A process for producing a metal alloy balance wheel by molding, the process including the following steps: a) making a mold in the negative shape of the balance wheel, b) getting hold of a metal alloy that has a thermal expansion coefficient of less than 25 ppm/° C. and is able to be in an at least partly amorphous state when it is heated to a temperature between its glass transition temperature and its crystallization temperature, c) putting the metal alloy into the mold, the metal alloy being heated to a temperature between its glass transition temperature and its crystallization temperature so as to be hot-molded and to form a balance wheel, d) cooling the metal alloy to obtain a balance wheel made of the metal alloy, e) releasing the balance wheel obtained in step d) from its mold.

A balance for timepieces includes a rim, a hub, and at least one arm connecting the hub to the rim. At least one portion of the balance is made of an at least partially amorphous metal alloy. The at least partially amorphous metal alloy is based on an element chosen from the group consisting of platinum, zirconium and titanium, and has a coefficient of thermal expansion comprised between 7 ppm/° C. and 12 ppm/° C. The balance can be manufactured by moulding. A resonator can include such a balance and a monocrystalline quartz balance spring.

Some embodiments are directed to adjusting the oscillation frequency of an oscillating system for a watch movement, including: selecting a hairspring, selecting a balance belonging to a predetermined class, without a balance rim, at least two weight elements for balancing in a predetermined batch, pairing the hairspring with the balance and the at least two weight elements, measuring an oscillation frequency of the oscillating system including the hairspring, the balance and the at least two weight elements, and selecting at least one of a balance of another class or of the at least two weight elements of another batch if the measured oscillation frequency does not correspond to a desired oscillation frequency.

An electronically controlled mechanical watch includes a mechanical energy source, a power generator including a rotor driven by the mechanical energy source, a capacitor configured to be chargeable and accumulate electrical energy generated by the power generator, and a crystal oscillation circuit including a crystal oscillator and an oscillation circuit and configured to stop oscillating when a voltage of the capacitor falls below an oscillation stop voltage and to start oscillating when the voltage exceeds an oscillation start voltage higher than the oscillation stop voltage. The watch also includes a temperature compensation circuit configured to perform a temperature compensation function operation compensating for variation of a reference signal due to a temperature, a first voltage detection circuit configured to detect that the voltage exceeded a first voltage that is set higher than the oscillation start voltage, and a control circuit configured to stop the temperature compensation function operation of the temperature compensation circuit until the first voltage detection circuit detects that the voltage exceeded the first voltage.

An electronically controlled mechanical watch includes a mechanical energy source, a power generator including a rotor driven by the mechanical energy source, a capacitor configured to be chargeable and accumulate electrical energy generated by the power generator, and a crystal oscillation circuit including a crystal oscillator and an oscillation circuit and configured to stop oscillating when a voltage of the capacitor falls below an oscillation stop voltage and to start oscillating when the voltage exceeds an oscillation start voltage higher than the oscillation stop voltage. The watch also includes a temperature compensation circuit configured to perform a temperature compensation function operation compensating for variation of a reference signal due to a temperature, a first voltage detection circuit configured to detect that the voltage exceeded a first voltage that is set higher than the oscillation start voltage, and a control circuit configured to stop the temperature compensation function operation of the temperature compensation circuit until the first voltage detection circuit detects that the voltage exceeded the first voltage.

A process for producing a metal alloy balance wheel by molding includes a) making a mold in the negative shape of the balance wheel; b) obtaining a metal alloy that has a thermal expansion coefficient of less than 25 ppm/° C. and is able to be in an at least partly amorphous state when it is heated to a temperature between its glass transition temperature and its crystallization temperature; c) putting the metal alloy into the mold, the metal alloy being heated to a temperature between its glass transition temperature and its crystallization temperature so as to be hot-molded and to form a balance wheel; d) cooling the metal alloy to obtain a balance wheel made of the metal alloy; and e) releasing the balance wheel obtained in step d) from its mold. The process also includes a step for over-molding flexible centering components in the hub.

A process for fabricating a hairspring having a final stiffness includes the steps of fabricating a hairspring to thickened dimensions, and determining the initial stiffness of the hairspring formed in order to remove the volume of material to obtain the hairspring having the dimensions required for said final stiffness.

A balance spring for a balance with a blank containing: niobium: the remainder to 100 wt %, titanium: between 40 and 60 wt %, traces of elements selected from the group formed of O, H, C, Fe, Ta, N, Ni, Si, Cu, Al, between 0 and 1600 ppm by weight individually, and less than 0.3 wt % combined, a step of β-quenching the blank with a given diameter, such that the titanium of the alloy is essentially in solid solution form with β-phase niobium, the α-phase titanium content being less than or equal to 5% by volume, at least one deformation step of the alloy alternated with at least one heat treatment step such that the niobium and titanium alloy obtained has an elastic limit higher than or equal to 600 MPa and a modulus of elasticity lower than or equal to 100 GPa, a winding step to form the balance spring being performed prior to the final heat treatment step, prior to the deformation step, a step of depositing, on the alloy blank, a surface layer of a ductile material such as copper, the surface layer of ductile material being retained on the balance spring, the thermoelastic coefficient of the niobium and titanium alloy being adapted accordingly.

A balance for timepieces includes a rim, a hub, and at least one arm connecting the hub to the rim. At least one portion of the balance is made of an at least partially amorphous metal alloy. The at least partially amorphous metal alloy is based on an element chosen from the group consisting of platinum, zirconium and titanium, and has a coefficient of thermal expansion comprised between 7 ppm/° C. and 12 ppm/° C. The balance can be manufactured by moulding. A resonator can include such a balance and a monocrystalline quartz balance spring.

A bimetallic device, the difference in expansion coefficient of which is between 10 and 30 10.sup.−6 K.sup.−1, for providing a resonator with thermal compensation via the balance wheel.