Horology: time measuring systems or devices – Power supply details – Electrical
Reexamination Certificate
1998-09-29
2002-04-16
Miska, Vit (Department: 2859)
Horology: time measuring systems or devices
Power supply details
Electrical
C322S008000, C322S029000
Reexamination Certificate
active
06373789
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electronically controlled mechanical timepiece for accurately driving hands fixed to a train wheel by converting the mechanical energy of a mechanical energy source, such as a mainspring, into electrical energy by a generator and controlling the rotational cycle of the generator by actuating a rotation controller powered by the electric energy.
Japanese Examined Patent Publication No. 7-119812 and Japanese Unexamined Patent Publication No. 8-101284 disclose electronically controlled mechanical timepieces for displaying time by driving hands fixed to a train wheel by converting mechanical energy generated by the release of a mainspring into electrical energy by a generator and controlling the value of the current flowing to the coil of the generator by actuating a rotation controller by the electrical energy.
In the timepieces of the above references, it is important to increase braking torque when the mainspring has high torque and prevent a drop of generated power at the same time to increase the time with which the timepiece may be powered by the electrical energy. For this purpose, the electronically controlled mechanical timepiece disclosed in Japanese Examined Patent Publication No. 7-119812 provides an angular range where the rotating velocity of a rotor is increased by turning off a brake to increase the amount of generated power each time the rotor rotates. That is, a brake is released during each rotation of the rotor to permit more power to be generated to compensate for the drop in generated power when the brake is applied over an angular range.
Further, the timepiece disclosed in Japanese Unexamined Patent Publication No. 8-101284 increases braking torque and prevents a drop of a generated voltage at the same time by boosting the voltage of the power induced by a generator with a number of stages of a boosting circuit.
However, in the timepiece disclosed in Japanese Examined Patent Publication No. 7-119812, the rotor is switched from a state in which it rotates at a high rotating velocity to a state in which it rotates at a low rotating velocity. The abrupt velocity change is difficult to realize as the rotor almost stops during each rotation. In particular, because a fly wheel is typically provided to increase the rotational stability of the rotor, it is difficult to abruptly change the velocity of the rotor.
Further, since generated power is reduced when the brake is applied, a limit is reached in suppressing the reduction in the loss of generated power while increasing braking torque.
On the other hand, because the electronically controlled mechanical timepiece disclosed in Japanese Unexamined Patent Publication No. 8-101284 requires a number of switches and capacitors, the cost of the design is increased.
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 can include a mechanical energy source, a generator driven by the mechanical energy source coupled therewith through a train wheel. The generator generating induced power and supplying electrical energy from first and second terminals of the generator, and hands coupled with the train wheel. A rotation controller, driven by the electric energy can be provided to control the rotational cycle of the generator, and can include a switch for short-circuiting the respective terminals of the generator, and wherein the rotation controller uses chopping to control the generator by intermittently actuating the switch.
The electronically controlled mechanical timepiece of the present invention drives the hands and the generator by a mainspring and regulates the number of rotations of a rotor (and thereby the rotation of the hands) by applying a brake to the generator by the rotation controller. The generator rotation is controlled by chopping the generator by activating and deactivating the switch that short circuits the ends of the generator coil. When the switch is activated, a short-circuit brake is applied to the generator by chopping and energy is stored in the coil of the generator. Whereas, when the switch is deactivated, the generator is operated and a voltage generated thereby is increased by the energy stored in the coil. As a result, when the generator is controlled by chopping, a loss of generated power caused when the brake is applied can be compensated by an increase in the generated voltage when the switch is deactivated. Thus, brake torque can be increased while keeping the generated power to at least a prescribed level so that the timepiece can have a long life.
Since the effect of increasing the generated voltage is diminished when the chopping frequency is lower than five times the waveform frequency of the generated voltage, it is preferable that a chopping frequency for intermittently activating the switch by the rotation controller is at least five times as large as the waveform frequency of the voltage generated by the rotor of the generator at a set velocity. It is more preferable that the chopping frequency is five to one hundred times as large as the waveform frequency of the voltage generated by the rotor of the generator at the set velocity.
When the chopping frequency is more than one hundred times as large as the waveform frequency of the generated voltage, an IC for executing chopping consumes a large amount of power. Thus, it is preferable that the chopping frequency is one hundred times or less the waveform frequency of the generated voltage. Further, because the changing ratio of torque to the changing ratio of a duty cycle approaches a prescribed level when the chopping frequency is five times to one hundred times as large as the waveform of the generated voltage, the control can be easily carried out. However, the chopping frequency may be set to less than five times or greater than one hundred times the value of the generated voltage waveform depending upon the use and the control method.
In a preferred embodiment, the timepiece includes first and second power supply lines for charging the electrical energy of the generator to a power supply circuit, wherein the switch is composed of a first and a second switch, preferably transistors, interposed between the first and second terminals of the generator and one of the first and second power supply lines, respectively, and the rotation controller continuously activates the switch connected to one of the first and second terminals of the generator as well as intermittently activates the switch connected to the other terminal of the generator.
With this arrangement, since the control of the power generating process and the rotation process of the generator can be simultaneously carried out in addition to the brake control by chopping, cost can be reduced by decreasing the number of parts as well as an improvement can be attained in power-generating efficiency by controlling the timing at which the respective switches are activated.
Further, it is preferable that the rotation controller includes comparators for comparing the waveforms of the voltage generated by the generator with a reference waveform, a comparison circuit for comparing the output from each comparator with a time standard signal and outputting a difference signal, a signal output circuit for outputting a pulse-width varied clock signal based on the difference signal, and a logic circuit for ANDing the clock signal and the output from each comparator and outputting an ANDed signal to the transistors.
With this arrangement, because the power consumed to intermittently control the transistors can be reduced, a circuit may be arranged that is suitable for the generator of a clock that generates a small amount of power.
A preferred embodiment of the timepiece includes a first switch that includes a first field effect transistor having a gate connected to the second terminal of the generator and a second field effect transistor co
Koike Kunio
Shimizu Eisaku
Shinkawa Osamu
Takahashi Osamu
Miska Vit
Seiko Epson Corporation
Stroock & Stroock & Lavan LLP
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