CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority under 35 U.S.C. § 119 to Japanese Application No. 2017-039606, filed on Mar. 2, 2017, entitled “HOUSING FOR TURBOCHARGER AND METHOD FOR MANUFACTURING THE SAME”. The contents of this application are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION
Field of the Invention

The present invention relates to a housing for a turbocharger and a method for manufacturing the same.

Description of the Related Art

A turbocharger to be mounted on an internal combustion engine of an automobile or the like includes a compressor impeller and a turbine impeller, which are housed in a housing. The compressor impeller is disposed in an air flow path that is formed inside of the housing. The air flow path is provided with an intake port for sucking in air toward the compressor impeller, a diffuser passage through which compressed air discharged from the compressor impeller passes through, and a discharge scroll chamber into which the compressed air passing through the diffuser passage flows. The discharge scroll chamber discharges the compressed air into the internal combustion engine side.

The internal combustion engine of an automobile or the like is, in some cases, provided with a positive crankcase ventilation system (hereinafter referred to as PCV) for purifying the inside of a crankcase and/or a head cover by reflowing a blowby gas (mainly composed of unburned gas) that has generated in the crankcase. In this case, oil (oil mist) may flow out from the PCV into an intake passage that is positioned upstream of the compressor in the turbocharger.

At that time, if air pressure at the outlet port of the compressor is high, air temperature at the outlet port of the compressor is made high, so that the oil flowing out from the PCV is concentrated and thickened by evaporation to have high viscosity. In some cases, the oil is accumulated as deposit on, for example, a diffuser surface of the housing for a turbocharger and/or the surface of a bearing housing which opposes the diffuser surface. And, there is a risk that the accumulated deposit may narrow the diffuser passage to thereby cause reduction in performance of the turbocharger and reduction in output of the internal combustion engine.

In the conventional technique to prevent such deposit accumulation in the diffuser passage as described above, the air temperature at the outlet port of the compressor was controlled to some extent. As a result, a turbocharger was not able to satisfactorily exhibit its performance, and the output of an internal combustion engine was not satisfactorily raised.

Patent Document 1 discloses a configuration to prevent deposit accumulation in a diffuser passage, in which a refrigerant flow path is provided inside of a housing for a turbocharger to allow a refrigerant to pass therethrough, thereby inhibiting an increase in the temperature of compressed air passing through an air flow path inside of the housing. In the configuration disclosed in Patent Document 1, the housing for a turbocharger is composed of a first piece, a second piece and a third piece, and these components are assembled to each other to define the refrigerant flow path.

PRIOR ART LITERATURE

Patent Document

Patent Document 1

JP-A-2016-176353

In the configuration disclosed in Patent Document 1, however, it is necessary to form a holding portion for holding an O-ring serving as a sealing member between the first piece and the second piece and to fit the sealing member into the holding portion, and in addition, to hold the sealing member by the first piece and the second piece. Thus, parts count is indispensably increased, which causes increase in manufacturing cost and reduction in assembling workability.

Further, in the configuration disclosed in Patent Document 1, each piece is formed in a shape having no undercut, employing dies-cutting which enables each piece to be molded by die casting. Because the cross-sectional shape of the scroll chamber largely differs from a circle accordingly, reduction in compression efficiency of supplied air cannot be avoided.

As a method to form the refrigerant flow path in the housing for a turbocharger, it is conceivable to use gravity casting with a sand core. According to this method, high flexibility in shape can be expected to thereby address complicated shapes. On the other hand, this method requires long casting cycle, and the method needs a sand shakeout operation for removing the sand core and an inspection work for checking remaining casting sand. Therefore, the number of manufacturing processes is increased, and the productivity is reduced accordingly. In addition, there is a risk that the refrigerant flow path may communicate with outside due to a cavity defect and may have a leak of the refrigerant to the outside.

The present invention has been made in view of this background, and it is intended to provide a housing for a turbocharger which can be prevented from having deposit accumulation, while exhibiting an excellent assembling workability and having a capability of being easily formed by die casting.

SUMMARY OF THE INVENTION

One aspect of the present invention provides a housing for a turbocharger in which a compressor impeller is housed, the housing including:

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 formed on an outer peripheral side of the compressor impeller in the circumferential direction and forms a diffuser passage, the diffuser passage allowing compressed air to pass therethrough;

a scroll chamber formation part that forms a scroll chamber for guiding the compressed air passing through the diffuser passage to an outside; and

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, wherein

the housing is composed of a scroll piece including at least part of the scroll chamber formation part, and a shroud piece including at least part of the scroll chamber formation part, the diffuser part, and the shroud part and being inserted in an inner side of the scroll piece,

the refrigerant flow path is composed of an annular space that is defined by a first flow-path formation part of the scroll piece and a second flow-path formation part of the shroud piece, the first flow-path formation part and the second flow-path formation part being formed respectively in each opposing part of the scroll piece and the shroud piece which face each other,

the first flow path formation part and the second flow path formation part are brought into contact with each other to form a contact portion at a position corresponding to an outermost periphery of an inside surface of the refrigerant flow path,

the contact portion has a groove that is formed by recessing the inside surface of the refrigerant flow path outwardly in a radial direction and is continuous in a circumferential direction, and

the groove is filled with a sealing material for sealing the contact portion.

According to the aforementioned aspect, the housing for a turbocharger is dividedly formed, and the refrigerant flow path is defined by the first flow-path formation part of the scroll piece and the second flow-path formation part of the shroud piece, both of which are formed respectively in each opposing part of the scroll piece and the shroud piece facing each other. At the position corresponding to the outermost periphery of the inside surface of the refrigerant flow path, the first flow path formation part and the second flow path formation part are brought into contact with each other to form the contact portion. The contact portion has the groove that is formed by recessing the inside surface of the refrigerant flow path outwardly in the radial direction and is continuous in the circumferential direction. The groove is filled with a sealing material for sealing the contact portion. In such a configuration, a space between the first flow path formation part and the second flow path formation part, which forms the flow path, can be sealed only by filling the groove with the sealing material. Consequently, it is not necessary to interpose an O-ring between the first flow path formation part and the second flow path formation part, and the assembling workability is satisfactory. Further, because the O-ring itself is not necessary, reduction of the parts count can be achieved.

Further, the housing for a turbocharger is dividedly formed and includes the scroll piece and the shroud piece. The scroll chamber is formed by assembling at least both pieces to each other. Thus, the scroll chamber can be formed to have a circular cross section, and the scroll chamber formation part can be formed into a shape having no undercut, which can be formed by die-cutting. As a result, the scroll chamber can be more readily formed by die casting, and the compression efficiency of the supplied air can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

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

FIG. 2 is a sectional view taken along arrows II-II in FIG. 1.

FIG. 3 is a partially enlarged view of the cross sectional view of the housing for a turbocharger according to Embodiment 1.

FIG. 4 is a flow chart showing a method for manufacturing the turbocharger according to Embodiment 1.

FIG. 5 is a schematic diagram for illustrating the method for manufacturing the turbocharger according to Embodiment 1.

FIG. 6 is another schematic diagram for illustrating the method for manufacturing the turbocharger according to Embodiment 1.

FIG. 7 is further another schematic diagram for illustrating the method for manufacturing the turbocharger according to Embodiment 1.

DETAILED DESCRIPTION OF THE INVENTION

“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 shaft center 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.

The groove is preferably formed such that an imaginary circle centered on a shaft center of the compressor impeller is positioned inside of the groove. In such a configuration, it becomes easy to fill the groove uniformly with the sealing material utilizing a centrifugal force generated by rotation around the shaft center of the compressor impeller, which further improves assembling workability.

The groove preferably has a shape notched into a V shape outwardly in the radial direction such that the deepest position of the groove in the cross section including the shaft center of the compressor impeller is positioned on the boundary between the first flow path formation part and the second flow path formation part. In such a configuration, the sealing material filling the groove is easily held in the groove, and easily enters into a space between the first flow path formation part and the second flow path formation part at the contact portion. Consequently, the sealability between the first flow path formation part and the second flow path formation part can be further enhanced.

The sealing material is preferably provided between the scroll piece and the shroud piece at the contact portion and seals a space between the scroll piece and the shroud piece. In such a configuration, the sealability between the scroll piece and the shroud piece can be further improved.

At the contact portion, a contact surface of the scroll piece and a contact surface of the shroud piece are preferably parallel to a surface perpendicular to the shaft direction. In such a configuration, the sealing material filling the groove easily enters into a space between the first flow path formation part and the second flow path formation part at the contact portion utilizing the centrifugal force generated by rotation around the shaft center of the compressor impeller. Consequently, the sealability between the first flow path formation part and the second flow path formation part can be further improved.

As a method for manufacturing the aforementioned housing for a turbocharger, it is preferable to utilize a method for manufacturing the housing for a turbocharger including:

a preparation step of preparing the scroll piece and the shroud piece;

an assembling step of assembling the shroud piece to the scroll piece by press-fitting, and bringing the first flow-path formation part into contact with the second flow-path formation part, thereby forming the refrigerant flow path composed of the annular space;

a providing step of providing a sealing material having a fluidity by feeding the sealing material to the refrigerant flow path after the assembling step, or by applying the sealing material to at least one of the first flow-path formation part and the second flow-path formation part prior to the assembling step;

a filling step of filling the groove with the sealing material by rotating the scroll piece and the shroud piece around the shaft center of the compressor impeller; and

a curing step of curing the sealing material filling the groove.

Lathe machining for forming the shroud surface is preferably performed in the filling step simultaneously with filling the groove with the sealing material. In such a configuration, the groove can be filled with the sealing material simultaneously with formation of the shroud surface, so that the manufacturing process can be simplified.

EMBODIMENT
Embodiment 1

Hereinafter, an embodiment of the aforementioned housing for a turbocharger will be described.

As shown in FIG. 1, a housing 1 for a turbocharger houses a compressor impeller 13, and is provided with an intake port 11, a shroud part 20, a diffuser part 30, a scroll chamber formation part 120 and a refrigerant flow path 5. The shroud part 20 surrounds the compressor impeller 13 in the circumferential direction and has a shroud surface 22 facing the compressor impeller 13.

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

The scroll chamber formation part 120 forms a scroll chamber 12 for guiding the compressed air passing through the diffuser passage 15 to the outside.

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.

The housing 1 is composed of a scroll piece 2 including at least part of the scroll chamber formation part 120, and a shroud piece 3 including at least part of the scroll chamber formation part 120, the diffuser part 30, and the shroud part 20 and being inserted in the inner side of the scroll piece 2.

The refrigerant flow path 5 is composed of an annular space 50 that is defined by a first flow-path formation part 51 of the scroll piece 2 and a second flow-path formation part 52 of the shroud piece 3, the first flow-path formation part 51 and the second flow-path formation part 52 being formed respectively in each opposing part of the scroll piece 2 and the shroud piece 3 which face each other.

The first flow path formation part 51 and the second flow path formation part 52 are brought into contact with each other to form a contact portion 53 at a position corresponding to the outermost periphery of an inside surface 54 of the refrigerant flow path 5.

The contact portion 53 has a groove 55 that is formed by recessing the inside surface 54 of the refrigerant flow path 5 outwardly in the radial direction and is continuous in the circumferential direction.

The groove 55 is filled with a sealing material 56 for sealing the contact portion 53 as shown in FIG. 3.

Hereinafter, the housing 1 for a turbocharger will be described in detail.

As shown in FIG. 1, the housing 1 for a turbocharger is formed by assembling the scroll piece 2, the shroud piece 3, and an outer periphery piece 4 in the shaft direction Y, each of which has been manufactured as a separate member.

As shown in FIGS. 1 and 2, the scroll piece 2 includes the intake port 11, a first scroll chamber formation part 121, an outer peripheral portion 125, and the first flow-path formation part 51. The intake port 11 is defined by an intake port formation part 110 that has a cylindrical shape penetratingly formed in the shaft direction Y. The first scroll chamber formation part 121 forms a wall surface of the scroll chamber 12 on the intake side Y1. The outer peripheral portion 125 corresponds to a part of the first scroll chamber formation part 121 on the side Y2 opposite to the intake side Y1, and forms the outer peripheral portion of the housing 1 for a turbocharger. The outer peripheral portion 125 is provided with the outer peripheral portion 4. The outer peripheral portion 4 is annular, and includes an insertion part 41 to be press-fitted into the outer peripheral portion 125 and a third scroll chamber formation part 123 constituting the wall surface of the scroll chamber 12 on the outer peripheral side.

As shown in FIG. 1, the first flow-path formation part 51 of the scroll piece 2 is configured to form the refrigerant flow path 5 with the second flow-path formation part 52 to be described later, and is provided on the Y2 side of the intake port formation part 110. As shown in FIG. 3, the first flow-path formation part 51 has a first wall surface 511 corresponding to the wall surface of the refrigerant flow path 5 on the intake side Y1. In this embodiment, the first wall surface 511 is made gradually inclined so as to approach the Y2 side opposite to the intake side Y1 as the first wall surface 511 goes outward in the radial direction. The first flow-path formation part 51 has a first contact surface 531, which is parallel to the radial direction, at the radially outside end part of the first wall surface 511. The first contact surface 531 is in contact with a second contact surface 532 of the shroud piece 3, which will be described later. The first flow-path formation part 51 is provided with a penetration hole 513 penetrating from the first wall surface 511 to the surface opposite to the first wall surface 511. Although not shown in any figure, the penetration hole 513 is provided in two locations.

The shroud piece 3 includes a shroud press-fit portion 31, a second scroll chamber formation part 122, the shroud part 20, the diffuser part 30, and the second flow-path formation part 52, as shown in FIG. 1. The shroud press-fit portion 31 is formed in a cylindrical shape, and is press-fitted into the intake port 11. The second scroll chamber formation part 122 forms an inner-periphery side wall surface of the scroll chamber 12. The shroud part 20 forms a shroud surface 22 that faces the compressor impeller 13. The diffuser part 30 forms a diffuser surface 34 that extends from the shroud surface 22 to the scroll chamber 12. The diffuser surface 34 faces a facing surface formed in a seal plate of a bearing housing that is not shown in any figure, leaving a predetermined space to form the diffuser passage 15 with the opposing surface.

As shown in FIG. 1, the second flow-path formation part 52 is configured to form the refrigerant flow path 5 with the aforementioned first flow-path formation part 51, and is formed in the diffuser part 30 on the intake side Y1 radially outside of the shroud part 20. As shown in FIG. 3, the second flow-path formation part 52 includes a second wall surface 521 corresponding to the wall surface of the refrigerant flow path 5 on the Y2 side. In this embodiment, the second wall surface 521 is recessively formed toward the Y2 side, and has a U-shape in the cross section parallel to the shaft direction. At the same time, the second wall surface 521 forms an annular recess extending in the circumferential direction radially outside of the shroud surface 22 as shown in FIG. 2. As shown in FIG. 3, the second flow-path formation part 52 has the second contact surface 532, which is parallel to the radial direction, at the radially outside end part of the second wall surface 521. The second contact surface 532 is in contact with the first contact surface 531 of the scroll piece 2.

As shown in FIGS. 1 and 3, an outer peripheral surface 311 of the shroud press-fit portion 31 is brought in contact with an inner peripheral surface 112 of the intake port 11 with no space by press-fitting the shroud press-fit portion 31 into the inside of intake port 11, and at the same time, the second contact surface 532 is made abut on the first contact surface 531. Thus, the first contact surface 531 and the second contact surface 532 is brought in contact with each other to form the contact portion 53 and to form an annular space, i.e. the refrigerant flow path 5 between the first flow-path formation part 51 and the second flow-path formation part 52. The first wall surface 511 of the first flow-path formation part 51 and the second wall surface 521 of the second flow-path formation part 52 form the inside surface 54 of the refrigerant flow path 5. As shown in FIG. 3, the contact portion 53 is positioned on the outermost periphery of the inside surface 54 in the refrigerant flow path 5.

As shown in FIG. 1, the contact portion 53 has the groove 55 formed therein. The groove 55 is formed by recessing the inside surface 54 of the refrigerant flow path 5 outwardly in the radial direction and is continuous in the circumferential direction to form an annular shape. The groove 55 has a V shape, in other words, a shape notched into wedged shape outwardly in the radial direction in the cross section parallel to the shaft direction. The deepest position 551 of the groove 55 is positioned on the boundary between the first flow path formation part 51 and the second flow path formation part 52. As shown in FIGS. 2 and 3, an imaginary circle 16 centered on a shaft center 13a of the compressor impeller 13 is positioned inside of the groove 55.

In the present embodiment, the groove 55 is formed to have a shape notched into a V shape outwardly in the radial direction in the cross section parallel to the shaft direction. In place of such a configuration, the groove 55 may have a shape such as a U shape or a circular-arc shape notched outwardly in the radial direction in the cross section parallel to the shaft direction. Also in such a configuration, the deepest position 551 of the groove 55 is preferably positioned on the boundary between the first flow path formation part 51 and the second flow path formation part 52. Further, although in the present embodiment, the groove 55 is formed by notching both of the first flow path formation part 51 and the second flow path formation part 52, the groove 55 may be formed by notching either one of the first flow path formation part 51 and the second flow path formation part 52.

The groove 55 is filled with a sealing material 56. The kinds of the sealing material 56 are not limited to specific ones, but are preferably selected to have a quick-drying property. For instance, the sealing material to be used as a liquid gasket can be used. In the present embodiment, the sealing material 56 enters also into a space between the first contact surface 531 and the second contact surface 532.

In the present embodiment, as shown in FIG. 3, the first contact surface 531 and the second contact surface 532 as the boundary between the first flow-path formation part 51 and the second flow-path formation part 52 at the contact portion 53 are parallel to a surface perpendicular to the shaft direction. The scroll piece 2 has a stepped portion 57 that is formed outside of the contact portion 53 in the radial direction and protrudes toward the Y2 side. The shroud piece 3 has a stepped opposing portion 58 cut along the contour of the stepped portion 57. It is noted that the first contact surface 531 and the second contact surface 532 are brought in contact with each other, but the stepped portion 57 and the stepped opposing portion 58 are not brought in contact with each other.

Next, a method for manufacturing the housing 1 for a turbocharger according to the present embodiment will be described.

The method for manufacturing the housing 1 for a turbocharger includes a preparation step S1, an assembling step S2, a providing step S3, a filling step S4, and a curing step S5, as shown in FIG. 4.

Firstly in the preparation step S1, the scroll piece 2, the shroud piece 3, and the outer periphery piece 4 are prepared. The scroll piece 2, the shroud piece 3, and the outer periphery piece 4 are separately formed by die casting. As shown in FIG. 5, in preparation of the shroud piece 3, a shroud piece precursor 3a serving as a raw material for the shroud piece 3 is firstly molded by die casting. In the shroud piece precursor 3a, a shroud surface 22 and an inside surface 312 of the shroud press-fit portion 31 have not been formed, and thus an inside surface 22a of the shroud piece precursor 3a is cylindrical. Except for this, the shroud piece precursor 3a has an outer shape equivalent to that of the shroud piece 3.

Next in the assembling step S2, the shroud press-fit portion 31 of the shroud piece precursor 3a is press-fitted into the inside of the intake port formation part 110 of the scroll piece 2 in the direction as indicated by an arrow P in FIG. 5. The second contact surface 532 of the shroud piece precursor 3a is made abut on the first contact surface 531 of the scroll piece 2. In this way, as shown in FIG. 6, the refrigerant flow path 5 composed of an annular space is formed between the first flow-path formation part 51 and the second flow-path formation part 52. The penetration hole 513 formed in the scroll piece 2 is made communicate with the refrigerant flow path 5.

Subsequently in the providing step S3, the sealing material 56 having a fluidity is fed from the penetration hole 513 to the refrigerant flow path 5 to provide the sealing material 56 to the refrigerant flow path 5. In the providing step S3, the sealing material 56 is in the state of staying in the bottom of the refrigerant flow path 5. The amount of the seal material 56 to be fed is not specified. In the present embodiment, the amount is adjusted to be equivalent to the volume of the groove 55.

As shown in FIG. 7, in the filling step S4, the scroll piece 2 and the shroud piece precursor 3a which have been assembled to each other are rotated around the shaft center 13a of the compressor impeller 13. Due to a centrifugal force acting on the sealing material 56 at that time, the groove 55 that is positioned on the outermost periphery of the inside of the refrigerant flow path 5 is filled with the sealing material 56. The filling step S4 is continuously performed until the groove 55 is uniformly filled with almost all amount of the sealing material 56 fed into the refrigerant flow path 5, and the refrigerant flow path 5, in substance, has no sealing material 56 flowing therethrough. In the present embodiment, lathe machining for forming the shroud surface 22 on the shroud piece precursor 3a is performed in the filling step S4. In the lathe machining, an assembled structure composed of the scroll piece 2 and the shroud piece precursor 3a is rotated around the shaft center 13a of the compressor impeller 3 in order to cut the inside surface 22a of the shroud piece precursor 3a. In the present embodiment, the filling step S4 is performed utilizing this rotation.

Subsequently, in the curing step S5, the state of the sealing material 56 held in the groove 55 is maintained for a predetermined period while the rotation is continued. Thus, the sealing material 56 is cured in the state of being held in the groove 55. If the sealing material 56 having a quick-drying property is used, the sealing material 56 can be cured in the state of being held in the groove 55 during the lathe machining. After the sealing material 56 has been cured, the outer periphery piece 4 is press-fitted into the scroll piece 2 to produce the housing 1 for a turbocharger.

In the housing 1 for a turbocharger, the penetration hole 513 communicating with the refrigerant flow path 5 shown in FIG. 3 is connected to a refrigerant introduction tube and a refrigerant discharge tube which are not shown in any figure. The diffuser surface 34 can be cooled by flowing the refrigerant through the refrigerant flow path 5 via the refrigerant introduction tube and the refrigerant discharge tube.

In the present embodiment, the sealing material 56 is fed into the refrigerant flow path 5 in the providing step S3 after the assembling step S2. Instead, the providing step S3 in which the sealing material 56 is applied to at least one of the first flow-path formation part 51 and the second flow-path formation part 52 may be performed prior to the assembling step S2. In such a configuration, it is preferable to use a sealing material having high viscosity as the sealing material 56 in consideration of the workability in the assembling step S2 to be performed after the providing step S3 and to apply the sealing material to a portion for forming the groove 55 in the first flow-path formation part 51 or the second flow-path formation part 52, as shown in FIG. 5. In addition, a sealing material such as FIPG may be applied to at least one of the first contact surface 531 and the second contact surface 532 in the providing step S3 prior to the assembling step S2.

Hereinafter, operational effects of the housing for a turbocharger according to the present embodiment will be described in detail.

According to the housing 1 for a turbocharger of the present embodiment, the housing 1 for a turbocharger is dividedly formed, and the refrigerant flow path 5 is defined by the first flow-path formation part 51 of the scroll piece 2 and the second flow-path formation part 52 of the shroud piece 3, both of which are formed respectively in each opposing part of the scroll piece 2 and the shroud piece 3 facing each other. At the position corresponding to the outermost periphery of the inside surface 54 of the refrigerant flow path 5, the contact portion 53 in which the first flow path formation part 51 and the second flow path formation part 52 are brought into contact with each other is formed. The contact portion 53 has the groove 55 that is formed by recessing the inside surface 54 of the refrigerant flow path 5 outwardly in a radial direction and is continuous in the circumferential direction. The groove 55 is filled with the sealing material 56 for sealing the contact portion 53. In such a configuration, the space between the first flow path formation part 51 and the second flow path formation part 52, which forms the refrigerant flow path 5, can be sealed only by filling the groove 55 with the sealing material 56. Consequently, it is not necessary to interpose an O-ring between the first flow path formation part 51 and the second flow path formation part 52, and thus the assembling workability is satisfactory. Further, because the O-ring itself is not necessary, reduction of the parts count can be achieved.

Further, the housing 1 for a turbocharger is dividedly formed and includes the scroll piece 2 and the shroud piece 3. The scroll chamber 12 is formed by assembling at least both pieces to each other. 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 scroll chamber 12 can be more easily formed by die casting, while enhancing compression efficiency of the supplied air. In the present embodiment, the housing 1 for a turbocharger is of a three-piece structure that is composed of the scroll piece 2, the shroud piece 3, and the outer periphery piece 4. The housing 1 composed of the scroll piece 2 and the shroud piece 3 as a two-piece structure also exhibits the operational effects equivalent to those in the three-piece structured housing.

Further, the refrigerant flow path 5 in the housing 1 of the present embodiment can be formed without necessity to largely change the basic configuration of the scroll piece and/or shroud piece in the conventional housings for a turbocharger, so that the refrigerant flow path 5 can be readily applied to the conventional housings for a turbocharger.

In the present embodiment, the groove 55 is formed such that the imaginary circle 16 centered on the shaft center 13a of the compressor impeller 13 is positioned inside of the groove 55. In such a configuration, it becomes easy to fill the groove 55 uniformly with the sealing material 56 by utilizing the centrifugal force generated by rotation around the shaft center 13a of the compressor impeller 13, which further improves assembling workability.

In the present embodiment, the groove 55 has a shape notched into a V shape outwardly in the radial direction such that the deepest position 551 of the groove 55 in a cross section including the shaft center 13a of the compressor impeller 13 is positioned on the boundary between the first flow path formation part 51 and the second flow path formation part 52. In such a configuration, the sealing material 56 in the groove 55 is easily held in the groove 55, and easily enters into a space between the first flow path formation part 51 and the second flow path formation part 52 at the contact portion 53. Consequently, the sealability between the first flow path formation part 51 and the second flow path formation part 52 can be improved.

The second wall surface 521 of the second flow path formation part 52 may be formed as an inclined surface that inclines gently towards the groove 55. In such a configuration, the sealing material 56 easily reaches the groove 55 along the second wall surface 521 in the filling step S4.

The sealing material 56 may be provided between the scroll piece 2 and the shroud piece 3 at the contact portion 53 and seal a space between the scroll piece 2 and the shroud piece 3. In such a configuration, the sealability between the scroll piece 2 and the shroud piece 3 at the contact portion 53 can be further improved.

In the present embodiment, the first contact surface 531 of the scroll piece 2 and the second contact surface 532 of the shroud piece 3 at the contact portion 53 are parallel to a surface perpendicular to the shaft direction. In such a configuration, the sealing material 56 in the groove 55 easily enters into a space between the first flow path formation part 51 and the second flow path formation part 52 at the contact portion 53 by utilizing the centrifugal force generated by rotation around the shaft center 13a of the compressor impeller 13. Consequently, the sealability between the first flow path formation part 51 and the second flow path formation part 52 can be further improved.

In the present embodiment, the scroll piece 2 has the stepped portion 57 that is formed outside of the contact portion 53 in the radial direction and protrudes toward the Y2 side. The shroud piece 3 has the stepped opposing portion 58 cut along the contour of the stepped portion 57. In such a configuration, the sealing material 56 that has flowed into the space between the first contact surface 531 and the second contact surface 532 from the deepest position 551 of the groove 55 in the filling step S4 can be prevented from escaping into the scroll chamber 12. Consequently, the sealing material 56 easily stays in the groove 55 and the space between the first contact surface 531 and the second contact surface 532, so that the sealability between the first flow-path formation part 51 and the second flow-path formation part 52 can be further improved. In the present embodiment, the stepped portion 57 and the stepped opposing portion 58 are provided each singly. Besides, the stepped portion 57 may be formed into a shape having plural steps, and the stepped opposing portion 58 may be formed into a shape having plural steps formed along the contour of the plural steps of the stepped portion 57. Such a configuration can more surely prevent the sealing material 56 from escaping into the scroll chamber 12, so that the sealability between the first flow-path formation part 51 and the second flow-path formation part 52 can be further improved.

The method for manufacturing the housing for a turbocharger according to the present embodiment includes:

the preparation step S1 of preparing the scroll piece 2 and the shroud piece 3 (the shroud piece precursor 3a);

the assembling step S2 of assembling the shroud piece 2 to the scroll piece 3 (the shroud piece precursor 3a) by press-fitting, and bringing the first flow-path formation part 51 into contact with the second flow-path formation part 52, thereby forming the refrigerant flow path 5 composed of the annular space;

the providing step S3 of providing the sealing material 56 having a fluidity by feeding the sealing material 56 to the refrigerant flow path 5 after the assembling step S2, or by applying the sealing material 56 to at least one of the first flow-path formation part 51 and the second flow-path formation part 52 prior to the assembling step S2;

the filling step S4 of filling the groove 55 with the sealing material 56 by rotating the scroll piece 2 and the shroud piece 3 (the shroud piece precursor 3a) around the shaft center 13a of the compressor impeller 13; and

the curing step S5 of curing the sealing material 56 in the groove 55.

In this method, the sealing material 56 can be easily filled into the groove 55 in the filling step S4.

In the present embodiment, lathe machining for forming the shroud surface 22 is performed in the filling step S4 simultaneously with filling the groove 55 with the sealing material 56. According to such a configuration, the groove 55 can be filled with the sealing material 56 simultaneously with formation of the shroud surface 22, so that the manufacturing process can be simplified.

The present invention is not limited to the aforementioned embodiments and modifications, and can be applied to various embodiments and modifications within the scope that does not extend beyond the purposes of the present invention.