Device and method for controlling stop of hydraulic press and device and method for detecting trouble of speed selector valve

摘要

A rod pressure holding instruction section (67) controls a servo motor (37) to rotate a two-way pump (29) in a counter direction, and to supply hydraulic oil with pressure, which does not exceed pressure applied by an own weight of a ram (5U), to a two-way pump-side piping (49), increasing pressure. A difference between pressure in a rod-side cylinder chamber-side piping (43) of a speed switching valve (47) and pressure in a two-way pump-side piping (49) of the speed switching valve (47) is decreased, thereby decreasing an impact generated when switching the speed switching valve (47) and stopping the ram (5U) at a predetermined position.