Vehicle Security System

This invention relates to vehicle security systems which include movement sensors for detecting movement within the vehicle. In such a system, when the vehicle is left by the driver, the alarm is set and any subsequent movement sensed within the vehicle is assumed to be that of an intruder and an alarm is raised accordingly. Thus the successful operation of such an alarm relies on the movement sensing means always being in functioning order.

In prior systems, it has been possible for the movement sensing means to develop a fault which at least partially prevents movement being detected in the vehicle and for the driver not to know the fault has developed. In such a situation, the alarm will provide little or no protection against intrusion although no indication of this lack of protection will be given.

Such a vehicle alarm is disclosed in International Patent Application No. WO/GB93/19385.

It is an object of the present invention to automatically detect a fault in the movement sensing means of a vehicle alarm.

Accordingly the present invention provides a vehicle security system comprising movement detecting means for detecting movement inside a vehicle, sensing means for sensing the state of at least one component of the vehicle, and control means, the control means being arranged to identify by means of the sensing means a period when movement inside the vehicle would be expected, to monitor for movement within that period, and, if movement is not detected during said period, to initiate an error procedure.

Preferably the error procedure comprises altering a count value, which may be reset when movement is sensed in the said time period.

Preferably the system further comprises fault indication means, and the control means is arranged to indicate an error via the fault indication means when said count value reaches a predetermined value.

Preferably the sensing means comprises switch sensing means for sensing when an ignition switch is put in a predetermined position, and said period is started when the ignition switch is put in said predetermined position.

Preferably the system further comprises door sensing means for sensing a door being closed, and said period is that between the ignition switch being put in said predetermined position and the door being closed.

The putting of the ignition switch in a predetermined position in many cases indicates the beginning of a particular action by the driver. For example, if the predetermined position is an "off" position then usually the driver will next remove the key from the ignition switch and exit the vehicle, closing the driver's door behind him. Thus in most cases, the movement sensing means should if it is functioning correctly, sense movement during the said time period. By allowing the count value to reach a predetermined value, 5 for example, before generating a fault signal, the confidence of the fault detection is increased. Advantageously, the door sensed by the door sensing means is the drivers door.

In a preferred embodiment, the count value is reduced and is preferably reset to zero when movement is successfully sensed during the time period. Preferably the control means is operable to ignore a failure to detect movement during the time period in certain predetermined situations by neither incrementing nor reducing the count value. One such situation may occur when a driver has switched off the ignition and is just sitting in the car without having opened and closed the door. The driver may not be making enough movement to be sensed and thus a failure to detect movement may not indicate a fault with the movement sensing means. Preferably therefore, the control unit is operable to ignore a failure to detect movement when the time period after putting the ignition switch in the predetermined position exceeds a predetermined length (60 seconds for example), when the ignition switch is moved from its predetermined position, from "off" to "on" for example, and/or when the vehicle is locked during the said time period.

The movement sensing means may be activated automatically when the switch sensing means senses the predetermined switch position of the ignition switch. Preferably and particularly when the movement sensing means is sensitive to air movement in the vehicle, automatic activation of the movement sensing means does not occur unless all doors, windows, sunroof, tailgate and the like are closed. Alternatively, the movement sensing means may be activated at all times. In either case, even though movement may be detected by the sensing means, an alarm is not raised unless the alarm has been set.

The fault signal may advantageously cause the display of a fault message on a display device in the vehicle. The message may be caused to appear only in response to an attempt to set the alarm. Furthermore, if a fault has been detected other security features of the vehicle such as deadlocking of the doors (i.e. preventing the doors from being unlockable from inside the vehicle), may be deliberately disabled.

The invention will now be described by way of example, with reference to the accompanying drawings in which:

FIG. 1 is a side view of a vehicle including a security system according to the invention, and

FIG. 2 is a schematic block diagram of the system of FIG. 1.

The security system for a vehicle 1 in accordance with the present invention includes control means comprising an engine control unit 2 which operates the vehicle immobilisation, and a body electrical control module BeCM. The control module has direct links with sensors 4, 6, 8, 10 for both rear windows 12, both rear doors 14, the tailgate 16 and the sunroof 18 which detect whether they are open or shut and when they move between those two conditions. The control module BeCM also has direct links with motors (not shown) for both rear windows 12, both rear door locks 14, and the sunroof 18, as well as an ultrasonic sensor 20 for detecting movement in the vehicle, a message centre and audible warning unit 22 which communicates information to the driver 24, and a radio frequency (R.F.) receiver 28 which receives R.F. signals from a hand held transmitter (not shown). It is to be appreciated that the movement detection means comprises a transmitter and receiver for transmitting and receiving respectively radiant energy of a predetermined waveband. The control module BeCM is also linked through a centre console outstation 32 to window and sunroof operating switches 34, and through left and right hand side front door outstations 36 to respective lock motors (not shown), sensors 38, window sensors 40 and window motors (not shown) for the front passenger and driver doors 41.

In operation, the control unit 2 coordinates a self-check procedure to determined whether the ultrasonic sensor 20 is operating correctly. If a fault is found, the driver is warned via a suitable message appearing on the message centre 22. Furthermore, if a fault has been detected other security features of vehicle 1, such as deadlocking doors 14, 41, may be deliberately disabled.

The procedure starts when the driver turns the ignition switch 42 to the off position. This event can be detected by the control unit 2 by monitoring the voltage level on the ignition circuit. When the ignition is off, the control unit 2 checks that all doors, sunroof and tailgate are shut. If they are shut then the ultrasonic sensor 20 is automatically activated regardless of any driver action to arm the alarm or alternatively, it may be activated at all times. If the control unit 2 then detects, within 60 seconds from when the ignition was turned off, is that the driver's door 41 has opened and then closed without any movement being detected by the ultrasonic sensor 20, the sensor is deemed to have failed and this failure is added to a count of such failures maintained by the control unit 2. When the count reaches five, the message centre 22 is instructed to display a fault message telling the driver that the ultrasonic sensor 20 has failed. The factor which determines the end of the period is dependent on the sequence of events after the start of the period. If movement is detected within 60 seconds of the ignition switch 42 being turned to the off position and before the driver's door 41 has closed, then the count of failures is reset to zero since the ultrasonic sensor 20 is deemed to be working correctly. If during the period of time between the ignition being switched off and the driver's door 41 being closed, the ignition switch 42 is turned on again, the vehicle 1 is locked, or a time period of 60 seconds elapses, as the driver in the car may not be making enough movement to be sensed, then the count of failures is neither reset to zero nor incremented.

In the preferred embodiment, the fault message is not displayed on the message centre 22 until the driver 24 attempts to arm the security system at which time he will be warned that there is a fault with the ultrasonic sensor by a message such as "ALARM FAULT" for example.