Brake system

Abstract

To provide an improved brake system.SOLUTION: The present invention discloses a brake system including: a drive unit, in particular, a brake pedal 1; a first piston-cylinder unit THZ allowing brake circuits BK1, BK2 to receive a pressure medium through a valve device FV and including two pistons 12, 16, one piston 16 configured to be driven by the drive unit; a second piston-cylinder unit including an electric motor driving body 8, a transmission device 7, and at least one piston 10 for supplying the pressure medium through the valve device to the brake circuit BK1; and a motor pump unit ESP including valve devices HSV, USV, EV, AV for supplying the pressure medium to the brake circuit. The brake system further includes a hydraulic stroke simulator WS including a pressure chamber or an operation chamber 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 cars with autonomous driving (AD) places high demands on the brake system, 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 computing functions (ECU). So-called one-box and two-box systems are favored. The latter consists of an electric brake booster (BKV), the so-called e-booster and an ESP system. This provides redundancy for the generation of brake pressure etc. by an electric motor and an electronic control unit (ECU) for an e-booster and return pump with electric motor and ECU.

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

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

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

[0006] WO 2012 / 019802 (hereinafter variant C) shows a similar arrangement to WO 2011 / 098178 with a coaxial drive in which the electric motor acts on the HZ piston via gears and pistons. Here an auxiliary piston-cylinder unit is used which acts on a stroke simulator piston (WS). The pedal stroke is therefore independent of fade phenomena, brake circuit failures etc. However, it becomes very complicated and the structure becomes long.

[0007] DE 10 2009 033 499 (hereinafter also referred to as variant D) shows a brake booster (BKV) with a hydraulically actuated booster piston and a further ESP unit with an external pressure supply. This arrangement with four or five pistons and six solenoid valves (MV) is complex and also disadvantageous in terms of length. A non-hydraulic actuated 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 the pump ensures the braking function in autonomous mode as well as the assistance function using the vacuum BKV.

[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 a common pressure control for all four wheels and does not optimize the braking distance.

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

[0011] Known systems with e-booster and ESP have only one redundancy in 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 guaranteed 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 invention is based on the object of creating a braking system for use in automated driving operation (hereinafter AD) and / or electric / hybrid vehicles with increasingly powerful regenerative power (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 brake system for autonomous driving is created which meets not only the highest 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 ABS functionality 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 improvement is characterized in that the brake booster structure is cost-effective by having very few simple components with low precision requirements (e.g. valves with only open / close operations), the structure is very short and slim, and in particular allows constant pedal stroke characteristics together with powerful regeneration.

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

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

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

[0021] Furthermore, the invention achieves a compact design of the brake booster with a small box volume, which is very short and narrow, has many redundancies, e.g., for pressure generation, electrical supply, pump motor failure of the ESP unit, and also includes the ABS function with limited performance in case of ESP unit failure. In emergency driving without ESP, the ABS function should include at least individual regulation per axle ("select low" pressure regulation) to improve braking distance.

[0022] The installation space of the unit compartment is becoming smaller and smaller. The dimensions of the brake unit should therefore be as small as possible, in particular with regard to width and length. This compact construction 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 is described below together with a parallel-arranged pressure supply (hereinafter 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 therefore the ESP pump function does not influence 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 pressure supply DV of the X-Boost with the drive motor or engine only has to be designed for low mechanical loads and that the electric motor requires a low torque, for example 80-100 bar, compared to the maximum pressure of the ESP pump of about 200 bar. This allows the use of cost-efficient ball screw drives (KGT) or trapezoidal spindles with plastic nuts.

[0026] Secondly, the pump (ESP pump) can be designed in such a way that the pump motor is only loaded with a differential pressure of 200 bar-(80-100) bar (=100-120 bar). Conventional ESP pumps are loaded with a maximum pressure of, for example, 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 in the case of a quick actuation of the pedal, for example at 20 bar. This results either in a more rapid pressure increase to 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 a separate eccentric for each piston in the case of piston pumps.

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

[0030] Various solutions can be envisaged for the pedal stroke simulator. In the entire pressure range (150-200 bar), the pedal stroke simulator must have a good pedal stroke characteristic, for example with a flat characteristic curve up to 30 bar and then a gradual rise, without any influence, regardless of whether the X-boost or the ESP unit supplies the pressure. In the embodiment of the e-booster as a follower booster (variant A according to the prior art), the pedal force characteristic curve changes significantly on the transition from e-booster 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 operation of the ESP pump has no influence on the pedal characteristic, since the pedal is decoupled via the stroke simulator.

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

[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). If a plunger simulator is provided, 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 it on or off as required, but 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 hereby incorporated 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 resulting in 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 which drives the piston via a spindle. Both ball screw drives (KGT) and trapezoidal spindles with a nut can be used as transmissions. The latter are cheaper and quieter, but less efficient and self-locking. The latter has the advantage that in the case of engine failure, for example, in the pressure supply DV, the piston remains in a fixed position so that the brake pressure does not affect the brake circuit fluid volume.

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

[0039] The flow path to the piston stroke simulator can be closed by a solenoid valve (WA) to generate brake pressure at the so-called fallback level (RFE) by the pedal force acting on the main cylinder (HZ) as in the case of a pressure supply failure (DV). 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, with redundant power supplies, so that the fallback level (RFE) is only active when towing, and only for extreme loads in practice, e.g. when the vehicle transmission can be cut off. This gives more flexibility to the system and piston construction, e.g. 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 pads. This seal can create the required clearance, among other things, by means of deformation energy stored in the seal, which generates a return force that pulls the brake pads away from the brake disc (clearance or gap) as soon as pressure no longer builds up in the brake circuit. This is preferably possible with the present invention, because the separation has no effect on the brake pedal.

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

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

[0044] In this way, pedal failure I) can be avoided, because 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, for example in variants A and B, directly affect the pedal feel, so that 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 also of the wheel brakes II) is made possible by the solution according to the invention, because in the event of a failure 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 is considerably more freedom for per-axle or per-wheel control than in the solutions of the follower booster (variants A and B). For this reason, the inventive pressure control through piston stroke and motor current (DE 10 2005 018649 in the Applicant's patent) and pressure gradient regulation (DE 10 2005 055751 in the Applicant's patent) is used for a high degree of pressure control, which cannot be achieved by pulse width modulation (PWM) control of the valves of the ESP unit (these patents are hereby incorporated by reference in this respect).

[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 control (IV) is becoming more and more important due to the increasing hybridization and prevalence of electric vehicles. Brake pressure varies depending on the possible generator braking effect and the total braking effect requested by the driver. This is called brake pressure blending. Brake pressure blending can involve all wheel brakes (4-wheel blending), only one vehicle axle (2-wheel blending) or single wheel brakes individually. Brake pressure blending requires appropriate brake pressure control and valve control, which will be explained in detail in the drawing description.

[0048] The regenerative control (IV) according to the solution of the invention is exclusively implemented by piston stroke control of the pressure supply DV in the simplest solution (4-wheel blending). Depending on the retarding effect of the vehicle's generator or of 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 influence the pedal feel. This has considerable advantages, in particular 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 dampen the deceleration while maintaining the same pedal feel. This prior art requires an intervention in the ESP and a very complex control of the drain valve of the ESP unit. Furthermore, in the case of the solution according to the invention, it is possible to avoid various ESP variants for different brake circuit distributions (diagonal and parallel / brake circuits per axle, rear and front drives), because the control is exclusively performed by the piston, independent of the brake circuit distribution and the drive type. In particular, the following advantages of X-Boost are also brought about by regeneration.

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

[0051] Part of the solution according to the invention, in particular X-Boost, provides 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 XBoot provides the following benefits: Generator torque => precise brake pressure regulation even when simple point braking changes suddenly, - No perceptible noise, e.g. from the switching valve of the ESP unit, Blending throughout the vehicle deceleration range, Much simpler blending software 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 full hydraulic braking and vice versa; Changes in the wheel brakes acting on the non-driven 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 the pedal (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 volume 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 case of a system failure at the fallback level RFE, this results in a higher pedal force for the same pedal stroke in a braking system with a higher volume 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 amount of fluid in the brake circuit can be further increased against the brake fade phenomenon by continuing to deliver it with the DV. This additional amount 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 an embodiment according to DE 10 2005 018649 and DE 10 2005 055751 by the applicant, 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 as a function of the pedal stroke (these patents are hereby incorporated by reference in this respect). The pressure is measured in the ESP unit and is supplied by the pressure supply DV through the corresponding piston stroke. In the event of a pressure sensor failure, this pressure signal is not available. The failure of the pressure sensor is detected by the pressure supply DV through the evaluation of a 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, a current measurement of the DV motor can also be used instead of a pressure measurement. In general, it is also conceivable to use only a current measurement. With regard to the accuracy of the pressure increase and decrease, 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) by any selection, e.g. with a correction value due to the correlation between current and vehicle deceleration.

[0057] This concept has further possibilities for enhancing functionality and error safety through: a) Function A small accumulator, also called 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 suction 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 fault in brake circuit 1 (BK1). Elimination of the need for a shutoff valve (WA) in the stroke simulator, which also eliminates its possible errors. -Measures to prevent sensor operation. A 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 shutoff valve (36) for the hydraulic connection from the auxiliary piston chamber to the reservoir (VB). Redundant seals with diagnostic options for main cylinder (THZ) and pressure supply (DV). · Redundancy measures in the return line from the pressure supply (DV) to the storage vessel (VB) in case of failure of the suction valve (28), e.g. an additional shutoff valve (MV). · A partially redundant control unit (ECU) for reading and processing the sensor signals and controlling the FV and PD1 valves. 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 extremely high requirements regarding fail-operationality (FO) can also 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 match the low 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. The other module can be connected to a DC / DC converter or to a 48V vehicle electrical system or to another vehicle electrical system with 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 to a 12V battery and a DC / DC converter. The transmission of the pressure supply unit may have a self-locking trapezoidal spindle which performs an automatic locking operation in the event of a drive 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 underneath 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 off allows 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 the brake fluid has vapor bubbles 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 case of ESP failure can be achieved by introducing isolating 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 supplemented.

[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 description of the drawings]

[0061] Text description of the illustration image024.gif. [Figure 1] Shown is the full X-Boost system with ESP. [Diagram 2] The pedal characteristics are shown. [Diagram 3] The main components of the system are shown. [Figure 4] Showing an extended X-boost. [Figure 4a] Shows redundancy of valve FV to increase functional safety. [Diagram 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] Shown is a pressure supply with additional valving for increased functional safety. [Figure 7] Shown is a pressure supply with redundant seals for increased functional safety. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0062] FIG. 1 shows a schematic diagram of a brake system with a drive, in particular a brake pedal 1, a first piston-cylinder unit THZ that can be driven by means of the drive, a second piston-cylinder unit with electric drive and transmission (hereinafter X-boost or booster) and an ABS / ESP unit. The ABS / ESP unit is known, including the main components pump P with motor M, valves HSV1, HSV2, valves USV1, USV2, drain valves EV and AV assigned to the wheel brakes and a storage chamber (SpK). This system is described in many publications and patent applications. This system is already on the market as an e-booster and is mainly used in electric and hybrid vehicles, since the brake system is controlled in conjunction with the brake 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 automatic driving. The focus here is on redundancy of functions such as error safety, 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 in order to achieve a short overall length, also shown in FIG. 3.

[0063] The main cylinder HZ basically 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 operates 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 build-up 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 fade phenomena.

[0064] Normally, the valve FV is closed at the start of braking and the auxiliary piston HiKo acts on the stroke simulator WS. The function and variants of the stroke simulator WS are explained later. The auxiliary piston HiKo has two functions: one for normal operation and one for a fall-back level in case of 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 fall-back level in case of 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 activated simultaneously. Moreover, these sensors can be decoupled via an elastic element KWS, as described in DE 11 2011 103274 by the applicant, which is hereby incorporated by reference in this respect. The advantage is, on the one hand, that it detects that the auxiliary piston (HiKo) 16 is stopped, and, on the other hand, that the stroke difference between the sensors when the auxiliary piston (HiKo) 16 is stopped results in 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 of the THZ piston connected to a reservoir VB. It is well known that the brake circuit will fail if the main seal fails. This can be avoided by using a check valve RV and a throttle, used for venting, in the connecting line to VB. 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 stroke 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 combination of a WS piston and a spring. This combination gives 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 case of a very sudden release of the pedal. ab The throttle D is used to provide the desired regulated 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 at the fallback level (RFE). The intake volume of the stroke simulator WS does not influence the delivery 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 a failure of the X-boost. 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 comes from the BKV control, which controls the pressure from the pedal stroke 2a / 2b by means of a 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 with current measurement, the pressure control with current measurement is based on the P of the characteristic map. auf and P ab This requires recording of the pressure loss in the vehicle and, optionally, further improved by 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 a suction valve (SV) 28 that 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. Or it can be designed with a smaller volume (piston and stroke) by 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 is required, which is not shown in FIG. 1 (see FIG. 4). Pressure reduction P ab In case of a full liquid volume guarantee, the piston must move to its initial position with the breather hole open. 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, the piston of the DV moves accordingly. Normally, the X-boost pumps a volume into the brake circuit BK up to the cut-off limit of 80-120 bar. If a higher brake pressure is required for fade phenomena, the 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 that corresponds to a maximum pressure of e.g. 200 bar by ASR operation. With a suitable pump design, e.g. a two-circuit gear pump or a separate eccentric for the pump piston, 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(=200bar)-XBoost(=80-120bar)=80-120bar, so that only 80-120bar, and not 200bar, is required for the design of the ESP pump, so that a correspondingly smaller ESP motor is sufficient. Furthermore, with this design of the pump, it is possible to arrange the E-Boost and ESP pumps in parallel already from the low pressure range, for example from 20bar, for rapid deceleration. This therefore means that P auf This gives the potential for faster (TTL) and smaller X-Boost motors.

[0072] If during the braking process the pressure supply DV fails, the DV piston is pushed back under the pressure in the brake circuit BK1, so that the brake pressure can be completely reduced. If an automatic 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 breather hole of the Hiko to the reservoir VB.

[0073] In the unlikely event of a failure of the electronic control or regulation units (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 the brake pressure. The brake pressure in the main cylinder HZ moves the SK piston and the pressure in the brake circuit BK2 increases. To prevent this volume from leaking out through the open breather hole in the DV, a normally closed solenoid valve PD1 is provided (not shown in FIG. 1, see FIG. 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 and 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, then there is 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 closing the four valves EV in succession, provided that the leak is not in the unit, for example in a wheel cylinder. For example, if the leak is in the brake circuit BK1, the valve EV of the brake circuit BK1 is closed. The pressure supply DV then acts on the brake circuit BK2 via the SK piston (similar to the explanation of the diagnostic logic in the patent applications DE10 2015 106 089.2 and DE10 2016 112 971.2, which are cited here). If this does not work, then the pressure supply DV is not functioning and neither is the brake booster BKV. In this case, the ESP pump functions as the brake booster BKV in the brake circuit BK2.

[0076] The SK piston (12) serves as an important safety gate together with the separation of the brake circuits BK1 and BK2, so that a malfunction of the brake circuit BK2 does not cause a malfunction in the pressure supply part DV.

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

[0078] ABS function in the event of pump / motor failure in ESP ABS pressure reduction signal P ab If this occurs, the DV control modifies 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 the brake circuit is closed, the pressure in the other brake circuit is reduced by closing the valve USV.ab This can be optimized without parallel check valves RV and with individual wheel adjustment by adjusting valves EV, as explained in patent application DE11 2009 004636 (E112), which is incorporated herein by reference.

[0080] Figure 2 shows the pedal stroke S p 1 shows the pedal characteristic over a range of 100-200 bar. 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 actions. This process can be implemented via a pedal return spring. A more progressive portion B then acts up to the blocking limit, followed by a higher pressure region, for example in the case of fade phenomena. In this case, the driver also feels that there has been a change in the brake system.

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

[0082] A modified pedal characteristic with a larger pedal travel is obtained by decreasing the amplification factor of the X-Boost, 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 In the case of ABS function, the preload provided by the DV is constantly changed. This preload acts on plunger 16a and can be felt as small force variations acting on the associated pedal plunger 3. This is desired by many brake experts. This preload can be varied by briefly increasing the intake pressure at the beginning of the 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 defines the ratio of generator brake torque (electrical brake torque) and brake pressure (hydraulic brake torque) for the required vehicle deceleration. Both quantities can be varied arbitrarily during deceleration. Regeneration can apply a. the same brake pressure on all four wheel cylinders, b. axle-by-axle brake pressure on the vehicle axles, or c. wheel-by-wheel brake pressure on 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 forces. The required total 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 pressure generation 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 a corresponding movement of the DV piston. A pressure sensor of the ESP is used for feedback of the piston movement. In this way, the pressure supply DV can set the target pressure both during pressure increase and during pressure reduction. Due to the high-precision position control of the DV piston, the pressure setting is very accurate. Pressure control by the DV is carried out according to the P auf and P ab It is extremely quiet because no valves need to be operated for the ESP unit. No valves and pumps that cause noise in the ESP unit are required. Furthermore, this regenerative control can be used uniformly for front-wheel, rear-wheel and all-wheel drive vehicles, and for X and II brake circuit splits. The pedal characteristics remain unchanged.

[0088] In case b. with per-axle brake pressure at the vehicle axles, the valves and pump motors of the ESP may also have 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 first 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 (for vehicle stabilization 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 an appropriate PWM control of the EV of the non-driven axle. If the hydraulic target brake force has to 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 done by suitable control of the pressure supply DV at the driven axle, where the valve EV is open. Pressure reduction at the non-driven axle is done by the (possibly clocked) opening of the valve AV together with control of the ESP pump and pulse width modulation (PWM) control of the valve (EV) of the non-driven axle. The PWM control of the valve EV is intended to prevent an excessive drop in pressure 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, the valve opens at the driven axle and the valves EV, AV close at the driven axle. The AV of the driven axle always remains closed 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 the case of c., with brake pressure per wheel on all four cylinders, the ESP valves and pump motors may also have to be controlled. The control of the pressure supply DV, the valves and the ESP pump is performed in a similar manner to 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 cylinder wipes the thin film of water off the brake discs during rainfall, so that maximum braking effect is achieved immediately on the next braking.

[0091] In these assistance functions, the pressure supply DV can generate 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. 1-3 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 for feedback of the piston movement. As with regeneration, the brake pressure setting is very accurate due to the precise position control of the DV piston. Pressure control by the pressure supply DV is also very quiet in the 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 including the pedal joint or main cylinder HZ The motor 8 including the housing pressure supply l(DV) 25, advantageously arranged parallel to the main cylinder (also can 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 HZ and HCU, facing inwards towards the centre of the unit to allow the corresponding connectors to be brought 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 a storage container (VB) and to electrical connections e of the sensors, solenoid valves and motor. The control unit (ECU) has a partially redundant partial control unit (ECU2) for actuating safety-related components such as the FV valve with an optional independent 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 analogue evaluation of the height of the brake fluid in the reservoir (VB) and aids in the diagnosis of the system. For example, if the pressure increases by the pressure supply (DV) and then decreases again, resulting in a lower height, then there is 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 conduction to the body (38) and to the spray wall (39). At peak load, the outside temperature of the control unit (ECU) can be 120°C and 60°C at the spray wall (39), while the maximum temperature of the following passenger compartment (39a) is 30°C due to cooling. The aluminum plate allows a significant temperature reduction to be achieved at the MOSFETs (33a). The tabs of the MOSFETs (33a) are transferred 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, in particular due to the Arrhenius law.

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

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

[0099] As already explained in FIG. 1, in order to deliver a subsequent amount of brake fluid to the brake circuit 1 (BK1), by pulling back the DV piston (10), a volume is sucked in from the reservoir (VB) via the intake valve (28). For this, the valve PD1 is closed and the DV piston (10) moves back. The DV piston (10) sucks in brake fluid from the reservoir (VB) via the intake valve (28) and the hydraulic connection (R). Once the re-delivery volume has been sucked into the DV chamber (10), the valve PD1 is opened and the DV piston (10) moves forward. The DV piston (10) pushes the re-delivery volume into the brake circuit 1 (BK1). During the intake phase of the pressure supply (DV), a vacuum is created in the brake circuit 1 (BK1) when the ESP return pump (P, FIG. 1) actively builds up pressure in the wheel brake cylinders. In this case, the volume delivery of the ESP return pump (P, FIG. 1) stalls and possibly the ESP return pump (P, FIG. 1) in the brake circuit 1 (BK1) sucks in a make-up volume through the seal D4 and the make-up hole (47) of 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 the brake circuit 1 (BK1) can be provided to prevent this stall in the volume delivery or this backward movement of the SK piston from occurring. During the intake phase of the pressure supply (DV), the mini reservoir (35) supplies the ESP return pump (P, FIG. 1) with a volume. The required capacity of the mini-reservoir (35) depends on the duration of the suction phase and on the volume delivery capability of the ESP return pump (P, FIG. 1).

[0100] To increase the availability of X-boost and to check the functioning of the stroke simulator (WS), a shutoff valve (36) can be provided in the hydraulic connection (44) between the auxiliary piston's fill hole (42) and the reservoir (VB). For example, in case of a leak in the auxiliary piston seal (D2), the shutoff valve (36) can be closed, thus avoiding a failure of the stroke simulator (WS).

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

[0102] In case of stroke simulator (WS) failure, valve FV is normally open even if, for example, valve FV has a leak. When actuating the brake pedal (1), the driver pushes volume from the auxiliary piston chamber (43) into the ESP return pump (P, FIG. 1) in brake circuit 1 (BK1). The ESP can then apply pressure to the cylinders by its active braking function depending on the position of the pedal (1). The pedal stroke is significantly longer to achieve a certain 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 the pedal force with intact X-boost function. For this, the pressure in brake circuit 1 (BK1) and therefore also in the auxiliary piston chamber (43) is adjusted by the pressure supply (DV) to reproduce the standard pedal force / pedal stroke characteristic of the stroke simulator as intended by the vehicle manufacturer. If this reproduction is successful, the driver will not be surprised by longer pedal strokes and his behavior will become more predictable. In this example, the stroke simulator (WS) functions as normal, but the brake pressure build-up in the 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 shutoff valve (36) is used. However, when using the active braking function of the ESP, 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 whole system of X-Boost with ESP. X-Boost with THZ, valves 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 refill hole (50) for the auxiliary piston (16), together with the throttled discharge (Dr2.1) to the reservoir (VB). The throttle Dr2.1 is designed narrow so that in case of a leak in the seal (D2), only a small leakage flow can pass from the auxiliary piston chamber (43) through the refill hole (50) to the reservoir (VB), but this only results in a slow and short non-interfering extension of the stroke of the brake pedal (1) during the limited braking time. This leakage flow is detected by the pedal stroke sensors (2a, 2b) in a plausibility check, but also by the system diagnostics described in E144.

[0105] As a redundancy for the seal D4, a further seal D4.1 is also shown. If this seal D4.1 fails, then the brake circuit BK1 and the pressure supply DV also fail. In this case, the ESP unit performs the work of the pressure supply, i.e. the pressure increase. This can be avoided by the combination of seals D4, D4.1 and a fill hole 52, whose connection to the storage container is provided with a throttle Dr4.1 as well as an auxiliary piston (HiKo) 16. A failure of this seal 4.1, with a small leakage flow through the throttle D44.1, does not result in a failure of the brake circuit BK1 or the pressure supply DV. Furthermore, a diagnosis of the seal D4.1 is preferably possible with this arrangement. Alternatively, a normally open valve TV can be provided in the connection to the storage container. This valve can be closed in the event of a leak in the seal D4 or the seal D5.

[0106] For seal D3, a redundant seal D3.1 can also be used with the refill hole 51 and the throttle Dr3.1. Furthermore, the stroke simulator seal D6 can also be equipped redundantly with seal D6.1, refill 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 safety level against fail operational (FO). This seal configuration can also be used with a one-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 brake fluid can be lost to the environment due to a leak. As a countermeasure, the ESP can close both intake valves (EV) of brake circuit 1 (BK1). If a fault 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 does not detect a leak in brake circuit 1 (BK1), brake fluid would be constantly lost. For this situation, an isolation 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 fault, the valve TV1 can be used to provide optimized braking distances on slippery roads. For legal reasons, when braking on slippery roads, the wheels of the front axle must lock before the wheels of the rear axle. This results in the wheels of the rear axle being under-braked when the vehicle decelerates slightly. In the case of X-Boost, the valve TV1 can be closed if the wheels of the front axle in brake circuit 1 (BK1) of the II brake circuit division tend 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 by means of the pressure supply (DV) of X-Boost until the wheels of the rear axle also tend to lock. This means that almost maximum deceleration can be achieved on slippery roads. Naturally, it is also possible to further increase the pressure in the wheel brake cylinders of the front axle by briefly opening the valve TV1 after increasing the pressure in the wheel brake cylinders of the rear axle. In the case of an X brake circuit division, the valve TV1 can be closed if the front wheels of brake circuit 1 (BK1) tend to lock. After the valve TV1 is closed, the pressure in brake circuit 2 (BK2) can be increased further until the rear wheels of brake circuit 2 (BK2) tend to lock. Since the pressure in brake circuit 1 (BK1) is low, the vehicle is still stable enough, whereas 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 the brake circuit 2 (BK2). As with the 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) are suppressed by refilling when the SK piston (12) of the main cylinder (THZ) stops. In this case, further pressure build-up is only possible in brake circuit 1 (BK1). The stopping of the SK piston (12) is recognizable because the pressure in brake circuit 1 (BK1) then increases twice as quickly with the increase in volume in brake circuit 1 (BK1). When the SK piston stops, the separation valves TV1, TV2 are accordingly closed 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) possibly retracts to the initial position, transferring the 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) leading to the reservoir (VB), draws the volume from the reservoir (VB) through the seal D5 of the SK piston (12) and via the hole 47 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 the front area, and when the piston (10) of the pressure supply (DV) retracts, no volume is 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 separation 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 both the pressure in brake circuit 1 (BK1) and the pressure in brake circuit 2 (BK2) can become even higher. The pressure supply (DV) is preferably controlled using a pressure reference value of X-boost. 2. The isolating 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 leads to cost and weight savings. 3. As already explained, in case of ESP failure, the ABS function of brake circuit 1 (BK1) can be fulfilled by means of the separation valve TV1 and the pressure supply (DV). With the separation valve TV2, the ABS function can be fulfilled both in brake circuit 1 (BK1) and in brake circuit 2 (BK2). With that, four intake valves (EV) can be used, if each wheel of the brake circuit is ABS controlled separately. This is a great advantage, especially with regard to the diagonal division of the brake circuits. Here, the control process is not shown. The pressure control is always performed by the pressure supply (DV).

[0110] A partially redundant control unit (partially redundant ESP-ECU) instead of the main control unit of the ESP (ESP-ECU) can be used in the ESP for the control of the intake valve (EV) and also the separation valves (TV1, TV2). The functions preferably include the processing of the sensor signals of the speed sensor and also the yaw speed 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 the 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 of X-boost (X-boost ECU) can also have a partially redundant part (partially redundant X-boost_ECU), which preferably supplies the following components shown with "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 envisaged to perform the work of a partially redundant control unit of ESP (partially redundant ESP-ECU), since the emergency function of ABS must also be provided in the partially redundant control unit of 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 for increasing safety using the example of a pedal stroke sensor (2a). In the unlikely event that the sensor 2a is stuck when the brake pedal (1) is actuated, the pedal cannot be moved and the brakes do not function. A preload spring (41a) is provided inside the sensor (2a), whose plunger (2a1) can move against the preload force of the spring (41a) when the sensor (2a) is blocked. Errors can be determined by a plausibility check of the signals of the two pedal stroke sensors (2a, 2b) with elastic members (KWS). Two redundant return springs 18a, 18b, which come into action when the brake pedal (1) is actuated, replace the center return spring 18. If the sensor 2a is stuck when the brake pedal (1) is released, it is not possible to fully release the brake pedal (1). As a result, the vehicle remains continuously braked against the driver's will. For this situation, a notch (2a11) is provided in the plunger 2a1, which is dimensioned in such a way 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 in order 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) instead of 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): The DV piston (10) of the pressure supply (DV) is provided with an additional suction hole (46) and an additional seal (D9) of the DV piston (10) at the intermediate position. 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, the failure of the suction valve (28) has no effect on the pressure increase function of the pressure supply (DV). When the DV piston (10) retracts to the intermediate position, it only sucks in the volume from the reservoir (VB) via the sleeve (D9), the suction hole (46), the suction valve (28) and the return line (R), but with two pressure losses (seal D9 and suction valve 28). Only before the intermediate position of the DV piston (10) can the suction valve (28) function again. Since the suction function only works at the next transfer, no further disadvantages can be found. Further transfer is necessary if a supplementary volume is required for high pressure levels or to compensate for insufficient ventilation.

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

[0119] From the above, 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 Plunger 2a1 notch of pedal stroke sensor 2a 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 Pressure chamber or working chamber of DV 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 Body 39 Spray Wall 39a cabin 40 Motor Sensor 41a Pedal stroke sensor 2a preload spring 41b Preload spring of pedal stroke sensor 2b 42 Supply 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 Supply hole for auxiliary piston (16) 51 Supply 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 Throttling Orifice DV Pressure Supply DG Pressure Transducer Dr2.1~Dr6.1, Dr8.1 Throttling in return flow to storage vessel (VB) D1 Seal 1 of auxiliary piston (16) D2 Seal 2 of auxiliary piston (16) 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) Additional seal for D9 DV piston (10) 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 Solenoid valve (normally closed) to the 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 Solenoid valve (normally open) 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, can be driven by means of the drive device; a second piston-cylinder unit having an electric drive, - a transmission device, at least one piston (pressure supply DV) for supplying pressure medium via a valve arrangement 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 brake 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 a 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 a second working chamber to which at least one brake circuit is connected, the brake circuits being connected to the pressure chamber or working chamber of the second piston-cylinder unit (pressure supply DV) via hydraulic lines, 2. The brake system of claim 1 .

3. the first piston-cylinder unit has a partition wall with a seal for a through plunger (16a) for forming 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. A brake system as claimed in claim 3, characterized in that

5. the plunger (16a) comprises a cross-sectional area significantly smaller than the piston of the first piston-cylinder unit, in particular a cross-sectional area five times 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 brake system as claimed in claim 4, characterized in that

6. the stroke simulator being in particular a piston simulator (WS) connected to the working chamber of the auxiliary piston via a hydraulic connection line, or / and 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 the second piston-cylinder unit (DV) and the motor of the 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, the pressure supply unit generating a preload for each connection, 9. Brake according to claim 8, characterized in that

10. said ESP pump (P) being 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 in particular implemented 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 certain pressure range, in particular up to the wheel lock limit of 80-100 bar, and the motor-pump unit (ABS / ESP) is used for pressure generation 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 ensure that the pump motor of the ABS / ESP unit has a low maximum torque (p ｍａｘ，ＥＳＰ = Maximum pressure system p ｍａｘ -p ｖｏｒ，ＤＶ ) to be designed assuming the eccentric piston of the piston pump / step piston pump of the ESP unit; A brake 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 lower power output than the required maximum, in particular for 50% of the respective maximum, and the preload of the pressure supply DV is used in the eccentric pump, effectively in parallel, 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 up to 70-90 bar and for even higher pressure ranges >70 to 90 bar, the motor-pump unit (ABS / ESP) and the pressure supply DV for further pressure increase operate in series simultaneously, 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 brake system of claim 13.

16. The second piston-cylinder unit (pressure supply DV) is adapted to ensure that the pump motor of the ABS / ESP unit has a low maximum torque (p ｍａｘ，ＥＳＰ = Maximum pressure system p ｍａｘ -p ｖｏｒ，ＤＶ ) to be designed assuming the above-mentioned eccentric piston of the piston pump / stage piston pump of the ABS / ESP unit.

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, e.g. in a rapid pedal movement, to achieve, for example, a rapid pressure increase or a reduction in the power of the motor of the second piston-cylinder unit (pressure supply DV); A braking system according to any one of the preceding claims.

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. A braking system according to any one of the preceding claims.

19. Using the 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 to perform diagnostics. A braking system according to any one of the preceding claims.

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; A braking system according to any one of the preceding claims.

22. a stroke simulator, and a switching valve (WA) is disposed upstream of the stroke simulator to turn the stroke simulator on and off as required; A braking system according to any one of the preceding claims.

23. Only a plunger simulator (16a) is provided, a control pressure acting on said plunger depending on the pedal stroke, A braking system according to any one of the preceding claims.

24. the pistons of the first piston-cylinder unit (main cylinder) have different diameters, and in particular the auxiliary piston (16) is dimensioned smaller 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 other 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 the preceding claims.

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.

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 (HiKo, SK) can be driven by means of the drive device; a second piston-cylinder unit having an electric drive, - a transmission device, at least one piston (pressure supply DV) for supplying pressure medium via a valve arrangement 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 brake system having 4-wheel blending is used for regenerative 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 the preceding claims.

28. 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 can be driven by means of the drive device; a second piston-cylinder unit having an electric drive, - a transmission device, at least one piston (pressure supply DV) for supplying pressure medium via a valve arrangement 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 brake 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. A braking system, in particular according to any one of the preceding claims.

29. the transmission of the pressure supply (DC) includes a self-locking trapezoidal spindle, the self-locking being activated in the event of failure of the driver, A braking system according to any one of the preceding claims.

30. The valve (FV) is controlled by pulse width modulation (PWM) to generate force feedback to the brake pedal (tactile feedback with ABS). A braking system according to any one of the preceding claims.

31. The active return action of the brake pads is achieved by means of 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 the preceding claims.

32. a stroke simulator, 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 the preceding claims.

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

33. A braking system according to 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 brake system according to any one of claims 32 to 34.

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

38. 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 can be driven by means of the drive device; a second piston-cylinder unit having an electric drive, - a transmission device, at least one piston (pressure supply DV) for supplying pressure medium via a valve arrangement 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 brake system having the second piston (SK, 12) of the first piston-cylinder unit (main cylinder) has, in addition to the flow passage (breather hole) of the line to the reservoir (VB) provided with two seals (D4, D5), a further seal (4.1) and a further flow 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, characterized in that (Figure 5)

39. A redundant seal (D2.1, D3.1) is arranged 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 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 vessel (VB) directly or via a hydraulic line connected to the flow paths, and a throttle (Dr2.1, Dr3.1) is arranged in the hydraulic flow paths (50, 51) or in the hydraulic line, A braking system according to any one of the preceding claims.

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), and between the parallel-arranged seals (D6, D6.1), a hydraulic flow passage (53) arranged in the cylinder wall or in the piston leads to the cylinder, the flow passage connecting 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), or to a non-pressure area of ​​the stroke simulator (WS), or to the outside, and a throttle (Dr6.1) is arranged in the flow passage or the hydraulic line. A braking system according to any one of the preceding claims.

41. a height sensor (33, 34) is 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 the preceding claims.

42. Heat is dissipated from the printed circuit board (PCB) to the housing and end walls (39) of the main cylinder (THZ) using a thermal conductor (37). A braking system according to any one of the preceding claims.

43. a redundant isolation valve (FVred) is disposed in series with said valve (FV) in the hydraulic line so as to enable selective isolation of said hydraulic line by one of said two valves (FV, FVred); A braking system according to any one of the preceding claims.

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). A braking system according to any one of the preceding claims.

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 the preceding claims.

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 the preceding claims.

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 the preceding claims.

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

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

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) in order 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 the preceding claims.

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

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 said function of the pressure supply (DV) in particular in the event of leakage of the intake valve (28); A braking system according to any one of the preceding claims.

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

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 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) as a replacement for the switching valves (USV1, USV2). A braking system according to any one of the preceding claims.

58. The switching valves (TV1, TV2) are used in particular for ABS and blending, separately for each brake circuit. A braking system according to any one of the preceding claims.

59. The intake valve (EV) is used for wheel-specific ABS in case of a malfunction of the ESP system. A braking system according to any one of the preceding claims.

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

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 the preceding claims.

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