Injection apparatus

An injection apparatus comprising:

• an injection piston configured to be capable of being driven along an axial direction of a heating barrel, the injection piston being connected to a screw provided in the heating barrel to be rotatable and driving the screw along the axial direction;
• an injection hydraulic cylinder configured to drive the injection piston housed therein in the axial direction by pressure of hydraulic oil, inside of the injection hydraulic cylinder being partitioned into a first chamber in which pressure oil is supplied to drive the injection piston and a second chamber from which hydraulic oil is discharged;
• an oil discharge port provided in the injection hydraulic cylinder and configured to discharge the hydraulic oil from the second chamber;
• a first valve inserted in a path for discharging the hydraulic oil discharged from the second chamber through the oil discharge port;
• and
• a second valve configured to be supplied with a part of the hydraulic oil supplied to the first chamber and to open when the pressure of the provided oil is higher than a first threshold value, wherein
• the first valve is configured to close when the pressure of the hydraulic oil supplied through the second valve is applied to the first valve,
• an oil supply port is provided in the injection hydraulic cylinder and configured to supply the first chamber with the hydraulic oil, and
• the second valve is provided between the oil supply port and the first valve.