Plunger pump is a kind of oil supply device, commonly used in the lubrication system of the machine. Its working principle is: rely on cam rotation, by the cam role in the spring pressure on the plunger, so that the plunger to do reciprocating motion, and thus constantly change the volume and pressure of the pump chamber, the lubricant will be sucked into the pump chamber, and discharged into the lubrication system. Plunger reciprocating distance, depending on the eccentricity of the cam size of 5mm, when the cam rotates in the counterclockwise direction, the cam rotation radius gradually decreases, the plunger in the compression of the spring force, gradually move to the right, the volume of the pump chamber gradually increased, and the pressure gradually decreased, the lubricant by the outside world under the action of atmospheric pressure, push open the upper one-way valve (suction valve) of the ball and enter the pump chamber.