Timepiece driven by a source of mechanical energy and regulated by an electric circuit

Abstract

The hands of the timepiece are connected to a barrel spring which also drives the rotor of a generator at a speed greater than a desired speed Vc. The electric energy supplied by the generator energizes a slaving circuit that includes a transistor which short-circuits the coil of the generator and thus brakes the rotor down to a speed less than the desired speed Vc when a comparator indicates that this rotor is ahead with respect to its theoretical angular position. A limiting circuit limits the duration of the braking action of the rotor to a fraction of the period of the a.c. voltage supplied by the generator. This arrangement ensures that the slaving circuit is adequately energized even if the rotor is substantially ahead.

Description

BACKGROUND OF THE INVENTIONThe present invention relates to a timepiece having:an electrical energy generator comprising a rotor and means for supplying electrical energy in response to rotation of the rotor;a source mechanical energy mechanically coupled to the rotor to cause rotation of the rotor at a speed greater than a set desired speed; andslaving means for slaving the rotational speed of the rotor to the desired speed which is energized by the electrical energy and which includes:measuring means coupled to the generator for producing a plurality of measurement pulses, each of the measurement pulses being produced in response to the rotor travelling through a particular angular position;reference means for producing a plurality of periodic reference pulses having a period equal to that of the measurement pulses when the rotor is rotating at the desired speed;comparing mean for supplying a comparison signal representative of the difference between, on the one hand, a first numb...

AI Technical Summary

Benefits of technology

which, on the one hand, adds to the braking resistance and reduces the rotor's braking torque and, on the other hand, causes a drop in the a.c. voltage produced by the generator when the current supplied by the generator flows through the coil.

An object of the present invention is to propose a timepiece of the same kind as that described in patent U.S. Pat. No. 3 937 001 mentioned above, but which does not suffer from its drawbacks, i.e. a timepiece wherein the value of the rotor's braking resistance may be very low, possibly even nil, without having to provide the generator's coil with a large number of turns and without there being any risk, under whatever circumstances, of the voltage energizing the electronic circuits becoming insufficient for the latter to operate properly. Further, this very low, possibly even nil, value of this braking resistance makes it possible to select the barrel spring that drives the generator's rotor in such a manner that its maximum torque will be large and that the timepiece's autonomy will hence be greater, all other things being equal, than that of the above-mentioned known timepiece.

Problems solved by technology

However, the smaller the braking resistance, the greater the braking torque which is applied to the generator's rotor, the braking torque being greatest when the braking resistance is nil.

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