| 摘要 |
PURPOSE:To effect the tool contact detection stably and with high accuracy regardless of the variance of the voltage in the electric power source, the temperature drift of the like so as to detect the contact between the tool and the work from the difference between the reference wave-form and the detected wave-form. CONSTITUTION:An AC power source 14 is connected to a coil 12 which is provided in the vicinity of the tool, and a circuit for detecting an AC wave-form (a resistor 13) is provided between the coil 12 and the AC power source 14. In parallel with the AC power source 14 are connected reference wave-form generating circuits 30, 34 for forming the same wave-form as the detected wave-form when the tool and the work are not in contact with each other. Said detection circuit and reference wave-form generating circuits 30, 34 are connected to a comparator circuit 36 and the contact between said tool and work is detected by the occurrence of difference between said detected wave-form and reference wave-form. If the tool contact is detected in such a way, both the wave-forms integrally vary regardless of the variance of the voltage of the power source and the temperature drift at the time when the tool and the work are not in contact with each other, thereby it becomes possible to effect the detection of tool contact stably, with high accuracy and without varying the setting level. |
