Horology: time measuring systems or devices – Power supply details – Electrical
Reexamination Certificate
2000-07-17
2003-06-24
Miska, Vit (Department: 2841)
Horology: time measuring systems or devices
Power supply details
Electrical
Reexamination Certificate
active
06584043
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to an electronically controlled mechanical timepiece and an overcharge-prevention method therefor. More particularly, the invention relates to an electronically controlled mechanical timepiece having a mechanical energy source, a generator for outputting electrical energy and being driven by this mechanical energy source and by generating induction power, a storage device for storing the electrical energy output from the generator, and a rotation control device for controlling the rotation period of the generator and being driven by the electrical energy supplied from the storage device. The invention also pertains to an overcharge-prevention method for the electronically controlled mechanical timepiece.
2. Background Art
In general, regular replacement of batteries is required for timepieces. These days, however, easy-to-handle and environmentally friendly timepieces are known in which the replacement of batteries is eliminated by charging power generated by a generator, such as an oscillating weight, a mainspring, a solar cell, etc., in a storage device, such as a capacitor or a secondary cell, and by using the charged power as a driving source.
Among such generators for use in timepieces, unlike a solar cell, a generator for generating power by rotating a rotor by a mainspring is not subject to constraints, such as environment, place, time, and so on, and can stably and reliably generate power by a user winding the mainspring. Accordingly, the above type of generator is widely used.
Electronic apparatuses using a mainspring generator include, for example, an electronically controlled mechanical timepiece. In the electronically controlled mechanical timepiece, mechanical energy generated when a mainspring is unwound is converted into electrical energy by a generator. A rotation control device is operated by this electrical energy so as to control the current value flowing in a coil of the generator, thereby correctly driving the hands fixed to a wheel train. As a result, the time can be correctly displayed. According to this type of timepiece, by detecting the generated waveform of the generator, the rotational speed of the rotor is determined, and braking control is performed so that the rotational speed (phase) of the rotor is matched to the speed (phase) of a reference signal from a time standard source, which is formed of a quartz oscillator, thereby implementing the indication of the correct time, which is the basic function of the timepieces.
The storage device for charging the generated power has a withstand voltage, and exceeding the withstand voltage of the storage device causes a deterioration in the characteristics, such as a decreased capacitance, or destruction and leakage due to expansion, which may lead to a fault in the timepiece having a built-in generator.
Thus, in order to prevent an unusual surge of the charging voltage of a storage device, a circuit, such as the one disclosed in Japanese Unexamined Patent Application Publication No. 21-236332, is used for a generator which generates power by the oscillation of an oscillating weight or a generator using a solar cell. According to this circuit, the voltage of the storage device is detected by a comparator, and when the voltage reaches a predetermined value, both ends of the generator are short-circuited so as to prevent any further current from flowing into the storage device. By the provision of this type of circuit, with an increase of the voltage of the storage device, the generator is short-circuited so as to interrupt the supply of power to the storage device, thereby preventing overcharging.
In the circuit disclosed in Japanese Unexamined Patent Application Publication No. 21-236332, however, since both ends of the generator are short-circuited, the waveform generated at both ends of the generator is deformed or the voltage level is reduced. Accordingly, by integrating the circuit disclosed in Japanese Unexamined Patent Application Publication No. 21-236332 in the above described electronically controlled mechanical timepiece, the rotational speed of the rotor cannot be correctly determined from the generated waveform, thereby failing to perform control of matching the rotational speed of the rotor to the reference signal of the time standard source. As a result, the time cannot be indicated correctly.
Accordingly, it is an object of the present invention to provide an electronically controlled mechanical timepiece in which overcharging of a storage device can be prevented and in which the time can be correctly indicated, and also to provide an overcharge-prevention method for the electronically controlled mechanical timepiece.
SUMMARY OF THE INVENTION
The present invention provides an electronically controlled mechanical timepiece including a mechanical energy source, a generator for outputting electrical energy and being driven by this mechanical energy source and by generating induction power, a storage device for storing the electrical energy output from the generator, and a rotation control device for controlling a rotation period of the generator and being driven by the electrical energy supplied from the storage device, the electronically controlled mechanical timepiece being characterized by comprising: a bypass circuit connected in parallel with the storage device with respect to the generator; a bypass circuit switch provided for the bypass circuit; and a voltage detection circuit for controlling this bypass circuit switch on and off according to a voltage of the storage device.
The electrical energy output from the generator is input into the storage device and is stored therein. In the present invention, the bypass circuit is provided in parallel with the storage device. Thus, when the voltage detection circuit turns on the bypass circuit switch of the bypass circuit according to the voltage of the storage device, the bypass circuit conducts so as to allow the electrical energy from the generator to flow into the bypass circuit. Accordingly, the current input into the storage device can be decreased so as to reduce the voltage of the storage device, thereby preventing the overcharging of the storage device.
Moreover, the input current into the storage device can be decreased without short-circuiting the generator so as to eliminate a deformation of the generated waveform and a reduction in the voltage level, thereby obtaining a generated waveform corresponding to the rotation period of the generator. Accordingly, since the rotation period of the generator can be correctly obtained from the generated waveform, the rotation period of the generator can be controlled highly precisely and reliably based on this generated waveform, thereby implementing the indication of the correct time.
An increase in the voltage of the storage device decreases the charging current into the storage device, and the braking effect is weakened, making it difficult to reserve the total required braking amount. In the present invention, however, when the voltage of the storage device exceeds the set voltage, the charging current flows into the bypass circuit, thereby interrupting the voltage surge of the storage device. A decrease of the braking effect, which would be caused by the charging current flowing into the storage device, can thus be prevented from being weakened, thereby reserving the overall required braking amount.
Additionally, when the timepiece is set in a test mode in which braking is not applied, the rotor may rotated at a high speed (for example, from two to ten times higher than the normal rotational speed). In this case, a generated current greater than a normal current is supplied from the generator to the storage device so as to increase the voltage. According to the present invention, however, an increase in the voltage can be prevented by allowing the charging current to flow in the bypass circuit, which serves as a limiter.
Further, since the voltage increase of the storage device can be prevented, the lifetime of
Koike Kunio
Nakamura Hidenori
Shimizu Eisaku
Goodwin Jeanne-Marguerite
Miska Vit
Seiko Epson Corporation
Watson Mark P.
LandOfFree
Electronically controlled mechanical watch and method of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electronically controlled mechanical watch and method of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electronically controlled mechanical watch and method of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3151078