Press load controlling apparatus for mechanical press

摘要

In a mechanical press, the pressure (cylinder force) of a hydraulic pressure chamber of a cylinder-piston mechanism provided in a slide of the mechanical press can be variably controlled with a high responsiveness by a hydraulic pump/motor driven by an electric servomotor, in response to a cylinder force command corresponding to the press load command. Accordingly, even if a die height value is set to a value small enough to cause an overload, the press load can be restricted before the occurrence of the overload, and this can save the trouble of strictly adjusting the die height value. Further, pressure-application time in the vicinity of a bottom dead center can be lengthened, and a breakthrough phenomenon can be suppressed from occurring at the end of pressure application. Still further, because the overload does not occur, pressure oil is not relieved, so that the interruption of a press operation is avoided.

主权项

1. A press load controlling apparatus for a mechanical press, comprising:
a cylinder-piston mechanism provided in a slide of the mechanical press, the slide having one part of a die and being configured to move the one part of the die toward another part of the die to shape a workpiece; a relief valve configured to act when a pressure of a hydraulic pressure chamber of the cylinder-piston mechanism exceeds a set overload pressure; a hydraulic pump/motor connected to the hydraulic pressure chamber of the cylinder-piston mechanism; an electric servomotor connected to a rotating shaft of the hydraulic pump/motor; a pressure detecting device configured to detect the pressure of the hydraulic pressure chamber of the cylinder-piston mechanism; a pressure commanding device configured to command the pressure of the hydraulic pressure chamber on a basis of a preset press load command; and a controlling device configured to control a torque of the electric servomotor on a basis of a pressure command from the pressure commanding device and the pressure detected by the pressure detecting device, to thereby control the pressure of the hydraulic pressure chamber of the cylinder-piston mechanism.