THERMALLY COMPENSATED HAIRSPRING MADE FROM CERAMIC COMPRISING SILICON IN THE COMPOSITION OF SAME AND METHOD FOR ADJUSTING SAME

摘要

The invention concerns a hairspring (1) intended to equip a balance-hairspring resonator of a movement of a timepiece or another precision instrument, the hairspring (1) comprising a core (2) made from a ceramic material comprising silicon in the core of same and comprising a cross-section, the core (2) having a first stiffness (k A) and a first thermoelastic coefficient (β A); and a coating (4) made from silicon dioxide of thickness (t R) and at least partially covering the core (2), the coating (4) having a second thickness (k R ) and a second thermoelastic coefficient (β R) of opposite sign to the first thermoelastic coefficient (β A); in which the cross-section of the core (2) and the thickness (t R) of the coating (4) can be adjusted separately in such a way as to obtain a desired value for the thermoelastic coefficient of the hairspring (β S) and a thickness of the hairspring (k S). The invention also concerns a balance-hairspring resonator comprising the hairspring and a balance wheel and a method for adjusting the hairspring. The hairspring has invariant expansion and elasticity properties.