GB2110891A - Electrical wiring system - Google Patents

Abstract

A vehicle wiring system has a central interconnection unit 11, local control units 12-15 disposed on the vehicle adjacent respective groups of electrical loads 16-27 of the vehicle, electrically operated switching devices carried by said local control units and electrically connected to respective loads of their respective load group, power supply leads 11a-15a each supplying power to a respective local control unit, and by way of that local control unit to the electrically operated switching devices thereof, manually operable switches 44 for controlling operation of the loads of said load groups, means 44a electrically connecting said manually operable switches to said central interconnection unit 11 and low power signal carrying leads 36-39 connecting said central interconnection unit to said local control units, said central interconnection unit providing appropriate electrical connections between said manually operable switches and said signal leads whereby operation of a manually operable switch causes, by way of said means, said central interconnection unit, and one or more of said signal leads, operation of an appropriate one or more electrically operated switching device at appropriate one or more local control units to effect switching of the power supply to one or more loads of said local groups. <IMAGE>

Description

SPECIFICATION Electrical wiring system This invention relates to an electrical wiring system for a vehicle, particularly but not exclusively a road vehicle.

In a conventional vehicle wiring system electrically insulated leads are collected together to form a harness, the leads making electrical connections between the battery of the vehicle, and the current consuming units of the vehicle, for example the lights, the horn, and various electric motors, by way of fuses and appropriate control switches. Thus the lead or leads associated with any one of the current consuming units must be capable, throughout the length of the lead, of carrying the maximum current which the respective unit may draw in use. The switches similarly are intended to carry the respective maximum current. The conventional wiring harness is therefore bulky, and additionally is expensive since it involves the use of large quantities of copper in the leads.Moreover, since the majority of the control switches are positioned adjacent the dashboard of the vehicle then in the region of the dashboard of the vehicle the wiring harness if of considerable bulk and complexity. A bulky harness has a relatively high degree of mechanical stiffness, and thus can prove difficult and therefore expensive to install in the vehicle.

In an attempt to overcome the disadvantages of the conventional harness system there has been proposed a wiring system utilizing multiplexing. In a proposed multiplexing sstem a single power lead extends in a ring around the vehicle, and at predetermined points around the ring lead power is tapped off into receiver modules each associated with a group of current consuming units. A central transmitter module receives signals from the various control switches and in accordance with these signals supplies coded control pulses around a ring of control leads. The control leads are few in number, and follow the ring defined by the power lead. Thus the receiver modules receive the control pulses by way of the control ring and decode those pulses which are relevant to their respective current consuming units.Switching takes place at the receiver modules in accordance with the control pulses to supply power from the power lead to the appropriate current consuming units. The presently proposed multiplexing systems suffer from the disadvantage of being expensive, probably three times the cost of an existing equivalent harness system, and on the basis of existing technology the proposed transmitting and receiving modules are of suspect reliability, particularly in that radiated interference from external sources may give rise to spurious pulses in the control ring causing eitherfailure of the receivers to recognise correct control pulses or alternatively giving rise to unwanted operation of a receiver or receivers with consequential unwanted operation of current consuming units.The cost of such systems thus must take account of the efficient screening which is necessary to minimise problems arising from radiated interference.

It is an object of the present invention to provide a wiring system wherein the aforementioned disadvantages of both the conventional harness system, and the proposed multiplexing system are minimised.

A vehicle wiring system according to the invention comprises a central interconnection unit, a plurality of local control units, said local control units being disposed on the vehicle adjacent respective groups of electrical loads of the vehicle, electrically operated switching devices carried by said local control units and electrically connected to respective loads of their respective load group, a plurality of power supply leads, each power supply lead supplying power to a respective local control unit, and by way of that local control unit to the electrically operated switching devices thereof, a plurality of manually operable switches for controlling operation of the loads of said load groups, means electrically connecting said manually operable switches to said central interconnection unit and low power signal carrying leads connecting said central interconnection unit to said local control units, said central interconnection unit providing appropriate electrical connections between said manually operable switches and said signal leads whereby operation of a manually operable switch causes, by way of said means, said central interconnection unit, and one or more of said signal leads operation of an appropriate one or more electrically operated switching device at appropriate one or more local control units to effect switching of the power supply to one or more loads of said load groups.

The accompanying drawing is a simplified, diagrammatic representation of a road vehicle wiring system in accordance with one example of the present invention.

Referring to the drawing, the wiring system which is illustrated is the wiring system of a road vehicle, for example, a car. For the purposes of this description the system is simplified in that some of the current consuming units normally found on a car are omitted from the drawing. The system includes a central interconnection unit 11 which, conveniently, will be positioned within the dashboard assembly of the vehicle. Additionally, there are first, second, third and fourth local control units 12-15. The current consuming units of the vehicle are separated into groups insofar as their control is concerned, each group being associated with a respective local control unit.Thus the first local control unit (L.C.U.) 12 is positioned in the engine compartment of the vehicle adjacent the left hand side thereof and is associated with the left - hand headlamp, sidelamp, and indicator lamp cluster 16, the electric pump 17 for supplying washing liquid to the windscreen of the vehicle and the vehicle horn 18. The L.C.U. 13 is associated with the right - hand headlamp, sidelamp, and indicator lamp cluster 19, the electric pump 21 The drawing originally filed was informal and the print here reproduced is taken from a later filed formal copy.

for supplying washing liquid to both the left and right hand headlamp lenses of the vehicle, the ignition coil 22 of the ignition system of the vehicle, and the engine 23 of the vehicle. The L.C.U. 13 is conveniently positioned within the engine compartment of the vehicle, but to the right - hand side thereof. The third L.C.U 14 is conveniently positioned within the dashboard assembly of the vehicle and has associated with it the windscreen wiper motor 24 and the fan motor 25 of the vehicle heating and ventilation system. The fourth L.C.U. 15 is conveniently positioned in the boot of the vehicle, and has associated with it the left - hand 26 and right - hand 27 rear lamp clusters of the vehicle, the fuel tank level sensor 28, the fuel pump 29, the heater 31 of the rear window, and the rear number plate lamps 34.

Each of the central interconnection unit 11 (C.l.U.) and the four L.C.U.'s includes a printed circuit board having a live rail. In the case of a negative earth vehicle wiring system then the live rail of each of the printed circuit boards will be a positive rail. The live rail of each of the printed circuit boards is supplied with power from the battery of the vehicle by way of a circuit breaker of a circuit breaker assembly 35. A battery main power lead 36 extends from one pole of the battery to the assembly 35 and supplies each of the circuit breakers. Each of the circuit breakers is connected by way of a high current capacity power lead to the live rail of the appropriate printed circuit board.Thus with reference to the drawing the power lead 12a interconnects a circuit breaker of the assembly 35 and the live rail of the printed circuit board of the L.C.U. 12. Similarly the live rail of the C.l.U. 11 is connected to the appropriate circuit breaker of the assembly 35 by a power lead 1 lea.

Power leads 13a, 14a, and 15a make similar connectionstothe L.C.U.'s 13,14 and 15. The printed circuit board of each of the L.C.U.'s 12 - 15 carries a plurality of relays each of which, upon receipt of an appropriate control signal, makes an electrical connection between the live rail on the board and an appropriate terminal region of each of the printed circuit boards is a small section of conventional wiring harness making the electrical connections between the output terminals of each board and the appropriate current consuming units associated therewith. The leads of the conventional harness sections are indicated in the drawing by the reference numeral of their respective current consuming unit with the added suffix a.In the case of the L.C.U. 13 more than one lead extends to the engine 23, and in the drawing two are shown, the second being labelled 23b. It will be recognised that when a relay of any of the four L.C.U.'s is closed by receipt of an appropri ate signal (to be described in more detail later) it will cause energisation of the appropriate current con suming unit by way of the respective lead. It should be understood that while electromagnetic relays are mentioned as the mechanism whereby switching occurs at the L.C.U.'s 12 - 15 the electromagnet relays could be replaced if desired by solid state semi-conductor switching devices Radiating from the C.l.U. 11 are four ribbon cables 36,37,38, and 39.Each of the ribbon cables includes a large number of very fine, individually insulated, low current capacity lead, the cables 36,37,38, and 39 making connections from the printed circuit board of the C.I.U. 11 to respectively the printed circuit boards of the L.C.U.'s 12, 13, 14, and 15. The C.l.U. is conveniently mounted within the dashboard of the vehicle, and thus is closely adjacent the dashboard controls and instruments of the vehicle.

Flexible printed circuits, or ribbon cable connections 42a, 44a, 45a extend from the C.l.U. into the instrument and warning light assembly 42, Ihe switch panel 44, and the steering column monted switches 45 of the vehicle. Connections between the ribbon cables 3639 and their respective printed circuit boards both atthe L.C.U.'s and at the C.l.U.

are conveniently made by edge connectors so arranged as to be couplable only in the correct orientation. The printed circuit of the C.l.U. establishes the necessary connections between the ribbon cables 36-39 and the ribbon orflexable printed circuit connection 41. The connection 41 may be connected to the printed circuit board of the C.l.U. 11 by an edge connector, or alternatively may be permanently connected thereto. There are known techniques whereby rigid printed circuit boards and flexible printed circuits are produced integral with one another. One end of each of the relaywindings on each of the printed circuit boards of the L.C.U.'s is connected to its respective live rail, the other end being connected to its appropriate wire of the respective ribbon cable.Each of the switches on the switch panel 44 and the steering column mounted switch assembly 45 is connected to the appropriate ribbon cable wire byway of the conductors in the connections 44a, 45a and the conductors of the printed circuit board of the C.I.U. 1 1. Each of the switches has its other pole earthed. Each of the current consuming units has its return circuit made in the conventional manner, thus in the case of the lamps and the horn there will be an earth return by way of the body of the vehicle. It will be recognised therefore that closure of any of the switches will result in energisation of the appropriate relay.

Taking the horn control switch as an example, then closure of the horn control switch which will probably be part of the steenng column switch assembly 45, will, by way of the appropriate conductor of the connection 45a, the printed circuit of the C.l.U.11, and the appropriate wire of the ribbon cable 36, cause energisation of the appropriate relay of the L.C.U. 12. Energisation of the relay will complete the electrical circuit from the power lead 12a to the distribution lead 28a thus energisingthe horn.

Incorporated within the system are certain circuits which do not require switching. Thus although not shown in the drawing it will be recognised that there is a class of instruments such as the temperature gauge, the oil pressure guage, and the tachometer which do not have a switch as such, but which have a signal sender for example on the engine.Taking the case of the water temperature gunge then a temperature sensor on the water jacket of the engine is the sender, and signals from the sendor pass along appropriate leads, for example the lead 236 two the L.C.U. 13. On the printed circuit board of the L.C.U. there are tracks which extend directly from an input terminal to an output terminal, and thus in the case of the water temperature gauge a direct connection is made from the lead 23b by way of the printed circuit board of the L.C.U. to the ribbon cable 37.The temperature signal thus passes along an appropriate wire of the cable 37, an appropriate conductor of the printed circuit of the C.l.U. 11, and an appropriate conductor of the connection 42a to the temperature gauge of the panel 42.Moreover, it will be recognised that certain switches control a number of current consuming units. Thus for example the side light switch may be incorporated in the steering column control switch assembly 45, controls energisation of a bulb of each of the lamp units 16, 19,26, and 27. Although only one conductor of the connection 45a extends from the side lamp switch to the printed circuit of the C.I.U. 11 that conductor is electrically connected by way of the printed circuit of the C.l.U. 11 to respective wires of each of the four ribbon cables 36-39. In this respect it will be recognised that the leads 16a, 198, 26a and 27a are in fact representative of a number of distribution leads. Similar comments apply to the operation of the flashing direction indicator lamps of the vehicle.

Since the four flashing indicator lamps are controlled by respective relays of the four L.C.U.'s then the timer switch which provides the intermittent signal energising the flashers can be positioned on the printed circuit board of the C.l.U. Moreover, while a thermally operated timer switch would normally be utilized to control the flashers it is to be understood that an integrated circuit timing device could be substituted if desired. Similarly, if the windscreen wiping arrangement is to include an intermittent wipe facility then the timing arrangement either electronic or thermoelectric can be incorporated in the circuit of the C.l.U.

As mentioned previously the drawing represents a considerable simplification of a practical wiring system. However, it is believed that the addition to the drawing, and the foregoing description, of each and every item of the system would not add to the clarity. It is to be recognised however that many additional current consuming units, indicators, and control switches will be incorporated in a practical version of the system. The main circuit breakers control the supply of power to the L.C.U.'s and the C.l.U. and thus provide overall protection. However, each of the individual relay output circuits to the current consuming units of the L.C.U.'s may, if desired, incorporate an individual protective fuse or equivalent protective device. Moreover if desired the circuit breakers could be replaced by fuses or similar protective devices.

It will be understood that the individual wires of the ribbon cables 36-39 are very considerably finer than the wires of a conventional harness, and thus the ribbon cables are compact, and very flexible.

Thus the dashboard assembly of the vehicle is considerably simplified by the removal of the great bulk and complexity of a conventional harness.

Moreover, the system is relatively simple to install and maintain by comparison with a conventional harness, and exhibits a considerable saving in weight, and usage of copper by comparison with the conventional harness.

While ribbon cable is preferred for the connections between the C.l.U. and the L.C.U.'s it is to be understood that separate wires individually insulated and of a similar diameter and current carrying capacity to the wires of the ribbon cable could be utilized if desired.

Certain circuits of the system may interact to give unwanted feed back paths. Such feed back paths can be prevented by the appropriate use of diodes in those circuits where the problem may occur.

High current circuits of the vehicle such as the battery charging circuit and the starter motor circuit do not form part of the system, such circuits being individually wired in the conventional manner.

Claims (2)

1. A vehicle wiring system comprising a central interconnection unit, a plurality of local control units, said local control units being disposed on the vehicle adjacent respective groups of electrical loads of the vehicle, electrically operated switching devices carried by said local control units and electrically connected to respective loads of their respective load group, a plurality of power supply leads, each power supply lead supplying power to a respective local control unit, and by way of that local control unit to the electrically operated switching devices thereof, a plurality of manually operable switches for controlling operation of the loads of said load groups, means electrically connecting said manually operable switches to said central interconnection unit and low power signal carrying leads connecting said central interconnection unit to said local control units, said central interconnection unit providing appropriate electrical connections between said manually operable switches and said signal leads whereby operation of a manually operable switch causes, by way of said means, said central interconnection unit, and one or more of said signal leads operation of an appropriate one or more electrically operated switching device at appropriate one or more local control units to effect switching of the power supply to one or more loads of said load groups.

2. A vehicle wiring system substantially as hereinbefore described with reference to the accompanying drawings.