Electrical transmission or interconnection systems – Vehicle mounted systems – Automobile
Patent
1985-02-25
1987-01-20
Leung, Philip H.
Electrical transmission or interconnection systems
Vehicle mounted systems
Automobile
3071414, 315 84, B60Q 302
Patent
active
046381740
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a switching device for lighting the interior of a motor vehicle having an ignition switch.
Such circuits have the advantage that the seat belts can be put on and the key inserted in the ignition lock or the driver's door locked from the outside while the interior lights are switched on. It is however a disadvantage that the battery of the vehicle may become discharged if a door of the vehicle is inadvertently left open over a longer period of time and for this reason the interior lights remain switched on by the door contact switch, which in this case is in the closed position.
It is an object of the invention to provide a switching device, with which discharging of the vehicle battery, when the door is left open for long periods, is prevented.
This objective is accomplished by the distinguishing features described below.
When the door is open (that is, when the door contacts are in the closed position), the inventively provided second timing element switches off the interior lighting after several minutes, however only if the ignition switch is open and the engine thus is not running, since it is normally not possible to discharge a battery when the engine is running and it would be unacceptable that, when the is engine running and the vehicle thus normally is occupied, the interior lights go out when a vehicle door is open for some time.
Preferably, the second timing element remains set through closing the ignition switch is closed, so that, after the door is closed and the ignition switched on, the interior lighting remains switched on even when a vehicle door stays open for some time.
With a conventional delay circuit, the interior lighting, after the door is closed, remains switched on through a transistor, whose base is connected with the output of an operational amplifier, whose +ve input is taken to a reference voltage and whose -ve input is at a potential, which is lower when the when the door contact switch is closed and higher when the door contact switch is open, that its +ve input. With such a circuit, the +ve input of an operational amplifier can be connected to the output of a comparator, the -ve input of which sees a reference voltage and the +ve input of which is brought by the second time element to a potential lower than that of its -ve input at a specified time after the door contact switch is closed and to a potential higher than that of its -ve input by closing the ignition switch.
An example of the operation of the invention is described in the following with reference to the drawing which shows a schematic diagram for a preferred embodiment of the invention.
The interior light L of a motor vehicle is connected, on the one hand, to the positive pole of the vehicle battery and, on the other, can be connected by manual switch S either directly (position 1) or through relay contacts RK (position 2) to the negative pole, that is, to ground. In addition, switch S has an open position 0. The relay contacts RK are closed when current is flowing in the coil of relay R. This coil is connected, on the one hand, to the positive pole of the vehicle battery and, on the other, through a transistor T to ground. The base of transistor T is connected to the output of an operational amplifier OP whose inverting (-) input is connected through a resistance R1 to the positive pole and through a door contact switch TK, which is closed when the vehicle door is open, and two diodes D1 and D2 to ground. In addition, a capacitor C1 is arranged between the (-) input of the operational amplifier OP and ground. The noninverting (+) input of the operational amplifier is connected to a reference voltage node A, which is formed by resistances R3 and R4, R5.
Resistance R1 and capacitor C1 form a first timing element, which continues to maintain the excitation of relay R over a predetermined period of time after the door of the vehicle is closed, that is, after the previously closed door contact switch TK is opened. Through opening TK, the potential at the (-) input of the OP is increased con
REFERENCES:
patent: 4071805 (1978-01-01), Brock
patent: 4122371 (1978-10-01), Talmage et al.
patent: 4123668 (1978-10-01), Decota
Audi NSU Auto Union Aktiengesellschaft
DeBoer T.
Leung Philip H.
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