Backflow prevention device of light metal injection device and backflow prevention method of light metal injection device

A backflow prevention device of a light metal injection device, which

• connects a melting unit which melts an unmelted light metal material into a molten metal and an injection unit which injects the molten metal into a mold by a communication path, wherein the molten metal is injected into the mold after being metered,
• opens the communication path when the molten metal in the melting unit is supplied to the injection unit, and
• closes the communication path when the molten metal in the injection unit is injected to the mold,
• the backflow prevention device of a light metal injection device comprising:
• a valve which has a valve body made of a corrosion-resistant and heat-resistant steel and a valve seat made of a ceramic, and in which the valve body advances and is seated on the valve seat to close the communication path, and the valve body retracts and is separated from the valve seat to open the communication path;
• a valve body drive device which moves a drive body to which the valve body is connected in a front-rear direction together with the valve body;
• a position sensor which detects that the drive body has reached at least a predetermined advance limit position and outputs a signal indicating that the drive body has reached the predetermined position;
• and
• a valve body drive control device which connects the valve body drive device and the position sensor respectively, and controls the valve body drive device based on the signal of the position sensor.