Brake system and method for controlling brake system

Abstract

To provide a brake system and a method for controlling the same.SOLUTION: There is provided a brake system, the brake system is configured to execute adjustment of a pressure in a wheel brake in actuation of a first pressure supply unit, and at least one of a brake pressure adjusting valve of a second module, and a cutoff valve of the second module, for providing an anti-lock brake system function. In the brake system, for adjusting the pressure, pressure reduction occurs in the first pressure supply unit through at least one outlet valve at least temporarily, and at least temporarily, pressure reinforcement occurs through at least one inlet valve using the first pressure supply unit.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a braking system and a method for controlling a braking system. [Background technology]

[0002] The trend towards vehicles being configured for autonomous driving places high demands on fail-safe designs from the perspective of braking systems on the one hand and on the other hand redundancy functions, for example of brake pressure generation functions, power supply functions and computer functions.

[0003] So-called one-box and two-box systems are usually preferred. These consist of an electric brake booster (BKV) (so-called e-booster) and an electronic stability control system (ESP / ESC).

[0004] Known solutions have a relatively long installation length and / or a high weight.

[0005] DE 10 2014 205 645 A1 and WO 2011 / 098178 describe a solution with a coaxial drive in which an electric motor acts on the master cylinder piston (HZ piston) via a gear mechanism and a piston (hereinafter referred to as variant A or follower booster or e-booster). The BKV control is carried out by an electric element and a reaction disc as a so-called follower booster, and the pedal travel is a function of the brake pressure and the volumetric absorption of the brake system, which requires a long pedal travel in the event of fading or a brake circuit failure.

[0006] WO 2009 / 065709 also shows an e-booster (hereinafter referred to as variant B, or follower booster or e-booster) with follower booster function. Here, the BKV control is via the pedal travel and / or pedal pressure, i.e. the pressure used to activate the pedal. A separate pressure supplier with an electric motor and plunger acts on the HZ piston via the booster piston.

[0007] WO 2012 / 019802 shows an assembly similar to WO 2011 / 098178 (hereinafter referred to as variant C) with a coaxial drive in which an electric motor acts on the HZ piston via a gear mechanism and piston. An additional piston / cylinder unit acting on a travel simulator piston is used here. In this way, the pedal travel is independent of, for example, fading and brake circuit failures, but the complexity is high and the installation length is long.

[0008] DE 10 2009 033 499 A1 shows a brake booster (hereinafter also referred to as variant D) with an additional ESP unit and an external pressure supplier with hydraulic activation of the booster piston. This assembly with four or five pistons and six solenoid valves (MV) is complex and unfavorable in terms of installation length. The hydraulically inactive stroke simulator (WS) is located in a piston / cylinder unit arranged upstream of the master cylinder and cannot be damped or switched by the solenoid valves (MV).

[0009] All the above solutions have a redundant brake booster function, since the braking function in the event of a BKV motor failure is guaranteed by the ESP unit with a pump similar to the assistance function by the vacuum BKV in autonomous driving mode.

[0010] In the event of ESP motor failure, the ABS can continue to function due to the possibility of pressure modulation by the brake booster motor, the piston of the master brake cylinder being moved in a reciprocating manner to build up and dissipate pressure, as described in WO 2010 / 088920. If a brake booster is used in combination with an ESP unit having a typical valve circuit of an ESP unit, as outlined in detail, for example, in FIG. 1 of DE 10 2014 205 645 A1, the pressure can be boosted and dissipated by inlet valves (reference numbers 32a, 32b, 34b, 34a in FIG. 1 of DE 10 2014 205 645 A1) and switch valves (USV) (reference numbers 30a, 30b in FIG. 1 of DE 10 2014 205 645 A1) that are open when deactivated: i.e., a common pressure control of all four wheels can be implemented, but this does not result in optimal stopping distances.

[0011] All one-box systems known to date use so-called travel simulators to implement a progressive pedal travel characteristic. It has a brake-by-wire system.

[0012] Known systems with e-boosters and ESPs have only one redundancy in the pressure supply, i.e. there is a redundant pressure supply with a redundant output for braking by the ESP in case of e-booster failure, and higher requirements in terms of safety are not taken into account.

[0013] Packaging the individual components of a brake system to form a ready-to-install unit, and therefore the arrangement and installation volume of this unit, is of great importance. Particularly for brake systems used in motor vehicles configured for semi-automatic or fully automated driving, many variants, such as tandem master (brake) cylinders or a single master (brake) cylinder, must be considered. Examples of known packaging variants are the arrangement of the pressure supply unit perpendicular to the axis of the master (brake) cylinder (as described, for example, in EP 2 744 691) or parallel to the axis of the master (brake) cylinder (as described, for example, in DE 10 2016 105 232). The latter is distinguished in particular by a smaller installation width compared to the first-mentioned packaging variant. Summary of the Invention [Problem to be solved by the invention]

[0014] Going beyond the prior art, it is an object of the present invention to provide an improved braking system. [Means for solving the problem]

[0015] The invention is based in particular on the object of realizing a braking system for use in autonomous driving (hereinafter also referred to as AD) and / or for electric / hybrid vehicles with increasingly high recovery power (in generator operation, recovering energy by braking via the generator / or the drive motor, respectively), preferably with minimized weight and / or reduced system dimensions and / or increased reliability.

[0016] A cost-effective braking system for autonomous driving is preferably realized which meets all the necessary redundancies and very high requirements in terms of safety.

[0017] Furthermore, sufficient ABS functionality in terms of braking distance and stability as well as sufficient recovery capability are achieved by the brake system in the event of an ESP failure.

[0018] Redundant pressure supply, extremely large range of functionality and availability, especially in the event of a brake circuit failure It is a particular object of the present invention to provide an improved braking system together with a method for controlling the braking system, which at the same time has a very short installation length and low cost. Furthermore, what is provided is a method that allows a very high degree of availability even in the event of a partial failure / leak.

[0019] From a braking system perspective, the object is achieved according to the invention by a braking system having the features of claim 1. From a method perspective, the object is achieved according to the invention by a method having the features of claim 18.

[0020] The object focused on braking systems is achieved according to the invention in particular by a braking system comprising: ● a first module comprising a first pressure supply unit with an electric drive, an optional second pressure supply unit and a first control device for controlling the first pressure supply unit, the first module being defined to impinge at least one first brake circuit via a first connection point and at least one second brake circuit via a second connection point to a pressurized medium, the first module being allocated wheel brakes to the first and second brake circuits; a second module including a third pressure supply unit, in particular a motor / pump unit, brake pressure regulating valves and shut-off valves, in particular outlet and input valves for regulating the pressure in the wheel brakes, and a second control device for controlling the brake pressure regulating valves; ● A detection unit for detecting a first error event, in particular at least a partial failure of the third pressure supply unit, wherein the brake system in the first error event for providing ABS function and / or yaw torque mediation is provided to perform (wheel-individual and / or selective) adjustment of the pressure in the wheel brakes while activating at least one of the brake pressure regulating valves of the second module and / or the shut-off valves of the second module and the first pressure supply unit.

[0021] A pressure supply unit in this specification may be generally understood to mean a unit (particularly a construction unit) of a brake system that provides brake pressure. The pressure supply unit therefore serves to impinge at least one brake circuit with a pressurized medium. The third pressure supply unit is preferably an ESP unit of the type described at the beginning. A shut-off valve in this specification may be configured to be bidirectional: i.e., hydraulically permeable in two flow directions. A brake system and / Or depending on the design embodiment of the application of the brake system, the optional second pressure supply unit can be configured as an electronic pedal or a central computer.

[0022] At least partial failure of the third pressure supply unit here may be understood to mean that the motor / pump unit fails while other parts of the third pressure supply unit are still able to function.

[0023] The brake pressure regulating valves as well as the shut-off valves, in particular the pressure boost valves and the pressure relief valves (hereinafter also referred to as inlet valves EV and outlet valves AV), are in particular configured as solenoid valves, which have proven advantageous in particular due to their simple actuation capabilities.

[0024] In one embodiment, the first pressure supply unit in the first error event is controlled in a manner that creates a pressure drop having a pressure lower than the pressure in the wheel brake when the first pressure supply unit dissipates pressure to provide ABS braking operation.

[0025] In another embodiment, at least some of the shut-off valves of the first module are arranged and configured to establish a hydraulic connection between the brake pressure regulator valve, in particular the outlet valve, and the connection point. The braking system in a first error event to dissipate pressure in one of the wheel brakes is preferably configured here to open the assigned outlet valve.

[0026] In one embodiment, at least some of the shut-off valves of the first module are preferably arranged and configured to establish a hydraulic connection between the brake pressure regulating valve, in particular the outlet valve, and the connection point, and the brake system in a first error event to dissipate pressure in one of the wheel brakes is preferably configured to open the assigned outlet valve.

[0027] Advantageously, a communication link, in particular a bus link, is arranged between the first and second control devices, the first control device being preferably arranged to receive the pressure measurements and / or wheel rotation speed signals of the second module via the communication link, which may alternatively be an Ethernet or Flexray link.

[0028] Further alternatively, the communication link may also be configured to be a wireless or analog connection, for example for determining measurements.

[0029] Alternatively, a communication link, in particular a bus link, can be provided between the first and second control devices, which are preferably configured to receive pressure measurements and / or wheel rotation speed signals of the third pressure supply unit via the communication link. In the event of a failure of the communication link, ABS control can be performed using the data imported by the two control devices in this way. In this specification, receiving can also be understood to mean importing sensor values ​​and signals of this type from one of the control devices via the communication link.

[0030] In one embodiment, in the event of a first error, the first control device and / or the second control device and / or the third control device are configured to control the first pressure supply unit and the brake pressure regulating valve so as to implement wheel-individual and / or brake circuit-individual pressure feedback control of the wheel brakes or brake circuits. According to the invention, indirect control of actuators (e.g., valves) can also occur via the respective other control devices. The third control device can be understood to mean, for example, a central control unit.

[0031] In another embodiment, the first shut-off valve of the first module is arranged in the first hydraulic line between the first pressure supply unit and the first connection point. Furthermore, according to this embodiment, a second shut-off valve is arranged in the second hydraulic line between the first pressure supply unit and the second connection point. The brake system here is configured to detect a second error event (particularly a total failure of the third pressure supply unit). A total failure here can be understood to mean that all components of the third pressure supply unit have failed and can no longer function. Furthermore, in the second error event, the brake system is configured to control the first pressure supply unit and the first and second shut-off valves to perform individual pressure feedback control of at least one brake circuit in the at least two brake circuits. This control preferably occurs via the first control device.

[0032] According to one embodiment, the brake system, and in particular the first control device, is defined to detect a non-homogeneous road condition, in particular a μ-split situation, and is defined to control the first pressure supply unit in the second error event and in the detected non-homogeneous road condition, the control serving to adjust a target brake pressure in at least one selected one of the brake circuits, said target brake pressure being determined as a function of a wheel blocking pressure of a wheel brake of the selected brake circuit having a higher coefficient of friction compared to the other wheel brakes of the selected brake circuit, wherein the non-homogeneous road condition is defined as a friction coefficient between two wheel blocking pressures. The pressure difference is detected in such a way that a non-homogeneous road condition exists when this pressure difference has a percentage value greater than 30% or 40%.

[0033] In a third error event, in particular in the event of an additional failure of the wheel sensor mentioned above, or in the communication of the wheel rotation speed signal from the second module to the first module, the brake system (particularly in the first control device) in one embodiment in the third error event by the first pressure supply unit is defined to control pressure buildup and pressure dissipation to implement single-channel ABS using the wheel rotation speed sensor, and / or in a fourth error event, the brake system is defined to implement intermittent braking by modulating pressure between two fixedly adjusted pressure levels in both brake circuits. Thus, improved vehicle handling and braking performance compared to brake systems known in the prior art is achieved also in other error events and in the event of additional failure of other components of the brake system associated therewith.

[0034] Conveniently, at least one pressure sensor is provided for detecting brake pressure in at least one brake circuit.

[0035] In one embodiment, the first hydraulic line between the first pressure supply unit and the first connection point is configured without a valve, and the second hydraulic line between the first pressure supply unit and the second connection point is configured without a valve, where "valveless" may be understood to mean that no valve is disposed in the first hydraulic line or the second hydraulic line between the first pressure supply unit and the first or second connection point, respectively.

[0036] According to another embodiment, the first module comprises a rotary pump, in particular a single-circuit single-piston pump or a multi-piston pump for pressure buildup and dissipation. Furthermore, the first module according to this embodiment comprises a solenoid valve hydraulically connected to the reservoir and at least one optional pressure transducer. The optional pressure transducer for feedback control of pressure buildup and pressure dissipation is preferably communicatively connected to the first controller.

[0037] According to an alternative embodiment, the first pressure supply unit is configured as a gear pump for boosting and dissipating pressure. The gear pump is controlled using a pressure transducer or expertly depending on current measurements (in particular the phase current i of the electric drive of the gear pump and the rotor angle α of the electric drive). In the case of this pressure transducer, said measurements can be used to provide redundancy (hot or cold).

[0038] Considering the various variants of the design configuration of the first pressure supply unit, the first pressure supply unit thus takes into account the various variant configurations.

[0039] In another embodiment, at least one third shut-off valve is provided that is arranged and configured in such a way that in a closed state of the third shut-off valve, the first brake circuit is hydraulically isolated from the first and second pressure supply units.

[0040] Furthermore, the first hydraulic line and / or the second hydraulic line (in each case) is preferably connected to the reservoir via an intake valve, which is used so that the third pressure supply unit can rapidly transfer a volume directly from the reservoir with little hydraulic resistance and so that during transfer the first and second pressure supply units are decoupled as a result of the operation of the third pressure supply unit and are not damaged by this operation.

[0041] According to another design embodiment, an activation element, in particular a brake pedal, is arranged on the second pressure supply unit, which can be activated by the activation element. The master brake cylinder includes a single piston and includes a pressurized chamber as well as a stroke simulator connected to the pressurized chamber, the pressurized chamber being connected to at least one brake circuit via a switchable electromagnetic feed valve FV.

[0042] As a result of the above-described embodiment of the braking system according to the invention, a safety-conscious operation is possible, in particular in the following error events (either in all of these error events or in selected ones): Error event 1: failure of the motor of the third pressure supply unit (ESP unit); 4-channel ABS with feedback control by valves and the first pressure supply unit; Error event 2: Complete failure of the third pressure supply unit (ESP unit); 2-channel ABS with atypical "Select Low" / "Select High" feedback control in normal operation; Error event 3: complete failure of the third pressure supply unit (ESP unit), wheel rotation speed sensors are available in a redundant manner and imported directly from the wheel brakes into the first module; one-channel ABS established; Error event 4: Complete failure of the third pressure supply unit (ESP unit) and failure of the wheel rotation speed sensors; automatic intermittent braking established.

[0043] Alternatively or additionally to ABS control in error event 1, in this error event yaw torque control may also occur so that brake pressure is selectively generated in selected wheels.

[0044] In a method aspect, the object is achieved in particular by a method for controlling a braking system, in particular a braking system as described above, said method comprising the following steps: - controlling a first pressure supply unit of a first module by a first controller during normal operation; ● controlling the plurality of brake pressure regulator valves in the second module during normal operation; detecting a first error event, in particular a partial failure of the second module; ● Controlling the brake system in a first error event in such a way that (wheel-individual and / or selective) adjustment of the pressure in the wheel brakes occurs while using at least one (particularly bidirectional) shut-off valve of the second module and the first pressure supply unit to provide ABS braking operation and / or yaw torque mediation.

[0045] In one embodiment, the method further comprises the steps of: - detecting a second error event, in particular a total failure of the third pressure supply unit; - controlling the first pressure supply unit and the at least two shut-off valves of the first module in such a way that in a second error event brake circuit individual pressure feedback control is implemented in at least two brake circuits.

[0046] According to another embodiment, the method comprises the steps of: - detecting non-homogeneous road conditions, in particular μ-split situations; ● Controlling the first pressure supply unit in a second error event in a manner such that in non-homogeneous road conditions, wheel brakes of a selected brake circuit having a higher coefficient of friction compared to other wheel brakes are utilized to determine the target brake pressure.

[0047] In another embodiment, the method further comprises the steps of: detecting a third error event, in particular a total failure of the third pressure supply unit and a failure of the wheel sensor; In a third error event, a one-channel ABS is implemented, or in a fourth error event, two locations in at least one of the brake circuits (BK1, BK2) are implemented. Controlling the first pressure supply unit in a manner such that intermittent braking is implemented by modulating pressure between constant pressure levels.

[0048] According to an alternative embodiment, the method further comprises the steps of: ● determining a first wheel blocking pressure on a first wheel brake assigned to one of the two brake circuits; ● A process of determining a second wheel blocking pressure on a wheel brake assigned to the same brake circuit, wherein a non-homogeneous road condition is detected if the first wheel blocking pressure and the second wheel blocking pressure differ by more than 30%.

[0049] Similar advantages to those described in relation to the braking system are derived for this method. [Brief explanation of the drawings]

[0050] Exemplary embodiments of the invention are explained in more detail below with reference to the accompanying drawings, in which, in some cases in highly simplified illustrations:

[0051] [Figure 1a] 1 shows a circuit diagram of a first exemplary embodiment of a brake system having a first pressure supply unit according to a first embodiment; [Figure 1b] 2 shows a circuit diagram of a second exemplary embodiment of a brake system having a first pressure supply unit according to the first embodiment; [Figure 2] 3 shows a circuit diagram of a first exemplary embodiment of a brake system with a first pressure supply unit according to a second embodiment; [Figure 3] 1 shows a circuit diagram of a first exemplary embodiment of a brake system with a first pressure supply unit according to a third embodiment; [Figure 4] 1 shows a circuit diagram of the third pressure supply unit (ESP unit). [Figure 5] 1 shows a circuit diagram of the third pressure supply unit (ESP unit) during pressure dissipation in the first error event in four-channel ABS control. [Figure 6] 1 shows a circuit diagram of the third pressure supply unit (ESP unit) during pressure boosting in the first error event in four-channel ABS control. [Figure 7a] Schematic time profile of the "Select High" control in a brake circuit with two wheel brakes. [Figure 7b] Schematic time profile of the "Select Low" control in a brake circuit with two wheel brakes. [Figure 8] 1 shows a circuit diagram of a first exemplary embodiment of a braking system according to the invention having two shut-off valves and one feed valve; [Figure 9] 3 shows a circuit diagram of a second exemplary embodiment of a braking system according to the invention having four shut-off valves and one feed valve; [Figure 10] Schematic diagram of the third pressure supply unit (ESP unit) during pressure augmentation in the first error event in yaw torque control. [Figure 11] The circuit diagram of the third pressure supply unit (ESP unit) during pressure dissipation in the first error event in the yaw torque control is shown.

[0052] In the accompanying drawings, in some instances, parts having equivalent functions are given the same reference numerals. DETAILED DESCRIPTION OF THE INVENTION

[0053] The braking system 2 according to the first exemplary embodiment shown in Figure 1a comprises in the first embodiment a first pressure supply unit 6. In this embodiment, the first pressure supply unit 6 comprises an electric drive 8 acting on the piston of the piston / cylinder unit. Furthermore, the brake The rake system 2 (in particular the first pressure supply unit 6 ) comprises a first control device 9 which in particular supplies control signals to the electric drive 8 .

[0054] The first pressure supply unit 6 serves here to impinge the first brake circuit BK1 and the second brake circuit BK2 with pressurized medium, and to this end, the cylinders of the first pressure supply unit 6 are hydraulically connected via hydraulic lines to the first brake circuit BK1 (see connection point A1) and to the second brake circuit BK2 (see connection point A2).

[0055] In the exemplary embodiment according to Fig. 1a, a shut-off valve PD1 is additionally arranged in this hydraulic line, which can hydraulically reversibly isolate the first pressure supply unit 6 from the first brake circuit BK1 and the second brake circuit BK2. The shut-off valve PD1 here is configured as a solenoid valve.

[0056] In addition, the first pressure supply unit 6, and in particular the cylinder of the first pressure supply unit 6, has a hydraulic connection line to a reservoir 40 in which a check valve is arranged. The hydraulic connection to the reservoir 40 serves to suck pressurized medium from the reservoir 40.

[0057] Furthermore, the brake system 2 has a third pressure supply unit 90, which is only diagrammatically shown in Figure 1a. The third pressure supply unit 90 is also called an ESP unit: i.e. the ESP units each comprise a third supply unit 90. Furthermore, a second control device 95 is provided which controls the third pressure supply unit 90.

[0058] A communication link 100 (in particular a CAN bus link) is arranged between the first controller 9 and the second controller 95. The communication link 100 serves to exchange data and / or signals between the two controllers 9, 95.

[0059] In particular, no valves are arranged in the hydraulic lines of the first brake circuit BK1 and the second brake circuit BK2 in the exemplary embodiment according to FIG. 1a.

[0060] Furthermore, a pressure transducer p / U is provided in the hydraulic line, which is arranged between the shut-off valve PD1 and the first or second brake circuit BK1, BK2, respectively, and serves to provide pressure information relating to the brake circuits BK1, BK2 so that the pressure can be regulated in the brake circuits BK1, BK2, in particular in the event of an error (see embodiments below).

[0061] As an alternative to the pressure transducer p / u, in this embodiment the item of information related to the pressure regulated by the first pressure supply unit 6 is generated by estimating the pressure via the motor rotary encoder α / U and / or the motor current i / u.

[0062] FIG. 1b shows a circuit diagram of a second exemplary embodiment of a brake system 2 having a first pressure supply unit 6 according to the first embodiment.

[0063] This exemplary embodiment corresponds substantially to the previously described exemplary embodiment of the brake system 2 according to Fig. 1a. The difference here is the shut-off valves BP1, TV BK2 In either case, the shutoff valves BP1 and TV are arranged in the hydraulic lines leading to the brake circuits BK1 and BK2. BK2 Regulation of the brake pressure in the individual brake circuits by this is possible, particularly in the event of an error.

[0064] A circuit diagram of a first exemplary embodiment of a brake system 2 having a first pressure supply unit 6 according to a second embodiment is shown in Figure 2. This exemplary embodiment of the brake system 2 Similarly, it largely corresponds to the design embodiment of the brake system 2 according to FIG. 1a. However, the first pressure supply unit 6 in the exemplary embodiment according to FIG. 2 is configured as a rotary pump, in particular as a single-circuit piston pump, in particular as a pump with one or more, in particular three, pistons. The piston pump is embodied in a manner corresponding to an ESP pump drive, in which one or more pistons via an eccentric are driven by the shaft of an electric motor. In this design embodiment, a valve PD2 is additionally provided for enabling pressure buildup or pressure dissipation, respectively. When building up pressure, the PD2 valve can also advantageously be used to compensate for pressure pulses of the pump driven by the eccentric, which are particularly high in the case of a one-piston pump.

[0065] The brake system 2 according to the first exemplary embodiment, having a first pressure supply unit 6 according to the third embodiment as shown in FIG. 3, corresponds to the brake system 2 according to FIG. 1a, except for the embodiment of the first pressure supply unit 6. In the exemplary embodiment according to FIG. 3, the first pressure supply unit 6 is configured as a gear pump. As an alternative to pressure transducers p / u, the pressure-related information provided by the pressure supply unit 6 in this exemplary embodiment is generated by estimating the pressure using a motor rotary encoder α / U and / or the motor current i / u. Due to the gear pump's mechanical and functional design, no valve PD2 is required in this exemplary embodiment, since pressure can also be dissipated by reversing the direction of rotation (e.g., by implementing the gear pump's drive motor as a brushless electric motor operated via a B6 bridge circuit and operating the electric motor in four-quadrant operation). Furthermore, for reasons related to the operating principle, pressure pulses are significantly weaker than in the case of an eccentric piston pump.

[0066] FIG. 4 shows a circuit diagram of a third pressure supply unit 90 (also called an ESP unit) with a motor / pump unit 91 for use in a brake system 2 according to the present invention. ESP units are well known and include a motor M, inlet and outlet valves EV1-EV4 and AV1-AV4 assigned to the valves HSV1, HSV2, USV1, and USV2, and the wheel brakes RB1, RB2, RB3, and RB4, and a main component pump P with one reservoir (SpK) per brake circuit. This system has been described in numerous publications and patent applications. Such a system is already commercially available as a two-box brake system "e-booster+ESP" and is used, inter alia, in electric and hybrid vehicles. In this application, only the outlet valve of the ESP unit is actuated by the e-booster via a CAN interface, which interacts with the generator's shaft torque (i.e., recovery to avoid brake pressure buildup in the wheel brakes), and the reservoir SpK is used to contain the pressurized medium.

[0067] One aspect of the present invention is that the first control unit 9 is communicatively connected to a second control unit 95 of the ESP unit ("ECU-ESP") via a communication link 100, and in order to achieve safety aspects, at least the inlet valves EV1 to EV4 can be controlled by the first control unit 9.

[0068] Another aspect of the present invention is wheel-specific pressure dissipation during use of the outlet valves AV1-AV4 and HSV valves of the ESP unit.

[0069] The circuit diagram of the third pressure supply unit 90 (ESP unit) during pressure dissipation in a first error event is shown as an example in the brake circuit in Figure 5. The first error event here can be understood to mean that the motor M of the third pressure supply unit 90 has failed. In this case, pressure dissipation for the purposes of feedback control occurs via the first pressure supply unit 6. This is specifically the case when the piston of the first pressure supply unit 6 is returned (to the right in the plane of the drawing, as identified by the arrow) and the outlet valves AV4, AV3 are opened. This occurs in the sense that the opening of the shut-off valves HSV1 and HSV2 occurs, while the outlet valves AV4 and AV3 in the normal state are closed if not activated. Valves that are open for flow in this state are in each case marked with an asterisk ("*") in FIG. 5 to highlight their open state (left half of FIG. 5). The states of the other solenoid valves are not explicitly described. Thus, at least the inlet valves EV1-EV4 are closed by active activation, for example, when dissipating pressure. Pressure dissipation from the wheel brakes RB3 and RB4 is particularly shown in FIG. 5 in an exemplary manner (the flow direction of the pressurized medium from the wheel brakes to the first pressure supply unit 6 is identified by an arrow). For this purpose, the pressure supply unit 90 according to the invention can be equipped with shut-off valves HSV1 and HSV2, which are operated bidirectionally according to the invention, in contrast to their typical use in ESP units. The shut-off valves HSV1 and HSV2 are also used to resupply fluid from the reservoir 40 during normal ESP operation with an active pump. Thanks to the given configuration, pressure from wheel brakes RB1, RB2 or RB3, RB4 (not shown), respectively, can be selectively dissipated by opening or closing shut-off valves HSV1, HSV2 when shut-off valves USV1, USV2 are closed. Wheel-individual pressure regulation can occur by switching outlet valves AV1-AV4 accordingly.

[0070] In a first error event, actuation of the valves, in particular the shut-off valves USV1, USV2, HSV1, HSV2 and the outlet valves AV1 to AV4, may also occur by the first control device 9 and not by the second control device 95, as is the normal case. When controlled by the first control device 9, the control signals required for the purposes herein are transmitted by the communication link 100 to the third pressure supply unit 90. However, in normal operation in the absence of an error event, the second control device 95 is responsible for activating the valves. Normal operation here may be understood to mean the pressure boost required, for example, to brake the vehicle, compared to the pressure boost for feedback control purposes (to prevent wheel slippage or jamming).

[0071] The inlet valves EV1 to EV4 are closed (by activation) when dissipating pressure. The hydraulic connection to the first pressure supply unit 6 is established by opening the shut-off valve HSV2; the outflow of pressurized medium here is then facilitated by the first pressure supply unit 6, and not by the pump P, as is customary.

[0072] The pressure dissipation shown and explained by way of example for the two wheel brakes RB3, RB4 in Figure 5 can alternatively also occur in a similar manner for each brake circuit or for each wheel brake. Wheel brake circuit individual feedback control (also called yaw torque feedback control) is used for four-channel ABS operation and yaw torque arbitration.

[0073] The pressure is preferably sensed by a pressure transducer p / U in the ESP unit during this feedback control so that pressure-related information is present at all times for feedback control of the pressure dissipation.

[0074] The pressure buildup in the first error event is shown by way of example in the circuit diagram of the third pressure supply unit 90 according to FIG. 6. In this case, the second control device 95 controls the inlet valves EV1-EV4 of the third pressure supply unit 90 as in normal operation of the third pressure supply unit 90. The outlet valves AV1-AV4 are closed (deactivated) during pressure buildup. In addition, the valve USV2 or USV1 opens during pressure buildup, while the valves HSV1 and HSV2 remain closed (deactivated). Since the pressure buildup in the two wheel brakes RB3 and RB4 is shown by way of example in FIG. 6, reference is made in both cases to the shut-off valves HSV2 and USV2 located in this brake circuit BK1. Alternatively, the pressure buildup shown and described by way of the example of the two wheel brakes RB3 and RB4 in FIG. 6 can also occur in a similar manner for individual brake circuits or individual wheel brakes, resulting in wheel-specific pressure buildup and yaw torque mediation.

[0075] The shut-off valve PD1 (if provided), which isolates the first pressure supply unit 6 from the brake circuits BK1, BK2, is operated to open during pressure build-up. The first pressure supply unit 6 delivers pressurized medium via hydraulic lines to the wheel brakes RB3, RB4. Also, in this exemplary embodiment, a pressure transducer p / U (arranged in the second brake circuit BK2 according to FIG. 6) is preferably used to detect pressure-related information. Alternatively, control of the valve of the third pressure supply unit 90 in this exemplary embodiment can also be taken over by the first control device 9 via the communication link 100.

[0076] Vehicle speed V F , wheel peripheral speed V R , reference speed V RFE , "High wheel" brake circuit pressure P h , "low wheel" brake circuit pressure P L The time profiles of the slip coefficient λ are shown in Figures 7a and 7b. The slip coefficient λ is the wheel speed at which the wheel becomes unstable, and the reference speed V RFE In this way, the λ limit or (reference speed V RFE ) and other typical key indicators, such as pressure dissipation P ab Subpoints 1, 1', 2, 4 (exceeding the slip coefficient λ), pressure increase P auf The time points 3 and 5 (below the slip factor λ) are shown in Figures 7a and 7b.

[0077] In homogeneous conditions (i.e., all wheels on asphalt), a switchover occurs for the "Select Low" feedback control (Fig. 7b), i.e., a corresponding pressure is adjusted that is so low that no wheel is blocked. In this way, about 20% of all braking efforts are avoided.

[0078] In non-homogeneous conditions, such as μ-splitting, i.e., when one vehicle's wheels are on ice and the other vehicle's wheels are on wet or dry roads, the "Select High" feedback control (Fig. 7a) kicks in, i.e., the wheels with a low friction coefficient remain blocked while the unblocked wheels are feedback controlled. Here again, about 20% of the optimal braking effort is foregone.

[0079] As already explained, Figure 7a shows the "Select High" feedback control. The description of ABS feedback control is based on general principles known from several patent applications, brake manuals and brake brochures. As a result of tire slip characteristics, the vehicle speed V F and wheel peripheral speed V R A slip between the wheel and the tire, i.e., wheel slip, is thus formed as a result of the increase in brake pressure. For a slip coefficient λ, which is a function of many factors, the maximum value of the circumferential force is exceeded and the circumferential force without feedback control leads to wheel blocking. A feedback controller that evaluates the wheel acceleration (positive and negative) and the slip λ determines the pressure dissipation P ab and pressure enhancement P auf The pressure feedback control according to the present invention is effective in terms of the desired optimum braking and cornering forces. The reference speed = λ limit (corresponding to the optimum slip λ) is likewise formed by the feedback controller using a complex algorithm.

[0080] Thus, FIG. 7a shows in particular an exemplary time profile of a "select-high" feedback control in a brake circuit with two wheel brakes. At time 1, a pressure boost P auf As a result, the wheel V R1 The blocking limit at (low friction coefficient low μ) is reached at pressure p1, and this wheel is auf As a result, the wheel peripheral speed V R = 0, thus reaching wheel blockage. Consequently, the pressure continues to build up. Further pressure buildup P auf is the pressure level p2 of wheel V at time 2 shortly after exceeding the λ limit.R2 becomes unstable and the wheel peripheral speed V R2 has the effect that the pressure drops sharply. Consequently, the pressure is reduced by the pressure supplier, for example by restoring the piston. The pressure difference ΔP between the previously determined pressures p1 and p2 is evaluated. If the pressure difference ΔP = P2 - P1 is large, i.e. if pressure p2 exceeds pressure p1 by more than 30%, the "select-high" feedback control (also called selective "high μ" control) is initiated. The pressure is then reduced in both brake circuits by ΔP ab =20% moderate that is, the circuit shutoff valves (BP1 / BP2, TV BK2 ; see FIG. 9) is unavailable and in the open state for selective pressure dissipation.

[0081] As a result, the wheel V R2 is not blocked at time 3 and again undershoots the λ slip limit at time 3. A stepwise pressure build-up follows from time 3. In the first stage, the pressure is increased, for example, by the previous ΔP ab The pressure is increased by 70% of the value, and in a second step by a further 30%. In this phase, a pressure transducer p / U is preferably used for pressure measurement. The slip limit is again exceeded at time 4. The pressure is then reduced again as at time 2, and then increased again in steps so that the wheel again undershoots the slip limit at time 5. This feedback control method continues for the duration of the feedback control.

[0082] Figure 7b shows an example time profile of a "select low" feedback control, specifically for a brake circuit with two wheel brakes. Here, the pressure difference ΔP = P2 - P1 is relatively small, in the range of 10% to 20%. As a result, wheels with small pressure differences become unstable, which is an indication of operation on a homogeneous roadway. As explained earlier in the context of "select high" feedback control, the pressure is proportional to ΔP abIn contrast to the "Select High" feedback control, however, the pressure in the case of the "Select Low" feedback control is dissipated more strongly (e.g., ΔP ) so that the low wheels are released from blocking at time 6, i.e., in contrast to the "Select High" feedback control, no wheels are actuated in blocking. ab = 40%). The pressure is first applied to the wheel V R2 And then the wheel V R1 is kept low until it undershoots the λ limit at time 3; then it is only increased stepwise again. R1 The slip limit is exceeded again at time 4 and the pressure is reduced again and then increased stepwise.

[0083] Figures 7a and 7b show only general aspects of "Select Low" / "Select High" feedback control. Many enhancements are possible, such as another test in "Select High" feedback control when the pressure level is reduced at the "High" wheel. Alternatively, the "Select Low" wheel could also exit the blocked state and exceed the λ limit again without feedback control. This potential wheel speed profile is identified by an X in Figure 7a. Another "Select Low" / "Select High" test could then occur, optionally switching from "Select High" feedback control to "Select Low" feedback control.

[0084] As already explained, in one exemplary embodiment, in the second error event, a switchover from "select low" feedback control to "select high" feedback control occurs via the first control device 9 when the first control device 9 detects that the vehicle is positioned on a non-uniform hard surface (e.g., a partially icy road). For this purpose, it is necessary that the brake system 2 according to the present invention, via the first pressure supply unit 6, is able to regulate different pressures in the individual brake circuits BK1, BK2. The design embodiments already shown schematically in FIGS. 1b, 8, and 9 are particularly suitable for this purpose. To implement this control strategy, the control device 9 monitors the pressures in the individual wheel brakes RB1, RB2, RB3, and RB4 that lead to wheel blocking. If these pressures between two wheels (particularly in the brake circuits BK1 and BK2) deviate from each other by more than 30%, a switchover by the first control device 9 occurs from "select low" feedback control to "select high" feedback control, so as to still achieve a very positive braking result even in the error event.

[0085] FIG. 8 shows a brake system including a first module (called X-Boost) and a second module. A circuit diagram of the system 2 is shown. The first module (X-Boost) comprises a first pressure supply unit 6 with an electric drive 8, a second pressure supply unit 14 with a master brake cylinder 22, and an activation element 26 with a brake pedal. Also provided is a valve installation with various solenoid valves and check valves.

[0086] The second module (in particular the third pressure supply unit 90) comprises an electrically driven motor / pump unit 91 having a pump with an electric drive. The third pressure supply unit 90 can be any ESP unit. Suitable ESP units are described in detail in DE 10 2014 205 645 A1. Alternatively, a standard ABS unit without ESP functionality can be used as the second module.

[0087] Two modules (X-Boost and ESP unit) are defined to impinge pressurized medium with two brake circuits BK1, BK2, where the modules are preferably fluidly connected in series. In one exemplary embodiment, X-Boost is fixed to the vehicle's scuttle, and the second module (ESP unit) at two hydraulic interface or connection points A1, A2 (see bold dots in FIG. 8 relating to BK1, BK2), respectively, is connected to the vehicle's scuttle by hydraulic lines.

[0088] The first pressure supply unit 6 is connected via a first hydraulic line HL1 to the first brake circuit BK1 or a corresponding interface, respectively. Further provided is a second hydraulic line HL2 for connecting the first pressure supply unit to the second brake circuit or a corresponding interface, respectively.

[0089] According to the present invention, the X-Boost second pressure supply unit 14 has only one master brake cylinder 22 with a piston 24 and a piston chamber. In the exemplary embodiment, the second pressure supply unit 14 is embodied by a single circuit and via a third hydraulic line HL3, with the feed valve 69 connected to the brake circuit BK1 or a corresponding hydraulic interface, respectively. The fluid connection to the second hydraulic line HL2 is performed via an optional first shut-off valve BP1 (highlighted by a dotted border). The second pressure supply unit 14 can be isolated from the brake circuits BK1, BK2 by closing the feed valve 69 in such a way that the activation element 26 acts only on the stroke simulator 28 during normal brake-by-wire operation without an error (e.g., without a brake circuit fault).

[0090] In an exemplary embodiment such as that shown in FIG. 8, the brake circuits BK1, BK2 can be isolated by an optional first shut-off valve BP1, if present, which preferably opens when not activated. According to the invention, in the event of a failure of the first pressure supply unit 6, the master brake cylinder 22 of the second pressure supply unit 14 can thus be connected either to the first brake circuit BK1 only or to both the first and second brake circuits BK1, BK2 by opening the first shut-off valve BP1. For this emergency operation, the feed valve 69 is configured as a valve that opens when not activated. As long as current is still applied, said feed valve 69 opens so that the second pressure supply unit 14 is no longer hydraulically isolated from the brake circuits BK1, BK2.

[0091] The first pressure supply unit 6 likewise selectively acts on the second brake circuit BK2 (first shut-off valve BP1 is closed) or on both brake circuits BK1, BK2 (first shut-off valve BP1 is open when not activated). The first shut-off valve BP1 is open in normal operation so that the first pressure supply unit 6 supplies pressure to both brake circuits BK1, BK2 and the second pressure supply unit 14 is isolated from the first brake circuit BK1 by the closed feed valve 69. If it is established that volume is lost from the brake circuits BK1, BK2, the brake circuit BK1 will be shut off to the second brake circuit in the event of a leak in the first brake circuit BK1. The second brake circuit BK2 can be isolated from the first pressure supply unit 6 by the first shut-off valve BP1 so that it can continue to operate without hydraulic fluid loss.

[0092] In the exemplary embodiment, the shut-off valve BP1 is embodied as a solenoid valve, and a ball seat of the shut-off valve BP1 by means of a connector (valve seat connector) is connected to a part of the hydraulic line leading to the first pressure supply unit 6. In this way, the shut-off valve BP1 can also be reliably closed by activation in the event of a failure of the first brake circuit BK1 and is not forced open by high pressure when the first pressure supply unit 6 is in operation.

[0093] The second pressure supply unit 14 supplies a stroke simulator 28 via a vent hole in the wall of the master brake cylinder 22 so that, when the activation element 26 is activated, a progressive tactile resistance in the form of a restoring force can be felt as a function of an activation variable of the activation element 26. The activation variable here can be understood to mean how "firmly and / or how far" the driver activates the activation element 26 configured as a brake pedal and thus pushes the piston 24 into the master brake cylinder 22. The progressive tactile resistance is also called a pedal characteristic.

[0094] A stroke simulator valve 29 may be provided to block connection to the stroke simulator 28 .

[0095] The second pressure supply unit 14 has at least one vent hole 38 which is connected via a hydraulic line to a reservoir 40 which is also part of the brake system 2.

[0096] In an exemplary embodiment, a check valve RVHZ as well as a throttle DR can be arranged in the hydraulic line between the exhaust hole 38 and the reservoir 40. This check valve RVHZ and the first pressure supply unit 6 make it possible to carry out diagnostics relating to the state of preservation of sealing elements arranged in the first pressure supply unit 6 as well as in the stroke simulator 28. The stroke simulator valve 29 (if present) can be closed when checking the tightness of the master brake cylinder 22.

[0097] As shown, the master brake cylinder 22 has two sealing elements 42a, 42b configured as annular seals. The exhaust hole 38 is disposed between the two sealing elements 42a, 42b. The throttle DR is disposed in the connection between the exhaust hole 38, which is disposed between the two sealing elements 42a, 42b and the reservoir 40.

[0098] The throttle DR is dimensioned in terms of its flow rate so that the pedal characteristic remains almost unchanged in the event of failure of the sealing element 42a (3 mm pedal travel in 10 seconds). Furthermore, a temperature-related volume compensation of the pressurized medium can occur via the throttle DR.

[0099] High pressure peaks in the brake circuits BK1, BK2, which can significantly stress the first pressure supply unit 6, can be generated during ABS operation of the third pressure supply unit 90. In a variant of the design embodiment according to Figure 8, the pressure limiting valve UV is connected via a hole to the piston chamber of the first pressure supply unit 6 so that high pressure peaks are dissipated and damage to the system is avoided.

[0100] The intake valve NV is likewise fluidly connected to the piston chamber of the first pressure supply unit 6 and allows pressurized medium to be re-supplied from the reservoir 40. In this way, the first pressure supply unit 6 can independently introduce additional pressurized medium into the brake circuits BK1, BK2. An additional exhaust hole provided in the cylinder of the first pressure supply unit 6 allows volume compensation in the initial position of the piston of the first pressure supply unit 6.

[0101] The third pressure supply unit 90 is only shown diagrammatically in Figure 8. Said pressure supply unit 90 finally supplies four wheel brakes RB1, RB2, RB3, RB4. In the schematic diagram, wheel brakes RB1, RB2 actuate the front axle VA of the vehicle, and wheel brakes RB3, RB4 actuate the rear axle HA of the vehicle. An electric drive motor for driving the vehicle is located on the rear axle HA of the vehicle. The vehicle can be a pure electric vehicle or a hybrid vehicle.

[0102] The first brake circuit BK1 is connected to the wheel brakes RB1, RB2, and the second brake circuit BK2 is connected to the wheel brakes RB3, RB4. A corresponding allocation is advantageous for the hydraulic assembly shown in FIG.

[0103] The third pressure supply unit 90 further carries a control unit 95 ("ECU-ESP").

[0104] The second pressure supply unit 14 similarly carries a printed circuit board having a level detector NST for detecting the position of a magnetic float gauge NS within the reservoir 40. The PCB further has sensors 30a, 30b for detecting the pedal travel as well as the difference in the travel distance between the piston 24 and the pedal travel.

[0105] An intake valve 70b connecting the pump of the third pressure supply unit 90 to the reservoir 40 is provided in the first brake circuit BK1 to provide additional pressurized medium for the third pressure supply unit 90.

[0106] When the pump of the third pressure supply unit 90 requires pressurized medium from the second brake circuit BK2, the pressurized medium can thus be provided from the reservoir 40 via the intake valve 70c.

[0107] Thus, for sucking in pressurized medium, the two brake circuits BK1, BK2 are connected by respective hydraulic lines HL1, HL2 to the reservoir 40 via in each case one intake valve 70b or 70c respectively. In order to achieve optimal sucking in of pressurized medium, the intake valve 70c preferably has a diameter in the range of 30 mm to 50 mm, in particular a diameter of 40 mm.

[0108] Exemplary embodiments optionally include a controller for the clearance between the brake pads and the disc brakes. The wheel brakes RB1, RB2, RB3, and RB4 (see FIG. 8) may be configured as frictionless wheel brakes RB1, RB2, RB3, and RB4. In a brake-by-wire system, disc brakes with brake pads spaced apart by a clearance allow for reduced friction resistance without pressure in the brake system. This may be achieved by the use of rollback seals in the brake pads, restoring springs, or by actively retracting the brake pads by creating a vacuum with a pressure supplier 6, as described by the applicant in EP 2,225,133.

[0109] The clearances in the wheel brakes RB1, RB2, RB3, RB4, which are variable during operation, can be measured in a wheel- or brake circuit-specific manner by evaluating the pressure profile by the first pressure supply unit 6. According to the invention, the corresponding measurements can occur during service or otherwise while the vehicle is in operation. The measurements are preferably performed with the vehicle stationary or after braking.

[0110] Clearance when activating wheel brakes RB1, RB2, RB3, RB4 using known clearance values ​​for wheel brakes RB1, RB2, RB3, RB4 is initially overcome quickly by the piston stroke control of the first pressure supply unit 6. In this respect, the use of a brushless motor as the electric drive 8 of the first pressure supply unit 6, which has a small time constant, will be preferred, since the act of overcoming the clearance can be performed without the driver perceiving the clearance when activating the brake.

[0111] Furthermore, the brake system 2 can be controlled so that the vehicle electric motor is active in the clearance phase, in this way braking action is generated immediately upon activating the brake.

[0112] In an exemplary embodiment of the invention, the clearance differences of the wheel brakes RB1, RB2, RB3, RB4 are compensated in that the inlet valves EV1 to EV4 of the second module (ESP unit) are activated and / or the electric motors of one or more vehicle axles are used to generate the braking action at the beginning of braking. Due to the clearances, the stick-slip effect of the new brake system at low speeds can generally be reduced or avoided.

[0113] In one exemplary embodiment, the braking system 2 according to the invention in the event of ESP unit failure (error event 4) implements a very simple variant of intermittent braking. Wheel locking is avoided and drivability is maintained by moving the piston of the first pressure supply unit 6 in a reciprocating manner between upper and lower pressure ranges. In contrast to one-channel ABS operation, no measurements (e.g. pressure, wheel speed) are required in this form of deceleration.

[0114] Automatic intermittent braking results in sufficient stopping distance (approximately 200% of the stopping distance in ABS mode) compared to full-blown wheel-specific ABS, and acceptable stability by maintaining maneuverability.

[0115] The braking system according to the invention may offer the decisive advantage that the brake pedal acts only on the piston 24 and is isolated from the brake circuits BK1, BK2 by the feed valve 69. In this way, the function of the automatic intermittent braking with X-boost or X-booster, respectively, cannot be interfered with by the driver, in contrast to the prior art (WO 2011 / 098178).

[0116] Instead of intermittent braking, one-channel ABS operation with "select-low" feedback control (in error event 3) can be implemented. This leads to a further deterioration of the stopping distance (approximately 400% compared to the stopping distance with full-fledged wheel-individual ABS), but leads to unlimited vehicle stability and is superior to intermittent braking in this respect. This form of one-channel ABS operation requires measurements such as pressure and wheel speed, which can be imported from the ESP unit via a communication link / interface (e.g., CAN interface).

[0117] To further increase the availability of the brake system 2 according to the present invention according to FIG. 8, the electric drive 8 of the first pressure supply unit 6 is connected to the X-Boost control unit 9 (ECU-DV) via two redundant three-phase strands, and the electric system is embodied in a (partially) redundant manner. For example, two B6 bridges may be provided per strand. Furthermore, in at least one exemplary embodiment, the electronic system is connected to two redundant power sources. In this way, the failure probability of the electric drive 8 can be reduced by a factor of 4-10, and an error event (failure of the first pressure supply unit 6) can be further significantly reduced.

[0118] Control device 95 of ESP unit 90 and X-Boost control unit 9 (ECU-DV) are connected to each other via a communication link 100 (e.g. a CAN bus). At this point, control commands can be released to the third pressure supply unit 90, causing activation of the drives 91 and / or activation of the provided valves (see also FIG. 8).

[0119] The following safety-related redundancies can be implemented by using the brake system 2 as in FIG. 8: - ensuring sufficient braking action to fulfil the legal requirements in the event of a) failure of the second pressure supply unit 14, b) failure of the first pressure supply unit 6 or c) failure of the first pressure supply unit 6 and the third pressure supply unit 90 (simultaneous), i.e. also fulfilling the legal requirements in the event of a double fault: Error event 1 - failure of the third pressure supply unit 90: deceleration by increasing the braking force via the first pressure supply unit 6 in both brake circuits BK1, BK2; Error event 2 - failure of the third pressure supply unit 90 and brake circuit BK1: deceleration by increasing the braking force via the first pressure supply unit 6 on the rear axle, for example; Error event 3 - failure of the third pressure supply unit 90 and the second brake circuit BK2: e.g. deceleration by the second pressure supply unit 14 on the front axle (first shut-off valve BP1 closed) Error event 4 - failure of the first pressure supply unit 6: deceleration by increasing the braking force via the third pressure supply unit 90; o Error event 5 - failure of the first pressure supply unit 6 and the first brake circuit BK1 or the second brake circuit BK2: deceleration by augmenting the braking force via the third pressure supply unit 90 in one of the brake circuits BK1, BK2 (optionally assisted by the vehicle electric motor on one axle); Error event 6 - failure of the first pressure supply unit 6 and the third pressure supply unit 90: braking by the master brake cylinder on the front axle VA and optionally by the electric drive motor on the rear axle HA; Error event 7 - failure of the on-board network: braking by the second pressure supply unit 14 optionally on the front axle VA and rear axle HA; - generating pressure in the first brake circuit BK1 via the third pressure supply unit 90, generating pressure in the second brake circuit BK2 via the first pressure supply unit 6 with the first shut-off valve BP1 closed, and electronic brake force distribution (EBV) in the event of failure of the ESP unit by controlling the first pressure supply unit 6 via the sensor assembly of the second pressure supply unit 14. What is required for this is a S / W brake circuit division, i.e. the wheels of the front axle VA are connected to a first brake circuit BK1, and the wheels of the rear axle HA are connected to a second brake circuit BK2; - Controlling the clearance between the brake pads and the disc brake; - 4-channel ABS operation and / or yaw torque feedback control when actuating the valves of the ESP unit; - 1-channel ABS operation or implementation of automatic intermittent braking.

[0120] Figure 9 shows an alternative design embodiment of the X-Boost according to Figure 8. In contrast to the exemplary embodiment according to Figure 8, the second shut-off valve TV BK2is disposed in the second hydraulic line HL2 of FIG. 9. This second shutoff valve TV BK2 allows the second brake circuit BK2 to be hydraulically disconnected from the first pressure supply unit 6. In this way, the first pressure supply unit 6 can selectively provide pressurized medium in the first brake circuit BK1, or in the second brake circuit BK2, or in both brake circuits. If a volume loss is detected in the second brake circuit BK2, the second brake circuit BK2 can be disconnected.

[0121] 9 further differs in that a third shut-off valve BP2 is provided in the first hydraulic line HL1 between the first shut-off valve BP1 of the first brake circuit BK1 and the first connection point A1. This third shut-off valve BP2 is preferably arranged such that the third hydraulic line in the hydraulic connection between the first shut-off valve BP1 and the third shut-off valve BP2 opens into the first hydraulic line HL1. The third shut-off valve BP2 allows the first brake circuit BK1 to be hydraulically disconnected not only from the first pressure supply unit 6 but also from the second pressure supply unit 14. Thus, in the event of a failure of the first pressure supply unit 6, the pressurized medium originating from the second pressure supply unit 14 is supplied to the feed valve 69, the first shut-off valve BP1 and the second shut-off valve TV. BK2 No pressurized medium is administered into the first brake circuit BK1 when the third shut-off valve BP2 is closed.

[0122] The following safety-related redundancies can be implemented by using the brake system 2 as in Figure 9: - ensuring sufficient braking action in the event of failure of one or more pressure supply units; Error events 1-7: see embodiment 1; Error event 8 - failure of the feed valve 69 (e.g. leakage) or failure of the electrical actuation: closing of the third hydraulic line HL3 by the shut-off valves BP1 and BP2 so that the stroke simulator 28 is fully effective; the first pressure supply unit 6 regulates the wheel pressure in the brake circuit BK2 and / or the ESP unit regulates the wheel pressure in both brake circuits BK1 and BK2; Further flexibility: selectively supplying the master brake cylinder pressure into the brake circuits BK1 or BK2 in the event of a brake circuit failure; - Ensuring 4-channel ABS feedback control and / or yaw torque feedback control when actuating the valves of the ESP unit; - 2-channel ABS operation with select-low and select-high method or 1-channel ABS with select-low method by wheel rotation speed sensor; - Electronic brake force distribution (EBV) in the event of failure of the ESP unit by generating pressure in the brake circuit BK1 via the second pressure supply unit 14, generating pressure in the brake circuit BK2 via the first pressure supply unit 6 with the first shut-off valve BP1 closed, and controlling the pressure supply via the sensor assembly of the second pressure supply unit 14. To achieve this goal, what is needed is a S / W brake circuit distribution, and the brake force distribution in the brake circuits is controlled by the shut-off valves BP1, BP2 and TV. BK2 According to the invention, the piston of the first pressure supply unit 6 for applying the appropriate pressure can be controlled with a reciprocating stroke movement. Optionally, regulation of the pressure can occur via PWM control of a valve, in particular a shut-off valve; - Clearance control is already implemented in the exemplary embodiment of Fig. 8. The exemplary embodiment as in Fig. 9 is implemented using the shut-off valves BP1, TV BK2This presents an additional possibility of compensating for unequal clearances in the wheel brakes RB1, RB2, RB3, RB4 of the brake circuits BK1, BK2 by corresponding pilot control prior to the brake force boost operation by sequentially opening the valves RB1, RB2, RB3, RB4. Alternatively, PWM operation can also be used so that different flow cross sections to the brake circuits BK1, BK2 can be established and the unequal clearances can be simultaneously compensated. A S / W brake circuit split is preferred here. This method is easily possible since the brake circuit shut-off valves are components of the X-Boost module and can be implemented without any time delay and vulnerability to failure (e.g., by utilizing the interface between the X-Boost and ESP units). In this way, the brake system can be designed in such a way that, for example, clearances are not provided on the brake pads on the front axle but on the rear axle. In this way, a failure of the first pressure supply unit 6 does not lead to a time delay in braking when pressure is generated by the activation unit and acts according to the invention on the wheel brakes RB1, RB2, RB3, RB4 of the front axle VA. Furthermore, a larger braking action can be achieved. It can be generated by the front axle VA.

[0123] 10 and 11 show circuit diagrams of the third pressure supply unit (ESP unit) during pressure dissipation (see FIG. 11) or pressure buildup (see FIG. 11) during a first error event during yaw torque feedback control. In principle, the feedback control here is performed in a manner similar to that of a four-channel ABS, which is also possible during a first error event. However, in the case of yaw torque feedback control, pressure buildup as well as pressure dissipation (in contrast to four-channel ABS feedback control) occurs not only through the USV valves but also through the inlet valves EV1-EV4. Open valves appropriate for flow are marked with an asterisk (*) in FIG. 10 as well as in FIG. 11. The states of other solenoid valves are not explicitly described. For example, at least the inlet valves EV2, EV3, and EV4 are thus closed by active activation during pressure dissipation. Insofar as the valves are operable by a PWM signal, "open" in the context of this application can also be understood to mean that these valves are actuated by the PWM signal so that a predetermined opening cross-section is established. In this manner, the flow rate through each valve can be controlled by actuating the valve with a PWM signal. Specifically, the inlet valves EV1-EV4 and the valves USV1 and USV2 in Figures 10 and 11 can be actuated with a PWM signal. In this manner, the flow rate through these valves can be feedback controlled or controlled, respectively, in the circumstances described below.

[0124] Wheel-selective yaw torque feedback control during pressure buildup in wheel brake RB4 is shown in an exemplary manner in FIG. 10. To this end, the inlet valve EV1 assigned to the respective wheel brake (here, wheel brake RB4) and the shutoff valve USV2 assigned to the respective brake circuit (here, the first brake circuit BK1) are perforated by the flow of pressurized medium. In this embodiment, the valves do not need to be actively activated, since they are passively open in a deactivated open state and allow the flow of pressurized medium in both directions. For selective pressure generation in wheel brake RB4, the other inlet valves EV1-EV3 (of RB1-RB3) that are not subjected to pressure buildup are actuated in such a way that their solenoid valves are moved from an open state to an activated closed state. In this context, actuation of valves that are open when not actuated can be understood to mean that the inlet valves EV1-EV3 are closed (i.e., switched so as not to conduct pressurized medium). Similarly, the HSV valves for selective pressure generation in wheel brake RB4 are closed (i.e., switched so as not to conduct pressurized medium).

[0125] In this way, the pressure from the first pressure supply unit 6 via the shut-off valve USV2 and the inlet valve EV4 is applied exclusively to the wheel brake RB4 (schematically indicated by the arrows). In addition to the wheel brakes RB1, RB2, RB3, and RB4, yaw torque can be generated in several wheel brakes RB1, RB2, RB3, and RB4. To this end, the inlet valves EV1-EV4 in the wheel brakes RB1, RB2, RB3, and RB4 are closed in each case, and no pressure buildup occurs. This buildup allows yaw torque to be generated simultaneously, for example, in two wheel brakes RB1, RB2, RB3, and RB4 on one vehicle side. Since brake circuits are usually embodied in a black-and-white or diagonal configuration, in this case, one wheel brake RB1, RB2, RB3, and RB4 of one brake circuit is consequently affected by the pressure in each case. The circuit shut-off valves BP1 / BP2 and TV of the first module are connected to the circuit shut-off valves BP1 / BP2 and TV. BK2A further potential enhancement of the yaw torque feedback control is possible as a result of sequential or simultaneous multiple actuation of the wheel brakes RB1, RB2, RB3, RB4 (for example RB4 of the right rear wheel) via the circuit interruption valve TV. BK2 Once this pressure reaches the pressure valve, it can be brought to a pressure level where it closes to maintain this pressure.

[0126] In addition, different pressure levels are applied to the wheel brakes RB1, RB2, RB3 of the other brake circuits. , RB4 (for example, RB2 on the right front wheel), and the second brake circuit shut-off valve BP1 or alternatively BP2 is closed to maintain pressure. BK2 are required to maintain pressure since the inlet valves of the wheel brakes RB1, RB2, RB3, RB4 have check valves connected in parallel. In this way, maintaining pressure in the second module (ESP unit) is not possible if the pressure dissipates or if a lower pressure level is regulated in the second brake circuit. The following conditions are therefore the result of the associated valves of the third pressure supply unit 90 for pressure boosting according to Figure 10: HSV1: Closed (inactivated) HSV2: Closed (inactive) EV4: Open (opened when not activated or activated by PWM method: i.e., partially open) EV1-EV3: Closed (activated) All other valves are in a hydraulic (especially deactivated) initial state.

[0127] In the case of pressure dissipation shown in Figure 11, for example, the return of pressurized medium occurs in a similar but reversed manner from wheel brake RB4 via inlet valve EV4 and shut-off valve USV2 to the first pressure supply unit 6. In a similar manner, pressure dissipation then also occurs in the case of yaw torque mediation in several wheel brakes. Here too, a multiplexing method is preferably used.

[0128] In one embodiment, multiple wheel brakes RB1, RB2, RB3, RB4 (particularly all four) may additionally be individually and wheel-selectively actuated in a similar manner, thus implementing wheel-selective yaw torque feedback control. Alternatively or additionally, yaw torque feedback control in one embodiment may occur in a brake circuit-selective manner, such that two wheel brakes of one brake circuit are actuated together in each case.

[0129] Specifically, the following conditions are derived for the associated valves of the third pressure supply unit 90 for pressure dissipation according to FIG. 11: HSV1: Closed (inactivated) HSV2: Closed (inactive) EV4: Open (opened when not activated or activated by PWM method: i.e., partially open) USV1: Closed (closes when activated) EV1-EV3: Closed (activated) All other valves are in a hydraulic (especially deactivated) initial state.

[0130] At this point, it is pointed out that all the above-mentioned components are in each case to be considered individually - even without additionally described features in the respective context, even if said features are not individually and explicitly identified as optional features in the respective context, for example by using "in particular", "preferably", "for example" (e.g. "optionally", brackets, etc.) - and in combination or any sub-combination as independent design embodiments or refinements of the invention, as defined in particular in the introduction to the present description and claims, respectively. Deviations from these are possible. In particular, it is pointed out that the term "in particular" or brackets do not identify features that are mandatory in the respective context. [Explanation of symbols]

[0131] 2. Brake system 6 First pressure supply unit 8 Electric Drive 9 Control unit (ECU-DV) 14 Second pressure supply unit 22 Master brake cylinder 24 pistons 26 Activation elements 28. WS Process Simulator 28a, 28b Sealing elements of the stroke simulator 29 stroke simulator valve 30a, 30b Pedal travel sensor 38 Exhaust hole of second pressure supply unit 40 Reservoir 42a, 42b Auxiliary piston sealing element 69 Feed valve 70b, 70c, 80d Suction valve (check valve) RV1, RV2, NV Suction valves (check valves) RVHZ check valve (master cylinder) 74, PD1, PD2 shutoff valves 80, UV pressure limiting valve 90 Third pressure supply unit 91 Motor / Pump Unit 95 ESP unit control device 100 communication links (CAN bus) A1, A2 connection points B1, B2 Electrical connection (three phase) P pump Medium motor BP1, TV1 First shutoff valve TV BK2 , TV2 Second shutoff valve BP2 Third shutoff valve RB1, RB2, RB3, RB4 wheel brakes DR Throttle BK1 First brake circuit BK2 Second brake circuit HL1 First hydraulic line HL2 Second hydraulic line HL3 3rd hydraulic line HL4 4th hydraulic line VA front axle HA rear axle NS Float Gauge NST Level Detector Shut-off valve for HSV1, HSV2 ESP units Shut-off valve for USV1 and USV2 ESP units Outlet valves for AV1, AV2, AV3, AV4 ESP units Inlet valves for EV1, EV2, EV3, EV4 ESP units

Claims

1. A braking system (2), comprising: a first module comprising a first pressure supply unit (6) with an electric drive (8), an optional second pressure supply unit (14) and a first control device (9) for controlling said first pressure supply unit (6), said first module being configured to supply pressurized medium via a first connection point (A1) to at least one first brake circuit (BK1) and via a second connection point (A2) to at least one second brake circuit (BK2), said brake circuits (BK1, BK2) being assigned wheel brakes (RB1, RB2, RB3, RB4); ● a second module comprising a third pressure supply unit (90), in particular a motor / pump unit (91), brake pressure regulating valves and shut-off valves (USV1, USV2, HSV1, HSV2) for regulating the pressure in said wheel brakes (RB1, RB2, RB3, RB4), in particular outlet valves (AV1, AV2, AV3, AV4) and inlet valves (EV1, EV2, EV3, EV4), as well as a second control device (95) for controlling said brake pressure regulating valves (AV1-AV4, EV1-EV4); a detection unit for detecting a first error event, in particular an at least partial failure of the third pressure supply unit (90), wherein the brake system (2) in the first error event is configured to perform (wheel-individual and / or selective) adjustment of the pressure in the wheel brakes while activating at least one of the brake pressure regulating valves (AV1-AV4, EV1-EV4) of the second module and / or the shut-off valves (USV1, USV2, HSV1, HSV2) of the second module, and the first pressure supply unit (6), in order to provide an ABS function and / or yaw torque arbitration; A brake system (2) having:

2. 2. The brake system (2) of claim 1, wherein the first pressure supply unit (6) in the first error event is controlled in a manner that produces a pressure drop having a pressure lower than the pressure in the wheel brakes (RB1, RB2, RB3, RB4) when the first pressure supply unit (6) dissipates pressure to provide the ABS braking operation.

3. 3. A brake system (2) according to claim 1 or 2, wherein at least some of the shut-off valves (USV1, USV2, HSV1, HSV2) of the first module are arranged and configured to establish a hydraulic connection between the brake pressure regulating valves (AV1-AV4, EV1-EV4), in particular the outlet valves (AV1, AV2, AV3, AV4), and the connection points (A1, A2), and wherein the brake system (2) in the first error event is preferably configured to open the assigned outlet valve (AV1, AV2, AV3, AV4) in order to dissipate pressure in one of the wheel brakes.

4. 4. A brake system (2) according to claim 1, wherein a communication link (100), in particular a bus link, is configured between the first control device (9) and the second control device (95), the first control device (9) being preferably configured to receive pressure measurement values ​​and / or wheel rotation speed signals of the third pressure supply unit (90) via the communication link (100).

5. 4. A brake system (2) according to claim 1, wherein a communication link (100), in particular a bus link, is configured between the first control device (9) and the second control device (95), the first control device (9) and the second control device (95) being preferably configured to receive pressure measurement values ​​and / or wheel rotation speed signals of the third pressure supply unit (90) via the communication link (100).

6. 6. The brake system (2) according to claim 1, wherein the first control device (9), the second control device (95), or the third control device is configured to control the first pressure supply unit (6) and the brake pressure regulating valves (AV1-AV4, EV1-EV4) in the first error event to perform wheel-individual and / or brake circuit-individual pressure feedback control in the wheel brakes (RB1, RB2, RB3, RB4) or the brake circuits (BK1, BK2).

7. - a first shut-off valve (BP1) of the first module is arranged in a first hydraulic line (HL1) between the first pressure supply unit (6) and the first connection point (A1), and a second shut-off valve (TV ＢＫ２ 7. The brake system (2) according to claim 1, wherein a second hydraulic line (HL2) between the first pressure supply unit (6) and the second connection point (A2) is arranged in the second hydraulic line (HL2) between the first pressure supply unit (6) and the second connection point (A2). to detect a second error event, in particular a total failure of said second module; and - in the second error event, the first pressure supply unit (6) and the first and second shut-off valves (BP1, TV2) are controlled to carry out at least one brake circuit individual pressure feedback control in the at least two brake circuits (BK1, BK2). ＢＫ２ ) a braking system (2) configured to control the

8. The braking system, in particular the first control device (9), - To detect non-homogeneous road conditions, in particular μ-split situations, and A brake system (2) according to any one of claims 1 to 7, in particular according to claim 7, configured to control the first pressure supply unit (6) to adjust, in the second error event and in the non-homogeneous road condition, in at least one selected one of the brake circuits (BK1, BK2), a target brake pressure determined as a function of the wheel cut-off pressure of a wheel brake (RB1, RB2, RB3, RB4) of the selected brake circuit (BK1, BK2) which has a higher coefficient of friction compared to the other wheel brakes (RB1, RB2, RB3, RB4) of the selected brake circuit (BK1, BK2).

9. 9. A brake system (2) according to any one of claims 1 to 8, wherein at least the second module comprises a wheel sensor for detecting a wheel speed, and the wheel sensor is configured to transmit a wheel rotational speed signal generated from the detected wheel speed or the detected wheel speed to the first module, in particular the first control device (9), via the communication link (100).

10. 10. The brake system (2) according to any one of claims 1 to 9, wherein the brake system, in particular the first control device (9), is configured to control the pressure build-up and pressure dissipation by the first pressure supply unit (6) in a third error event so as to implement one-channel ABS using sensors, and / or to implement intermittent braking in a fourth event by modulating the pressure between two fixedly adjusted pressure levels in the two brake circuits (BK1, BK2).

11. 11. A braking system (2) according to any one of the preceding claims, wherein at least one pressure sensor is provided for detecting a brake pressure in the at least one brake circuit (BK1, BK2).

12. The first module: - rotary pumps, in particular one-piston or three-piston pumps, for building up and dissipating pressure; - a solenoid valve (PD2) hydraulically connected to the reservoir (40); A braking system (2) according to any one of claims 1 to 11, optionally comprising at least one pressure transducer preferably communicatively connected to said first control device (9) for feedback control of said pressure build-up and said pressure dissipation.

13. 12. A braking system (2) according to any one of the preceding claims, wherein the first pressure supply unit (6) is configured as a gear pump for building up and dissipating pressure.

14. 14. A braking system (2) according to claim 13, wherein the gear pump is controlled using a pressure transducer or in response to current measurements, in particular the phase current i of the electric drive of the gear pump and the rotor angle α of the electric drive.

15. 15. A brake system (2) according to any one of claims 1 to 14, further comprising at least one third shut-off valve (BP2) arranged and configured such that, in a closed state of the third shut-off valve (BP2), the first brake circuit (BK1) is hydraulically isolated from the first and second pressure supply units (6, 14).

16. 16. A brake system (2) according to any one of claims 1 to 15, wherein the first hydraulic line (HL1) and / or the second hydraulic line (HL2) are connected to a reservoir (40) via (in each case) an intake valve (70b, 70c).

17. 17. A brake system (2) according to any one of claims 1 to 16, wherein an activation element (26), in particular a brake pedal, is arranged on the second pressure supply unit (14), the second pressure supply unit (14) including a master brake cylinder (22) having a single piston (24) that can be activated by the activation element (26).

18. - controlling the first pressure supply unit (6) of the first module by a first control device (9) during normal operation; ● controlling a plurality of brake pressure regulating valves (AV1-AV4, EV1-EV4) in the second module during normal operation; detecting a first error event, in particular a partial failure of said second module; ● controlling the braking system (2) in the first error event in such a way that a (wheel-individual and / or selective) modulation of the pressure in the wheel brakes occurs while actuating at least one of the brake pressure regulating valves (AV1-AV4, EV1-EV4) of the second module and / or in particular the two-way shut-off valves (USV1, USV2, HSV1, HSV2) of the second module and in particular the first pressure supply unit (6) in order to provide ABS braking operation and / or yaw torque mediation; 18. A method for controlling a brake system (2), in particular a brake system (2) according to any one of claims 1 to 17, comprising:

19. detecting a second error event, in particular a total failure of said third pressure supply unit (90); and the pressure supply unit (6) of the first module and at least two shut-off valves (BP1, TV2) are controlled in such a way that in the second error event a brake circuit-individual pressure feedback control is implemented in the at least two brake circuits (BK1, BK2); ＢＫ２ ) controlling the 20. The method of claim 18, comprising:

20. - detecting non-homogeneous road conditions, in particular μ-split situations; ● In non-homogeneous road conditions, other wheel brakes (RB1, RB2, RB3, RB4) controlling the first pressure supply unit (6) in the second error event in such a way that the wheel brakes (RB1, RB2, RB3, RB4) of the selected brake circuits (BK1, BK2) having a higher coefficient of friction compared to the first brake circuit (BK1, BK2) are utilized to determine the target brake pressure.

20. The method of claim 19, comprising:

21. detecting a third error event, in particular a total failure of said third pressure supply unit (90) and / or a failure of a wheel sensor; controlling the first pressure supply unit (6) in such a way that in a third error event a one-channel ABS is implemented, or in a fourth error event an intermittent braking is implemented by modulating the pressure between two predetermined pressure levels in at least one of said brake circuits (BK1, BK2); 21. The method according to any one of claims 18 to 20, in particular claim 19 or 20, comprising:

22. determining a first wheel blocking pressure on a first wheel brake (RB1, RB2, RB3, RB4) assigned to one of said two brake circuits (BK1, BK2); determining a second wheel blocking pressure on the wheel brakes (RB1, RB2, RB3, RB4) assigned to the same brake circuit (BK1, BK2), whereby a non-homogeneous road condition is detected if the first and second wheel blocking pressures differ by more than 30%; 22. The method according to any one of claims 18 to 21, in particular claim 18, comprising:

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