| 摘要 |
PURPOSE:To form a tough, lightweight crank shaft at high yield and low cost by forming a recessed part including a crank journal shaft line in the end surface of a crank arm on a crank pin side during forging of a crank shaft prototype. CONSTITUTION:A raw material is struck as shown by arrows A with a hammer which is not shown in figure to form such a crank shaft original prototype that axis lines of crank pins 4 (a, b, c, d, e, and f) are in the same plane including the axis line of a crank journal 2. During the hammer percussion, a recessed part 8 including the journal axis line is formed at the same time. Then, this crank shat prototype is twisted so that the axis lines of the crank pins 4a and 4f, those of the crank pins 4b and 4e, and those of the crank pins 4c and 4d are at 120 deg. to one another. Thus, a crank shaft for a six-cylinder engine is formed. |
