BRAKE SYSTEM AND VEHICLE

The disclosure relates to a brake system for a vehicle having four brakeable wheels, the brake system comprising an actuation unit for detecting a driver braking request, a main brake module, which comprises a hydraulic brake actuator unit, which is configured for braking the front wheels, and an electromechanical brake actuator unit, which is configured for braking the rear wheels, and having a hydraulic auxiliary brake module, which is coupled hydraulically to the hydraulic brake actuator unit for braking the front wheels and is connected electronically to the electromechanical brake actuator unit. In addition, a vehicle having a brake system is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to DE Patent Application No. 102023125074.4 filed on Sep. 15, 2023, the disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The disclosure relates to a brake system for a vehicle having at least four brakeable wheels and to a vehicle having a brake system.

In particular, the brake system comprises a main brake module having a hydraulic brake actuator unit, which is configured for braking the front wheels, and an electromechanical brake actuator unit, which is configured for braking the rear wheels.

BACKGROUND

Brake systems that serve as service brakes must have a sufficiently high level of fail safety to enable an adequate braking power to be ensured in all cases in order to allow the vehicle to be driven safely to a destination or at least to be safely parked.

In the case of hydraulic brake systems, in which all the wheels of the vehicle are actuated by a hydraulic brake actuator unit, the vehicle can still be handled safely by a hydraulic through connection if the electronics fail.

However, hydraulic systems are complex and require a large amount of installation space.

In the case of electronic brake systems which do not include hydraulics, some components of the brake system, e.g. communication lines, must be redundant, thereby likewise making the brake system complex and expensive.

What is needed is to specify a brake system which has a high level of fail safety and, at the same time, is of compact and low-cost design.

SUMMARY

According to the disclosure, a brake system for a vehicle having at least four brakeable wheels is disclosed. The brake system has an actuation unit for detecting a driver braking request, a main brake module, which comprises a hydraulic brake actuator unit, which is configured for braking the front wheels, and an electromechanical brake actuator unit, which is configured for braking the rear wheels, and having a hydraulic auxiliary brake module, which is coupled hydraulically to the hydraulic brake actuator unit for braking the front wheels and is connected electronically to the electromechanical brake actuator unit.

Since the front wheels are braked by a hydraulic brake actuator unit, and the rear wheels are braked by an electromechanical brake actuator unit, the share of the hydraulics in the brake system is reduced, thereby simplifying the brake system.

The auxiliary brake module, which is coupled hydraulically to the hydraulic brake actuator unit for braking the front wheels, represents a fallback level, ensuring that the braking power at the front wheels is not impaired if there is a fault in the hydraulic brake actuator unit of the main brake module.

The fail safety is additionally enhanced by the fact that the hydraulic auxiliary brake module is connected electronically to the electromechanical brake actuator unit. This enables the electromechanical brake actuator unit to be controlled via the auxiliary brake module.

The electromechanical brake actuator unit can additionally serve as a parking brake.

Both the main brake module and the auxiliary brake module comprise a dedicated control unit. The brake system therefore has two independent control units, thus providing additional redundancy. As a result, not only can signals for the electromechanical brake actuator unit be transmitted to the electromechanical brake actuator unit via the auxiliary brake module but, in the event of a failure of the electronics of the main brake module, the electromechanical brake actuator unit can be controlled directly by the auxiliary brake module. In addition, the hydraulic brake actuator unit of the main brake module can be controlled by the control unit of the auxiliary brake module when required.

According to one exemplary arrangement, the electromechanical brake actuator unit comprises two electromechanical brake actuators, wherein each rear wheel is assigned an electromechanical brake actuator. In this way, a sufficiently high braking force can be exerted on the rear wheels. In addition, the use of two independent electromechanical brake actuators makes it possible to brake the two rear wheels independently of one another. That is to say that, if one of the two brake actuators fails, it is still possible for at least one of the rear wheels to be braked and thus to contribute to the overall braking power.

The brake system can comprise a first power supply unit and a second power supply unit, wherein the first power supply unit supplies the control unit of the main brake module and one of the two brake actuators with electric power, and the second power supply unit supplies the control unit of the auxiliary brake module and the additional one of the two brake actuators with electric power. Due to the interconnection of the two power supply units, it is still possible to brake the front wheels and one of the two rear wheels if one power supply unit fails, whereby a sufficiently high braking power for safe guidance of the vehicle is achieved.

The actuation unit for detecting a driver braking request is coupled hydraulically to the hydraulic brake actuator unit, for example. In other words, the actuation unit is a component part of the main brake module, wherein a hydraulic direct connection of the actuation unit to the hydraulic brake actuator unit is possible. This means that, even if there is a complete failure of the electronics of the brake system, a certain brake pressure is still possible by actuating the actuation unit.

In an alternative arrangement, the actuation unit for detecting a driver braking request is coupled electronically to the main brake module and the auxiliary brake module. The actuation unit is thus arranged separately from the main brake module, and therefore a hydraulic through connection to the hydraulic brake actuator unit is not possible. In this context, the term “brake-by-wire” brake system is also used, in which system a braking request by a driver is detected purely electronically.

In a “brake-by-wire” brake system, the actuation unit can be connected by signals both to the control unit of the main brake module and to the control unit of the auxiliary brake module.

The main brake module can be connected electronically to the auxiliary brake module, wherein the control unit of the main brake module is connected electronically to the control unit of the auxiliary brake module. This allows a signal exchange between the main brake module and the auxiliary brake module. For example, the control unit of the main brake module can communicate a braking request by the driver to the auxiliary brake module in the event of a failure of the mechanical components of the hydraulic brake actuator unit. In the case of a “brake-by-wire” brake system, it is thus possible, even in the event of a failure of one of the signal lines between the actuation unit and the main brake module or the auxiliary brake module, to pass on the brake signal accordingly.

Each wheel can be assigned a wheel speed sensor, wherein the wheel speed sensors assigned to the front wheels are connected electronically to the main brake module, and the wheel speed sensors assigned to the rear wheels are each connected electronically to one of the brake actuators. Due to the wheel speed sensors, it is possible to balance the braking power at the different wheels of the vehicle.

In one exemplary arrangement, both the main brake module and the auxiliary brake module comprise a respective hydraulic pump. The hydraulic pump of the main brake module is, for example, a component part of the hydraulic brake actuator unit. Since both the main brake module and the auxiliary brake module have a hydraulic pump, the fail safety of the brake system is further enhanced.

According to the disclosure, a vehicle having a brake system according to the disclosure and having a vehicle bus system, is also disclosed, wherein the electromechanical brake actuator unit is coupled to the vehicle bus system by signals. In addition to the advantages already described in connection with the brake system, it is possible in the case of a vehicle of this kind to pass on signals to the electromechanical brake actuator unit, for example to the two brake actuators, via the vehicle bus system, even when the signal link with the control units of the main brake module and the auxiliary brake module has been interrupted.

If, for example, braking is taking place at the front wheels and a corresponding deceleration is detected by the wheel speed sensors, the information on the vehicle deceleration can be passed on to the brake actuators, wherein the latter accordingly apply an auxiliary braking force to the rear wheels.

For this purpose, the electromechanical brake actuator unit may comprise at least one further control unit. For example, each brake actuator is assigned a control unit.

DETAILED DESCRIPTION

The brake system20has an actuation unit22for detecting a driver braking request, a main brake module24and a hydraulic auxiliary brake module26.

In one exemplary arrangement, the actuation unit22comprises a pedal, which can be actuated by a driver's foot to indicate a braking request.

A braking request by a driver may be detected electronically.

The main brake module24comprises a hydraulic brake actuator unit28, which is configured for braking the front wheels12,14, and an electromechanical brake actuator unit30, which is configured for braking the rear wheels16,18.

For example, the main brake module24has a hydraulic pump32and optionally valves to enable a hydraulic pressure to be built up in the hydraulic brake actuator unit28.

The electromechanical brake actuator unit30comprises two electromechanical brake actuators31, wherein each rear wheel16,18is assigned an electromechanical brake actuator31.

The hydraulic auxiliary brake module26is coupled hydraulically to the hydraulic brake actuator unit28for braking the front wheels. That is to say that the hydraulic brake actuator unit28can be actuated both by the main brake module24and by the auxiliary brake module26.

For this purpose, the hydraulic auxiliary brake module26likewise comprises a hydraulic pump34.

Both the main brake module24and the auxiliary brake module26comprise a dedicated control unit36,38.

The control unit36of the main brake module24is connected to the electromechanical brake actuator unit30by signals via signal lines40. To be more precise, the control unit36is connected to each of the two electromechanical brake actuators31via a respective signal line40.

The main brake module24is connected to the auxiliary brake module26by signals via a signal line42, enabling the main brake module24to exchange data with the auxiliary brake module26. To be more precise, the control unit36of the main brake module24is connected electronically to the control unit38of the auxiliary brake module26.

The auxiliary brake module26is likewise connected to the electromechanical brake actuator unit30by signals. To be more precise, the control unit38of the auxiliary brake module26is connected to each of the two electromechanical brake actuators31via a respective signal line44.

Consequently, the electromechanical brake actuators31can be controlled by the control unit36of the main brake module24and by the control unit38of the auxiliary brake module26.

In the exemplary arrangement shown inFIG.1, the actuation unit22is coupled hydraulically to the hydraulic brake actuator unit28.

Each wheel12,14,16,18is assigned a wheel speed sensor46, wherein the wheel speed sensors46assigned to the front wheels12,14are connected electronically to the main brake module24, for example to the control unit36, and the wheel speed sensors46assigned to the rear wheels16,18are each connected electronically to one of the brake actuators31.

The brake system20furthermore comprises a first power supply unit48and a second power supply unit50.

The first power supply unit48is connected to the control unit36of the main brake module24and one of the two brake actuators31and supplies them with electric power.

The second power supply unit50is connected to the control unit38of the auxiliary brake module26and the additional one of the two brake actuators31and supplies them with electric power.

In the figures, the first power supply unit48and the second power supply unit are shown in duplicate for the purposes of illustration.

The vehicle10has a vehicle bus system52, to which the electromechanical brake actuator unit30is coupled by signals. In this way, information can be transferred to the brake actuators31even when signal transmission between the control unit36of the main brake module24as well as the auxiliary brake module26and the brake actuators31has been interrupted.

The operation of the brake system20will be described below with reference toFIGS.1to4.

FIG.1illustrates a braking operation in which the brake system20is functioning correctly.

In this case, a braking request by a driver is correctly detected from the actuation of the actuation unit22and processed in the control unit36of the main brake module24.

In accordance with the brake signal, both the hydraulic brake actuator unit28and the electromechanical brake actuator unit30are controlled by the control unit36in order to build up a braking force at the wheels12,14,16,18.

This is accomplished by operation of the hydraulic pump32of the main brake module24in the case of the hydraulic brake actuator unit28and by the brake actuators31in the case of the electromechanical brake actuator unit30.

For the sake of illustration, the active modules and signal lines are shown with a thick outline or with a thicker line inFIG.1.

In this case, the auxiliary brake module26is in standby, but it is not actively participating in the braking process.

In the scenario illustrated inFIG.1, a braking performance of 100% is achieved.

FIG.2illustrates a scenario in which the main brake module24has a fault. The hydraulic pump32has failed, for example.

The actuation unit22is continuing to function correctly, thus enabling a braking request by a driver to be detected and processed.

For example, a braking request by a driver is passed on to the control unit38of the auxiliary brake module26via the signal line42.

The auxiliary brake module26then activates the electromechanical brake actuator unit30and builds up a hydraulic pressure in the hydraulic brake actuator unit28by the hydraulic pump34.

The auxiliary brake module26can thus fully compensate for the malfunction of the main brake module24and, as a result, a braking performance of 100% continues to be achievable.

FIG.3illustrates a scenario in which both the main brake module24and the auxiliary brake module26have failed.

In this case, both hydraulic pumps32,34are out of operation.

However, since the actuation unit22is coupled hydraulically to the hydraulic brake actuator unit28, a hydraulic through connection of the actuation unit22is possible. This means that, by actuating the actuation unit22, for example by depressing the brake pedal, a hydraulic pressure can be built up in the hydraulic brake actuator unit28and thus a braking effect can be achieved.

Due to the hydraulic through connection, it is possible to achieve a braking performance of approximately 70%, this being sufficient to be able to manoeuvre the vehicle10safely.

There is no signal transmission by the control units36,38to the electromechanical brake actuator unit30.

As an option, however, it is conceivable for the brake actuator unit30to receive information on a braking process via the vehicle bus system52and then to control the brake actuators31accordingly.

More specifically, it is possible, during a braking process, for a vehicle deceleration to be detected by wheel speed sensors46assigned to the front wheels12,14.

This vehicle deceleration is communicated via the vehicle bus system52to the electromechanical brake actuator unit30, whereupon the brake actuators31are controlled accordingly and can thus contribute to the braking performance. It is thereby possible to achieve a braking performance of significantly over 70%.

For this purpose, the brake actuators31may each have a dedicated control unit54.

FIG.4illustrates a scenario in which the first power supply unit48has failed.

As a result, the main brake module24and one of the brake actuators31is no longer being supplied with electric power.

In this case, in a manner similar to the scenario already described in connection withFIG.2, the auxiliary brake module26takes over the control of the hydraulic brake actuator unit28and of the remaining, right-hand brake actuator31.

In this way, a braking performance of approximately 85% is achieved.

If, instead of the first power supply unit48, the second power supply unit50fails, the main brake module24remains active, with only one of the brake actuators31failing. This likewise leads to a braking performance of approximately 85%.

In the text which follows, the same reference signs are used for identical structures with identical functions which are known from the above exemplary arrangement, and, to this extent, attention is drawn to the above explanations, while it is the differences between the respective arrangements that are explored below, in order to avoid repetition.

The vehicle10illustrated inFIG.5differs from the vehicle illustrated in the previous figures in the arrangement of the actuation unit22.

For example, the actuation unit22is not coupled hydraulically to the main brake module24; instead, the actuation unit22is coupled electronically to the main brake module24and to the auxiliary brake module26.

This means that the brake system illustrated inFIG.5is a “brake-by-wire” brake system, in which no hydraulic or mechanical through connection can be made to the wheels12,14,16,18of the vehicle10.

To connect the actuation unit22electronically, additional signal lines56,58are provided, which connect the actuation unit22to the control unit36of the main brake module24and to the control unit38of the auxiliary brake module26by signals.

Apart from the fact that hydraulic through connection cannot occur, the operation of the brake system20shown inFIG.5is identical with that in the brake system20described inFIGS.1to4.

If the main brake module24fails, as illustrated inFIG.6, the auxiliary brake module detects a braking signal via the signal line58and controls the hydraulic brake actuator unit28and the electromechanical brake actuator unit30accordingly.

If the first power supply unit48fails, as illustrated inFIG.7, the auxiliary brake module26controls the hydraulic brake actuator unit28and the remaining brake actuator31accordingly.