roller gear

例句：

1. 1. The car has a roller gear that makes it easy to start and stop.
   这辆车有一个滚动齿轮，使启动和停止变得容易。
2. 2.The machine uses roller gears to reduce friction and increase efficiency.
   这台机器使用滚轮齿轮来减少摩擦并提高效率。
3. 3.The train has roller gears on its wheels to help it move smoothly over rough terrain.
   火车的车轮上有滚轮齿轮，有助于它在崎岖的地形上平稳行驶。