Patent ID: 8239058

Claim:
A method for controlling a mold clamping device which performs mold opening control by driving a mold clamping cylinder by a variable, discharge-type hydraulic pump which can control a discharge flow rate by varying the control of the number of revolutions of a drive motor, comprising: preliminarily setting a predetermined speed control pattern including, at least, a mold opening section in which mold opening is performed at a predetermined mold opening speed, a deceleration section in which the speed is gradually decelerated from an end point of the mold opening section toward a virtual stop position, and a last-transition section for which a predetermined last-transition speed is set before the virtual stop position; in controlling mold opening, in the mold opening section, performing mold opening control at the mold opening speed, and sequentially forecasting, based on a current mold opening speed and a current mold opening position, which are both detected, a deceleration starting position of the deceleration section where a current mold opening speed becomes a zero (O) at the virtual stop position, at each predetermined time interval by calculation; starting the deceleration section upon reaching the deceleration starting position, and in the deceleration section, obtaining, based on the detected current mold opening position, a speed command value corresponding to the speed control pattern sequentially by calculation, and according to the speed command value, performing decelerated mold opening processing; and upon reaching the last-transition speed, performing a predetermined stop controlling processing, wherein, in the deceleration section, a time period required for the deceleration section, and then the time period between a deceleration starting position of the deceleration section and the virtual stop position is so controlled as to be the required time period, and wherein distance (Lmd) of the deceleration section is estimated to be Lmd=(Vd·Td)/2 (wherein Vd is a detected current mold opening speed and Td is a time period required for the deceleration section), when the condition of Xso−Lmd≦Xd (wherein Xso is a virtual stop position and Xd is a detected current mold opening position) is satisfied, it is determined that the deceleration starting position is reached.