GB2262074A

GB2262074A - Motor vehicle security systems

Info

Publication number: GB2262074A
Application number: GB9125054A
Authority: GB
Inventors: Frederick William Latimer
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-11-26
Filing date: 1991-11-26
Publication date: 1993-06-09
Anticipated expiration: 2011-11-26
Also published as: GB2262074B; GB9125054D0

Abstract

The system protects a vehicle by restricting the starting of the vehicle and access into the engine compartment to the keyholder. The engine and bonnet release are disabled unless both the door lock and the ignition lock have been correctly operated. <IMAGE>

Description

MOTOR VEHICLE SECURITY SYSTEMS This invention relates to motor vehicle security systems: In general a locked vehicle can only normally be started if the key is used o a) open the door lock, and b) turn the ignition lock. Similarly the bortet can only normally be opened if the key is used firstly to open the door lctk to provide access to the bonnet release lever inside the passetrer compartment, and secondly is used to turn the ignition lock.

Ereaking into a motor vehicle is normally achieved by breaking a window forcing open a door lock or using a stiff tape pushed aground the door frame to prize up the locking button. Once inside, the thief usually breaks off the ignition lock to expose the end of the ignition switch. Application of a screw driver (or similar) into the exposed slot allows the vehicle to be started.

Alternatively, "hot wiring" can be achieved by short circuiting the battery live supply to the starter solenoid connection on the igion swi; Failing this the bonnet can be opened giving access to the engine compartme-, again allowing for "hot wiring" by connection of the battery live directly to the starter solenoid, or general interference with the engine and its controls.

An aim of the present invention is to make it more difficult for a vehicle to be stolen.

In accordance h rh2 present invention, here i providied a motor vehicule security system comprisi.ng: a switch (not necessarily mechanical) operable by a key externally of the vehicle; a switch (not necessarily mechanical) operable by a key internally of the vehicle; means to disable a release for an engine compartment access cover of the vehicle; means to disable operation of the engine of the vehicle; and control means responsive to the switches and controlling the disabling means so that both the access cover release and the engine are disabled unless signals from the switches each have a respective predetermined state.

Thus the vehicle cannot be started and access cannot be obtained to the engine compartment, unless both lock operated switches have been correctly used.

Preferably, at least one of the switches (and preferably both) comprise at least two (and preferably four) sub-switches with at least one having a state complementary to the other, and the control means does not operate unless all the states are correct. Thus, different vehicles can be set up with different switch state combinations so that a thief will have difficulty in finding the appropriate combinations for a particular vehicle.

Specific embodiments of the present invention will now he je-ct by we of example with reference to the accompanying drawings in which: Figure 1 is a circuit diagram for a vehicle without central locking; and Figure 2 is a circuit diagram for a vehicle with central locking.

Referring to figure 1, the security system has as a sub power supply (in this case) a simple resistor (RI) and zener diode (ZDI, 5.1V) fed from the battery supply via inductor/capacitor (L-C) filter (L1, and C1) which is necessary to remove undesirable electrical spikes and such associated interference.

The logic elements (in this case Cx1OS 74HCXXX series) are powered from the 5.lV sub power supply and connected to the vehicle chassis for signal return.

The logic input signals are derived from the 5.IV sub power supply via the control switches (S1, S2 and S3). In most vehicles the driver's door switch (S1) and passenger door switch (53) will operate independently and either being operated provides the first enabling operation. However, for venice with a central locking system only switches S1 and S2 would be required (refer to later section and Fig. 2 for an outline of the logic operation fcr a central locking system).

There are four switch contacts per function, two normally open and two normally closed (S1, S2 and S3). The common side is connected to the 5.1V sub power supply via the wiring harness.

The two normally open contacts of each switch connect to the monitoring, AND gates (Lgl, Lg2 and Lg3) and the to normally closed contact o of switch Fc-d or Thr, Lg5 and Lg6, all via a multipin connecter (gay I 10 way) and the associate wiring harness (also 10 way) to the logic unit multiway connector.

The switch contacts will be assigned connections at the time of manufacture and these will vary from vehicle to vehicle.

These connections will be on the basis of four out of nine (two normally open and two normally closed) for a ten way cable. The associated connections into the logic gates will be made to match for a particular vehicle.

At the logic unit end of the wiring harness each of the wires other than the one carrying the 5.lV sub power supply will be taken to chassis (OV) via a resistor. These resistors perform two functions; a) they hold the logic inputs low when the associated switches are open, b) if interfered with, it is not possible to define which of the connections are active because each wire impedance to chassis will be the same, thus making it extremely difficult to resolve which pair of wires should be connected to 5V and which pair should be left open circuit.

Taking the condition in which the vehicle is locked; The normally open contacts of these switches ensure that the outputs of AND gates Lgl, Lg2 and Lg3 and OR gate Lg9 are low.

The normally closed contacts of the switches supply 5V inputs to CR gate Lg4, Lg5 and Lg6, ensuring that these gate outputs are held high.

Lg5 feeds NAND gate Lg8 which because of its inversing characteristic will have a low output.

Thus because all the inputs to AND gate LglO are low its output will also be low, holding off drive transistors TRl and TR2. Because TRl and TR2 are not conducting, relay RL1 and solenoid SLl are de-energised making it impossible to start the vehicle engine or gain access into the engine compartment despite application of the internal bonnet release lever.

When the driver side door is unlocked with the key, switch S1 is activated causing Lgl and Lg9 outputs to rise to logic 1 (or high) states and Lg4 and LG7 outputs o fall to logic 0 (or low) state.

When the ignition switch is operated by the key, switch S2 is activated causing Lg2 output to rise to logic 1 (high) and the inputs to Lg5 to fall to logic 0 (low). As all three inputs to Lg5 are low its output becomes low thereby causing Lg8 output to rise to its high (logic l) state.

Now all three inputs to Lg10 are high, its output becomes high turning on transistors TRl and TR2, thus energising relay (RLl) and solenoid (SL1). this allows the vehicle engine to be started by virture of the fact that current can now flo to the starter solenoid through the momentarily closed ignition switch contact and the relay (RLl) contact.

The starter solenoid and starter motor now operate in the normal mode.

With the bonnet lock solenoid (SL1) energised, access t the.engine compartment can he gained ny operating the bonnet release mechanium as This system is designed to make it extremely difficult for a would be thief to steal a vehicle without the appropriate key. Even if after breaking into the vehicle and disconnecting the multiway connectors from switches Si, S2 and S3 it would be a complex and time consuming operation for the would be thief to find the right combination of high and low connections for each function to allow him to proceed.

Any one of the inputs to LglO becoming low (logic O) will ensure that relay RLi and bonnet lock solenoid SLl remain de-energised.

If a vehicle has the feature of central locking, switch S3 and logic gates Lg3, Lg6, Lg7 and Lg9 become redundant. NAND gate Lg8 has two inputs which are fed from Lg4 and Lg5. However the principles of operation remain essentially as previously described. (see figure 2).

The specific embodiments of the invention described above have, or can be provided with, the following features: 1) The first enabling switch (door) can only be operated by the key and is an integral part of the lock. It cannot be operated by the dcor lock button.

2) The second enabling switch (ignition) can only be operated by the key and is an integral part of the lock.

3) The control logic is contained in a RFI/EDIC proof enclosure under the bonne in the engine compartment.

4) The logic power supply (approximately 5V for CMOS logic) has a limited power capability to ensure that it cannot be used for "hot wiring" of the starter solenoid.

5) The ignition enabling relay contact is placed between the ignition switch contact and the starter solenoid coil to prevent "hot wiring" of the vehicle.

6) The solenoid activated bonnet release device prevents access to the engine compartment unless the key enabling sequence is completed.

7) Wiring between door switch and logic unit, and between ignition lock switch and logic unit is protected by the use of multiway connectors and cables in which random pairs of pins are used to convey the switch contacts to the logic sequencer. (This will vary from vehicle to vehicle).

Claims

1) A motor vehicle security system, comprising: a switch operable by a key operated door lock of the vehicle; a switch operable by a key operated ignition lock of the vehicle; means to disable a release for an engine compartment access cover or the vehicle; means to disable operation of the engine of the vehicle; and control means responsive to the switches and controlling the disabling means so that both the access cover release and the engine are disabled unless signals from the switches each have a respective pre determined state.

2) A system as claimed in claim 1, wherein at least one of the switches comprises at least two sub-switches whose states are complementary, and wherein the control means disables the release and the engine unless signals from the sub-switches each have a respective pre-determined state.

3i A system as claimed in claim 2, wherein said at least one switch comprises four such sub-switches, two of whose states are complementary to the other two.

4) A system according to any preceding claim, in which the door lock switch is an integral part of the lock.

5) A system according to any preceding claim, in which the door lock switch can only be activated by the vehicle key.

6) A system according to any preceeding claim, in which the external lock switch is only operable by a separate key.

7) A system according to any preceding claim, in which the ignition lock switch is an integral part of the lock.

8) A system according to any preceding claim in which the ignition lock switch can only be activated by the vehicle key.

9) A system according to any preceeding claim, in which the internal lock switch is only operable by a separate key.

10) A system according to any preceding claim, wherein the access cower release disabling means comprises a solenoid operates mechanical coupling between a manually operable release member and a lock for the access cover, the solenoid being operable by the control means.

11) A system according to any preceding claim wherein the engine disabling means comprises and electrically controllable switch in a starter solenoid circuit of the vehicle, the electrically controllable switch being operable by the control means.

12) A motor vehicle having a security system according to any preceding claim.

12) A system according to any preceding claim wherein the control means comprises an array of logic gates.

13) A motor vehicle security system substantially as described with reference to the drawings.

14) A motor vehicle having a security system according to any preceding claim.

Amendments to the claims have been filed as follows 1) A motor vehicle security system which comprises: a switch operable by a key operated door lock of the vehicle together with a switch operable by a key operated ignition lock of the vehicle; means to disable a release for an engine compartment access cover of the vehicle including means to disable operation of the engine of the vehicle; and control means responsive to the switches and controlling the disabling means so that both the access cover release and the engine are disabled unless signals from the switches each have a respective pre-determined state wherein at least one of the switches comprises at least two sub switches whose states are complementary, and function to provide enabling or disabling logic gates wherein the control means disables the release and the engine unless signals from the sub-switches each have a respective pre-determined state.

2) A system as claimed in claim 1, wherein said at least one switch comprises four such sub-switches, two of whose states are complementary to the other two.

3) A system according to any preceding claim, in which the door lock switch is an integral part of the lock.

4) A system according to any preceding claim, in which the door lock switch can only be activated by the vehicle key.

5) A system according to any preceding claim, in which the external lock switch is only operable by a separate key.

6) A system according to any preceding claim, in which the ignition lock switch is an integral part of the lock.

7) A system according to any preceding claim in which the ignition lock switch can only be activated by the vehicle key.

8) A system according to any preceding claim, in which the internal lock switch is only operable by a separate key.

9) A system according to any preceding claim, wherein the access cover release disabling means comprises a solenoid operated mechanical coupling between a manually operable release member and a lock for the access cover, the solenoid being operable by the control means.

10) A system according to any preceding claim wherein the engine disabling means comprises an electrically controllable switch in a starter solenoid circuit of the vehicle, the electrically controllable switch being operable by the control means.

11) A motor vehicle security system substantially as described with reference to the drawings.