GB2286634A - Vehicle theft prevention system - Google Patents

Abstract

A code transmitter carried by the driver permits continuous vehicle operation only when the transmitter is in proximity to a control module in the vehicle. The starter relay or fuel pump circuit, the ignition or engine management system or an automatic gearbox may be inhibited a predetermined period after the transmitter ceases to provide a periodic signal to the control module.

Description

SECURITY DEVICE This invention relates to security devices and in particular to an anti-theft system for a vehicle.

Vehicle theft is a major problem. Over the last five years, the incidence of car crime has risen greatly, associated with the increase in the number of opportunistic thefts, commonly called "joy riding". A newer and perhaps more worrying trend is that of car hijacking, where the occupant of the vehicle is overpowered, often when the car stops at a junction, enabling the thief to obtain all the keys and controls for the security system of an operating vehicle.

Various means of preventing such thefts have been proposed, but most require additional operations with keys or controlling devices.

A conventional security system allows operation, e.g.

access to a building or continuous operation of a vehicle, only in the presence of an independent device, commonly a mechanical key, that can be carried by an authorised user.

In buildings, especially office buildings, it is increasingly common to use a corresponding system in which the independent device is a remote key, i.e. requires no physical interaction with the system but rather, say, modification of a field in a predetermined manner. Such systems are commonly used as "intermediate" security, to allow selective entry while the conventional system is unlocked.

The present invention is based on the realisation that a combination of such security systems can be of particular utility in vehicles. Thus, it is not necessarily intended that the use of a key-operated ignition (or even "hot-wiring" if a thief has no conventional key) should be prevented, but to immobilise the vehicle, e.g. gradually or after a predetermined lapse of time.

Therefore, if a thief breaks into a vehicle according to the invention, the engine can be started but the vehicle cannot be driven for long, in the absence of the remote device. Alternatively, hijacking leaves the vehicle running for a time, perhaps even after the authorised user and the remote device that the user carries are ejected from the vehicle. This reduces the likelihood of a thief causing casual damage because of frustration that the vehicle will not start, or continue to run. Evidence suggests that a thief usually leaves a car that stops for no apparent reason, rather than attempting to work out the problem.

An anti-theft device, according to the present invention, marries a conventional multiple circuit electronic immobiliser (which is widespread technology) to a receiver and transmitter device. The receiver and transmitter "talk" to one another at regular intervals. If the correct code is not received by the immobiliser kit, then the electrical system immobilisation will operate, causing the car to slow down in a controlled manner, or stop.

The technology is available for a huge number of individual codes, so reducing the likelihood of "scanning" the system, and incorporation of a rolling code will enable "grabbing" to be prevented. "Blocking" is not a viable option, to get round the security device, since if the receiver does not receive the code, the immobilisation will of course come into operation.

As for known building security systems, the remote key may be of roughly the same dimensions as a credit card.

Transmission and reception ranges may be about 10 metres, or more or less. This will ensure that when the holder of the remote key moves further than this range away from the vehicle, immobilisation will be implemented.

As indicated above, the remote key can act both as a traditional electronic immobiliser, and also as an antihijack device. To ensure that the vehicle is driven far enough away, a time lag can be built in from unauthorised starting to halting the vehicle.

An anti-hijack device may have a time delay of, say, one minute before the engine falters. This allows the car occupant to move well away from the hijacker and also makes it impossible for activation of the device to cause immediate loss of power. This prevents "false alarms" from endangering the driver by, for example, leaving the vehicle stranded across a junction.

The present invention may utilise conventional radio or infrared transmitter/receiver apparatus, or an inductive field. In order that the power requirement and range should be low and high, respectively, low power drain, small transmitters and receivers may be used.

Alternatively, an electric field data transmission system may be used. Most convenient, especially considering the desired range of only a few metres, is to use radio frequency transponder tags such as those sold by Texas Instruments, AEG and Micron. These contain a coil of wire which is used to transmit a coded radio frequency. There are numerous types of transponder, those using power in the design, or passive tags, which use the current induced by the radio signal being received to power transmission of its radio signal. For short ranges, either type of tag may be used, but for greater reliability a tag with its own onboard power source would be recommended rather than an active tag. However, should size constraint become a problem, or battery life a problem, a passive tag could be substituted.

The invention may involve a complete cut-out of vehicle transmission, in the absence of transmission signal receipt, or reduced power, optionally after a time lag.

The system may be linked to the Engine Management System.

In use, the authorised driver has nothing to do other than what is normally required to operate a vehicle. For example, the ignition can only start the vehicle when the remote key or card is inside the transmitting range of the device, which may be up to 5 m, e.g. approximately 2 m.

When the card is outside this range, the vehicle is immobilised immediately or after a predetermined time lag.

In particular embodiments of the invention, the "remote key" is a small RF tag which can be either imbedded in the ignition lock key or on a small tag attached to the ignition key, or within a credit card carried by an authorised user. In this last case, for example, interrogation is done by an inductive antenna mounted in the vehicle's door mirror or the top capping of the driver's door. Range may be approximately 50 cm, with a capture area of 90 degrees from a central axis in line with and at a right angle to the driver's door. Validation of the RF tag may be by means of a control module hidden in the vehicle and connected to the antenna by a single pair of wires. Such a system can provide security code combinations in excess of 2.5 million, and each control module will be capable of reacting to more than one, e.g.

up to a maximum of ten RF tags with different codes.

The antenna may be connected directly to the control board which is suitably housed in a plastic casing and installed behind the instrument panel. This module also contains any warning buzzer that may be provided, and controls any flashing LED visual warning device that may be provided.

Connection between the control box and the immobiliser section is suitably by means of fibre optic cable or protected monitored, hard-wired cables. Power, earth, ignition and accessory circuit should all be made as close as possible to the mounting position of the control box.

The immobiliser unit is suitably mounted in a tamperproof module, and should be mounted in a concealed position, as far away from the control module as practical.

For example, the device will disconnect four separate circuits, on activation. Thus, immobilisation is effected by (i) four heavy duty relays, (ii) four high current MOSFET devices, or (iii) combination of both types of device.

Power and earth for the device may be picked up local to its mounting position.

Circuit cuts should be typically as follows: (1) Starter relay circuit.

(2) Fuel pump circuit.

(3) Ignition or engine management system.

(4) Automatic gearbox inhibit switch or lighting supply circuit.

In its quiescent state, i.e. normal operation of the vehicle, if used, relays should be in their normally closed and relaxed condition. Failure to the power supply to this device when in operation should not interfere with the normal operation of the vehicle.

Claims (4)

1. A vehicle equipped with a security system that allows continuous operation of the vehicle only in the local presence of a remote device that can be carried by an authorised user.

2. A vehicle according to claim 1, additionally comprising a conventional mechanical key-operated ignition system.

3. A vehicle according to claim 1 or claim 2, comprising a transmitter and a receiver, the transmitter being adapted to transmit a signal to the receiver periodically, and the receiver being adapted to control the vehicle's performance, and in which the remote device is a portable signal-transcription device.

4. A vehicle according to any preceding claim, in which the security system is adapted to allow operation of the vehicle for a predetermined period, in the absence of the remote device.