Brake system

Abstract

To provide an improved brake system.SOLUTION: The invention relates to a brake system comprising: an actuating device, in particular a brake pedal; a first piston-cylinder unit having two pistons subjecting the brake circuits to a pressure medium via a valve device, where one of the pistons can be actuated by the actuation device; a second piston-cylinder unit having an electric motor drive, a transmission, and at least one piston to supply at least one of the brake circuits with a pressure medium via a valve device; and a motor pump unit with a valve device to supply the brake circuits with a pressure medium, also comprising a hydraulic stroke simulator with a pressure or working chamber which is connected to the first piston-cylinder unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The invention relates to a braking system according to the preamble of claim 1. [Background technology]

[0002] The trend towards autonomous driving (AD) vehicles places high demands on brake systems, on the one hand in terms of fault tolerance and on the other hand in terms of redundancy for brake pressure generation, power supply, and computer functions (ECU). So-called one-box and two-box systems are gaining popularity. The latter consists of an electric brake booster (BKV), also known as an e-booster, and an ESP system. This provides redundancy for brake pressure generation by an electric motor and an electronic control unit (ECU) as opposed to an e-booster and return pump with an electric motor and ECU.

[0003] Known solutions have a relatively long overall length and a high weight.

[0004] WO 2011 / 098178 (hereinafter referred to as variant A or "following booster" or "e-booster") describes such a solution, in which an electric motor has a coaxial drive that acts on the HZ piston (= main cylinder piston) via a gear and a piston. The BKV control is carried out via an electric element and a reaction disc as a so-called following booster, and the pedal travel is determined by the brake pressure and the volume absorption of the brake system. This requires a long pedal travel in the event of brake fade or a malfunction in the brake circuit.

[0005] WO 2009 / 065709 (hereinafter referred to as variant B or follower booster or e-booster) also shows the e-booster as a follower BKV, where the BKV control is via pedal stroke and pressure: an independent pressure supply with an electric motor and plunger acts on the HZ piston via an amplifier piston.

[0006] WO 2012 / 019802 (hereinafter referred to as Variant C) shows a similar configuration to WO 2011 / 098178, in which an electric motor acts on a coaxial drive via a gear and a piston on the HZ piston. Here, an auxiliary piston-cylinder unit is used, which acts on a stroke simulator piston (WS). The pedal stroke is therefore independent of brake fade and malfunctions in the brake circuit. However, this configuration is very complex and long.

[0007] DE 10 2009 033 499 (hereinafter also referred to as variant D) shows a brake booster (BKV) with a hydraulically operated booster piston and an additional ESP unit with an external pressure supply. This arrangement with four or five pistons and six solenoid valves (MV) is complex and disadvantageous in terms of length. A non-hydraulic operated stroke simulator (WS) is arranged in the piston-cylinder unit upstream from the main cylinder and cannot be braked or switched via the solenoid valves (MV).

[0008] All of the solutions mentioned above have a redundant brake force multiplication (BKV) function, because in case of a BKV motor failure, the ESP unit with pump as well as the assistance function using the vacuum BKV ensures braking function in autonomous driving mode.

[0009] As explained in the applicant's WO 2010 / 088920, in the event of ESP motor failure, the ABS functions through pressure regulation made possible by the BKV motor, but this only allows for common pressure control for all four wheels and does not optimize braking distances.

[0010] All known one-box systems have so-called stroke simulators (especially for brake-by-wire) to refine the pedal stroke characteristics.

[0011] Known systems with e-booster and ESP have only one redundant configuration for the pressure supply (DV), i.e., in case of e-booster failure, the redundant pressure supply (DV) uses the redundant output for the brake booster (BKV) by the ESP, and higher safety requirements are not taken into account. Also, in case of ESP failure, sufficient ABS function is ensured by the e-booster. Summary of the Invention [Problem to be solved by the invention]

[0012] In light of the prior art, it is an object of the present invention to provide an improved braking system.

[0013] The present invention is based on the object of creating a braking system for use in automated driving operations (hereinafter AD) and / or electric / hybrid vehicles with increasingly powerful regenerative outputs (energy recovery by braking via generator / or drive motor in generator operation), which braking system is significantly improved compared to the prior art.

[0014] Furthermore, a cost-effective braking system for automated driving is created, which not only meets extremely high safety demands but also all the required redundancies.

[0015] Furthermore, in the event of ESP failure, the braking system can be used to achieve both full functionality of ABS in terms of braking distance and stability, and full functionality with regard to regeneration. [Means for solving the problem]

[0016] This object is solved according to the invention with the features of patent claim 1.

[0017] Among other things, the improvements are characterized by the fact that the brake booster structure is cost-effective, has very few simple components with low precision requirements (e.g. valves with only open / close operations), has a very short and slim structure, and allows for constant pedal stroke characteristics, particularly with powerful regeneration.

[0018] Advantageous embodiments or structures of the invention are contained in the further claims and in the drawings and diagrammatic description, which are incorporated herein by reference.

[0019] The solution of the present invention and its embodiments and structures results in a braking system that is extremely short in structure and has beneficial pedal characteristics.

[0020] In particular, a two-box system (hereinafter referred to as the two-box system and also as the X-Boost and ESP / ABS unit) is formed according to the present invention, which has an electric brake booster connected to a standard ESP unit via two hydraulic lines, and which has a pedal characteristic that is independent of the volume absorption and regeneration of the brake system.

[0021] Furthermore, the present invention achieves a compact design of the brake booster with a small box volume. This brake booster is very short and narrow, has many redundancies, for example, for pressure generation, electrical supply, and failure of the pump motor of the ESP unit, and also includes an ABS function with limited performance in the event of an ESP unit failure. In emergency driving without ESP, the ABS function should at least include individual adjustment for each axle ("Select Low" pressure adjustment) to improve braking distance.

[0022] The installation space of the unit compartment is becoming increasingly smaller. Therefore, the dimensions of the brake unit should be as small as possible, especially with regard to width and length. This compact design is made possible, on the one hand, by decoupling the main cylinder (HZ) piston from the motor drive, and, on the other hand, by the specially short main cylinder (HZ) according to the applicant's WO 2016 / 023994. This specially short main cylinder will be described below together with a parallel-arranged pressure supply (hereinafter referred to as pressure supply or DV) consisting of an electric motor with a piston drive.

[0023] The pressure supply (DV) is only effective up to a wheel lock limit of 80-100 bar. For higher pressures (e.g. for driver assistance functions), the ESP pump is activated. This can therefore be achieved with the solution according to the invention rather than with the prior art variant A described above, because the brake pedal is decoupled and the ESP pump function does not affect the pedal feel.

[0024] The purpose of the X-Boost with DV is to provide a corresponding volume of fluid at a maximum pressure of 80-100 bar to increase the pressure of the ESP pump.

[0025] This has the advantage that the X-Boost pressure supply DV with the drive motor or engine only needs to be designed for low mechanical loads and that the electric motor requires a low torque of, for example, 80-100 bar compared to the ESP pump's maximum pressure of approximately 200 bar. This allows the use of cost-effective ball screw drives (KGT) or trapezoidal spindles with plastic nuts.

[0026] Secondly, the pump (ESP pump) can be designed so that the pump motor is only loaded with a differential pressure of 200 bar - (80-100) bar (= 100-120 bar). Conventional ESP pumps, for example, are loaded with a maximum pressure of 200 bar. This advantage results in a beneficial reduction in the power or torque of the pump motor.

[0027] In this case, there are also further possibilities for interconnection: the ESP pump can not only be activated together with the activation of X-Boost (80-120 bar), but also with a quick actuation of the pedal at, for example, 20 bar. This results either in a more rapid pressure increase relative to the lock time (TTL) or in a further reduction in the power of the motor of the DV of X-Boost.

[0028] This connection of pumps in series and / or parallel in the case of ESP pumps requires a two-circuit gear pump or, in the case of piston pumps, a separate eccentric for each piston.

[0029] The pedal characteristic should exclude any retroactive effects from volume absorption, for example, in the event of a brake circuit malfunction. On the other hand, it should be possible to provide the desired pedal feedback, for example, small pedal movements, when the ABS function is optionally used intermittently. A parallel pedal movement can also signal a fault, for example, a brake circuit malfunction, via a warning lamp.

[0030] Various solutions for the pedal stroke simulator are conceivable. Over the entire pressure range (150-200 bar), the pedal stroke simulator must exhibit a good pedal stroke characteristic, e.g., a flat characteristic curve up to 30 bar and then a gradual increase, regardless of whether the pressure is supplied by the X-boost or ESP unit. In the case of an e-booster embodiment as a follower booster (variant A according to the prior art), the pedal force characteristic curve changes significantly when transitioning from e-boost to ESP, which requires a lot of software work for the PWM operation of the valves required for this. This is not the case with the solution according to the invention, since the pedal is decoupled via the stroke simulator and the operation of the ESP pump does not affect the pedal characteristic.

[0031] By using a return spring (18) in the flat part of the pedal stroke characteristic curve to reduce the volume of the structure, the piston stroke simulator has a smaller volume and only corresponds to the progressive part of the characteristic curve, as also shown in the applicant's WO 2013 / 072198, which is incorporated herein by reference.

[0032] The stroke simulator may preferably be a piston simulator (WS) connected to the working chamber of the auxiliary piston via a hydraulic connection line and / or a plunger simulator connected to the working chamber of the second piston (SK), where a control pressure dependent on the pedal stroke acts on the plunger.

[0033] It is also advantageous if the stroke simulator can be switched off in further development and is not effective in the first range, the brake pedal force being determined exclusively by the return spring and in the second range by the return spring and the stroke simulator piston.

[0034] Furthermore, a switching valve can be connected upstream of the stroke simulator to switch the stroke simulator on or off as required. However, if a switching valve is not connected upstream of the stroke simulator, a switching valve (WA) must be placed in the branch line branching from the pressure chamber or working chamber of the auxiliary piston connected to the stroke simulator to the storage container.

[0035] It would also be advantageous if pressure-volume characteristics were used for pressure supply control and diagnostics.

[0036] Another possibility for realising a pedal stroke simulator is the THZ (= tandem main brake cylinder) with plunger and without piston stroke simulator, as described or shown in the applicant's WO 2016 / 023994, which is incorporated herein by reference in this respect, in which case a control pressure to the BKV, which is dependent on the pedal stroke, acts on the plunger, thereby providing a pedal feedback effect.

[0037] Depending on the pedal position, pressure is sent from the piston of the pressure supply to the SK piston of the main brake cylinder (T)HZ, which generates the brake pressure. The pressure supply consists of an electric motor that drives the piston via a spindle. Both a ball screw drive (KGT) and a trapezoidal spindle with a nut can be used as a transmission. The latter is cheaper and quieter, but less efficient and has a self-locking mechanism. The latter has the advantage that in the pressure supply DV, for example in the event of an engine failure, the piston remains in its fixed position, so the brake pressure does not affect the fluid volume in the brake circuit.

[0038] In the case of the ball screw drive (KGT), an additional shut-off valve must be used for this failure. The intake of liquid from the reservoir (VB) is carried out via an intake valve or a piston sleeve seal with a breather hole, just like in the main cylinder (HZ).

[0039] The flow path to the piston stroke simulator can be closed by a solenoid valve (WA), and in the same way as in the case of a pressure supply failure (DV), the pedal force acts on the main cylinder (HZ) to generate brake pressure at the so-called fallback level (RFE). In the absence of the valve (WA), the pedal stroke at the fallback level (RFE) is extended by the volume absorption of the piston stroke simulator (WS).

[0040] The interconnection of the X-Boost and ESP units results in two redundant systems for pressure generation, along with redundant power supplies, so the fallback level (RFE) is only active when towing, and only for extreme loads in practice, such as when the vehicle's transmission can be shut off. This allows for greater flexibility in the system and piston design, for example by eliminating the need for a WA solenoid valve.

[0041] One possibility for pad clearance control is to use a strong rollback seal of the wheel brake to return the pad. This seal can create the required clearance, among other things, by means of deformation energy stored in the seal. The stored deformation energy generates a return force that pulls the brake pad away from the brake disc (clearance or gap) as soon as pressure no longer builds up in the brake circuit. This is advantageously possible in the present invention, because the separation has no effect on the brake pedal.

[0042] The X-Boost and ESP units have separate power supplies, for example the ESP is connected to a 12V battery and the X-Boost is connected to a DC / DC converter in the multi-voltage vehicle electrical system. Alternatively, the X-Boost and ESP units can both be connected to both the 12V battery and the DC / DC converter. Thus, both modules in the two-box brake system have redundant power supplies.

[0043] The solution according to the invention has even more advantages over prior art variant A, including: I. The pedal will not become inoperable if the brake circuit fails. II. In case of ESP motor failure, the pressure can be controlled per axle or per wheel, which makes it possible to significantly reduce braking distances. III. Many driver assistance functions can be performed by X-Boost and with greater precision than they can be performed by the ESP unit. IV. Regeneration control is easier, quieter, and more accurate via the DV than via the ESP unit's intake and exhaust valves and pumps.

[0044] In this way, pedal failure I) can be avoided, since the stroke simulator is disconnected and therefore leakage in the system does not affect the pedal feel. In contrast to the solution according to the invention, leakage in the system would directly affect the pedal feel, for example in variants A and B, and in the worst case scenario, the pedal stroke would suddenly be extended, a change which the driver would not be able to control, leading to an accident.

[0045] Individual pressure regulation of the axles and even wheel brakes (II) is made possible by the solution according to the invention, since in the event of a malfunction of the ESP motor, the electric motor of the X-boost pressure supply DV takes over the pressure regulation, which does not affect the pedal. This means that there are significantly more degrees of freedom for axle- or wheel-specific control than in the solutions of the follower boosters (variants A and B). For this reason, the pressure control according to the invention through piston stroke and motor current regulation (DE 10 2005 018649 in the Applicant's patent) and pressure gradient regulation (DE 10 2005 055751 in the Applicant's patent) is used to achieve a high degree of pressure control that cannot be achieved with pulse-width modulation (PWM) control of the valves of the ESP unit (these patents are hereby incorporated by reference in this regard).

[0046] System isolation (system pedals) is also very important for the implementation of III) driver assistance functions, as will be explained in more detail below.

[0047] Regenerative braking (IV) is becoming increasingly important with the increasing adoption of hybrid and electric vehicles. Brake pressure varies depending on the available generator braking effect and the total braking effect required by the driver. This is called brake pressure blending. Brake pressure blending can involve all wheel brakes (four-wheel blending), only one vehicle axle (two-wheel blending), or individual single wheel brakes. Brake pressure blending requires appropriate brake pressure control and valve control, which is explained in more detail in the drawing description.

[0048] The regenerative control (IV) according to the solution of the present invention is implemented exclusively by controlling the piston stroke of the pressure supply DV in the simplest solution (four-wheel blending). Depending on the retarding effect of the vehicle's generator or the drive motor of an electric vehicle operating in generator mode, the corresponding brake pressure is set by adjusting the piston so that the sum of the hydraulic braking force and the braking effect of the drive motor results in the desired total retarding force.

[0049] This is possible in a completely variable manner, since the pressure state of the X-Boost pressure supply DV does not affect the pedal feel. This has considerable advantages, especially compared to variants A and B of the prior art, in which the connection between the pedal and the HZ volume means that the storage chamber of the ESP unit must be emptied in order to reduce deceleration while maintaining the same pedal feel. This prior art requires interventions within the ESP and a very complex control of the drain valve of the ESP unit. Furthermore, the solution according to the invention makes it possible to eliminate various ESP variants for different brake circuit distributions (diagonal and parallel brake circuits per axle, rear and front drive), since control is exclusively performed by the piston, regardless of the brake circuit distribution and drive type. In particular, the following advantages of X-Boost are also achieved by regeneration.

[0050] As will be explained in greater detail below, axle-by-axle blending (two-wheel blending or axle-by-axle blending) is much easier to implement.

[0051] Some of the solutions according to the invention, in particular X-Boost, provide the following advantages in pedal feel compared to the prior art: - There is no change in pedal feel due to blending. · There is no change in pedal feel due to changes in the brake system (e.g., changes in brake release clearance, changes in PV characteristic curve).

[0052] In summary, blending with X-Boot provides the following benefits: Generator torque => precise brake pressure regulation even when simple point braking changes suddenly, - No perceptible noise, e.g. from the ESP unit's switching valve, Blending throughout the vehicle deceleration range, Blending software that is much simpler than traditional e-boosters, Uniform blending for diagonal (X) and axially parallel (II) brake circuit divisions; The braking force distribution can be freely displayed up to the wheel lock limit, avoiding ESP intervention for vehicle stabilization, especially on slippery and uneven roads, and interruption of the recuperation process with complex switching from recuperation to fully hydraulic braking and vice versa. - Changes in the wheel brakes acting on the non-driving axle (e.g. pressure-volume characteristic or pV characteristic) do not affect the hydraulic brakes; No additional components required to hold hydraulic fluid (e.g., no "smart actuators"); Stronger return spring for pedals (RFE P max (important to · The changes in the PV characteristic curve of the brake system are analyzed.

[0053] In the known system according to variant A with a follower booster, the pedal stroke is determined by the volumetric absorption. To prevent the pedal stroke from becoming too large during normal operation, it is necessary to adjust the volume of the main cylinder HZ for different vehicle types with different piston diameters. In the event of a system failure at fallback level RFE, this would result in a higher pedal force for the same pedal stroke in a braking system with a higher volumetric absorption. According to the ECE-13H requirements, a vehicle deceleration of at least 0.24 to 0.3 g is required for a maximum foot force of 500 N.

[0054] Part of the solution according to the invention, in particular X-Boost, allows for a higher brake pressure at fallback level RFE at 500N foot force by allowing the use of a smaller auxiliary piston diameter compared to the SK piston. Furthermore, the fluid volume in the brake circuit can be further increased against brake fade phenomena by continuing to deliver DV. This additional volume must be able to be delivered from the SK piston to the floating circuit by using a larger SK piston diameter than the auxiliary piston or by using a longer stroke of the SK piston.

[0055] In one embodiment according to the applicant's DE 10 2005 018649 and DE 10 2005 055751, the BKV is controlled by applying a pressure according to a BKV-specific curve to the brake circuit by a piston of a pressure supply DV depending on the pedal stroke (these patents are hereby incorporated by reference in this regard). The pressure is measured in the ESP unit and supplied by the pressure supply DV through the corresponding piston stroke. If the pressure sensor fails, this pressure signal is unavailable. The pressure sensor malfunction is detected by the pressure supply DV through evaluation of the pressure-volume characteristic curve (pV characteristic curve). In this case, the corresponding pressure value is not known during the piston stroke.

[0056] In this case, the DV motor current measurement can be used instead of the pressure measurement. Generally, it is also conceivable to use only the current measurement. For accuracy in increasing and decreasing pressure, the hysteresis due to the frictional forces of the driver must be included in the characteristic curve of the pressure supply DV (piston stroke and pressure or alternatively current) optionally together with a correction value, for example, due to the correlation between the current and the deceleration of the vehicle.

[0057] This concept has further possibilities to enhance functionality and error safety through: a) Function A small accumulator, also called a mini reservoir, connected to brake circuit 1 (BK1), which enables the ESP pump to further increase the pressure in the wheel brake cylinders during the intake stroke of the pressure supply (DV). Hydraulic pedal force blending with fallback level. b) Safety · Use of additional isolation valve (TV1) in brake circuit 1 (BK1) in case of a malfunction in brake circuit 1 (BK1). Eliminates the need for a shut-off valve (WA) in the stroke simulator, which also eliminates its possible errors. -Measures to prevent sensor activation. Linear level transmitter for brake fluid in the reservoir (VB). This transmitter detects small fluid level changes in the reservoir (VB) and can provide an early warning in case of a leak in the brake system. Additional shut-off valve (36) for the hydraulic connection from the auxiliary piston chamber to the reservoir (VB). Redundant seals including diagnostic options for the main cylinder (THZ) and pressure supply (DV). · Redundant measures in the return line from the pressure supply (DV) to the storage vessel (VB) in case of failure of the intake valve (28), for example an additional shut-off valve (MV). Partially redundant control unit (ECU) for reading and processing sensor signals and controlling the FV valve and PD1 valve. Heat dissipation from PCB to the body, and therefore to the cooler spray wall, reducing the temperature of electronic components and lowering the failure rate of electronic components. · 2x3 phase control of the motor, i.e. redundant windings.

[0058] This means that even the highest requirements regarding fail-operationality (FO) can be met.

[0059] In the following, further possible advantageous features are listed for the possible embodiments described above, which may be added to the embodiments in combination or alone. For example, the piston of the first piston-cylinder unit (main cylinder) can have different diameters. In particular, the auxiliary piston can be smaller in size to accommodate the lower pedal force of the fallback level (RFE). Furthermore, one module of the two-box configuration (X-Boost / ESP) can be connected to a 12V battery or a 12V voltage source, while the other module can be connected to a DC / DC converter or a 48V vehicle electrical system or another vehicle electrical system with a higher voltage. In particular, X-Boost is powered by a DC / DC converter or a 48V vehicle electrical system. For increased safety, both modules can be redundantly connected to both vehicle electrical systems, in particular the 12V battery and the DC / DC converter. The transmission of the pressure supply unit may have a self-locking trapezoidal spindle that performs an automatic locking operation in the event of a driver failure. The valve (FV) can be controlled by pulse width modulation (PWM) to generate force feedback to the brake pedal (haptic feedback with ABS). The plug connections for the system can be located below the storage container and point inwards towards the centre of the device, allowing the corresponding plug to be pulled out to the side. The second piston-cylinder unit (pressure supply DV) can advantageously be aligned parallel or perpendicular to the axis of the first piston-cylinder unit (main cylinder). Topping up allows for a larger amount of brake fluid to be available, which is advantageous in heavier vehicles or when there are air bubbles in the brake fluid or when there are vapor bubbles in the brake fluid which can occur as a result of the brakes overheating. Improved fault tolerance can be achieved through partial redundancy of the ESP and X-Boost control units. Proper functioning in terms of braking distance and driving stability in the event of ESP failure can be achieved by introducing isolation valves (TV1, TV2) into the brake circuits (BK1, BK2) and by hydraulic multiplexing of the pressure supply DC. Individual regeneration for each brake circuit can also be achieved. In addition, brake circuit 2 (BK2) can be replenished.

[0060] Further features and advantages of the present invention will become apparent from the following description of the embodiments, examples and structures of the present invention. [Brief explanation of the drawings]

[0061] Text description of the illustration image022.gif. [Figure 1] Shown is the full X-Boost system with ESP. [Figure 2] The pedal characteristics are shown. [Figure 3] The main components of the system are shown. [Figure 4] Showing the extended X boost. [Figure 4a] This shows the redundancy of valves FV to enhance functional safety. [Figure 5] It shows X-Boost, which includes measures to enhance functional safety. [Figure 5a] 1 shows a pedal stroke sensor including measures to increase functional safety. [Figure 6] The pressure supply is shown with additional valves for increased functional safety. [Figure 7] The pressure supply is shown with redundant seals for increased functional safety. DETAILED DESCRIPTION OF THE INVENTION

[0062] FIG. 1 shows a schematic diagram of a brake system having a drive, in particular a brake pedal 1, a first piston-cylinder unit THZ that can be driven by the drive, a second piston-cylinder unit (hereinafter referred to as X-boost or booster) with an electric drive and transmission, and an ABS / ESP unit. The ABS / ESP unit is known, including the main components: a pump P with a motor M, valves HSV1, HSV2, valves USV1, USV2, exhaust valves EV and AV assigned to the wheel brakes, and a storage chamber (SpK). This system has been described in many publications and patent applications. This system, known as an e-booster, is already on the market and is primarily used in electric and hybrid vehicles, since the brake system is controlled in conjunction with the braking torque of the generator, i.e., regeneration. As is well known, both the e-booster and the ESP elements can play a role, in particular, in the pedal characteristic. Another field of application is vehicles with automated driving. The focus here is on fault safety, redundancy of functions such as pressure supply and ABS functions. The main difference in the system architecture is the new X-Boost concept, which consists of a special main cylinder HZ containing a stroke simulator WS and a pressure supply DV, which is arranged parallel or perpendicular to the main cylinder HZ to achieve a short overall length, also shown in Figure 3.

[0063] The main cylinder HZ essentially consists of an auxiliary piston (HiKo) 16 and a SK piston (floating piston) (12) with a return spring 12a. The auxiliary piston 16 is connected to a plunger 16a, which moves through a partition wall 14 with a seal into a pressure chamber 12d. Approximately 50% of the stroke of the auxiliary piston (HiKo) 16 is between the end of the plunger and the SK piston. The plunger (16a) has a significantly smaller cross-sectional area (>5 times smaller) than the piston of the first piston-cylinder unit and contributes little to the pressure buildup and pressure detection in the brake circuit, but transmits this force to the brake pedal, thereby generating haptic feedback to the brake pedal, especially during ABS operation and / or brake fade.

[0064] Normally, the valve FV is closed when braking and the auxiliary piston HiKo acts on the stroke simulator WS. The function and variants of the stroke simulator WS are explained below. The auxiliary piston HiKo has two functions: one for normal operation and one for a fallback level in case of a failure of the pressure supply DV. In the first case, which is normal operation, the auxiliary piston delivers fluid to the stroke simulator WS with the valve FV closed and the pedal stroke is the input signal for the pressure supply DV. In the fallback level in case of a failure of the pressure supply DV, the auxiliary piston also delivers fluid to the stroke simulator WS when the valve FV is closed, but now the pedal stroke is the input signal for the ESP booster.

[0065] When the brake pedal 1 is actuated together with the pedal plunger 3, the redundant pedal stroke sensors 2a / 2b are simultaneously activated. Furthermore, these sensors can be decoupled via an elastic element KWS, as described in the applicant's DE 11 2011 103274, which is incorporated herein by reference. The advantage is that, on the one hand, the auxiliary piston (HiKo) 16 is detected as stopped, and, on the other hand, the stroke difference between the sensors when the auxiliary piston (HiKo) 16 is stopped provides a control signal for the auxiliary brake. The elastic element can also be part of the spring characteristic of the WS stroke simulator. The auxiliary piston (HiKo) 16 has a standard breather hole for the THZ piston, connected to a reservoir VB. It is well known that if the primary seal fails, the brake circuit will fail. This can be avoided by using a check valve RV and a throttle in the connecting line to the VB, which is used for venting. The throttle is positioned for a small flow so that even if a seal fails and can still be diagnosed, the pedal characteristics do not change significantly (3 mm pedal travel in 10 seconds). The same configuration can also be used for a floating piston (SK) 12 (not shown), which makes failure of both seals non-fatal. Alternatively, a normally open solenoid valve can be used in the feedback line. The solenoid valve closes after pedal actuation or diagnosis. This applies to both pistons of the HZ (auxiliary piston HiKo and second piston SK).

[0066] The stroke simulator WS can be designed in various ways. The illustrated structure corresponds to the prior art described in various patent applications, consisting of a WS piston and spring combination. This combination provides a pedal stroke characteristic as a function of the pedal stroke. The valve RV allows a rapid pressure reduction P from the stroke simulator WS in the event of a very sudden release of the pedal. ab The throttle D is used to provide the desired adjusted pressure increase P with a corresponding pedal characteristic. aufFurthermore, the stroke simulator WS can be deactivated by the valve WA. This is essential for a non-redundant system with a fallback level (RFE). The intake volume of the stroke simulator WS does not affect the output volume of the auxiliary piston HiKo to the brake circuit BK1 and the pressure chamber 12d. In this system (Figure 1), the ESP functions redundantly in the event of an X-boost failure. The ESP pump draws volume from the reservoir via the main cylinder THZ and the pressure supply DV. The valve WA can therefore be eliminated. The auxiliary piston (HiKo) 16 with the pedal plunger 16a is moved to its initial position by the pedal return spring 18 after braking.

[0067] A pressure supply or DV is required for the BKV function. It consists of an EC motor 8 which moves a piston 10 via a spindle 7 and a nut, delivering pressure medium to the brake circuit BK1 and to the pressure chamber 12d. The fluid volume is provided by the BKV control, which controls the pressure from the pedal stroke 2a / 2b according to the BKV characteristic curve measured by a pressure transducer DG in the ESP. Alternatively, instead of pressure, the motor current measured via a flow divider can be used. To improve the accuracy of the pressure control by current measurement, the pressure control by current measurement is based on the P of the characteristic curve. auf and P ab This requires recording of the pressure loss in the engine and optionally further improving it by means of a correction factor, such as by comparison with the deceleration of the vehicle. This is particularly important when the spindle drive is not a ball screw drive KGT but, for example, a trapezoidal spindle with a plastic nut.

[0068] The piston 10 has a breather hole 27 at the starting position, similar to the main cylinder THZ. Volume can be sucked in through a temperature independent sleeve or suction valve (SV) 28, which requires only a low vacuum to open.

[0069] When a trapezoidal spindle is used, the piston remains in a position where the motor drive cannot operate due to the piston self-locking.

[0070] The dimensioning of the pressure supply DV can be adjusted so that the full stroke of the DV piston corresponds to the volume consumption of the brake circuit BK2 or the stroke of the SK piston 2. The SK piston can be designed with a larger diameter and therefore a larger stroke for a larger volume intake. On the other hand, the pressure supply DV can be designed accordingly. Alternatively, it can be designed with a smaller volume (piston and stroke), making the missing volume available by making up for the piston return stroke via the SV intake valve. For this purpose, a normally closed solenoid valve PD1, not shown in FIG. 1 (see FIG. 4), is required. Pressure reduction P ab In case of an overflow, the piston must move to its initial position with the breather hole open to ensure full fluid flow. The intake valve 28 and the breather hole 27 are connected to the return line to VB. All components of the pressure supply DV are integrated in one housing 25.

[0071] Pressure increase P in brake circuit BK1 and brake circuit BK2 auf and pressure reduction P ab is achieved through the BKV control and the pedal stroke sensor, and the DV piston moves accordingly. Normally, X-boost pumps a volume into the brake circuit BK up to the shut-off limit of 80-120 bar. If a higher brake pressure is required for the fade phenomenon, X-boost pumps 80-120 bar to the ESP pump, which results in a higher pressure level. Previously, the ESP pump had to be sized for a delivery volume corresponding to a maximum pressure of, for example, 200 bar with ASR operation. With a suitable pump design, for example a two-circuit gear pump or a separate eccentric for the pump piston, and furthermore a stepped piston, the ESP pump only has to deal with the pressure difference between the brake circuit pressure and the X-boost pressure. For example, P Bremskreis(=200 bar) - X Boost (=80-120 bar) = 80-120 bar, so that only 80-120 bar, not 200 bar, is required for the design of the ESP pump, and therefore a correspondingly smaller ESP motor is sufficient. Furthermore, with this design of the pump, it is possible to arrange the E Boost and ESP pump in parallel already in the low pressure range, for example from 20 bar, for rapid deceleration. This therefore means that P auf This allows for faster (TTL) and smaller X-Boost motors.

[0072] If the pressure supply DV fails during the braking process, the DV piston is pushed back under the pressure in the brake circuit BK1, so that the brake pressure can be completely reduced. If a self-locking gear is used for the DV piston (trapezoidal spindle with plastic nut), such a pressure reduction is not possible. In this case, a normally closed solenoid valve AV is provided in the brake circuit BK1 with a connection to a reservoir (not shown) or a connection from the Hiko breather hole to the reservoir VB.

[0073] In the unlikely event of a malfunction of the electronic control or regulation unit (ECU) of both X-Boost and ESP, at fallback level RFE, the auxiliary piston (HiKo) 16 transfers volume through the open valve FV to the brake circuit BK1 and to the main cylinder HZ behind the SK piston, increasing brake pressure. The brake pressure in the main cylinder HZ moves the SK piston, increasing pressure in the brake circuit BK2. To prevent this volume from leaking through the open breather hole in the DV, a normally closed solenoid valve PD1 is provided (not shown in Figure 1, see Figure 1a).

[0074] Function when a malfunction occurs in the brake circuit (BK) Faults in the brake circuit are detected by the pressure supply DV as part of a diagnostic cycle at specific intervals by comparing the pV characteristic curve of the brake system with a stored characteristic map.

[0075] For example, if the piston stroke / volume is greater than the standard value, this indicates the presence of air or a leak in the brake circuit (BK). This can be identified by the pV characteristic curve. If a leak occurs, it can be identified by sequentially closing the four valves EV, provided that the leak is not in the unit, e.g., in a wheel cylinder. For example, if the leak is in brake circuit BK1, the valve EV of brake circuit BK1 is closed. The pressure supply DV then acts on brake circuit BK2 via the SK piston (similar to the diagnostic logic described in patent applications DE10 2015 106 089.2 and DE10 2016 112 971.2, cited herein). If this does not work, the pressure supply DV is not functioning and the brake booster BKV is also not functioning. In this case, the ESP pump functions as the brake booster BKV in brake circuit BK2.

[0076] The SK piston (12) separates the brake circuits BK1 and BK2 and serves as an important safety gate, so that a malfunction in the brake circuit BK2 will not cause a malfunction in the pressure supply unit DV.

[0077] In both cases the pedal characteristics are the same and the pedal does not fail.

[0078] ABS function in the event of ESP pump / motor failure ABS pressure reduction signal P ab If this occurs, the DV control will modify the brake pressure to prevent the wheels from locking up. ab is necessary to prevent the wheels of one of the two brake circuits from locking up, however this does not mean optimal braking effect, although this can be improved.

[0079] For example, in the event of wheel lock, a corresponding pressure reduction P ab When this is done, the other brake circuit reduces pressure by closing the valve USV.ab This can be optimized without parallel check valves RV by adjusting the valves EV for the individual wheels, as explained in patent application DE 11 2009 004636 (E112), which is incorporated herein by reference.

[0080] Figure 2 shows the pedal stroke S p The diagram shows the pedal characteristic over a range of 100-150°C. In region A, the force increase in curve 1 is relatively constant up to a brake pressure of approximately 30 bar, which corresponds to approximately 85% of all braking operations. This process can be implemented via the pedal return spring. A more progressive portion B then acts up to the brake protection limit, followed by a higher pressure region, for example in the case of brake fade. In this case, the driver also feels that there has been a change in the brake system.

[0081] Curve 1 corresponds to X-boost with stroke simulator WS. Without WS, i.e., in the case of a follower booster, the pedal stroke changes due to venting or fade phenomena, as shown in curve 2. Therefore, in the event of a brake circuit (BK) malfunction, there is an even more extreme diffusion to 2a (not shown). In the case of a conventional e-booster, the BKV is switched from e-booster to ESP booster at x. This changes the pedal characteristic. Without affecting the BKV control, with the same pressure and the same pedal force, the pedal with the main cylinder (HZ) piston sends additional volume to the ESP pump until the pressure in the wheel cylinder reaches the target value. This volume is returned to the main cylinder HZ overflowing the valve USV.

[0082] A modified pedal characteristic with a larger pedal travel can be obtained by reducing the X-Boost gain, which results in a more clearly defined scatter band. Additionally, the valves HSV1 and HSV2 can be adjusted.

[0083] Here, the X-Boost according to the invention with the stroke simulator WS behaves like curve A with a corresponding progressive force increase depending on the pedal stroke.

[0084] Pedal feedback with ABS During ABS operation, the preload provided by the DV is constantly varied. This preload acts on plunger 16a and can be felt as small force changes acting on the associated pedal plunger 3, as desired by many braking experts. This preload can be varied by briefly increasing the intake pressure at the beginning of ABS or intermittently during deceleration.

[0085] When the reaction is more pronounced, the FV valve opens and the control pressure of the DV acts directly on the auxiliary piston HiKo.

[0086] Regeneration using stroke simulator WS The pedal characteristic is determined by the stroke simulator WS. Here, the generator-assisted brake management determines the ratio between generator brake torque (electric brake torque) and brake pressure (hydraulic brake torque) for the required vehicle deceleration. Both quantities can be varied as desired during deceleration. Regeneration can be applied a. with the same brake pressure for all four wheel cylinders, b. with axle-specific brake pressure for the vehicle axle, or c. with wheel-specific brake pressure for all four wheel cylinders. Here, special control methods are required for the pressure supply DV and, in cases b and c, for the corresponding valve structure or the corresponding valve and pump control of the ESP unit.

[0087] The calculation of the brake pressure during regeneration according to a. is preferably based on the wheel force. The total required brake force (target brake force) acting on the wheel is determined from the pedal stroke. If the target brake force can be applied electrically, the hydraulic brake force is 0 N (0 bar brake pressure in the cylinder). If the target brake force exceeds the maximum possible electric brake force, the difference between the target brake force and the electric brake force is the hydraulic target brake force. The hydraulic target brake force is realized by the pressure supply DV by generating pressure in the wheel cylinder. For this purpose, the individual Cp values ​​of the wheel brakes are used to calculate the target brake pressure, which represents the ratio of the brake force to the brake pressure. The target pressure is generated by the corresponding movement of the DV piston. A pressure sensor in the ESP is used to feedback the piston movement. In this way, the pressure supply DV can set the target pressure both during pressure increase and pressure decrease. Due to the high-precision position control of the DV piston, the pressure setting is very accurate. Pressure control by the DV is performed by P auf and P ab It is extremely quiet because no valves need to be operated for the brake pedal. The valves and pumps that cause noise in ESP units are not required. Furthermore, this regenerative control can be used uniformly on front-wheel, rear-wheel, and all-wheel drive vehicles, and on X and II brake circuit splits. The pedal characteristics remain unchanged.

[0088] In case b., which uses axle-specific brake pressure at the vehicle axles, the ESP valves and pump motors may also need to be controlled. If the target brake force exceeds the maximum possible electric brake force, the difference between the target brake force and the electric brake force is the hydraulic target brake force. This hydraulic target brake force is initially applied only to the driven axle by the pressure supply. The EV of the non-driven axle is closed. The non-driven axle must also be hydraulically braked (to stabilize the vehicle during braking) from a certain vehicle deceleration (e.g., from 0.2 g). The hydraulic target brake force must then be applied to both vehicle axles together. The brake pressure at the non-driven axle is equal to or less than the brake pressure at the driven axle. The pressure at the driven axle is increased by the DV when the EV is opened. The pressure at the non-driven axle is regulated by appropriate PWM control of the EV of the non-driven axle. If the hydraulic target brake force must be reduced, for example, because the driver has released the brake pedal or because the generator time has increased, the brake pressure at both axles is reduced. This is achieved by appropriate control of the pressure supply DV at the driven axle, which opens the valve EV. Pressure reduction at the non-driven axle is achieved by the (possibly clocked) opening of the valve AV in conjunction with control of the ESP pump and pulse-width modulation (PWM) control of the valve (EV) at the non-driven axle. The PWM control of the valve EV is intended to prevent excessive pressure drops at the rear axle. As a result, if the pressure at the rear axle drops to 0 bar, a further reduction of the hydraulic target brake force occurs exclusively via the pressure supply DV, opening the valve at the driven axle and closing the valves EV and AV at the driven axle. The AV at the driven axle remains closed at all times during these processes. For this reason, valve and pump noise is only generated at the non-driven axle above a certain vehicle deceleration (e.g., 0.2 g).

[0089] In case c., where brake pressure is applied to each wheel on all four cylinders, the ESP valves and pump motors may also have to be controlled. The control of the pressure supply DV, valves, and ESP pump is performed in the same way as in the situation described in b.

[0090] Driver assistance features There are many driver assistance features that require automatic braking intervention, such as: · ACC (Adaptive Cruise Control) where the desired vehicle deceleration is set by active brake intervention. -AWB (Automatic Alert Brake) where a brake impulse wakes up a sleeping driver. BDW (Brake Disc Wiping) - extremely low brake pressure in the wheel cylinders wipes the thin film of water off the brake discs during rain, ensuring maximum braking effect immediately on the next braking attempt.

[0091] In these assistance functions, the DV pressure supply generates the required brake pressure in the wheel cylinders. The target brake pressure is specified by the various driver assistance systems. In the case of ACC, the target brake pressure is variable and depends on the required vehicle deceleration. In contrast, in the case of BDW, the target pressure has a small value (e.g., 1 to 3 bar). As with regeneration, the brake pressure is generated by a corresponding movement of the DV piston. In this case, a pressure sensor in the ESP is used to provide feedback on the piston movement. As with regeneration, the brake pressure setting is extremely accurate due to the precise position control of the DV piston. Pressure control by the DV pressure supply is also very quiet in the case of driver assistance systems.

[0092] The diagrammatic representation of FIG. 2 shows in particular the overall length as well as other crucial advantages of the invention.

[0093] Figure 3 shows a spatial representation of the main components of X-Boost: Pedal plunger 3 Mounting flange BF on the front wall First piston-cylinder unit or main cylinder HZ including the pedal linkage Advantageously, the motor 8 includes a housing pressure supply 1 (DV) 25 arranged parallel to the main cylinder (although it can also be aligned perpendicular to the axle of the HZ). Hydraulic control and regulation unit HCU Electronic control and regulation unit (ECU) Storage Container VB The plug connectors ST are located below the storage vessels VB and above the HZ and HCU, facing inwards towards the centre of the unit to allow the corresponding connectors to be pulled out to the side.

[0094] Figure 4 shows an addition to Figures 1 and 1a and is based on this description. The addition is a control unit (ECU) connected to the storage container (VB) and the electrical connections e of the sensors, solenoid valves, and motor. The control unit (ECU) has a partially redundant partial control unit (ECU2) for operating safety-related components such as the FV valve with an optional standalone vehicle electrical system connection. This partial control unit (ECU2), in which the signals of the pedal stroke sensors (2a, 2b) are used, for example, can be integrated into an existing ASIC, preferably with a redundant power supply.

[0095] The assembly of the sensor element (33) on the printed circuit board (PCB) at the connection to the reservoir (VB) is provided with a float (34) and a target (T) in the reservoir (VB). This allows an analog evaluation of the brake fluid level in the reservoir (VB) and aids in diagnosing the system. For example, if the pressure increases via the pressure supply (DV), then decreases again, followed by a lower level, this indicates a leak in the system.

[0096] The printed circuit board (PCB) is preferably mounted on an aluminum plate or aluminum carrier (37) with good thermal conductivity to the body (38) and the spray wall (39). At peak loads, the temperature outside the control unit (ECU) can be 120°C and 60°C at the spray wall (39), while the maximum temperature in the subsequent passenger compartment (39a) is 30°C due to cooling. The aluminum plate allows a significant temperature reduction to be achieved at the MOSFET (33a). The tabs of the MOSFET (33a) are connected to the aluminum plate (37) through so-called via holes (V). As is well known, the failure rate of electronic components has a strong temperature dependence, particularly due to the Arrhenius law.

[0097] The EC motor (8) has a redundant connection e red The EC motor (8) can be controlled redundantly by a 2x3 phase control via the EC motor (8). The process is known. Normally, an EC motor (8) requires an angle encoder as the motor sensor (40).

[0098] Here, the pressure supply DV has an additional solenoid valve PD1 that is normally closed. This solenoid valve is necessary when the DV piston is pushed back under pressure at the fallback level, resulting in a corresponding loss of fluid volume in the brake circuits BK1 and BK2. This can be compensated for by the large-volume auxiliary piston HiKo, but this has a negative effect on the pedal response. When the DV piston reaches its initial position, a breather hole opens, allowing brake fluid to flow into the reservoir. At fallback level RFE, valve PD1 is closed. Valve PO1 can be reopened in the event of ESP interference or ESP boost.

[0099] As already explained in FIG. 1, to deliver a subsequent amount of brake fluid to brake circuit 1 (BK1), the DV piston (10) is retracted, and a volume is drawn from the reservoir (VB) via the intake valve (28). For this, the valve PD1 is closed and the DV piston (10) moves backward. The DV piston (10) draws brake fluid from the reservoir (VB) via the intake valve (28) and the hydraulic connection (R). Once the return volume has been drawn into the DV chamber (10), the valve PD1 is opened and the DV piston (10) moves forward. The DV piston (10) pushes the return volume into brake circuit 1 (BK1). During the intake phase of the pressure supply (DV), a vacuum is created in brake circuit 1 (BK1) when the ESP return pump (P, FIG. 1) actively increases the pressure in the wheel brake cylinders. In this case, the volume delivery of the ESP return pump (P, FIG. 1) stalls, and the ESP return pump (P, FIG. 1) in brake circuit 1 (BK1) may draw in supplementary volume through seal D4, the fill hole (47) in the main cylinder (THZ), and the hydraulic connection (48) from the reservoir (VB). The SK piston (12) is pushed back by the SK piston spring (12a). In this case, the position of the SK piston no longer corresponds to the pressure in the wheel brake cylinder. This can have a negative effect on the pressure reduction when the driver releases the brake pedal (1). A mini reservoir (35) in brake circuit 1 (BK1) can be provided to prevent this stall in volume delivery or this backward movement of the SK piston. During the intake phase of the pressure supply (DV), the mini reservoir (35) supplies volume to the ESP return pump (P, FIG. 1). The required capacity of the mini-reservoir (35) depends on the duration of the intake phase and the volume delivery capacity of the ESP return pump (P, FIG. 1).

[0100] To increase the availability of X-boost and check the function of the stroke simulator (WS), a shut-off valve (36) can be provided in the hydraulic connection (44) between the auxiliary piston fill hole (42) and the reservoir (VB). For example, if there is a leak in the auxiliary piston seal (D2), the shut-off valve (36) can be closed, thus avoiding a malfunction of the stroke simulator (WS).

[0101] The shutoff valve 36 can also be used to check various diagnostic functions. For this purpose, the valve PD1 is opened and the shutoff valve 36 is closed. When the pressure supply DV is activated, pressure is applied to the brake circuit 1 BK1, and this pressure can be measured, for example, using the pressure sensor DG of the ESP. At this time, for example, the closing function of the stroke simulator shutoff valve WA can be checked. If the valve FV is opened when the DV piston 10 is in a fixed position, the pressure in the brake circuit 1 drops only slightly if the stroke simulator shutoff valve WA is functioning properly. Then, when the stroke simulator shutoff valve WA is opened, the pressure in the brake circuit 1 BK1 drops significantly more than if the stroke simulator shutoff valve WA were intact. If the stroke simulator shutoff valve WA is leaking, the pressure in the brake circuit 1 BK1 drops significantly even when the stroke simulator shutoff valve WA is not yet activated, and does not drop any more when the stroke simulator shutoff valve WA is opened. If the piston seal D6 of the stroke simulator piston (49) is leaking, the pressure in the brake circuit 1 (BK1) will continue to drop further after the stroke simulator shut-off valve (WA) is opened.

[0102] Even if the stroke simulator (WS) fails, for example, if there is a leak in the valve FV, the valve FV is normally open. When actuating the brake pedal (1), the driver forces volume from the auxiliary piston chamber (43) into the ESP return pump (P, FIG. 1) in the brake circuit 1 (BK1). The ESP can then apply pressure to the cylinders through its active braking function, depending on the position of the brake pedal (1). The pedal stroke is significantly longer to achieve a specific pressure in the wheel brake cylinder than with intact X-boost. This can surprise the driver and result in unpredictable behavior. To avoid this, a pressure supply (DV) can be used to generate a hydraulic pedal reset force, so that the pedal force is similar to that with an intact X-boost function. For this purpose, the pressure in the brake circuit 1 (BK1), and therefore the pressure in the auxiliary piston chamber (43), is adjusted by the pressure supply (DV) to reproduce the standard pedal force / pedal stroke characteristics of the stroke simulator as intended by the vehicle manufacturer. If this simulation is successful, the driver will not be surprised by longer pedal strokes and the driver's behavior will become more predictable. In this example, the stroke simulator (WS) functions normally, but the brake pressure increase in brake circuit 1 (BK1) by the pressure supply (DV) can occur with shorter pedal strokes only after the auxiliary piston's sniff hole (45) is closed or only if the shut-off valve (36) is used. However, when using the ESP's active braking function, the pressure in the wheel brake cylinders can already be high before the auxiliary piston breather hole (45) is closed.

[0103] 4a shows a way to increase the functional safety of X-Boost: the valve FV can be extended for redundancy by FVred, preferably with a regulated flow from the sealing ball to the valve seat.

[0104] Figure 5 shows the complete X-Boost system with ESP. The X-Boost with THZ valve and pressure supply DV are similar to those in Figure 4, except for the improved connection of the intake valve (28), also shown in Figure 7. Figure 5 shows the redundant seal (D2.1) and fill hole (50) for the auxiliary piston (16), along with the throttled discharge (Dr2.1) to the reservoir (VB). The throttle Dr2.1 is designed narrow so that if the seal (D2) is leaking, only a small leakage flow can pass from the auxiliary piston chamber (43) through the fill hole (50) to the reservoir (VB). This merely results in a slow, short, non-interfering extension of the brake pedal (1) stroke during the limited braking time. This leakage flow is detected by the pedal stroke sensors (2a, 2b) during a plausibility check, but also by the system diagnostics described in E144.

[0105] A further seal D4.1 is also shown as a redundancy for seal D4. If this seal D4.1 fails, the brake circuit BK1 and the pressure supply DV will also fail. In this case, the ESP unit will activate the pressure supply, i.e., increase the pressure. This can be avoided by the combination of seals D4, D4.1 and the fill hole 52, whose connection to the reservoir is equipped with a throttle Dr4.1 as well as an auxiliary piston (HiKo) 16. Failure of this seal D4.1, which allows a small leakage flow through the throttle Dr4.1, will not result in a failure of the brake circuit BK1 or the pressure supply DV. Furthermore, diagnostics of seal D4.1 are preferably possible with this configuration. Alternatively, a normally open valve TV can be provided at the connection to the reservoir. This valve can be closed if a leak occurs in seal D4 or seal D5.

[0106] For seal D3, a redundant seal D3.1 can also be used with the fill hole 51 and throttle Dr3.1. Furthermore, the stroke simulator seal D6 can also be equipped with a redundant seal D6.1, fill hole 53, and throttle Dr6.1. This means that all functionally important seals are redundant and leaks can be detected during braking and diagnostics. This achieves a high level of safety against fail-operation (FO). This seal configuration can also be used with a single-circuit main cylinder (THZ) with a pressure rod piston and no floating circuit.

[0107] If there is a leak in brake circuit 1 (BK1) between the ESP and the wheel cylinders of brake circuit 1 (BK1), the pressure supply (DV) of brake circuit 1 (BK1) and X-Boost will not function. There is also a risk that a leak could result in brake fluid being lost to the environment. As a countermeasure, the ESP can close both intake valves (EV) of brake circuit 1 (BK1). If a malfunction is detected in X-Boost but X-Boost does not have access to these valves (EV), X-Boost must switch over to the active braking function of the ESP. In this case, the ESP regulates the pressure in the wheel brake cylinders of brake circuit 2 (BK2). Without regulating the pressure in the wheel brake cylinders of brake circuit 1 (BK1), the ESP would have to constantly send volume to brake circuit 1 (BK1). If the ESP did not detect a leak in brake circuit 1 (BK1), brake fluid would be constantly lost. For this situation, a separation valve TV1 is provided in brake circuit 1 (BK1) between the pressure chamber (12d) of the main cylinder (THZ) and the ESP. If X-Boost detects a leak in brake circuit 1 (BK1), the valve TV1 is closed. The pressure supply (DV) can then supply pressure to the pressure chamber (12d) of the main cylinder (THZ) and thus to brake circuit 2 (BK2) without losing brake fluid.

[0108] Furthermore, in the event of an ESP malfunction, the TV1 valve can be used to optimize braking distances on slippery roads. For legal reasons, when braking on slippery roads, the wheels on the front axle must lock before the wheels on the rear axle. This results in insufficient braking on the rear axle when the vehicle decelerates slightly. With X-Boost, the TV1 valve can be closed when the wheels on the front axle in brake circuit 1 (BK1) of the II brake circuit division begin to lock. In this case, the brake pressure in the wheel brake cylinders of the rear axle in brake circuit 2 (BK2) can be further increased using the X-Boost pressure supply (DV) until the wheels on the rear axle also begin to lock. This means that nearly maximum deceleration can be achieved on slippery roads. Naturally, after increasing the pressure in the wheel brake cylinders of the rear axle, the TV1 valve can be briefly opened to further increase the pressure in the wheel brake cylinders of the front axle. In the case of an X brake circuit division, valve TV1 can close if the front wheels of brake circuit 1 (BK1) begin to lock. After valve TV1 closes, the pressure in brake circuit 2 (BK2) can be increased further until the rear wheels of brake circuit 2 (BK2) begin to lock. Because the pressure in brake circuit 1 (BK1) is low, the vehicle is still sufficiently stable, while the high pressure in brake circuit 2 (BK2) results in a short braking distance.

[0109] In the supply line BK2 from THZ to the ESP, the isolation valve TV2 is used in brake circuit 2 (BK2). As with isolation valve TV1, the output of the valve seat is connected to the ESP, so the hydraulic connection is important. These two isolation valves TV1, TV2 can be used to perform the following functions: 1. Refilling, step 2. As already explained with respect to FIG. 4, the fluid volume in brake circuit 1 (BK1), and therefore the achievable pressure levels in brake circuit 1 (BK1) and brake circuit 2 (BK2), is suppressed by refilling when the SK piston (12) of the main cylinder (THZ) stops. In this case, further pressure buildup is only possible in brake circuit 1 (BK1). The stoppage of the SK piston (12) can be recognized because the pressure in brake circuit 1 (BK1) then increases twice as quickly as the volume in brake circuit 1 (BK1). When the SK piston stops, the isolation valves TV1, TV2 close accordingly, and the piston (10) of the pressure supply (DV) retracts. The pressure in brake circuit 1 (BK1) drops very quickly. Under the influence of the return spring 12a of the SK piston 12, the SK piston 12 may retract to its initial position, transferring volume from the main chamber 12d of the main cylinder THZ through the line of the brake circuit 1 BK1, through the valve PD1, and into the chamber of the pressure supply DV. At the same time, the SK piston 12, using the hydraulic connection 48 of the main cylinder THZ to the reservoir VB, draws volume from the reservoir VB through the seal D5 of the SK piston 12, via the hole 47, and into the chamber in front of the SK piston 12 of the main cylinder. Due to the modified connection of the intake valve 28, the intake valve is not active while the piston 10 of the pressure supply DV is in its front region, and when the piston 10 of the pressure supply DV retracts, volume is not drawn from the reservoir via the intake valve 28 and the connection R (see also the explanation for FIG. 7). At the end of this intake process, the isolation valves TV1, TV2 are reopened. With the next forward stroke of the piston (10) of the pressure supply (DV), the SK piston (12) of the main cylinder (THZ) advances again, and the pressure in both brake circuit 1 (BK1) and brake circuit 2 (BK2) can increase further. The pressure supply (DV) is preferably controlled using the pressure reference value of X-boost. 2. The isolation valves TV1, TV2 can also be integrated into the ESP as a replacement for the directional control valves (US1, USV2), with the above prerequisite that the valve outlets are hydraulically connected to the wheel cylinders via the intake valves (EV). This results in cost and weight savings. 3. As already explained, in the event of ESP failure, the ABS function of brake circuit 1 (BK1) can be fulfilled by means of isolation valve TV1 and pressure supply (DV). With isolation valve TV2, the ABS function can be fulfilled in both brake circuit 1 (BK1) and brake circuit 2 (BK2). If each wheel of the brake circuit is ABS controlled individually, four intake valves (EV) can be used therewith. This is a great advantage, especially with regard to the diagonal division of the brake circuits. The control process is not shown here. Pressure control is always performed by pressure supply (DV).

[0110] A partially redundant control unit (partially redundant ESP-ECU) can be used in the ESP to control the intake valve (EV) and also the isolation valves (TV1, TV2). The functions preferably include processing of sensor signals from a speed sensor and also a yaw rate sensor for the ABS emergency function. However, this partially redundant control unit (partially redundant ESP-ECU) can also be connected to the control unit of X-Boost (X-Boost ECU).

[0111] All control units (ECUs) and partially redundant control units (partially redundant ECUs) have redundant connections to the vehicle electrical system, including the power supply and bus systems (Sn), in addition to a connection to the vehicle electrical system (S1). The partially redundant connections to the ESP are indicated by a "circle with a cross" symbol.

[0112] As already mentioned in the description of FIG. 4, the control unit for X-boost (X-boost ECU) can also have a partially redundant part (partially redundant X-boost_ECU), which preferably supplies the following components indicated by circles: pedal stroke sensors (2a, 2b), isolation valve FV, and DV valve PD1. This partially redundant control unit (partially redundant X-boost ECU) can also be expected to perform the tasks of a partially redundant control unit for ESP (partially redundant ESP-ECU), since the emergency function of the ABS must also be provided in the partially redundant control unit for X-boost (partially redundant X-boost ECU).

[0113] Each ECU or partially redundant ECU has redundant connections to the vehicle electrical system.

[0114] FIG. 5a illustrates a solution to this problem, using the example of a pedal stroke sensor (2a). In the extremely unlikely event that sensor 2a becomes stuck when the brake pedal (1) is actuated, pedal movement is impossible, resulting in a brake failure. A preload spring (41a) is installed inside sensor (2a), and the sensor's plunger (2a1) can move against the preload of spring (41a) when sensor (2a) is blocked. Errors can be detected by checking the validity of the signals from the two pedal stroke sensors (2a, 2b) with elastic elements (KWS). Two redundant return springs (18a, 18b), which are activated when the brake pedal (1) is actuated, replace the center return spring (18). If sensor 2a becomes stuck when the brake pedal (1) is released, it is impossible to fully release the brake pedal (1). As a result, the vehicle remains continuously braked, even against the driver's will. For this situation, a notch (2a11) is provided in the plunger 2a1, which is dimensioned so that under the influence of the plunger force the plunger breaks at the notch (2a11). Naturally, this solution can also be used together with the pedal stroke sensor 2b to increase the safety of the pedal stroke sensor 2a.

[0115] 6 and 7 show a solution to the problem of a failure of the intake valve 28 of the pressure supply DV. A failure of the intake valve 28, e.g., a leak, will impair the function of the pressure supply DV because the volume in the working chamber 11 of the pressure supply will return to the reservoir VB via the intake valve 28 and the return line R, rather than entering brake circuit 1 BK1 via valve PD1.

[0116] Solution 1 (Fig. 6): A solenoid valve (MV) is used as a shutoff valve in the return line (R) between the intake valve (28) and the reservoir (VB). If a leak in the intake valve (28) is detected, the solenoid valve (MV) closes. The solenoid valve (MV) can open to draw brake fluid into the DV chamber in the pressure supply (DV).

[0117] Solution 2 (Fig. 7): An additional suction hole 46 and an additional seal D9 on the DV piston 10 are provided at an intermediate position of the DV piston 10 of the pressure supply unit DV. The additional suction hole 46 connects the DV working chamber 11 to the reservoir VB via the suction valve 28 and the return line R. As a result, if the seal D9 is intact and pressure increases, the suction valve 28 cannot function after the DV piston 10 has passed the intermediate position. In this case, a failure of the suction valve 28 does not affect the pressure increase function of the pressure supply unit DV. When the DV piston (10) retracts to the intermediate position, it only draws in the volume from the reservoir (VB) via the sleeve (D9), the intake hole (46), the intake valve (28), and the return line (R), with two pressure losses (seal D9 and intake valve 28). Only before the intermediate position of the DV piston (10) can the intake valve (28) function again. Since the intake function only functions at the next transfer, no further disadvantages can be found. Further transfer is necessary when a supplementary volume is required for high pressure levels or to compensate for insufficient ventilation.

[0118] Similar to seal D4 of the main cylinder (THZ), a redundant seal D8.1 can be used for piston seal D8 together with breather hole (53) and throttle Dr8.1. In this way, the pressure supply (DV) also meets the requirement of "fail operational" (FO).

[0119] From the above explanation, the measures detailed above lead to further modifications of the braking system according to the invention, which modifications also fall within the scope of the claims of the invention. [Explanation of symbols]

[0120] List of reference numbers 1 brake pedal 2a Master pedal stroke sensor 2a1 Plunger of pedal stroke sensor 2a 2a11 Pedal stroke sensor 2a plunger 2a1 notch 2b Slave pedal stroke sensor 2b1 Pedal stroke sensor plunger 2b 3 Pedal Plunger 7 Spindle (KGT), Trapezoidal Spindle 8 EC motor 10 Piston (DV) 11 DV pressure chamber or working chamber 12 SK Piston 12a Return spring SK piston 12d Pressure chamber or working chamber of floating piston SK (rear) 14 Partition Wall 16 Auxiliary piston 16a plunger 18 Pedal return spring 18a Pedal return spring for pedal stroke sensor 2a 18b Pedal return spring for pedal stroke sensor 2b 25 DV Housing 27 Breather hole 28 Intake valve 33 Sensor Elements 33a element, e.g., MOSFET 34 Floating Body 35 Mini Storage Container 36 Shut-off valve for storage vessel (VB) 37 Aluminum plate or support 38 Main Unit 39 Spray Wall 39a cabin 40 Motor Sensor 41a Pedal stroke sensor 2a preload spring 41b Pedal stroke sensor 2b preload spring 42 Refill hole for auxiliary piston (16) 43 Chamber of auxiliary piston (16) 44 Hydraulic Connection 45 Breather hole of auxiliary piston (16) 46 Pressure supply (DV) intake hole 47 Main cylinder (THZ) refill hole 48 Hydraulic Connection 49 Stroke Simulator (WS) Piston 50 Refill hole for auxiliary piston (16) 51 Refill hole for auxiliary piston plunger (16a) 52 Main cylinder (THZ) refill hole 53 Pressure supply (DV) refill hole AV exhaust valve ABS B1 Vehicle Electrical System Connection 1 B2 Vehicle electrical system connection 2 BF End wall mounting flange BK Brake circuit BK1 Brake circuit 1 BK2 Brake circuit 2 D Throttle orifice DV pressure supply DG pressure transducer Dr2.1~Dr6.1, Dr8.1 Throttling during return flow to storage vessel (VB) D1 Seal 1 of auxiliary piston (16) D2 Auxiliary piston (16) seal 2 D2.1 Redundant seal (D2) D3 Auxiliary piston plunger (16a) seal D3.1 Redundant Seal (D3) D4 SK Piston (12) Seal 4 D4.1 Redundant Seal (D4) D5 SK Piston (12) Seal 5 D6 Stroke simulator piston (49) seal 6 D6.1 Redundant Seal (D6) D7 DV Piston (10) Seal 7 D8 DV Piston (19) Seal 8 D8.1 Redundant Seal (D8) D9 DV piston (10) additional seal e Electrical connection e red Redundant Electrical Connections ECU X-Boost control unit (electronic control unit) ECU2 XBoost partially redundant controller EV intake valve ABS FO Fail Operational FV Isolation valve, normally open HZ Main Cylinder KGT ball screw driver (spindle) KWS Force-Displacement Sensor MV shutoff valve, normally closed PCB printed circuit board PD1 (normally closed) solenoid valve for DV working chamber R Return to storage vessel VB R Return line to storage vessel VB Check valve for RV auxiliary piston breather hole S1 Vehicle power supply connection Sn Redundant vehicle power supply connection SK floating circuit ST plug connector SV suction valve T Target THZ (tandem type) main cylinder TTL Lock Time TV1 Brake circuit 1 (BK1) isolation valve, normally open TV2 Brake circuit 2 (BK2) isolation valve 2, normally open (Normally open) solenoid valve to TV storage vessel (VB) V via hole VB Storage Container WA solenoid valve (normally closed) WS Stroke Simulator

Claims

1. - the drive, in particular the brake pedal, a first piston-cylinder unit (main cylinder) comprising two pistons, in particular an auxiliary piston (HiKo) and a second piston (SK), for supplying pressure medium to the brake circuit via a valve device, one of the pistons, in particular the auxiliary piston, being driveable by means of the drive device; a second piston-cylinder unit with an electric drive, - a transmission; at least one piston (pressure supply DV) for supplying pressure medium via a valve device to at least one of said brake circuits; a motor-pump unit including a valve device (ABS / ESP unit) for supplying pressure medium to said brake circuit; A braking system comprising: a hydraulic stroke simulator (WS) connected to the pressure chamber or working chamber of the first piston-cylinder unit; A brake system characterized by:

2. the first piston-cylinder unit has a first pressure chamber or first working chamber in which a (single) piston (SK) is arranged and to which at least one brake circuit is connected, and a second pressure chamber or second working chamber to which at least one brake circuit is connected, the brake circuits being connected via hydraulic lines to the pressure chamber or working chamber of the second piston-cylinder unit (pressure supply DV); 2. The braking system of claim 1 .

3. the first piston-cylinder unit has a partition wall with a seal for a through plunger (16a) to form a third pressure chamber or a third working chamber, in which a piston (auxiliary piston 16) is arranged, the third pressure chamber being connected in particular to a brake circuit (BK1) via a valve device (FV); 3. A brake system according to claim 1 or 2, characterized in that:

4. In the event of a malfunction of the brake circuit (BK1), the plunger (16a) generates pressure in the second brake circuit (BK2) by transmitting the force of the brake pedal to the second piston (SK).

4. The brake system according to claim 3, wherein:

5. the plunger (16a) comprises a cross-sectional area that is significantly smaller than the piston of the first piston-cylinder unit, in particular one fifth smaller, and contributes little to the pressure build-up and contributes to pressure detection in the brake circuit, the plunger transmitting a force to the brake pedal thereby providing haptic feedback to the brake pedal, in particular during ABS operation and / or deceleration, 5. A braking system according to claim 4, characterized in that:

6. the stroke simulator is in particular a piston simulator (WS) connected to the working chamber of the auxiliary piston via a hydraulic connection line and / or a plunger simulator (16a) connected to the working chamber of the second piston (SK), A brake system according to any one of claims 1 to 5.

7. The pressure supply (DV) is connected to a brake circuit (BK1), and a second brake circuit (BK2) is supplied with pressure via a piston (SK). A brake system according to any one of claims 1 to 6.

8. a brake system comprising a drive device, in particular a brake pedal, a first piston-cylinder unit (main cylinder) which can be driven by means of said drive device in order to supply pressure medium to at least one brake circuit via a valve device, a second piston-cylinder unit (pressure supply) having an electric drive and a transmission in order to supply pressure medium to at least one brake circuit via a valve device, and a motor-pump unit (ABS / ESP unit) having a valve device for supplying pressure medium to said brake circuits, wherein by means of a control device the motor of the electric drive of said second piston-cylinder unit (DV) and the motor of said motor-pump unit (ABS / ESP) can be used in conjunction with each other or independently, A braking system, in particular according to any one of claims 1 to 7.

9. the pressure supply by the second piston-cylinder unit (DV) and the motor pump unit (ABS / ESP unit) are connected in parallel or in series, and the pressure supply unit generates a preload for each connection; 9. Brake according to claim 8, characterized in that

10. said ESP pump (P) is in particular a two-circuit gear pump or a piston pump / stepped piston pump with an independent eccentric for each piston; A brake system according to any one of claims 7 to 9.

11. In the event of a failure of the pressure supply of the motor-pump unit, the ABS function is carried out in particular by a piston control of the pressure supply unit (DV) together with a pressure regulating valve of the motor-pump unit (ABS / ESP), A brake system according to any one of claims 1 to 10.

12. the second piston-cylinder unit (pressure supply DV) is only effective in a specific pressure range, in particular up to a wheel lock limit of 80-100 bar, and the motor-pump unit (ABS / ESP) is used for generating pressure for further, in particular higher, pressure ranges; A brake system according to any one of claims 1 to 11, characterized in that

13. The second piston-cylinder unit (pressure supply DV) is adapted to allow the pump motor of the ABS / ESP unit to operate at a low maximum torque (p ｍａｘ，ＥＳＰ = Maximum pressure system p ｍａｘ -p ｖｏｒ，ＤＶ ) to be designed assuming a preload to the eccentric piston of the piston pump / stage piston pump of the ESP unit. A braking system according to any one of claims 1 to 12, characterized in that

14. the electric motors of the motor-pump unit (ABS / ESP) and the second piston-cylinder unit (pressure supply (DV)) operate simultaneously, in particular during rapid pressure build-up (TTL), so that each motor is designed for a power output lower than the required maximum, in particular 50% of the maximum power, and the preload of the pressure supply DV is used in the eccentric pump in an effective parallel connection; 14. A braking system according to claim 13, characterized in that

15. the second piston-cylinder unit (pressure supply DV) operates in a pressure range of up to 70-90 bar, and for even higher pressure ranges >70-90 bar, the motor-pump unit (ABS / ESP) and the pressure supply DV for further pressure increase operate in series, simultaneously, so that the pre-pressure in the pump of the ABS / ESP unit can be used via the pressure supply DV for rapid further pressure increase, 14. The braking system of claim 13.

16. The second piston-cylinder unit (pressure supply DV) is adapted to allow the pump motor of the ABS / ESP unit to operate at a low maximum torque (p ｍａｘ，ＥＳＰ = Maximum pressure system p ｍａｘ -p ｖｏｒ，ＤＶ a preload is applied to the eccentric piston of the piston pump / stage piston pump of the ABS / ESP unit so that the ABS / ESP unit can be designed assuming 14. A braking system according to claim 13, characterized in that

17. the pump of the motor-pump unit (ABS / ESP unit) starts to operate in certain situations, for example with a rapid pedal movement, to achieve, for example, a rapid pressure increase or a power reduction of the motor of the second piston-cylinder unit (pressure supply DV), A braking system according to any one of claims 1 to 16, characterized in that

18. The control of the second piston-cylinder unit (ABS / ESP unit) is performed via the pedal stroke and the pressure with a corresponding brake booster (BKV) characteristic. Braking system according to any one of claims 1 to 17, characterized in that

19. Using motor current instead of pressure to control the pressure supply DV, especially with fast pilot control; 20. A braking system according to claim 18, characterized in that

20. The pressure-volume characteristic curve is used to control the pressure supply and for diagnostic purposes. Braking system according to any one of claims 1 to 19, characterized in that

21. a stroke simulator (WS) that can be switched off and is ineffective in a first range, and the brake pedal force is determined exclusively by a return spring (18), and in a second range by the return spring (18) and a stroke simulator piston; Braking system according to any one of claims 1 to 20, characterized in that

22. a stroke simulator, and a switching valve (WA) is arranged upstream of the stroke simulator to turn the stroke simulator on and off as needed; Braking system according to any one of claims 1 to 21, characterized in that

23. Only a plunger simulator (16a) is provided, a control pressure acting on said plunger depending on the pedal stroke, Braking system according to any one of claims 1 to 22, characterized in that

24. the pistons of the first piston-cylinder unit (main cylinder) have different diameters, and in particular the auxiliary piston (16) is smaller in size to accommodate the smaller pedal force at fallback level (RFE); A brake system according to any one of claims 1 to 23, characterized in that

25. One module of the two-box (X-Boost / ESP) is connected to a 12V battery or a 12V voltage source, and the other module is connected to a DC / DC converter, a 48V vehicle electrical system, or another vehicle electrical system with a higher voltage, in particular the X-Boost is powered by the DC / DC converter or the 48V vehicle electrical system. A braking system according to any one of claims 1 to 24, characterized in that

26. Both modules are redundantly connected to both vehicle electrical systems, in particular the 12V battery and the DC / DC converter, respectively.

26. A braking system according to claim 25, characterized in that

27. - the drive, in particular the brake pedal, a first piston-cylinder unit (main cylinder) with two pistons, an auxiliary piston (HiKo 16) and a second piston (SK), for supplying pressure medium to the brake circuit via a valve device, one of which pistons (HiKo, SK) can be driven by means of the drive device; a second piston-cylinder unit with an electric drive, - a transmission; at least one piston (pressure supply DV) for supplying pressure medium via a valve device to at least one of said brake circuits; a motor-pump unit with a valve device (ABS / ESP unit) for supplying pressure medium to said brake circuit; A braking system having: Four-wheel blending is used for regeneration control, and pressure control is performed by the DV piston when the valves (USV1, USV2, EV Open) of the ESP unit are opened. A braking system, in particular according to any one of claims 1 to 26.

28. - the drive, in particular the brake pedal, a first piston-cylinder unit (main cylinder) with two pistons, an auxiliary piston (HiKo16) and a second piston (SK), for supplying pressure medium to the brake circuit via a valve device, one of which can be driven by means of the drive device; a second piston-cylinder unit with an electric drive, - a transmission; at least one piston (pressure supply DV) for supplying pressure medium via a valve device to at least one of said brake circuits; a motor-pump unit with a valve device (ABS / ESP unit) for supplying pressure medium to said brake circuit; A braking system having: Two-wheel blending is performed, and the pressure control is performed through the DV piston and the valves (USV1, USV2, EV open) of the ESP unit. Braking system, in particular according to any one of claims 1 to 27.

29. the transmission of the pressure supply (DC) comprises a self-locking trapezoidal spindle, the self-locking being activated in the event of failure of the driver; Braking system according to any one of claims 1 to 28, characterized in that

30. The valve (FV) is controlled by pulse width modulation (PWM) to generate force feedback to the brake pedal (tactile feedback with ABS). Braking system according to any one of claims 1 to 29, characterized in that

31. The active return action of the brake pads is achieved using a strong rollback seal, which provides 30-50% more clearance, especially compared to the rollback seals currently used in such braking systems. A braking system according to any one of claims 1 to 30.

32. a stroke simulator, wherein at least one seal of at least one wheel brake, in particular in the form of a rollback seal, sets the clearance of the wheel brake; A braking system, in particular according to any one of claims 1 to 31.

33. A restoring force generated by deformation of the seal is used to create the clearance.

33. The braking system of claim 32.

34. The clearance is 30 to 50% larger than conventional clearances.

34. A braking system according to claim 32 or 33, characterized in that

35. the seal establishes the clearance as soon as there is no pressure increase in the associated brake circuit; A braking system according to any one of claims 32 to 34, characterized in that

36. a plug connector (ST) for the system is located below the storage container (VB) and is oriented inwards towards the centre of the unit to allow subsequent removal of the corresponding plug; A brake system according to any one of claims 1 to 35. (Fig. 3)

37. the second piston-cylinder unit (pressure supply DV) is oriented parallel or perpendicular to the axis of the first piston-cylinder unit (main cylinder), A braking system according to any one of claims 1 to 36, characterized in that

38. - the drive, in particular the brake pedal, a first piston-cylinder unit (main cylinder) with two pistons, an auxiliary piston (HiKo16) and a second piston (SK), for supplying pressure medium to the brake circuit via a valve device, one of which can be driven by means of the drive device; a second piston-cylinder unit with an electric drive, - a transmission; at least one piston (pressure supply DV) for supplying pressure medium via a valve device to at least one of said brake circuits; a motor-pump unit with a valve device (ABS / ESP unit) for supplying pressure medium to said brake circuit; A braking system having: the second piston (SK, 12) of the first piston-cylinder unit (main cylinder) has, in addition to the passage (breather hole) of the line to the reservoir (VB) provided with two seals (D4, D5), a further seal (4.1) and a further passage connected to the line to the reservoir, in particular via a throttle (Dr4.1); A braking system, in particular according to any one of claims 1 to 37 (Fig. 5).

39. redundant seals (D2.1, D3.1) are arranged in parallel to at least one piston seal (D2, D3) of the first piston-cylinder unit (main cylinder); hydraulic flow paths (50, 51) between the seals arranged in parallel to each other lead to the cylinder; the flow paths are arranged in the cylinder wall and connect the cylinder interior of the first piston-cylinder unit (main cylinder) to a storage container (VB) directly or via a hydraulic line connected to the flow paths; throttles (Dr2.1, Dr3.1) are arranged in the hydraulic flow paths (50, 51) or the hydraulic line; A braking system according to any one of claims 1 to 38, characterized in that

40. a redundant seal (D6.1) is arranged in parallel to the piston seal (D6) of the piston-cylinder unit of the stroke simulator (WS); a hydraulic flow path (53) arranged in the cylinder wall or in the piston leads to the cylinder between the parallel-arranged seals (D6, D6.1); the flow path connects the inside of the cylinder of the piston-cylinder unit of the stroke simulator (WS) directly or via a hydraulic line to a storage vessel (VB), to a non-pressure region of the stroke simulator (WS), or to the outside; and a throttle (Dr6.1) is arranged in the flow path or the hydraulic line. Braking system according to any one of claims 1 to 39, characterized in that

41. height sensors (33, 34) are arranged or integrated in or on a printed circuit board (PCB), by means of which a particularly continuous evaluation of the liquid level in the storage vessel (VB) is carried out, in particular for the early detection of leaks, A braking system according to any one of claims 1 to 40.

42. Heat is dissipated from the printed circuit board (PCB) to the housing and end walls (39) of the main cylinder (THZ) using a heat conductor (37). Braking system according to any one of claims 1 to 41, characterized in that

43. a redundant isolation valve (FVred) is arranged in series with said valve (FV) in the hydraulic line so that said hydraulic line can be selectively isolated by one of said two valves (FV, FVred); Braking system according to any one of claims 1 to 42, characterized in that

44. a shut-off valve (36) is provided to protect the function of the stroke simulator (WS) in case of a failure of the seal (D2) of the main cylinder (THZ) and to diagnose the function of the stroke simulator (WS); Braking system according to any one of claims 1 to 43, characterized in that

45. a mini hydraulic fluid reservoir (35) for continuously supplying hydraulic fluid to the ESP return pump (P) and / or for positioning the SK piston (10); A braking system according to any one of claims 1 to 44, characterized in that

46. an additional isolation valve (TV1) in the first brake circuit (BK1) to protect the function of the pressure supply unit (DV) in the event of a leak in the first brake circuit (BK1); A braking system according to any one of claims 1 to 45, characterized in that

47. said pressure supply (DV) is controlled in such a way that the pedal characteristic, determined in particular by the relative pedal force to the pedal stroke and by the stroke simulator, is maintained in the event of a fault or is not altered by other influences; A braking system according to any one of claims 1 to 46, characterized in that

48. In order to avoid the brake pedal (1) being blocked, a preload spring (41a) and / or a predetermined breaking point (2a11) is provided on the sensor plunger (2a1), so that in particular if the pedal stroke sensor (2a) becomes stuck, the brake pedal (1) does not interfere. A braking system according to any one of claims 1 to 47, characterized in that

49. the return of the pedal (1) is effected and / or assisted by means of at least one spring (18a, 18b) arranged parallel to or coaxial with the plunger (2a1, 2b1) of the pedal stroke sensor (2a, 2b); A braking system according to any one of claims 1 to 48.

50. an additional solenoid valve (MV) is provided or arranged between the intake valve (28) and the return line (R) to the storage vessel (VB) to protect the function of the pressure supply (DV) in case of leakage of the intake valve (28); A braking system according to any one of claims 1 to 49.

51. a redundant seal (D8.1) is arranged in parallel to at least one piston seal (D8) of the pressure supply (DV); a hydraulic flow path (53) arranged in the cylinder wall leads to the cylinder between the parallel arranged seals (D8, D8.1), the flow path connecting the inside of the cylinder of the pressure supply (DV) to a storage container (VB) directly or via a hydraulic line connected to the flow path; and a throttle (Dr8.1) is arranged in the hydraulic flow path (53) or in the hydraulic line. A braking system according to any one of claims 1 to 50.

52. an additional seal (D9) is arranged in the pressure supply (DV) in the region of the intermediate position of the piston (10), said additional seal (D9) serving to protect the function of the pressure supply (DV), in particular in the event of leakage of the intake valve (28); Braking system according to any one of claims 1 to 51, characterized in that

53. 53. A method for braking on slippery roads in the event of a malfunction of the electronic stability program ESP using a braking system according to any one of claims 1 to 52, wherein locking of the wheels of the front axle is prevented by means of a switching valve (TV1). A method characterized by:

54. the valve (TV1) is closed in the case of a II brake circuit division when the wheels of the front axle assigned to the first brake circuit (BK1) show a tendency to lock, in which case the brake pressure in the wheel brake cylinders acting on the rear axle assigned to the second brake circuit (BK2) is further increased by means of the pressure supply (DV) until the wheels of the rear axle also show a tendency to lock.

54. The method of claim 53.

55. After the pressure in the wheel brake cylinder of the rear axle has been increased, the pressure in the wheel brake cylinder of the front axle is further increased by briefly opening the valve TV1.

55. The method of claim 54.

56. In an X brake circuit division, the valve (TV1) is closed when the front wheels of the first brake circuit (BK1) show a tendency to lock, and the pressure in the second brake circuit (BK2) increases further when the valve (TV1) is closed until the rear wheels of the second brake circuit (BK2) show a tendency to lock.

56. The method of claim 55.

57. The switching valves (TV1, TV2) are incorporated into the ESP module (ESP) in place of the switching valves (USV1, USV2). A braking system according to any one of claims 1 to 56.

58. The switching valves (TV1, TV2) are used for ABS and blending, respectively, for each brake circuit. A braking system according to any one of claims 1 to 57.

59. Intake valves (EV) are used for wheel-specific ABS in the event of a malfunction of the ESP system. A braking system according to any one of claims 1 to 58.

60. The hydraulic medium is continuously replenished using the switching valves (TV1, TV2). A braking system according to any one of claims 1 to 59.

61. the X-Boost and ESP use redundant ECUs, in particular for special functions, which are connected to the vehicle electrical supply via at least two connections (S1, Sn), in particular for redundancy reasons, A braking system according to any one of claims 1 to 60.

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