pinion-gear

例句：

1. 1. The car's engine is running smoothly with the new gear.
   汽车的引擎运行得很顺畅，换了新的齿轮。
2. 2.The old gearbox was worn out and needed to be replaced.
   旧的齿轮箱磨损严重需要更换。
3. 3. The engineer adjusted the gear ratio for better efficiency.
   工程师调整了齿轮比以提高效率。