WO2004056608A1

WO2004056608A1 - Method and device for connecting a trailer lighting system to a vehicle lighting system

Info

Publication number: WO2004056608A1
Application number: PCT/NL2003/000857
Authority: WO
Inventors: Peter De Bruijn; Glenn Raymond Van Maenen
Original assignee: Ecs Electronics B.V.
Priority date: 2002-12-06
Filing date: 2003-12-04
Publication date: 2004-07-08
Also published as: NL1022097C1; AU2003289676A1

Abstract

The invention relates to a method for connecting a trailer lighting system to a vehicle lighting system, wherein the function of a part of the vehicle lighting system, for instance the rear fog lights, is taken over b7y a corresponding part of the trailer lighting system. A power supplied by a power source to the relevant part of the vehicle lighting system is herein compared to a power demanded by the corresponding part of the trailer lighting system and, when the supplied power is greater than the demanded power, the excess power is dissipated or fed back to the power source. The excess power can for instance be dissipated in another, non-corresponding part of the trailer lighting system, for instance a tail light unit. The invention also relates to a device for performing this method.

Description

METHOD AND DEVICE FOR CONNECTING A TRAILER LIGHTING SYSTEM TO A VEHICLE LIGHTING SYSTEM

The invention relates to a method for connecting a lighting system of a trailer to a lighting system of a vehicle pulling the trailer, wherein the function of at least a part of the lighting system of the vehicle is taken over by a corresponding part of the lighting system of the trailer. Such a method of connecting the lighting systems of trailer and vehicle is already known in practice.

When a trailer is coupled to a tractive vehicle and the lighting systems are electrically connected, so that the lighting of the trailer is controlled from the vehicle, special legal requirements apply for the lighting of the thus formed combination. In specific countries it is thus mandatory, when the trailer is equipped with one or more fog lights, to switch off the rear fog lights of the vehicle. This prevents the rearward view of the driver of the vehicle being impeded by the reflection of the light from the - relatively bright - rear fog lights against the front side of the trailer. This applies particularly when the trailer is a caravan, which is usually light in colour and forms a large reflective surface.

Most modern vehicles are however equipped with monitoring systems which monitor the operation of the lighting and which generate an error message when a malfunction is determined in one or more lamps. If the rear fog lights of a vehicle are now switched off when a trailer is coupled thereto, the monitoring system will then interpret this as a malfunction, which results in an error signal. Such an error signal will not be generated when the function of the rear fog lights of the vehicle are wholly taken over by a corresponding number of equally strong fog lights of the trailer. The same power will in that case be taken up as if the rear fog lights of the vehicle were in operation, so that the load of the lighting system remains the same, and the monitoring system does not therefore detect any deviation from the normal operating status .

When however the trailer is provided on only one side with a fog light, the power taken up thereby will only be half the power normally taken up by the rear fog lights of the vehicle, which is considered by the monitoring system as an indication that a rear fog light of the vehicle has failed, whereupon an error message then ensues. Such an error message, which is displayed on the instrument panel of the vehicle, is irritating in that it distracts the driver. There is moreover the risk that a malfunction does indeed occur in one of the other lamps of the vehicle but which then remains unnoticed because the driver will assume that the error message is the result of the rear fog lights being switched off during the coupling of the trailer.

The invention therefore has for its object to provide a method for connecting the lighting of a trailer to that of a vehicle, wherein unnecessary error messages, resulting from deliberate switching-off of a part of the vehicle lighting, for instance the rear fog lights, are avoided. This is achieved according to the invention in that a power supplied by a power source to the relevant part of the vehicle lighting system is compared to a power demanded by the corresponding part of the trailer lighting system and, when the supplied power is ^greater than the demanded power, the excess power is dissipated or fed back to the power source. By thus dissipating or feeding back by one method or other a possible difference between the power taken up during normal use of the rear fog lights of the vehicle and the power actually taken up by the fog lighting of the trailer, particularly when it has only one fog light, this difference is as it were "concealed" from the monitoring system of the vehicle lighting, thus preventing unnecessary error messages. The excess power is preferably dissipated in another, non-corresponding part of the trailer lighting system. This power is in this way used efficiently, for instance to turn on one or more of the tail lights of the trailer.

A simple control is achieved when a power taken up by the corresponding part of the trailer lighting system is compared to a first limit value, and a current supplied by the power source is dissipated or fed back when the taken-up power is less than the first limit value, which is chosen for instance in the order of 2.5 A.

In order to prevent a part of the lighting of the vehicle being switched off in cases where the trailer is provided with no corresponding lighting at all, it is recommended that in the absence of the corresponding part of the trailer lighting system the take-over of function is prevented and the power is taken up by the relevant part of the vehicle lighting system.

This can be regulated in simple manner by comparing the current taken up by the corresponding part of the trailer lighting system to a second limit value, and by having the current supplied by the power source taken up by the relevant part of the vehicle lighting system when the taken-up current is less than the second limit value which is below the first limit value and which can be chosen to be for instance about 1.2 A.

The invention also relates to a device for performing the above described method. Starting from a usual device for connecting a lighting system of a trailer to a lighting system of a vehicle pulling the trailer such that the function of at least a part of the lighting system of the vehicle is taken over by a corresponding part of the lighting system of the trailer, this is achieved according to the invention by adding means for comparing a power supplied by a power source to the relevant part of the vehicle lighting system to a power demanded by the corresponding part of the trailer lighting system, and means connected controllably to the comparing means for dissipating or feeding back the excess power to the power source when the supplied power is greater than the demanded power.

In a structurally simple connecting device in accordance with this principle, the dissipation means comprise at least one circuit for breaking the connection between the power source and the relevant part of the vehicle lighting system on the one hand and connecting another, non- corresponding part of the trailer lighting system to the power source on the other. In order to allow a ready comparison of the powers, the comparing means advantageously comprise at least one ammeter.

The dissipation circuit preferably then comprises a first switching element for connecting the other, non- corresponding part of the trailer lighting system to the power source when the ammeter measures a current taken up by the corresponding part of the trailer lighting system that is lower than a first limit value. This limit value can for instance be 2.5 A, which is a normal current when the trailer has two fog lights.

In addition, the dissipation circuit can advantageously comprise a second switching element for connecting the power source and the relevant part of the vehicle lighting system when the ammeter measures a current taken up by the corresponding part of the trailer lighting system that is lower than a second limit value below the first one. When this second limit value is set for instance at 1.2 A, it forms a reliable indication of the complete lack of fog lights on the trailer.

The invention is now elucidated on the basis of an embodiment, wherein reference is made to the annexed drawing, in which: Fig. 1 shows a schematic representation of a lighting system on the rear of a vehicle and a lighting system of a trailer connected thereto via a device according to the invention, and

Fig. 2 shows a detailed circuit diagram of the connecting device of fig. 1.

A device 1 (fig. 1) for connecting a lighting system 2 of a trailer 3 to a lighting system 4 of a vehicle 5 pulling the trailer 3 is embodied such that during normal use the function of a part of the vehicle lighting system 4, in particular the rear fog lights 6L, 6R, is taken over by a corresponding part, thus the fog lights 7L, 7R, of trailer lighting system 2.

In addition to rear fog lights 6L, 6R, the vehicle lighting system 4 normally comprises on either side of vehicle 5 one or more tail lights 8L, 8R and brake lights 9 (only one of which is shown here) . In addition, lighting system 4 further comprises indicator lights and generally one or more reverse lights, which are not of significance for the invention and are therefore not shown. In similar manner the trailer lighting system 2 comprises on either side one or more tail lights 10L, 10R and brake lights 11 (only one being shown here also) , indicator lights (not shown) and possibly also one or more reverse lights.

So as not to add an extra load to the vehicle lighting system 4 when a trailer 3 is coupled to vehicle 5, tail lights 10L, 10R and brake lights 11 of trailer 3 are powered respectively by buffer circuits 11L, 11R and 12 via respective lines 29L, 29R and 30. These buffer circuits 11L, 11R, 12 are provided with on-board voltage V of vehicle 5 via a line 13 with branches 14L, 14R, 15, and are controlled by control signals transmitted via lines 16L, 16R, 17 respectively from the corresponding parts of the vehicle lighting system 4.

The presence of trailer lighting system 2 is as it were "concealed" from vehicle lighting system 4 by interposing the buffer circuits 11L, 11R, 12. This is important in preventing the operation of a malfunction detection system hereby being influenced, this being included as standard in vehicle lighting system 4 for detecting and informing the driver of vehicle 5 of faults in one or more lights . The fog lighting 7 of trailer 3 is not however powered via a buffer circuit, but directly from the vehicle lighting system 4 by switching through the power supply for rear fog light 6L, 6R. The reason for this is that in some countries it is required by law, when trailer 3 is provided with fog lights 7, to switch off the rear fog lights 6L, 6R of tractive vehicle 5. The connecting device 1 is therefore provided with a switching element 18, in the shown embodiment a relay, which operates two switches 19L, 19R which are incorporated in power supply lines 20L, 20R of rear fog lights 6L, 6R of vehicle 5. By turning the switches 19L, 19R to the position shown in broken lines, these power supply lines 20L, 20R are connected to a single line 21 which carries the supply voltage for rear fog lights 6L, 6R to the fog lighting 7 of trailer 3. This line 21 has a branch 28 which will be discussed below.

It is however conceivable for the trailer lighting system 2, which will generally be of relatively simple design, to comprise only one or no fog lights at all. In order to determine this, connecting device 1 further comprises comparing means 22 comprising, among other parts, an ammeter 23 which is connected to power supply line 21 and a power supply line 31 of the trailer fog lighting 7. Comparing means 22 are adapted, when it is determined from the output signal of ammeter 23 that trailer 3 is not provided with fog lights,, to displace switching element 18 to its shown rest position in which switches 19L, 19R connect power supply lines 20L, 20R to rear fog lights 6L, 6R of vehicle 5. When a trailer 3 without fog lights is coupled to vehicle 5, this prevents the rear fog lights 6L, 6R of vehicle 5 being switched off, whereby the visibility of vehicle 5 would .-be greatly reduced.

In addition, connecting device 1 is provided with means 24 for dissipating or feeding back a difference between the current determined by ammeter 23 which is taken up by rear fog lights 6L, 6R in normal use and the current which is actually taken up by the fog lighting 7 of trailer 3. Dissipation of this current somewhere or feedback thereof to the power source, generally a battery of vehicle 5, prevents the malfunction detection system, which monitors the vehicle lighting 4, from regarding the lower load as an indication of a malfunction in vehicle lighting system 4.

The current difference could per se be taken up by connecting the line 21 to a resistance. In view of the relatively great power of fog lights 6L, 6R however, such a resistance would generate very much heat which, at the location of connecting device 1 usually at the back of vehicle 5, could not be readily discharged. In addition, the power consumption of vehicle 5 would hereby be increased unnecessarily. In the shown embodiment the excess power is therefore employed usefully by supplying it to another part of trailer lighting system 2. Since this must involve a part of lighting system 2 that is in continuous operation and must be able to take up a considerable power, a choice has been made for one of the tail lights 10R.

The dissipation means 24 comprise for this purpose a switching element 25, here a relay, which operates a switch 26 in power supply line 14R of tail light 10R. Comparing means 22 are adapted to displace switching element 25 from its shown rest position to an operating position shown in broken lines when it is determined from the output signal of ammeter 23 that trailer 3 is only provided with one fog light 7L and the power taken up thereby is thus less than that of both fog lights 6L, 6R of vehicle 5. In this position the switch 26 connects branch 28 of the power supply line 21 to a line 27 to buffer circuit 11R of tail light 10R, so that the sum of the power taken up by this buffer circuit and the power taken up by the single fog light 7L of trailer 3 is substantially equal to the power of the two rear fog lights 6L, 6R of vehicle 5. The malfunction detection system of the vehicle lighting 4 will therefore not indicate a malfunction. The connecting device 1 is shown in detail in fig.

2, in which the different signals signify the following: V supply voltage (9-14 Volt; 15 Ampere) 54 input signal brake light 9

54T output signal trailer brake light 11 (max. 52 W) 54G_L input signal rear fog light 6L 54G_R input signal rear fog light 6R 54G_LR output signal rear fog light 6L (21 W) 54G_RR output signal rear fog light 6R (21 W) 54G_T output signal trailer fog light 7 (21-42 W) 58L input signal tail light 8L 58R input signal tail light 8R 58LT output signal trailer light 10L, (10-52 W) 58RT output signal trailer light 10R (10-52 W) As can be seen here, comparing means 22 comprise two operational amplifiers (OPAMP) 32, 33 which are each supplied with a voltage V_DD which is derived by a voltage divider 34 from the input signal 54G_L. In the shown embodiment these OPAMPs 32, 33 are accommodated in a single housing, so that only one supply voltage V_DD is indicated. The signal 54G_L is present at a first input 35, 36 of each OPAMP 32, 33, while the output signal of ammeter 23 is present at a second input 37, 38 thereof. The output of OPAMP 32 is connected in controlling manner to both switching elements 18, 25, while the output of OPAMP 33 only controls switching element 25. The output signal of OPAMP 32 is presented to a transistor 39 in a power supply line 41 of relay 18 and to a transistor 40 in a power supply line 42 of relay 25. In addition, the output signal of this OPAMP 32 is connected to the collector of a transistor 43, the base of which is connected to OPAMP 33.

Ammeter 23 comprises two transistors 44, 45 which are connected in parallel to a resistance 46 in line 21, 31, and the bases of which are mutually connected. The collector of transistor 45 is connected to OPAMPs 32, 33.

The operation of comparing means 22 and the dissipation circuit 24 controlled thereby is now as follows. When trailer 3 is not provided with a fog light, ammeter 23 generates a high output voltage which is presented to inputs 37, 38 of OPAMPs 32, 33. The reference signal 54G_L attenuated by resistances 47, 48 is present at the other inputs 35, 36 respectively of the OPAMPs. Because the voltage . „ ,

10 at inputs 37, 38 is higher than the reference voltage at inputs 34, 35, the output of the two OPAMPs 32, 33 becomes low, whereby the three transistors 39, 40, 43 remain blocked. This has the result that power supply lines 41, 42 of switching elements 18, 25 remain voltage-free, whereby switches 19L, 19R and 26 occupy their positions shown in full lines. The input signals 54G_L, 54G_R are thus transmitted as output signals 54G_LR, 54G_RR to the rear fog lights 6L, 6R of vehicle 5, while buffer circuit 11R of the trailer tail light 10R is supplied with the on-board voltage V via line 14R.

When trailer 3 is provided with two fog lights 7L, 7R, the output voltage of ammeter 23 presented to inputs 37, 38 of OPAMPs 32, 33 is lower than the voltage 54G_L attenuated by resistances 47, 48 respectively and present at the other inputs 35, 36. The outputs of OPAMPs 32, 33 hereby both become high, whereby transistors 39 and 43 become conductive. Because transistor 39 has been switched into its transmitting state, power supply line 41 of relay 18 becomes current-carrying, whereby this relay 18 is energized and switches 19L, 19R are turned to the position shown in broken lines. Input signals 54G_L, 54G_R are thus transmitted as output signal 54G_L to fog lights 7L, 7R of trailer 3. Because both transistor 39 and transistor 43 are conductive, the transistor 40 is blocked so that power supply line 42 of relay 25 remains voltage-free and switch 26 continues to occupy its position indicated with full lines. Buffer circuit 11R of trailer tail light 10R is therefore also supplied in this situation with on-board voltage V via line 14R. In the case trailer 3 is provided with only a single fog light 7L, the output voltage of ammeter 23 presented to inputs 34, 35 of OPAMPs 32, 33 is lower than the voltage 54G L attenuated by resistance 47 and present at input 35 of OPAMP 32. The output of this OPAMP 32 hereby becomes high, so that transistor 39 becomes conductive. Conversely, the output voltage of ammeter 23 is higher than the reference voltage at input 36 of OPAMP 33 attenuated even further by resistance 48, so that the output of this OPAMP 33 becomes low, and transistor 43 is thus blocked. This in turn has the result that transistor 40 becomes conductive. Since both transistors 39, 40 are thus now switched into their transmitting state, both power supply lines 41, 42 of relay 18, 25 become current-carrying, whereby these relays 18, 25 are energized and the three switches 19L, 19R, 26 are turned to their position shown in broken lines. Input signals 54G_L, 54G_R are thus transmitted as output signal 54G_L to fog light 7L of trailer 3, while buffer circuit 11R of the trailer tail light 10R is supplied in this situation via branch line 28 with signal 54G__L, which is transmitted to its power supply line 27 as output signal 58V_CC.

In this manner the connecting device according to the invention thus enables coupling to a vehicle of random trailers without fog lighting, with a single fog light or with two fog lights without the operation of the lighting system of the vehicle being influenced thereby and without false malfunction messages being generated.

Although the invention is elucidated above with reference to an embodiment, it will be apparent that the invention is by no means limited thereto. The current for the missing fog light could thus be supplied to a part of the trailer lighting other than the tail lights if this part can take up sufficient power. As already noted, the power could also be dissipated in other manner than in a part of the lighting of the trailer. In addition, the current could be fed back by a special circuit to the battery of the vehicle. Finally, this connecting method could of course also be applied for other elements of the lighting systems if similar requirements were to apply thereto. The scope of the invention is therefore defined solely by the appended claims.

Claims

1. Method for connecting a lighting system of a trailer to a lighting system of a vehicle pulling the trailer, wherein the function of at least a part of the lighting system of the vehicle is taken over by a corresponding part of the lighting system of the trailer, characterized in that a power supplied by a power source to the relevant part of the vehicle lighting system is compared to a power demanded by the corresponding part of the trailer lighting system and, when the supplied power is greater than the demanded power, the excess power is dissipated or fed back to the power source.

2. Method as claimed in claim 1, characterized in that the excess power is dissipated in another, non- corresponding part of the trailer lighting system.

3. Method as claimed in claim 1 or 2, characterized in that a power taken up by the corresponding part, of the trailer lighting system is compared to a first limit value, and a current supplied by the power source is dissipated or fed back when the taken-up power is less than the first limit value.

4. Method as claimed in any of the foregoing claims, characterized in that in the absence of the corresponding part of the trailer lighting system the takeover of function is prevented and the power is taken up by the relevant part of the vehicle lighting system.

5. Method as claimed in claim 4, characterized in that the current taken up by the corresponding part of the trailer lighting system is compared to a second limit value, and the current supplied by the power source is taken up by the relevant part of the vehicle lighting system when the taken-up current is less than the second limit value which is below the first limit value.

6. Method as claimed in any of the foregoing claims, characterized in that the corresponding parts of the lighting systems whose powers are compared comprise fog lights, and the other non-corresponding part of the trailer lighting system in which the excess power is dissipated comprises at least one tail light.

7. Device for connecting a lighting system of a trailer to a lighting system of a vehicle pulling the trailer such that the function of at least a part of the lighting system of the vehicle is taken over by a corresponding part of the lighting system of the trailer, characterized by means for comparing a power supplied by a power source to the relevant part of the vehicle lighting system to a power demanded by the corresponding part of the trailer lighting system, and means connected controllably to the comparing means for dissipating or feeding back the excess power to the power source when the supplied power is greater than the demanded power.

8. Connecting device as claimed in claim 7, characterized in that the dissipation means comprise at least one circuit for breaking the connection between the power source and the relevant part of the vehicle lighting system on the one hand and connecting another, non-corresponding part of the trailer lighting system to the power source on the other.

9. Connecting device as claimed in claim 7 or 8, characterized in that the comparing means comprise at least one ammeter.

10. Connecting device as claimed in claims 8 and 9, characterized in that the dissipation circuit comprises a first switching element for connecting the other, non- corresponding part of the trailer lighting system to the power source when the ammeter measures a current taken up by the corresponding part of the trailer lighting system which is lower than a first limit value.

11. Connecting device as claimed in claim 10, characterized in that the dissipation circuit comprises a second switching element for connecting the power source and the relevant part of the vehicle lighting system when the ammeter measures a current taken up by the corresponding part of the trailer lighting system which is lower than a second limit value below the first one.

12. Connecting device as claimed in any of the claims 7-11, characterized in that the corresponding parts of the lighting systems whose powers are compared comprise fog lights, and the other non-corresponding part of the trailer lighting system in which the excess power is dissipated comprises at least one tail light.