Controller of AC generator for use in vehicles

Details Controller of AC generator for use in vehicles Controller of AC generator for use in vehicles

1999-09-21

2002-02-05

Ramirez, Nestor (Department: 2834)

Electricity: single generator systems

Automatic control of generator or driving means

Voltage of generator or circuit supplied

C322S024000, C322S099000, C322S025000

Reexamination Certificate

active

06344734

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an AC generator control apparatus for automobiles for switching the output voltage of an AC generator into any of plural variations according to an external signal having a variable duty ratio.
BACKGROUND ART
FIG. 3
shows the configuration of the conventional AC generator control apparatus for automobiles. This AC generator control apparatus for automobiles includes an AC generator
1
having a field coil
102
which is driven by a car engine (system) not shown and generates a rotating field, and an armature winding
101
generates an AC voltage through the generated rotating field and outputs the AC voltage; a rectifier
2
for rectifying the generated voltage of the AC generator
1
and providing the generated voltage to a battery
5
or an electric load
6
through a main output terminal
201
; a voltage regulator
3
for controlling the exciting current of the field coil
102
depending on the charged voltage of the battery
5
or the rectified output voltage provided for the electric load
6
, and for regulating the generated voltage of the AC generator
1
; a load switch
7
for connecting the rectified voltage from the rectifier
2
or the charged voltage of the battery
5
to the electric load
6
; and a key switch
8
transmitting an exciting current from the battery
5
to the field coil
102
through a charge indication lamp
9
when the system (engine) is started.
The rectifier
2
is provided with an auxiliary output terminal
202
. The auxiliary output terminal
202
is connected to one end of the charge indication lamp
9
. When the electric potential of the auxiliary output terminal
202
becomes equal to that of the charging terminal of the battery
5
, the charge indication lamp
9
is turned off and the charging operation is started.
The voltage regulator
3
connects voltage dividing resistors
301
,
302
, and
303
serially connected between the charge detection terminal of the battery
5
and the ground through a lead wire C for use in detecting a charged voltage, and a transistor
320
, whose collector and emitter are connected across the voltage dividing resistor
303
, having a positive electric potential applied to the base through a resistor
300
for a resistor shunt. The collector of a transistor
400
forming part of the engine control unit (ECU)
4
is connected to the base of the transistor
320
through a lead wire A. The emitter of this transistor
400
is grounded, and an ECU signal is input to the base from various sensors.
Connected between the auxiliary output terminal
202
and the ground are voltage dividing resistors
304
and
305
for output voltage detection through a serially connected lead wire; a control transistor
321
whose emitter is connected to the ground and whose collector is connected to the auxiliary output terminal
202
through a resistor
306
; and an output transistor
322
, whose emitter is connected to the earth, whose base is connected to the collector of the control transistor
321
, and whose collector is connected to the auxiliary output terminal
202
through a diode
313
D. The ends of the field coil
102
are connected to the connection points among the auxiliary output terminal
202
, the collector of an output transistor
322
, and the anode of the diode
313
D.
The anodes of diodes
310
and
311
are respectively connected to the connection points between the voltage dividing resistors
301
and
302
and the voltage dividing resistors
304
and
305
. The cathodes of the diodes
310
and
311
are commonly connected to the base of the control transistor
321
through a Zener diode
312
.
The operations of the conventional apparatus are described below by referring to the views showing the characteristics of the output voltage shown in FIG.
4
.
If the key switch
8
is turned on when the engine is started, an electric current flows through the output transistor from the battery
5
through the key switch
8
, the charge indication lamp
9
, and the resistor
306
. At this time, the battery voltage is not charged enough to set the Zener diode
312
in a continuity state. Therefore, the control transistor
321
remains in the OFF state.
When the output transistor
322
is turned on, an exciting current flows through the battery
5
, the key switch
8
, the charge indication lamp
9
, the field coil
102
, the output transistor
322
, and the field coil
102
through the loop of the ground. At this time, the charge indication lamp
9
is turned on.
After the exciting current flows through the field coil
102
and the AC generator
1
is driven by the engine, the generated output is rectified by the rectifier
2
and output to the auxiliary output terminal
202
, thereby raising the terminal voltage. When the terminal voltage of the auxiliary output terminal
202
equals or exceeds a predetermined value and becomes approximately equal to the battery voltage, the charge indication lamp
9
is turned off to indicate that the generating state is entered.
During the generating operation, if the charged voltage of the battery
5
is detected by the voltage dividing resistors
301
,
302
, and
303
from the charge detection terminal through the lead wire C, and if the charged voltage equals or exceeds a predetermined value (14.5V or 12.5V) described later, then the Zener diode
312
is set in a continuity state and the control transistor
321
is turned on.
When the control transistor
321
is turned on, the electric potential of the base of the output transistor
322
falls down to the electric potential of the ground, and the output transistor
322
is turned off with the exciting current reduced. As a result, if the output voltage drops, and the charged voltage of the battery
5
becomes lower than a predetermined value, then the output transistor
322
is turned on, the exciting current increases, the output voltage rises, and the charged voltage of the battery
5
also increases. These operations are repeated to adjust the output voltage into a predetermined value.
Described below is the operation to be performed when the output voltage is adjusted into 14.5V. When the ECU signal to a transistor
400
forming part of an ECU
4
is set OFF and the transistor
400
is set in the OFF state, a base current flows in the transistor
320
through the resistor
300
. When the transistor
320
is turned on and shunts the voltage dividing resistor
303
, the voltage dividing resistor is a serially connected voltage dividing resistors
301
and
302
. If the battery voltage becomes equal to or higher than 14.5 V in this resistance ratio, then the divided voltage obtained using the voltage dividing resistor reaches the voltage level at which the Zener diode can be set in the continuity state. With the control transistor
321
set ON and the output transistor
322
set OFF, the exciting current decreases and the output voltage drops, thereby lowering the charged voltage of the battery
5
.
If the charged voltage is equal to or lower than 14.5V and the control transistor
321
is turned off again, then the output transistor
322
is turned on and the exciting current increases, thereby raising the output voltage. These operations are repeated to adjust the output voltage into 14.5V.
However, if the engine is in the idle state and the electric load is almost zero, and the battery voltage is set to 12.5V to attenuate the load of the engine for the AC generator
1
, then the ECU signal is set ON and the transistor
400
is set ON. As a result, the electric potential of the base of the transistor
320
becomes the electric potential of the ground, and the voltage dividing resistor is a serially connected voltage dividing resistor
301
,
302
, and
303
. If the battery voltage becomes equal to or higher than 12.5 V in this resistance ratio, then the divided voltage obtained using the voltage dividing resistor reaches the voltage level at which the Zener diode can be set in the continuity state. The subsequent operations are the same as in the case that the output voltage is

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