GB2130030A

GB2130030A - Switching unit for vehicles

Info

Publication number: GB2130030A
Application number: GB08231825A
Authority: GB
Inventors: Peter John Bennison
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-11-08
Filing date: 1982-11-08
Publication date: 1984-05-23

Abstract

The headlights of a vehicle are arranged to be switched on automatically by the operation of the vehicle windscreen wipers for a preselected time period. Continuous use of the wipers for 1 to 2 minutes for example will switch on the headlights. The unit can also be such that intermittent use of the wipers beyond a fixed threshold will also initiate switching on of the headlights; alternatively the unit may be arranged to ignore intermittent wiper operation. The unit is connected to the wiper circuit via a lead 14 and a rectifier 12 which allows use of the same unit for positive and negative earth systems. A relay 16 has contacts controlling the headlights. The time delay may be provided by an RC circuit R1, C or by a counter counting pulser generated by the reciprocating motion of the wiper. <IMAGE>

Description

SPECIFICATION Switching unit for vehicles This invention relates generally to switching circuits and switching units utilised in vehicles for particular purposes.

In this country and in many other countnes it is mandatory that the drivers of motor vehicles should switch on their headlights, on dipped beam, when driving through inclement weather such as rain, fog or snow, and legal penalties can be imposed on such drivers if they fail to do this.

However, many drivers fail to switch on their headlights under such conditions, for whatever reason, and this constitutes a continuing and needless hazard both to themselves and to other road users.

It is therefore a primary object of the present invention to provide means whereby the headlights of a motor vehicle will be switched on automatically when ambient conditions of rain or fog require such action to be taken. The invention is based upon an appreciation of the fact that under conditions when visibility is curtailed sufficiently by rain or fog to require the headlights to be switched on, the driver will need to use his windscreen wipers. The essence of the present invention therefore lies in the provision of electrical circuit means adapted to be connected between the headlamp circuit of a vehicle and the windscreen wipers or some other component which is responsive to actuation of the windscreen wipers.

In its broadest form the present invention comprises a switching circuit or switching unit connected on the one hand to the electrical circuit which incorporates the vehicle headlights, and on the other hand to the windscreen wipers of the vehicle or to a component which is responsive to actuation of the windscreen wipers.

Preferably, the switching device or unit is constructed and arranged so that it initiates the switching on of the vehicle headlights only after the windscreen wipers have been used continuously for a preselected time interval. This may be of the order of 1 to 2 minutes for example, preferably about 121 minutes. This means that occasional use of the wipers, for example just to clear the windscreen of dirt, does not cause illumination of the headlights.

In the case of intermittent use of the windscreen wipers, for example in conditions of spray or drizzle, one can provide for either of two alternatives. On the one hand, one can arrange that the switching device does not respond at all to such intermittent action of the windscreen wipers, on the basis that ambient conditions which only require intermittent use of the wipers will not require use of the headlights.

On the other hand, one can arrange that the switching device includes circuit means which are advanced gradually towards a threshold level, at which the switching device will initiate the switcing on of the headlights.

It should be appreciated that the automatic switching on of the headlights by the device of the present invention does not inhibit the manual positive operation of the headlamp switch by the driver under any circumstances. The device of the present invention is intended primarily as a "backup" device which will automatically initiate a desirable function if the driver should on.;t to do so.

Although the switching device of the present invention can be embodied in various forms, one presently preferred embodiment of switching device in accordance with the invention will now be described by way of example and with reference to the accompanying drawing which is a schematic circuit diagram of the device.

Referring to the drawing, the switching device, which is indicated generally at 10, comprises a rectifier 1 2 which has one junction 1 2b connected to earth and the opposite junction 1 2a connected to a wire or lead 14. This lead 14 is connected to the windscreen wiper motor or coil, on the nonearth side of the battery, so that when the wiper motor is energised by the driver switching on the wipers a 12-volt signal will be passed by way of the lead 14 to the rectifier 12. The lead 14 can be connected directly to the wiper motor switch or into the wiring harness. The use of the rectifier 12 means that the same switching unit can be used regardless of whether the motor vehicle has a positive or a negative earth system.

A switching circuit is connected across the other two junctions 1 2c and 1 2d of the rectifier bridge 1 2. An RC circuit comprising a resistance R1 and a capacitance C is connected across the rectifier junctions 1 2c and 1 2d, and a further resistance R2 is connected in parallel with R1C. The junction between resistance R, and capacitance C is connected to a field effect transistor T1. Also connected to the field effect transistor T1 is a transistor T2 and a Zener diode D1. The collector of the transistor T2 is connected to a relay 1 6. The relay contacts are connected to two output wires or leads which are arranged to be connected either to the headlight on/off switch or to some other appropriate part of the headlight circuit.

In operation, when the driver switches on the vehicle windscreen wipers, a 12volt signal is passed over lead 14 to the rectifier 12, and capacitance C charges up through resistance R,.

The values of the circuit components are chosen so that after a preselected interval of time the capacitance C will have charged up to a threshold value, at which the transistor T, turns on. Up until this moment the Zener diode D1 holds the transistor T1 off. Resistor R2 is kept low in value to permit fairly rapid discharge of capacitance C. The preselected interval of time may be of whatever length one desires, although a period of between 1 and 2 minutes, desirably around 1 F minutes, has proved suitable. When transistor T1 turns on, a signal is fed to the base of transistor T2, turning transistor T2 on and energising the relay 16.

Because the relay contacts are connected directiy across the headlight switch or equivalent part of the headlight circuit, the headlights are immediately switched on and remain on until the switching device is deactivated by the windscreen wipers being turned off.

As mentioned above, in the case of intermittent operation of the windscreen wipers, one can either arrange the switching circuit to ignore such intermittent signals, or alternatively it can be arranged that these intermittent signals gradually charge up the capacitance C until the threshold value is reached, whereupon the headlights will be switched on as explained above.

The switching device of the present invention can be embodied in a relatively small modular unit, having just three, or perhaps four, connection wires. In the 3-wire unit, two of these wires, i.e.

those connected to the relay contacts, are connected across the headlight switch or to an equivalent part of the vehicle circuit, while the remaining wire is the lead 14 which is connected to the wiper motor or other component responsive to the operation of the wipers. A fourth wire may be needed for certain vehicles where the existing wiring is such that an additional connection must be made to ensure that the side and/or rear lights come on at the same time as the headlights.

It should be appreciated that the particular circuit described above is given by way of example only, and that various changes or modifications can be made within the scope of the present invention. In its broadest aspect the invention is directed to a means whereby the headlights of a motor vehicle are switched on automatically in response to actuation of the windscreen wipers.

For example, in one alternative embodiment, instead of relying upon the building up of a voltage on a capacitance to initiate the required action, one could arrange for the reciprocating motion of the wipers to generate a pulsed signal which is fed to a counting device designed so that when a particular count state is reached the headlights are switched on. The counting device could be a count-up counter or a count-down counter.

Additionally, although reference has been made above to a 12 volt supply and 12 volt input signal, the invention is applicable equally well to vehicles which have a different value power supply, e.g.

a 6 volt or 24 volt battery.

Claims

1. A vehicle electrical switching circuit comprising first connection means connected to the electrical circuit which incorporates the headlights of the vehicle, second connection means connected to the windscreen wipers of the vehicle or to a component which is responsive to actuation of the windscreen wipers, and timing means having an input from said second connection means and an output to said first connection means and arranged to provide an output signal effective to switch on the headlights in response to an input representing operation of the windscreen wipers for a predetermined time.

2. A circuit as claimed in claim 1, in which said timing means is arranged to provide said output signal only after the wipers have been operative continuously for a preselected time period.

3. A circuit as claimed in claim 1 or 2, which includes means which are advanced gradually towards a threshold level by the receipt of signals from said second connection means, at which threshold level the switching on of the headlights is initiated.

4. A circuit as claimed in claim 3, in which said advanced means comprises a capacitor responsive to the build-up of a voltage.

5. A circuit as claimed in claim 3, in which said advanced means comprises a counting device responsive to signal pulses.

6. A circuit as claimed in any preceding claim, in which said timing means comprises an RC circuit having an ouput via transistor means to a relay.

7. A circuit as claimed in any preceding claim, which includes a rectifier between said second connection means and said timing means.

8. A vehicle electrical switching circuit substantially as hereinbefore described with reference to the accompanying drawing.