Citizen Watch Company, Ltd.

Citizen Holdings Company, Ltd.

Yu Takyo

Toshiaki Fukushima

Daisuke Iri

Masaaki Namekawa

Nobuaki Suzuki

Akira Shiota

Toshinari Maeda

Yosuke Abe

Takuya Shirai

Yusaku Niida

Shogo Sezaki

A mechanical timepiece includes: a hairspring; a permanent magnet; a soft magnetic core; a control circuit for performing rate adjustment based on a counter-electromotive voltage caused in a coil by a motion of the permanent magnet accompanying a forward direction motion and a reverse direction motion of the balance wheel. The permanent magnet is arranged so that, under a state in which the hairspring is brought to an equilibrium length, a direction of magnetization is directed to the first end portion side or the second end portion side.

Mechanical timepiece

A step motor drive device includes a step motor including a rotor, stators, and a coil, a drive circuit that outputs a drive signal including a plurality of partial signals that are output intermittently, a detecting circuit that detects an electromagnetic induced current that is generated in the coil after the partial signals are output, and a control unit that controls the drive circuit. The drive circuit outputs one of the partial signals included in the drive signal to the coil, and, in response to a change in an electromagnetic induced current generated in the coil after the partial signal is output, outputs a next partial signal to the coil. The control unit determines a control method of the step motor based on an interval of the plurality of partial signals, and controls the drive circuit based on the determined control method.

Step motor drive device

Provided is an electronic watch which achieves a highest-speed fast-forward operation of a step motor based on various environments under which the watch is placed, and enables low-power driving. The electronic watch includes: a normal pulse generator circuit configured to output a normal pulse SP for driving a step motor; a detection pulse generator circuit configured to output, after the step motor has been driven with the normal pulse SP, detection pulses DPand DPfor detecting whether or not the step motor has been rotated; a pulse selection circuit configured to selectively output the normal pulse SP and the detection pulses DPand DP; a rotation detector circuit configured to input detection signals DSand DSgenerated from the detection pulses DPand DP, and to determine whether or not the step motor has been rotated; and a frequency selection circuit configured to determine a driving interval of the normal pulse SP, in which the rotation detector circuit is configured to instruct the frequency selection circuit to select a frequency corresponding to a position at which the detection signals DSand DShave been generated.

Electronic watch

Provided is an electronic timepiece, including: a step motor; a motor driver; a normal drive pulse generation circuit configured to output a normal drive pulse at a designated drive rank; a rotation detection pulse generation circuit configured to output a detection pulse; a rotation detection circuit which comprises at least a first detection mode determination circuit configured to conduct determination in a first detection mode and which is configured to detect rotation or non-rotation of a rotor; a rotation determination counter circuit configured to count a number of times that the rotation has been successively detected by the rotation detection circuit; a first detection mode determination counter circuit configured to count a number of times that a detection signal generated by the detection pulse becomes a predetermined detection pattern in the first detection mode; and a drive rank selection circuit configured to designate a drive rank of the normal drive pulse based on results of the counting conducted by the rotation determination counter circuit and the first detection mode determination counter circuit.

Electronic timepiece

Provided is an electronic clock which is capable of finely controlling a driving force of a normal driving pulse and suppresses variation in current consumption without an increase in circuit size. The electronic clock is configured so that while a chopped driving pulse is output and in an interval in which coil terminals have heretofore been short-circuited, a pulse is output (hereinafter referred to as adjustment pulse) for control from a terminal that is different from a terminal of a motor driver from which the normal driving pulse has been output. The output pattern of the adjustment pulse is changed with reference to a driving rank selecting circuit to increase or decrease a motor driving current and hence change the driving force.

Electronic clock

When recovering power from a motor driver, a forward voltage across a parasitic diode can reduce the recovery efficiency, and control of a power recovery operation can take an unnecessarily long time. In order to address this problem, the power recovery operation is performed as follows without being affected by a parasitic diode: near a peak position of a waveform of an induced current resulting from free oscillation of a rotor after a drive pulse is output, a recovery pulse having such a level that the rotor does not rotate is output from a terminal different from a motor driver terminal to which the drive pulse was output. Also, by adjusting the width and output timing of the recovery pulse based on a power supply voltage, the power recovery can be optimized for the power supply voltage.

Provided is an electronic watch capable of, even if an indicating hand having a large moment of inertia is used, accurately determining success and failure of rotation. The electronic watch detects rotation by using a first detection mode determination circuit () and a second detection mode determination circuit (). In the electronic watch, a timing counter () for measuring a time after an output of a normal drive pulse is followed by a detection pulse selection circuit () provided as changing means for changing a width or a frequency of a detection pulse in accordance with an output time of the detection pulse. The detection pulse detects the rotation and simultaneously serves as an electromagnetic brake for a rotor (). The electromagnetic brake for the rotor () is controlled by changing the width or the frequency of the detection pulse in a predetermined period, thereby achieving an accurate rotation detection. Alternatively, the setting of the width or the frequency of the detection pulse may be changed in accordance with a determination result in a first detection mode, an output voltage of a power supply, and a driving power of the normal drive pulse, instead of the output timing of the detection pulse.

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Nishitokyo, Japan

Yu Takyo