The invention discloses an
injection pump and a transmission device thereof.The transmission device comprises a screw rod, a semi nut, a moving component, a sliding seat, an
elastic component and an electrical driving
assembly; the semi nut and the moving component are both slidably arranged on the sliding seat; the moving component can move relative to the semi nut, and the
elastic component is connected to the semi nut; when the electrical driving
assembly drives the moving component t move to a first position in the direction far away from the screw rod, the semi nut is driven by the moving component to move to the position where the semi nut is separated from the screw rod; when the electrical driving
assembly drives the moving component to move to a second position in the direction close to the screw rod, the semi nut is meshed with the screw rod under the action of elastic force of the
elastic component, and the moving component and the semi nut are in clearance fit in the sliding direction of the moving component and the semi nut.The electrical driving assembly can be utilized for driving the semi nut to be completely separated from the screw rod, abrasion of threaded teeth is avoided, the service life is prolonged, operation is convenient to conduct, and labor is saved; the semi nut is meshed with the screw rod through elastic force, meshing reliability is guaranteed, the whole structure is simple, and process and
machining difficulty is lowered.