GB2309496A

GB2309496A - Braking a motor vehicle

Info

Publication number: GB2309496A
Application number: GB9701609A
Authority: GB
Inventors: Alfred James Boyd
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-01-25
Filing date: 1997-01-27
Publication date: 1997-07-30
Anticipated expiration: 2017-01-27
Also published as: GB2309496B; GB9701609D0

Abstract

A motor vehicle includes a first, mechanical braking system operated by a hand lever 3, and a second braking system, such as a hydraulic system operated by a foot pedal 11, the braking systems being coupled by means of, for example, an electromagnet 23 connected to the vehicle ignition 21 whereby the second braking system is actuated to apply the wheel brakes of the vehicle upon application of the mechanically operated braking system when the vehicle ignition is switched on. This greatly improves the braking efficiency of the vehicle. The second system may be pneumatically or electrically operated.

Description

TITLE: Improvements in and relating to braking systems DESCRIPTION This invention concerns improvements in and relating to braking systems, particularly for motor vehicles.

Conventionally, a motor vehicle is equipped with a mechanically operated braking system acting on the rear wheels, known as a parkbrake, and a hydraulic braking system operated by a foot pedal which acts on all four wheels. The former braking system is primarily employed for parking purposes, being the system that remains applied to the wheels of the vehicle when the engine is switched off and the vehicle is left unoccupied. This braking system is applied by the hand operation of a mechanical lever which results in force being applied through a system of wires and levers, to block hrakes acting on the rear wheels of the vehicle.

The presence of a mechanically operated braking system in a motor vehicle is a legal requirement since it is necessary to have a supplemental braking system separate from the hydraulic braking system. The mechanical braking system, referred to throughout this disclosure as the "parkbrake", should not be applied by the driver whilst a vehicle is in motion except in an emergency, for example, should the hydraulic braking system fail.

The hydraulic braking system, for example using disc brakes, is normally applied hefore operation of the parkbrake to slow down or stop movement of the vehicle. This system is far more efficient than the parkbrake hut is released as soon as the foot is removed from the pedal. The system operates by depression of a foot pedal which causes a piston in a master cylinder to move thereby exerting pressure on hydraulic fluid contained therein. This results in the movement of the fluid through connecting pipelines to hydraulic wheel cylinders causing the application of brake pads to discs which are then applied to the wheel of the vehicle to stop movement thereof.

Alternative braking systems may be employed in a vehicle in place of the hydraulic braking system, such as electric, pneumatic or vacuum-assisted braking systems or even a further mechanical brake-by-wire system.

The efficiency of the mechanically operated braking system is dependent upon the amount of force used in applying the lever which activates the block brakes.

Even if the parkbrake is applied with maximum force it is often not enough to stop the movement of a vehicle when, for example, pressure is removed from the clutch pedal whilst the vehicle is still in gear and the engine is running or when the vehicle is started when it has been left in gear, termed "driver's unintentional movement initiation". This is due firstly to the parkbrake being less efficient than the other braking systems employed in vehicles and secondly, due to the parkhrake being applied to the rear wheels only which, in any event, are less powerful than the front wheels. Thus, if a vehicle is accidentally started in gear with only the conventional parkbrake applied, the vehicle may unintentionally move which may result in damage to the vehicle and/or injury to a person.

It is an object of the present invention to provide an improved braking system for a vehicle which ensures that a vehicle will remain stationary when the parkbrake is on and power is applied to the wheels thereof. It is a further object of the invention to provide an improved braking system in which a vehicle remains stationary when power is applied to the wheels thereof even if the parkbrake has been insufficiently applied, for example by a person with reduced physical ability.

Another object of the invention is to provide an improved braking system which will enable a vehicle towing a trailer or caravan to remain stationary on a steep incline thereby opening up new routes to the foregoing. Yet a further object of the present invention is to provide an improved braking system which enables a parkbrake to be released and applied sufficiently with reduced physical effort.

According to the present invention there is provided an improved braking system for a motor vehicle comprising a mechanically operated braking system, another braking system operated by another medium and means for coupling operation of the mechanically operated braking system to said another braking system when the vehicle ignition is on, whereby said another braking system operates in conjunction with operation of the mechanically operated braking system.

It is preferable that said another braking system be a hydraulic braking system.

Alternatively, said another braking system may be a pneumatic, vacuum-assisted, mechanical or electrically operated braking system.

Preferably, the means for coupling the two braking systems is an electromagnet connected to the vehicle ignition system by means of an electric cable, the ignition being powered by an electric battery provided in the vehicle. The electric cable is preferably connected to the electromagnet by means of a plug and socket connector to enable the independent operation of the two braking systems, if necessary.

Preferably, the electromagnet is contained within an electromagnetic coupling unit consisting of a housing and a lid. Preferably, an armature plate is provided spaced apart from the electromagnet for making contact therewith when electricity is supplied from the battery of the vehicle. The electromagnet and plate may be provided with mechanical means to prevent excessive separation thereof. It is preferable that the electromagnet and plate are surrounded by a sleeve guide to define the extent of travel and are spring biased towards each other. Preferably, the magnet is min 700N and is provided with a suitable earth return connection.

It is to be appreciated that alternative means may be employed to couple the two braking systems when the vehicle ignition is switched on, for example, a solenoid.

The coupled systems are preferably linked by means of a plurality of actuators such that the conventional operation of one system results in the simultaneous operation of the other braking system when the vehicle ignition is switched on.

Preferably, the actuators are in the form of a plurality of wire cables connected to respective ends of the electromagnetic coupling unit. Preferably, a first cable leads from one end of the unit to means for operating the mechanical braking system and a second cable leads from the opposite end of the unit to means for operating the said another braking system.

Preferably, the first cable leads to an equalising yoke which causes application of the mechanical brakes to the rear wheels of the vehicle upon movement of a hand operated lever. The equalising yoke is preferably connected to the lever by means of a tension spring. It is preferable that the means for operating the said another braking system is a foot pedal which causes a piston in a master cylinder to move thereby exerting pressure on hydraulic fluid contained therein, resulting in application of the hydraulic brakes. Preferably, the second wire cable is directly linked to the underside of the foot pedal.In this manner, operation of the mechanical braking system by movement of the lever when the vehicle ignition is on causes a corresponding movement of the wire cable linked to the foot pedal which pulls the pedal and results in application of the hydraulic brakes to the wheels of the vehicle.

Alternatively, the second cable may be connected to an arm which drives a separate hydraulic system for exerting pressure on the foot pedal to cause application of the hydraulic brakes. The separate hydraulic system may comprise a master cylinder having a piston which is moved by the arm connected to the wire cable thereby causing hydraulic fluid to move through a hydraulic pipe connected to the foot pedal. The master cylinder is preferably provided with a remote reservoir for replenishment of the system with hydraulic fluid. Alternatively, the separate system may comprise a compression barrel having a piston which is movable by the arm connected to the wire cable to cause hydraulic fluid to move through the hydraulic pipe. Preferably, the compression barrel is provided with a charge nipple to allow for replenishment of the system during servicing of the vehicle. The hydraulic pipe is preferably connected to the foot pedal by means of a slave cylinder and support bracket.

It is to be appreciated that the cable wires may be connected to various elements of the braking system by any suitable fastening means, such as for example, a tunnel bracket or stirrup clamp.

It is preferable that the electromagnet is activated by the ignition switch in Position 3, thereby enabling the hydraulic brakes to be released whilst other electric facilities of the vehicle remain available.

For a better understanding of the present invention and to show more clearly how it may be carried into effect, reference will now be made by way of example only, to the accompanying drawings in which: Figure 1 is a schematic diagram of a conventional braking system of a motor vehicle having separate mechanical lever operated and hydraulic braking systems; Figure 2 is a generalised, schematic diagram of a braking system according to the present invention, the mechanically operated braking system being coupled to a hydraulic braking system; Figure 3 is an enlarged view of the boxed area shown in Figure 2; Figure 4 is a schematic diagram of a preferred embodiment of an electromagnetic coupling unit for use in the present invention; Figure 5 is a schematic view of a preferred embodiment of the present invention in which the braking systems are actuated via cable linkage;; Figure 6 is a schematic view of an alternative embodiment of the present invention in which the braking systems are actuated via cable linkage, an independent compression barrel and a slave cylinder; and Figure 7 is a schematic view of vet a further embodiment of the present invention in which the braking systems are actuated via cable linkage, an independent hydraulic cylinder and a slave cylinder.

Referring to Figure 1 of the accompanying drawings, a conventional braking system for application to the wheels of a motor vehicle is illustrated. The vehicle has a mechanical parkbraking system which is applied to the rear wheels 6 only and a hydraulic braking system which works on both the front and rear wheels 8, 6.

The parkbrake is operated by the movement of a mechanical lever 3 which is connected by a series of wires and levers 5 to a block brake 7 on each of the rear wheels 6. These brakes are used for parking purposes and remain applied to the wheels of the vehicle when the engine is switched off and the vehicle is unattended.

The hydraulic brakes are operated by depressing a foot pedal 11 which is connected to a master cylinder 13 containing hydraulic fluid. The depression of the foot pedal causes movement of a piston within the master cylinder which experts pressure on the hydraulic fluid. This fluid is incompressible and thus is forced along the connecting pipelines 15 to wheel cylinders 17 (shown on one wheel only in Figure 1 for simplicity) on each of the four wheels. Movement of the pistons in these cylinders results, where disc brakes are employed, in the application of disc pads to disc plates which produce friction to stop the motion of the wheel.

The two braking systems described above work completely independently to each other. The hydraulic brakes are released as soon as the foot is removed from the foot pedal. Thus, when the car is unattended it is only the parkbrake which is operative to prevent movement of the vehicle. Accordingly, when the vehicle is started, it is only the parkbrake which acts to prevent movement of the vehicle should it have been left in gear. This is unsatisfactory given that these brakes are only applied to the rear wheels of the vehicle, are less efficient than the hydraulic brakes and may often be applied with insufficient force.

Referring to Figures 2 and 3 of the accompanying drawings, a generalised, schematic diagram showing the basic features of the present invention is illustrated.

For the sake of good order and simplicity, the identical features already described in relation to Figure 1 are given the same reference number and only the differences will be described in detail. The invention provides an improved braking system for a motor vehicle having a mechanically operated braking system coupled to a hydraulic braking system. The hydraulic brakes are coupled to the operation of the mechanical parkbrake by the activation of an electromagnet 23. The contacts of the magnet are closed when the ignition switch 21 of the vehicle is turned to the on-position and electric current is fed from the vehicle battery to the electromagnet. Thus, the electromagnet is activated whilst the engine is running.In this manner, movement of the mechanical lever 3 not only results in the application of the block brakes 7 to the rear wheels 6 but, whilst the electromagnet is closed, operates the hydraulic brakes via an actuator 25 attached thereto.

Referring to Figure 4 of the accompanying drawings, a preferred embodiment of an electromagnetic coupling unit 33 for use in the present invention is illustrated.

The unit 33 contains an electromagnet 23 and an armature plate 26 surrounded by a sleeve guide 29. An electric cable (not shown) is connected at one end to a terminal of the vehicle ignition switch and, at the opposite end, to a connector 40 which, in turn, is connected to the electromagnet 23 (preferably min 700N). The connector enables the electromagnet to be disconnected from the vehicle ignition to allow independent testing of all three braking systems, ie., the parkbrake, hydraulic brakes and the enhanced system of the present invention. A further sleeved wire cable 42a is attached to the electromagnet which is routed and connected to a modified equalising yoke 41 which links operation of the mechanical lever 3 to the application of block brakes to the rear wheels 6 of the vehicle.The armature plate 26 is also connected to a wire cable 42b, preferably being sleeved, leading to the foot pedal to allow for operation of the hydraulic brakes.

The electromagnet 23 is powered by the battery of the vehicle via the connection 40. When the ignition of the vehicle is switched off, no electric current flows to the magnet 23, the magnet and armature plate remain spaced apart and the hydraulic brakes are not activated by movement of the mechanical lever of the parkbrake. Hence, when the vehicle is parked only the mechanical parkbrake is operative. When a driver returns to a vehicle, turning the ignition switch to the "on" position allows electric current to flow from the car battery to the electromagnet 23.

This causes the magnet to contact the plate 26 to provide an unbroken connection between the lever which operates the mechanical brakes on the rear wheels and the hydraulic brakes acting on all four wheels. Hence, operation of the foot pedal when the ignition is on also results in the simultaneous application of the block brakes to the rear wheels of the vehicle and, more importantly, operation of the mechanical lever 3 causes the application of the hydraulic brakes to all four wheels.

Generally, the ignition switch of motor vehicles is provided with four positions. The first position frees the steering wheel lock and the second allows the auxillary electric to be powered, for example, enabling operation of the vehicle lights, windscreen wipers, stereo etc. The third switches on the ignition without starting the vehicle, whilst the fourth, being spring loaded, energises the starter motor to start the engine and is returned to position no. 3 once the engine running. Preferably, in the system of the present invention the wire leading from the battery live terminal to the ignition switch feeding the electromagnet is connected to the No. 3 position of the ignition switch.This is so that if the driver remains in a stationary vehicle for a long period, such as when there is traffic congestion, the ignition key may be turned to the second position to release the pressure exerted on the hydraulic fluid thereby preventing brake fluid contamination at the wheel cylinders whilst other electric facilities of the vehicle remain available to the driver.

Referring to Figures 5, 6 and 7 of the accompanying drawings, three types of connection for actuating the hydraulic, or other, braking system upon application of the parkbrake are illustrated. Again, features already discussed are given the same reference number and only the differences will be described. Figure 7 is a cheap and practical means of actuating the hydraulic brakes. Wire cables 42a, 42b, preferably being sleeved, are attached to either end of the electromagnetic coupling unit 33. The opposite end of the wire cable 42a is connected to an equalising yoke 41 by suitable fastening means, such as a tunnel bracket 48. The yoke causes application of the block brakes onto the rear wheels by movement of the mechanical lever 3.The opposite end of wire cable 42b is linked to the underside of the foot pedal 11 by suitable fastening means, such as by the provision of an eyelet in the end of the cable which is secured by a pin to a stirrup which is clamped to the foot pedal (not shown).

When the vehicle ignition is switched on, an unbroken circuit occurs between the cables 42a and 42b thereby causing the application of the mechanical braking system by the lever 3 to result in the pulling of the foot pedal towards the bulkhead (shown by broken lines) which causes movement of the piston and thus, activation of the hydraulic brakes.

Preferably, the conventional parkbrake link which connects the lever 3 to the yoke 41 is replaced with a tension spring 46. Use of the conventional link causes the wires actuating the rear brake wheels to become taut. This may prevent further movement of the lever to pull the wire actuating the foot pedal 11, thus hindering the actuation of the hydraulic brakes. The use of the tension spring 46 allows the lever 3 to be pulled to such an extent that the rear brakes are applied and further, allows additional movement to result in the complete application of the hydraulic brakes via movement of the foot pedal 11.This also provides a number of other advantages such as reducing the gauge of the wire required to activate the brakes thereby enabling easier routing of the cable, reducing the amount of effort required to apply the braking system by operation of the lever, reducing the possibility of early fracture of the wires due to repeated stress of the wires and increasing the extent of application of the hydraulic brakes thus enhancing the efficiency thereof.

Alternatively, the cable linkage may be connected to an arm 80 by means of, for example, a tunnel bracket 48, which drives a separate hydraulic system 90 for depression of the foot pedal towards the bulkhead as though applied by foot, as illustrated in Figures 6 and 7 of the accompanying drawings. For example, referring to Figure 6, the cable linkage 42b running from the electromagnet opposite that running to the lever 3 may be connected to an arm 80 linked to a piston in a compression barrel 84. Movement of the arm when the parkbrake is applied using the mechanical lever and whilst the ignition of the vehicle is on moves the piston which causes hydraulic fluid to flow through a hydraulic pipe 86 which, via a slave cylinder and support bracket 88, results in application of the hydraulic brakes via the foot pedal 11.Again, the conventional parkbrake link connecting the lever to the yoke may be replaced with the tension spring. The compression barrel 84 is provided with a charge nipple 85 to allow for replenishment of the system with hydraulic fluid during servicing of the vehicle.

Alternatively, the supplemental hydraulic system 90 may be provided with a master cylinder 92 in place of the compression barrel to allow for application of the hydraulic brakes by depression of the foot pedal 11. The master cylinder has a remote reservoir 94 for replenishment of the system with hydraulic fluid, as shown in Figure 7.

Whilst the present invention has been described with particular reference to a vehicle having a mechanically operated braking system and a hydraulic braking system, it is to be appreciated that a similar mechanism could be employed to couple the mechanical braking system to other types of braking system such as pneumatic, vacuum-assisted or electrically operated braking systems, or even a further brake-bywire system.

Additionally, alternative coupling means to enable the application of the hydraulic brakes simultaneously with the application of the lever operated braking system may be used instead of an electromagnet such as a solenoid which acts as a har magnet when current is passed through the coil of the solenoid from the vehicle battery when the ignition is switched on. This type of coupling may be compatible with vehicles equipped with anti-lock braking systems.

The use of a mechanically operated braking system coupled to another braking system greatly improves the overall efficiency of the braking system of a vehicle. It curtails the driver initiated unintentional movements of a vehicle when the vehicle is accidently started in gear. It also assists in enabling vehicles to remain stationary on steep inclines, particularly in adverse weather conditions, due to the brakes being applied to all four wheels instead of only the rear ones. The greater efficiency of the hydraulic brakes also enables vehicles towing caravans and trailers to be able to stop on steep inclines.Additionally, the application and release of the parkbrake by means of the mechanical lever requires less effort due to the superior activating power of the hydraulics taking up the strain on the mechanical parkbrake wires to effect easier release and application of the mechanical parkbrake.

It has also been known to start a motor vehicle and drive off with the parkbrake still applied to the rear wheels of the vehicle. The enhanced efficiency of the parkbrake of the present invention when the engine of the vehicle is on prevents accidental movement of the vehicle whilst the parkbrake is still applied, thus preventing damage to the vehicle.

It is emphasised that the improved system does not effect the existing independent braking systems in any manner. Should the electromagnet fail, the mechanically operated braking system and hydraulic braking system (or other braking system) remain operahle independently of one another by use of the mechanical lever and foot pedal respectively.

The braking system of the present invention may he applied to all forms of multiple axled road vehicles, such as private cars, light commercial vehicles and heavy goods vehicles. The supplemental braking system may be fitted as original equipment to a new vehicle or may be installed to existing vehicles during a routine service.

Claims

1. A braking system for a motor vehicle comprising a mechanically operated braking system, another braking system operated by another medium and means for coupling operation of the mechanically operated braking system to said another braking system when the vehicle ignition is on, whereby said another braking system operates in conjunction with operation of the mechanically operated braking system.

2. A braking system as claimed in claim 1, wherein the said another braking system is a hydraulic braking system.

3. A braking system as claimed in claim 1 or 2, wherein the means for coupling the two braking systems is an electromagnet.

4. A braking system as claimed in claim 3, wherein the electromagnet is connected to the vehicle ignition by means of an electric cable.

5. A braking system as claimed in claim 4, wherein the electric cable is connected to the electromagnet by means of a plug and socket connector.

6. A braking system as claimed in claim 3, 4 or 5, wherein the electromagnet is contained within an electromagnetic coupling unit having a housing and a lid.

7. A braking system as claimed in any one of claims 3 to 6, wherein an armature plate is provided spaced apart from the electromagnet for making contact therewith when the vehicle ignition is on.

8. A braking system as claimed in claim 7, wherein the electromagnet and armature plate are provided with mechanical means to prevent excessive separation thereof.

9. A braking system as claimed in claim 8, wherein the electromagnet and armature plate are surrounded by a sleeve guide.

10. A braking system as claimed in claim 8 or 9, wherein the electromagnet and armature plate are spring biased towards each other.

11. A braking system as claimed in any one of claims 3 to 10, wherein the electromagnet is min 700N.

12. A braking system as claimed in any one of claims 3 to 11, wherein the electromagnet is provided with a earth return connection.

13. A braking system as claimed in claim 1 or 2, wherein the coupling means is a solenoid.

14. A braking system as claimed in any one of the preceding claims wherein the coupled systems are linked by means of a plurality of actuators such that the normal operation of one system results in simultaneous operation of the said another braking system when the vehicle ignition is on.

15. A braking system as claimed in claim 14, wherein the actuators are in the form of a plurality of wire cables connected to respective ends of the coupling means.

16. A braking system as claimed in claim 15, wherein a first cable leads from one end of the coupling means to means for operating the mechanical braking system and a second cable leads from the opposite end of the coupling means to means for operating the said another braking system.

17. A braking system as claimed in claim 16, wherein the first cable leads to an equalising yoke which causes application of the mechanical brakes to rear wheels of the vehicle upon movement of a lever.

18. A braking system as claimed in claim 17, wherein the equalising yoke is linked to the lever by means of a tension spring.

19. A braking system as claimed in claim 16, 17 or 18, wherein the means for operating the said another braking system is a foot pedal which causes a piston in a master cylinder to move thereby exerting pressure on hydraulic fluid contained therein to result in the application of hydraulic brakes.

20. A braking system as claimed in claim 19, wherein the second wire cable is directly linked to the foot pedal by suitable fastening means.

21. A braking system as claimed in claim 19, wherein the second wire cable is connected to an arm for driving a separate hydraulic system for exerting pressure on the foot pedal to cause application of the hydraulic brakes.

22. A braking system as claimed in claim 21, wherein the separate hydraulic system comprises a master cylinder having a piston connected to the arm for exerting pressure on hydraulic fluid in a pipe leading to the foot pedal.

23. A braking system as claimed in claim 22, wherein the master cylinder is provided with remote reservoir for replenishment of the system with hydraulic fluid.

24. A braking system as claimed in claim 21, wherein the separate hydraulic system comprises a compression barrel having a piston connected to the arm for exerting pressure on hydraulic fluid in a pipe leading to the foot pedal.

25. A braking system as claimed in claim 24, wherein the compression barrel is provided with a charge nipple for replenishment of the system with hydraulic fluid.

26. A braking system as claimed in any one of claims 21 to 25, wherein the hydraulic pipe is connected to the foot pedal by means of a slave cylinder and support bracket.

27. A braking system as claimed in any one of the preceding claims wherein the coupling means is activated by the ignition switch of the vehicle being in position 3 which switches the ignition on without starting the vehicle thereby enabling the said another braking system to be released whilst other auxillary electric facilities of the vehicle remain available.

28. A braking system as claimed in claim 1, wherein the said another braking system is selected from a pneumatic, vacuum-assisted, mechanical or electrically operated braking system.

29. A braking system substantially as hereinbefore described with reference to, or as illustrated in Figures 2 and 3, 4, 5, 6 and 7 of the accompanying drawings.