Brake system and valve with switchable holding force - Patents.com

Abstract

The present invention relates to a brake system comprising: 1-4 At least two wheel brake cylinders (RZ 1-4 ), - at least wheel brake cylinders (RZ 1-4 ) pressure increase (P auf At least one pressure supply (DV) for the engine (SV2K), at least one reservoir tank (VB), at least one electronic open-loop or closed-loop control unit (ECU), 1-4 ), each wheel brake cylinder (RZ 1-4 ) are connected to each wheel brake cylinder (RZ 1-4 ) and a switching valve (SV2K 1-4 ) with at least one other hydraulic main line that can be connected or is connected to at least a pressure supply (DV), 1-4 ) connected to the switching valve (SV2K 1-4 ), and the wheel brake cylinder (RZ 1-4 ) each refers to one wheel circuit (RK 1-4 In the brake system, which is a component of the wheel circuit (RK 1-4 ) is diagnosed for each non-closure, and depending on the diagnosis result, the electronic open loop control or closed loop control unit (ECU) controls the wheel circuit (RK 1-4 ) to the above switching valve (SV2K 1-4 ) determines whether to shut off or to further activate to generate a braking action.

Description

[Technical field]

[0001] Prior Art The current dual-braking system with two brake circuits has been in place for almost 80 years for safety reasons and can be switched between different brake circuits depending on the vehicle concept. a) Diagonal and b) White / black or front / rear axle Brake circuit piping is used. In the event of a failure of one brake circuit, the braking effect is reduced by approximately 50% in a) and approximately 70% in b). Statistics show that 0.001% of brake circuit failures are expected per year. There is a significant risk of accident due to reduced braking effect or complete brake failure.

[0002] DE 10 202018213 306 A1 describes a system for detecting brake circuit faults due to non-tightness of the brake circuit by evaluating the pressure gradient.

[0003] Nearly all vehicles have an electronic brake control system for all four wheels that are primarily hydraulically braked. Each wheel brake cylinder is connected to at least one or two electromagnetically controlled regulator valves that are electronically controlled by an electronic control unit (ECU), for example to prevent the wheels from locking.

[0004] In today's typical brake systems with ABS / EPS function, each wheel brake cylinder is usually assigned one inlet and one outlet valve, and the inlet valve often has a check valve connected in parallel to prevent the inlet valve, also often called the switching valve, from closing due to dynamic pressure in the event of a rapid pressure reduction.

[0005] If an inlet valve with its associated check valve fails and becomes non-sealing, in today's dual-circuit brake systems, the failure of a wheel brake cylinder usually results in the failure of one of the entire brake circuits, which reduces braking effect by at least 30%.

[0006] Problem to be solved by the invention The object of the present invention is to prevent the failure of one entire brake circuit in the event of failure or non-sealing of only one wheel circuit. By wheel circuit is understood in this case the wheel brake cylinder including its hydraulic connection to the valve, e.g. the inlet valve, up to the wheel brake cylinder. By four-circuit brake system is understood in this case a brake system in which in the event of failure of one, two or three wheel circuits, the other three, two or one brake circuits can still function.

[0007] Advantages of the invention To achieve this, as few components as possible that can fail must be fitted in the line connections between the pressure supply and the outlet of the hydraulic control unit. Such components include, for example, electromagnetically or mechanically operated valves. Finally, it is important that only one valve of the "normally open" design is used at the end of the line connections from the pressure supply to each wheel brake cylinder. The inlet valves normally used for ABS / ESP have a parallel check valve, which is no longer usable as it is considered to be insecure in its sealing. As mentioned above, the check valve was provided to prevent the inlet valve from being closed by the dynamic pressure during rapid pressure reduction.

[0008] A valve SV2k according to the invention is understood to be a valve assigned to a wheel brake cylinder, through which hydraulic medium flows for boosting the pressure of this wheel brake cylinder only. A wheel circuit is understood in this case to be a wheel brake cylinder including the hydraulic connection of the valve to the wheel brake cylinder. Of course, hydraulic medium can also flow from the assigned wheel brake cylinder through the valve SV2k back into the brake circuit BK1 or BK2 for pressure reduction.

[0009] In order to avoid the above-mentioned problems, the present invention uses a valve SV2k or a "normally open" type switching valve, the valve member of which is adjusted by a first electromagnetic actuator from an open position to a closed position in which the valve member is pressed against a valve seat. When the electromagnetic actuator is not or not fully energized, a valve spring presses the valve operating member to an initial position, i.e. the open position. The present invention envisages a force adding device which, in the open position, applies an additional force to the valve member directed in the direction of the open position and thus assists or replaces the valve spring, thereby generating an increased resultant force loading the valve member towards the open position.

[0010] The force application device may be switchable and may be formed, for example, by an additional electromagnet in addition to the actual valve drive. The force application device may therefore also be called an active force application device, since the force additionally applied to the valve member can be selectively switched on and off depending on the state of the brake system. However, it is also possible for the force application device to act passively, for example by using a permanent magnet. It is also according to the invention if the force application device comprises an electromagnet as well as a permanent magnet. In all the above-mentioned embodiments, advantageously, a force assisting the valve spring is applied to the valve member by the force application device in order to hold the valve member in an open position so that the valve is not sucked closed unintentionally.

[0011] Therefore, with a purely active force application device, in order to close the valve SV2k, the valve actuator only has to act against the force of a valve spring, which can be dimensioned more compactly based on the switchable force application device, so that the valve SV2k is reliably closed and sealing is guaranteed by the high pressure.

[0012] In a purely passive force application device, the actual actuation drive of the valve SV2k only has to apply a high force at the beginning of the stroke movement from the open position to the closed position in order to overcome the passive and therefore permanently acting additional force. As the air gap increases, the force of the passive force application device decreases more rapidly and acts less strongly in the closed position of the valve.

[0013] The valve SV2k is thus a safety gate for the brake circuit BK to the wheel brake cylinder RZ. If in the brake system according to the invention one of the four hydraulic connections from the hydraulic control unit to the wheel brake cylinders fails or if the wheel brake cylinder is not sealed, the valve SV2k according to the invention makes it possible to isolate the failed hydraulic connection or the failed wheel brake cylinder from the remaining brake system with high reliability.

[0014] The force adding device only needs to be switched on or function if a rapid pressure reduction must take place. In all other operating states of the brake system, the additional holding or supporting force of the force adding device is not required, which advantageously saves energy. In the brake system according to the invention, therefore, in the event of a failure of one wheel circuit, only the braking action of this failed brake circuit is omitted, while the braking action of the remaining three wheel circuits remains available. Thus, there is still only a reduction in the braking action from four complete wheel circuits to three complete wheel circuits, so that in the event of a failure of one wheel circuit on the front axle, the loss of braking action is only about 35%, which differs from the 70% mentioned above for the black / white brake circuit piping in the event of a failure of one complete brake circuit and thus of two wheel circuits.

[0015] The valve described above is claimed both on its own and in combination with the braking system described below, which advantageously comprises the valve described above, although it is also conceivable that the braking system according to the invention is operated with other types of valves.

[0016] The brake system according to the invention therefore has four wheel circuits, of which two wheel circuits are respectively assigned to one brake circuit, and in the event of a failure of one wheel circuit, the other three brake circuits are advantageously provided for braking action.

[0017] The functional safety of the brake system according to the invention can be increased with respect to contaminant particles in the brake fluid by additionally integrating at least one filter with a small mesh width at the inlet and / or outlet of the valve, the mesh width being preferably selected so small that these small contaminant particles can be compensated for by the pressure supply in the closed state of the valve SV2k, but only result in a small non-tightness and thus a small flow rate that can be detected both by diagnostics via the pumped volume of the pressure supply and by diagnostics via the level in the reservoir tank.

[0018] To check the function of the valve SV2k according to the invention, for example, a measurement of the time course of the volume and pressure in each wheel circuit and a comparison with previously determined pressure-volume characteristic curves of the wheel circuits can be carried out during diagnostics, whereby diagnostics can be carried out during each braking and / or also at standstill or during maintenance.

[0019] The valve SV2k operates without a non-return valve as described above, but takes into account various requirements: it must therefore remain reliably open even with high flow rates in both directions, i.e. it must not have the typical weakness of today's valves that at high flow rates forces act on the valve cone and valve spring, causing the valve to close automatically.

[0020] Advantageously, in addition to the force application device, the valve SV2k can be optimized by correspondingly configuring the dimensions of the sealing cone, the return spring and the valve plunger. In the closed position of the valve, which can also be called an inlet valve, but which can also reduce the pressure in the wheel brake cylinder, the opening pressure has a higher force in this position than in the open position, which is desirable in terms of the dimensioning of the magnet circuit, significantly smaller than when using a progressive spring, which is undesirable since the required forces are correspondingly higher.

[0021] The braking system according to the invention can have various valve circuits: a) 4 valves SV2k for each of the 4 wheel brake cylinders, which both boost and reduce pressure for each assigned wheel brake cylinder; b) 4 valves SV2k for each of the 4 wheel brake cylinders, as well as 2 outlet valves; c) 4 valves SV2k and 4 outlet valves.

[0022] When using one outlet valve per wheel circuit, wheel-specific control of the pressure boost Pauf and pressure reducer Pab is possible. In the event of a non-tightness in one wheel circuit, a diagnostic circuit can advantageously identify the wheel circuit that is faulty both when braking and when parking and close the valve SV2k belonging to this wheel circuit, so that in the event of this single error, three wheel circuits are still available, and in the event of a double error, i.e. if two wheel circuits fail simultaneously, two wheel circuits are available as a "worst case", whereas in conventional brake systems the "worst case" would be a complete brake failure.

[0023] It can therefore be seen that, in conclusion, a high safety benefit can be advantageously achieved by the slight modification of the inlet valve and the omission of the check valve in accordance with the valve SV2k. With a corresponding constructional design of the valve SV2k, additional cost savings are possible in addition to the safety benefit.

[0024] The brake system according to the invention can also be designed not with four hydraulic wheel circuits, but as a mixed hydraulic-electric brake system, the design of which is known, for example with hydraulic lines leading to the hydraulically operated front wheel brakes and a simple electrical connection to an electric motor operated brake (EMB) on the rear axle, with the same advantages being obtained in this case, provided that the hydraulic wheel circuits are designed in accordance with the above-mentioned configuration.

[0025] Besides the valve concepts described, different concepts of the pressure supply are also possible, for example only one pressure supply for level 2 of autonomous driving or two pressure supplies for levels 3 to 5 of autonomous driving, in which case the second redundant pressure supply may contain a piston pump or a rotary pump. Rotary pumps have significant cost advantages. In the case of piston pumps, a simple check valve can be used at the outlet of the pressure supply instead of a magnet valve, which has similar advantages in the event of a failure of the pressure supply and is more cost-effective. In this brake system, pressure reduction during normal braking cannot be achieved via control of the piston of the pressure supply, but via control of the outlet valve using the pressure transducer signal of the pressure transducer. Since at least two outlet valves AV are used, redundant pressure reduction is also achieved. Depending on the requirements of the pressure reduction speed and depending on the number of outlet valves AV, one, two or more outlet valves can be opened.

[0026] A solenoid valve may be provided to separate the pressure supply from the brake circuit. However, if a pressure supply with a redundant winding circuit, e.g. 2 × 3 phases, and / or a drive with a redundant control device is provided, the switching valve SV2k assigned to the wheel circuit may be switched to the 1-4 Such an isolating valve can also be omitted so that no valve is provided between the pressure supply DV and the pressure supply DV, in which case compensation is provided by additional pressure supply to prevent breakdowns of the brake system due to, for example, non-sealing piston seals or small piston play.

[0027] Advantageously, with the above-described braking system, typical vehicle adjustments in various areas such as logistics, maintenance and certification can be omitted.

[0028] Description of the drawings Various possible embodiments of the braking system according to the invention and the valves used are explained in more detail below with reference to the drawings. [Brief description of the drawings]

[0029] [Figure 1] FIG. 2 shows the structure of a brake system according to the invention with four hydraulic wheel brakes connected to a hydraulic unit via four hydraulic lines, which brake system has further valves in addition to the valves SV2k according to the invention each assigned to one of the four wheel brakes. [Figure 1a] FIG. 4 is a diagram showing a typical brake pressure transition in an ABS control cycle. [Figure 1b] FIG. 1 shows the structure of a mixed brake system with hydraulically operated brakes on the front axle and electrically operated brakes on the rear axle. [Diagram 2] FIG. 1 shows the fundamental structure of a valve SV2k equipped with a force application device. [Figure 2a] FIG. 13 shows the force progression of the force application device with respect to the valve armature stroke. [Figure 2b] FIG. 4 shows the progression of the electromagnetic valve force and the return spring force over the valve armature stroke. [Figure 2c] 11A and 11B are diagrams showing the valve current during current control, the transition of the electromagnetic valve force during current control, and the force of the force applying device with respect to the valve armature stroke. [Figure 2d] FIG. 3 shows the structure of the valve SV2k according to FIG. 2 as a modification of the standard valve. [Figure 3a] FIG. 2 shows a possible valve circuit for a braking system according to the invention with four wheel circuits. [Figure 3b] FIG. 2 shows a possible valve circuit for a braking system according to the invention with four wheel circuits. [Figure 3c] FIG. 2 shows a possible valve circuit for a braking system according to the invention with four wheel circuits. [Figure 3d] FIG. 2 shows a possible valve circuit for a braking system according to the invention with four wheel circuits. [Figure 4a] FIG. 4 shows a diagnostic process during braking for a brake system according to the invention. [Figure 4b] FIG. 11 is a diagram showing a diagnostic process while the vehicle is stopped. [Figure 4c1] FIG. 4 shows a diagnostic procedure in the event of a leak in the wheel brake cylinder and a leak in the valve SV2k. [Figure 4c2] FIG. 4 shows a diagnostic procedure in the event of a leak in the wheel brake cylinder and a leak in the valve SV2k. [Figure 4c3] FIG. 4 shows a diagnostic procedure in the event of a leak in the wheel brake cylinder and a leak in the valve SV2k. [Figure 4d] FIG. 2 shows a first alternative diagnostic procedure for a brake system according to the invention for a single error during braking or when the vehicle is stopped. [Figure 4e] FIG. 4 shows a second alternative diagnostic procedure for a brake system according to the invention for a single error during braking or when the vehicle is stopped. [Figure 4f] 3 shows a diagnostic procedure for a brake system according to the invention, which is configured on the basis of a first alternative diagnostic procedure for a double error during braking or when the vehicle is stationary.

[0030] FIG. 1 shows a simplified construction of a brake system according to the invention with four wheel circuits, which have hydraulic connections HL1-HL4 between the wheel brake cylinders RZ1-RZ4 and the valves SV2k1-SV2k4. In this case, for example, the wheel circuit 1 consists of the wheel brake cylinder RZ1 and the hydraulic line HL1. An outlet valve may be provided as an option, in which case one, two or four outlet valves may be provided. The hydraulic connection between the optional outlet valve AV and the reservoir tank VB is shown with dashed lines. The valve SV2k has a hydraulic connection to the pressure supply DV via the brake circuits BK1 and BK2. The brake circuits BK1 and BK2 can be selectively connected to one another via a non-energized open circuit isolating valve KTV, the structure of which is shown in more detail in FIGS. 3a-3c under the reference BP1. For safety reasons, the circuit isolation valve KTV may be configured as a 3 / 2-way valve, in which one port of the valve is connected to the pressure supply DV and the other two ports are connected to the two brake circuits, so that the pressure supply can be selectively connected to one brake circuit BK1 or the other brake circuit BK2. As is known, piston pumps with so-called stepless single-stroke pistons and piston pumps with stepped pistons as double-stroke pistons performing a reciprocating stroke are used as pressure supply DV. A pressure supply DV with a single-stroke piston has only one pressure outlet, whereas a pressure supply DV with a double-stroke piston has two pressure outlets. A pressure supply DV with only one pressure outlet can be formed, for example, by a motor-driven piston-cylinder unit with only one pressure chamber or, for example, by a rotary pump. The pressure supply DV with two pressure outlets may, for example, be formed by a motor-driven double-stroke pump with two pressure chambers, in which case each pressure chamber or working chamber is connected to or forms one outlet.A pressure supply DV with a double-stroke piston is advantageously used for continuous pumping and has the advantage of an additional supply for leakage compensation even in the event of a fault in a four-circuit brake system. A pressure supply DV with a double-stroke piston requires a valve switching for the two-way stroke. Both piston types also selectively utilize a circuit isolation valve KTV for the isolation of the two brake circuits BK1 and BK2. In a four-circuit brake system with SV2k as a safety valve and also in a safer n-circuit brake system, the circuit isolation valve KTV and the two-circuit supply of the pressure supply DV can be omitted. Due to the advantage of the safety provided by the valve SV2k in the event of a failure of one of the wheel circuits RK1, ..., RK4, the valve KTV can be omitted, with the elimination of double failure safety measures, such as non-sealing of the wheel brake cylinder 1 and non-sealing of the valve SV2k1.

[0031] If a pressure supply with only one outlet is used, the valve KTV is used to selectively connect or disconnect the pressure supply to or from the brake circuits BK1 and BK2. If, on the other hand, a pressure supply with two outlets is used, then each outlet of the pressure supply DV is connected to one brake circuit BK1 or BK2, in which case, as shown in FIG. 1, a circuit disconnection valve KTV is used to selectively connect or disconnect the two brake circuits BK1 and BK2. 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 guaranteed. One or two pressure transducers DG may be provided in both brake circuits BK1, BK2 to determine the actual pressure Pist. The master brake cylinder may alternatively be configured as a single master brake cylinder SHZ or as a tandem master brake cylinder THZ, via which pressure can be generated by the brake pedal in the event of a failure of the pressure supply DV. A reservoir tank VB may be connected or arranged to the master brake cylinder HZ, the reservoir tank having a float on which a sensor target 2 is arranged, and in the open-loop / closed-loop control unit ECU a sensor element 1 is provided for detecting the filling level of the reservoir tank.

[0032] FIG. 1a shows a typical brake pressure profile P in a wheel brake cylinder during a standard ABS control cycle. RZAt time 1 after the brake pressure reduction due to unstable wheel slip, the brake pressure is kept constant until time 2 so that a stable wheel slip can be produced. At time 2, the brake pressure is increased rapidly, i.e. with a large gradient, in order that a stable wheel slip is achieved and the maximum value of the braking force between the tire and the road is reached again quickly. At time 3, the braking force is slightly below the maximum value between the tire and the road. The brake pressure is now increased slowly, i.e. with a small gradient, so that the braking force is maintained long-term near the maximum value of the braking force between the tire and the road. At time 4, despite the increase in brake pressure, the braking force between the tire and the road is reduced. The wheel decelerates significantly, the wheel slip is unstable and the pressure is reduced by opening the outlet valve AV. Between time 4 and time 5, the wheel slip is unstable and can increase very quickly, so that during this period the brake pressure must be reduced very quickly, i.e. with a large gradient. At time 5, the wheel is accelerated again and the pressure is kept constant so that a stable wheel slip can be created again. At time 6, a stable wheel slip is reached and the brake pressure can be increased again. A small gradient in the brake pressure between time 3 and time 4 is achieved by current open-loop or current closed-loop control of the valve SV2k. For this, a valve connection as shown in FIG. 1 is mandatory. The brake pressure gradient between time 4 and time 5 depends on the brake pressure in the wheel brake cylinder, i.e. the pressure P in the wheel brake cylinder. RZ If is high, the gradient is large and the pressure P RZ If the braking pressure in the wheel brake cylinder is small, e.g., P RZ For a large braking pressure in the wheel brake cylinder, for example, P RZ= 100 bar, a larger hydraulic resistance of the outlet valve AV is desirable in order to avoid too large a gradient for accurate pressure regulation and to reduce noise. As a result, the hydraulic resistance of the outlet valve can always only be a compromise.

[0033] As already explained, a small gradient of the brake pressure build-up in the wheel brake cylinder between time 3 and time 4 is achieved by current open-loop or current closed-loop control of the valve SV2k. For this, a hydraulic connection of the valve SV2k, for example SV2k1, as shown in FIG.

[0034] For example, for gradient control of the brake pressure buildup in the wheel brake cylinder RZ1, the hydraulic resistance of the valve SV2k1 is influenced by current open-loop control or current closed-loop control. If the valve SV2k1 is open, a volume flow from the brake circuit BK1 into the wheel brake cylinder RZ1 during brake pressure buildup in the wheel brake cylinder RZ1. In this case, the volume flow passes through a narrow valve gap between the valve armature (in the figure the ball of SV2k1) and the valve seat of the valve SV2k1. As a result, the brake pressure upstream of the valve gap, i.e. on the side of the brake circuit BK1, is greater than the brake pressure downstream of the valve gap. This pressure difference acts on the valve armature, which is thus subjected to a pressure difference acting in the direction of the valve opening. When the valve SV2k1 is energized, a magnetic force is generated which acts on the valve armature in the direction of the valve closing position. Such a magnetic force causes the armature to move in the valve closing direction, the valve gap is reduced, and thus the volume flow and thus the pressure build-up gradient in the wheel brake cylinder RZ1 is reduced. The higher the current to the valve SV2k1, the smaller the brake pressure build-up gradient in the wheel brake cylinder RZ1. In this way, the brake pressure build-up gradient in the wheel brake cylinder RZ1 can be influenced by an open-loop or closed-loop current control of the valve SV2k1.

[0035] FIG. 1b shows a mixed brake system with hydraulically operated brakes on the front axle and electrically operated brakes EMB on the rear axle. The hydraulic switching of the front axle with the SV2k valve is the same as in the embodiment according to FIG. 1 and has a single connection to the pressure supply DV. An additional isolation valve for the single master cylinder SHZ, which can also be provided in the embodiment shown in FIG. 1, is arranged in the connecting line HL5. This valve is closed in normal operation. The pressure supply DV is preferably driven redundantly by an EC motor which is driven via a 2×3-phase winding control. This makes it possible to still provide a braking effect of about 70% in the case of a single error in one winding.

[0036] FIG. 2 shows a special valve SV2k required for the embodiment described above, which functions reliably in both flow directions, i.e., for example, 100 cm 3 / sec~120cm 32a) exerts a force FM1 which is significantly progressive over the stroke h, and the return spring 13 which is also a return force FRF. In the left partial view of FIG. 2, the armature 6 is connected to a second force-generating element which constitutes the force-applying device according to the invention. The second force-generating element may consist of a second electromagnetic circuit EM2 including an armature 6a, whose switchable force FM2 acts in the opposite direction to the force FM1 of the first electromagnetic circuit EM1. As a cheaper alternative, a small permanent magnet switched magnet circuit with a pole plate 10 may also be used as a passive force-applying device. The force action of FM2 acts in the opposite direction to FM1 and acts with a relatively strong force at the opening of the valve, with a significant drop in the desired force over the stroke h. The force FM2 is still large enough to perform the normal return of the armature at the end of the stroke (see FIG. 2b) and may therefore be substituted for the normal return spring 13. FIG. 2c shows the interaction of the force source FM1 with the permanent magnet FM2 as a function of the current strength. When the pressure P2 is greater than the pressure P1, a pressure difference P2-P1 with a force FP directed in the direction of the valve opening acts on the valve seat in the closed position. In the open position, the volume flow Q through the valve causes the above-mentioned hydraulic force FH to act on the valve seat which, depending on how the valve SV2k is connected to the pressure supply DV and to the wheel brake cylinder RZ and in which direction of the volume flow, can, without countermeasures, retract and close the valve both in the event of a pressure increase Pauf and in the event of a pressure decrease Pab, as will be explained in more detail below in Figures 3 to 3b.

[0037] The hydraulic force on the valve armature FH, which acts on the volume flow Q when flowing through the valve, is in each case active in the open position of the valve. It is therefore preferable in particular for the force FM2 of the force application device to act in this position, so that it can be set higher in the open position than in the case of a spring with a force FRF that increases with the armature movement in the closing direction of the valve, since the force of FM2 decreases over the entire movement of the armature in the closing direction of the valve.

[0038] The valve plunger 7 may have a special shape that provides a hydraulic flow force counterforce and reduces the suction closing force.

[0039] FIG. 2c shows the electrical control of valve i. The current strength i1 is selected such that in the closed position FM1 is greater than FM2. In this case, the current may be variable depending on the hydraulic differential pressure P2-P1 across the valve in the closed position of valve i2. Since in this position the force FM2 is in the range of the normal spring force for the reasons described, the valve may be operated, for example, by current open-loop control or current closed-loop control. To hold the valve in the closed position, the differential force, FV,zu = FM1,zu - FM2,zu must be greater than the force FP generated by the pressure differential P2-P1 across the valve in the closed position.

[0040] FIG. 2d shows the structural design of a directional control valve SV2k according to the invention based on an inlet valve set. All parts correspondingly present as part of the set are marked with the reference S. The check valve integrated into the valve set is omitted. Only four further parts are required for the force application device. These are: 1. Permanent Magnets 9 2. Magnetic pole plate 10 3. Electromagnetic coil flux guide 11 and 4. A plastic body 12 that joins together multiple members including the mover.

[0041] 3a-3d show various valve circuits for ABS / ESP functions that rely on a system of pressure control for pressure boost Pauf and pressure reduction Pab. The embodiments differ in the number of valves, where the differentiating feature is the outlet valve AV and thus the pressure reduction control. The arrows respectively indicate the volume flows at which the risk of suction closure of the valves SV2k1,...,SV2k4 occurs. Suction closure or retraction closure of a valve means that the valve, open in the de-energized state, closes automatically due to the volume flow through the valve. For example, FIG. 3a shows a pressure boost Pauf in the wheel brake cylinder 2, RZ2, where the hydraulic volume flows from the brake circuit BK1 through the open valve SV2k2 into the wheel brake cylinder 2, RZ2. When the valve SV2k2 is open, the volume flow passes through a narrow valve gap between the valve armature (in FIG. 2, the ball of SV2k2) and the valve seat. The brake pressure upstream of the valve gap is thus greater than the brake pressure downstream of the valve gap. This pressure difference acts on the valve armature, which exerts a pressure differential on the valve armature in the direction of valve closure. If this pressure differential is greater than the force that the valve spring exerts on the valve armature, it closes the valve, which is called suction closing of the valve due to volume flow. Such automatic closure is undesirable because the valve is not controlled to close.

[0042] FIG. 3b shows a valve circuit similar to that of FIG. 1a, which allows standard ABS control in a similar manner as described for FIG. 1a.

[0043] Fig. 3c shows a possible embodiment for a diagonal brake circuit piping, in which the outlet valve AV is used only in the wheel brake cylinder of the front axle VA. In this use, the front brake cylinders can be operated with standard ABS control, as described in Fig. 1a. In this case, pressure reduction Pab in both rear brake cylinders is only possible if there is no simultaneous pressure increase in any of the front brake cylinders. Since pressure reduction is time-critical, as described in detail in Fig. 1a, a mixed operation of, for example, standard ABS control in the front brake cylinders and Pauf and Pab control via the valve SV2k in the rear brake cylinders entails disadvantages in the ABS control in the rear brake cylinders.

[0044] Fig. 3c shows the example of use for pressure increase Pauf and pressure reduction Pab at the rear axle via valves SV2k3 and SV2k4 with modified ABS control. With open-loop or closed-loop current control of valves SV2k3 and SV2k4, the pressure gradient during pressure reduction can be adjusted, since the valve connection allows this. In this case, the open-loop or closed-loop current control is similar to the control of the pressure increase gradient as described with reference to Fig. 1a. In this case, there is no need to compromise the gradient during pressure reduction via outlet valve AV, as described with reference to Fig. 1a.

[0045] For example, for the suction closure of the valves SV2k1,...,SV2k4, such a situation can occur in the valves of Fig. 3c, for example in the valves SV2K1 in BK1 and SV2k2 in BK2 during the pressure reduction Pab, if the pressure reduction Pab is performed via the control of the DV, and in the valves SV2k3 in BK2 and SV2k4 in BK1 during the Pauf, if the Pauf is performed via the control of the DV. In Fig. 3b, the suction closure can occur in all SV2k only in the case of a pressure reduction Pab via the control of the pressure supply DV. In Fig. 3a, the suction closure can occur in all valves SV2k only in the case of a pressure increase Pauf via the control of the pressure supply DV.

[0046] The embodiment according to Fig. 3d corresponds to the embodiment according to Fig. 1a and Fig. 3b, with the addition of a single master brake cylinder SHZ, an isolation valve 9, an optional circuit isolation valve BP1, an optional safety valve MVDV1 and a safety valve MVDV2 in the case of a two-circuit pump, and a pressure supply DV. In many systems, for example in DE 10 2017219598 A1, a non-energized closing safety valve MVDV1 / MVDV2 is used at the outlet of the pressure supply DV. The safety valve MVDV1 / MVDV2 is a non-energized closing valve, the structure of which corresponds to the outlet valve AV in Fig. 3b. This safety valve MVDV1 / MVDV2 is closed in the event of a failure of the pressure supply DV, for example in the event of a failure of the motor of the pressure supply or of the piston seal D1 during boosting, in order to prevent an uncontrolled backflow of the volume flow from the wheel brake cylinder to the pressure supply DV and thus an undesired uncontrolled pressure reduction in the wheel brake cylinder. When using a pressure supply DV with a double-stroke piston that seals and separates the two working chambers from one another, two solenoid valves MVDV and MVDV2 can be used in the hydraulic connection connecting the two outlets of the working chamber to the brake circuits BK1 and BK2 to selectively block and open both outlets. In this case too, the two brake circuits BK1 and BK2 can be selectively connected via the valve BP1.

[0047] Instead of a piston pump, a rotary pump, for example a gear pump, can also be used, in which case instead of the magnet valve MVDV1 a simple check valve RVDV1 can be provided at the pump outlet. This check valve RVDV1 performs a similar function to the magnet valve MVDV1 in the event of a failure of the pressure supply DV. Unlike the magnet valve MVDV1, which can perform a pressure reduction via the pressure supply DV via an opened valve, this is not possible with the check valve RVDV1. The pressure reduction Pab in a system with a rotary pump is therefore performed via the outlet valve AV. In the event of a slow pressure reduction, the outlet valves AV can be controlled individually or all together via the pressure transducer DG1 for the pressure reduction Pab. The combination of a rotary pump with a check valve RVDV1 at the pump outlet is the cheapest solution for the pressure supply DV. In some rotary pumps a combination of the pressure supply with the magnet valve MVDV1 is also possible, which has the advantage of a well controllable pressure reduction speed via the rotary pump, for example in the case of a gear pump.

[0048] As shown in FIG. 1a, in some brake systems with two brake circuits BK1 and BK2, a non-energized open circuit isolation valve KTV is provided, the structure of which is similar to that of the isolation valve BP1 in FIG. 3a, which is controlled and thus closed in the event of a fault, for example in the event of non-sealing of the brake circuit BK1, so that the other brake circuit BK2 can still be loaded with pressure by the pressure supply DV.

[0049] The optional switching valves BP1 and MVDV1 can be used in various embodiments: 1. Use both valves; 2. Only use safety valve MVDV1, no circuit isolation valve BP1; 3. Only the circuit isolation valve BP1 is used, and there is no safety valve MVDV1.

[0050] The first embodiment is in this case the most expensive brake system of all three embodiments and, as already mentioned above, has the advantage of high safety in the event of a failure of the pressure supply DV or of one of the brake circuits BK1 or BK2.

[0051] In the above embodiment 2, a fault in one brake circuit, for example an open brake circuit BK1, can be detected by diagnosis. It is therefore also possible to detect which wheel circuit is faulty, for example an open wheel brake cylinder RZ1, and then the associated valve SV2k1 can be closed. The remaining wheel brake cylinders RZ2, RZ3 and RZ4 can still be loaded with pressure via the pressure supply DV.

[0052] In the embodiment 3 above, i.e. without the safety valve MVDV1, in the event of a failure of the pressure supply DV, for example due to non-sealing of its piston seal, the switching valve 9 can be opened and the circuit isolation valve BP1 can be closed. In this case, the driver can control the pressure in the brake circuit BK1 via the brake pedal. In this case, only the brake circuit BK2 is faulty. In the event of a pressure supply failure during braking, the pressure in the wheel brake cylinders RZ1,...,RZ4 is reduced via the valve AV with the valves SV2k1,...,SV2k4 closed.

[0053] 4a and 4b show a test cycle for checking the tightness of a brake system in diagnostics. FIG. 4a shows tests T0-T4 during braking. At the beginning of braking, in test T0 from point A0 to point A, the pressure and, for example, the storage volume V of the wheel brake cylinder are measured during pressure buildup via the piston stroke Sk of the pressure supply DV. The setpoint value Sk soll is fed as a function of pressure by the stored pressure-volume characteristic curve of the brake, the PV characteristic curve, and the actual value of the piston travel distance Sk ist At point A, the pressure is held constant. At point A, Sksoll and Sk ist If no difference between RZ and the valve SV2k is measured and this comparison is maintained throughout the braking phase up to the point A1, then the test T0 is negative. If the test T0 is negative, then no further tests (T1, T2, T3, T4) are necessary. If a difference is measured, then there is a non-tightness in one wheel circuit, i.e. between one wheel brake cylinder RZ and the associated valve SV2k, and the test T0 is positive. If the test is positive, but at the point A, Sk soll and Sk ist If only one very small difference between T1 and T2 is measured, no further tests (T1, T2, T3, T4) are necessary. A warning on the display invites the driver to visit the workshop at the first opportunity. If, despite a volume loss from the brake system due to a non-tightness in the wheel circuits, the volume in the reservoir tank is sufficient for a large number of further brakings, for example 1000, and the volume loss can be compensated for by the volumetric flow pumping of the pressure supply DV, then the brake system is stopped. soll and Sk ist The difference between the test T0 and point A is very small. soll and Sk istIf two or more very small differences between the pressures are measured, it must be determined in which wheel circuit the non-sealing exists. For this purpose, at point A, a test T1 is performed with the closing of the valve SV2k1 assigned to the wheel brake cylinder RZ1. If the wheel circuit 1 is non-sealed, then after the closing of the valve SV2k1, no piston movement Sk is required to keep the measured pressure constant, and the test T1 is positive. If the test T1 is positive, the valve SV2k1 remains closed until the end of braking A01, the piston stroke distance Sk of the pressure supply DV remains constant from point A to point A1, and no further tests (T2, T3, T4) are required. The test time of the test T1, the test phase, is selected to be short, for example 20 ms, so that the braking process, and possibly also the driver, is not disturbed by the test. If, for example, the driver wants to reduce the pressure during the test phase, this is done via the piston movement of the pressure supply DV only after the end of the test phase or immediately after the wheel circuit has already been identified as non-sealed. If the driver attempts to increase the pressure during the test phase, the test is interrupted. If the test T1 is negative, i.e. in order to keep the pressure constant despite the closure of the valve SV2k1, an increase in the piston stroke Sk of the pressure supply DV is necessary, then the wheel circuit 1 is not sealed, but the other wheel circuit is not sealed, so that after the point A, in the extreme case, a leakage flow acts up to the test T4 of the wheel circuit 4, and thus the piston stroke Sk of the pressure supply DV advances. In this case, the piston stroke Sk of the pressure supply DV ist increases during the test phase T1 from point A to point B and reaches point B. After a negative test T1, the valve SV2k1 is opened. If the test T1 is positive, no further tests are performed and the valve SV2k1 remains closed during the subsequent braking, and the value of Sk at point A soll and Sk ist The difference between is maintained throughout the braking phase up to the point in time A01. A warning on the display prompts the driver to visit a repair shop immediately.

[0054] (At point A, Sk soll and Skist After a positive test T0 and a negative test T1 (two or more very small differences between the pressures are measured) and a negative test T2 for the wheel circuit 2 is carried out at point B. The test T2 is carried out in the same way as the test T1. For this purpose, at point B, the test T2 is carried out with the valve SV2k2 assigned to the wheel brake cylinder RZ2 closed. If the wheel circuit 2 is non-sealing, after the closing of the valve SV2k2, no piston movement Sk is required to keep the measured pressure constant, and the test T2 is positive. If the test T2 is positive, the valve SV2k2 remains closed until the end of braking A01, and from point B to point B1 the piston stroke distance Sk of the pressure supply DV remains constant, and no further tests (T3, T4) are required. The test time, the test phase, of the test T2 is selected to be short, for example 20 ms, so that the braking process and possibly also the driver are not disturbed by the test. If the driver, for example, wants to reduce the pressure during the test phase, this is done via the piston movement of the pressure supply DV only after the end of the test phase or immediately after the wheel circuit has already been identified as non-sealed. If the driver wants to increase the pressure during the test phase, the test is interrupted. If the test T2 is negative, i.e., despite the closure of the valve SV2k2, an increase in the piston stroke Sk of the pressure supply DV is necessary to keep the pressure constant, then the wheel circuit 2 is not non-sealed, but another wheel circuit is non-sealed, so that after the time point B, in the extreme case, a leakage flow acts up to the test T4 of the wheel circuit 4, and thus the piston stroke Sk of the pressure supply DV advances. In this case, the piston stroke Sk of the pressure supply DV increases during the test phase T2 from the time point B to the time point C, and reaches point C. After the negative test T2, the valve SV2k2 is opened. If the test T2 is positive, no further tests are performed and the valve SV2k2 remains closed during the subsequent braking, and the valve Sk at the time of point B soll and Sk ist The difference between is maintained throughout the braking phase up to the point in time A01. A warning on the display prompts the driver to visit a repair shop immediately.

[0055] (At point A, Sk soll and Sk ist After a positive test T0 (two or more very small differences between the pressures are measured) and negative tests T1 and T2, a test T3 for the wheel circuit 3 is carried out at point C. The test T3 is carried out similarly to the test T1. For this purpose, at point C, the test T3 is carried out with the valve SV2k3 assigned to the wheel brake cylinder RZ3 closed. If the wheel circuit 3 is non-sealing, after the closing of the valve SV2k3, no piston movement Sk is required to keep the measured pressure constant, and the test T3 is positive. If the test T3 is positive, the valve SV2k3 remains closed until the end of braking A01, and from point C to point C1 the piston stroke distance Sk of the pressure supply DV remains constant, and no further test (T4) is required. The test time, the test phase, of the test T3 is selected to be short, for example 20 ms, so that the braking process and possibly also the driver are not disturbed by the test. If the driver, for example, wants to reduce the pressure during the test phase, this is done via the piston movement of the pressure supply DV only after the end of the test phase or immediately after the wheel circuit has already been identified as non-sealed. If the driver wants to increase the pressure during the test phase, the test is interrupted. If the test T3 is negative, i.e., in spite of the closure of the valve SV2k3, an increase in the piston stroke Sk of the pressure supply DV is necessary to keep the pressure constant, then the wheel circuit 3 is not non-sealed, but another wheel circuit is non-sealed, so that after the point C, in the extreme case, a leakage flow acts up to the test T4 of the wheel circuit 4, and thus the piston stroke Sk of the pressure supply DV advances. In this case, the piston stroke Sk of the pressure supply DV increases during the test phase T3 from the point C to the point D and reaches the point D. After the negative test T3, the valve SV2k3 is opened. If the test T3 is positive, no further tests are performed and the valve SV2k3 remains closed during the subsequent braking, and the Sk at the time of point C soll and Sk ist The difference between is maintained throughout the braking phase up to the point in time A01. A warning on the display prompts the driver to visit a repair shop immediately.

[0056] (At point A, Sk soll and Sk ist After a positive test T0 and negative tests T1, T2 and T3 (two or more very small differences between the pressure and the pressure are measured), a non-tightness of the wheel circuit 4 is assumed and the valve SV2k4 is immediately closed. On the other hand, in order to exclude the possibility of non-tightness in other parts of the brake system, a test T4 for the wheel circuit 4 can also be carried out at point D. The test T4 is carried out analogously to the test T1. For this purpose, at point D, the test T4 is carried out with the valve SV2k4 assigned to the wheel brake cylinder RZ4 closed. If the wheel circuit 4 is non-tight, after the closing of the valve SV2k4, no piston movement Sk is required to keep the measured pressure constant, the test T4 is positive and the point D1 is reached. If the test T4 is positive, the valve SV2k4 remains closed until the end of braking A01 and from point D to point D1 the piston stroke distance Sk of the pressure supply DV remains constant and no further tests are required. The test time, the test phase, of the test T4 is chosen to be short, for example 20 ms, so that the braking process, and possibly also the driver, is not disturbed by the test. If, for example, the driver tries to reduce the pressure during the test phase, this is done via the piston movement of the pressure supply DV only after the end of the test phase or only immediately after the wheel circuit has already been identified as non-tight. If the driver tries to increase the pressure during the test phase, the test is interrupted. If the test T4 is negative, i.e., despite the closure of the valve SV2k4, an increase in the piston stroke Sk of the pressure supply DV is necessary to keep the pressure constant, then after the point D, a leakage flow acts and thus the piston stroke Sk of the pressure supply DV advances, since non-tightness exists elsewhere in the brake system. In this case, the piston stroke Sk of the pressure supply DV increases during the test phase T4 from the point D to the end of braking A01 (not shown). After a negative test T4, the valve SV2k4 is opened. If the test T4 is positive, the valve SV2k4 will remain closed during the subsequent braking, and the valve Sk at point D will soll and Sk istThe difference between is maintained throughout the braking phase up to the point in time A01. The execution of test T4 ends the test cycle. In both the positive case (wheel circuit 4 is not sealed) and the negative case (other parts of the brake system are not sealed), a warning on the display prompts the driver to visit a workshop immediately.

[0057] At test T4, the test cycle ends at point D1 and the braking process with pressure reduction ends at point E. This diagnosis presupposes appropriate accuracy and dynamic properties of the sensors, for example piston travel, pressure.

[0058] In Fig. 4b a test cycle with the vehicle stationary is shown, which almost completely corresponds to Fig. 4a, with the small difference that the pressure is determined by the DV and not by the driver. For the sake of simplicity, in this case the non-tightness of RZ4 is identified only in test 4. In this case the test time of, for example, 20 ms may be doubled, for example.

[0059] Another situation arises if, in addition to the non-tightness of the wheel circuit, which is not very small, the associated valve SV2k also contains a non-tightness, for example due to contaminant particles between the valve armature and the valve seat. If this is the case, for example, in the wheel circuit 1 and the valve SV2k1, the piston stroke distance Sk during the test T1 for keeping the pressure constant does not remain constant. The volume loss due to the non-tightness in the valve SV2k is small and can be compensated for by the pressure supply, so that the wheel circuit 1 is faulty, but the other wheel circuits are not. A warning on the display prompts the driver to visit a repair shop at an early stage.

[0060] 4c1 to 4c3 show the basic test process.

[0061] Fig. 4c1 shows the piston stroke progression Sk of the DV piston when no non-sealing exists, in which case tests T0,...,T4 are not necessary.

[0062] FIG. 4c2 shows, for example, a case in which the wheel brake cylinder RZ1 is not sealed and the associated valve SV2k1 is not switched on, and possibly a high leakage volume flow Q that is not throttled by the associated closed SV2k. SV2k,Leck 4 shows the piston stroke distance transition Sk of the DV piston when

[0063] FIG. 4c3 shows, for example, that the wheel brake cylinder RZ1 is not sealed, in which case the leakage volume flow Q SV2k1,Leck shows the piston stroke profile Sk of the DV piston when it is small due to the closure of the non-sealing valve SV2k1. If instead of the valve SV2k1 a normal inlet valve EV1 with a parallel check valve RV1 is used, in which case a piston stroke profile Sk similar to that of FIG. 4c3 is obtained if the inlet valve EV1 or the check valve RV1 is non-sealing or if both are non-sealing. If, for example, the wheel brake cylinder RZ1 is non-sealing, then the leakage volume flow Q EV1,Leck The non-sealed wheel brake cylinder RZ1 is 3 / s, but to a small value, e.g., in the worst case, EV1 and RV1 are both non-sealing and the leakage flow is, for example, Q EV1,Leck =20cm 3 / s.

[0064] Sk at time A0 during test T0 soll and Sk istIf the difference between is very small, then normal braking can be maintained. However, if the difference is not very small, then a fault in the wheel circuit, for example a non-sealing of the wheel brake cylinder seal leading to closure of the associated valve SV2k, results in a smaller deceleration of the vehicle than normal and a yaw moment for the vehicle occurs during braking. The electronic stability program ESP can in this case normally (except in the case of full braking) compensate for the deceleration of the vehicle so that it is normal. This ensures that the braking sensation for the driver remains approximately normal and reduces the driver's startle reaction. Furthermore, the electronic stability program ESP can partially compensate for the yaw moment, which also reduces the driver's startle reaction.

[0065] FIG. 4d shows by way of example a first alternative diagnostic course for checking for individual defects, which course includes a piston stroke course Sk of the pressure supply DV, which increases from time 0 to time t0 and remains constant from time t0 onwards, and a setpoint pressure course Psoll, which is derived from the piston stroke course Sk by means of a PV characteristic curve (pressure-volume characteristic curve) of the brake system. Furthermore, FIG. 4d shows the actual pressure course Pist, which is measured by the pressure sensor DG (see FIG. 3a). At time t0, a difference between the setpoint pressure Psoll and the actual pressure Pist is observed, from which an error behavior of the brake system can be inferred. For this reason, at time t0, all valves SV2k1,...,SV2k4 are closed and the actual pressure course Pist is observed in the test period from time t0 to time t1. If the actual pressure Pist falls from time t0 to time t1, as shown by the dashed line 1, the faulty behavior of the brake system is not due to non-sealing of the wheel circuits RK1, ..., RK4, but for example due to non-sealing of the piston seals of the pressure supply DV. The valves SV2k1, SV2k2, SV2k3 and SV2k4 can be opened again and, via the piston movement of the pressure supply DV, the actual pressure Pist can be increased to the target pressure Psoll, which is reached at point A. Due to the non-sealing of the piston seals of the pressure supply DV, a continuous piston movement is necessary from point A onwards in order to maintain the actual pressure Pist at the target pressure level Psoll. This has the advantage that, despite the fault, a normal braking action continues to be maintained in all wheel brake cylinders. However, if, at the target pressure level Psoll, the leakage rate of the piston seals exceeds the maximum pumping rate of the pressure supply DV, a switchover is made to a fallback level without the pressure supply DV.

[0066] If the actual pressure Pist does not decrease in the test period from t0 to t1, as shown by the solid line 2 at the actual pressure Pist from time t0 to time t1, the valve SV2k1 is opened at time t1 and the actual pressure profile Pist is observed in the test period from time t1 to time t2. If the actual pressure Pist decreases from time t1 to time t2, as shown by the dashed line 3, the faulty behavior of the brake system is due to a non-tightness of the wheel circuit 1. In this case, the valve SV2k1 is closed at time t2, while the valves SV2k2, SV2k3 and SV2k4 are opened again, and the actual pressure Pist can be increased by the piston movement of the pressure supply DV to the target pressure Psoll, which is reached at point B.

[0067] If the actual pressure Pist does not decrease in the test period from t1 to t2, as shown by the solid line 4 at the actual pressure Pist from time t1 to time t2, the valve SV2k1 is opened at time t2 and the actual pressure profile Pist is observed in the test period from time t2 to time t3. If the actual pressure Pist decreases from time t2 to time t3, as shown by the dashed line 5, the faulty behavior of the brake system is due to a non-tightness of the wheel circuit 2. In this case, the valve SV2k2 is closed at time t3, while the valves SV2k1, SV2k3 and SV2k4 are opened again, and the actual pressure Pist can be increased by the piston movement of the pressure supply DV to the target pressure Psoll, which is reached at point C.

[0068] If the actual pressure Pist does not decrease in the test period from time t2 to time t3, as shown by the solid line 6 at the actual pressure Pist from time t2 to time t3, the valve SV2k3 is opened at time t3 and the actual pressure profile Pist is observed in the test period from time t3 to time t4. If the actual pressure Pist decreases from time t3 to time t4, as shown by the dashed line 7, the faulty behavior of the brake system is due to a non-tightness of the wheel circuit 3. In this case, the valve SV2k3 is closed at time t4, while the valves SV2k1, SV2k2 and SV2k4 are opened again, and the actual pressure Pist can be increased by the piston movement of the pressure supply DV to the target pressure Psoll, which is reached at point D.

[0069] If the actual pressure Pist does not decrease in the test period from time t3 to time t4, as shown by the solid line 8 at the actual pressure Pist from time t3 to time t4, the valve SV2k4 is opened at time t4 and the actual pressure profile Pist is observed in the test period from time t4 to time t5. If the actual pressure Pist decreases from time t4 to time t5, as shown by the dashed and dotted line 9, the faulty behavior of the brake system is due to a non-tightness of the wheel circuit 4. In this case, the valve SV2k4 is closed at time t5, while the valves SV2k1, SV2k2 and SV2k3 are opened again, and the actual pressure Pist can be increased by the piston movement of the pressure supply DV to the setpoint pressure Psoll, which is reached at point E.

[0070] If the actual pressure Pist does not decrease in the test period from time t4 to time t5, as shown by the solid line 10 at the actual pressure Pist from time t4 to time t5, then the faulty behavior of the brake system is not due to non-tightness of the wheel circuits RK1,...,RK4 but is due, for example, to air bubbles in the brake fluid. At time t5, the valves SV2k1, SV2k2, SV2k3 and SV2k4 can be opened again and, via the piston movement of the pressure supply DV, the actual pressure Pist can be increased to the target pressure Psoll, which is reached at point F.

[0071] The sequence in which the valves are opened and the magnitude of the non-tightness of the piston seals of the wheel circuits RK1,...,RK4 and the pressure supply DV are selected here by way of example and are not binding. The sequence can be selected, for example, depending on driving dynamics considerations. If a wheel circuit, for example the wheel circuit 1, is non-tight, as in the case of non-tight piston seals of the pressure supply DV, the associated valve SV2k1 can remain open in order to maintain the actual pressure Pist at the desired pressure level Psoll by continuous piston movement. As already mentioned, this has the advantage that, despite an error, a normal braking action continues to be maintained in all wheel brake cylinders. It also applies in this case that, at the desired pressure level Psoll, if the leakage rate of the wheel circuit 1 exceeds the maximum pumping rate of the pressure supply DV, the desired pressure Psoll is not reached and the actual pressure Pist remains lower than the desired pressure Psoll. In this case, the valve SV2k1 is closed. If, with the valve SV2k1 open, brake fluid escapes from the brake system, which is recognized by a decrease in the level in the reservoir tank VB, the compensation of the leakage flow can be limited in time and the valve SV2k1 can be closed in time, so that sufficient brake fluid remains in the reservoir tank VB for the subsequent braking. If brake fluid escapes from the brake system, it is necessary to take into account, on the one hand, the risk that the environment may be polluted by the brake fluid, and, on the other hand, the risk that a fire may break out if the flammable brake fluid hits a hot part, such as a brake disc. Such a risk can be reduced by not opening the valve SV2k1.

[0072] FIG. 4e shows by way of example a second alternative diagnostic process for checking individual errors, which includes a piston stroke profile Sk of the pressure supply DV, which increases from time 0 to time t0 and remains constant from time t0 onwards, and a setpoint pressure profile Psoll, which is derived from the piston stroke profile Sk using a PV characteristic curve (pressure-volume characteristic curve) of the brake system. Furthermore, FIG. 4e shows the pressure profile Pist, which is measured by the pressure sensor DG (see FIG. 3a). At time t0, a difference between the setpoint pressure Psoll and the actual pressure Pist is observed, from which fault behavior of the brake system can be inferred. For this reason, at time t0, the valve BP1 (see FIG. 3a) is closed and the actual pressure profile Pist in the brake circuit BK2 (see FIG. 3a) is observed in a test period from time t1 to time t2. The valves SV2k3 and SV2k4 remain open. In the event that a non-tightness of the wheel circuits RK1 or RK2 in the brake circuit 1 exists, the valves SV2k1 and SV2k2 are closed so that brake fluid does not flow out of both wheel circuits RK1, RK2 during the test period from time t1 to time t2.

[0073] As regards the further course of the diagnosis, it is now determined whether or not the pressure Pist decreases in the period from time t0 to time t1.

[0074] 1. If the actual pressure Pist in the brake circuit 2 measured by the pressure sensor DG from time t0 to time t1 drops, as shown by the fine dashed line 1, then the faulty behavior of the brake system is due to a non-tightness of the wheel circuit RK3 or RK4 in the brake circuit BK2. Therefore, at time t1, the valve SV2k3 is closed and the actual pressure profile Pist in the brake circuit BK2 is observed in the test period from time t1 to time t2.

[0075] If the actual pressure Pist drops from time t1 to time t2, as shown by the rough dashed line 2, then the faulty behavior of the brake system is due to a non-tightness of the wheel circuit 4. In this case, at time t2, the valve SV2k4 is closed and the valves BP1 and SV2k1, SV2k2 and SV2k3 are open. Via the piston movement of the pressure supply DV, the actual pressure Pist in the wheel brake cylinders RZ1, RZ2 and RZ3 can be increased from time t2 onwards to the setpoint pressure Psoll, which is reached at point A.

[0076] If the actual pressure Pist from time t1 to time t2 does not decrease, as shown by the fine dashed line 1a at the actual pressure from time t1 to time t2, the wheel circuit 3 is not sealed and at time t2 the valve BP1 and the valves SV2k1 and SV2k2 are opened. Via the piston movement of the pressure supply DV, the actual pressure Pist in the wheel brake cylinders RZ1, RZ2 and RZ4 can be increased from time t2 onwards to the target pressure, which is reached at point B.

[0077] 2. If the actual pressure Pist in the brake circuit 2, measured by the pressure sensor DG (see FIG. 3a), does not decrease from time t0 to time t1, as shown by the solid line 3, then the faulty behavior of the brake system is not due to a non-sealing of the wheel circuit RK3 or RK4 in the brake circuit BK2. Thus, at time t1, the valve BP1 is opened and the actual pressure profile Pist in the brake circuit BK2 is observed in the test period from t1 to t2. If the actual pressure Pist from time t1 to time t2 decreases, as shown by the somewhat rough dashed line 4, then the valves SV2k1 and SV2k2 are still closed, so that the faulty behavior of the brake system is not due to a non-sealing of the wheel circuit 1 or wheel circuit 2, but for example to a non-sealing of the pressure supply DV. In this case, at time t2, the valves SV2k1 and SV2k2 are opened, in which case the valves SV2k3 and SV2k4 are also open, and via the piston movement of the pressure supply DV, the actual pressure Pist in all wheel brake cylinders RZ1, RZ2, RZ3 and RZ4 can be increased to the target pressure Psoll, which is reached at point C. Due to the non-sealing piston seals of the pressure supply DV, continuous piston movement is necessary from point C onwards in order to maintain the actual pressure Pist at the target pressure level Psoll. As already mentioned, this has the advantage that, despite an error, a normal braking action continues to be maintained in all wheel brake cylinders. However, if at the target pressure level Psoll the leakage rate of the piston seals exceeds the maximum pumping rate of the pressure supply DV, a switchover is made to a fallback level without the pressure supply DV.

[0078] If the actual pressure Pist from time t1 to time t2 does not decrease, as shown by the solid line 5 in the actual pressure Pist from time t1 to time t2, the wheel circuit 1 or the wheel circuit 2 is not sealed. Therefore, at time t2, the valve SV2k1 is opened and the actual pressure progression Pist is observed in the test period from time t1 to time t2.

[0079] If, furthermore, as shown by the somewhat rough dashed line 6, the actual pressure Pist drops from the time t2 to the time t3, then the faulty behavior of the brake system is due to a non-tightness of the wheel circuit 1. In this case, at the time t3, the valve SV2k1 is closed and the valve SV2k2 is opened, with the valves SV2k3 and SV2k4 also being open, so that from the time t3 onwards, via the piston movement of the pressure supply DV, the actual pressure Pist in the wheel brake cylinders RZ2, RZ3 and RZ4 can be increased to the setpoint pressure Psoll, which is reached at point D.

[0080] If the actual pressure Pist does not decrease from time t2 to time t3, as shown by the solid line 7, then the faulty behavior of the brake system is not due to a non-tightness of the wheel circuit 1. Therefore, at time t3 the valve SV2k2 is opened and the actual pressure profile Pist is observed in the test period from time t3 to time t4.

[0081] If, as shown by the dashed-dotted line 8, the actual pressure Pist drops from time t3 to time t4, then the faulty behavior of the brake system is due to a non-tightness of the wheel circuit 2. In this case, at time t4, the valve SV2k2 is closed, while the valves SV2k1, SV2k3 and SV2k4 are still open, and via the piston movement of the pressure supply DV, the actual pressure Pist in the wheel brake cylinders RZ1, RZ3 and RZ4 can be increased from time t4 onwards to the setpoint pressure Psoll, which is reached at point E.

[0082] If the actual pressure Pist from time t3 to time t4 does not decrease, as shown by the solid line 9 at the actual pressure Pist from time t3 to time t4, then the faulty behavior of the brake system is not due to non-tightness of the wheel circuits RK1,...,RK4 but is due, for example, to air bubbles in the brake fluid. At time t4, with the valves SV2k1, SV2k2, SV2k3, SV2k4 open, the actual pressure Pist can be increased via the piston movement of the pressure supply DV to the setpoint pressure Psoll, which is reached at point F.

[0083] The sequence in which the valves are opened and closed and the magnitude of the non-tightness of the piston seals of the wheel circuits and the pressure supply DV are selected here by way of example and are not binding. The sequence can be selected, for example, depending on driving dynamics considerations. If the wheel brake circuits, for example the wheel brake circuit 1, are non-tight, as in the case of non-tight piston seals of the pressure supply DV, the associated valve SV2k1 can remain open in order to maintain the actual pressure Pist at the desired pressure level Psoll by continuous piston movement. As already mentioned, this has the advantage that, despite an error, a normal braking action continues to be maintained in all wheel brake cylinders. It also applies in this case that, at the desired pressure level Psoll, if the leakage rate of the wheel circuit 1 exceeds the maximum pumping rate of the pressure supply DV, the desired pressure Psoll is not reached and the actual pressure Pist remains lower than the desired pressure Psoll. In this case, the valve SV2k1 is closed. If, with the valve SV2k1 open, brake fluid escapes from the brake system, which is recognized by a decrease in the level in the reservoir tank VB, the compensation of the leakage flow can be limited in time and the valve SV2k1 can be closed in time, so that sufficient brake fluid remains in the reservoir tank VB for the subsequent braking. If brake fluid escapes from the brake system, it is necessary to take into account, on the one hand, the risk that the environment may be polluted by the brake fluid, and, on the other hand, the risk that a fire may break out if the flammable brake fluid hits a hot part, such as a brake disc. Such a risk can be reduced by not opening the valve SV2k1.

[0084] FIG. 4f shows by way of example a first alternative diagnostic procedure for checking for double errors in the form of a logic tree, which includes a piston stroke profile Sk of the pressure supply DV, which increases from time 0 to time t0 and remains constant from time t0 onwards, and a setpoint pressure profile Psoll, which is derived from the piston stroke profile Sk by means of a PV characteristic curve (pressure-volume characteristic curve) of the brake system. Furthermore, FIG. 4f shows the actual pressure profile Pist, which is measured by the pressure sensor DG (see FIG. 3a). At time t0, a difference between the setpoint pressure Psoll and the actual pressure Pist is observed at point 1, from which a faulty behavior of the brake system can be inferred. For this reason, at time t0, all valves SV2k1,...,SV2k4 are closed and the actual pressure profile Pist is observed in a test period from time t0 to time t1. If the actual pressure Pist drops from time t0 to time t1, the faulty behavior of the brake system is at least due to a non-sealing other than the possibly present non-sealing in the wheel circuits RK1, ..., RK4, for example a non-sealing of the piston seal of the pressure supply DV. To additionally check the tightness of the wheel circuits RK1, ..., RK4, at point 2 the pumping speed of the pressure supply DV is adjusted so that the leakage flow due to the non-sealing of the piston seal of the pressure supply DV is compensated. This is shown by a fine dashed line in the piston stroke Sk from time t1 onwards. However, if the leakage flow is greater than the maximum pumping speed of the pressure supply DV, the diagnosis is interrupted and a switch is made to the fallback level without a pressure supply. Otherwise, at the same time, the valve SV2k1 is opened at point 2. If the measured pressure drops, point 3 is reached at time t2, which indicates a double error << pressure supply DV non-sealing and wheel circuit 1 non-sealing >>. If the measured pressure does not decrease, point 4 is reached at time t2. At point 4, valve SV2k1 is closed and valve SV2k2 is opened. If the measured pressure decreases, point 5 is reached at time t3, which indicates a double error <<pressure supply DV not sealed and wheel circuit 2 not sealed>>. If the measured pressure does not decrease, point 6 is reached at time t3.At point 6, the valve SV2k2 is closed and the valve SV2k3 is opened. If the measured pressure drops, point 7 is reached at time t4, which indicates a double error <<pressure supply DV is not sealed and wheel circuit 3 is not sealed>>. If the measured pressure does not drop, point 8 is reached at time t4. At point 8, the valve SV2k2 is closed and the valve SV2k4 is opened. If the measured pressure drops, point 9 is reached at time t5, which indicates a double error <<pressure supply DV is not sealed and wheel circuit 4 is not sealed>>. If the measured pressure does not drop, point 10 is reached at time t5, which indicates that there is no double error since only the pressure supply DV is not sealed and the wheel circuits RK1,...,RK4 are not not sealed. Due to the piston seal of the pressure supply DV being not sealed, continuous piston movement is necessary from point 10 onwards in order to maintain the actual pressure Pist at the target pressure level Psoll. If the wheel circuit at point 3 or point 5 or point 7 or point 9, for example the wheel circuit 1 at point 3, is additionally not sealed, the associated valve SV2k2 can also be kept open in order to maintain the actual pressure Pist at the desired pressure level Psoll by the continuous piston movement of the pressure supply DV. As already mentioned, this has the advantage that, despite an error, the normal braking action continues to be maintained in all wheel brake cylinders. In this case too, it applies if, at the desired pressure level Psoll, the sum of the leakage rate of the piston seal and the leakage rate of the wheel circuit 1 exceeds the maximum pumping rate of the pressure supply DV, the desired pressure Psoll is not reached and the actual pressure Pist remains lower than the desired pressure Psoll. In this case, the valve SV2k1 is closed. If, with the valve SV2k1 open, brake fluid flows out of the brake system, which is noted by a decrease in the level in the reservoir tank, the compensation of the leakage flow in the wheel brake cylinder RZ1 can be limited in time and the valve SV2k1 can be closed in time, so that sufficient brake fluid remains in the reservoir tank VB for subsequent braking.If brake fluid escapes from the brake system, it must be taken into account, on the one hand, that the brake fluid may pollute the environment, and, on the other hand, that there may be a fire risk if the flammable brake fluid comes into contact with a hot surface, such as a hot brake disc. Such a risk can be reduced by not opening the valve SV2k1.

[0085] If the actual pressure Pist does not decrease from time t0, after point 1, until time t1, then at time t1, point 11 is reached and it is checked whether the error behavior is due to a non-tightness of one or two wheel circuits RK1, RK2, RK3 or RK4. To check the tightness of the wheel circuit 1, the valve SV2k1 is opened at point 11. If the measured pressure then decreases, then there is a non-tightness in the wheel circuit 1, and at time t2, point 12 is reached. From time t2, point 12 onwards, a second error is checked, in which case at time t2, the valve SV2k1 is closed and the valve SV2k2 is opened. If the measured pressure then decreases, then point 13 is reached at time t3, which indicates a double error <<wheel circuit 1 non-tightness and wheel circuit 2 non-tightness>>. If the measured pressure then does not decrease, then point 14 is reached at time t3, which indicates that there is no non-tightness in the wheel circuit 2. At time t3, point 14, valve SV2k2 is closed and valve SV2k3 is opened. If this results in a drop in the measured pressure, then point 15 is reached at time t4, which indicates a double error <<wheel circuit 1 is not sealed and wheel circuit 3 is not sealed>>. If this does not result in a drop in the measured pressure, then point 16 is reached at time t4, which indicates that there is no non-tightness in wheel circuit 3. At point 16, valve SV2k3 is closed and valve SV2k4 is opened. If this results in a drop in the measured pressure, then point 17 is reached at time t5, which indicates a double error <<wheel circuit 1 is not sealed and wheel circuit 4 is not sealed>>. If this does not result in a drop in the measured pressure, then point 18 is reached at time t5, in which case only wheel circuit 1 is not sealed and there is no double error.

[0086] If the actual pressure Pist does not decrease from time t1, after point 11, until time t2, then at time t2, point 19 is reached and it is checked whether the faulty behavior of the brake system is not due to a non-sealing of the wheel circuit 1, but rather due to a non-sealing of one or two wheel circuits RK2, RK3 or RK4. To check the tightness of the wheel circuit 2, the valve SV2k1 is closed at point 19 and the valve SV2k2 is opened. If the measured pressure then decreases, then there is a non-sealing in the wheel circuit 2, and at time t3, point 20 is reached. In this case, at time t3, after point 20, a second fault is checked, in this case the valve SV2k2 is closed at time t3 and the valve SV2k3 is opened. If the measured pressure then decreases, then point 21 is reached at time t4, which indicates a double fault << wheel circuit 2 non-sealing and wheel circuit 3 non-sealing >>. If the measured pressure then does not decrease, then point 22 is reached at time t4. This suggests that there is no non-tightness in wheel circuit 3. At time t4, point 22, valve SV2k3 is closed and valve SV2k4 is opened. If this causes the measured pressure to drop, then point 23 is reached at time t5, which suggests a double error <<wheel circuit 2 non-tight and wheel circuit 4 non-tight>>. If this does not cause the measured pressure to drop, then point 24 is reached at time t5, which suggests that there is no non-tightness in wheel circuit 4, and that only wheel circuit 2 is non-tight, and there is no double error.

[0087] If the actual pressure Pist does not decrease from time t2, after point 19, until time t3, then at time t3, point 25 is reached and it is checked whether the faulty behavior of the brake system is not due to a non-sealing of the wheel circuit RK1 or RK2, but rather due to a non-sealing of one or two wheel circuits RK3 or RK4. To check the tightness of the wheel circuit 3, the valve SV2k2 is closed at point 25 and the valve SV2k3 is opened. If the measured pressure then decreases, then there is a non-sealing in the wheel circuit 3 and point 26 is reached at time t4. In this case, after time t4, point 26, a second fault is checked, in which case at time t4 the valve SV2k3 is closed and the valve SV2k4 is opened. If the measured pressure then decreases, then point 27 is reached at time t4, which indicates a double fault << non-sealing of the wheel circuit 3 and non-sealing of the wheel circuit 4 >>. If the measured pressure then does not decrease, then point 28 is reached at time t5. This suggests that there is no non-hermeticity in wheel circuit 4 and that only wheel circuit 3 is non-hermetic and there is no double error.

[0088] If the actual pressure Pist does not decrease from time t3 after point 25 to time t4, then at time t4, point 29 is reached and it is checked whether the faulty behavior of the brake system is not due to a non-sealing of the wheel circuits RK1, RK2 or RK3, but rather due to a non-sealing of the wheel circuit 4. To check the tightness of the wheel circuit 4, the valve SV2k3 is closed at point 29 and the valve SV2k4 is opened. If the measured pressure then decreases, then there is a non-sealing in the wheel circuit 4 and point 30 is reached at time t5. However, there is no double fault. If the measured pressure then does not decrease, then point 31 is reached at time t5. This suggests that there is no non-sealing in the wheel circuit 4. If point 31 is reached, then there is no non-sealing in the wheel circuits RK1, ..., RK4 and the faulty behavior of the brake system must have another cause, for example air bubbles in the brake fluid.

[0089] The order in which the valves are opened and the degree of non-sealing in the wheel circuits RK1, ···, RK4 and the piston seal of the pressure supply DV are selected here by way of example and are not restrictive. The order can be selected, for example, according to driving dynamics aspects such as braking distance and driving stability. As described above, in the case of a double error <<DV is non-sealed and wheel circuit 1 is non-sealed>>, due to the continuous piston movement of the pressure supply DV, the associated valve SV2k1 can be left open in order to maintain the actual pressure Pist at the target pressure level Psoll. Thereby, also in the case of a double error, for example <<wheel brake cylinder RZ1 is non-sealed and wheel brake cylinder RZ2 is non-sealed>>, both valves SV2k1 and SV2k2 can be left open due to the continuous piston movement of the pressure supply DV in order to maintain the actual pressure Pist at the target pressure level Psoll. As already mentioned, this has the advantage that the normal braking action continues to be maintained in all wheel brake cylinders despite the error. Also in this case, if the sum of the leakage rates of both wheel circuits RK1 and RK2 at the target pressure level exceeds the maximum pumping speed of the pressure supply DV, the target pressure Psoll is not reached and the actual pressure Pist remains lower than the target pressure Psoll. If the individual leakage rates of both wheel circuits, for example RK1 and RK2, already exceed the maximum pumping output of the pressure supply DV, both valves SV2k1 and SV2k2 are closed. If only the leakage rate of one wheel circuit, for example RK1, exceeds the maximum pumping output of the pressure supply DV, only valve SV2k1 is closed. If only the sum of the leakage rates of both wheel circuits, for example RK1 and RK2, exceeds the maximum pumping output of the pressure supply DV, it is determined from the perspective of driving dynamics, such as braking distance and driving stability, which of the valves SV2k1 or SV2k2 is to be closed.It also applies in this case, i.e. if brake fluid escapes from the brake system in this state, despite the non-sealing of the wheel circuit 1, for example if the valve SV2k1 remains open, this is recognized by a decrease in the level in the reservoir tank VB, so that the compensation of the leakage flow can be limited in time and the valve SV2k1 can be closed in time, so that sufficient brake fluid remains in the reservoir tank VB for a subsequent braking. In the case of brake fluid escaping from the brake system, it is necessary to take into account, on the one hand, the risk that the environment may be polluted by the brake fluid, and, on the other hand, the risk that a fire may break out if the flammable brake fluid hits a hot part, such as a brake disc. Such a risk can be reduced by not opening the valve SV2k1.

[0090] In a complete brake system, a certain pressure, i.e. a target pressure in the master brake cylinder SHZ / HZ (see FIG. 1), is assigned to each brake pedal travel, which defines the pedal characteristic. The pressure in the master brake cylinder is measured either directly, for example by pressure sensor DG-SHZ, as the actual pressure, or indirectly, for example by a force-distance sensor (not shown), which can measure the pedal force. The brake pedal travel is measured via a pedal travel sensor, not shown. A target pressure in the master brake cylinder can thus be defined for each brake pedal travel. If the master brake cylinder SHZ / HZ or the valve 9 (see FIG. 1) is non-sealing, the volume in the master brake cylinder changes, which causes the actual pressure in the master brake cylinder SHZ / HZ to deviate from the target pressure value.

[0091] Errors are detected by permanently comparing the actual pressure in the master brake cylinders SHZ / HZ with the target pressure. If the difference between the actual pressure and the target pressure exceeds a selectable boundary value, then in the fallback level, the valves SV2k1,...,SV2k4 are closed and the valve 9 is opened. The volume fluctuations in the master brake cylinders SHZ / HZ are compensated via the pressure supply DV in such a way that in the case of a volume loss from the master brake cylinder, a volume is supplied to the master brake cylinder from the pressure supply, or in the case of an increase in the volume in the master brake cylinders SHZ / HZ, a volume from the pressure supply is drawn from the master brake cylinder until the actual pressure and the target pressure are the same. Then the valve 9 is closed and the valves SV2k1,...,SV2k4 are opened. Now again the pressure supply DV is used for brake pressure control in the wheel brake cylinders RZ1,...,RZ4 until the difference between the actual pressure and the target pressure again exceeds a selectable boundary value, after which the fallback level process is repeated. Brake pedal characteristics and brake pedal feel are thereby maintained approximately as normal, although slight vibration of the brake pedal may occur.

[0092] The table below lists reference values ​​for diagnosis.

[0093] [Table 1] [Explanation of symbols]

[0094] 1 Sensor element 2 Targets in Floats 3 Backflow pipe to VB 4 DV dedicated valve circuit 5 Single circuit pressure supply 6 Mover 6 / 6a 7 / 7a Valve Plunger 8 Valve seat 9. Isolation valve RZ1-RZ4 Wheel brake cylinder BK1 / BK2 brake circuit RK1 Wheel circuit 1 RK2 Wheel Circuit 2 RK3 Wheel Circuit 3 RK4 Wheel Circuit 4 HCU Complete hydraulic unit including DV and valves VB Reservoir Tank HL1-HL4 Hydraulic lines to RZ outside HCU HL5 SHZ to BV hydraulic line KTV Circuit Isolation Valve DV Pressure Supply DG Pressure Transducer EM1 / 2 Electromagnet circuit 1 / 2 ElV Electric valve control device elEM Electric motor control for electromechanical brakes 9. Permanent Magnets 10 Pole Plate 11 Electromagnetic coil flux guide 12 Plastic Body 13 Return spring SV2k Equipped with a force application device, this is a non-energized open type magnet valve without a check valve.

Claims

1. A braking system comprising: Separate wheel circuits (RK １－４ At least two wheel brake cylinders (RZ １－４ )and, At least the wheel brake cylinder (RZ １－４ ) pressure increase (p ａｕｆ At least one pressure supply (DV) serving for At least one reservoir tank (VB); at least one electronic open-loop and closed-loop control unit (ECU); Switching valve (SV2K １－４ ) and each wheel brake cylinder (RZ １－４ ) are connected to each of the wheel brake cylinders (RZ) via one hydraulic connecting line. １－４ ) and the switching valve (SV2K １－４ ) with at least one other hydraulic main line that can be connected to or is connected to the pressure supply (DV), １－４ ) connected to the switching valve (SV2K １－４ )and, Equipped with the hydraulic pressure connecting pipe, and the wheel brake cylinder (RZ １－４ ) each refers to one wheel circuit (RK １－４ ) in a braking system that is a component of Each of the wheel circuits (RK １－４ ) is diagnosed for each non-sealing condition, and depending on the diagnosis result, the electronic open-loop and closed-loop control unit (ECU) controls the wheel circuits (RK1-RK4) to the associated switching valves (SV2k １－４ ) determines whether to shut off or further activate to generate braking action.

2. Wheel circuit (RK １－４ ) non-containment or leakage flow (Q ｌｅｃｋ ) was measured by the following methods a) to e), namely: a) each of the wheel circuits (RK １－４ ) at the target pressure (p ｓｏｌｌ - detecting the required quantity of hydraulic fluid that must be pumped by said pressure supply (DV) in addition to the predefined fluid quantity in order to generate b) the absolute pressure reduction (dp ａｂ ) and / or pressure drop gradient (p ａｂ / dt), c) the target pressure (p ｓｏｌｌ A predetermined amount of fluid (q) is supplied to the wheel circuit (RK １－４ ) and then pumped to the actual pressure (p ｉｓｔ ) to calculate the number of the wheel circuits (RK １－４ The target pressure (p ｓｏｌｌ ) pressure deviation (dp = p ｓｏｌｌ -p ｉｓｔ ) detection, d) When the pressure is increased by the pressure supply unit (DV) or when the pressure supply unit (DV) is shut off, the switching valve (SV2K １－４ ) and the pressure supply unit (DV) in the hydraulic line (p ｉｓｔ ) through the time measurement of the wheel circuit (RK １－４ ) diagnosis of non-hermeticity, e) Target pressure (p ｓｏｌｌ each wheel circuit (RK) via the pressure supply (DV) to generate １－４ ) measuring the volume (Q) of the pressure supply (DV), which volume (Q) is determined by the pressure supply (DV), in particular via a current measurement of the drive motor (M) of the pressure supply (DV) and / or via the piston stroke (ds) of the piston of the pressure supply (DV), The brake system of claim 1 , wherein the brake system is determined based on one or more of the following:

3. Wheel circuit (RK １－４ ) the upper limit of non-hermeticity (Q ｈｉｇｈ ) or upper limit range (dQ ｈｉｇｈ ) exceed the respective associated switching valves (SV2K １－４ ) is permanently closed, and thus this wheel brake cylinder (RZ １－４ ) is no longer applied, and the upper limit value (Q ｈｉｇｈ ) and less than the lower limit (Q ｌｏｗ ) and each wheel brake cylinder (RZ １－４ ) to be set at ｓｏｌｌ 3. The brake system according to claim 1, wherein a time-limited and / or continuous additional pressure supply is provided to obtain the required pressure.

4. The upper limit (Q ｈｉｇｈ 4. A braking system according to claim 3, wherein the maximum pumping power of the pressure supply (DV) for boosting pressure is determined.

5. Leakage current (Q ｌｅｃｋ ) is 50 to 90% of the maximum pumping power of the pressure supply (DV), the leakage flow (Q ｌｅｃｋ 5. The brake system according to claim 4, wherein the pressure supply (DV) compensates for the pressure difference (P) of the brake fluid.

6. To optimize braking action and driving stability, the electronic open-loop and closed-loop control unit (ECU) controls the non-sealed wheel circuits (RK １－４ ) to the respective switching valves (SV2K １－４ ) and which non-sealed wheel circuit (RK １－４ ) to the respective switching valves (SV2K １－４ 4. The brake system of claim 3, wherein the brake system determines whether to disconnect by a sustained closure of said brake control valve.

7. The outlet valve (AV) associated with the wheel brake cylinder １－４ ) is the wheel circuit (RK １－４ 3. The brake system according to claim 1, wherein the brake is a component of the brake system.

8. 3. The brake system according to claim 1, wherein the brake system comprises a brake pedal, in particular in the form of a brake pedal that acts mechanically on a master brake cylinder (SHZ, THZ) or in the form of an electronic brake pedal for a brake-by-wire brake system.

9. 3. The brake system of claim 1, wherein the diagnostics detect single errors, double errors, and leakage rates (dQ; dQ / dt) in the brake system.

10. The switching valve (SV2K １－４ 3. A brake system according to claim 1, wherein no non-return valve (RV) is connected in parallel to said first and second brakes.

11. At least one wheel circuit (RK １－４ ) or the sum of all the leakage flows (ΣQ ｌｅｃｋ，１－４ ) at a given leakage current (Q ｌｅｃｋ，ｍｉｎ ), the brake system issues a warning message, in particular an optical and / or acoustic warning, in particular by means of a display, to the at least one wheel circuit (RK １－４ 3. The brake system of claim 1, wherein the brake system indicates a failure of the brake pedal.

12. Wheel circuit (RK １－４ When a diagnosis of a non-sealing condition occurs in each wheel circuit (RK １－４ 3. The brake system according to claim 1, wherein the pressure-volume characteristic curve (DVK) of the brake fluid is taken into account or used.

13. The pressure supply unit (DV) and the switching valve (SV2K １－４ 3. A brake system according to claim 1, wherein a maximum of two further valves (BP1, MVDV1, MVDV2), in particular switching valves, are arranged in the hydraulic connection line between said valves (BP1, MVDV1, MVDV2).

14. The pressure supply unit (DV) and the switching valve (SV2K) of at least one of the wheel circuits (RK1, RK2) １－４ ), a maximum of two further valves (MVDV1, MVDV2, BP1), in particular switching valves, are arranged in the hydraulic connection line between the pressure supply (DV) and at least one further switching valve (SV2K) of the other wheel circuit (RK3, RK4). １－４ 3. A brake system according to claim 1, wherein only one further valve (MVDV1, MVDV2), in particular a switching valve, is arranged in the hydraulic connection line between said first and second valves (MVDV1, MVDV2).

15. All wheel circuits (RK １ , R.K. ２ , R.K. ３ , R.K. ４ ) belong to one brake circuit (BK) and are connected to one common hydraulic main line (HL) a) connected to only one working chamber (A) of the plunger system of said pressure supply (DV) or separable from said working chamber (A) via at least one valve (MVDV1), or b) connected or connectable to both working chambers (A1, A2) of the double-acting piston-cylinder system of the pressure supply (DV), in which case at least one wheel circuit (RK) is connected in both stroke directions of the double-acting piston. １－４ ) pressure reduction and / or pressure increase can be performed in 3. The brake system according to claim 1 or 2.

16. One brake circuit (BK1, BK2) has two wheel circuits (RK １ , R.K. ２ ;RK ３ , R.K. ４ 3. A brake system according to claim 1, further comprising hydraulic brake circuit lines (HL1, HL2) for each of the brake circuits.

17. 17. The brake system according to claim 16, wherein the brake circuits (BK1, BK2) are hydraulically connectable to one another or hydraulically separable from one another via a circuit isolation valve (BP1).

18. 17. A brake system according to claim 16, wherein each brake circuit (BK1, BK2) is connected or connectable to each working chamber (A1, A2) of the double-acting piston-cylinder system of the pressure supply (DV) via a separate hydraulic line, in which case, optionally, an isolation valve can be arranged in each hydraulic line.

19. 8. A brake system according to claim 7, wherein an outlet valve is assigned to at least one wheel brake cylinder (RZ1-RZ4), in particular to each wheel brake cylinder per brake circuit (BK1, BK2), or wherein only one outlet valve (AV) is provided for the entire brake system.

20. At least one wheel brake cylinder (RZ １－４ 16. Brake system according to claim 15, characterized in that each of the wheel brake cylinders, in particular two or all of the wheel brake cylinders, is assigned an outlet valve (AV).

21. The wheel circuit (RK １－４ In addition to the above diagnosis of a) The switching valve (SV2K １－４ and / or performing a diagnostic of the valves (MVDV1, MVDV2, BP1, BP2) arranged between the pressure supply and the valves (MVDV1, MVDV2, BP1, BP2) with respect to function and / or sealing; and / or b) the switching valve (SV2K １－４ ) and / or to diagnose the function and / or sealing of the c) performing a diagnosis of the function and / or seal of the pressure supply (DV); 3. The brake system according to claim 1 or 2.

22. One or more wheel circuits (RK １－４ To diagnose a leak in the wheel circuit (RK), first check all the １－４ All switching valves (SV2K) １－４ ) in the wheel circuit, and the target pressure (p ｓｏｌｌ ) is set using the pressure supply (DV), and the actual pressure (p ｉｓｔ ) to the target pressure (p ｓｏｌｌ ) and if the deviation exceeds a predetermined value, the individual wheel circuits (RK １－４ ) further diagnosis, a) One wheel circuit (RK ｉ ) a non-tightness is determined, which is adapted in particular to the deviation between the previously determined actual pressure (pist) and the target pressure (psoll), or b) Sequentially until all wheel circuits (RK1-4) have been tested for leaks in turn; 3. The brake system of claim 2.

23. To check the tightness of only one wheel circuit (RKi), first all the switching valves (SV2k1-SV2k4) of all wheel circuits of one or all brake circuits (BK1, BK2) are closed, and then the wheel circuit (RKi) to be checked is closed. ｉ The switching valve (SV2K) ｉ ) is released, and then a) each wheel circuit (RK ｉ ) or brake cylinder of each wheel circuit (RZ ｉ ) target pressure (p ｓｏｌｌ ) is set by the pressure supply unit, and the actual pressure (p ｉｓｔ ) is determined using a pressure transducer (DG) and / or based on the measured drive current of the drive motor (M) of the pressure supply unit (DV), and the determined target pressure (p ｓｏｌｌ ) and the actual pressure (p ｉｓｔ ) determining or estimating the degree of non-hermeticity based on a deviation from the b) determining the actual pressure in each wheel or brake circuit without using the pressure supply (DV) to change the pressure, in particular by using a pressure transducer (DG), and determining or estimating the degree of the non-tightness based on the determined pressure reduction; 23. The braking system of claim 22.

24. The pressure supply (DV) comprises an electric motor drive (M), which a) a piston and cylinder system, aa) a single-stroke piston and one working chamber, or bb) Double-stroke piston and two working chambers or driving a piston-cylinder system comprising b) driving a rotary pump; 3. The brake system according to claim 1 or 2.

25. 25. A braking system according to claim 24, wherein, when a rotary or piston pump is used for the pressure supply (DV), a solenoid valve (MVDV) or a non-return valve (RV) is provided to separate the pressure outlet of the pump from one brake circuit (BK1, BK2).

26. The wheel brake cylinder (RZ ｉ 26. A brake system according to claim 25, wherein the pressure reduction (Pab) is effected via outlet valves (AV) assigned to said first and second brake valves (AV), and in particular one, two or more outlet valves (AV) are opened in order to obtain a target gradient of the pressure reduction (Pab).

27. The diagnostics for checking for seal leaks in the brake system or in the individual wheel circuits (RK1-4) are carried out at the following times or driving situations: a) During braking, b) When the vehicle is stopped or at maximum speed (v ｍａｘ ) at speeds below 30 km / h, in particular at speeds below 30 km / h, c) a predetermined time interval; d) For each vehicle start, 3. A brake system according to claim 1 or 2, wherein the brake system is or can be performed in one of the following ways:

28. a) checking for faults during the diagnosis of each wheel circuit of the brake system; and / or b) During the diagnosis, the actual piston position (Sk ｉｓｔ ) and the actual pressure of the brake system (p ｉｓｔ ) and / or using stored pressure-volume characteristic curves (DKV) of the brake system and / or the wheel circuits during the diagnosis; and / or c) determining a target piston position (Sk) of the pressure supply (DV) from the pressure in the brake system using the pressure-volume characteristic curve (DKV) ｓｏｌｌ ) and / or d) deriving an error function of the braking system from the difference between the actual piston position and the target piston position; and / or e) in the event of a fault due to a non-tight seal, the leakage volume flow is compensated for by a corresponding additional pressure from the pressure supply (DV), 3. The brake system according to claim 1 or 2.

29. 9. A brake system according to claim 8, wherein one or both hydraulic main lines (HL1, HL2) of the brake circuit (BK) or of the two brake circuits (BK1, BK2) are hydraulically connected to one or each one working chamber of a master brake cylinder, in particular in the form of a single master brake cylinder (SHZ) or a tandem master brake cylinder (THZ), and this connection can be interrupted by one or two, in particular "normally open" switching valves (9).

30. 3. A brake system according to claim 1, wherein at least one brake circuit (BK, BK1) or a plurality of brake circuits (BK1, BK2) can be isolated from the pressure supply (DV) by one or two, in particular "normally closed" switching valves (MVe, BP1, BP2), in particular in the event of a fault.

31. Electromagnetic switching valve (SV2K １－４ 3. A brake system according to claim 1, wherein the drive of the pressure supply (DV) and / or the drive of the pressure supply (DV) has at least two redundant windings and / or controls.

32. 9. A brake system according to claim 8, wherein the wheel circuits (RK1-RK4) are divided into two brake circuits (BK1, BK2), the two brake circuits (BK1, BK2) being connected by hydraulic lines which can be disconnected by a circuit isolation valve (BP1), one brake circuit (BK2) being rigidly connected or coupled to the pressure supply without an intervening magnetic valve, and the other brake circuit (BK1) being connected to the master brake cylinders (SHZ, THZ) via a hydraulic connection (HL5), the hydraulic connection (HL5) being disconnectable by a "normally open" switching valve (9).

33. The brake system a) Purely hydraulically acting wheel brake cylinders (RZ1-4) 3. A braking system according to claim 1, further comprising purely hydraulically acting wheel brake cylinders (Rz1, RZ2) and wheel brakes (EMB1, EMB2) operated by electric motors.

34. 3. A braking system according to claim 1 or 2, wherein the braking system comprises or mimics an anti-lock braking system (ABS) and / or an electronic stability program (ESP).

35. At least one wheel circuit (RK １－４ 3. A brake system according to claim 1, wherein a yaw moment control of an electronic stability control system (ESP) is used or intervenes during pressure control in the event of a yaw moment occurring during a failure of the brake control unit.

36. 30. A brake system according to claim 29, wherein the detection of volume changes in the master brake cylinder (SHZ / HZ), in particular due to non-sealing of the master brake cylinder (SHZ / HZ) or non-sealing of the valve (9), is carried out by permanently comparing a target pressure in the master brake cylinder (SHZ / HZ), derived from the measured pedal travel, with an actual pressure in the master brake cylinder (SHZ / HZ), and / or, if a selectable limit value is exceeded, the volume changes are compensated for by the pressure supply (DV) in such a way as to maintain a normal brake pedal characteristic, and pressure control in the wheel brake cylinders is stopped during the compensation.

37. The wheel circuit (RK １－４ The switching valve (SV2K) assigned to １－４ 3. A braking system according to claim 1, wherein no valve is provided between the pressure supply (DV) and the pressure supply (DV).

38. A switching valve (SV2K) for hydraulically functioning brake systems, in particular as claimed in claim 1 or 2. １－４ ) and the switching valve (SV2K １－４ ) is a switching valve (SV2K) which is a solenoid valve equipped with an electromagnetic drive device (EM1) that can adjust a valve member or a valve plunger (7) between an open position and a closed position. １－４ ) in The switching valve (SV2K １－４ The switching valve (SV2K) is characterized in that it has a force applying device (EM2, 9) that applies a force (FM2) to the valve member or valve plunger (7) by means of a specific magnetic field. １－４ ).

39. The switching valve (SV2K １－４ 39. The directional control valve (SV2K) according to claim 38, further comprising a return spring (RF) for applying a force to the valve member or valve plunger (7) to prevent the valve from retracting and closing. １－４ ).

40. The switching valve (SV2K) according to claim 38, wherein the valve (SV2k) is a non-energized open valve or a non-energized close valve, in which the non-energized valve means that the electromagnetic drive device (EM1) is not energized. １－４ ).

41. 39. The switching valve (SV2K) according to claim 38, wherein the force (FM2) of the force application device (EM2, 9) can be or is generated by an energizable electromagnet and / or a permanent magnet. １－４ ).

42. 41. The switching valve (SV2K) according to claim 40, wherein the force (FM2) of the force adding device (EM2, 9) acts in a direction opposite to the force (FM1) of the electromagnetic driving device (EM1). １－４ ).

43. 43. A switching valve (SV2K) according to claim 42, wherein the force (FM2) of the force applying device (EM2, 9) is equivalent to the force (FRF) of a possible return spring (RF), and if the magnetic circuit is dimensioned accordingly, a return spring (RF) is not required. １－４ ).

44. The state of the brake system is determined by the switching valve (SV2K １－４ 39. The switching valve (SV2K) according to claim 38, wherein the force (FM2) is generated by the force applying device (EM1) by energizing the coil only when an undesired retraction closure of the valve (SV2K) is expected, so that the force applying device (EM1) only consumes energy in such a state. １－４ ).

45. 39. The switching valve (SV2K) according to claim 38, wherein the electromagnetic holding force is diagnosed by a diagnostic function via the current strength and the movement of the armature. １－４ ).

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