BRAKING SYSTEM FOR A MOTOR VEHICLE

Description

[0001] The invention relates to a braking system for a motor vehicle.

[0002] In the prior art, braking systems with an electro-hydraulic partial braking system and an electromechanical partial braking system are known. Both systems are typically controlled by a single control unit, which is usually assigned to the electro-hydraulic partial braking system. The electro-hydraulic partial braking system typically includes a hydraulic fallback system that allows the vehicle to be decelerated by the hydraulic partial braking system even if the control unit fails.

[0003] Document DE 103 19 194 B3 describes such a combined hydraulic and electromechanical vehicle braking system with a hydraulic service brake system for the front wheels and an electromechanical service brake system for the rear wheels, in particular for a passenger car. The document proposes connecting each hydraulic wheel brake to two brake pressure build-up valves and two brake pressure release valves. This is intended to achieve an increased speed of wheel brake pressure build-up and release.

[0004] Furthermore, document DE 10 2015 206 572 A1 describes another braking system for motor vehicles that can be controlled in a "brake-by-wire" mode both by a driver and independently of the driver. The braking system has a first electrically controlled pressure source with a first electronic control unit, by means of which the wheel brakes can be actuated, and a second electrically controlled pressure source with a second electronic control unit, by means of which the wheel brakes can also be actuated. This is intended to provide a braking system suitable for automated driving and, in particular, to ensure the necessary safety requirements regarding the availability of the braking function, even in the event of a fault.

[0005] Such a system has a high number of potential faults that can lead to a complete loss of electrical braking power. This applies to both electro-hydraulic and electromechanical partial braking systems.

[0006] In contrast, the present application is based on the task of specifying a braking system that provides a reduction in the probability of a complete loss of the electrical amplification of the braking effect due to an electrical fault, as well as high braking performance in the case of individual electrical faults.

[0007] This problem is solved with the braking system according to claim 1.

[0008] The invention relates to a braking system for a motor vehicle comprising an electro-hydraulic partial braking system with hydraulically actuated wheel brakes and an electromechanical partial braking system with electromechanically actuated wheel brakes. The braking system has two control units and two independent power supplies, wherein a first control unit is configured to control the electromechanical partial braking system and a second control unit is configured to control the electro-hydraulic partial braking system. The first control unit is powered exclusively by the first power supply, and the second control unit is powered exclusively by the second power supply.The first control unit is connected to the electromechanically actuated wheel brakes via a primary communication bus, and the second control unit is connected to the electromechanically actuated wheel brakes via a secondary communication bus. The first control unit is configured to transmit control information, in particular the target braking forces to be applied by the electromechanical wheel brakes, to the electromechanically actuated wheel brakes via the primary communication bus. The second control unit is configured to transmit actuation information from the electrohydraulic partial braking system, in particular a pedal travel or pedal angle of an actuating pedal and / or a force acting on the actuating pedal and / or a displacement travel of a cylinder piston arranged in the master cylinder, to the electromechanically actuated wheel brakes via the secondary communication bus.The electromechanical wheel brakes each have wheel control units, the wheel control units being designed to control a braking force applied by the respective electromechanical wheel brake depending on information received via the primary and / or secondary communication bus, in particular control information or actuation information.

[0009] The control unit of the braking system is therefore divided into a first control unit and a second control unit. The first control unit and the second control unit each preferably control a part of the electro-hydraulic partial braking system. Furthermore, the first control unit and the second control unit preferably communicate with the electromechanical partial braking system via a separate bus. Particularly preferably, the first control unit is configured to exchange information with the second control unit. This information can include, in particular, actuation information, applied brake pressures or forces, or other operating information of the respective partial braking system.

[0010] This ensures high braking performance even in the event of a single electrical fault, because if one of the control units fails, the electro-hydraulic and electromechanical partial braking systems can each be controlled by the still-functioning control unit in a way that guarantees a minimum deceleration from the braking system. A "single fault" is understood to mean a malfunction of a component of the braking system, such as a power supply or a control unit.

[0011] The hydraulic partial braking system preferably has exactly two hydraulically actuated wheel brakes, wherein the hydraulically actuated wheel brakes are particularly preferably designed to apply a braking force to the wheels of a front axle of the motor vehicle.

[0012] Accordingly, the electromechanical partial braking system preferably has exactly two electromechanically actuated wheel brakes, wherein the electromechanically actuated wheel brakes are particularly preferably designed to apply a braking force to the vehicle wheels of the vehicle assigned to the electromechanically actuated wheel brakes, in particular the vehicle wheels of a rear axle of the motor vehicle, depending on a received information, in particular a control information, in particular a target braking force.

[0013] Preferably, the braking system is designed with an axle-wise distribution of the electromechanical and electrohydraulic wheel brakes, whereby a main load of the deceleration is usually borne by the electrohydraulically actuated wheel brakes of the front axle.

[0014] The electromechanically actuated wheel brakes can be, for example, disc brakes or, preferably, electromechanical drum brakes. Preferably, the electromechanically actuated wheel brakes are further configured to implement a parking brake function. Particularly preferably, the first control unit is configured to activate the parking brake function of the electromechanically actuated wheel brakes.

[0015] In a preferred embodiment, the electro-hydraulic partial brake system comprises an electromechanical pressure supply device for generating hydraulic brake pressure, with the second control unit being configured to actuate the electromechanical pressure supply device to generate hydraulic brake pressure. The electromechanical pressure supply device can, for example, be a linear actuator. Preferably, a drive shaft of an electric motor is connected to a rotary-translation transmission such that a rotation of the drive shaft is translated into a translation of a pressure piston. The pressure piston is arranged in a pressure cylinder and is configured to displace a fluid, in particular brake fluid, located in the pressure cylinder.to apply pressure. In normal operating mode of the electro-hydraulic partial braking system, hydraulic pressure for generating a braking force through the hydraulically actuated wheel brakes is generated exclusively by the electromechanical pressure supply device.

[0016] To ensure control of the pressure supply device by the second control unit, it is preferably provided that the second control unit includes power electronics for providing an operating voltage for the electromechanical pressure supply device. The power supply for the power electronics, and thus for the pressure supply device, is accordingly also provided by the second power supply.

[0017] In a further embodiment, the electro-hydraulic partial brake system is provided with a pressure supply valve, wherein the pressure supply valve is configured to establish or disconnect a hydraulic connection between the electromechanical pressure supply device and the hydraulically actuated wheel brakes. Preferably, the pressure supply valve is normally closed (normally de-energized). Accordingly, in the event of a power failure of the pressure supply valve, a hydraulic connection between the electromechanical pressure supply device and the hydraulically actuated wheel brakes would be interrupted.

[0018] In a further embodiment, the electro-hydraulic partial brake system comprises a hydraulic master cylinder, which can be pressurized by a pedal. The electro-hydraulic partial brake system includes a master cylinder valve, configured to establish or disconnect a hydraulic connection between the master cylinder and the hydraulically actuated wheel brakes. Preferably, the master cylinder valve is normally open (de-energized), so that in the event of a power failure, a hydraulic connection between the master cylinder and the hydraulically actuated wheel brakes is automatically established. In this way, even in the event of a single fault, direct actuation of the hydraulically actuated wheel brakes via the pedal and the master cylinder remains possible.

[0019] As previously explained, in normal operation of the braking system, hydraulic pressure for actuating the electro-hydraulically operated wheel brakes is generated exclusively by the electromechanical pressure supply device. Preferably, the master cylinder is hydraulically isolated from the wheel brakes. To ensure that the driver continues to experience a familiar feel when operating the pedal or brake pedal, a further embodiment provides that the electro-hydraulic partial braking system includes a pedal feel simulator. This pedal feel simulator is hydraulically connected to the master cylinder, and the electro-hydraulic partial braking system includes a simulator valve configured to establish or disconnect a hydraulic connection between the master cylinder and the pedal feel simulator.The simulator valve is preferably closed when de-energized, so that in the event of a malfunction the master cylinder is decoupled from the pedal feel simulator and the hydraulic pressure generated in the master cylinder can act fully on the wheel brakes.

[0020] As previously explained, it is preferably provided that each control unit controls a part of the electro-hydraulic partial braking system, so that deceleration via the hydraulic partial braking system remains possible even if one of the control units or its associated power supply fails. Accordingly, in a preferred embodiment, the second control unit is configured to control the electromechanical pressure supply device, the simulator valve, the master cylinder valve, and the pressure supply valve.

[0021] According to a further embodiment, the electro-hydraulic partial braking system is further provided to have a first pressure sensor for determining the hydraulic pressure generated by the master cylinder and / or a motor position sensor for determining the motor position of a drive of the electromechanical pressure supply device and / or a displacement sensor for determining the displacement of a cylinder piston in the master cylinder. In this case, the second control unit is preferably configured to read out information determined by the pressure sensor and / or the motor position sensor and / or the displacement sensor. This information can then either be transmitted to the electromechanically actuated wheel brakes in the form of actuation information or communicated to the first control unit.

[0022] In addition to transmitting the information thus determined to the electromechanical partial brake system, a further embodiment provides that the second control unit is designed to control the electromechanical pressure supply device to generate a hydraulic brake pressure through the electromechanical pressure supply device as a function of a determined displacement of the cylinder piston in the master cylinder and / or as a function of a hydraulic pressure generated by the master cylinder and / or as a function of an actuation angle of the actuating pedal and / or as a function of an actuation travel of the actuating pedal and / or as a function of a force acting on the actuating pedal.An actuation angle or actuation path of the actuating pedal or a force acting on the actuating pedal can also be used as actuation information for controlling the electromechanical wheel brakes.

[0023] For wheel-specific adjustment of the brake pressure applied to the hydraulically actuated wheel brakes, for example for the implementation of an ABS function, a further embodiment provides that the electro-hydraulic partial brake system has a pressure modulation device, wherein the pressure modulation device is designed to modulate the hydraulic brake pressure applied to the hydraulically actuated wheel brakes, in particular individually for each wheel, and wherein the first control unit is designed to control the pressure modulation device.

[0024] It is particularly preferred that the electro-hydraulic partial brake system has, for each hydraulically actuated wheel brake, a preferably normally open inlet valve and a preferably normally closed outlet valve, wherein the inlet and outlet valves form the pressure modulation device. The inlet valves are preferably configured to establish or disconnect a hydraulic connection between the respective wheel brake and the electromechanical pressure supply and / or the master cylinder, while the outlet valves are each configured to establish or disconnect a hydraulic connection between the respective wheel brake and a brake fluid reservoir. Preferably, the brake fluid reservoir is at atmospheric pressure. The first control unit is correspondingly preferably configured to control the inlet valves and / or the outlet valves of the electro-hydraulic partial brake system.

[0025] According to a further embodiment, the electromechanically actuated wheel brakes are supplied with energy from the first power supply. In this embodiment, the electromechanical wheel brakes are thus supplied with energy from the same power supply that also supplies energy to the control unit primarily assigned to the electromechanical wheel brakes.

[0026] It was previously explained that the electromechanical wheel brakes are controlled based on control information that identifies, in particular, the target braking force to be applied by the respective wheel brake. According to a further embodiment, the first control unit is designed to determine the target braking forces to be applied by the electromechanically actuated wheel brakes as a function of a determined displacement of the cylinder piston in the master cylinder, and / or as a function of a hydraulic pressure generated by the master cylinder, and / or as a function of an actuation angle of the actuating pedal, and / or as a function of an actuation travel of the actuating pedal, and / or as a function of a force acting on the actuating pedal.

[0027] According to a further embodiment, the braking system according to one of the preceding claims is further provided, wherein the braking system comprises wheel speed sensors, and the first control unit is configured to modulate the braking forces applied to the vehicle wheels based on the wheel speeds. In particular, it can be provided that a driving function, in particular an ABS function or an ESC function, is implemented by modulating the braking forces applied to the vehicle wheels, especially by a corresponding change in the clamping force of the electromechanically actuated wheel brakes or the hydraulic pressure in the hydraulically actuated wheel brakes.

[0028] It is preferably provided that the electro-hydraulic partial braking system has a pre-pressure sensor for determining the hydraulic pressure applied upstream of the wheel brake inlet valves, wherein the first control unit is configured to read out the information obtained from the pre-pressure sensor. Based on such a pre-pressure, the deceleration behavior of the hydraulically actuated wheel brakes can then be controlled by selectively opening and closing the inlet and outlet valves to implement an ABS or ESC function.

[0029] In addition to activating the braking system by pressing the brake pedal or actuator pedal, it can also be provided that the braking system is activated autonomously by a driving function of the vehicle, without the driver actively influencing it. According to a further embodiment, the first control unit is connected to a vehicle bus of the motor vehicle, whereby control commands, in particular braking requests, can be transmitted to the first control unit via the vehicle bus. Such braking requests can be triggered, for example, within the framework of active cruise control or an ESC function.

[0030] Preferred embodiments of the invention are explained in more detail below with reference to the drawings. These show Figure 1 is a schematic representation of an exemplary braking system and Figure 2 is a simplified representation of the exemplary braking system.

[0031] In the following, similar or identical features are marked with the same reference symbols.

[0032] The Figure 1 Figure 1 shows a braking system 100 for a motor vehicle with a hydraulic partial braking system 102 and an electromechanical partial braking system 104. The electrohydraulic partial braking system 102 comprises hydraulically actuated wheel brakes 106 and 108, which act on the front wheels of the motor vehicle. The wheel brakes 106 and 108 can be, in particular, hydraulically actuated disc brakes. During operation of the braking system 100, the wheel brakes 106 and 108 are subjected to hydraulic brake pressure by a hydraulic arrangement 110, which is translated by the wheel brakes 106 and 108 into a braking force acting on the respective vehicle wheels assigned to the wheel brakes 106 and 108.

[0033] For this purpose, the hydraulic arrangement 110 comprises a master cylinder 112 with a cylinder piston 114 slidably mounted within the master cylinder 112. The cylinder piston 114 can be moved within the master cylinder 112 by actuating an actuating pedal 116 connected to the cylinder piston 114, or brake fluid located in the master cylinder 112 can be pressurized with hydraulic pressure. The hydraulic pressure generated in this process is detected by a pressure sensor 118. Furthermore, the displacement of the cylinder piston 114 is determined by a displacement sensor 120.

[0034] The master cylinder 112 is hydraulically connected to a pedal feel simulator 122, with a normally closed simulator valve 124 arranged between the master cylinder 112 and the pedal feel simulator 122. The simulator valve 124 can therefore establish or break a hydraulic connection between the master cylinder 112 and the pedal feel simulator 122.

[0035] Furthermore, the master cylinder 112 is hydraulically connected to a pressure modulation device 126, which in turn is hydraulically connected to the wheel brakes 106 and 108. A normally open master cylinder valve 128 is arranged between the master cylinder 112 and the pressure modulation device 126, and the master cylinder valve 128 can establish or break a hydraulic connection between the master cylinder 112 and the pressure modulation device 126. A pressure sensor 130 is also arranged between the master cylinder valve 128 and the pressure modulation device 126, and the pressure sensor 130 is designed to detect the hydraulic pressure applied upstream of the pressure modulation device 126.

[0036] The pressure modulation device 126 has a normally open inlet valve 132 and a normally closed outlet valve 134 for each connected hydraulically actuated wheel brake 106 and 108. The outlet valves 134 are designed to establish or interrupt a hydraulic connection between the wheel brakes 106 and 108 and a brake fluid reservoir 136, so that the hydraulic brake pressure applied to the wheel brakes 106 and 108 can be reduced via the outlet valves 134. Simultaneously, the hydraulic brake pressure applied to the wheel brakes 106 and 108 can be modulated from the applied pre-pressure by selectively opening and closing the inlet valves 132.

[0037] The hydraulic arrangement 110 further comprises an electromechanical pressure supply device 138. The pressure supply device 138 includes a hydraulic cylinder 140 and a pressure piston 142 that is displaceable within the hydraulic cylinder 140. The pressure piston 142 is connected to an electrically driven spindle drive 144 such that a rotation of a drive shaft of the drive or electric motor 146 connected to the spindle drive 144 is translated into a translation of the pressure piston 142 within the hydraulic cylinder 140, thereby pressurizing brake fluid located in the hydraulic cylinder. The rotational position of a rotor of the electric motor 146, and thus the current position of the pressure piston 142 within the hydraulic cylinder, is monitored by a motor position sensor 154.

[0038] The hydraulic cylinder 140 of the pressure supply device 138 is also hydraulically connected to the pressure modulation device 126, with a normally closed pressure supply valve 188 arranged between the pressure modulation device 126 and the hydraulic cylinder 140 of the pressure supply device 138. The pressure supply valve 188 can therefore establish or interrupt a hydraulic connection between the pressure supply device 138 and the pressure modulation device 126.

[0039] The electromechanical partial braking system 104, in the illustrated configuration, has two electromechanically actuated wheel brakes 148 and 150, which are designed as electromechanical drum brakes. The wheel brakes 148 and 150 are assigned to the rear axle wheels of the vehicle. Furthermore, the wheel brakes 148 and 150 are designed to implement a parking brake function.

[0040] The brake system 100 comprises two control units 200 and 300, wherein, in the illustrated embodiment, the control units 200 and 300 are configured as part of the electro-hydraulic partial brake system 102. A first control unit 200 is configured to control the pressure modulation device 126, specifically the inlet valves 132 and the outlet valves 134, in order to modulate the hydraulic brake pressure applied to the wheel brakes 106 and 108, starting from a hydraulic pre-pressure applied upstream of the pressure modulation device 126. In this way, the first control unit 200 can, in particular, implement ABS control or ESC control. Furthermore, the first control unit 200 is configured to read out a hydraulic pressure determined by the pre-pressure sensor 130.

[0041] The second control unit 300 is configured to control the pressure supply device 138, the simulator valve 124, the master cylinder valve 128, and the pressure supply valve 188. Furthermore, the second control unit 300 includes power electronics 152 for providing and controlling an operating voltage for the electromechanical pressure supply device 138 and the corresponding electric motor 146. The second control unit 300 is configured to read out a displacement of the cylinder piston 114 determined by the displacement sensor 120, a pressure generated by the master cylinder 112 determined by the pressure sensor 118, and the motor position of the electric motor 146 detected by the motor position sensor 154.

[0042] The first control unit 200 has a first microcontroller 156, while the second control unit 300 has a second microcontroller 158 for implementing the control functions of the respective control units 200 and 300. The microcontrollers 156 and 158 are connected to each other via a communication link 190, so that control information can be exchanged between the microcontrollers 156 and 158 and thus between the control units 200 and 300.

[0043] To control the electromechanically actuated wheel brakes 148 and 150, the first control unit 200 is connected via a common primary communication bus 164 to the electromechanically actuated wheel brakes 148 and 150, or to the control units 166 and 168 contained in the electromechanically actuated wheel brakes 148 and 150. The first control unit 200 is configured to transmit control information, in particular the target braking forces to be applied by the wheel brakes 148 and 150, to the control units 166 and 168 via this primary communication bus 164. The control units 166 and 168 are then designed to regulate the braking force of the respective wheel brake 148 or 150 to the corresponding target braking force with the aid of torque sensors 170 and 172 arranged in the wheel brakes.

[0044] The second control unit 300 is also connected to the electromechanically actuated wheel brakes 148 and 150 via a common secondary communication bus 174 and is configured to transmit control information to the control units 166 and 168 of the electromechanically actuated wheel brakes 148 and 150 in a fallback operating mode. This will be discussed in more detail below.

[0045] The depicted braking system further comprises a first power supply 160 and a second power supply 162. The first power supply 160 is completely independent of the second power supply 162. In particular, the first power supply 160 and the second power supply 162 can be two separate electrical systems, which are designed in such a way that a failure or malfunction of one of the electrical systems does not affect the functionality of the other.

[0046] The first power supply 160 is designed to supply energy to the first control unit 200 and the electromechanically operated wheel brakes 148 and 150, while the second power supply 162 is designed to supply energy to the second control unit 300 and thus also to the electromechanical pressure supply device 138 via the power electronics 152.

[0047] The first control unit 200 is further connected to a parking brake switch 176, so that when the parking brake switch 176 is actuated, the first control unit 200 can process the corresponding information. The first control unit 200 is then configured to transmit the corresponding control information for activating the parking brake function to the electromechanical wheel brakes 148 and 150 via the primary communication bus 164, so that the parking brake function is activated by the control units 166 and 168 of the wheel brakes 148 and 150.

[0048] The first control unit 200 is also connected to an ESC switch 178, which can be used to activate or deactivate the ESC functionality of the brake system 100. Furthermore, the first control unit 200 is connected to a vehicle bus 180, via which control information, particularly in the form of braking requests, can also be received. Such braking requests can be triggered, for example, within the context of an automated driving function, such as an autopilot.

[0049] To provide control functions such as ABS and ESC via the first control unit 200, the brake system 100 also includes wheel speed sensors 182, which are assigned to those vehicle wheels that can be subjected to a braking force by one of the wheel brakes 106, 108, 148, or 150. Wheel speed information from those vehicle wheels assigned to the hydraulically actuated wheel brakes 106 and 108 is transmitted to the first control unit 200 via a corresponding interface 184, while the wheel speed information from those vehicle wheels assigned to the electromechanically actuated wheel brakes 148 and 150 is transmitted to the first control unit 200 via the primary communication bus 164.

[0050] The connection of the first power supply 160, the second power supply 162, the wheel speed sensors 182 of the front wheels, the parking brake switch 176, the ESC switch 178, the vehicle bus 180, the primary communication bus 164 and the secondary communication bus 174 to the control units 200 and 300 of the brake system 100 is realized via a common interface 186, which can be implemented in particular as part of the first control unit 200.

[0051] The following describes the operation of the brake system 100. In normal operating mode, the master cylinder 112 is decoupled from the hydraulically actuated wheel brakes 106 and 108 by a closed master cylinder valve 128, so that hydraulic pressure built up by actuating the actuating pedal 116 is detected by the pedal feel simulator 122. For this purpose, the simulator valve 124 is open in normal operating mode. The pressure generated is detected by the pressure sensor 118, while simultaneously the displacement of the cylinder piston 114 is detected by the displacement sensor 120. Furthermore, actuation information such as the actuation travel or angle of the actuating pedal, or the actuating force acting on the actuating pedal 116, can also be determined.

[0052] The actuation information thus acquired is read out by the second control unit 300 and interpreted as a braking request. Based on this braking request, the second control unit 300 uses the power electronics 152 to control the pressure supply unit 138 so that a hydraulic brake pressure corresponding to the braking request is generated in the hydraulic cylinder 140 of the pressure supply unit 138 and thus in the wheel brakes 106 and 108, so that the desired braking force is generated by the wheel brakes 106 and 108. This brake pressure is detected by the pre-pressure sensor 128 and read out by the first control unit 200.

[0053] The first control unit 200 is designed to determine a target braking force, based on the measured brake pressure and / or on actuation information transmitted from the second control unit 300 to the first control unit 200. This target braking force is then applied by the electromechanically actuated wheel brakes 148 and 150 to implement the braking request. A fixed or dynamically variable brake force distribution between the wheel brakes 106 and 108 of the front axle and the wheel brakes 148 and 150 of the rear axle can be taken into account.

[0054] The target braking force thus determined is then transmitted by the first control unit 200 via the primary communication bus 164 to the control units 166 and 168 of the wheel brakes 148 and 150, whereupon the control units 166 and 168 adjust the braking force applied by the wheel brakes 148 and 150 accordingly.

[0055] InSimilarly, a braking request or braking demand received via vehicle bus 180 can also be implemented.

[0056] During the deceleration process, the first control unit 200 continuously monitors the wheel speeds of the vehicle wheels to determine whether the slip of at least one of the vehicle wheels exceeds a certain limit. If this occurs at a rear axle wheel, the first control unit 200 adjusts the target braking force of the corresponding wheel brake 148 or 150 so that the slip is reduced to a permissible level. If slip is detected at a front axle wheel, the first control unit 200 activates the pressure modulation device 126 so that, for example, by temporarily opening the corresponding outlet valves 134, the brake pressure in the corresponding wheel brakes 106 or 108 is briefly reduced to a permissible level.

[0057] Furthermore, the first control unit 200 can also trigger targeted braking of individual vehicle wheels as a result of a control request from an ESC control system in the manner described.

[0058] In the described brake system 100, a variety of electrical faults can prevent parts of the brake system 100 from functioning as intended. Four exemplary cases of such faults are described below.

[0059] In one scenario, the first control unit 200 may fail due to an electrical defect. In this case, wheel-specific modulation of the braking forces is no longer possible to the extent described above. Such a fault can be signaled to the driver by the illumination of a corresponding warning light.

[0060] The hydraulic partial braking system 102 can, however, continue to operate normally, apart from modulating the brake pressures applied to the individual wheel brakes 106 and 108, so that electrical amplification of the braking force remains possible. In this case, the electromechanical wheel brakes 148 and 150 of the rear axle can still be controlled by the second control unit 300. For this purpose, in the event of a failure of the first control unit 200, the second control unit 300 transmits the determined actuation information to the control units 166 and 168 via the secondary communication bus 174. The control units 166 and 168 are then configured to locally regulate the braking force of the corresponding wheel brake 148 and 150, respectively, based on this actuation information.It may also be provided that the wheel brakes 148 and 150 exchange the respective determined wheel speeds with each other, so that local control of the wheel slip remains possible.

[0061] In a second scenario, the second control unit 300 may fail due to a technical defect, preventing electrical amplification of the hydraulic brake pressure by the pressure supply device 138. In this case, the simulator valve 124 and the pressure supply valve 188 close automatically, while the master cylinder valve 128 opens. Consequently, the master cylinder 112 is directly connected to the wheel brakes 106 and 108, so that an actuating force acting on the actuating pedal 116 is directly translated into a brake pressure applied to the wheel brakes 106 and 108. This brake pressure is further detected by the pre-pressure sensor 130, whereupon the first control unit 200 actuates the electromechanically actuated wheel brakes 148 and 150 accordingly.Furthermore, it may be provided that the first control unit 200 continues to have access to the actuation information of the actuating pedal 116 and / or the master cylinder 112. Consequently, in this fallback operating mode, electrical amplification of the braking force at the wheel brakes 106 and 108 of the front wheels is no longer possible. However, the rear axle of the vehicle can still be subjected to the maximum possible braking force, so that sufficient deceleration of the vehicle remains possible.

[0062] A similar scenario arises if the second power supply 162 fails.

[0063] If the primary power supply 160 fails, the rear axle wheel brakes 148 and 150 can no longer be used. However, in this case, the front axle wheel brakes 106 and 108 can still be operated with electrical braking force amplification, so that sufficient deceleration of the vehicle can still be achieved.

[0064] The Figure 2 shows a simplified representation of the in Figure 1 brake system shown 100.

Claims

1. A brake system (100) for a motor vehicle having an electrohydraulic partial brake system having hydraulically actuated wheel brakes (106, 108) and having an electromechanical partial brake system having electromechanically actuated wheel brakes (148, 150), wherein the brake system has two control units (200, 300) and two mutually independent energy supplies (160, 162), wherein a first of the control units (200) is designed for controlling the electromechanical partial brake system, and a second of the control units (300) is designed for controlling the electrohydraulic partial brake system, wherein the first control unit (200) is supplied with energy exclusively by a first of the energy supplies (160) and wherein the second control unit (300) is supplied with energy exclusively by a second of the energy supplies (162), wherein the first control unit (200) is connected to the electromechanically actuated wheel brakes (148, 150) via a primary communication bus (164), and wherein the second control unit (300) is connected to the electromechanically actuated wheel brakes (148, 150) via a secondary communication bus (174), wherein the first control unit (200) is designed, to transmit control information to the electromechanically actuated wheel brakes (148, 150) via the primary communication bus (164), wherein the second control unit (300) is designed to transmit actuation information of the electrohydraulic partial brake system to the electromechanically actuated wheel brakes (148, 150) via the secondary communication bus (174), wherein the electromechanical wheel brakes (148, 150) each have wheel control units (166, 168), wherein the wheel control units (166, 168) are designed to control a braking force applied by the respective electromechanical wheel brake (148, 150) depending on information received via the primary (164) and / or secondary communication bus (174).

2. The brake system (100) as claimed in claim 1, characterized in that the electrohydraulic partial brake system has an electromechanical pressure provision device (138) for generating a hydraulic brake pressure, wherein the second control unit (300) is designed to actuate the electromechanical pressure provision device (138) to generate a hydraulic brake pressure by way of the electromechanical pressure provision device (138).

3. The brake system (100) as claimed in claim 2, wherein the electrohydraulic partial brake system has a pressure supply valve (188), wherein the pressure supply valve (188) is designed to establish or disconnect a hydraulic connection between the electromechanical pressure provision device (138) and the hydraulically actuated wheel brakes (106, 108).

4. The brake system (100) as claimed in either one of claims 2 or 3, characterized in that the electrohydraulic partial brake system has a hydraulic master cylinder (112), wherein the master cylinder (112) can be subjected to hydraulic pressure by an actuation pedal (116), wherein the electrohydraulic partial brake system has a master cylinder valve (128), wherein the master cylinder valve (128) is designed to establish or disconnect a hydraulic connection between the master cylinder (112) and the hydraulically actuated wheel brakes (106, 108).

5. The brake system (100) as claimed in claim 4, characterized in that the electrohydraulic partial brake system has a pedal feel simulator (122), wherein the pedal feel simulator (122) is hydraulically connectable to the master cylinder (112), wherein the electrohydraulic partial brake system has a simulator valve (122), wherein the simulator valve (122) is designed to establish or disconnect a hydraulic connection between the master cylinder (112) and the pedal feel simulator (122).

6. The brake system (100) as claimed in claims 3 and 5, characterized in that the second control unit (300) is designed to control the electromechanical pressure provision device (138), the simulator valve (124), the master cylinder valve (128), and the pressure supply valve (188).

7. The brake system (100) as claimed in any one of claims 2 to 6, characterized in that the electrohydraulic partial brake system has a first pressure sensor (118) for determining a hydraulic pressure generated by the master cylinder (112) and / or a motor position sensor (154) for determining a motor position of a drive (146) of the electromechanical pressure provision device (138) and / or a travel sensor (120) for determining a displacement travel of a cylinder piston (114) in the master cylinder (112).

8. The brake system (100) as claimed in any one of preceding claims 2 to 7, characterized in that the second control unit (300) is designed to actuate the electromechanical pressure provision device (138) to generate a hydraulic brake pressure by way of the electromechanical pressure provision device (138) depending on a determined displacement travel of the cylinder piston (114) in the master cylinder (112) and / or depending on a hydraulic pressure generated by the master cylinder (112) and / or depending on an actuation angle of the actuation pedal (116) and / or depending on an actuation travel of the actuation pedal (116) and / or depending on a force acting on the actuation pedal (116).

9. The brake system (100) as claimed in any one of the preceding claims, characterized in that the electrohydraulic partial brake system has a pressure modulation device (126), wherein the pressure modulation device (126) is designed to modulate, in particular in a wheel-specific manner, the hydraulic brake pressure applied at the hydraulically actuated wheel brakes (106, 108), wherein the first control unit (200) is designed to control the pressure modulation device (126).

10. The brake system (100) as claimed in any one of the preceding claims, characterized in that the electromechanically actuated wheel brakes (148, 150) are supplied with energy by the first energy supply (160).

11. The brake system (100) as claimed in any one of the preceding claims, characterized in that the first control unit (200) is designed to determine target braking forces to be applied by the electromechanically actuated wheel brakes (148, 150) depending on a determined displacement travel of the cylinder piston (114) in the master cylinder (112) and / or depending on a hydraulic pressure generated by the master cylinder (112) and / or depending on an actuation angle of the actuation pedal (116) and / or depending on an actuation travel of the actuation pedal (116) and / or depending on a force acting on the actuation pedal (116).

12. The brake system (100) as claimed in any one of the preceding claims, characterized in that the brake system (100) has wheel speed sensors (182), wherein the first control unit (200) is designed to modulate the braking forces applied to the vehicle wheels on the basis of the wheel speeds.

13. The brake system (100) as claimed in any one of the preceding claims, characterized in that the first control unit (200) is connected to a vehicle bus (180) of the motor vehicle, wherein control commands, in particular braking requests, can be transmitted to the first control unit (200) via the vehicle bus (180).