Automotive Brake Systems

Abstract

The invention relates to a braking system (100) for a motor vehicle comprising an electro-hydraulic partial braking system with hydraulically actuated wheel brakes (106, 108) and an electro-mechanical partial braking system with electro-mechanically actuated wheel brakes (148, 150), the braking system having two mutually independent control units (200, 300) and two energy supplies (160, 162), a first control unit (200) designed to control the electro-mechanical partial braking system and a second control unit (300) designed to control the electro-hydraulic partial braking system, the first control unit (200) being supplied with energy exclusively by the first energy supply source (160) and the second control unit (300) being supplied with energy exclusively by the second energy supply source (162).

Description

[Technical field]

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

[0002] In the prior art, braking systems are known that comprise an electrohydraulic partial braking system and an electromechanical partial braking system, where these two systems are usually controlled by one control unit, which is usually assigned to the electrohydraulic partial braking system, where the electrohydraulic partial braking system usually has a hydraulic fallback level, so that the hydraulic partial braking system still allows deceleration of the vehicle even in the event of a control unit failure. Summary of the Invention [Problem to be solved by the invention]

[0003] There are many failures that can occur in this type of system that can lead to a loss of complete electrical augmentation of braking action. This is true for both electrohydraulic and electromechanical partial braking systems.

[0004] In contrast, the present application is based on the objective of specifying a braking system that provides high braking performance even in the event of an individual electrical failure, reducing the probability of failure in which the electrical boost of the braking action is completely lost as a result of the electrical failure. [Means for solving the problem]

[0005] The above mentioned object is achieved by a braking system according to claim 1.

[0006] 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 electro-mechanical partial braking system with electro-mechanically actuated wheel brakes, the braking system having two mutually independent control units and two energy supplies, a first control unit adapted to control the electro-mechanical partial braking system and a second control unit adapted to control the electro-hydraulic partial braking system, the first control unit being supplied with energy exclusively by the first energy supply source and the second control unit being supplied with energy exclusively by the second energy supply source. wherein a first control unit is connected to the electro-mechanically actuated wheel brakes via a primary communication bus and a second control unit is connected to the electro-mechanically actuated wheel brakes via a secondary communication bus, the first control unit being configured to transmit control information, in particular setpoint braking forces applied by the electro-mechanically actuated wheel brakes, via the primary communication bus, and the second control unit is configured to transfer actuation information of the electro-hydraulic partial braking system, in particular a pedal travel or pedal angle of an actuation pedal and / or a force acting on the actuation pedal and / or a displacement travel of a cylinder piston arranged in a master cylinder, to the electro-mechanically actuated wheel brakes via the secondary communication bus. The electro-mechanical wheel brakes each have a wheel control unit configured to control the braking forces applied by the respective electro-mechanical wheel brakes in a manner dependent on information items, in particular control information items or actuation information items, received via the primary communication bus and / or the secondary communication bus.

[0007] The control unit of the brake system is therefore divided into a first control unit and a second control unit, where the first control unit and the second control unit preferably each control a part of the electro-hydraulic partial brake system. Furthermore, the first control unit and the second control unit preferably communicate with the electro-mechanical partial brake system via separate buses. Here, the first control unit is particularly preferably configured to exchange information with the second control unit. This may in particular be activation information, main brake pressure or braking force or further operating information of the respective partial brake system.

[0008] The electrohydraulic and electromechanical partial braking systems each ensure high braking performance even in the event of an individual electrical failure, since they can be operated by a still functioning control unit even if one of the control units fails, in order to ensure minimal deceleration by the brake system, where "individual failure" is understood to mean a malfunction of an element of the brake system, i.e., for example, the energy supply or the control unit.

[0009] Here, the hydraulic partial braking system preferably comprises exactly two hydraulically actuated wheel brakes, which are particularly preferably adapted to apply a braking force to the wheels of the front axle of the vehicle.

[0010] Correspondingly, the electro-mechanical partial braking system preferably has exactly two electro-mechanically actuated wheel brakes, which are particularly preferably configured to apply a braking force to a vehicle wheel of the vehicle assigned to the electro-mechanically actuated wheel brake, in particular a vehicle wheel of the rear axle of the motor vehicle, in a manner dependent on the received information item, in particular a control information item, in particular a set point braking force.

[0011] The braking system is therefore preferably designed to distribute the braking force by axle between electro-mechanical and electro-hydraulic wheel brakes, with the deceleration task usually being primarily carried out by the electro-hydraulic operated wheel brakes on the front axle.

[0012] The electromechanically actuated wheel brakes can be, for example, disc brakes or preferably electromechanical drum brakes, where the electromechanically actuated wheel brakes are further preferably configured to realize a parking brake function, where the first control unit is particularly preferably configured to activate the parking brake function of the electromechanically actuated wheel brakes.

[0013] According to a preferred embodiment, the electrohydraulic partial braking system comprises an electromechanical pressurizing device for generating a hydraulic brake pressure, the second control unit being configured to operate the electromechanical pressurizing device in order to generate the hydraulic brake pressure by means of the electromechanical pressurizing device. The electromechanical pressurizing device can be, for example, what is known as a linear actuator. Here, an electric motor-driven drive shaft is preferably connected to a rotation / translation gear mechanism such that a rotation of the drive shaft is converted into a translation of a pressure piston. The pressure piston is arranged in a pressure cylinder and is configured to expel and / or pressurize a liquid present in the pressure cylinder, in particular the brake fluid, out of the pressure cylinder. During normal operation of the electrohydraulic partial braking system, the hydraulic pressure for generating the braking force by the hydraulically actuated wheel brakes is generated here exclusively by the electromechanical pressurizing device.

[0014] In order to ensure the control of the pressure device by the second control unit, it is preferably provided here that the second control unit comprises an electronic power system which supplies the electromechanical pressure device with an operating voltage, the energy supply of the electronic power system and thus of the pressure device being likewise ensured by the second energy supply.

[0015] According to a further embodiment, the electrohydraulic partial braking system comprises a pumping valve which is adapted to establish or break a hydraulic connection between the electromechanical pressure device and the hydraulically actuated wheel brakes, the pumping valve being preferably normally closed, so that in the event of a current supply failure of the pumping valve, the hydraulic connection between the electromechanical pressure device and the hydraulically actuated wheel brakes is interrupted.

[0016] According to a further embodiment, the electrohydraulic partial braking system has a hydraulic master cylinder, which can be energized by an actuation pedal, and has a master cylinder valve, which is configured to establish or break a hydraulic connection between the master cylinder and the hydraulically actuated wheel brakes. The master cylinder valve is preferably normally open, so that in the event of an interruption in the energy supply of the master cylinder valve, a hydraulic connection between the master cylinder and the hydraulically actuated wheel brakes is automatically established. In this way, direct actuation of the hydraulically actuated wheel brakes by the actuation pedal and the master cylinder remains possible even in the event of a corresponding respective failure.

[0017] As already mentioned above, in normal operation of the brake system, the hydraulic pressure for operating the electrohydraulic wheel brakes is generated exclusively by the electromechanical pressure device, whereby the master cylinder is correspondingly preferably hydraulically decoupled from the wheel brakes. In order to continue to provide the vehicle driver with a normal operating feel even when the operating or brake pedal is actuated, according to a further embodiment, the electrohydraulic partial braking system comprises a pedal feel simulator which is hydraulically connectable to the master cylinder and which comprises a simulator valve which is configured to establish or break a hydraulic connection between the master cylinder and the pedal feel simulator. Here, the simulator valve is preferably normally closed, 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 fully act on the wheel brakes.

[0018] As already mentioned above, preferably in each case each control unit controls a part of the electrohydraulic partial braking system, so that deceleration by the hydraulic partial braking system is still possible even in the event of failure of one of the control units or the associated energy supply. Therefore, according to a preferred embodiment, the second control unit is arranged to control the electromechanical pressurizing device, the simulator valve, the master cylinder valve and the pumping valve.

[0019] Furthermore, according to a further embodiment, the electrohydraulic partial brake system comprises 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 the drive of the electromechanical pressure device and / or a displacement sensor for determining the displacement movement 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 information determined by the motor position sensor and / or information determined by the displacement sensor. This information can be forwarded to the electromechanically actuated wheel brakes in the form of actuation information or communicated to the first control unit.

[0020] In addition to the transfer of such determined information to the electromechanical partial braking system, according to a further embodiment, the second control unit is further configured to operate the electromechanical pressurizing device in order to generate hydraulic brake pressure by means of the electromechanical pressurizing device in a manner dependent on the determined displacement travel of a cylinder piston in the master cylinder and / or dependent on the hydraulic pressure generated by the master cylinder and / or dependent on an actuation angle of an actuation pedal and / or dependent on an actuation travel of the actuation pedal and / or dependent on a force acting on the actuation pedal, whereby the actuation angle or the actuation travel of the actuation pedal or the force acting on the actuation pedal can also be used as actuation information for controlling the electromechanical wheel brakes.

[0021] In order to adapt the brake pressure prevailing at the hydraulically actuated wheel brakes wheel-individually, for example to achieve an ABS function, according to a further embodiment the electrohydraulic partial braking system has a pressure regulator which is configured in particular for adjusting the hydraulic brake pressure prevailing at the hydraulically actuated wheel brakes wheel-individually, and the first control unit is configured for controlling the pressure regulator.

[0022] Particularly preferably here, the electrohydraulic partial braking system has for each hydraulically actuated wheel brake a preferably normally open inlet valve and a preferably normally closed outlet valve, the inlet valves and the outlet valves forming a pressure regulator, where the inlet valves are each preferably configured for establishing or breaking a hydraulic connection between the respective wheel brake and the electromechanical pressurizing means and / or the master cylinder, whereas the outlet valves are each configured for establishing or breaking a hydraulic connection between the respective wheel brake and a brake fluid reservoir, where the brake fluid reservoir is preferably under atmospheric pressure. The first control unit is correspondingly preferably configured for controlling the inlet valves and / or the outlet valves of the electrohydraulic partial braking system.

[0023] Furthermore, according to a further embodiment, the electro-mechanically actuated wheel brakes are supplied with energy by a first energy supply source, which according to this embodiment is thus supplied with energy by the same energy supply source which also supplies energy to the control unit assigned to the basic electro-mechanical wheel brakes.

[0024] It has already been mentioned above that the electromechanical wheel brakes are actuated on the basis of control information, in particular information specifying a wheel brake setpoint braking force to be applied by the respective wheel brake. To this end, according to a further embodiment, the first control unit is adapted to determine a setpoint braking force to be applied by the electromechanically actuated wheel brakes in a manner dependent on the determined displacement movement of a cylinder piston in the master cylinder and / or in a manner dependent on the hydraulic pressure generated by the master cylinder and / or in a manner dependent on the actuation angle of the actuation pedal and / or in a manner dependent on the actuation movement of the actuation pedal and / or in a manner dependent on the force acting on the actuation pedal.

[0025] Furthermore, a braking system as claimed in one of the preceding claims is provided according to a further embodiment, which comprises wheel rotational speed sensors, and the first control unit is configured for adjusting the braking forces prevailing at the wheels of the vehicle on the basis of the wheel rotational speed, where in particular a drive function, in particular an ABS function or an ESC function, is realised by adjusting the braking forces prevailing at the wheels of the vehicle, in particular by a corresponding change in the brake braking force of an electromechanically actuated wheel brake or in the hydraulic pressure of a hydraulically actuated wheel brake.

[0026] It is preferred here that the electrohydraulic partial braking system has a pilot pressure sensor upstream of the inlet valves of the wheel brakes, determining the prevailing hydraulic pressure, and the first control unit is designed to read out the information determined by the pilot pressure sensor, such that, following a pilot pressure of this kind, the deceleration action of the hydraulically actuated wheel brakes can be controlled by defined opening and closing of the inlet and outlet valves in order to realize ABS or ESC functions.

[0027] In addition to activation of the brake system by actuation of the brake pedal or actuation pedal, the brake system is furthermore to be activated autonomously by the driving functions of the vehicle, without the driver of the vehicle actively influencing this. For this purpose, according to a further embodiment, the first control unit is connected to a vehicle bus of the motor vehicle and is able to transmit control commands, in particular braking requests, to the first control unit via the vehicle bus. Such braking requests can be triggered, for example, within the scope of an active cruise control or ESC function.

[0028] In the following text, preferred refinements of the invention are explained in more detail on the basis of the drawings. [Brief description of the drawings]

[0029] [Figure 1] FIG. 1 is a block diagram illustrating an exemplary braking system. [Diagram 2] 1 is a simplified diagram of an exemplary braking system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Similar or identical features will be designated with the same designation in the following description.

[0031] 1 shows a braking system 100 for a motor vehicle comprising a hydraulic partial braking system 102 and an electromechanical partial braking system 104. Here, the electrohydraulic partial braking system 102 comprises hydraulically actuated wheel brakes 106, 108 acting on the front wheels of the motor vehicle. The wheel brakes 106, 108 may in particular be hydraulically actuated disc brakes. Here, during a start-up operation of the braking system 100, the wheel brakes 106, 108 are subjected by a hydraulic arrangement 110 to a hydraulic brake pressure which is converted by the wheel brakes 106, 108 into a braking force acting on the wheels of the vehicle assigned in each case to the wheel brakes 106, 108.

[0032] For this purpose, the hydraulic arrangement 110 comprises a master cylinder 112 with a cylinder piston 114 displaceably mounted therein, whereby the cylinder piston 114 is displaceable within the master cylinder 112 by the action of an actuation pedal 116 connected to the cylinder piston 114, or capable of applying hydraulic pressure to the brake fluid present in the master cylinder 112. The hydraulic pressure generated here is detected by a pressure sensor 118. Furthermore, the displacement of the cylinder piston 114 is determined by a displacement sensor 120.

[0033] The master cylinder 112 is initially hydraulically connected to the pedal feel simulator 122, and a normally closed simulator valve 124 is arranged between the master cylinder 112 and the pedal feel simulator 122. Thus, the hydraulic connection between the master cylinder 112 and the pedal feel simulator 122 can be established or interrupted by the simulator valve 124.

[0034] Furthermore, the master cylinder 112 is hydraulically connected to a pressure regulator 126, which is also hydraulically connected to the wheel brakes 106, 108. Here, a normally open master cylinder valve 128 is arranged between the master cylinder 112 and the pressure regulator 126, and the hydraulic connection between the master cylinder 112 and the pressure regulator 126 can be established or interrupted by the master cylinder valve 128. Furthermore, a pilot pressure sensor 130 is arranged between the master cylinder valve 128 and the pressure regulator 126, and the pilot pressure sensor 130 is configured to determine the hydraulic pressure prevailing upstream of the pressure regulator 126.

[0035] For each connected hydraulically actuated wheel brake 106, 108, the pressure regulator 126 comprises a normally open inlet valve 132 and a normally closed outlet valve 134, whereby the outlet valve 134 is configured to establish or interrupt a hydraulic connection between the wheel brake 106, 108 and a brake fluid reservoir 136, so that the hydraulic brake pressure prevailing at the wheel brake 106, 108 can be reduced via the outlet valve 134. At the same time, the hydraulic brake pressure prevailing at the wheel brake 106, 108 can be adjusted by defined opening and closing of the inlet valve 132, starting from the main pilot pressure.

[0036] The hydraulic arrangement 110 further comprises an electromechanical pressure device 138, which comprises a hydraulic cylinder 140 and a pressure piston 142 displaceable within said hydraulic cylinder 140. The pressure piston 142 is connected to a spindle drive 144 driven by an electric motor, so that the rotation of the drive shaft of the drive connected to the spindle drive 144 or the electric motor 146 is converted into a translational movement of the pressure piston 142 within the hydraulic cylinder 140, thereby applying pressure to the brake fluid present within the hydraulic cylinder. The rotational position of the rotor of the electric motor 146, and therefore the current position of the pressure piston 142 within the hydraulic cylinder, is monitored by a motor position sensor 154.

[0037] Here, the hydraulic cylinder 140 of the pressurizing device 138 is also hydraulically connected to the pressure adjusting device 126, and a normally closed pumping valve 188 is disposed between the pressure adjusting device 126 and the hydraulic cylinder 140 of the pressurizing device 138. Thus, the hydraulic connection between the pressurizing device 138 and the pressure adjusting device 126 can be established or cut off by the pumping valve 188.

[0038] In the illustrated embodiment, the electromechanical partial braking system 104 comprises two electromechanically actuated wheel brakes 148, 150 configured as electromechanical drum brakes, where the wheel brakes 148, 150 are assigned to the vehicle wheels of the rear axle of the vehicle, and further configured to realize a parking brake function.

[0039] The braking system 100 comprises two control units 200, 300, which in the illustrated embodiment are configured as part of the electrohydraulic partial braking system 102. Here, a first control unit 200 is configured to control the pressure regulator 126, i.e. in particular the inlet valve 132 and the outlet valve 134, in order to regulate the hydraulic brake pressure prevailing at the wheel brakes 106, 108, starting from the hydraulic pilot pressure prevailing upstream of the pressure regulator 126. In this way, in particular ABS or ESC control actions can be performed by the first control unit 200. Furthermore, the first control unit 200 is configured to read out the hydraulic pressure determined by the pilot pressure sensor 130.

[0040] Here, the second control unit 300 is configured to control the pressurizing device 138, the simulator valve 124, the master cylinder valve 128 and the pumping valve 188. Furthermore, the second control unit 300 has an electronic power system 152 that provides and controls the operating voltage to the electromechanical pressurizing device 138 or the corresponding electric motor 146. The second control unit 300 is configured to read the displacement travel of the cylinder piston 114 determined by the displacement sensor 120, the pressure generated by the master cylinder 112 determined by the pressure sensor 118, and the motor position of the electric motor 146 sensed by the motor position sensor 154.

[0041] The first control unit 200 comprises a first microcontroller 156, whereas the second control unit 300 comprises a second microcontroller 158 which respectively realises the control functions of each control unit 200, 300. Here, the microcontrollers 156 and 158 are connected to each other via a communication connection 190 so that control information can be exchanged between the microcontrollers 156 and 158 and therefore between the control units 200, 300.

[0042] For controlling the electromechanically actuated wheel brakes 148, 150, the first control unit 200 is connected to the electromechanically actuated wheel brakes 148, 150 or to the control units 166, 168 included in the electromechanically actuated wheel brakes 148, 150 via a common primary communication bus 164. Here, the first control unit 200 is arranged to transmit control information, in particular setpoint braking forces to be applied by the wheel brakes 148, 150, to the control units 166, 168 via said primary communication bus 164. The control units 166, 168 are therefore arranged to adjust the braking forces of the respective wheel brakes 148, 150 to the corresponding setpoint braking forces, aided by torque sensors 170, 172 arranged in the wheel brakes.

[0043] The second control unit 300 is similarly connected to the electro-mechanically actuated wheel brakes 148, 150 via a common secondary communication bus 174 and is configured as a fallback level type to transmit control information to the control units 166, 168 of the electro-mechanically actuated wheel brakes 148, 150, as will be described in more detail below.

[0044] Furthermore, the illustrated brake system comprises a first energy supply source 160 and a second energy supply source 162, where the first energy supply source 160 is completely independent of the second energy supply source 162. In particular, the first energy supply source 160 and the second energy supply source 162 may be two on-board electrical systems that are isolated from each other, in particular configured such that a failure or malfunction of one on-board electrical system does not affect the functional capability of the other on-board electrical system.

[0045] Here, the first energy supply source 160 is configured to supply energy to the first control unit 200 and the electromechanically actuated wheel brakes 148, 150, while the second energy supply source 162 is configured to supply energy to the second control unit 300 and, consequently, also to the electromechanical pressurizing device 138 via the electronic power system 152.

[0046] Here, furthermore, the first control unit 200 is connected to the parking brake switch 176, so that upon actuation of the parking brake switch 176 a corresponding item of information can be processed by the first control unit 200. The first control unit 200 is therefore configured to transmit a corresponding item of control information for activating the parking brake function via the primary communication bus 164 to the electromechanically actuated wheel brakes 148, 150, so that the parking brake function is activated by the control units 166, 168 of the wheel brakes 148, 150.

[0047] The first control unit 200 is also connected to an ESC switch 178 and is thereby able to activate or deactivate the ESC function of the braking system 100. Furthermore, the first control unit 200 is connected to a vehicle bus 180 and is able to receive control information via the vehicle bus 180, in particular in the form of a braking request. A braking request of this kind can for example be activated within the scope of an automated driving function, for example an autopilot function.

[0048] In order to provide control functions such as ABS and ESC by the first control unit 200, the braking system 100 further comprises wheel rotational speed sensors 182 assigned to vehicle wheels which can be braked by one of the wheel brakes 106, 108, 148 or 150. Here, wheel rotational speed information of the vehicle wheels which are assigned to the hydraulically actuated wheel brakes 106, 108 is transferred to the first control unit 200 via a corresponding interface 184, whereas wheel rotational speed information of the vehicle wheels which are assigned to the electromechanically actuated wheel brakes 148, 150 is transferred to the first control unit 200 via the primary communication bus 164.

[0049] Here, the attachment of the first energy supply source 160, the second energy supply source 162, the front wheel rotation speed sensor 182, 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, 300 of the brake system 100 is achieved via a common interface 186 which can in particular be configured as part of the first control unit 200.

[0050] The operation of the braking system 100 is described below, whereby during normal operation of the braking system 100 the master cylinder 112 is separated from the hydraulically actuated wheel brakes 106, 108 by a closed master cylinder valve 128, so that the hydraulic pressure built up by actuation of the actuation pedal 116 is received by the pedal feel simulator 122. For this purpose, the simulator valve 124 is open during normal operation. The pressure generated here is detected by the pressure sensor 118, while the displacement travel of the cylinder piston 114 is detected by the displacement sensor 120. Furthermore, the actuation travel or actuation angle of the actuation pedal or the actuation force acting on the actuation pedal 116 can also be determined as actuation information.

[0051] The actuation information thus detected 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 activates the pressurizing device 138 by means of the electronic power system 152 in such a way that a hydraulic brake pressure corresponding to the braking request is generated in the hydraulic cylinder 140 of the pressurizing device 138 and thus in the wheel brakes 106, 108, so that the desired braking force is generated by the wheel brakes 106, 108. This brake pressure is detected by the pilot pressure sensor 128 and read out by the first control unit 200.

[0052] Here, the first control unit 200 is configured to determine, based on the determined brake pressure and / or on actuation information sent by the second control unit 300 to the first control unit 200, a setpoint braking force to be applied by the electromechanically actuated wheel brakes 148, 150 to implement the braking request, taking into account a fixed or dynamically variable braking force distribution between the front axle wheel brakes 106, 108 and the rear axle wheel brakes 148, 150.

[0053] The set point braking forces so determined are then transmitted from the first control unit 200 via the primary communication bus 164 to the control units 166, 168 of the wheel brakes 148, 150, which in turn correspondingly adjust the braking forces applied by the wheel brakes 148, 150.

[0054] In a similar manner as described above, braking requests or commands received via vehicle bus 180 may also be executed.

[0055] Here, during the deceleration operation, the wheel rotation speeds of the vehicle wheels are constantly monitored by the first control unit 200 as to whether the slip of at least one of the vehicle wheels exceeds a defined limit value. If this occurs at a vehicle wheel of the rear axle, the setpoint braking force of the corresponding wheel brake 148 or 150 is adjusted by the first control unit 200, so that the slip is adjusted back to an acceptable value. If slip is detected at a vehicle wheel of the front axle, the first control unit 200 activates the pressure regulator 126 so that the brake pressure of the corresponding wheel brake 106 or 108 is reduced for a short time, for example by a time-limited opening of the corresponding outlet valve 134, so that the slip returns to an acceptable value again.

[0056] Furthermore, defined braking of individual vehicle wheels as a result of a control request of the ESC controller can also be initiated by the first control unit 200 in the manner described above.

[0057] In the braking system 100 described above, a number of electrical failures can result in components of the braking system 100 being unable to be used to the desired extent. Four exemplary cases of this type of failure are described below.

[0058] In a first scenario, the first control unit 200 may fail due to an electrical defect. In this case, wheel-by-wheel adjustment of the braking force is no longer possible in the above-mentioned range. A fault of this kind can be indicated to the vehicle driver by the illumination of a corresponding warning lamp.

[0059] Apart from the regulation of the brake pressures prevailing at the individual wheel brakes 106, 108, the hydraulic partial braking system 102 can still be operated normally, so that an electrical boosting of the braking force is still possible. In this case, the rear axle electromechanical wheel brakes 148, 150 can still be actuated by the second control unit 300. For this purpose, in case of failure of the first control unit 200, the second control unit 300 shall transmit determined actuation information to the control units 166, 168 via the secondary communication bus 174. The control units 166, 168 are thus configured to locally adjust the braking force of the corresponding wheel brakes 148, 150 on the basis of said actuation information. Here, it is further considered that the wheel brakes 148, 150 exchange their determined wheel rotational speeds with each other, so that local control of the wheel slip is still possible.

[0060] In a second scenario, the second control unit 300 may fail due to a technical defect, as a result of which the electronic boosting of the hydraulic brake pressure by the pressurizing device 138 is no longer possible. In this case, the simulator valve 124 and the pumping valve 188 are automatically closed, whereas the master cylinder valve 128 is opened. In this case, the master cylinder 112 is consequently connected directly to the wheel brakes 106, 108, so that the actuation force acting on the actuation pedal 116 is directly converted into a brake pressure prevailing at the wheel brakes 106, 108. Furthermore, this brake pressure is detected by the pilot pressure sensor 130, as a result of which the first control unit 200 actuates the electromechanically actuated wheel brakes 148, 150. Here, it is further conceivable that the first control unit 200 may also have access to actuation information of the actuation pedal 116 and / or the master cylinder 112. As a result, in this type of fallback operation, electronic boosting of the braking force acting on the front wheel brakes 106, 108 is no longer possible, but the maximum possible braking force can still be applied to the rear axle of the vehicle, so that sufficient deceleration of the vehicle is still possible.

[0061] A similar scenario to that described above results in the second energy source 162 failing.

[0062] In the event of failure of the first energy supply 160, by contrast, it is no longer possible to use the wheel brakes 148, 150 of the rear axle. However, even in this case the wheel brakes 106, 108 of the front axle can still be operated with electronic boosting of the braking force, so that a sufficiently pronounced deceleration of the vehicle can still be achieved.

[0063] FIG. 2 shows a simplified schematic of the brake system 100 shown in FIG. The present invention may also include the following aspects: 1. A braking system (100) for a motor vehicle comprising an electro-hydraulic partial braking system with hydraulically actuated wheel brakes (106, 108) and an electro-mechanical partial braking system with electro-mechanically actuated wheel brakes (148, 150), The brake system comprises two independent control units (200, 300) and two energy sources (160, 162), a first control unit (200) configured to control the electro-mechanical partial braking system and a second control unit (300) configured to control the electro-hydraulic partial braking system; the first control unit (200) is supplied with energy only by a first energy supply source (160), and the second control unit (300) is supplied with energy only by a second energy supply source (162); the first control unit (200) is connected to the electro-mechanically actuated wheel brakes (148, 150) via a primary communication bus (164), and the second control unit (300) is connected to the electro-mechanically actuated wheel brakes (148, 150) via a secondary communication bus (174); the first control unit (200) is configured to transmit control information to the electro-mechanically actuated wheel brakes (148, 150) via the primary communication bus (164), and the second control unit (300) is configured to transfer electro-hydraulic partial braking system operation information to the electro-mechanically actuated wheel brakes (148, 150) via the secondary communication bus (174); A braking system (100) wherein the electro-mechanical wheel brakes (148, 150) each have a wheel control unit (166, 168), the wheel control units (166, 168) configured to control the braking force applied by the respective electro-mechanical wheel brakes (148, 150) in a manner dependent on items of information received via the primary communication bus (164) and / or the secondary communication bus (174). 2. The brake system (100) described in 1 above, wherein the electro-hydraulic partial brake system has an electro-mechanical pressurizing device (138) for generating hydraulic brake pressure, and the second control unit (300) is configured to operate the electro-mechanical pressurizing device (138) to generate hydraulic brake pressure by the electro-mechanical pressurizing device (138). 3. The brake system (100) described in 2. above, wherein the electro-hydraulic partial brake system has a pumping valve (188) configured to establish or disconnect a hydraulic connection between the electro-mechanical pressurizing device (138) and the hydraulically actuated wheel brakes (106, 108). 4. A brake system (100) as described in 2. or 3. above, wherein the electro-hydraulic partial brake system has a hydraulic master cylinder (112) and an actuation pedal (116) is capable of applying hydraulic pressure to the master cylinder (112), and the electro-hydraulic partial brake system has a master cylinder valve (128) configured 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) described in 4. above, wherein the electro-hydraulic partial brake system has a pedal feel simulator (122) that is capable of being hydraulically connected to the master cylinder (112), and the electro-hydraulic partial brake system has a simulator valve (122) that is configured to establish or disconnect a hydraulic connection between the master cylinder (112) and the pedal feel simulator (122). 6. The brake system (100) described in 3. or 5. above, wherein the second control device (300) is configured to control the electromechanical pressure device (138), the simulator valve (124), the master cylinder valve (128) and the pressure delivery valve (188). 7. The brake system (100) described in any one of 2. to 6. above, wherein the electro-hydraulic partial brake system has a first pressure sensor (118) that determines the oil pressure generated by the master cylinder (112), and / or a motor position sensor (154) that determines the motor position of the drive unit (146) of the electro-mechanical pressure device (138), and / or a displacement sensor (120) that determines the displacement movement amount of a cylinder piston (114) in the master cylinder (112). 8. The brake system (100) described in any one of 2. to 7. above, wherein the second control unit (300) is configured to operate the electromechanical pressurizing device (138) to generate hydraulic brake pressure by the electromechanical pressurizing device (138) in a manner dependent on the determined displacement movement of the cylinder piston (114) in the master cylinder (112), and / or in a manner dependent on the hydraulic pressure generated by the master cylinder (112), and / or in a manner dependent on the actuation angle of the actuation pedal (116), and / or in a manner dependent on the actuation movement of the actuation pedal (116), and / or in a manner dependent on the force acting on the actuation pedal (116). 9. A brake system (100) as described in any one of 1. to 8. above, wherein the electro-hydraulic partial braking system has a pressure regulator (126) configured to regulate the hydraulic brake pressure prevailing at the hydraulically actuated wheel brakes (106, 108), in particular in a wheel-independent manner, and the first control unit (200) is configured to control the pressure regulator (126). 10. The brake system (100) according to any one of 1. to 9. above, wherein the first energy supply source (160) supplies energy to the electromechanically actuated wheel brakes (148, 150). 11. A brake system (100) as described in any one of 1. to 10. above, wherein the first control unit (200) is configured to determine a set point braking force to be applied by the electromechanically actuated wheel brakes (148, 150) in a manner dependent on the determined displacement movement of the cylinder piston (114) in the master cylinder (112), and / or in a manner dependent on the oil pressure generated by the master cylinder (112), and / or in a manner dependent on the actuation angle of the actuation pedal (116), and / or in a manner dependent on the actuation movement of the actuation pedal (116), and / or in a manner dependent on the force acting on the actuation pedal (116). 12. A brake system (100) described in any one of 1. to 11. above, wherein the brake system (100) has a wheel rotational speed sensor (182), and the first control unit (200) is configured to adjust the braking force prevailing at the vehicle wheels based on the wheel rotational speed. 13. A brake system (100) described in any one of 1. to 12. above, wherein the first control unit (200) is connected to a vehicle bus (180) of the motor vehicle, and a control command, in particular a braking request, can be transmitted to the first control unit (200) via the vehicle bus (180).

Claims

1. A braking system (100) for a motor vehicle comprising an electro-hydraulic partial braking system with hydraulically actuated wheel brakes (106, 108) and an electro-mechanical partial braking system with electro-mechanically actuated wheel brakes (148, 150), The brake system comprises two independent control units (200, 300) and two energy sources (160, 162), a first control unit (200) configured to control the electro-mechanical partial braking system and a second control unit (300) configured to control the electro-hydraulic partial braking system; the first control unit (200) is supplied with energy only by a first energy supply source (160) and the second control unit (300) is supplied with energy only by a second energy supply source (162); the first control unit (200) is connected to the electro-mechanically actuated wheel brakes (148, 150) via a primary communication bus (164), and the second control unit (300) is connected to the electro-mechanically actuated wheel brakes (148, 150) via a secondary communication bus (174); the first control unit (200) is configured to transmit control information to the electro-mechanically actuated wheel brakes (148, 150) via the primary communication bus (164), and the second control unit (300) is configured to transfer electro-hydraulic partial braking system operation information to the electro-mechanically actuated wheel brakes (148, 150) via the secondary communication bus (174); 1. A braking system (100) in which the electro-mechanical wheel brakes (148, 150) each have a wheel control unit (166, 168), the wheel control units (166, 168) configured to control the braking force applied by the respective electro-mechanical wheel brakes (148, 150) in a manner dependent on items of information received via the primary communication bus (164) and / or the secondary communication bus (174).

2. 2. The brake system (100) of claim 1, wherein the electrohydraulic partial brake system includes an electromechanical pressurizing device (138) for generating hydraulic brake pressure, and the second control unit (300) is configured to operate the electromechanical pressurizing device (138) to generate hydraulic brake pressure through the electromechanical pressurizing device (138).

3. 3. The braking system (100) of claim 2, wherein the electrohydraulic partial braking system includes a pumping valve (188), the pumping valve (188) configured to establish or break a hydraulic connection between the electromechanical pressurizing device (138) and the hydraulically actuated wheel brakes (106, 108).

4. 4. The braking system (100) of claim 3, wherein the electro-hydraulic partial braking system includes a hydraulic master cylinder (112) and an actuation pedal (116) is capable of applying hydraulic pressure to the master cylinder (112), and wherein the electro-hydraulic partial braking system includes a master cylinder valve (128) configured to establish or break a hydraulic connection between the master cylinder (112) and the hydraulically actuated wheel brakes (106, 108).

5. 5. The braking system (100) of claim 4, wherein the electro-hydraulic partial braking system comprises a pedal feel simulator (122), the pedal feel simulator (122) hydraulically connectable to the master cylinder (112), and the electro-hydraulic partial braking system comprises a simulator valve (124), the simulator valve (124) configured to establish or break a hydraulic connection between the master cylinder (112) and the pedal feel simulator (122).

6. 6. The braking system (100) of claim 5, wherein the second control unit (300) is configured to control the electromechanical pressurizing device (138), the simulator valve (124), the master cylinder valve (128), and the pumping valve (188).

7. 5. The braking system (100) of claim 4, wherein the electrohydraulic partial brake system comprises a first pressure sensor (118) for determining an oil 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 device (138), and / or a displacement sensor (120) for determining a displacement travel of a cylinder piston (114) in the master cylinder (112).

8. 5. The braking system of claim 4, wherein the second control unit is configured to operate the electromechanical pressurizing device to generate hydraulic brake pressure by the electromechanical pressurizing device in a manner dependent on the determined displacement travel of a cylinder piston in the master cylinder, and / or dependent on a hydraulic pressure generated by the master cylinder, and / or dependent on an actuation angle of the actuation pedal, and / or dependent on an actuation travel of the actuation pedal, and / or dependent on a force acting on the actuation pedal.

9. 4. The braking system (100) according to claim 1, wherein the electrohydraulic partial braking system comprises a pressure regulator (126), the pressure regulator (126) being configured to regulate the hydraulic brake pressure prevailing at the hydraulically actuated wheel brakes (106, 108), in particular in a wheel-independent manner, and the first control unit (200) being configured to control the pressure regulator (126).

10. The braking system (100) of any one of claims 1 to 3, wherein the electro-mechanically actuated wheel brakes (148, 150) are supplied with energy by the first energy supply source (160).

11. 5. The braking system (100) of claim 4, wherein the first control unit (200) is configured to determine a set point braking force to be applied by the electromechanically actuated wheel brakes (148, 150) in a manner dependent on the determined displacement travel of a cylinder piston (114) in the master cylinder (112), and / or in a manner dependent on the hydraulic pressure generated by the master cylinder (112), and / or in a manner dependent on the actuation angle of the actuation pedal (116), and / or in a manner dependent on the actuation travel of the actuation pedal (116), and / or in a manner dependent on a force acting on the actuation pedal (116).

12. 4. The brake system (100) of claim 1, wherein the brake system (100) comprises a wheel rotational speed sensor (182), and the first control unit (200) is configured to adjust the braking force prevailing at the wheels of the vehicle based on the wheel rotational speed.

13. 4. The braking system (100) according to claim 1, wherein the first control unit (200) is connected to a vehicle bus (180) of the motor vehicle, and a control command, in particular a braking request, can be transmitted to the first control unit (200) via the vehicle bus (180).

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