GB2335717A

GB2335717A - Motor vehicle security device

Info

Publication number: GB2335717A
Application number: GB9806545A
Authority: GB
Inventors: Samuel Gibson
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-03-26
Filing date: 1998-03-26
Publication date: 1999-09-29
Also published as: GB9806545D0

Abstract

A motor vehicle security device comprises a valve arrangement, in a vehicle brake fluid line 5, 19, which can be switched between a secure mode in which fluid can only flow towards the vehicle brake, so that the brake cannot be released once applied and a normal, drive mode in which bidirectional brake fluid flow is permitted for normal brake operation. As illustrated, the valve arrangement comprises a solenoid operated, on/off valve 21 and a one-way valve 25. The arrangement may comprise a single valve which can be switched between two-way and one-way states, may be integral with a master cylinder, and may be manually operable.

Description

2335717

1 DESCRIPTION MOTOR VEHICLE SECURITY DEVICE

The present invention is concerned with motor vehicle security.

To prevent theft of motor vehicles, it is known to provide an immobiliser which prevents the vehicle from being driven unless and until a specific input has been given by a user. For example, the driver may be required to insert and turn a key or enter a code number on a keypad to deactivate the immobiliser and so allow the vehicle to be driven away. A potential thief, lacking the key or the code number, is thus prevented from stealin. the vehicle.

A common type of vehicle immobiliser works by opening a switch in the vehicle ignition circuit, preventing the engine from being started. Unfortunately, it can prove possible to bypass the switch, completing the ianition circuit and allowing the car to be driven. Also, a potential thief is not prevented from towing the car away.

An object of the present invention is to make possible an improved motor vehicle security device which can prevent the vehicle being driven away by an unauthorised driver and which can prevent unauthorised towing of the vehicle.

In accordance with the present invention, there is provided a motor vehicle security device comprising a valve arrangement for incorporation in a brake fluid line of the motor vehicle and means whereby an authorised driver can control the valve arrangement to operate in a secure 1 2 mode, in which the valve arrangement permits flow of brake fluid toward a vehicle brake but prevents flow of brake fluid away from the brake so that the brake can be applied but cannot be released, and a driving mode in which bidirectional flow of brake fluid is permitted and the brake can be operated norTnally.

A security device having these features can, in the secure mode, prevent release of the brakes following their actuation, entirely immobilising the vehicle.

The term "motor vehicle" as used herein should be understood to include not only cars but also heavy goods vehicles, vans, plant such as tractors and excavators, articulated vehicles and other vehicles to which the present invention is applicable.

Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:- FIG. 1 is a stylised illustration of a vehicle brake system constructed in accordance with the invention; and FIG. 2 is an illustration of a valve arrangement for use in the brake system shown in FIG. 1.

The brake system illustrated in Fig. 1 has, in conventional manner, a brake pedal 1 coupled to a piston within a master brake cylinder 3 from which issue two brake fluid conduits 5,7. The front brake fluid conduit 5 is bifurcated at 9 and subsequently led to the two front vehicle brakes 11, 3 while the rear conduit 7 is likewise bifurcated and led to the rear brakes 13.

In accordance with the present invention, there is a valve arrangement 15 incorporated in both of the fluid conduits 5,7.

Fig. 2 shows the components of a suitable valve arrangement, the front brake fluid conduit again being labelled 5, and being led on one side 17 to the brake master cylinder and on its other side 19 to the brakes. A valve 21 is incorporated in the conduit 5 to selectively open/close same, while an alternative route for brake fluid-flow is provided by a further conduit 23 which. bypasses the valve 21. Incorporated in this bypass conduit 23 is a non-return valve 25 oriented to permit brake fluid-flow in the direction from the master brake cylinder toward the brakes but to prevent flow through the bypass conduit in the opposite direction - from the brakes toward the master cylinder.

A similar arrangement of a solenoid and a non return valve is provided in the rear brake fluid conduit 7.

The valve 21 of the present embodiment is a solenoid valve connected to and controlled by electronic control circuitry (not illustrated). The circuitry comprises a security input device such as a keypad for entry of a code number or a switch controllable using a security key, positioned to be accessible to the vehicle driver.

In use, when the vehicle is parked and is to be left unattended, the system is set (eg by entering a code or by removing the security key) in a secure mode, in which the solenoid valve 21 is closed. Consequently, the only route for brake fluid flow between the master brake cylinder 33 and the brakes 4 11, 13 is via the non return valve 25. Upon depression of the brake pedal, fluid flows to the brakes which are thereby applied, arresting the vehicle. However, fluid is prevented from subsequently flowing away from the brakes ic the brakes cannot be released - since flow in this direction is prevented by the non-return valve 25. The driver may choose, when leaving the vehicle, to depress the brake pedal and hence lock the brakes on. Even if this is not done, a potential thief, lacking the key or code needed to cause the solenoid valve 21 to open, will be unable to drive the vehicle very far since it will not be possible to release the brakes after their first application.

An authorised driver, returning to the vehicle, will provide via the security input device the input necessary to change the system to a driving mode, in which the solenoid valve 21 is open to provide a route for return of brake fluid from the brakes toward the master cylinder so that the brakes can be operated normally.

A variety of valve arrangements may be used in systems according to the present invention. For example, in place of the two valves (non return valve 25 and solenoid valve 21) a single valve could be used which is selectively switchable between an open condition, permitting fluid flow in either direction, and a non-retum condition in which flow is permitted in one direction only.

The valve arrangement may be integrally formed with the master brake cylinder. Alternatively, a respective valve arrangement could be provided for each brake.

The valve arrangement may, instead of being electrically controlled, comprise a tap or other manual control means by which the driver changes between secure and driving modes.

6 CLAMS 1 - A motor vehicle security device comprising a valve arrangement for incorporation in a brake fluid line of the motor vehicle and means whereby an authorised driver can control the valve arrangement to operate in a secure mode, in which the valve arrangement permits flow of brake fluid toward a vehicle brake but prevents flow of brake fluid away from the brake so that the brake can be applied but cannot be released, and a driving mode in which bi-directional flow of brake fluid is permitted by the valve arrangement and the brake can be operated normally.

2. A motor vehicle security device as claimed in claim 1, wherein the valve arrangement comprises a parallel combination of a controllable valve and a non-return valve, such that the controllable valve can be opened in the driving mode to permit bi-directional brake fluid flow and can be closed in the secure mode so that brake fluid flow must be through the nonreturn valve which is arranged to permit flow only toward the vehicle brake.

3. A motor vehicle security device as claimed in claim 1, wherein the valve arrangement comprises a valve controllable between an open configuration for the driving mode, in which it permits bi-directional flow, and a non-return configuration for the secure mode, in which it allows brake fluid flow toward the brake but prevents return of brake fluid.

4. A motor vehicle security device as claimed in any preceding claims in which the valve arrangement is controlled by electrical circuitry having secure means for receiving control inputs from an authorised driver.

7 5. A motor vehicle security device as claimed in any preceding claim in which the valve arranaement shares a common housing with or is integrally formed with the vehicle master brake cylinder.

6. a motor vehicle comprising a security device as claimed in any preceding claim.

7. A motor vehicle security device substantially as herein described with reference to, and as illustrated in, the accompanying drawings.

8. A motor vehicle provided with a security device substantially as herein described with reference to, and as illustrated in the accompanying drawings.