| 摘要 |
PURPOSE:To prevent an accident from leading to a great loss, by a method wherein while a boat loader for loading and unloading a boat having wafers mounted thereon into and from a heat-treating oven is driven, the torque variation of a motor as a drive source is monitored at all times. CONSTITUTION:A motor current detecting resistor 7 connected to a motor 4 in series applies to a torque variation detector 8 a voltage proportional to a current (i) flowing through the motor. The detector 8 reads the degree and time of the voltage variation to make a decision and transmits an abnormality, if any, to a motor controller 1. If there is any abnormality such as the coming off of a wafer from a boat and the catching of a wafer while the boat loader is driven, the current (i) flowing through the motor 4 varies. Thus, if a torque variation exceeding a predetermined value continues more than a given time, the torque variation detector 8 transmits the fact to the motor controller 1, which, on receipt of the information, suspends the motor 4 as well as informs the operator of the abnormality through a buzzer. |
