To uniformize the follow-up load of a high frequency induction heating coil to a pin part or a journal part in a crankshaft without depending on the rotational position of the pin part or the journal part by continuously controlling the follow-up load so as to set the load in the absolute minimum at the time when the pin part or the journal part is subjected to high frequency induction heating for subjecting the same to quenching treatment, tempering treatment or the like, and thus suppressing the generation of flaws and bending to the minimum.
A sensor 22 for load detection continuously detecting a follow-up load to the pin part 3 or the journal part 2 in a follow-up part M following up the pin part 3 or the journal part 2 at the time when a high frequency induction heating coil 6 follows up the pin part 3 or the journal part 2, and a follow-up load controlling mechanism 21 controlling the follow-up load based on a detection signal from the sensor 22 for load detection are provided, respectively, and the follow-up load is controlled in accordance with the detection signal from the sensor 22 for load detection.
YAMAGUCHI RYOICHI
KOMIYA MAKOTO
Arihara Koichi
Matsushima Tetsuo
Akiyama Noburi