GB2175462A

GB2175462A - Vehicle deceleration indicator

Info

Publication number: GB2175462A
Application number: GB08608555A
Authority: GB
Inventors: Barrie Hepburn
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-05-14
Filing date: 1986-04-08
Publication date: 1986-11-26
Also published as: GB8608555D0; GB8512176D0

Abstract

A pulse generator 1 produces pulses at a frequency proportional to the vehicle road speed, and the pulses are counted for a predetermined period by a counter. The current count and the previous count, stored in a memory 4, are compared in a comparator 3 which in response to a negative difference causes a switch 5 to energise a deceleration indicator 6. The indicator 6 may be turned on only if each of a succession of counts is less than the preceding count. The indicator 6 may be the brake lights, hazard lights or reversing lights, or any combination thereof. The system may also keep the indicator lights on when the vehicle is stopped, actuate the reversing lights on sensing reversing, and actuate the hazard lights on sensing very rapid deceleration or very rapid acceleration (e.g. wheel spin). <IMAGE>

Description

SPECIFICATION An indicator system The present invention relates to an indicator system for a road vehicle, and in particular, to an indicator system which indicates when the road vehicle is de-celerating.

When the brake pedal of a vehicle is depressed brake lights at the rear of the vehicle are turned on to indicate to drivers behind that the vehicle is slowing down. However, with a conventional brake circuit the brake lights do not turn on if the vehicle is decelerating other than as a result of braking, for example, as a result of the driver removing his foot from the accelerator pedal or because the vehicle is climbing a hill. This absence of any slowing signal can result in drivers behind approaching very close to the rear of the vehicle, before they realise that the vehicle is slowing down which represents a serious hazard.

It is an object of the present invention to provide an indicator system for a road vehicle which indicates when the vehicle is de-celerating regardless of whether or not the brake pedal has been depressed.

According to the present invention there is provided an indicator system for a road vehicle comprising a sensor for sensing the current road speed of the vehicle, a detector for detecting any negative change in the vehicle's road speed and switching means operable by the detector to turn on an indicator when a negative change in the vehicle's road speed is detected.

Preferably, the sensor comprises a pulse generator which produces a pulse train, the frequency of which is directly proportional to the vehicle road speed, and a clock which produces an output corresponding to the number of pulses produced over a given period of time.

Preferably, the detector comprises a comparator which compares the current output of the clock with the previous output of the clock, and the previous output of the clock is held in a memory and is constantly up-dated to store the current output of the clock once the comparison has been made.

When the current output of the clock is less than the previous output of the clock held in the memory then an output is produced from the comparator which turns on the switching means. Alternatively, a succession of outputs from the clock may be compared, each with the immediately preceding output, and the switching means turned on only when each output in the succession is less than the output immediately preceding it.

Preferably, the switching means comprises a semi-conductor switch.

Preferably, the pulse generator is driven by an output on the vehicle transmission system.

Preferably, the indicator comprises the vehicle brake lights, but may also include the hazard lights and the reversing lights.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawing, which shows a block diagram of an indicator system in accordance with the present invention.

Referring to the accompanying drawing there is shown a block diagram of an indicator system in accordance with the present invention which comprises a pulse generator 1 which is driven by an output of the vehicle transmission system or any other convenient take-off point. The output of the pulse generator is applied to a clock 2 which counts the number of pulses output from the pulse generator 1 over a given period of time and produces an output proportional thereto. The output of the clock 2 is connected to a comparator 3 which compares the current output of the clock 2 with the immediately preceding output of the clock 2 which is held in a memory 4. Once the comparison has been made then the contents of the memory 4 are up-dated with the current output of the clock 2.The output of the comparator 3 is applied to a switching unit 5, which in turn controls the indicator lights 6 of the vehicle. The indicator system is supplied with power from the vehicle battery via a voltage stabiliser 7 which eliminates fluctuations in the battery voltage.

In operation the pulse generator 1 produces a train of pulses, the frequency of which is directly proportional to the angular frequency of the transmission system and hence to the vehicle road speed. Typically, the pulse generator 1 produces approximately 8,000 pulses per minute at 60 km per hour. The train of pulses output from the pulse generator 1 is applied to the clock 2 which counts the number of pulses produced over a given period of time and produces an output proportional thereto. The output of the clock 2 is applied to an input of the comparator 3, where it is compared with the previous output of the clock 2 held in the memory 4. Should the difference between the current output of the clock 2 and the previous output of the clock 2 be zero or positive then the vehicle is maintaining the same speed or accelerating.However, if the difference between the two outputs is negative then the vehicle is de-celerating. Where this is the case an output is produced from the comparator 3 which turns on the switching unit 5. In turn the switching unit 5 controls the vehicle indicator lights 6 which are turned on to indicate to drivers behind that the vehicle is de-celerating. The indicator lights 6 may include the brake lights, the hazard lights or the reversing lights, or any com bination thereof.

In a second embodiment of the present in vention the memory 4 and the comparator 3 are so arranged as to compare several suc cessive outputs to determine a trend before providing an output to turn on the switching unit 5 Consecutive speed measurements V1, V2, V3, V4, and V5 can be taken and if the V1 is greater than V2 is greater than V3 is greater than V4 is greater than V 5 then it can be safely assumed that the vehicle speed is decreasing and that the vehicle indicator lights should therefore be turned on. If, however, V1 is greater than V2 is less than V3 is greater V4 is less than V5 it may be that the vehicle speed is fluctuating about a particular level. As a consequence no output is provided to the drive unit to turn on the indicator lights.

If desired, the indicator system according to the present invention can be arranged to sense when the vehicle is stopped and to keep the indicator lights turned on until the vehicle starts up again.

The indicator system according to the present invention can also be arranged to sense when the vehicle is reversing and to turn on the reversing lights when this condition is sensed.

Using the indicator system according to the present invention it is also possible to detect very rapid de-celeration and to actuate the hazard warning lights when this condition is sensed.

Using the indicator system according to the present invention it is possible to detect very rapid acceleration, for example wheelspin on ice, and to actuate the hazard warning lights when this condition is sensed. Alternative to existing vehicle brake lights, hazard warning lights and reversing lights can also be implemented.

It would be appreciated that the indicator system in accordance with the present invention provides a backup to the vehicle's conventional braking circuit, in that should this fail the brake lights will still turn on as a result of the indicator system sensing the deceleration of the vehicle.

Claims

1. An indicator system for a road vehicle comprising a sensor for sensing the current road speed of the vehicle, a detector for detecting any negative change in the vehicle's road speed and switching means operable by the detector to turn on an indicator when a negative change in the vehicle's road speed is detected.

2. An indicator system as claimed in claim 1 wherein the sensor comprises a pulse generator which produces a pulse train, the frequency of which is directly proportional to the vehicle road speed, and a clock which produces an output corresponding to the number of pulses produced over a given period of time.

3. An indicator system as claimed in claim 1 or claim 2 wherein the detector comprises a comparator which compares the current output of the clock with the previous output of the clock, and the previous output of the clock is held in a memory and is constantly up-dated to store the current output of the clock once the comparison has been made.

4. An indicator system as claimed in any preceding claim wherein when the current output of the clock is less than the previous output of the clock held in the memory then an output is produced from the comparator which turns on the switching means.

5. An indicator system as claimed in any one of claims 1 to 3 wherein a succession of outputs from the clock may be compared, each with the immediately preceding output, and the switching means turned on only when each output in the succession is less than the output immediately preceding it.

6. An indicator system as claimed in any preceding claim wherein the switching means comprises a semi-conductor switch.

7. An indicator system as claimed in any one of claims 2 to 6 wherein the pulse generator is driven by an output on the vehicle transmission system.

8. An indicator system as claimed in any preceding claim wherein the indicator comprises the vehicle brake lights, but may also include the hazard lights and the reversing lights.

9. An indicator system substantially as hereinbefore described with reference to the accompanying drawing.