Liquid feeding device using ball screw, and analyzer

A liquid feeding device, comprising:

• a syringe having a piston capable of sliding in a cylinder, and having a liquid inlet/outlet port at a distal end of the cylinder, in which a piston rod that is integrated with the piston protrudes to a proximal end side of the cylinder, the syringe performing suction and discharge of a liquid from the inlet/outlet port by causing the piston to slide through the piston rod;
• a syringe support unit comprising a piston rod support body that is attached to the piston rod, and a ball screw that is screwed together with the piston rod support body, the syringe support unit using the ball screw as a linear feed mechanism to move the piston rod support body by rotation of the ball screw;
• a pulse motor that causes the ball screw to rotate;
• a rotation detection mechanism comprising a coupling formed in a disk shape that has a slit in a radial direction and that is attached integrally with the ball screw so as to rotate together with the ball screw, and a photo sensor that is combined with the coupling so as to detect a position of the slit of the coupling;
• and
• a control device that controls driving of the pulse motor so as to discharge a liquid that is sucked into the syringe in a single suction process over a plurality of discharge processes, and so that rotation of the ball screw for executing each discharge process starts from an identical rotational angle position relative to the slit.