| 摘要 |
<p>PURPOSE:To detect the change in the relative position between an induction heating coil and the work and the point on the work where the shape changes by moving the induction heating coil and the work relatively while supplying the detecting current from an electric power source separated from a heating power source to the induction heating coil and detecting the change in the level of the detecting current. CONSTITUTION:Detecting current fs is supplied to an induction heating coil 2, and the coil is fed toward the part R 42 of the work 4. When a detector 32 detects and outputs the detecting current Is in excess of the current level which is set beforehand with respect to the part 42, a switch 8 is opened to stop feeding of the coil 2. Thereafter, the electric power source switch 8 is turned on to start the backward feeding of the coil 2 and to start hardening operation. The detector 32 outputs the detecting signal (g) when the distance between the feeding start position of the coil 2 and the part 42 is made nearly zero irrespectively to the feeding start position of the coil 2; therefore, the collision of the coil 2 against the head part 43 of the work is prevented.</p> |
