LIQUID MEDICINE INJECTION DEVICE, DRUG INJECTION DEVICE, AND METHOD FOR DETERMINING REMAINING AMOUNT OF DRUG THEREOF

Provided is a medical liquid injection device including a base body, a needle assembly mounted on the base body, a reservoir fluidly connected to the needle assembly and having an inner space in which a medical liquid is stored, a plunger disposed inside the reservoir, and configured to move in a longitudinal direction of the reservoir according to an amount of the medical liquid stored in the reservoir, and a first sensor unit configured to measure the amount of the medical liquid stored in the reservoir according to the movement of the plunger.The medical liquid injection device may include a storage unit, a plunger, a connector member, a processor, and a sensor unit. A medical liquid may be stored in the storage unit. The plunger may seal the storage unit, and may move along a longitudinal direction of the storage unit as a medical liquid is replenished in the storage unit or discharged from the storage unit. The connector member may be attached to one side of the plunger. The processor may receive a contact detection signal or a non-contact detection signal from the sensor unit disposed adjacent to the storage unit. The connector member may be in contact with or not in contact with the sensor unit while moving together with the plunger.