Method and braking system for braking a vehicle

Abstract

The present invention relates to a method (M) for braking a vehicle, the method comprising: detecting (M1) a braking demand signal representative of a target deceleration of the vehicle; generating (M21) in the wheel brake cylinder (1) a hydraulic brake pressure based on the detected braking demand signal using a first pressure generator (10) fluidly connected to the wheel brake cylinder (1); detecting (M3) a fault condition of the first pressure generator (10); calculating (M4) an alternative braking demand signal upon detection of a fault condition of the first pressure generator (10), wherein the alternative braking demand signal is calculated based on a target deceleration that is established at a preset time point prior to detection of the fault condition; and generating (M5) an alternative brake pressure in the wheel brake cylinder (1) based on the calculated alternative braking demand signal using a brake pressure control device (120) having a second pressure generator (20) fluidly connected to the wheel brake cylinder. Furthermore, the present invention relates to a method (M) for braking a vehicle, in which an alternative braking request signal is calculated on the basis of a target deceleration, which is determined at a predetermined time before the detection of the fault condition, on the basis of a braking torque generated by an electric machine kinematically coupled to the wheels of the vehicle. Another aspect of the present invention relates to a braking system (100) for a vehicle.

Description

Technical Field

[0001] The present invention relates to a method for braking a vehicle and a braking system for a vehicle.

Background Art

[0002] In road vehicles, such as passenger cars or trucks, hydraulic braking systems are used in a standard form. Such braking systems are increasingly operated according to the "brake-by-wire" principle, in which the operation of the brake pedal is detected by a sensor, and from the result, a braking demand representing the desired deceleration of the vehicle is calculated. From this braking demand, the hydraulic pressure generated in the wheel brake cylinder to brake the vehicle wheels is calculated using a pressure generating device, such as an electrically driven plunger.

[0003] Furthermore, the braking system of a road vehicle generally has a brake pressure control device for individual wheel brake pressure control, for example, to implement an anti-lock function (ABS). In a standard form, such a brake pressure control device has its own pressure generating device and a valve device for individual wheel pressure changes.

[0004] In a braking system operating according to the brake-by-wire principle, when the pressure generating device fails, in a standard form, the master brake cylinder operable by the brake pedal is fluid-connected to the wheel brake cylinder, so that the necessary brake pressure can be generated manually.

[0005] Patent Document 1 describes a braking system in which the pressure generating device of a brake pressure control device designed to generate brake pressure individually for each wheel takes over the generation of the desired brake pressure when the first externally controlled pressure generating device fails.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

[0007] According to the present invention, there are provided a method for braking a vehicle having the features of claim 1, a method for braking a vehicle having the features of claim 10, and a braking system having the features of claim 12.

[0008] According to a first aspect of the present invention, there is provided a method for braking a vehicle. The method includes detecting a braking demand signal representing a target deceleration of the vehicle, for example, based on an operation of a braking operation device; generating a hydraulic brake pressure in a wheel brake cylinder based on the detected braking demand signal using a first pressure generating device fluidly connected to the wheel brake cylinder; detecting a defective state of the first pressure generating device; when the defective state of the first pressure generating device is detected, calculating an alternative braking demand signal, and calculating the alternative braking demand signal based on a target deceleration determined at a preset time point before the detection of the defective state; and generating an alternative brake pressure in the wheel brake cylinder based on the calculated alternative braking demand signal using a brake pressure control device having a second pressure generating device fluidly connected to the wheel brake cylinder.

[0009] According to a second aspect of the present invention, a method for braking a vehicle includes detecting a braking request signal representing a target deceleration of the vehicle, for example, based on an operation of a braking operation device; generating a braking torque using an electromechanical device kinematically coupled to a wheel of the vehicle based on the braking request signal; maintaining a first pressure generating device fluidly connected to a wheel brake cylinder to generate a brake pressure in the wheel brake cylinder based on the braking request signal; detecting a defective state of the first pressure generating device; when the defective state of the first pressure generating device is detected, calculating an alternative braking request signal, and in this case, calculating the alternative braking request signal based on a target deceleration determined at a preset time point before the detection of the defective state based on the braking torque generated by the electromechanical device; and generating an alternative brake pressure in the wheel brake cylinder based on the calculated alternative braking request signal using a brake pressure control device having a second pressure generating device fluidly connected to the wheel brake cylinder.

[0010] According to a third aspect of the present invention, a braking system for a vehicle is provided. The braking system includes a sensor for detecting a braking request or a braking request signal, a wheel brake cylinder for generating a frictional force on a wheel of the vehicle, a first pressure generating device fluidly connected to the wheel brake cylinder and designed to generate a hydraulic pressure in the wheel brake cylinder, a brake pressure control device including a second pressure generating device fluidly connected to the wheel brake cylinder and designed to generate a hydraulic pressure in the wheel brake cylinder independently of the first pressure generating device, and a control system signal-connected to the operation sensor, the first pressure generating device, and the brake pressure control device and designed to give an instruction to the braking system to execute the method according to the first aspect of the present invention. When the method is executed according to the third aspect of the present invention, the control system may particularly have an interface for connecting to the electromechanical device.

[0011] The idea underlying the present invention is that in a braking system in which hydraulic braking pressure is generated by using a pressure generating device connected to a braking operation device such as an auxiliary power-driven or non-kinematic brake pedal or brake lever, the failure of the pressure generating device is corrected by a brake pressure control device provided for executing, for example, an ABS function or an ESP function. In this case, when a failure state or a defective state of the pressure generating device is detected, the brake pressure control device first adjusts the brake pressure corresponding to the brake pressure determined before the failure is detected or equal to the brake torque generated electromechanically. That is, for example, it is not necessary to use the detection of a braking request signal generated by a driver, and first, the brake pressure corresponding to a desired target deceleration determined at a past predetermined time point is automatically adjusted. Therefore, such an alternative brake pressure is generated based only on a calculated or correspondingly generated alternative braking request signal, and the alternative braking request signal may be particularly constant only for at least a preset time interval. In this case, the present invention can be used not only for purely hydraulic braking, but also for braking in which the braking torque is partially generated by an electromechanical device operated as a generator and partially by a hydraulic or wheel brake cylinder, and also for purely regenerative braking in which the braking torque is first completely generated by an electromechanical device operated as a generator. In regenerative braking, or according to a second aspect of the present invention, a first pressure generating device is maintained, for example, as a backup or for subsequent intervention supplementarily. If the first pressure generating device fails during purely regenerative braking before generating a brake pressure in the wheel brake cylinder, the regenerative braking is terminated, and the brake pressure control device generates a brake pressure in the wheel brake cylinder based on the last effective brake torque generated by the electromechanical device before the first pressure generating device fails.

[0012] The defective state of a first pressure generating device, which may be, for example, a plunger driven by an electric motor, is generally detected when the pressure generating device is no longer in a state to adjust the desired braking pressure. This is the case, for example, when the pressure generating device has failed because the electric motor is overheated or damaged in some other way, or when the pressure generating device does not receive an operating signal. The pressure generating device not receiving an operating signal occurs, for example, when the detection of the braking demand signal no longer functions or when the calculation of the braking pressure by the control unit, for example, no longer functions.

Advantages of the Invention

[0013] An advantage of the present invention is that as soon as the first pressure generating device fails, the braking pressure is generated based on the braking demand determined before the failure, using the second pressure generating device of the brake pressure control device. That is, first of all, it is not necessary to wait for the driver's reaction that occurs, for example, when the brake pedal is depressed or when the brake lever is tightened. Therefore, the braking distance is shortened in a suitable manner.

[0014] Preferred embodiments and implementation modes are described in the specification with reference to the other dependent claims and the figures of the drawings.

[0015] According to many examples, the detection of the braking demand signal may include the detection of the operation of the braking operation device. For example, the control stroke of the brake pedal or the brake lever is detected using an operation sensor, and in this case, the braking demand signal is generated based on the detected control stroke. Other forms of operation detection are also conceivable. For example, the detection of the pressure generated in the simulator by the operation of the braking operation device is also conceivable. Generally, the detection of the braking demand signal is performed based on the operation of the braking operation device.

[0016] According to many embodiments, the calculation of the alternative braking demand signal may include calculating the control stroke of the braking actuator at a preset time point before detection of the defective state. For example, the control stroke of a braking actuator such as a pedal or lever can be calculated, as described above, in particular by a control stroke sensor. The calculated control stroke is detected in a time-resolved manner, and the detected values can be stored, in particular, for a particularly flexible preset time interval, so that even if the control stroke sensor and / or the first pressure generating device fails, the last valid value can be determined, which is then used to calculate the alternative braking demand. Safety is thus further improved in such a manner.

[0017] According to many embodiments, the calculation of the alternative braking demand signal may include calculating the brake pressure in the wheel brake cylinder at a preset time point before detection of the defective state. For example, in a hydraulic line connecting the first pressure generating device to the wheel brake cylinder, the pressure is detected by a sensor, in particular in a time-resolved manner, and in this case the detected values can be stored, in particular, for a particularly flexible preset time interval, so that even if the first pressure generating device fails, the last valid value can be determined, which is then used to calculate the alternative braking demand. Safety is thus further improved in such a manner.

[0018] According to many embodiments, this method may include generating a braking torque based on a braking demand signal using an electromechanical device kinematically connected to a wheel of the vehicle. This may be suitable, for example, in an electrically driven vehicle or a hybrid vehicle, in which case the desired target deceleration is effected partly by operation of the electromechanical device as a generator and partly by using the wheel brake cylinder. Thus, the hydraulic brake pressure generated by the first and / or second pressure generating device in the wheel brake cylinder also depends on the extent to which the electromechanical device is involved in the target deceleration.

[0019] According to many embodiments, the alternative braking torque may be calculated based on the braking torque generated by the electromechanical machine. For example, a control unit of the electromechanical machine, such as power electronics, can output a mechanical control signal representing the braking torque generated by the electromechanical machine to the control system of the hydraulic braking system, and this control system uses this mechanical control signal to calculate how much braking torque needs to be generated by the friction brake cylinder.

[0020] According to many embodiments, the brake pressure control device has a first control unit that operates a second pressure generating device, and the defective state of the first pressure generating device may be detected using a control signal transmitted to the first control unit. For example, if no control signal is received or a defective signal is transmitted to the first control unit instead of the control signal, the defective state is detected. The first control unit may have, for example, a processor unit, in particular with one or more CPUs, FPGAs, ASICs, etc., and a data memory, in particular a non-volatile data memory such as an HDD memory or an SSD memory. For example, software executable by the processor unit for outputting an output signal, in particular an operating signal, to the second pressure generating device and optionally to a valve to operate them may be stored in the data memory. The output signal is generated, for example, based on the control signal and / or based on a pressure signal representing the actual pressure generated on the suction side of the second pressure generating device. For this purpose, the first control device may be designed to give an instruction to the pressure generating device, optionally in cooperation with a valve device, to execute an anti-lock function and / or to give an instruction to vary the brake pressure individually for each wheel.

[0021] According to many embodiments, the first pressure generating device may be operated by the second control unit based on a braking demand signal, and the second control unit may generate a first control signal and transmit it to the first control unit. The second control unit may include, for example, a processor unit equipped with one or more CPUs, FPGAs, ASICs, etc., and a data memory, particularly a non-volatile data memory such as an HDD memory or an SSD memory. For example, software executable by the processor unit may be stored in the data memory to output an output signal, particularly an operation signal, to the first pressure generating device and optionally to a valve to operate them. For example, the second control unit may calculate a braking pressure based on a braking demand signal output by, for example, a control stroke sensor connected to a brake operating device, and operate the first pressure generating device accordingly. The second control device may transmit, to the first control device, for example, the calculated braking pressure, the control stroke of the brake operating device, or others, to the first control device as a control signal in proportion to the target deceleration. Optionally, the first control device may store the control signal obtained from the second control device in the data memory for a flexible predetermined time interval, so that when a defective state exists in the pressure generating device, the stored values can be used to more easily calculate an alternative braking demand signal.

[0022] According to many embodiments, the generation of an alternative braking pressure may include the generation of a linearly, stepwise, and / or progressive or regressive pressure increase within the wheel brake cylinder.

[0023] According to many embodiments, by operating a brake operating device which may be, for example, a brake pedal or a brake lever as described above, a hydraulic reset pressure is generated in the reset simulator using a master brake cylinder. When a defective state of the first pressure generating device is detected, the master brake cylinder is fluidly connected to the wheel brake cylinder, and the first pressure generating device may be fluidly separated from the wheel brake cylinder in a suitable manner. The master brake cylinder may be fluidly connected to the wheel brake cylinder by, for example, a first separate valve and may be separated from this wheel brake cylinder. The first pressure generating device may be fluidly connected to the wheel brake cylinder by a second separate valve in a similar manner and may be separated from this wheel brake cylinder. If the first pressure generating device is in a normal operating state, the first separate valve is closed, and the master brake cylinder kinematically connected to the brake operating device is thereby fluidly separated from the wheel brake cylinder. If the first pressure generating device is in a defective state, the first separate valve is opened and optionally the second separate valve is closed. Thereby, the master brake cylinder is fluidly connected to the wheel brake cylinder. As a result, the driver no longer senses only the reset force of the simulator in the brake operating device, but rather senses the actual braking pressure that he controls. Moreover, when the first separate valve is opened, a volume movement from the wheel brake cylinder into the master brake cylinder occurs, thereby causing a decrease in the braking pressure. This needs to be corrected by further operating the brake operating device by the driver, for example by depressing the brake pedal. However, according to the invention, the brake pressure control device can completely take over the pressure generation at least in a transition mode and can adjust the finally determined brake pressure, so that the driver is given a lot of time for reaction, thereby improving the operating comfort and safety in an advantageous manner.

[0024] According to many embodiments, an alternative brake pressure is generated based on a calculated alternative braking demand signal for a preset first time interval, and then the alternative braking demand signal is particularly linearly decreased to zero within a transition time interval, and the alternative brake pressure is generated using a brake pressure control device based on the sum of the alternative braking demand signal and the detected braking demand signal during the transition time interval. Thus, after an alternative brake pressure adjusted based on the alternative braking demand signal is obtained, the alternative braking demand signal decreases, which simultaneously causes a decrease in the alternative brake pressure. In order to maintain a constant deceleration of the vehicle, such a decrease must be corrected by the operation of the brake operating device and thus by the generation of a corresponding braking demand signal. Therefore, a transition process is provided, during which the alternative braking demand signal is gradually decreased, for example linearly decreased.

[0025] According to many embodiments of the brake system, the sensor for detecting the braking demand signal may be an operating sensor configured to detect the operation of the brake operating device, particularly the control stroke. For example, the detection of the control stroke of a pedal or a brake lever is preferably relatively less prone to failure. Further, the operation signal detected by the operating sensor can be converted and stored in a simple form, which simplifies the generation of the alternative braking demand signal.

[0026] The features and advantages disclosed herein for one aspect of the present invention are also disclosed for each other aspect of the present invention, and vice versa.

Brief Description of the Drawings

[0027]

Fig. 1A

Fig. 1B

Fig. 2

Fig. 3

Fig. 4

Embodiments for Carrying Out the Invention

[0028] The present invention will be described below with reference to the figures in the drawings.

[0029] In the drawings, the same or functionally equivalent components are given the same reference numerals unless otherwise indicated.

[0030] FIGS. 1A and 1B schematically show a braking system 100 for a vehicle, in particular a road vehicle, such as a passenger car, a bus or a goods vehicle. The braking system 100 has at least one wheel brake cylinder 1, a braking force generating device 110, a brake pressure control device 120 and a control system 130. The braking force generating device 110 is shown in FIG. 1A, and the brake pressure control device 120 is shown in FIG. 1B. Parts of the control system 130 are present in both FIG. 1A and FIG. 1B.

[0031] As shown by way of example in FIG. 1B, each wheel may be provided with in particular one wheel brake cylinder 1 each. The wheel brake cylinder 1 is configured to convert hydraulic pressure into the movement of a friction lining and press this friction lining against a friction member 101 coupled to the wheel with a pressing force proportional to the hydraulic pressure, thereby generating a frictional force or braking force that hinders the rotation of the wheel.

[0032] As shown in FIG. 1A, the braking force generating device 110 has an operation sensor 30 and a first pressure generating device 10. Optionally, the braking force generating device 110 further has a master brake cylinder 12 kinematically connected to the brake pedal 2 and a reservoir tank 15 for storing brake fluid. Instead of the brake pedal 2, a brake lever or a general brake operating device may be provided. Hereinafter, the brake pedal 2 is shown for clarity, but the present invention is not limited to the brake pedal.

[0033] The operation sensor 30 is used to detect a braking request representing the target deceleration of the vehicle. For example, the operation sensor 30 may be a control stroke sensor designed to detect the control stroke or the amount of movement of the brake pedal 2 operable by the driver.

[0034] The master brake cylinder 12 is kinematically connected to the brake pedal 2 and is operable by the brake pedal 2. When the brake pedal 2 moves, the brake fluid is discharged from the master brake cylinder 12. As shown as an example in FIG. 1A, the master brake cylinder 12 is fluidly connected to a reset simulator 14 that generates a return force proportional to the operation stroke of the pedal 2. Further, the master brake cylinder 12 can be fluidly connected to the wheel brake cylinder 1 via a first separate valve 13A and can be fluidly separated from the wheel brake cylinder 1. In FIG. 1A, as an example, the first separate valve 13A is open, and thus the state in which the master brake cylinder 12 is fluidly connected to the wheel brake cylinder 1 is shown. The first separate valve 13A may be, for example, a switchable solenoid valve that is open when de-energized.

[0035] As shown by way of example in FIG. 1A, the first pressure generating device 10 may be configured, for example, as a plunger 11 which has a piston 11B movable by a motor, in particular an electric motor 11A. The first pressure generating device 10 is fluidly connected to the wheel brake cylinder 1. In particular, as shown by way of example in FIGS. 1A and 1B, the first pressure generating device 10 can be fluidly connected to the wheel brake cylinder 1 via a second separate valve 13B and can be fluidly separated from this wheel brake cylinder 1. In FIG. 1A, purely by way of example, a state is shown in which the second separate valve 13B is closed, whereby the first pressure generating device 10 is fluidly separated from the wheel brake cylinder 1. The second separate valve 13B may be, for example, a normally closed switchable solenoid valve.

[0036] The brake pressure control device 120 is generally used to adjust the brake pressure for each wheel and to implement an anti-lock function such as ABS or ESP. As schematically shown in FIG. 1B, the brake pressure control device 120 has a second pressure generating device 20, which can be operated independently of the first pressure generating device 10. As an example shown in FIG. 1B, the second pressure generating device 20 may have, for example, one pump 21 for each of two wheels or wheel brake cylinders 1. In this case, the pump 21 is operated by one common motor 22, for example an electric motor. However, it is also conceivable that one pump 21 is provided for each wheel or each wheel brake cylinder 1. As schematically shown in FIG. 1B, the pump 21 is arranged in a hydraulic flow path, which connects the first pressure generating device 10 to each wheel brake cylinder 1 and, when the first separate valve 13A is open, connects the master brake cylinder 12 to each wheel brake cylinder 1. As further schematically and purely by way of example shown in FIG. 1B, the brake pressure control device 120 has one suction valve 23 and one discharge valve 24 for each wheel brake cylinder 1. In this case, the suction valve 23 is arranged in a hydraulic flow path connecting the pressure outlet of the pump 21 to the wheel brake cylinder 1, and the suction valve 23 is arranged in a hydraulic flow path connecting the suction port of the pump 21 to the wheel brake cylinder 1. Since the suction valve and the discharge valves 23, 24 may in particular be switchable solenoid valves, the brake pressure can be adjusted individually for each wheel by operating the second pressure generating device 20 and the suction valve and the discharge valves 23, 24.

[0037] The control system 130 may particularly have a first control unit 131 and a second control unit 132. However, basically, it is also conceivable that only one control unit is provided. The control unit 130 may particularly have a processor unit (not shown), for example with one or more CPUs, FPGAs, ASICs, etc., and a data memory (not shown), particularly a non-volatile data memory such as an HDD memory or an SSD memory. For example, software executable by each processor unit to generate an output signal may be stored in the data memory.

[0038] The first and second control units 131, 132 are signal-connected by a data bus 133 such as a CAN bus. Further, the operation sensor 30 is connected to the first and / or second control units 131, 132 via, for example, the data bus 133 or other wireless or wire connections. The first pressure generating device 10 is further signal-connected to the second pressure generating device 20 and also, in some cases, to the intake valve and discharge valve 23, 24. This signal connection can be realized via, for example, the data bus 133 or other wire or wireless connections. The second control unit 132 is signal-connected to the first pressure generating device 10 and the first and second separate valves 13A, 13B via, for example, the data bus 133 or other wire or wireless connections. Thereby, the control system 130 is signal-connected to the operation sensor 30, the first pressure generating device 10, and the brake pressure control device 120. Optionally, the control system 130 may further be signal-connected to the electric machine 150 via, for example, the data bus 133 or other wire or wireless connections. The electric machine 150 is kinematically connected to one or more wheels of the vehicle and can be operated as a motor and also as a generator. For example, the first and / or second control units 131, 132 may have an interface for connecting to the electric machine 150.

[0039] Figure 2 schematically shows the process of method M for braking a vehicle. This method M can be particularly executed using the braking system 100 described above. In particular, the control system 130 is designed to instruct the braking system 100 to execute this method M. Next, this method M will be described below with reference to the braking system 100 shown in FIGS. 1A and 1B.

[0040] In the first step M1 of this method, a braking demand signal representing the target deceleration of the vehicle is detected. This braking demand signal is detected, for example, using an operation sensor 30 based on the operation of the brake pedal 2 or generally the operation of a braking operation device.

[0041] In the next step M21, a braking pressure is generated in the wheel brake cylinder 1 by the first pressure generating device 10 based on the detected braking demand signal. For example, the second control unit 132 calculates the braking pressure to be adjusted in the wheel brake cylinder to obtain the desired deceleration from the detected braking demand signal, outputs a corresponding operation signal to the first pressure generating device 10, and thereby instructs this first pressure generating device 10 to prompt it to adjust the braking pressure. Instead of or in addition to step M21, in step M22, a braking torque is generated based on the braking demand signal by the electromechanical device 150 kinematically connected to the wheel of the vehicle. In particular, in the case of an electric drive vehicle or a hybrid vehicle, the electromechanical device 150 that drives the wheel is operated as a generator to brake the vehicle. It should be noted that the braking force generating device 110 and the braking pressure control device 120 are also maintained when pure regenerative braking is solely executed by the electromechanical device 150, for example, when the braking torque generated by the electromechanical device 150 is not sufficient to obtain the desired deceleration of the vehicle.

[0042] In step M3, detection M3 of a defective state of the first pressure generating device 10 is performed. For example, in step M30, the functional state of the first pressure generating device 10 is calculated. In the next step M31, it is calculated whether this functional state corresponds to a defective state. A defective state of the first pressure generating device 10 exists when the first pressure generating device 10 is no longer in a state where it can adjust the desired brake pressure. Such a case is, for example, when the pressure generating device 10 has failed because the electric motor 11 is damaged, or when the pressure generating device 10 no longer receives an operation signal from the second control unit 132. The latter case occurs, for example, when detection of a braking demand signal no longer functions based on a failure of the sensor 30, or when calculation of the brake pressure by the second control unit 132 no longer functions. Detection of the defective state can be performed using the first control unit 131 by evaluating a control signal transmitted to the first control unit 131. For example, the second control unit 132 can transmit a first control signal to the first control unit 131. The first control signal may include, for example, a brake pressure, a braking demand signal, and / or a status signal representing a functional state calculated by the second control unit 132. Thus, the first control unit 131 detects the defective state of the first pressure generating device 10, for example, based on the functional state included in the control signal, based on the fact that no control signal returns from the second control unit 132, or based on a characteristic value characterizing the control signal, for example, a gradient.

[0043] In step M31, if it is determined that there is no defective state as indicated by the symbol "-" in FIG. 2, the method returns to step M30. In step M31, if it is determined that there is a defective state as indicated by the symbol "+" in FIG. 2, the method proceeds to step M4 and optionally to M40. In optional step M40, the first separate valve 13A is opened, for example, by the second control unit 132, and the second separate valve 13B is further optionally closed, for example, by the second control unit 132. Thereby, when a defective state of the first pressure generating device is detected, the master brake cylinder 12 is fluidly connected to the wheel brake cylinder 1, and the first pressure generating device 10 is fluidly separated from the wheel brake cylinder 1.

[0044] In step M4, an alternative braking demand signal is calculated based on a target deceleration speed that has been determined at a preset time point before the defective state is detected. This can be done, for example, using the first control unit 131. The first control unit 131 can calculate, for example, the control stroke of the brake pedal 2 at a preset time point before the defective state is detected. This can be done, for example, by the first control unit 131 receiving the signal of the operating sensor 30 directly from the operating sensor 30 or from the second control unit 132 and temporarily storing this value for a predetermined time interval. For example, this value can always be stored for 500 ms after the actual time point. The last valid value is considered to calculate the brake pressure to be adjusted in the wheel brake cylinder 1 from the control stroke. Optionally or additionally, the calculation of the alternative braking demand signal may include the calculation of the brake pressure in the wheel brake cylinder 1 at a preset time point before the defective state is detected. For example, the first control unit 131 may be connected to the pressure sensor 31, and this pressure sensor 31 detects the pressure in the hydraulic flow path connecting the first pressure generating device 10 to the wheel brake cylinder 1, particularly at a position in front of the suction port of the pump 21 of the second pressure generating device 20 as shown by way of example in FIG. 1B. Also in this case, the first control unit 131 can temporarily store the value recorded by the pressure sensor 31 for a predetermined time, for example, 500 ms after the actual time point. The last valid value can be considered as the target pressure to be adjusted in the wheel brake cylinder 1. For example, the last valid value may be a value after a preset time interval, for example, 200 ms has elapsed. When an electromechanical device 150 is added to the brake system 100 and is operated as a generator to brake the vehicle as described above, the alternative brake torque may optionally or additionally be calculated based on the brake torque generated by the electromechanical device 150. For example, the first control unit 131 is connected to the power electronics of the electromechanical device 150, and the brake torque generated by the electromechanical device 150 can be obtained from this power electronics.The final effective braking requirement can be back-calculated from this braking torque, and the necessary hydraulic braking pressure can be calculated from the result. When the braking torque is solely generated by the electromechanics 150 in step M22, an alternative braking torque based on the braking torque generated by the electromechanics 150 is calculated. In this case, optionally, the calculation of the alternative braking requirement signal may additionally include the calculation of the braking pressure in the wheel brake cylinder 1 at a preset time point before detecting the defective state using, for example, the pressure sensor 31 as described above. Generally, the alternative braking requirement signal is calculated as a certain value corresponding to the last effective braking requirement signal.

[0045] In step M5, an alternative braking pressure is generated in the wheel brake cylinder 1 based on the calculated alternative braking requirement signal using the second pressure generating device 20 of the brake pressure control device 120. For this purpose, the first control unit 131 outputs an operation signal to the second pressure generating device 20, thereby instructing the second pressure generating device 20 to adjust the calculated alternative braking pressure. Further, the first control unit 131 opens the suction valve 23 and closes the discharge valve 24 of each wheel brake cylinder 1. For example, the generation M5 of the alternative braking pressure includes the generation of a linear, stepwise, and / or progressive or regressive pressure increase in the wheel brake cylinder 1. Optionally, in step M5, the generation of the braking torque may be stopped using the electromechanics 150. Optionally, in step M5, the alternative braking requirement signal may be generated for a preset first time interval based on the calculated alternative braking requirement signal. During the first time interval, the alternative braking requirement signal may be particularly constant. Following the first time interval, the alternative braking requirement signal is decreased to zero within a transition time interval. During the transition time interval, the alternative braking pressure is generated by the brake pressure control device based on the sum of the alternative braking requirement signal and the detected braking requirement signal.

[0046] The advantage of the method M is that, as soon as a failure of the first pressure generating device is detected, an alternative braking request is calculated based on the input value calculated before the first pressure generating device fails. Therefore, for example, when the brake pressure in the wheel brake cylinder 1 decreases based on the opening of the first separate valve 13A, there is no need for the driver to wait until he operates the brake pedal again in order to generate a new valid input value. Using the alternative braking request, the control system 130 can very quickly calculate a target brake pressure corresponding to at least approximately the last valid target brake pressure, and moreover, it can be adjusted immediately by the brake pressure control device.

[0047] In FIGS. 3 and 4, the aforementioned advantages and further advantages of the method M become apparent. FIG. 3 shows four graphs (A), (B), (C), (D), and in these four graphs, the abscissa is a time axis valid for all graphs (A) to (D) respectively. The ordinate of graph (A) shows the actual brake pressure in the wheel brake cylinder 1. The ordinate of graph (B) shows the actual braking request signal or the actual alternative braking request signal. The control stroke of the brake pedal 2 is shown on the ordinate of graph (C). Shown on the ordinate of graph (D). From the graphs (A) to (D) shown in FIG. 3, the braking process executed by the brake system 100 according to the method M is shown, and at this time, the deceleration of the vehicle is completely or at least partially executed by the brake system 100.

[0048] At the time point t0 shown in FIG. 3, the generation of the brake pressure by the first pressure generating device 10 is performed in the above form. That is, steps M1, M21 and M3 are executed. In the graph (C) of FIG. 3, it can be seen that the pedal 2 is moved and maintained by a certain control stroke. Accordingly, the braking request shown in the graph (B) of FIG. 3 and the reaction force on the pedal 2 shown in the graph (D) of FIG. 3 are constant. Correspondingly, the first pressure generating device 10 generates a constant brake pressure in the wheel brake cylinder 1 as shown in the graph (A) of FIG. 3.

[0049] At time t1, a defective state of the first pressure generating device 10 is detected during the execution of step M3. Thereby, as described above, the first separate valve 13A is opened, and the second separate valve 13B is preferably closed. In the graph (A) of FIG. 3, a further change in the brake pressure generated by using the brake pressure control device 120 by the execution of method M is shown by a solid line. The broken line shown in the graph (A) of FIG. 3 indicates the brake pressure that would be generated by the brake pressure control device 120 when the brake pressure control device 120 is operated based solely on the braking demand signal and not based on the alternative braking demand signal. As can be seen from the graph (A) of FIG. 3, the brake pressure drops sharply at time t1. This is because high-pressure brake fluid flows into the master brake cylinder 12 based on the opening of the first separate valve 13A. Accordingly, the pedal 2 is pushed back (graph (C) of FIG. 3), and the reaction force at the pedal 2 increases (graph (D) of FIG. 3). Based on the change in the pedal control stroke 2, as can be seen from the graph (B) of FIG. 3, the braking demand also decreases. Optionally, when a defective state is detected in the braking force generating device 110 or the first pressure generating device 10, for example, the operation sensor 30 stops operating, so the braking demand signal is first generated based on the pressure detected by the pressure sensor 31. In this case, the braking demand is decreased at time t1. This is because the brake pressure is decreased by the opening of the first separate valve 13A. In the graph (B), the braking demand corresponding to the braking demand signal, which is given only by the operation of the brake pedal 2, is shown by a broken line. The dashed-dotted line in the graph (B) of FIG. 3 indicates the alternative braking demand signal generated in step M4 of the above-described method M.

[0050] As can be seen from the dashed line in graph (B) of FIG. 3, an alternative braking demand signal is generated at time t2 (step M4 of method M). The deceleration at time t1 is obtained, for example, based on the evaluation time or calculation time required for the control system 130, in particular the first control unit 131, to calculate the alternative braking demand signal. As can be seen from graph (B) of FIG. 3, the alternative braking demand signal is generated to correspond to the last valid braking demand signal before time t1. Based on this alternative braking demand signal, the second pressure generating device 20 of the brake pressure control device 120 begins to increase the brake pressure in the wheel brake cylinder 1 again. At this time, as can be seen from the change in the solid line in graph (A) of FIG. 3, the brake pressure that existed before the first pressure generating device in the wheel brake cylinder 1 failed is obtained again at time t4. Therefore, the time interval t24 between times t2 and t4 may be referred to as the response time of the brake pressure control device 120. As can be seen from the dashed line in graph (A) of FIG. 3, if the method M is not executed, the pressure will decrease until a balance is obtained between the reaction force at the brake pedal 2 and the brake pressure at time t3. Therefore, the driver requires a predetermined reaction time to further depress the pedal 2 again. Further depressing the pedal 2 again is performed again from time t5 as can be seen from graphs (C) and (D) of FIG. 3. Therefore, the time interval t25 between times t2 and t5 may be regarded as the driver's reaction time.

[0051] The dashed lines in graphs (A) to (C) indicate the changes that would be obtained without the method M respectively when the operation of the pedal 2 is solely used to generate a braking demand signal. As can be seen from the change in the dashed lines of graphs (C) and (D) in FIG. 3, from time point t5, the control stroke of the pedal 2 is increased again based on the increase in the pedal effort. Accordingly, a braking demand signal is calculated, and as can be seen from the dashed line in graph (B) of FIG. 3, the braking demand rises again, whereby the brake pressure control device 120 is instructed to adjust the brake pressure accordingly. In this case, at time point t6, the brake pressure that existed before the failure of the first pressure generating device 10 is obtained (the dashed line in graph (A) of FIG. 3). Therefore, time point t46 indicates a shortening of the time that can be obtained by the method M to generate again the brake pressure that existed before the failure of the first pressure generating device 10.

[0052] As shown as an example in graphs (B) to (D) of FIG. 3, when method M is executed, a transition process may be executed starting from time point t5. As described above, during the execution of step M5, the actual braking demand signal calculated based on the operation of the brake pedal 2 may be ignored, and only the calculated alternative braking demand signal is used to generate a braking pressure in the wheel brake cylinder 1 for at least a preset time interval corresponding to time interval t25 in FIG. 3. In graph (B) of FIG. 3, a double-dashed line indicates the braking demand generated by the operation of the brake pedal 2 after the failure of the first pressure generating device 10 in the method M. In this case, the corresponding control stroke of the pedal 2 and the associated pedal force are shown by solid lines in graphs (C) and (D) of FIG. 3. In graph (B) of FIG. 3, an alternate-dot line indicates the alternative braking demand signal. In graph (B) of FIG. 3, a solid line indicates the sum of the alternative braking demand signal and the braking demand signal generated by the operation of the brake pedal 2. As can be seen from graphs (B) to (D) of FIG. 3 and as shown as an example in FIG. 3, for example, due to a linear decrease in the alternative braking demand signal, the alternative braking demand signal is decreased from time point t5 until it reaches zero within a preset transition time interval t57. In order to keep the sum of the braking demand signal generated by the operation of the brake pedal 2 and the alternative braking demand signal constant, the driver needs to compensate for the decrease in the alternative braking demand signal by operating the pedal 2. This is shown as an example in FIG. 3. In this case, at time point t7, the alternative braking demand is decreased to zero, and the braking demand signal is provided again only by the operation of the brake pedal 2. As described above, thereby, within the transition time interval t57, an alternative braking pressure is generated based on the sum of the braking demand signal and the alternative braking demand signal. The advantage of this method type is that in order to correctly maintain the deceleration of the vehicle, the pedal 2 does not need to be operated very quickly or strongly by the driver.

[0053] In graphs (A) to (D) shown in FIG. 4, a braking process performed by the brake system 100 according to the method M is shown when the braking torque is generated only by the generator-like operation of the electromechanical device 150 (step M22 of method M is executed).

[0054] At time t0 shown in FIG. 4, the generation of the brake pressure by the first pressure generating device 10 is not performed. This is because the electromechanics generates the desired brake torque alone. That is, steps M1, M22 and M3 of the method M in FIG. 2 are executed. As can be seen from graph (C) in FIG. 4, the pedal 2 is moved and maintained by a certain control stroke. Accordingly, the braking demand shown in graph (B) in FIG. 4 and the reaction force of the pedal 2 shown in graph (D) in FIG. 4 are constant.

[0055] When step M3 is executed at time point t1, a defective state of the first pressure generating device 10 is detected. In this embodiment, this may be, for example, a failure of the operation sensor 30. Therefore, as described above, the first separate valve 13A is opened, and the second separate valve 13B is preferably closed. When the first separate valve 13A is opened, based on the operation of the pedal 2 by the driver, the pedal 2 is moved again (graph (C) in FIG. 4). In this case, the pedal force decreases based on the missing return force of the simulator 14 at this time point (graph (D) in FIG. 4). In the graph (A) of FIG. 4, a further change in the brake pressure generated by using the brake pressure control device 120 by the execution of the method M is shown by a solid line. The broken line shown in the graph (A) of FIG. 4 indicates the brake pressure that would be generated by the brake pressure control device 120 when the brake pressure control device 120 is not operated based on the alternative braking request signal but only based on the braking request signal. As can be seen from the graph (A) of FIG. 4, the brake pressure slightly increases at time point t1. This is because the brake fluid flows out of the master brake cylinder 12 due to the opening of the first separate valve 13A and the operation of the pedal 2. Since the operation sensor 30 is faulty in this embodiment, the braking request decreases at time point t1. Optionally, when a defective state is detected in the braking force generating device 110 or the first pressure generating device 10, it may be designed such that a braking request signal is first generated based on the pressure detected by the pressure sensor 31. Also in this case, the braking request is very small at time point t1. This is because only pressure correction is performed by the opening of the first separate valve 13A.

[0056] As indicated by the dashed-dotted line in graph (B) of FIG. 4, an alternative braking request signal is generated starting from time point t2 (step M4 of method M). The deceleration at time point t1 is obtained, for example, based on the evaluation time or calculation time required for the control system 130, in particular the first control unit 131, to calculate the alternative braking request signal. As can be seen from graph (B) of FIG. 4, the alternative braking request signal is generated to correspond to the last valid braking request signal before time point t1. Based on the alternative braking request signal, the second pressure generating device 20 of the brake pressure control device 120 starts to increase the brake pressure in the wheel brake cylinder 1. At this time, as indicated by the solid line change in graph (A) of FIG. 4, at time point t4, a brake pressure corresponding to the brake torque represented by the braking request is obtained. For example, this brake torque corresponds to the brake torque previously generated by the electromechanical device 150, and in this case, the generator operation of the electromechanical device 150 is stopped. Therefore, the time interval t24 between time points t2 and t4 may be referred to as the response time of the brake pressure control device 120. As indicated by the dashed line in graph (A) of FIG. 4, if the method M is not executed, the pressure is first kept constant until the driver reacts and further presses the pedal 2. The driver's reaction to further press the pedal 2 is performed again starting from time point t5, as shown in graphs (C) and (D) of FIG. 4. Therefore, the time interval t25 between time points t2 and t5 may be regarded as the driver's reaction time.

[0057] In graphs (A) to (C), the dashed lines show the changes obtained without performing method M when only the operation of pedal 2 for generating a braking demand signal is used or when the pressure detected by pressure sensor 31 as a result is used. As shown by the dashed lines in graphs (C) and (D) of FIG. 4, based on the increase in pedal force, the control stroke of pedal 2 increases again from time point t5. Accordingly, as shown by the dashed line in graph (B) of FIG. 4, the brake volume is moved into wheel brake cylinder 1, the pressure detected by pressure sensor 31 increases, and the actual braking demand generated by the driver increases again, whereby brake pressure control device 120 is urged to adjust the brake pressure accordingly. In this case, at time point t6, the brake pressure that existed before the failure of first pressure generating device 10 is obtained (dashed line in graph (A) of FIG. 3). Therefore, time interval t46 represents the shortening of the time that can be obtained by the above method M to recover the braking torque that existed before the failure of first pressure generating device 10.

[0058] As shown as an example in graphs (B) to (D) of FIG. 4 and as previously described in connection with FIG. 3, during the execution of this method M, a transition process can be executed starting from time point t5. As previously described, during the execution of step M5, the actual braking demand signal calculated based on the operation of the brake pedal 2 may be ignored, and only the calculated alternative braking demand signal is utilized for at least a preset time interval corresponding to the time interval t25 in FIG. 4 to generate a brake pressure in the wheel brake cylinder 1. In FIG. 4, graph (B) shows, by a double-dashed line, the braking demand generated by the operation of the brake pedal 2 in the method M after the failure of the first pressure generating device 10. In this case, the control stroke of the pedal 2 and the associated pedal force are shown by solid lines in graphs (C) and (D) of FIG. 4. The dash-dotted line in graph (B) of FIG. 4 indicates the alternative braking demand signal. The solid line in graph (B) of FIG. 4 indicates the sum of the alternative braking demand signal and the braking demand signal generated by the operation of the brake pedal 2. As can be seen from graphs (B) to (D) of FIG. 4, the alternative braking demand signal decreases to zero from time point t5 to time point t7, as shown linearly in FIG. 4. Therefore, the time interval between t5 and t7 is called the transition time interval t57. In order to keep the sum of the braking demand signal generated by the operation of the brake pedal 2 and the alternative braking demand signal constant, the driver needs to correct the decrease in the alternative braking demand signal by operating the pedal 2. In the example shown in FIG. 4, when the alternative braking demand becomes zero at time point t7, the braking demand signal is generated again only by the operation of the brake pedal 2. As described above, thereby, within the transition time interval t57, an alternative brake pressure is generated based on the sum of the braking demand signal and the alternative braking demand signal. The advantage of this method type is that the pedal 2 does not need to be operated very quickly or strongly by the driver in order to correctly maintain the deceleration of the vehicle.

[0059] Although the present invention has been specifically described as above using a plurality of embodiments, it is not limited to these embodiments and can be changed in various forms. In particular, combinations of the above embodiments are also conceivable.

Explanation of Reference Numerals

[0060] 1 Wheel brake cylinder 2 Brake operating device, brake pedal 10 First pressure generating device 11 Plunger 11A Electric motor 11B Piston 12 Master brake cylinder 13A First separate valve 13B Second separate valve 14 Reset simulator 15 Reservoir tank 20 Second pressure generating device 21 Pump 22 Motor, electric motor 23 Suction valve 24 Discharge valve 30 Operation sensor 100 Brake system 101 Friction member 110 Braking force generating device 120 Brake pressure control device 130 Control system 131 First control unit 132 Second control unit 133 Data bus 150 Electromechanics M Method for braking a vehicle M1,M3,M4,M5,M21,M22,M30,M31 Steps M40 Optional step t0~t7 Time points t24,t25,t46,t57 Time intervals

Claims

1. In a method (M) for braking a vehicle, detecting a braking demand signal representing a target deceleration of the vehicle (M1), generating a hydraulic brake pressure in the wheel brake cylinder (1) based on the detected braking demand signal using a first pressure generating device (10) fluidly connected to the wheel brake cylinder (1) (M21), detecting a defective state of the first pressure generating device (10) (M3), when the defective state of the first pressure generating device (10) is detected, calculating an alternative braking demand signal (M4), and in this case, calculating the alternative braking demand signal based on a target deceleration determined at a preset time point before the detection of the defective state, generating an alternative brake pressure in the wheel brake cylinder (1) based on the calculated alternative braking demand signal using a brake pressure control device (120) having a second pressure generating device (20) fluidly connected to the wheel brake cylinder (M5), A method (M) for braking a vehicle, comprising the above.

2. The method (M) according to claim 1, wherein the detection (M1) of the braking demand signal includes detecting an operation of a brake operating device (2), and / or the calculation (M4) of the alternative braking demand signal includes calculating a control stroke of the brake operating device (2) at a preset time point before the detection of the defective state.

3. The method (M) according to claim 1 or 2, wherein the calculation (M4) of the alternative braking demand signal includes calculating a brake pressure in the wheel brake cylinder at a preset time point before the detection of the defective state.

4. Additionally, generating a braking torque based on the braking demand signal using an electromechanical device (150) kinematically connected to a wheel of the vehicle (M22), the method (M) according to any one of claims 1 to 3.

5. The method according to claim 4, wherein an alternative braking torque is calculated based on the braking torque generated by the electromechanical device (150).

6. The method (M) according to any one of claims 1 to 5, wherein the brake pressure control device (120) has a first control unit (131) for operating the second pressure generating device (20), and the defective state of the first pressure generating device (10) is detected using a control signal transmitted to the first control unit (131).

7. The method (M) according to claim 6, wherein the first pressure generating device (10) is operated by a second control unit (132) based on the braking demand signal, and the second control unit (132) generates the control signal and transmits it to the first control unit (131).

8. The method (M) according to any one of claims 1 to 7, wherein the generation of the alternative brake pressure (M5) includes the generation of a linearly increasing, stepwise, and / or progressive or regressive pressure increase within the wheel brake cylinder (1).

9. By operating the brake operating device (2), a hydraulic reset pressure is generated in the reset simulator (14) using the master brake cylinder (12). When a defective state of the first pressure generating device is detected, the master brake cylinder (12) is fluidly connected to the wheel brake cylinder (1), and the first pressure generating device (10) is fluidly separated from the wheel brake cylinder (1) in a suitable manner. The method (M) according to claim 2

10. In a method (M) for braking a vehicle, Detecting a braking demand signal representing the target deceleration of the vehicle (M1), Generating a braking torque using an electromechanical machine (150) kinematically connected to the wheels of the vehicle based on the braking demand signal (M22), Maintaining a first pressure generating device (10) fluidly connected to the wheel brake cylinder (1) to generate a brake pressure within the wheel brake cylinder (1) based on the braking demand signal, Detecting a defective state of the first pressure generating device (10) (M3), When a defective state of the first pressure generating device (10) is detected, calculating an alternative braking demand signal (M4), and calculating the alternative braking demand signal based on the braking torque generated by the electromechanical machine, the alternative braking demand signal being based on the target deceleration determined at a preset time point before the detection of the defective state. Generating an alternative brake pressure within the wheel brake cylinder (1) based on the calculated alternative braking demand signal using a brake pressure control device (120) having a second pressure generating device (20) fluidly connected to the wheel brake cylinder (M5). A method (M) for braking a vehicle, comprising the steps above.

11. Generate the calculated alternative braking demand signal based on the alternative brake pressure for a preset first time interval (t25), and then particularly linearly reduce the alternative braking demand signal to zero within the transition time interval (t57). During the transition time interval (t57), generate the alternative brake pressure using the brake pressure control device (120) based on the sum of the alternative braking demand signal and the detected braking demand signal. The method (M) according to any one of claims 1 to 10.

12. In a brake system (100) for a vehicle, a sensor (30) for detecting a braking demand; a wheel brake cylinder (1) for generating a frictional force on the vehicle wheel; a first pressure generating device (10) fluidly connected to the wheel brake cylinder (1) and designed to generate a hydraulic pressure in the wheel brake cylinder (1); a brake pressure control device (120) fluidly connected to the wheel brake cylinder (1) and including a second pressure generating device (20) designed to generate a hydraulic pressure in the wheel brake cylinder (1) independently of the first pressure generating device (10); a control system (130) signal-connected to the sensor (30), the first pressure generating device (10), and the brake pressure control device (120) and designed to give an instruction to the brake system (100) to execute the method (M) according to any one of claims 1 to 11; A brake system (100) for a vehicle having the above components.

13. The brake system (100) according to claim 12, wherein the sensor for detecting the braking demand signal is an operating sensor (30), and the operating sensor (30) is configured to detect the operation of a brake operating device (2), particularly the control stroke.

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