GB1564504A

GB1564504A - Headlamp control system

Info

Publication number: GB1564504A
Application number: GB3508875A
Authority: GB
Original assignee: Rover Co Ltd
Current assignee: Rover Co Ltd
Priority date: 1975-08-23
Filing date: 1975-08-23
Publication date: 1980-04-10
Also published as: IT1067933B; DE2637592A1; FR2322024A1

Description

(54) HEADLAMP CONTROL SYSTEM (71) We, BL CARS LIMITED, formerly known as British Leyland UK Limited, a British Company of Leyland House, 174 Marylebone Road, London NWl 5AA, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a headlamp control system for a vehicle. In particular it is concerned with a control system for a headlamp which is displaceable between a first, elevated, working position and a second, retracted, position. Hereinafter this is referred to as being of the type described.

According to the present invention there is provided a vehicle headlamp control system of the type described comprising: (i) a motor for driving the headlamp between the elevated and the re tracted positions; (ii) a switch operable between a first position in which the headlamp fila ment is isolated from a power source and a second position in which the headlamp filament is connected to the source; and iii) a solid state time delay means con nected to a relay controlling the sup ply of current to the motor and con nectable to the source by way of said switch; the arrangement being such that operation of the switch from the first to the second position causes the headlamp to be driven to the elevated position and the restoration of the switch to the first position from the second causes, a predetermined period after the restoration, the driving of the headlamp to the retracted posi tion.

In a preferred form of the invention the switch is resiliently biassed from the second position towards the first.

An embodiment of the invention will now be described with reference to the accompanying drawings of circuit diagram from a passenger road vehicle electrical system of which: Figure 1 shows part of the main electrical circuit; and Figure 2 shows in detail selected ' items from Figure 1.

The vehicle has a pair of hedlamps' each lamp being enclosed in a housing represented by broken outline A, B which:when the lamp is in use, project from the vehicle body. When not in use the housing is retracted into the vehicle body to improve stream-lining. Main filament 11 and dipped beam filament 12 are incorporated in enclosure A, enclosure B incorporates main beam filament 13 and dipped beam filament 14.

Master light switch 15 enables voltage on lines 16, 17 and fed to switch terminals 3, 6 to be connected to, or isolated from, terminal 7 for sidelights or terminal 8 for headlamp filaments.

Extension or retraction of housing A is powered by motor 18 and governed by limit switch 19. Likewise housing B is powered by motor 20 and governed by limit switch 21.

Dip and Hash switch 22 incorporates a Slash switch 23 enabling the headlamps to he used for signalling, typically in daylight.

Dip switch 22A operates in a conventional manner to enable the driver to select dipped or main beam filament operation.

Switch 22 enables voltage on line 5 to be fed: to main filaments 11, 13 by way of line 6; and to dipped filaments 12, 14 by way of line 7.

Flash switch 23 enables voltage on line 8 to be fed to the main filaments 11, 13 by way of line 6.

Since flashing will require extension of enclosures A, B from the vehicle body a flash control unit 24 is provided which is described in more detail hereafter with reference to Figure 2.

The control unit 24 is coupled through flash relay 25 to the headlamp motors limit switches 19, 21. Motor relays 26. 27 operable simultaneously with relay 25 are used to apply voltage to the motors 18, 20 from circuit breaker 29.

Figure 2 shows four items from Figure 1 namely: master light switch 15, dip and flash switch 22, flash control unit 24 and flash relay 25. The terminals of all except flash switch 22 are numbered, in Figure 2, to correspond with the numbering of Figure 1.

Figure 2 shows the circuit components of control unit 24 including: diodes D1 to D4 zener diode ZD1 transistor TR1 resistors R1, R2 and capacitor Cl The flash relay 25 has solenoid 31 connected across terminals 3, 4. With the solenoid quiescent terminals 1 and 5 are connected; and terminal 5 is coupled to 'down' contacts 33, 34 of, respectively, limit switches 19, 21.

The control unit 24 will operate to delay headlamp retraction only in response to operation of flash switch 23 when dip switch 22a is switched to line 7 and the main lighting switch 15 is in 'off' or 'sidelights' position. As can be seen, in the 'headlamps on' position (with terminal 8 linked to terminal 3 and/or 6) or when the switch 23 is closed with switch 22a switched to line 6, the terminal 2 of control limit 24 will no longer be at a negative potential the capacitor will not be charged, and so the unit will be inoperative. Diode D1 acts as a reverse voltage protection. Zener diode ZD1 and diode D3 act as transient protection.

When voltage is fed to the anode of diode D2 from line 8 by operation of switch 23 transistor TRI will turn on due to base current through resistor Rl. Solenoid 31 will then be energised to switch the relay 25 from connecting terminal 1 to terminal 5 to connect terminal I to terminal 2. In this way voltage on terminal 4 of master switch 15 is fed to 'up' terminals 35, 36 of, respectively, limit switches 19, 21. Simultaneously with energisation of relay 25. relays 26, 27 will feed power to their associated motors, 18, 20. Thereafter enclosures A, B will be motored to their extended positions, and illuminated. Capacitor Cl will be charged, due to current through resistance R2, as long as a voltage is applied to terminal 6 of the control unit. Resistor R2 acts as a surge limiter to protect diode D2 from the initial charging current of capacitor Cl.

When voltage disappears from diode D2 (such as will occur on ceasing to flash the headlamps) the capacitor discharges through resistors R2 and Rl on to the base of the transistor which will remain turned on. However, after a period of between 2 and 4 seconds the capacitor will have discharged to a point that provides insufficient base current to hold on the transistor. Thereafter the solenoid 31 is de-energised and relay 25 reverts to the disposition shown in Figure 2 with terminals 1 and 5 connected. Voltage is then fed to terminals 33, 34 (across which, respectively, limit switches 19, 21 will be connected). in addition relays 26, 27 will connect a voltage across motors 18, 20 to cause the headlamp enclosures to be motored down to the retracted position.

The embodiment enables the headlamp to be repeatedly flashed without rapid cycling of the headlamp housings. Such cycling would be both visually and mechanically unacceptable. In the embodiment the 2 > second delay period of unit 24 ensures that the headlamps remain extended until the end of the period after the final release of the flash switch 23.

WHAT WE CLAIM IS:- 1. A headlamp control system for a vehicle headlamp which is displaceable between a first, elevated, working position and a second, retracted, position, comprising: (i) a motor for driving the headlamp between the elevated and the re tracted positions; (ii) a switch operable between a first position in which the headlamp fila ment is isolated from a power source and a second position in which the headlamp filament is connected to the source; and (iii) a solid state time delay means con nected to a relay controlling the sup ply of current to the motor and con nectable to the source by way of said switch; the arrangement being such that operation of the switch from the first to the second position causes the headlamp to be driven to the elevated position and the restoration of the switch to the first position from the second causes, a predetermined period after the restoration, the driving of the headlamp to the retracted posi tion.

2. A headlamp control system as claimed in Claim 1 characterised in that the solid state time delay means comprises a transistor having a base coupled to a capacitor and to the switch; the transistor having an emitter and a collector connected between a solenoid in said relay and earth; the solenoid, when energised causing the relay to connect the motor to the source to drive the headlamp to the elevated position; the capacitor being adapted to discharge for the predetermined period to the base of the transistor when the switch is moved from the second to the first position.

3. A headlamp control system as claimed

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. flash relay 25 to the headlamp motors limit switches 19, 21. Motor relays 26. 27 operable simultaneously with relay 25 are used to apply voltage to the motors 18, 20 from circuit breaker 29. Figure 2 shows four items from Figure 1 namely: master light switch 15, dip and flash switch 22, flash control unit 24 and flash relay 25. The terminals of all except flash switch 22 are numbered, in Figure 2, to correspond with the numbering of Figure 1. Figure 2 shows the circuit components of control unit 24 including: diodes D1 to D4 zener diode ZD1 transistor TR1 resistors R1, R2 and capacitor Cl The flash relay 25 has solenoid 31 connected across terminals 3, 4. With the solenoid quiescent terminals 1 and 5 are connected; and terminal 5 is coupled to 'down' contacts 33, 34 of, respectively, limit switches 19, 21. The control unit 24 will operate to delay headlamp retraction only in response to operation of flash switch 23 when dip switch 22a is switched to line 7 and the main lighting switch 15 is in 'off' or 'sidelights' position. As can be seen, in the 'headlamps on' position (with terminal 8 linked to terminal 3 and/or 6) or when the switch 23 is closed with switch 22a switched to line 6, the terminal 2 of control limit 24 will no longer be at a negative potential the capacitor will not be charged, and so the unit will be inoperative. Diode D1 acts as a reverse voltage protection. Zener diode ZD1 and diode D3 act as transient protection. When voltage is fed to the anode of diode D2 from line 8 by operation of switch 23 transistor TRI will turn on due to base current through resistor Rl. Solenoid 31 will then be energised to switch the relay 25 from connecting terminal 1 to terminal 5 to connect terminal I to terminal 2. In this way voltage on terminal 4 of master switch 15 is fed to 'up' terminals 35, 36 of, respectively, limit switches 19, 21. Simultaneously with energisation of relay 25. relays 26, 27 will feed power to their associated motors, 18, 20. Thereafter enclosures A, B will be motored to their extended positions, and illuminated. Capacitor Cl will be charged, due to current through resistance R2, as long as a voltage is applied to terminal 6 of the control unit. Resistor R2 acts as a surge limiter to protect diode D2 from the initial charging current of capacitor Cl. When voltage disappears from diode D2 (such as will occur on ceasing to flash the headlamps) the capacitor discharges through resistors R2 and Rl on to the base of the transistor which will remain turned on. However, after a period of between 2 and 4 seconds the capacitor will have discharged to a point that provides insufficient base current to hold on the transistor. Thereafter the solenoid 31 is de-energised and relay 25 reverts to the disposition shown in Figure 2 with terminals 1 and 5 connected. Voltage is then fed to terminals 33, 34 (across which, respectively, limit switches 19, 21 will be connected). in addition relays 26, 27 will connect a voltage across motors 18, 20 to cause the headlamp enclosures to be motored down to the retracted position. The embodiment enables the headlamp to be repeatedly flashed without rapid cycling of the headlamp housings. Such cycling would be both visually and mechanically unacceptable. In the embodiment the 2 > second delay period of unit 24 ensures that the headlamps remain extended until the end of the period after the final release of the flash switch 23. WHAT WE CLAIM IS:-

1. A headlamp control system for a vehicle headlamp which is displaceable between a first, elevated, working position and a second, retracted, position, comprising: (i) a motor for driving the headlamp between the elevated and the re tracted positions; (ii) a switch operable between a first position in which the headlamp fila ment is isolated from a power source and a second position in which the headlamp filament is connected to the source; and (iii) a solid state time delay means con nected to a relay controlling the sup ply of current to the motor and con nectable to the source by way of said switch; the arrangement being such that operation of the switch from the first to the second position causes the headlamp to be driven to the elevated position and the restoration of the switch to the first position from the second causes, a predetermined period after the restoration, the driving of the headlamp to the retracted posi tion.

3. A headlamp control system as claimed

in Claim 1 or Claim 2 characterised in that the switch incorporates a resilient bias acting to drive the switch from the second position to the first position.

4. A headlamp control system as hereinbefore described with reference to, and as illustrated in, Figure 1 and 2 of the accompanying drawing.

5. A road vehicle equipped with a headlamp control system as claimed in any preceding claim.