Micro-injection pump

A micro-injection pump is provided with a guide rod and a screw. A fixed holder is fixedly connected with a frame. A movable clamping plate is equipped on a guide rod and a screw. A stepping motor is connected with the screw. The movable clamping plate is provided with an open nut. According to the micro-injection pump, higher precision is realized through the structure, and furthermore the operation is more reliable. The equipped open nut totally covers the screw, and therefore smaller pitch can be adopted for the screw. The transmission is more reliable. The stepping motor which rotates for 0.9 DEG in each pulse is adopted, and therefore a higher precision can be obtained. Furthermore a transmission mechanism at the central part is canceled, thereby preventing effect by the transmission error. A grating sensor is adopted for correcting injection stroke, thereby preventing a problem of low precision of a photoelectric switch. Commonly the detection precision of the grating sensor can reach mu m grade, and in