Compressor housing for turbocharger and method for manufacturing the same

Abstract

A compressor housing for a turbocharger dividably composed of a plurality of pieces including a scroll piece, and a shroud piece. The scroll piece and the shroud piece are assembled to each other by press-fitting a press-fitting portion of the shroud piece into a press-fitted portion of the scroll piece. Pressure-contacting portions that are provided on either one of the scroll piece and the shroud piece are pressure-contacted with pressure-contacted portions that are provided on the other one of the scroll piece and the shroud piece, respectively. As a result, the pressure-contacting portions plastically flow to form seal parts for sealing the scroll piece and the shroud piece, respectively.

Claims

1. A compressor housing for a turbocharger configured to house a compressor impeller, the compressor housing comprising: an intake port part that defines an intake port configured to suck in air toward the compressor impeller; a shroud part that surrounds the compressor impeller in a circumferential direction and has a shroud surface facing the compressor impeller; a diffuser part that is on an outer circumferential side of the compressor impeller in the circumferential direction and forms a diffuser passage configured to allow compressed air discharged from the compressor impeller to pass therethrough; and a scroll chamber part that forms a scroll chamber configured to guide the compressed air passing through the diffuser passage to outside; wherein the compressor housing is dividably composed of a plurality of pieces including a scroll piece having at least the intake port part and a portion of the scroll chamber part, and a shroud piece having at least a portion of the scroll chamber part, a portion of the diffuser part, and the shroud part, wherein the scroll piece and the shroud piece are assembled to each other by press-fitting a press-fitting portion of the shroud piece into a press-fitted portion of the scroll piece, and wherein a seal part that seals the scroll piece and the shroud piece comprises a pressure-contacting portion on one of the scroll piece and the shroud piece and a pressure-contacted portion on the other one of the scroll piece and the shroud piece that are in pressure contact with one another such that there is plastic deformation in the pressure-contacting portion.

2. The compressor housing for a turbocharger according to claim 1, further comprising a refrigerant flow path that is along the diffuser part in the circumferential direction, and allows a refrigerant for cooling the diffuser part to pass therethrough; wherein the refrigerant flow path is an annular space that comprises a first refrigerant flow-path part of the scroll piece and a second refrigerant flow-path part of the shroud piece, the first refrigerant flow-path part and the second refrigerant flow-path part respectively at each opposing part of the scroll piece and the shroud piece which oppose each other, wherein the seal part includes an inner circumferential seal part configured to seal the refrigerant flow path on the inner circumferential side thereof, and an outer circumferential seal part configured to seal the refrigerant flow path on the outer circumferential side thereof, wherein the inner circumferential seal part is formed by pressure-contacting an inner circumferential pressure-contacting portion that is on either one of the scroll piece and the shroud piece with an inner circumferential pressure-contacted portion that is on the other one of the scroll piece and the shroud piece so that the inner circumferential pressure-contacting portion plastically flows, and wherein the outer circumferential seal part comprises an outer circumferential pressure-contacting portion that is on either one of the scroll piece and the shroud piece and an outer circumferential pressure-contacted portion that is on the other one of the scroll piece and the shroud piece that are in pressure contact with one another such that there is plastic deformation in the outer circumferential pressure-contacting portion.

3. The compressor housing for a turbocharger according to claim 1, wherein the seal part is located within the press-fitting portion on a further rear side in an inserting direction of the press-fitting portion.

4. The compressor housing for a turbocharger according to claim 2, wherein the seal part is located within the press-fitting portion on a further rear side in an inserting direction of the press-fitting.

5. A method for manufacturing a compressor housing for a turbocharger according to claim 1, the method comprising: molding the scroll piece and the shroud piece by die-casting; forming the pressure-contacting portion on either one of the scroll piece and the shroud piece and the pressure-contacted portion on the other one of the scroll piece and the shroud piece by machining; and assembling the shroud piece to the scroll piece by press-fitting the press-fitting portion into the press-fitted portion, and by pressure-contacting the pressure-contacting portion with the pressure-contacted portion so as to cause plastic deformation in the pressure-contacting portion to thereby form the seal part.

6. A method for manufacturing a compressor housing for a turbocharger according to claim 2, the method comprising: molding the scroll piece and the shroud piece by die-casting; forming the pressure-contacting portion on either one of the scroll piece and the shroud piece and the pressure-contacted portion on the other one of the scroll piece and the shroud piece by machining; and assembling the shroud piece to the scroll piece by press-fitting the press-fitting portion into the press-fitted portion, and by pressure-contacting the pressure-contacting portion with the pressure-contacted portion so as to cause plastic deformation in the pressure-contacting portion to thereby form the seal part.

7. A method for manufacturing a compressor housing for a turbocharger according to claim 3, the method comprising: molding the scroll piece and the shroud piece by die-casting; forming the pressure-contacting portion on either one of the scroll piece and the shroud piece and the pressure-contacted portion on the other one of the scroll piece and the shroud piece by machining; and assembling the shroud piece to the scroll piece by press-fitting the press-fitting portion into the press-fitted portion, and by pressure-contacting the pressure-contacting portion with the pressure-contacted portion so as to cause plastic deformation in the pressure-contacting portion to thereby form the seal part.

8. A method for manufacturing a compressor housing for a turbocharger according to claim 4, the method comprising: molding the scroll piece and the shroud piece by die-casting; forming the pressure-contacting portion on either one of the scroll piece and the shroud piece and the pressure-contacted portion on the other one of the scroll piece and the shroud piece by machining; and assembling the shroud piece to the scroll piece by press-fitting the press-fitting portion into the press-fitted portion, and by pressure-contacting the pressure-contacting portion with the pressure-contacted portion so as to cause plastic deformation in the pressure-contacting portion to thereby form the seal part.

9. The method according to claim 5, wherein the pressure-contacting portion is formed by machining in a mountain shape that protrudes in the radial direction in a cross section including the rotation axis of the compressor impeller, having a front-end side inclined plane that is located on the front-end side in a press-fitting portion inserting direction and a rear-end side inclined plane that is located on the rear-end side in the inserting direction such that an acute-angle between the rear-end side inclined plane and the rotation axis is set larger than an acute-angle between the front-end side inclined plane and the rotation axis in the cross section.

10. The method according to claim 6, wherein the pressure-contacting portion is formed by machining in a mountain shape that protrudes in the radial direction in a cross section including the rotation axis of the compressor impeller, having a front-end side inclined plane that is located on the front-end side in a press-fitting portion inserting direction and a rear-end side inclined plane that is located on the rear-end side in the inserting direction such that an acute-angle between the rear-end side inclined plane and the rotation axis is set larger than an acute-angle between the front-end side inclined plane and the rotation axis in the cross section.

11. The method according to claim 7, wherein the pressure-contacting portion is formed by machining in a mountain shape that protrudes in the radial direction in a cross section including the rotation axis of the compressor impeller, having a front-end side inclined plane that is located on the front-end side in a press-fitting portion inserting direction and a rear-end side inclined plane that is located on the rear-end side in the inserting direction such that an acute-angle between the rear-end side inclined plane and the rotation axis is set larger than an acute-angle between the front-end side inclined plane and the rotation axis in the cross section.

12. The method according to claim 8, wherein the pressure-contacting portion is formed by machining in a mountain shape that protrudes in the radial direction in a cross section including the rotation axis of the compressor impeller, having a front-end side inclined plane that is located on the front-end side in a press-fitting portion inserting direction and a rear-end side inclined plane that is located on the rear-end side in the inserting direction such that an acute-angle between the rear-end side inclined plane and the rotation axis is set larger than an acute-angle between the front-end side inclined plane and the rotation axis in the cross section.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a cross-sectional view of a compressor housing for a turbocharger according to Embodiment 1.

(2) FIG. 2 is a schematic diagram for illustrating a method for manufacturing the compressor housing for a turbocharger according to Embodiment 1.

(3) FIG. 3 is a perspective, cross-sectional view of a scroll piece according to Embodiment 1.

(4) FIG. 4 is a perspective view of a shroud piece according to Embodiment 1.

(5) FIG. 5 is a perspective, cross-sectional view of the shroud piece according to Embodiment 1.

(6) FIGS. 6A, 6B, and 6C are a series of schematic diagrams of an enlarged substantial part for illustrating a method for manufacturing a compressor housing for a turbocharger according to Embodiment 1.

(7) FIGS. 7A, 7B, and 7C are a series of schematic diagrams of an enlarged substantial part for illustrating a method for manufacturing a compressor housing for a turbocharger according to Embodiment 1.

(8) FIG. 8 is a cross-sectional view of a compressor housing for a turbocharger according to Modification 1.

(9) FIG. 9 is a schematic diagram for illustrating a method for manufacturing the compressor housing for a turbocharger according to Modification 1.

(10) FIG. 10 is a schematic diagram for illustrating a method for manufacturing the compressor housing for a turbocharger according to Modification 1.

(11) FIG. 11 is a schematic diagram of an enlarged substantial part for illustrating a method for manufacturing a compressor housing for a turbocharger according to Embodiment 2.

(12) FIG. 12 is a schematic diagram of an enlarged substantial part for illustrating the method for manufacturing the compressor housing for a turbocharger according to Embodiment 2.

DETAILED DESCRIPTION OF THE INVENTION

(13) “Circumferential direction” in the present specification means the rotation direction of a compressor impeller, “shaft direction” means the direction of the rotation shaft of the compressor impeller, “radial direction” means the radius direction of an imaginary circle centered on the rotation shaft of the compressor impeller, and “outwardly in the radial direction” is defined to be in the direction straightly extending from the center of the imaginary circle to the circumference of the circle.

(14) The compressor housing for a turbocharger further includes a refrigerant flow path that is formed along the diffuser part in the circumferential direction, and allows a refrigerant for cooling the diffuser part to pass therethrough;

(15) wherein the refrigerant flow path is formed as an annular space that is constituted by a first refrigerant flow-path formation part of the scroll piece and a second refrigerant flow-path formation part of the shroud piece, the first refrigerant flow-path formation part and the second refrigerant flow-path formation part being formed respectively at each opposing part of the scroll piece and the shroud piece which oppose each other,

(16) wherein the seal part includes an inner circumferential seal part configured to seal the refrigerant flow path on the inner circumferential side thereof, and an outer circumferential seal part configured to seal the refrigerant flow path on the outer circumferential side thereof,

(17) wherein the inner circumferential seal part is formed by pressure-contacting an inner circumferential pressure-contacting portion that is provided on either one of the scroll piece and the shroud piece with an inner circumferential pressure-contacted portion that is provided on the other one of the scroll piece and the shroud piece so as to cause plastic flow in the inner circumferential pressure-contacting portion, and

(18) wherein the outer circumferential seal part is formed by pressure-contacting an outer circumferential pressure-contacting portion that is provided on either one of the scroll piece and the shroud piece with an outer circumferential pressure-contacted portion that is provided on the other one of the scroll piece and the shroud piece so as to cause plastic flow in the outer circumferential pressure-contacting portion. According to such a configuration, in the compressor housing for a turbocharger having the refrigerant flow path provided therein, improvement in sealability can be achieved compatibly with cost reduction.

(19) The seal part is preferably located on further rear side in a press-fitting portion inserting direction with respect to the press-fitting portion. In this case, when the shroud piece is assembled to the scroll piece, the pressure-contacting portion is pressure-contacted with the pressure-contacted portion after the press-fitting portion is press-fitted into the press-fitted portion, so that dispersal of a plastic flow portion of the seal part can be curtailed. Therefore, the sealability can be surely improved.

(20) Another aspect of the present disclosure provides a method for manufacturing a compressor housing for a turbocharger according to claim 1, the method including:

(21) molding the scroll piece and the shroud piece by die-casting;

(22) forming the pressure-contacting portion on either one of the scroll piece and the shroud piece and the pressure-contacted portion on the other one of the scroll piece and the shroud piece by machining; and

(23) assembling the shroud piece to the scroll piece by press-fitting the press-fitting portion into the press-fitted portion, and by pressure-contacting the pressure-contacting portion with the pressure-contacted portion so as to cause plastic flow in the pressure-contacting portion to thereby form the seal part.

(24) According to this configuration, the above-mentioned compressor housing for a turbocharger can be manufactured. Because the pressure-contacting portion and the pressure-contacted portion are formed by machining, the surfaces thereof can be made rough to some extent in comparison with a cast surface made by die-casting, which makes it possible to easily cause plastic flow in the pressure-contacting portion in the assembling, so that the sealability can be further enhanced.

(25) In the machining, the pressure-contacting portion is preferably formed by machining in a mountain shape that protrudes in the radial direction in a cross section including the rotation axis of the compressor impeller, having a front-end side inclined plane that is located on the front-end side in the press-fitting portion inserting direction and a rear-end side inclined plane that is located on the rear-end side in the inserting direction such that an acute-angle between the rear-end side inclined plane and the rotation axis is set larger than an acute-angle between the front-end side inclined plane and the rotation axis in the cross section. In this case, the pressure-contacting portion is shaped by machining such that the rear-end side inclined plane stands more steeply with respect to the rotational axis than the front-end side inclined plane does, so that the width of the pressure-contacting portion can be narrowed with the inclination angle of the front-end side inclined plane and the protruding amount of the pressure-contacting portion being kept unchanged. Thus, in the assembling step, plastically flow in the pressure-contacting portion is easily caused without deterioration of assemblability. Consequently, at each seal part formed in the assembling step, a micro gap can be filled more surely, so that the sealability can be further improved. Otherwise, by narrowing the width of the pressure-contacting portion with the plastic flow amount of the pressure-contacting portion being kept unchanged, dimension tolerances in the pressure-contacting portion and the pressure-contacted portion can be eased in the machining. As a result, productivity can be improved and cost reduction can be achieved.

EMBODIMENTS

Embodiment 1

(26) Hereinafter, embodiments of the above-mentioned compressor housing for a turbocharger will be described with reference to FIGS. 1 to 7.

(27) As shown in FIG. 1, a compressor housing 1 for a turbocharger has a compressor impeller 13 housed therein, and is provided with an intake port formation part 10, a shroud part 20, a diffuser part 30, and a scroll chamber formation part 120.

(28) The intake port formation part 10 defines an intake port 11 configured to suck in air toward the compressor impeller 13.

(29) The shroud part 20 surrounds the compressor impeller 13 in the circumferential direction and has a shroud surface 22 facing the compressor impeller 13.

(30) The diffuser part 30 is formed on the outer circumferential side of the compressor impeller 13 in the circumferential direction and forms a diffuser passage 15 configured to allow compressed air discharged from the compressor impeller 13 to pass therethrough.

(31) The scroll chamber formation part 120 forms a scroll chamber 12 configured to guide the compressed air passing through the diffuser passage 15 to outside.

(32) And the compressor housing 1 is dividably composed of a plurality of pieces including the scroll piece 2 and the shroud piece 3.

(33) The scroll piece 2 has at least the intake port formation part 10 and a portion of the scroll chamber formation part 120.

(34) The shroud piece 3 has at least a portion of the scroll chamber formation part 120, a portion of the diffuser part 30, and the shroud part 20.

(35) The scroll piece 2 and the shroud piece 3 are assembled to each other by press-fitting a press-fitting portion 53b of the shroud piece 3 into a press-fitted portion 53a of the scroll piece 2. In addition, seal parts 541 and 542 that seal the scroll piece 2 and the shroud piece 3 are formed by pressure-contacting pressure-contacting portions 541b and 542b that are provided on the shroud piece 3 with pressure-contacted portions 541a and 542a that are provided on the scroll piece 2 so as to cause plastic flow in the pressure-contacting portions 541b and 542b.

(36) Hereinafter, the compressor housing 1 for a turbocharger according to the present embodiment will be described in detail.

(37) As shown in FIG. 1, the compressor housing 1 is dividably formed of the scroll piece 2 and the shroud piece 3 that have been prepared separately. And the compressor housing 1 is attached to a flange part, or a seal plate 40 formed in the case of dividable structure, of a bearing housing (not shown in any figure) that houses a bearing unit for bearing a shaft 14 on one end of which the compressor impeller 13 is attached.

(38) As shown in FIGS. 2 and 3, the scroll piece 2 includes the intake port formation part 10, a first scroll chamber formation part 121, an outer peripheral portion 125, and a first refrigerant flow-path formation part 51. As shown in FIG. 2, the shroud piece 3 includes a second scroll chamber formation part 122, the shroud part 20, a first diffuser part 35, and a second refrigerant flow-path formation part 52.

(39) As shown in FIGS. 2 and 3, the intake port formation part 10 of the scroll piece 2 has a cylindrical shape penetratingly formed in the shaft direction Y. The first scroll chamber formation part 121 constitutes a wall surface of the scroll chamber 12 on an intake side Y1. As shown in FIG. 1, the outer peripheral portion 125 is located on a side Y2 that is opposite to the intake side Y1 to form an outer peripheral portion of the compressor housing 1. And, the seal plate 40 is attached inside the outer peripheral portion 125.

(40) As shown in FIG. 1, the second scroll chamber formation part 122 of the shroud piece 3 constitutes a wall surface of the scroll chamber 12 on the inner circumferential side. The shroud part 20 forms the shroud surface 22 that faces the compressor impeller 13. The first diffuser part 35 forms a diffuser surface 34 that extends from the shroud surface 22 toward the scroll chamber 12. It is noted that as shown in FIG. 2, the outer peripheral edge of the shroud piece 3 at the tip end on the intake side Y1 is chamfered to form a third chamfered portion 591.

(41) As shown in FIGS. 1 and 2, the intake port formation part 10 of the scroll piece 2 has the press-fitted portion 53a provided on the side Y2 opposite to the intake side Y1. As shown in FIG. 3, the press-fitted portion 53a has a cylindrical inner peripheral surface. As shown in FIG. 1, the shroud piece 3 has the press-fitting portion 53b provided on the intake side Y1. As shown in FIGS. 4 and 5, the press-fitting portion 53b has a cylindrical outer peripheral surface. And, as shown in FIGS. 1 and 2, the press-fitting portion 53b of the shroud piece 3 is press-fitted into the inside of the press-fitted portion 53a of the scroll piece 2, and the shroud piece 3 is assembled to the scroll piece 2. The press-fitting portion 53b and the press-fitted portion 53a are in contact with each other entirely in the circumferential direction. It is noted that a tightening margin of the press-fitting portion 53b and the press-fitted portion 53a can be set in the range such that sufficient slip-out load can be obtained and no breakage will be caused. In the present embodiment, the scroll piece 2 and the shroud piece 3 are made of an aluminum alloy, and the tightening margin of both is set within the range of 40±20 μm.

(42) As shown in FIG. 1, a refrigerant flow path 5 is defined by the first refrigerant flow-path formation part 51 of the scroll piece 2 and the second refrigerant flow-path formation part 52 of the shroud piece 3 by assembling the shroud piece 3 to the scroll piece 2. As shown in FIG. 3, the first refrigerant flow-path formation part 51 of the scroll piece 2 is located inside the first scroll chamber formation part 121, and has a first wall surface 511 that is a wall surface of the refrigerant flow path 5 on the intake side Y1. In the present embodiment, the first wall surface 511 forms a flat surface that is perpendicular to the axial direction Y, however, the first wall surface 511 is not necessarily flat, and may be recessed toward the intake side Y1. It is noted that as shown in FIG. 2, the corner portion that connects the first wall surface 511 and the inner circumferential pressure-contacted portion 541a to be described later is chamfered to form a first chamfered portion 581.

(43) As shown in FIG. 1, the second refrigerant flow-path formation part 52 of the shroud piece 3 is provided on the first diffuser part 35 on the intake side Y1. As shown in FIG. 5, the second refrigerant flow-path formation part 52 has a second wall surface 521 that is formed in a recessed shape recessed toward the Y2 side opposite to the intake side Y1. In the present embodiment, the second wall surface 521 is recessively formed in a U-shape in the cross section parallel to the shaft direction Y, and forms an annular recess that extends in the circumferential direction outside of the shroud surface 22 in the radial direction as shown in FIG. 5. As shown in FIG. 1, the second refrigerant flow-path formation part 52 has the second contact surface 562 that forms a wall surface parallel to the radial direction outside the second wall surface 521 in the radial direction. As shown in FIG. 1, the second contact surface 562 is in contact with the first contact surface 561 of the scroll piece 2. And, an annular space 50 that is defined by the first refrigerant flow-path formation part 51 and the second refrigerant flow-path formation part 52 is formed as the refrigerant flow path 5. The refrigerant flow path 5 is formed along the diffuser part 30 in the circumferential direction, and allows a refrigerant for cooling the diffuser part 30 to pass therethrough. It is noted that as shown in FIG. 2, the corner portion (an end part of the outer circumferential pressure-contacted portion 542a on the Y2 side) that connects the first contact surface 561 of the scroll piece 2 and the outer circumferential pressure-contacting portion 542a to be described later is chamfered to form a second chamfered portion 582.

(44) As shown in FIG. 1, with regard to the refrigerant flow path 5, the boundary between the first refrigerant flow-path formation part 51 and the second refrigerant flow-path formation part 52 is sealed by the seal parts 541 and 542. The seal part 541 (542) is formed by pressure-contacting the pressure-contacting portion 541b (542b) with the pressure-contacted portion 541a (542a) so as to cause plastic flow substantially in the pressure-contacting portion 541b (542b). The present embodiment includes an inner circumferential seal part 541 for sealing the refrigerant flow path 5 on the inner circumferential side thereof, and an outer circumferential seal part 542 for sealing the refrigerant flow path 5 on the outer circumferential side thereof as the seal parts 541 and 542, respectively. The inner circumferential seal part 541 is composed of the inner circumferential pressure-contacted portion 541a and the inner circumferential pressure-contacting portion 541b, and the outer circumferential seal part 542 is composed of the outer circumferential pressure-contacted portion 542a and the outer circumferential pressure-contacting portion 542b.

(45) As shown in FIG. 3, with regard to the inner circumferential seal part 541, the inner circumferential pressure-contacted portion 541a, which is formed on the scroll piece 2, is located on further Y2 side with respect to the press-fitted portion 53a to form a cylindrical inner peripheral surface continuously to the press-fitted portion 53a. On the other hand, the inner circumferential pressure-contacting portion 541b, which is formed on the shroud piece 3 as shown in FIGS. 4 and 5, is located on further Y2 side with respect to the press-fitting portion 53b, that is, on the rear side in the inserting direction of the press-fitting portion 53b to form a cylindrical outer peripheral surface continuously to the press-fitting portion 53b. The inner circumferential pressure-contacting portion 541b in the non-assembled state protrudes outward in the radial direction. Although the shape of the inner circumferential pressure-contacting portion 541b is not limited, in the present embodiment, the inner circumferential pressure-contacting portion 541b is formed in a mountain shape that protrudes outward in the radial direction, having rising portions smoothly continuous forward and backward respectively in the axial direction Y in a cross section including a rotation axis 13a of the compressor impeller 13, as shown in FIG. 6A. In addition, the top of the inner circumferential pressure-contacting portion 541b in the protruding direction is also smoothly curved in the cross section. Furthermore, as shown in FIG. 4, the inner circumferential pressure-contacting portion 541b is continuous in the circumferential direction to form an annular shape.

(46) As shown in FIG. 6A, the inner circumferential pressure-contacting portion 541b in the non-assembled state protrudes outward from the press-fitting portion 53b in the radial direction in a protrusion amount T1 predetermined with respect to the press-fitting portion 53b in the cross section including the rotation axis 13a. The protrusion amount T1 may be set in the range where the inner circumferential pressure-contacting portion 541b can plastically flow, and may be set to, for example, 80 μm-120 μm. In the present embodiment, it is set to 100 μm. Although the length in the axial direction Y, of the inner circumferential pressure-contacting portion 541b, that is, a formation range H1 in the axial direction Y, of the inner circumferential pressure-contacting portion 541b is not particularly limited, it may be set to, for example, 0.5 to 1.5 mm. In the present embodiment, it is set to 1.0 mm.

(47) As shown in FIG. 6A, the inner circumferential pressure-contacting portion 541b protrudes in the protrusion amount T1 predetermined with respect to the press-fitting portion 53b, and thus, the inner circumferential pressure-contacting portion 541b of the shroud piece 3 is press-contacted with the inner circumferential pressure-contacted portion 541a of the scroll piece 2 by press-fitting the press-fitting portion 53b of the shroud piece 3 into the press-fitted portion 53a of the scroll piece 2, so that plastic flow is caused substantially in the inner circumferential pressure-contacting portion 541b as shown by a sign M. As a result, a micro gap between both is filled to form the inner circumferential seal part 541. It is noted that although in the present embodiment, the shroud piece 3 is provided with the inner circumferential pressure-contacting portion 541b, and the scroll piece 2 is provided with the inner circumferential pressure-contacted portion 541a, instead of such a configuration, the inner circumferential pressure-contacted portion 541a may be provided on the shroud piece 3, and the inner circumferential pressure-contacting portion 541b may be provided on the scroll piece 2. In this regard, it is preferable to provide the inner circumferential pressure-contacted portion 541a on either piece that has a higher rigidity than the other does.

(48) As shown in FIG. 7A, also with regard to the outer circumferential seal part 542, the outer circumferential pressure-contacting portion 542b protrudes outward in the radial direction in the same manner as the inner circumferential pressure-contacting portion 541b. A protrusion amount T2 and a formation range H2, of the outer circumferential pressure-contacting portion 542b may be set to be equivalent to the protrusion amount T1 and the formation range H1, of the inner circumferential pressure-contacting portion 541b. In the present embodiment, the T2 and the H2 are set to the same values as those of the T1 and the H1. It is noted that at the end part on the intake side Y1 of the wall surface having the outer circumferential pressure-contacting portion 542b provided thereon, its outer peripheral edge is chamfered to form a fourth chamfered portion 592. Then, by press-fitting the press-fitting portion 53b of the shroud piece 3 into the press-fitted portion 53a of the scroll piece 2, the outer circumferential pressure-contacting portion 542b of the shroud piece 3 is pressure-contacted with the outer circumferential pressure-contacted portion 542a of the scroll piece 2, so that plastic flow is caused as shown the sign M substantially in the outer circumferential pressure-contacting portion 542b, as shown in FIG. 7C. As a result, a micro gap between both is filled to form the outer circumferential seal part 542. It is noted that although in the present embodiment, the shroud piece 3 is provided with the outer circumferential pressure-contacting portion 542b, and the scroll piece 2 is provided with the outer circumferential pressure-contacted portion 542a, instead of such a configuration, the outer circumferential pressure-contacted portion 542a may be provided on the shroud piece 3, and the outer circumferential pressure-contacting portion 542b may be provided on the scroll piece 2. In this regard, it is preferable to provide the outer circumferential pressure-contacted portion 542a on either piece that has a higher rigidity than the other does.

(49) As shown in FIGS. 1 and 2, the scroll piece 2 has a refrigerant feed part 513 and a refrigerant discharge part 514 that are formed as through-holes formed through the first refrigerant flow-path formation part 51 and communicated with the refrigerant flow path 5. The refrigerant feed part 513 is configured to feed a refrigerant to the refrigerant flow path 5, and the refrigerant discharge part 514 is configured to discharge the refrigerant. In the present embodiment, the refrigerant feed part 513 and the refrigerant discharge part 514 are formed from the first wall surface 511 toward the intake side Y1 in parallel to the axial direction Y, and then directed outward in the radial direction.

(50) The seal plate 40 has a third scroll chamber formation part 123, a seal plate insertion portion 41, and a second diffuser part 36 as shown in FIG. 1. The third scroll chamber formation part 123 constitutes a wall surface of the scroll chamber 12 on the outer circumference side. The seal plate insertion portion 41 is inserted into the inside of the outer peripheral portion 125. The second diffuser part 36 constitutes the diffuser part 30 with the first diffuser part 35. The second diffuser part 36 has a facing surface 37 that faces the diffuser surface 34 of the first diffuser part 35 spaced at a predetermined distance. The space formed between the diffuser surface 34 and the facing surface 37 defines the diffuser passage 15. It is noted that as shown in FIG. 1, the first scroll chamber formation part 121 of the scroll piece 2 and the third scroll chamber formation part 123 of the seal plate 40 are configured so as not to be in contact with each other, having a small gap C therebetween. According to such a configuration, the seal plate 40 is inserted into a predetermined position, and the diffuser passage 15 is formed in a predetermined width.

(51) Next, a manufacturing method of the compressor housing 1 for a turbocharger according to the present embodiment will be described.

(52) First of all, as shown in FIG. 2, the scroll piece 2 and a shroud piece precursor 3a serving as a raw material for the shroud piece 3 are separately molded by die casting. Then, by machining, the press-fitted portion 53a, the inner circumferential pressure-contacted portion 541a, and the outer circumferential pressure-contacted portion 542a are formed on the scroll piece 2, and the press-fitting portion 53b, the inner circumferential pressure-contacting portion 541b, and the outer circumferential pressure-contacting portion 542b are formed on the shroud piece 3. And, a cut part 57 that is a bottom portion of the second wall surface 521 is cut. It is noted that the shroud piece precursor 3a has no shroud surface 22 formed thereon, and an inside surface 22a of the shroud piece precursor 3a is formed of a cylindrical surface.

(53) Next, the shroud piece 3 is assembled to the scroll piece 2 in the assembling step as shown by an arrow P in FIG. 2. In more detail, with regard to the inner circumferential seal part 541, the press-fitting portion 53b of the shroud piece 3 is inserted toward the inner circumferential pressure-contacted portion 541a of the scroll piece 2 in the axial direction Y as shown by the arrow P in FIG. 6A, and then the press-fitting portion 53b is press-fitted into the inner circumferential pressure-contacted portion 541a as shown in FIG. 6B. And, by further inserting in the direction shown by the arrow P, the press-fitting portion 53b is press-fitted so as to reach the press-fitted portion 53a that is located on further intake side Y1 with respect to the inner circumferential pressure-contacted portion 541a as shown in FIG. 6C. In association with this action, the inner circumferential pressure-contacting portion 541b of the shroud piece 3 is brought in contact with the first chamfered portion 581, and the inner circumferential pressure-contacting portion 541b is substantially caused to plastically flow along the inner circumferential pressure-contacted portion 541a of the scroll piece 2. Consequently, as shown in FIG. 6C, the inner circumferential pressure-contacting portion 541b is brought in close contact with the inner circumferential pressure-contacted portion 541a of the scroll piece 2. Then, the second contact surface 562 of the shroud piece 3 is press-fitted so as to abut on the first contact surface 561 of the scroll piece 2, thus the inner circumferential seal part 541 is completely formed.

(54) Also in the outer circumferential seal part 542, in association with the action that the press-fitting portion 53b of the shroud piece 3 is press-fitted into the press-fitted portion 53a of the scroll piece 2, the outer circumferential pressure-contacting portion 542b of the shroud piece 3 is brought in contact with the second chamfered portion 582 of the scroll piece 2 as shown in FIGS. 7A and 7B in the same manner as in the inner circumferential seal part 541, and the outer circumferential pressure-contacting portion 542b is substantially caused to plastically flow along the outer circumferential pressure-contacted portion 542a of the scroll piece 2, so that the outer circumferential pressure-contacting portion 542b is brought in close contact with the outer circumferential pressure-contacted portion 542a of the scroll piece 2 as shown in FIG. 7C. Thus, the outer circumferential seal part 542 is completely formed. As a result, the refrigerant flow path 5 serving as the annular space 50 that is sealed with the inner circumferential seal part 541 and the outer circumferential seal part 542 is formed as shown in FIG. 1. Then, the shroud surface 22 is formed by machining the inside surface 22a. In this way, the compressor housing 1 for a turbocharger as shown in FIG. 1 is manufactured.

(55) In the compressor housing 1 for a turbocharger, a refrigerant introduction tube and a refrigerant discharge tube, which are not shown in any figure, are connected respectively to the refrigerant feed part 513 and the refrigerant discharging part 514 each communicated with the refrigerant flow path 5 as shown in FIGS. 1 and 2. The diffuser surface 34 can be cooled by circulating the refrigerant in the refrigerant flow path 5 via these tubes.

(56) It is noted that although in the inner circumferential seal part 541 according to the present embodiment, the scroll piece 2 is provided with the inner circumferential pressure-contacted portion 541a, and the shroud piece 3 is provided with the inner circumferential pressure-contacting portion 541b, the inner circumferential pressure-contacting portion 541b may be provided on the scroll piece 2, and the inner circumferential pressure-contacted portion 541a may be provided on the shroud piece 3. Similarly, in the outer circumferential seal part 542, the scroll piece 2 is provided with the outer circumferential pressure-contacted portion 542a, and the shroud piece 3 is provided with the outer circumferential pressure-contacting portion 542b. Alternatively, the outer circumferential pressure-contacting portion 542b may be provided on the scroll piece 2, and the outer circumferential pressure-contacted portion 542a may be provided on the shroud piece 3. In this regard, it is preferable to provide the pressure-contacted portions 541a and 542a on either piece that has a higher rigidity than the other does.

(57) It is noted that although in the present embodiment, the press-fitting portion 53b is provided at further Y1 side than the location of the inner circumferential pressure-contacting portion 541b of the shroud piece 3 in order to curtail dispersal of a plastic flow portion, instead of or concurrently with such a configuration, the press-fitting portion may be formed on further Y1 side with respect to the outer circumferential pressure-contacting portion 542b of the shroud piece 3, and the press-fitted portion may be formed on further Y1 side with respect to the inner circumferential pressure-contacted portion 541a of the scroll piece 2.

(58) Next, operational effects of the compressor housing 1 for a turbocharger according to the present embodiment will be described in detail.

(59) According to the compressor housing 1 for a turbocharger of the present embodiment, the seal parts 541 and 542 between the scroll piece 2 and the shroud piece 3 are formed by pressure-contacting the pressure-contacting portions 541b and 542b that are provided on either one of the scroll piece 2 and the shroud piece 3 with the pressure-contacted portions 541a and 542a that are provided on the other one of the scroll piece 2 and the shroud piece 3 so as to cause plastic flow in the pressure-contacting portions 541b and 542b. Thus, micro gaps are filled by the plastic flow substantially of the pressure-contacting portions 541b and 542 b in the seal parts 541 and 542, so that improvement in sealability can be achieved in comparison with the case where the seal parts are formed by just press-fitting of both. In addition, because there is no need to apply any sealing material separately at the seal parts 541 and 542, cost reduction can be achieved.

(60) The present embodiment includes the refrigerant flow path 5 that is formed along the diffuser part 30 in the circumferential direction, and allows a refrigerant for cooling the diffuser part to pass therethrough. The refrigerant flow path 5 is formed as an annular space 50 that is constituted by the first refrigerant flow-path formation part 51 of the scroll piece 2 and the second refrigerant flow-path formation part 52 of the shroud piece 3, the first refrigerant flow-path formation part 51 and the second refrigerant flow-path formation part 52 being formed respectively at each opposing part of the scroll piece 2 and the shroud piece 3 which oppose each other. This embodiment includes, as the seal parts 541 and 542, the inner circumferential seal part 541 configured to seal the refrigerant flow path 5 on the inner circumferential side thereof, and the outer circumferential seal part 542 configured to seal the refrigerant flow path 5 on the outer circumferential side thereof, and the inner circumferential seal part 541 is formed by pressure-contacting the inner circumferential pressure-contacting portion 541b that is provided on either one of the scroll piece 2 and the shroud piece 3 with the inner circumferential pressure-contacted portion 541a that is provided on the other one of the scroll piece 2 and the shroud piece 3 so as to cause plastic flow substantially in the inner circumferential pressure-contacting portion 541b to thereby form the seal part. The outer circumferential seal part 542 is formed by pressure-contacting the outer circumferential pressure-contacting portion 542b that is provided on either one of the scroll piece 2 and the shroud piece 3 with the outer circumferential pressure-contacted portion 542a that is provided on the other one of the scroll piece 2 and the shroud piece 3 so as to cause plastic flow substantially in the outer circumferential pressure-contacting portion 542b to thereby form the seal part. According to such configurations, in the compressor housing 1 for a turbocharger provided with the refrigerant flow path 5, the sealability at the inner circumferential seal part 541 and the outer circumferential seal part 542 can be achieved compatibly with cost reduction.

(61) In the present embodiment, the inner circumferential pressure-contacting portion 541b is located on further rear side Y2 in the inserting direction of the press-fitting portion 53b with respect to the press-fitting portion 53b. Therefore, when the shroud piece 3 is assembled to the scroll piece 2, the inner circumferential pressure-contacting portion 541b is pressure-contacted with the inner circumferential pressure-contacted portion 541a after the press-fitting portion 53b is press-fitted, so that dispersal of a plastic flow portion at the inner circumferential seal part 541 can be curtailed. Thus, the sealability can be surely improved.

(62) Furthermore, the compressor housing 1 for a turbocharger is dividably formed to include the scroll piece 2 and the shroud piece 3, and the scroll chamber 12 is defined by assembling at least both pieces. Thus, the scroll chamber 12 can be formed to have a circular cross section, and the scroll chamber formation part 120 can be formed into a shape having no undercut, which can be formed by die-cutting. As a result, the compression efficiency for the supplied air can be improved, and the scroll chamber can be easily formed by die casting.

(63) It is noted that although in the present embodiment, the housing 1 for a turbocharger is of a two-piece structure that is composed of the scroll piece 2 and the shroud piece 3, the housing 1 may be of a three-piece structure that is composed of the scroll piece 2, the shroud piece 3, and an outer circumference annular piece 4 as in Modification 1 shown in FIG. 8. The outer circumference annular piece 4 forms an annular shape, and includes a third scroll chamber formation part 123 and an outer circumference annular piece insertion portion 410. The outer circumference annular piece insertion portion 410 is press-fitted into the outer peripheral portion 125 to form a press-fit part 42. Note that components in Modification 1 that are equivalent to those in Embodiment 1 are allotted with the same reference numerals to simplify the description.

(64) A method for manufacturing the compressor housing 1 for a turbocharger according to Modification 1 will be described hereinafter. First of all, as shown in FIG. 9, the scroll piece 2 is molded by die-casting in the same way as in Embodiment 1. And, an integral piece 3b is molded by die casting. The integral piece 3b is composed of the outer peripheral portion of the shroud piece 3 in Embodiment 1 and the inner circumference part of an outer circumference annular piece 4 with a contour of the outer circumference annular piece 4 both of which are integrated through a connecting portion 4a. Then, by machining, the press-fitted portion 53a, the inner circumferential pressure-contacted portion 541a, and the outer circumferential pressure-contacted portion 542a are formed on the scroll piece 2, and the press-fitting portion 53b, the inner circumferential pressure-contacting portion 541b, and the outer circumferential pressure-contacting portion 542b are formed on the shroud piece 3. And then, the cut part 57 that is a bottom portion of the second wall surface 521 is cut. Thereafter, the press-fitting portion 53b of the integral piece 3b is press-fitted into the press-fitted portion 53a of the scroll piece 2 in the direction of the arrow P, and the inner circumferential pressure-contacting portion 541b and the outer circumferential pressure-contacting portion 542b, of the integral piece 3b are pressure-contacted with the inner circumferential pressure-contacted portion 541a and the outer circumferential pressure-contacted portion 542a so as to cause plastic flow in the inner circumferential pressure-contacting portion 541b and the outer circumferential pressure-contacting portion 542b so that the inner circumferential seal part 541 and the outer circumferential seal part 542 are formed. Then, by cutting off the connecting portion 4b shown in FIG. 10, the shroud piece 3 and the outer circumference annular piece 4 are separated from each other under the state in which the shroud piece 3 and the outer circumference annular piece 4 are press-fitted into the scroll piece 2. In this way, the housing 1 for a turbocharger according to Modification 1 is produced.

(65) The housing 1 for a turbocharger according to Modification 1 also exhibits operational effects equivalent to those in Embodiment 1. A tightening margin of the press-fit part 42 into which the outer circumference annular piece 4 is press-fitted is preferably set smaller than that of the inner circumferential seal part 53b. In this case, the integral piece 3b can be easily press-fitted into the scroll piece 2. In addition, misalignment between the press-fitting portion 53b of the shroud piece 3 and the press-fitting portion 42 of the outer circumference annular piece 4 can be absorbed.

(66) In the housing 1 for a turbocharger according to Modification 1, a part of the integrated piece 3b for constituting the outer circumference annular piece 4 is not brought into contact with the scroll piece 2 in the shaft direction S2 so as to form a gap B, as shown in FIGS. 8 and 10. Therefore, the first contact surface 561 can be brought in contact with the second contact surface 562 when the integral piece 3b is press-fitted. Consequently, the integral piece 3b can be positioned further accurately when being press-fitted in the shaft direction. In other words, the shroud piece 3 can be positioned further accurately in the shaft direction for completion.

Embodiment 2

(67) In Embodiment 1, the inner circumferential pressure-contacting portion 541b in the non-assembled state protrudes in the radial direction in a cross section including the rotation axis 13a of the compressor impeller 13 to form a mountain shape, as shown in FIG. 6A. In the mountain shape, a front-end side inclined plane that is located on the front-end side in the inserting direction of the press-fitting portion 53b and a rear-end side inclined plane that is located on the rear-end side in the inserting direction are symmetric with respect to the peak of the mountain shape, and the inclination angles of the both planes are equivalent. Further, in Embodiment 1, the outer circumferential pressure-contacting portion 542b in the non-assembled state is configured similarly to the inner circumferential pressure-contacting portion 541b, as shown in FIG. 7A.

(68) According to Embodiment 2, instead of the above-mentioned configurations, the inner circumferential pressure-contacting portion 541b in the non-assembled state is formed in a mountain shape that protrudes in the radial direction X in a cross section including the rotation axis 13a of the compressor impeller 13, and has a front-end side inclined plane 545 that is located on the front-end side in the press-fitting portion inserting direction (on the intake side Y1 in the present embodiment) and a rear-end side inclined plane 546 that is located on the rear-end side in the inserting direction (on the opposite side Y2 to the intake side Y1 in the present embodiment), as shown in FIG. 11. In the above-mentioned cross section, an acute-angle θ2 between the rear-end side inclined plane 546 and the rotation axis 13a is set larger than an acute-angle θ1 between the front-end side inclined plane 545 and the rotation axis 13a. And, a formation range H3 for the inner circumferential pressure-contacting portion 541b that is shown in FIG. 11 is smaller than the formation range H1 in Embodiment 1 that is shown in FIG. 6A. In the present embodiment, the protrusion amount T1 of the inner circumferential pressure-contacting portion 541b, which is shown in FIG. 11, is set the same as that in Embodiment 1. It is noted that the rotation axis 13a shown in FIG. 11 is imaginarily moved in parallel to the vicinity of the inner circumferential pressure-contacting portion 541b for the purpose of description, thus FIG. 11 does not show the actual position of the rotation axis 13a. However, θ1 shown in FIG. 11 represents the acute angle of the front-end side inclined plane 545 with respect to the rotation axis 13a actually located, and θ2 shown in FIG. 11 represents the acute angle of the rear-end side inclined plane 546 with respect to the rotation axis 13a actually located.

(69) The acute-angle θ1 formed between the front-end side inclined plane 545 and the rotation axis 13a in FIG. 11 may be set, for example, to 5°-15°, and is set to 10° in the present embodiment. The acute-angle θ2 formed between the rear-end side inclined plane 546 and the rotation axis 13a in FIG. 11 may be set, for example, to 30°-60°, and is set to 45° in the present embodiment. Both of θ1 and θ2 are constant entirely in the circumferential direction.

(70) As shown in FIG. 12, the outer circumferential pressure-contacting portion 542b in the non-assembled state is also formed in a mountain shape that protrudes in the radial direction X in a cross section including the rotation axis 13a in the same manner as in the inner circumferential pressure-contacting portion 541b, and has a front-end side inclined plane 547 that is located on the front-end side in the inserting direction (on the intake side Y1 in the present embodiment) and a rear-end side inclined plane 548 that is located on the rear-end side in the inserting direction (on the opposite side Y2 to the intake side Y1 in the present embodiment). In the above-mentioned cross section, an acute-angle θ4 between the rear-end side inclined plane 548 and the rotation axis 13a is set larger than an acute-angle θ3 between the front-end side inclined plane 547 and the rotation axis 13a. And, a formation range H4 for the outer circumferential pressure-contacting portion 542b that is shown in FIG. 12 is smaller than the formation range H2 in Embodiment 1 that is shown in FIG. 7A. And, the protrusion amount T2 of the outer circumferential pressure-contacting portion 542b, which is shown in FIG. 12, is set the same as that in Embodiment 1. It is noted that the rotation axis 13a shown in FIG. 12 is imaginarily moved in parallel to the vicinity of the outer circumferential pressure-contacting portion 542b for the purpose of description, thus FIG. 12 does not show the actual position of the rotation axis 13a. However, θ3 shown in FIG. 12 represents the acute angle of the front-end side inclined plane 547 with respect to the rotation axis 13a actually located, and θ4 shown in FIG. 12 represents the acute angle of the rear-end side inclined plane 548 with respect to the rotation axis 13a actually located.

(71) The acute-angle θ3 formed between the front-end side inclined plane 547 and the rotation axis 13a in FIG. 12 may be set, for example, to 5°-15° as with the acute-angle θ1, and is set to 10° in the present embodiment. The acute-angle θ4 formed between the rear-end side inclined plane 548 and the rotation axis 13a may be set, for example, to 30°-60°, as with the acute-angle θ2, and is set to 45° in the present embodiment. Both of θ3 and θ4 are constant entirely in the circumferential direction. It is noted that other configurations in the present embodiment are equivalent to those in Embodiment 1, and the same reference numerals as those in Embodiment 1 are allotted to simplify the description.

(72) Next, a method for manufacturing the compressor housing 1 for a turbocharger according to Embodiment 2 will be described.

(73) First of all, the scroll piece 2 and the shroud piece precursor 3a are separately molded by die casting in the same manner as in Embodiment 1 shown in FIG. 2. Then, machining is performed in the same manner as in Embodiment 1. However, in the present embodiment, the inner circumferential pressure-contacting portion 541b and the outer circumferential pressure-contacting portion 542b are formed by machining in a mountain shape that protrudes in the radial direction, having front-end side inclined planes 545 and 547 that are located on the front-end side Y1 in the press-fitting portion inserting direction of the press-fitting portion and rear-end side inclined planes 546 and 548 that are located on the rear-end side Y2 in the inserting direction such that in the cross section, the acute-angle θ2 between the rear-end side inclined plane 546 and the rotation axis 13a, and the acute-angle θ4 between the rear-end side inclined plane 548 and the rotation axis 13a are set larger than the acute-angle θ1 between the front-end side inclined plane 545 and the rotation axis 13a, and the acute-angle θ3 between the front-end side inclined plane 547 and the rotation axis 13a, respectively. And, in the present embodiment, as mentioned above, θ1 and θ3 are set to 10°, and θ2 and θ4 are set to 45°. Then, the assembling step is performed in the same manner as in Embodiment 1 so as to cause plastic flow in the inner circumferential pressure-contacting portion 541b and the outer circumferential pressure-contacting portion 542b to thereby form the inner circumferential seal part 541 and the outer circumferential seal part 542. In this way, the refrigerant flow path 5 is formed. Then, the inside surface 22a is machined to form the shroud surface 22. Thus, the compressor housing 1 for a turbocharger is manufactured.

(74) The compressor housing 1 for a turbocharger of Embodiment 2 exhibits the same operational effects as in Embodiment 1. Further, in the method for manufacturing the compressor housing 1 for a turbocharger according to the present embodiment, the inner circumferential pressure-contacting portion 541b and the outer circumferential pressure-contacting portion 542b are each formed by machining in a mountain shape that protrudes in the radial direction in a cross section including the rotation axis 13a, having the front-end side inclined planes 545 and 547 respectively that are located on the front-end side in the inserting direction of the press-fitting portion and the rear-end side inclined planes 546 and 548 respectively that are located on the rear-end side in the inserting direction such that in the cross section, the acute-angles θ2 and θ4 of the rear-end side inclined plane 546 and 548 are respectively set larger than the acute-angles θ1 and θ3 of the front-end side inclined planes 545 and 547. In this way, at the pressure-contacting portions 541b and 542b, the rear-end side inclined planes 546 and 548 are machined to stand more steeply with respect to the rotational axis 13a respectively than the front-end side inclined planes 545 and 547. Consequently, the formation ranges (i.e. the widths) H3 and H4 respectively of the pressure-contacted portions 541b and 542b can be narrowed while the inclination angles θ1 and θ3 respectively of the front-end side inclined planes 545 and 547, and the protrusion amounts T1 and T2 respectively of the pressure-contacted portions 541b and 542b are set to be the same as in Embodiment 1. Therefore, plastic flow in the pressure-contacting portions 541b and 542b can be easily caused without deterioration of assemblability. Consequently, at each seal part 541 and 542, a micro gap can be filled more surely, so that the sealability can be further improved. Otherwise, when plastic flow amounts at the pressure-contacting portions 541b and 542b are set to the same as in Embodiment 1, dimension tolerances in the pressure-contacting portions 541b and 542b, and the pressure-contacted portions 541a and 542a in machining can be eased by narrowing the widths H3 and H4 of the pressure-contacting portions. As a result, productivity can be improved and cost reduction can be achieved.

(75) In the present embodiment, the shroud piece 3 is provided with the inner circumferential pressure-contacting portion 541b, and the scroll piece 2 is provided with the inner circumferential pressure-contacted portion 541a, however, instead of such a configuration, the inner circumferential pressure-contacted portion 541a may be provided on the shroud piece 3, and the inner circumferential pressure-contacting portion 541b may be provided on the scroll piece 2. Further, in the present embodiment, the shroud piece 3 is provided with the outer circumferential pressure-contacting portion 542b, and the scroll piece 2 is provided with the outer circumferential pressure-contacted portion 542a, however, instead of such a configuration, the outer circumferential pressure-contacted portion 542a may be provided on the shroud piece 3, and the outer circumferential pressure-contacting portion 542b may be provided on the scroll piece 2. In both cases, it is preferable to provide the inner circumferential pressure-contacted portion 541a, and the outer circumferential pressure-contacted portion 542a on either piece that has a higher rigidity than the other does.

(76) It is noted that in the present embodiment, the inner circumferential pressure-contacting portion 541b and the outer circumferential pressure-contacting portion 542b are provided on the shroud piece 3 as shown in FIGS. 11 and 12, so that the front-end side inclined planes 545 and 547 are located on the intake side Y1, and the rear-end side inclined planes 546 and 548 are located on the opposite side Y2. On the other hand, when the inner circumferential pressure-contacting portion 541b and the outer circumferential pressure-contacting portion 542b are provided on the scroll piece 2, the intake side Y1 shifts to the rear-end side in the inserting direction, and the opposite side Y2 shifts to the front-end side in the inserting direction, so that the rear-end side inclined planes 546 and 548 are located on the intake side Y1, and the front-end side inclined planes 545 and 547 are located on the opposite side Y2.

(77) It is noted that in the present embodiment, the front-end side inclined planes 545 and 547, and the rear-end side inclined planes 546 and 548 are formed to have a shape that is shown by a straight line when viewed in the cross section including the rotation axis 13a, however, it is not necessary for the line to be an exact straight line in the cross section, and the line may be slightly curved.

(78) The present disclosure is not limited to the above-mentioned embodiments and modifications, and can be applied to various embodiments within the range that does not depart from the gist of the present disclosure.