DIE DEVICE FOR INJECTION-MOLDING OF MOLDING WITH HOLLOW STRUCTURE AND INJECTION-MOLDING METHOD

PURPOSE: To provide a die device which forms a hollow structure in a molding by injecting a pressurized liquid into a molten resin injected into a cavity and expanding the volume of the cavity halfway through a molding step, and is capable of injecting the pressurized liquid at high pressure, with a simple structure. CONSTITUTION: This die device consists of a fixed die 14, a movable die 24 which can slide in a die closing direction, an intermediate die 30 which is arranged between the fixed die 14 and the movable die 24 and can slide in a die closing direction between the dies and at least, one liquid cylinder 40A, 40B which can slide the intermediate die 30 in the die closing direction. A cavity 60 is formed of the die cavity faces 14A, 30A, 24A of the fixed die, intermediate die and movable die. Consequently, the thickness of the cavity 60 can be increased by moving the movable die 24 in a die opening direction in such a state that the intermediate die 30 is attached closely to the fixed die 14 by the liquid cylinders 40A, 40B.