GB2197108A

GB2197108A - Speed limit alarm for motor vehicle

Info

Publication number: GB2197108A
Application number: GB08626468A
Authority: GB
Inventors: Maxwell Bruce Watherston
Original assignee: PAMAX NOMINEES Pty Ltd
Current assignee: PAMAX NOMINEES Pty Ltd
Priority date: 1986-11-05
Filing date: 1986-11-05
Publication date: 1988-05-11
Also published as: GB8626468D0

Abstract

The alarm includes a sensing unit (Figs. 2 and 3, not shown) connected to the vehicle speedometer cable to emit a series of electrical pulses whose frequency is dependent on vehicle speed. Circuitry receives these pulses and includes a frequency to voltage converter whose output is applied to a network of comparators IC2B each receiving a respective reference signal representative of a respective set speed. The output of such comparator is fed to a gate circuit which switches an alarm device on and off as the speed of the vehicle passes through each selected speed limit for both increasing and decreasing speed of the vehicle. The sensing unit preferably includes a rotor (8) with a series of holes (14) rotating passed a light emitting diode (17) and a phototransistor (18). <IMAGE>

Description

SPECIFICATION Automatic speed limit alarm unit This invention relates to an automatic speed limit alarm unit for motor vehicles, the unit being such that it may be fitted to passenger vehicles, transport vehicles and motor cycles.

BACKGROUND OF THE INVENTION There is a specific need for limiting the speed of vehicles for safety reasons, and an indication should be given to the vehicle or driver so that the driver is aware of the speed range in which he is driving.

In many driving situations the driver's attention is to be focused fully on the road, and it is desirable that the driver shouid be given an indication of the speed of the vehicle without having to take his eyes off the road and focus the eyes on a speedometer.

In Australian specification No. 77535/75 there is described in general terms a warning device which can operate by detecting the engine revolutions, or from the drive train to actuate a simple electronic circuit to give an audible warning or a visual warning when a specific value of engine or road speed has been reached.

Australian Patent specification No.

72505/74 describes a vehicle speed warning device whereby by switching means the driver may select the speed at which the warning device activates, which warning includes external devices such as lights or a horn to warn other vehicles excess speed.

Australian Patent specification No.

35912/71 shows a similar unit to actuate external warning devices, the sensing means being a centrifugal unit connected to the speedometer cable.

Australian Patent No. 481723 describes a warning and/or control system in which a signal representing vehicle speed actuates a warning when the vehicle speed is above a predetermined speed when the motor speed is below a predetermined motor speed.

It is an object of this invention to provide an alarm unit which will give an indication to the driver of the vehicle as he passes from one speed range to another.

STATEMENT OF THE INVENTION Thus there is provided according to the invention an automatic speed limit alarm unit which is connected to give a short audible signal to the driver of the vehicle as he passes from one speed range to another, i.e.

when he passes through the 25 kilometres per hour speed limit range an audible signal is given, and then another short audible signal is given as the vehicle passes through each of the other speed ranges, i.e. 60 kilometres per hour, 80 kilometres per hour and 100 kilometres per hour. The invention can be applied to mechanical type speedometers in which the unit consists of two main parts, a sensing unit, and an electronic control unit The unit can also be used with the electronic type speedometers, with the unit consisting of two main parts, a frequency to voltage conversion unit, and an electronic control unit.

The sensing unit may be one of several types, that is, magnets and coils fitted to the tail shaft of the vehicle, a light or infra-red beam and photo transistor with the beam being interrupted or switched on and off by a slotted disc rotating on the inner cable of the speedometer cable, or proximity detectors, Vane or Hall effective type sensors which can be used in a similar manner by a rotating metal disc.

The type of sensor which is preferred is of the infra-red diode and photo transistor type, which is chosen for cheapness and reliability and because it provides a unit that would be universal to fit all types and sizes of speedometer cables that are in use by cars, trucks or motor cycles.

BRIEF DESCRIPTION OF THE DRA WINGS FIG. 1 shows a circuit diagram of the control circuit, FIG. 2 is a side view of the sensing unit, and FIG. 3 is a cross-section of FIG.2.

DESCRIPTION OF THE PREFERRED EMBODI MENT Referring firstly to FIG8. 2 and 3, the sensing unit 1 is connected to the speedometer cable 2, the outer sheath 3 being cut and removed, the ends of which are-clamped by lock nuts 4 while the inner cable 5 passes uninterrupted through the sensing unit 1.

The sensing unit comprises an outer body 6 and a outer body cap 7. The rotor 8 is fitted into a rotor housing 9 having a bearing 10, a hollow spigot 11 on the rotor 8 fitting into the bearing 10, and the rotor housing 9 fitting into the outer body 6. The rotor 8 has fitted into its bore a rubber or other resilient material sleeve 12 through which the inner cable 5 passes. A rotor clamp screw 13 passes over the inner cable 5 and on tightening compresses the sleeve 12 to clamp the rotor 8 to the inner cable 5. The rotor 8 has a series of equally spaced holes 14 around its periphery.

A rotor housing cap 15 is fitted into the open end of the rotor housing 9. In order to hold and lock the rotor 8 while the clamp screw 13 is tightened, a pin 16 is passed through the hole 17 in the rotor housing cap 1 5 through one of the holes 14 in the rotor, the pin being removed after tightening the rotor clamp screw 13.

For assembly on the speedometer cable 2, the required cut out of the outer sheath 2 is cut out, the end of the inner cable 5 threaded through the sensor, the rotor clamp screw 13 threaded over the inner cable 5 is tightened, the locking pin 16 removed and then the outer body cap threaded over the cable, the remaining end of the outer cable replaced and the locking nuts 4 tightened to clamp the sensor 1 in position on the cable 2.

The rotor housing 9 carries in an aperture a transmitting diode 17 in iine with the holes 14 in the rotor, and the rotor housing end cap carries in an aperture the photo transistor 18.

These being connected by wiring 19 to the control circuit in FIG. 1. The rotor 8 preferably has ten holes 14, so that in operation the photo transistor 18 will transmit ten signals or pulses for each revolution of the speedometer cable 5.

If sensing units are used that operate by coil and magnet or other means producing an A.C. frequency, a frequency to voltage conversion circuit converts the frequency to pulses which are fed into the electronic control unit.

The electronic control unit will now be briefly explained, with reference to FIG. 1.

Terminal 5 is connected to the positive of the battery and terminal 4 is connected to the negative of the battery. Terminal 1 is connected to the wire leading to the wire from the photo transistor 18, and the terminal 3 is connected to the wire leading to the transmitting diode 17, while terminal 2 is the common earth to both units 17 and 18. Thus terminals 1, 2 and 3 are connected to the wires to the sensing unit. The frequency control unit converts the pulses received from the sensing unit or the frequency to voltage conversion unit an A.C. frequency or coil type sensing unit depending upon which type is used.

The pulses are fed into a pulse conditioning and amplifier circuit which is controlled by the number and speed of the pulses received. The converted voltage is fed to a buffer circuit via a range adjusting and control circuit which adjusts the whole range by raising or lowering the voltage into the buffer circuit which controis a network of comparators and voltage divider network which is adjusted with the "ON" and "OFF" voltages of the various speed limits being 25, 60, 80 and 100 kilometres per hour the maximum voltage which operates at approximately 120 kilometres per hour can only be switched off by reducing the vehicle's speed, thus, at about 120 kilometres per hour and above the alarm sounds continuously or if switched to a pulsed alarm which operates a short alarm at approximately every ten seconds via a timer circuit until the vehicle's speed is reduced. Each comparator is then fed to an alarm gate circuit which switches the alarms "ON" and "OFF" as the speed is increased or decreased as the case may be through the various speed limits.

At the bottom of the figure there is shown a series of switches 1, 2, 3 and 4, the first being a spare for connection so that if the switch is actuated it will switch the 25 kilometres per hour off. If switches 2 and 3 are activated each will give a continuous alarm above 80 kilometres per hour and 100 kilometres per hour respectively, the 110 kilometres per hour is normally left in the continuous alarm mode and when switch 4 is activated it will change the mode to a short alarm operating approximately every ten seconds until switched off by reducing the speed.

The unit also provides a safety precaution that if the battery connections are reversed, it will not damage the unit in any way. The voltage to operate the unit is also controlled through a voltage regulator circuit and is switched on by the ignition switch of the vehicle.

There are no switches or controls for the driver to operate or to change during the driving of the vehicle, for once the unit is installed and adjusted the unit can be mounted anywhere out of sight under the dash.

The alarm can be heard over any road, radio or engine noise that is experienced in the driving of the vehicle. The alarms operate automatically at the various speed limits whether the vehicle's speed is increasing as the vehicle passes through one alarm to the next, and the next alarm is the maximum of that speed limit.

It also applies as the vehicle speed is reduced as the alarm operates and then goes off once the vehicle passes into the lower speed limit.

Thus, it will be seen that as the vehicle is accelerating, the alarm will operate at the sensed speeds for a brief period of time so that the driver of the vehicle will know in which speed range he is operating. Thus on approaching a school crossing, the vehicle's speed is reduced and when the lowest speed limit is reached the alarm will operate and the driver will then know that he is below the 25 kilometre per hour limit. After passing the speed in the restriction zone, the driver then accelerates, hears the alarm as the vehicle passes through the 25 kilometre per hour signal, and then when the next signal is heard the driver knows that he has reached the limit of 60 kilometres per hour.

Similarly as the driver passes into the 80 kilometre per hour speed zone when the next signal is heard the driver knows that he has reached the maximum for that speed zone and will reduce his speed accordingly.

The invention is also particularly suitable for decreasing the vehicle's speed after long periods of highway driving, for the driver will then know when he passes through each speed range until he knows that he is driving in the selected speed range for that particular area.

Preferably the unit is adjusted so that the signal will be given at 1 or 2 kilometres per hour above the speed limit, so that the driver on reaching the speed range will know that he is exceeding the limit and will slightly reduce his speed accordingly.

Thus there is provided according to the invention, an automatic speed limit alarm unit which gives an indication to the driver of the vehicle of the speed range in which he is driving, this unit giving an audible warning as he passes through the selected speed and thus the unit does not have to be reset for various speed ranges as is common with other units on the market.

Claims

1. An automotive speed limit alarm for motor vehicles, said alarm comprising a space sensing unit connected to a vehicle component moving with a speed proportional to the road speed of a vehicle to emit a series of electrical pulses whose frequency is dependent on the vehicle speed, the alarm circuit receiving the pulses to be conditioned and fed to a buffer circuit through a range adjusting and control circuit which controls a network of comparators and voltage divider network adjusted to the desired speed limits, the output of each comparator being fed to an alarm controlled gate circuit-which switches the alarm on and off as the speed passes through each selected speed limit for both increasing and decreasing speed to the vehicle.

2. An automotive speed limit alarm as defined in claim 1 wherein a short signal is given as the speed passes through 25 kilometres per hour, 60 kilometres per hour, 80 kilometres per hour, 100 kilometres per hour and at and above 110 kilometres per hour the signal is continuous, or switched to a short alarm which will operate at approximately every ten seconds via a timer circuit until the speed is reduced.

3. An automotive speed limit alarm as defined in claim 1 wherein the sensing unit is connected to the speedometer cable.

4. An automotive speed limit alarm as defined in claim 3 wherein the sensing unit contains a transmitting diode and a photo transistor spaced on opposite sides of an apertured rotor.

5. An automotive speed limit alarm as defined in claim 4 wherein the rotor is clamped to the inner drive cable of the speedometer cable, the sensing unit having a housing clamped to the outer sheath of the speedometer cable.

6. An automotive speed limit alarm as defined in claim 3 wherein the rotor has ten equally spaced apertures so that the sensing unit emits ten pulses from the photo transistor for each revolution of the speedometer cable.

7. An automotive speed limit alarm as defined in claim 4 wherein the sensing unit is fitted to the speedometer cable by removing a portion of the outer sheath of the speedometer cable, threading the inner cable through the sensing unit, clamping the rotor to the inner cable, and clamping a sensing unit to the outer sheath.

8. An automotive speed limit alarm as defined in claim 4 wherein the rotor has a bore therethrough, a resilient sleeve in the bore, the inner cable passing through the sleeve and a rotor clamp screw passing over the inner cable and screwed into the bore of the rotor to compress the sleeve to clamp the rotor to the inner cable.

9. An automotive speed limit alarm as defined in claim 8 wherein the rotor is locked for rotation while clamping the rotor to the inner cable by a pin passing through a fixed portion of the sensing unit and one of the apertures in the rotor.

10. A sensing unit for an automotive vehicle speed alarm being adapted to be clamped to the speedometer cable and said sensing unit comprising an outer housing, a rotor adapted to be clamped to the inner cable of the speedometer cable, the rotor having a circumferential series of equally spaced apertures, a transmitting diode and a photo transistor spaced on opposite sides of the rotor in line with the circumferential series of apertures, and means for clamping the outer housing to the other sheath of the speedometer cable.

11. A sensing unit as defined in claim 10 wherein the rotor is mounted in a bearing in a rotor housing fitted into the outer housing, the rotor housing containing the transmitting diode, a rotor housing cap closing the rotor housing, the rotor housing cap containing the photo transistor.

12. A sensing unit as defined in claim 10 wherein the rotor has a bore therethrough, a resilient sleeve in said bore and adapted to receive the inner cable of the speedometer cable, and a hollow clamping screw threaded into said bore to compress said sleeve to clamp the rotor to said inner cable.

13. A sensing unit as defined in claim 10 wherein the outer casing is clamped to the outer sheath of the speedometer cable.

14. An automotive speed limit alarm for motor vehicles substantially as hereinbefore described with reference to the accompanying drawings.