self-changing gear

例句：

1. 1. Thecar's self-changing gear system is incredibly efficient.
   汽车的自调速系统非常高效。
2. 2. The self-adjusting gear in the machine allows for easy adjustment of speed.
   机器中的自调速装置允许轻松调整速度。
3. 3. The self-regulating gear ensures that the engine runs smoothly even during high load conditions.
   自调节齿轮确保即使在高负载条件下，发动机也能平稳运行。