Horology: time measuring systems or devices – Electrical time base – Solid state oscillating circuit type
Patent
1994-09-19
1996-08-27
Roskoski, Bernard
Horology: time measuring systems or devices
Electrical time base
Solid state oscillating circuit type
318696, 368160, G04F 500, G04B 1900
Patent
active
055507956
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an electronic timepiece and a method of driving a stepping motor of electronic timepiece in which plural detection assisting pulses are output to a stepping motor after turning off a main drive pulse, thereby performing stable detection of the rotation of the stepping motor.
BACKGROUND ART
In a stepping motor of a conventional electronic timepiece, a stepping motor driving means has been used in which a main driving pulse train having low effective power is output to the stepping motor to reduce current-consumption, and wherein the rotational state of a rotor is detected by known means to output a correction drive pulse to the stepping motor in accordance with the detection result. Practical examples of this is known technology are disclosed in Japanese publication of applications No. 61-8392 and No. 63-18148, for example.
With respect to the practical example illustrated in Japanese publication of application No. 61-8392, FIG. 2 diagrammatically shows a drive voltage waveform of a correction drive system, and FIG. 3 diagrammatically shows a voltage waveform after turning off a main drive pulse obtained by the drive system as shown in FIG. 2.
The drive voltage waveform diagram as shown in FIG. 2 is constructed by a main drive pulse P1 (hereinafter referred to as "P1") which is output to the stepping motor every second, a section DT for detecting the rotation of the stepping motor after P1, goes low and a correction drive pulse P2 (hereinafter referred to as "P2") which is output when the stepping motor is in non-rotational state. P1 automatically alters its pulse width in accordance with a load state to be applied to the stepping motor. P2 is output
FIG. 3 shows a voltage waveform which is induced in a detection resistor by forming a closed loop in a coil after pulse turning off through the control of a MOS gate for driving the stepping motor or the like. As shown in FIG. 3, a rotation detecting method is used for detecting rotation of the rotor by electrically detecting whether the induced level reaches a predetermined voltage on the basis of the fact that the induced voltage in the section DT is different between a rotational state (as indicated by a solid line in FIG. 3) and a non-rotational state (as indicated by a dotted line in FIG. 3).
This detection means is characterized in that the rotor which is rotated with the main drive pulse makes free attenuating motion due to residual magnetic potential energy in the rotor after the main drive pulse goes low, and the variation of the induced voltage occurring in the coil during the attenuating motion is used as the rotation detecting means.
With respect to the practical example which is illustrated in Japanese publication of application No. 63-18148, FIG. 4 shows an example of a drive voltage waveform diagram of a correction drive system, and FIG. 5 shows an example of a current waveform generated when the rotor is driven by the detection pulse.
The driving voltage waveform diagram of FIG. 4 is constructed by a main drive pulse P1 which is output to the stepping motor every second, detection pulses Px and Py which are used to detect the rotation of the stepping motor after P1 goes low, and a correction drive pulse P2 which is output when the stepping motor is in a non-rotational state at P1. P1 and P2 are identical to those of FIG. 2. The detection pulses Px, Py have such a short pulse width that the stepping motor cannot be rotated.
FIG. 5 shows the current waveform when the rotor is driven with the detection pulse, and the current waveform is varied as shown by a characteristic curve a or characteristic curve b of FIG. 5 in accordance with the orientation of the magnetic pole of the rotor. The reason for the difference in current waveform is that the current waveform is determined in accordance with whether the magnetic pole formed in a stator with detection pulse is in a state where the magnetic pole of the rotor magnet has a repulsive orientation or an attractive orientation. As shown by curve
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patent: 4599005 (1986-07-01), Kawamura et al.
patent: 4715725 (1987-12-01), Kawamura et al.
patent: 5038329 (1991-08-01), Kawamura et al.
Hirotomi Jun
Takakura Akira
Roskoski Bernard
Seiko Instruments Inc.
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