EP4320018A1

EP4320018A1 - Fail-safe braking system

Info

Publication number: EP4320018A1
Application number: EP22721283.4A
Authority: EP
Inventors: Heinz Leiber
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-04-07
Filing date: 2022-04-06
Publication date: 2024-02-14
Also published as: WO2022214521A1; US20240157923A1

Abstract

The invention relates to a braking system, comprising: - at least two wheel brake cylinders (RZ₁-₄), which are part of respective separate wheel circuits (RK₁-₄); - at least one pressure supply (DV), which is used at least for the pressure build-up (_Pauf) in the wheel brake cylinders (RZ₁-₄); - at least one reservoir (VB); - at least one electronic open-loop and closed-loop control device (ECU); - switching valves (SV2K₁-₄); wherein each wheel brake cylinder (RZ₁-₄) is connected, by means of an associated hydraulic connecting line, to a switching valve (SV2K₁-₄), which is used to disconnect and connect the hydraulic connection between the associated wheel brake cylinder (RZ₁-₄) and at least one additional hydraulic main line, by means of which the switching valve ((SV2K₁-₄) can be or is connected at least to the pressure supply (DV), at least the hydraulic connecting line and the wheel brake cylinder (RZ₁-₄) connected thereto being part of a wheel circuit (RK₁-₄). The braking system is characterized in that, in the case of at least one, more particularly all, of the switching valves (SV2K₁-₄), the electric drive or individual components thereof is/are redundantly implemented and/or the switching valve (SV2K₁-₄) has a force auxiliary device (EM2, 9), which applies, by means of its own magnetic field, a force (FM2) to a valve actuator or valve tappet (7), and/or the switching valve (SV2K₁-₄) has a restoring spring, which applies a force to the valve actuator or the valve tappet (7), said force preventing the corking of the switching valve (SV2K₁-₄), more particularly in one of two flow directions, and/or the braking system has at least one isolation valve (KTV, DV/TV), by means of which at least two wheel circuits (RK₁-₄) or brake circuits (I, II) can be disconnected from or connected to each other.

Description

Fail-safe braking system

State of the art

For almost 80 years, today's 2-circuit brake system with two brake circuits has prevailed for safety reasons and is used depending on the vehicle design in a brake circuit layout a) diagonal and b) black/white or front axle/rear axle. In the event of a brake circuit failure, the braking effect is reduced by a) by 50% and by b) by up to approx. 70%. In the statistics, 10 ppm/J is calculated for a brake circuit failure. Due to the reduced braking effect or total failure of the brake, there is a considerable risk of an accident.

DE 10 20 2018 213 306 describes a system with detection of brake circuit failure due to a leak in the brake circuit by evaluating the pressure gradient.

Almost all vehicles have electronic brake control systems for all four vehicle wheels, which are usually braked hydraulically. Each wheel brake cylinder is connected to at least one or two electromagnetically controlled control valves, which are electrically controlled by an electronic control unit (ECU), e.g. to prevent the wheel from locking.

In today's conventional brake systems with ABS/ESP function, each wheel brake cylinder is usually assigned an inlet valve and an outlet valve, with the inlet valve usually having a check valve connected in parallel so that the inlet valve, which is often also referred to as a switching valve, does not function during rapid pressure reduction closes due to the dynamic pressure.

If an inlet valve with its associated non-return valve fails and becomes leaky, today's dual-circuit brake systems fail if the Wheel brake cylinder usually takes up an entire brake circuit, so that the braking effect is reduced by at least 30%.

object of the invention

The object of the invention is to provide a very fail-safe brake system which makes do with as few valves as possible.

solution to the task at hand

This object is advantageously achieved with a brake system having the features of claim 1. Further advantageous refinements of this braking system result from the features of the dependent claims.

Advantages of the Invention

The invention is characterized in that the most fail-safe components are used and/or appropriate safety valves, in particular in the form of isolating valves, are provided between the pressure supply and the wheel brake cylinders and/or between wheel circuits or brake circuits.

An inlet valve commonly used for ABS/ESP has a parallel non-return valve, which is considered to be unsafe in terms of tightness and can therefore no longer be used. As described above, the non-return valve was provided so that the inlet valve does not close due to the dynamic pressure during rapid pressure reduction.

It is therefore advantageous if, instead of an inlet valve with a parallel non-return valve, a switching valve is used which is designed to be secure against being closed at least in one direction of flow, even at high flow speeds or high pressure gradients.

The switching valve, which is assigned to each wheel brake cylinder, should also be designed to be as fail-safe as possible, so that in principle no further valves, in particular isolating valves, are required to decouple a leaky wheel circuit or brake circuit. Should the si- safety can be increased, at least one of the isolating valves described above can also be provided.

To increase the reliability and braking effect in the event of a fault, switching valves for the wheel brake cylinders can also be used, in which case the electromagnetic drive or at least some of its components are provided or designed redundantly, i.e. at least twice. For example, the switching valve can have at least two coils and two coil controls, which can switch the switching valve separately from one another, so that if one coil or its control fails, the other can take over its function, so that the switching valve is significantly more fail-safe and thus the entire coil Braking system is advantageously fail-safe.

The coils can also be designed in such a way that they can safely switch the valve alone up to a certain pressure of e.g.

The valve according to the invention is understood to mean the valve assigned to a wheel brake cylinder in each case, via which hydraulic medium flows to build up pressure in only this wheel brake cylinder. The wheel circuit here is then understood to mean the wheel brake cylinder including the hydraulic connection from the valve to the wheel brake cylinder. Of course, the hydraulic medium can also flow from the associated wheel brake cylinder through the valve SV2k back into the brake circuit BK1 or BK2 to reduce the pressure. An outlet valve assigned to a wheel brake cylinder also belongs to the respective wheel circuit.

To avoid the problems described above, a switching valve of the "normally open" type described above can be used for the braking system according to the invention, the valve actuator of which can be moved by means of a first electromagnetic drive from the open valve position to the closed valve position, in which the valve actuator is pressed against a valve seat , is adjusted. If the electromagnetic drive is not or not sufficiently powered, a valve spring presses the valve actuator into the Starting position, ie in the open valve position. In an advantageous development of the switching valve described above, this has an additional additional force device that generates an additional force on the valve actuator, which is directed in the direction of the open valve position and thus supports or replaces the valve spring, resulting in an increased resulting force , with which the valve actuator is subjected to a force in the open valve position.

The additional power device can be switchable, e.g. by an additional electromagnet to the actual valve drive. It can therefore also be referred to as an active additional power device, since the additional power generated on the valve actuator can be switched on or off depending on the state of the brake system. However, it is also possible for the additional power device to act passively, e.g. by using a permanent magnet. It is also within the meaning of the invention if the additional power device has an electromagnet and a permanent magnet. In all of the above-described embodiments, a force supporting the valve spring is advantageously exerted on the valve actuator by means of the additional force device in order to keep it in its open position so that the valve does not accidentally close.

In the case of an only active additional power device, in order to close the switching valve, its drive only has to act against the force of the valve spring, which can be made smaller due to the switchable additional power device, which means that the switching valve closes securely and the tightness is guaranteed by a high contact pressure.

With a purely passive additional power device, the actual actuator of the switching valve only has to apply increased force at the start of the stroke movement from the open position in the direction of the closed position in order to overcome the passive and therefore permanent additional force. As the air gap increases, the force of the passive additional power device will decrease rapidly and will have less of an effect when the valve is in the closed position. Because the switching valve is the safety gate for the brake circuits BK to the wheel brake cylinder RZ. If one of the four hydraulic connections from the hydraulic control unit to a wheel brake cylinder fails in the brake system according to the invention, or if there is a leak in the wheel brake cylinder, the faulty hydraulic connection or the faulty wheel brake cylinder can be decoupled from the rest of the brake system with a high degree of certainty by the switching valve according to the invention.

The additional power device only has to be switched on or take effect when a rapid pressure reduction has to take place. In all other operating states of the braking system, the additional holding or supporting force of the additional power device is not required, so that advantageously energy can be saved. In the brake system according to the invention, if one wheel circuit fails, only the braking effect of this one failed wheel circuit is lost, with the braking effect of the remaining three wheel circuits still being available. There is therefore only a reduction in the braking effect from four to three intact wheel circuits, so that if one wheel circuit on the front axle fails, only approx. 35% loss of braking effect is recorded in contrast to 70%, as described above for one black/white brake circuit division, if an entire brake circuit and thus two wheel circuits fail.

The possible embodiments of the switching valve described above can, but do not have to, be used in the brake system according to the invention.

So it is quite possible that only the isolating valves described have to be used in braking systems.

The brake system according to the invention generally has four wheel circuits, in which either two wheel circuits are assigned to a brake circuit or three wheel circuits are assigned to a first brake circuit and a fourth wheel circuit forms its own brake circuit. If one wheel circuit fails, the three remaining wheel circuits are advantageously available for the braking effect. In the event of dirt particles in the brake fluid, the functional reliability of the brake system according to the invention can be additionally increased by installing at least one filter with a small mesh size at the inlet and/or outlet of the valve. The mesh size should be selected so small that when the switching valve is closed, these small dirt particles only produce small leaks and thus only small flow rates, which can be compensated for by the pressure supply, but which can be determined by the diagnosis both via the flow rate of the pressure supply and via the level in the reservoir can be detected.

In order to check the function of the switching valve according to the invention, a measurement of the volume intake and the time profile of the pressure in the respective wheel circuit and a comparison with the previously determined pressure-volume characteristic curve of the wheel circuit can be carried out during diagnosis, for example. The diagnosis can be carried out each time the brakes are applied and/or when the vehicle is stationary or during servicing.

As described above, the switching valve that is to be used with preference does not require a check valve, and still meets a wide variety of requirements. It must remain securely open in both directions even at high flow rates, i.e. the weak point that is typical of today's valves, that at high flow rates a force acts on the valve cone and valve spring due to effects on the valve seat and the valve closes automatically, must not occur.

In addition to the additional force device, the switching valve can advantageously be optimized by a corresponding design of the sealing cone, the dimensions of the restoring spring and the valve tappet. In the closed position of the valve, which can also be called the inlet valve, but which can also be used to reduce the pressure in the wheel brake cylinder, the opening force should be significantly smaller than when using a progressive spring, which has a higher force in this position than in the open position , which is unfavorable for the dimensioning of the magnetic circuit because of the correspondingly higher power requirement. The brake system according to the invention can have various valve circuits: a) four switching valves for four wheel brake cylinders each, via which both the pressure build-up and the pressure reduction for the respectively assigned wheel brake cylinders take place; b) four switching valves for four wheel brake cylinders each and two outlet valves; c) four switching valves and four exhaust valves.

When using an outlet valve for a wheel circuit, wheel-specific regulation of pressure build-up Pauf and pressure reduction Pab is possible. Should a leak occur in a wheel circuit, a diagnostic circuit can advantageously identify the faulty wheel circuit both when braking and when parking and close the switching valve belonging to the wheel circuit, so that in the case of this single fault three more wheel circuits and in the case of a double fault, i.e. if two wheel circuits fail at the same time, two wheel circuits are available in the "worst case". With conventional brake systems, on the other hand, the "worst case" results in total brake failure.

In summary, it can thus be stated that a high level of safety can advantageously be achieved by small changes to the inlet valve and the omission of the check valve with the switching valve. With a corresponding structural design of the switching valve, a cost reduction is possible in addition to the safety gain.

The brake system according to the invention can also be designed in such a way that instead of four hydraulic wheel circuits, a mixed hydraulic-electrical brake system is provided with, for example, hydraulic lines to the hydraulically operated front wheel brakes and only electrical connections to the electromotive brakes (EMB) on the rear axle, the structure of which is known is. Here, too, the same advantages result if the hydraulic wheel circuits are designed in accordance with the above-described versions. If a circuit separating valve is also used between the two brake circuits or additional circuit separating valves between the brake circuit and the pressure supply, even if one wheel circuit fails, it can be separated via the circuit separating valve so that the remaining wheel circuit of the respective brake circuit is still effective. In this way, double error security is achieved with a vehicle deceleration of 0.65 g.

In addition to the valve concepts described, different pressure supply concepts are also possible, e.g. a single pressure supply for level 2 of automated driving or two pressure supplies for level 3 to level 5 of automated driving, whereby the second, redundant, pressure supply can contain a piston pump or a rotary pump. The rotary pumps have a clear cost advantage. In the case of the piston pump, a simple non-return valve can be used at the outlet of the pressure supply instead of the solenoid valve, which has the same advantages if the pressure supply fails and is more economical. In this braking system, the pressure reduction during normal braking cannot take place via the control of the piston of the pressure supply, but via the control of the outlet valves using the pressure sensor signal from the pressure sensor. Since at least two outlet valves are used, there is also redundant pressure reduction. One, two or more exhaust valves can be opened depending on the pressure reduction speed requirement and the number of exhaust valves.

Solenoid valves can be provided to isolate the pressure supply from the brake circuits. However, it is also possible to dispense with such isolation valves if the pressure supply is provided with a drive with redundant winding wiring, e.g. 2x3 phases and/or redundant control, such that no further valves are provided between the switching valves assigned to the wheel circuits and the pressure supply are. In order to prevent a failure of the brake system, e.g. due to a leaking piston seal or small piston clearance, compensation is provided by replenishment.

Advantageously, the usual vehicle Coordination in various areas such as logistics, service and homologation is no longer necessary.

The brake system according to the invention thus has four wheel circuits that are controlled individually. As described above, two wheel circuits can be assigned to one brake circuit. Other allocations to the brake circuits, as described above, are also possible.

However, the 4-wheel circuit braking system can also be activated by the controller as a 2-circuit braking system. Thus, the 4-wheel circuit braking system can be combined with 2-circuit braking systems with four hydraulically braked wheels and thus even achieves double error safety, which means that a leak in a wheel brake cylinder and the failure of the control of the associated switching valve do not lead to a total failure of the braking system leads, whereby this double fault occurs with the low probability of failure of approx. 10 ¹⁹ /J, which is still significantly better than nuclear power safety. Even with this double error, the braking system according to the invention would still achieve a braking effect of a conventional 2-circuit braking system.

The brake system can thus be described as fail-safe and fail-safe.

Advantageously, the leaks in the individual wheel circuits are diagnosed at intervals or continuously, with the electronic control and regulating device of the brake system deciding, depending on the diagnosis result, whether a wheel circuit is switched off by permanently closing the associated switching valve or whether it continues to be operated to generate a braking effect . During further operation, a corresponding additional promotion or re-delivery of braking medium is calculated and carried out on the basis of the leakage determined, so that the required braking effect of the respective wheel brake cylinder is achieved.

In order to get to the brake system according to the invention starting from the known brake systems, the known inlet valves with check valve only have to be replaced by the modified switching valve, with almost no additional costs arising. The switching valve has another potential, which is used if the outlet valve assigned to the respective wheel circuit fails. If, for example, the control of the exhaust valve fails, ABS pressure reduction via the exhaust valve is no longer possible, ie the corresponding wheel locks with loss of braking distance and lateral stability. However, since the switching valve can be used in both directions for pressure build-up and pressure reduction, since it cannot be pulled shut, it can also be used for pressure reduction if, for example, the pressure supply can accommodate the volume required for pressure reduction. Since the switching valves do not contain a non-return valve, the pressure in one wheel brake cylinder, e.g. RZ1 via SV2kl, is not reduced at the same time as the pressure in the other wheel brake cylinders, e.g. wheel brake cylinders RZ2, RZ3 and RZ4 when valves SV2k2, SV2k3, SV2k4 are closed. As described in earlier patent applications, this can advantageously be implemented with volume control of the piston of the pressure supply or also with a rotary pump. There is only a small disadvantage for the ABS control due to a small time delay of the pump for the volume intake for the pressure reduction, as well as for the volume provision for the pressure build-up. This is extremely rare, however, as it only happens when the exhaust valve fails. However, locking a wheel during the ABS function must be avoided at all costs, especially with braking systems for automated driving at level >3.

The switching valve thus has a wide range of functions in the safety-relevant braking system according to the invention:

1. Improved braking effect if a wheel brake cylinder or wheel circuit fails

2. Maintenance of the pressure reduction control function with ABS in the event of failure of the exhaust valve to open

3. Saving of additional isolating valves to prevent circuit failure

For these types of faults, it is advisable to design the switching valve with redundant coils with a connection, since the coil with an electrical connection is the main point of failure. character description

Various possible embodiments of the brake system according to the invention and the valves used are explained in more detail below with reference to drawings. They show: FIG. 1: shows a first known brake system with its main components and its possible sources of error;

1a: shows a second known brake system with its main components and its possible sources of error; 2: shows the structural design of a switching valve according to the invention with a conventional coil and a redundant double coil;

2a/2b/2c show the operating principle of the modified switching valve with an additional electromagnetic or permanent-magnetic force-generating device;

FIG. 3 shows the first known brake system from FIG. 1 with tandem brake master cylinder THZ, pressure supply DV and control and regulating valves and with switching valves according to the invention instead of inlet valves with parallel check valves.

3a: shows a third known brake system with tandem brake master cylinder THZ, pressure supply DV and control and regulating valves and with switching valves according to the invention instead of inlet valves with parallel check valves; 3b: shows a fourth known system with tandem master brake cylinder THZ, pressure supply DV and control and regulating valves and with switching valves according to the invention instead of inlet valves with parallel check valves; Fig. 3.1 shows different valve circuits DV/TV in addition to SV2k for connecting the wheel brake cylinders to the pressure supply DV and the single master brake cylinder SHZ;

4: shows the second known brake system from FIG.

Fig. 4.1 shows different valve circuits DV/TV in addition to SV2k for connecting the wheel brake cylinders to the pressure supply DV and the single master brake cylinder SHZ;

5: shows different valve circuits 3/2 MV in addition to SV2k for connecting the wheel brake cylinders to the pressure supply DV and the single master brake cylinder SHZ; FIG. 5.1 shows a redundant pressure supply DV2 for brake circuit BK1 for the brake system according to FIG. 5;

FIG. 5.2 shows two redundant pressure supplies DV2 and DV3 for brake circuit BK1 and brake circuit BK2 for the brake system according to FIG. 5; 5.3 shows for the brake system according to FIG. 5 a redundant pressure supply DV2 for brake circuit BK1 or brake circuit BK2 with switchover valve TV 3/2 for failure BK1 or BK2;

6 shows different valve circuits DV/TV in addition to SV2k for connection to the pressure supply DV and the single master brake cylinder SHZ;

FIG. 7 shows a time profile of the pedal force in the event of a fault for generating an acceptable pedal feel;

Fig. 8: shows a further time profile of the pedal force in the event of a fault for generating an acceptable pedal feel. 1 and FIG. 1a show the main points of failure that lead to circuit failure in two different known systems. these are

1) The RZ wheel brake cylinder, the failure of which can contribute to the following component failures

1.1 Connection to the hydraulic unit HCU

1.2 Brake line

1.3 Connection of brake hose to brake line (not marked in the figures) 1.4 Brake hose

1.4 Connection of brake hose to brake caliper (not marked in the figures)

1.5 caliper

1.6 Wheel brake cylinder seal RZ 1.7 Check valve of the inlet valve El - E4

1.8 AV outlet valve: The AV is a critical component for brake circuit failure with ABS, e.g. dirt particles in the valve seat can cause a brake circuit failure with a significant loss of braking effect. 2) The circuit separating valve KTV

3) The DV/TV valve: isolating valve from the brake circuit to the pressure supply

4) The valve HZ/T V: Isolating valves from the brake circuit to the master brake cylinder HZ

5) The pressure supply DV Fig. 2 shows the special switching valve SV2k required in the above-described embodiments, which works reliably in both flow directions, ie even with large flow rates, such as 100cm ³ /s - 120cm ³ /s, and large pressure differences across the switching valve, such as eg 160bar - 220bar. In particular for the above-described area, this SV2k valve ensures that it cannot close unintentionally on its own. The switching valve SV2k according to the invention has the typical structure of a solenoid valve with an electromagnetic circuit EMI with armature 6, valve actuator or valve tappet 7 and valve seat 8 and return spring 13 (see also FIG. 2a). The restoring spring 13 can be dispensed with if the additional force device, which is formed by the permanent-magnetic circuit EM2 in FIG. 2, is designed accordingly (see also FIGS. 2a-2c). The SV2k switching valve is shown on the left with a conventional single spool and on the right with a redundant spool. The background is the analysis of the valve function «valve closing». Essentially, only the mechanical interference function "armature jammed" needs to be considered, with the switching valve SV2k being protected against dirt particles by filters F at the inlet and outlet. On the other hand, many influencing factors can occur, such as an electrical wire break, faults in the electrical connections EA (more than 4 connections) and in the ASIC. Since the switching valve SV2k is only relevant, for example, in the event of a double fault in the wheel circuit, a redundant design brings an enormous increase in safety, which is of great importance for level 3 automated driving, for example a system with an electronic brake pedal. This makes the SV2k switching valve double-fault-proof for various applications. In order to save installation space, the two coils only have 50% flow (ixn), so that only both coils together can switch the maximum pressure load of >200 bar. This means that in the normal case where the blocking limit is 100 bar, a single coil appears to be sufficient in the rare case of a fault. The valve drive EMI generates (see FIG. 2b) a strong progressive force FM1 over the armature stroke h, and the return spring 13 for restoring the armature generates a restoring force FRF which is progressive over the stroke h. In the left-hand part of FIG. 2a, the anchor 6 is coupled to a second force-generating element, which forms the additional force device according to the invention. This can consist of a second electromagnetic circuit EM2 with anchor 6a hen whose switchable force FM2 counteracts the force FM1 of the first magnetic circuit EMI. As a cheaper variant, a permanent magnetic circuit can also be used as a passive additional force device, consisting of a small permanent magnet 9 with a pole plate 10. The force effect of FM2 counteracts FM1 and acts with relatively strong force when the valve is open with a strong desired drop in force across the hub h. The force FM2 is (see Figure 2c) at the end of the stroke still large enough to take over the usual armature return, and can thus replace the usual restoring spring 13. In the closed valve position, the pressure difference P2-P1 acts on the valve seat with the force FP, which is directed towards the valve opening if the pressure P2 is greater than the pressure PI. In the open valve position, the described hydraulic force FH acts on the valve seat due to the volume flow Q through the valve, which the valve can tear open without countermeasures, both during pressure build-up Pauf and also during pressure reduction Pab, depending on how the valve SV2k is connected to the pressure supply DV and the wheel brake cylinder RZ is connected, and depending on the direction in which the volume flow is running.

The hydraulic force on the valve armature FH, which acts when the flow rate Q flows through the valve, acts in the open position of the valve. For this reason, the force of the additional force device FM2 should primarily act in this position and therefore, because of the falling force of FM2, it can close via the armature movement in the direction of the valve, so that in the open position it can be dimensioned higher than when using a spring with increasing force Close FRF in the direction of the valve when the armature moves.

The valve stem 7 can also have a special shape, which provides the counterforce through hydraulic flow forces and can adorn the closing force redu.

FIG. 24 shows the structural design of the switching valve SV2k according to the invention based on a series inlet valve. The corresponding parts in the standard part are all marked with an S. The non-return valve integrated in the series valve is not required. Only four additional parts are required for the additional power unit. these are 1. The permanent magnet 9

2. the pole plate 10

3. the electromagnetic yoke 11 and

4. a plastic body 12, which connects the parts together including the anchor.

Fig. 3 and Fig.4 show the two known systems of Fig. 1, respectively. 1a and FIG. 3a and FIG. 3b show two other known systems with master brake cylinder HZ, pressure supply DV and control and regulating valves. Here the well-known intake valve is replaced by the switching valve SV2k. This means that the advantages described can be achieved, e.g. if a wheel brake cylinder fails due to leaks and leaks in the associated outlet valve AV, possibly even with cost savings. This also applies to ABS/ESP, where conceptually not all boundary conditions for the function and advantages can be realized. For example, if a wheel brake cylinder RZ is leaking, then there can be no ABS function on the associated wheel, and ESP intervention on this wheel is then also not possible.

Fig. 3.1 corresponds to the patent application of Fig. 3 with master brake cylinder THZ, reservoir VB, pressure supply DV and solenoid valves MV 9 and 9a, master brake cylinder THZ, and solenoid valves DV/TV, pressure supply DV, and also the control valves AV1-AV4 and SV2kl-SV2k4 for ABS, whereby the associated valve SV2k can be closed if a wheel brake cylinder fails.

The two brake circuits BK1 and BK2 are connected to the wheel brake cylinders RZ1-RZ4 via hydraulic lines HL1-HL4. The reservoir is also connected to the wheel brake cylinders RZ1-RZ4 via hydraulic lines HL1-HL4. The two brake circuits BK1 and BK2 are connected to the DV via the isolating valves DV/TV and to the master brake cylinder THZ via the hydraulic line HL5 and the solenoid valves 9 and 9a.

A diagnostic system detects a leak and, if there is a leak in a wheel brake cylinder, eg RZ1, closes it via the corresponding solenoid valve SV2k, eg SV2kl, the connection from the wheel brake cylinder, eg RZ1, to the corresponding brake circuit, eg BK2 (so-called individual errors). If a double error occurs, eg an additional switching error SV2kl, the DV/TV valve assigned to the BK, eg BK2, closes. The pressure supply DV is driven by an EC motor. The individual functions are described in great detail in the corresponding patent application of FIGS. 3, 3a, 3b and 4.

Fig. 3.1 shows the simplified structure of a brake system according to the invention with four wheel circuits with the hydraulic connections HL1 - HL4 between the wheel brake cylinders RZ1 - RZ4 and the valves SV2kl - SV2k4. Here, for example, wheel circuit 1 consists of wheel brake cylinder RZ1 and hydraulic line HL1. The outlet valves can be provided optionally, with one, two or also four outlet valves being able to be provided. The hydraulic connections between the optional outlet valves AV and the reservoir VB are shown in dashed lines. The valves SV2k have a hydraulic connection to the pressure supply DV via the brake circuits BK1 and BK2. As is well known, DV piston pumps with so-called non-stepped single-stroke pistons and stepped pistons as double-stroke pistons with advance and return strokes are used as the pressure supply. The pressure supply DV with single-stroke piston has only one pressure outlet, while the pressure supply DV with double-stroke piston has two pressure outlets, see Fig. 5. A pressure supply DV with only one pressure outlet can be provided, for example, by a motor-driven piston-cylinder unit with only one pressure chamber or, for example, by a Be formed rotary pump. A pressure supply DV with two pressure outlets can be formed, for example, by a motor-driven double stroke piston pump with two pressure chambers, in which case each pressure or working chamber is connected to an outlet or forms it. The DV pressure supply with double piston is used advantageously for continuous delivery and also has advantages in the event of a fault in the four-circuit brake system when delivering to compensate for leaks. The DV pressure supply with double-stroke piston requires valve switching for the forward and return stroke. Both piston types also optionally use the KTV circuit separating valve to separate the two brake circuits BK1 and BK2. In the four-circuit braking system with SV2k as a safety valve and in the safe n-circuit braking system, in turn the KTV circuit separating valve and the two-circuit feed from the DV pressure supply can be dispensed with. With the safety advantages of switching valve SV2k in the event of failure of a wheel circuit RK1, RK4, the circuit separating valve KTV can be dispensed with if there is no double error safety, eg leakage from wheel brake cylinder 1 and leakage from valve SV2kl. The circuit separating valve KTV is not necessary even when using redundant switching valves SV2k or only in the case of extreme safety requirements.

If, on the other hand, a pressure supply with two outlets is used, see Fig. 5, one brake circuit BK1 or BK2 is connected to each outlet of the pressure supply DV, with the circuit separating valve KTV then being used to selectively connect or separate the two brake circuits BK1 and BK2. as shown in Figure 1. The notes on the redundant valve SV2k also apply here. The pressure supply DV preferably has an EC motor with one or two phases and a corresponding number of winding controls, so that redundant operation is ensured. One or two pressure transmitters DG for determining the ACTUAL pressure P actual _can be provided in the two brake circuits BK1, BK2. The master brake cylinder can optionally be designed as a single master brake cylinder SHZ or as a tandem master brake cylinder THZ, via which pressure can be generated in a brake circuit by means of the brake pedal if the pressure supply DV fails. The reservoir VB, which has a float with a sensor target 2 arranged thereon, can be connected or arranged on the master brake cylinder HZ, with the sensor element 1 being provided in the control and regulation unit ECU in order to detect the filling level of the reservoir. The function of the diagnostic system is important.

All of the system concepts considered here are related to brake-by-wire systems,

BBW, which have coupled a pedal travel simulator with isolation valve to the THZ or SHZ, and belong to the prior art and are therefore not described. It is also possible to equip non-BBW systems, eg ABS/ESP, by replacing the EV inlet valve with the SV2k valve with a 4-circuit function with a corresponding increase in safety.

The various brake circuits in different states are shown here in different drawings:

• 4-circuit in normal state from valve SV2k and valve AV to the wheel brake cylinder RZ with a thick line (see Fig. 3.1)

• 2-circle in the case of the double error of leaking wheel brake cylinder RZ and switching error of valve SV2k, thick dashed lines from SV2k to the valves DV/TV and to the master brake cylinder THZ/SHZ (see Fig. 5)

This also applies to Fig. 4.1, 5 and 6

Fig. 4.1 corresponds to Fig. 3.1 with minor differences, reduction in the solenoid valve MV to the single HZ (SHZ) and to the pressure supply DV with only 1 separating valve 9 or DV/TV. The optional separating valve KTV creates an additional upstream dual-circuit brake system with brake circuits BK1 and BK2, which, as already described, acts in the event of a double fault, e.g. if a wheel brake cylinder RZ is leaking and the associated valve SV2k has a switching fault, with fallback levels as in the 2-circuit system ( Failure of brake circuit BK1 with failure of pressure supply DV or failure of brake circuit BK2).

Fig. 5 contains a pressure supply DV with double-stroke piston DHK with 2 x 3/2 MV for perfect pressure control both in the forward and return stroke and extremely small volume. The KTV circuit separating valve is preferably used here for symmetrical volume control, since the 3/2 MV already cause a circuit separation. The SV2k valves can also be used redundantly, eg with a redundant coil, in order to still achieve a reliable braking effect in the event of the above-mentioned double fault: leakage in the wheel brake cylinder RZ + failure of the switching of the associated valve SVk. The facts about the redundant valve SV2k also apply here. This means that the circuit separating valve KTV is no longer necessary, since both connections can be connected to the double-stroke piston DHK. Fig. 5.1, Fig. 5.2 and Fig. 5.3 show the system 5 without master brake cylinder SHZ for SAE L3 with electric brake pedal, with redundant DV (DV1 and DV2).

In Fig. 5.1, a 4-circuit brake system is shown in which both outputs of the pressure supply DV1 are directly connected to each other. The redundant pressure supply DV2 is also connected directly to the two outlets of the pressure supply DV1, so that, for example, if the pressure supply DV1 fails, the pressure supply of the 4-circuit brake system can be ensured from the pressure supply DV2. A check valve RV is arranged between the valve DV/TV and the pump P of the pressure supply DV2 so that the double fault of leakage in the valve DV/TV and leakage in the pump P of the pressure supply DV2 does not result in a total failure of the brake. To diagnose the valve DV/TV for switching capability and leakage, the hydraulic connection between the check valve and the valve DV/TV is connected to the reservoir VB2 via the hydraulic line HL5, with an orifice DR being provided in this hydraulic line.

Normally, the legislator for braking requests only requires safety in the case of single errors. With the errors considered here, these systems with redundant data processing are at least secure against double errors, sometimes even against triple errors. This is achieved in Fig. 5.1 e.g. with the following double error in the event of failure of a wheel brake cylinder RZ due to a leak (1st error) and valve SV2k (2nd error), and in the case of triple error in the event of failure of a wheel brake cylinder RZ due to a leak (1st error), Leakage valve SV2k (2nd error) and switching error of the redundant (e.g. redundant coil) valve SV2k (3rd error) with vehicle deceleration z=65%.

If pressure supply DV1 fails, pressure supply DV2 is switched on via valve DV/TV (single error safety). With the pressure supply DV1 with ECE motor and 2 x 3-phase winding and low probability of failure of the ECE motor, almost double error safety of the pressure supply DV1 can be achieved here.

As in FIG. 5.1, FIG. 5.2 shows a second pressure supply DV2, but with a normally open valve KTV for separating the brake circuits BK1 and BK2 of the upstream 2-circuit brake system. In the three failures leakage Wheel brake cylinder RZ, failure of coil 1 and failure of redundant coil 2 of the associated valve SV2k, switching valve KTV can prevent both brake circuits BK1 and BK2 from failing. For example, if there is a leak in the wheel brake cylinder RZ1 and the switching of the valve SV2kl fails, the brake circuit BK2 fails and the valve KTV is then closed, with the brake pressure in the brake circuit BK1 being maintained with the second output of the pressure supply DV1. As an alternative to the pressure supply DV1, for example in the event of a failure of the pressure supply DV1, the brake pressure in the brake circuit BK1 can be maintained with the pump PI of the pressure supply DV2 in the case of this error combination. Depending on the brake circuit distribution, the remaining vehicle deceleration is z = 30% - 70%. This means that there is security in the event of a triple error. For the same reason as explained in Fig. 5.1, the check valves RV1 and RV2, the hydraulic lines HL5.1 and HL5.2 and the throttle DR1 and DR2 are provided for the pressure supply DV2.

If the pressure supply DV1 fails (4th error), the redundant pressure supply DV2 with two electric motors and two pumps is switched on. Inexpensive brush motors are sufficient here. Thus, with the DV2, security is achieved in the case of quadruple errors.

As in FIG. 5.2, FIG. 5.3 shows a second pressure supply DV2 with a normally open circuit separating valve KTV. In this concept, as in Fig. 5.2, in the event of a triple error, e.g be switched over to the intact brake circuit BK1. For example, if there is a leak in the wheel brake cylinder RZ1 and the switching of the valve SV2kl fails, the brake circuit BK2 fails and the valve KTV is then closed, with the brake pressure in the brake circuit BK1 being maintained with the second output of the pressure supply DV1. As an alternative to the pressure supply DV1, for example if the pressure supply DV1 fails, the brake pressure in the brake circuit BK1 can be maintained with the pump P of the pressure supply DV2 in the case of this error combination. With triple error security, a probability of failure in the range of approx. 10 ¹⁸ /year can be achieved with costs that can still be realized. In addition, with the low Stress duration during the error case and also pressure load of approx. 100 bar, in the case of rare failure both in performance, eg 70% and pressure range 70% and stress duration 20%, considerable costs can be saved. In the case of the double fault of a leak in the non-return valve RV and a leak in the pump P of the pressure supply DV2, the circuit separating valve KTV is closed. In this case, brake circuit BK1 fails, with the pressure in brake circuit BK2 being maintained via the pressure supply DV1. Alternatively, with this double fault, the KTV circuit separating valve can be closed and the DV/TV valve switched. The brake circuit BK2 then fails, the pressure in the brake circuit BK1 being maintained via the pressure supply DV1.

FIG. 6 shows a similar braking system to the system shown and described in FIG. 4.1. In this system, the 2-circuit brake system is constructed with 1st circuit BK1 made up of 3 RZ (RZ1, RZ3, RZ4) and the 2nd circuit BK2 with 1 RZ (RZ2). To do this, the optional circuit separating valve KTV must be placed between brake circuit BK1 and valve SV2k2. The advantage is the greater vehicle deceleration z = 65% in the event of a double error Failure of wheel brake cylinder RZ2 (front wheel) due to leakage and failure of the activation of valve SV2k2. The facts about the redundant SV2k also apply here.

FIG. 7 shows the progression over time of the pedal force in the event of an error in order to produce an acceptable pedal feel.

The error can be caused by a leak in valve 9 (e.g. Fig. 4.1). When the valve 9 is actuated, for example, there may be a leak in the hydraulic connection between the master brake cylinder and the brake circuit BK2 due to the ingress of dirt particles. In this case, a fallback level can be formed with the brake system according to the invention, in which the preservation of the brake pedal characteristics or the pedal feel is produced by brake pedal force blending with the pressure supply DV.

Normally, when the driver brakes, the valve 9 is closed and with the pressure supply DV the pressures in the wheel brake cylinders RZ1 - RZ4 are adjusted to target pressures, which are derived from the brake pedal travel. set. When the driver brakes (no recuperation, or the brake pressure in brake circuit BK2 is greater than the pressure in the master brake cylinder SHZ or THZ), brake fluid flows from brake circuit BK2 via the leaking valve 9 into the master brake cylinder SHZ or THZ, as a result of which the brake pedal is pressed back, the brake pedal force or the pressure in the master brake cylinder SHZ or THZ is increased and the brake pedal travel is reduced.

In an intact brake system, each brake pedal travel has a defined pedal force or a defined pressure in the main brake cylinder SHZ or THZ, which defines the pedal characteristics and is determined by the design of the travel simulator WS (see Fig. 3.1). The pressure in the master brake cylinder is measured, e.g. directly with a pressure sensor DG-SHZ (see Fig.

3.1), or indirectly with a force-displacement sensor (not shown) which can measure the pedal force, for example. The brake pedal travel is measured with a pedal travel sensor Sp, which is shown in FIG. 3.1. A setpoint pressure in the master brake cylinder or setpoint pedal force can thus be determined for each brake pedal travel. The pedal characteristics are designed in such a way that the pressure in the brake circuit is greater than the pressure in the master brake cylinder.

In the following, the process after discovering the fault is described using a pressure sensor DG-SHZ, which can measure the pressure in the master brake cylinder SHZ, as an example. The fault is detected by constantly comparing the actual pressure in the master brake cylinder SHZ, which is measured using the pressure sensor DG-SHZ, with the target pressure in the master brake cylinder SHZ, which is determined using the pedal characteristics and the measured brake pedal travel. In the fallback level, if the difference between the actual pressure that is measured and the target pressure exceeds a selectable upper limit value, eg lbar, the pressure supply DV is stopped and the valves SV2kl-SV2k4 to the wheel brake cylinders RZ1-RZ4 are closed. The activation of the valve 9 is switched off and the pressure in the pressure supply DV is reduced by the activation of the pressure supply DV. As a result, brake fluid flows out of the master brake cylinder SHZ, through the open connection from the master brake cylinder SHZ to brake circuit BK2, into brake circuit BK2 and through valve DV/TV into the pressure supply DV. If the difference between the actual pressure and the target pressure in the master brake cylinder SHZ falls below a selectable lower limit value, e.g Wheel cylinders RZ1 - RZ4 are set to target pressures again with the pressure supply DV. As already described, this causes the actual pressure in the master brake cylinder SHZ to be increased again due to the error and the brake pedal travel is reduced again. If the difference between the actual pressure and the target pressure in the master brake cylinder SHZ again exceeds the selectable upper limit value, then the switching valves SV2kl - SV2k4 to the wheel cylinders RZ1 - RZ4 are closed, valve 9 in the brake circuit is opened and the pressure supply DV is used to Pressure in the main brake cylinder SHZ reduced, which repeats the process. As a result, the brake pedal feel remains largely normal. However, the brake pedal may vibrate slightly.

FIG. 8 shows a further progression over time of the pedal force in the event of an error in order to produce an acceptable pedal feel. When the driver brakes in this way with recuperation, or the pressure in brake circuit BK2 is lower than the pressure in the master brake cylinder SHZ, brake fluid flows out of the master brake cylinder SHZ via the leaking valve 9 into brake circuit BK2 due to a fault, causing the brake pedal to move forward, the brake pedal force or The brake pressure in the main brake cylinder SHZ is reduced and the brake pedal travel is increased.

Here, too, the fault is discovered by constantly comparing the actual pressure with the target pressure in the main brake cylinder SHZ. In the fallback level, if the difference between the actual pressure and the desired pressure falls below the selectable lower limit value, the pressure supply DV is stopped and the valves SV2kl-SV2k4 to the wheel brake cylinders RZ1-RZ4 are closed. The activation of the valve 9 is switched off and the pressure in the pressure supply DV is increased by the activation of the pressure supply DV. As a result, brake fluid flows from the pressure supply DV, through the valve DV/TV into the brake circuit BK2, and through the opened connection from the brake circuit BK2 into the master brake cylinder SHZ. If the difference between the actual pressure and the target pressure in the main brake cylinder SHZ the selectable exceeds the upper limit value, the pressure supply is stopped, valve 9 is actuated again, the switching valves SV2kl - SV2k4 to the wheel cylinders RZ1 - RZ4 are opened again and the pressures in the wheel cylinders RZ1 - RZ4 are set to the target pressures again with the pressure supply DV. As already described, this causes the actual pressure in the main brake cylinder SHZ to be reduced again due to the fault and the brake pedal travel to be increased again. If the difference between the actual pressure and the target pressure in the master brake cylinder SHZ falls below the selectable lower limit value again, then the switching valves SV2kl - SV2k4 to the wheel cylinders RZ1 - RZ4 are closed, valve 9 in the brake circuit is opened, and via the pressure supply DV the pressure in the master brake cylinder SHZ is increased, with which the process is repeated. As a result, the brake pedal feel remains largely normal.

However, the brake pedal may vibrate slightly.

A leak in the master brake cylinder SHZ or in the travel simulator WS leads to a failure of the actuating unit (combination of master brake cylinder SHZ and travel simulator WS). When the driver brakes, brake fluid flows out of the brake master cylinder SHZ due to the leak from the actuating unit, causing the brake pedal to move forward, reducing the brake pedal force or brake pressure in the brake master cylinder SHZ and increasing the brake pedal travel. The faulty function of the actuating unit is therefore similar to that described for FIG. 8. The detection of the fault and the fallback level as described for FIG. 8 can therefore also be used for these faults.

reference list

1 sensor element

2 target in the float

3 Return line to VB with suction valve SV DV/TV DV specific valve switching

5 single circuit pressure supply

6 anchors 6 / 6a

7 / 7a valve lifters

8 valve seat

9/9a separating valve to THZ/SHZ B on-board network

B Redundant vehicle electrical system connection

RZ1 - RZ4 wheel brake cylinder

BK1/BK2 brake circuits

RK1 wheel circle 1

RK2 wheel circle 2

RK3 wheel circle 3

RK4 wheel circuit 4

HCU Complete hydraulic unit with DV and valves VB reservoir

HL1 - HL4 hydraulic lines outside the HCU to the RZ

HL5 hydraulic lines from SHZ to BV

KTV circuit isolation valve

DHK double piston

DV pressure supply

DG pressure transmitter

EA Electrical connection

EM 1/2 electric magnetic circuit Vi

EIV Electrical valve control elEM Electrical motor control of the electromechanical brake MV Solenoid valve RV Non-return valve P/TV Pump isolation valve Sp pedal travel sensor

TV isolation valve

P pump

F filters

9 permanent magnet

10 pole plate

11 electromagnetic inference

12 plastic bodies

13 return spring

SV2k normally open solenoid valve without check valve, in particular with an additional power device

Overview of the electrical valve circuit SO = normally open SG = normally closed AV = SG SV = SO

Isolation valve 9, 9a = SO

DV/TV (specific valve circuit: SG, possibly with spring-assisted valve closing for failure BK (can be omitted with SVv)

KTV = SO, if necessary with a special application in Fig. 1 also SG depending on requirements for residual braking effect in the event of a vehicle electrical system failure

Claims

patent claims

1. Braking system with

- at least two wheel brake cylinders (RZ _I- ), each of which is part of a separate wheel circuit (RK _I-4 ),

- at least one pressure supply (DV), which serves at least to build up pressure (p _aUf ) in the wheel brake cylinders (RZ _I- ),

- at least one reservoir (VB),

- at least one electronic control and regulation unit (ECU)

- Switching valves (SV2K _I- ), with each wheel brake cylinder (RZ _I- ) being connected via a respective hydraulic connecting line to a switching valve (SV2K _I- ) which is used to disconnect and connect the hydraulic connection of the respective wheel brake cylinder (RZ _I- ) and at least another main hydraulic line, via which the switching valve (SV2K _I- ) can be or is connected to at least the pressure supply (DV), with at least the hydraulic connecting line and the wheel brake cylinder (RZ _I- ) connected to it being part of a wheel circuit (RKi - ) are characterized in that either

- In at least one, in particular all, switching valve(s) (SV2K _I- ), the electric drive or individual components thereof is or are redundant and/or the switching valve (SV2K _I- ) has an additional power device (EM2, 9) which exerts a force (FM2) on a valve actuator or valve tappet (7) by means of its own magnetic field and/or the switching valve (SV2K _I- ) has a return spring (RF) which exerts a force on the valve actuator or valve tappet (7). , Which prevents tearing, in particular in one of two flow directions, of the switching valve (SV2K _I- ) and/or

- The brake system has at least one isolating valve (KTV, DV/TV), by means of which at least two wheel circuits (RK _I- ) or brake circuits (I, II) can be separated or connected from one another.

2. Braking system according to claim 1, characterized in that electrical components of the electric drive of a switching valve (SV2K _I- ), inter alia whose drive coil, electronic control and electrical connection cables are.

3. Braking system according to the preamble of claim 1 or according to one of claims 1 or 2, characterized in that in a functional state in which at least one wheel circuit (RK1-4) has a functional error which is above a certain degree of error threshold, the pressure control either

- This wheel circuit (RK1-4) is decoupled at least temporarily or permanently from the rest of the brake system or the other wheel circuits (RK1-4) and/or the pressure supply (DV) by permanently closing the switching valve (SV2K _I- ) assigned to this wheel circuit and/or

- At least two by means of an optional circuit separating valve (KTV) or separating valve (DV/TV).

Wheel circuits (RK _I-4 ) or brake circuits (I, II) are separated from one another - or connected to one another.

4. Brake system according to one of Claims 1 to 3, characterized in that by means of the optional circuit separating valve (KTV, DV/TV) two brake circuits (I, II), of which at least one is assigned at least two wheel circuits, can be separated from one another or connected to one another are connectable.

5. Brake system according to one of the preceding claims, characterized in that a diagnosis of the respective leak in the individual wheel circuits (RK _I- ) is carried out and that, depending on the diagnosis result, the electronic control and regulating unit (ECU) decides whether a wheel circuit (RKI -4) is switched off by permanently closing the associated switching valve (SV2K _I- ) or continues to be operated to generate a braking effect.

6. Brake system according to one of the preceding claims, characterized in that the switching valve (SV2K _I- ) is a solenoid valve with an electromagnetic drive (EMI), via which a valve actuator or valve tappet (7) between an open valve position and a closed valve position is adjustable, whereby the switching valve (SV2K _I- ) has a force set device (EM2, 9) which exerts a force (FM2) on the valve actuator or valve tappet (7) by means of its own magnetic field.

7. Brake system according to one of claims 1 to 5, characterized in that the switching valve (SV2K _I- ) has a restoring spring (RF) which exerts a force on the valve actuator or the valve tappet (7) which prevents the valve from tearing open .

8. Braking system according to claim 7, characterized in that the force of the restoring spring (RF) is dimensioned such that it is at least equal to the sum of the friction force (Fr) and the tearing force (Fzu), in particular the 1.2-1, 5 times the sum of these powers is strong.

9. Brake system according to one of the preceding claims, characterized in that the brake system is in the first basic functional state or will operate as long as no wheel circuit (RK1-4) has a functional error which is above a specific error level threshold.

10. Brake system according to one of the preceding claims, characterized in that the brake system has two pressure supplies (DV1, DV2).

11. Brake system according to claim 10, characterized in that in the first functional state either one pressure supply (DV1, DV2) is always assigned to one brake circuit (BK1, BK2) for its pressure control in its wheel circuits (RK1-4), or that both pressure supplies ( DV1,

DV2) for both brake circuits (BK1, BK2) or in the case of only a single brake circuit (BK), for this together responsible for the pressure control.

12. Brake system according to claim 10 or 11, characterized in that in the event of a failure of a pressure supply (DV1, DV2), the other takes over its function, in particular for all wheel circuits or only some of them.

13. Brake system according to one of the preceding claims, characterized characterized in that the brake system also has a master brake cylinder (SHZ, THZ) which can be actuated via a brake pedal, in particular if the pressure supply (DV, DV1, DV2) fails, with the master brake cylinder being designed in particular as a single master brake cylinder (SHZ) or as a Tandem master cylinder (THZ) is formed.

14. Braking system according to claim 12, characterized in that the pressure chamber or chambers (A1, A2) of the master brake cylinder (SHZ, THZ) is or is connected to a brake circuit (BK, BK1, BK2) by means of a hydraulic line (). are, wherein at least one separating valve (TV), in particular a normally open separating valve, for selectively shutting off the hydraulic line () is used.

15. Brake system according to one of the preceding claims, characterized in that either a) two wheel circuits each have a brake circuit (/I, II), b) three wheel circuits have a first brake circuit (I) and one wheel circuit has a second brake circuit (II) ( asymmetric brake circuits), c) all wheel circuits are assigned to only one brake circuit.

16. Brake system according to one of the preceding claims, characterized in that each wheel brake cylinder (RZ _I- ) is connected via a respective hydraulic connecting line to a switching valve (SV2K _I-4 ) which is used to disconnect and connect the hydraulic connection of the respective Wheel brake cylinder (RZ _I- ) and at least one other hydraulic main line (), via which the switching valve (SV2K _I- ) can be or is connected to at least the pressure supply (DV), with the hydraulic connecting line and the one connected to it serving Wheel brake cylinders (RZ _I- ) are part of a wheel circuit (RK _I- ), a diagnosis of the respective leak in the individual wheel circuits (RK _I- ) is carried out and that, depending on the diagnosis result, an electronic control and regulating unit (ECU) decides whether a wheel circuit (RKI-4) is switched off by permanently closing the associated switching valve (SV2K _I- ) or continues to generate a Br ems effect is operated.

17. Brake system according to one of the preceding claims, characterized in that the degree of leakage or the leakage flow CQieck) in a wheel circuit (RK _I- ) is determined using one or more of the following methods a) to e): a) determination the required amount of hydraulic fluid, which to achieve a target pressure (p _SOii ) in the respective wheel circuit (RK _I-4 ) must be replenished in addition to the predetermined amount of fluid by means of the pressure supply (DV); b) determination of a determined absolute pressure drop (dp _ab ) and/or pressure drop gradient (p _ab /dt) in the respective wheel circuit (RKI-4); c) Determination of the pressure deviation (dp = p _SOii - Pactual) from the setpoint pressure value (p _SOii ) during the pressure build-up in the respective wheel circuit (RK _I- ) by introducing a fluid quantity (q) predetermined to achieve the setpoint pressure (p _SOii ) into the wheel circuit ( RK _I- ) is funded and then the actual pressure (p actual) _is determined; d) Diagnosis of the leak in the wheel circuit (RK _I- ) by measuring the pressure (p _ist ) over time in the hydraulic line connecting the switching valve (SV2K _I- ) and the pressure supply (DV) during the pressure build-up by means of the pressure supply (DV) or when it is switched off pressure supply (DV); e) Measurement of the absorption volume (Q) of the respective wheel circuit (RK _I- ) via the pressure supply (DV) to achieve a target pressure (p _SOii ), the absorption volume (Q) being determined by means of the pressure supply (DV), in particular via Current measurement of the drive motor (M) of the pressure supply (DV) and/or the piston travel (ds) of the piston of the pressure supply (DV).

18. Brake system according to Claim 17 or 18, characterized in that when an upper limit value (Qhigh) or limit value range (dQhigh) of the leak in a wheel circuit (RK _I- ) is exceeded, the respective associated switching valve (SV2K _I- ) is permanently closed and thus there is no longer any braking effect with this wheel brake cylinder (RZ _I- ), and that below the upper limit value (Qhigh) and above a lower limit Value (Q _{| 0} ) a time-limited and / or permanent after-promotion to achieve the brake pressure to be set (p _SOii ) in the respective wheel brake cylinder (RZ _I- ) takes place.

19. Brake system according to claim 19, characterized in that the upper limit value (Q _high ) is determined by the maximum capacity of the pressure supply (DV) for increasing the pressure.

20. Brake system according to claim 19 or 20, characterized in that with a leakage flow (Qi _eCk ) of 50-90% of the maximum delivery rate of the pressure supply (DV), the leakage flow (Qi _eCk ) is compensated for by means of the pressure supply (DV) by subsequent delivery, such that there is no or only a slight reduction in the braking effect.

21. Brake system according to one of claims 19 to 21, characterized in that to optimize the braking effect and driving stability, in particular the yaw moment, an electronic control and regulating unit (ECU) determines whether and which leaking wheel circuit(s) (RK _1-4 ) is or are switched off by permanently closing the respective switching valve (SV2K _I- ).

22. Brake system according to one of the preceding claims, characterized in that a belonging to a wheel brake cylinder outlet valve (AV _1-4 ) is part of the respective wheel circuit (RK _1-4 ).

23. Braking system according to one of the preceding claims, characterized in that the force (FM2) of the additional force device (EM2, 9) can be generated or is generated by means of an energizable electromagnet and/or a permanent magnet.

24. Braking system according to one of the preceding claims, characterized in that the force (FM2) of the additional power device (EM2, 9) of the force (FM1) of the electromagnetic drive (EMI) is directed in the opposite direction.

25. Braking system according to claim 25, characterized in that the force (FM2) of the additional force device (EM2, 9) is equivalent to the force (FRF) of a possible restoring spring (RF), and with appropriate dimensioning tion of the magnetic circuit no return spring (RF) is required.

26. Braking system according to one of Claims 24 to 26, characterized in that a force (FM2) is only generated by energizing the coil with the additional force device (EMI) if the state of the braking system permits an unintentional closing of the switching valve (SV2K _{I -} ) can be expected, so that only in such a state, the power accessory device (EMI) consumes energy.

27. Brake system according to one of claims 24 to 27, characterized in that the electromagnetic holding force is diagnosed by means of diagnostic functions via the current intensity and movement of the armature.

28. Brake system according to one of the preceding claims, characterized in that the brake system has a level sensor () for determining the filling level of the reservoir (VB), which is arranged in particular on the printed circuit board (PCB) of the control and regulating unit (ECU).

29. Brake system according to one of the preceding claims, characterized in that at least one pressure supply (DV1) is a piston-cylinder system driven by an electric motor.

30. Brake system according to one of the preceding claims, characterized in that the at least one pressure supply (DV) is an electric motor driven rotary pump (RP).

31. Braking system according to one of the preceding claims, characterized in that a pressure supply serves as a redundant pressure supply and only serves as a backup in the event of failure of the other pressure supply(s) (DV, DV1, DV2) and/or to support the other pressure supply sorgungien) (DV, DV1, DV2), in particular to generate high pressures and / or to achieve greater dynamics of the brake system.

32. Brake system according to one of the preceding claims, characterized in that the pressure supply (DV) has a first and a second motor as a drive, the first motor being a brushless motor (ECE motor) with 2x3 phases and redundant control and the second motor is a 1-phase motor.

33. Brake system according to one of the preceding claims, characterized in that at least one pressure supply can be separated from the brake circuit(s) by means of a separating valve, in particular in the form of a switchable, in particular normally closed, solenoid valve.

34. Brake system according to one of the preceding claims, characterized in that in the case of two brake circuits (I, II), the circuit separating valve (KTV) for separating or connecting the brake circuits (I, II) is used.

35. Brake system according to one of the preceding claims, characterized in that the brake pedal is an electric pedal.

36. Brake system according to one of the preceding claims, characterized in that the number of outlet valves (AV) per brake circuit (BK1, BK2) is different.

37. Brake system according to one of the preceding claims, characterized in that if the outlet valve (AV) is faulty, in particular if there is an electronic/electrical fault in the outlet valve (AV), the pressure reduction and pressure build-up in a wheel circuit is carried out via the redundant switching valve (SV2k) of the respective Radkreises takes place.

38. Brake system according to one of the preceding claims, characterized in that in the event of a leak in the path simulator (WS), the master brake cylinder (SHZ, THZ) or the isolating valve (9) which is intended to separate the brake circuit (BK) from the master brake cylinder (SHZ, THZ). , the pressure supply (DV) is controlled accordingly in order to control a pressure in the master brake cylinder (SHZ, THZ) in order to achieve a desired pedal characteristic or pedal force Fp depending on the pedal travel Sp using the pressure transmitter (DG-SHZ) or a pedal force sensor.