Electricity: single generator systems – Automatic control of generator or driving means – Voltage of generator or circuit supplied
Patent
1995-08-04
1997-06-10
Dougherty, Thomas M.
Electricity: single generator systems
Automatic control of generator or driving means
Voltage of generator or circuit supplied
322 20, H02P 900
Patent
active
056379862
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a power control device of an alternator for a vehicle which controls the field current and prevents abrupt increase in the torque of the alternator when an electric load is connected to the alternator.
BACKGROUND ART
Such a device is disclosed in Japanese patent unexamined publication Sho 62-64299 and its U.S. Pat. No. 4,636,706 to Bowman as one of the conventional power control devices of alternators.
However, the device disclosed in the above publication is equipped with an up-down counter (a binary counter which can count up and down) which is controlled according to a result of comparison of an output voltage of an alternator with a reference voltage and a PWM circuit (pulse width modulation circuit) which includes a down-counter and generates pulse signals having pulse width changing according to the number counted by the up-down counter to supply a field current to the alternator field coil. Therefore, many digital circuit elements are required and, consequently, the digital circuit becomes complicated.
Another object of the present invention is to provide a simple digital circuit which changes the field current gradually.
Another object of the present invention is to provide means for controlling the field-current switching means to have different conducting times between increasing the field current and decreasing the field current without difficulty.
A further object of the present invention is to provide means for controlling the field current switching means to synchronize an output timing of comparison between the alternator output voltage and a reference voltage with the switching timing of the field-current switching means so that the switching means can switch on or off steadily even under an abrupt output voltage change.
DISCLOSURE OF THE INVENTION
The power control device of an alternator for a vehicle according to the present invention comprises an alternator driven by an engine for supplying electric current to vehicle electric loads, a comparator for comparing an alternator output voltage with a reference voltage, an oscillator-couple having first and second oscillators for generating oscillating signals having a phase difference therebetween which varies according to the output signal of the comparator, switching means for controlling the field current in response to the phase difference supplied to the alternator field coil when an electric signal is applied thereto, and a phase difference control circuit for shortening the oscillation cycle of the second oscillator relative to the oscillation cycle of the first oscillator to decrease the phase difference between the signals of the first and the second oscillators when the alternator output voltage, becomes higher than a reference voltage and for elongating the oscillation cycle of the second oscillator relative to the oscillation cycle of the first oscillator thereby to increase the the phase difference between the signals of the first and second oscillators when the alternator output voltage becomes lower than the reference voltage, thereby increasing the phase difference.
According to the above structure, when the alternator output voltage becomes higher than the reference voltage, the phase difference between the oscillating signals of the two oscillators is controlled shorter. On the other hand, when the alternator output voltage becomes lower than the reference voltage, the switching means is made conductive by an electric signal having a pulse width corresponding to the phase difference. Thus, the abrupt increase of the generation torque can be prevented. Thereafter, the phase difference between the two oscillation signals gradually increases and the conduction rate of the switching means increases.
According to the present invention as described above, the pulse width of the electric signal can be controlled by the phase difference between the two oscillation signals, and the up-down counter is not necessary and the circuit can be made simpler.
The device according to the
REFERENCES:
patent: 4613808 (1986-09-01), Edwards
patent: 4636706 (1987-01-01), Bowman et al.
patent: 5140253 (1992-08-01), Itoh
patent: 5173654 (1992-12-01), Boella et al.
patent: 5262711 (1993-11-01), Mori et al.
patent: 5319299 (1994-06-01), Maehara
patent: 5448154 (1995-09-01), Kanke et al.
Kanazawa Wakako
Maehara Fuyuki
Maruyama Toshinori
Dougherty Thomas M.
Nippondenso Co. Ltd.
Ponomarenko Nicholas
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