GB2331330A

GB2331330A - Production of vehicle security systems with portable transmitters

Info

Publication number: GB2331330A
Application number: GB9828316A
Authority: GB
Inventors: Jeremy John Greenwood
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1995-11-25
Filing date: 1996-09-26
Publication date: 1999-05-19
Anticipated expiration: 2016-09-26
Also published as: GB9828316D0; GB9620069D0; GB2307514B; GB2331330B; GB2307514A

Abstract

Each of a set of two ignition keys 21 has an RF transmitter unit 22 attached to it for transmitting coded signals to the control unit 10 of a passive re-mobilise type of security system. The units 22 of a set respond differently to the control unit 10, eg after a different number of pulses from coil 34 to ensure that simultaneous command signals cannot be transmitted from both transmitter units. The transmitter units 22 may be produced in large numbers without security codes but carrying an identifying number in their memories according to whether they are the first or the second of the set of two. The transmitter units 22 are then sorted into two groups by these identifying numbers. To make a set of units 22 for an individual vehicle, one unit is taken from each group and a security code specific to the vehicle is put into the pair of units. During this procedure, the vehicle's security control unit 10 checks the numbers of the units 22 and stops the matching if the numbers are the same eg by warning the person carrying out the matching or by refusing to accept the duplicated number.

Description

1 VEHICLE SECURITY SYSTEM 2331330 The present invention relates to vehicle

security systems,, and in particular to those including 'passive re-mobilization' which ensures that the vehicle will not remain immobilized if the driver has entered the vehicle and 5 wants to start it using the proper key.

This application is a divisional application based on GB 9620069.6.

It is known to provide a transmitter unit attached to an ignition key of a vehicle, either as part of the key head or as a separate unit, which will respond to request signals transmitted from the vehicle when the ignition switch is used by transmitting a remobilize signal to the security control unit. However it is a problem with such systems that, if two transmitter units from the set for the vehicle are attached to the same ignition key, or to the same key ring, they can both transmit remobilize signals at the same time which results in neither of them being recognized by the control unit.

is Accordingly, the present invention provides a vehicle security system comprising a security control means and a receiver and a set of transmitter units for transmitting coded signals to the control means via the receiver, wherein the control means is arranged, on matching the transmitter units to the security control means, to receive an identifier from each transmitter unit in the set, if the identffiers indicate that all of the transmitters would be suitable for use with the same security control means to match all of the transmitter units in the set to the control unit by causing a code associated with the security control means to be stored in each of them, and to respond in a predefined manner if one or more of the received identffiers indicate that any two or more of the transmitters would be unsuitable for use with the same security control means.

2 Preferred embodiments of the present invention will now be described by way of example only with reference to Figure 1 of the accompanying drawing which is a diagrammatic view of a vehicle security system in accordance with the invention.

A security control unit 10 which is mounted on a vehicle 11 has various outputs 12 enabling it to immobilize the engine 14 of the vehicle, by disabling the fuel injection system 15, and operate locks 16 on the vehicle doors 18. The control unit 10 is connected to a radio frequency (R.F.) receiver 20 and is arranged to unlock the doors 18 and re-mobilize the engine 14 upon receipt of a lo command signal comprising a coded R.F. unlock signal, and to lock the doors and immobilize the engine upon receipt of a command signal comprising a coded lock signal. Each of a set of two ignition keys 21 for the vehicle has an R.F. transmitter unit 22 attached to it. Each transmitter unit 22 comprises an R.F. transmitter circuit 24 arranged to send coded R.F. unlock and lock signals, a is power source 26 for the transmitter circuit, and an unlock button 28 for activating the transmitter manually to send the unlock signal by connecting the power supply 26 to the transmitter circuit 24. A lock button (not shown) is also provided to cause the transmitter to send the coded lock signal. Each transmitter unit further comprises a control circuit 30 and a receiver in the form of a coil 32 connected so that signals received by the coil are fed into the control circuit 30 which includes switching means to connect the power supply to the transmitter circuit 24. The control circuit includes a counter and is arranged to count pulses of radio signals received by the coil 32 and to transmit a command signal when the number of pulses in a series reaches a particular number. The counter is arranged to increase by 1 on receipt of each pulse in the series, but to return to zero if no pulses are recdived for a predetermined period, for example three times the normal gap between pulses in the series. Each transmitter in the set has a different identifying number, for example 1 and 2 for a set of two transmitters. Each transmitter unit 22 is housed in a plastics housing and is arranged to be attached to the head of the ig-mtiou-key 21 by a key ring 33.

3 A second coil 34 forms a transmitting aerial and is connected to the control unit 10 and is housed in a cowl 36 of the vehicle, close to a vehicle ignition lock 38. The control unit 10 is connected to the normal electrical outputs from the ignition lock 38 so that it can sense when the ignition key is present in the ignition lock, and when it is in the auxiliary, ignition and crank positions.

Normally when the driver approaches the vehicle he will re-mobilize the engine 14 and unlock the doors 18 by pressing the unlock button 28. However if he has unlocked the doors using the key 21 in the door locks 16 the engine may still be immobilized when he enters the vehicle. This is particularly likely to happen if the security control unit 10 is programmed to immobilize the engine automatically when the driver leaves the vehicle. The control unit 10 is therefore arranged to detect the situation when the engine is immobilized and the key 21 is turned to the auxiliary position in the ignition lock 38.

In this situation the control unit begins to transmit a series of pulses is using the transmitter coil 34. If transmitter No. 1 is present in the ignition lock it will transmit a command signal via the transmitter circuit 24 when the first pulse in the series is received. If transmitter No. 2 is present it will transmit a command signal when the second pulse in the series is received. When a valid command signal is received from one of the transmitter units 22 through the receiver 20 the control unit remobilizes the engine and stops sending pulses. If no response is received by the end of the series of pulses the series will be retransmitted after a short interval. If no response is received after a number of transmissions of the series, then the transmission of the pulses wffi cease.

Since each of the transmitters will transmit its command signal after a different pulse, there should never be two command signals transmitted simultaneously by two transmitter units. This can avoid problems which can arise with known systems if two transmitter units are attached to the same ignition key.

4 During vehicle production it is usual to produce the transmitter units in large numbers and match them to individual vehicles at a convenient point in the production process. Where the transmitter units are to be supplied in sets, this can be done as follows. Firstly the transmitter units 22 are produced with no security code in memory, but with each having an identitring number stored in memory indicating which transmitter in a set it will be, for example 1 or 2 if only two transmitters will be supplied per vehicle. Apart from the identifier all the transmitter units are identical. All transmitter units can then be grouped according to those numbers, all those with an identifying number of 1 forming lo one group, and all those with an identifying number of 2 forming another group. When a set of transmitter units is required for a vehicle, one transmitter unit from each group is selected to form the set, and then each transmitter from the set is matched to the vehicle. This will entail putting a security code, specific to the vehicle, into the memory of each transmitter unit of the set, either by transmitting it from the vehicle security control unit, or by inputting it from another source from which it is also entered into the vehicle security control unit. For each transmitter unit, the matching process will also entail transmitting from the transmitter unit to the vehicle security control unit the identifying number of the transmitter unit. The security control unit is then programmed to check the numbers of the transmitter units which are being matched to it and, if two transmitter units of the same number are used, the security control unit will prevent the matching from proceeding. This can be done, for example, by programming the control unit either to issue a warning to the person carrying out the matching process, or to refuse to accept the duplicated number, or both. This process ensures that, when the transmitter units are being matched to the vehicle, it is not possible for two units of the same number to be matched to the same vehicle. Therefore it is not possible for there to be two transmitters which will respond at the same time in the series of pulses from the vehicle mounted transmitter coil 34.

Claims

CIAIMS

A vehicle security system comprising a security control means and a receiver and a set of transmitter units for transmitting coded signals to the control means via the receiver, wherein the control means is arranged, on matching the transmitter units to the security control means, to receive an identifier from each transmitter unit in the set, if the identifiers indicate that all of the transmitters would be suitable for use with the same security control means to match all of the transmitter units in the set to the control unit by causing a code associated with the security control means to be stored in each of them, but to respond in a predefined manner if one or more of the received identifiers indicate that any two or more of the transmitters would be unsuitable for use with the same security control means.
2. A vehicle security system according to claim 1, wherein the control means is arranged to respond in said predefined manner if it receives the same identifier from two transmitter units.
3. A vehicle security system according to claim 1 or claim 2, wherein said predefined manner comprises the producing of a warning.
4. A vehicle security system according to any preceding claim, wherein said predefined manner comprises stopping the matching process.