Apparatus for controlling AC generator in vehicle

Abstract: An apparatus for controlling an AC generator in a vehicle, the AC generator including an exciting coil and driven by an engine to generate an AC output which is rectified and fed to a battery, includes a pilot-lamp switching transistor device constituted by a Darlington-connection of transistors (326,327), the pilot-lamp switching transistor device having a base and a collector for turning a pilot lamp (6) on/off, the pilot lamp being fed with a current from the battery (4) through a key switch (5), a resistor (329) connected between the base and the collector of the pilot-lamp switching transistor, an initial exciting transistor for controlling a current for the initial excitation of the exciting coil by the battery, a voltage detection circuit for detecting a voltage of the battery, and a voltage detection circuit switching transistor for controlling a switching operation of the voltage detection circuit. In the control apparatus, at least one of the initial exciting transistor and the voltage detection circuit switching transistor is driven by a collector potential of the pilot-lamp switching transistor.

Description: BACKGROUND OF THE INVENTION (Field of the Invention) The present invention relates to an apparatus for controlling an AC generator in a vehicle having the features of the preamble of claim 1. (Prior Art) Fig. 1 shows the arrangement of a conventional control apparatus for an AC generator in a vehicle, in which reference numeral 1 designates an AC generator to be driven by a car engine; 101, an armature coil; 102, a field coil; 2, a rectifier; 201, a main rectification output terminal; 202, an auxiliary rectification output terminal for exciting the field coil 102 by the output; and 203, a grounding terminal. Reference numeral 3 designates a voltage regulator; 301, 304, 311, 318, and 324, transistors; 305, 310, and 323, Zener diodes; 302, 319, and 328 diodes; 303, 306, 307, 314, 315, 317, 319, 320, 321, 322, and 325, resistors; 308, an initial exciting transistor; 313, an initial excitation driving transistor; 316, a voltage detection circuit connecting/disconnecting transistor; 326 and 327, NPN-type Darlington transistors; 312, an oscillator; 4, a battery to be charged by the output of the rectification output terminal 201; 5, a key switch; and 6, a pilot lamp. The operation of the control device thus arranged will be described hereunder. When the key switch 5 is turned on, a voltage is applied from the battery 4 to the pilot lamp 6 and the resistors 319 and 320 through the key switch 5 to thereby turn the transistor 318 on. Accordingly, the transistors 316 and 313 are also turned on, the initial exciting transistor 308 is actuated to operate, a current is allowed to flow into the field coil 102 to thereby make the field coil 102 be in an initial exciting state. At the same time, a voltage is applied from the battery 4 to the resistors 306 and 307 through the transistor 316 so that the voltage is detected. Further, the transistor 313 is turned on so that base current flows respectively into the transistors 326 and 327 through the resistor 325 to thereby turn the transistors 326 and 327 on. A current flows from the battery 4 through the key switch 5, the pilot lamp 6, the diode 328, and the transistors 326 and 327 to thereby light the pilot lamp 6. At that time, the sum of the forward voltage drop (about 0.7 V) of the diode 328 and the saturation voltage (about 1.2 V) between a collector of the transistor 326 and an emitter of the transistor 327 becomes about 1.9 V, so that the transistor 318 is maintained in the on-state. However, if the voltage of the AC generator 1 becomes high as an engine rotate so that the voltage of the battery 4 rises, the Zener diode 305 is rendered conductive so that the transistor 304 is turned on, the transistor 301 is turned off, and the current is stopped flowing into the field coil 102. Further, at that time, the output at the auxiliary output terminal 202 also becomes high and the Zener diode 323 is rendered conductive so that the transistor 324 is turned on, the Darlington transistors 326, 327 are turned off, and the pilot lamp 6 is also turned off. In the conventional apparatus described above, the forward voltage drop of the diode 328 is utilized to keep the transistor 318 in the on-state, that is, to keep the initial exciting transistor 308 and the voltage detection circuit connecting/disconnecting transistor 316 in the on-state. Accordingly, the configuration is complicated and expensive. From DE-OS-22 08 415 an apparatus for controlling an AC generator having the features of the preamble of claim 1 is known. SUMMARY OF THE INVENTION The present invention has been attained to solve the problems as described above, and an object thereof is to provide a control apparatus for an AC generator in a vehicle, which is simple in configuration and inexpensive in cost. This object is solved by an apparatus for controlling an AC generator of the initially defined type having the characterizing features of claim 1. Preferred embodiments are listed in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a circuit diagram of a conventional apparatus; and Fig. 2 is a circuit diagram of the apparatus according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to Fig. 2. Fig. 2 shows a diagram of a control circuit for an a.c. generator in a vehicle according to the present invention, in which reference numeral 329 designates a resistor connected between respective collectors of Darlington transistors 326 and 327 and the base of Darlington transistor 327. The diode 328 and the base resistor 325 of the Darlington transistors 326 and 327 driven by the transistor 313 in the conventional apparatus have been removed here. The other configuration is the same as that of the conventional apparatus. The operation will be described hereunder. When a key switch 5 is turned on, a base current flows from a battery 4 into the Darlington transistors 326 and 327 through a pilot lamp 6 and the resistor 329. At that time, the collector potential of the Darlington transistors 326 and 327 becomes the sum of a voltage V BE2 (about 0.7V) between a base and an emitter of the transistor 327, a voltage V BE1 between a base and an emitter of the transistor 326, and the product of a base current I B and the value of the resistor 329. Accordingly, when the value of the base resistance of the resistor 329 is suitably selected, the potential difference equivalent to that of the forward voltage drop of the conventional diode 328 can be obtained. That is, when the self-bias resistor 329 is inserted between the collector and base of the NPN-type Darlington transistors 325 and 327 for driving the pilot lamp 6, the saturation voltage can be made high, so that the diode 328 inserted for increasing the voltage drop in the conventional apparatus can be omitted. Accordingly, the on-state of the transistors 318, 313, 315, and 308 can be maintained by this collector potential, so that the on-state of the initial exciting circuit and the voltage detection circuit can be maintained. Although the example in which the pilot-lamp switching transistor is constituted by the NPN-type Darlington transistors 326 and 327 has been described in the above embodiment, the same effect can be obtained even in the case where individual transistors are Darlington-connected. Further, although the case in which the negative pole of the battery is grounded has been described in the above embodiment, the case in which the positive pole of the battery is grounded may be preferable, and at that time, it is needless to say that PNP-type transistors must be used to constitute the pilot-lamp switching transistor. As described above, according to the present invention, a resistor is inserted between a collector and a bases of the Darlington-connected pilot-lamp switching transistors to thereby make the saturation voltage high, so that the initial exciting transistor and the voltage-detection circuit connecting/disconnecting transistor are maintained continuously conductive by the collector potential of the Darlington-connected transistors. It is therefore possible to obtain a control apparatus for an AC generator in a vehicle which is simple in configuration and inexpensive in cost.

Claims: An apparatus for controlling an AC generator (1) in a vehicle, said AC generator including an exciting coil (102) and driven by an engine to generate an AC output which is rectified and fed to a battery (4), said apparatus comprising: a pilot-lamp switching transistor device (326, 327) constituted by a Darlington-connection of transistors, said pilot-lamp switching transistor device having a base and a collector for turning a pilot lamp (6) on/off, said pilot lamp (6) being fed with a current from said battery (4) through a key switch (5); a resistor (329) connected between said base and said collector of said pilot-lamp switching transistor device (326, 327); an initial exciting transistor (308) for controlling a current for the initial excitation of said exciting coil (102) by said battery (4); a voltage detection circuit (306, 307) for detecting a voltage of said battery (4); and a voltage detection circuit switching transistor (316) for on/off controlling a switching operation of said voltage detection circuit (306, 307); wherein at least one of said initial exciting transistor (308) and said voltage detection circuit switching transistor (316) is driven by a collector potential of said pilot-lamp switching transistor device (326, 327); characterized in that the pole of said resistor (329) which is coupled to the collector of said pilot-lamp switching transistor device (326, 327) is connected to a node downstream of said pilot lamp (6); and the resistance of the resistor (329) is selected to enhance a saturation voltage between the collector and the base of the pilot-lamp switching transistor device (326, 327), so that the conductive state of the initial exciting transistor (308) or the battery voltage detection circuit switching transistor (316) is maintained by the collector potential of the pilot lamp switching transistor (326, 327). An apparatus as claimed in claim 1, wherein said pilot lamp switching transistor device (326, 327) comprises NPN-type transistors. An apparatus as claimed in claim 2, wherein a negative pole of said battery (4) is grounded. An apparatus as claimed in claim 1, wherein said pilot lamp switching transistor device (326, 327) comprises PNP-type transistors. An apparatus as claimed in claim 4, wherein a positive pole of said battery (4) is grounded.

Inventors: MORISHITA MITSUHARU, SATOH KIYOKATSU, MORISHITA, MITSUHARU, SATOH, KIYOKATSU, Morishita, Mitsuharu, c/o Mitsubishi Denki K.K., Satoh, Kiyokatsu, c/o Sanken Electric Co., Ltd.
Applicants: MITSUBISHI ELECTRIC CORP, SANKEN ELECTRIC CO LTD, MITSUBISHI DENKI KABUSHIKI KAISHA, SANKEN ELECTRIC CO., LTD.
Application year: 1992
Main classification: H02J7
IPC codes: H02P9, H02J7