HIGH-FREQUENCY SURFACE HARDENING METHOD FOR CRANK SHAFT

摘要

PURPOSE:To prevent the fluctuation in a quench-hardened layer by energizing and de-energizing an induction heating coil in a specific position according to the rotation of the crank shaft at the time of hardening the part to be heated of the crank shaft by heating with the heating coil. CONSTITUTION:The hardening coil 30 of the pin part 12 of the crank shaft 10 is brought into contact with the pin part 12 at a specified spacing from said part via a spacer 31 at the time of subjecting the pin part 11-14 of said crank shaft to the surface hardening by high-frequency heating. The coil is moved back and forth in arrow R and S directions in accordance with the movement of the pin part 12 so as to follow up said movement. The crank shaft 10 is rotated around an axial center 22 and the pin part 12 revolves in a P direction while rotating in a Q direction. An angle detector 32 detects the rotating angle alpha1 of the pin part 12 upon arrival of the center 21 of said part at the point S from the point C and sends a detection signal to a controller 34 which energizes the coil 30 to start heating of the pin part 12. The detector 32 detects the rotating angle (alpha1+nX360 deg.+alpha2) and stops the energization to the coil 30 to end the heating of the pin part 12 when the center 21 rotates n times from the point S and arrives at the point T after arriving again at the point S. The pin part 12 having no fluctuations in the width and depth of the hardened layer is thus obtd.