piston gudgeon pin

例句：

1. 1.The piston is the part that moves up and down inside the cylinder.
   活塞是气缸内上下移动的部分。
2. 2. The rod is a long piece of metal that connects two parts of a machine together.
   杆是连接机器两个部分的长金属片。
3. 3.The pin is a small metal object that holds things together.
   销是一个小金属物体，用于固定东西。