Brake device for a vehicle's braking system and braking system for a vehicle

Abstract

Brake device for a vehicle's braking system with: a master brake cylinder (10) with at least one first pressure chamber (12), which is or can be subdivided into at least a first partial volume (12a) and a second partial volume (12b), wherein the first partial volume (12a) is limited by a first piston wall (14a) of at least one adjustable rod piston (16) such that a first volume of the first partial volume (12a) can be varied by moving the first piston wall (14a), and the second partial volume (12b) is limited by a second piston wall (14b) of the at least one adjustable rod piston (16) such that a second volume of the second partial volume (12b) can be varied by moving the second piston wall (14b), wherein the first partial volume (12a) can be hydraulically connected to or is connected to a brake fluid reservoir (24), and wherein a first brake circuit (28) is connected to the first partial volume (12a) is hydraulically connectable or connected; and a valve assembly (38), wherein the second partial volume (12b) can be connected or is connected to the brake fluid reservoir (24) and to at least the first brake circuit (28) via at least one partial component of the valve assembly (38); characterized by the fact that The valve assembly (38) is mechanically designed such that a pressure build-up up to a limit pressure mechanically predetermined in the valve assembly (38) can be achieved by moving the second piston wall (14b), wherein a pressure threshold for a pressure difference between a pressure in the second partial volume (12b) and a brake circuit pressure in the first brake circuit (28) is mechanically defined such that, if the pressure threshold is exceeded, brake fluid can be transferred via the respective component (38a, 80, 112b) of the valve assembly (38) at least into the first brake circuit (28) until either the pressure threshold is undercut by an increase in the brake circuit pressure or the limit pressure in the second partial volume (12b) is reached.where, despite a further displacement of the second piston wall (14b), an exceedance of the limit pressure in the second partial volume (12b) is prevented by a brake fluid transfer from the second partial volume (12b) into the brake fluid reservoir (24).

Description

[0001] The invention relates to a braking device for a braking system of a vehicle. Furthermore, the invention relates to a braking system for a vehicle. State of the art

[0002] DE 102011 006 327 A1 describes a braking system for motor vehicles. The braking system comprises a master brake cylinder with a stepped piston, which defines a pressure chamber formed in the master brake cylinder with a first effective surface and a filling chamber arranged upstream of the pressure chamber with a second effective surface. A valve arrangement is formed in a central bore of the stepped piston, by means of which a hydraulic connection between the pressure chamber and the filling chamber can be released in such a way that, after reaching a vehicle deceleration of approximately 0.3 g, a driver brakes only with the first effective surface against the master brake cylinder.

[0003] The pressure chamber and the filling chamber are hydraulically connected to a brake fluid reservoir / pressure tank via bores. Furthermore, a brake circuit can be hydraulically connected to the pressure chamber. In addition, the brake system according to DE 10 2011 006 327 A1 is also intended to be able to interact with a pneumatic, electric, or electrohydraulic pressure supply unit for applying pressure to the wheel brakes. Disclosure of the invention

[0004] The invention provides a braking device for a braking system of a vehicle having the features of claim 1 and a braking system for a vehicle having the features of claim 9. Advantages of the invention

[0005] By additionally transferring brake fluid from the second partial volume at least in the first brake circuit due to the advantageous design of the valve device, the brake pressure that can be built up in at least one first wheel brake cylinder of the first brake circuit can be increased. As explained in more detail below, by means of the present invention, the brake pressure that can be built up in at least one wheel brake cylinder of the brake circuit can be significantly increased due to the advantageous design of the valve device, particularly when air is present in at least one brake circuit.

[0006] The braking device preferably comprises an electrically controllable valve, via which the second partial volume can be or is connected to the brake fluid reservoir in such a way that, when the electrically controllable valve is in its open state, the second partial volume is depressurized despite the displacement of the second piston wall, and, when the electrically controllable valve is in its closed state, the pressure buildup up to the limit pressure mechanically predetermined in the valve device can be effected by displacing the second piston wall. By advantageously equipping the braking device with the electrically controllable valve, it can be ensured that, in a normal operating mode of the braking device, the driver brakes into the first pressure chamber only by means of a first surface of the first piston wall.Even before pressure builds up in the master cylinder, the electrically controlled valve can be controlled to its open state so that the second partial volume is depressurized, thus offering no resistance to the simultaneous displacement of the second piston wall along with the first piston wall. Therefore, in normal operating mode, the driver only needs to brake with the first surface of the first piston wall into the first pressure chamber of the master cylinder. This provides the driver with a pleasant braking feel (pedal feel) in the brake device's normal operating mode.

[0007] Furthermore, the braking device can be operated in a fallback mode, in which the braking area, by means of which the driver brakes into the first pressure chamber, can be increased compared to the normal operating mode. By (automatically) controlling the electrically controllable valve in its closed state, an additional pressure buildup in the second partial volume can be achieved. In addition, the advantageous mechanical design of the valve device ensures that the pressure present in the second partial volume (barely) exceeds a mechanically predetermined limit pressure. Thus, even in the fallback mode, it is guaranteed that the driver perceives the actuation of their brake actuation element, such as a brake pedal, as pleasant.

[0008] In an advantageous embodiment, the master brake cylinder can comprise a second pressure chamber and a floating piston adjustably arranged between the first partial volume of the first pressure chamber and the second pressure chamber, wherein a second brake circuit can be or is hydraulically connected to the second pressure chamber. The brake device can thus also be advantageously used in a dual-circuit braking system.

[0009] In particular, the second partial volume can be connected or can be connected to the second brake circuit via at least one further subcomponent of the valve device in such a way that brake fluid can be transferred into the second brake circuit via at least the further subcomponent of the valve device. In this way, a brake pressure that can be built up in at least one second wheel brake cylinder of the second brake circuit can also be increased. Above all, this can be used to counteract, for example, the presence of air in the second brake circuit.

[0010] In a further advantageous embodiment, the master brake cylinder has a stepped bore within which at least the first pressure chamber is formed, wherein the master brake cylinder comprises a stepped piston as the at least one adjustable rod piston, which delimits the first partial volume with the first piston wall and the second partial volume with the second piston wall. However, it should be noted that such a design of the master brake cylinder is optional. For example, the master brake cylinder can also be equipped with multiple stepped pistons, which can be adjusted into separate chambers of the master brake cylinder by actuating a brake actuating element. Thus, a variety of different designs of the master brake cylinder are suitable for implementing the advantageous braking device.

[0011] For example, the valve device may comprise an overpressure relief valve, via which the second partial volume is or can be connected to the brake fluid reservoir, and, as a subcomponent of the valve device, at least one check valve, via which the second partial volume is or can be connected to at least the first brake circuit. Thus, cost-effective components can be used to implement the valve device.

[0012] As a further development, the valve device can additionally comprise a further check valve, via which the second partial volume can be connected or is connected to the second brake circuit. Due to the additional transferability of brake fluid from the second partial volume to the second brake circuit, an increase in the brake pressure that can be built up in the at least one second wheel brake cylinder of the second brake circuit can be achieved using a cost-effective valve device.

[0013] As an alternative to the embodiments described above, the valve device can comprise a regulated check valve, via which the second partial volume can be or is connected to the brake fluid reservoir, and, as a subcomponent of the valve device, at least one check valve, via which the second partial volume can be or is connected to at least the first brake circuit. This embodiment of the braking device can also be manufactured cost-effectively.

[0014] The advantages described above are also achieved with an appropriately designed braking system.

[0015] In an advantageous development, the braking system can include a power braking device. The power braking device can be used in the above-described realizable normal operating mode of the braking system to build up / increase the braking pressure in the wheel brake cylinders of the braking system.

[0016] In an advantageous embodiment, the valve device can comprise an overpressure relief valve, via which the second partial volume can be or is connected to the brake fluid reservoir, and, as a subcomponent of the valve device, at least one lip seal of the power brake device designed as a plunger. Thus, with such a cost-effective design of the power brake device, the use of at least one check valve can be dispensed with. In this way, the installation space requirement and the manufacturing costs of the advantageously designed brake system can be reduced.

[0017] In a further advantageous development, the braking system comprises a control device which, in normal mode, is designed to control at least one component of the braking system such that the pressure buildup up to the limit pressure mechanically predetermined in the valve device can be effected by displacing the second piston wall in the second partial volume. To achieve the pressure buildup, a piston, for example, can be moved by means of a motor which is, for example, mechanically and / or hydraulically connected to the piston. Thus, the braking system is also suitable for parallel feeding. This advantage can accordingly also be transferred to a braking device with such a control device. Short description of the drawings

[0018] Further features and advantages of the present invention are explained below with reference to the figures. They show: Fig. 1 is a schematic representation of a first embodiment of the braking system; Fig. 2 a schematic representation of a second embodiment of the braking system; Fig. 3 is a schematic representation of a third embodiment of the braking system; Fig. 4 is a schematic representation of a fourth embodiment of the braking system; and Fig. 5a to 5e show a schematic representation of a fifth embodiment of the braking system and coordinate systems for explaining its operation. Embodiments of the invention

[0019] Fig. 1 shows a schematic representation of a first embodiment of the braking system.

[0020] The Fig. The braking system for a vehicle, schematically illustrated in Figure 1, has a master brake cylinder 10 with at least one first pressure chamber 12, which is or can be divided into at least a first partial volume 12a and a second partial volume 12b. The first partial volume 12a is delimited by a first piston wall 14a of at least one adjustable rod piston 16 such that a first volume of the first partial volume 12a can be varied by displacing the first piston wall 14a. Furthermore, the second partial volume 12b is delimited by a second piston wall 14b of the at least one adjustable rod piston 16 such that a second volume of the second partial volume 14b can be varied by displacing the second piston wall 14b. The partial volumes 12a and 12b can, for example, be designed as two separate chambers or as chambers that can be hydraulically separated by means of a valve component.

[0021] In the embodiment of the Fig. 1, the master brake cylinder 10 also includes a second pressure chamber 18 and a floating piston 20 adjustably arranged between the first partial volume 12a of the first pressure chamber 12 and the second pressure chamber 18. The master brake cylinder 10 can thus also be used as a "modified" tandem master brake cylinder. However, it should be noted that a design of the master brake cylinder with two pressure chambers 12 and 18 is optional.

[0022] In the embodiment of the Fig. 1, the master brake cylinder 10 also has a stepped bore, within which at least the first pressure chamber 12 is formed. For example, the stepped bore can have a first (inner) inner diameter d1 oriented perpendicular to an adjustment direction 22 of the at least one adjustable rod piston 16 and / or the floating piston 20, which is smaller than a second (outer) inner diameter d2 of the stepped bore oriented perpendicular to the adjustment direction 22. The first partial volume 12a and / or the second pressure chamber 18 can have the first / inner diameter d1 perpendicular to the adjustment direction 22, while the second partial volume 12b has the second / outer inner diameter d2 perpendicular to the adjustment direction 22.The master brake cylinder 10 can also comprise a stepped piston 16 as the at least one adjustable rod piston 16, which defines the first partial volume 12a with the first piston wall 14a and the second partial volume 12b with the second piston wall 14b. The second partial volume 12b can thus also be designed as an annular volume. However, it should be noted that the arrangement shown in . Fig. 1 is to be interpreted merely as an example. Even a design different from the illustration in Fig. 1 different design of the master brake cylinder 10 can be used to realize the braking system described below.

[0023] The braking system also includes a brake fluid reservoir 24, wherein at least the first partial volume 12a and the second partial volume 12b are hydraulically connectable / connected to the brake fluid reservoir 24. The second pressure chamber 18 can also be connected / connected to the brake fluid reservoir 24. For example, the volumes 12a, 12b, and 18 can each be hydraulically connected / connected to the brake fluid reservoir 24 via a sniffer bore 26.

[0024] The braking system also has at least a first brake circuit 28 with at least one first wheel brake cylinder 30, wherein the first brake circuit 28 is hydraulically connectable / connected to the first partial volume 12a. Preferably, a second brake circuit 32 with at least one second wheel brake cylinder 34 is also hydraulically connectable / connected to the second pressure chamber 18. However, the braking system described here is not limited to a design with two brake circuits 28 and 32. Likewise, the number of wheel brake cylinders 30 and 34 that can be used in a brake circuit 28 and 32 can be selected relatively freely. Furthermore, a variety of different hydraulic components, such as pumps and / or valves, can be used in the brake circuits 28 and 32.

[0025] The braking system preferably also includes an electrically controllable valve 36, via which the second partial volume 12b is connected to the brake fluid reservoir 24. In this case, the electrically controllable valve 36 is inserted between the second partial volume 12b and the brake fluid reservoir 24 such that, when the electrically controllable valve 36 is in its open state, the second partial volume 12 is depressurized despite a displacement of the second piston wall 14b. However, equipping the braking system with the electrically controllable valve 36 is optional.

[0026] The braking system has a valve device 38, wherein the second partial volume 12b is connected at least to the first brake circuit 28 via at least one partial component 38a of the valve device 38. Furthermore, the valve device 38 is mechanically designed such that (when the electrically controllable valve 36, if present, is in its closed state) a pressure build-up in the second partial volume 12b up to a limit pressure mechanically predetermined in the valve device 38 can be effected by means of the displacement of the second piston wall 14b. Furthermore, brake fluid can be transferred at least into the first brake circuit 28 via at least the partial component 38a of the valve device 38. Furthermore, the design of the valve device 38 ensures that, despite further displacement of the second piston wall (14b), the limit pressure in the second partial volume (12b) is prevented from being exceeded.The limit pressure can be, for example, between 1 and 3 bar, in particular 2 bar. A pressure threshold above which brake fluid flows from the second partial volume 12b at least into the first brake circuit 28 can be approximately 0.5 bar.

[0027] Due to its advantageous design, the braking system can be operated in a normal operating mode, in which the driver brakes at least into the first pressure chamber 12 using only a first area A1 of the first piston wall 14a delimiting the first partial volume 12a. This can be ensured by controlling the electrically controllable valve 36 in its open state. This can also be described as meaning that in the normal operating mode, the second partial volume 12b is short-circuited to the brake fluid reservoir 24 by opening the electrically controllable valve 36. The time of this actuation can be shifted back in time if rapid deceleration is detected, such as in particular during emergency braking, in order to improve the pressure build-up dynamics in this operating case.A co-displacement of the second piston wall 14b together with the first piston wall 14a is not associated with a pressure buildup in the second partial volume 12b after the opening of the electrically controllable valve 36. Therefore, in the normal operating mode of the braking device / braking system, the driver has a pleasant braking application feel (pedal feel) due to the comparatively small braking surface for braking, at least in the first pressure chamber 12, equal to the first surface A1.

[0028] The braking system can also be operated in a fallback mode, in which the braking area (for braking at least into the first pressure chamber 12) is increased compared to the normal operating mode. By (automatically) controlling the electrically controllable valve 36 in its closed state, an additional pressure buildup in the second partial volume 12b is possible. The (total) braking area effective in the fallback mode (for braking at least into the first pressure chamber 12) thus corresponds to a sum of the first area A1 and a second area A2 of the second piston wall 14b delimiting the second partial volume 12b. By enlarging the braking area (for braking at least into the first pressure chamber 12) to the sum of the areas A1 and A2, the ratio of the master brake cylinder 10 is increased, so that the driver can achieve even greater braking pressures in the wheel brake cylinders 30 and 34 of the braking system with a specific driver braking force.This also reduces the impact of the operating conditions to be taken into account.

[0029] At the same time, the advantageous mechanical design of the valve device 38 ensures that the pressure present in the second partial volume 12b (barely) exceeds a mechanically predetermined limit pressure. This ensures that the driver perceives the actuation of their brake actuation element as pleasant even in the fallback mode. By transferring brake fluid from the second partial volume 12b at least in the first brake circuit 28, the brake pressure that can be built up in the at least one first wheel brake cylinder 30 of the first brake circuit 28 can also be increased. It is expressly pointed out that a sudden emptying of the second partial volume 12b after a comparatively strong pressure buildup in the second partial volume 12b is prevented by the present design of the valve device 38. This also prevents a sudden drop in the driver's braking force in the fallback mode.This ensures that no irregularities occur during brake application, even in fallback mode.

[0030] The braking system can be operated in fallback mode, particularly in the event of a partial or complete failure of at least one electrical component of the braking system, or in the event of a failure of the vehicle's electrical system. This reliably ensures that the driver can still comfortably bring the vehicle equipped with the braking system to a standstill, even in such a fault situation.

[0031] The electrically controllable valve 36 is controlled in its closed state in the fallback mode / mechanical fallback level. If the electrically controllable valve 36 is designed as a normally closed valve, this can be achieved automatically by interrupting the power supply to the electrically controllable valve 36.

[0032] The valve device 38 can, for example, be mechanically designed for a brake pressure between 1 bar and 3 bar, such as in particular for a brake pressure of 2 bar. The mechanical design of the valve device 38 for determining the brake pressure ensures that the valve device 38 still reliably performs its desired function in the fallback mode, even in the event of a total failure of the vehicle's electrical system.

[0033] The electrically controllable valve 36 is preferably installed in a line 40 extending from a bore 42 of the master brake cylinder 10 at the second partial volume 12b to the brake fluid reservoir 24. It should be noted that the bore 42 is not to be understood as a sniffing opening 26. Thus, the bore 42 remains exposed even when the second piston wall 14b is significantly displaced into the second partial volume 12b.

[0034] Preferably, the braking system also includes a power brake device 44, by means of which the brake pressure buildup in the wheel brake cylinders 30 and 34 can be carried out or supported during normal operating mode. The power brake device 44 can be a pneumatic, electric, or electrohydraulic power brake device 44. Thus, during normal operating mode, the driver only needs to brake with a relatively low driver braking force and the comparatively small first area A1 in the master brake cylinder 10.

[0035] In the embodiment of the Fig. 1, the externally powered brake device 44 is a plunger 44, the two pressure chambers 46a and 46b of which are each delimited by a piston 50a and 50b adjustable by operation of a motor 48. The first brake circuit 28 is connected to the first pressure chamber 46a of the plunger 44, while the second pressure chamber 46b of the plunger 44 is assigned to the second brake circuit 32. Each of the pressure chambers 46a and 46b of the plunger is hydraulically connected to the master brake cylinder 10 via a line 52a and 52b, each with a separating valve 54a and 54b inserted therein, wherein the first pressure chamber 46a of the plunger 44 is hydraulically connected to the first partial volume 12a and the second pressure chamber 46b of the plunger 44 is hydraulically connected to the second pressure chamber 18. The master brake cylinder 10 can thus be decoupled from the brake circuits 28 and 32 by closing the isolation valves 54a and 54b.In this way, it can be ensured that when the braking system is in the normal operating mode, brake pressure buildup in the wheel brake cylinders 30 and 34 is achieved exclusively by means of the plunger 44, while in the fallback mode, the master brake cylinder 10 can be used to build up the desired high brake pressure in the wheel brake cylinders 30 and 34. The plunger 44 is preferably self-locking.

[0036] The electrically controllable valve 36 can be designed as a normally closed valve. Accordingly, normally open valves can be used as isolation valves 54a and 54b. This ensures that the braking system can be automatically controlled from normal operating mode to fallback mode in the event of a vehicle electrical system failure.

[0037] In the embodiment of the Fig. 1, the valve device 38 has a check valve 38a as the at least one subcomponent 38a, via which the second partial volume 12b is connected at least to the first brake circuit 28. The check valve 38a, via which brake fluid can be transferred from the second partial volume 12b to the first brake circuit 38, can be installed in a line 58 that extends from a further bore 60 of the master brake cylinder 10 at the second partial volume 12b in the direction of the first brake circuit 28. For example, the line 58 can open into the line 52a. The further bore 60 is designed on the master brake cylinder 10 such that it remains exposed even if the second piston wall 14b is significantly displaced. In addition, the valve device 38 comprises an overpressure relief valve 38b, via which the second partial volume 12b is connected to the brake fluid reservoir 24.The overpressure relief valve 38b can in particular be arranged in a bypass line 56 running parallel to the electrically controllable valve 36.

[0038] In addition, the braking system of the Fig. 1 also has an optional simulator device 62. The simulator device 62 comprises a pressure chamber 62a, a spring chamber 62b, and a piston 62c adjustably arranged between the pressure chamber 62a and the spring chamber 62b, which piston can be adjusted into the simulator chamber 62b against a spring force of at least one simulator spring 62b. The pressure chamber 62a is connected via a line 64 either to the first partial volume 12a or to the second pressure chamber 18. By means of a further isolating valve 66, which is preferably designed as a normally closed valve, the simulator device 62 can be automatically decoupled from the braking system in the event of an on-board power supply failure. This ensures that the simulator device 62 does not counteract the driver's ability to build up braking pressure in the wheel brake cylinders 30 and 34 during the fallback mode.

[0039] Fig. 2 shows a schematic representation of a second embodiment of the braking system.

[0040] The Fig. In contrast to the embodiment described above, the braking system schematically illustrated in Figure 2 has a power brake device 44, which is designed as a plunger 44 with only one pressure chamber 46 and a piston 50 adjustable by means of the motor 48. The pressure chamber 46 of the plunger 44 is connected via a bore / seal 70 to a section of the line 58 located between the bore 60 and the check valve 38a. In addition, the pressure chamber 46 of the plunger 44 is connected to each brake circuit 28 and 32 via a line 72, each with a normally closed isolating valve 74 inserted therein. Even with such a design of the power brake device 44, the brake pressure present in all wheel brake cylinders 30 and 34 of the brake circuits 28 and 32 can be freely adjusted in the normal operating mode.

[0041] In the braking system of the Fig. 2, the second partial volume 12b is also additionally connected to the second brake circuit 32 via at least one further partial component 38c of the valve device 38 such that brake fluid can be transferred into the second brake circuit 32 via at least the further partial component 38c of the valve device 38. Thus, the driver braking force exerted by the driver on the second partial volume 12b in the fallback mode can also be used to increase the brake pressure in the at least one second wheel brake cylinder 34 of the second brake circuit 33. As explained in more detail below, the brake pressure that can be exerted in the at least one second wheel brake cylinder 34 of the second brake circuit 32 can thus be significantly increased. The valve device 38 has, as a further partial component 38c, a further check valve 38c, via which the second partial volume 12b is connected to the second brake circuit 32.This can be realized in a simple manner by inserting the further check valve 38b into a line 76 which leads from a section of the line 58 located between the bore 60 and the check valve 38a to the second brake circuit 32.

[0042] Fig. 3 shows a schematic representation of a third embodiment of the braking system.

[0043] The Fig. 3, in contrast to the embodiment of the Fig. 1 a valve device 38 which, in addition to the overpressure relief valve 38b, via which the second partial volume 12b is connected to the brake fluid reservoir 24, also comprises at least one lip seal 80 of the external power brake device 44 designed as a plunger 44. In this way, the brake system can be designed without at least one check valve. In this way, the manufacturing costs and installation space requirements of the brake system of the Fig. 3 can be reduced.

[0044] Fig. 4 shows a schematic representation of a fourth embodiment of the braking system.

[0045] The Fig. The brake system shown in Figure 4 has a master brake cylinder 10, whose rod piston 16, designed as a stepped piston 16, is adjustably arranged between the first pressure chamber 12 and a pressure build-up chamber 90. An output piston 92 extends from the stepped piston 60 toward a brake actuating element 94, such as a brake pedal 94. The output piston 92 is guided through an opening in an outer wall 96 of the master brake cylinder 10, which delimits the pressure build-up chamber 90 on a side aligned with the brake actuating element 94. The outer wall 96 is designed to be liquid-tight such that, by displacing the piston 50 of the power brake device 44, a volume of brake fluid can be transferred between the pressure chamber 46 of the power brake device 44 and the pressure build-up chamber 90. The power brake device 44 can thus also be connected upstream of the master brake cylinder 10.

[0046] The simulator device 62 is also connected to the pressure buildup chamber 90. This is achieved by the line 64 with the isolating valve 66 opening into a line 98 with a (preferably normally open) isolating valve 100, which connects the pressure buildup chamber 90 to a pre-chamber (not shown) between the outer wall 96 and the brake actuating element 94. The power brake device 44 can also be connected to the line 98, with the power brake device 44 preferably being connected between the pressure buildup chamber 90 and the isolating valve 100, and the simulator device 62 being connected between the isolating valve 100 and the pre-chamber.

[0047] The braking system of the Fig. 4, the electrically controllable valve 36 and the overpressure relief valve 38b are arranged in series in the line 40. The electrically controllable valve 36 is preferably inserted in a section of the line 40 extending between the overpressure relief valve 38b and the brake fluid reservoir 24.

[0048] In addition to the previously described embodiments, the brake system also has a normally closed isolation valve 102, which is inserted into a line 104 running parallel to the check valve 38a. The brake system of the Fig. 4 reliably guarantees all the advantages described above.

[0049] The Fig. The embodiment of the braking system schematically illustrated in Figure 4 can also be operated in a manner different from the above embodiments. In a normal operating mode, the second partial volume 12b is switched such that a pressure build-up therein can be brought about by means of a displacement of the second piston surface 14b and the two partial volumes 12a and 12b can be used for parallel feeding. The corresponding "switching" of the second partial volume 12b can be carried out by means of a control device (not sketched) which is designed to control at least one component of the braking system, such as at least the electrically controllable valve 36, in normal mode such that the pressure build-up up to the limit pressure mechanically predetermined in the valve device 38 can be brought about by means of the displacement of the second piston wall 14b in the second partial volume 12b.In a fallback level, the coupling of surfaces A1 and A2 can be adjusted depending on a pressure.

[0050] By operating the motor 48, the piston 16 can be moved for brake braking or for brake boosting. As an alternative to the Fig. In addition to the hydraulic power transmission shown in Figure 4, a mechanical power transmission between the piston 16 and the motor 48 is also possible.

[0051] Fig. 5a to 5e show a schematic representation of a fifth embodiment of the braking system and coordinate systems for explaining its operation.

[0052] The Fig. The brake system shown in Figure 5a has a master brake cylinder 10, in whose second partial volume 12b only a bore 42 is formed. The line 40 with the electrically controllable valve 36 inserted therein runs between the bore 42 and a line 110, via which the pressure chamber 46 of the plunger 44 is connected to the brake fluid reservoir 24. (The pressure chamber 46 of the plunger 44 can optionally be connected to the spring chamber 62b of the simulator device 62 via a line 114.)

[0053] The valve device 38 has a controlled check valve 112a, which is inserted into the bypass line 56, which is guided parallel to the electrically controllable valve 36, and via which the partial volume 12b is connected to the brake fluid reservoir 24. In addition, the valve device 38 comprises at least one check valve 112b and 112c, via which the second partial volume 12b is connected at least to the first brake circuit 28. In the embodiment of the Fig. 5a, the second partial volume 12b is hydraulically connected to the first brake circuit 28 via a first check valve 112b inserted into the line 58 and to the second brake circuit 32 via a second check valve 112c inserted into the line 76. As a supplement, the braking system can optionally also comprise a check valve 116 arranged parallel to the isolation valve 66 of the simulator device 62 and at least one sensor 118.

[0054] Also by means of the valve device 38 of the Fig. 5a, a brake fluid transfer from the second partial volume 12b into the brake circuits 28 and 32 and into the brake fluid reservoir 24 is mechanically controllable via the closing pressures of the check valves 112a to 112c. The controlled check valve 112a defines the limit pressure as the maximum permissible pressure in the second partial volume 12b. A pressure threshold (pressure difference) between the brake circuits 28 and 32 and the second partial volume 12b can be defined via the check valves 112b and 112c. If the pressure in the second partial volume 12b exceeds this pressure threshold, brake fluid flows from the second partial volume 12b into the brake circuits 28 and 32. This condition persists until either the pressure falls below the pressure threshold due to an increase in the brake circuit pressures or the limit pressure in the second partial volume 12b specified by the controlled check valve 112a is exceeded.

[0055] The braking system of the Fig. 5a thus enables braking in the fallback level in both brake circuits 28 and 32 with an increased braking area equal to the sum of the hydraulically effective areas A1 and A2. This represents a significant improvement in braking behavior in the mechanical fallback level compared to braking with the two hydraulically effective areas A1 and A2 in only one of the two brake circuits 28 and 32.

[0056] Fig. 5b to 5e show coordinate systems whose abscissas represent a pedal travel s (in mm) and whose ordinates represent a pressure p1 / p2 (in bar). Fig. 5b to 5e below explain how much the brake pressure in the brake circuits 28 and 32 can be increased during the fallback mode by means of the brake fluid transfer.

[0057] The coordinate systems of the Fig. 5b and Fig. 5c shows a situation in which there is no air in brake circuits 28 and 32 at the beginning of braking: Using the coordinate system of the Fig. 5b shows the second brake pressures p2 (in bar) that can be achieved in the second brake circuit 32. The graph g02 indicates the second brake pressure p2 present in the second brake circuit 32 in the conventional manner, i.e. without transferring brake fluid from the second partial volume 12b to one of the two brake circuits 28 and 32. The graph g12 shows the second brake pressure p2 that would be present in the second brake circuit 32 if brake fluid were only fed into the first brake circuit 28 from the second partial volume 12b. The second brake pressure p2 that can be achieved by feeding brake fluid from the second partial volume 12b into both brake circuits 28 and 32 is shown by the graph g22.It can be seen that, by transferring brake fluid from the second partial volume 12b to both brake circuits 28 and 32, the second brake pressure p2 that can be achieved in the second brake circuit 32 at a comparatively high pedal travel s can be significantly increased. For example, graph g22 shows a maximum pressure of 100 bar, while graphs g02 and g12 each have a maximum pressure of 93 bar.

[0058] In the coordinate system of the Fig. 5c shows the first brake pressure p1 (in bar) that can be achieved in the first brake circuit 28. The graph g01 shows the first brake pressure p1 that can be achieved in the first brake circuit 28 in the conventional manner, i.e. without transferring brake fluid from the second partial volume 12b to one of the two brake circuits 28 and 32. The values ​​of the graph g11 correspond to the values ​​of the first brake pressure p1 that can be achieved when brake fluid from the second partial volume 12b is fed only into the first brake circuit 28. By additionally feeding brake fluid from the second partial volume 12b into the second brake circuit 32 while simultaneously filling the first brake circuit 28 (from the second partial volume 12b), the first brake pressure p1 is hardly affected at a comparatively high pedal travel s, as can be seen from the graph g21.Although graph g21 has a slightly reduced maximum pressure of 97 bar compared to a maximum pressure of 99 bar of graph g11, these values ​​are significantly higher than the maximum pressure of 89 bar of graph g01.

[0059] As can be seen from the coordinate systems of Fig. 5d and Fig. 5e, the pressure increase caused by the additional supply of brake fluid from the second partial volume 12b into the brake circuits 28 and 32 is even more significant if air (e.g. 2cm 3) is present in the brake circuits 28 and 32. The graphs g01' and g02' indicate the brake pressures p1 and p2 that can be achieved in the conventional manner, i.e. without transferring brake fluid from the second partial volume 12b into one of the two brake circuits 28 and 32. The graphs g11' and g12' show brake pressures p1 and p2 that can be achieved by feeding brake fluid only in the first brake circuit 28. The brake pressures p1 and p2 that can be achieved by feeding brake fluid from the second partial volume 12b into both brake circuits 28 and 32 are shown by the graphs g21' and g22'. The volume feed from the second partial volume 12b thus enables the air volume to be filled with brake fluid, whereby the achievable maximum pressure increases are significantly increased. The graph g22' shows a significantly increased maximum pressure of 46 bar compared to the maximum pressures of 33 bar of the graphs g02' and g12'.Likewise, the graph g21' has a slightly reduced maximum pressure of 52 bar compared to a maximum pressure of 58 bar of the graph g11', but these values ​​are still significantly higher than the maximum pressure of 35 bar of the graph g01'.

[0060] In summary, it can be stated that by supplying an additional amount of brake fluid from the second partial volume 12b, the brake pressure achievable in the mechanical fallback level is increased during emergency braking. In this way, the maximum possible vehicle deceleration can also be increased. In particular, this effect also compensates for any air bubbles contained in brake circuits 28 and 32, which enables an additional increase in maximum brake pressure in the fallback level and thus a significantly shortened stopping distance for the vehicle. The additional volume gained also improves braking behavior from a pressureless braking state by overcoming the dead volume more quickly, particularly in the first brake circuit 28. These measures can also significantly increase the deceleration achievable in a mechanical fallback level without adversely affecting the pedal travel due to operating conditions.Using the braking systems described above, the vehicle behavior in the mechanical fallback level can be further improved.

[0061] In addition, by decoupling the pedal stroke and the pedal force during operation, it is possible to design a fallback level independently of the volumes to be pumped during operation.

[0062] The master brake cylinder 10, the electrically controllable valve 36, and the valve device 38 can be arranged as several separately arranged components. Likewise, the master brake cylinder 10, the electrically controllable valve 36, and the valve device 38 can also be designed as a compact (one-piece) braking device. It should be noted that the advantages outlined above can also be achieved by such a braking device for a vehicle's braking system.

Claims

[1] Braking device for a braking system of a vehicle with: a master brake cylinder (10) with at least one first pressure chamber (12), which is or can be subdivided into at least a first partial volume (12a) and a second partial volume (12b), wherein the first partial volume (12a) is delimited by a first piston wall (14a) of at least one adjustable rod piston (16) such that a first volume of the first partial volume (12a) can be varied by means of a displacement of the first piston wall (14a), and the second partial volume (12b) is delimited by a second piston wall (14b) of the at least one adjustable rod piston (16) such that a second volume of the second partial volume (12b) can be varied by means of a displacement of the second piston wall (14b), wherein the first partial volume (12a) is or can be connected hydraulically to a brake fluid reservoir (24), and wherein a first brake circuit (28) is connected to the first partial volume (12a) is hydraulically connectable or connected; and a valve device (38), wherein the second partial volume (12b) can be or is connected to the brake fluid reservoir (24) and at least to the first brake circuit (28) via at least one partial component of the valve device (38); characterized by , that the valve device (38) is mechanically designed such that a pressure build-up in the second partial volume (12b) up to a limit pressure mechanically predetermined in the valve device (38) can be effected by means of the displacement of the second piston wall (14b), wherein a pressure threshold for a pressure difference between a pressure in the second partial volume (12b) and a brake circuit pressure in the first brake circuit (28) is mechanically defined such that, when the pressure threshold is exceeded, brake fluid can be transferred via the respective subcomponent (38a, 80, 112b) of the valve device (38) at least into the first brake circuit (28) until either the pressure threshold is undershot due to an increase in the brake circuit pressure or the limit pressure in the second partial volume (12b) is reached,wherein, despite a further displacement of the second piston wall (14b), an exceeding of the limit pressure in the second partial volume (12b) is prevented by a brake fluid transfer from the second partial volume (12b) into the brake fluid reservoir (24). [2] Braking device according to claim 1, wherein the braking device comprises an electrically controllable valve (36) via which the second partial volume (12b) can be connected or is connected to the brake fluid reservoir (24) in such a way that when the electrically controllable valve (36) is in its open state, the second partial volume (12b) is depressurized despite the displacement of the second piston wall (14b) and when the electrically controllable valve (36) is in its closed state, the pressure build-up up to the limit pressure mechanically predetermined in the valve device (38) can be effected by means of the displacement of the second piston wall (14b). [3] Braking device according to claim 1 or 2, wherein the master brake cylinder (10) comprises a second pressure chamber (18) and a floating piston (20) adjustably arranged between the first partial volume (12a) of the first pressure chamber (12) and the second pressure chamber (18), and wherein a second brake circuit (32) is or can be hydraulically connected to the second pressure chamber (18). [4] Braking device according to claim 3, wherein the second partial volume (12b) is or can be additionally connected to the second brake circuit (32) via at least one further partial component (38c, 80, 112c) of the valve device (38) in such a way that brake fluid can be transferred into the second brake circuit (32) via at least the further partial component (38c, 80, 112c) of the valve device (38). [5] Braking device according to one of the preceding claims, wherein the master brake cylinder (10) has a stepped bore within which at least the first pressure chamber (12) is formed, and wherein the master brake cylinder (10) comprises a stepped piston (16) as the at least one adjustable rod piston (16), which delimits the first partial volume (12a) with the first piston wall (14a) and the second partial volume (12b) with the second piston wall (14b). [6] Braking device according to one of the preceding claims, wherein the valve device (38) comprises as a subcomponent (38b) an overpressure relief valve (38b), via which the second partial volume (12b) is or can be connected to the brake fluid reservoir (24), and as a subcomponent (38a) at least one check valve (38a), via which the second partial volume (12b) is or can be connected to at least the first brake circuit (28). [7] Braking device according to claim 6, wherein the valve device (38) additionally comprises a further check valve (38c) as the further subcomponent (38c), via which the second subvolume (12b) can be or is connected to the second brake circuit (32). [8] Braking device according to one of claims 1 to 5, wherein the valve device (38) comprises as subcomponent (112a) a controlled check valve (112a), via which the second partial volume (12b) is or can be connected to the brake fluid reservoir (24), and as subcomponent (112b) at least one check valve (112b), via which the second partial volume (12b) is or can be connected to at least the first brake circuit (28). [9] Braking system for a vehicle with at least one first brake circuit (28); a brake fluid reservoir (24); and a master brake cylinder (10) with at least one first pressure chamber (12), which is or can be subdivided at least into a first partial volume (12a) and a second partial volume (12b), wherein the first partial volume (12a) is delimited by a first piston wall (14a) of at least one adjustable rod piston (16) in such a way that a first volume of the first partial volume (12a) can be varied by means of a displacement of the first piston wall (14a), and the second partial volume (12b) is delimited by a second piston wall (14b) of the at least one adjustable rod piston (16) in such a way that a second volume of the second partial volume (12b) can be varied by means of a displacement of the second piston wall (14b); wherein the first partial volume (12a) is hydraulically connected to the brake fluid reservoir (24), wherein the first brake circuit (28) is hydraulically connected to the first partial volume (12a), and wherein the brake system comprises a valve device (38), wherein the second partial volume (12b) is connected to the brake fluid reservoir (24) and at least to the first brake circuit (28) via at least one partial component of the valve device (38), characterized by , that the valve device (38) is mechanically designed such that a pressure build-up in the second partial volume (12b) up to a limit pressure mechanically predetermined in the valve device (38) can be effected by means of the displacement of the second piston wall (14b), wherein a pressure threshold for a pressure difference between a pressure in the second partial volume (12b) and a brake circuit pressure in the first brake circuit (28) is mechanically defined such that, when the pressure threshold is exceeded, brake fluid can be transferred via at least the respective subcomponent (38a, 80, 112b) of the valve device (38) at least into the first brake circuit (28) until either the pressure threshold is undershot due to an increase in the brake circuit pressure or the limit pressure in the second partial volume (12b) is reached,wherein, despite a further displacement of the second piston wall (14b), an exceeding of the limit pressure in the second partial volume (12b) is prevented by a brake fluid transfer from the second partial volume (12b) into the brake fluid reservoir (24). [10] Brake system according to claim 9, wherein the brake system comprises an electrically controllable valve (36) via which the second partial volume (12b) is connected to the brake fluid reservoir (24) in such a way that when the electrically controllable valve (36) is in its open state, the second partial volume (12b) is depressurized despite the displacement of the second piston wall (14b) and when the electrically controllable valve (36) is in its closed state, the pressure build-up up to the limit pressure mechanically predetermined in the valve device (38) can be effected by means of the displacement of the second piston wall (14b). [11] Brake system according to claim 9 or 10, wherein the master brake cylinder (10) comprises a second pressure chamber (18) and a floating piston (20) adjustably arranged between the first partial volume (12a) of the first pressure chamber (12) and the second pressure chamber (18), and wherein a second brake circuit (32) is hydraulically connected to the second pressure chamber (18). [12] Brake system according to claim 11, wherein the second partial volume (12b) is additionally connected to the second brake circuit (32) via at least one further partial component (38c, 80, 112c) of the valve device (38) in such a way that brake fluid can be transferred into the second brake circuit (32) via at least the further partial component (38c, 80, 112c) of the valve device (38). [13] Brake system according to one of claims 9 to 12, wherein the master brake cylinder (10) has a stepped bore within which at least the first pressure chamber (12) is formed, and wherein the master brake cylinder (10) comprises a stepped piston (16) as the at least one adjustable rod piston (16), which delimits the first partial volume (12a) with the first piston wall (14a) and the second partial volume (12b) with the second piston wall (14b). [14] Brake system according to one of claims 9 to 13, wherein the valve device (38) comprises as a subcomponent (38b) an overpressure relief valve (38b), via which the second partial volume (12b) can be connected to the brake fluid reservoir (24), and as a subcomponent (38a) at least one check valve (38a), via which the second partial volume (12b) can be connected at least to the first brake circuit (28). [15] Brake system according to one of claims 9 to 13, wherein the valve device (38) comprises as subcomponent (112a) a controlled check valve (112a), via which the second partial volume (12b) is connected to the brake fluid reservoir (24), and as subcomponent (112b) at least one check valve (112b), via which the second partial volume (12b) is connected at least to the first brake circuit (28). [16] Braking system according to one of claims 9 to 15, wherein the braking system comprises a power braking device (44). [17] Brake system according to claim 16, wherein the valve device (38) comprises as a subcomponent (38b) an overpressure relief valve (38b), via which the second partial volume (12b) is connected to the brake fluid reservoir (24), and as a subcomponent (80) at least one lip seal (80) of the external power brake device (44) designed as a plunger (44). [18] Braking system according to one of claims 9 to 17, wherein the braking system comprises a control device which is designed to control at least one component (36) of the braking system in normal mode such that the pressure build-up up to the limit pressure mechanically predetermined in the valve device (38) can be effected by means of the displacement of the second piston wall (14b) in the second partial volume (12b).

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