Method for producing compressor housing

Abstract

A compressor housing is constructed by assembling a scroll piece and a shroud piece. The scroll piece includes an inlet cylindrical portion, a front side wall section, and an outlet cylindrical portion in which the inner wall surface of the outlet communicating section is curved to connect an inner wall surface of a scroll chamber and that of an outlet port. Fabrication of the scroll piece includes a die casting step that uses a back mold having a first projecting portion and a front mold having a second projecting portion projecting toward the back side to form an intermediate formed body wherein both the first and second projecting portions are disposed within the outlet cylindrical portion, and a cutting and removal step that removes residue portions in the intermediate formed body by cutting.

1 . A method for producing a compressor housing for a turbocharger, the compressor housing being able to house an impeller, the compressor housing including an inlet port formed adjacent to a front side of the impeller, the inlet port opening to the front side in an axial direction; a scroll chamber formed on an outer circumferential side of the impeller in a circumferential direction; an outlet port on an outer circumferential side of the inlet port, the outlet port opening to the front side in the axial direction; and an outlet communicating section communicating between the outlet port and the scroll chamber, the compressor housing being constructed by assembling a scroll piece and a shroud piece, each formed as a discrete part, together in the axial direction, the scroll piece comprising: an inlet cylindrical portion making the inlet port and having a through hole in the axial direction; a front side wall section on an outer circumferential side of the inlet cylindrical portion, the front side wall section making a front area of a wall surface of the scroll chamber; and an outlet cylindrical portion extending from a region in a circumferential direction of the front side wall section, the outlet cylindrical portion making the outlet communicating section and the outlet port, the outlet cylindrical portion being configured such that an inner wall surface of the outlet communicating section is curved so as to smoothly connect between an inner wall surface of the scroll chamber and an inner wall surface of the outlet port, the shroud piece including a shroud press-fit portion in a cylindrical shape to be press-fitted into the inlet cylindrical portion; an inner circumferential wall section making an inner circumferential area of the wall surface of the scroll chamber; a shroud surface opposed to the impeller; and a diffuser surface extending from the shroud surface toward the scroll chamber, the method comprising:
 a die casting step of forming an intermediate formed body by die casting, the intermediate formed body having a residue portion including a metal material left within the outlet cylindrical portion, the die casting using a back mold having a first projecting portion projecting toward the front side and a front mold having a second projecting portion projecting toward a back side, the front mold being movable back and forth relative to the back mold in the axial direction; and   a cutting and removal step of removing the residue portion in the intermediate formed body by cutting so as to obtain the scroll piece,   wherein, in the die casting step, both the first projecting portion and the second projecting portion are disposed within the outlet cylindrical portion.   
     
     
         2 . The method according to  claim 1  for producing the compressor housing,
 wherein the intermediate formed body has the residue portion only partly existing on an inner wall surface of the outlet cylindrical portion. 
 
     
     
         3 . The method according to  claim 2  for producing the compressor housing,
 wherein the first projecting portion has a first projecting mold surface for forming a part of the inner wall surface of the outlet cylindrical portion in the intermediate formed body and the second projecting portion has a second projecting mold surface for forming another part of the inner wall surface of the outlet cylindrical portion in the intermediate formed body. 
 
     
     
         4 . The method according to  claim 1  for producing the compressor housing,
 wherein, in the die casting step, a projection end of the first projecting portion is located closer to the front side of the intermediate formed body than a projection end of the second projecting portion. 
 
     
     
         5 . The method according to  claim 1  for producing the compressor housing,
 wherein, in the die casting step, the first projecting portion and the second projecting portion are abutted against each other.