the intake air inlet 22 in the equipped orientation. Therefore, the oil temporarily evacuated to the groove 68 by the swirl flow during steady operation, when subsequently releasing the accelerator pedal, runs along the groove 68 by way of its own weight, and flows into the intake air inlet 22 provided therebelow, as shown by the arrow 68c in FIG. 8; therefore, it is possible to decrease the amount of oil collecting in the recess 65.

(37) According to the compressor housing 1 of the present embodiment, the following effects are exerted.

(38) (1) The compressor housing 1 forms an arc-shaped step part 67 along the circumferential direction of the compressor impeller 5, more to the upstream side along the axis line C than the intake air inlet 22 in the inner circumferential face 62 of the intake air duct 6 thereof. Since the step part 67 serves as a barrier relative to the flow of oil running along the inner circumferential face 62, even when strong swirl flow is produced from the downstream side towards the upstream side within the intake air duct 6 in a state in which oil has collected in the recess 65 in the vicinity of the intake air inlet 22 within the intake air duct 6, it is possible to suppress oil from overcoming the step part 67 and blowing back further to the upstream side. In addition, it is thereby possible to prevent the air-flow meter 94 provided on the upstream side from the intake air duct 6 from being dirtied by oil.

(39) (2) The compressor housing 1 provides the breather duct 8 extending along the radial direction of the compressor impeller 5, and recirculates blow-by gas from this breather duct 8 within the intake air duct 6. With a conventional compressor housing, when recirculating blow-by gas within the intake air duct of the compressor housing, oil tends to collect within the intake air duct, and the problem of blowback of oil to the intake air upstream side is more remarkably exhibited. In contrast, with the compressor housing 1, since the outward flow of oil to upstream side is suppressed by the step part 67 formed in the intake air duct 6, even if recirculating blow-by gas within the intake air duct 6, the problem of blowback of oil as mentioned above will not actualize.

(40) (3) With the compressor housing 1, the blow-by gas inlet 83 is provided vertically above the intake air inlet 22 in the equipped orientation thereof, and further, the connecting face 66 which connects the blow-by gas inlet 83 and the intake air inlet 22 in the shoulder face 63 of the intake air duct 6 is substantially perpendicular to the axis line C. Since most of the oil in the blow-by gas is thereby flowed into the intake air inlet 22, it is possible to reduce the amount of oil collecting in the recess 65 inside the intake air duct 6, and possible to further suppress blowback of oil.

(41) (4) With the compressor housing 1, the step part 67 is formed more to the upstream side along the axis line C than the recess 65 serving as the bottom in the equipped orientation of the inner circumferential face 62 of the intake air duct 6. It is thereby possible to suppress the outward flow to further upstream side by this step part 67, even if oil collected in the recess 65 is flowed to the upstream side by a strong reverse swirl flow as mentioned above.

(42) (5) With the compressor housing 1, the step part 67 is formed in a portion other than the base 64 of the inner circumferential face 62. It is thereby possible to suppress the outward flow to the upstream side thereof, without increasing the amount of oil collecting in the recess 65 within the intake air duct 6.

(43) (6) With the compressor housing 1, the step part 67 extends along the circumferential direction of the compressor impeller 5 to the side of the blow-by gas inlet 83 provided vertically above the intake air inlet 22 from a position, which is higher than the lowest point 221 of the intake air inlet 22, on a lateral part in the equipped orientation of the inner circumferential face 62. When a strong reverse swirl flow is produced, the oil collected in the recess 65 thereby flows from the side of the base 64 along the step part 67 to the side of the blow-by gas inlet 83 which is vertically above, and runs along the connecting face 66 formed to be substantially perpendicular to the axis line C and flows into the intake air inlet 22. It is thereby possible to flow the oil collected in the recess 65 into the intake air inlet 22, while configuring so as not to blow back to the upstream side.

(44) (7) The compressor housing 1 forms the groove 68 extending along the radial direction from a position, which is higher than the lowest point 221 of the intake air inlet 22 in the equipped orientation, on the circumferential edge of the intake air inlet 22, more to an upstream side along the axis line C than the intake air inlet 22 in the shoulder face 63 of the intake air duct 6 thereof. Since it is thereby possible to temporarily cause the oil swirling around the intake air inlet 22 during steady operation to evacuate to this groove 68, it is possible to reduce the amount of oil collecting in the recess 65 upon releasing the accelerator pedal. It is thereby possible to reduce the amount of oil blown back from the upstream side to the downstream side when a strong reverse swirl flow is produced from the downstream side towards the upstream side inside the intake air duct 6. In addition, it is thereby possible to prevent the air-flow meter 94 provided on the upstream side of the intake air duct 6 from being dirtied by oil.

(45) (8) The compressor housing 1 provides the EGR duct 7 extending along the radial direction of the compressor impeller 5 and introducing EGR gas into the intake air duct 6, and the groove 68 extends from the circumferential edge of the intake air duct 22 to the side of the inner circumferential face 72 of the EGR duct 7. In other words, with the compressor housing 1, it is possible to cause a sufficient amount of oil to evacuate to the groove 68, by providing the groove 68 using the space formed by providing the EGR duct 7.

(46) (9) With the compressor housing 1, the groove 68 extends from the apex 222 of the circumferential edge of the intake air inlet 22 in the equipped orientation to the side of the inner circumferential face of the EGR duct 7. The oil temporarily evacuating to the groove 68 by way of the swirl flow during steady operation, when releasing the accelerator pedal, runs along the groove 68 to flow into the intake air inlet 22 further below; therefore, it is possible to reduce the amount of oil collecting in the recess 65.

(47) Although an embodiment of the present invention has been explained above, the present invention is not to be limited thereto. The detailed configurations may be modified as appropriate within the scope of the gist of the present invention.

(48) In the above-mentioned embodiment, an example is explained in which the rotational direction of the compressor impeller 5 is established as clockwise when viewed from the upstream side; however, the rotational direction of the compressor impeller 5 may be reversed from this.

(49) In the above-mentioned embodiment, an example is explained in which the reference point of the groove 68 is established as the apex 222 in the equipped orientation of the circumferential edge of the intake air inlet 22; however, the present invention is not to be limited thereto. The reference point of the groove 68 may be any portion of the circumferential edge of the intake air inlet 22, so long as being higher than the lowest point 221 of the intake air inlet 22 in the equipped orientation.