Braking system for a vehicle

Abstract

Braking system for a vehicle with: a master brake cylinder (10); at least one brake circuit (12a, 12b) with at least one wheel brake cylinder (14a to 14d); and a motorized piston-cylinder device (16) which is connected via at least one control valve (18a to 18d) to the single wheel brake cylinder of the brake system or to at least one of the wheel brake cylinders (14a to 14d) of the brake system in such a way that, if the at least one control valve (18a to 18d) is at least partially open, brake fluid can be transferred from the motorized piston-cylinder device (16) through the at least one control valve (18a to 18d) to the at least one wheel brake cylinder (18a to 18d) connected to the motorized piston-cylinder device (16) by means of operation of the motorized piston-cylinder device (16); characterized by the fact that Each wheel brake cylinder (14a to 14d) connected to the motorized piston-cylinder assembly (16) is connected exclusively via one valve-free line path (20a to 20d) to the single control valve of the brake system or to at most one of the control valves (18a to 18d) of the brake system, wherein the control valve (18a to 18d) connected to the respective wheel brake cylinder (14a to 14d) via the at least one valve-free line path (20a to 20d) is connected exclusively via at least one further valve-free line path (22) to the motorized piston-cylinder assembly (16).

Description

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

[0002] German patent DE 10 2011 004 983 A1 describes a vehicle braking system with a master brake cylinder and a brake pressure equalization device in the form of a tandem cylinder. Each wheel brake cylinder of the braking system is assigned one wheel inlet valve and one wheel outlet valve. Two of the wheel inlet valves are connected to the master brake cylinder via a first solenoid valve and to the brake pressure equalization device via a second solenoid valve.

[0003] Furthermore, DE 10 2016 211 982 A1 and DE 36 24 344 C2 each disclose a braking system with an electronically controlled pressure source for increasing the respective brake pressure in wheel brake cylinders of the respective braking system. Disclosure of the invention

[0004] The invention provides a braking system for a vehicle with the features of claim 1. Advantages of the invention

[0005] The present invention provides braking systems in which the brake pressure present in the at least one wheel brake cylinder can be adjusted independently of at least one internal pressure in the master brake cylinder by means of the operation of the motorized piston-cylinder assembly. Optionally, the brake pressure in the at least one wheel brake cylinder can be set independently of the motorized piston-cylinder assembly by means of the master brake cylinder (i.e., by actuating a brake actuator by the driver and / or by means of a brake booster), or it can be reduced / increased independently of the master brake cylinder by means of the operation of the motorized piston-cylinder assembly. Simultaneously, the hydraulic resistance that must be overcome to move brake fluid between the motorized piston-cylinder assembly and the at least one wheel brake cylinder connected to it is reduced in these braking systems.Each of the brake systems according to the invention has a valve arrangement in which, for the transfer of brake fluid between the motorized piston-cylinder device and the at least one wheel brake cylinder connected thereto, essentially only the hydraulic resistance of an intervening control valve needs to be overcome. Due to the advantageous valve arrangement of the brake systems according to the invention, reduced hydraulic losses result when reducing / increasing the brake pressure in the at least one wheel brake cylinder connected to the motorized piston-cylinder device by means of operating the motorized piston-cylinder device.

[0006] The motorized piston-cylinder assembly of the braking systems according to the invention therefore does not need to be equipped with a high-performance motor or with a transmission suitable for interaction with a high-performance motor. A variety of motorized piston-cylinder assemblies are therefore suitable for the braking systems according to the invention; these are inexpensive to manufacture, consume little energy, and require little installation space. The braking systems according to the invention are therefore inexpensive to manufacture and easy to install on a vehicle, such as a hybrid or electric vehicle.

[0007] Preferably, during operation of the motorized piston-cylinder device, the transfer of brake fluid from the motorized piston-cylinder device to the single connected wheel brake cylinder, or to at least one of the connected wheel brake cylinders, can be controlled exclusively by the single control valve of the brake system, or by at most one of the control valves of the brake system. The hydraulic power required for such a transfer of brake fluid, which is generally largely determined by throttling losses at each valve through which the fluid flows, is therefore particularly low in this case.The fact that only the respective control valve needs to be flowed through for the displacement of brake fluid is therefore an advantageous innovation compared to the conventional need to flow through at least two valves connected in series in order to vary a brake pressure in at least one wheel brake cylinder by means of a pressure equalization device.

[0008] For example, only the single wheel brake cylinder of the brake system or one of the wheel brake cylinders of the brake system is connected to the motorized piston-cylinder assembly, wherein the wheel brake cylinder connected to the motorized piston-cylinder assembly is connected to the single control valve of the brake system exclusively via the valve-free line path, and wherein the single control valve is connected to the motorized piston-cylinder assembly exclusively via the further valve-free line path.

[0009] Alternatively, several wheel brake cylinders of the brake system connected to the motorized piston-cylinder assembly can be connected exclusively to the brake system's at least one control valve via their respective valve-free lines, with the at least one control valve of the brake system being connected to the motorized piston-cylinder assembly exclusively via at least one other line. In both cases, only one control valve needs to be flowed through per wheel brake cylinder in which a brake pressure increase or decrease is desired. The requirements regarding the flow capacity of the respective control valve are thus reduced. This eliminates the need for the development of control valves that meet high flow capacity requirements.

[0010] Advantageously, the braking system has exactly one assigned control valve for each wheel brake cylinder connected to the motorized piston-cylinder assembly. During operation of the motorized piston-cylinder assembly, the transfer of brake fluid from the assembly to the respective wheel brake cylinder can be controlled exclusively by means of the assigned control valve. Since the control valves assigned to each wheel brake cylinder only need to meet relatively low requirements regarding their flow capacity, assigning one control valve to each wheel brake cylinder connected to the motorized piston-cylinder assembly hardly increases the cost or installation space required for the braking system.The invention thus provides a cost-effective and space-saving way to assign exactly one control valve to several wheel brake cylinders, whereby the brake pressure present in the associated wheel brake cylinders can be adjusted individually for each wheel during operation of the motorized piston-cylinder device.

[0011] In particular, the braking system can have exactly one assigned control valve for each wheel brake cylinder, as well as at least one control valve. Individual pressure adjustment for each wheel is therefore possible by means of operating the motorized piston-cylinder device for all wheel brake cylinders of the braking system / wheels of the vehicle equipped with it.

[0012] For example, the at least one control valve can be a shut-off valve and / or a continuously controllable valve. Therefore, a wide variety of different valve types can be used as the at least one control valve.

[0013] In an advantageous further development of the brake system, the single wheel brake cylinder of the brake system, or at least one of the wheel brake cylinders of the brake system, is connected to a brake fluid reservoir via at least one wheel outlet valve. Brake pressure reduction in the at least one wheel brake cylinder connected to the brake fluid reservoir can thus be carried out quickly and reliably, without the need to design the motorized piston-cylinder device for extracting brake fluid from the respective wheel brake cylinder.

[0014] The single wheel exhaust valve of the brake system, or at least one of the wheel exhaust valves of the brake system, can be a continuously controllable wheel exhaust valve. Alternatively or additionally, at least one isolating valve can be used for the at least one wheel exhaust valve of the brake system. The at least one control valve and the at least one wheel exhaust valve of the brake system can also be of the same type. Using this concept of uniformity results in cost advantages when equipping the brake system with the at least one control valve and the at least one wheel exhaust valve.

[0015] In a further advantageous embodiment, the braking system can also include a control device by means of which the motorized piston-cylinder assembly and the at least one control valve of the braking system can be controlled. In this case, the control device can be integrated into a common housing together with the braking system.

[0016] Preferably, the control device is designed for sequential control of the motorized piston-cylinder assembly and the control valves of the brake system. In this case, individual brake pressure adjustment in the wheel brake cylinders connected to the control valves can be easily and reliably implemented. Brief description of the drawings

[0017] 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 braking system; and Fig. 2 a schematic representation of a second embodiment of the braking system. Embodiments of the invention

[0018] Fig. Figure 1 shows a schematic representation of a first embodiment of the braking system.

[0019] The in Fig. One schematically depicted braking system can be used in a vehicle / motor vehicle, such as a hybrid or electric vehicle. It should be noted that the applicability of the braking system is not limited to a specific vehicle type.

[0020] The braking system has a master brake cylinder 10 and at least one brake circuit 12a and 12b with at least one wheel brake cylinder 14a to 14d. The in Fig. The depicted configuration of the master brake cylinder 10 as a tandem master brake cylinder 10 is only to be interpreted as an example. For instance, instead of the sketched two-chamber master brake cylinder 10, a three-chamber master brake cylinder (with pre-filling function) could also be used in the brake system. The equipment of the brake system of Fig. The example shown here is for illustrative purposes only: 1 with two brake circuits 12a and 12b, each with two wheel brake cylinders 14a to 14d. The configuration of the brake system is not limited to a specific number of brake circuits 12a and 12b or wheel brake cylinders 14a to 14d. Furthermore, a brake system with exactly four wheel brake cylinders 14a to 14d can have either a parallel brake circuit distribution (II brake circuit distribution) or an X brake circuit distribution on the vehicle equipped with this system.

[0021] The braking system also includes a motorized piston-cylinder device 16. The motorized piston-cylinder device 16 can be understood to be a device comprising an adjustable piston connected via a thread to an (external or internal) motor of the motorized piston-cylinder device 16. Preferably, the piston is linearly adjustable along a predetermined straight line by means of the motor. In particular, the piston can be selectively adjustable in two directions by means of operation of the motorized piston-cylinder device 16. The motorized piston-cylinder device 16 can, for example, be an electromechanical plunger. It should be noted that the motorized piston-cylinder device 16 is not a pump.

[0022] The motorized piston-cylinder assembly 16 is connected to at least one of the wheel brake cylinders 14a to 14d of the brake system via at least one control valve 18a to 18d. The connection of the motorized piston-cylinder assembly 16 via the at least one control valve 18a to 18d to the at least one of the wheel brake cylinders 14a to 14d is designed such that, provided that the at least one control valve 18a to 18d is at least partially open, brake fluid can be transferred from the motorized piston-cylinder assembly 16 to the at least one wheel brake cylinder 14a to 14d connected to the motorized piston-cylinder assembly 16 by means of its operation.In particular, if the at least one control valve 18a to 18d is at least partially open, brake fluid can also be transferred from the at least one wheel brake cylinder 14a to 14d connected to the motorized piston-cylinder device 16 into the motorized piston-cylinder device 16 by means of operation of the motorized piston-cylinder device 16.

[0023] Each wheel brake cylinder 14a to 14d connected to the motorized piston-cylinder assembly 16 is connected exclusively via one valve-free line 20a to 20d to the single control valve of the brake system or to at most one of the control valves 18a to 18d of the brake system. (The number of valve-free lines 20a to 20d can be equal to the number of control valves 18a to 18d through which each connected wheel brake cylinder 14a to 14d is connected to the motorized piston-cylinder assembly 16.) The control valve 18a to 18d connected to the respective wheel brake cylinder 14a to 14d via at least one valve-free line 20a to 20d is connected exclusively to the motorized piston-cylinder assembly 16 via at least one further valve-free line 22. The valve-free pipeline routes 20a to 20d and 22 are understood to be pipelines / pipe sections without a valve.It should be noted that one of the pipe routes 20a to 20d and 22 may also be composed of several interconnected pipes / pipe sections (all without a valve). The valve-free pipe routes 20a to 20d and 22 may merge into one another or branch off into separate pipe sections.

[0024] Each connected wheel brake cylinder 14a to 14d is thus connected to the motorized piston-cylinder assembly 16 in such a way that a hydraulic connection extends between the motorized piston-cylinder assembly 16 and each of these wheel brake cylinders 14a to 14d, along which only a single control valve 18a to 18d flows. Therefore, the hydraulic power required to transfer brake fluid from the motorized piston-cylinder assembly 16 to the at least one connected wheel brake cylinder 14a to 14d is comparatively low. (As a rule, the required hydraulic power results primarily from the throttling losses at the single control valve 18a to 18d per hydraulic connection.) The motorized piston-cylinder assembly 16 thus requires only a less powerful and therefore smaller motor (as a drive motor) compared to the prior art.The gearbox of the motorized piston-cylinder device 16, which interacts with the motor, can also be smaller and lighter. The motorized piston-cylinder device 16 can therefore be designed cost-effectively with less weight and a smaller installation space requirement. A control device 24 for actuating the motorized piston-cylinder device 16, described in more detail below, can also be designed so simply that its installation space requirement and manufacturing costs are low. Furthermore, due to the relatively low hydraulic power required, the operation of the motorized piston-cylinder device 16 consumes less energy than is typical in the prior art, even under highly dynamic operating conditions.

[0025] During operation of the motorized piston-cylinder device 16, the displacement of brake fluid from the motorized piston-cylinder device 16 into at least one of the connected wheel brake cylinders 14a to 14d can be controlled exclusively by means of the single control valve of the brake system or by means of at most one of the control valves 18a to 18d of the brake system. Thus, only the respective control valve 18a to 18d is subject to brake fluid flow for such a displacement. Even for highly dynamic brake pressure build-up, the requirements regarding the permeability of the respective control valve 18a to 18d are therefore comparatively low. The at least one control valve 18a to 18d can, in particular, be a simple valve, such as a shut-off valve (switching valve) and / or a continuously controllable valve (continuously adjustable valve, control valve).If the brake system is equipped with several control valves 18a to 18d, these can also be configured as a combination of isolating valves (switching valves) and continuously controllable valves (continuously adjustable valves, control valves). For example, isolating valves can be used as control valves 18a to 18d on a first axle (e.g., a front axle), and continuously controllable valves can be used as control valves 18a to 18d on a second axle (e.g., a rear axle).

[0026] In the embodiment of the Fig. 1. Each control valve 18a to 18d is a directional control valve with two switching positions. However, it should be noted that the in Fig. The control valves 18a to 18d shown in Figure 1 are only one possible example.

[0027] The at least one wheel brake cylinder 14a to 14d connected to the motorized piston-cylinder assembly 16 can additionally be connected to the master brake cylinder 10 via at least one switching valve 26a to 26d. This allows the motorized piston-cylinder assembly 16 to be arranged in parallel with the master brake cylinder 10. Therefore, after the at least one switching valve 26a to 26d is closed and the at least one control valve 18a to 18d is opened, the brake pressure present in the at least one connected wheel brake cylinder 14a to 14d can be adjusted by operating the motorized piston-cylinder assembly 16 independently of the internal pressure in the master brake cylinder 10. The brake system thus exhibits full volume blending capability.In contrast, after closing the at least one control valve 18a to 18d and opening the at least one switching valve 26a to 26d, the brake pressure present in the at least one wheel brake cylinder 14a to 14d can be varied by actuating a brake actuation element 28 (e.g., a brake pedal) connected to the master brake cylinder 10 and / or by means of a (not shown) brake booster.

[0028] Furthermore, by closing only some of the control valves 18a to 18d and only some of the switching valves 26a to 26d, it can be ensured that the driver can apply the brakes via the master brake cylinder 10 into some of the wheel brake cylinders 14a to 14d, while the brake pressure in other wheel brake cylinders 14a to 14d is adjustable by means of the piston-cylinder device 16.

[0029] The braking system of Fig. 1. Several wheel brake cylinders 14a to 14d are connected to the motorized piston-cylinder assembly 16 (exclusively via the respective valve-free line path 20a to 20d) and to the at least one control valve 18a to 18d. Furthermore, the at least one control valve 18a to 18d is connected to the motorized piston-cylinder assembly 16 exclusively via the additional valve-free line path 22. The brake system of the Fig. 1 has exactly one assigned control valve 18a to 18d for each wheel brake cylinder 14a to 14d connected to the motorized piston-cylinder assembly 16. During operation of the motorized piston-cylinder assembly 16, the movement of brake fluid from the motorized piston-cylinder assembly 16 to the respective wheel brake cylinder 14a to 14d can therefore only be controlled by means of the assigned control valve 18a to 18d.

[0030] Specifically, the braking system of the Fig. 1. For each of its wheel brake cylinders 14a to 14d, exactly one assigned control valve 18a to 18d is provided as at least one control valve 18a to 18d. This allows the brake pressures in all wheel brake cylinders 14a to 14d to be individually adjusted by means of the operation of the motorized piston-cylinder device 16.

[0031] In the brake system equipped with four wheel brake cylinders 14a to 14d, a volume flow generated by the motorized piston-cylinder assembly 16 is distributed directly to the four wheel brake cylinders 14a to 14d, with the hydraulic resistance to be overcome being determined essentially solely by the four parallel control valves 18a to 18d. This is an advantage over the prior art, in which such a volume flow generally has to be driven by at least two valves connected in series. (Conventionally, such a volume flow often has to be driven by at least one valve per brake circuit 12a and 12b and one wheel inlet valve for each wheel brake cylinder 14a to 14d.) The in Fig. The brake system described in 1 thus exhibits, compared to the prior art, an easier transfer of brake fluid from the motorized piston-cylinder device 16 to its wheel brake cylinders 14a to 14d.

[0032] The braking system of Fig. 1. This can also be described as combining the function of the control valves 18a to 18d with that of the eliminated wheel intake valves. By eliminating wheel intake valves in the brake system, its weight and installation space requirements can be reduced. Furthermore, eliminating wheel intake valves makes the brake system cheaper to manufacture. By combining a wheel intake valve and a valve for connecting the motorized piston-cylinder assembly 16 into a control valve 18a to 18d, the flow requirements for each control valve 18a to 18d are halved (compared to the conventional valve used in addition to the wheel intake valve for connecting the motorized piston-cylinder assembly 16).

[0033] The braking system of Fig. Furthermore, at least one of the wheel brake cylinders 14a to 14d of the brake system is connected to a brake fluid reservoir 32 via at least one wheel outlet valve 30a to 30d. Specifically, each wheel brake cylinder 14a to 14d of the brake system is connected to the brake fluid reservoir 32 via one wheel outlet valve 30a to 30d. Each wheel / wheel brake cylinder 14a to 14d is thus assigned exactly one control valve 18a to 18d, one switching valve 26a and 26d, and one wheel outlet valve 30a to 30d.

[0034] The at least one wheel outlet valve 30a to 30d can, for example, be a continuously controllable / adjustable valve (control valve). However, at least one isolating valve can also be used instead of the at least one wheel outlet valve 30a to 30d. As explained in more detail below, the brake system can also be equipped without at least one wheel outlet valve 30a to 30d.

[0035] Optionally, the braking system of the Fig. 1. A simulator device 34 is also included, which is connected to at least one chamber of the master brake cylinder 10 via a simulator valve 36. After the switching valves 26a to 26d have closed and the simulator valve 36 has opened, the driver can engage the simulator device 34 by actuating the brake actuation element 28. Thus, despite the closing of the switching valves 26a to 26d to decouple the wheel brake cylinders 14a to 14d, the driver has a comfortable (standard) brake actuation feel (pedal feel).

[0036] The control device 24 mentioned above is designed to actuate the motorized piston-cylinder assembly 16 and the at least one control valve 18a to 18d of the brake system. Specifically, the control device 24 is designed for simultaneous actuation of the motorized piston-cylinder assembly 16 and the control valves 18a to 18d of the brake system. Optionally, the at least one switching valve 26a to 26d, the at least one wheel outlet valve 30a to 30d, and / or the simulator valve 36 can also be actuated / switched by means of the control device 24.

[0037] For example, the control device 24 can be configured to perform the advantageous function described below. The control device 24 can be supported by at least one pressure sensor 38, at least one brake actuation element sensor 40, and at least one sensor 42 of the motorized piston-cylinder unit 16. However, the configuration of the control device 24 described below is only optional. When the driver actuates the brake actuation element 28, the control device 24 can set at least one target brake pressure for at least one of the wheel brake cylinders 14a to 14d, taking into account the actuation force of the brake actuation element 28. To set the at least one defined target brake pressure in the at least one wheel brake cylinder 14a to 14d, the control device 24 can first control the at least one switching valve 26a to 26d and the at least one wheel outlet valve 30a to 30d to the closed position, while the simulator valve 36 is opened by the control device 24. Therefore, by actuating the brake actuation element 28, the driver only moves brake fluid via the open simulator valve 36 into the simulator device 34.Setting a target brake pressure corresponding to the driver's braking request in the at least one wheel brake cylinder 14a to 14d can be achieved by moving brake fluid into the at least one wheel brake cylinder 14a to 14d by means of the operation of the motorized piston-cylinder device 16.

[0038] If maintaining a constant brake pressure of a preset pressure, in particular a brake pressure of (nearly) zero, is desired in at least one of the wheel brake cylinders 14a to 14d, the at least one associated control valve 18a to 18d can remain closed during operation of the motorized piston-cylinder device 16. Otherwise, to set / achieve a specified target brake pressure, pressure can be selectively increased or decreased in the respective wheel brake cylinder 14b to 14d by operating the motorized piston-cylinder device 16, while the at least one control valve 18a to 18d associated with the respective wheel brake cylinder 14b to 14d is controlled to be open. (For pressure increase, the piston of the motorized piston-cylinder device 16 is moved in a pressure increase direction.)Likewise, pressure reduction can be achieved by adjusting the piston of the motorized piston-cylinder device 16 in a reverse direction opposite to the pressure build-up direction.

[0039] Furthermore, different non-zero brake pressures can also be achieved in the wheel brake cylinders 14a to 14d. In particular, different target brake pressures can be set sequentially in several wheel brake cylinders 14a to 14d by operating the motorized piston-cylinder device 16. During each setting, only the corresponding control valve 18a to 18d in exactly one of the different target brake pressures is held open by the control device 24 in exactly one of the wheel brake cylinders 14a to 14d, while the wheel brake cylinders 14b to 14d with differing target brake pressures remain decoupled from the motorized piston-cylinder device 16 by keeping their corresponding control valves 18b to 18d closed. Various pressure build-up strategies are possible in this process.

[0040] In one possible pressure build-up strategy, the highest specified target brake pressure can be built up first, followed by the lowest specified target brake pressure, in the respective wheel brake cylinders 14a to 14d using the motorized piston-cylinder device 16. However, this sequence for pressure setting in the wheel brake cylinders 14a to 14d is by no means fixed, but can be selected from a variety of different pressure build-up strategies. For example, a suitable pressure build-up strategy might involve a pressure reduction in one wheel brake cylinder 14a to 14d before a pressure build-up in another wheel brake cylinder 14a to 14d. Another suitable pressure build-up strategy involves building up the lowest specified target brake pressure in the respective wheel brake cylinders 14a to 14d first, followed by the highest specified target brake pressure in the respective wheel brake cylinders 14a to 14d.

[0041] Alternatively, different target brake pressures can be built up simultaneously in several wheel brake cylinders 14a to 14d by keeping only the respective wheel brake cylinder 14a to 14d constantly open while the highest target brake pressure is being built up using the motorized piston-cylinder device 16, and simultaneously setting at least one target brake pressure between zero and the highest target brake pressure in the respective wheel brake cylinder 14a to 14d by means of pulsed switching or delta-p control of the associated control valve 18a to 18d. (Optionally, at least one wheel outlet valve 30a to 30d can also be briefly opened for this purpose.)

[0042] If the working volume of the motorized piston-cylinder assembly 16 is exhausted during the realization of at least one target brake pressure, brake fluid can be drawn from the brake fluid reservoir 32 via a suction line 44 connected to the motorized piston-cylinder assembly 16. If, for this purpose, the piston of the motorized piston-cylinder assembly 16 is moved in a reverse direction opposite to the pressure build-up direction, the control valves 18a to 18d can be closed simultaneously.

[0043] Overloading of the motor or the transmission / transmission mechanism of the motorized piston-cylinder device 16 can be avoided, even with precise pressure settings, by not closing all control valves 18a to 18d simultaneously while the piston of the motorized piston-cylinder device 16 is being moved in the pressure build-up direction. Keeping at least one control valve 18a to 18d open during piston movement in the pressure build-up direction creates an elastic pressure chamber, thus preventing overloading of the motorized piston-cylinder device 16.

[0044] In the event of a malfunction or failure of the motorized piston-cylinder assembly 16, the driver can still apply the brakes to all wheel brake cylinders 14a to 14d by actuating the brake actuating element 28. In such a situation, the switching valves 26a to 26d can be controlled open by means of the control device 24, while the control valves 18a to 18d (and the simulator valve 36, if present) are kept closed. A wheel lockup can be resolved by briefly opening the switching valve 26a to 26d assigned to the respective wheel brake cylinder 14a to 14d.

[0045] Preferably, the at least one control valve 18a to 18d is at least a normally closed valve. If present in the brake system, at least one normally open valve is preferred for the at least one switching valve 26a and 26b, and / or at least one normally closed valve is preferred for the at least one outlet valve 30a to 30d and / or the simulator valve 36. In this case, in the event of a power supply failure to the brake system or a failure of the vehicle electrical system, the valves 18a to 18d, 26a and 26b, 30a to 30d, and / or 36 are automatically switched so that the driver can still brake directly into the wheel brake cylinders 14a to 14d. (Due to the advantageous design of valves 18a to 18d, 26a and 26b, 30a to 30d and / or 36, in such a situation valves 18a to 18d, 30a to 30d and 36 are automatically closed, while switching valves 26a to 26d remain open.In such a situation, one often speaks of a backup system. Due to the omission of a wheel inlet valve in the brake system, the hydraulic resistance of the brake system that the driver has to overcome in backup mode is also reduced. Even in backup mode, this makes it easier for the driver to apply pressure to the wheel brake cylinders 14a to 14d. Furthermore, this ensures a greater degree of freedom in the design of the surfaces of the master brake cylinder 10 (suitable for advantageous backup behavior) and in the design of at least one surface of the motorized piston-cylinder assembly 16 (suitable for volume absorption under all operating conditions). This also increases the design freedom in the construction of the brake system. Fig. 1.

[0046] In an advantageous embodiment, the control device 24 is further designed to detect a leak in at least one of the wheel brake cylinders 14a to 14d by controlling the motorized piston-cylinder device 16 and individual control valves 18a to 18d and comparing the resulting pressure build-up in the respective wheel brake cylinders 14a to 14d with at least one suitable test / comparison sample, and also to identify the at least one affected wheel brake cylinder 14a to 14d. The at least one affected wheel brake cylinder can then be shut off / disconnected by the control device 24 keeping the at least one switching valve 26a to 26d of the affected wheel brake cylinder 14a to 14d closed. This function is also possible during a partially active backup. Emergency operation of the brake system can thus be maintained despite the leak.Alternatively, in this case the control device 24 can also be designed to execute only a limited version of the wheel-specific pressure setting.

[0047] Fig. Figure 2 shows a schematic representation of a second embodiment of the braking system.

[0048] As can be seen from the braking system of the Fig. As can be seen in section 2, wheel outlet valves can be omitted entirely or on an axle-by-axle basis when designing the brake system. By omitting the wheel outlet valves (as well as the wheel inlet valves) at least on an axle-by-axle basis, the brake system can be manufactured to be lighter, more compact, and less expensive. (In particular, the weight and size of the brake system's hydraulic unit can be reduced in this way.) The brake system can thus be advantageously converted from an open to a closed system.

[0049] Especially when the motor of the motorized piston-cylinder assembly 16 is capable of highly dynamic operation, wheel exhaust valves can be omitted in the respective brake system. During ABS control, the brake pressures in the individual wheel brake cylinders 14a to 14d can be adjusted sequentially. The volume in the brake system is therefore known at all times. Consequently, the working volume of the motorized piston-cylinder assembly 16 cannot be exhausted under normal operating conditions.

[0050] In particular, if the motorized piston-cylinder device 16 is fast enough for sequentially adjusting the brake pressures in the wheel brake cylinders 14a to 14d, wheel outlet valves can be omitted entirely. Brake systems are also possible in which the wheel outlet valves are only located on a first axle (e.g., the front axle), while the sequential brake pressure adjustment is only performed on the second axle (e.g., the rear axle).

[0051] The braking system of the Fig. Version 2 offers a combination of parallel pressure generation with multiplex wheel modulation. The brake actuation and wheel pressure modulation components can be partially or fully integrated to almost any degree.

[0052] The brake systems described above have exactly four wheel brake cylinders 14a to 14d and four control valves 18a to 18d, each of the wheel brake cylinders 14a to 14d being connected to the motorized piston-cylinder assembly 16 via exactly one of the control valves 18a to 18d.

[0053] The braking systems described above can be adapted for use in a single-track vehicle. This requires simply reducing the number of components 14a to 14d, 18a to 18d, 16a to 26d (and possibly 30a to 30d) to one wheel brake cylinder 14a to 14d per brake circuit 12a and 12b, one control valve 18a to 18d per brake circuit 12a and 12b, possibly one wheel outlet valve 30a to 30d per brake circuit 12a and 12b, and one switching valve 26a to 26d per brake circuit 12a and 12b.

[0054] In an alternative embodiment, only the single wheel brake cylinder of the brake system or one of the wheel brake cylinders of the brake system can be connected to the motorized piston-cylinder device 16. In this case, the wheel brake cylinder connected to the motorized piston-cylinder device 16 is connected exclusively to the single control valve of the brake system via the valve-free line, the single control valve being connected exclusively to the motorized piston-cylinder device 16 via the further valve-free line.

Claims

[1] Braking system for a vehicle with: a master brake cylinder (10); at least one brake circuit (12a, 12b) with at least one wheel brake cylinder (14a to 14d); and a motorized piston-cylinder device (16) which is connected via at least one control valve (18a to 18d) to the single wheel brake cylinder of the brake system or to at least one of the wheel brake cylinders (14a to 14d) of the brake system in such a way that, if the at least one control valve (18a to 18d) is at least partially open, brake fluid can be transferred from the motorized piston-cylinder device (16) through the at least one control valve (18a to 18d) to the at least one wheel brake cylinder (18a to 18d) connected to the motorized piston-cylinder device (16) by means of operation of the motorized piston-cylinder device (16); characterized by , that Each wheel brake cylinder (14a to 14d) connected to the motorized piston-cylinder assembly (16) is connected exclusively via one valve-free line path (20a to 20d) to the single control valve of the brake system or to at most one of the control valves (18a to 18d) of the brake system, wherein the control valve (18a to 18d) connected to the respective wheel brake cylinder (14a to 14d) via the at least one valve-free line path (20a to 20d) is connected exclusively via at least one further valve-free line path (22) to the motorized piston-cylinder assembly (16). [2] Brake system according to claim 1, wherein during the operation of the motorized piston-cylinder device (16) a displacement of brake fluid from the motorized piston-cylinder device (16) into the single connected wheel brake cylinder or into at least one of the connected wheel brake cylinders (14a to 14d) can be controlled exclusively by means of the single control valve of the brake system or by means of at most one of the control valves (18a to 18d) of the brake system. [3] Brake system according to claim 1 or 2, wherein only the single wheel brake cylinder of the brake system or one of the wheel brake cylinders of the brake system is connected to the motorized piston-cylinder device (16), wherein the wheel brake cylinder connected to the motorized piston-cylinder device (16) is connected exclusively via the valve-free line path to the single control valve of the brake system, and wherein the single control valve is connected exclusively via the further valve-free line path to the motorized piston-cylinder device (16). [4] Brake system according to claim 1 or 2, wherein several wheel brake cylinders (14a to 14d) of the brake system connected to the motorized piston-cylinder device (16) are connected exclusively via the respective valve-free line path (20a to 20d) to the at least one control valve (18a to 18d) of the brake system, and wherein the at least one control valve (18a to 18d) of the brake system is connected exclusively via the at least one further valve-free line path (22) to the motorized piston-cylinder device (16). [5] Brake system according to claim 4, wherein the brake system has exactly one associated control valve (18a to 18d) for each wheel brake cylinder (14a to 14d) connected to the motorized piston-cylinder device (16), and wherein, during operation of the motorized piston-cylinder device (16), the displacement of brake fluid from the motorized piston-cylinder device (16) into the respective wheel brake cylinder (14a to 14d) can be controlled exclusively by means of the associated control valve (18a to 18d). [6] Brake system according to claim 5, wherein the brake system has exactly one associated control valve (18a to 18d) for each wheel brake cylinder (14a to 14d) as the at least one control valve (18a to 18d). [7] Brake system according to one of the preceding claims, wherein the at least one control valve (18a to 18d) is a separating valve and / or a continuously controllable valve. [8] Brake system according to one of the preceding claims, wherein the single wheel brake cylinder of the brake system or at least one of the wheel brake cylinders (14a to 14d) of the brake system is connected to a brake fluid reservoir (32) via at least one wheel outlet valve (30a to 30d). [9] Brake system according to claim 7, wherein the single wheel outlet valve of the brake system or at least one of the wheel outlet valves (30a to 30d) of the brake system is a continuously controllable wheel outlet valve. [10] Brake system according to one of the preceding claims, wherein the brake system comprises a control device (24) by means of which the motorized piston-cylinder device (16) and the at least one control valve (18a to 18d) of the brake system can be controlled. [11] Brake system according to claim 9, wherein the control device (24) is designed for sequential control of the motorized piston-cylinder device (16) and the control valves (18a to 18d) of the brake system.

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