Field of the Invention

This invention relates to a warning system for use in motor vehicles, and particularly to a warning system which operates in response to the speed of the motor vehicle.

Discussion of the Prior Art

It is well known that drivers of motor vehicles must regulate the speed at which they drive on public roads to that a determined by law. This requires that the driver maintain a continuous watch on the speed of the vehicle by regularly checking the speedometer which is provided with the vehicle.

Despite speed limits set by law, speeding motor vehicles continue to be a serious problem for the community as a whole, and are often the cause of collisions with other motor vehicles or with pedestrians, which results in loss of life and substantial expense to the community by way of the attendance of emergency services, hospitalisation and rehabilitation costs.

A common reaction to the correlation between speed and traffic accidents adopted by governments is to lower speed limits for particular roads, and to educate the driving public as to the dangers of speeding. Further, increased fines and penalties are imposed upon speeding drivers by way of discouragement even to the point were a driver's license can be suspended or cancelled.

Despite these measures aimed at reducing the incidence of speeding, it still occurs and is a very serious problem to the community.

The present invention is directed to a system which will alert the driver of a motor vehicle to the fact they may be travelling at excessive speed, and thereby encourage the driver to decrease the speed of the motor vehicle.

Summary of the nvention

Therefore, the invention provides a warning system for a motor vehicle comprising: means to allow a driver of the motor vehicle to select a maximum speed for the motor vehicle; means for sensing the actual speed of the motor vehicle; processor means having connection with the speed selection means and the speed sensing means for comparison of the actual speed with the maximum speed; and warning means having connection with the processor means and operable to alert the driver of excessive motor vehicle speed when the actual speed is in excess of the maximum speed.

Description of the Drawings

In order that a better understanding of the invention may be obtained preferred embodiments will now be described with reference to the accompanying drawings, in which Figure 1 shows a generalised layout of a motor vehicle warning system and Figure 2 shows a circuit diagram for the system of Figure 1.

Description of Preferred Embodiments

Figure l shows a motor vehicle warning system 10 which has speed determining means in the form of a sensor 12 connected to a buffer decoder 14. The buffer decoder 14 is in communication with a micro-processor 16. The micro-processor 16 performs the necessary arithmetic and logical functions to operate the system 10, including providing comparisons between two or more quantities. The system 10 also has a speed selection means 18 connected to the micro-processor 16, the selection means 18 being provided with five push buttons 20. Also connected with the processor 16 is a warning means in the form of a beeper or speaker 22 and a display 24. The display 24 is shown with five LEDs 32.

The dashed box 26 relates to a casing which envelopes all the integers shown, and in the realisation of

the system 10 in a motor vehicle the casing 26 would be of the size that it could compactly mount on the dashboard of the vehicle, else be integrally fitted into the dashboard. The sensor 12 would be mounted either on the dashboard or in some other location such that its function of detecting the actual speed of the vehicle can take place.

In general terms, the operation of the system 10 is as follows: Before commencing any journey, the driver can select a maximum speed via a one of the push buttons 20, which speed will be registered by the micro-processor 16. This maximum speed need not be the legal allowable speed limit for a road upon which the vehicle is to be driven, but could be a maximum speed based on the motor vehicle's engine performance under load, such as when towing a trailer or carrying a load.

As the motor vehicle travels off, the sensor 12 detects the actual speed of the vehicle and signals this actual speed to the decoder 14. In one embodiment the sensor 12 can comprise an emitter section and a detector section (not shown) . The emitter section emits electromagnetic radiation in pulsed bursts which is frequency shifted and reflected in a diffuse manner from the road surface to be, in part, returned towards the vehicle. The returning radiation is received by the detector then passed to the decoder 14. The propagation speed of the electromagnetic radiation is far above that of the vehicle, so there is no timing error introduced in the determination of the actual speed of the vehicle.

Typically infra-red or ultrasonic frequencies could be implemented, although the frequency and type of the emitted electromagnetic radiation should be such as to allow reflection from the road surface rather than absorption. From the decoder 14, the actual speed is provided to the micro-processor 16 where it may be scaled then is compared against the maximum speed selected by the driver. This comparison can occur in virtual real time with the result being that for any instance when the actual speed of

the vehicle is in excess of the maximum speed the micro-processor 16 causes operation of the beeper 22 to alert the driver to having exceeded the maximum speed.

The audible alarm would be of sufficient sound pressure level for the driver to become instantly aware of exceeding the maximum speed. The visual warning could also be provided by a flashing of a respective LED 32. That is, each LED 32 has the dual function of being continuously lit to indicate the selected maximum speed and to flash when the actual speed exceeds that selected maximum speed. Some degree of hysteresis would be required so that the warning would not be too intermittent.

The sensor 12 in the preferred embodiment described above will act independently of the motor vehicle by interaction with the road upon which the vehicle is travelling to determine the actual speed. It is equally possible to provide for the detection of the actual speed in conjunction with means integral with the motor vehicle. A possibility would be to take a signal from the existing speedometer 28 of the motor vehicle and provide this to the decoder 14. Alternatively, the speedometer signal could be provided directly to the micro-processor 16. Figure 2 shows these possibilities in a dashed form.

The push buttons 20 would typically be five in number, which would allow five separate maximum speeds to be selected by the driver. A greater number of push buttons could be included if desired. Since these maximum speeds would most usually relate to the legally allowable speed limit in operation the driver must change from one to another maximum speed depending on the speed limit of the road upon which the vehicle is travelling.

It is also possible to provide for programming of the push buttons 20 to suit other circumstances, such as a personally imposed maximum speed which may be less than any legally allowable speed limit, as might be implemented on passenger-carrying buses, or for drivers who are only newly licensed. To achieve this software adjustment function, some interface means 30 would need to be provided in conjunction with the micro-processor 16. Typically this

could be achieved by external programming element to connect to an interface 30 to effect the reprogramming. By such a method, it could be possible to disallow a driver to change any of the maximum speeds, rather only allowing authorised persons to do so.

The embodiments will be further described in detail with reference to Figure 2, which shows a circuit diagram for the dashboard mounted unit 26. The single input is equivalent to either the speed sensor 12 or speedo 28, which preferably is a cruise control adaptor such as that manufactured by the company VDO, Part No. 412 009.

Figure 2 shows an output 34 which has no equivalent in Figure 1. This output 34 is optional, and can provide a signal suitable for achieving automatic fuel cut-off if a selected maximum speed is exceeded. It is conceivable this output could also be used with an overriding system to decrease the throttle opening and causes the motor vehicle to decelerate automatically. Discussing then the component parts of the circuitry. IC1 is a type 87C51 prototype integrated circuit having an S83C751 standard mask and an S83C751-IN24 custom program mask. IC2 is a type 9306N non-volatile RAM 36. The other elements of the circuit are readily identifiable to one skilled in electronics, including the buzzer which is equivalent to the alarm 22. The LEDs 24 are shown, as are the push buttons 20. The crystal, XI, is a 12.000 MHz oscillator.

The system 10 features a simple start up operation which allows the user to calibrate and set defaults according to individual requirements. Calibration need only to be done once, as these defaults will be stored and reset automatically.

The system features five speed settings of 60, 75, 90, 100 or 110 km/hr, that can be selected or changed while driving. The alarm can be muted for 30 seconds, or can be turned off permanently before each trip. A flashing display shows the driver that he/she is exceeding the speed limit even if the audio alarm has been muted.

The operational features of the system will now

be described:

1. Program Mode

On initial power up (turn ignition on) the system 10 will automatically enter Program Mode (all LEDs flash) . The user then has up to 5 seconds to press the desired function, otherwise it will enter Run Mode (only one LED on) .

Program Mode allows the user to change or set any one of several default settings:

a) Calibrate Default: For the system to work accurately in all types of vehicles it may be necessary to recalibrate for each type of vehicle, especially ones that have had their drive chain modified.

The steps are: (i) Press the 60 km/hr button (LED will flash continuously)

(ii) Operate the vehicle at a precisely known speed of 60 km/hr

(iii) Press the 60 km/hr button while maintaining this speed.

Calibration is then complete and the vehicle will now operate accurately in each speed zone. There is no need to calibrate each speed zone individually.

b) Speed Zone Default: The user may require the system to automatically be set at a particular speed zone on power up. The default setting is set to the 60 km/hr zone.

The steps to change this setting are:

(i) Press the 75 km/hr button (all LEDs will flash)

(ii) Press the desired speed zone. i.e. 60

km/hr, 75 km/hr, ..., etc. (selected speed zone LED remains lit)

Each time the user turns the unit on, the speed zone now programmed will automatically be set.

c) Default Reset: The user can reset the system to the original state of purchase.

(i) Press the 90 km/hr button (60 km/hr LED will be lit)

The preset defaults. Calibrate and Speed Zone, will automatically be reset to 60 km/hr.

d) Mute Function: An additional function is to be able to de-activate the audio alarm from sounding when speed is exceeded.

(i) Press the 110 km/hr button (selected default is lit)

Activating this function will mute the alarm 22 when speeding occurs, however the user will be able to acknowledge that he is speeding by the visual display flashing.

2. Run Mode

After 5 seconds, or after selecting a desired default, Run Mode is operational (only the selected speed zone lamp will illuminate) .

The vehicle is driven as normal. When entering a new speed zone, the user will be required to select the appropriate speed zone setting by depressing the respective push button (that zone setting LED will now be lit) .

If the zone speed is exceeded the alarm will be activated (unless muted) , and the present zone LED will flash. The alarm will be de-activated when the zone speed is no longer exceeded (LED will go steady) . The user may

also de-activate the alarm for 30 seconds by pressing any button on the display panel. Note that the preset zone setting will still flash while the audio alarm is muted. During this time the user may change to another zone setting, otherwise the audio alarm will resume after 30 seconds.

The system is designed to operate in a speed range of 0 - 200 km/hr. The power requirements are simply 12 volt D.C. with negative ground, as is common in most motor vehicles.

As to the speed limits selected, it is possible to allow a slight tolerance on the nominal values. Typically, the alarm values will be as follows:

SPEED SELECTED SPEED ALARM ACTIVATED 60 km/hr 63 km/hr

75 km/hr 79 km/hr

90 km/hr 95 km/hr

100 km/hr 105 km/hr

110 km/hr 116 km/hr

Programming of RAM 36 to achieve the functions described above would be readily apparent and within the non-inventive capacity of one skilled in the art.

It can be seen the embodiments herein described present a system which, in virtual real time, can alert the driver of a vehicle to instances of exceeding a maximum speed, which should assist in discouraging the tendency for drivers to speed.