DE102021206562A1 - Method for braking a vehicle, braking system for a vehicle and control system for a braking system for a vehicle - Google Patents

Abstract

A method for braking a vehicle includes detecting a braking request signal which represents a target deceleration of the vehicle, generating a hydraulic brake pressure in a wheel brake cylinder based on the detected braking request signal using a first pressure generating device which is hydraulically connected to the wheel brake cylinder, sending an operating state the status signal representing the first pressure generation device to a brake pressure control system, which has a second pressure generation device hydraulically coupled to the wheel brake cylinder, detection of a transmission error in the status signal, modulation of the brake pressure by means of the first pressure generation device if a transmission error is detected, detection of a preliminary pressure in a hydraulic path between the first pressure generating device and the wheel brake cylinder at a point between the first pressure generating device and is located in the second pressure-generating device, determining the operating state of the first pressure-generating device using the recorded admission pressure based on the modulation of the brake pressure, and at least partially generating the brake pressure by means of the second pressure-generating device if an error state is determined as the operating state of the pressure-generating device.

Description

technical field

The present invention relates to a method for braking a vehicle, a braking system for a vehicle and a control system for a braking system of a vehicle.

State of the art

Hydraulic braking systems are typically used in road vehicles such as cars or trucks. Increasingly, such hydraulic brake systems are operated according to a "brake-by-wire" principle, with actuation of a brake actuation device such as a brake pedal being detected by sensors and a braking request being determined therefrom, which represents a desired deceleration of the vehicle. A hydraulic pressure is then determined from the braking request, which is generated by means of a pressure generating device, such as an electrically driven plunger, in a wheel brake cylinder for braking a wheel of the vehicle.

Furthermore, brake systems of road vehicles usually have brake pressure control systems for wheel-specific brake pressure control, e.g. to perform an anti-lock braking function (ABS). Typically, such brake pressure control systems have their own pressure generation device and a valve arrangement for wheel-specific pressure variation.

If the pressure generating device fails in brake systems working according to the brake-by-wire principle, a master brake cylinder, which can be actuated by the brake actuation device, is typically hydraulically connected to the wheel brake cylinder, so that the required brake pressure can be generated manually.

In the DE 10 2014 225 954 A1 describes a brake system in which a pressure generation device of a brake pressure control system, which is set up to generate wheel-specific brake pressures, takes over the generation of the desired brake pressure if a first externally controlled pressure generation device fails.

In brake systems in which the brake pressure control system takes over the generation of the desired brake pressure if the externally controlled pressure generating device fails, the externally controlled pressure generating device usually communicates its operating status to the brake pressure control system. If the operating status is no longer transmitted or if an error condition is reported to the brake pressure control system, this intervenes as a backup. Situations can arise in which the brake pressure control system cannot clearly determine whether the externally controlled pressure generating device is actually in an error state or whether only the transmission of the operating status fails, although the externally controlled pressure generating device is working correctly.

Disclosure of Invention

The present invention provides a method having the features of claim 1, a braking system having the features of claim 8 and a control system having the features of claim 9.

According to a first aspect of the invention, a method for braking a vehicle includes detecting a braking request signal which represents a target deceleration of the vehicle, generating a hydraulic brake pressure in a wheel brake cylinder based on the detected braking request signal using a first pressure generating device which is hydraulically connected to the wheel brake cylinder , sending a status signal representing an operating state of the first pressure generating device to a brake pressure control system, which has a second pressure generating device hydraulically coupled to the wheel brake cylinder, detecting a transmission error of the status signal, modulating the brake pressure by means of the first pressure generating device if a transmission error is detected, detecting a form in a hydraulic path between the first pressure generating device and the wheel brake cylinder at a point between the first pressure-generating device and the second pressure-generating device, determining the operating state of the first pressure-generating device using the recorded form based on the modulation of the brake pressure and at least partially generating the brake pressure by means of the second pressure-generating device if an error state is determined as the operating state of the pressure-generating device.

According to a second aspect of the invention, a brake system for a vehicle is provided. The brake system includes a sensor for detecting a brake request signal, a wheel brake cylinder for generating a frictional force on a wheel of the vehicle, a first pressure generating device which is hydraulically coupled to the wheel brake cylinder and is set up to generate a hydraulic pressure in the wheel brake cylinder, a brake pressure control system with a second pressure generating device, which hydraulically coupled to the wheel brake cylinder and is set up to generate a hydraulic pressure in the wheel brake cylinder independently of the first pressure generation device, a admission pressure sensor for detecting a admission pressure in a hydraulic path between the first pressure generation device and the wheel brake cylinder at a point between the first pressure generation device and the second pressure generation device is located, and a control system which is signal-connected to the actuation sensor, the first pressure generation device and the brake pressure control system and is set up to cause the brake system to carry out a method according to one of the preceding claims.

According to a third aspect of the invention, a control system for a brake system of a vehicle is provided. The control system can be used, for example, in the braking system according to the second aspect of the invention and is generally arranged to cause a braking system to carry out the method according to the first aspect of the invention. The control system according to the invention comprises a first control unit with an input interface for connection to a sensor for detecting a braking request signal representing a target deceleration of the vehicle, an output interface for connection to a first pressure generating device which is hydraulically connected to a wheel brake cylinder, and a communication interface, the first control unit is set up to output an actuation signal for actuating the first pressure generating device based on the brake request signal at the output interface, to output a status signal, which represents an operating state of the first control unit, at the communication interface, to detect a transmission error of the status signal and, if a transmission error is detected, modulate the actuation signal to modulate the brake pressure generated by the first pressure generating device. Furthermore, the control system has a second control unit with an output interface for connection to a second pressure generation device of a brake pressure control system, which is hydraulically coupled to the wheel brake cylinder, an input interface for connection to a admission pressure sensor for detecting a admission pressure in a hydraulic path between the first pressure generation device and the wheel brake cylinder at a point, located between the first pressure generating device and the second pressure generating device, and a communication interface, which is connected to the communication interface of the first control unit, wherein the second control unit is set up to use the form to indicate an error state of the first pressure generating device based on the modulation of the brake pressure detect and output an actuation signal at the output interface to the brake pressure at least partially by means of the zw ei to generate pressure generating device.

One of the ideas on which the invention is based is that, in the event of a communication failure between a first, externally controlled pressure generating device and a brake pressure control system, which can be set up, for example, to carry out an anti-lock function such as ABS or ESP, the brake pressure is modulated with the first pressure generating device, which by means of a Form sensor is detected in a hydraulic path between the first pressure generating device and the wheel brake cylinder as a form. The recorded admission pressure is evaluated by the brake pressure control system, e.g. by a control unit of the brake pressure control system. Thus, the operating status of the first pressure generating device can be transmitted to the brake pressure control system despite the failure of the communication or despite the inability to send a status signal directly to the brake pressure system. If it is determined on the basis of the recorded pressure profile of the form that the first pressure generating device has failed, e.g. if no modulation of the form can be detected in a case in which no status signal is received at the brake pressure control system or at the control unit of the brake pressure control system, the second takes effect Pressure generating device of the brake pressure control system and generates at least partially the desired brake pressure in the wheel brake cylinder.

One advantage of the invention is that situations in which the operating status of the first pressure-generating device is no longer transmitted as a signal, e.g. via a bus system, to the brake pressure control system can still be reliably determined on the basis of the recorded form whether the first pressure-generating device is functional or not Generation of the brake pressure is to be carried out at least in part as an alternative by means of the second pressure generating device of the brake pressure control system. As a result, an unintentional activation of the brake pressure control system can advantageously be avoided when the first pressure generating device is functional. In particular, communication between the first control unit, which controls the first pressure generating device, and the second control unit, which controls the brake pressure control system, is made possible independently of the signal exchange between their communication interfaces. This improves the reliability of the control of the entire braking system.

Advantageous refinements and developments result from the further dependent claims and from the description with reference to the figures of the drawing.

According to some specific embodiments, it can be provided that the determination of the operating state of the first pressure generating device based on the detected admission pressure based on the modulation of the brake pressure includes an evaluation of a frequency and/or an amplitude of the admission pressure. For example, various error states can be encoded by the frequency and/or the amplitude that are impressed on the form by the pressure modulation performed by the first pressure-generating device.

According to some specific embodiments, it can be provided that the error state of the pressure generating device is determined when the amplitude is outside a predetermined amplitude range. For example, an error condition can be assumed if the amplitude is less than a predetermined threshold value. One advantage of evaluating the amplitude is that it can be determined in a simple computational manner from a pressure signal detected by the admission pressure sensor.

According to some specific embodiments, it can be provided that the error state of the pressure generating device is determined when the frequency lies outside a predetermined frequency range. Based on the frequency, an error state can advantageously be distinguished very reliably from other states that are associated with a pressure change, such as dynamic pressure fluctuations as a result of the displacement of a plunger of the first pressure generating device or the like.

According to some specific embodiments, it can be provided that the detection of the brake request signal includes detection of an actuation of a brake actuation device. For example, the travel of the brake actuation device can be detected using a travel sensor. The brake actuation device can be a brake pedal or a brake lever, for example.

According to some specific embodiments, provision can be made for a hydraulic reset pressure to be generated in a reset simulator as a result of the actuation of the brake actuation device by means of a master brake cylinder coupled to the brake actuation device. This offers the advantage that the pressure modulation can take place independently of the actuation of the brake actuation device or the driver cannot feel it at the brake actuation device.

According to some specific embodiments, provision can be made for the master brake cylinder to be hydraulically coupled to the wheel brake cylinder if an error state of the first pressure-generating device is determined. The master brake cylinder thus forms a further fallback level. For example, if an error state of the first pressure-generating device is determined, the brake pressure can be generated jointly by the master brake cylinder and the second pressure-generating device. In particular, it can be provided that the second pressure generating device interprets the determined form, which is built up by actuating the master brake cylinder, as a braking request and generates the brake pressure in the wheel brake cylinder based on the determined form. The brake pressure control system thus causes a brake pressure boost.

According to some specific embodiments, it can be provided that if an error state of the first pressure-generating device is determined, the first pressure-generating device is preferably hydraulically separated from the wheel brake cylinder.

According to some specific embodiments, it can be provided that, if an error state of the first pressure generating device is determined, the brake pressure is at least partially generated by means of the second pressure generating device based on the recorded admission pressure. For example, the second control unit can generate the actuation signal for actuating the second pressure-generating device based on the recorded form. This offers the advantage that, alternatively or in addition to the brake request signal, a reliable input variable can be used to determine the desired deceleration.

According to some specific embodiments, it can be provided that if an error state of the first pressure generation device is determined, the first control unit is integrated in a first control device of a brake pressure generation arrangement and the second control unit is integrated in a second control device of the brake pressure control system. In general, each control unit can have its own processor unit, e.g., a CPU, a microprocessor, an ASIC, an FPGA or the like. According to some embodiments, the control units can be implemented as completely separate hardware components. This offers the advantage that they can be installed in a vehicle in a space-saving, spatially separate manner.

The features and advantages disclosed herein in connection with one aspect of the invention parts are also disclosed for the other aspects of the invention, respectively.

• 1A, 1B eine schematische Darstellung eines hydraulischen Schaltbilds einer Bremsanlage gemäß einem Ausführungsbeispiel der Erfindung;
• 2 eine schematische Blockdarstellung eines Steuerungssystems gemäß einem Ausführungsbeispiel der Erfindung;
• 3 ein Flussdiagramm eines Verfahrens zum Bremsen eines Fahrzeugs gemäß einem Ausführungsbeispiel der Erfindung; und
• 4 ein Diagramm, in welchem der zeitliche Verlauf von Signalen und Zustandsgrößen einer Bremsanlage während der Durchführung des in 3 gezeigten Verfahrens dargestellt sind.

The invention is explained below with reference to the figures of the drawings. From the figures show:

• 1A , 1B a schematic representation of a hydraulic circuit diagram of a brake system according to an embodiment of the invention;
• 2 a schematic block diagram of a control system according to an embodiment of the invention;
• 3 a flowchart of a method for braking a vehicle according to an embodiment of the invention; and
• 4 a diagram in which the time course of signals and state variables of a brake system during the implementation of in 3 shown method are shown.

In the figures, the same reference symbols designate identical or functionally identical components, unless otherwise stated.

the 1A and 1B 1 schematically show an exemplary brake system 100 for a vehicle, in particular for a road vehicle such as a passenger car, a bus or a truck. The brake system 100 has one or more wheel brake cylinders 1, a braking force generation arrangement 110, a brake pressure control system 120 and a control system 130. The braking force generating arrangement 110 is in 1A shown, the brake pressure control system 120 is in 1B shown. Parts of the control system 130 can be found both in 1A as well as in 1B .

As in 1B is shown as an example, in particular one wheel brake cylinder 1 can be provided for each wheel. The wheel brake cylinder 1 is designed to convert a hydraulic pressure into a movement of a friction lining in order to press it against a friction piece 101 coupled to the wheel with a contact pressure force proportional to the hydraulic pressure, so that a friction or braking force inhibiting the rotation of the wheel is produced.

As in 1A shown, the braking force generating arrangement 110 has a first pressure generating device 10 and an actuation sensor 30 . Optionally, the braking force generation arrangement 110 can also have a brake master cylinder 12 kinematically coupled to a brake pedal 2 and a reservoir 15 for holding brake fluid. Instead of a brake pedal 2, a brake lever or, in general, a brake actuation device could also be provided. For reasons of clarity, reference is made below to a brake pedal 2, although the invention is not limited thereto.

The actuation sensor 30 is used to detect a variable that is proportional to a braking request signal and represents a target deceleration of the vehicle. For example, actuation sensor 30 can be a travel sensor that is set up to detect a travel or displacement of a brake pedal 2 that can be actuated by a driver. The travel is proportional to the driver's braking request.

The master brake cylinder 12 is kinematically coupled to the brake pedal 2 and can be actuated by it. By moving the brake pedal 2, brake fluid is transported out of the master brake cylinder 12. As in 1A shown by way of example, the master brake cylinder 12 can be hydraulically coupled to a resetting simulator 14 which generates a resetting force proportional to the actuation path of the pedal 2 . Furthermore, the master brake cylinder 12 can be hydraulically coupled to and separated from the wheel brake cylinder 1 via first isolating valves 13A. In 1A a state is shown by way of example in which the first isolating valves 13A are opened and the master brake cylinder 12 is thus hydraulically coupled to the wheel brake cylinder 1 . The first separating valves 13A can be switchable solenoid valves, for example, which are open when there is no current.

As in 1A Also shown as an example, the first pressure generating device 10 can be designed, for example, as a plunger 11, which has a piston 11B that can be displaced by a motor, in particular an electric motor 11A. The first pressure generating device 10 is hydraulically connected to the wheel brake cylinder 1 . In particular, the first pressure generating device 10 can be hydraulically coupled to and separated from the wheel brake cylinder 1 via second isolating valves 13B, as is shown in 1A is shown as an example. In 1A purely by way of example, a state is shown in which the second isolation valves 13B are closed and the first pressure-generating device 10 is thus hydraulically isolated from the wheel brake cylinder 1 . The second isolating valves 13B can be switchable solenoid valves, for example, which are closed when de-energized.

The brake pressure control system 120 is generally used to set a wheel-specific brake pressure, for example to perform an anti-lock function, such as ABS or ESP. As in 1B shown schematically, the brake pressure control system 120 comprises a second pressure generating device 20, which can be actuated independently of the first pressure generating device 10, and a admission pressure sensor 31. The second pressure generating device 20 can, as in 1B shown by way of example, for example, have a pump 21 for each two wheels or wheel brake cylinders 1, the pumps 21 being actuated by a common motor 22, for example an electric motor. However, it is also conceivable that one pump 21 is provided for each wheel or wheel brake cylinder 1 . As in 1B shown schematically, the pump 21 is arranged in a hydraulic path which connects the first pressure generating device 10 and, when the first isolating valves 13A are open, the master brake cylinder 12 to the respective wheel brake cylinder 1 . In general, the second pressure-generating device 20 is connected in parallel with the first pressure-generating device 10 . In particular, the second pressure generating device 20, as in 1B shown schematically, connected at a point between the wheel brake cylinder 1 and the first pressure generating device 10 to the first pressure generating device 10 and the wheel brake cylinder 1 connecting hydraulic path.

As in 1B is also shown schematically and purely by way of example, the brake pressure control system 120 can have an inlet valve 23 and an outlet valve 24 for each wheel brake cylinder 1, with the inlet valve 23 being arranged in a hydraulic path which connects a pressure outlet of the pump 21 with the wheel brake cylinder 1, and with the Inlet valve 23 is arranged in a hydraulic path which connects a suction inlet of the pump 21 to the wheel brake cylinder 1 . The inlet and outlet valves 23, 24 can in particular be switchable solenoid valves, so that by operating the second pressure generating device 20 and actuating the inlet and outlet valves 23, 24, wheel-specific brake pressure adjustment is possible.

The admission pressure sensor 31 is coupled to the hydraulic path connecting the first pressure generating device 10 to the wheel brake cylinder 1 and is set up to detect a pressure in the hydraulic path at a point between the first and the second pressure generating device 10 , 20 . As in 1B shown by way of example, a measuring point at which the pressure sensor 31 detects the pressure can be arranged in front of the suction inlet of the pump 21 of the second pressure-generating device 20 . Since the pressure is detected by the sensor 31 at a point in front of or upstream of the second pressure generating device 20, the sensor 31 is referred to as the admission pressure sensor and the detected pressure is referred to as the admission pressure. When the first separating valves 13A are closed, the pressure detected by the admission pressure sensor 31 corresponds to the pressure in the hydraulic path provided by the first pressure-generating device 10 . When the first separating valves 13A are open and the second separating valves 13B are closed, the pressure detected by the admission pressure sensor 31 corresponds to the pressure provided to the master brake cylinder 12 in the hydraulic path.

As in the 1A and 1B shown schematically, the control system 130 has a first control unit 131 and a second control unit 132 . The control system 130 is in 2 shown as a block diagram. As in 2 shown schematically, each control unit 131, 132 can have a processor unit 131D, 132D, e.g. in the form of a CPU, a microprocessor, an FPGA, an ASIC or the like, and a data memory 131E, 132E, in particular a non-volatile data memory such as a hard disk, a flash have memory or the like. For example, software can be stored in the data memory, which can be executed by the respective processor unit in order to generate output signals.

As in 2 Also shown, the first control unit 131 has an input interface 131A, an output interface 131B and a first communication interface 131C. In 2 purely by way of example, it is shown that the first communication interface 131C and the input interface 131A can be combined physically into one interface. However, the invention is not limited to this. In principle, all or only some of the interfaces 131A-C of the first control unit 131 can be physically separated or combined.

The second control unit 132 has an input interface 132A, an output interface 132B and a second communication interface 131C, as shown in FIG 2 is shown schematically. In 2 purely by way of example, it is shown that the second communication interface 132C and the input interface 132A can be combined physically into one interface. However, the invention is not limited to this. In principle, all or only some of the interfaces 132A-C of the first control unit 132 can be physically separated or combined.

The first and the second control unit 131, 132 are signal-connected, for example by a data bus 133 such as a CAN bus, as in the 1A and 1B is shown schematically. In particular, the first communication interface 131A of the first control unit 131 and the second communication interface 132B of the second control unit 132 are signal-connected, as shown in FIG 2 is shown schematically, eg above the data bus 133. How 2 shown further schematically, each control unit 131, 132 can have its own electrical supply connection 131F, 132F. In general, the first control unit 131 and the second control unit 132 can be integrated into different control devices, in particular with different housings. For example, the first control unit 131 can be integrated in a first control device of the brake pressure generation arrangement 110 and the second control unit 132 in a second control device of the brake pressure control system 120 . Alternatively, it would also be conceivable to integrate the control units 131, 132 with their own processor units 131D, 132D and their own electrical supply connections 131E, 131F into a common control unit. In this case, both processor units can optionally share a common memory unit.

The control system 130 can be as in the 1A and 1B be provided as part of the brake system 100 as an example. As in the 1A and 1B shown, the actuation sensor 30 can be connected to the input interface 131A, 132A of the first and/or the second control unit 131, 132, eg via the data bus 133 or another wireless or wired connection. The first pressure generating device 10 and optionally the first and second isolating valves 13A, 13B are signal-connected to the first control unit 131, in particular to its output interface 131B.

The second control unit 132 is signal-connected to the second pressure-generating device 20 and optionally to the inlet and outlet valves 23 , 24 . This signal connection can also be implemented, for example, via the data bus 133 or another wired or wireless connection. Furthermore, the admission pressure sensor 31 is signal-connected to the second control unit 132, in particular to its input interface 131A, e.g. via the data bus 133 or in a similar manner. In general, the control system 130 is thus signal-connected to the actuation sensor 30 , the admission pressure sensor 31 , the first pressure-generating device 10 and the brake pressure control system 120 .

When the brake system 100 is in a fully functional state, a driver actuates the brake pedal 2 in order to brake a vehicle, as a result of which the brake master cylinder 12 is displaced against the restoring force of the simulator 14 . The first isolating valves 13A are closed. The actuation sensor 30 detects the actuation, e.g. the travel of the brake pedal 2, and outputs a corresponding measurement signal. First control unit 131 receives the measurement signal at input interface 131A, determines a brake request signal based on the actuation signal, and outputs a control or actuation signal at output interface 131B based on the brake request signal, which causes first pressure-generating device 10 to generate a brake pressure corresponding to the brake request signal Wheel brake cylinder 1 to generate. In this case, the second isolating valves 13B are open. The first control unit 131 transmits or sends a status signal to the communication interface 132C of the second control unit 132 via the first communication interface 131C. The status signal represents an operating state of the first pressure generating device 10. For example, the status signal can represent the states “functional” and “error state”. Optionally, the brake request signal can also be transmitted to second control unit 132 or second control unit 132 can receive the actuation signal from actuation sensor 30 . Also optionally, the second control unit 132 can output an actuation or control signal at its output interface 132B to the second pressure generating device 20 and the inlet and outlet valves 23, 24 in order to carry out an anti-lock function, i.e. to vary the brake pressure in the wheel brake cylinders 1 in such a way that a The wheels are prevented from locking.

3 shows the sequence of a method M for braking a vehicle, which can be carried out using the brake system 100 described above. The method M is therefore described below with reference to the 1A and 1B brake system shown or the in 2 control system 130 shown explained. Furthermore, in 4 a diagram is shown, in which the following are plotted over a common time axis X: in relation to a first vertical axis Y1, the wheel brake pressure present in the wheel brake cylinder 1; with respect to a second vertical axis Y2, the admission pressure detected by the admission pressure sensor 31; in relation to a third vertical axis Y3, the total brake pressure generated by the first pressure generating device 10; in relation to a fourth vertical axis Y4, the brake request component of the brake pressure that is generated by the first pressure generating device 10; in relation to a fifth vertical axis Y5, the modulation component of the brake pressure that is generated by the first pressure generating device 10; with respect to a sixth vertical axis Y6, the status signal output from the first control unit 131; and with respect to a seventh vertical axis Y7, a transmission state of the status signal detected by the first control unit 131.

As in 3 shown schematically, in a first step M1 there is a detection M1 of a brake request signal, which is a target deceleration of the vehicle represents. As described above, this can include detecting an actuation of a brake actuation device, for example brake pedal 2 , using actuation sensor 31 .

In a further step M2, the brake pressure in the wheel brake cylinder 1 is generated by means of the first pressure generating device 10 based on the detected braking request signal. As described above, first control unit 131 emits an actuation signal for actuating first pressure-generating device 10 based on the brake request signal at output interface 131B, with first isolating valves 13A being closed and second isolating valves 13B being open.

The status signal is sent to brake pressure control system 120 in step M3. As described above, the first control unit 131 transmits the status signal to the second control unit 132. In step M4, a transmission error of the status signal is detected. Step M4 can, for example, include an evaluation by the first control unit 131 of a confirmation signal that the second control unit 132 sends to the first control unit 131 after receiving the status signal. For example, if no confirmation signal is received at the first control unit 131 after the status signal has been sent, the first control unit 131 can detect a transmission error. In 4 shows by way of example that no transmission error of the status signal occurs up to time t1 and the status signal represents the operating state “functional” of the first pressure generating device 10. The transmission state plotted with respect to the seventh vertical axis Y7 therefore has the value zero. Likewise, the status signal can have the value zero, as in relation to the sixth vertical axis Y6 in 4 applied. If no transmission error is detected in step M4, as is the case in 3 represented by the symbol "-", the method may optionally proceed directly to step M7, as indicated in 3 is shown. In 4 up to time t1, the pressures plotted on the vertical axis Y1-Y4 thus correspond to one another. A modulation component of the brake pressure (fifth vertical axis Y5 in 4 ) is zero.

If a transmission error is detected in step M4, as is the case in 3 represented by the symbol “+”, the method goes to step M5, in which the brake pressure is modulated by means of the first pressure generating device 10 . For this purpose, the first control unit 131 can, for example, modulate the actuation or control signal output at its output interface 131B in order to modulate the brake pressure generated by the first pressure-generating device 10 . In 4 a transmission error is detected at time t1, for example. In 4 the transmission state plotted with respect to the first vertical axis Y1 therefore assumes a non-zero value. At time t1, however, the first pressure generating device 10 is functional per se, which is 4 can be recognized by the status signal plotted with respect to the second vertical axis Y2, which represents the “functional” state. From time t1, in addition to the brake pressure component generated based on the brake request signal (fourth vertical axis Y4 in 4 ) a modulation part (fifth vertical axis Y5 in 4 ) generated by the first pressure generating device 10. As at the fifth vertical axis Y5 in 4 can be read, the brake pressure can be modulated, for example, with a predetermined frequency f1 and a predetermined amplitude a1. In 4 a modulation in a square-wave function is shown purely by way of example. Of course, other modulation profiles are also conceivable, for example a sinusoidal, a triangular or a sawtooth modulation or other similar modulations. As in 4 can be seen on the vertical axes Y1-Y4, this pressure modulation is applied to the other pressures in the brake system, in particular the admission pressure (second vertical axis Y2 in 4 ).

In step M6, which can already be carried out before step M4, in particular at the same time as steps M1-M4, the admission pressure is detected by means of the admission pressure sensor 31. As in 4 shown schematically, a modulating form is detected by the form sensor 31 from time t1, i.e. from the point in time at which the first pressure generating device 10 carries out a pressure modulation, and transmitted to the input interface 132A of the second control unit 132.

In step M7, the operating state of the first pressure generating device 10 is determined using the detected admission pressure based on the modulation of the brake pressure. In step M7, for example, the second control unit 132 evaluates the modulation of the detected admission pressure, which is proportional to the pressure generated by the first pressure generating device 10, at least as long as the first isolating valves 13A are closed and the second isolating valves 13B are open. For example, the second control unit 132 can evaluate the amplitude and/or the frequency of the form and determine from this whether the operating state of the first pressure generating device 10 is “faulty” or “functional”. An error state of the pressure generating device 10 can be determined in step M7, for example, if the amplitude is outside a predetermined amplitude range and/or if the frequency is outside a predetermined frequency range. In general, different information, for example about the operating state or other information, can be transmitted to the second control unit 132, for example by the frequency and/or the amplitude of the pressure modulation. One advantage is that this information transmission path is also available if the signal communication between the communication interfaces 131C, 132C of the control units 131, 132 fails.

In 4 it is shown by way of example that the status signal (sixth vertical axis Y6) changes from “functional” to “error status” at time t2. Accordingly, it can be read on the fifth vertical axis Y5 that the pressure is no longer modulated by the first pressure generating device 10 . Consequently, also in the form (second vertical axis Y2 in 4 ) no longer detects any modulation, which the second control unit 132 detects in step M7 or determines as an error state. Thus, the second control unit 132 can reliably determine the operating state of the first pressure generating device 10 between the times t1 and t2 despite an interrupted signal communication between the communication interfaces 131C, 132C of the control units 131, 132.

As long as no transmission error is detected, the status signal can be evaluated by the second control unit 132 in step M7 and the operating state of the first pressure-generating device 10 can be determined on the basis of the status signal.

If no error state is determined as the operating state in step M7 or the operating state is determined to be "functional", as in 3 represented by the symbol "-", the method M can return to step M2, for example. If an error condition is determined as the operating condition in step M7, as in 3 indicated by the symbol “+”, the brake pressure is generated at least partially by means of the second pressure generating device 10 in step M8.

This means that second control unit 132 emits an actuation or control signal at its output interface 132B, which causes second pressure-generating device 20 to set a predetermined pressure in wheel brake cylinder 1 . If an error condition is determined as the operating condition in step M7, the master brake cylinder 12 can optionally be hydraulically coupled to the wheel brake cylinder 1, e.g. by opening the first isolating valves 13A. Optionally, the first pressure generating device 10 can also be hydraulically separated from the wheel brake cylinder 1, e.g. by closing the second separating valves 13B. In order to determine the pressure required in the wheel brake cylinders 1, the second control unit 132 can, for example, evaluate the admission pressure detected by the admission pressure sensor 31. When the first isolating valves 13A are open, the admission pressure is proportional to the pressure generated by the master brake cylinder 12, which in turn is proportional to the travel of the pedal 2. The form is therefore proportional to the brake request signal. Accordingly, the second control unit 132 can cause the second pressure generation device 10 to generate the brake pressure based on the recorded admission pressure.

As in 4 shown schematically, at time t2 the pressure generated by the first pressure generating device 10 returns to zero, as can be read on the vertical axes Y3 and Y4. At the same time, the other pressures in the hydraulic path between the first pressure generating device 10 and the wheel brake cylinder 1 also drop, as is the case on the vertical axes Y1 and Y2 in 4 is recognizable. This is due to the fact that the isolating valves 13A, 13B can only be actuated quickly and only after a certain delay at time t3 is there any appreciable pressure in the hydraulic path again, which pressure is generated by the master brake cylinder 12, for example. From point in time t3, the second pressure-generating device 20 generates pressure in addition to the pressure generated by master brake cylinder 12, which is recorded as the admission pressure (second vertical axis Y2 in 4 ) a hydraulic pressure in the wheel brake cylinder (first vertical axis Y1 in 4 ).

The method M described thus offers the advantage that the second pressure generation device 20 of the brake pressure control system 120 is reliably activated as a backup for generating or boosting the brake pressure if the first pressure generation device 10 fails. Furthermore, in the method M, an unintentional activation of the second pressure generating device 20 for generating or boosting the brake pressure is reliably avoided in that, if the signal communication between the communication interfaces 131C, 132C of the control units 131, 132 of the brake pressure generating arrangement 110 and the brake pressure control system fails, from the first pressure generating device 10 a pressure modulation is carried out, which is detected using the admission pressure sensor 31. The second control unit 132 of the brake pressure control system 120 can thus continue to reliably determine the operating state of the first pressure generating device 10 on the basis of the form.

Although the present invention above with reference to exemplary embodiments exempla has been explained technically, it is not limited to this, but can be modified in many ways. In particular, combinations of the above exemplary embodiments are also conceivable.

QUOTES INCLUDED IN DESCRIPTION

This list of the documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102014225954 A1 [0005]

Claims (10)

Method (M) for braking a vehicle, comprising: detecting (M1) a braking request signal which represents a target deceleration of the vehicle; Generating (M2) a hydraulic brake pressure in a wheel brake cylinder (1) based on the detected braking request signal by means of a first pressure generating device (10) which is hydraulically connected to the wheel brake cylinder (1); Sending (M3) a status signal representing an operating state of the first pressure generating device (10) to a brake pressure control system (120) which has a second pressure generating device (20) hydraulically coupled to the wheel brake cylinder; detecting (M4) a transmission error of the status signal; modulating (M5) the brake pressure by means of the first pressure generating device (10) when a transmission error is detected; Detecting (M6) an admission pressure in a hydraulic path between the first pressure generating device (10) and the wheel brake cylinder (1) at a point which is located between the first pressure generating device (10) and the second pressure generating device (20); Determination (M7) of the operating state of the first pressure generating device (10) using the detected admission pressure based on the modulation of the brake pressure; and at least partially generating (M8) the brake pressure by means of the second pressure generating device (10) if an error state is determined as the operating state of the pressure generating device (10). Procedure (M) according to claim 1 , wherein the determination (M6) of the operating state of the first pressure generating device (10) based on the detected form based on the modulation of the brake pressure comprises an evaluation of a frequency and / or an amplitude of the form. Procedure (M) according to claim 2 , wherein the error state of the pressure generating device (10) is determined when the amplitude is outside a predetermined amplitude range. Procedure (M) according to claim 2 or 3 , wherein the error state of the pressure generating device (10) is determined when the frequency is outside a predetermined frequency range. Method (M) according to one of the preceding claims, wherein the detection (M1) of the brake request signal includes detecting an actuation of a brake actuation device (2). Procedure (M) according to claim 5 , wherein a hydraulic reset pressure is generated in a reset simulator (14) by actuating the brake actuation device (2) by means of a brake master cylinder (12) coupled to the brake actuation device (2), and optionally, if an error state of the first pressure generation device (10) is determined , the master brake cylinder (12) is hydraulically coupled to the wheel brake cylinder (1), and the first pressure generating device (10) is preferably hydraulically separated from the wheel brake cylinder (1). Method according to one of the preceding claims, wherein the at least partial generation (M8) of the brake pressure takes place by means of the second pressure generation device (10) based on the detected admission pressure. Brake system (100) for a vehicle, comprising: a sensor (30) for detecting a braking request signal; a wheel brake cylinder (1) for generating a frictional force on a wheel of the vehicle; a first pressure generating device (10) which is hydraulically coupled to the wheel brake cylinder (1) and is set up to generate a hydraulic pressure in the wheel brake cylinder (1); a brake pressure control system (120) with a second pressure generating device (20) which is hydraulically coupled to the wheel brake cylinder (1) and set up to generate a hydraulic pressure in the wheel brake cylinder (1) independently of the first pressure generating device (10); an admission pressure sensor (31) for detecting an admission pressure in a hydraulic path between the first pressure generating device (10) and the wheel brake cylinder (1) at a point which is located between the first pressure generating device (10) and the second pressure generating device (20); and a control system (130) connected to the actuation sensor (30), the admission pressure sensor (31), the first pressure generation device (10) and the brake pressure control system (120) and is set up to cause the brake system (100) to carry out a method (M) according to one of the preceding claims. Control system (130) for a braking system (100) of a vehicle, comprising: a first control unit (131) with an input interface (131A) for connection to a sensor (30) for detecting a braking request signal representing a target deceleration of the vehicle, an output interface (131B) to the connection with a first pressure generating device (10), which is hydraulically connected to a wheel brake cylinder (1), and a communication interface (131C), wherein the first control unit (131) is set up to transmit an actuating signal for actuating the first pressure generating device (10) based on the to output a braking request signal at the output interface (131B), to output a status signal, which represents an operating state of the first control unit (131), to the communication interface (131C), to detect a transmission error in the status signal and, if a transmission error is detected, to modulate the actuation signal, to modulate the braking pressure generated by the first pressure generating device (10); and a second control unit (132) with an output interface (132B) for connection to a second pressure generating device (20), hydraulically coupled to the wheel brake cylinder (1), of a brake pressure control system (120), an input interface (132A) for connection to an admission pressure sensor (31) for detecting a form in a hydraulic path between the first pressure generating device (10) and the wheel brake cylinder (1) at a point which is located between the first pressure generating device (10) and the second pressure generating device (20), and a communication interface (132C), which is connected to the communication interface (131C) of the first control unit (131), the second control unit (132) being set up to use the form to detect an error state of the first pressure generating device (10) based on the modulation of the brake pressure and to send an actuation signal the output interface (132B) output in order to generate the brake pressure at least partially by means of the second pressure generating device (20). Control system (130) according to claim 9 , wherein the first control unit (131) is integrated in a first control device of a brake pressure generating arrangement (110) and the second control unit (132) in a second control device of the brake pressure control system (120).

Images