Lighting systems for vehicles

• US 3,879,617 A
• Filed: 09/06/1973
• Issued: 04/22/1975
• Est. Priority Date: 09/16/1972
• Status: Expired due to Term

• Current Assignee: Hermann Faller
• Original Assignee: Hermann Faller
• Inventors: Faller, Hermann
• Primary Examiner(s): Schaefer, Robert K.
• Assistant Examiner(s): Ginsburg, M.
• Application Number:
  US05/394,847
• Time in Patent Office: 593 Days
• Field of Search: 307/1R,1LS,77,82,83,83.1,116,117 315/149,156 340/22 250/206
• US Class Current: 307/10.8
• CPC Class Codes: B60Q 1/1423 Automatic dimming circuits, i.e. switching between high beam and low beam due to change of ambient light or light level in road traffic
• CPC Class Codes: B60Q 2300/052 Switching delay, i.e. the beam is not switched or changed instantaneously upon occurrence of a condition change
• CPC Class Codes: B60Q 2300/146 Abnormalities, e.g. fail-safe
• CPC Class Codes: B60Q 2300/314 Ambient light

Abstract

An automatic control device for the exterior lighting system of a motor or like vehicle contains a Schmitt trigger whose switching-off threshold is higher than its switching-on threshold to provide a switching hysteresis and also contains a switching delay device for delaying the trigger response, whereby long term slight fluctuations and short term greater fluctuations in the environmental illumination through which the vehicle is being driven do not cause repeated switching on and off of the vehicle lamps. Means may be provided for displacing the switching threshold when the vehicle windshield wipers are switched on, whereby the vehicle lamps are first switched on at a somewhat brighter environmental illumination when it is raining or snowing.

Claims

1. Apparatus powered by a d.c. network for the switching on and off a vehicle exterior lighting system as a function of environmental illumination, comprising light sensing means for sensing said illumination and an automatic control device, said control device including:

threshold value means for switching states in response to said light sensing means, said threshold value means having a switching hysteresis such that it effects a switching off at a greater illumination than that at which the switching-on occurs;

means for switching said exterior lighting system on and off in response to said threshold value means; and

switching delay means for delaying the switching off and the switching on at illumination values above and below the switching-on and switching-off illumination values, respectively, said switching delay means having a switching off delay greater than its switching on delay.

2. A control device in accordance with claim 1, in which said threshold value means comprises a Schmitt-trigger containing input and output transistors and a common emitter resistor connected to the emitters of said transistors for producing a voltage drop when the Schmitt-trigger switches on said lighting system for producing said switching hysteresis.

3. A control device in accordance with claim 2 in which means for bridging the switching-on delay of said switching delay means are provided which are effective on operating a switch for headlamp flashing of the vehicle and in which the control device contains a capacitor which is connected between said switch for headlamp flashing on the base of said input transistor of said Schmitt-trigger in such a way that it is discharged on operating said switch for headlamp flashing and is again recharged with reversed polarity.

4. A control device in accordance with claim 2, in which said Schmitt-trigger has a base bias resistor and a voltage divider network connected to the base of said input transistor, and said means for switching comprises a switching relay means controlled by said output transistor, said relay means including contact means for connecting the base of said input transistor via said base bias resistor to one pole of the d.c. network so as to affect the voltage divider ratio when the switch relay means is operated.

5. Apparatus in accordance with claim 1, in which said light sensing means has a light entry aperture and means for adjusting the size of said light entry aperture.

6. Apparatus in accordance with claim 5 in which said light sensing means further comprises a photo-resistor and a screw-threaded, transparent light conducting element for conducting environmental illumination to said photo-resistor and in which said aperture adjusting means comprises a light obturating part threaded adjustably on to said light conducting element.

7. Apparatus in accordance with claim 6, in which said light conducting element comprises a screw bolt, and said light obturating part comprises a sleeve which can be screwed on said bolt and is in the form of an adjusting knob.

8. Apparatus in accordance with claim 7, in which said screw bolt comprises a fixing bolt for said photo-resistor.

9. Apparatus in accordance with claim 6 in which said light conducting element has a thickened end portion with a recess therein, said photo-resistor being received in said recess and in which a substance in which said photo-resistor is embedded is also received in said recess.

10. A vehicle exterior lighting system in accordance with claim 1 which includes a low beam filament, a side lamp and a tail lamp, all adapted to be switched on and off by said control device.

11. A control device in accordance with claim 1, in which said switching delay means comprises switching-off delay circuit means for producing a greater delay of the switching-off when the switching-off brightness value is exceeded, and separate switching-on delay circuit means for producing a shorter delay of the switching-on when said illumination is below the switching-on brightness value.

12. A control device in accordance with claim 11 in which said threshold value means comprises a Schmitt-trigger having an input transistor and output transistor in which said switching on delay circuit means comprises a capacitor connected between the base and the collector of said output transistor and also serving to suppress voltage fluctuations and peaks.

13. A control device in accordance with claim 12 in which a resistor is connected in series with the last-mentioned capacitor.

14. A control device in accordance with claim 1 in which said switching delay means is responsive to said sensing means, whereby the length of said delay by said switching delay menas depends upon said environmental illumination.

15. A control device in accordance with claim 1 in which said switching delay means includes at least one electrolytic capacitor the time constant of which causes the delay of at least one of said switching off and switching on of the exterior lighting system.

16. Apparatus in accordance with claim 1 in which said vehicle exterior lighting system has a main beam filament and a low beam filament and in which said control device is connected to said main beam filament in such a way that the control device switches off said low beam filament when said main beam filament is switched on.

17. A control device in accordance with claim 1, which further comprises a switching on delay means responsive to starting up of the vehicle for delaying the switching on of said exterior lighting system for a period of time normally sufficient for the starting of the engine of the vehicle.

18. A control device in accordance with claim 17, in which said switching on delay means comprises a thermal relay.

19. Apparatus in accordance with claim 1, in combination with a vehicle, in which said vehicle is fitted with a generator and in which said control device is connected to an output terminal of said vehicle generator.

20. Apparatus in accordance with claim 1, in combination with a vehicle in which said vehicle is fitted with a parking lamp and in which a change-over switch is provided for transferring said control device from said exterior lighting system to said parking lamp.

21. Apparatus in accordance with claim 1 in which said light sensing means comprises a light sensor and light conducting means for conducting said environmental illumination to said sensor.

22. A control device in accordance with claim 1 which further comprises threshold value displacement means containing a moisture probe for increasing illumination values at which switching on and off of said exterior lighting system responsive to precipitation.

23. A control device in accordance with claim 1, in combination with a windshield wiper motor and wiper motor switch, wherein said control device further includes threshold value displacement means responsive to the switching on of said motor by said motor switch, said threshold value displacement means being connected to said threshold value means for causing an increase in the illumination values at which said switching on and off of the exterior lighting system of the vehicle take place.

24. The combination in accordance with claim 23 in which said threshold value displacement means includes time delay means whose delay period starts with the switching on of said windshield wiper motor for delaying said threshold value displacement means from becoming effective for a predetermined time thereafter.

25. The combination in accordance with Claim 24, in which said time delay means comprises a thermal relay having a heating resistor connected to said wiper motor to be switched on therewith.

26. The combination in accordance with claim 24, in which said time delay means comprises at least one temperature-variable resistance element and means connecting the latter whereby it is heated as a function of the switching on of the windshield wiper motor.

27. The combination in accordance with claim 26, in which said time delay means comprises a transistor switching element connected to said temperature-variable resistance element.

28. The combination in accordance with claim 24, in which said time delay means comprises a capacitor and a resistor in series therewith.

29. The combination in accordance with claim 23 in which said threshold value means includes a voltage divider and in which said threshold value displacement means is connected to said voltage divider for displacing the voltage divider ratio when said windshield wiper motor is switched on.

30. The combination in accordance with claim 23 in which said threshold value displacement means includes means rendering it non-responsive to brief switching on and off of said windshield wiper motor.

31. The combination in accordance with claim 23, in which said wiper motor has a first terminal connected to one pole of said d.c. network and a second terminal connected to said threshold value displacement means and said wiper motor switch, said motor switch being connected between the second terminal of said wiper motor and the other pole of said d.c. network, whereby said threshold value displacement means receives one polarity when said wiper motor is switched off and receives the other polarity when said wiper motor is switched on.

32. Apparatus in accordance with claim 1 in which said light sensing means comprises two light sensors connected in series and each comprising a photo-resistor, said light sensors being arranged on said vehicle at two points located at a distance from one another in longitudinal direction of said vehicle.

33. A control device in accordance with claim 1, in which means for bridging the switching-on delay of said switching delay means are provided which are effective on operating a switch for headlamp flashing of the vehicle.

34. Apparatus in accordance with claim 1 further including a manually operated switch with one side connected to one pole of said d.c. network and wherein said control device further includes threshold value displacement means connected to the other side of said manually operated switch and to said threshold value means for causing an increase in the illumination values at which said switching on and off of the exterior lighting system of the vehicle takes place when said manually operated switch is closed.

35. Apparatus powered by a d.c. network for the switching on and off of a vehicle exterior lighting system as a function of environmental illumination, comprising light sensing means for sensing said illumination, an automatic control device and a windshield wiper motor, said control device including:

threshold value means for switching states in response to said light sensing means, said threshold value means having a switching hysteresis such that it effects a switching off at a greater illumination than that at which the switching-on occurs;

threshold value displacement means responsive to the switching on of said wiper motor and connected to said threshold value means for causing an increase in the illumination values at which the switching of said threshold value means takes place;

means for switching said exterior lighting system on and off in response to said threshold value means; and

switching delay means for delaying the switching off and the switching on at illumination values above and below the switching-on and switching-off illumination values, respectively.