Braking System for a Wheeled Vehicle

Abstract

A braking system for a vehicle includes two meterable metering brake circuits and a non-meterable parking brake circuit. Each of the two metering brake circuits has a metering brake device which is assignable to a wheel of the vehicle. The two metering brake circuits have a common metering operating device, with which the two metering brake devices are operable simultaneously. The metering operating device has a tandem brake cylinder, with two chambers which are each part of one of the metering brake circuits. The parking brake circuit has two parking brake devices, which are each assignable to a respective wheel of the vehicle. The parking brake circuit has a parking operating device with which the two parking brake devices are operable simultaneously.

Claims

1. A braking system for a vehicle, comprising: two meterable metering brake circuits; and a non-meterable parking brake circuit, wherein each of two metering brake circuits has a metering brake device which is assignable to a wheel of the vehicle; the two metering brake circuits have a common metering operating device, with which the two metering brake devices are operable simultaneously; the metering operating device has a tandem brake cylinder, with two chambers which are each part of one of the metering brake circuits; the parking brake circuit has two parking brake devices, which are each assignable to a wheel of the vehicle; and wherein the parking brake circuit has a parking operating device with which the two parking brake devices are operable simultaneously.

2. The braking system as claimed in claim 1, wherein the two chambers of the tandem brake cylinder are separated from each other by a floating piston.

3. The braking system as claimed in claim 1, wherein a branch to the two parking brake devices is provided in the parking brake circuit.

4. The braking system as claimed in claim 1, wherein, in each case, one metering brake device and one parking brake device are assignable to the same wheel of the vehicle.

5. The braking system as claimed in claim 1, wherein all of the brake devices are arrangeable on a common axle of the vehicle.

6. The braking system as claimed in claim 1, wherein each of the parking brake devices comprises a spring-loaded brake,

7. The braking system as claimed in claim 6, wherein the spring--loaded brake has a spring-loaded brake piston which, in the event of a pressure build up in the parking brake circuit, is liftable off a brake disk pack, and which, in the event of a zero-pressure situation in the parking brake circuit, acts against the brake disk pack because of the spring loading.

8. The braking system as claimed in claim I, wherein a pressure limiting valve is provided in each of the metering brake circuits.

9. The braking system as claimed in claim 1, wherein a throttle non-return valve is, in each case, provided in the parking brake circuit.

10. The braking system as claimed in claim 1, wherein the parking operating device comprises a binary switching device.

11. A working vehicle, comprising two axles, on which, in each case, at least one left wheel and at least one a right wheel are arranged rotatably on the associated axle; wherein one of the axles is a brakeable axle, on which at least one brake device is arranged; the other axle is a freely rotatable axle, on which no brake device is arranged; and wherein the brake device is part of a braking system including two meterable metering brake circuits; and a nor-meterable parking brake circuit, wherein each of two metering brake circuits has a metering brake device which is assignable to a wheel of the vehicle; the two metering brake circuits have a common metering operating device, with which the two metering brake devices are operable simultaneously; the metering operating device has a tandem brake cylinder, with two chambers which are each part of one of the metering brake circuits; the parking brake circuit has two parking brake devices, which are each assignable to a wheel of the vehicle; and wherein the parking brake circuit has a parking operating device with which the two parking brake devices are operable simultaneously.

12. The working vehicle as claimed in claim 11, wherein the two axles are connected to one another by a cardan shaft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1 shows a braking system known from the prior art; and

[0034] FIG. 2 shows a braking system according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0035] FIG. 2 schematically illustrates a vehicle, the mechanical design of which corresponds to the vehicle of FIG. 1. The vehicle thus has a rear axle 1 and a front axle 2. The motor power is distributed via a drive shaft 3, a distribution transmission 4 and cardan shaft 5 to the two axles 1, 2. Rotatably mounted hubs 7, on which corresponding wheels (not illustrated) can be fastened, are arranged at the respective ends of the axles 1, 2.

[0036] Analogously to the vehicle of FIG. 1, also in the case of the vehicle of FIG. 2 only the front axle 2 is brakeable, while the rear axle 1 freely rotates at the same time. For this purpose, a brake device 12 is provided on each hub 7 of the front axle 2.

[0037] Each of the axles 1, 2 has a differential transmission 20 in order to decouple the two wheels of the axle from each other.

[0038] Therefore, if one of the brake devices 12 on the front axle 2 fails, the brake device 12 of the other wheel takes over the braking of the vehicle. The braking torque is then also transmitted by means of the cardan shaft 5 to the other axle (rear axle 1), and therefore, although the (still functional) brake is only positioned on one wheel, it acts indirectly on all four wheels via the cardan shaft 5 and the differential transmission 20.

[0039] For the activation of the brake devices 12, separate systems are provided, namely two meterable metering brake circuits 21 (or 21a, 21b) and a non-meterable parking brake circuit 22.

[0040] The metering brake circuits 21 are illustrated in FIG. 2 as a left metering brake circuit 21a (for the left wheel or the left hub 7 of the front axle 2) and a right metering brake circuit 21b (analogously for the right wheel or the right hub 7 of the front axle 2).

[0041] Each of the metering brake circuits 21 has an equalizing container 23 for brake fluid which is in each case conducted via a dedicated line 24 to a common tandem brake cylinder 25. The tandem brake cylinder 25 is coupled to a foot pedal 26 via which the operator can exert a compressive force on a piston 27.

[0042] The tandem brake cylinder 25 has two chambers 28a (for the left metering brake circuit 21a) and 28b (for the right metering brake circuit 21b). The chambers 28a, 28b are separated from each other by a floating piston 29. The floating piston 29 ensures that the same hydraulic pressure always prevails in the two chambers 28a, 28b. Possibly occurring pressure differences are directly equalized by shifting of the floating piston 29. It can thereby be achieved that a standard, uniform braking action is obtained by the two separate metering brake circuits 21.

[0043] A pressure limiting valve 30 is provided in each of the metering brake circuits 21a, 21b in order to limit the maximum pressure. Damage to the brake is thereby intended to be avoided.

[0044] The metering brake circuits 21a, 21b each lead to the brake device 12 assigned thereto and act there upon one (or more) pistons 31.

[0045] The braking pressure is metered by the operator by actuation of the foot pedal 26. The pressure in the chambers 28a, 28b is higher the more powerfully the operator presses on the foot pedal 26, and therefore the brake pistons 31 are correspondingly likewise acted upon with increased pressure and pressed against an assigned disk pack 32.

[0046] The parking brake circuit 22 has a switching device 33 serving as a parking operating device. The switching device 33 can be an electric button or switch or else a hydraulic or mechanical lever or switch. The switching device 33 serves to conduct pressure from a pressure supply 34 belonging to the vehicle to the brake (also explained below) or to remove the pressure in the brake fluid to a tank 35.

[0047] The parking brake circuit 22 in each case includes a spring-loaded brake 36 which is assigned to the corresponding brake device 12 and therefore hub 7. The spring-loaded brake 36 has a piston which is pressed in a spring-loaded manner against the disk pack 32. Only in the event of pressurization via the parking brake circuit 22 and correspondingly present pressure supply 34 is the piston in the spring-loaded brake 36 lifted off the disk pack 32 and thus releases the rotation.

[0048] A branch 37 is provided for the uniform distribution of the braking pressure in the parking brake circuit 32.

[0049] A throttle non-return valve 38 is each case provided between the branch 37 and the respective spring-loaded brake 36, The throttle non-return valve 38 on account of its throttling action prevents too rapid a pressure drop in the parking brake circuit 22 when the pressure supply 34 is interrupted or the brake line to the tank 35 is opened. As a result, it is possible not to carry out the braking operation abruptly, but in a somewhat delayed manner in order to avoid sudden braking of the vehicle and to ensure stability in all operating states. This can be comfortable in particular whenever the vehicle is still moving slowly while the driver has already activated the parking brake.

[0050] In a reverse direction of flow, the non-return valve in the throttle non-return valve 38 is opened, and therefore, when the brake is released, the brake (spring-loaded brake 36) can be immediately acted upon with braking pressure and therefore released.

[0051] A pressure sensor 39 is provided in one of the metering brake circuits 21a, 21b (in the left metering brake circuit 21a in the example shown in FIG. 2) in order to monitor the braking pressure, On account of the interaction of the two metering brake circuits 21a, 21b via the tandem brake cylinder 25, only one pressure sensor 39 is required. A further pressure sensor, e.g. in the parking brake circuit 22, is not required. By contrast, in the prior art explained in conjunction with FIG. 1, two pressure sensors 16, 17 have to be provided. The pressure sensor 39 serves firstly for coordinating the braking system at the factory and secondly for monitoring during operation.

[0052] The design according to the invention of a braking system that is shown in FIG. 2 therefore differs from the prior art braking system shown in FIG. 1 in particular in that, although three brake circuits (2 brake circuits in the prior art in FIG. 1) are now assembled, they permit a simpler design. By means of the use of the tandem brake cylinder 25 and of the two meterable metering brake circuits 21 (foot brake), the StVZO regulations are met. The hand brake or parking brake formed in a non-meterable manner as the parking brake circuit 22 can therefore be constructed more simply.