Liquid medicine injection device

1. A medical liquid injection device comprising:

a base body;

a needle assembly mounted on the base body;

a reservoir fluidly connected to the needle assembly and having a plunger therein;

a driving unit that linearly moves the plunger; and

an encoder unit disposed at an end of the driving unit to measure rotation of the driving unit, wherein

the encoder unit comprises:

a base cover mounted on the end of the driving unit and rotating together with the driving unit;

a first contact end connected to contact one side of the base cover; and

a second contact end disposed on another side of the base cover and selectively contacting the base cover according to rotation of the driving unit,

the base cover comprises:

a cover end extending in a circumferential direction of the driving unit which rotates; and

a plurality of tooth ends extending from the cover end and spaced apart from each other along the circumferential direction of the cover end,

the driving unit comprises:

a protruding end disposed between adjacent tooth ends of the plurality of tooth ends, and a height of the protruding end varies in a radial direction thereof so that the protruding end and the tooth ends have a step in a circumferential direction, and

the protruding end has a first wall and a second wall on one side and another side thereof, respectively, wherein a height of the first wall is smaller than a height of each of the tooth ends and the height of the second wall is greater than the height of the tooth end, and a height of the protruding end is increased from the first wall to the second wall.

2. The medical liquid injection device of claim 1 ,

wherein the first contact end and the second contact end each have elasticity.