VEHICLE BRAKE SYSTEM AND METHOD FOR OPERATING A VEHICLE BRAKE SYSTEM

Abstract

A brake system in a motor vehicle, the friction brake system of which, on the front and rear wheels, each case including vehicle wheel brakes which can be actuated via an electronic control device which includes an axle-specific braking force distributor unit by which a front axle target deceleration and a rear axle target deceleration can be determined from a friction brake system target deceleration, and which includes a wheel-specific braking force distributor unit by which front wheel target decelerations can be determined from the front axle target deceleration, and rear wheel target decelerations can be determined from the rear axle target deceleration, on the basis of which the wheel-specific braking force distributor unit generates control signals for the actuation of the vehicle wheel brakes.

Claims

1-9. (canceled)

10. A brake system in a motor vehicle, comprising: a friction brake system of which, on front wheels and on rear wheels, in each case have a vehicle wheel brake which can be actuated via an electronic control device which has an axle-specific braking force distributor unit by which a front axle target deceleration and a rear axle target deceleration can be determined from a friction brake system target deceleration, wherein a wheel-specific braking force distributor unit by which front wheel target decelerations can be determined from the front axle target deceleration, and rear wheel target decelerations can be determined from the rear axle target deceleration, on the basis of which the wheel-specific braking force distributor unit generates control signals for the actuation of the vehicle wheel brakes, wherein a determination component is associated with the electronic control device of the friction brake system, by which a current actual wheel circumference ratio between the front wheels and the rear wheels can be determined, wherein the control device determines the front wheel target decelerations and the rear wheel target decelerations taking into consideration the current actual wheel circumference ratio.

11. The brake system according to claim 10, wherein a sensor system is associated with the determination component, by which parameters correlating with the wheel circumference or wheel diameter of the front and rear wheels, in particular front axle rotational speed and rear axle rotational speed, can be acquired, on the basis of which the actual wheel circumference ratio can be determined in an evaluation unit of the determination component.

12. The brake system according to claim 10, wherein the axle-specific braking force distributor unit, on the basis of a braking force distribution stored therein, divides the friction brake system target deceleration into the front axle target deceleration and into the rear axle target deceleration, wherein the braking force distribution can be varied as a function of driving dynamics and/or driving status variables during a braking process.

13. The brake system according to claim 10, wherein the electronic control device of the friction brake system comprises a compensating unit by which the front wheel target decelerations, and rear wheel target decelerations determined in the control device can be adapted.

14. The brake system according to claim 13, wherein the compensating unit is arranged in a signal flow direction upstream of the axle-specific braking force distributor unit, and in particular the compensating unit, on the basis of the friction brake system target deceleration and of the actual wheel circumference ratio, determines a compensated target deceleration which is applied on the signal input of the axle-specific braking force distributor unit and processed there.

15. The brake system according to claim 14, wherein the compensating unit determines the compensated target deceleration not only on the basis of the friction brake system target deceleration and of the actual wheel circumference ratio but also on the basis of the braking force distribution.

16. The brake system according to claim 10, wherein at least one vehicle axle can be driven via an electric machine, and the electric machine can be actuated in a motor operating mode by a target acceleration specification and, in a recovery operating mode, is part of the vehicle brake system.

17. The brake system according to claim 16, wherein the vehicle brake system comprises an adding unit which, in a case of vehicle deceleration, adds up all the deceleration demands, such as from a brake pedal, a driver assistance system, an emergency brake system and/or an additional autonomous driving system, to a total target deceleration, wherein the control device includes a coordinating unit which, on the basis of driving operating parameters, divides the total target deceleration into the friction brake system target deceleration and into an electric machine target deceleration for the actuation of the electric machine working in the generator operation.

18. The brake system according to claim 11, wherein the axle-specific braking force distributor unit, on the basis of a braking force distribution stored therein, divides the friction brake system target deceleration into the front axle target deceleration and into the rear axle target deceleration, wherein the braking force distribution can be varied as a function of driving dynamics and/or driving status variables during a braking process.

19. The brake system according to claim 11, wherein the electronic control device of the friction brake system comprises a compensating unit by which the front wheel target decelerations, and rear wheel target decelerations determined in the control device can be adapted.

20. The brake system according to claim 12, wherein the electronic control device of the friction brake system comprises a compensating unit by which the front wheel target decelerations, and rear wheel target decelerations determined in the control device can be adapted.

21. The brake system according to claim 11, wherein at least one vehicle axle can be driven via an electric machine, and the electric machine can be actuated in a motor operating mode by a target acceleration specification and, in a recovery operating mode, is part of the vehicle brake system.

22. The brake system according to claim 12, wherein at least one vehicle axle can be driven via an electric machine, and the electric machine can be actuated in a motor operating mode by a target acceleration specification and, in a recovery operating mode, is part of the vehicle brake system.

23. The brake system according to claim 13, wherein at least one vehicle axle can be driven via an electric machine, and the electric machine can be actuated in a motor operating mode by a target acceleration specification and, in a recovery operating mode, is part of the vehicle brake system.

24. The brake system according to claim 14, wherein at least one vehicle axle can be driven via an electric machine, and the electric machine can be actuated in a motor operating mode by a target acceleration specification and, in a recovery operating mode, is part of the vehicle brake system.

25. The brake system according to claim 15, wherein at least one vehicle axle can be driven via an electric machine, and the electric machine can be actuated in a motor operating mode by a target acceleration specification and, in a recovery operating mode, is part of the vehicle brake system.

Description

[0025] Hereafter, an embodiment example of the invention is described in reference to the accompanying figures. The figures show:

[0026] FIG. 1 in a block circuit diagram, a vehicle brake system of an electrically driven vehicle; and

[0027] FIG. 2 in an additional block circuit diagram, a basic software architecture in an electronic control device of a friction brake system of the vehicle brake system.

[0028] In FIG. 1, in a rough diagram, a brake system or a brake installation for an at least partially electrically driven vehicle is indicated. In FIG. 1, the brake system is represented only to the extent necessary for understanding the invention. Accordingly, in the block circuit diagrams of FIGS. 1 and 2, the signal processing occurs on the basis of deceleration values V.sub.EM, V.sub.RBS, etc. In an actually implemented embodiment variant, the signal processing would instead occur on the basis of physical variables which correlate with the deceleration values (namely, brake pressure, torque and force) and which are commonly used in calculating the actuator actuation (friction brake and electric motor).

[0029] Accordingly, both the front wheels VR and also the rear wheels HR of the vehicle respectively comprise a vehicle wheel brake 1. The vehicle wheel brake 1 is made of a brake caliper 3 which can be actuated via a hydraulic cylinder (not shown) and a brake disk 5. For the actuation of the vehicle wheel brake 1, its hydraulic cylinder is pressurized, whereby the brake caliper 3, by means of its brake linings, comes in compressive contact with the brake disk 5.

[0030] In FIG. 1, each vehicle wheel brake 1 comprises, as control element, hydraulic components, and namely a hydraulic pump 7 which acts as a pressure buildup actuator, as well as a hydraulic control valve 9. An electronic control device 10 of the friction brake system RBS, in the case of a braking demand, i.e., in the case of a friction brake system target deceleration V.sub.RBS, generates control signals for the actuation of the vehicle wheel brakes 1. In FIG. 1, the control signals are a rotational speed signal n for the actuation of a pump motor 11 of the hydraulic pump 7 and a valve control signal S for the actuation of the hydraulic control valve 10.

[0031] It should be emphasized, that in an actually implemented embodiment variant, as a rule, only a central hydraulic actuator with motor is provided, while the wheel- and axle-selective closed loop control occurs just by the control valves 9. Thereby, the wheel brake pressures cannot be closed loop controlled in an axle-specific manner without a valve actuation.

[0032] As apparent moreover from FIG. 1, the vehicle comprises an electrified rear axle HA, wherein the rear wheels HR are driven by means of an electric machine EM. In FIG. 1, the power electronics LE of the electric machine EM is actuated by means of a target acceleration specification B which, in FIG. 1, is generated by actuation of an accelerator pedal 15. In the case of a vehicle acceleration, the electric machine EM works in the motor operating mode. Alternatively, in the case of a vehicle deceleration, the electric machine EM can work as generator in a recovery operating mode.

[0033] In FIG. 1, the brake system can be activated by means of a driver-side actuatable brake pedal 15, a driver assistance system 17, an emergency brake system 19 and/or an additional autonomous driving system 21, which are all in signal connection with an adding unit 23. In the adding unit 23, all the braking demands are added up and therefrom a total target deceleration V.sub.ges is calculated. The total target deceleration V.sub.ges is transmitted in FIG. 1 to a coordinating component 25, in which, as a function of driving operating parameters, the total target deceleration V.sub.ges is divided into the friction brake system target deceleration V.sub.RBS and into an electric machine target deceleration V.sub.EM by means of which the electric machine EM working in the generator operation is actuated in order to achieve a braking effect.

[0034] The friction brake system target deceleration V.sub.RBS generated in the coordinating unit 25, in FIG. 1, is applied on the signal input of the electronic control device 10, by means of which, during the braking process Δt (FIG. 2), the vehicle wheel brakes 1 on the front axle VA and/or on the rear axle HA are actuated.

[0035] In FIG. 1, a determination component 29 is associated with the electronic control device 10 of the friction brake system RBS. In the determination component 29, a current actual wheel circumference ratio k(t) between the front axle wheels VR and the rear axle wheels HR is calculated. For example, in FIG. 1, the rear wheels HR have a wheel diameter d.sub.HA which is greater in size than the wheel diameter d.sub.VA of the front wheels VR. Taking into consideration the current actual wheel circumference ratio k(t), the electronic control device 10 determines the front wheel target decelerations V.sub.VA as well as the rear wheel target decelerations V.sub.VA, on the basis of which the electronic control device 10 generates the control signals S, n for the actuation of the vehicle wheel brakes 1.

[0036] A sensor system 31 is associated with the determination component 29, by means of which the current front axle rotational speed n.sub.VA and the current rear axle rotational speed n.sub.HA can be acquired. On the basis of these rotational speeds, an evaluation unit 33 of the determination component 29 can determine the actual wheel circumference ratio k(t) and transmit it via a signal line 35 to the electronic control device 10. In FIG. 1, the determination component 29 in addition comprises a converter unit 37, by means of which the front axle rotational speed n.sub.VA is used as reference rotational speed n.sub.ref in the evaluation unit 33.

[0037] In FIG. 2, the software architecture of the electronic control device 10 is indicated in more detail and namely with program components for generating the front wheel target decelerations V.sub.VA as well as the rear wheel target decelerations V.sub.HA on the basis of which the electronic control device 10 generates the control signals S, n for vehicle wheel brakes 1.

[0038] Accordingly, the electronic control device 10 comprises an axle-specific braking force distributor unit 39 and a wheel-specific braking force distributor unit 41. In the axle-specific braking force distributor unit 39, a front axle target deceleration V.sub.VA and a rear axle target deceleration V.sub.HA are determined from the friction brake system target deceleration V.sub.RBS. In the wheel-specific braking force distributor unit 41, front wheel target decelerations V.sub.VR and rear wheel target decelerations V.sub.HR are determined from the front axle target deceleration V.sub.VA. On the basis of these decelerations, the wheel-specific braking force distributor unit 41 generates the already mentioned control signals S, n by which the hydraulic components 7, 9 of the vehicle wheel brakes 1 can be actuated.

[0039] In the axle-specific braking force distributor unit 39, the friction brake system target deceleration V.sub.RBS is divided, on the basis of a braking force distribution BKV(t) stored therein, into the front axle target deceleration V.sub.VA and into the rear axle target deceleration V.sub.HA. As is apparent from FIG. 1, during the braking process Δt, the braking force distribution BKV(t), as a function of driving dynamics and driving status variables x, z, is not constant but instead varies.

[0040] In FIG. 2, a compensating unit 43 is arranged in signal flow direction upstream of the axle-specific braking force distributor unit 39. In the compensating unit 43, a learning algorithm, shown in FIG. 2, is stored, by which, on the basis of the friction brake system target deceleration V.sub.RBS, of the actual wheel circumference ratio k(t) as well as on the basis of the braking force distribution BKV(t), a compensated target deceleration V.sub.RBS,komp is determined. The braking force distribution BKV(t) is fed back via a feedback line 45 from the axle-specific braking force distributor unit 39 to the compensator component 43.

CLAIMS

[0041] 1. Vehicle wheel brake

[0042] 3 Brake caliper

[0043] 5 Brake disk

[0044] 7 Hydraulic pump

[0045] 9 Control valve

[0046] 10 Electronic control device

[0047] 11 Pump motor

[0048] 13 Brake pedal

[0049] 17 Driver assistance system

[0050] 19 Emergency system

[0051] 21 Additional autonomous driving system

[0052] 23 Adding unit

[0053] 25 Coordinating unit

[0054] 29 Determination component

[0055] 31 Sensor system

[0056] 33 Evaluation unit

[0057] 35 Signal lines

[0058] 37 Converter unit

[0059] 39 Axle-specific braking force distributor unit

[0060] 41 Wheel-specific braking force distributor unit

[0061] 43 Compensating unit

[0062] 45 Feedback line

[0063] RBS Friction brake system

[0064] x Driving dynamics variables

[0065] z Driving status variables

[0066] V.sub.ges Total target deceleration

[0067] V.sub.RBS Friction brake system target deceleration

[0068] V.sub.EM Electric machine target deceleration

[0069] V.sub.RBS,komp Compensated target deceleration

[0070] V.sub.VA Front axle target deceleration

[0071] V.sub.HA Rear axle target deceleration

[0072] V.sub.VR Front wheel target deceleration

[0073] V.sub.HR Rear wheel target deceleration

[0074] k(t) Actual wheel circumference ratio

[0075] S Control valve signal

[0076] n Rotational speed signal

[0077] n.sub.VA Front axle rotational speed

[0078] n.sub.HA Rear axle rotational speed

[0079] n.sub.ref Reference rotational speed

[0080] EM Electric machine

[0081] LE Power electronics

[0082] B Acceleration specification

[0083] BKV(t) Variable braking force distribution

[0084] d.sub.VA Front wheel diameter

[0085] d.sub.HA Rear wheel diameter

[0086] γt Braking process

[0087] d.sub.HA Rear wheel diameter

[0088] d.sub.VA Front wheel diameter