Braking system for a vehicle and a method for operating the braking system

Abstract

Braking system (10) for a vehicle, comprising: - a master brake cylinder (30) with at least one pre-filling ring chamber (40) designed as a second independent volume, wherein the master brake cylinder (30) has at least two hydraulically effective surfaces (46, 47) that can be fluidically coupled to one another and act on a hydraulic fluid located in the master brake cylinder; a hydraulic fluid reservoir (50) which is fluidically coupled to the master brake cylinder (30); - at least one first and one second brake circuit, each of which is fluidically coupled on the one hand to chambers (31, 32) of the master brake cylinder (30), and on the other hand is fluidically coupled to brake torque-generating wheel brake cylinders, wherein the wheel brake cylinders are coupled to wheels of the vehicle, wherein normally open changeover valves (105, 205) are arranged in the first brake circuit and in the second brake circuit; and - an actuator (400) which is designed to generate a hydraulic fluid pressure separately from the master brake cylinder (30), and which is fluidically coupled to the first brake circuit and the second brake circuit and the hydraulic fluid reservoir (50) via fluid lines (100, 200) in which a switching valve (105, 205) is arranged, wherein two valves (610, 611) connected in series are fluidically coupled for a series hydraulic fluid supply, wherein a force can be transmitted by means of a mechanical and / or hydraulic transmission, and wherein the actuator (400) acts fluidly on the rod piston (45) of the master brake cylinder (30).

Description

[0001] The invention relates to a braking system for a vehicle and a method for operating the braking system. State of the art

[0002] WO 2009 / 121645 A1 describes a hydraulic vehicle braking system. The master brake cylinder of the hydraulic vehicle braking system comprises a first pressure chamber and a second pressure chamber. Additionally, the master brake cylinder has an integrated pedal travel simulator 22 at an end that widens towards the brake pedal. The volume of this simulator that can be filled with brake fluid is hydraulically connected to a brake fluid reservoir via a simulator valve. The brake fluid-fillable volume of the pedal travel simulator and the adjacent first pressure chamber are delimited by a rod and simulator piston designed as a stepped piston.

[0003] Furthermore, DE 10 2011 006 327 A1 discloses a brake system of the "brake-by-wire" type, comprising a master brake cylinder with two pistons slidably arranged therein, wherein one piston is designed as a stepped piston with at least two hydraulically actuated surfaces of different sizes, resulting in an annular volume that can be filled with hydraulic fluid or brake fluid due to the stepped piston shape. In "brake-by-wire" operating mode, when the master brake cylinder is actuated by the driver, the smaller actuated surface is effective for generating a braking torque at the vehicle wheels, and in a fallback scenario, i.e., if a malfunction occurs, the larger actuated surface is used, with the switch from the smaller actuated surface to the larger actuated surface depending on the hydraulic pressure in a pressure chamber in the master brake cylinder or the applied pedal force.

[0004] Furthermore, a hydraulic braking device with a powerful hydraulic pressure source is described in JP 2003 - 154 930 A.

[0005] In externally driven braking systems, it is possible to design the backflow area independently of the hydraulic fluid volume to be delivered during operation by decoupling the pedal stroke and pedal force. Typically, the hydraulically effective area for such a backflow area is determined by the volumetric capacity of the braking system, taking into account certain operating conditions. Disclosure of the invention

[0006] The invention provides a braking system for a vehicle with the features of claim 1 and a method for operating the braking system with the features of claim 9. Advantages of the invention

[0007] The invention provides for operating a braking system in such a way that, in the event of a partial or complete failure, for example, a failure and / or malfunction of the integrated braking system, the driver can directly access two connectable hydraulically effective surfaces. By cleverly coupling them, i.e., activating one of the surfaces until a certain pressure is reached, the effects of various operating conditions can be reduced, and it is thus possible to achieve higher pressures and therefore greater deceleration with a given force.

[0008] This measure significantly increases the deceleration achievable in a mechanical fallback position without adversely affecting the pedal travel through operating conditions.

[0009] In another advantageous embodiment, it is proposed to feed the additionally displaced volume into more than one brake circuit.

[0010] In the Fig. Diagrams 3 to 6 are shown, each depicting a pedal travel (in mm) versus a wheel pressure (in bar), with further details below explaining how much the brake pressure in the two brake circuits can be increased during the fallback level by means of brake fluid transfer. Brief description of the drawings

[0011] The invention is explained below with reference to embodiments in conjunction with the figures, wherein: Fig. 1 shows a schematic hydraulic circuit diagram of a brake system according to a first embodiment of the invention; Fig. 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. Figure 4 shows a diagram of the wheel pressure in brake circuit 1 as a function of the pedal travel; Fig. 5 a diagram of the wheel pressure in brake circuit 1 at 2 cm 3 Air in both brake circuits depending on pedal travel is shown; Fig. 6 a diagram of the wheel pressure in brake circuit 2 at 2 cm 3 Air in both brake circuits depending on pedal travel is shown; Fig. 7 a detailed view of an exemplary embodiment of a master brake cylinder including some essential components; Fig. 8 a detailed view of another exemplary embodiment of a master brake cylinder including some essential components; Fig. 9 a detailed view of yet another exemplary embodiment of a master brake cylinder including some essential components; Fig. 10 a detailed view of yet another exemplary embodiment of a master brake cylinder including some essential components; and Fig. 11a to 11c show further exemplary embodiments schematically depicted in cross-sectional view of only a part of the master brake cylinder with regard to the combination of hydraulically effective surfaces on the piston or on several pistons. Embodiments of the invention

[0012] Fig. Figure 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 the operation of the brake system 10 are housed in a unit marked with reference numeral 11 and provided with a dash-dotted border.

[0013] The aforementioned approach with a stepped piston 45 forming a ring volume, the operation of which is described in more detail below, shifts additional brake fluid volume into the first brake circuit 100 when the pressure in the ring volume piston chamber is limited and low, and the first brake circuit is designated with reference numeral 100. This additional quantity increases the brake pressure achievable in the mechanical fallback level during full braking in the first brake circuit 100 and thus the maximum possible vehicle deceleration.

[0014] Furthermore, this effect compensates for any air bubbles that may be present in the first brake circuit, which allows for a higher maximum brake pressure in the fallback level, and thus a relatively shorter stopping distance of the vehicle.

[0015] The additional volume also improves braking performance from a depressurized brake state by more quickly overcoming a so-called dead volume in the first brake circuit 100. This well-known principle corresponds to that in Fig. 1 hydraulic path or fluid line marked with reference numeral 15 with check valve 20.

[0016] One variant of the invention consists in extending the benefits described above to a second brake circuit 200 by duplicating this fluid line 15, thereby further improving the vehicle's braking performance in a mechanical fallback position. However, the brake system can also be designed such that hydraulic fluid can be supplied to only one of the brake circuits.

[0017] According to Fig. 1. A primary chamber or pre-filling ring chamber 40 is positioned upstream of the two pressure chambers 31, 32 of a conventional master brake cylinder 30. The volume of this primary chamber can be varied by the stepped piston 45 with one (46) of the two hydraulically effective surfaces 46 and 47, as will be explained further below. A brake input element 48 is coupled to the stepped piston 45 in a known manner and is pivotable about a point 49.

[0018] In normal operation (i.e., by-wire), chamber 40 is short-circuited to a brake fluid (hydraulic fluid) reservoir 50 by controlling a (normally closed) solenoid valve 35.

[0019] The timing of this activation can be delayed if rapid braking (e.g., emergency braking) is detected, in order to improve the pressure build-up dynamics in this operating condition. In the "mechanical fallback" operating mode, solenoid valve 35 remains closed (since it is usually not energized).

[0020] The flow into brake circuits 100 and 200 and the return flow into reservoir 50 are controlled by the closing pressures of check valves 210, 110, and 55. Check valve 55 defines the maximum permissible pressure in the annular piston volume 40 (pressure limit), while check valves 210 and 110 in brake circuits 100 and 200 define a minimum pressure differential between brake circuits 100 and 200 and the annular piston volume 40.

[0021] If the pressure in the annular piston volume 40 exceeds this pressure threshold, brake fluid flows from the annular piston chamber 40 into the brake circuits 100 and 200. This condition persists until either the pressure threshold is undercut by an increase in the brake circuit pressures or until the maximum pressure in the annular piston chamber 40, as determined by the check valve 35, is exceeded. The described operating principle has so far only been used in brake circuit 100.

[0022] By implementing a hydraulic parallel path 115, the effect is also utilized in brake circuit 200. The achievable maximum pressure increases compared to a standard master brake cylinder without a ring piston and a ring piston effect used only in one circuit are shown in the diagrams in the Fig. 3 to 6 can be removed.

[0023] For the sake of completeness, it should be mentioned at this point that switching valves 105, 205 are arranged in the fluid lines 100, 200 (normally open) in a known manner, which allow a direct connection (i.e. supply with hydraulic fluid) to a wheel modulation 300 which will be briefly explained below.

[0024] In Fig. 1 is an arrangement generally known as wheel modulation, designated by reference numeral 300, wherein the wheel modulation 300 comprises vehicle wheels (not shown separately here), wheel brake cylinders assigned to them, and inlet and outlet valves, the functions of which are known to those skilled in the art and are therefore not to be explained here for the sake of brevity.

[0025] Furthermore, in Fig. 1 with reference numeral 400 is an actuator, which in the example shown is in Fig. 1. The actuator 400 is to be electro-hydraulically operable, i.e., for example, via an electric motor marked "M". The actuator 400 is supplied with hydraulic fluid from the reservoir 50 via a fluid line 425. The electric motor M can be controlled such that it can move a piston 405 back and forth in a housing via a forward or reverse drive 415 in order to move hydraulic fluid located in a volume 410. B. to compress, i.e., to pressurize, in order to transfer hydraulic fluid via fluid lines 430, 440 to feed connections 450, 460 into the wheel modulation 300 (for example, as an ESP function), independently of actuation of the master brake cylinder 30. In a known manner, switching valves 470, 480 with filter devices 475, 485 upstream (i.e., viewed from the actuator 400) are arranged in the fluid lines 430, 440, as well as at other locations of the brake system 10, which will not be discussed in detail here, as this is assumed to be known.For the sake of completeness, it should also be mentioned that 10 pressure sensors are located at various points in the braking system, the function of which should also be familiar to those skilled in the art. The one in [location] serves as an example. Fig. 1 pressure sensor marked with reference number 500 at the end of fluid line 440 is listed.

[0026] Furthermore, for the sake of completeness, a Fig. 1. Pedal feel simulator device 600, designated by reference numeral 600, comprising a pressure accumulator 605, a switching valve 610, and a bypass fluid line 615 with a check valve 210. A switching valve 620 may be arranged in parallel. However, it should be emphasized that the pedal feel simulator device 600 is known from the prior art and is optionally included in the illustrated embodiment in Fig. It can be arranged in 1.

[0027] Fig. Figure 2 shows a further embodiment of the braking system 10, it should be noted that with regard to Fig. 1. The same reference symbols refer to the same elements, and not all of them in Fig. The two components shown are labelled with reference symbols, unless otherwise necessary.

[0028] The difference in Fig. 2 embodiment of the brake system 10 shown in comparison to the one in Fig. In the embodiment shown in Figure 1, a throttle 710 is arranged in a fluid line 700, which is fluidically coupled between fluid line 425 and pre-filling ring chamber 40, to increase the outflow resistance of the hydraulic fluid to the reservoir 50. This ensures that the hydraulic fluid pressure that builds up in front of the wheel modulation 300 is maintained for as long as possible, or in other words, that a positive pressure differential between the pre-filling ring chamber 40 and the pressure applied to the wheel modulation 300 is maintained for as long as possible, since otherwise the wheel brake cylinders (located in the wheel modulation 300 and therefore not visible) would not be adequately supplied with hydraulic fluid to generate braking torque.

[0029] It should be noted that the throttle 710 may additionally be arranged in the brake system 10, but according to the principle of the present disclosure it does not necessarily have to be arranged.

[0030] Fig. Figures 3 to 6 each show diagrams in which curves (each marked for differentiation with only a fine continuous curve = "without injection of hydraulic fluid", a curve with a fine continuous line and points = "with injection into one brake circuit" and a curve with a fine continuous line and short thick bars along this curve = "with injection into both brake circuits") are plotted with respect to a wheel pressure of one brake circuit as a function of the brake pedal travel.

[0031] As in Fig. 3 and Fig. As can be seen in section 4, the maximum pressures achievable without and with injection into the brake circuits (see right side of the diagram) differ only slightly from each other, i.e., in the examples shown, the maximum pressures are slightly below 100 bar.

[0032] Fig. 5 and Fig. Figure 6 shows comparable diagrams, but with approximately 2 cm.3 trapped air in both brake circuits.

[0033] It can now be seen that feeding power into one and / or both brake circuits results in a significantly increased maximum final pressure in every case (see the right-hand side of the diagrams in each case). Fig. 5 and Fig. 6) in relation to the case without feed-in, and thus the implementation of the parallel path 15 (see Fig. 1) provides a significant advantage with regard to vehicle deceleration in the event of the application of a fallback level.

[0034] The diagrams of Fig. 3 and Fig. Figure 4 represents a situation in which there is no air in the brake circuits at the start of braking.

[0035] Using the diagram of Fig. Figure 3 shows the second brake pressures achievable in the second brake circuit. The lower curve (solid line) represents the pressure in the second brake circuit in the conventional manner, i.e., without transferring brake fluid from volume 32 (see, for example, Figure 3). Fig. 1) The brake pressure present in one of the two brake circuits. The dotted curve represents the brake pressure that would be present in the second brake circuit if brake fluid from volume 32 were only fed into the first brake circuit. The brake pressure achievable by feeding brake fluid from volume 32 into both brake circuits is shown by the dashed curve. It can be seen that by transferring brake fluid from volume 32 into both brake circuits, the brake pressure achievable in the second brake circuit at a comparatively high pedal travel can be significantly increased. The latter curve, for example, shows a maximum pressure of approximately 100 bar, while the other curves each show a maximum pressure of approximately 93 bar.

[0036] In the diagram of Fig. Figure 4 shows the brake pressure achievable in the first brake circuit. The lower curve (solid line) indicates the brake pressure achievable in the first brake circuit using conventional methods, i.e., without transferring brake fluid from volume 32 to either of the two brake circuits. The values ​​of the dotted curve correspond to the brake pressure values ​​achievable in the first brake circuit only when brake fluid is supplied from volume 32. By additionally supplying brake fluid from volume 32 to the second brake circuit while simultaneously filling the first brake circuit (from volume 32), the brake pressure is hardly affected at a comparatively high pedal travel, as can be seen from the upper curve (dashed line).Although this curve has a slightly reduced maximum pressure of 97 bar compared to a maximum pressure of 99 bar in the middle curve, these values ​​are significantly higher than the maximum pressure of 89 bar in the lower curve.

[0037] As shown in the diagrams in Fig. 5 and Fig. As can be seen in Figure 6, the pressure increase caused by the additional injection of brake fluid from volume 32 into the two brake circuits is even more significant if air (e.g. 2 cm) is present before the start of braking. 3 ) is present in both brake circuits. The lower curves of each are Fig. 5 and Fig. Figure 6 indicates the brake pressures achievable in the conventional manner, i.e., without transferring brake fluid from volume 32 into either of the two brake circuits. The respective middle curves in Fig. 5 and Fig. Figure 6 shows brake pressures that can only be achieved in the first brake circuit by supplying brake fluid. The brake pressures achievable by supplying brake fluid from volume 32 to both brake circuits are shown using the figures in the Fig. 5 and Fig. The upper curves are shown in the six diagrams. The volume feed from volume 32 thus allows the air volume to be filled with brake fluid, which significantly increases the achievable maximum pressure increases. The upper curve in Fig. 6 shows 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. 6. Likewise, the (dashed) curve in Fig. 5, although with 52 bar a slightly reduced maximum pressure compared to a maximum pressure of 58 bar of the dotted (middle) curve in Fig. 5, however, these values ​​are still significantly above the maximum pressure of 35 bar of the lower curve in Fig. 5.

[0038] In summary, adding an additional quantity of brake fluid from volume 32 increases the achievable brake pressure in the mechanical fallback system during full braking. This also increases the maximum possible vehicle deceleration. In particular, this effect compensates for any air bubbles that may be present in the two brake circuits (fluid lines 100 and 200), resulting in a further increase in maximum brake pressure in the fallback system and thus a significantly shorter stopping distance. The additional volume also improves braking performance from a depressurized brake state by overcoming the dead volume more quickly, especially in the first brake circuit (fluid line 100). These measures also allow for a significant increase in the achievable deceleration in the mechanical fallback system without adversely affecting the pedal travel due to operating conditions.The braking systems described above can therefore be used to further improve vehicle behavior in the mechanical fallback level.

[0039] Furthermore, by decoupling the pedal stroke and pedal force during operation, it is possible to design a fallback level independent of the volumes to be pumped during operation.

[0040] The master brake cylinder 30, the electrically controlled valve 35, and the associated valve assembly can be several separately arranged components. Likewise, the master brake cylinder 30, the electrically controlled valve 35, and the associated valve assembly can also be designed as a compact (one-piece) brake unit. It should be noted that the advantages described above can also be achieved by such a brake unit for a vehicle's braking system.

[0041] With regard to the Fig. Sections 7 to 11 (i.e., 11a, 11b, 11c) briefly discuss possible embodiments of the master brake cylinder 30, each shown in a schematic cross-sectional view, and their respective operating principles. Fig. Figures 7 to 10 each show a detailed view of a part of the braking system. Fig. 1, namely the part which shows the master brake cylinder 30 in conjunction with the actuator 400 and the pedal feel simulator 600. Fig. Figures 11a to 11c merely show further possible design forms of the master brake cylinder with regard to the combination of hydraulically effective surfaces on the piston ( Fig. 11a and Fig. 11c) or on several pistons ( Fig. 11b).

[0042] Fig. Figure 7 shows a cross-sectional view of the master brake cylinder 30 (a so-called “parallel plunger”) and the rod piston 45 with the hydraulically effective and coupling surfaces 46 and 47, the pre-filling ring chamber 40, the pressure chambers 31, 32, a floating piston 33 which separates the pressure chambers 31 and 32 from each other, and the hydraulic fluid reservoir 50.

[0043] In the representation in Fig. Figure 7 shows a pressure relief valve 51 and a so-called “Fast-Fill-Disable” valve 52 above the master brake cylinder 30 next to the reservoir 50, the function of which is explained below.

[0044] The pedal feel simulator 600 includes the valve 610, which is also shown in the figure. Likewise, the fluid lines 100, 200 of the first and second brake circuits with the corresponding valves 105, 205 are shown, with the fluid lines 100, 200 running "downwards" (relative to the drawing) to the wheel modulation (not shown here) and being coupled to it.

[0045] 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, pressure chambers 410, 411, which can be filled with hydraulic fluid, are formed.

[0046] Furthermore, a check valve 800 is shown in a fluid line 810, which is fluidically coupled between pre-filling ring chamber 40 and fluid line 100.

[0047] Reservoir 50 is fluidically coupled to the master brake cylinder pressure chambers 31, 32, 40 via sniffing bores 34a, 34b, 34c.

[0048] In the event of a malfunction of the brake system 10, the driver still has the option of moving the rod piston 45 to the left in the drawing by applying a force indicated by arrow 900, i.e., pressing the brake pedal (not shown here). This builds up pressure in the pressure chambers 31, 32, which is then transmitted directly via the fluid lines 100, 200 to the wheel modulation (not shown here) to generate braking torque at the wheels. This is possible because the pressure building up in chamber 40 by the hydraulically effective surface 46, which would make effective braking very difficult and against which the driver would have to exert a correspondingly large force, is reduced by (opening) the valve 52, so that the driver ultimately "brakes" using the hydraulically effective surface 47. Therefore, the hydraulically effective surfaces 46, 47 are functionally coupled to each other.

[0049] Fig. 8 shows one of the in Fig. The embodiment shown in Figure 7 is similar in design, with the difference that the fluid line 810 is fluidically coupled to the housing 420 of the actuator 400 via sniffing bores 811a, 811b, wherein the sniffing bores 811a, 811b each act as check valves, analogous to the one shown in Figure 7. Fig. 7 shown check valve 800.

[0050] Another exemplary embodiment shows Fig. 9. In this context, with reference to the presentation in Fig. 8 as a difference instead of the sniffing bores 811a, 811b acting as check valves only one sniffing bore 811 in the housing 420 of the actuator 400 is shown, as well as fluidically coupled check valves 800a, 800b with the first and the second brake circuit (fluid lines 100, 200) and the pressure chamber 40.

[0051] Fig. Figure 10 (so-called "serial plunger") shows an exemplary embodiment in which a check valve 800 and a parallel isolation valve 801 are fluidically coupled between pressure chamber 40 and fluid line 100 of the first brake circuit. Furthermore, the master brake cylinder 30 is designed such that a pressure plate 48a is arranged in one end of the master brake cylinder 30, which is coupled to the brake pedal 48 and guided in the master brake cylinder housing via seals 48a, 48b. It should be noted that the pressure plate 48a is mechanically decoupled from the stepped piston 45. Between pressure plate 48a and stepped piston 45 a pressure chamber 41 is formed, which is fluidically coupled to the pedal travel simulator 600, wherein two valves 610, 611 connected in series are fluidically coupled to both the actuator 400 (hydraulic transmission) and the pressure accumulator 605. Although pressure plate 48a (orSince the brake pedal 48) is not mechanically coupled to the stepped piston 45, a corresponding pedal feel can be conveyed to the driver via the pedal travel simulator 600, which is fluidically coupled to the pressure chamber 41. The above refers to... Fig. The fallback level function described in sections 7 to 9 is also related to the one in Fig. The embodiment shown in section 10 ensures this. Alternatively, the power transmission from the actuator 400 to the piston 45 can also be achieved via a mechanical gearbox.

[0052] Fig. Figures 11a to 11c show, for the purpose of providing an overview of other possible piston shapes with hydraulically effective surfaces, only a part of the master brake cylinder 30 or at least two pistons 30a, 30b coupled with respect to a force 900 exerted by the driver by means of the brake pedal or brake input element 48 ( Fig. 11b), including the aforementioned sniffing boreholes 34b, 34c and 34c' respectively ( Fig. 11b), see for example also Fig. 7, and piston seals 46', 46a', 46b', 47' or also 45' ( Fig. 11c). The ones shown in Fig. further embodiments shown in 11a to 11c (which are in Fig. The embodiment shown in 11a essentially corresponds to the one shown in Fig. The embodiment shown in Figure 7 is, however, shown again in Figure 7 for the purpose of providing an overview comparison. Fig.Figure 11a (also listed) is intended to illustrate that there are several differently designed types of master brake cylinders or brake devices with at least two or more hydraulically effective and force-controlled surfaces, and that further designs are conceivable, i.e., not limited to the embodiments shown here. It should also be noted that the brake device functions described above can be switched on or off for so-called "OK" operation (OK = OK, i.e., operation without malfunction), and that hydraulic fluid can be fed into one and / or two (or more) brake circuits of the vehicle. Advantageously, the hydraulically effective surfaces (see, for example, Figure reference numbers 46 and 47) can be coupled via valves 801 and 52 during normal operation.

Claims

[1] Braking system (10) for a vehicle, comprising: - a master brake cylinder (30) with at least one pre-filling ring chamber (40) designed as a second independent volume, wherein the master brake cylinder (30) has at least two hydraulically effective surfaces (46, 47) that can be fluidically coupled to one another and act on a hydraulic fluid located in the master brake cylinder; a hydraulic fluid reservoir (50) which is fluidically coupled to the master brake cylinder (30); - at least one first and one second brake circuit, each of which is fluidically coupled on the one hand to chambers (31, 32) of the master brake cylinder (30), and on the other hand is fluidically coupled to brake torque-generating wheel brake cylinders, wherein the wheel brake cylinders are coupled to wheels of the vehicle, wherein normally open changeover valves (105, 205) are arranged in the first brake circuit and in the second brake circuit; and - an actuator (400) which is designed to generate a hydraulic fluid pressure separately from the master brake cylinder (30), and which is fluidically coupled to the first brake circuit and the second brake circuit and the hydraulic fluid reservoir (50) via fluid lines (100, 200) in which a switching valve (105, 205) is arranged, wherein two valves (610, 611) connected in series are fluidically coupled for a series hydraulic fluid supply, wherein a force can be transmitted by means of a mechanical and / or hydraulic transmission, and wherein the actuator (400) acts fluidly on the rod piston (45) of the master brake cylinder (30). [2] Brake system (10) according to claim 1, further comprising a parallel fluid line (115) which is fluidically coupled to the second brake circuit at one end and fluidically coupled to the pre-filling ring chamber (40) at another end, wherein a check valve (110) is arranged in the parallel fluid line (115) which can be opened fluidically towards the second brake circuit, and thus additionally supplies the second brake circuit with hydraulic fluid when the master brake cylinder (30) is actuated. [3] Brake system (10) according to claim 2, wherein the master brake cylinder (30) has at least two hydraulically effective surfaces (46, 47) and / or at least three pressure chambers (31, 32, 40) that can be filled with hydraulic fluid, which are fluidically separated from each other by a floating piston (33) and a rod piston (45), wherein the rod piston (45) is designed as a stepped piston which can be coupled to a brake input element (48) that can be actuated by the driver. [4] Braking system (10) according to one of the preceding claims, wherein the actuator (400) is electro-hydraulically operable. [5] Braking system (10) according to one of the preceding claims, further comprising a pedal feel simulator (600) which can be operated over an entire brake pedal travel or sections thereof which can be actuated by the driver, and which is fluidically coupled to the pre-filling ring chamber (40) via a fluid line (36) in which a normally closed solenoid valve (35) is arranged. [6] Brake system (10) according to claim 5, wherein optionally a normally closed valve (620) is arranged parallel to the pedal feel simulator arrangement (600). [7] Brake system (10) according to one of the preceding claims, further comprising an additional fluid line (700) of which one end is fluidically coupled to the pre-filling ring chamber (40) and of which the other end is fluidically coupled to the hydraulic fluid reservoir (50). [8] Brake system (10) according to claim 7, wherein an adjustable check valve (55) and / or a throttle (710) are arranged in the additional fluid line (700). [9] Brake system (10) according to one of the preceding claims, wherein the brake system (10) is designed such that hydraulic fluid can be supplied to only one of the brake circuits. [10] Method for operating a brake system (10) according to claim 3, wherein in the event of a malfunction of the brake system (10), the brake input element (48) is actuated by the driver and the check valve (110) of the parallel fluid line (115) opens, so that hydraulic fluid flows into the second brake circuit (fluid line 200), and finally to wheel brake cylinders to generate braking torques on the wheels assigned to the second brake circuit (fluid line 200).

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