主发条

例句：

1. 1. The mainspring of the clock is responsible for keeping it running.
   钟表的主发条负责使其运行。
2. 2. The mainspring of the car engine is vital for its operation.
   汽车发动机的主发条对其运行至关重要。
3. 3. The mainspring of the door lock has to be adjusted regularly to ensure proper functioning.
   门锁的主发条需要定期调整以确保正常工作。