Die-casting method and die-casting apparatus

Abstract

A method of producing a die-cast article by die-casting, the die-cast article having at least one of an inner and an outer circumferential surface, the method comprising the steps of: preparing a mold assembly including a hollow portion having a molding surface for molding one of the inner and outer circumferential surfaces of the die-cast article; closing the mold assembly to define therein a mold cavity having a configuration corresponding to that of the die-cast article; subjecting the hollow portion to an elastic deformation in a direction toward the one of the inner and outer circumferential surfaces of the die-cast article to be produced; introducing a molten metal into the mold cavity while the hollow portion is subjected to the elastic deformation; opening the mold assembly and permitting the elastic deformation to be removed from the hollow portion after the molten metal has solidified; and removing the die-cast article from the mold assembly. An apparatus for practicing the method is also disclosed.

What is claimed is:  
     
         1 . A method of producing a die-cast article by die-casting, said die-cast article having at least one of an inner circumferential surface and an outer circumferential surface, the method comprising the steps of: 
 preparing a mold assembly including a hollow portion which has a molding surface for molding one of said inner and outer circumferential surfaces of said die-cast article;    closing said mold assembly so as to define therein a mold cavity having a configuration which corresponds to that of said die-cast article;    subjecting said hollow portion to an elastic deformation in a direction toward said one of said inner and outer circumferential surfaces of said die-cast article to be produced;    introducing a molten metal into said mold cavity while said hollow portion is subjected to said elastic deformation;    opening said mold assembly and permitting said elastic deformation to be removed from said hollow portion after said molten metal has solidified in said mold cavity; and    removing said die-cast article formed in said mold cavity from said mold assembly.    
     
     
         2 . A method according to  claim 1 , wherein said hollow portion has a non-molding surface which is opposite to said molding surface, said non-molding surface being a tapered surface, a dimension of which in a direction perpendicular to a direction parallel to a centerline of said hollow portion gradually changes in said direction, said step of subjecting a hollow portion to an elastic deformation comprising steps of preparing a tapered member having a tapered surface which corresponds to said tapered surface of said hollow portion, and causing said elastic deformation of said hollow portion by an interference fit between said tapered surface of said hollow portion and said tapered surface of said tapered member.  
     
     
         3 . A method according to  claim 1 , wherein said hollow portion is a hollow cylindrical member having a circular shape in transverse cross section.  
     
     
         4 . A method according  claim 1 , wherein said die-cast article is a cylinder block which is used for a swash plate type compressor and which includes a plurality of cylinder bores, said at least one of said inner and outer circumferential surfaces of said die-cast article being an inner circumferential surface of each of said cylinder bores.  
     
     
         5 . A method according to  claim 1 , wherein said die-cast article is a front housing which is used for a swash plate type compressor and which includes a hollow cylindrical recess, said at least one of said inner and outer circumferential surfaces of said die-cast article being an inner circumferential surface of said hollow cylindrical recess of said front housing.  
     
     
         6 . A die-casting apparatus for producing a die-cast article having at least one of an inner circumferential surface and an outer circumferential surface, comprising: 
 a mold assembly including a hollow portion which has a molding surface for molding one of said inner and outer circumferential surfaces of said die-cast article; and    deforming device for elastically deforming said hollow portion such that said hollow portion is subjected to an elastic deformation in a direction toward said one of inner and outer circumferential surfaces of said die-cast article to be produced.    
     
     
         7 . An apparatus according to  claim 6 , wherein said mold assembly includes a first mold and a second mold which are moved toward and away from each other, so that said first mold and said second mold are opened and closed, said hollow portion extending in a direction parallel to a direction in which said first mold and said second mold are opened and closed.  
     
     
         8 . An apparatus according to  claim 6 , wherein said mold assembly has a main body in which an engaging portion is formed, said hollow portion being provided by a member separate from said main body, and wherein at least a part of said hollow portion, which part is adjacent to said molding surface, and said engaging portion are positioned relative to each other such that there is a clearance in a radial direction therebetween.  
     
     
         9 . An apparatus according to  claim 6 , wherein said molding surface of said hollow portion for molding said one of said inner and outer circumferential surfaces of said die-cast article is an outer circumferential surface of said hollow portion, and wherein said deforming device for elastically deforming said hollow portion includes: an expanding member which engages an inner circumferential surface of said hollow portion; and a pushing device which forces said expanding member onto said inner circumferential surface of said hollow portion, so that said hollow portion is expanded.  
     
     
         10 . An apparatus according to  claim 6 , wherein said molding surface of said hollow portion for molding said one of said inner and outer circumferential surfaces of said die-cast article is an inner circumferential surface of said hollow portion, and wherein said deforming device for elastically deforming said hollow portion includes: a contracting member which engages an outer circumferential surface of said hollow portion; and a pushing device which forces said contracting member onto said outer circumferential surface of said hollow portion, so that said hollow portion is contracted.  
     
     
         11 . An apparatus according to  claim 6 , wherein said hollow portion has a non-molding surface which is opposite to said molding surface, said non-molding surface being a tapered surface, a dimension of which in a direction perpendicular to a direction parallel to a centerline of said hollow portion gradually changes in said direction, said deforming device for elastically deforming said hollow portion including: a tapered member having a tapered surface which corresponds to said tapered surface of said hollow portion; and a device for effecting an interference fit between said tapered surface of said hollow portion and said tapered surface of said tapered member.  
     
     
         12 . An apparatus according to  claim 11 , wherein said tapered member is held by said main body of said mold assembly such that said tapered member and said hollow portion are axially movable relative to each other, said device for effecting an interference fit including an axial moving for moving said tapered member and said hollow portion relative to each other in an axial direction of said tapered member.  
     
     
         13 . An apparatus according to  claim 12 , wherein said axial moving device includes a hydraulic cylinder which is fixed to said mold assembly.  
     
     
         14 . An apparatus according to  claim 11 , wherein said mold assembly includes a first mold and a second mold which are moved toward and away from each other, said tapered member being fixed to one of said first and second molds, which one mold is opposite to the other of said first and second molds which is equipped with said hollow portion, said first and second molds being opened and closed by an opening and closing device which also functions as said device for effecting an interference fit.  
     
     
         15 . An apparatus according to  claim 7 , wherein the other of said first and second molds which is equipped with said hollow portion includes an ejecting device which pushes said die-cast article in a direction away from the other mold to remove said die-cast article from said hollow portion.  
     
     
         16 . An apparatus according to  claim 6 , wherein said hollow portion is a hollow cylindrical portion having an annular shape in transverse cross section, and wherein said deforming device for elastically deforming said hollow portion includes: a collet which engages, at one of inner and outer circumferential surfaces thereof, a non-molding surface of said hollow portion, which non-molding surface is opposite to said molding surface for molding said one of said inner and outer circumferential surfaces of said die-cast article; and a collet-diameter changing device for changing a diameter of said collet so as to force said collet onto said non-molding surface.  
     
     
         17 . An apparatus according to  claim 16 , wherein the other of said inner and outer circumferential surfaces of said collet, which the other circumferential surface is opposite to said one circumferential surface which engages said non-molding surface of said hollow cylindrical portion, is tapered to give a first tapered surface whose diameter gradually changes in an axial direction of said hollow cylindrical portion, and wherein said collet-diameter changing device includes: a tapered member having a second tapered surface which corresponds to said first tapered surface; a multiplicity of balls interposed between said collet and said tapered member such that said balls maintain a constant position relative to each other, and such that said balls are rotatable independently of each other, at least while said first and second tapered surfaces engage each other; and an axial moving device which moves said tapered member and said hollow cylindrical portion relative to each other in an axial direction of said tapered member and said hollow cylindrical portion, so that said first and second tapered surfaces engage each other with an interference fit therebetween via said balls.