US-20260125038-A1 - BRAKE SYSTEM, IN PARTICULAR FOR AUTOMATIC DRIVING

Abstract

A brake system for a motor vehicle may comprise an actuating device, in particular a brake pedal, a pressure supply device, in particular a hydraulic piston-cylinder unit driven by an electric motor driven, for hydraulically adjusting a brake piston of at least one wheel brake, wherein the pressure supply device works in particular on wheel brakes of the front axle of the motor vehicle, and having at least one electromechanically actuatable wheel brake, for electrically adjusting a brake piston of the wheel brake, in particular for the rear wheels of the motor vehicle. For electromechanically actuating the wheel brake, an electric motor and a first transmission, which transmits the driving force of the motor to a further transmission, in particular a ball-screw transmission, are provided. One or more (hydraulic and/or electric) components or subsystems of the brake system are designed to have at least one layer of redundancy.

Inventors

• Heinz Leiber

Assignees

• IPGATE AG

Dates

Publication Date

20260507

Application Date

20251210

Priority Date

20180509

Claims (20)

1. 1 . A brake system for a motor vehicle, comprising: a pressure supply device comprising a hydraulic piston-cylinder unit driven by an electric motor configured to hydraulically adjust a brake piston of wheel brakes of a front axle; wherein individual pressure regulation in the front-axle wheel brakes is performed via respective valves assigned to respective brake circuits associated with the front-axle wheel brakes; at least one electromechanically actuatable wheel brake, including an electric motor and a gear mechanism to implement electromechanical actuation; wherein the brake system is configured to detect occurrence of a leakage flow; wherein, when a leak is detected in one of the brake circuits of the front axle, the respective valve assigned to the respective brake circuit is closed such that a remaining front-axle brake circuit and the at least one electromechanically actuatable wheel brake provide a braking function.
2. 2 . The brake system according to claim 1 , wherein the brake system has an e-pedal, which is electrically connected to an electronic open-loop and closed-loop control unit of the brake system and/or to a central control and regulation unit of the vehicle.
3. 3 . The brake system according to claim 1 , wherein the brake system has a single-circuit master cylinder, a hydraulic chamber of which is configured to be hydraulically connected to the wheel brakes of the front axle via at least one isolating valve, wherein the isolating valve is opened in the event of a failure of the pressure supply device.
4. 4 . The brake system according to claim 1 , wherein brake-pressure control is performed via a pressure-volume characteristic curve, wherein a brake-circuit failure is detected via an increased volume.
5. 5 . The brake system according to claim 1 , wherein the brake system is configured to perform permanent diagnosis during operation and full diagnosis during parking.
6. 6 . The brake system according to claim 1 , wherein the pressure supply device and/or the electromechanically actuatable wheel brakes have redundant seals.
7. 7 . The brake system according to claim 1 , wherein the electric motor of the pressure supply device and/or the electric motor of the at least one electromechanically actuatable wheel brake comprises an electric motor having redundant motor control comprising multiple motor windings or winding groups, wherein, in an event of a failure of one motor winding or winding group, the electric motor having redundant motor control is enabled to continue to be operated with the remaining motor windings or winding groups.
8. 8 . The brake system according to claim 1 , further comprising redundant switching valves provided for at least one of the wheel brakes.
9. 9 . The brake system according to claim 1 , wherein the respective valves assigned to respective brake circuits associated with the front-axle wheel brakes are designed and hydraulically connected such that a connection to the pressure supply device is situated on an inner side of the respective valve and an outlet to the front-axle wheel brake associated with the respective brake circuit to which the respective valve is assigned is downstream of a valve seat, such that the respective valve opens automatically upon an event of a failure of the pressure supply device and a wheel pressure condition.
10. 10 . The brake system according to claim 8 , wherein the switching valves are enabled to be actuated in both directions depending upon pressure differences between an inlet from the pressure supply device and an outlet to the at least one of the wheel-brake.
11. 11 . The brake system according to claim 1 , further comprising redundant isolating valves in a hydraulic line to the pressure supply device and/or to the master cylinder.
12. 12 . The brake system according to claim 1 , wherein the at least one electromechanically actuatable wheel brake is/are associated with the rear axle and comprise(s) a hydraulically actuatable adjustment device which, in normal operation, is actuated hydraulically in order to support the electrical adjustment.
13. 13 . The brake system according to claim 1 , wherein, upon detection of a brake-circuit failure, an associated switching valve is closed.
14. 14 . The brake system according to claim 1 , wherein the brake system is designed for autonomous driving level 4 or level 5, and wherein, in an event of a fault, the vehicle is not required to be parked immediately after occurrence of the fault.
15. 15 . The brake system according to claim 1 , wherein the brake system is connected to a redundant on-board electrical system having at least two independent power supplies, the power supplies providing voltages in the range from 12 V to 800 V, such that, in an event of failure of a first one of the power supplies, the brake system is enabled to continue to be operated with a second one of the power supplies.
16. 16 . The brake system according to claim 1 , further comprising a redundant electromagnetic parking lock configured to electromechanically actuate rear-axle wheel brakes of the motor vehicle.
17. 17 . The brake system according to claim 1 , further comprising an actuation unit, wherein the actuation unit and the pressure supply device are implemented in separate housings.
18. 18 . The brake system according to claim 1 , wherein a modular configuration and construction is used to enable different safety levels.
19. 19 . The brake system according to claim 1 , wherein the at least one electromechanically actuatable wheel brake is a rear axle brake, the brake system further comprising a hydraulic connection from the pressure supply device to the rear axle via which wheel brakes of the rear axle are actuatable in addition to electromechanical actuation.
20. 20 . The brake system according to claim 1 , further comprising an electronic open-loop and closed-loop control unit and an electronic sub-control unit associated with the at least one electromechanically actuatable wheel brake, wherein the electronic sub-control unit is connected to the electronic open-loop and closed-loop control unit via redundant on-board electrical system connections.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation of co-pending U.S. patent application Ser. No. 17/053,009, filed on Nov. 4, 2020 as a Section 371 of International Application No. PCT/EP2019/061909, filed May 9, 2019, which was published in the German language on Nov. 14, 2019 under International Publication No. WO 2019/215278 A1, which claims priority under 35 U.S.C. § 119(b) to German Patent Application No. 10 2018 111 126.6, filed May 9, 2018, the disclosures of which are incorporated herein by reference. FIELD OF ENDEAVOR The invention relates to a brake system. PRIOR ART Future brake systems must satisfy various increased or additional requirements. These are in particular extreme fail safety (“fail-operational” FO) for automated driving (AD), a reliable immobilizing brake in electrically driven vehicles (electric vehicles), in the case of which the conventional redundant mechanical parking lock in the transmission is omitted. So-called combination brakes (EHC) are known in which a hydraulically actuated braking device is provided at the front axle (VA) and an electrically actuated braking device is provided at the rear axle (HA). Such a combination brake is presented for example in DE 103 19 194 B3. In the case of EHC solutions, self-locking and non-self-locking reduction gear mechanisms have been proposed for the electrically actuated braking device. A parking lock is necessary in the case of non-self-locking reduction gear mechanisms. However, in the event of failure of the lock, no immobilizing brake action is available. The electric motor power of such brakes is determined by the requirement for so-called “time to lock” up to, for example, 100 bar (TTL). Self-locking reduction gear mechanisms are used predominantly in electric immobilizing brakes or electric parking locks (EPB), for example of DE 10 2015 213866, because the TTL requirements are low. Here, legislators stipulate primarily a sufficient EPB action or parking brake action on slopes. In the case of self-locking reduction gear mechanisms, the gear ratio can also be selected to be high, which, in spite of poor efficiency, results in a motor with low power. In the case of the combination brake (EHC), the motor power is determined by TTL and efficiency, which means that the motor cannot be dimensioned to be small despite the relatively low electrical braking action at the rear axle. The electronic open-loop and closed-loop control unit (ECU), which is positioned with the complete electrical control means at the brake calliper, is expensive owing to the high temperatures, and the failure rate is accordingly high. Force sensors are required for exact setting of the braking force. Without additional measures, this combination brake (EHC) does not satisfy the “fail-operational” (FO) requirements for higher levels greater than 4 (according to the VDA/SAE standard). In the case of the known combination brakes with simpler safety, if the hydraulic braking device fails, electrical braking is performed at the rear axle and vice versa. Such a failure however leads to considerable losses in braking action of up to more than 50% in the event of failure of the hydraulically braked front-axle brake. A failure of the electric brake moreover possibly leads to the failure of the immobilizing brake. Self-locking reduction gear mechanisms are therefore used. Here, there is however the problem that, in the case of an electric service brake being used in the event of blocking of the gear mechanism during travel, the brake can quickly overheat, with the risk of fire, in the case of very high braking power. Also known are electric parking brakes (EPB) with hydraulic assistance and with a motor of reduced size, as presented for example in DE 198 17 892 (E99). These have however not become established because, in the event of failure of the hydraulics, a failure of the immobilizing brake also occurs. OBJECT OF THE INVENTION The invention is based on the object of creating a cost-effective brake system with a small installation space, versatile application possibilities and a high level of fail safety, even for autonomous driving up to level 5 (according to VDA/SAE: “no driver required from starting point to destination”). ACHIEVEMENT OF THE OBJECT AND ADVANTAGES OF THE INVENTION The object of the invention may be achieved by means of the features of the various appended claims. It is therefore the basic concept of the solution according to the invention that, in the case of a combination brake system with a hydraulic brake at the front axle (VA) and electrical or electromechanical brake at the rear axle (HA), one or more (hydraulic and/or electrical) components or subsystems of the brake system are implemented redundantly. Advantageous embodiments and configurations of the invention are contained in the further claims and described in more detail in the description of the figures. Here, the electromechanically actuatable wheel brake advanta