Fail-safe braking system

Abstract

The invention relates to a braking system comprising: at least two wheel brake cylinders (RZ1-4) which are each part of separate wheel circuits (RK1-4); at least one electric-motor-driven pressure supply (DV) which is used at least for building up pressure (pauf) and reducing pressure (pab) in the wheel brake cylinders (RZ1-4); at least one reservoir (VB); at least one electronic open-loop and closed-loop control device (ECU); at least two switching valves (SVi=1-4), wherein each wheel brake cylinder (RZ1-4) is connected via an associated hydraulic connection line to a switching valve (SVi=1-4) which is used to disconnect and connect the hydraulic connection of the associated wheel brake cylinder (RZ1-4) and at least one further hydraulic main line, via which the switching valve (SVi=1-4) can be or is connected at least to the pressure supply (DV), and the switching valves (SVi=1-4) are 2 / 2-way valves which are open in a de-energised state, wherein at least the hydraulic connection line (HLRK1-4) and the wheel brake cylinder (RZ1-4) connected thereto are part of a wheel circuit (RK1-4), and at least one switching valve (SVi=1-4) or all switching valves (SVi=1-4) do not have a check valve, or no check valve is connected in parallel with a switching valve (SVi=1-4), characterised in that various measures are provided, either alone or in combination, in order to prevent a switching valve (SVi=1-4) from closing when the pressure is reduced (pab) via said switching valve (SVi=1-4).

Description

[0001] Fail-safe braking system

[0002] State of the art

[0003] For almost 80 years, the current dual-circuit braking system with two brake circuits has prevailed for safety reasons. Depending on the vehicle design, it is used with a) diagonal and b) black / white or front / rear brake circuit layout. In the event of a brake circuit failure, the braking effect is reduced by 50% in a) and by up to approximately 70% in b). Statistics estimate a brake circuit failure rate of 10 ppm / year. Due to the reduced braking effect or total brake failure, there is a significant risk of accidents.

[0004] DE 10 20 2018 213 306 describes a system for detecting brake circuit failure due to a leak in the brake circuit by evaluating the pressure gradient.

[0005] Almost all vehicles have electronic brake control systems for all four 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), for example, to prevent the wheel from locking.

[0006] In today's common brake systems with ABS / ESP function, each wheel brake cylinder is usually assigned an inlet and an outlet valve, whereby the inlet valve usually has a check valve connected in parallel so that the inlet valve does not close due to the back pressure when the pressure is reduced quickly.

[0007] If an inlet valve with its associated check valve fails and becomes leaky, in today's dual-circuit braking systems, a complete brake circuit usually fails when the wheel brake cylinder fails, so that the braking effect is reduced by at least 30%.

[0008] In many modern braking systems, the failure of the wheel brake cylinder is detected via diagnostics and the corresponding inlet valve is closed. However, if the check valve, which is connected in parallel to the inlet valve, is leaking, the entire brake circuit fails. For this reason, this measure is described as an improvement, but is not considered fail-safe because the check valve cannot be diagnosed before each braking application during ongoing operation. When pressure is reduced, or, for example, when hydraulic medium flows towards the opening of the check valve due to temperature changes, a particle can be washed in despite the filter, causing the check valve to leak when pressure builds up. This means that if a wheel cylinder fails, the inlet valve loses its function as a safety element.

[0009] Object of the invention

[0010] The object of the invention is to provide a very fail-safe braking system that requires as few valves as possible.

[0011] Solution to the task

[0012] This object is advantageously achieved by a braking system having the features of claim 1. Further advantageous embodiments of this braking system result from the features of the subclaims.

[0013] Advantages of the invention

[0014] The invention is characterized in that components that are as fail-safe as possible are used and / or corresponding 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.

[0015] An intake valve commonly used for ABS / ESP has a parallel check valve, which is considered to be unreliable in terms of leak tightness and therefore cannot be used where high reliability requirements are required. As described above, the check valve was provided to prevent the intake valve from closing due to back pressure during rapid pressure reduction.

[0016] It is therefore advantageous if, instead of an inlet valve with a parallel check valve, a switching valve is used which is designed to be secure against closing in at least one flow direction even at high flow velocities or high pressure gradients, or if the braking system is designed and / or its controllable and / or adjustable components are operated in such a way that the closing of the switching valve is prevented even at high flow velocities.

[0017] To prevent a switching valve from closing when the pressure is reduced via this switching valve, the following measures can be provided alone or in combination: a. The valve actuator of the switching valve can be subjected to a return force in its open position which is at least 30-50% greater than that of standard inlet valves of ABS systems, whereby the increased return force is generated by a stronger return spring and / or by means of a magnetic force which acts in addition to the force of the return spring, whereby the additional magnetic force can be generated, for example, by at least one permanent magnet or an electromagnet. b) That the pressure reduction rate is set or regulated, in particular limited, by means of the electric motor-driven pressure supply in such a way that the switching valve does not close.c) That in the hydraulic connecting line connecting the pressure supply to the switching valves, a parallel circuit consisting of a throttle and a check valve is arranged, with the check valve blocking in the direction of the pressure supply. The throttle advantageously limits the volume flow and thus prevents the switching valve from closing when the pressure is reduced. The pressure can build up unhindered via the check valve connected in parallel to the throttle. d) That the isolating valve, by means of which the wheel circuits can be separated from or connected to a master brake cylinder, has a flow cross-section which is dimensioned such that in the event of a pressure reduction in a wheel circuit via the isolating valve, the switching valve is prevented from closing.e) That the isolating valve, by means of which the wheel circuits can be separated from or connected to the master brake cylinder and via which the pressure is reduced in a wheel circuit, is opened and closed in pulse width mode in order to limit the flow rate or flow rate to a level such that the switching valve is prevented from closing. f) the drive of the pressure supply (DV) is a multi-phase motor whose electrical wiring of the windings is designed such that in the event of failure of the motor control and / or the electrical control unit (ECU) of the braking system, the electric motor is operated in generator mode and the winding circuit of the electric motor acts as a brake for the piston of the pressure supply (DV) and thus the pressure reduction rate (dpab / dt) is limited or slowed down.

[0018] By taking measures b) to f) it is possible to reliably prevent a conventional inlet valve with or without a check valve from closing.

[0019] Advantageously, the switching valve used according to the invention, which is assigned to each wheel brake cylinder, should be designed to be as fail-safe as possible, so that, in principle, no additional valves, especially isolation valves, are required to isolate a leaking wheel circuit or brake circuit. If safety is nevertheless to be increased, at least one of the isolation valves described above can be additionally provided.

[0020] To increase reliability and braking efficiency in the event of a failure, switching valves can also be advantageously used for the wheel brake cylinders, in which the electromagnetic drive or at least some of its components are provided or designed redundantly, i.e., at least in duplicate. 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. If one coil or its control fails, the other can take over its function. This makes the switching valve significantly more fail-safe and, thus, the entire braking system more fail-safe.

[0021] The coils can also be designed in such a way that they each switch the valve safely up to a certain pressure of, for example, 100 bar and that higher pressures can only be switched by the joint energization or control of both coils.

[0022] The switching valve according to the invention is understood to be the valve assigned to a wheel brake cylinder, through which hydraulic medium flows to build up pressure in this wheel brake cylinder only. The wheel circuit here is understood to mean the wheel brake cylinder including the hydraulic connection from the switching valve to the wheel brake cylinder. The invention provides that in order to reduce pressure in a wheel brake cylinder, the hydraulic medium from the assigned wheel brake cylinder is fed into the brake circuit via the switching valve. The switching valve can be a conventional inlet valve for existing ABS systems which does not have a check valve. According to the invention, this can additionally be modified in such a way that, for example, closing the valve is made more difficult by additional magnetic force or a stronger spring. An outlet valve assigned to a wheel brake cylinder also belongs to the respective wheel circuit, if provided.

[0023] 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. Its valve actuator is 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 and adjusted. The closing function and, if applicable, the tearing shut of the switching valve SVi can be detected by a diagnosis or diagnostic circuit. The switching valve SVi according to the invention is the safety gate for the brake circuits BK to the wheel brake cylinder RZ. If, in the braking system according to the invention, one of the four hydraulic connections from the hydraulic control unit to a wheel brake cylinder fails, or if the wheel brake cylinder is leaking, the faulty hydraulic connection orThe faulty wheel brake cylinder can be decoupled from the rest of the braking system with a high degree of safety.

[0024] In principle, the additional measures to prevent the switching valve from closing only need to be activated or activated when a rapid pressure reduction in one flow direction via the switching valve is required. In all other operating states of the braking system, these measures or the additional holding or assisting force, which is generated, for example, by permanent magnets, an additional coil, or an additional force device, are not required, thus advantageously saving energy. This also allows the worldwide used PWM method for finely controlling the pressure build-up to be retained.

[0025] Should a wheel circuit actually fail in the braking system according to the invention, only the braking effect of that one failed wheel circuit is lost, while the braking effect of the remaining three wheel circuits remains available. This results in a reduction in braking effect from four to three intact wheel circuits, so that in the event of a wheel circuit failure on the front axle, only approximately 35% of braking effect is lost, compared to 70%, as described above for a black / white brake circuit split, when an entire brake circuit and thus two wheel circuits always fail.

[0026] The braking system according to the invention generally has four wheel circuits, in which either two wheel circuits are assigned to one 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 still available for braking. The functional reliability of the braking system according to the invention can be further increased in the presence of dirt particles in the brake fluid 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 to be small enough that these small dirt particles only create small leaks and thus only small flow rates when the switching valve is closed, which can be compensated by the pressure supply, but which can be detected by the diagnosis both via the flow rate of the pressure supply and via the level in the storage tank.

[0027] To verify the function of the switching valve according to the invention, a measurement of the volumetric absorption and the temporal progression of the pressure in the respective wheel circuit can be performed during diagnosis, for example, and a comparison can be made with the previously determined pressure-volume characteristic curve of the wheel circuit. The diagnosis can be performed during each braking application and / or even at a standstill or during servicing.

[0028] The preferred switching valve, as described above, does not require a check valve, yet still meets a wide range of requirements. It must remain reliably open in both directions, at least at high flow rates, during pressure buildup. This means that the typical weakness of today's valves, namely that at high flow rates, effects on the valve seat exert a force on the valve actuator, usually in the form of a valve ball with a valve cone, and the valve spring, causing the valve to close automatically, must not occur.

[0029] The switching valve can advantageously be optimized by appropriately designing the sealing cone, the dimensions of the return spring and the valve tappet, in addition to the additional force device. In the closed position of the valve, via which the pressure in the wheel brake cylinder can also be reduced, the pressing force should be significantly lower 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 due to the correspondingly higher force requirement. The braking system according to the invention can have various valve circuits: a) four switching valves for each of four wheel brake cylinders, via which both the pressure build-up and the pressure reduction for the respectively assigned wheel brake cylinders takes place; b) four switching valves for each of four wheel brake cylinders and two outlet valves; c) four switching valves and four outlet valves.

[0030] Using an outlet valve for a wheel circuit, individual wheel control 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 during braking and parking and close the switching valve associated with that wheel circuit. This allows three wheel circuits to continue operating in the event of a single fault, and two wheel circuits to remain available in the event of a double fault—i.e., if two wheel circuits fail simultaneously—in the worst case scenario. With conventional braking systems, however, the worst case scenario results in total brake failure.

[0031] In summary, it can be stated that by making minor changes to the inlet valve and eliminating the check valve, a significant safety improvement can be achieved with the switching valve. With an appropriate design of the switching valve, in addition to the safety improvement, a cost reduction is possible.

[0032] The braking system according to the invention can also be designed such that, instead of four hydraulic wheel circuits, a mixed hydraulic-electric braking system is provided, for example, with hydraulic lines to the hydraulically operated front wheel brakes and only electrical connections to the electric motor-operated brakes (EMB) on the rear axle, the design of which is known. Here, too, the same advantages arise if the hydraulic wheel circuits are designed according to the embodiments described above. With the additional use of a circuit isolation valve between the two brake circuits or additional circuit isolation valves between the brake circuit and the pressure supply, even if one wheel circuit fails, this circuit can be isolated via the circuit isolation valve, so that the remaining wheel circuit of the respective brake circuit is still effective. Thus, double-fault safety is achieved with a vehicle deceleration of 0.65g.

[0033] 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 Levels 3 to 5 of automated driving, whereby the second, redundant, pressure supply can contain a piston pump or a rotary pump. Rotary pumps offer a significant cost advantage. With the piston pump, a simple check valve can be used at the pressure supply outlet instead of the solenoid valve. This offers the same advantages in the event of a pressure supply failure and is more cost-effective. In this braking system, pressure reduction during normal braking can occur not by controlling the pressure supply piston, but by controlling the outlet valves using the pressure sensor signal.

[0034] 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 equipped with a drive with redundant winding circuitry, e.g., 2x3-phase and / or redundant control, such that no additional valves are provided between the switching valves assigned to the wheel circuits and the pressure supply. To prevent a failure of the brake system, e.g., due to a leaking piston seal or small piston play, compensation is provided by additional pressure.

[0035] The braking systems described above can advantageously eliminate the need for the usual vehicle adjustments in various areas such as logistics, service and homologation.

[0036] The braking system according to the invention thus has four wheel circuits that are individually controlled. As described above, two wheel circuits can be assigned to each brake circuit. Other distributions among the brake circuits, as described above, are also possible.

[0037] The 4-wheel brake system can also be controlled by the control system as a 2-circuit brake system. This allows the 4-wheel brake system to be combined with 2-circuit brake systems with four hydraulically braked wheels, thus achieving double-fault safety. This means that even a leak in a wheel brake cylinder and the failure of the control of the associated switching valve will not lead to a total failure of the brake system. This double fault, with its low failure probability of approximately 10', 19 / J, which is still significantly better than nuclear safety. Even with this double fault, the braking system according to the invention would still achieve the braking effect of a conventional dual-circuit braking system.

[0038] This means that the braking system can be described as fail-safe and fail-proof.

[0039] It is advantageous to diagnose the leaks in the individual wheel circuits at intervals or continuously. Depending on the diagnostic results, the electronic control and regulation unit of the brake system decides whether a wheel circuit should be shut off by permanently closing the corresponding switching valve or whether it should continue to operate to generate a braking effect. If operation continues, the detected leakage is used to calculate and implement an appropriate additional supply or subsequent supply of brake fluid to achieve the required braking effect of the respective wheel brake cylinder.

[0040] In order to arrive at the braking system according to the invention from the known braking systems, it is only necessary to replace the known inlet valves with check valves with the modified switching valve, whereby almost no additional costs arise.

[0041] 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 outlet valve fails, ABS pressure reduction via the outlet valve is no longer possible, i.e. the corresponding wheel locks with a 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, as it is pull-proof, it can also be used for pressure reduction if, for example, the pressure supply can absorb the necessary volume for pressure reduction. Since the switching valves do not contain a check valve, when the pressure is reduced in one wheel brake cylinder, e.g. RZ1 via the SVi, the pressure in the other wheel brake cylinders is not reduced at the same time, e.g. wheel brake cylinders RZ2, RZ3 and RZ4 when valves SV2, SV3, SV4 are closed.This can be advantageously achieved, as described in previous patent applications, with volume control of the pressure supply piston or a rotary pump. For ABS control, the only disadvantage is a small time delay in the pump taking up volume to reduce pressure, as well as in the volume supply for pressure build-up. However, this is extremely rare, as it only occurs when the outlet valve fails. However, locking a wheel during ABS function must be avoided at all costs, especially in braking systems for automated driving at levels >3. Since this method requires no changes or costs other than a software modification, this solution can also be used in braking systems designed for level 2 requirements.

[0042] The switching valve therefore has a variety of functions in the safety-relevant braking system according to the invention:

[0043] 1. Improved braking effect in case of failure of a wheel brake cylinder or wheel circuit

[0044] 2. Maintaining the pressure reduction control function in ABS in case of failure of the exhaust valve opening

[0045] 3. Saving of additional isolation valves to prevent circuit failure

[0046] For these fault cases, it is advisable to design the switching valve with redundant coils with connection, since the coil with electrical connection represents the main point of failure.

[0047] Diagnosing the switching device is of great importance to prevent tearing or when a switching valve (SV, SVx, or S 2k) fails to switch. The following main faults (not exhaustive) must be diagnosed:

[0048] 1. Pressure supply DV: Failure during pressure reduction control, resulting in greater pressure reduction speed.

[0049] Measure 1 : Winding circuit in case of motor failure of the

[0050] Pressure supply or failure of the electronic control unit ECU.

[0051] Measure 2: Check valve / throttle combination in the hydraulic line from the pressure supply to the brake circuit (see Fig. 4 and Fig. 6).

[0052] 2. Switching valve SVi is leaking:

[0053] Diagnosis 1 : during the general diagnostic test of the valves;

[0054] Diagnosis 2: If a wheel brake cylinder fails and the associated switching valve (SV) is leaking, additional pressure is supplied via the pressure supply as described. Detection is based on the brake system's volume consumption during pressure buildup using the pressure-volume characteristic curve.

[0055] 3. Isolating valve TV is leaking:

[0056] Diagnosis of the volume intake of the brake system during pressure build-up using the pressure-volume characteristic curve and subsequent delivery with the pressure supply;

[0057] 4. Isolating valve TV has too small a cross-section:

[0058] Pressure reduction is too slow. Detection is based on the volume flowing through the master cylinder over time during pressure reduction in the brake circuit.

[0059] In the described system with an electromotor brake (EMB) on the rear axle, the so-called redundant outlet valve AVred, as an outlet valve AV with redundant coil and / or redundant control, together with the switching valve with redundant coil can be regarded as a double-fault-proof hydraulic front axle control, so that in the event of a failure of an electromotor brake (EMB) on the rear axle, more than 70% braking effect is still available, which is not achieved by a comparable full EMB with EMB on the rear axle and on the front axle in the event of a failure of the EMB on the front axle and is to be rated significantly worse due to the high complexity and thus high failure rate.

[0060] Character description

[0061] In the following, various possible embodiments of the braking system according to the invention and the valves used are explained in more detail with reference to drawings.

[0062] They show:

[0063] Fig. 1 : shows the system concept with four wheel circuits and each

[0064] Inventive switching valve SVi assigned to wheel circuit RKi;

[0065] Fig. 2: shows the conventional ABS inlet valve with check valve EV and two valve variants of the switching valve SVi or SVx and SVzk according to the invention for the four wheel circuits RKi;

[0066] Fig. 3 and 4: show a previously known 1-box brake system with switching valves SVi, SV4 according to the invention instead of the conventional inlet valves;

[0067] Fig. 5: shows a braking system according to the invention with a single-

[0068] Master brake cylinder SHZ, which can be used in particular for a 1-box solution, with switching valves SVi, SV4 according to the invention instead of the conventional inlet valves EV with check valve;

[0069] Fig. 6: shows the known ABS / ESP systems, as they have been used for years and are standard worldwide, whereby these are specially connected to the four-wheel circuit braking system according to the invention, with switching valves SVi, ..., SV4 according to the invention instead of the usual ABS inlet valves EV and a throttle check valve parallel circuit RV / Dr3 in each braking circuit;

[0070] Fig. 7: shows an extension of the braking system shown and described in Figure 1 with ABS and ESP function, whereby the previously described measures are provided in the form of the switching device for the switching valves SVi, SN of the four wheel circuits and the redundant outlet valve AVred;

[0071] Fig. 8: Brake system according to Figure 1 with a double-acting piston and two 3 / 2-way valves with an additional pressure relief valve for the 3 / 2-way valve HZ-BK-WS;

[0072] Fig. 9: Braking system according to Figure 1 with an electromechanical

[0073] Brake on the rear axle and 4-circuit and redundant exhaust valve AVred;

[0074] Fig. 10: Braking system according to Figure 9 with E-pedal and second pressure supply.

[0075] Figure 1 shows a first possible embodiment of the braking system according to the invention. The braking system has four wheel circuits RKi to RK4, with the components of a wheel circuit RKi being the respective switching valve SVi, the wheel brake cylinder RZi arranged downstream of it, the hydraulic connecting line HLßKi connecting the switching valve SVi to the associated wheel brake cylinder RZi, and the optional outlet valve AV.

[0076] The braking system has only a single brake circuit BK, to which all four wheel circuits RK1-4 are connected via at least one hydraulic line HL2 via its hydraulic line HLi.

[0077] The pressure build-up p aU f in a wheel brake cylinder RZi always occurs via the opening of the corresponding switching valve SVi. The pressure reduction p a b in a wheel brake cylinder RZi occurs either via the open associated switching valve SVi into the brake circuit BK and / or via the open associated outlet valve AVi and the hydraulic line HLs into the reservoir VB.

[0078] The braking system also has an electric motor-driven pressure supply DV, which has a piston-cylinder system and is designed in Figure 1 as a double-stroke piston system (DHK) with two working chambers Al and A2. It is also possible for the piston-cylinder system of the pressure supply DV to be designed with only one working chamber. The two working chambers Al and A2 are each connected via hydraulic lines HL5 and HL6 to a isolating valve DV / TV, which is designed as a 3 / 2-way valve and connects the associated working chamber Al or A2 to the reservoir VB when de-energized. If the respective 3 / 2-way isolating valve DV / TV is energized, the respective working chamber Al or A2 is connected to the brake circuit BK and a pressure build-up pauf or a pressure reduction pab can occur in at least one wheel brake cylinder Zi by adjusting the piston of the pressure supply DV.

[0079] Hydraulic medium can be sucked from the storage tank VB into the respective working chambers A1 and A2 of the pressure supply DV via the hydraulic lines HL9 and HL10 and the suction valves SaV arranged therein. Optionally, a further hydraulic line HLn with a redundant seal can be provided for safety and diagnostic purposes. This line opens into an area of ​​the pressure supply cylinder which is separated or sealed from the second working chamber A2 on one side by a seal and on the other side by another redundant seal, connecting this opening area to the storage tank VB. The failure of the first seal is detected by diagnostics via volume loss when pressure builds up. The failure of the second seal leads to volume loss, whereby the volume loss is detected by the fluid level sensor in the storage tank VB.

[0080] The braking system also has a master brake cylinder HZ, which is designed as a single master brake cylinder SHZ in Figure 1. The single master brake cylinder SHZ is adjusted by applying a foot force FFUB to the brake pedal 1, with the adjustment being detected by a travel sensor Sp, and the braking system adjusts or regulates the braking effect based on this input variable, among other things.

[0081] The single brake master cylinder DHZ has a hydraulically acting working chamber AR, which is connected to a 3 / 2-way valve HZ-BK-WS via a hydraulic line HL12. The 3 / 2-way valve HZ-BK-WS connects the hydraulic line HL12 to the hydraulic line HLi of the brake circuit BK when de-energized, so that in an emergency, pressure can be built up in the working chamber AR and thus in the braking system via brake pedal 1 and the associated adjustment of the piston of the single brake master cylinder SHZ, thus achieving a braking effect. During normal operation of the braking system, however, the switching valve HZ-BK-WS is switched and the working chamber AR of the single brake master cylinder SHZ is connected to the travel simulator WS or the connecting line HL13. This serves to achieve a desired reaction force on the brake pedal 1 to generate a desired pedal feel.In the hydraulic line HL13 there is a parallel circuit consisting of a throttle and a check valve, which is necessary for the travel simulator function.

[0082] The single brake master cylinder SHZ is connected to the reservoir via the two hydraulic lines HL14 and HL15, with a throttle Drl arranged in the hydraulic line HL15. The opening areas of the hydraulic lines HL14 and HL15 in the single brake master cylinder are sealed from each other and from the rest of the cylinder area by three seals Dl, D2 and D3. When the piston K is retracted, which in the figure corresponds to a movement to the right, the hydraulic line HL14 opens in the area of ​​the piston K, with the two seals Dl and D2 still sealingly contacting the outer surface of the piston K. In this piston position, however, the seal D3 is not sealingly contacting the piston, so that the working chamber AR is connected to the hydraulic line HL15. This arrangement is previously known from WO 2019 / 086502. The brake system also has the two pressure sensors DG for measuring the pressure in the hydraulic lines HLi and HL12.

[0083] The hydraulic components shown in Figure 1 can be arranged and combined in a single hydraulic unit (HCU). The braking system also includes an electronic control unit (ECU) (not shown).

[0084] The switching valves SVi are modified conventional ABS inlet valves, the structure and function of which are shown and explained in Figure 2.

[0085] Figure 2 shows three different 2 / 2-way valves. The standard valve shown on the left corresponds to the ABS inlet valve EV. A description of this valve can be found in DE 10 2015 203733. It is a so-called SO valve with a check valve RV and a return spring 13 with a special valve seat contour. The other two 2 / 2-way valves are variants of the inventive switching valve SVi, which are modified standard ABS inlet valves without a check valve.

[0086] The inventive switching valve SV2k shown on the right is already known from PCT / EP 2022 / 073463 and features an additional permanent magnet 9, magnetic return element 11, and pole plate 10. This replaces the conventional weak return spring 13 with a significantly higher return force and advantageously decreasing force at the end of the stroke. This is intended to prevent closing, for example, at high flow rates and volumes.

[0087] The inventive switching valve SVx, shown in the center, is designed without a permanent magnet and also without a check valve. It has a significantly higher return force of approximately 4N than the standard valve EV shown on the left. In extreme cases, a tearing action during pressure reduction from the wheel circuits RK to the brake circuit BK is prevented by the stronger return spring 13 and by the following optional additional measures 1a) to 2a).

[0088] The closing of the switching valve SVi at extremely high volume flow at

[0089] Pressure reduction can normally only occur in two situations: 1. Uncontrolled piston speed of the pressure supply, which can occur in the event of a failure of the engine control unit and a failure of the ECU;

[0090] 2. If the flow cross-section of the isolating valve TV from the brake circuit BK to the master brake cylinder SHZ is too large;

[0091] Additional measures to 1. and 2.: la: Closing the DV / TV isolating valve separates the BK brake circuit from the DV pressure supply so that the tightness of this valve can be diagnosed lb: If the DV / TV valve is not present or if this valve fails, a parallel connection of throttle Dr3 with a parallel check valve RV can be provided in the connecting line; this only throttles the pressure reduction but not the pressure build-up (see Fig. 4). lc: Limiting the engine speed in the event of a failure of the engine control unit or the electrical control and regulation unit ECU of the braking system by wiring the winding of the pressure supply electric drive only in this fault situation;

[0092] 2a: Limitation of the valve cross sections of the 2 / 2- or 3 / 3-way isolating valve TV for pressure reduction, already in series for cost reasons, since only effective in the fallback level in case of failure of the pressure supply DV

[0093] The diagnosis is just as important as the additional measures.

[0094] Diagnosis for 1 :

[0095] • la: Isolating valve TV is activated (closed). Measurement of the DHK stroke with calculation of the displaced volume and pressure in the brake circuit BK. If, during the forward stroke of the double-stroke piston DHK, the volume displaced from the working chamber A1 and the resulting pressure change in the brake circuit BK correspond to the pressure-volume characteristic curve stored in the control unit, then the 3 / 2-way valve DV / TV belonging to the working chamber A2 is sealed. Conversely, if, during the return stroke of the double-stroke piston DHK, the volume displaced from the working chamber A2 and the resulting pressure change in the brake circuit BK correspond to the pressure-volume characteristic curve stored in the control unit, then the 3 / 2-way valve DV / TV belonging to the working chamber A1 is sealed.

[0096] This diagnosis can also be carried out with the valves SV closed, but then using a different pressure-volume characteristic curve. lb: See Fig. 4. Isolating valve TV is activated (closed). Measurement of pressure and calculation of pressure drop rate in brake circuit BK. Pressure is generated in brake circuit BK using pressure supply DV, e.g. to 100 bar. The pressure in brake circuit BK is then reduced as quickly as possible using pressure supply DV. If the pressure drop rate in brake circuit BK is significantly lower than that stored in the control unit, then throttle Dr3 is blocked. If the pressure drop rate in brake circuit BK is significantly higher than that stored in the control unit, then check valve RV is leaking.

[0097] • For diagnosis of the winding circuit of the motor during pressure reduction: temporal volume change with the pressure supply DV and measurement of piston travel and pressure

[0098] • lc: Isolating valve TV is activated (closed). Pressure is measured and the pressure drop rate is calculated in the BK brake circuit. Pressure is generated in the BK brake circuit using the DV pressure supply, e.g., to 100 bar. The engine control unit is then shut down. If the pressure drop rate in the BK brake circuit is significantly greater than the value stored in the control unit, then the wiring of the winding of the pressure supply's electric drive is faulty.

[0099] • Diagnosis of the switching valves SV

[0100] Isolating valve TV and switching valves SVi, ..., SV4 are controlled (closed). Measurement of pressure in brake circuit BK, and DHK piston displacement. The brake circuit BK is pressurized with pressure, e.g. 100 bar, using the pressure supply DV. If the pressure in the brake circuit BK can then be maintained without the DHK piston having to be moved significantly, then all switching valves SV are tight. If this is not the case, then switching valve SVi is opened, and the pressure supply DV is used to bring the pressure in the brake circuit BK back to e.g. 100 bar. If the pressure in the brake circuit BK can then be maintained without the DHK piston having to be moved significantly, then switching valve SVi is leaking. If this is not the case, then switching valve SV2 is opened, and the pressure supply DV is used to bring the pressure in the brake circuit BK back to e.g. 100 bar.If the pressure in the BK brake circuit can then be maintained without the DHK piston having to be moved significantly, then switching valve SV2 is leaking. If this is not the case, then switching valve SV3 is opened and the pressure in the BK brake circuit is brought back to, for example, 100 bar using the pressure supply DV. If the pressure in the BK brake circuit can then be maintained without the DHK piston having to be moved significantly, then switching valve SV3 is leaking. If this is not the case, then switching valve SV4 is opened and the pressure in the BK brake circuit is brought back to, for example, 100 bar using the pressure supply DV. If the pressure in the BK brake circuit can then be maintained without the DHK piston having to be moved significantly, then switching valve SV4 is leaking. If this is not the case, then all SV valves are tight and the leak is somewhere else, e.g. isolating valve TV.

[0101] Regarding 2a:

[0102] • Pressure reduction via the master brake cylinder, e.g. measurement of pressure drop over time with the isolating valve TV open from the brake circuit BK to the master brake cylinder SHZ / THZ and the switching valves SVi open

[0103] A hydraulically optimized valve seat design can also contribute to minimizing the tear-off force. The return spring force RF is determined by the valve control during pressure build-up via PWM and is used as a global standard for finely dosed, precise pressure build-up, which is also possible with the higher return spring force FR, if necessary with optimized control. Figures 3 to 6 show known brake systems from well-known manufacturers, which are slightly modified according to the invention by replacing the inlet valves with switching valves SVi. Without these modifications, certain single and double faults can occur, resulting in only a limited braking effect in these brake systems. Conventionally, a double fault in two brake circuits means a total failure of the brake system with a failure probability

[0104] AW = 10 x ppm / J x 10 x ppm / J = 100-10' 12 / year, which corresponds to about 100 failures in 1 trillion vehicles per year.

[0105] The main failure points of the previously known braking systems are the following:

[0106] 1. Connection to the hydraulic unit HCU

[0107] 2. Brake line

[0108] 3. Connecting the brake hose to the brake line (not shown in the figures)

[0109] 4. Brake hose

[0110] 5. Connecting the brake hose to the brake caliper (not shown in the figures)

[0111] 6. Brake caliper

[0112] 7. Seal wheel brake cylinder RZ

[0113] 8. Inlet valve check valve

[0114] 9. Outlet valve AV: The AV is a critical component for brake circuit failure in ABS, e.g. dirt particles in the valve seat can cause brake circuit failure with significant loss of braking effect.

[0115] By using the switching valves according to the invention, which are modified conventional ABS inlet valves without a check valve, as well as the additional measures b) to f) described above to prevent the switching valve from closing during rapid pressure reduction, these braking systems can be made more fail-safe without major effort or modification of the entire braking system concept. Due to the elimination of the check valves RV in the switching valves, the braking systems shown in Figures 3 to 5 have a significantly lower failure focus. This significantly reduces the probability of failure compared to the original braking systems and also advantageously provides increased braking efficiency, since now usually only one wheel circuit fails.

[0116] In the following, it is explained in more detail for the individual brake systems in Figures 3 to 6 how the additional measures prevent the switching valves SVi from closing when the pressure is reduced pa b can be safely avoided.

[0117] In the braking system according to Figure 3, the pressure control for p aU f and p a b as in the system according to Figure 1 using the pressure supply DV. In case of failure of the pressure supply DV or the electrical control and regulation unit ECU, the switching valves ESV1 and ESV2 close and the pressure reduction p a b takes place via the tandem master brake cylinder THZ, whereby the temporal flow rate which flows through the switching valves SVi from the wheel brake cylinders into the brake circuit is limited by the correspondingly small flow cross-section of the isolating valves TV1 and TV2, so that closing of the switching valves SVi=i-4 is reliably avoided, see additional measure 2a.

[0118] The braking system shown in Figure 4 is very similar to the braking system shown in Figure 3. In contrast to the braking system shown in Figure 3, the braking system shown in Figure 4 has a check valve-throttle parallel circuit RV / Dr3 in the brake line. The parallel circuit, referred to as measure c), results in a throttling of the volume flow during pressure reduction p a b by means of the throttle Dr3 and guarantees an unlimited pressure build-up p aU f via the check valve RV. In case of failure of the pressure supply DV or the electrical control and regulation unit ECU, the 3 / 2-way isolating valves TV1 and TV2 switch to the valve positions shown, so that the pressure reduction p ab via the tandem master brake cylinder THZ, whereby the flow rate which flows through the switching valves SVi=i-4 from the wheel brake cylinders into the brake circuits BK1 and BK2 is limited by the correspondingly small flow cross-section of the 3 / 2-way isolating valves TV1 and TV2, so that closing of the switching valves SVi=i-4 is reliably avoided in this case too.

[0119] The additional measure lb can be used here as redundancy for possible errors in valve TV1 and valve TV.

[0120] In the braking system shown in Figure 5, the temporal volume flow limitation during pressure reduction in normal operation takes place via the pressure supply DV, in particular via the piston speed, whereas in the event of a failure of the pressure supply or the ECU, the pressure reduction takes place via the 2 / 2-way isolating valve TV and master brake cylinder SHZ with corresponding cross section to the single master brake cylinder SHZ, with corresponding temporal limitation of the volume flow to the master brake cylinder SHZ / THZ.

[0121] In the system shown in Fig. 5 without the switching valves SV according to the invention, i.e. with the previous ABS inlet valves EV with check valve RV, the circuit isolation valve KTV remains open if the electronic control and regulation unit ECU fails. A further failure of a wheel brake cylinder RZ then causes a total brake failure. With the switching valves SVi according to the invention, if one wheel brake cylinder RZ fails, only one wheel circuit fails, thus leaving a residual braking effect of at least 65%. If two wheel brake cylinders RZ fail and the ECU fails, two wheel brake cylinders still remain effective if the circuit isolation valve KTV is switched differently (normally closed).

[0122] The throttling of the flow rate during pressure reduction can be limited to the corresponding control of the pressure supply DV. In the event of a failure of the pressure supply DV or the electronic control and regulation unit ECU, the corresponding solenoid valves close and the pressure reduction p a b is carried out via the 2 / 2-way isolating valve TV, which limits the flow rate by dimensioning its flow cross-section.

[0123] For all braking systems shown and described in Figures 3 to 5, a redundant outlet valve AV, AVred, can also be used, as known from PCT / EP 2022 / 059069. Furthermore, if an outlet valve AV fails, e.g., to reduce pressure in ABS due to its defective electrical control, the pressure supply DV can, in this case, take over not only the pressure build-up but also the pressure reduction via the switching valves SVi, which is explained in more detail in the following Figure 7. This measure is particularly advantageous because, apart from minor changes to the software, no additional technical measures or costs are necessary.

[0124] In the braking system shown in Figure 6, two parallel circuits consisting of a throttle Dr3 and a check valve RV (see additional measure 2b) are provided to throttle the flow rate and prevent the switching valves SVi from closing during pressure reduction. The parallel circuit consisting of a check valve RV and a throttle Dr3 can also be arranged outside the ESP system in a brake line leading to the master cylinder.

[0125] The braking system functions in principle like the braking systems described in Figures 3 to 5. In the system shown in Figure 6, a hydraulic brake booster, electric brake booster, hydraulic E-Boost, or vacuum booster can be used as the master brake cylinder. Its failure can lead to excessive pressure reduction when the pedal is released, which can cause the switching valve SVi to close. Therefore, a combination of check valve RV and throttle Dr3 is used in the main line to the brake booster or booster, which only controls the pressure reduction p a b throttles. The check valve RV enables rapid pressure buildup, as previously explained for the other braking systems.

[0126] The braking system shown in Figure 7 corresponds to a new system design and is based on the braking system shown in Figure 1. The wheel circuits RKi, the pressure supply DV and the single master brake cylinder SHZ are taken from the braking system shown in Figure 1. The difference to the braking system shown in Figure 1 is that a circuit isolation valve KTV is provided, which separates the brake circuits BK1 and BK2. In addition, the 3 / 2-way valves DV / TV have been replaced by valves PD1 and PD2, and a pressure relief valve ÜV is provided, which connects the master brake cylinder SHZ / THZ to the brake circuit BK once a certain pressure difference has been reached. The pressure sensor DG1 is used to monitor the pressure in the master brake cylinder SHZ / THZ together with the travel simulator WS, which are hydraulically connected to one another during normal operation via the 3 / 2-way valve 3 / 2-MV.

[0127] The pressure sensor DG2 is used to control the pressure supply DV. The circuit isolation valve KTV is a normally closed valve, in contrast to the circuit isolation valve KTV in the braking system shown in Figure 5, which is a normally open valve.

[0128] As shown in Fig. 5, the circuit isolation valve KTV can therefore be selected to be normally closed, in contrast to the prior art, in which the circuit isolation valve KTV is normally open, and in the event of an ECU failure, in which the brake booster fails, and an additional failure of the brake circuit BK2, the master brake cylinder SHZ / THZ acts without boost only on one brake circuit BK1 and in the limiting case only a braking force of approximately 0.3 g is achieved.

[0129] Furthermore, the system consists of the standard ABS valve circuit with SVi=i-4 and AV. This makes the system redundant even in the event of a wheel brake cylinder RZ failure and extremely safe even in the event of an exhaust valve AV failure. If, for example, the control of an exhaust valve AV is defective and control is no longer possible, pressure reduction is essentially no longer possible. In this case, the pressure supply DV reduces the pressure in the wheel circuit RK with the failed exhaust valve AV via the piston movement and takes over the pressure reduction p a b, with the remaining switching valves SVi closed. The subsequent pressure build-up occurs as usual, ie in the extreme case of failure of an outlet valve AV with 1 ppm / year, this measure would be necessary. The small restriction that during this time of pressure reduction in a wheel brake cylinder, an individual pressure build-up p aU f is not possible, is completely negligible.

[0130] The cost of the software change is minimal. A failure probability AW of 4 x 1 ppm = 4 ppm / year is likely, although the failure of a locking wheel, for example, on a wet road surface, could result in an accident. For braking systems from Level 3 upwards, this is likely a requirement to be met. Alternatively, a redundant outlet valve AVred can be used.

[0131] The pressure supply DV is a pressure supply described in DE 102017000472 with a so-called double-stroke piston and two 2 / 2-way valves PD1 and PD2 for the forward and return stroke. In the initial position of the piston, there is a connection from the brake circuit BK2 to the reservoir VB. For the 4-circuit system, failure of the motor or the electrical control and regulation unit ECU must be expected. In this case, for example, at high pressure in the brake circuit, an unbraked return of the piston can lead to the switching valve SVi being closed. For this purpose, the parallel connection of the throttle Dr3 and the check valve RV is provided, which, when the pressure decreases p a b prevents excessive flow velocities.

[0132] In this context, a second throttle Dr2 is provided, which allows a small leakage flow, i.e., loss of pedal travel, in the event of the aforementioned failure. Alternatively, the normally closed KTV can also assume this function. In the event of a failure of the electric drive of the pressure supply DV, possibly resulting in rapid engine reversal, an additional electrical circuit can be used, which, in the event of an ECU failure, short-circuits at least one winding of the drive, so that the drive acts as a brake for the piston movement of the pressure supply DV.

[0133] The bottom right of Figure 7 shows the basic circuit diagram of the 3 / 2-way solenoid valve, where two special features must be taken into account. The pressure in the brake circuit BK1 opens valve SV2, meaning that if the pressure supply DV or the ECU fails via the 3 / 2-MV, the pressure in the brake circuit is not trapped. On the other hand, the parallel-connected pressure relief valve ÜV is used, which, in the event of extremely high pressure in the (single) master brake cylinder SHZ / THZ and also if the pressure supply DV or ECU fails, still allows a pressure build-up p aU f from the (single) master brake cylinder SHZ / THZ into the brake circuit BK1. The parallel-connected pressure relief valve ÜV thus allows a p aUf into the brake circuit BK1 via the SHZ. Figure 8 shows a braking system similar to Figure 1, with the difference that the pressure relief valve ÜV described in Figure 7 is also used. This braking system meets extreme requirements for double-fault safety, e.g., failure of a wheel circuit RK and failure of its switching valve SVi with a failure probability AW of 10 ppm*lppm = 10xl0' 12 / J, which is a factor of 10 smaller than double brake circuit failure with 100*10' 12 / J. To increase the reliability, further measures can be taken, e.g. the switching valve SVi can be additionally controlled redundantly, e.g. with a redundant coil, which reduces the failure probability AW in the example to the range of 10' 17 / J brings.

[0134] This concept is more cost-effective than providing a circuit separation valve KTV, which eliminates the disadvantage of a pressure difference in both brake circuits BK1 and BK2 during rapid pressure build-up p aU f compensated.

[0135] In this system, the conventional travel simulator with piston has been removed. Instead, a pedal force control is used, in which the pressure in the master brake cylinder SHZ / THZ is controlled according to the desired pedal characteristics stored in the ECU using the pressure supply DV, the pressure sensor DG1, the pedal travel sensor Sp, and two valves: the isolating valve TV and the travel simulator valve MVws. Together with the pressure sensor DG1 and the pedal travel sensor Sp, the isolating valve TV, together with an overflow valve ÜV, is used to increase the pressure in the master brake cylinder SHZ / THZ (increase pedal force) using the pressure supply DV, and the second solenoid valve MVws is used to reduce the pressure in the master brake cylinder SHZ / THZ (reduce pedal force).

[0136] To limit the pressure reduction p a b the pressure supply is used in normal operation and the isolating valve TV with reduced cross-section is used in case of failure of the pressure supply or ECU.

[0137] To prevent the switching valves SVi from closing in the event of a double fault, failure of the DHK, or failure of a 3 / 2-way valve 3 / 2-MV-RH, additional measure 1b is available, and for pressure reduction via the master brake cylinder SHZ / THZ, additional measure 2a is available. The double-acting piston DHK of the pressure supply DV has two suction valves SaV and, optionally, an additional return line HL11 to the reservoir VB. Here, a 3 / 2 MV is provided for both the forward stroke VH and the return stroke RH of the double-acting piston DHK. This allows all necessary control functions such as pressure build-up p aU f and pressure reduction p ab, both for the forward stroke VH and the return stroke RH. In addition, if a 3 / 2-MV-RH or 3 / 2-MV-VH fails, the other 3 / 2-MV is always available for the forward or return stroke, with the small disadvantage that if a 3 / 2-MV valve fails and switching from 100 to 200 bar occurs, the switching time also acts as lost time. Statistically, a pressure greater than 100 bar is only required for around 10% of braking applications. In addition, this valve circuit has the advantage of what is known as area switching of the pistons, i.e. in the higher pressure range only the small area of ​​approx. 50% is effective, with the advantage of the correspondingly lower spindle force and dimensioning of the motor torque.

[0138] The braking system according to Figure 9 corresponds to the braking system of Figures 7 and 8 in its main components: reservoir VB, single master brake cylinder SHZ, 3 / 2-way isolating valve TV to the travel simulator WS and pressure supply DV.

[0139] The difference lies in the rear axle brake, which is equipped with the well-known electromotive brake (EMB) with an integrated ECU. Therefore, a description of the EMB is omitted here. The difference lies in the hydraulic control of the front axle brake. This is achieved either via a 2x3 phase control of the EC motor of the pressure supply (DV) or via the proposed 4-circuit system with the inventive switching valves (SVi) and possibly a redundant exhaust valve (AVred).

[0140] This means that if wheel circuit RK 1 or RK2 fails, the other wheel circuit is still functional, and a total braking effect of over 60% is still achieved, along with additional safety thanks to the inventive switching valves SVi, a potentially redundant control of the switching valves SVi, and a potentially redundant coil of the switching valve SVi. In addition, a failure of an ABS outlet valve with control of the pressure supply DV and the switching valve SV, as described in Figure 7, can be avoided.

[0141] This braking system according to the invention therefore has a very high level of safety and is also advantageously characterized by its simple design, which saves not only manufacturing costs but also service costs.

[0142] If installation space on the bulkhead is limited, the master brake cylinder SHZ / THZ can be separated from the other hydraulic components and integrated into the pedal bracket.

[0143] The electrical control and regulation unit (ECU) is not described in detail for the reasons stated above. Shown here is the electrical control and regulation unit (ECU) with the on-board power supply connection, which can optionally be configured redundantly (Bred) with the appropriate ECU configuration, with the EA connection to all electrical and electronic consumers.

[0144] If necessary, a redundant pressure supply (DV) can be used for levels L3 and L4 of automated driving, despite the full functionality of the rear axle EMB for the front axle. A redundant ECU can also be used for the above-mentioned requirements. The additional measures for preventing break-in, as shown and described in Fig. 8, also apply here.

[0145] Figure 10 shows a similar system design, with the difference that instead of the master brake cylinder (SHZ / THZ), a so-called e-pedal or, at Level L5 of automated driving, a fully electronic brake control without a pedal can be used. Since the mechanical-hydraulic fallback level is eliminated here, high safety requirements are placed on it, preferably with triple redundancy, as described in aircraft construction and for the e-pedal in DE102019483.

[0146] In addition to the first pressure supply DV, DV1 with optional 2x3-phase redundancy, a second pressure supply DV2 can be provided, which may also have an additional 2x3-phase control. The level indicator NG in the reservoir VB can also advantageously be designed redundantly and preferably arranged with a sensor element in the control and regulation unit ECU.

[0147] The measures 1a to 2a can also be provided in this system according to the invention. Here, too, the switching device is required; for example, in the event of a motor failure, the winding short circuit shown in Fig. 7 can be used. The diagnosis to prevent the tearing of a switching valve SVi=i-4 is carried out with the following measures:

[0148] 1. In the event of a pressure supply failure, the pressure curve and / or the piston speed of the pressure supply is monitored during pressure reduction, whereby if a certain piston speed is exceeded or the pressure change rate is too high, the motor winding of the drive motor of the pressure supply is switched on, in particular short-circuited, by means of an electrical switching device, so that the drive acts as a brake;

[0149] Measures against tearing SV:

[0150] 2. In case of failure or leakage of a switching valve or wheel brake cylinder:

[0151] These faults can only be reliably detected when the switching valve fails, with appropriate diagnosis, e.g. when the vehicle is stationary via the pressure curve in the brake circuit when all switching valves SVi=i-4 are closed. If a wheel brake cylinder fails, volume is equalized via the pressure supply and the wheel brake cylinder or wheel circuit can continue to operate up to a certain degree of leakage, whereby the braking effect of this wheel brake cylinder is not completely lost; a. The isolating valve TV to the master brake cylinder SHZ / THZ is leaking. Detection via pressure curve in the brake circuit BK and master brake cylinder SHZ / THZ, also additional compensation via the control of the pressure supply DV and the isolating valve TV. The motor speed is dampened via the motor winding; b. Combination of check valve RV and throttle Dr3 in the hydraulic line to the pressure supply DV; 3.The switching valve SVi=i-4 is torn shut due to the piston speed of the pressure supply DV being too high during pressure reduction.

[0152] Detection based on the pressure gradient in the brake circuit: Pressure reduction is faster because the SV in one wheel cylinder is closed; 4. Isolating valve with a modified cross-section when pressure is reduced in the master brake cylinder (SHZ / THZ). Detection based on the pressure gradient.

[0153] List of reference symbols

[0154] 1 brake pedal

[0155] 2 Target in the float

[0156] 5 single-circuit pressure supply

[0157] 6 anchors 6 / 6a

[0158] 7 / 7a valve tappet

[0159] 8 Valve seat

[0160] 9 Permanent magnet

[0161] 10 Pole plate

[0162] 11 electromagnetic inference

[0163] 12 plastic bodies

[0164] 13 Return spring

[0165] Al working chamber during pre-stroke

[0166] A2 Working chamber during return stroke

[0167] AR workroom of the SHZ

[0168] B on-board network

[0169] Bred on-board power supply redundant

[0170] BK brake circuit

[0171] BK1 / BK2 Brake circuit 1 or brake circuit 2

[0172] DG pressure sensor

[0173] DHK double-acting piston

[0174] DV pressure supply

[0175] DV1 First pressure supply

[0176] DV2 Second pressure supply

[0177] DV / TV 3 / 2-way isolating valve, DV specific valve circuit

[0178] EA Electrical connection

[0179] ECV Electrical valve control elEM Electrical motor control of the electromechanical brake

[0180] EM 1 / 2 electrical magnetic circuit 1 or 2

[0181] EMB Electromotive Brake

[0182] EV inlet valve with check valve of a conventional ABS

[0183] F Filter

[0184] FFUB Foot force FR. Restoring force

[0185] HCU Complete hydraulic unit with DV and valves

[0186] HL1 HL15 hydraulic lines

[0187] HL1 - HL4 Hydraulic lines outside the HCU to the data center

[0188] HL5 hydraulic lines from SHZ to BV

[0189] HL10 return line to VB with suction valve SaV

[0190] HL11 Return line to VB

[0191] HZ master brake cylinder

[0192] KTV circuit isolation valve

[0193] MV solenoid valve

[0194] MVws travel simulator valve

[0195] P Pump

[0196] P / TV pump isolation valve

[0197] RF return spring force

[0198] RK1 Wheel Circle 1

[0199] RK2 Wheel Circle 2

[0200] RK3 Wheel Circle 3

[0201] RK4 Wheel Circle 4

[0202] RV check valve

[0203] RZ1 - RZ4 wheel brake cylinder

[0204] SHZ / THZ Single master cylinder / Tandem master cylinder

[0205] Sp pedal travel sensor

[0206] SV switching valve, modified conventional ABS inlet valve without check valve

[0207] SV 2k Switching valve, normally open solenoid valve without check valve, especially with an additional power device

[0208] SVx switching valve without additional power device

[0209] TV 2 / 2-way isolating valve, 3 / 2-way isolating valve

[0210] TV1 3 / 2-way isolating valve

[0211] TV2 3 / 2-way isolating valve

[0212] ÜV pressure relief valve

[0213] VB reservoir overview of the electrical valve circuit

[0214] SO = normally open

[0215] SG = normally closed

[0216] AV = SG SV = SO

[0217] 2 / 2-way isolating valve TV = SO

[0218] DV / TV (specific valve circuit: SG, if necessary with spring-assisted valve closure in case of BK failure (can be omitted with SV)

[0219] KTV = SO, if necessary for special application in Fig. 1 also SG depending on requirements in case of on-board power supply failure on residual braking effect

Claims

Patent claims 1. Braking system with - at least two wheel brake cylinders (RZ1-4), each of which is part of separate wheel circuits (RK1-4), - at least one electric motor-driven pressure supply (DV), which is used at least to build up pressure (p aU f) and pressure reduction (p a b) in the wheel brake cylinders (RZ1-4), - at least one storage container (VB), - at least one electronic control unit (ECU) - at least two switching valves (S i=i-4), each wheel brake cylinder (RZ1-4) being connected via a respective hydraulic connecting line to a switching valve (SVi=i-4), which is used to separate and connect the hydraulic connection of the respective wheel brake cylinder (RZ1-4) and at least one further hydraulic main line, via which the switching valve (SVi=i-4) can be connected or connected at least to the pressure supply (DV).connected, and that the switching valves (SVi=i-4) are normally open 2 / 2-way valves, wherein at least the hydraulic connecting line (H LRKI-4) and the wheel brake cylinder (RZ1-4) connected thereto are components of a wheel circuit (RK1-4), and that at least one switching valve (SVi=i-4) or all switching valves (SVi=i-4) do not have a check valve or no check valve is connected in parallel to a switching valve (SVi=i-4), characterized in that to prevent a switching valve (SVi=i-4) from closing during pressure reduction (p. ab) the following measures are provided, alone or in combination, via this switching valve (SVi=i-4): a. that the valve actuator (7) of the switching valve (SVi=i-4) is subjected to a return force (FR) in its open position which is at least 30-50% greater than that of standard inlet valves of ABS systems, wherein the increased return force (FR) is generated by a stronger return spring (13) and / or by means of a magnetic force which acts in addition to the force of the return spring (RF); b) by means of the pressure supply (DV) the pressure reduction rate (dp a b / dt) is set or regulated in such a way that a contraction of the switching valve (SVi=i-4) is avoided; c) that in the hydraulic connecting line (HLx) connecting the pressure supply (DV) to the switching valves (SV1-4), a parallel circuit comprising a throttle (Dr3) and a check valve (RV) is arranged, wherein the check valve (RV) blocks in the direction of the pressure supply (DV); d) that the isolating valve (TV), by means of which the wheel circuits (RK1-4) can be separated from or connected to a master brake cylinder (HZ; SHZ; THZ), has a flow cross-section which is dimensioned such that in the event of a pressure reduction (pab) in a wheel circuit (RK1-4) via the isolating valve (TV), a tearing of the switching valve (SVi=i-4) is prevented; e) that the isolating valve (TV), by means of which the wheel circuits (RK1-4) can be separated or connected from the master brake cylinder (HZ; SHZ; THZ) and via which the pressure is reduced in a wheel circuit (RK1-4), is opened and closed in pulse width mode in order to determine the flow rate orFlow rate to a level such that a tearing of the switching valve (SV1-4) is prevented; f) the drive of the pressure supply (DV) is a multi-phase motor, the electrical wiring of the windings of which is designed such that in the event of failure of the motor control and / or the electrical control unit (ECU) of the braking system, the electric motor is operated in generator mode and, due to the winding circuit, the electric motor acts as a brake for the piston of the pressure supply (DV) and thus the pressure reduction rate (dp. a b / dt) in the wheel circuits (RKi=i-4) is limited or slowed down.

2. Brake system according to claim 1, characterized in that a, in particular almost unthrottled, pressure build-up (Pauf) takes place via the check valve (RV) by means of the pressure supply (DV).

3. Braking system according to one of claims 1 to 2, characterized in that hydraulically acting wheel brake cylinders (RZ) are provided for the front axle (VA), and that electromechanical wheel brakes (EMB) are provided for the rear axle (HA), wherein the wheel brake cylinders (RZ) for the front axle is each part of a separate wheel circuit (K1-2).

4. Brake system according to one of claims 1 to 3, characterized in that the master brake cylinder (HZ) is a single master brake cylinder (SHZ) with only one hydraulic working chamber (Al) or a tandem master brake cylinder (THZ) with two working chambers (Al, A2), wherein the master brake cylinder (HZ) is coupled to a brake pedal (1).

5. Braking system according to one of claims 1 to 4, characterized in that the brake pedal has an E-pedal.

6. Brake system according to one of the preceding claims, characterized in that the brake system has a travel simulator (WS) which can be hydraulically connected to the master brake cylinder (HZ; SHZ; THZ) via a switching valve, in particular in the form of a 3 / 2-way valve (TV).

7. Brake system according to claim 6, characterized in that the 3 / 2-way valve (3 / 2-MV) connects the master brake cylinder (SHZ; THZ) to a brake circuit (BK1) without current.

8. Brake system according to one of the preceding claims, characterized in that a pressure relief valve (ÜV) connects the hydraulic line coming from the master brake cylinder (SHZ; THZ) to a brake circuit (BK1), wherein the pressure relief valve (ÜV) blocks the flow direction towards the master brake cylinder (SHZ; THZ).

9. Brake system according to one of the preceding claims, characterized in that a circuit isolation valve (KTV), in particular a normally closed valve, serves for the selective separation or connection of two brake circuits (BK1, BK2).

10. Braking system according to one of the preceding claims, characterized in that only the front axle (VA) has hydraulic brakes, the braking effect of which is regulated or controlled by the pressure supply (DV) and that electromechanical brakes (EMB) are provided on the rear axle of the vehicle to achieve a braking effect.

11. Braking system according to one of the preceding claims, characterized in that a particularly redundant outlet valve (AV re d) is used to limit the volume flow through a switching valve (SVi) by opening the outlet valve (AVred) when the pressure is reduced via this switching valve (SVi).

12. Braking system according to one of the preceding claims, characterized in that the pressure supply (DV) has a double reciprocating piston (DHK), the two working chambers (A1, A2) of which can be connected selectively to the brake circuit (BK) or the reservoir (VB) by means of two 3 / 2-way valves (3 / 2-MV-VH, 3 / 2-MV-RH).

13. Braking system according to one of the preceding claims, characterized in that at least one switching valve (SVi) has a redundant drive coil and / or a redundant control.

14. Braking system according to one of the preceding claims, characterized in that in the event of failure of a 3 / 2-way valve (3 / 2-MV-VH, 3 / 2-MV-RH), the braking system builds up pressure either only in the forward stroke or only in the return stroke of the pressure supply (DV), 15. Braking system according to one of the preceding claims, characterized in that by means of the two 3 / 2-way valves (3 / 2-MV-VH, 3 / 2-MV-RH) between two modes for pressure build-up (p aUf) is switchable, wherein in the first mode a lower pressure can be generated by means of the pressure supply (DV) than in the second mode, in which the pressure is conveyed via the differential surfaces of the double-acting piston.

16. Brake system according to one of the preceding claims, characterized in that the master brake cylinder (SHZ, THZ) is arranged separately from the hydraulic unit (HCU), in particular together with the pedal block or integrated therein.

17. Braking system according to one of the preceding claims, characterized in that the reservoir (VB) has a redundant level sensor.

18. Brake system according to one of the preceding claims, 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 error level threshold, the pressure control either - decouples this wheel circuit (RK1-4) at least temporarily or permanently from the rest of the braking system or the other wheel circuits (RK1-4) and / or the pressure supply (DV) by permanently closing the switching valve (SVi=i-4) assigned to this wheel circuit and / or - by means of an optional circuit isolation valve (KTV), which is in particular a normally closed valve, or by means of at least one isolation valve (TV, TV1, TV2) at least two wheel circuits (RK1-4) or brake circuits (I, II) are separated from one another - or connected to one another.

19. Braking system according to claim 18, characterized in that by means of the circuit isolation valve (KTV, TV1, TV2) two brake circuits (BK1, BK2), of which at least one is assigned at least two wheel circuits (RKi), can be separated from one another or connected to one another.

20. Braking system according to one of the preceding claims, characterized in that a diagnosis of the respective leakage of the individual wheel circuits (RK1-4) is carried out and that, depending on the diagnosis result, the electronic control and regulating device (ECU) decides whether a wheel circuit (RK1-4) is switched off by permanently closing the associated switching valve (SVi=i-4) or continues to be operated to generate a braking effect.

21. Braking system according to one of the preceding claims, characterized in that the switching valve (SVi=i-4) has a return spring (13) which exerts a force on the valve actuator or the valve tappet (7) which prevents the valve from tearing shut, at least at low pressures.

22. Braking system according to one of the preceding claims, characterized in that the braking system is in a first basic functional state or is operated as long as no functional error occurs in any wheel circuit (RK1-4) which lies above a certain error degree threshold.

23. Braking system according to one of the preceding claims, characterized in that the braking system has two pressure supplies (DV1, DV2).

24. Braking system according to claim 23, characterized in that in a first functional state either one pressure supply (DV1, DV2) is always assigned to a respective 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), are jointly responsible for pressure control.

25. Braking system according to claim 23 or 24, characterized in that in the event of a failure of one pressure supply (DV, DV1, DV2), the other takes over its function, in particular for all wheel circuits or only some of them.

26. Braking system according to one of the preceding claims, characterized in that either a) two wheel circuits are each assigned to one brake circuit (BK1, BK2), b) three wheel circuits are assigned to a first brake circuit (BK1) and one wheel circuit is assigned to a second brake circuit (BK2) (asymmetric brake circuits), or c) all wheel circuits are assigned to only one brake circuit.

27. Brake system according to one of the preceding claims, characterized in that each wheel brake cylinder (RZ1-4) is connected via a respective hydraulic connecting line (H IRKI) to a switching valve (SVi=i-4), which serves to separate and connect the hydraulic connection (HI_RKi) of the respective wheel brake cylinder (RZ1-4) and at least one further hydraulic main line (HL2), via which the switching valve (SVi=i-4) can be connected or is connected at least to the pressure supply (DV), wherein the hydraulic connecting line (H LRKI) and the wheel brake cylinder (RZ1-4) connected thereto are each part of a wheel circuit (RK1-4), and that a diagnosis of the respective leakage of the individual wheel circuits (RK1-4) is carried out and that depending on the diagnostic Based on the result, the electronic control and regulation unit (ECU) decides whether a wheel circuit (RK1-4) is switched off by permanently closing the associated switching valve (SVi=i-4) or whether it continues to operate to generate a braking effect.

28. Brake system according to one of the preceding claims, characterized in that the degree of leakage or leakage flow (Qieck) in a wheel circuit (RK1-4) is determined using one or more of the following diagnostic methods a) to e): a) Determination of the required quantity of hydraulic fluid required to achieve a target pressure (p S0 n) in the respective wheel circuit (RK1-4) additional fluid must be supplied by means of the pressure supply (DV) in addition to the predetermined amount; b) determination of a determined absolute pressure drop (dp a b) and / or pressure drop gradients (p a b / dt) in the respective wheel circuit (RK1-4); c) Determination of the pressure deviation (dp = p S0n - Pist) from the target pressure value (p S0 n) when pressure is built up in the respective wheel circuit (RK1-4) by achieving the desired pressure (p S oii) a predetermined amount of fluid (q) is pumped into the wheel circuit (RK1-4) and then the actual pressure (p is t) is determined; d) Diagnosis of the leak in the wheel circuit (RK1-4) by measuring the pressure (Pact) in the hydraulic line connecting the switching valve (SV1-4) and the pressure supply (DV) over time during pressure build-up by means of the pressure supply (DV) or when the pressure supply (DV) is switched off; e) Measurement of the intake volume (Q) of the respective wheel circuit (RK1-4) via the pressure supply (DV) to achieve a target pressure (p S oii), wherein the receiving volume (Q) is determined by means of the pressure supply (DV), in particular by measuring the current of the drive motor (M) of the pressure supply (DV) and / or the piston travel (ds) of the piston of the pressure supply (DV).

29. Braking system according to claim 27 or 28, characterized in that when an upper limit value (Qhigh) or limit value range is exceeded (dQhigh) of the leakage of a wheel circuit (RKI-4) the respective associated switching valve (SV1-4) is permanently closed and thus a braking effect with this wheel brake cylinder (RZ1-4) no longer occurs, and that below the upper limit value (Qhigh) and above a lower limit value (Qiow) a temporary and / or permanent additional supply to achieve the set brake pressure (p S0 n) in the respective wheel brake cylinder (RZ1-4).

30. Braking system according to claim 29, characterized in that the upper limit value (Qhigh) is determined by the maximum delivery capacity of the pressure supply (DV) for pressure increase.

31. Braking system according to claim 29 or 30, characterized in that at a leakage flow (Qieck) of 50 - 90% of the maximum delivery capacity of the pressure supply (DV), the leakage flow (Qieck) is compensated by means of the pressure supply (DV) by subsequent delivery, such that no or only a slight reduction in the braking effect results.

32. Braking system according to one of claims 29 to 31, characterized in that in order to optimize the braking effect and driving stability, in particular the yaw moment and its control by an additional stabilization control system (ESC), an electronic control and regulating device (ECU) determines whether and which leaky wheel circuit(s) (RK1-4) is / are switched off by permanently closing the respective switching valve(s) (SV1-4).

33. Brake system according to one of the preceding claims, characterized in that an outlet valve (AV1-4) belonging to a wheel brake cylinder is a component of the respective wheel circuit (RK1-4).

34. Braking system according to one of the preceding claims, characterized in that the braking system has a level sensor for determining the fill level of the reservoir (VB), which is arranged in particular on the printed circuit board (PCB) of the control and regulating device (ECU).

35. Braking system according to one of the preceding claims, characterized in that at least one pressure supply (DV) is an electric motor-driven piston-cylinder system.

36. Braking 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).

37. Braking system according to one of the preceding claims, characterized in that one 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(s) (DV, DV1, DV2), in particular to generate high pressures and / or to achieve higher dynamics of the braking system.

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

39. Braking 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.

40. 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.

41. Braking system according to one of the preceding claims, characterized in that in the event of a faulty outlet valve (AV), in particular in the event of an electronic / electrical fault in the outlet valve (AV), the pressure reduction and pressure build-up in a wheel circuit takes place via the redundantly designed switching valve (SV) of the respective wheel circuit.

42. Diagnostic procedure for a braking system according to any one of the preceding Claims, characterized in that during the journey and / or when the vehicle is stationary, the target brake pressure (p S0n) with the actual brake pressure (pist), optionally also its change over time (dt / dp), by means of the at least one pressure sensor (DG) and taking into account at least some other components of the brake system, such as the valves, the pressure supply, the master brake cylinder, the brake pedal, the e-pedal, and their control or switching state and optionally vehicle parameters such as vehicle speed, vehicle deceleration, etc.a plausibility check is carried out by means of which the function of the individual components of the braking system is monitored, and that if a fault is detected by the braking system the following measures are actively carried out individually or in combination: a) the isolating valve (TV) is operated in pulse width mode (PWM) in order to limit the volume flow through the valve; b) at least some drive windings of the drive motor of the pressure supply are short-circuited by means of a switching device so that the drive motor acts as a brake and thus the piston speed of the pressure supply is reduced, which also limits the volume flow through the respective switching valve (SVi=i-4) and thus prevents the switching valve (SVi=i-4) from closing.

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