Communications system for a hydraulic brake system

A communications system is described for a hydraulic brake system, including a communications bus, a connected, first control device, a connected, second control device, and a further connected communications unit. In response to a loss of its communication with the first control device in spite of its regular communication with the at least one further communications unit, at least one instance of functional impairment of the first control device and/or of a first motorized device controlled by the first control device is detectable with the aid of the second control device. A hydraulic brake system for a vehicle, a method for checking a communications system, and a method for operating a hydraulic brake system of a vehicle, are also described.

FIELD

The present invention relates to a communications system for a hydraulic brake system, as well as to a hydraulic brake system for a vehicle. The present invention also relates to a method for checking a communications system. Furthermore, the present invention relates to a method for operating a hydraulic brake system of a vehicle.

BACKGROUND INFORMATION

A communications system of a brake system, made up of a control device used for controlling a brake booster and a control unit used for controlling a hydraulic system, is described in German Patent Application No. DE 10 2015 204 757 A1. The control device is connected to the control unit via a signal transmission device in such a manner, that bidirectional/bilateral communication between the control device and the control unit is possible. As soon as the control device recognizes that at least one instance of functional impairment of the control unit, the hydraulic system and/or the signal transmission device is present, the control device is configured to autonomously activate the brake booster in such a manner, that brake pressure may be built up by the brake booster in at least one wheel brake cylinder of the brake system.

SUMMARY

The present invention provides a communications system for a hydraulic brake system, a hydraulic brake system for a motor vehicle, a method for checking a communications system, and a method for operating a hydraulic brake system of a vehicle.

The present invention provides options for checking a communications system and for differentiating between a first fault condition, “at least one instance of functional impairment (possibly, a functional failure) of the first control device and/or of the first motorized device, while the communications bus is operational,” and a second fault condition, “at least one instance of functional impairment (possibly, a functional failure) of the communications bus.” This eliminates the conventional necessity of already reacting to an instance of functional impairment/a functional failure of only the communications bus, as if the first control device connected to the communications bus and/or the first motorized device had (also) stopped functioning. Consequently, use of the present invention allows, in each instance, a more selective reaction to the fault condition currently present. The more selective reaction may allow the current fault condition to be responded to in an improved manner.

In one advantageous specific embodiment of the communications system in accordance with the present invention, the first control device in the first operating mode is configured for regular communication with the at least one further communications unit, in such a manner, that with the aid of the first control device, in response to a loss of its communication with the second control device in spite of its regular communication with the at least one further communications unit, at least one instance of functional impairment of the second control device and/or of the second motorized device is detectable. Thus, in this specific embodiment of the communications system, it is also possible to differentiate between a functional failure of the second control device and/or of the second motorized device and a functional failure of the communications bus.

In one further advantageous specific embodiment of the communications system in accordance with the present invention, in response to a loss of its communication with the first control device in spite of its regular communication with the at least one further communications unit, the second control device is configured to execute a predetermined bypass program. Consequently, an instance of functional impairment (and/or a functional failure) of the first control device and/or of the first motorized device may be overcome. Alternatively or additionally, in response to a loss of its communication with the second control device in spite of its ongoing communication with the at least one further communications unit, the first control device may also be configured to execute a further, predetermined bypass program. Therefore, an instance of functional impairment (and/or a functional failure) of the second control device and/or of the second motorized device may also be overcome with the aid of the bypass program of the first control device (and of the controlled, first motorized device).

The present invention also provides an example hydraulic brake system for a vehicle, including: such a communications system; an electromechanical brake booster, which is controllable by the first control device as a first motorized device, in such a manner, that with the aid of the controlled, electromechanical brake booster, brake fluid may be transferred from a master brake cylinder of the hydraulic brake system, situated downstream from the electromechanical brake booster, into at least one wheel brake cylinder of the hydraulic brake system; and a motorized hydraulic device, which is controllable by the second control device as the second motorized device, in such a manner, that brake fluid may be transferred into the at least one wheel brake cylinder with the aid of the motorized hydraulic device. Since in such a brake system (in contrast to the related art described above), it is possible to differentiate at least between the first fault condition, “at least one instance of functional impairment (possibly, a functional failure) of the first control device and/or of the first motorized device, while the communications bus is operational,” and the second fault condition, “at least one instance of functional impairment (possibly, a functional failure) of the communications bus,” in each instance, the fault situation present may also be responded to in a more selective manner. In the related art described above, a functional failure of the communications bus already initiates the autonomous activation of the brake booster, although it has not yet been clearly discerned, that autonomous buildup of brake pressure in the at least one wheel brake cylinder by the activated brake booster is necessary. This disadvantage is eliminated in the hydraulic brake system described here.

For example, the hydraulic brake system may be designed such that as long as at least the first control device and the electromechanical brake booster are operational, the first control device is configured to control the electromechanical brake booster in view of a provided setpoint brake pressure buildup signal regarding an instance of autonomous braking requested by an automatic speed control system of the vehicle, an instance of externally powered braking requested by a driver of the vehicle, or braking force assistance requested by the driver, in such a manner, that with the aid of the controlled electromechanical brake booster, a volume of brake fluid corresponding to the setpoint brake pressure buildup signal is transferable from the master brake cylinder into the at least one wheel brake cylinder; the second control device being configured to control the motorized hydraulic device as a bypass program, in such a manner, that with the aid of the controlled, motorized hydraulic device, the volume of brake fluid corresponding to the setpoint brake pressure buildup signal is transferable into the at least one wheel brake cylinder. Thus, only if a functional failure of the first control device and/or of the electromechanical brake booster is reliably detected, is the motorized hydraulic device selectively deployed for overcoming the functional failure.

Alternatively, the hydraulic brake system may also be designed such that as long as at least the second control device and the motorized hydraulic device are operational, the second control device is configured to control the motorized hydraulic device in view of a provided setpoint brake pressure build-up signal regarding an instance of autonomous braking requested by an automatic speed control system of the vehicle, an instance of externally powered braking requested by a driver of the vehicle, or braking force assistance requested by the driver, in such a manner, that with the aid of the controlled, motorized hydraulic device, a volume of brake fluid corresponding to the setpoint brake pressure buildup signal is transferable into the at least one wheel brake cylinder; the first control device being configured to control the electromechanical brake booster as a bypass program, in such a manner, that with the aid of the controlled electromechanical brake booster, the volume of brake fluid corresponding to the setpoint brake pressure buildup signal is transferable from the master brake cylinder into the at least one wheel brake cylinder. Therefore, in this specific embodiment of the hydraulic brake system, as well, it is ensured that only when a functional failure of the second control device and/or of the motorized hydraulic device is reliably detected, is the electromechanical brake booster used for overcoming the functional failure.

The advantages already described above are also brought about by executing a corresponding example method for checking a communications system. It should be pointed out that the method for checking a communications system may be refined further in accordance with the specific embodiments of the communications system described above.

In addition, executing a corresponding example method for operating a hydraulic brake system of a vehicle also produces the advantages already described above. Furthermore, the method for operating a hydraulic brake system of a vehicle may be refined further in accordance with the above-described specific embodiments of the communications system and/or of the hydraulic brake system.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1shows a schematic representation of a specific embodiment of the communications system, that is, of the hydraulic brake system equipped with it.

The communications system represented schematically inFIG. 1includes a communications bus10, a first control device12connected to communications bus10, and a second control device14connected to communications bus10. An ability to develop communications bus10is not limited to a particular bus topology. For example, a bus topology of communications bus10may be star-shaped or linear.

At least one (further) communications unit16is also situated on/connected to communications bus10. It is emphasized that neither first control device12, nor second control device14falls under the at least one further communications unit16. However, the at least one communications unit may be understood, in each instance, as a unit made up of a plurality of different communications subscribers. An ability to develop the at least one communications unit is not limited to a particular type, such as a communications node.

First control device12may be a subunit of a first motorized device18controlled with the aid of first control device12. As an alternative, however, first control device12may also be positionable/positioned separately from the first motorized device18controlled with the aid of first control device12. As long as first control device12and/or the first motorized device18controlled with the aid of first control device12are operational, first control device12is in a first operating mode (e.g., fully functional operating mode).

Second control device14may also be a subunit of a second motorized device20controlled with the aid of second control device14. However, a form of second control device14is also possible, in which second control device14(as an independent component) is positionable/positioned separately from the second motorized device20controlled with the aid of second control device14. As long as second control device14and/or the second motorized device20controlled with the aid of second control device14are operational, second control device14is also in a second operating mode (e.g., fully functional operating mode).

The first control device12in the first operating mode and the second control device14in the second operating mode are configured for regular communication22with each other. In other words, the first control device12in the first operating mode and the second control device14in the second operating mode carry on regular communication22with each other. The regular communication22of the at least one further communications unit16, situated on communications bus10, of the first control device12in the first operating mode, with the second control device14in the second operating mode, may be understood as the transmitting and receiving (that is, exchanging) of indicating signals and/or reply signals. For example, the first control device12in the first operating mode and the second control device14in the second operating mode may transmit indicating signals regularly to each other (in particular, at a predefined repetition frequency).

Alternatively, one of the two control devices12and14may also be configured to transmit interrogation signals regularly (in particular, at a predefined interrogation frequency) to the other of the two control devices12and14; the other of the two control devices responding to the interrogation signals by transmitting reply signals immediately. Consequently, one may also speak of a cyclical communication22or permanent communication22between the first control device12in the first operating mode and the second control device14in the second operating mode.

In addition, the second control device14in the second operating mode is designed for regular communication24with the at least one further communications unit16situated on communications bus10. Therefore, the second control device14in the second operating mode and the at least one communications unit16have regular communication24with each other. The regular communication24of the second control device14in the second operating mode with the at least one further communications unit16may also be understood as the transmitting and receiving (that is, exchanging) of indicating signals and/or reply signals. For example, the second control device14in the second operating mode and the at least one communications unit16may transmit indicating signals regularly to each other (in particular, at a predetermined repetition frequency). Alternatively, the second control device14in the second operating mode or the at least one communications unit16may be configured to transmit interrogation signals regularly (in particular, at a predetermined interrogation frequency) to the other communications subscriber14or16; the other communications subscriber14or16reacting to the interrogation signals by sending reply signals immediately. Consequently, one may also speak of cyclical communication24or permanent communication24between the second control device14in the second operating mode and the at least one further communications unit16.

Due to the advantageous design of components12,14and16, in response to a loss of its communication22with first control device12in spite of its regular communication24with the at least one further communications unit16, at least one instance of functional impairment of first control device12and/or of first motorized device18is, as such, reliably and correctly detectable with the aid of second control device14. Provided that a loss of its communication22with first control device12in spite of its regular/uninterrupted communication24is detected with the aid of second control device14, present operability of communications bus10may be reliably assumed. (Otherwise, communication24of the second control device14in the second operating mode with the at least one further communications unit16would be lost, as well.) Consequently, the loss of communication22in spite of the regular/uninterrupted communication24may be reliably attributed to at least one instance of functional impairment (possibly, a functional failure) of first control device12and/or of first motorized device18.

While the above-described related art is only able to detect at least one instance of functional impairment of a control device/control unit, of a device controlled by it, and/or of a signal transmission device (using bidirectional/bilateral communication), the communications system described here is also configured to differentiate between a first fault condition, “at least one instance of functional impairment (possibly, a functional failure) of first control device12and/or of first motorized device18, with an operational communications bus10,” and a second fault condition, “at least one instance of functional impairment (possibly, a functional failure) of communications bus10.” (By use of the at least one further communications unit16,) The communications system allows improved communications monitoring and clearer recognition of a fault condition currently present, which means that the fault condition currently present may also be reacted to more selectively.

In particular, in response to a loss of its communication22with first control device12in spite of its regular communication24with the at least one further communications unit16, second control device14may be configured to execute a predetermined bypass program, that is, to compensate for/overcome the functional impairment/functional failure of first control device12and/or of first motorized device18, by adapting the operation of the second motorized device20controlled by second control device14. (This is explained below in even more detail with the aid of an example.)

In the form of a further refinement, the first control device12in the first operating mode may also be configured for regular communication26with the at least one further communications unit16in such a manner, that with the aid of first control device12, in response to a loss of its communication22with second control device14in spite of its regular communication26with the at least one further communications unit16, at least one instance of functional impairment of second control device14and/or of second motorized device20is detectable. The regular communication26of the first control device12in the first operating mode with the at least one further communications unit16may include the above-mentioned features of the communication24of the second control device14in the second operating mode with the at least one further communications unit16.

If a loss of its communication22with second control device14in spite of its regular communication26with the at least one further communications unit16is detected by first control device14, it may also be reliably assumed that communications bus10is presently operational. Consequently, the loss of communication22in spite of regular communication26may be reliably attributed to at least one instance of functional impairment (possibly, a functional failure) of second control device14and/or of second motorized device20. Thus, the communications system described here is also configured to differentiate between the second fault condition, “at least one instance of functional impairment (possibly, a functional failure) of communication bus10,” and a third fault condition, “at least one instance of functional impairment (possibly, a functional failure) of second control device14and/or second motorized device20, while communications bus10is presently operational.” In response to a loss of its communication22with second control device14in spite of its regular communication26with the at least one further communications unit16, first control device12may also be configured to execute a (further) predetermined bypass program, that is, to compensate for/overcome the functional impairment/functional failure of second control device14and/or of second motorized device20, by adapting the operation of the first motorized device18controlled by first control device12.

It should be pointed out that the hardware schematically represented inFIG. 1is, generally, already installed in a conventional communications system. Thus, in order to develop the communications system according toFIG. 1, it is often sufficient to redesign/reprogram the operation of components12,14and16.

In the example ofFIG. 1, the communications system is part of a hydraulic brake system of a vehicle/motor vehicle. An ability to use the communications system is not limited to either a particular type of hydraulic brake system, or a particular type of vehicle/motor vehicle. An electromechanical brake booster18of the hydraulic brake system is (as a first motorized device10) controllable by first control device12in such a manner, that brake fluid may be/is transferred by controlled electromechanical brake booster18, from a master brake cylinder30of the hydraulic brake system, situated downstream from electromechanical brake booster18, into at least one wheel brake cylinder32of the hydraulic brake system. With the aid of controlled electromechanical brake booster18, for example, a booster force34may be applied to at least one movable piston of master brake cylinder30in such a manner, that brake fluid may be pressed into the at least one hydraulically connected wheel brake cylinder32, by moving the at least one piston into master brake cylinder30.

The brake system schematically represented with the aid ofFIG. 1also includes a motorized hydraulic device20(as second motorized device20), which is controllable by second control device14in such a manner, that with the aid of motorized hydraulic device20, brake fluid may be/is transferred into the at least one wheel brake cylinder32. Motorized hydraulic device20may be, for example, a pump system including at least one hydraulic pump, which may be driven by at least one pump motor in such a manner, that brake fluid may be/is pumped into the at least one wheel brake cylinder32. Alternatively, or in addition, motorized hydraulic device20may also include a motorized piston-cylinder device (plunger device), with the aid of which brake fluid may be/is pressed into the at least one connected wheel brake cylinder32.

The hydraulic brake system ofFIG. 1is designed such that, (at least) as long as first control device12and electromechanical brake booster18are operational, first control device12is configured to control electromechanical brake booster18in view of a provided setpoint brake pressure buildup signal36, in such a manner, that with the aid of controlled electromechanical brake booster18(in place of motorized hydraulic device20), a volume V of brake fluid corresponding to the setpoint brake pressure buildup signal may be/is transferred by controlled electromechanical brake booster18from master brake cylinder30into the at least one wheel brake cylinder32. Thus, as long as first control device12, second control device14, electromechanical brake booster18, and motorized hydraulic device20are operational, first control device12has a master status; (with the aid of the electromechanical brake booster18controlled by first control device12, a brake pressure requested via setpoint brake pressure buildup signal36being able to be produced in the at least one wheel brake cylinder32); while second control device14has a slave status. (Motorized hydraulic device20preferably remains deactivated, while second control device14has the slave status.)

However, (in response to a loss of its communication22with second control device14in spite of its regular communication26with the at least one further communications unit16), second control device14is configured to control motorized hydraulic device20as a bypass program in such a manner, that with the aid of controlled, motorized hydraulic device20(in place of electromechanical brake booster18), the volume V of brake fluid corresponding to setpoint brake pressure buildup signal36may be/is transferred into the at least one wheel brake cylinder32. In other words, in response to a loss of its communication22with second control device14in spite of its regular communication26with the at least one further communications unit16, second control device14may be switched from the slave status to a master status. Since with the aid of the communications system (in contrast to the related art described above), it is possible to reliably differentiate between the first fault condition, “at least one instance of functional impairment (possibly, a functional failure) of first control device12and/or of first motorized device18, while communications bus10is presently operational,” and the second fault condition, “at least one instance of functional impairment (possibly, a functional failure) of communications bus10,” there is, in response to the presence of the second fault condition, no risk of second control device's14being switched from the slave status to the master status and decelerating the vehicle excessively with the aid of its bypass program executed during the master status. Therefore, second control device14may be configured, without risk, to produce, without restriction, the brake pressure requested via setpoint brake pressure buildup signal36in the at least one wheel brake cylinder32, using controlled, motorized hydraulic device20, after it is switched to master status. (In the related art, in order to prevent “excessive braking of the vehicle” while bypassing the control unit with the aid of the control device, the control device is often only configured to partially compensate for the control unit that is actually or supposedly nonfunctional.) Thus, with the aid of the hydraulic brake system ofFIG. 1, both maximum vehicle deceleration and effective vehicle stabilization may also be achieved in the case of a fault.

For example, setpoint brake pressure buildup signal36may be understood as a signal, which is outputted by an automatic speed control system of a vehicle equipped with the hydraulic brake system, and by which the automatic speed control system requests autonomous braking of the vehicle. Consequently, the brake system ofFIG. 1may be used reliably for autonomously decelerating (and/or autonomously controlling/regulating a speed of) the vehicle. Alternatively, or in addition, however, setpoint brake pressure buildup signal36may also represent externally powered braking requested by a driver of the vehicle. Setpoint brake pressure buildup signal36may also indicate braking force assistance requested by the driver. In both cases, setpoint brake pressure buildup signal36may be outputted by a brake actuation sensor, in order to ascertain an instance of manipulation of a brake actuating element/brake pedal by the driver. Such a brake actuation sensor may be, for example, a brake pedal sensor, a rod travel sensor, and/or a differential travel sensor.

In one alternative specific embodiment, (at least) as long as second control device14and motorized hydraulic device20are operational, second control device14may be configured to control motorized hydraulic device20in such a manner, that with the aid of controlled, motorized hydraulic device20, the volume V of brake fluid corresponding to setpoint brake pressure buildup signal36may be transferred into the at least one wheel brake cylinder32; first control device12controlling electromechanical brake booster18as a (further) bypass program, in such a manner, that with the aid of controlled electromechanical brake booster18, a volume V of brake fluid corresponding to setpoint brake pressure buildup signal36may be/is transferred from master brake cylinder30into the at least one wheel brake cylinder32. Consequently, this specific embodiment also produces the advantages explained above.

FIG. 2shows a flow chart for explaining a specific embodiment of the method for checking a communications system.

In a method step S1, if a first control device connected to a communications bus of the communications system and/or a first motorized device controlled with the aid of the first control device are operational, the first control device is operated in a first operating mode. At the same time, if a second control device connected to the communications bus and/or a second motorized device controlled with the aid of the second control device are operational, the second control device is operated in a second operating mode. The first control device in the first operating mode and the second control device in the second operating mode conduct (uninterrupted) communication with each other. In addition, the second control device in the second operating mode undertakes (uninterrupted) communication with at least one further communications unit situated on the communications bus. Examples of the at least one further communications unit and the instances of communication listed here are already mentioned above.

A further method step S2is carried out with the aid of the second control device (preferably regularly), in order to ascertain if its communication with the first control device and/or its communication with the at least one further communications unit has been interrupted in the meantime. In this manner, in response to a loss of its communication with the first control device in spite of its regular communication with the at least one further communications unit, the second control device detects at least one instance of functional impairment of the first control device and/or of the first motorized device. For example, in response to a loss of its communication with the first control device in spite of its regular communication with the at least one further communications unit, the second control device executes a predetermined bypass program.

In addition, as an optional method step S3, if the first control device in the first operating mode conducts (uninterrupted) communication with the at least one further communications unit, then, in response to a loss of its communication with the second control device in spite of its regular communication with the at least one further communications unit, at least one instance of functional impairment of the second control device and/or of the second motorized device may be detected. In response to a loss of its communication with second control device14in spite of its regular communication with the at least one further communications unit16, first control device12may also execute a (further) predetermined bypass program.

Consequently, execution of the method described here also produces the advantages mentioned above.

FIG. 3shows a flow chart for explaining a specific embodiment of the method for operating a hydraulic brake system of a vehicle.

The method described here includes at least method steps S1and S2, with the aid of which the communications system of the hydraulic brake system is checked; the first motorized device being used for controlling an electromechanical brake booster of the hydraulic brake system (in the form of the first motorized device), in such a manner, that with the aid of the controlled electromechanical brake booster, brake fluid is transferred from a master brake cylinder of the hydraulic brake system, situated downstream from the electromechanical brake booster, into at least one wheel brake cylinder of the hydraulic brake system. In addition, the second motorized device is used for controlling at least one motorized hydraulic device of the hydraulic brake system (as the second motorized device) in such a manner, that with the aid of the controlled, motorized hydraulic device, brake fluid is transferred into the at least one wheel brake cylinder.

As long as the first control device and the electromechanical brake booster are operational, then, in a method step S10, the first control device is activated to control the electromechanical brake booster in view of a provided setpoint brake pressure build-up signal regarding an instance of autonomous braking requested by an automatic speed control system of the vehicle, an instance of externally powered braking requested by a driver of the vehicle, or braking force assistance requested by the driver, in such a manner, that with the aid of the controlled electromechanical brake booster, a volume of brake fluid corresponding to the setpoint brake pressure buildup signal is transferred from the master brake cylinder into the at least one wheel brake cylinder.

However, in method step S2, if a loss of its communication with the first control device in spite of its regular communication with the at least one further communications unit is detected by the second control device, this initiates a method step S11in the form of a bypass program, in which the second control device controls the motorized hydraulic device in such a manner, that with the aid of the controlled, motorized hydraulic device, the volume of brake fluid corresponding to the setpoint brake pressure buildup signal is transferred into the at least one wheel brake cylinder. Therefore, the reliably detected instance of functional impairment (and/or the failure) of the first control device and/or of the electromechanical brake booster may be overcome/compensated for effectively.

An ability to implement the methods described above is not limited to either a particular type of hydraulic brake system, or a particular type of vehicle/motor vehicle.