Electronically controlled mechanical timepiece and control method therefor

Abstract

An electronically controlled mechanical timepiece includes: a voltage-controlled oscillator ( 25 ) including a generator that uses a rotor ( 12 ) driven by a spring ( 1 a) to rotate, and a brake circuit ( 23 ) for controlling the rotation cycle of the generator ( 20 ); and a rotation control circuit ( 50 ) for controlling the rotation cycle of the generator ( 20 ) by controlling the brake circuit ( 23 ). The rotation control circuit ( 50 ) includes a phase-comparison circuit ( 54 ) for comparing the phases of rectangular-wave pulses fr output from a VCO ( 25 ) and time standard signal fs, and a brake control circuit ( 56 ) for inputting, based on an output from the phase-comparison circuit ( 54 ), a signal for controlling the brake circuit ( 23 ) to voltage-controlled oscillator ( 25 ). By providing the VCO ( 25 ) and the phase-comparison circuit ( 54 ), PLL control is realized to enable a rapidly responsive system.

We claim:  
     
       1. An electronically controlled mechanical timepiece comprising: 
       a mechanical energy source;  
       a wheel train bridge ;  
       a generator driven by said mechanical energy source and connected to said mechanical energy source by said wheel train bridge , said generator generating induced electric power for supplying electric energy;  
       a brake circuit that brakes said generator in response to a braking control signal;  
       pointers connected to said wheel train bridge ;  
       and a rotation control circuit that controls said brake circuit to control the rotation cycle of said generator;  
       wherein said rotation control circuit comprises:  
       a rotation detection circuit that generates a rotation signal of said generator;  
       a target-signal generating circuit that generates a target signal corresponding to a target number of revolutions;  
       a phase-difference compensating circuit that detects a phase difference between said rotation signal output from said rotation detection circuit, and said target signal output from said target-signal generating circuit, and outputs a phase-difference compensation signal that is input to said brake circuit as said braking control signal.  
     
     
       2. An electronically controlled mechanical timepiece according to  claim 1 , wherein said phase-difference compensating circuit comprises a phase-comparison circuit that compares the phases of said rotation signal and said target signal; and a brake control circuit that inputs said phase-difference compensation signal to said brake circuit. 
     
     
       3. An electronically controlled mechanical timepiece according to  claim 2 , wherein said rotation control circuit comprises a waveform shaping circuit that converts an output waveform of said generator into rectangular wave pulses and outputs said rectangular-wave pulses as said rotation signal to said phase-comparison circuit. 
     
     
       4. An electronically controlled mechanical timepiece according to  claim 2  or  3 , wherein said rotation control circuit comprises a frequency-to-velocity converter that converts the frequency of an output signal from said generator into velocity, and said brake control circuit outputs said braking control signal to said brake circuit in response to an output from said phase-comparison circuit and an output from said frequency-to-velocity converter. 
     
     
       5. An electronically controlled mechanical timepiece according to  claim 1 , wherein said phase-difference compensation circuit comprises a phase-difference detection circuit and a compensation-signal generating circuit that receives an output from said phase-difference detection circuit, 
       said rotation signal and said target signal are repetitive pulses,  
       said phase-difference detection circuit includes counters for counting the number of times the rotation and target signals rise or fall, and  
       one of said counters increments or decrements when said target or rotation signal rises or falls, and outputs a phase-difference signal to said compensation-signal generating circuit.  
     
     
       6. An electronically controlled mechanical timepiece according to  claim 5 , wherein said phase-difference detection circuit comprises: 
       an integral counter for measuring a total number of the phase excursion periods of said rotation signal and said target signal;  
       a proportional counter for measuring phase excursion periods;  
       and an adder for increasing or reducing the value of each counter in accordance with a lead or lag of the phase excursion of said rotation signal with respect to said target signal.  
     
     
       7. A control method for an electronically controlled mechanical timepiece including a mechanical energy source; a generator driven by said mechanical energy source, said mechanical energy source connected to said generator by a wheel train bridge , the generator generating induced electric power for supplying electric energy, a brake circuit for braking said generator, pointers connected to said wheel train bridge , and a rotation control circuit that controls the rotation cycle of said generator by controlling said brake circuit, the method comprising: 
       generating a target signal corresponding to a target number of revolutions;  
       generating a rotation signal of said generator;  
       comparing said target signal to said rotation signal to detect a phase difference therebetween and generating a phase-difference compensation signal in accordance with said detected phase difference; and  
       controlling said brake circuit in accordance with said phase-difference compensation signal.  
     
     
       8. A control method for an electronically controlled mechanical timepiece, according to  claim 7 , wherein said control method comprises: 
       measuring a total number of the phase excursion periods of said rotation signal and said target signal with an integral counter;  
       measuring phase excursion periods using a proportional counter;  
       determining a lead or lag of the phase excursion of said rotation signal with respect to said target signal;  
       computing a phase-difference compensation signal for setting a braking time by increasing or reducing the value of each counter in accordance with said determined lead or lag; and  
       using said phase-difference compensation signal to control said brake circuit.