GB2216317A

GB2216317A - Vehicle antitheft device

Info

Publication number: GB2216317A
Application number: GB8903706A
Authority: GB
Inventors: Umberto Cardini
Original assignee: GEMEL Srl
Current assignee: GEMEL Srl
Priority date: 1988-02-25
Filing date: 1989-02-17
Publication date: 1989-10-04
Anticipated expiration: 2009-02-17
Also published as: IT8819551A0; FR2627732B1; IT1218057B; GB8903706D0; FR2627732A1; GB2216317B

Abstract

The device is characterised by comprising: a) a diversification of power supply points 2, 3, 4 in order to allow the voltage of at least one of such points to be present when all the other voltages are lacking due to defective contacts, said voltage being able to keep the antitheft circuit 1 inactive particularly during vehicle running, and which would otherwise be activated by the voltage originating from said defective contacts; b) a delay circuit (67, 69 Fig 2, not shown) for delaying, even when all the power supply signals are lacking, the operation of a device on which the antitheft circuit acts to shut off the engine, said circuit not acting however on acoustic and/or optical warning devices to which the antitheft device is connected so that for a predetermined time period following the operation of the antitheft device a prealarm signal is provided which causes said warning devices to operate but not the device which shuts off the engine, so allowing the user to stop the engine. <IMAGE>

Description

IKPROVEXBJTS IN ANTI THEFT DEVICES FOR VEHICLES This invention relates to an antitheft device for vehicles, and particularly for motor vehicles.

Commercially available antitheft devices generally comprise only one feed point for each voltage phase. For example, a connection is generally made to the battery for the positive supply whereas the negative supply is obtained by connecting a terminal of the antitheft circuit to the vehicle body. This connection is normally made by screws which clamp said terminal to the body.

Those antitheft devices for which the voltage phases are fed in the stated manner have various drawbacks. Of these, the most obvious and the most dangerous for the driver of an automobile fitted with such an antitheft device is the possible operation of the antitheft device during the actual running of the vehicle.

This is caused by a sudden temporary opening of the electrical connections feeding the device, this opening generating false signals which activate the device to interrupt operation of the vehicle engine (in addition to operating the usual acoustic and/or optical warning devices to which the antitheft device is connected). The defective contacts which generate said signals occur either for reasons inherent in the manner in which the electrical connections between the antitheft device and its power supply are made or because of actual oxidation or corrosion of the electrical contacts. Other reasons for defective contacts include ageing or oxidation of the mechanical parts to which the anti theft device is connected or of the antitheft device itself, and defects originating in the electrical system (such as badly made joints or insufficiently tightened terminals).

An object of the present invention is therefore to provide a vehicle antitheft device which obviates the aforesaid problems by allowing the vehicle to continue running should defective contacts arise within the connections between the antitheft circuit.

This and further objects which will be apparent to the expert of the art are attained by an antitheft device for vehicles, particularly motor vehicles, characterised by comprising: a) a diversification of the supply points for the signals carrying the voltage phases in order to allow at least one of such signals to be present for each voltage phase when all the other signals are lacking due to defective contacts, said signal being able to keep the antitheft device inactive during vehicle running, and which would otherwise be activated by the signals originating from said defective contacts; b) a delay circuit for delaying the operation, even when all the power supply signals are lacking, of the device on which the antitheft circuit acts to shut off the engine, said circuit not acting however on acoustic and/or optical warning devices to which the antitheft device is connected so that for a predetermined time period following the operation of the antitheft device a prealarm signal is provided which causes said warning devices to operate but not the device which shuts off the engine, so allowing the user to stop the vehicle.

The present invention will be more apparent from the accompanying drawing given by way of non-limiting example and in which: Figure 1 is a block diagram of the antitheft device according to the present invention; Figure 2 is an example of a circuit diagram of the antitheft device according to the present invention; Figure 3 is a modification of part of the circuit of Figure 2.

With reference to said figures and in particular to Figure 1, the antitheft device comprises: a antitheft circuit 1 powered in known manner by a principle power supply or battery 2. The power is obtained for example by taking the positive from the battery of the vehicle on which the antitheft device is mounted and completing the circuit to earth by connecting a terminal of said circuit to the vehicle body.

The antitheft circuit comprises further points powered by other signals carrying the two voltage phases (positive and negative), besides the battery 2. In this respect, the circuit 1 is connected to vehicle components or services which are normally at positive or negative voltage. Said services thus supply further power to the antitheft circuit 1. Said services can comprise for example the direction indicators 3, the electrical circuit of the ignition system 4 and the electrical system which connects the internal lights of the vehicle passenger compartment to the doors.

Specifically, a branch 6 extends from the battery to the antitheft circuit 1, a branch 7 and a branch 8 extend from the direction indicators 3 and from the electrical system 5 to connect these components to the antitheft circuit 1, and a branch 9 extends from the electrical circuit of the ignition system 4 to the antitheft circuit 1.

Return branches 10 and 12 extend from the antitheft circuit to the direction indicators 3 and ignition system 4, the antitheft device acting on the direction indicators 3 and ignition system 4 in known manner through these branches when the antitheft device is activated.

In the branch 12 there is connected a protection circuit 13 for the ignition system 4 which prevents instant shut-off of the vehicle engine on which the system 1 acts when the antitheft circuit 1 is activated as a result of defective contacts originating at the supply points. These defective contacts can arise for various reasons, such as a defect in the electrical connections between the antitheft circuit and one or more of the various supply points, or defects in the antitheft system itself.

The protection circuit 13 comprises in detail a delay circuit which when the antitheft circuit 1 has been activated due to signals originating from defective contacts enables the shut-off of the vehicle engine to be delayed for a certain time beyond the moment in which the antitheft circuit 1 acts on the direction indicators and/or acoustic warning devices.

Let it be assumed that the antitheft circuit 1 receives an activation signal from a supply point (for example the battery 2) at which a defective contact has arisen due to badly made connections. This signal is due in practice to a sudden lack of power and its restoration after a few moments.

Because of the diversified supply points, the signal from the battery 2 is Uignored" by the antitheft circuit 1 which is therefore kept deactivated by the other said supply points (direction indicators 3, electrical system 5 of the vehicle passenger compartment, ignition system 4) which are still in perfect condition.

If however bad contacts should arise at the other supply points, the antitheft circuit 1 is inade to operate the direction indicators 3 through the circuit branch 7 and also to act on the vehicle ignition system. However, because of the delay circuit in the protection circuit 13, this latter action is delayed for a certain period (set by the manufacturer of the antitheft device) so that the vehicle driver can stop the vehicle. Then the vehicle driver after deactivating the antitheft circuit 1 and restoring at least one of the connections between the power supply and antitheft circuit can drive to the nearest garage to check the connections. The main fact is that with an anti theft device of the aforesaid type the vehicle on which the device is mounted does not stop suddenly during running if bad contacts at the power supply points cause activation of the antitheft circuit.

Figure 2 is a schematic representation of one embodiment of the electrical circuit of the antitheft device according to the present invention. The special elements of the device are shown to allow the invention to be better understood.

In Figure 2, components identical to those shown in Figure 1 are indicated by the same reference numerals.

The antitheft circuit 1 is shown schematically. It comprises a block 14 enclosing the electronic circuit, of known type, for operating the antitheft device. Said block 14 is connected to a sequential logic switching circuit of flip-flop (or memory) type 19 by means of a capacitor 15, which receives a positive voltage phase, a parallel-connected resistor 16 and diode 17 (connected to earth), and a branch 18. The circuit 19 has an output branch indicated by 12 in Figure 1 which connects it to the protection circuit 13, and a feedback branch 19A comprising a logic gate 193 connected by a branch 12A to the protection circuit 13.

In the circuit of Figure 2 the direction indicators 3 are connected to earthing points 22 and, by way of branches 20 and 21 and a switch 22, to points of positive voltage. The switch 22 is operated by a pushbutton positioned for example on the vehicle instrument panel. When the circuit formed in this manner (indicators 3, branches 20 and 21, switch 22, positive voltage points 24) is closed, the indicators 3 can operate with continuous flashing during vehicle emergency parking.

The indicators 3 are connected by circuit branches 26 and switches 27 to the return branch 10 from the antitheft circuit 1. The branches 26 are also connected to earth by the branch 7, in which two diodes 28 are connected. The branch 7 ensures that the antitheft circuit is always earthed if the negative voltage phase from the battery 2 should be lacking.

The circuit of the electric lighting system 5 of Figure 2 comprises a lamp 29 connected to a positive volt;age point 30 and, by way o a switch 31 operated by the vehicle door, to an earthing point 32. When the vehicle is running under normal conditions the switch 31 is open and the lamp 29 is therefore unlit. In this manner a positive voltage phase is supplied to the antitheft circuit 1 through the branch 8 (comprising a diode 33) connected thereto.

The ignition system 4 is shown only schematically in Figure 2. It comprises a positive voltage point 34 and a coil 35 connected together by a relay 36.

When the antitheft circuit 1 is activated the relay is open so that the electrical parts of the vehicle engine are not powered.

When the vehicle is running the relay 36 is closed.

The protection circuit 13 comprises a circuit block which acts on the relay 36 to open it if the signal is received from the antitheft circuit 1.

Specifically, as stated the protection circuit 13 is arranged to prevent the engine stopping if the antitheft circuit 1 is activated by bad contacts while the vehicle is running.

The protection circuit 13 comprises a branch 40 connected to the branch 9 from the ignition system 4 and also connected at the node 41 to the input branch 12A to the logic part (of AND type) 19B of the antitheft circuit 1. A branch 42 extends from the node 41 and comprises a transistor 43 having its emitter connected to earth and its collector connected by a branch 44 to a node 45 which receives the branch 18 and a branch 46 leading to the flip-flop 19 of the antitheft circuit 1.

The protection circuit 13 also comprises a branch 47 connected to the coil 35 and splitting at the node 48 into two branches 4 and 50, the first terminating at the base of a transistor 51 and the second connecting said branch 47 to a control member 52 for the relay 36. A branch 53 extends from the control member to split at the node 54 into two branches 55 and 56, the first terminating at the collector of a transistor 57 having its emitter 58 earthed, and the second terminating at the collector of the transistor 51, the emitter of which is connected by a branch 59 to the branch 12 from the antitheft circuit 1.

A branch 61 extends from a node 60 at which said branches 12 and 59 meet, and terminates at the base of a transistor 62 having its emitter earthed and its collector 63 connected at a node 64 to a branch 65 terminating at the base of the transistor 57, and to a branch 66 comprising a capacitor 67 connected to earth. Finally, a branch 68 extends from the node 64 and can be connected either to the branch 9 originating from the ignition system or to the block 14.

The capacitor 67 in the branch 66 and a resistor 69 in the branch 68 act as a delay device for the operation of the member 52 controlling the relay 36. In this manner, the opening of said relay 36 can be delayed if the antitheft circuit 1 is activated by defective contacts during vehicle running.

Vith regard to the use of the device shown schematically in Figure 2, it can be seen that if for example the positive voltage phase from the battery 2 should temporarily fail, the branches 8, 9 maintain a positive voltage on the antitheft circuit 1.

Again, if the negative phase from the battery should temporarily fail, the antitheft circuit 1 will not be activated because of the earth connection provided for the circuit 3.

In addition, the fact that the relay 36 is closed during vehicle running means that the transistor 43 remains active by way of the branch 40. This enables any signal passing through the branch 18 to be discharged to earth. This is because such a signal does not enter the flip-flop 19 through the branch 46 but instead passes through the branch 44 and then discharges through the transistor 43 to earth by way of its emitter. The same effect can be obtained by positioning elements (such as an inverter plus transistor) before the node 45 to open the circuit in the branch 18 and prevent activation of the flip-flop and consequent shut-off of the vehicle engine.

Engine shut-off, ie opening of the relay 36, is prevented even when the antitheft circuit 1 is activated in error. When the antitheft circuit is in the deactivated state a current circulates through the protection circuit 13 to keep the control member for the relay 36 inactive. In this respect, the currents I1 and I2 circulate through the branches 50, 49 to pass into the transistor 51 and reach the branch 59 to combine in the node 60 with the current I3 generated by the flip-flop 19 when deactivated.

The three currents pass to the branch 61 and through the transistor 62 to discharge to earth. If circulation of the current I3 through the branch 12 should be interrupted because the flip-flop 19 passes into its activated state, the currents I and 12 which still circulate through the branch 59 and thus through the branch 61 continue to discharge to earth through the emitter of the transistor 62, to thus keep the control member 52 of the relay 36 inactive. By thus means the relay does not open, and the engine is not shut off.

The antitheft circuit 1 and consequently the flip-flop are activated when all the voltage phase supply points suffer from defective contacts. In this case the transistor 43 no longer conducts and the signal from the branch 18 can reach and thus activate the flip-flop 19 through the branch 46.

At this point, should the voltage phase from the system 4 fail temporarily due to a defective contact arising downstream of the system 4, the relay 36 still remains closed.

Because the flip-flop 19 is activated the antitheft circuit acts on the acoustic and/or optical warning devices to which it is connected, and suppresses the current Is but is not yet able to shut off the engine both because'of the action of the delay circuit of the protection circuit 13 defined by the resistor 69 and capacitor 67, and because the inhibiting function of the current I3 is immediately assumed by the currents Ii + I2 which are taken from the ignition system.

Now if the ignition system 4 is switched off the currents I1 and 12 disappear within the circuit 13, but there still circulates within this circuit a current I, originating from the branch 9 and passing into the branches 68 and 65 to switch the transistor 57 to conducting with a delay defined by the resistor 60 and capacitor 67.

Because of this, when the vehicle ignition is again switched on a current 15 circulates through the branches 50 and 55 and the control member 52 of the relay 36 to pass through the transistor 57 and discharge to earth to thus energise the relay 36, which opens.

The protection circuit 13 can operate with positive signals taken from the electrical circuit associated with the vehicle ignition key or from a special circuit which senses signals originating from the vehicle alternator. Specifically (see Figure 3), this circuit 4A would comprise an amplifier 80 for the alternating component of the battery voltage, a rectifier 81 and a comparator 82.

In the circuit 4A the positive voltage phase is obtained by amplifying a portion of the alternating signal and then rectifying this signal and comparing it with a threshold signal. The signal thus obtained is used as the positive voltage phase.

Summarising, the protection circuit 13 operates at three independent levels. Specifically (see Figure 3): a) at the first level it prevents changes in the state of the antitheft circuit and therefore its undesirable activation (by defective contacts), by virtue of the transistor 43; b) at the second level it maintains the presence of currents I1 4 12 even when the current 13 fails due to an operational defect at the first level (because the circuit is automatically powered by the vehicle ignition system 4); c) if the first two protection levels should be by-passed, the circuit 13 delays the action of the antitheft circuit on the engine, so preventing instantaneous shut-off of this latter when said defective contacts activate the antitheft circuit.

The device of the present invention can also be constructed differently from the aforegoing. For example it could comprise a cascade of logic gates (OR or Aid), and by comparing the signals from the various points from which the supply phases are taken could either cause the antitheft circuit to act or not act on the vehicle, and in particular on its engine.

A device constructed in accordance with the present invention is reliable and overcomes the problems associated with known antitheft devices of the state of the art.

Claims

1. A vehicle antitheft device, characterised by comprising: a) a diversification of the supply points for the signals carrying the voltage phases in order to allow at least one of such signals to be present for each voltage phase when all the other signals are lacking due to defective contacts, said signal being able to keep the antitheft circuit inactive particularly during vehicle running, and which would otherwise be activated by the signals originating from said defective contacts; b) a delay circuit for delaying the operation, even when all the power supply signals are lacking, of a device on which the antitheft circuit acts to shut off the engine, said circuit not acting however on acoustic and/or optical warning devices to which the antitheft device is connected so that for a predetermined time period following the operation of the antitheft device a prealarm signal is provided which causes said warning devices to operate but not the device which shuts off the engine, so allowing the user to stop the engine.

2. An antitheft device as claimed in claim 1, characterised in that the supply points for the signals carrying the voltage phases include not only the vehicle battery but also vehicle components or services which are normally at positive or negative voltage during vehicle running.

3. An antitheft device as claimed in claim 2, characterised in that said services are advantageously the direction indicators, the electrical circuit of the ignition system and the electrical system which connects the internal lights of the vehicle passenger compartment to the doors.

4. An antitheft device as claimed in claim 1, 2 or 3 characterised in that the delay circuit comprises at least one capacitor and at least one resistor

5. An antitheft device as claimed in claims 1,2 3 or 4, characterised in that the delay circuit is provided within a protection circuit arranged to prevent the antitheft circuit shutting off the vehicle engine while running, as the result of defective contacts arising at the voltage phase supply points.

6. An antitheft device as claimed in claim 5, characterised in that the protection circuit operates with signals received from the vehicle ignition system.

7. An antitheft device as claimed in claim 6, characterised in that the protection circuit operates with signals received from the electrical circuit associated with the vehicle ignition key.

8. An antitheft device as claimed in claim 5, characterised in that the protection circuit operates with signals received from a circuit which processes the signals originating from an alternator located on the vehicle.

9. An antitheft device as claimed in claim 8, characterised in that the circuit which processes the signals originating from the alternator comprises an amplifier , a rectifier and a comparator

10. A vehicle antitheft device having a diversification of the supply points for the signals carrying the voltage phases in order to allow at least one of such signals to be present for each voltage phase when all the other'signals are lacking due to defective contacts, said signal being able to keep the antitheft circuit (1) inactive particularly during vehicle running, and which would otherwise be activated by the signals originating from said defective contacts.

11. A vehicle antitheft device having a delay circuit for delaying the operation, even when all the power supply signals are lacking, of a device on which the antitheft circuit acts to shut off the engine, said circuit not acting however on acoustic and/or optical warning devices to which the antitheft device is connected so that for a predetermined time period following the operation of the antitheft device a prealarm signal is provided which causes said warning device to operate but not the device which shuts off the engine, so allowing the user to stop the engine.

12. A vehicle antitheft device substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.