Metal hollow member and method for manufacturing the same

Abstract

A metal hollow member having a plurality of hollow portions extending in a longitudinal direction thereof and communication apertures formed in a partitioning wall partitioning adjacent hollow portions is formed by: extruding a molten extrusion material through a die comprising a female die for forming an outer peripheral portion of the metal hollow member and a male die including a plurality of hollow-portion-forming protrusions corresponding to the plurality of hollow portions; and intermittently supplying fluid insoluble in the molten extrusion material into the partitioning wall from a bottom portion of a groove formed between the adjacent hollow-portion-forming protrusions while extruding the molten extrusion material, whereby the plurality of communication apertures are formed by fluid-released-apertures from which the fluid is released.

What is claimed is:  
     
         1 . A metal hollow member, comprising: 
 an integrally extruded metal article having a plurality of hollow portions extending in a longitudinal direction of said metal article,    wherein a partitioning wall partitioning adjacent hollow portions is provided with communication apertures by which said adjacent hollow portions are communicated with each other at predetermined intervals, said communicating apertures being apertures formed while said partitioning wall is being extruded.    
     
     
         2 . The metal hollow member as recited in claims  1 , wherein said plurality of hollow portions are arranged in parallel with each other in a widthwise direction of said extruded metal article, and wherein said communication apertures formed in adjacent partitioning walls are shifted each other in a longitudinal direction of said extruded metal article.  
     
     
         3 . The metal hollow member as recited in  claim 1 , wherein said communication aperture is a fluid-released-aperture formed by fluid entered into said partitioning wall while said partitioning wall is being extruded and then released therefrom, and wherein said fluid is insoluble in molten extrusion material of said metal article.  
     
     
         4 . The metal hollow member as recited in  claim 2 , wherein said communication portion is a fluid-released-aperture formed by fluid entered into said partitioning wall while said partitioning wall is being extruded and then released therefrom, and wherein said fluid is insoluble in molten extrusion material of said metal article.  
     
     
         5 . The metal hollow member as recited in  claim 1 , wherein said communication aperture is a gas-released-aperture formed by gas entered into said partitioning wall while said partitioning wall is being extruded and then released therefrom.  
     
     
         6 . The metal hollow member as recited in  claim 2 , wherein said communication aperture is a gas-released-aperture formed by gas entered into said partitioning wall while said partitioning wall is being extruded and then released therefrom.  
     
     
         7 . The metal hollow member as recited in any one of  claims 1  to  6 , wherein said metal hollow member is a multi-bored flat tube for use in heat exchangers.  
     
     
         8 . The metal hollow member as recited in  claim 7 , wherein said metal hollow member is made of aluminum or its alloy.  
     
     
         9 . A method for manufacturing a metal hollow member having a plurality of hollow portions extending in a longitudinal direction of said metal hollow member and a plurality of communication apertures formed in a partitioning wall partitioning adjacent hollow portions, said method, comprising: 
 extruding molten extrusion material through a die comprising a female die for forming an outer peripheral portion of said metal hollow member and a male die including a plurality of hollow-portion-forming protrusions corresponding to said plurality of hollow portions; and    intermittently supplying fluid insoluble in said molten extrusion material into said partitioning wall from a bottom portion of a groove formed between said adjacent hollow-portion-forming protrusions while extruding said molten extrusion material, whereby said plurality of communication apertures are formed by fluid-released-apertures from which said fluid is released.    
     
     
         10 . The method for manufacturing a metal hollow member as recited in  claim 9 , wherein said male die comprises a fluid outlet formed at said bottom portion of said groove and a fluid passage connecting an outside of said male die with said fluid outlet.  
     
     
         11 . The method for manufacturing a metal hollow member as recited in  claim 9 , wherein said male die comprises: 
 a holding die;    a mandrel including a pair of half-divided base members held by said holding die;    a plurality of rigid pins each having a front end constituting said hollow-portion-forming protrusion and pinched between said pair of half-divided base members along a fore-and-aft direction;    a fluid outlet formed at said bottom portion of said groove; and    a fluid passage connecting an outside of said male die with said fluid outlet,    wherein a part of said fluid passage is formed on opposing surfaces of said half-divided base members at a location between said adjacent rigid pins.    
     
     
         12 . The method for manufacturing a metal hollow member as recited in  claim 9 , wherein said male die comprises: 
 a holding die including a ring portion, a bridge portion integrally formed in said ring portion so as to cross said ring and material introducing holes formed at both sides of said bridge portion;    a mandrel having said plurality of hollow-portion-forming protrusions, said mandrel being inserted into a holding slit formed in said bridge portion;    a lid member covering a rear end of said mandrel inserted in said holding slit;    a fluid outlet formed at said bottom portion of said groove;    a fluid passage formed in said holding die, said lid member and said mandrel so as to connect an outside of said male die with said fluid outlet; and    a pipe fitted in a connecting portion connecting a portion of said fluid passage formed in said lid member and a portion of said fluid passage formed in said mandrel.    
     
     
         13 . The method for manufacturing a metal hollow member as recited in any one of  claims 9  to  12 , wherein gas insoluble in molten extrusion material is used as said fluid.  
     
     
         14 . The method for manufacturing a metal hollow member as recited in  claim 13 , wherein said fluid passage includes an inlet side passage and a plurality of outlet side passages diverged from said inlet side passage and each communicated with each of said fluid outlets, and wherein adjacent outlet side passages are different in length, whereby said gases are injected from said adjacent fluid outlets with a time lag in accordance with a length difference between said adjacent outlet side passages when said gas is introduced into said inlet side passage.