Horology: time measuring systems or devices – Electrical time base – Solid state oscillating circuit type
Reexamination Certificate
1998-09-29
2001-11-06
Miska, Vit (Department: 2859)
Horology: time measuring systems or devices
Electrical time base
Solid state oscillating circuit type
C368S204000
Reexamination Certificate
active
06314059
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electronically controlled, mechanical timepiece and a control method for the timepiece, in which mechanical energy in a mechanical energy source such as a mainspring is converted into electric energy by a generator, a rotation controller is driven by the electric energy to control the rotation period of the generator, and a hand attached to a train wheel is thereby accurately driven.
Japanese Examined Patent Publication No. 7-119812 and Japanese Unexamined Patent Publication No. 8-50186 disclose electronically controlled, mechanical timepieces that present accurate time by driving accurately hands attached onto train wheels. In such watches, a mainspring, when unwound, releases mechanical energy, which is converted into electrical energy by a generator. The electrical energy is then used to drive a rotation controller so that the current flowing through a coil of the generator is controlled.
The watch disclosed in Japanese Examined Patent Publication No. 7-119812 features two angular ranges: an angular range in which a brake is turned off each time a rotor makes every turn (namely, for each period of a reference signal) to heighten the rotational speed of a rotor so that the generated power is increased, and an angular range in which the rotor is turned at a low speed with the brake applied. The efficiency in power generation is increased during a high-speed rotation to compensate for a drop in power generation that takes place during the braking period.
In the watch disclosed in Japanese Unexamined Patent Publication No. 8-50186, a reference pulse and a measurement pulse detected in the course of rotation of a rotor are counted. The numbers of reference pulses and measurement pulses are compared with each other. In a first state in which the number of reference pulses is smaller than the number of measurement pulses, a controller generates a brake signal for brake control, the width of which is determined by the measurement pulse.
In either of the previously described electronically-controlled, mechanical timepieces, torque (mechanical energy) applied by a mainspring to a generator is set such that a hand is turned at a speed faster than a reference speed, and the rotational speed of the hand is adjusted by applying a brake through a rotation controller.
The watch disclosed in Japanese Examined Patent Publication No. 7-119812 performs brake-activation control and brake-deactivation control for each rotation of the rotor; namely, every reference signal. When the generator initially starts up or when the generator is largely out of control, however, the rotational control amount applied to the rotor cannot be set large enough for every reference signal to adjust the speed of the rotor in a timely fashion. Thus, a long period is required before the watch reaches its normal control state.
In the watch disclosed in Japanese Unexamined Patent Publication No. 8-50186, the pulse width of the brake signal generated for each reference signal is constant. Even with the watch largely out of control, the amount of braking for each reference signal remains constant. The watch thus needs a long period of time before reaching its normal control state.
In addition to a circuit for detecting first and second states by comparing the counts of the reference pulses and measurement pulses, a controller is required to generate a brake signal having a pulse width determined in response to the measurement pulse. Such an arrangement requires a complicated construction, which increases the cost of the watch.
In an electronically-controlled, mechanical timepiece, when the torque of the generator becomes insufficient due to the unwinding of the mainspring and the corresponding weakening of its spring force, the number of revolutions of the generator drops, thereby lowering the speed of a hand, which causes the watch to continuously lose time for a long period of time. Since the hand continuously moves even at a slow speed in this case, a user may glance at the watch and may be under the mistaken impression that the watch works correctly, even if the watch presents an incorrect time.
Accordingly, it is desirable to provide a timepiece that overcomes the drawbacks of the prior art.
SUMMARY OF THE INVENTION
Generally speaking, in accordance with the invention, an electronically-controlled, mechanical timepiece preferably includes a mechanical energy source, a generator, connected to the mechanical energy source via a train wheel and driven by the mechanical energy source, for generating induced power to feed electrical energy, a hand connected to the train wheel, a rotation controller, driven by the electrical energy, for controlling the rotation period of the generator, wherein the rotation controller includes a rotation detector for detecting the rotation period of the generator and for outputting a rotation signal corresponding to the rotation period, a reference signal generator for generating a reference signal based on a signal from a time reference source, a first counter for counting the reference signal from the reference signal generator, a second counter for counting the rotation signal from the rotation detector, and a brake controller which controls the generator so that the generator is braked when a first count provided by the first counter is smaller than a second count provided by the second counter and is not braked when the first count is equal to or greater than the second count.
The electronically-controlled, mechanical timepiece of the present invention drives the hand and the generator with a mechanical energy source, such as a mainspring, and applies a brake on the generator through the brake controller of the rotation controller, thereby governing the number of revolutions of a rotor and the hand. The first counter counts the reference signal from the reference signal generator, the second counter counts the rotation signal from the rotation detector to compare the first count and the second count, and the brake controller brakes the generator when the first count is smaller than the second count, and does not brake the generator when the first count is equal to or greater than the second count. In this way, the rotation controller of the generator governs the rotational speed of the generator.
When the first count remains smaller than the second count, namely, when the torque of the mechanical energy source, such as the mainspring, is large enough to rotate the generator, a brake is continuously applied until the difference between the two counts is eliminated. The watch thus governs the rotation of the generator, quickly allowing the generator to reach a normal rotational speed under fast response control.
Since the brake control is performed by simply comparing the two counts, a simply constructed rotation controller is provided, resulting in a cost reduction of the watch. The brake controller preferably comprises a comparator for comparing the first count with the second count. An up/down counter preferably includes a first counter, a second counter and a comparator. The use of the up/down counter permits counting while performing a comparison at the same time. With this arrangement, the construction is simplified, and the difference between counts is easily determined.
The up/down counter preferably counts at least three values. However, an up/down counter of two bits or more may be used to perform counting at multi levels and to store counts. With this arrangement, not only is a determination made of whether the second count leads or lags the first count as a reference, but also cumulative quantities of lead and lag therebetween are stored. As a result, cumulative error may be corrected.
The rotation controller, when initially supplied with electrical energy by the generator, may maintain the brake controller in an inoperative state until the number of revolutions of the generator reaches a predetermined value; for example, until the rotation signal is detected a predetermined number of times. In this way, a volt
Koike Kunio
Nakamura Hidenori
Shimizu Eisaku
Miska Vit
Seiko Epson Corporation
Stroock & Stroock & Lavan LLP
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