Master brake cylinder for a vehicle braking system and method for operating a master brake cylinder

Abstract

Master brake cylinder (10) for a braking system of a vehicle with: a first filling volume (12) that can be filled with liquid, the first size of which can be varied by adjusting at least one first piston wall (14); a second filling volume (16) that can be filled with liquid, the second size of which can be varied by adjusting at least one second piston wall (18); and a valve assembly (20, 20a, 20b); wherein the first filling volume (12) is connected to the second filling volume (16) via the valve assembly (20, 20a, 20b) in such a way that when the valve assembly (20, 20a, 20b) is controlled into a first valve state, a common first pressure chamber pressure is present in the first filling volume (12) and in the second filling volume (16); characterized by the fact that When the valve assembly (20, 20a, 20b) is in the first valve state, the braking volume of a first pressure chamber of the master brake cylinder (10) comprises at least the first filling volume (12) and the second filling volume (16), while when the valve assembly (20, 20a, 20b) is in a second valve state, the braking volume of the first pressure chamber comprises at least the first filling volume (12) and is separated from the second filling volume (16), wherein the braking force-brake pressure ratio in the first valve state is smaller than in the second valve state.

Description

[0001] The invention relates to a master brake cylinder for a vehicle's braking system. The invention also relates to a brake device for a vehicle's braking system and a braking system for a vehicle. Furthermore, the invention relates to a method for operating a master brake cylinder. State of the art

[0002] WO 2009 / 121645 A1 describes a hydraulic vehicle braking system. The master brake cylinder of the hydraulic vehicle braking system comprises a first pressure chamber and a second pressure chamber. Additionally, the master brake cylinder has an integrated pedal travel simulator 22 at an end that widens towards the brake pedal. The volume of this simulator that can be filled with brake fluid is hydraulically connected to a brake fluid reservoir via a simulator valve. The brake fluid-fillable volume of the pedal travel simulator and the adjacent first pressure chamber are delimited by a rod and simulator piston designed as a stepped piston.

[0003] US 5 970 710 A shows a master brake cylinder for a vehicle's hydraulic braking system.

[0004] US 6 226 993 B1 reveals a hydraulic brake booster or a master brake cylinder unit. Disclosure of the invention

[0005] The invention provides a master brake cylinder for a vehicle braking system with the features of claim 1, a brake device for a vehicle braking system with the features of claim 5, a brake system for a vehicle with the features of claim 10 and a method for operating a master brake cylinder with the features of claim 11. Advantages of the invention

[0006] The invention provides a master brake cylinder whose first pressure chamber, in a first operating mode of the master brake cylinder, can comprise at least a first filling volume and a second filling volume, wherein the size of each of the two filling volumes can be varied by adjusting the piston wall associated with it. However, the master brake cylinder can also be operated in a second operating mode in which the first pressure chamber comprises at least the first filling volume, while a reservoir pressure, in particular atmospheric pressure, is present in the second filling volume. This can also be described as selectively switching the second filling volume on and off. Thus, the size of the first pressure chamber of the advantageous master brake cylinder can be variably determined not only by adjusting the piston walls that limit the filling volumes, but also by switching the second filling volume on and off.

[0007] As explained in more detail below, by shutting off the second filling volume, or by adjusting the reservoir pressure in the second filling volume, the braking effect in the first pressure chamber of the master cylinder can be intensified. Thus, due to the reduction in the available volume of the first pressure chamber, a given braking force (driver's braking force) results in increased brake pressure. This can also be described as an increase in the braking force-brake pressure ratio by reducing the braking volume of the first pressure chamber.

[0008] The present invention thus enables switching the hydraulic transmission (braking force and pressure transmission), by means of which, in the event of a brake booster failure, a greater pressure build-up can be achieved in the braking volume of the first pressure chamber with a given pedal force. In this way, a higher deceleration for the rapid braking of a vehicle with a comparatively low driver braking force can also be achieved. For example, by switching off the second filling volume, a deceleration of at least 2.44 m / s² can be achieved despite a brake booster failure with a driver braking force (pedal force) of 500 N. 2 This can be achieved. Furthermore, the invention allows the master brake cylinder to be designed without regard to the deceleration still achievable in the event of a failure of the brake booster device.

[0009] Despite the ability to switch the second filling volume on and off, a favorable brake actuation feel (pedal feel) and a good volume balance of the master brake cylinder are still guaranteed.

[0010] A further advantage of the present invention is that a deceleration of at least 6.44 m / s² is possible. 2 The invention achieves a driver braking force of 500 N even with the ignition key removed, which is feasible for a large number of vehicles currently on the market. The deceleration can also be achieved (without the need for a wake-up function) in a "sleeping" brake system. Furthermore, the present invention reduces the complexity of many electric brake boosters and the systems equipped with them.

[0011] The present invention can be easily integrated as an additional component in a (hydraulic) braking system. The invention provides an advantageous, electrically or mechanically switchable fallback system in the event of a malfunction of a brake booster device, such as a brake booster failure. However, it should be noted that the applicability of the present invention is not limited to merely compensating for the malfunction of the brake booster device. Brief description of the drawings

[0012] Further features and advantages of the present invention are explained below with reference to the figures. They show: Fig. 1 a schematic representation of a first embodiment of the master brake cylinder; Fig. 2 a schematic representation of a second embodiment of the master brake cylinder; Fig. 3a and Fig. 3b a schematic overall representation and an enlarged partial representation of an embodiment of the braking system; Fig. 4 a schematic representation of a first embodiment of the braking device; Fig. 5 a schematic representation of a second embodiment of the braking device; and Fig. 6 a flowchart to illustrate an embodiment of the method for operating a master brake cylinder. Embodiments of the invention

[0013] Fig. Figure 1 shows a schematic representation of a first embodiment of the master brake cylinder.

[0014] The in Fig. A schematic representation of a master brake cylinder 10 is used in a vehicle's braking system. The master brake cylinder 10 has a first filling volume 12, which can be filled with fluid and whose volume can be varied by adjusting at least one piston wall 14. The master brake cylinder 10 also has a second filling volume 16, which can be filled with fluid and whose volume can likewise be varied by adjusting at least one piston wall 18. The first filling volume 12 is hydraulically connected to the second filling volume 16 via a valve assembly 20 such that when the valve assembly 20 is controlled to a first valve position, a common pressure chamber pressure exists in both the first filling volume 12 (as the first internal pressure) and the second filling volume 16 (as the second internal pressure).

[0015] The second filling volume 16 can be connected to a brake fluid reservoir 22 via the valve assembly 20 in such a way that when the valve assembly 20 is controlled to a second valve state, the reservoir pressure present in the brake fluid reservoir 22 is present in the second filling volume 16. During the control of the valve assembly 20 to the second valve state, a first internal pressure, differing from the reservoir pressure, can be introduced into the first filling volume 12. The reservoir pressure of the brake fluid reservoir 22 can, in particular, be atmospheric pressure.

[0016] The master brake cylinder 10 thus has a first pressure chamber which, when the valve assembly 20 is controlled to the first valve state, comprises at least the first filling volume 12 and the second filling volume 16. In contrast, when the valve assembly 20 is controlled to the second valve state, the first pressure chamber of the master brake cylinder 10 comprises at least the first filling volume 12, wherein a first internal pressure that differs from the reservoir pressure (present in the second filling volume 16) can be controlled in the first filling volume 12 (by adjusting the first piston wall 14).

[0017] Controlling the valve assembly 20 to the first or second valve state thus activates or deactivates the second filling volume 16 to the first pressure chamber of the master brake cylinder 10. By activating or deactivating this second filling volume 16, the volume of the first pressure chamber can be set / varied independently of the position of the piston walls 14 and 18. This can also be described as setting the settling volume of the first pressure chamber, whereby when the valve assembly 20 is in the first valve state, the settling volume of the first pressure chamber comprises (at least) the two filling volumes 12 and 16, while when the valve assembly 20 is in the second valve state, the settling volume of the first pressure chamber is separated from the second filling volume 16.

[0018] By shutting off the second filling volume 16, or by separating the braking volume of the first pressure chamber from the second filling volume 16, the braking force-brake pressure ratio (at least of the first pressure chamber) can be increased with respect to the ratio of a braking force exerted on the first piston wall 14, which limits the first filling volume 12, to a brake pressure built up in the first pressure chamber. Thus, after shutting off the second filling volume 16, a comparatively high brake pressure can be built up using a relatively small braking force exerted on the first piston wall 14. By shutting off the second filling volume 16, the deceleration resulting from the braking force / brake force can therefore be increased. By increasing the braking force-brake pressure ratio (at least of the first pressure chamber), a malfunction of a brake booster can, for example, be compensated for.However, the use of the master brake cylinder 10 described here is not limited to compensating for a failure of a brake booster.

[0019] Optionally, the master brake cylinder 10 can also have a second pressure chamber 24, into which a floating piston component 26 can be at least partially adjusted so that a second brake pressure present in the second pressure chamber 24 can be varied. However, it should be noted that the design of the master brake cylinder 10 described here is not limited to a tandem master brake cylinder. Thus, the master brake cylinder 10 can also comprise only a single (first) pressure chamber, the brake-in volume of which can be set / varied by means of the valve assembly 20.

[0020] The brake fluid reservoir 22, to which the second filling volume 16 can be connected via the valve assembly 20, can, for example, be a central brake fluid reservoir 22 to which the first filling volume 12, the second filling volume 16, and / or the second pressure chamber 24 are hydraulically connected via a vent hole 28. Likewise, a second brake fluid reservoir 22 can be used to selectively adjust the reservoir pressure in the second filling volume 16.

[0021] In an advantageous embodiment, the piston walls 14 and 18, which define the first filling volume 12 and the second filling volume 16, can be formed on a common piston component 30. In this case, the common piston component 30 is preferably designed as a stepped piston. The piston component 30 can have, at an inner end oriented towards a center of the master brake cylinder 10, a first piston section 30a with a first diameter d1 perpendicular to an adjustment direction 31 of the piston component 30, which is smaller than a second diameter d2 perpendicular to the adjustment direction 31 of a second piston section 30b of the piston component 30 adjacent to the first piston section 30a.

[0022] A sealing element 32, such as a sealing ring and / or a lip seal, can be arranged between the first piston section 30a of the piston component 30, which is designed as a stepped piston, and an adjacent wall of the master brake cylinder 10. This prevents unwanted fluid exchange between the two filling volumes 12 and 16 along the piston component 30. Alternatively or additionally, leakage of fluid from the master brake cylinder 10 can be prevented by a sealing element 32, which can also be a sealing ring and / or a lip seal, arranged between the second piston section 30b and the adjacent wall of the master brake cylinder 10.

[0023] Preferably, when the piston component 30 is designed as a stepped piston, the shape of the filling volumes 12 and 16 is adapted to the stepped piston. For example, a first inner diameter di1 of the first filling volume 12, oriented perpendicular to the adjustment direction 31 of the piston component 30, can correspond to the first diameter d1 of the first piston section 30a and twice the ring thickness of the sealing element 32, and / or a second inner diameter di2 of the second filling volume 16, oriented perpendicular to the adjustment direction 31, can correspond to the second diameter d2 of the second piston component 30 and twice the ring thickness of the sealing element 32.

[0024] However, it should be noted that the formation of the piston walls 14 and 18, which define the filling volumes 12 and 16, on a common piston component 30 is merely optional. Likewise, the first piston wall 14 can be formed on a (not shown) first piston, which is adjustable independently of a separately formed (not shown) second piston with the second piston wall 18.

[0025] The shape of the master brake cylinder 10 can also be selected with a great deal of design freedom. The design of two different inner diameters di1 and di2 on the master brake cylinder 10 is therefore merely an example.

[0026] The valve assembly 20 can be directly integrated into the master brake cylinder 10 via a line / hydraulic connection linking the two filling volumes 12 and 16. Alternatively, the valve assembly 20 can also be a component of a brake circuit 34, through which the two filling volumes 12 and 16 are hydraulically connected to at least one wheel brake caliper 36 via a supply port 38. However, if a hydraulic connection between the two filling volumes 12 and 16 is provided at the master brake cylinder 10, a supply port 38 for connecting one of the two filling volumes 16 to the first brake circuit 34 is not required.

[0027] It should be noted that the applicability of the master brake cylinder 10 described here is not limited to a brake system with a specific number of brake circuits 34 and 40 or a predetermined number of wheel brake calipers 36 and 42. Instead, the number of brake circuits 34 and 40 and wheel brake calipers 36 and 42 can be adapted to the intended use of the brake system.

[0028] In an advantageous embodiment, the valve assembly 20 is designed such that it is de-energized in the second valve state, while the valve assembly 20 can be controlled by energizing it from the second valve state to the first valve state. This can also be described as the valve assembly 20 being controllable by energizing it to the first valve state and by interrupting the energizing to the second valve state. Thus, the valve assembly 20 is controllable in a simple manner.

[0029] The master brake cylinder 10 can be operated together with a brake booster 46 in a braking device / braking system. In this case, an actuator 44 of the brake booster 46 is preferably designed to exert a brake assist force Fu on a booster body 48 of the brake booster 46 such that, by adjusting the booster body 48, the brake assist force Fu can be transmitted to the at least one piston of the piston walls 14 and 18. In this way, in addition to the driver braking force Fb transmitted via a linkage 50 from a brake actuation element (not shown), the brake assist force Fu can also be applied to the master brake cylinder 10. This relieves the driver when braking the vehicle.

[0030] Preferably, the valve assembly 20, which is de-energized in the second valve state, can be integrated into a common circuit (not shown) with the actuator 44 of the brake booster 46. In this case, it is ensured that if the power supply to the actuator 44 is impaired, the valve assembly 20 can be (automatically) controlled to the second valve state. This results in the (automatic) shutdown of the second filling volume 16, or the (automatic) disconnection of the second filling volume 16 from the first pressure chamber, if the power supply to the actuator 44 is impaired. In this way, the braking force-brake pressure transmission ratio can be (automatically) increased with respect to the transmission of a braking force exerted on the first piston wall 14, which limits the first filling volume 12, into a brake pressure built up in the first pressure chamber.

[0031] As an alternative or supplement to integrating the valve assembly 20 into a common circuit with the actuator assembly 44, the power supply to the valve orientation 20, which is de-energized in the second valve state, can also be interrupted if the brake assist force Fu fails or if the brake booster device 46 malfunctions. This results in the high braking force-brake pressure transmission ratio of the first pressure chamber of the master brake cylinder 10, as described above. Thus, the driver can achieve a sufficiently high brake pressure in at least one wheel brake cylinder 36 and 42 even with a comparatively low driver braking force Fb.

[0032] Fig. Figure 2 shows a schematic representation of a second embodiment of the master brake cylinder.

[0033] The in Fig. The brake device / brake system, or rather the master brake cylinder 10 contained therein, shown schematically in Figure 2, has, in addition to the components described above, a pressure relief valve 52, via which the valve assembly 20 is hydraulically connected to the brake fluid reservoir 22. The pressure relief valve 52 is designed such that fluid displacement from the brake fluid reservoir 22 via the pressure relief valve 52 to the valve assembly 20 is prevented even at a comparatively high pressure, while the pressure relief valve 52 opens on the outlet side of the valve assembly 20 at a relatively high pressure.

[0034] The pressure relief valve 52 allows the second filling volume 16 to be used when brake application begins in backup mode. This further increases the brake-on volume. It also allows for an increase in the deceleration achievable with maximum pedal travel.

[0035] Fig. 3a and Fig. Figure 3b shows a schematic overall representation and an enlarged partial representation of an embodiment of the braking system.

[0036] The in Fig. 3a The brake system, schematically represented, comprises the master brake cylinder 10, the brake fluid reservoir 22, at least one brake circuit 34 with at least one wheel brake caliper 36, the brake booster device 46, and an ESP device 54. A brake actuation element 56, such as a brake pedal, is arranged on the linkage 50 of the brake booster device 46. Furthermore, in Fig. Figure 3a shows a schematic representation of a vehicle battery 58, by means of which the actuator 44 of the brake booster 46 and the ESP device 54 can be supplied with power. A section 60 of the schematically represented brake circuit 34, which lies between the master brake cylinder 10 and the ESP device 54, is shown in Fig. 3b is shown enlarged.

[0037] As shown by the Fig. As can be seen in Figure 3b, the valve assembly 20 can also be arranged at a distance from the master brake cylinder 10 in the at least one brake circuit 34. For example, the valve assembly 20 can be arranged between a first line 62 leading to the second filling volume 16 and a second line 64 leading to the ESP device 54. A third line 66, which connects the first filling volume 12 to the ESP device 54, can open into the second line 64. The valve assembly 20 can be connected to the brake fluid reservoir 22 via a fourth line 68, which is only partially shown. Likewise, another reservoir can be connected to the fourth line 68.

[0038] Even with the valve assembly 20 arranged at a distance from the master brake cylinder 10, a failure of the brake booster device 46 can still be compensated by separating the second filling volume 16 from the first pressure chamber in such a way that a sufficiently high brake pressure can still be achieved in the first pressure chamber separated from the second filling volume 16 by means of a comparatively low braking force applied as driver braking force Fb.

[0039] It should be noted that a component already conventionally present in the brake system, such as at least one valve of the ESP device 54, can also be (co-)used for the valve assembly 20. Likewise, the valve assembly 20 can also be used by the ESP device 54. This multifunctional design of the valve assembly 20 can reduce manufacturing costs.

[0040] Furthermore, a standard / conventional master brake cylinder 10 can also be used for the advantageous braking system with an optionally adjustable break-in volume of the first pressure chamber. To realize the in the Fig. 3a and Fig. A cost-effective master brake cylinder can also be used in the brake system shown in 3b.

[0041] Fig. Figure 4 shows a schematic representation of a first embodiment of the braking device.

[0042] The in Fig. The brake unit shown schematically in Figure 4 can be used in a vehicle's braking system. The brake unit comprises the master brake cylinder 10 and the brake booster unit 46 with the components already described above. Optionally, the brake unit can also include a brake fluid reservoir 22.

[0043] At the in Fig. In the brake device shown schematically in Figure 4, the valve assembly 20a and 20b is arranged / connected to the amplifier body 48 of the brake booster device 46 such that the valve assembly 20a and 20b can be mechanically switched from the first valve state to the second valve state by means of the amplifier body 48. Optionally, the valve assembly 20a and 20b can also be mechanically switched from the second valve state to the first valve state by means of the amplifier body 48. The amplifier body 48 can be understood as a component of the brake booster device 46, which is adjustable by means of the brake support force Fu provided by the actuator 44 of the brake booster device 46. The actuator 44 can, for example, comprise a hydraulic or electromechanical device.The transmission of the brake support force Fu from the actuator 44 to the amplifier body 48 can be effected via at least one intermediate component. Likewise, or alternatively, the switching of the valve assembly 20a and 20b from at least the first valve state to the second valve state by the amplifier body 48 can also be effected via at least one intermediate component.

[0044] For example, to switch the valve assembly 20a and 20b, at least from the first valve state, the amplifier body 48 is arranged on the valve assembly 20a and 20b such that when the amplifier body 48 is in an initial position, the valve assembly 20a and 20b is in the second valve state, while moving the amplifier body 48 from the initial position by a minimum adjustment travel causes the valve assembly 20a and 20b to switch from the second valve state to the first valve state. In this case, the initial position of the amplifier body 48 is preferably a position in which the amplifier body 48 is in a position where the driver braking force Fb is zero and / or the brake assist force Fu is zero.

[0045] In this way, if the brake booster device 46 malfunctions, which typically results in the booster body 48 remaining in its initial position (despite a non-zero driver braking force), the valve assembly 20a and 20b can be (automatically) switched to the second valve state. The mechanical switching of the valve assembly 20a and 20b to the second valve state by means of the booster body 48 remaining in its initial position thus results (automatically) in an advantageously small brake-up volume in the first pressure chamber when the brake assist force Fu ceases.

[0046] In contrast, when the booster body 48 is moved from its initial position, which is generally due to the (full) functionality of the brake booster device 46, the (automatic) presence of the valve assembly 20a and 20b in the first valve state is ensured. With the brake booster device 46 functioning correctly, the first pressure chamber thus (automatically) has an advantageously large brake-in volume.

[0047] The valve assembly 20a and 20b can be assigned at least one pressure-exertion component 74 of the amplifier body 48. In this case, moving the amplifier body 48 out of its initial position can cause the at least one pressure-exertion component 74 to move as well. By moving the at least one pressure-exertion component 74, a mechanical pressure / force can be exerted on at least one (not shown) switching mechanism of the valve assembly 20a and 20b such that the at least one (not shown) switching mechanism of the valve assembly 20a and 20b is mechanically switched.

[0048] The advantageous operation of the mechanically switchable valve assembly 20a and 20b can also be described as follows: when the amplifier body 48 moves parallel to the piston component 30, i.e., at a constant distance a (equal to a minimum distance) to the piston component 30, it is in the first valve state. In contrast, a decrease in the pressure and / or force exerted on the valve assembly 20a and 20b by the at least one pressure-exercise component 74 causes the valve assembly 20a and 20b to switch into the second valve state.

[0049] At the in Fig. In the schematically represented embodiment 4, the valve assembly 20a and 20b comprises two mechanically switchable valve units 20a and 20b.

[0050] A first valve unit 20a is arranged in a hydraulic connection 70 between the first filling volume 12 and the second filling volume 16. A second valve unit 20b is formed in a further hydraulic connection 72 between the second filling volume 16 and the brake fluid reservoir 22. Each of the two valve units 20a and 20b is assigned a pressure application component 74 of the amplifier body 48.

[0051] In particular, the first valve state of the valve assembly 20a and 20b formed from the valve units 20a and 20b can be defined such that the first valve unit 20a is in a first open state, while the second valve unit 20b is in a second closed state. Furthermore, in the second valve state, the first valve unit 20a can be in a first closed state and the second valve unit 20b in a second open state. In this case, by moving the amplifier body 48 out of its initial position and simultaneously moving the at least one pressure-exercise component 74, the first valve unit 20a can be mechanically switched to the first closed state and the second valve unit 20b to the second open state.Moving the amplifier body 48 parallel to the piston component 30 (distance a equal to the minimum distance) controls the first valve unit 20a from the first open state to the first closed state and the second valve unit 20b from the second closed state to the second open state. Conversely, a decrease in pressure applied to both valve units 20a and 20b (distance a greater than the minimum distance) causes the first valve unit 20a to switch back from the first closed state to the first open state and the second valve unit 20b to switch back from the second open state to the second closed state.

[0052] However, it should be noted that the mechanically switchable design of the valve assembly 20a and 20b is not limited to its equipping with two separate valve subunits 20a and 20b.

[0053] Fig. Figure 5 shows a schematic representation of a second embodiment of the braking device.

[0054] The in Fig. Figure 5, schematically depicted, has a valve assembly 20 which is at least partially adjustable in conjunction with the piston component 30 and connected to the amplifier body 48 via a connecting component 76 such that the valve assembly 20 can be mechanically switched between the first and second valve states by means of a relative movement of the amplifier body 48 with respect to the piston component 30. For this purpose, the valve assembly 20 has a housing component designed to be adjustable in conjunction with the piston component 30. The connecting component 76 can, in particular, be connected to or integrally formed with at least one adjustable locking component of the valve assembly 20.

[0055] In the illustrated embodiment, at least one flow opening 78 is formed in the piston component 30, which connects the first filling volume 12 with the second filling volume 16. A hydraulic connection 80 from the brake fluid reservoir 22 to the second filling volume 16 can also open into the flow opening 78. Optionally, the valve assembly 20 has a first valve body 82, which seals a reduction 84 of the flow opening 78 in a first closed position, while when the first valve body 82 is in a first open position, fluid transfer between the two filling volumes 12 and 16 via the flow opening 78 is ensured.Furthermore, the valve assembly 20 can have a second valve body 86, which in a second closed position seals an outlet opening 88 of the hydraulic connection 80 of the brake fluid reservoir 22 to the second filling volume 16, while when the second valve body 86 is in a second flow position, a fluid transfer through the outlet opening 88 between the second filling volume 16 and the brake fluid reservoir 22 is possible.

[0056] The first valve body 82 and the second valve body 86 can be arranged such that, during a relative movement of the amplifier body 48 with respect to the piston component 30, they perform a common adjustment movement relative to the piston component 30 (at a constant distance from each other). Preferably, a common adjustment movement of the two valve bodies 82 and 86 relative to the piston component 30 in a counter-pressure direction 92 opposite to a braking direction 90 of the piston component 30 causes the first valve body 82 to move from its first flow position to the first closed position and the second valve body 86 to move from its second closed position to its second flow position.Accordingly, a joint adjustment movement of the two valve bodies 82 and 86 relative to the piston component 30 in the braking direction 90 can cause the first valve body 82 to move from its first closed position to its first open position and the second valve body 86 to move from its second open position to its second closed position. In this case, it is ensured that when the amplifier body 48 moves parallel to the piston component 30, the first valve body 82 is in its first open position and the second valve body 86 is in its second closed position. This can also be described as follows: if a minimum distance a is maintained between the piston component 30 and the amplifier body 48, the valve assembly 20 is in the first valve state due to the first open position of the first valve body 82 and the second closed position of the second valve body 86.Since the adjustability of the amplifier body 48 at the minimum distance a to the piston component 30 is generally only guaranteed if the brake booster device 46 is functioning correctly, the preferred position of the valve assembly 20 in the first valve state is reliably realized in this situation.

[0057] In contrast, the distance a generally increases when the driver braking force Fb is not zero and when the brake booster 46 malfunctions. This is caused by the adjustment movement of the two valve bodies 82 and 86 relative to the piston component 30 in the counter-pressure direction 92, as described above, due to their connection to the booster body 48 via the connecting component 76. Thus, due to the malfunction of the brake booster 46, the first valve body 82 is moved from its first open position to its first closed position, while the second valve body 86 is moved analogously from its second closed position to its second open position. This results in the advantageous reduction of the brake-in volume of the first pressure chamber of the master cylinder 10 to the first filling volume 12, or the isolation / shutdown of the second filling volume 16, as described above.

[0058] Although the present invention is described in the preceding paragraphs with reference to the master brake cylinder 10, whose piston component 30 (primary piston) acts on two independent volumes / filling volumes 12 and 16, the present invention is not limited to such a design of the master brake cylinder 10. Instead, the invention also includes differently designed master brake cylinders 10, the volumes of which can act on a brake circuit in combination or separately by means of the valve assembly 20.

[0059] If the valve assembly 20 is designed as an additional valve, standard master brake cylinders 10 can also be used to implement the present invention. Implementation of the invention by switching one or more mechanical valves is also possible.

[0060] Fig. Figure 6 shows a flowchart illustrating one embodiment of the method for operating a master brake cylinder.

[0061] The method described below can be carried out, for example, using one of the embodiments already described above. However, the feasibility of the method described here is not limited to the use of these embodiments.

[0062] In process step S1, the size of a pressure chamber of a master brake cylinder is set to at least one fluid-fillable first filling volume of the master brake cylinder, the size of which can be varied by adjusting at least one first piston wall, and to a fluid-fillable second filling volume of the master brake cylinder, the size of which can be varied by adjusting at least one second piston wall. This is achieved by opening a first hydraulic connection between the first filling volume and the second filling volume and closing a second hydraulic connection between the second filling volume and a brake fluid reservoir. Process step S1 can be carried out by a single-piece valve assembly or by a valve assembly consisting of several separately designed valve units.

[0063] In a further process step S2, the size of the pressure chamber is set to at least the first filling volume that can be filled with fluid, while simultaneously the second internal pressure in the second filling volume is adjusted to the reservoir pressure (atmospheric pressure). This is done by closing the first hydraulic connection between the first filling volume and the second filling volume and opening the second hydraulic connection between the second filling volume and the brake fluid reservoir.

[0064] The procedure described above is not limited to executing process steps S1 and S2 in the specified order. Instead, process step S1 can also be executed before process step S1. Likewise, process steps S1 and S2 can be repeated any number of times.

[0065] The advantages already described above can be achieved by carrying out the procedure. A further description of these advantages is omitted here.

Claims

[1] Master brake cylinder (10) for a braking system of a vehicle with: a first filling volume (12) that can be filled with liquid, the first size of which can be varied by adjusting at least one first piston wall (14); a second filling volume (16) that can be filled with liquid, the second size of which can be varied by adjusting at least one second piston wall (18); and a valve assembly (20, 20a, 20b); wherein the first filling volume (12) is connected to the second filling volume (16) via the valve assembly (20, 20a, 20b) in such a way that when the valve assembly (20, 20a, 20b) is controlled into a first valve state, a common first pressure chamber pressure is present in the first filling volume (12) and in the second filling volume (16); characterized by , that When the valve assembly (20, 20a, 20b) is in the first valve state, the braking volume of a first pressure chamber of the master brake cylinder (10) comprises at least the first filling volume (12) and the second filling volume (16), while when the valve assembly (20, 20a, 20b) is in a second valve state, the braking volume of the first pressure chamber comprises at least the first filling volume (12) and is separated from the second filling volume (16), wherein the braking force-brake pressure ratio in the first valve state is smaller than in the second valve state. [2] Master brake cylinder (10) according to claim 1, wherein the second filling volume (16) can be connected to a brake fluid reservoir (22) via the valve assembly (20, 20a, 20b) in such a way that when the valve assembly (20, 20a, 20b) is controlled to the second valve state, a reservoir pressure present in the brake fluid reservoir (22) is present in the second filling volume (16), while a first internal pressure different from the reservoir pressure can be controlled in the first filling volume (12). [3] Master brake cylinder (10) according to claim 1 or 2, wherein the master brake cylinder (10) has a second pressure chamber (24) into which a floating piston component (26) can be adjusted at least partially so that a second pressure chamber pressure present in the second pressure chamber (24) can be varied. [4] Master brake cylinder (10) according to one of the preceding claims, wherein the valve assembly (20, 20a, 20b) can be controlled by energizing to the first valve state and by terminating the energizing to the second valve state. [5] Brake device for a vehicle braking system with: a master brake cylinder (10) according to one of the preceding claims; and a brake booster device (46); and / or a brake fluid reservoir (22). [6] Brake device according to claim 5, wherein the valve device (20, 20a, 20b) can be controlled by energizing it to the first valve state and by interrupting the energizing it to the second valve state, and wherein the energizing of the valve device (20, 20a, 20b) and an actuator device (44) of the brake booster device (46), via which a brake support force (Fu) can be provided, is carried out via a common circuit. [7] Brake device according to claim 5, wherein the valve device (20, 20a, 20b) is arranged on an amplifier body (48) of the brake booster device (46), which is adjustable by means of the brake support force (Fu) provided by the actuator device (44) of the brake booster device (46), such that the valve device (20, 20a, 20b) can be mechanically switched from the first valve state to the second valve state by means of the amplifier body (48). [8] Brake device according to claim 7, wherein a mechanical force can be exerted on at least one switching mechanism of the valve device (20, 20a, 20b) by means of at least one pressure application component (74) of the amplifier body (48) of the brake booster device (46) such that the at least one switching mechanism of the valve device (20, 20a, 20b) can be mechanically switched. [9] Brake device according to claim 7, wherein the valve assembly (20, 20a, 20b) has a housing component designed to be adjustable together with a piston component (30) of the master brake cylinder (10) and at least one adjustable locking component (82, 86) of the valve assembly (20, 20a, 20b) is connected to the amplifier body (48) of the brake booster device (46) via a connecting component (76). [10] Braking system for a vehicle with at least one brake circuit (34, 40); and a master brake cylinder (10) according to one of claims 1 to 4; or a braking device according to one of claims 5 to 7. [11] Method for operating a master brake cylinder (10) comprising the steps: Setting the size of a brake-in volume of a pressure chamber of the master brake cylinder (10) to at least one fluid-fillable first filling volume (12) of the master brake cylinder (10), the first size of which is varied by adjusting at least one first piston wall (14), and to a fluid-fillable second filling volume (16) of the master brake cylinder (10), the second size of which is varied by adjusting at least one second piston wall (18), by opening a first hydraulic connection between the first filling volume (12) and the second filling volume (16) and preventing a second hydraulic connection between the second filling volume (16) and a brake fluid reservoir (22); and Setting the size of the braking volume of the pressure chamber to at least the first filling volume (12) that can be filled with fluid by preventing the first hydraulic connection between the first filling volume (12) and the second filling volume (16) and enabling the second hydraulic connection between the second filling volume (16) and the brake fluid reservoir (22), thereby separating the braking volume of the first pressure chamber from the second filling volume (16) and increasing the braking force-brake pressure ratio.

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