Patent ID: 7896637

Claim:
An injection molding machine comprising: a plurality of hydraulic actuators, including: an injecting cylinder that moves back and forth a screw built in a heating cylinder of an injection unit; a measuring motor that rotates the screw; a mold clamping cylinder that opens or closes a mold and clamps the mold in a mold clamping unit; an ejecting cylinder that ejects a molded article formed in the mold; and an injection unit moving cylinder that moves the injection unit back and forth and attaches a nozzle to the mold or detaches the nozzle from the mold; a hydraulic drive member for driving the hydraulic actuators, the hydraulic drive member including: a plurality of hydraulic pumps, wherein the hydraulic pumps are variable discharge type hydraulic pumps where each of at least two different fixed discharge flow rates for each of the hydraulic pumps are preset for a corresponding one of a plurality of operation processes in a molding cycle; and a hydraulic oil supply circuit having one or more switching valves, the one or more switching valves being structurally configured to selectively merge and supply hydraulic oil discharged from the plurality of the hydraulic pumps or individually supply the hydraulic oil discharged from the plurality of the hydraulic pumps to a selected one or more of the hydraulic actuators in accordance with each of the plurality of operation processes of a molding cycle from the hydraulic actuators; wherein the hydraulic drive member structurally configured to select only one of the at least two different fixed discharge flow rates of the hydraulic pumps in each of the plurality of operation processes of the molding cycle and to variably control a number of revolutions of the servomotor, thereby controlling each of the plurality of operation processes in the molding cycle.