The piston pin is a cylindrical pin mounted on the skirt of the piston. Its middle part passes through the small head hole of the connecting rod to connect the piston and the connecting rod. Its function is to transfer the gas force on the piston to the connecting rod, or to make the connecting rod small head drive the piston to move. In order to reduce weight, piston pins are usually made of high quality alloy steel and hollow.

The piston pin is used to connect the piston to the connecting rod and transfer the force on the piston to the connecting rod or vice versa.

The piston pin bears a large periodic impact load at high temperature, and because the piston pin swings in the pinhole at a small angle, it is difficult to form a lubrication film, so the lubrication condition is poor. Therefore, the piston pin must have enough stiffness, strength and wear resistance. The quality is as small as possible. The pin and pinhole should have proper fit clearance and good surface quality. In general, the stiffness of the piston pin is particularly important. If the piston pin bends, it may damage the piston pin seat.

In a word, the working condition of piston pin is high pressure ratio, unable to form oil film and inconsistent deformation. Therefore, the design requirements are high enough mechanical strength and wear resistance, and high fatigue strength.