Patent Publication Number: US-2017350408-A1

Title: Compressor housing for turbocharger and method of manufacturing the same

Description:
TECHNICAL FIELD 
     The present invention relates to a compressor housing for a turbocharger and a method of manufacturing the same. 
     BACKGROUND ART 
     A compressor for use in a supercharger such as a turbocharger of an automobile includes a compressor housing that is configured to be able to house an impeller, and includes an intake port for sucking air toward the impeller, a scroll chamber for introducing air discharged by the impeller thereinto, the scroll chamber being formed in a circumferential direction at an outer circumferential side of the impeller, and a shroud surface opposed to the impeller. 
     With the compressor configured as above, compression efficiency of the compressor can be increased by minimizing a gap between blades of the impeller and the shroud surface of the compressor housing. 
     However, if the gap is decreased, there is a risk that the impeller may be damaged, for example, when the impeller blades come into contact with the shroud surface of the compressor housing due to vibrations, a runout of an impeller rotation shaft, or the like. 
     Thus, in one conventionally proposed structure, an abradable seal made of a resin or the like that is softer than the impeller blades is attached to a portion of the compressor housing, which forms the shroud surface (Patent Document 1). 
     In this case, even if the impeller blades come into contact with the shroud surface of the compressor housing due to vibrations, a runout of the impeller rotation shaft, or the like, only the abradable seal attached to the portion that forms the shroud surface is abraded, while the impeller suffers no damage, and the gap between the impeller blades and the shroud surface of the compressor housing is kept small. 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: JP-A-09-170442 
     SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
     However, in Patent Document 1, in order to fix the abradable seal to the shroud part, the abradable seal is expanded to a diffuser portion that is not opposed to the impeller, then, fastened and fixed thereto with a screw member through a screw hole provided in the diffuser portion. Further, a housing recess for housing a head of each screw member is provided on a diffuser surface of the abradable seal in order to avoid the head of the screw member from projecting into a fluid passage from the diffuser surface. However, the housing recess that opens to the fluid passage, affects intake air flowing through the fluid passage to thereby disturb a flow of airflow, which may reduce compression efficiency. 
     Also, if the housing recess has water or the like in, this may be a cause of corrosion. Thus, it is conceivable to fill the housing recess with putty or the like after placing the head of the screw member in the housing recess. However, such configuration has disadvantages such as increase of manufacturing processes and/or increase of material costs. 
     Also, because in order to prepare a region for fixing the screw member on the abradable seal, the abradable seal is expanded to the diffuser portion that is a region not opposed to the impeller, the abradable seal is relatively increased in size. A material for forming the abradable seal is generally more costly than a material for forming the compressor housing. Therefore, upsizing of the abradable seal is disadvantageous in terms of cost. 
     The present invention has been made in view of the conventional problems as mentioned above, and it is intended to provide a compressor housing for a turbocharger which makes it possible to prevent reduction of compression efficiency and to maintain holdability for the abradable seal, and which is advantageous in terms of cost, and a method of manufacturing the same. 
     Means for Solving the Problem 
     One aspect of the present invention provides a compressor housing for a turbocharger configured to house an impeller, the compressor housing including: 
     a housing body having an inner circumferential recess recessively formed on an annular inner circumference surface of the housing body along an outer circumference of the impeller; 
     an annular abradable seal that is disposed in the inner circumferential recess, an inner circumference surface of the abradable seal forming a shroud surface that opposes the impeller; and 
     a ring member that is formed in a ring shape along the inner circumferential recess and is press-fitted into the inner circumferential recess in the axial direction of the impeller. 
     In the compressor housing, the inner circumferential recess includes a recess press-contact surface that is formed along the press-fitting direction of the ring member, and press-contacts the radial-direction outside surface of the ring member; and a recess opposing surface that opposes a press-fitting direction forward surface of the ring member, the abradable seal includes a flange that projects outwardly in the radial direction of the abradable seal, and the flange is held between the press-fitting direction forward surface and the recess opposing surface by press-fitting the ring member into the inner circumferential recess. 
     Another aspect of the present invention provides a method of manufacturing the compressor housing. The method includes the steps of: 
     forming an integral raw material constructed from a housing raw material to be a raw material for the housing body, and a ring-shaped raw material to be a raw material for the ring member as a single body; and 
     machining and dividing the integral raw material to form the housing body and the ring member. 
     Effects of the Invention 
     According to the above-mentioned compressor housing for a turbocharger, because the abradable seal is fixed through the flange, there is no need for a screw member(s) for fixing the abradable seal. A housing recess as conventionally provided to keep a screw head of the screw member(s) from projecting from the diffuser surface into a fluid passage, needs not be provided. Consequently, reduction of the compression efficiency in the shroud surface of the abradable seal can be prevented without disturbing a flow of air discharged from the impeller. 
     Moreover, according to the compressor housing for a turbocharger, the flange of the abradable seal is held between the press-fitting direction forward surface of the ring member and the recess opposing surface of the inner circumferential recess by press-fitting the ring member into the inner circumferential recess of the housing body. 
     Furthermore, because there is no need to provide any housing recess on the diffuser surface as conventionally provided, there is no risk that the diffuser surface has water or the like in, which may cause corrosion. In addition, because it is not necessary to fill the housing recess with putty or the like, as conventionally done, material cost does not increase. Also, because it is not necessary to extend the abradable seal to the diffuser portion that is a region not opposed to the impeller to prepare a region for fixing a screw member(s) to the abradable seal, the abradable seal can be downsized, which is advantageous in terms of cost. 
     The above-mentioned method of manufacturing a compressor housing for a turbocharger makes it possible to manufacture a compressor housing that exhibits the operational effects as mentioned above. Further, an integral raw material constructed from a housing raw material to be a raw material for a housing body and a ring-shaped raw material to be a raw material for a ring member is formed in the step of forming an integral raw material, and in the step of machining and dividing the integral raw material, the integral raw material is machined, and then is divided to form the housing body and the ring member as separated bodies. That is, the ring-shaped raw material can be machined and divided simultaneously in the step of machining the housing body. In this way, the manufacturing processes can be simplified as compared to the case where both raw materials are separately prepared and machined independently. 
     Moreover, because the housing body and the ring member are formed from the housing raw material and the ring-shaped raw material respectively, both of which are cut out from the integral raw material, the housing body and the ring member are composed of the same forming material. Thus, the housing body and the ring member have the same linear thermal expansion coefficients, accordingly, even if temperature change causes heat expansion or heat contraction in the housing body and/or the ring member, reduction of the press-contact force at a position where the radial-direction outside surface of the ring member and the recess press-contact surface of the inner circumferential recess come into press-contact with each other, can be prevented. Thus, the press-fitted state of the ring member in relation to the inner circumferential recess of the housing body can be maintained. As a result, reduction of the holdability for the abradable seal, of the inner circumferential recess of the housing body can be prevented even if any temperature change occurs. 
     As mentioned above, according to the present invention, it is possible to provide a compressor housing for a turbocharger which makes it possible to prevent reduction of the compression efficiency and to maintain holdability for the abradable seal, and which is advantageous in terms of cost, and a method of manufacturing the same. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of a turbocharger equipped with a compressor housing for a turbocharger according to Embodiment 1. 
         FIG. 2  is a partially enlarged view of an abradable seal in  FIG. 1 . 
         FIG. 3  is a sectional view of the compressor housing for a turbocharger taken along the line III-III in  FIG. 1 . 
         FIG. 4  is a sectional view for describing a step of forming an integral raw material in a method of manufacturing the compressor housing for a turbocharger according to Embodiment 1. 
         FIG. 5  is a sectional view for describing a step of machining and dividing the integral raw material in a method of manufacturing the compressor housing for a turbocharger according to Embodiment 1. 
         FIG. 6  is a sectional view for describing a step of press-fitting a ring member in a method of manufacturing the compressor housing for a turbocharger according to Embodiment 1. 
         FIG. 7  is a sectional view for describing a step of forming a shroud surface in a method of manufacturing the compressor housing for a turbocharger according to Embodiment 1. 
         FIG. 8  is a sectional view of the compressor housing for a turbocharger after performing the step of forming a shroud surface according to Embodiment 1. 
         FIG. 9  is a sectional view of an integral raw material according to one variation. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     The compressor housing for a turbocharger according to the present invention can be used for a turbocharger for an automobile, and the like. 
     In the above-mentioned compressor housing, the ring member is preferably composed of the same forming material as the housing body. Thus, both the housing body and the ring member have the same linear thermal expansion coefficients, accordingly, even if heat expansion or heat contraction occur in the housing body and/or the ring member, reduction of the press-contact force at a position where the radial-direction outside surface of the ring member and the recess press-contact surface of the inner circumferential recess come into press-contact with each other, can be prevented. Thus, the press-fitted state of the ring member in relation to the inner circumferential recess of the housing body can be sufficiently maintained. As a result, reduction of the holdability for the abradable seal, of the inner circumferential recess of the housing body can be sufficiently prevented even if any temperature change occurs. 
     In the compressor housing, the flange is formed on an entire circumference of the abradable seal. In this case, the flange formed over the entire circumference of the abradable seal is held between the press-fitting direction forward surface of the ring member and the recess opposing surface of the inner circumferential recess in the housing body so as to fix the abradable seal, thereby reliably obtaining sufficient holdability for the abradable seal. 
     In the compressor housing, the abradable seal preferably includes the flange at a first end portion in the axial direction, and a second end portion of the abradable seal at the opposite side to the first end portion is preferably spatially apart from an opposing end surface that faces the second end portion in the inner circumferential recess. Under the condition that the second end portion is defined to be forward and the first end portion having the flange formed thereon is defined to be rearward, when the abradable seal is inserted into the inner circumferential recess with the second end portion being as a forward end, and the second end portion of the abradable seal is in contact with the opposing end surface of the inner circumferential recess, the abradable seal is prevented from expanding at the side of the second end portion and an amount of expansion at the side of the first end portion becomes large. As a result, a diffuser passage becomes narrow. However, in the above-mentioned configuration, the flange is formed at the first end portion close to the diffuser passage, and the second end portion is made spatially apart from the opposing end surface of the inner circumferential recess. Consequently, the abradable seal is allowed to expand at the side of the second end portion, so that the amount of expansion at the side of the first end portion can be made small. As a result, the diffuser passage can be prevented from being narrowed. 
     In the compressor housing, an outer circumference surface of the abradable seal is preferably spatially apart from an outer circumference surface of the inner circumferential recess. In this case, a space is formed between the abradable seal and the inner circumferential recess. Therefore, if the abradable seal expands, the outer circumference surface of the abradable seal expands inside of the space. Consequently, reduction of the diameter in the expanded abradable seal can be prevented. Thus, it is not necessary to set a tip clearance between the abradable seal and the impeller larger in advance in prospect of reduction of the diameter of the abradable seal due to the expansion. The tip clearance can be set to be small from the beginning. Further, when the abradable seal having the ring member attached thereto is installed on the housing body, the abradable seal can be inserted into the inner circumferential recess such that the outer circumference surface of the abradable seal is in no contact with the outer circumference surface of the inner circumferential recess, which improves assemble workability. 
     In the above-mentioned method of manufacturing a compressor housing for a turbocharger, the ring-shaped raw material can be formed as a single body with the housing raw material along a place for press-fitting the ring member in the step of forming an integral raw material. Thus, there is no need to prepare casting molds for the housing raw material and the ring-shaped raw material separately. It is only needed to prepare a single casting mold for forming an integral raw material constructed from a housing raw material and a ring-shaped raw material. Consequently, the molding cost can be reduced. Also, the casting cost can be reduced in the case of casting a single body as compared to the case of casting both raw materials separately. 
     In the method of manufacturing a compressor housing for a turbocharger, the ring-shaped raw material is formed in the step of forming an integral raw material as a single body with the housing raw material along an end portion of an intake port that is formed at an opposite side to a side on which the ring member is to be press-fitted. Also in this case, the molding cost and the casting cost can be reduced, to thereby totally reduce the manufacturing costs. 
     Embodiments 
     Embodiment 1 
     A compressor housing for a turbocharger according to the present embodiment will be described with reference to  FIGS. 1 to 9 . 
     A compressor housing  1  for a turbocharger according to the present embodiment (hereinafter also referred to as the “compressor housing  1 ”) is equipped with a housing body  20 , an abradable seal  30 , and a ring member  40  as shown in  FIG. 1 . 
     The housing body  20  is configured to be able to house an impeller  10 , and includes an inner circumferential recess  21  recessively formed on an annular inner circumference surface along an outer circumference  10   a  of the impeller  10 . 
     The abradable seal  30  is annularly formed and disposed in the inner circumferential recess  21 , and the inner circumference surface of the abradable seal  30  forms a shroud surface  31  that opposes the impeller  10 . 
     The ring member  40  is formed in a ring shape along the inner circumferential recess  21  of the housing body  20 , and is press-fitted into the inner circumferential recess  21  in the axial direction of the impeller. 
     In addition, as shown in  FIG. 2 , the inner circumferential recess  21  includes a recess press-contact surface  212  that is formed along the press-fitting direction (i.e. the axial direction X) of the ring member  40 , and press-contacts a radial-direction outside surface  42  of the ring member  40 ; and a recess opposing surface  213  that opposes a press-fitting direction forward surface  41  of the ring member  40 . 
     The abradable seal  30  includes a flange  32  that projects outwardly in a radial direction of the abradable seal  30 , and the flange  32  is held between the press-fitting direction forward surface  41  and the recess opposing surface  213  by press-fitting the ring member  40  into the inner circumferential recess  21 . 
     As shown in  FIG. 1 , the compressor housing  1  forms an outer shell of a compressor (compression machine) for use in a turbocharger of an automobile. 
     The compressor housing  1  according to the present embodiment will be described in detail below. 
     The housing body  20  is made of an aluminum cast product obtained by gravity casting, and is equipped with an intake port  11 , an intake passage  12 , and a scroll chamber  13 , as shown in  FIGS. 1 and 2 . 
     The intake port  11  and the intake passage  12  are defined by a cylindrical portion  23 . 
     The scroll chamber  13  is formed on the outer circumference side of the impeller  10  in the circumferential direction to introduce air discharged from the impeller  10  thereinto. 
     The inner circumferential recess  21  is formed on the inner circumference surface of the housing body  20  along the outer circumference of the abradable seal  30 . And, the inner circumferential recess  21  includes a first cylindrical recessed portion  210  that is recessively formed along a cylindrical abradable seal body part  310  that will be mentioned below, of the abradable seal  30 , and a second cylindrical recessed portion  220  that is formed recessively further than the first recessed portion  210  along an enlarged diameter part  311 . Thus, the inner circumferential recess  21  is configured to be able to have the abradable seal  30  disposed therein. The second cylindrical recessed portion  220  of the inner circumferential recess  21  includes the recess press-contact surface  212  that is formed along the press-fitting direction of the ring member  40  that will be mentioned below, and press-contacts the radial-direction outside surface  42  of the ring member  40 ; and the recess opposing surface  213  that extends in the radial direction in such a manner to oppose the press-fitting direction forward surface  41  that defines a press-fitting direction X forward side of the ring member  40 . 
     The abradable seal  30  is formed of an elastically deformable material. In the present embodiment, the abradable seal  30  is made of a polyimide resin. The material for forming the abradable seal  30  is not limited to this, and available materials include Teflon (registered trademark), PPS (polyphenylene sulfide) resin, and PEEK (polyetheretherketone) resin, and the like. As shown in  FIG. 3 , the abradable seal  30  has an annular shape, and the entire inner circumference surface forms the shroud surface  31 , opposing the impeller  10  ( FIG. 1 ). Further, the abradable seal  30  includes the cylindrical abradable seal body part  310 , and the enlarged diameter part  311  that is formed on the opposite side to the intake port  11  (i.e. the rearward side in the press-fitting direction to be mentioned below) with the abradable seal body part  310  in-between. The enlarged diameter part  311  is formed in the circumference direction of the abradable seal  30 . The enlarged diameter part  311  includes the flange  32  that projects outwardly in the radial direction. In the present embodiment, the flange  32  is formed on the entire circumference of the enlarged diameter part  311 . The abradable seal  30 , as shown in  FIGS. 1 and 2 , is disposed in the inner circumferential recess  21  such that the abradable seal body part  310  is positioned in the first recessed portion  210  of the inner circumferential recess  21  and the enlarged diameter part  311  is positioned in the second recessed portion  220 . 
     As shown in  FIG. 3 , the ring member  40  is formed in a ring shape along the recess press-contact surface  212  of the inner circumferential recess  21 , and has a substantially rectangular cross section as shown in  FIGS. 1 and 2 . The radial-direction outside surface  42  that oppose the recess press-contact surface  212  is formed over the entire outer periphery of the ring member  40  along the press-fitting direction X. And, the outer diameter of the ring member  40  is slightly larger than the inner diameter of the second recessed portion  220  of the inner circumferential recess  21 . The radial-direction outside surface  42  press-contacts the recess press-contact surface  212  by press-fitting the ring member  40  into the second recessed portion  220 . On the other hand, a radial-direction inside surface  43  that is positioned on the opposite side to the radial-direction outside surface  42  of the ring member  40  press-contacts an outer circumference surface  313  of the enlarged diameter part  311  of the abradable seal  30 . 
     As shown in  FIG. 2 , in the state in which the ring member  40  is press-fitted into the second recessed portion  220 , the press-fitting direction forward surface  41  of the ring member  40  opposes the recess opposing surface  213 . And, the flange  32  of the abradable seal  30  is held between the press-fitting direction forward surface  41  and the recess opposing surface  213 . Moreover, as shown in  FIG. 2 , although the flange  32  projects outwardly in the radial direction from the enlarged diameter part  311 , an outer circumference surface  32   a  of the flange  32 , which corresponds to the outer circumference surface that opposes the recess press-contact surface  212  and the recess press-contact surface  212  are not in contact with each other. Thus, a space  50  that is surrounded by the press-fitting direction forward surface  41 , the recess opposing surface  213  and the outer circumference surface  32   a  is formed. Furthermore, in the first recessed portion  210 , because the outer diameter of the abradable seal body part  310  is smaller than the inner diameter of the first recessed portion  210 , the outer circumference surface  310   a  of the abradable seal body part  310  is spatially apart from the outer circumference surface  210   a  of the first recessed portion  210 . Thus, a space  51  is formed between the outer circumference surface  310   a  of the abradable seal body part  310  and the outer circumference surface  210   a  of the first recessed portion  210 . Moreover, as shown in  FIG. 1 , the abradable seal  30  has the flange  32  formed at a first end portion  34  thereof in the axial direction X. And, a second end portion  35  at an opposite side to the first end portion  34  is spatially apart from an opposing end surface  210   b  that faces the second end portion  35  in the inner circumferential recess  21 . Thus, a space  52  is formed between the second end portion  35  and the opposing end surface  210   b.    
     Further, as shown in  FIG. 1 , a bearing housing or an end surface  70  of a backplate is located on the opposite side to the intake port  11  of the housing body  20 . A diffuser portion  14  that serves as a fluid passage that connects the impeller  10  side to a scroll chamber  12  is formed between the end surface  70  and the housing body  20 . In the housing body  20 , a surface that opposes the end surface  70  forms a diffuser surface  24 . 
     Further, as shown in  FIG. 1 , the impeller  10  is arranged on the side of the inner circumference surface (the shroud surface  31 ) of the abradable seal  30  in the housing body  20  in a rotatable manner around a rotation shaft  15 . In addition, the impeller  10  has a hub  16  and a plurality of blades  17  that are arranged in the circumferential direction of the hub  16  and project from the outer circumference surface thereof. The plurality of blades  17  are arranged facing the shroud surface  31  of the abradable seal  30 . 
     In a compressor provided with the compressor housing  1  according to the present embodiment, as shown in  FIG. 1 , intake air that is sucked from the intake port  11  through the intake passage  12 , is accelerated by the blades  17  of the impeller  10  and is fed to the diffuser part  14 . Then, the intake air is pressurized in the diffuser portion  14  and is fed into the scroll chamber  13 . 
     Next, a method of manufacturing the compressor housing  1  according to the present embodiment will be explained. 
     For manufacturing the compressor housing  1 , as shown in  FIG. 4 , an integral raw material  60  constructed from a housing raw material  20   a  which will be a raw material for the housing body  20 , and a ring-shaped raw material  40   a  which will be a raw material for the ring member  40 , is firstly formed (a step S 1  of forming an integral raw material). 
     According to the present embodiment, in the step S 1  of forming an integral raw material, the integral raw material  60  was formed from an aluminum alloy by a gravity casting method. As shown in  FIG. 4 , the intake port  11  and the intake passage  12  were formed in the integral raw material  60 , and the ring-shaped raw material  40   a  was formed in a ring shape protrudingly toward the opposite side to the intake port  11  along a place  40   b  (the second recessed portion  220  in  FIG. 2 ) at which the ring member  40  would be press-fitted in the housing raw material  20   a.  Moreover, the scroll chamber  13  was formed in the integral raw material  60  using a core. 
     Next, the integral raw material  60  ( FIG. 4 ) was machined and divided to form the housing body  20  and the ring member  40  as shown in  FIG. 5  (a step S 2  of machining and dividing the integral raw material). Specifically, in the step S 2  of machining and dividing the integral raw material, the integral raw material  60  in the state shown in  FIG. 4  is machined cutting an inner circumferential portion  20   b  of a part that will be the housing raw material  20   a  to form the inner circumferential recess  21  ( FIG. 5 ) including the first recessed portion  210  and the second recessed portion  220 , thereby forming a portion that will be the housing body  20 . At the same time, a portion that will be the ring member  40  is formed by grinding a part that will be the ring-shaped raw material  40   a.  After that, the integral raw material  60  thus machined was divided into two components so as to prepare the housing body  20  and the ring member  40 . 
     Subsequently, as shown in  FIG. 6 , the ring member  40  is press-fitted into the abradable seal  30  that has been prepared in advance, and is assembled thereto. Then, the resulting assembly is press-fitted into the inner circumferential recess  21  of the housing body  20  (a step S 3  of press-fitting). As shown in  FIG. 7 , the flange  32  was held between the press-fitting direction forward surface  41  of the ring member  40  and the recess opposing surface  213  of the inner circumferential recess  21  by press-fitting the ring member  40  into the second recessed portion  220  in the inner circumferential recess  21 . The outer diameter of the radial-direction outside surface  42  of the ring member  40  was slightly larger than the inner diameter of the recess press-contact surface  212  of the second recessed portion  220 . In the step S 3  of press-fitting, the radial-direction outside surface  42  of the ring member  40  was made press-contacted with the recess press-contact surface  212  of the second recessed portion  220  by press-fitting the ring member  40  into the second recessed portion  220 . It is noted that the radial-direction inside surface  43  of the ring member  40  press-contacts the outer circumference surface  311  of the enlarged part  313  of the abradable seal  30 . 
     Thereafter, an inner circumferential portion  30   b  ( FIG. 7 ) of the abradable seal  30  was cut along with the ring member  40  and the inner circumference surface of the housing body  20  to form the shroud surface  31  as shown in  FIG. 8  (a step S 4  of forming a shroud surface). Thus, a continuously smooth surface that continues from the intake port  11  to the diffuser surface  24  through the intake passage  12  and the shroud surface  31  was formed. In this way, the compressor housing  1  was completed. 
     Next, the operational effects of the compressor housing  1  for a turbocharger according to the present embodiment will be described in detail. In the compressor housing  1  according to the present embodiment, because the abradable seal  30  is fixed through the flange  32 , there is no need for a screw member(s) for fixing the abradable seal  30 . Thus, a housing recess as conventionally provided to keep a screw head of the screw member(s) from projecting from the diffuser surface  24  into a fluid passage, needs not be provided. Consequently, reduction of the compression efficiency in the shroud surface  31  of the abradable seal  30  can be prevented without disturbing a flow of air discharged from the impeller  10 . 
     Moreover, the flange  32  of the abradable seal  30  is held between the press-fitting direction forward surface  41  of the ring member  40  and the recess opposing surface  213  of the inner circumferential recess  21  by press-fitting the ring member  40  into the inner circumferential recess  21  of the housing body  20 . Thus, the abradable seal  30  is fixed to the inner circumferential recess  21  of the housing body  20 . 
     Furthermore, because there is no need to provide any housing recess on the diffuser surface  24  as conventionally provided, there is no risk that the diffuser surface  24  has water or the like, which may cause corrosion. In addition, because it is not necessary to fill the housing recess with putty or the like as conventionally done, material cost does not increase. Also, because it is not necessary to expand the abradable seal  30  to the diffuser surface  24  that is a region not opposed to the impeller  10  in order to prepare a region for fixing a screw member(s) to the abradable seal  30 , the abradable seal  30  can be downsized, which is advantageous in terms of cost. 
     Furthermore, the ring member  40  is composed of the same forming material as the housing member  20 . Thus, both the housing body  20  and the ring member  40  have the same linear thermal expansion coefficients, accordingly, even if heat expansion or heat contraction occur in the housing body  20  and/or the ring member  40 , reduction of the press-contact force at a position where the radial-direction outside surface  42  of the ring member  40  and the recess press-contact surface  212  of the inner circumferential recess  21  come into press-contact with each other, can be prevented. Thus, the press-fitted state of the ring member  40  in relation to the inner circumferential recess  21  of the housing body  20  can be maintained. As a result, reduction of the holdability for the abradable seal  30 , of the inner circumferential recess  21  of the housing body  20  can be sufficiently prevented even if any temperature change occurs. 
     Furthermore, the flange  32  is formed on an entire circumference of the abradable seal  30 . The flange  32  formed over the entire circumference of the abradable seal  30  is held between the press-fitting direction forward surface  41  of the ring member  40  and the recess opposing surface  213  of the inner circumferential recess  21  so as to fix the abradable seal, thereby reliably obtaining sufficient holdability for the abradable seal  30 . 
     Furthermore, the ring member  40  is formed along the recess press-contact surface  212  of the second recessed portion  220  in the inner circumferential recess  21 , the radial-direction outside surface  42  of the ring member  40  is formed on the entire circumference of the ring member  40 . Consequently, a position where the recess press-contact surface  212  and the radial-direction outside surface  42  come into press-contact with each other can be obtained widely, so that the ring member  40  can be reliably fixed to the housing body  20 . 
     In the present embodiment, the sectional shape of the ring member  40  is designed to be substantially rectangular. However, the sectional shape is not limited to this, and can be determined as appropriate in view of formability of the ring member  40 , easiness of press-fitting into the inner circumferential recess  21 , required holdability for the abradable seal  30 , manufacturing cost, and so on. 
     In the present embodiment, the flange  32  is protrudingly formed outward in the radial direction on the entire circumference of the abradable seal  30 . However, the flange  32  is not limited to this configuration. The flange  32  may be formed on part of the outer circumference of the abradable seal  30 . A position to form the flange  32  can be determined as appropriate in view of formability of the abradable seal  30 , manufacturing costs, required holdability for the abradable seal  30 , and so on. 
     In the present embodiment, the abradable seal  30  includes the flange  32  at the first end portion  34  in the axial direction, and the second end portion  35  of the abradable seal  30  at the opposite side to the first end portion  34  is spatially apart from the opposing end surface  210   b  that faces the second end portion  35  in the inner circumferential recess  21 . Under the condition that the second end portion  35  is defined to be forward and the first end portion  34  having the flange  32  formed thereon is defined to be rearward, when the abradable seal  30  is inserted into the inner circumferential recess  21  with the second end portion  35  being as a forward end, and the second end portion  35  of the abradable seal  30  is in contact with the opposing end surface  210   b  of the inner circumferential recess  21 , the abradable seal  30  is prevented from expanding at the side of the second end portion  35 . Consequently, the diffuser passage  14  becomes narrow. However, in the present embodiment, the flange  32  is formed at the first end portion  34  close to the diffuser passage  14 , and the second end portion  35  is made spatially apart from the opposing end surface  210   b  of the inner circumferential recess  21 . Thus, the abradable seal  30  is allowed to expand at the side of the second end portion  35 , so that the amount of expansion at the side of the first end portion  34  can be made small. As a result, the diffuser passage  14  can be prevented from being narrowed. 
     In the present embodiment, the outer circumference surface  310   a  of the abradable seal  30  is spatially apart from the outer circumference surface  210   a.  Thus, the space  51  is formed between the abradable seal  30  and the inner circumferential recess  21 . And, if the abradable seal  30  expands, the outer circumference surface  310   a  of the abradable seal  30  expands inside of the space  51 . Consequently, reduction of diameter in the expanded abradable seal  30  can be prevented. Thus, it is not necessary to set a tip clearance between the abradable seal  30  and the impeller  10  larger in advance in prospect of the reduction of diameter due to the expansion of the abradable seal  30 . The tip clearance can be set to be small from the beginning. Further, when the abradable seal  30  having the ring member  40  attached thereto is installed on the housing body  20 , it is possible to insert the abradable seal  30  into the inner circumferential recess  21  such that the outer circumference surface  310   a  of the abradable seal  30  is in no contact with the outer circumference surface  210   a  of the inner circumferential recess  21 , which improves assemble workability. 
     Moreover, according to the method of manufacturing the compressor housing  1  for a turbocharger in the present embodiment, it is possible to manufacture the compressor housing  1  that exhibits the above-mentioned operational effects. Specifically, in the step S 1  of forming an integral raw material, the integral raw material  60  constructed from the housing raw material  20   a  which will be a raw material for the housing body  20 , and the ring-shaped raw material  40   a  which will be a raw material for the ring member  40 , is formed, and in the step S 2  of machining and dividing the integral raw material, the integral raw material  60  is machined and divided to form the housing body  20  and the ring member  40 . In short, the ring member  40  is formed by machining and dividing in the step to process the housing body  20  by machining (the step S 2  of machining and dividing the integral raw material). In this way, the manufacturing processes can be simplified as compared to the case where both raw materials  20   a  and  40   b  are separately prepared and machined independently. 
     Furthermore, because the housing body  20  and the ring member  40  are formed from the housing raw material  20   a  and the ring-shaped raw material  40   a  respectively, both of which are cut out from the integral raw material  60 , the housing body  20  and the ring member  40  are composed of the same forming material. Thus, the housing body  20  and the ring member  40  have the same linear thermal expansion coefficients, accordingly, even if temperature change causes heat expansion or heat contraction in the housing body  20  and/or the ring member  40 , reduction of the press-contact force at a position where the radial-direction outside surface  42  of the ring member  40  and the recess press-contact surface  212  of the inner circumferential recess  21  come into press-contact with each other, can be prevented. Thus, the press-fitted state of the ring member  40  in relation to the inner circumferential recess  21  of the housing body  20  can be maintained. As a result, reduction of the holdability for the abradable seal  30 , of the inner circumferential recess  21  of the housing body  20  can be prevented even if any temperature change occurs. 
     Furthermore, in the method of manufacturing the compressor housing  1  for a turbocharger, the ring-shaped raw material  40   a  is formed in the step S 1  of forming an integral raw material, as a single body with the housing raw material  20   a  along a place in which the ring member  40  is to be press-fitted. Thus, there is no need to prepare casting molds for the housing raw material  20   a  and the ring-shaped raw material  40   a  separately. It is only needed to prepare a single casting mold for forming the integral raw material  60  constructed from the housing raw material  20   a  and the ring-shaped raw material  40   a.  Consequently, the molding cost can be reduced. Also, the casting cost can be reduced in the case of casting a single body compared to the case of casting both raw materials separately. Consequently, the manufacturing cost can be reduced. 
     According to the present embodiment, in the step S 1  of forming an integral raw material, the ring-shaped raw material  40   a  was formed in the housing raw material  20   a  at the opposite side to the intake port  11  along a place  40   b  in which the ring member  40  is to be press-fitted. Besides this, the following configuration can also be adopted. Specifically, as shown in  FIG. 9 , in the step S 1  of forming an integral raw material, the ring-shaped raw material  40   a  may be formed in the housing raw material  20   a  along an end portion  11   a  of the intake port  11  so as to protrude toward the opposite side to the side on which the ring member is to be press-fitted, as a single body with the housing raw material  20   a.  Also in this case, because it is only needed to prepare a single casting mold for forming the integral raw material constructed from both raw materials in the same way as mentioned above, the molding cost and the casting cost can be reduced, thereby exhibiting the operational effects of reducing the manufacturing cost. 
     In the present embodiment, the integral raw material  60  is formed by gravity casting in the step S 1  of forming an integral raw material. However, the forming method is not limited to this. The integral raw material  60  may be formed by a die-casting method or other conventional methods. When the die-casting method is adopted, the integral raw material  60  is divided into plural pieces as appropriate to eliminate any undercut. 
     As mentioned above, according to the present embodiment, it is possible to provide the compressor housing  1  for a turbocharger which makes it possible to prevent reduction of the compression efficiency and to maintain holdability for the abradable seal, and which is advantageous in terms of cost, and the method of manufacturing the same.