3 / 2 WAY VALVE CONCEPT FOR HYDRAULIC ACTUATOR SYSTEM

Description

[0001] The present invention relates to a hydraulic actuation system for a hydraulic system, in particular in the form of a brake system, comprising at least one hydraulic circuit with at least one hydraulic consumer, in particular in the form of a hydraulically actuated wheel brake, and with at least one pressure generating device comprising a piston pump or a rotary pump for pressure control or regulation, in particular for pressure build-up and pressure reduction in the at least one hydraulic circuit. Such hydraulic actuation systems are well known. In automotive engineering, 3 / 2-way valves are used in a variety of applications, as disclosed in DE 10 2017000472, where a 3 / 2-way valve serves for the selective connection of a brake circuit to the pressure supply or to a tandem master brake cylinder. By using a 3 / 2-way valve, one valve can advantageously be saved if previously only 2 / 2-way valves were used.

[0002] The following document WO 2016 / 146692 A1 can also be cited as the state of the art. 1

[0003] In many valve applications, the safety requirements for valve failure are high, as it can affect braking performance and pedal characteristics. Object of the invention

[0004] The object of the present invention is to design a generic hydraulic actuation system, in particular for a braking system, to be more reliable and cost-effective.

[0005] This problem is solved according to the invention with a hydraulic actuation system having the features of claim 1. Further advantageous embodiments of the actuation system according to claim 1 are defined by the features of the dependent claims.

[0006] The actuation system according to the invention allows the pressure to be advantageously regulated or controlled very precisely.

[0007] The pressure generating device can advantageously comprise a piston pump. In automotive engineering, there is a wide range of applications for the actuation systems according to the invention. Compared to rotary pumps, electrically driven piston-cylinder systems with plunger or double-stroke pistons offer significant advantages in continuous medium delivery, as well as in controlled volume delivery by means of piston stroke measurement or pressure measurement, where, for example, a specific volume of hydraulic medium is adjusted by controlled or regulated movement of the piston, thus allowing a predetermined pressure to be set or regulated, for example, based on a pressure-volume characteristic curve.

[0008] It is particularly advantageous, however, if the pressure generating device has a double-stroke piston, so that hydraulic fluid can be pumped during both the forward and return strokes, and if each working chamber of the pressure generating device can be connected to the reservoir via a 3 / 2-way valve, preferably one assigned to it. With this valve configuration described above, for example, any of the currently required functions of a brake system can be implemented or adjusted with the piston. In particular, it is also possible to adjust the double-stroke piston of the pressure generating device without pumping hydraulic fluid, which is generally referred to as a free stroke without fluid delivery to or from the hydraulic or brake circuits.

[0009] However, it is also possible that when using a double-stroke piston pump, only one working chamber or brake circuit is assigned a 3 / 2-way valve and the other only a 2 / 2-way valve. In this configuration, it is then only possible to connect one brake circuit to the reservoir to drain or receive hydraulic fluid.

[0010] In another possible embodiment, the two working chambers of the pressure generating unit can be connected to the reservoir via a single 3 / 2-way valve, whereby at least one working chamber is always hydraulically connected to the reservoir. If the 3 / 2-way valve can be held in an intermediate position by means of the electromagnetic actuator, it is also possible for both working chambers of the piston-cylinder unit of the pressure generating unit to be hydraulically connected to the reservoir simultaneously.

[0011] If the hydraulic actuation system with double-stroke piston according to the invention is used for pressure control of a brake system, it can supply the hydraulic medium to both brake circuits during both the forward and return strokes. In the event of a failure of one brake circuit (circuit failure), pressure control in the other, still intact brake circuit can continue to be carried out by means of the actuation system thanks to the advantageous valve circuit.

[0012] The braking system can advantageously include a master cylinder, which is designed either as a tandem or single master cylinder. The master cylinder thus has at least one working chamber, which can be connected via a 3 / 2-way valve either in the fallback position to a brake circuit or, normally, to a travel simulator for adjusting pedal feel. If the master cylinder is designed as a tandem master cylinder with two working chambers, one of its working chambers can be connected to the brake circuit and travel simulator via a 3 / 2-way valve as described above, and the other working chamber can be decoupled from the other brake circuit by means of a 2 / 2-way valve or connected to it in the fallback position.

[0013] As previously described, the pressure supply with a so-called dual-circuit double-stroke piston (DHK) enables continuous volume delivery. The double-stroke piston, which alternately delivers in a single circuit, can distribute the volume into the two brake circuits via the piston's forward and return strokes, thanks to the valve circuit according to the invention. Simultaneously, pressure equalization between the two brake circuits can occur via a circuit isolating valve connecting them, when in its open position.

[0014] The double-stroke piston can advantageously have two differently sized effective areas during the piston's forward and return strokes. Typically, the effective piston area during the return stroke is only 50% of the effective piston area during the forward stroke. This has the advantage that the piston force, and thus the motor torque (e.g., via a spindle drive), is only 50% of the piston force during the return stroke compared to the forward stroke, while maintaining the same pressure across the effective area. This is advantageously used to achieve twice the maximum pressure, e.g., up to 200 bar, during the return stroke with the same maximum motor torque. During the forward stroke, however, the maximum pressure is limited to 100 bar. This fulfills the primary requirement that pressure build-up and release are possible across the entire pressure range of 0–200 bar with precise pressure control through the piston's forward and return strokes at any piston position.

[0015] The double-stroke piston can be advantageously used with the valve circuit according to the invention for approximately twenty different operations, provided that these are to be performed without compromise in dynamics and positioning accuracy. In contrast to the complex valve circuits known from DE 10 20110830312 or DE 10 2018221783, the valve circuit of the hydraulic actuation system according to the invention is significantly simpler, more cost-effective, and smaller.

[0016] Even if one hydraulic circuit fails, the other circuit remains operational in the actuation system according to the invention. A redundant motor winding also contributes to increased drive reliability. Furthermore, the valve circuit according to the invention is flexible and can be used for a wide variety of hydraulic unit requirements in ABS, ESP, and other driver assistance systems.

[0017] To increase safety, an additional safety shut-off valve, particularly a normally open (NC) valve, can be installed in the connecting line between the pressure supply and the reservoir, where a 3 / 2-way valve is located. This shut-off valve disconnects the hydraulic connection between the reservoir and the 3 / 2-way valve, especially in the event of a malfunction or leakage of the 3 / 2-way valve. This allows pressure to be built up or changed in at least one wheel brake via the pressure supply, even if the 3 / 2-way valve is leaking, by closing the additional safety shut-off valve.

[0018] The hydraulic actuation system according to the invention and its operation are explained in more detail below with reference to drawings.

[0019] They show: Fig. 1: A possible embodiment of the hydraulic actuation system for supplying pressure to a brake system; Fig. 1a: Enlarged detail of the pressure generating device with two 3 / 2-way valves; Fig. 1b: Enlarged detail of the pressure generating device with only one 3 / 2-way valve; Figs. 2a and 2b: Schematic representations of the 3 / 2-way valve according to the invention in the de-energized ( Fig. 2a ) and energized state ( Fig. 2b ); Fig. 3: Schematic representation of the actuation system according to Figure 1a Fig. 4: Schematic representation of the actuation system according to Figure 1a during pressure build-up in the piston pre-stroke; Fig. 5: schematic representation of the actuation system according to Figure 1aduring pressure reduction in the piston return stroke; Fig. 6: second possible embodiment of the hydraulic actuation system according to the invention with only one 3 / 2-way valve, wherein a working chamber of the pressure generating device is always in hydraulic connection with the reservoir; Fig. 7: schematic representation of the actuation system according to Figure 6 Fig. 8: Use of the actuation system according to Figure 6 in a braking system with a master brake cylinder; Fig. 9: Cross-section through a possible embodiment of the 3 / 2-way valve according to the invention.

[0020] The Figure 1Figure 1 shows a system with a master brake cylinder HZ, e.g., a single master brake cylinder SHZ with one working chamber R1 or a tandem master brake cylinder THZ with two working chambers R1 and R2, together with a reservoir VB and a pedal travel sensor 2. In the case of the single master brake cylinder SHZ, a hydraulic line L1 leads via a 3 / 2-way valve MV to the pressure supply DV and to the brake circuit BK1. Via the 3 / 2-way valve MV, the working chamber R1 is optionally connected via hydraulic line L3 to the travel simulator WS or, in the de-energized normal position, to the brake circuit BK1. The hydraulic line L4 leads directly to the 3 / 2-way valve PD2 and via the circuit isolating valve KTV to the brake circuit BK2. The working chamber KV of the pressure generating unit DV is connected via the 3 / 2-way valve PD1 either to the second brake circuit BK2 or to the reservoir via the return line R. The 3 / 2-way valves PD1 and PD2 are the main components of the double-stroke piston DHK, which are used in the Figs. 3-5are described in detail. The two circuits of the pressure supply DV lead to the hydraulic control unit HCU for ABS, ESP and assistance functions, which are supplied with pressure by the pressure supply DV. The pressure generation unit can be used not only for pressure build-up but also for pressure reduction.

[0021] The Figure 1a The actuation system shows according to Figure 1Each work chamber (KV, KH) is assigned a 3 / 2-way valve. A normally closed 2 / 2 shut-off valve (MVs) is located in the return line (R) to the reservoir (VB). This valve is normally open and becomes effective in the event of a leaking valve seat (Se) in one of the valves (PD1 or PD2). In this case, the MVs valve closes. This occurs when, in the de-energized state, leakage occurs in valve PD1 or PD2 and flows into the return line (R). This can be detected, for example, by the additional volume uptake of brake circuit BK2 or BK1 using a pV characteristic curve, or by an unintended pressure change in brake circuit BK2 or BK1. The MVs valve is optional.

[0022] The Figure 1bFigure 1 shows an alternative embodiment in which the second 3 / 2-way valve PD2 is replaced by a 2 / 2-way valve, so that the working chamber KH can no longer be connected to the storage container VB.

[0023] The Figure 2a Figure 1 shows a schematic representation of a possible embodiment of a 3 / 2-way valve MV according to the invention for the brake system according to the invention. The 3 / 2-way valve MV has an excitation winding 5 arranged around a magnetic yoke 6 in which the magnetic armature 4 is adjustable in the axial direction relative to the bolt 7, 7a. A stop element 4a is arranged at the left end of the magnetic armature 4, which is located in the Figure 2aThe second, unenergized switching state of the valve MV, as depicted, abuts the inner wall of the magnetic yoke 6. The first valve closing element VSK1 is arranged at the right end of the connecting bolt 7, 7a and is rigidly connected to the end of the connecting bolt 7a. The first valve closing element VSK1 interacts with the first valve seat VS1, which may be part of the magnetic yoke 6. In the area of ​​the bolt section 7a, the magnetic yoke 6 forms a first valve chamber K1, which is connected via a hydraulic channel to the first valve port AN1 for the connection of the brake circuit BK1.

[0024] The 3 / 2-way valve MV also has a second valve chamber K2 in which the valve spring VF and a second valve closing element VSK2 are arranged.

[0025] The second valve chamber K2 is connected via a hydraulic channel to the second valve port AN2, to which the travel simulator WS is connected. The left side of the second valve chamber K2 forms the second valve seat VS2 of the valve MV, which interacts with the second valve closing element VSK2. A third valve chamber K3 is arranged between the two valve seats VS1 and VS2 and is connected to the third valve port AN3 for the master brake cylinder SHZ or THZ. A plunger ST is integrally formed or attached to the side of the first valve closing element VSK1 facing away from bolt 7, 7a. Its length is such that it extends through the first valve seat VS1 and the third valve chamber K3, and its free end can act on the second valve closing element VSK2 when the 3 / 2-way valve MV is energized. In the figure, the pressure supply device is connected to the second brake circuit BK2.

[0026] The Figure 2bFigure 1 shows the "energized" state of the solenoid valve MV, in which the armature is moved to the right by the magnetic field of the excitation coil. This causes the first valve closing element VSK1 to move to the right and, with the plunger ST, to press against the second valve closing element VSK2, pushing it away from the second valve seat VS2 against the spring force of the valve spring VF. This connects the pressure supply unit DV to the reservoir VB. The hydraulic connection HV1 between the first valve chamber K1 and the third valve chamber K3 is open, thus connecting the working chamber of the pressure generating unit DV to the reservoir VB and disconnecting the brake circuit.

[0027] The dimensioning of the valve spring VF determines the opening pressure in the fallback position, e.g., in the event of a failure of the primary brake circuit or the pressure supply unit DZ. Here, the legislator requires that a foot force of 500 N on the brake pedal 1 must be able to generate a vehicle deceleration of 0.24 g. By dimensioning the valve spring for an opening pressure of 75 bar in the master brake cylinder, almost three times the deceleration value can be achieved.

[0028] The valve spring VF should be dimensioned so that the magnetic armature 4 is reliably reset and the valve closing element VSK is reliably pressed against the first valve seat VS1 in a sealing manner.

[0029] Fig. 3The diagram shows the connections of the two 3 / 2-way valves PD1 and PD2 to the double-stroke piston DHK. In the depicted de-energized rest position, the valve closing elements VSK11 and VSK21 of both 3 / 2-way valves PD1 and PD2 are pressed against the respective valve seats VS11 and VS21, thus closing the hydraulic connection between the ports AN11 and AN13 or AN21 and AN23. When pressure is applied in the brake circuits BK1 or brake circuit BK2, the hydraulic fluid acting on the valve closing elements VSK11 and VSK21 exerts an additional force in the closing direction.

[0030] The chamber KV, which acts during the piston forward stroke, is connected via the hydraulic line HL2 to the central third valve port AN13 of the first 3 / 2-way valve PD1, whereas the chamber KH, which acts during the piston return stroke, is connected via the hydraulic line HL1 to the central third valve port AN23 of the second 3 / 2-way valve PD2.

[0031] The second valve ports AN12 and AN22 are connected to brake circuits BK2 and BK1, respectively. Brake circuits BK1 and BK2 are in turn connected to each other by a normally open circuit isolating valve KTV, which separates them when energized. The double-stroke piston DHK moves forward and backward to increase and decrease pressure. The pressure acting in the line / valve assists in opening the valve at both valve seats.

[0032] The circuit isolating valve KTV closes when a brake circuit BK1 or BK2 fails. To protect against a double fault: If a brake circuit BK1 or BK2 fails and the circuit isolating valve KTV fails simultaneously, this circuit isolating valve KTV can also be configured redundantly, e.g., by means of another circuit isolating valve KTV r connected in series.

[0033] Fig. 4The diagram shows the arrangement during the pressure build-up function with the double-stroke piston DHK during piston pre-stroke. In this process, the piston moves upwards, and the volume flow is directed via the energized 3 / 2-way valve PD1 with open valve seat VS22 and closed valve seat VS12 into brake circuit BK2 and via the circuit isolating valve KTV into brake circuit BK1. During the piston pre-stroke movement, the double-stroke piston draws volume from the reservoir VB via the open valve seat VS21 of valve PD2 and via the suction valve SV2.

[0034] Fig. 5 This shows the pressure drop during the return stroke of the double-stroke piston DHK with the valve seat VS12 open. Here again, pressure equalization between the two brake circuits BK1 and BK2 occurs via the circuit isolating valve KTV. The back pressure at valve seats VS12 and VS22 is caused by the pressure drop rate. This back pressure can be measured and regulated or controlled via the motor torque or via current or pressure from the pressure sensor.

[0035] From this piston position before the double-stroke piston return stroke, the pressure build-up can also be adjusted to high pressure ranges, up to, for example, 200 bar. In this process, the 3 / 2-way valve PD2 is energized, closing valve seat VS21 and opening valve seat VS22. This increases the pressure in brake circuit BK1 and, via the circuit isolating valve KTV, also in brake circuit BK2. During the piston return stroke, the double-stroke piston draws volume from reservoir VB via the open valve seat VS1 and the suction valves SV1 and VS11 of PD1.

[0036] The Figure 6Figure 1 shows another possible embodiment of the actuation system according to the invention, wherein only one 3 / 2-way valve PD1 is provided, with which either the first working chamber KV or the second working chamber KH is connected to the reservoir VB via the hydraulic line HL3. The controlled switching valve PD1s serves for the selective hydraulic connection of the first hydraulic line HL1 or the second working chamber KH to a first hydraulic circuit BK1. A second controlled switching valve PD2s, in turn, serves for the selective hydraulic connection of the second hydraulic line HL2 or the first working chamber KV to a second hydraulic circuit BK2, wherein, in particular, the second hydraulic line HL2 is connected to the second hydraulic circuit BK2 via a fifth hydraulic line HL5, and the second controlled switching valve PD2s serves for the selective closing or opening of the fifth hydraulic line HL5.A third controlled circular separation valve KTV allows both hydraulic circuits BK1 and BK2 to be hydraulically connected or separated from each other.

[0037] The Figure 7 shows the schematic setup of the circuit according to Figure 6 .

[0038] Figure 8 The actuation system according to the invention is shown in the Figure 6 and 7 in use with a brake system with a master cylinder, which can be designed as a single master cylinder (SHZ) with only one working chamber (R1) or as a tandem master cylinder (THZ) with two working chambers (R1 and R2). The connection of the master cylinder essentially corresponds to that in Figure 1 described.

[0039] The Figure 9Figure 1 shows a possible structural design of the 3 / 2-way valve. The upper part, consisting of the magnetic armature 4, excitation coil 5, and magnetic yoke 6, corresponds to the design of a standard 2 / 2-way inlet valve for an anti-lock braking system (ABS). Therefore, a detailed description of this part is omitted here, and only the lower part, which converts the 2 / 2-way valve into a 3 / 2-way valve, is described in detail.

[0040] The magnetic yoke 6 serves as a guide for the bolt 7, 7a, which is connected to the first valve closing element VSK1. Compared to the standard version of the 2 / 2-way inlet valve, the bolt 7 can be made smaller in diameter, thus increasing the effective pivot area. This also allows for the installation of a permanent magnet PM in the yoke 6 to provide force assistance to the return spring VF, as shown in Figure 6The first valve closing element VSK1 interacts with the first valve seat VS1 and is hemispherical to ensure a reliable seal. The first valve seat VS1 is located in the magnetic yoke 6. However, the first valve seat VS1 can also be integrated into the magnetic yoke 6 or implemented via a crimped plate. A plunger ST is integrally formed with the first valve closing element VSK1 or connected to the bolt 7a. The plunger extends through the first valve seat VS1 and acts on the second valve closing element VSK2, which is spherical and interacts with the second valve seat VS2.

[0041] As shown, the second valve seat VS2, together with the ball VSK2 and the valve spring VF, can be combined into a separate housing as a single unit. This offers advantages in pre-assembly and valve adjustment. The unit is pressed into the yoke housing for this purpose. To measure the tappet stroke, the ball stop has a bore to allow a measuring pin to detect the ball's travel. A power supply is recommended for a secure connection of the unit to the magnetic yoke. To protect the valve seats VS1 and VS2, all connections to the brake circuit, master cylinder, and travel simulator are protected by filters F1, F2, and F3.

[0042] The valve adjustment is carried out in such a way that the plunger ST has a small distance to the ball VSK2.

[0043] To reduce coil heating, the excitation winding 5 can be potted with the magnet housing 9. Additionally, a finned heat sink 10 can be provided. Reference symbol list:

[0044] 1 Pedal 2 Reservoir 3 Piston tappet 4 Magnetic armature 4a Magnetic armature stop 4 5 Excitation winding 6 Magnetic yoke 7, 7a Bolt 7, 7a Bolt AN1, AN2, AN3 Valve connections BK1, BK2 First and second brake circuit BP1, BP2 Isolating valves DVD Pressure supply device F1, F2, F3 Filter FP Force by hydraulic pressure H Stroke of the magnetic armature HV1 First hydraulic connection HV2 Second hydraulic connection K1, K2, K3 Valve chamber HLi Hydraulic lines MV, PD1, PD2 3 / 2-way valves PD1s, PD2s Isolating valve R1, R2 Working chambers of the master brake cylinder SHZ / THZ Single or tandem master brake cylinder VF Valve spring VS1, VS11 First valve seat VS2, VS22 Second Valve seat VSK11, VSK22, valve closing body WS, path simulator MVs, shut-off valve

Claims

1. Hydraulic actuation system for a hydraulic system, in particular in the form of a brake system, comprising: - at least one hydraulic circuit (BK) with at least one hydraulic consumer, in particular in the form of a hydraulically actuated wheel brake, - at least one pressure generating device (DV) comprising a pump, in particular in the form of a piston pump, which is suitable for pressure control or regulation, in particular for pressure build-up and pressure reduction (pup , pdown ), in the at least one hydraulic circuit (BK1, BK2), characterized in that the pressure generating device (DV) can be selectively connected to or disconnected from a reservoir (VB) by means of at least one controlled 3 / 2-way valve (PD1, PD2).

2. Hydraulic actuating system according to claim 1, characterized in that the pressure supply device (DV) has a piston pump, in particular with a plunger piston or double-stroke piston and at least one working chamber (KV, KH), and that a first controlled 3 / 2-way valve (PD1) is assigned to the first working chamber (KV), whereby the first controlled 3 / 2-way valve (PD1) can be used to connect either the first working chamber (KV) to a first hydraulic circuit (BK1) or to the reservoir (VB).

3. Hydraulic actuating system according to claim 2, characterized in that the pressure generating device (DV) has a double-acting piston (DHK) which seals off the first and second working chambers (KV, KH) from each other, and that a second controlled 3 / 2-way valve (PD2) is assigned to the second working chamber (KH), whereby the second working chamber (KH) can be connected either to a second hydraulic circuit (BK2) or to the reservoir (VB) by means of the second controlled 3 / 2-way valve (PD2).

4. Hydraulic actuating system according to claim 2, characterized in that a second controlled switching valve (PD2s) is assigned to the one second working chamber (KR), which is a 2 / 2-way valve via which the second working chamber (KH) can be selectively connected to or disconnected from the second hydraulic circuit (BK2).

5. Hydraulic actuating system according to one of claims 1 to 4, characterized in that a circuit isolating valve (KTR) is provided for selectively hydraulically connecting or disconnecting the two hydraulic circuits (BK1, BK2), which serves in particular to open or close a hydraulic line (HL1-2) connecting the two hydraulic circuits (BK1, BK2) to each other.

6. Hydraulic actuation system according to claim 5, characterized in that a further circuit isolating valve (KTRs) is arranged in series with the circuit isolating valve (KTR) in the hydraulic line (HL1-2).

7. Hydraulic actuating system according to claim 1, characterized in that the pressure generating device (DV) has a double-stroke piston (DHK) which seals off the first and second working chambers (KV, KH) from each other, and that at least one of the two working chambers (KV, KH) of the pressure generating device (DV) is always connected to a reservoir (VB) by means of a controlled 3 / 2-way valve (PD1).

8. Hydraulic actuating system according to claim 7, characterized in that, in an intermediate position of the controlled 3 / 2-way valve (PD1), both working chambers (KV, KH) of the pressure generating device (DV) are connected to the reservoir (VB) at the same time.

9. Hydraulic actuating system according to claim 7 or 8, characterized in that the pressure generating device (DV) has a double-acting piston (DHK) which seals off the two working chambers (KV, KH) from each other, wherein a first hydraulic line (HL1) connects one working chamber (KV) to a first valve connection (AN1) of the controlled 3 / 2-way valve (MV), and that a second hydraulic line (HL2) connects one second working chamber (KV) to a second valve connection (AN2) of the controlled 3 / 2-way valve (PD1), and that the third valve connection (AN3) of the controlled 3 / 2-way valve (PD1) is connected to the reservoir (VB) via a third hydraulic line (HL3).

10. Hydraulic actuating system according to claim 9, characterized in that in a first valve position of the controlled 3 / 2-way valve (PD1), only its first valve connection (AN1) is in hydraulic connection with the third valve connection (AN3), and that in a second, in particular energized, valve position of the controlled 3 / 2-way valve (PD1), only its second valve connection (AN2) is hydraulically connected to the third valve connection (AN3), whereby, in particular in the positions between the first and second valve positions, all three valve connections (AN1, AN2, AN3) of the controlled 3 / 2-way valve (PD1) are hydraulically connected to each other.

11. Hydraulic actuating system according to one of claims 7 to 10, characterized in that a first controlled switching valve (PD1s) serves to selectively hydraulically connect the first hydraulic line (HL1) or the second working chamber (KH) to a first hydraulic circuit (BK1), in particular the first hydraulic line (HL1) is connected to the first hydraulic circuit (BK1) via a fourth hydraulic line (HL4), wherein the first controlled switching valve (PD1s) serves to selectively shut off or open the fourth hydraulic line (HL4).

12. Hydraulic actuating system according to one of claims 7 to 11, characterized in that a second controlled switching valve (PD2s) serves to selectively hydraulically connect the second hydraulic line (HL2) or the first working chamber (KV) to a second hydraulic circuit (BK2), in particular the second hydraulic line (HL2) is connected to the second hydraulic circuit (BK2) via a fifth hydraulic line (HL5), wherein the second controlled switching valve (PD2s) serves to selectively shut off or open the fifth hydraulic line (HL5).

13. Hydraulic actuating system according to one of claims 11 or 12, characterized in that both hydraulic circuits (BK1, BK2) can be hydraulically connected to or disconnected from each other via a third controlled switching valve (KTV).

14. Hydraulic actuation system according to one of the preceding claims, characterized in that either the pressure generating device (DV) can draw hydraulic fluid from one or more supply containers (VB) into at least one working chamber (KV, KH) via at least one suction valve (SV1, SV2) and / or a pressure or piston position can be regulated or adjusted by means of the double-stroke piston (DHK) during both the forward and return strokes and / or a safety shut-off valve (MVs), which is open when de-energized, is arranged in the connecting line () connecting the valve (MV) to the reservoir (VB), which disconnects the hydraulic connection between the reservoir (VB) and the valve (MV), in particular in the event of a malfunction and / or leakage of the valve (MV).

15. Brake system with a hydraulic actuation system according to one of the preceding claims, with at least one brake circuit (BK1, BK2) in which at least one hydraulically acting wheel brake is arranged in each case.