| 摘要 |
PURPOSE:To suppress a temperature increase of a main spindle electric motor, by a method wherein the total of voltage corresponding to torque and a temperature of the main spindle electric motor is taken out by a main spindle load detecting circuit and a set speed of a feed spindle electric motor is reduced when the voltage becomes more than a set value. CONSTITUTION:A main spindle electric motor 1 and a feed spindle electric motor 2 are driven by a main spindle driving circuit 3 and a feed spindle driving circuit 4 respectively. A signal of a temperature sensor 10 consisting of a diode buried in a stator is detected as voltage V through a temperature detecting circuit 5 by a temperature increase theta of the main spindle electric motor 1, which is added to torque set voltage V of the main spindle electric motor 1, which is added to torque set voltage V of a main spindle by an adding circuit 6. When this output is compared with set voltage VB of a main spindle load setting circuit 8 by a speed correction circuit 7 and an inequality V +V >VB holds, voltage VC, which is in proportion to their difference, is applied to a subtraction circuit 9, feed spindle speed reference voltage VS is subtracted and the feed spindle electric motor 2 is decelerated through the feed spindle driving circuit 4. Load torque of a main spindle, therefore, is reduced and a temperature increase is suppressed. |
