Power transmission chain pin and manufacture method thereof

Abstract

A manufacture method of a power transmission chain pin includes a work step of working a bar-like member of a predetermined length into a pin having a final sectional shape and a final end portion shape with a guide portion to facilitate a press-fitting operation by a cold forging work. At this time, the manufacture method does not include a grinding step of grinding an end portion of the bar-like member of the predetermined length by a grinding stone.

1 . A power transmission chain pin which is press-fitted to links arranged in a chain width direction of a power transmission chain, the power transmission chain pin comprising:
 a guide portion disposed in at least one end portion of the power transmission chain pin and inclined so as to gradually increase a press-fitting margin to facilitate a press-fitting operation,   wherein the guide portion is formed by a cold forging work.   
   
   
       2 . A power transmission chain comprising:
 a plurality of links each of which has a front insertion through hole and a back insertion through hole through which pins are inserted; and   a plurality of first pins and a plurality of second pins connecting bendably the links in a chain longitudinal direction such that the front insertion through hole of one link corresponds to the back insertion through hole of another link which is arranged to overlap with said one link in a chain width direction,   wherein at least one of said first pins and second pins is the power transmission chain pin according to  claim 1 .   
   
   
       3 . A method of manufacturing a power transmission chain pin which connects links arranged in a chain width direction of a power transmission chain, the method comprising:
 a rough sectional shape formation step of drawing a wire rod so that a section thereof is formed in a substantially oval shape; and   a rough end portion shape formation step of cutting a continuous bar-like member which has been subjected to the drawing work into a predetermined length so that an end surface thereof has a predetermined angle with respect to an axial direction;   wherein a final sectional shape and a final end portion shape of the power transmission chain pin are formed by a cold forging work to the bar-like member cut into the predetermined length, which is a final shape formation step.   
   
   
       4 . A method of manufacturing a power transmission chain pin, according to  claim 3 ,
 wherein a lower die used in the cold forging for forming the final end portion shape of the power transmission chain pin includes a concave portion for forming a guide portion of the power transmission chain pin, and an upper die includes a concave portion for forming a surface of the power transmission chain pin coming into contact with a conical sheave surface of a pulley, and   the final end portion shape of the pin is formed by hitting a surface of the power transmission chain pin opposite to the guide portion by a punch.