WO2014154435A1

WO2014154435A1 - Brake system for a vehicle and a method for operating the brake system

Info

Publication number: WO2014154435A1
Application number: PCT/EP2014/053783
Authority: WO
Inventors: Urs Bauer; Bertram Foitzik; Suekrue SENOL; Dagobert Masur; Otmar Bussmann; Matthias Kistner
Original assignee: Robert Bosch Gmbh
Priority date: 2013-03-28
Filing date: 2014-02-27
Publication date: 2014-10-02
Also published as: DE102013205639A1

Abstract

The invention relates to a brake system for a vehicle, comprising a brake master cylinder with at least one pre-filling annular chamber which is configured as a second independent volume, wherein the brake master cylinder has at least two surfaces which can be coupled fluidically to one another and act hydraulically on a hydraulic fluid which is situated in the brake master cylinder; a hydraulic fluid reservoir which is coupled fluidically to the brake master cylinder; at least one first and one second brake circuit which firstly are coupled in each case fluidically to chambers of the brake master cylinder, and secondly are coupled fluidically in each case to wheel brake cylinders which generate braking torque, wherein the wheel brake cylinders are coupled to wheels of the vehicle, wherein in each case normally open switchover valves are arranged in the first brake circuit and in the second brake circuit; and optionally a parallel fluid line which is coupled fluidically to the second brake circuit at one end and is coupled fluidically to the pre-filling annular chamber at another end, wherein a non-return valve is arranged in the parallel fluid line, which non-return valve can be opened fluidically in the direction of the second brake circuit, and therefore additionally supplies the second brake circuit with hydraulic fluid upon actuation of the brake master cylinder.

Description

Description Title Brake system for a vehicle and a method for operating the brake system

The invention relates to a brake system for a vehicle and to a method for operating the brake system.

State of the art

WO 2009/121645 A1 describes a hydraulic vehicle brake system. The master cylinder of the hydraulic vehicle brake system includes a first pressure chamber and a second pressure chamber. In addition, the master cylinder at an extending to the brake pedal end an integrated Pedalwegsimulator 22, which is filled with brake fluid volume via a simulator valve with a brake fluid reservoir is connected to the brake fluid fillable volume of the pedal travel simulator and the adjacent first pressure chamber of a trained as a stepped piston Rod and simulator pistons limited.

Furthermore, a brake system of the "brake-by-wire" type is disclosed in DE 10 201 1 006 327 A1, comprising a master brake cylinder with two pistons displaceably arranged therein, one piston acting as a stepped piston with at least two hydraulic action surfaces of different sizes is formed, which results in a fillable with hydraulic fluid or brake fluid ring volume due to the steps piston shape. In the "brake-by-wire" mode, when the master cylinder is operated by the driver, the smaller effective area is effective to generate a braking torque on the vehicle wheels, and in a fallback level, ie when there is a malfunction to operate the brake system, the larger effective area, with a switch from the smaller effective area to the larger effective area in response to a hydraulic pressure in a pressure chamber in the master cylinder or the pedal force is applied.

In foreign-force brake systems, it is possible to design the declining plane independently of the hydraulic fluid volume to be delivered during operation by decoupling the pedal stroke and the pedal force during operation. In general, the hydraulic effective area for such a fallback level is determined by the volume of the brake system taking into account some operating conditions.

Disclosure of the invention

The invention provides a braking system for a vehicle with the features of claim 1 and a method for operating the brake system with the features of claim 11.

Advantages of the invention

The invention provides to operate a brake system so that in a partial failure or a complete failure, such as a failure and / or malfunction of the integrated braking system, a direct penetration of the driver on two hydraulically effective surfaces can be coupled. By skillful coupling, i. By switching on one of the surfaces until a certain pressure is reached, the effects of operating conditions to be considered can be reduced, and it is thus possible to achieve greater pressures and thus greater delays with a given force.

By this measure, the recoverable in a mechanical fallback delay can be significantly increased without affecting the pedal travel by operating conditions too disadvantageous.

In a further advantageous embodiment, it is proposed to feed the additionally displaced volume in more than just one brake circuit. In the figures 3 to 6 diagrams are shown, in each of which a pedal travel (in mm) over a wheel pressure (in bar) is shown, which will be explained in more detail below, how much by means of the brake fluid transfer in the two brake circuits and present brake pressure during the fallback level is steigerbar.

BRIEF DESCRIPTION OF THE DRAWINGS In the following, the invention is explained by means of embodiments in conjunction with the figures, in which:

FIG. 1 shows a schematic hydraulic circuit diagram of a brake system according to a first embodiment of the invention;

Figure 2 shows a schematic hydraulic circuit diagram of a brake system according to a second embodiment of the invention;

FIG. 3 shows a diagram of the wheel pressure in brake circuit 2 as a function of the pedal travel;

FIG. 4 shows a diagram of the wheel pressure in brake circuit 1 as a function of the pedal travel;

FIG. 5 shows a diagram of the wheel pressure in brake circuit 1 at 2 cm ³ air in both brake circuits as a function of the pedal travel; FIG. 6 shows a diagram of the wheel pressure in brake circuit 2 at 2 cm ^{3 of} air in both brake circuits as a function of the pedal travel; FIG. 7 shows a detailed view of an exemplary embodiment of a

Master brake cylinder including some essential components; Figure 8 is a detail view of another exemplary embodiment of a master cylinder including some essential components;

FIG. 9 is a detail view of yet another exemplary embodiment of a master cylinder including some essential components;

Figure 10 is a detail view of yet another exemplary embodiment of a master cylinder including some essential components; and

Figures 1 1 a to 1 1 c further schematically illustrated in cross-sectional view exemplary embodiments of only a portion of the master cylinder with respect to the combination of hydraulically effective surfaces on the piston or at several

Piston.

1 shows a schematic representation of a hydraulic circuit diagram of a first embodiment of a brake system 10 according to the invention, wherein essential components for operating the brake system 10 are accommodated in a unit marked with reference numeral 11 and indicated by dotted lines.

The above-mentioned approach with an annular piston forming a stepped piston 45, the operation of which will be described in more detail below, shifts at limited, low pressure in the annular volume piston chamber and one with The additional amount increases the achievable during full braking in the mechanical fallback level brake pressure in the first brake circuit 100 and thus the maximum possible vehicle deceleration.

Furthermore, this effect compensates for any air bubbles contained in the first brake circuit 100, which allows a higher maximum brake pressure in the fallback level, and thus a relatively shorter stopping distance of the vehicle. The additional volume also improves the braking behavior from pressureless

Brake condition by faster overcoming of a so-called dead volume in the first brake circuit 100. This known principle corresponds to the designated in Figure 1 by reference numeral 15 hydraulic path or fluid line with check valve 20th

A variant of the invention is to extend the above-described benefits by duplication of this fluid line 15 to a second brake circuit 200, whereby the vehicle braking behavior is further improved in a mechanical fallback. However, the brake system may also be designed such that a hydraulic fluid supply in only one of the brake circuits is feasible.

According to FIG. 1, the two pressure chambers 31, 32 of a conventional master cylinder 30 are preceded by a primary chamber or prefilling annular chamber 40 which is variable in volume by the stepped piston 45 with one (46) of the two hydraulically active surfaces 46 and 47, as explained below becomes. With the stepped piston 45, a brake input element 48 is coupled in a known manner, which is pivotable about a point 49. During normal operation (ie by-wire), the chamber 40 is short-circuited to a brake fluid (hydraulic fluid) reservoir 50 by triggering a (normally closed) solenoid valve 35. The timing of this control can be shifted in time when detected fast braking (eg emergency braking) to the rear to improve the pressure build-up dynamics in this case. In the "mechanical fallback mode" operating mode, the solenoid valve 35 remains closed (since as a rule not energized).

Inflow into the brake circuits 100 and 200 and reflux into the reservoir 50 are controlled by the closing pressures of check valves 210, 1 10, 55. Check valve 55 defines the maximum allowable pressure in the annular piston volume 40 (pressure relief), while the check valves 210, 110 in the brake circuits 100 and 200 define a minimum pressure difference between the brake circuits 100, 200 and the annular piston volume 40.

If the pressure in the annular piston volume 40 exceeds this pressure threshold, brake fluid flows from the annular piston region 40 into the brake circuits 100, 200. This state remains until either the pressure threshold has fallen below the brake circuit pressures or until the maximum pressure in the piston chamber 40 predetermined by the check valve 35 is exceeded , The described principle of action has hitherto been used only in brake circuit 100. By implementing a hydraulic parallel path 1 15, the effect is also used in brake circuit 200. The achievable maximum pressure increases compared to a standard master cylinder without an annular piston and a ring piston effect used only in a single circuit are shown in the diagrams in FIGS. 3 to 6.

For the sake of completeness, it should be mentioned at this point that switching valves 105, 205 are arranged in each case in the fluid lines 100, 200 (normally open) in a known manner, which direct penetration (ie supply of hydraulic fluid) to a shortly explained below Allow wheel modulation 300.

In Figure 1, a generally known as wheel modulation arrangement is designated by reference numeral 300, wherein the wheel modulation 300 (not shown here) vehicle wheels, these associated wheel brake cylinder and on and Exhaust valves includes, whose functions are known in the art and therefore should not be explained here for reasons of brevity.

Furthermore, in FIG. 1, reference numeral 400 denotes an actuator which, in the example shown in FIG. 1, should be capable of being operated electrohydraulically, i. for example, via an electric motor marked "M". The actuator 400 is supplied via a fluid line 425 from the reservoir 50 with hydraulic fluid. The electric motor M can be controlled in such a way that it can displace a piston 405 back and forth in a housing via a forward or reverse drive 415 in order to supply hydraulic fluid located in a volume 410 z. To compress, i. pressurized so as to transfer hydraulic fluid into the wheel modulation 300 via fluid lines 430, 440 at feed connections 450, 460 (for example as ESP function), independently of actuation of the master cylinder 30. As is known, in the fluid lines 430, 440 each switching valves 470, 480 with it (ie seen from the actuator 400) filter means 475, 485 arranged, as well as at other locations of the brake system 10, but what should not be discussed in more detail, since this is assumed to be known. For the sake of completeness, it should be mentioned that pressure sensors are arranged at different locations of the brake system, but their function should also be known to the person skilled in the art. By way of example, the pressure sensor marked 500 in FIG. 1 is listed at the end of the fluid line 440.

Furthermore, for the sake of completeness, a pedal feel simulator device 600 is shown in FIG. 1 with the reference number 600, comprising a pressure accumulator 605, a switching valve 610 and a by-pass fluid line 615 with a check valve 210. Parallel to this, a switching valve 620 can be arranged , It should be emphasized, however, that the pedal feel simulator device 600 is known from the prior art and may optionally be arranged in the illustrated embodiment in FIG.

FIG. 2 shows a further embodiment of the brake system 10, wherein it should be noted that with reference to FIG. relate and not all components shown in Figure 2 are provided with reference numerals, if this is not necessary.

The difference between the embodiment of the brake system 10 shown in FIG. 2 and the embodiment shown in FIG. 1 is that a fluid line 700, which is fluidically situated between the fluid line 425 and

Vorbefüllungsringkammer 40 is coupled, a throttle 710 is arranged to increase a flow resistance of the hydraulic fluid to the reservoir 50. Thus, it is ensured that a hydraulic fluid pressure accumulating in front of the wheel module 300 is maintained as long as possible, or in other words, that a positive pressure difference between the pre-fill ring chamber 40 and the pressure applied to the wheel modulation 300 is maintained as long as possible is obtained, because otherwise (located in the wheel modulation 300 and thus not visible) wheel brake cylinder for generating braking torque are not supplied with hydraulic fluid accordingly.

It should be understood that the throttle 710 may additionally be located in the brake system 10, but need not necessarily be located in accordance with the principle of the present disclosure.

Figures 3 to 6 respectively show diagrams in which curves (for distinction each marked with only a fine continuous curve = "without supply of hydraulic fluid", a curve with a fine continuous line and points = "fed into a brake circuit" and a curve with fine continuous line and short thick bars along this curve = "with feed into both brake circuits") are plotted with respect to a wheel pressure of a brake circuit as a function of the brake pedal travel.

As can be seen in FIGS. 3 and 4, the maximum pressures achievable without and with feed into the brake circuits (see in each case the right-hand side in the diagram) differ only insignificantly from one another, ie in the illustrated examples the maximum pressures are somewhat below 100 bar. Figures 5 and 6 show comparable diagrams, but with about 2 cm ^{3 of} trapped air in both brake circuits.

It can now be seen that an injection into one and / or both brake circuits in each case has a significantly increased end maximum pressure (see each right side in the diagrams in Figures 5 and 6) with respect to the case without feed result, and Thus, the implementation of the parallel path 15 (see FIG. 1) brings with it a considerable advantage with regard to a vehicle deceleration in the case of the application of a fallback level.

The diagrams of FIGS. 3 and 4 show a situation in which there is no air in the brake circuits at the beginning of braking.

By means of the diagram of FIG. 3, the second brake pressures which can be effected in the second brake circuit are shown. The lower curve (solid line) gives the conventional manner in the second brake circuit, i. without transferring brake fluid from the volume 32 (see, e.g., Figure 1) to brake pressure present in one of the two brake circuits. By means of the dotted curve of the brake pressure is reproduced, which would be present in the second brake circuit, if from the volume 32 brake fluid would be fed only in the first brake circuit. The effect of the supply of brake fluid from the volume 32 in both brake circuits effected brake pressure is represented by the dashed curve. It can be seen that by means of

Transferability of brake fluid from the volume 32 in both brake circuits which can be significantly increased in the second brake circuit effected at a relatively high pedal travel brake pressure. The latter curve has e.g. a maximum pressure of about 100 bar, while the other curves each have a maximum pressure of about 93bar. In the diagram of FIG. 4, the one which can be effected in the first brake circuit is shown

Brake pressure shown. In this case, the lower curve (continuous line) shows the conventional manner, ie without transferring brake fluid from the volume 32 in one of the two brake circuits, in the first brake circuit effectable brake pressure. The values of the dotted curve correspond to the values of the brake pressure which can be effected only when the brake fluid is supplied from the volume 32 into the first brake circuit. An additional supply of brake fluid from the volume 32 into the second brake circuit with a simultaneous filling of the first brake circuit (from the volume 32), the brake pressure at a relatively high pedal travel is hardly affected, as can be seen from the upper curve (dashed) , Although this curve has a slightly reduced maximum pressure of 97 bar compared to a maximum pressure of 99 bar of the mean curve, these values are well above the maximum pressure of 89 bar of the lower curve.

As can be seen from the diagrams in FIGS. 5 and 6, the pressure increase effected by means of the additional supply of brake fluid from the volume 32 into the two brake circuits is even more significant if air (for example ² cm ³ ) is present in the two brake circuits before the start of braking , The respective lower curves of Figures 5 and 6 indicate the conventional manner, ie without transferring brake fluid from the volume 32 in one of the two brake circuits, achievable brake pressures. By means of the respective middle curves in Figures 5 and 6 brake pressures are reproduced, which via an injection of

Brake fluid can be effected only in the first brake circuit. The brake pressures which can be achieved by supplying brake fluid from the volume 32 into both brake circuits are reproduced by means of the upper curves in FIGS. 5 and 6, respectively. The volume feed from the volume 32 thus makes it possible to fill up the volume of air with brake fluid, as a result of which the achievable maximum pressure increases are significantly increased. The upper curve in FIG. 6 has a significantly increased maximum pressure of approximately 46 bar compared to the maximum pressures of 33 bar of the lower and middle curves in FIG. Similarly, the (dashed) curve in Figure 5, although with 52 bar a slightly reduced maximum pressure against a maximum pressure of 58 bar of the dotted (middle) curve in Figure 5, but these values are still well above the maximum pressure of 35 bar lower curve in Figure 5. In summary, it can be stated that by means of the supply of an additional quantity of brake fluid from the volume 32, the brake pressure which can be achieved in the mechanical fallback level is increased during full braking. In this way, the maximum possible vehicle deceleration can be increased. In particular, this effect also compensates for any air bubbles contained in the two brake circuits (fluid lines 100 and 200), which allows an additionally increased maximum brake pressure in the fallback level and thus a significantly shortened stopping distance of the vehicle. The additional volume obtained also improves the braking behavior from a pressureless braking state by a faster overcoming of the dead volume, in particular in the first brake circuit (fluid line 100). These measures can also be significantly increased in a mechanical fallback delay achievable without affecting the pedal travel by operating conditions adversely. By means of the braking systems described above, the vehicle behavior in the mechanical fallback mode can thus be further improved.

In addition, by decoupling the pedal stroke and the pedal force during operation, it is possible to design a fallback level independent of the volume to be delivered during operation.

The master cylinder 30, the electrically controllable valve 35 and the associated valve device may be a plurality of separately arranged components. Likewise, the master cylinder 30, the electrically controllable valve 35 and the associated valve device may also be formed as a compact (one-piece) braking device. It should be noted that the advantages outlined above can also be met by such a braking device for a braking system of a vehicle.

With reference to FIGS. 7 to 11 (ie 1 1 a, 1 1 b, 1 1 c), brief reference is made to possible embodiments of the master brake cylinder 30 shown in schematic cross-sectional view and the respective mode of operation. Figures 7 to 10 each show a detailed view of a portion of the brake system 10 of Figure 1, namely the part which the master cylinder 30 in conjunction with the actuator 400 and the pedal feel simulator 600. Figures 1 1 a to 1 1 c show only further possible designs of the master cylinder with respect to the combination of hydraulically effective surfaces on the piston (Figures 1 1 a and 1 1 c) or on a plurality of pistons (Figure 1 1 b).

Figure 7 shows a cross-sectional view of the master cylinder 30 (a so-called "parallel plunger") and the rod piston 45 with the hydraulically active and couplable surfaces 46 and 47, Vorbefüllungsringkammer 40, the pressure chambers 31, 32, a floating piston 33, which the pressure chambers 31st and 32, and the hydraulic fluid reservoir 50.

In the representation in FIG. 7, above the master brake cylinder 30, in addition to the reservoir 50, there is a pressure limiting valve 51 and a so-called

"Fast-Fill Disable" valve 52, the function of which will be explained below.

The pedal feel simulator 600 also includes the valve 610 shown in FIG. 1. Likewise, the fluid lines 100, 200 of the first and second brake circuits are illustrated with the corresponding valves 105, 205, the fluid lines 100, 200 being shown "down" in FIG. relative to the drawing) for Radmodula- tion (not shown here) run and are coupled to this.

The actuator 400 has the housing 420 in which the piston 405 coupled to the drive (here: electric motor "M") and a floating piston 406 are located. Due to the arrangement of the pistons 405, 406 can be filled with hydraulic fluid pressure chambers 410, 41 1 are formed.

Furthermore, a check valve 800 is shown in a fluid line 810, which is fluidically coupled between Vorbefüllungsringkammer 40 and fluid line 100. The reservoir 50 is fluidly coupled via sniffer bores 34a, 34b, 34c respectively to the master cylinder pressure chambers 31, 32, 40. In case of a malfunction of the brake system 10, the driver still has the opportunity, by exerting a force indicated by an arrow 900, ie stepping on the (not shown) brake pedal to move the rod piston 45 in the drawing to the left to pressure in the pressure chambers 31, 32 build, which is finally transmitted directly via the fluid lines 100, 200 to the (not shown here) wheel modulation for generating braking torque at the wheels. This is possible because a pressure which builds up in the chamber 40 through the hydraulically active surface 46, which would make effective braking very difficult and against which the driver would have to apply a correspondingly large force, by switching the valve 52 on is degraded, so that the driver finally "brakes" with the hydraulically active surface 47. In this respect, the hydraulically active surfaces 46, 47 are functionally coupled together.

FIG. 8 shows an arrangement similar to the embodiment shown in FIG. 7, with the difference that the fluid line 810 is fluidically coupled to the housing 420 of the actuator 400 via sniffer bores 81 1 a, 81 1 b, wherein the sniffer bores 81 1 a, 81 1 each act as check valves, analogous to the check valve 800 shown in FIG.

A further exemplary embodiment is shown in FIG. 9. Here, with reference to the illustration in FIG. 8, as a difference instead of the sniffer bores 81 1 a, 81 1 b acting as check valves, only a sniffer bore 81 1 is shown in the housing 420 of the actuator 400, as well as with the first one and the second brake circuit (fluid lines 100, 200) and the pressure chamber 40 fluidly coupled check valves 800a, 800b.

FIG. 10 (so-called "serial plunger") shows an exemplary embodiment in which a check valve 800 and a separating valve 801 connected in parallel therewith are fluidically coupled between the pressure chamber 40 and the fluid line 100 of the first brake circuit. Furthermore, the master cylinder 30 is formed such that in one end of the master cylinder 30, a pressure plate 48 a is arranged, which is coupled to the brake pedal 48 and via seals 48 a, 48 b in Master cylinder housing is guided. It should be noted that the pressure plate 48a is mechanically decoupled from the stepped piston 45. Between pressure plate 48 a and stepped piston 45, a pressure chamber 41 is formed, which is fluidically coupled to the pedal travel simulator 600, wherein two series-connected valves 610, 61 1 are fluidically coupled both to the actuator 400 (hydraulic transmission) and to the pressure accumulator 605. Although the pressure plate 48a (or the brake pedal 48) is not mechanically coupled to the stepped piston 45, a corresponding pedal feel for the driver can be conveyed via the pedal travel simulator 600, which is fluidically coupled to the pressure chamber 41. The fallback function described above with reference to FIGS. 7 to 9 is also ensured with the embodiment shown in FIG. The power transmission from the actuator 400 to the piston 45 is alternatively realized via a mechanical transmission.

In the sense of an overview of further possible piston shapes with hydraulically active surfaces, FIGS. 11a to 11c show only a part of the master cylinder 30 or at least two pistons coupled with respect to a force 900 exerted by the driver by means of the brake pedal or brake input element 48 30a, 30b (FIG. 11 b), wherein in each case also the above-mentioned sniffer bores 34b, 34c and 34c '(FIG. 11b), see for example also FIG. 7, and piston seals 46', 46a ', 46b', 47 'and also 45' (Figure 1 1 c) are shown. The further embodiments shown in FIGS. 11a to 11c (the embodiment shown in FIG. 11a substantially corresponds to the embodiment shown in FIG. 7, but is again listed in FIG. 11a for the purposes of a comparison that gives an overview ) are intended to illustrate that there are several differently shaped types of master cylinder or

Brake device with at least two or more hydraulically effective and force-controlled surfaces are, with further design forms are conceivable, that is not limited to the embodiments shown here. It should also be noted that the above-described functions of the braking device can be switched on and off for the so-called "OK" operation (OK = in order, ie an operation without malfunction), and in each case hydraulic fluid in one and / or or two (or more) brake circuits of the vehicle can be fed. Advantageously hydraulically effective surfaces (see, for example, Figure reference numerals 46,) in normal operation via the valves 801 and 52 coupled.

Claims

A brake system (10) for a vehicle, comprising: a master cylinder (30) having at least one pre-fill ring chamber (40) formed as a second independent volume, the master cylinder (30) hydraulically engaging at least two hydraulic surfaces (46) hydraulically coupled to one another in the master cylinder , 47); a hydraulic fluid reservoir (50) fluidly coupled to the master cylinder (30); and at least a first and a second brake circuit, which are each fluidically coupled to chambers (31, 32) of the master cylinder (30), and on the other hand in each case with brake torque generating wheel brake cylinders are fluidly coupled, wherein the wheel brake cylinder coupled to wheels of the vehicle are, in each case normally open switching valves (105, 205) are arranged in the first brake circuit and in the second brake circuit.

The brake system (10) according to claim 1, further comprising a parallel fluid line (1 15) fluidly coupled to the second brake circuit at one end and fluidly coupled to the prefill ring chamber (40) at another end, wherein in the parallel Fluid line (1 15) a check valve (1 10) is arranged, which is fluidly in the direction of the second brake circuit out, and thus supplies the second brake circuit upon actuation of the master cylinder (30) additionally with hydraulic fluid.

Brake system (10) according to claim 1 or 2, wherein the master brake cylinder (30) at least two hydraulically active surfaces (46, 47) and / or we- at least three pressure chambers (31, 32, 40) which can be filled with hydraulic fluid and which are fluidically separated from one another by a floating piston (33) and a rod piston (45), wherein the rod piston (45) is designed as a stepped piston which is actuable by a driver

Brake input element (48) can be coupled.

A braking system (10) according to any one of the preceding claims, further comprising an actuator (400) adapted to generate a hydraulic fluid pressure separately from the master cylinder (30) and via fluid lines (100, 200) in each of which a switching valve (105, 205) is arranged, is fluidly coupled to the first brake circuit and the second brake circuit and the hydraulic fluid reservoir (50).

The brake system (10) of claim 4, wherein the actuator (400) is electro-hydraulically operable.

The brake system (10) of any one of the preceding claims, further comprising a pedal feel simulator (600) operable over an entire driver operable brake pedal travel or portions thereof, and a fluid line (36) in which a normally closed solenoid valve (35 ) is fluidly coupled to the prefill ring chamber (40).

A braking system (10) according to claim 6, wherein optionally in parallel to the pedal feel simulator assembly (600), a normally closed valve (620) is arranged.

The brake system (10) of any one of the preceding claims, further comprising an additional fluid line (700) having one end fluidly coupled to the prefill ring chamber (40) and the other end fluidly coupled to the hydraulic fluid reservoir (50).

9. brake system (10) according to claim 8, wherein in the additional fluid line (700) an adjustable check valve (55) and / or a throttle (710) are arranged. 10. A braking system (10) according to any one of claims 4 to 9, wherein for a serial hydraulic fluid feed two series-connected valves (610, 61 1) are fluidically coupled, wherein a force is transferable by means of a mechanical and / or hydraulic transmission, and wherein the actuator (400) acts fluidly on the rod piston (45) of the master cylinder (30).

1 1. Brake system (10) according to any one of the preceding claims, wherein the brake system (10) is designed such that a hydraulic fluid supply in only one of the brake circuits is feasible. 12. A method for operating a brake system (10) according to claims 1 to 1 1, wherein in case of malfunction of the brake system (10), the brake input member (48) is actuated by the driver and the check valve (1 10) of the parallel fluid line (1 15) opens, so that hydraulic fluid flows into the second brake circuit (fluid line 200), and finally to wheel brake cylinders for generating braking torques at the second

Brake circuit (fluid line 200) associated with wheels.