Communications: electrical – Land vehicle alarms or indicators – Of burglary or unauthorized use
Patent
1997-01-15
1999-02-02
Tong, Nina
Communications: electrical
Land vehicle alarms or indicators
Of burglary or unauthorized use
3404255, 34030915, 340514, 340522, 340566, 180287, 307 91, 307 102, 701 34, 367 95, B60R 2510
Patent
active
058670912
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
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.
BACKGROUND OF THE INVENTION
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.
SUMMARY OF THE INVENTION
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 t
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Rover Group Limited
Tong Nina
LandOfFree
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