Electronic device with variable chopping signal and duty...

Electricity: single generator systems – Automatic control of generator or driving means – Plural conditions

Reexamination Certificate

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C290S00100C, C290S00100C, C368S204000, C310S07500D, C310S07500D, C322S028000

Reexamination Certificate

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06483276

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic device, apparatuses employing the device such as an electronically controlled mechanical clock, and a method of controlling such a device and apparatuses. The device and clock of the present invention include a mechanical energy source; an electric power generator, driven by the mechanical energy source, for generating electric power by induction and supplying resulting electrical energy; and a rotation controller, driven by the electrical energy, for controlling the rotation period of the electric power generator.
2. Description of the Related Art
Japanese Examined Patent Publication No. 7-119812 is directed to an electronically controlled mechanical clock in which mechanical energy generated when a spring is released is converted to electrical energy using an electric power generator. A rotation controller is driven by the electric energy so as to control a current flowing through a coil of the electric power generator so that the clock hands connected to a wheel train are precisely driven to indicate precise time.
To operate such an electronically controlled mechanical clock for a long period of time, it is important to increase braking torque when the spring torque is large without causing a reduction in generated electric power. That is, in electronically controlled mechanical clocks, it is desirable to prioritize the braking torque applied to the electric power generator versus the electric power generated by the electric power generator, such that a higher priority is given to the braking torque when the spring torque is large, while a higher priority is given to the electric power when the spring torque is small because strong braking is not needed in this case.
As used herein, the expression “when the torque is large” or the like describes not only a state in which the spring torque is large because the spring is in a fully or sufficiently wound state, but also a state in which the driving torque applied to the rotor is increased due to a disturbance, such as vibration or mechanical shock. Similarly, the expression “when the torque is low” or the like describes not only a state in which the spring torque is low because the spring is in a fully or nearly fully unwound/released state, but also a state in which the driving torque applied to the rotor is reduced due to a disturbance, such as vibration or mechanical shock.
In the technique disclosed in Japanese Examined Patent Publication No. 7-119812, a “braking-off” angular range and a “braking-on” angular range are provided in each revolution of a rotor. In each period of a reference signal, the rotational speed of the rotor is increased and a greater amount of electric power is generated in the braking-off angular range, while the rotational speed of the rotor is decreased by applying braking in the braking on angular range. That is, the rotational speed is controlled such that the generated electric power is increased during a high-speed period thereby compensating for the reduction in the electric power which occurs when the electric power generator is braked. The braking-off operation is performed at a plurality of first points of time in respective successive periods of the reference signal generated by a quartz oscillator or the like, and a braking-on operation is performed at a second point of time apart from the first point of time in each period of the reference signal.
However, in the technique of Japanese Examined Patent Publication No. 7-119812, a reduction in electric power generated by the electric power generator occurs when the electric power generator is braked, and thus there is a limitation in suppressing the reduction in the electric power when the braking torque is increased. This problem occurs not only in electronically controlled mechanical clocks, but also in other various electronic devices, such as music boxes, metronomes, and electric shavers, each of which include a part rotated by a mechanical energy source such as a spring or rubber. Thus, there is a need for a technique which can solve the above problem.
Another problem associated with the technique in Japanese Examined Patent Publication No. 7-119812, is that a braking-on operation started at a second point of time in a certain reference period is forcibly switched to a braking-off operation at a first point of time in the following reference period, regardless of the state in terms of rotation of the electric power generator. This can cause the braking amount to become insufficient depending on the state, and thus it takes a long time to reach a target rotational speed. Even if the braking operation is performed using a control signal, the operation is switched to a mode in which braking is performed in synchronization with a reference period, regardless of the period of the control signal. This can cause degradation in the braking control accuracy.
Thus, there is a need to control the braking operation in a more precise manner so as to achieve higher accuracy in the operation of various operating parts. Such control is needed not only in electronically controlled mechanical clocks, but also in other various electronic devices which have a part which is rotated by a mechanical energy source such as a spring or rubber. Other devices in which such control is needed include, for example, music boxes (i.e, drums thereof), metronomes (i.e., pendulums thereof), various electronic toys, and electric shavers.
SUMMARY OF THE INVENTION
OBJECTS OF THE INVENTION
Therefore, it is an object of the present invention to overcome the aforementioned problems.
It is another object of the invention to provide an electronic device, an electronically controlled mechanical clock, and a method of controlling such a device and clock, which allow a braking torque applied to an electric power generator to be increased without causing a significant reduction in electric power generated by the electric power generator. Unlike the technique in Japanese Examined Patent Publication No. 7-119812, the electric power generator is controlled using a chopping signal, so as to increase the applied braking torque without causing a significant reduction in electric power.
It is a further object of the invention to provide an electronic device, an electronically controlled mechanical clock, and a method of controlling such a device and clock, which allow a precise and large amount of braking torque to be applied during a braking operation using a chopping signal, thereby ensuring that the rotational speed is controlled in a quick and highly reliable manner.
The present invention is based on the discovery made by the inventors herein that when an electric power generator is controlled in a chopping manner by applying a chopping signal to a switch such that the switch connects the two terminals of the electric power generator in a closed-loop state in response to the chopping signal, the driving torque (i.e., braking torque, damping torque) increases with decreasing frequency and/or with increasing duty ratio of the chopping signal, while the charged voltage (i.e., generated voltage) corresponding to electric power generated by the electric power generator increases with increasing chopping signal frequency but does not greatly decrease with increasing duty ratio of the signal, and, on the contrary, at frequencies higher than 50 Hz, the charged voltage increases with increasing duty ratio in a range where the duty ratio is less than 0.8 as shown in
FIGS. 32
to
35
.
Thus, in one aspect, the present invention provides an electronic device comprising a mechanical energy source; an electric power generator, driven by the mechanical energy source, for generating electric power by induction and supplying electrical energy; and a rotation controller, driven by the electrical energy, for controlling the rotation period of the electric power generator. The rotation controller includes a switch capable of connecting two terminals of the electric power generator in a closed-loop state;

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