TIMEPIECE MAINSPRING, TIMEPIECE DRIVE DEVICE, TIMEPIECE MOVEMENT, TIMEPIECE, AND MANUFACTURING METHOD OF TIMEPIECE MAINSPRING

摘要

A timepiece mainspring is accommodated inside a barrel, an inner end thereof is fixed to a barrel arbor included in the barrel, and an outer end thereof engages with an inner wall of the barrel. The timepiece mainspring includes a helical portion wound in a Bernoulli curve shape from the inner end in a free state having no applied load.