Parking braking in vehicles having conventional braking systems

Details Parking braking in vehicles having conventional braking systems Parking braking in vehicles having conventional braking systems

1999-10-22

2001-10-23

Butler, Douglas C. (Department: 3613)

Brakes

Elements

Locks

C188S031000, C188S10600P, C188S162000, C188S156000, C303S089000, C303S020000, C303S013000, C303S113200, C303S191000

Reexamination Certificate

active

06305511

ABSTRACT:

The present invention relates to parking braking in vehicles having conventional braking systems, ie. braking systems not of the type having so-called Electronic Braking (EBS). In conventional braking systems, there is a mechanical (including pneumatic/hydraulic) coupling between the brake pedal and the brakes, usually a hydraulic or pneumatic coupling. In EBS systems, there is no mechanical coupling between the brake pedal and the brakes, the brakes being applied via modulators which are operated via electrical signals generated in response to actuation of the brake pedal and controlled by a microcomputer.
The conventional approach to parking brakes in conventionally braked vehicles is, in the case of hydraulically operated brakes, to provide a mechanical linkage operated by a hand-brake lever which operates the brakes directly. In the case of pneumatically operated brakes, the conventional approach is to release air pressure from spring brake actuators to allow the spring forces to apply to brakes.
In our earlier unpublished applications nos. UK 9806544.4 and PCT/GB99/00953, we have described means by which parking braking can be integrated into Electronic Braking systems (EBS). The described proposals utilise the EBS, under the control of a hand-operated parking control, to apply the brakes to a desired level, which are then mechanically latched in place to maintain that desired level for parking purposes.
The present invention is concerned with the application of parking braking of this type to vehicles that do not have EBS.
In accordance with the present invention, there is provided a parking braking system in a vehicle not having EBS wherein, for parking braking, the brakes are arranged to be supplied with actuating fluid from a pressure source under the control of a manually operated electrical device and wherein, upon selecting parking braking by actuation of the electrical device, the brakes are arranged to be applied and mechanically locked or latched in place.
In some embodiments, use is made of the pressure source provided already for traction control for the supply of actuating fluid to apply the parking braking.
Most modern vehicles are equipped with an antilock braking system (A.B.S.) and increasingly, a traction control system (known typically as ASR) is also provided. ASR includes valving that is able to apply the brakes of the driven wheels independently of the foot brake control. This is used in conjunction with the ABS valves to arrest the motion of a spinning drive axle wheel. Via the differential, it is then possible to drive the vehicle forward utilising the non-spinning wheel. Advantageously, such valving can be used to apply and regulate the braking for parking, in much the same way that is proposed with the EBS based parking system in our abovementioned earlier patent applications.
If ASR is not available on a vehicle, then dedicated valving is provided, together with a suitable pressure source, to apply the brakes to a desired parking braking level prior to application of the mechanical lock or latch to maintain that parking braking level.
By providing such a mechanical latch or lock, the braking force applied to the brake actuators can be released/removed once the latch or lock has been actuated to hold the brakes in the brakes-applied condition.
In some embodiments, the manually operated electrical device is adapted to generate and transmit to a parking braking ECU an electrical parking braking signal, the vehicle brakes being arranged to be mechanically locked or latched via the parking braking ECU in a brakes-applied condition in response to the generation of said electrical parking brake signal.
In some embodiments, the manually operated electrical device is adapted to generate and transmit to a vehicle mounted ECU an electrical parking brake signal, the vehicle brakes being arranged to be mechanically locked or latched via said vehicle mounted ECU in a brakes-applied condition in response to the generation of said electrical parking brake signal.
In some embodiments the manually operated electrical device comprises a switch.
In some other embodiments, the manually operated electrical device comprises a variable transducer.
The variable transducer can be adapted to enable graduated braking to be provided between the brakes-off and park positions.
Preferably, the brake actuators are arranged to be released once the latch or lock has been actuated to hold the brakes in the brakes-applied condition.
Advantageously, following actuation of the manually operable electrical device, the initiation of the latching action is provided by a feedback quantity, taken from the sensed actuation level being exerted in the brake, reaching a preset or controlled level.
In some embodiments, the feedback quantity is the pressure developed inside the brake actuator against the internal brake forces being developed within the brake.
In some other embodiments, the feedback quantity is the displacement of a component within the brake actuation mechanism. In still further embodiments, the feedback quantity is the force developed inside the brake, measured by a sensor or sensors positioned so as to be subjected to the actuation/clamping stresses within the brake.
Advantageously, the mechanical latch/lock comprises a stop device which, when actuated, moves into a position to mechanically hold the brake in a parking braking condition, irrespective of whether the brake force generated is then reduced.
In some embodiments, the stop device is a solenoid operated pin.
In some other embodiments, the stop device comprises a pivotable latch which is selectively rotatable by an actuator for single position engagement with an operating or input lever or shaft of the brake to maintain the brake in the parking braking condition.
Preferably, the stop device is constructed so as to be capable of mechanically holding the brakes in any of a range of park load levels.
In some embodiments, the stop device comprises a pivotable latch which is selectively rotatable by an actuator to any of a plurality of engagement positions with an operating or input lever or shaft of the brake to maintain the brake in a selected parking braking condition.
In other embodiments, the stop device comprises a rotatable cam which engages an operating or input lever or shaft of the brake for maintaining the brake in a selected parking braking condition.
In still other embodiments, the stop device comprises a wedge which is arranged to be selectively driven by a controlled actuator into engagement with an operating or input lever or shaft of the brake to maintain the brake in a selected parking braking condition.
Preferably, the controlled actuator is an air cylinder or an electric motor.
Advantageously, the wedge is coupled to the electric motor by way of a mechanism which is non-reversible except by reverse driving of the motor.
Advantageously, said non-reversible mechanism is a high reduction gearbox.
Preferably, in order to enable parking braking to be released, the brake force is arranged to be re-applied up to a level at which the brake latch or lock can be released.
In some embodiments as described above, following selection of a parking braking release condition of said manually operated electrical device, initiation of release of the latching action is arranged to be dependent upon the aforementioned feedback quantity.
Using parking braking systems in accordance with the present invention, it is possible to emulate the principal features of conventional pneumatically controlled spring brakes, including the ability to modulate the amount of braking.
Using a single point latch arrangement which clamps the parking brake at a fixed position cannot take account of the variance in such brake condition tolerances as brake running clearance, new or worn linings and lining compressibility, without the possibility of overselling the clamp load. A system in accordance with embodiments of the present invention having a variable park latch arrangement can seek to overcome this problem by determining the level at which

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