DE102017202361A1 - Method for operating a brake system and brake system - Google Patents

Abstract

Method for driver brake request detection (P _setpoint ) in a brake system, which comprises
• at least two electrically actuated wheel brakes (42-48);
A simulator (14) for simulating a conventional brake pedal feel;
• a brake pedal (6) for operating the simulator (14);
A pedal travel sensor for measuring the pedal travel (X _pedal ) of the brake pedal (6), wherein the pedal travel (X _pedal ) is used to detect the driver braking request (P _target ), and the pedal foot force (F _pedal ) is measured and when detecting the Driver braking request (P _Soll , F _SP ) is used, and wherein the driver brake request detection comprises the determination of a driver brake request (P _{Soll, FWE} ), wherein the driver brake request detection is given by the maximum of the driver brake request (P _{Soll, FWE} ) and at least one additional brake request (P _{Soll , F_func1} , P _{setpoint, F_func2} ).

Description

The invention relates to a method for driver braking request detection in a brake system, which comprises at least two electrically actuated wheel brakes, a simulator for simulating a conventional brake pedal feeling, a brake pedal for operating the simulator, a pedal travel sensor for measuring the pedal travel of the brake pedal, wherein for detecting the driver's brake request of the pedal travel and wherein the pedal foot force is measured and used in detecting the driver brake request, and wherein the driver brake request detection comprises determining a driver brake request. It also relates to a brake system.

In automotive engineering, brake-by-wire brake systems are becoming increasingly widespread. Such brake systems often comprise, in addition to an actuatable by the driver master cylinder an electrically ("by-wire") controllable pressure supply device by means of which in the operating mode "brake-by-wire" takes place an actuation of the wheel brakes.

In these brake systems, in particular electro-hydraulic brake systems with the "brake-by-wire" mode, the driver is decoupled from the direct access to the brakes. Upon actuation of the pedal usually a pedal decoupling unit and a simulator are operated, which is detected by a sensor, the braking request of the driver. The pedal simulator serves to give the driver as familiar a brake pedal feel as possible. The detected braking request leads to the determination of a desired braking torque, from which then the target brake pressure for the brakes is determined. The brake pressure is then actively built up by a pressure-providing device in the brakes.

The actual braking thus takes place by active pressure build-up in the brake circuits with the aid of a pressure supply device, which is controlled by a control and regulation unit. As a result of the hydraulic decoupling of the brake pedal actuation from the pressure build-up, many functionalities such as ABS, ESC, TCS, hill-start assist etc. can be comfortably realized for the driver in such brake systems.

The pressure-providing device in brake systems described above is also referred to as an actuator or hydraulic actuator. In particular, actuators are designed as linear actuators in which a piston is axially displaced into a hydraulic pressure chamber to build up pressure, which is built in series with a rotational-translation gear. The angle of the motor shaft of an electric motor is converted by the rotation-translation gear in an axial displacement of the piston.

From the DE 10 2013 204 778 A1 is a "brake-by-wire" -Bremsanlage for motor vehicles is known which a brake pedal operable tandem master cylinder, the pressure chambers are connected via an electrically actuated release valve separable with a brake circuit with two wheel brakes, a hydraulically connected to the master cylinder, switched on and off simulation device , And an electrically controllable pressure-supplying device, which is formed by a cylinder-piston arrangement with a hydraulic pressure chamber whose piston is displaceable by an electromechanical actuator includes, wherein the pressure-supplying device is connected via two electrically actuated Zuschaltventile with the intake valves of the wheel brakes.

In such brake systems, a mechanical or hydraulic fallback stage is usually provided, by means of which the driver can decelerate or stop the vehicle by muscular force when the brake pedal is actuated, if the "by-wire" mode of operation fails or is disturbed. While in normal operation by a pedal decoupling unit, the above-described hydraulic decoupling between brake pedal operation and brake pressure build-up, this decoupling is canceled in the fallback so that the driver can move brake means directly into the brake circuits. In the fallback level is switched when with the help of the pressure supply device no pressure build-up is possible.

In normal operation, the driver actuates a pedal simulator in such an external power brake system, wherein this pedal operation is detected by pedal sensors and a corresponding pressure setpoint for the linear actuator is determined to actuate the wheel brakes. A movement of the linear actuator from its rest position forward into the pressure chamber displaces brake fluid volume from the linear actuator via the open valves in the wheel brakes and thus causes a pressure build-up. In the opposite case, the movement of the linear actuator back in the direction of its rest position leads to a pressure reduction in the wheel brakes. The setting of a required system pressure is carried out with the aid of a suitable pressure regulator or a suitable pressure control system in which, for example, a speed controller is subordinate to the pressure regulator. To demand and precise adjustment of the required pressures in the brake system is a Pressure-volume curve deposited, which represents the ratio of volume and pressure, so that for each volume of the associated pressure can be determined and vice versa.

Upon actuation of the brake pedal to request a brake pressure, the driver is no longer directly connected to the brake system, but operates a pedal simulator having a suitable pedal characteristic, so that the driver is a sufficiently accurate dosage of the requested braking desired. This pedal operation is detected by pedal sensors and determined therefrom a desired braking request of the driver pressure setpoint for the linear actuator to actuate the wheel brakes. For this purpose, the _pedal position X _pedal and the pressure generated by the driver in the simulator are usually detected by means of a pressure sensor (P _simulator ), the pedal position and possibly also the simulator pressure being determined redundantly for reasons of safety. Thus, for the driver request detection, two physically independent information are available for the driver actuation representing the driver brake request for the setpoint generation of the required brake force boost by means of the linear actuator. The result and output variable of a functional unit "driver request acquisition" to be provided in the control unit or ECU is a desired value for the boost pressure (target pressure in the linear actuator) determined on the basis of the driver pedal actuation.

In the presence of a braking request moves a movement of the linear actuator from its rest position forward brake fluid volume from the linear actuator on the open valves in the wheel brakes and thus causes a pressure build-up. In the opposite case, the movement of the linear actuator back in the direction of its rest position leads to a pressure reduction in the wheel brakes. Due to the design-related inertia of the linear actuator, it must first be accelerated to carry out this movement, so that there is a certain dynamic distortion between the placement of a pressure request on the basis of the detected braking request and its setting or implementation. This can be considerable depending on the design of the linear actuator and the demand on the dynamics of the braking process. Especially with fast pedal operations and the associated highly dynamic pressure requirements, it is therefore important to capture the driver's desire as early as possible.

The invention is therefore based on the object of specifying a method with which the driver's braking request is detected as early and precisely as possible. In addition, a brake system should be specified, which allows early and precise driver braking request detection.

With regard to the method, this object is achieved in that the driver brake request detection is given by the maximum of the driver brake request and at least one additional brake request.

Advantageous embodiments of the invention are the subject of the dependent claims.

The invention is based on the consideration that in brake-by-wire mode the precise and earliest possible detection of the driver's braking request is very important in order to be able to perform braking operations with active pressure build-up as well as possible in accordance with the driver's braking request. Especially with emergency braking early detection is important.

As has now been recognized, the driver's braking request can be detected as early and precisely as possible by measuring how much the driver presses on the brake pedal or how much he presses it. This means that the driver pedal force is measured. Particularly in simulators designed to not allow detection of a driver or simulator pressure signal, as is the case, for example, with a mechanical pedal simulator, the driver's foot force provides a useful signal for detecting the desired braking because a pressure signal is not available , By taking into account additional braking requirements, the driver's braking request can be detected more quickly, for example by parameterizing the response of the brake pedal or actuation of the brake pedal, which could indicate an emergency braking, by means of an additional braking request. These supplemental brake requirements may advantageously bear the fact that the pedal operation by the driver is initially recognizable in the signal of a sensor which measures the pedal foot force.

A first additional brake request is preferably set to a value of zero, if no pressure request is detected, and is set to a constant value as soon as a pedal actuation by the driver is reliably detected on the basis of the pedal force signal.

The first additional brake request is preferably set to zero if, during a predetermined time interval based on the pedal travel no pedal actuation is detected, a maximum request time has expired or the brake pedal is released again. The pedal operation is detected in this case when the pedal travel exceeds a predetermined pedal travel threshold for a predetermined number of sampling steps.

Preferably, a second supplemental brake request is set to a value of zero, unless a pressure request is detected, and is set to a constant value as soon as a pedal actuation by the driver which is faster than a predefined pedal speed threshold is reliably detected on the basis of the pedal force signal. A safe detection of the pedal operation is preferably performed when, during a predetermined period, the pedal force is greater than a predetermined pedal force threshold, said pedal force threshold being set to be exceeded only at the fast pedal speed values faster than the noted pedal speed threshold.

This force threshold represented by means of the pedal force threshold value is preferably selected to be so high that it can only be exceeded in the event of a rapid pedal actuation, which then leads to the initiation of emergency braking.

The second additional brake request function is preferably set to zero when no pedal operation is detected or a maximum request time has elapsed during a predetermined time interval based on the pedal travel.

The driver brake request is preferably given by the product of a weighting factor having a first function that depends on the pedal travel and / or the pedal speed, and a second contribution given by the product of a weighting factor having a function that depends on the pedaling force.

In a first preferred embodiment, the brake system is formed electro-hydraulically, wherein the wheel brakes are formed hydraulically, and wherein an electro-hydraulic pressure supply device for braking pressure buildup of at least one wheel brake, in which by means of an electric motor, a pressure piston in a hydraulic pressure chamber is displaceable.

Advantageously, in this case, the simulator on a hydraulic simulator chamber, in which upon actuation of the brake pedal pressure medium is conveyed from the master cylinder.

In a further preferred embodiment, the brake system is formed electromechanically, wherein the wheel brakes are designed as electromechanical wheel brakes.

Advantageously, the simulator is mechanically formed. This means that a pressure signal for detecting the driver's braking request is not available. Therefore, the pedal travel signal and the pedal pedal force signal are available for detecting the driver's brake request.

The invention also includes a method for a brake system comprising both hydraulic and electromechanical wheel brakes. For example, a brake circuit can be hydraulically designed, the other brake circuit electromechanical.

The term "electrically actuable wheel brakes" preferably designates that the corresponding wheel brake for setting a desired wheel brake pressure or wheel brake target pressure can be electrically actuated by a control and regulation unit. This applies to both hydraulic and electromechanical wheel brakes.

The driver's braking request or pressure requirements designate in the context of the application in an electro-hydraulically designed brake system each have a desired pressure or a pressure request for a desired pressure.

In the case of an electromechanically designed brake system, the driver's brake request or the pressure request designate a request for the application force with which the brake pads are pressed against the brake disk. The application force, which is necessary for the realization of the driver's brake request, is preferably determined separately for the front axle and the rear axle.

That the pedal foot force is used includes in particular their consideration in the calculation of the driver's brake request. It is in a sense an input variable in a module which calculates the driver's braking request.

The Pedalfußkraft is preferably measured by means of a sensor or force element, which is installed for example on the piston rod of the brake pedal module. As a result, taking into account the pedal ratio, the force is detected with the driver via the brake pedal actuates the pedal simulator.

The driver brake request detection preferably includes the determination of a driver brake request in which the pedal travel and the pedal foot force are used.

With regard to the brake system, the abovementioned object is achieved according to the invention by means of a method described above. In particular, the brake system comprises a control and regulation unit, in which the method is implemented in hardware and / or software.

In a first preferred embodiment, the brake system is formed electro-hydraulically with at least two, preferably four hydraulically designed wheel brakes.

In a second embodiment, the brake system is electromechanically formed with at least two electromechanically designed wheel brakes.

The advantages of the invention are, in particular, that the driver's safety is increased by an early and precise detection of the driver's braking request in connection with additional braking requirements.

• 1 eine Bremsanlage in einer bevorzugten Ausführungsform;
• 2 ein Ablaufdiagramm eines Verfahrens in einer ersten bevorzugten Ausführungsform; und
• 3 ein Ablaufdiagramm eines Verfahrens in einer zweiten bevorzugten Ausführungsform.

An embodiment of the invention will be explained in more detail with reference to a drawing. In it show in a highly schematic representation:

• 1 a brake system in a preferred embodiment;
• 2 a flowchart of a method in a first preferred embodiment; and
• 3 a flowchart of a method in a second preferred embodiment.

Identical parts are provided with the same reference numerals in all figures.

In 1 is an embodiment of a brake system according to the invention 2 shown. The brake system comprises one by means of an actuating or brake pedal 6 actuated master cylinder 10 , one with the master cylinder 10 cooperating simulation device 14 , a master cylinder 10 assigned, under atmospheric pressure medium reservoir 18 , an electrically controllable pressure supply device 20 , which by a cylinder-piston arrangement with a hydraulic pressure space 26 is formed, whose pistons 32 is displaceable by an electromechanical actuator, an electrically controllable pressure modulation device for setting wheel-individual brake pressures and an electronic control and regulation unit 40 ,

The unspecified pressure modulation device comprises, for example hydraulically actuated wheel brakes 42 . 44 . 46 . 48 and each operable wheel brake 42 to 48 an inlet valve 50 . 52 , 54, 56 and an exhaust valve 60 . 62 . 64 . 66 , the hydraulically interconnected in pairs via center ports and to the wheel brakes 42 to 48 are connected. The inlet connections of the inlet valves 50 to 56 be by means of brake circuit supply lines 70 . 72 supplied with pressures that are derived in a "brake-by-wire" mode from a system pressure in one to the pressure chamber 26 the pressure supply device 20 connected system pressure line 80 is present and corresponds to the pressure provided by the pressure supply device. The brake 42 . 44 are doing to a first brake circuit 84 , the brake 46 . 48 to a second brake circuit 88 hydraulically connected.

The inlet valves 50 to 56 is one to each of the brake circuit supply lines 70 . 72 back opening check valve 90, 92, 94, 96 connected in parallel. In a fallback mode, the brake circuit supply lines become 70 . 72 via hydraulic lines 100 . 102 with the pressures of the brake fluid from pressure chambers 120 . 122 of the master cylinder 10 applied. The outlet connections of the outlet valves 60 to 66 are via a return line 130 with the pressure medium reservoir 18 connected.

The master cylinder 10 points in a housing 136 two pistons arranged one behind the other 140 . 142 on top of the hydraulic pressure chambers 120 . 122 limit. The pressure chambers 120 . 122 on the one hand over into the piston 140 . 142 formed radial bores and corresponding pressure equalization lines 150, 152 with the pressure medium reservoir 18 in conjunction, wherein the connections by a relative movement of the pistons 140 , 42 in the housing 136 can be shut off. The pressure chambers 120 . 122 On the other hand, by means of the hydraulic lines 100 . 102 with the already mentioned brake circuit supply lines 70 . 72 in connection.

In the pressure compensation line 150 is a normally open valve 160 included. The pressure chambers 120 . 122 take unspecified return springs on which the pistons 140 . 142 with unoperated master cylinder 10 position in a starting position. A piston rod 166 in which the pedal force is preferably measured taking into account the pedal ratio or a signal representing the pedal force, couples the pivotal movement of the brake pedal 6 due to a pedal operation with the translational movement of the first master cylinder piston 140 or primary piston, whose actuation path of a, preferably redundantly running, displacement sensor 170 is detected. As a result, the corresponding piston travel signal is a measure of the brake pedal actuation angle. It represents a braking request of the driver.

In the to the pressure chambers 120 . 122 connected line sections 100 . 102 is ever a separating valve 180 . 182 arranged, which is designed as an electrically actuated, preferably normally open, 2/2-way valve. By separating valves 180, 182, the hydraulic connection between the pressure chambers 120 . 122 of the master cylinder 10 and the brake circuit supply lines 70 . 72 be shut off. One to the line section 102 connected pressure sensor 188 detects the in the pressure room 122 by a displacement of the second piston 142 built up pressure.

The simulation device 14 is hydraulic to the master cylinder 10 can be coupled and, for example, essentially comprises a simulator chamber 190 , a simulator spring chamber 194 and one the two chambers 190 . 194 mutually separating simulator piston 198 , The simulator piston 198 is supported by a simulator spring chamber 194 arranged elastic element (eg., A spring), which is advantageously biased on the housing 136 from. The simulator chamber 190 is by means of an electrically operated simulator valve 200 with the first pressure chamber 120 of the master cylinder 10 connectable. When setting a pedal force and open simulator valve 200 flows pressure medium from the master cylinder pressure chamber 120 into the simulator chamber 190 , A hydraulic anti-parallel to the simulator valve 200 arranged check valve 210 allows independent of the switching state of the simulator valve 200 a largely unhindered backflow of the pressure medium from the simulator chamber 190 to the master cylinder pressure chamber 120 , Other designs and connections of the simulation device to the master cylinder 10 are conceivable.

The electrically controllable pressure supply device 20 is designed as a hydraulic cylinder-piston arrangement or a single-circuit electrohydraulic actuator whose / whose pressure piston 32 which the pressure room 26 limited, by a schematically indicated electric motor 220 with the interposition of a likewise schematically illustrated rotational-translation gear, which is preferably designed as a ball screw (KGT), can be actuated. One of the detection of the rotor position of the electric motor 220 Serving, only schematically indicated rotor position sensor is denoted by the reference numeral 226 designated. In addition, a temperature sensor can also be used 228 be used to sense the temperature of the motor winding.

The by the force effect of the piston 32 the actuator pressure generated on the pressure medium enclosed in the pressure chamber 26 actuator pressure is in the system pressure line 80 fed and with a preferably redundant pressure sensor 230 detected. With open pressure switch valves 240 . 242 the pressure medium enters the wheel brakes 42 to 48 for their operation. By pushing back and forth the piston 32 takes place with open pressure switch valves 240 . 242 in a normal braking in the "brake-by-wire" mode a Radbremsdruckaufbau and degradation for all wheel brakes 42 to 48 ,

During pressure reduction, this flows from the pressure chamber before 26 in the wheel brakes 42 to 48 shifted pressure medium on the same way back into the pressure chamber 26 back. On the other hand, when braking with different individual wheel flows, with the help of the intake and exhaust valves 50 to 56 . 60 to 66 regulated wheel brake pressures (eg in the case of anti-lock control (ABS control)) via the exhaust valves 60 to 66 drained pressure medium content in the pressure fluid reservoir 18 and thus initially stands the pressure supply device 20 for actuating the wheel brakes 42 to 48 no longer available.

In an alternative embodiment, the brake system has four wheel brakes, in each case in a, preferably floating, caliper 254 two brake elements are arranged, on each of which is arranged with a brake pad, between which a brake disc is arranged. A pressure supply device, which is designed as a linear actuator and dedicates brake pressure in the respective wheel brake, has a hydraulic pressure chamber in which a pressure piston is displaced as required. In this case, the rotational movement of the motor shaft of an electric motor is converted by a rotation-translation gear in a translational movement of the pressure piston. For detecting the piston position, a preferably redundantly designed rotor position sensor is provided.

In a further alternative embodiment, instead of a pressure supply device, an electromechanical linear actuator may be provided, in which the rotational movement of the motor shaft of an electric motor is converted by a rotational-translation gear into a translational movement of a piston which is directly connected to a brake pad. Instead of a brake pressure in this electromechanical wheel brake then the operation by applying a predetermined application force with the brake pads are pressed against the brake disc. The brake system then preferably comprises two, more preferably four electromechanical wheel brakes of the type described.

In the control unit 40 a method, which is described below, implemented software and / or hardware.

A method in a first preferred embodiment is shown in FIG 2 shown.

In a block 280 a first driver brake request is calculated. For this purpose, the pedal travel X _{pedal is} used as input. In a hydraulic simulator, a pressure signal of the simulator pressure can be used in a known manner in the usual way as an input variable. However, this signal is replaced here by the Pedalfußkraft F _Pedal . The driver brake request P _{desired, PWE} is calculated to $${\text{P}}_{\text{Should}\text{, FWE}}={\text{P}}_{\text{Should}\text{X}}+{\text{P}}_{\text{Should}\text{, F}}={\mathrm{\lambda }}_{\text{X}}*{\text{f}}_{\text{X}}\left({\text{X}}_{\text{pedal}}.{\text{V}}_{\text{pedal}}\right)+{\mathrm{\lambda }}_{\text{P}}*{\text{f}}_{\text{P}}\left({\text{F}}_{\text{pedal}}\right)$$

• P_{Soll, X}: Pedalwegbasierter Solldruckanteil;
• P_{Soll, F}: Pedalkraftbasierter Solldruckanteil;
• f_X: Bremsdruck-Sollwertfunktion berechnet aufgrund von Pedalweg und ggf. Pedalgeschwindigkeit;
• f_P: Bremsdruck-Sollwertfunktion berechnet aufgrund der Pedalkraft;
• λ_X, λ_P: Gewichtungsfaktoren (= 0...1) für f_X bzw. f_P

Where:

• P _{desired, X} : pedal travel-based target pressure component;
• P _{target, F} : pedal force-based _target pressure component;
• f _X : Brake pressure setpoint function calculated based on pedal travel and, if applicable, pedal speed;
• f _P : Brake pressure setpoint function calculated based on pedal force;
• λ _X , λ _P : weighting factors (= 0 ... 1) for f _X and f _P, respectively

The weighting factors can be used, for example, to carry out a lowering of the brake pressure requirement at low _speeds depending on the vehicle speed V _Kfz . Another application is the different weighting of the target pressure components P _{target, X} and P _{target, F} z. B. depending on the pedal travel. Thus, it can be achieved, for example, that in the region of small pedal travel the desired brake pressure P _{Soll, FWE is} determined essentially on the basis of the pedal travel, while in the region of large pedal travel the target brake pressure P _{Soll, FWE is} predominantly determined based on pedaling force. The special definition and parameter selection for the brake pressure requirement by the driver is strongly vehicle and manufacturer-specific and thus application-specific.

An initiated by the driver emergency braking by a quick pedal operation is here essentially recognized by the evaluation of the pedal entry speed V _pedal , in block 280 from the pedal travel X _{pedal is} calculated. If this signal exceeds a predefined threshold, the maximum setpoint pressure is predetermined for P _{setpoint, FWE} , on the basis of the recognized emergency braking situation.

In a block 282 another driver brake request or a first additional brake _request P _{SOLL, F_func1 is} calculated. Input variables for block 282 are the Pedalweg X _pedal and the _pedal force F _pedal .

While in a slow operation of the brake pedal substantially only the static forces of the pedal simulator unit (spring force, frictional force) are overcome, the force for accelerating the pedal simulator unit in the signal F _{pedal is also} measurable at a fast operation, which is characterized by a depending on the operating speed expresses pronounced power increase.

To improve the response in the normal braking function, especially for large brake lining clearance, the additional pressure requirement P _{target, F_func1 of} the value 0 (No pressure request) to a, preferably constant, pressure setpoint P ₁ > 0 bar set as soon as a pedal operation by the driver is reliably detected by the signal F _pedal . The starting point for this reliable detection is initially the unactuated state (F _Pedal = 0 and X _Pedal = 0). A pedal operation is then reliably detected if in several successive controller loops F _Pedal > F ₁ applies, where F _{1 is} a predefined threshold value. The threshold value F ₁ is to be set so that it differs significantly from the force in the unactuated state and is below the above-mentioned static forces.

An activated pressure _request P _{Soll, F_func1} = P ₁ is withdrawn again if after a time T ₁ no pedal actuation in the path signal (X _pedal > 0) can be determined, a maximum request time T _{2 has} expired or the brake pedal is released again. The determination of T ₂ is made so that after this time in each case a brake pressure request P _{target, FWE} > 0 is expected. The preferably constant pressure value P ₁ is set so that it leads to overcoming the pad clearance and applying the pads. A typical value for this is therefore P ₁ = 1 ... 2 bar.

In order to support and respond more quickly to an emergency braking initiated by the driver by means of a rapid pedal actuation, it is further proposed that the pressure requirement P _{Soll, F_func2 be of} the value 0 (No pressure request) to a maximum pressure setpoint P ₂ = P _{setpoint, Max is} set as soon as a corresponding rapid pedal operation by the driver is reliably detected on the basis of the signal F _Pedal . The starting point here too is the unactuated state (F _Pedal = 0 and X _Pedal = 0). The fast pedaling required for activation is recognized when F is _pedal > F ₂ in several consecutive control loops F, the threshold F ₂ being set so that it can only be exceeded by those values F _Pedal which are due to the above mentioned power increase in a fast pedal operation result. The exact determination of the threshold F ₂ depends on the structural design and design of the pedal simulator unit and is also application-specific.

An activated pressure _request P _{setpoint, F_func2} = P ₂ = P _{setpoint, Max} is withdrawn again if no pedal actuation in the path signal (X _pedal > 0) can be ascertained or a maximum request time T _{4 has} elapsed after a time T _{3 has} elapsed. The determination of T ₄ is carried out here so that after expiration of this time in each case a detected by evaluation of the pedal entry speed V _Pedal emergency braking situation by specifying P _{Soll, FWE} = P _{Soll, Max was} treated. After expiration of the time T ₄ , this function is in any case inactive and can only be activated again if the unactuated state of the brake pedal has been determined by F _Pedal = 0 and X _Pedal = 0.

As a further deactivation condition can be monitored whether before the time T _4, the brake pedal is released again. As a result of the above determination of the value of T ₄ is relatively small, this condition is essentially used, a false tripping caused, for example, due to disturbances in the power signal by P _{Soll, F_func2} = P _{Soll, Max} withdraw again before the end of T. ₄

The two in 2 _Additional pressure requirements P _{, F_func1} and _{P_soll , F_func2} represent additional _{braking requirements} , which take particular account of the fact that the pedal operation by the driver is initially recognizable in the signal F _pedal . The driver's brake request P _desired now results in a block 290 due to a maximum value formation of the three brake pressure requirements described above: $${\text{P}}_{\text{Should}}=\text{MAX}\left({\text{P}}_{\text{Should}\text{, FWE}}.{\text{P}}_{\text{Should}\text{, F\_func1}}.{\text{P}}_{\text{Should}\text{, F\_func}2}.0\right),$$

Due to the combination of these three pressure requirements through a maximum value formation of the two additional braking demands, participate in detected by the signal F _pedal pedal operation only until the normal driver's intention detecting (P _{Soll, FWE)} is that the resulting braking request (P _Soll) determining signal. While the additional brake demands on the pedal actuation lead to an earlier reaction of the linear actuator and thus contribute to an improvement of the response, they are deactivated when releasing the pedal and have the value 0 ,

In a brake system with electromechanical wheel brakes results for the respective wheel brake of the resulting setpoint for the application force F _Sp , with which the brake pads are pressed against the brake disc, from the thus calculated braking request P _setpoint (which in this case represents a pure arithmetic operation) by multiplication with a scaling factor A _SC , this factor A _{SC being} dependent on the specific design and / or arrangement in the vehicle of the electromechanical wheel brake: $${\text{F}}_{\text{sp}}={\text{A}}_{\text{SC}}*{\text{P}}_{\text{Should}}$$

In 3 a further preferred embodiment of the method is shown, in particular in a brake system 2 is advantageously used with a mechanical pedal simulator. The driver's request is as in the prior art in block 280 determined from the Pedalweginformation and learns no further changes. The driver foot force information F _pedal is only in the blocks 282 . 284 for the two fußkraftbasierte additional brake requirements or functions P _{set, F_func1} and P _{Soll_F_func2} used.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• DE 102013204778 A1 [0006]

Claims (14)

Method for detecting driver braking request (P _desired ) in a brake system, comprising: • at least two electrically actuatable wheel brakes (42-48); A simulator (14) for simulating a conventional brake pedal feel; • a brake pedal (6) for operating the simulator (14); A pedal travel sensor for measuring the pedal travel (X _pedal ) of the brake pedal (6), wherein the pedal travel (X _pedal ) is used to detect the driver braking request (P _target ), and the pedal foot force (F _pedal ) is measured and when detecting the Driver braking request (P _Soll, F _SP ) is used, and wherein the driver brake request detection comprises the determination of a driver brake request (P _{Soll, FWE} ), characterized in that the driver brake request detection is given by the maximum of the driver brake request (P _{Soll, FWE} ) and at least one additional brake request (P _{command, F_func1} , P _{command, F_func2} ). Method according to Claim 1 wherein a first additional brake _request (P _{target, F_func1} ) is set to a value of zero, if no pressure request is detected, and set to a constant value as soon as a pedal operation by the driver is reliably detected. Method according to Claim 2 wherein the first additional brake _request (P _{target, F_func1} ) is set to zero when no pedal operation is detected during a predetermined time interval, a maximum request time has expired, or the brake pedal is released. Method according to one of Claims 1 to 3 wherein a second supplemental _{braking request} ( _{Pset, F_func2} ) is set to a value of zero unless a pressure request is detected and set to a constant value as soon as a pedal operation by the driver is detected which is faster than a predetermined pedal speed threshold. Method according to Claim 4 wherein the second supplemental brake _{request function} (P _{target, F_func2} ) is set to zero if no pedal actuation is detected during a predetermined time interval or a maximum request time has expired. Method according to one of Claims 1 to 5 wherein in the driver brake request (P _{target, FWE} ) the pedal travel (X _pedal ) and the pedal foot force (F _pedal ) are used. Method according to Claim 6 wherein the driver brake request (P _{target, FWE} ) is given by the product of a weighting factor (λ _X ) with a first function which depends on the pedal travel (X _pedal ) and / or the pedal speed (dX _pedal / dt), and a second one Contribution given by the product of a weighting factor (λ _P ) with a function that depends on the pedal force (F _Pedal ). Method according to one of Claims 1 to 7 wherein the wheel brakes (42-48) are hydraulically formed, and wherein an electrohydraulic pressure supply device (20) for braking pressure build-up of at least one wheel brake (42-48), in which by means of an electric motor (220, 290) a pressure piston (32, 286) , in a hydraulic pressure chamber (26, 282) is displaceable. Method according to Claim 8 , wherein the simulator (14) has a hydraulic simulator chamber (190), in which upon actuation of the brake pedal (6) pressure medium from a with the brake pedal (6) operable master cylinder (10) is promoted. Method according to one of Claims 1 to 7 wherein the wheel brakes (42-48) are designed as electromechanical wheel brakes. Method according to Claim 10 wherein the simulator (14) is mechanically formed. Brake system (2) with means (40) for carrying out a method according to one of the preceding claims. Brake system (2) after Claim 12 comprising at least two hydraulic wheel brakes (42-48). Brake system (2) after Claim 12 comprising at least two electromechanical wheel brakes.

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