Punch die for powder compacting, powder compacting equipment equipped with punch die, and forming method with an equipment

Abstract

In a punch die for powder compacting, a powder compacting equipment equipped with the punch die, and a forming method with the equipment, for suppressing the occurrence of stress concentration in the die without changing a shape of a powder compacting body, the punch die is used to form a cylindrical member by powder compacting, which has a substantially cylindrical shape and has a protrusion portion formed on the inner peripheral side thereof to protrude in the axial direction or a stepped portion or a concave portion formed on the inner peripheral side thereof in the radial direction. The punch die has a substantially cylindrical shape, and has a protrusion portion formed on at least a part of the inner peripheral surface or the outer peripheral surface thereof to protrude toward the center axis. The punch die is divided into two upper and lower parts at a surface forming the same surface as a lower surface of the protrusion portion, and the division surfaces are mechanically connected to each other or adhered to each other by adhesive.

1 . A punch die for powder compacting, which is used to form a cylindrical member by powder compacting, the cylindrical member having a substantially cylindrical shape and having a protrusion portion formed on the inner peripheral side or the outer peripheral side thereof to protrude in the axial direction or a stepped portion or a concave portion formed on the inner peripheral side or the outer peripheral side thereof in the radial direction,
 wherein the punch die has a substantially cylindrical shape, and has a protrusion portion formed on at least a part of the inner peripheral surface or the outer peripheral surface thereof to protrude toward the center axis, and   wherein the punch die is divided into two upper and lower parts at a surface forming the same surface as a lower surface of the protrusion portion, and the division surfaces are mechanically connected to each other or adhered to each other by adhesive.   
     
     
         2 . The punch die for powder compacting a cylindrical member according to  claim 1 , wherein the upper and lower divided punch dies are connected to each other at the division surfaces by bolt fastening, screw fastening, or fitting performed by forming a concave portion in one punch die and forming a convex portion in the other punch die. 
     
     
         3 . The punch die for powder compacting a cylindrical member according to  claim 1 , wherein the down punch die of the two upper and lower divided punch dies is exchangeable to correspond to the shape of the cylindrical member to be formed by powder compacting. 
     
     
         4 . A punch die for powder compacting a cylindrical member according to  claim 1 , wherein a corner portion as a connection portion connecting the lower surface of the protrusion portion to the inner peripheral surface of the down punch die has an angular shape with a non-curved surface, or a shape which satisfies at least any one of R/δ<0.2 mm or R<0.2 mm, where a curvature radius of the corner portion is denoted by R, and a radial width of the protrusion portion is denoted by δ. 
     
     
         5 . A powder compacting equipment for a cylindrical member, comprising:
 an upper punch die which is the punch die for powder compacting for the cylindrical member of  claim 1 ;   a lower punch die which is disposed to face the upper punch die in the axial direction;   a die which is disposed on the outside of the upper punch die and the lower punch die; and   a core die which is disposed on the inside of the upper punch die and the lower punch die,   wherein powder filled between the upper punch die and the lower punch die is subjected to powder compacting by relatively moving the upper punch die and the lower punch die.   
     
     
         6 . The powder compacting equipment according to  claim 5 ,
 wherein the lower punch die is divided into an inner punch die and an outer punch die to have a diameter substantially corresponding to the outer diameter of the protrusion portion of the cylindrical member, and   wherein the powder is subjected to powder compacting by relatively moving the upper punch die, the inner punch die, and the outer punch die.   
     
     
         7 . A method of forming a cylindrical member, comprising the steps of:
 disposing a lower punch die to face an upper punch die in the axial direction, the upper punch die having a protrusion portion formed in at least a part of the inner peripheral surface thereof to protrude toward the center axis, and being divided into two upper and lower parts at a surface forming the same surface as a lower surface of the protrusion portion, the divided surfaces being mechanically connected to each other or adhered to each other by adhesive;   disposing a die on the outside of the upper punch die and the lower punch die;   disposing a core die on the inside of the upper punch die and the lower punch die; and   subjecting powder filled between the upper punch die and the lower punch die to powder compacting by relatively moving the upper punch die and the lower punch die to thereby form a cylindrical member having a substantially cylindrical shape and having a stepped portion or a concave portion formed on the inner peripheral side thereof.   
     
     
         8 . The method according to  claim 7 , wherein the upper and lower divided punch dies are connected to each other at the division surfaces by bolt fastening, screw fastening, or fitting performed by forming a concave portion in one punch die and forming a convex portion in the other punch die. 
     
     
         9 . The method according to  claim 7 , wherein the down punch die of the two upper and down divided punch dies is exchangeable to correspond to the shape of the cylindrical member to be formed by powder compacting. 
     
     
         10 . The method according to  claim 7 , wherein a corner portion as a connection portion connecting the lower surface of the protrusion portion to the inner peripheral surface of the down punch die has an angular shape with a non-curved surface or a shape which satisfies at least any one of R/δ<0.2 mm or R<0.2 mm, where a curvature radius of the corner portion is denoted by R, and a radial width of the protrusion portion is denoted by δ. 
     
     
         11 . A powder compacting equipment for a cylindrical member, comprising:
 an upper punch die which is the punch die for powder compacting for the cylindrical member of  claim 7 ;   a lower punch die which is disposed to face the upper punch die in the axial direction;   a die which is disposed on the outside of the upper punch die and the lower punch die; and   a core die which is disposed on the inside of the upper punch die and the lower punch die,   wherein powder filled between the upper punch die and the lower punch die is subjected to powder compacting by relatively moving the upper punch die and the lower punch die.   
     
     
         12 . The powder compacting equipment according to  claim 11 ,
 wherein the lower punch die is divided into an inner punch die and an outer punch die to have a diameter substantially corresponding to the outer diameter of the protrusion portion of the cylindrical member, and   wherein the powder is subjected to powder compacting by relatively moving the upper punch die, the inner punch die, and the outer punch die.