GB2266924A

GB2266924A - Vehicle immobilisation system.

Info

Publication number: GB2266924A
Application number: GB9210031A
Authority: GB
Inventors: Christopher J Woodhouse
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1992-05-09
Filing date: 1992-05-09
Publication date: 1993-11-17
Also published as: GB9210031D0

Abstract

The unit 10 has input leads 12 connecting various essential circuits 14 of the vehicle to the connector block 20. By linking different combinations of pins 26 together by wiring links 24 the electronic relays 18 are connected to some of the essential circuits 14 such that a thief would not know which particular combination of essential circuits are disabled for any particular unit. The unit 10, including the wire links, is encapsulated in an opaque resin after assembly. The essential circuits are enabled by entering a predetermined code into the coded control interface 22 by means of a numeric keypad or a key operated device which results in the relays 18 being energised to complete the essential circuits to which they are connected and permit the vehicle to start. Another code entered into the control interface 22 initiates a diagnostic routine whereby a code is transmitted indicating the state (open or closed) of the relays to assess if the unit has failed in a case where the vehicle will not start. <IMAGE>

Description

Title VEHICLE IMMOBILISATION SYSTEM Field of the invention The present invention relates to a vehicle immobilisation system to prevent theft and unauthorised driving of the vehicle.

Background of the invention Key operated anti-theft devices are known which immobilise a vehicle by impairing the function of an essential circuit.

The function of a circuit can be impaired by cutting off an essential connection, for example one taking a live supply to the fuel pump, or by making a bad connection for example one which earths a low tension terminal of the coil or the signal from a sensor.

Any such immobilisation can unfortunately be overcome by an experienced thief and known systems rely on complexity to make the task of "hot wiring" the vehicle as time consuming as possible. Instead of interfering with a single essential circuit, numerous circuits are impaired using unmarked wiring. Each of the wires from the immobilisation system must be traced to know where it leads in order to determine whether it needs to be disconnected, connected to live, or connected to earth for the vehicle to operate. The time taken to undertake this task and the unique vehicle installation are relied upon to deter the would be thief.

Such a system however suffered from problems of cost, lengthy installation and unreliability. The cost results from the large number of relays that are required to alter the connections in the various protected circuits. The unreliability is caused by the fact that immobilisation system comprises numerous connections and relay contacts malfunction of any one of which will suffice to prevent vehicle operation.

Object of the invention The present invention seeks to provide an immobilisation system which offers the advantage of presenting the would be thief with a large number of wires to trace in order to complicate the task of bypassing the immobilisation system, but which reduces the problems of cost, unreliability and lengthy installation.

Summary of the invention According to the present invention, an immobilisation system comprises a unit having a large number of input leads to be connected to various essential circuits of the vehicle and switching means within the unit operative when the vehicle is to be immobilised to alter the connections of the input leads so as to prevent operation of the vehicle, characterised in that the switching means are connected to only some of the input leads so that the immobilisation system impairs the operation of only some of the essential circuits connected to the unit by the input leads and the unit being customisable during manufacture so that immobilisation systems fitted to different vehicles may impair the operation of different combinations of essential circuits.

In the system of the invention, though only some of the essential circuits connected to the immobilisation system have their function impaired, there is no way for a would be thief to know which circuits are affected in any given vehicle and the task of hot wiring the vehicle is as time consuming as if all the essential circuits were impaired.

However, the number of relays required is reduced and therefore the cost of the system is reduced and the reliability is improved.

Preferred features of the invention The switching means are preferably electronically controlled relays connected to a circuit for actuating the relays in response to receipt of an encoded signal.

The customisation of the units may conveniently be achieved by varying the configuration of wire links connecting the relays to selected ones of the input leads, the selection being dependent upon the position of the wire links.

To prevent tampering with the internal circuitry of the unit, it is preferred to set at least the relays and the wire links connecting the relays to the input lead in an opaque potting resin.

Brief description of the drawing The invention will now be described further, by way of example, with reference to the accompanying drawing which is a diagrammatic representation of an immobilisation system in accordance with the invention.

Description of the preferred embodiment The immobilisation system shown in the drawing comprises a sealed unit 10 with a bundle of wires 12 leading from it.

The wires 12 are marked at their ends with identifiers 14 which indicate the circuit to which each individual wire is to be connected but the wires 12 are indistinguishable from one another in other respects. Once installed in a vehicle, all one can see of the immobilisation system is the sealed unit 10 and a bundle of identical wires leading from it in all directions. If installed during manufacture of the vehicle, the wires 12 may be incorporated into the wiring loom, making them still more difficult to trace.

Within the unit 10, there is mounted a circuit board 16 which carries two so-called smart relays 18, a connector block 20 for the wires 12 and a circuit 22 which acts as a decoder and can carry out certain diagnostic functions.

The smart relays 18 are connected to the connector block by wire links 24 which are soldered between posts 26 on the circuit board 16. Not all the posts are connected to one another because it is possible to interfere with only two of the circuits to which the wires 12 lead, there being only two smart relays 18 in the described embodiment. The relays 18 can however be connected to different combinations of input wires 12 by appropriate selection of the wire links 24 so that different essential circuits are prevented from functioning correctly in difference installations.

The entire circuitry, including the wire links 24 is encapsulated in an opaque resin after assembly so that the components of the circuit can neither be accessed nor inspected when fitted to a motor vehicle.

In use, the unit 10 is mounted in an inaccessible position in a vehicle, such as behind the dashboard, and is wired into the wiring harness of the vehicle. When the vehicle is immobilised, the smart relays adopt a first state in which some of their relay contacts are closed and others are open.

These contacts are connected through the input wires 12 into essential circuits of the vehicle and for as long as the relays 18 remain in this first state the vehicle cannot be started. For example, the contacts may be arranged to disconnected the power supply to a fuel pump or to the fuel management system, to earth the low tension winding of an ignition coil or to earth the signal from a crankshaft position sensor.

There are many such circuits connected by the various wires 12 to the unit 10 but only some of them are active in any given installation. The remaining wires are dummy leads serving no purpose other than to confuse the would be thief.

It is now however possible for a thief to establish which of the wires are active and which are not as the unit 16 itself cannot be inspected and depending on how the wire links 24 have been inserted, different items of essential equipment will be prevented from operating in different vehicles. The only way of by-passing the immobilisation system reliably is to trace each and every one of the wires 12 and the time taken to undertake this task will deter many theft attempts.

The authorised user is provided with a numerical keypad or a key operated device to enable him to send a predetermined code to the control and interface circuit 22 which recognises this code and sends a signal to the smart relays 18 to change their states. This allows their relay contacts to complete the essential circuits to which they are connected and permits the vehicle to start.

If a vehicle ever fails to start, there is always the possibility that the fault lies within the immobilisation unit 10. Because this unit cannot be inspected, the interface circuit is designed to perform certain diagnostic tests on the unit. In particular, on receiving a predetermined code which initiates a diagnostic test, a code may be transmitted indicating the state (open or closed) of the individual relay contacts. While such information would allow a fault within the unit 10 to be detected, it offers no assistance to a thief to enable the immobilisation to be circumvented.

Claims

1. An immobilisation system comprises a unit having a large number of input leads to be connected to various essential circuits of the vehicle and switching means within the unit operative when the vehicle is to be immobilised to alter the connections of the input leads so as to prevent operation of the vehicle, characterised in that the switching means are connected to only some of the input leads so that the immobilisation system impairs the operation of only some of the essential circuits connected to the unit by the input leads and the unit being customisable during manufacture so that immobilisation systems fitted to different vehicles may impair the operation of different combinations of essential circuits.

2. An immobilisation system as claimed in claim 1, wherein the switching means are electronically controlled relays connected to a circuit for actuating the relays in response to receipt of an encoded signal.

3. An immobilisation system as claimed in claim 1 or 2, wherein customisation is achieved during assembly by varying the configuration of wire links connecting the relays to selected ones of the input leads, the selection being dependent upon the position of the wire links.

4. An immobilisation system as claimed in any preceding claim, wherein at least the relays and the wire links connecting the relays to the input leads are encapsulated in an opaque potting resin.

5. An immobilisation system constructed, arranged and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawing.