external spur gear

例句：

1. 1. The gearbox is designed to provide smooth transmission of power from the engine to the wheels.
   齿轮箱设计用来将发动机的动力平滑地传递给车轮。
2. 2.The external spur gear on the axle helps to reduce wear and extend the life of the drivetrain.
   轴上的外啮合齿轮有助于减少磨损并延长传动系统的使用寿命。
3. 3.In this case, the external spur gear was replaced with a more efficient alternative.
   在这种情况下，我们用更高效的替代方案替换了外部啮合齿轮。