Horology: time measuring systems or devices – Chronological – With supplemental power source
Reissue Patent
2001-03-23
2003-05-06
Miska, Vit (Department: 2841)
Horology: time measuring systems or devices
Chronological
With supplemental power source
C368S204000
Reissue Patent
active
RE038110
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electronically controlled mechanical timepieces that accurately drive pointers fixed to a wheel train
bridge
by using a generator to convert mechanical energy in the unwinding mode of a spring into electrical energy, and controlling the rotation cycle of the generator by driving a rotation control circuit with the electrical energy, and to control methods therefor.
2. Description of the Related Art
An electronically controlled mechanical timepiece described in Japanese Examined Patent Publication No. 7-119812 is known as one for indicating an accurate time that accurately drives pointers fixed to a wheel train
bridge
by using a generator to convert mechanical energy in the unwinding mode of a spring into electrical energy, and controlling a current flowing in the coil of the generator by driving a rotation control circuit with the electrical energy.
In the electronically controlled mechanical timepiece, by inputting a signal based on the rotation of the generator into a counter while inputting a signal from a quartz oscillator into the counter, comparing values in the counter, and controlling the generator based on the difference, rotation velocity is controlled. The counter compares the phase differences of reference clock pulses (Ref-pulses) and generator-rotation-cycle pulses (G-pulses), and increases the value of a U/D counter if the G-pulses are ahead, or decreases the value if the G-pulses are behind. The counter consists of a so-called integral counter.
When a value obtained by measuring the time of one cycle of the Ref-pulses is equal to a value obtained by the integral counter, braking of the generator is performed, and braking is continuously performed until measurement of the time of one cycle of the Ref-pulses terminates. Accordingly, the value of the integral counter sets a braking release time. That is, the value of the integral counter is multiplied by braking release time N at which the average velocity of the G-pulses is equal to a target velocity (Ref-pulses). In other words, integral control is employed in this system.
According to the integral control, the average velocity of a rotor over a sufficient duration can be controlled to a velocity in a set time, whereby pointers can be accurately moved at a controlled velocity because signals output in each cycle are compared, while the signals are being counted. However, the integral control has a problem in that the rotation velocity of the rotor cannot be instantly adjusted, which causes slow responsiveness. The integral control also has a problem in that a plurality of phase excursions is generated until the relationship between spring force and braking force is set so as to correspond to a target frequency.
The integral control can be expressed in the block diagram in FIG.
20
.
In general, it is known that a transfer function used for a generator or motor is 1/s(sT+1). This consists of a first-order-lag transfer function
101
and an integral term
102
of 1/s. Accordingly, an integral factor is included in the generator as an object to be controlled. Bode diagrams on the assumption that only the integral control is performed for the object are shown in
FIGS. 21 and 22
.
In the Bode diagrams, it is required as a condition for stable rotation control that a phase allowance, i.e., the phase at a gain of zero db (gain intersection), be ahead of −180° and that gain allowance, i.e., the gain at a phase of −180° (phase intersection), be not more than zero db.
However, in the case where only the integral control is performed, a phase delay of −90° occurs in the object, and a further phase delay of −90° occurs due to the integral control, as shown in
FIG. 21
, so that the phase is at approximately −180°. Thus, stable control is difficult because the integral control alone cannot obtain phase allowance and gain allowance. Accordingly, the timepiece in Japanese Examined Patent Publication No. 7-119812 must perform control at a very low frequency, and its responsive characteristic is positioned at approximately 0.016 Hz or less.
A case where the gain of the integral counter is set to be 100 times greater is shown in FIG.
22
. Also, in this case, phase allowance is behind −180°, and stable control cannot be anticipated.
As is clear from the above-described data, by performing control using only the conventional integral control, average velocity control can be performed, but a problem occurs in that phase excursions cannot be eliminated.
In addition, slow control response causes a problem in that almost nothing can compensate for a rapid disturbance as in the case when acceleration is generated in a watch by a swing of an arm.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide an electronically controlled mechanical timepiece that is free from phase excursions and has rapid control system response, and to a control method therefor.
SUMMARY OF THE INVENTION
According to the present invention, there is provided an electronically controlled mechanical timepiece including: a mechanical energy source; a generator driven by the mechanical energy source connected to the generator via a wheel train
bridge
, which generates induced electric power for supplying electric energy; a brake circuit for braking the generator; pointers joined to the wheel train
bridge
; and a rotation control circuit for controlling the rotation cycle of the generator by controlling the brake circuit; wherein the rotation control circuit includes: a rotation detection circuit for generating a rotation signal of the generator; a target-signal generating circuit for generating a target signal corresponding to a target number of revolutions; and a phase-difference compensating circuit for detecting the phase difference of the target signal output from the rotation detection circuit, and the target signal output from the target-signal generating circuit, and outputting a phase-difference compensation signal which is used as a braking control signal in the brake circuit.
An electronically controlled mechanical timepiece of the present invention uses a mechanical energy source such as a spring to drive pointers and a generator, and controls the number of rotations of a rotor, i.e., the pointers by braking the generator. At this time, the electronically controlled mechanical timepiece compares the phases of a rotation signal of the generator and a target signal such as a timepiece's standard signal, and inputs based on the phase difference a brake control signal to a brake circuit for the generator, whereby a so-called phase-synchronization circuit or phase-locked-loop control (PLL control) is realized in an electronically controlled mechanical timepiece. Accordingly, since a braking level can be set by comparing the waveforms of generated power in each cycle, the activation of a locked range realizes a stable, rapidly responsive system and enables the elimination of phase excursions unless the waveforms of generated power remarkably change suddenly.
Under these circumstances, it is preferable that the generator and the brake circuit constitute a voltage-controlled oscillator, and that the phase-difference compensating circuit include: a phase-comparison circuit for comparing the phases of the rotation signal and the target signal; and a brake control circuit for inputting to the voltage-controlled oscillator the phase-difference compensation signal for controlling the brake circuit based on an output from the phase-comparison circuit.
Under these circumstances, it is preferable that the rotation control circuit include a waveform shaping circuit for converting the output waveform of the voltage-controlled oscillator into rectangular-wave pulses, and outputting as the rotation signal to the phase-comparison circuit.
The output waveform of the voltage-controlled oscillator changes in accordance with a control method therefor. However, by providing the waveform shaping circuit, the different
Koike Kunio
Shinkawa Osamu
Miska Vit
Seiko Epson Corporation
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