Control device of A.C. generator for vehicle

Details Control device of A.C. generator for vehicle Control device of A.C. generator for vehicle

1999-11-17

2001-04-10

Ponomarenko, Nicholas (Department: 2834)

Electricity: single generator systems

Automatic control of generator or driving means

Plural conditions

C322S027000, C322S028000

Reexamination Certificate

active

06215284

ABSTRACT:

TECHNICAL FIELD
The present invention relates to control on a vehicular a.c. generator just after the start of an engine which supplies electrical power to an electrical load.
BACKGROUND ART
An a.c. generator for a vehicle is in general driven by an engine through a V belt and the like to convert rotational energy into electrical energy to thereby output the electrical energy thus obtained. In recent years, a generator having a large output has been required as an electrical load on a vehicle increases. However, if the output of the generator increases, then the load torque of the engine which is developed by driving the generator increases all the time. For this reason, in particular, for a period of time in which the explosion and combustion are unstable as right after the engine having been started, the revolution of the engine is liable to be in an unstable state. In addition, upon starting the engine, the generator outputs a maximum output in order to charge a battery which has been over-discharged by activating a starter motor, so that the load imposed on the engine is increased all the more and hence the revolution of the engine is more and more liable to be led into an unstable state. Such a phenomenon is particularly remarkable in the cold time.
Heretofore, in order to solve the inconveniences as described above, a control device has been proposed in Japanese Patent Application Laid-open No. Hei 3-173324, in which for a predetermined period of time after an a.c. generator has started power generation, the conducting rate of a switch connected in series with a field coil is set to a minimum value, whereby the load torque which is generated by driving the generator just after the starting of the engine is perfectly excluded to achieve the stabilization of engine revolution, and also after a lapse of a predetermined time, the setting of the above-mentioned conducting rate is controlled in such a way as to gradually increase from the above-mentioned minimum value up to a maximum value to prevent a drastic increase in the engine load as well as the generation of belt slipping noise in the cold time, and also to prevent the generation of belt slipping noise and a reduction of engine revolution when the generator output is recovered.
A circuit diagram of such a control device for a vehicular a.c. generator is shown in
FIG. 6 and a
control characteristic diagram is shown in FIG.
7
.
The operation of this control device will hereinafter be described.
Reference numeral
1
designates a generator; reference numeral
2
, a rectifier; reference numeral
3
, a voltage regulator; reference numeral
4
, a field current controller; reference numeral
5
, battery; reference numeral
6
, a key switch; reference numeral
7
, an electrical load applied to a vehicle; reference numeral
8
, a switch; and
10
, an initial exciting resistor.
Since at a time point when the key switch
6
has been turned on, the generator
1
does not yet start power generation, a comparator
307
of the voltage regulator
3
is in the low state and a timer
402
of the field current controller
4
is also in the low state. Therefore, at this time, a comparator
409
of the field current controller
4
is in the high state and a power transistor
310
is turned on so that an initial exciting current is caused to flow through a field coil
102
via the initial exciting resistor
10
. Then, at the time when the generator
1
is driven by the engine to start power generation, the timer
402
becomes the high state to start the measurement of time. For a predetermined period of time T
1
in which the timer
402
is in operation, the voltage at a point C is at a level which is set by voltage division resistors
403
and
404
.
The relationship between this setting level and a chopping wave signal at a point B is as shown at (a) of
FIG. 7
, and those signals are compared with each other in a comparator
409
of the field current controller
4
, and on the basis of the comparison output, a conducting waveform of the power transistor
310
as shown at (b) of
FIG. 7
is obtained. At this time, the conducting rate of the power transistor
310
is at the minimum setting value and the power generation voltage resulting therefrom is made equal to or lower than the voltage of the battery. Therefore, for the predetermined period of time T
1
, as shown at (c) of
FIG. 7
, the output of the generator
1
is zero.
Next, at the time when after a lapse of the predetermined period of time T
1
, the timer
402
becomes the low state, the voltage at point C is multiplied by another predetermined period of time T
2
which is set by a time constant circuit comprising a capacitor
407
and a resistor
406
to be decreased down to a predetermined level as shown at (a) of FIG.
7
. The conducting waveform of the power transistor
310
which is obtained on the basis of the comparison output of the comparator
409
for this period of time is as shown at (b) of
FIG. 7
, and hence the conducting rate of the power transistor
310
is gradually increased to reach the maximum value (100%) after a lapse of the predetermined period of time T
2
. Then, for the predetermined period of time T
2
, the output of the generator is gradually increased from 0 up to 100% as indicated by a solid line at (c) of FIG.
7
. Thereafter, the operation proceeds to the original control based on the comparison output of the comparator
307
of the voltage regulator
3
.
In this prior art, the period of time T
1
, in which the load torque generated by driving the generator right after the engine having been started is removed to stabilize the revolution of the engine, and the period of time T
2
, following the period of time T
1
, in which the output of the generator is gradually increased up to 100%, are both made to the fixed values, respectively.
However, such control on the generator is required only at low temperatures and hence it is unnecessary at high temperatures because the startability of the engine is better at hot time than at cold time.
If, however, the generator is controlled at high temperatures, the output of the generator is suppressed right after the engine having been started, so the battery
5
is discharged, thus resulting in a reduction of the charging performance thereof. This is undesirable.
Therefore, it is preferable that at high temperatures, the period of time T
1
in which the output of the generator is suppressed and the period of time T
2
in which the output of the generator is gradually increased are both shortened to speedily increase the output of the generator up to 100%.
In addition, while for a period of time required to detect the start of the engine (for a period of time in which the revolution of the engine is equal to or lower than a threshold), i.e., during an initial excitation period, the output of the generator is suppressed to the low level to make the load applied to the battery small, it is preferable that the initial excitation period be shortened since the startability of the engine is better at hot time.
DISCLOSURE OF THE INVENTION
An object of the present invention is to shorten, in a control device of an a.c. generator for a vehicle which is designed such that the output of a generator is suppressed to a minimum value for a fixed period of time right after the starting of an engine with the output of the generator being then gradually increased up to a maximum value, at least one of a period of time in which the generator output is made to a minimum value and another period of time in which the generator output at high temperatures is gradually increased to prevent a reduction in the charging performance of a battery.
In addition, another object of the present invention is to set both of a period of time in which the generator output after engine starting is made to a minimum value and another period of time in which the generator output at low temperatures is gradually increased up to a maximum value, to a long period in order to exclude the load torque generated by driving the generator, thereby stabilizi

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