Method of manufacturing pipe member

Abstract

A method of manufacturing a pipe member includes arranging a pre-pipe member between first and second dies, moving one of the first and second dies to be closer to another one and holding the pre-pipe member with first and second recess portions, by the moving of the one of the first and second dies, and pressing an outer peripheral surface of the pre-pipe member with first and second inner surfaces in a closed state of the dies. By the pressing of the outer peripheral surface of the pre-pipe member, reducing a diameter of a portion of the pre-pipe member and forming a reduction portion having a polygonal shape so that the reduction portion has a same number of outer surfaces as a total number of the first inner surfaces and the second inner surfaces.

1 . A method of manufacturing a pipe member, the method comprising:
 arranging a first die including a first recess portion that has first inner surfaces and a second die including a second recess portion that has second inner surfaces, such that the first recess portion is opposite to the second recess portion;   arranging a pre-pipe member between the first die and the second die, the pre-pipe member having an elongated tubular shape; and   moving one of the first die and the second die to be closer to another one of the first die and the second die and holding the pre-pipe member with the first recess portion and the second recess portion, wherein   the moving of the one of the first die and the second die comprises pressing an outer peripheral surface of the pre-pipe member with the first inner surfaces and the second inner surfaces in a closed state where the first die and the second die are closed, and   the pressing of the outer peripheral surface of the pre-pipe member comprises reducing a diameter of a portion of the pre-pipe member and forming a reduction portion having a polygonal shape so that the reduction portion has a same number of outer surfaces as a total number of the first inner surfaces and the second inner surfaces.   
     
     
         2 . The method according to  claim 1 , wherein
 the polygonal shape is a regular hexagonal shape,   the first recess portion has three first inner surfaces including two first side inner surfaces, and a first recessed inner surface that is between the first side inner surfaces,   the second recess portion has three second inner surfaces including two second side inner surfaces, and a second recessed inner surface that is between the second side inner surfaces,   the arranging of the first die and the second die comprises arranging the first die and the second die such that the first recessed inner surface faces the second recessed inner surface,   the pressing of the outer peripheral surface comprises pressing the outer peripheral surface of the pre-pipe member with the three first inner surfaces and the three second inner surfaces, and   in the closed state where the first die and the second die are closed, a distance Y between the first recessed inner surface and the second recessed inner surface is from 0.77X to 0.95X where X is an outer diameter of the pre-pipe member.   
     
     
         3 . The method according to  claim 1 , wherein
 the pre-pipe member is a shaft of a camshaft to be included in an engine.   
     
     
         4 . The method according to  claim 1 , further comprising
 before the pressing of the outer peripheral surface, holding portions of the pre-pipe member with a holding member, the portions of the pre-pipe member being near a portion of the pre-pipe member to be pressed with the first die and the second die.   
     
     
         5 . The method according to  claim 4 , wherein
 the holding member has a tubular shape having a through hole therein, and   the holding of the portions comprises inserting the pre-pipe member in the through hole.   
     
     
         6 . The method according to  claim 1 , wherein
 the polygonal shape is a regular hexagonal shape,   the first recess portion has three first inner surfaces including two first side inner surfaces, and a first recessed inner surface that is between the first side inner surfaces,   the second recess portion has three second inner surfaces including two second side inner surfaces, and a second recessed inner surface that is between the second side inner surfaces,   the arranging of the first die and the second die comprises arranging the first die and the second die such that the first recessed inner surface faces the second recessed inner surface, and   the pressing of the outer peripheral surface comprises:
 pressing the outer peripheral surface of the pre-pipe member with the first side inner surfaces and the second side inner surfaces first and then, according to further pressing of the outer peripheral surface, the first recessed inner surface and the second recessed inner surface being in contact with the outer peripheral surface; and 
 pressing the outer peripheral surface of the pre-pipe member with the first side inner surfaces, the first recessed inner surface, the second side inner surfaces, and the second recessed inner surface in the closed state where the first die and the second die are closed, and forming the reduction portion having a hexagonal cross-sectional shape. 
   
     
     
         7 . The method according to  claim 6 , wherein in the closed state, a distance between the first recessed inner surface and the second recessed inner surface is smaller than an outer diameter of the pre-pipe member.