A battery-recharging system for a motor vehicle

Abstract: The system includes a current generator (2) including an alternator (4) and an associated rectifier (7) whose output is connected by a cable (9) to a terminal of the battery (1). A switch (10) is connected to that terminal of the battery (1) and an indicator lamp (11) connected in series with the switch (10) is switched on when no current is supplied by the generator (2). A voltage regulator (3) is connected to the field winding (6) of the generator (2) and has first and second inputs (A,L) connected to the output of the generator (2) and to the lamp (11) respectively. The voltage regulator (3) includes a control circuit (15) for monitoring the potential difference between the first and second inputs (A,L) of the voltage regulator (3) and for switching on the lamp (11) if that potential difference is greater than a pre-established reference value when the generator (2) is operating. This enables any interruption of the connection between the generator (2) and the battery (1) to be indicated to the user.

Description: The present invention relates to a battery-recharging system for a motor vehicle according to the preamble of Claim 1. A battery-recharging system of this kind is disclosed in EP-A-0 118 779. The system according to this document comprises a generator including two output rectifiers, one of which is connected to the battery by means of a conductor, the other one being connected to the field winding of the generator and to an indicator lamp which can in turn be connected to the battery through a key-operable switch. The system also includes a control circuitry with a voltage regulator arranged for controlling the field current of the generator as a function of the battery voltage. Said circuitry also includes a circuit which monitors the potential difference between one output of the generator and the battery, for stopping the generator upon occurrence of a disconnection/interruption of the conductor which couples the generator to the battery. Other battery-recharging systems are disclosed in DE-A-33 08 415 and WO-A-81/02956. These prior systems can detect and provide an indication of a disconnection/interruption of the cable coupling the generator output to the battery whenever such a disconnection/interruption causes an excessive increase of the generator output voltage. The detection is achieved by comparing a voltage proportional to the generator output voltage with a fixed, predetermined voltage value. The object of the present invention is to provide a new and improved battery-recharging system of the aforementioned type. According to the invention, this object is achieved by means of a system of the type specified above having the features defined in claim 1. Further characteristics and advantages of the invention will become clear from the detailed description which follows with reference to the appended drawings, provided purely by way of non-limiting example, in which: Figure 1 is a diagram of a system according to the invention, and Figure 2 is a diagram showing a circuit included in the system of Figure 1 in greater detail. With reference to Figure 1, the system according to the invention for recharging the battery 1 of a motor vehicle includes a current generator 2 and a voltage regulator, generally indicated 3, preferably in the form of an integrated circuit. The generator 2 comprises, in known manner, an alternator 4 with a three-phase armature winding 5 (connected in a star arrangement in the embodiment shown) and a field winding 6. The armature winding 5 of the alternator is connected to a three-phase full-wave rectifier 7 formed by semiconductor diodes 8. The output of the rectifier 7, which constitutes the output of the generator 2 as a whole, is connected to a pole of the battery 1 by a connecting cable 9. A switch, indicated 10, is connected to the positive pole of the battery 1 and is operable manually, for example, by a key. The switch may be incorporated, for example, in the ignition and starter switch of the motor vehicle. One terminal of an indicator lamp 11 is connected to the switch 10 and its other terminal is connected to an input L of the voltage regulator 3. The switch 10 and the lamp 11 are thus connected in series between the battery 1 and the input L of the regulator 3. In known manner, the lamp 11 is intended to be switched on (lit) when the switch 10 is closed and no current is supplied by the generator 2. The voltage regulator includes a voltage supply 12 and has a further 4 terminals indicated A, Ph, DF and GND, respectively. The terminal A is connected to the output of the generator 2 and to an input of the supply 12. The terminal Ph is connected to one phase of the armature winding 5 of the alternator 4. The terminal DF is connected to one end of the field winding 6, the other end of that winding being connected to the output of the generator 2. Finally, the terminal GND is connected to the earthed terminal of the recitifier circuit 7. The integrated regulator includes, in known manner, a driver circuit 13 for the lamp 11. The input of this driver circuit 13 is connected to the terminal Ph and hence to one phase of the alternator 4. The driver circuit also includes an output transistor 13a which is connected between the terminal L of the regulator and earth. In operation, when the switch 10 is closed and the alternator 2 is stationary, the transistor 13a is made conductive in known manner and the lamp 11 is lit. As soon as the alternator 4 is activated and the signal at the input Ph of the regulator exceeds the threshold of a comparator circuit within the driver circuit 13, the transistor 13a is made non-conductive and the lamp 11 consequently goes out. The regulator 3 also includes (again in known manner) a voltage regulator circuit 14 with an input connected to the terminal A, and hence to the output of the generator, and its output connected to the terminal DF, and hence to the field winding 6. In known manner, the circuit 14 regulates the current in the field winding 6 of the alternator in a predetermined manner in dependence on the voltage supplied by the generator 2. Finally, the voltage regulator 3 includes a control circuit 15 with a first input 15a connected to the terminal A and a second input 15b connected to the terminal L. The circuit 15 has an output connected to the driver circuit 13 of the lamp 11, for example, to the base of the final transistor 13a of that circuit. In operation, the control circuit 15 monitors the potential difference between the terminals A and L of the regulator 3; if that potential difference exceeds a pre-established reference value when the generator 2 is operating, the circuit 15 makes the transistor 13a conductive, causing the lamp 11 to be lit. This enables any disconnection between the output of the generator 2 and the battery 1, for example, as a result of the disconnection or breakage of the cable 9, to be detected and indicated. The user can thus take measures to prevent excessive discharge of the battery. As will be explained further below with reference to Figure 2, the circuit 15 can be arranged, in particular, to make the lamp 11 flash on and off when the potential difference between the terminals A and L exceeds the threshold. With reference to Figure 2, the circuit 15 may include, for example, a resistive voltage divider formed by two resistors 16 and 17 at its input between the terminal 15a and earth. This voltage divider is connected to a first input of a differential amplifier 18 formed, for example, with the use of an operational amplifier. The other input of the differential amplifier is connected to the input 15b of the circuit. Preferably, the differential amplifier 18 has an integrating effect so that it also acts, to advantage, as a filter for eliminating, or at least reducing, the ripple produced by the alternator. The output of the differential amplifier 18 is connected to a first input of a threshold comparator 19 whose other input is connected to a reference-voltage source 20. When the signal output by the differential amplifier 18 exceeds the level of the signal supplied by the source 20, the comparator 19 activates an intermittent control circuit 21, for example an astable multivibrator, whose output is connected to the base of the transistor 13a which consequently makes the lamp 11 flash on and off. As stated above, the output of the threshold comparator 19 could, however, be connected directly to the base of the transistor 13a so as to switch on the lamp 11 permanently should the battery 1 be disconnected from the generator 2. Naturally, the principle of the invention remaining the same, the forms of embodiment and details of construction may be varied widely with respect to those described and illustrated purely by way of non-limiting example, without thereby departing from the scope of the present claims.

Claims: A battery-recharging system for a motor-vehicle, including a current generator (2) including an alternator (4) with an armature winding (5), a field winding (6) and a rectifier (7); the output of the generator (2) being connected to a terminal of the battery (1) by a cable (9); a hand-operable switch (10) connected to said terminal of the battery (1); an indicator lamp (11) connectable to said terminal of the battery (1) through said switch (10) and arranged so as to be switched on when no current is supplied by the generator (2) although said switch (10) is closed; a control circuit (3) with first and second inputs (A; L) connected to the output of the generator (2) and to the lamp (11) respectively, and including a voltage regulator (14) which has a first terminal (DF) connected to the field winding (6) of the generator (2) and a second terminal (A) connected to the output voltage of the generator (2) and which is arranged to modify the current supplied to the field winding (6) in a predetermined manner in dependence on the voltage supplied by the generator (2), and a detecting circuit (15) for monitoring the potential difference between the first and second input (A,L) of the control circuit (3) and for switching on the lamp (11) when that potential difference is greater than a predetermined value while the generator (2) is operating; characterised in that the current generator (2) has a single output rectifier (7) which is connected to said second terminal (A) of the voltage regulator (14), whereby the voltage regulator (14) is arranged to modify the current in the field winding (6) in dependence on the output voltage of the generator (2); said single output rectifier (7) being also connected to both the battery (1), through said cable (9) and to said detecting circuit (15); and in that said control circuit (3) also includes a lamp driving circuit (13) interposed between the armature winding (6) of the generator (L) and the indicator lamp (11), and including an electronic switch (13a) arranged for controlling the operation of said lamp (11); said detecting circuit (15) having an output coupled to a control input of said electronic switch (13a) of the lamp driving circuit (13) for causing, through said electronic switch (13a), the activation of said lamp (11) when said monitored potential difference exceeds said predetermined value; the battery (1) and the hand operable switch (10) being connected to the detecting circuit (15) solely through said indicator lamp (11), which is in series with said hand operable switch (10). A battery-recharging system for a motor vehicle / according to Claim 1, characterised in that the detecting circuit (15) includes a differential amplifier (18) with first and second inputs connected respectively to the first and second inputs (A, L) of the control circuit (3); a threshold comparator (19) connected to the output of the differential amplifier (18) and a circuit (21) which controls the lighting of the lamp (11) and is intended to be activated when the signal output by the differential amplifier (18) exceeds the threshold associated with the comparator (19). A battery-recharging system for a motor vehicle according to Claim 2, characterised in that the detecting circuit (15) includes an intermittent control circuit (21) which is activated by the threshold comparator (19) to make the lamp (11) flash on and off when the signal output by the differential amplifier (18) exceeds the pre-established threshold level. A battery-recharging system for a motor vehicle according to Claim 2 or Claim 3, characterised in that the differential amplifier (18) has an integrating effect.

Inventors: BETTINI ROBERTO, VERCESI ROBERTO, BETTINI, ROBERTO, VERCESI, ROBERTO
Applicants: MAGNETI MARELLI SPA, MAGNETI MARELLI S.p.A.
Application year: 1991
Main classification: H02J7
IPC codes: B60R16, H02J7