ELECTROHYDRAULIC BRAKE SYSTEM FOR AN OFF-ROAD VEHICLE

Abstract

An electrohydraulic brake system of an off-road vehicle includes a first hydraulic brake circuit for a first vehicle axle; a second hydraulic brake circuit for at least one second vehicle axle; a respective wheel brake for each vehicle wheel per vehicle axle; an electronic control unit having a brake force distribution function; a brake signal generator; at least one central brake force distribution valve per brake circuit, a signal input of the control unit for registering a braking signal of the brake signal generator; and at least one signal output of the control unit per brake force distribution valve. A brake pressure for applying a hydraulic pressure fluid to the brake cylinders of the wheel brakes on the respective vehicle axles can be fed to the respective brake circuit by the control unit in conjunction with the central brake force distribution valve and the brake signal generator.

Claims

1. An electrohydraulic brake system (1) of an off-road vehicle, comprising: a first brake circuit (14) associated with a first vehicle axle (2), a second brake circuit (15) associated with at least one second vehicle axle (3, 4), at least one respective wheel brake (8a, 8b, 9a, 9b, 10a, 10b) associated with a vehicle wheel (5a, 5b, 6a, 6b, 7a, 7b) for each of the first and second vehicle axles (2, 3, 4), wherein the wheel brake has a brake cylinder (11a, 11b, 12a, 12b, 13a, 13b) configured to be pressurized by a hydraulic pressure fluid, an electronic control unit (26) having a brake force distribution function, a brake signal generator (19), at least one respective central brake force distribution valve (18, 21) for each of the first and second brake circuits (14, 15), at least one signal input of the electronic control unit (26) for receiving a braking signal of the brake signal generator (19), and at least one respective signal output of the electronic control unit (26) for each of the at least one brake force distribution valve (18, 21), wherein the electronic control unit is configured to hydraulically pressurize the brake cylinders (11a, 11b, 12a, 12b, 13a, 13b) of the wheel brakes (8a, 8b, 9a, 9b, 10a, 10b) on respective vehicle axles (2, 3, 4) by directing the hydraulic pressure fluid to at least one of the first and second brake circuits (14, 15) in cooperation with the central brake force distribution valve (18, 21) and the brake signal generator (19).

2. The brake system as claimed in claim 1, wherein the brake force distribution valves (18, 21) are embodied as proportional valves.

3. The brake system as claimed in claim 1, wherein at least one of the first and second brake circuits (14, 15) has a central pressure sensor (27, 28) for monitoring a prevailing brake pressure, and wherein the electronic control unit (26) has a signal input for each of the at least one central pressure sensor (27, 28).

4. The brake system as claimed in claim 1, wherein a respective wheel speed sensor (24a, 24b, 24c, 24d, 24e, 24f) is associated with each vehicle wheel (5a, 5b, 6a, 6b, 7a, 7b), wherein the electronic control unit (26) has a signal input for each respective wheel speed sensor (24a, 24b, 24c, 24d, 24e, 24f).

5. The brake system as claimed in one of claim 1, wherein at least one of the first and second brake circuits (14, 15) has a respective central temperature sensor (23a, 23b) for monitoring the temperature of the hydraulic pressure fluid in the brake circuit (14, 15), and wherein the electronic control unit (26) has a signal input for each respective temperature sensor (23a, 23b).

6. The brake system as claimed in one of claim 1, wherein the electrohydraulic brake system (1) forms an anti-lock brake system (20), wherein the anti-lock brake system (20) has a respective anti-lock brake control valve (22a, 22b, 22c, 22d, 22e, 22f) for each vehicle wheel (5a, 5b, 6a, 6b, 7a, 7b), the respective anti-lock brake control valve cooperating with the brake force distribution valve (18, 21) of the first or second brake circuit (14, 15) to generate an anti-lock braking function, wherein the electronic control unit (26) has a respective signal output for controlling each respective anti-lock brake control valve (22a, 22b, 22c, 22d, 22e, 22f).

7. The brake system as claimed in claim 6, wherein the anti-lock brake control valves (22a, 22b, 22c, 22d, 22e, 22f) of the anti-lock brake control system (20) are embodied as pulse-width-modulated valves, wherein the electronic control unit (26) is configured to perform pulse control of these valves.

8. The brake system as claimed in one of claim 1, wherein the electrohydraulic brake system (1) has a starter control system which cooperates with the anti-lock brake control system (20) to generate a starter control function.

9. The brake system as claimed in one of claim 1, wherein the electrohydraulic brake system (1) has a hydraulic redundancy brake circuit (25) with two redundancy valves (25a, 25b) configured to be actuated and to be hydraulically connected to one of the two brake force distribution valves (18, 21), the two redundancy valves being electrically connected to the electronic control unit (26) and enable the electronic control unit to activate an emergency braking function of the off-road vehicle in the event of a malfunction of the brake system.

10. An off-road vehicle comprising an electrohydraulic brake system (1) according to claim 1.

11. The off-road vehicle as claimed in claim 10, wherein the off-road vehicle is an agricultural tractor, a construction vehicle, a military vehicle, a truck, or a tractor-trailer vehicle combination.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0023] In the drawing, the single figure shows an electrohydraulic plan of a brake system of an off-road vehicle.

DETAILED DESCRIPTION OF THE DRAWING

[0024] In the drawing, the single figure shows an electrohydraulic plan of a brake system 1 of an off-road vehicle. For the sake of improved differentiation, a prefix of H is placed in front of all the hydraulic connecting lines, and a prefix E is placed in front of all the electrical connecting lines.

[0025] Accordingly, the off-road vehicle in the example shown comprises a first vehicle axle 2 which is embodied as a front axle, and two second and third vehicle axles 3, 4 which are embodied as rear axles. In order to brake the front vehicle wheels 5a, 5b and the rear vehicle wheels 6a, 6b and 7a, 7b, each vehicle wheel 5a, 5b, 6a, 6b, 7a, 7b is assigned a wheel brake 8a, 8b, 9a, 9b, 10a, 10b. The wheel brakes 8a, 8b, 9a, 9b, 10a, 10b can be actuated hydraulically and each have a brake cylinder 11a, 11b, 12a, 12b, 13a, 13b. The wheel brakes 8a, 8b, 9a, 9b, 10a, 10b correspondingly apply a braking force, in accordance with the hydraulic pressure which is respectively present in the brake cylinder 11a, 11b, 12a, 12b, 13a, 13b, to the rotating vehicle wheel 5a, 5b, 6a, 6b, 7a, 7b. The brake cylinders 12a, 12b or 13a, 13b of the front vehicle wheels 6a, 6b or 7a, 7b of a rear vehicle axle 3, 4 can additionally be provided with spring mechanisms for a parking brake function.

[0026] In the example shown, the wheel brakes 8a, 8b of the front vehicle axle 2 are assigned to a common first hydraulic brake circuit 14, while the wheel brakes 9a, 9b, 10a, 10b or the rear vehicle axles 3, 4 can be actuated by a second hydraulic brake circuit 15. A first pressure reservoir 16 is assigned here to the first brake circuit 14 and is connected via a first hydraulic brake line H1 to the first brake cylinder 11a, and via a second hydraulic brake line H2 to the second brake cylinder 11b of the front first vehicle axle 2. The second brake circuit 15 is assigned a second pressure medium reservoir 17 which is connected via a third hydraulic brake line H3 to the third brake cylinder 12a, and via a fourth hydraulic brake line H4 to the fourth brake cylinder 12b of the rear second vehicle axle 3, and via a fifth hydraulic brake line H5 to the fifth brake cylinder 13a, and via a sixth hydraulic brake line H6 to the sixth brake cylinder 13b of the rear third vehicle axle 4.

[0027] In the first brake circuit 14 a first brake force distribution valve 18, which is embodied as a 3/3-way proportional solenoid switching valve is arranged. This first brake force distribution valve 18 is connected via a seventh hydraulic connecting line H7 to a brake signal generator 19, and via an eighth hydraulic connecting line H8 to an input of a first ABS module 20a, assigned to the first brake circuit 14 and to the second brake circuit 15, of an anti-lock brake system 20.

[0028] In the second brake circuit 15, a second brake force distribution valve 21, embodied as a 3/3-way proportional switching valve, is arranged. The second brake force distribution valve 21 is connected via a ninth hydraulic connecting line H9 to the brake signal generator 19, and via a tenth hydraulic connecting line H10 to an input of the first ABS module 20a assigned to the first brake circuit 14 and the second brake circuit 15, and to an input of a second ABS module 20b, assigned to the second brake circuit 15, of the anti-brake system 20.

[0029] The brake signal generator 19 is coupled to a braking request means, in particular to a brake pedal not illustrated in the driver's cab of the vehicle, wherein pedal travel, a pedal position or the like are transferred via sensor means to the signal generator 19 which makes this data available continuously or for retrieval. The driver of the vehicle can request, by activating the brake pedal, hydraulic brake pressure for acting on the brake cylinders 11a, 11b, 12a, 12b, 13a, 13b.

[0030] Each of the two ABS modules 20a, 20b has three anti-lock brake control valves 22a, 22b, 22c, 22d, 22e, 22f which are embodied as pulse-width-modulated valves, wherein each brake cylinder 11a, 11b, 12a, 12b, 13a, 13b of the wheel brakes 8a, 8b, 9a, 9b, 10a, 10b is respectively assigned an anti-lock brake control valve 22a, 22b, 22c, 22d, 22e, 22f for controlling the brake pressure of an anti-lock brake function. In addition, the two ABS modules 20a, 20b each have a temperature sensor 23a, 23b for monitoring the temperature of the hydraulic fluid of the two brake circuits 14, 15. The vehicle wheels 5a, 5b, 6a, 6b, 7a, 7b are each assigned a wheel speed sensor 24a, 24b, 24c, 24d, 24e, 24f for detecting slip and controlling slip via the anti-lock brake system.

[0031] Furthermore, the electrohydraulic brake system 1 has a redundancy brake circuit 25 in order to be able to safely brake the vehicle in the event of a fault-induced failure of the brake system 1 or of parts thereof. The redundancy brake circuit 25 has two redundancy valves 25a, 25b which are each embodied as 3/2-way solenoid switching valves. In this context, a first redundancy valve 25a is connected upstream of the first brake circuit 14 and is connected via an eleventh hydraulic connecting line H11 to the brake signal generator 19, on the input side, and to the first brake force distribution valve 18, on the output side. A second redundancy valve 25b is connected upstream of the second brake circuit 15 and is connected via a twelfth hydraulic connecting line H12 to the brake signal generator 19 on the input side, and to the brake force distribution valve 21 on the output side.

[0032] The electrohydraulic brake system 1 is controlled by a central electronic control unit 26. The driver of the motor vehicle can, by activating the brake pedal, signal a braking request, but the subsequent braking behavior of the vehicle is influenced by the control unit 26.

[0033] The electronic control 26 has a plurality of electrical interfaces. They relate to connections for: four electrical connecting lines E1, E2, E3, E4 to the brake signal generator 19 for two braking requirements sensors and for two braking requirement switches which are assigned to the brake signal generator 19, but are not illustrated further here; two electrical connecting lines E5, E6 to in each case one brake force distribution valve 18, 21; two electrical connecting lines E7, E8 to in each case one redundancy valve 25a, 25b; six electrical connecting lines E9, E10, E11, E12, E13, E14 to in each case one anti-lock brake control valve 22a, 22b, 22c, 22d, 22e, 22f, two electrical connecting lines E15, E16 to in each case one temperature sensor 23a, 23b; and six electrical connecting lines E17, E18, E19, E20, E21, E22, each associated with one respective wheel speed sensor 24a, 24b, 24c, 24d, 24e, 24f.

[0034] Furthermore, two further interfaces or electrical connections can be formed for connecting lines E23, E24 on the control unit 26, which interfaces or electrical connections are connected to in each case one pressure sensor 27, 28 per brake circuit 14, 15, in order to implement a pressure control mode with a closed-loop control circuit.

[0035] The electronic control unit 26 is for this purpose embodied and configured to act automatically on a braking process in the manner of a brake-by-wire system. For this purpose, the control unit 26 determines, on the basis of the information supplied to it, control signals for the brake force distribution valves 18, 21, in order to open them dependent on the brake signal generator 19 in a first switched position, and independently of the brake signal generator 19 in a second switched position, and to apply pressure individually to each of the brake circuits 14, 15. As a result, the braking force is distributed between the front vehicle axle 2 and the rear vehicle axles 3, 4. In the event of a brake control operation by the anti-lock brake function, the anti-lock brake control valves 22a, 22b, 22c, 22d, 22e, 22f are supplied with pulsed control signals. The braking behavior of the individual wheel brakes 8a, 8b, 9a, 9b, 10a, 10b is set with these control signals. In the event of a failure or fault in the electrohydraulic brake system 1, the redundancy valves 25a, 25b disconnect at least the wheel brakes 9a, 9b, 10a, 10b of the rear vehicle axles 3, 4 from the pressure medium supply, as result of which the parking brake is activated by the abovementioned spring mechanism.

LIST OF REFERENCE SYMBOLS (PART OF THE DESCRIPTION)

[0036] 1 Electrohydraulic brake system

[0037] 2 First vehicle axle, front axle

[0038] 3 Second vehicle axle, rear axle

[0039] 4 Third vehicle axle, rear axle

[0040] 5a First vehicle wheel

[0041] 5b Second vehicle wheel

[0042] 6a Third vehicle wheel

[0043] 6b Fourth vehicle wheel

[0044] 7a Fifth vehicle wheel

[0045] 7b Sixth vehicle wheel

[0046] 8a First wheel brake

[0047] 8b Second wheel brake

[0048] 9a Third wheel brake

[0049] 9b Fourth wheel brake

[0050] 10a Fifth wheel brake

[0051] 10b Sixth wheel brake

[0052] 11a First brake cylinder

[0053] 11b Second brake cylinder

[0054] 12a Third brake cylinder

[0055] 12b Fourth brake cylinder

[0056] 13a Fifth brake cylinder

[0057] 13b Sixth brake cylinder

[0058] 14 First hydraulic brake circuit

[0059] 15 Second hydraulic brake circuit

[0060] 16 First pressure medium reservoir

[0061] 17 Second pressure medium reservoir

[0062] 18 First brake force distribution valve

[0063] 19 Brake signal generator

[0064] 20 Anti-lock brake system, ABS

[0065] 20a First ABS module

[0066] 20b Second ABS module

[0067] 21 Second brake force distribution valve

[0068] 22a First anti-lock brake control valve

[0069] 22b Second anti-lock brake control valve

[0070] 22c Third anti-lock brake control valve

[0071] 22d Fourth anti-lock brake control valve

[0072] 22e Fifth anti-lock brake control valve

[0073] 22f Sixth anti-lock brake control valve

[0074] 23a First temperature sensor

[0075] 23b Second temperature sensor

[0076] 24a First wheel speed sensor

[0077] 24b Second wheel speed sensor

[0078] 24c Third wheel speed sensor

[0079] 24d Fourth wheel speed sensor

[0080] 24e Fifth wheel speed sensor

[0081] 24f Sixth wheel speed sensor

[0082] 25 Redundancy brake circuit

[0083] 25a First redundancy valve

[0084] 25b Second redundancy valve

[0085] 26 Electronic control unit

[0086] 27 Pressure sensor at first hydraulic brake circuit

[0087] 28 Pressure sensor at second hydraulic brake circuit

[0088] E1-E24 First to twenty-fourth electrical connecting lines

[0089] H1-H12 First to twelfth hydraulic connecting lines, brake lines