Method and Device for Processing Crankshaft and Burnishing Roller for Crankshaft

Abstract

A pair of burnishing rollers formed in a roughly disk shape are linearly disposed oppositely to each other on both sides of the shaft part of a crankshaft. The crankshaft is rotated about its axis by the rotatingly driving action of a rotating driving source (M). The pair of burnishing rollers are displaced in a direction apart from each other while the shaft part of the crankshaft is held by the outer peripheral surfaces of the pair of burnishing rollers to apply a rolling to the crankshaft.

1 . A method of machining a crankshaft, comprising the steps of placing a pair of burnishing rollers in opposite relation to each other across a shank of a crankshaft therebetween, gripping the shank of the crankshaft with outer circumferential surfaces of said burnishing rollers, and rotating said crankshaft and said burnishing rollers to rollingly press said shank. 
   
   
       2 . A method according to  claim 1 , wherein after said burnishing rollers are displaced toward the shank of the crankshaft and grip a substantially central area of said shank, said burnishing rollers are caused to slid in respective directions away from each other along an axial direction of said crankshaft to rollingly press said shank. 
   
   
       3 . A method according to  claim 1 , wherein said shank is burnished by being rollingly pressed prior to a heat treatment of said crankshaft including at least a high-frequency heat-treatment. 
   
   
       4 . An apparatus for machining a crankshaft, comprising:
 holding mechanisms for holding both axial ends of a crankshaft so that the crankshaft is rotatable; and   a pair of burnishing rollers disposed in opposite relation to each other across a shank of the crankshaft therebetween;   wherein the shank of the crankshaft is gripped by outer circumferential surfaces of said burnishing rollers, and said crankshaft and said burnishing rollers are rotated to rollingly press said shank.   
   
   
       5 . An apparatus according to  claim 4 , wherein each of said burnishing rollers is of a substantially disk-like identical shape, and the outer circumferential surface for rollingly pressing said shank comprises a single flat surface. 
   
   
       6 . An apparatus according to  claim 4 , wherein said burnishing rollers are disposed in mutually opposite relation to each other linearly perpendicular to the axis of the crankshaft. 
   
   
       7 . An apparatus according to  claim 4 , wherein said burnishing rollers are disposed in opposite relation to each other at respective positions that are offset in opposite directions by equal distances parallel to the axis of said crankshaft from a linear position perpendicular to the axis of said crankshaft. 
   
   
       8 . An apparatus according to  claim 4 , wherein each of said burnishing rollers is cantilevered on one side thereof by a support member or supported on both sides thereof by support members. 
   
   
       9 . An apparatus according to  claim 5 , wherein the outer surface of each of said burnishing rollers for contacting the shank of said crankshaft has a round corner having a radius (r 2 ) of curvature smaller than a radius (r 1 ) of curvature of round corners on both axial ends of said shank. 
   
   
       10 . A crankshaft burnishing roller for burnishing a shank of a crankshaft by rollingly pressing the shank, comprising:
 a pair of burnishing rollers disposed in opposite relation to each other across the shank of the crankshaft therebetween;   each of said burnishing rollers being of a substantially disk-like identical shape and having an outer circumferential surface for rollingly pressing said shank, said outer circumferential surface having a plurality of ridges having respective crests axially spaced at equal intervals;   said crests of adjacent two of said ridges being spaced from each other by a distance S which is greater than the inside diameter T of an oil hole defined in said shank.   
   
   
       11 . A crankshaft burnishing roller according to  claim 10 , wherein said ridges comprise at least three ridges. 
   
   
       12 . A crankshaft burnishing roller according to  claim 10 , wherein the outer surface of the ridges for contacting the shank of said crankshaft has a round corner having a radius (r 2 ) of curvature smaller than a radius (r 1 ) of curvature of round corners on both axial ends of said shank.