Brake system for vehicles with at least two axles

Abstract

The present invention relates to a front axle unit (10) having at least one first motor-driven brake pressure generating device (12), a first front wheel brake cylinder (14a) that can be mounted on a first front wheel of the vehicle, and a second front wheel brake cylinder (14b) that can be mounted on a second front wheel of the vehicle, and a front axle unit (10) having at least one second motor-driven brake pressure generating device (20) that is hydraulically separated from the front axle unit (10), a first rear wheel brake cylinder (22a) that can be mounted on a first rear wheel of the vehicle, and a second rear wheel brake cylinder (22b) that can be mounted on a second rear wheel of the vehicle. and a rear axle unit (18) having a rear wheel brake cylinder (22b), wherein at least one second motor-driven brake pressure generator (20) is hydraulically coupled to the first rear wheel brake cylinder (22a) via a first rear axle hydraulic path and to the second rear wheel brake cylinder (22b) via a second rear axle hydraulic path, and a first isolation valve (26a) is arranged in the first rear axle hydraulic path and / or a second isolation valve (26b) is arranged in the second rear axle hydraulic path.

Description

[Technical field]

[0001] The present invention relates to a braking system for a vehicle with at least two axles.The present invention also relates to a method for operating a braking system for a vehicle with at least two axles. [Background technology]

[0002] From the prior art, for example from US Pat. No. 5,399,433, braking systems for vehicles with at least two axles are known, each of which has four wheel brake cylinders, each of which is hydraulically connected to a master brake cylinder of the respective brake system, the brake pedal of which is provided upstream of the master brake cylinder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] DE 102016208529 Summary of the Invention

[0004] The invention provides a braking system for a vehicle with at least two axles having the features of claim 1 and a method for operating a braking system for a vehicle with at least two axles having the features of claim 10.

[0005] The present invention provides a brake system for vehicles with at least two axles, which has a relatively compact structure and can be produced with relatively low manufacturing costs. As will become clear on the basis of the following description, in the brake system according to the invention, conventional hydraulic lines between at least two axles of the vehicle each equipped with the brake system are omitted. This saves a relatively large amount of construction space on the respective vehicle. Furthermore, this also makes it easier to install the brake system according to the invention on the respective vehicle.

[0006] Furthermore, as will become clear on the basis of the following description, the brake pressure of the brake system according to the invention in each of its front and rear wheel brake cylinders can be adjusted fully automatically / autonomously, i.e. without the driver having to provide a driver braking force, which can also be called fully automatic / autonomous pressure adjustment, and which is possible for all wheel brake cylinders of the brake system according to the invention.

[0007] Furthermore, the brake pressure of at least each of the rear wheel brake cylinders of the brake system according to the invention can be adjusted individually. This can also be translated as fully automatic / autonomous wheel-individual pressure regulation of at least the rear wheel brake cylinders of the brake system according to the invention. However, it should be noted that the switching of the valves of the brake system according to the invention for the fully automatic / autonomous wheel-individual pressure regulation of at least the rear wheel brake cylinders of the brake system according to the invention is usually only required for modulation, e.g. ESP control or ABS control. Therefore, valve switching noise occurs relatively rarely during operation of the brake system according to the invention. The brake system according to the invention is therefore also said to have good NVH characteristics (noise, vibration and harshness characteristics).

[0008] In an advantageous embodiment of the brake system, the rear axle control device of the rear axle unit is designed and / or programmed to control the at least one second motor-driven brake pressure generator, the first isolation valve and / or the second isolation valve, taking into account at least one brake setting signal outputted to the rear axle control device by at least one brake operating element sensor of the vehicle, by the automatic speed control device of the vehicle, by the front axle control device of the front axle unit and / or by other stabilization devices of the brake system, so that, at least temporarily, by operation of the at least one second motor-driven brake pressure generator, brake fluid can be transferred to the second rear wheel brake cylinder via the second rear axle hydraulic path while the at least first isolation valve is controlled in its closed state, and / or, by operation of the at least one second motor-driven brake pressure generator, brake fluid can be transferred to the first rear wheel brake cylinder via the first rear axle hydraulic path while the at least second valve is controlled in its closed state. Thus, wheel-independent pressure regulation in the two rear wheel brake cylinders of the brake system embodiments described herein can be performed by rear axle control-controlled activation of the at least one second motor-driven brake pressure generator. Alternatively, the rear axle unit can be operated while the first and second isolation valves are open.

[0009] In particular, the rear axle unit is formed hydraulically separated from the front axle unit such that the rear axle unit and the front axle unit are connected to one another at most via at least one signal line and / or bus line coupled to the rear axle control unit and the front axle control unit, whereby in the embodiments of the brake system described herein, conventional hydraulic lines between the front and rear axles of a vehicle equipped with the brake system described herein are omitted.

[0010] For example, the first front axle hydraulic path and the second front axle hydraulic path may extend through a common front axle brake circuit of the front axle unit, and / or the first rear axle hydraulic path and the second rear axle hydraulic path may extend through a common rear axle brake circuit of the rear axle unit. However, alternatively, the first front axle hydraulic path can also extend through a first front axle brake circuit of the front axle unit, while the second front axle hydraulic path extends through a second front axle brake circuit of the front axle unit, and / or the first rear axle hydraulic path can extend through a first rear axle brake circuit of the rear axle unit, while the second rear axle hydraulic path extends through a second rear axle brake circuit of the rear axle unit. Thus, a large design freedom is possible when forming the brake circuits of the brake system.

[0011] Preferably, the front axle unit further comprises at least one first front axle isolation valve arranged in the first front axle hydraulic path and / or a second front axle isolation valve arranged in the second front axle hydraulic path, in which case wheel-individual pressure regulation is also possible in both front axle wheel brake cylinders.

[0012] In an advantageous development, the front axle unit can further comprise a master brake cylinder, to which a brake operating element of the vehicle can be coupled or is coupled, such that at least one piston of the master brake cylinder, which defines at least one chamber of the master brake cylinder, is displaceable by operation of the brake operating element by the driver of the vehicle, and at least one chamber of the master brake cylinder is hydraulically connected to at least one first motor-driven brake pressure generator, the first front axle hydraulic path and / or the second front axle hydraulic path via at least one valve-free or valve-equipped connecting line. The driver can thus directly act on the front wheel brake cylinders with his driver braking force and can thus still trigger (additional) brake pressure generation in the front wheel brake cylinders. The embodiments of the brake system described herein therefore also have a mechanical fallback level.

[0013] Preferably, the at least one first motor-driven brake pressure generating device is a plunger device, and at least one chamber of the master brake cylinder is hydraulically connected to at least one plunger chamber of the plunger device via at least one connecting line, in which a respective junction of at least one connecting line is formed in such a way that when at least one displaceable plunger piston of the plunger device is in its respective starting position, brake fluid can be transferred from the master brake cylinder through at least one junction of the at least one connecting line to the plunger device, whereas when the at least one displaceable plunger piston is displaced from its respective starting position, transfer of brake fluid from the master brake cylinder through at least one junction of the at least one connecting line to the plunger device is prevented by at least one sealing element attached to the at least one plunger piston and / or the respective plunger chamber. Thus, during operation of the plunger device, the master brake cylinder is automatically "disconnected" from the plunger device. Nevertheless, the embodiments of the braking system described herein automatically transition to their fallback level in the event of a plunger device failure, where the driver can act on the front wheel brake cylinders via the master brake cylinder and the plunger device with his or her driver braking force, and therefore no valve switching is required to transition the embodiments of the braking system described herein to the mechanical fallback level.

[0014] Alternatively, at least one master brake cylinder disconnect valve can be arranged in at least one connecting line, so that transition to the mechanical fallback level of the embodiments of the brake system described herein is also possible by switching on the at least one master brake cylinder disconnect valve.

[0015] The above-mentioned advantages are also ensured when carrying out a corresponding method for operating a brake system of a vehicle with at least two axles. It is explicitly mentioned that the method for operating a brake system of a vehicle with at least two axles can be developed according to the above-mentioned embodiment of the brake system. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram of a first embodiment of a brake system. [Diagram 2] FIG. 4 is a schematic diagram of a second embodiment of a brake system. [Diagram 3] FIG. 4 is a schematic partial view of another embodiment of a brake system. [Figure 4] FIG. 4 is a schematic partial view of another embodiment of a brake system. [Diagram 5] FIG. 4 is a schematic partial view of another embodiment of a brake system. [Figure 6] FIG. 4 is a schematic partial view of another embodiment of a brake system. [Figure 7] FIG. 4 is a schematic partial view of another embodiment of a brake system. [Figure 8] FIG. 4 is a schematic partial view of another embodiment of a brake system. [Figure 9] 1 is a flow chart illustrating an embodiment of a method for operating a braking system of a vehicle with at least two axles. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Other features and advantages of the present invention will be described below with reference to the accompanying drawings.

[0018] FIG. 1 shows a schematic diagram of a first embodiment of a brake system.

[0019] The brake system shown diagrammatically in FIG. 1 can be / is installed in a vehicle / automobile with at least two axles, and the applicability of the brake system is not limited to two-axle vehicles / automobiles of a particular vehicle / automobile type.

[0020] The brake system has a front axle unit 10 including at least one first motor-driven brake pressure generator 12, a first front wheel brake cylinder 14a that can be mounted / assembled on a first front wheel of the vehicle, and a second front wheel brake cylinder 14b that can be mounted / assembled on a second front wheel of the vehicle. The at least one first motor-driven brake pressure generator 12 is hydraulically coupled to the first front wheel brake cylinder 14a via a first front axle hydraulic path and to the second front wheel brake cylinder 14b via a second front axle hydraulic path. Thus, in the brake system of FIG. 1, the front wheel brake pressure of the first front axle wheel brake cylinder 14a and the same front wheel brake pressure of the second front axle wheel brake cylinder 14b can be regulated fully automatically / fully autonomously by the at least one first motor-driven brake pressure generator 12, i.e. without providing a driver brake force by the driver of the respective vehicle. In the embodiment of Fig. 1, the first front wheel hydraulic path and the second front wheel hydraulic path extend through a common front wheel brake circuit 16 of the front wheel unit 10, merely by way of example. The form of the at least one first motor-driven brake pressure generator 12 shown in Fig. 1 as at least one pump 12 should also be interpreted as merely by way of example. Instead of or as a complement to the at least one pump 12, a plunger device having at least one displaceable plunger piston can also be used as the at least one first motor-driven brake pressure generator 12 of the front axle unit 10.

[0021] The brake system also comprises a rear axle unit 18 formed hydraulically separated from the front axle unit 10. The rear axle unit 18 comprises at least one second motor-driven brake pressure generator 20, a first rear wheel brake cylinder 22a which can be mounted / assembled on a first rear wheel of the vehicle, and a second rear wheel brake cylinder 22b which can be mounted / assembled on a second rear wheel of the vehicle. The at least one second motor-driven brake pressure generator 20 is hydraulically connected to the first rear wheel brake cylinder 22a via a first rear axle hydraulic path and to the second rear wheel brake cylinder 22b via a second rear axle hydraulic path. In that case, the first rear axle hydraulic path and the second rear axle hydraulic path exemplarily run through a common rear axle brake circuit 24 of the rear axle unit 18. In the example of Fig. 1, the at least one second motor-driven brake pressure generator 20 is a motor-driven plunger device 20, whose single displaceable plunger piston is displaceable by the operation of a motor of the motor-driven plunger device. However, it should be noted that the form of the at least one first motor-driven brake pressure generator 20 as a plunger device 20 having only a displaceable plunger piston illustrated in Fig. 1 should be interpreted as merely exemplary. Similarly, a plunger device having multiple displaceable plunger pistons or at least one pump (instead of or in addition to a plunger device) can also be installed in the rear axle unit 18 as the at least one second motor-driven brake pressure generator 20.

[0022] Furthermore, the rear axle unit 18 has a first isolation valve 26a arranged in the first rear axle hydraulic path and / or a second isolation valve 26b arranged in the second rear axle hydraulic path. Thus, in the brake system of Fig. 1, a first rear wheel brake pressure in the first rear wheel brake cylinder 22a and a second rear wheel brake pressure in the second rear wheel brake cylinder 22b, which is different from the first rear wheel brake pressure, can also be regulated fully automatically / autonomously by at least one second motor-driven brake pressure generator 20 and at least one of the isolation valves 26a and 26b. This can also be called wheel-individual fully automatic / autonomous pressure regulation in the two rear wheel brake cylinders 22a and 22b or wheel-individual fully automatic / autonomous brake pressure generation in the two rear wheel brake cylinders 22a and 22b.

[0023] However, it should be noted that such wheel-individual fully automatic / fully autonomous pressure regulation in the rear wheel brake cylinders 22a and 22b is usually only necessary for modulation, e.g., ESP control or ABS control. During "standard operation" of the rear axle unit 18, the same rear brake pressure is generally regulated fully automatically / fully autonomously to the two rear wheel brake cylinders 22a and 22b, so that no valve switching noises can occur. The driver of the vehicle is therefore not disturbed by valve switching noises in such situations.

[0024] By forming the front axle unit 10 hydraulically separate from the rear axle unit 18, it should be understood that no hydraulic lines extend between the front axle unit 10 and the rear axle unit 18. Since the front axle unit 10 is formed hydraulically separate from the rear axle unit 18, the brake system of FIG. 1 does not require hydraulic lines that are previously required between the axles with the wheel brake cylinders 14a, 14b, 22a and 22b. The brake system therefore has a very compact and space-saving construction. In particular, the modular construction of the brake system can be realized with relatively low manufacturing costs. Furthermore, the front axle unit 10 and the rear axle unit 18 can be assembled as two separate units on a two-axle vehicle equipped with them. This also facilitates the assembly of the brake system described here.

[0025] At least one of the isolation valves 26a and 26b may selectively be a switching valve or a continuously controllable valve suitable for differential pressure regulation. In particular, at least one of the isolation valves 26a and 26b is a de-energized open valve.

[0026] Preferably, the rear axle unit 18 also comprises a rear axle control device 28 designed and / or programmed to control at least the at least one second motor-driven brake pressure generator 20, the first isolation valve 26a and / or the second isolation valve 26b with at least one control signal 28s, taking into account at least one brake setting signal 30. In particular, the rear axle control device 28 is designed to operate the rear axle unit 18 in a mode in which, by the operation of the at least one second motor-driven brake pressure generator 20, brake fluid can / is transferred via the second rear axle hydraulic path to the second rear wheel brake cylinder 22b, at least temporarily, while the at least first isolation valve 26a is controlled in its closed state and, if present, the second isolation valve 26b is controlled in an at least partially open state, so that an individual brake pressure build-up is performed in the second rear wheel brake cylinder 22b. Alternatively or supplementarily, the rear axle unit 18 may also be operable in a mode in which brake fluid can / is transferred via the first rear wheel brake cylinder 22a to the first rear wheel brake cylinder 22a by operation of the at least one second motor-driven brake pressure generator 20 while at least the second isolation valve 26b is controlled to its closed state at least temporarily by the rear axle control device 28 and, if present, the first isolation valve 26a is controlled to at least a partially open state, which causes a separate brake pressure increase in the first rear wheel brake cylinder 22a.

[0027] The at least one brake setting signal 30 can be output to the rear axle control device 28, for example, by a brake operating element sensor 32 of the vehicle, an automatic speed control device (not shown) of the vehicle, an (optional) front axle control device 34 of the front axle unit 10, and / or another stabilization device (not shown) of the brake system. The at least one brake operating element sensor 32 can be, for example, a rod stroke sensor and / or a displacement sensor. The automatic speed control device can be, for example, a driverless automatic driving device of the vehicle, an adaptive cruise control and / or an emergency braking system. Other stabilization devices of the vehicle can be understood in particular as an ESP control unit or an ABS control unit. The rear axle control device 28 can therefore cooperate with a number of different electronic components for pressure regulation of the rear wheel brake cylinders 22a and 22b. As an advantageous development, the rear axle control device 28 can also be configured to receive and evaluate sensor signals of a (not shown) preload sensor (Vordrucksensor) of the rear axle unit 18, at least one (not shown) wheel pressure sensor of the rear axle unit 18 and / or at least one (not shown) wheel speed sensor of the rear wheels. As a further advantageous development, the rear axle control device 28 can also be designed to jointly control at least one motor of the vehicle, not depicted in FIG. 1, which is used as a generator for regenerative braking of the vehicle.

[0028] In the embodiment of FIG. 1, the front axle unit 10 is additionally configured with a first front axle isolation valve 36a arranged in the first front axle hydraulic path and / or a second front axle isolation valve 36b arranged in the second front axle hydraulic path. Thus, wheel-individual, fully automatic / fully autonomous pressure regulation is possible also in the two front wheel brake cylinders 14a and 14b. At least the front axle isolation valves 36a and 36b can alternatively be switching valves or continuously controllable valves suitable for differential pressure regulation. In particular, at least one of the front axle isolation valves 36a and 36b is a de-energized open valve. Insofar as the front axle unit 10 is equipped with at least one front axle isolation valve 36a and 36b, it also has in particular a front axle control device 34 by means of which at least one first motor-driven brake pressure generator 12, the first front axle isolation valve 36a and / or the second front axle isolation valve 36b can be controlled with at least one control signal 34s.

[0029] In particular, the rear axle unit 18 and the front axle unit 10 are connected to one another at the most via at least one signal line and / or bus line 38 which is coupled to the rear axle control unit 28 and the front axle control unit 34. The connection realized by the signal line and / or bus line 38 between the rear axle unit 18 and the front axle unit 10 is thus space-saving, while still allowing good cooperation between the rear axle unit 18 and the front axle unit 10. The at least one signal line and / or bus line 38 can be, for example, a vehicle bus of the vehicle.

[0030] Advantageously, in the embodiment of Fig. 1, the front axle unit 10 additionally also has a master brake cylinder 40, to which a brake operating element 42 of the vehicle can be coupled or is coupled, such that at least one piston of the master brake cylinder 40, which defines at least one chamber of the master brake cylinder 40, is displaceable / displaceable by operation of the brake operating element 42 by the driver of the vehicle. It is explicitly mentioned in this case that the rear axle unit 18 is not hydraulically coupled to the master brake cylinder 40 of the front axle unit 10.

[0031] The brake actuating element 42 can be, for example, a brake pedal 42. Furthermore, at least one chamber of the master brake cylinder 40 is hydraulically connected to at least one first motor-driven brake pressure generator 12, the first front axle hydraulic path and / or the second front axle hydraulic path via at least one connecting line 44. Thus, in the brake system of FIG. 1, a mechanical fallback level is formed, by which the driver can still trigger brake pressure generation in the front wheel brake cylinders 14a and 14b by his own driver braking force applied to the brake actuating element 42, in particular in the event of failure of at least one first motor-driven brake pressure generator 12 and / or at least one second motor-driven brake pressure generator 20. Thus, in the event of a failure of the vehicle electrical system of the host vehicle, the driver himself can still reliably stop the vehicle by the brake pressure increase brought about in the front wheel brake cylinders 14a and 14b.

[0032] The at least one connecting line 44 can be selectively a valve-free or valve-equipped connecting line 44. As an advantageous development, at least one master brake cylinder disconnecting valve 46 can furthermore be arranged in the at least one connecting line 44. Thus, during operation of the at least one first motor-driven brake pressure generator 12, the master brake cylinder 40 can be disconnected from the at least one motor-driven brake pressure generator 12 by closing the at least one master brake cylinder disconnecting valve 46, so that the driver braking force applied to the brake operating element 42 has no influence on the at least one front wheel brake pressure present in the front wheel brake cylinders 14a and 14b. The at least one master brake cylinder disconnecting valve 46 is in particular a de-energized open valve. Although not shown in FIG. 1, a simulator can furthermore be coupled to the master brake cylinder 40, so that the driver who operates the brake operating element 42 when the at least one master brake cylinder disconnecting valve 46 is in the closed state obtains a standard brake operating / pedal feel.

[0033] Additionally, at least one brake pressure generator disconnecting valve 48 can be provided in the front axle brake circuit 16 so that the at least one first motor-driven brake pressure generator 12 can be disconnected / disconnected from the at least one connecting line 44 by closing the at least one brake pressure generator disconnecting valve 48 during the mechanical fallback mode, so that it does not become a "volume sink" and thus prevent the brake pressure build-up in the front wheel brake cylinders 14a, 14b caused by the driver's braking force. A non-energized closed valve is preferred for the at least one brake pressure generator disconnecting valve 48.

[0034] In the brake system of Fig. 1, a single chamber of the master brake cylinder 40 is connected to the front axle brake circuit 16 via only one connecting line 44 having a single master brake cylinder disconnect valve 46, and the junction of the single connecting line 44 in the front axle brake circuit 16 is located between at least one first motor-driven brake pressure generator 12 and a branch of the front axle brake circuit 16. Since the brake system of Fig. 1 has only a single first motor-driven brake pressure generator 12, the front axle unit 10 is also provided with only a single brake pressure generator disconnect valve 48. In this case, the junction of the single connecting line 44 is preferably located between the single brake pressure generator disconnect valve 48 and the branch of the front axle brake circuit 16.

[0035] FIG. 2 shows a schematic diagram of a second embodiment of a braking system.

[0036] In the braking system of Fig. 2, the at least one first motor-driven brake pressure generating device 12 of the front axle unit 10 is a first plunger device 12 having two plunger pistons displaceable by a motor of said device. Thus, a first front axle hydraulic path extends through a first front axle brake circuit 16a of the front axle unit 10 coupled to a first plunger chamber of the first plunger device 12, whereas a second front axle hydraulic path extends through a second front axle brake circuit 16b of the front axle unit 10 coupled to a second plunger chamber of the first plunger device 12. Furthermore, the master brake cylinder 40 coupled to the first plunger device 12 is a tandem master brake cylinder 40, in which the first chamber of the master brake cylinder 40 is connected to the first plunger chamber of the first plunger device 12, and the second chamber of the master brake cylinder 40 is connected to the second plunger chamber via each of the first plunger devices 12, and the connecting lines 44 are each connected to one master brake cylinder isolation valve 46.

[0037] 2, at least one second motor-driven brake pressure generator 20 is configured as a second plunger device 20 having two displaceable plunger pistons. Correspondingly, a first rear axle hydraulic path extends through a first rear axle brake circuit 24a of the rear axle unit 18 coupled to a first plunger chamber of the second plunger device 20, whereas a second rear axle hydraulic path extends through a second rear axle brake circuit 24b of the rear axle unit 18 coupled to a second plunger chamber of the second plunger device 20.

[0038] For further features of the braking system of FIG. 2 and their advantages, reference is made to the embodiment of FIG. 1 already described.

[0039] FIG. 3 shows a schematic partial view of a third embodiment of a brake system.

[0040] The front axle unit 10 shown diagrammatically in FIG. 3 is distinguished from that shown in FIG. 1 in that the junction of the connecting line 44 with the master brake cylinder disconnecting valve 46 is located between the first front axle separating valve 36a and the first front wheel brake cylinder 14a. Thus, as an advantageous development, the front axle unit 10 of FIG. 3 further comprises a brake circuit connecting line 50 including a switchable valve 52, the first junction of which is located between the first front axle separating valve 36 and the first front wheel brake cylinder 14a and the second junction of which is located between the second front axle separating valve 36b and the second front wheel brake cylinder 14b. In the case of the brake system of FIG. 3, the driver can still trigger a brake pressure generation in the two front wheel brake cylinders 14a and 14b by his own driver braking force applied to the brake actuating element 42 in the mechanical fallback level. The switchable valve 52 is in particular a de-energized open valve.

[0041] For further features and their advantages of the brake system of Fig. 3, reference is made to the embodiment of Fig. 1. In particular, the rear axle unit 18 cooperating with the front axle unit 10 of Fig. 3 can be made corresponding to Fig. 1 or Fig. 2.

[0042] FIG. 4 shows a schematic partial view of a fourth embodiment of a brake system.

[0043] In the front axle unit 10 shown diagrammatically in Figure 4 (in contrast to the embodiment in Figure 2), a first connecting line 44, which is connected to a first chamber of the master brake cylinder 40, merges between the first front axle isolation valve 36a and the first front wheel brake cylinder 14a, and a second connecting line 44, which is connected to a second chamber of the master brake cylinder 40, merges between the second front axle isolation valve 36b and the second front wheel brake cylinder 14b. Neither connecting line 44 has a valve.

[0044] For further features and their advantages of the brake system of Figure 4, reference is made to the embodiment of Figures 1 and 2. In particular, the rear axle unit 18 cooperating with the front axle unit 10 of Figure 4 can be formed corresponding to Figure 1 or 2.

[0045] FIG. 5 shows a schematic partial view of a fifth embodiment of a brake system.

[0046] Unlike the embodiment of FIG. 4, in the front axle unit 10 shown diagrammatically in FIG. 5, a first connecting line 44 connected to a first chamber of the master brake cylinder 40 merges between a second plunger chamber of the plunger device 12 and the second front axle separation valve 36b, and a second connecting line 44 connected to a second chamber of the master brake cylinder 40 merges between the first plunger chamber of the plunger device 12 and the first front axle separation valve 36a.

[0047] For further features and their advantages of the brake system of Figure 5, reference is made to the embodiments of Figures 1, 2 and 4. In particular, the rear axle unit 18 cooperating with the front axle unit 10 of Figure 5 can be formed according to Figure 1 or 2.

[0048] FIG. 6 shows a schematic partial view of a sixth embodiment of a brake system.

[0049] In the front axle unit 10, which is shown diagrammatically in Fig. 6, the at least one first motor-driven brake pressure generating device 12 is a plunger device 12. At least one chamber of a master brake cylinder 40 of the front axle unit 10 is hydraulically connected to at least one plunger chamber of the plunger device 12 via at least one connecting line 44. A respective junction of the at least one connecting line 44 in the at least one plunger chamber is formed in such a way that brake fluid can be transported from the master brake cylinder 40 through the at least one junction of the at least one connecting line 44 to the plunger device 12 when the at least one displaceable plunger piston of the plunger device 12 is in its respective starting position. However, if the at least one displaceable plunger piston is displaced from its respective starting position, the transfer of brake fluid from the master brake cylinder 40 through the at least one junction of the at least one connecting line 44 to the plunger device 12 is prevented by the at least one plunger piston and / or the at least one sealing element 54a, 54b and 54c attached to the respective plunger chamber. The advantageously formed junction of the at least one connecting line 44 and the at least one plunger piston and / or the at least one sealing element 54a, 54b and 54c attached to the respective plunger chamber thus ensure that, upon actuation of the plunger device 12 in which they are in a functional state, the master brake cylinder 40 is "automatically" decoupled from the plunger device 12 and thus the driver braking force applied to the brake operating element 42 does not affect the at least one front wheel brake pressure present in the front wheel brake cylinders 14a and 14b.In the event of a failure of the vehicle's plunger device 12 and / or the vehicle electrical system, at least one displaceable plunger piston is normally in its respective starting position, so that the brake system "automatically" transfers to its mechanical fallback level, where the driver can still reliably cause, by means of his driver braking force, a sufficient brake pressure build-up in the front wheel brake cylinders 14a and 14b to brake his vehicle. Therefore, it is unnecessary to provide the brake system of FIG. 6 with a master brake cylinder disconnect valve 46.

[0050] Exemplarily, in the brake system of FIG. 6, a single chamber of the master brake cylinder 40 is connected with a single plunger chamber of the plunger device 12 only via a valveless connecting line 44. The single plunger piston of the plunger device 12 supports three seal elements 54a, 54b and 54c attached to it. The first seal element 54a, which is located closest to the junction of the connecting line 44 when the plunger piston is in its starting position, blocks pressure from the junction direction and passes pressure from the (reverse) motor direction. The second seal element 54b, adjacent to the first seal element 54a, passes pressure from the junction direction and blocks pressure from the (reverse) motor direction. The third seal element 54c, which is located closest to the motor of the plunger device 12, also blocks pressure from the junction direction and passes pressure from the (reverse) motor direction.

[0051] For further features and their advantages, reference is made to the previously described embodiments of the braking system of FIG. 6. In particular, the rear axle 18 cooperating with the front axle unit 10 of FIG. 6 can be configured according to FIG. 1 or FIG. 2.

[0052] FIG. 7 shows a schematic partial view of a seventh embodiment of a brake system.

[0053] Unlike the embodiment of Figure 6, in the brake system of Figure 7 the plunger piston is fitted with "only" a first sealing element 54a, which, when the plunger piston is in its starting position, is closest to the junction of the connecting line 44, blocks pressure from the junction direction and passes pressure from the (reverse) motor direction, and a third sealing element 54c, which is closest to the motor of the plunger arrangement 12, likewise blocks pressure from the junction direction and passes pressure from the (reverse) motor direction. Therefore, a master brake cylinder disconnecting valve 46 is further arranged in the connecting line 44.

[0054] For further features of the braking system of Fig. 7 and their advantages, reference is made to the previously described embodiments. In particular, the rear axle unit 18 cooperating with the front axle unit 10 of Fig. 7 can be made according to Fig. 1 or 2.

[0055] FIG. 8 shows a schematic partial view of an eighth embodiment of a brake system.

[0056] In the case of the front axle unit 10 shown in Figure 8, the first chamber of the master brake cylinder 40 is also connected with the first plunger chamber via a first connecting line 44 and the second chamber of the master brake cylinder 40 with the second plunger chamber via a second connecting line 44, the junction of the respective connecting lines 44 at the assigned plunger chamber being formed corresponding to Figure 6. Furthermore, each of the two plunger pistons supports the above-mentioned sealing elements 54a, 54b and 54c.

[0057] For further features of the braking system of FIG. 8 and their advantages, reference is made to the previously described embodiments. In particular, the rear axle unit 18 cooperating with the front axle unit 10 of FIG. 8 can be made corresponding to FIG. 1 or FIG. 2.

[0058] All the above-mentioned braking systems do not require new technologies for their manufacture, instead existing components / components can be used for the manufacture of the above-mentioned braking systems.

[0059] FIG. 9 shows a flow chart illustrating an embodiment of a method for operating a braking system of a vehicle with at least two axles.

[0060] The method described below can be implemented with any brake system comprising a front axle unit having at least one first motor-driven brake pressure generator hydraulically coupled to a first front wheel brake cylinder of a first front wheel of the vehicle via a first front axle hydraulic path and to a second front wheel brake cylinder of a second front wheel of the vehicle via a second front axle hydraulic path, and a rear axle unit having at least one second motor-driven brake pressure generator hydraulically coupled to a first rear wheel brake cylinder of a first rear wheel of the vehicle via a first rear axle hydraulic path and to a second rear wheel brake cylinder of a second rear wheel of the vehicle via a second rear axle hydraulic path, formed hydraulically separate from the front axle unit. One of the implementation possibilities is not limited to a specific brake system type, nor to a specific vehicle type / automobile type of vehicle / automobile equipped with the brake system.

[0061] As at least one of method steps S1 and S2, the at least one second motor-driven brake pressure generator, the first isolation valve arranged in the first rear axle hydraulic path and / or the second isolation valve arranged in the second rear axle hydraulic path are controlled taking into account at least one brake setting signal. At least one brake setting signal is output by at least one brake operating element sensor of the vehicle, an automatic speed control device of the vehicle, a front axle control device of the front axle unit and / or another stabilization device of the brake system. As method step S1, the at least one second motor-driven brake pressure generator, the first isolation valve and / or the second isolation valve are controlled such that brake fluid is transferred via the second rear axle hydraulic path to the second rear wheel brake cylinder by the operation of the at least one second motor-driven brake pressure generator, at least temporarily, while the at least first isolation valve is controlled and / or held in its closed state. Alternatively or additionally, as method step S2, the at least one second motor-driven brake pressure generator, the first isolation valve and / or the second isolation valve are controlled such that, at least temporarily, while the at least second isolation valve is controlled and / or held in its closed state, the brake fluid is transferred to the first rear wheel brake cylinder via the first rear axle hydraulic path by the operation of the at least one second motor-driven brake pressure generator. The implementation of the method described herein results in the advantages already enumerated above. Optionally, in further method steps not shown, the at least one second motor-driven brake pressure generator can be operated when the first isolation valve is open and when the second isolation valve is open.

[0062] All the above-mentioned front and rear axle units can be used to carry out the method described herein, but the applicability of the method is not limited to the use of the above-mentioned front and rear axle units. [Explanation of symbols]

[0063] 10 Front axle unit 12 First motor-driven brake pressure generating device 14a First front wheel brake cylinder 14b Second front wheel brake cylinder 16 Front axle brake circuit 16a First front axle brake circuit 16b Second front axle brake circuit 18 Rear axle unit 20 Second motor-driven brake pressure generating device 22a First rear wheel brake cylinder 22b Second rear wheel brake cylinder 24 Front axle control device 24a 1st rear axle brake circuit 24b Second rear axle brake circuit 26a First isolation valve 26b Second isolation valve 28 Rear axle control device 30 Brake setting signal 32 Brake operation element sensor 34 Front axle control device 36a First front axle isolation valve 36b Second front axle isolation valve 38 Bus Line 40 Master brake cylinder 42 Brake operation element 44 Connection Lines 46 Master brake cylinder disconnect valve 54a, 54b, 54c sealing elements

Claims

1. a front axle unit (10) having at least one first motor-driven brake pressure generator (12), a first front wheel brake cylinder (14a) that can be mounted on a first front wheel of a vehicle, and a second front wheel brake cylinder (14b) that can be mounted on a second front wheel of the vehicle, the at least one first motor-driven brake pressure generator (12) being hydraulically coupled to the first front wheel brake cylinder (14a) via a first front axle hydraulic path and to the second front wheel brake cylinder (14b) via a second front axle hydraulic path; a rear axle unit (18) formed hydraulically separated from the front axle unit (10), comprising at least one second motor-driven brake pressure generating device (20), a first rear wheel brake cylinder (22a) that can be mounted on a first rear wheel of the vehicle, and a second rear wheel brake cylinder (22b) that can be mounted on a second rear wheel of the vehicle, the at least one second motor-driven brake pressure generating device (20) being hydraulically coupled to the first rear wheel brake cylinder (22a) via a first rear axle hydraulic path and to the second rear wheel brake cylinder (22b) via a second rear axle hydraulic path; 1. A braking system for a vehicle with at least two axles, comprising: a first isolation valve (26a) is arranged in the first rear axle hydraulic path, and / or a second isolation valve (26b) is arranged in the second rear axle hydraulic path; The at least one second motor-driven brake pressure generating device (20) is formed as a second plunger device (20) and has a second plunger device (20) first plunger chamber and a second plunger device (20) second plunger chamber; a first rear axle hydraulic path extending through a first rear axle brake circuit (24a) of the rear axle unit (18) coupled to a first plunger chamber of the second plunger device (20), and a second rear axle hydraulic path extending through a second rear axle brake circuit (24b) of the rear axle unit (18) coupled to a second plunger chamber of the second plunger device (20).

2. The rear axle control device (28) of the rear axle unit (18) is designed and / or programmed to control the at least one second motor-driven brake pressure generator (20), the first isolation valve (26a) and / or the second isolation valve (26b) taking into account at least one brake setting signal (30) outputted to the rear axle control device (28) by at least one brake operating element sensor (32) of the vehicle, an automatic speed control device of the vehicle, a front axle control device (34) of the front axle unit (10) and / or other stabilization devices of the brake system, thereby at least temporarily controlling the brake pressure setting signal (30) of the at least one second motor-driven brake pressure generator (20), the first isolation valve (26a) and / or the second isolation valve (26b).

2. The brake system according to claim 1, wherein, while at least the first isolation valve (26a) is controlled to its closed state, brake fluid can be transferred to the second rear wheel brake cylinder (22b) through the second rear axle hydraulic path by operation of the at least one second motor-driven brake pressure generator (20), and / or, while at least the second isolation valve (26b) is controlled to its closed state, brake fluid can be transferred to the first rear wheel brake cylinder (22a) through the first rear axle hydraulic path by operation of the at least one second motor-driven brake pressure generator (20).

3. 3. A brake system according to claim 2, wherein the rear axle unit (18) is formed hydraulically separated from the front axle unit (10) such that the rear axle unit (18) and the front axle unit (10) are connected to each other at most via at least one signal line and / or bus line (38) coupled to the rear axle control device (28) and the front axle control device (34).

4. 4. The brake system of claim 1, wherein the first front axle hydraulic path and the second front axle hydraulic path extend through a common front axle brake circuit (16) of the front axle unit (10) and / or the first rear axle hydraulic path and the second rear axle hydraulic path extend through a common rear axle brake circuit (24) of the rear axle unit (18).

5. The at least one first motor-driven brake pressure generating device (12) is formed as a first plunger device (12) and has a first plunger chamber of the first plunger device (12) and a second plunger chamber of the first plunger device (12); 5. The brake system according to claim 1, wherein the first front axle hydraulic path extends through a first front axle brake circuit (16a) of the front axle unit (10) coupled to a first plunger chamber of the first plunger device (12), and the second front axle hydraulic path extends through a second front axle brake circuit (16b) of the front axle unit (10) coupled to a second plunger chamber of the first plunger device (12).

6. 6. The brake system according to claim 1, wherein the front axle unit (10) further comprises at least one first front axle isolation valve (36a) arranged in the first front axle hydraulic path and / or a second front axle isolation valve (36b) arranged in the second front axle hydraulic path.

7. 7. The brake system according to claim 1, wherein the front axle unit (10) further comprises a master brake cylinder (40) to which a brake operating element (42) of the vehicle can be coupled or is coupled such that at least one piston of the master brake cylinder (40), which defines at least one chamber of the master brake cylinder (40), is displaceable by operation of the brake operating element (42) by a driver of the vehicle, and the at least one chamber of the master brake cylinder (40) is hydraulically connected to the at least one first motor-driven brake pressure generator (12), the first front axle hydraulic path and / or the second front axle hydraulic path via at least one connecting line (44) that is valveless or equipped with a valve.

8. The at least one first motor-driven brake pressure generating device (12) is a plunger device (12), and the at least one chamber of the master brake cylinder (40) is hydraulically connected to at least one plunger chamber of the plunger device (12) via the at least one connecting line (44), and the at least one plunger chamber is supplied with brake fluid from the master brake cylinder (40) through at least one junction of the at least one connecting line (44) to the plunger piston when the at least one displaceable plunger piston of the plunger device (12) is in its respective starting position.

8. A brake system according to claim 7, wherein the at least one connecting line (44) is formed such that, when the at least one displaceable plunger piston is displaced from its respective starting position, transfer of brake fluid from the master brake cylinder (40) through the at least one junction of the at least one connecting line (44) to the plunger device (12) is prevented by at least one sealing element (54a, 54b, 54c) attached to the at least one plunger piston and / or the respective plunger chamber.

9. 9. A braking system according to claim 7 or 8, wherein at least one master brake cylinder disconnect valve (46) is arranged in said at least one connecting line (44).

10. a front axle unit (10) having at least one first motor-driven brake pressure generator (12) hydraulically coupled to a first front wheel brake cylinder (14a) of a first front wheel of a vehicle via a first front axle hydraulic path and to a second front wheel brake cylinder (14b) of a second front wheel of the vehicle via a second front axle hydraulic path; and a rear axle unit (18) having at least one second motor-driven brake pressure generator (20) formed hydraulically separated from the front axle unit (10) and hydraulically coupled to a first rear wheel brake cylinder (22a) of a first rear wheel of the vehicle via a first rear axle hydraulic path and to a second rear wheel brake cylinder (22b) of a second rear wheel of the vehicle via a second rear axle hydraulic path, The at least one second motor-driven brake pressure generating device (20) is formed as a second plunger device (20) and has a second plunger device (20) first plunger chamber and a second plunger device (20) second plunger chamber; 1. A method of operating a braking system of a vehicle with at least two axles, wherein the first rear axle hydraulic path extends through a first rear axle brake circuit (24a) of the rear axle unit (18) coupled to a first plunger chamber of the second plunger device (20) and the second rear axle hydraulic path extends through a second rear axle brake circuit (24b) of the rear axle unit (18) coupled to a second plunger chamber of the second plunger device (20), comprising the steps of: controlling said at least one second motor-driven brake pressure generator (20), a first isolation valve (26a) arranged in said first rear axle hydraulic path and / or a second isolation valve (26b) arranged in said second rear axle hydraulic path, taking into account at least one brake setting signal (30) output by at least one brake operating element sensor (32) of said vehicle, an automatic speed control device of said vehicle, a front axle control device (34) of said front axle unit (10) and / or other stabilization devices of said brake system, so that at least said first isolation valve (26a) is at its and / or controlling (S1) said at least one second motor-driven brake pressure generator (20) to transfer brake fluid to said second rear wheel brake cylinder (22b) via said second rear axle hydraulic path while at least said second isolation valve (26b) is controlled and / or held in its closed state, said at least one second motor-driven brake pressure generator (20) to transfer brake fluid to said first rear wheel brake cylinder (22a) via said first rear axle hydraulic path while at least said second isolation valve (26b) is controlled and / or held in its closed state,

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