WO2013017396A1

WO2013017396A1 - Method for operating a brake system for motor vehicles and brake system

Info

Publication number: WO2013017396A1
Application number: PCT/EP2012/063868
Authority: WO
Inventors: Jürgen Böhm; Georg Roll
Original assignee: Continental Teves Ag & Co. Ohg
Priority date: 2011-07-29
Filing date: 2012-07-16
Publication date: 2013-02-07
Also published as: DE102012210434A1

Abstract

A method for operating a motor vehicle brake system comprising a master brake cylinder (22), which can be actuated by a brake pedal and is disengageably connected (39a, 39b) to a brake-circuit pressure line portion (12, 13), a simulation device (40), interacting with the master brake cylinder (22), and an electrically controllable pressure-supplying device (3), which is disengageably connected (45a, 45b) to the brake-circuit pressure line portion (12, 13), wherein, in a first operating mode (Z_P), the simulation device (40) is switched off and the brake-circuit pressure line portion (12, 13) is subjected to the pressure of the master brake cylinder (22) and, in a second operating mode (Z_A), the simulation device (40) is switched on and the brake-circuit pressure line portion (12, 13) is subjected to a pressure of the pressure-supplying device (3), determined according to a first prescribed relationship (F_A), and wherein, if a prescribed condition (S, 51) is satisfied during the first operating mode (Z_P), a transition (53, 54, 55) is carried out from the first operating mode (Z_P) into a third operating mode (Z_Ü), in which the brake-circuit pressure line portion (12, 13) is subjected to a pressure (P_Br,soll) of the pressure-supplying device (3) determined according to a second prescribed relationship (F_Ü), and a brake system.

Description

Method for operating a brake system for motor vehicles and brake system

The invention relates to a method according to the preamble of claim 1 and a brake system according to the preamble of FIG. 14.

There are known hydraulic vehicle brake systems, which are designed as power-brake systems and in addition to a muscle-operated master cylinder, are hydraulically connected to the wheel brakes and the pressure and volume for actuating wheel brakes, a further, electrically controllable pressure and Volumenbereitstel ^¬ lunge means include in a "brake-by-wire" - mode controls the wheel brakes Upon failure of the electrically controlled pressure and volume providing means to actuate the wheel brakes takes place solely by the muscular effort of the driver (Rückfallbe ^¬ triebsart)..

From the international patent application WO 2011/029812 AI is a "brake-by-wire" -Bremsanlage with a

Brake pedal operable master cylinder, a waysimulator and a pressure delivery device known. The wheel brakes are pressurized by the pressure providing means in a brake-by-wire mode Pressure applied. The application does not elaborate on how to make a transition between the fallback mode and the brake-by-wire mode.

It is an object of the present invention to provide a method for operating a brake system for motor vehicles and a brake system for motor vehicles, wel ^¬ ches / which provides the driver a comfortable transition from a fallback mode in a "brake-by-wire" - mode.

This object is achieved by a ge ^¬ claim according to claim 1 and a brake system according to claim 14 ge ^¬ triggers.

The invention is based on the idea that in addition to a first operating mode of the brake system, in which a brake circuit pressure line section is acted upon by the pressure of the Hauptbremszy ^¬ Linders, and a second operating mode in which the brake circuit pressure line section with a pressure of the pressure supply device according to a first predetermined relationship is applied, a third operating mode is provided, in which the Bremskreis- pressure line section is acted upon by a pressure of the Druckbereit ^¬ positioning device according to a second predetermined relationship, wherein in the presence of a pre ^¬ given condition during the first operating mode, a transition from the first operating mode in the third operating mode is performed. An advantage of the method and of the braking system is as ^¬ rin that the driver in case of a restart of the brake system with brake pedal an as equal as possible ^¬ consistent brake pedal feel is provided. Furthermore, as soon as possible after the restart of the brake system, a brake booster function is provided.

Preferably, the predetermined condition is starting or restarting or activating the brake system during operation of the brake pedal.

The brake system comprises a first detecting means for detecting an actuation of the brake pedal characterizing first measurement variable and a second Erfas ^¬ sungseinrichtung for detecting a pressure of the master cylinder characterizing the second measured variable.

It is preferred operation of the brake pedal, he ^¬ withdrawn if at least the first measured parameter, which characterizes a Be ^¬ tätigungsweg of the brake pedal is greater than or equal to a predetermined first control threshold value. This prevents that at a low Be ^¬ actuation of the brake pedal when a significant Beeinflus ^¬ solution of the brake pedal feel is not expected that over ^¬ transition is carried out in the third operating mode.

According to a preferred development of the method according to the invention the pressure in the pressure supply device to the current value of the pressure of the master cylinder is set in the transition from the first Betriebsmo ^¬ dus in the third mode of operation first. This pressure adjustment process ensures that when occurs in the third mode of operation a comfortable transition and no changes in the wheel brake pressures occur.

In order to be able to take into account the brake pressure already set by the driver by the brake pedal actuation in the first operating mode, the value of the second measured variable, and particularly preferably the value of the first measured variable which is at or a predetermined time threshold before entering the third operating mode, is preferred. saved.

According to one embodiment of the invention, in the third operating mode, the pressure of the pressure-providing device is determined taking into account the stored value of the second measured variable, or particularly preferably the stored values of first and second measured variable. This provides a crack-free course of the pressure is achieved in the pressure READY ^¬ averaging means especially upon entry into the third operating mode.

For entry into the third operating mode, the master brake cylinder is preferably separated from the brake circuit pressure line section and the pressure supply device is connected to the brake circuit pressure line section.

The entry in the third mode of operation is preferably performed only after the pressure in the pressure already ^¬ tellungseinrichtung is set to the value of the pressure of the main brake cylinder ^¬ to keep reactions on the brake pedal as low as possible. Particularly preferably, the entry into the third operating mode is only performed by ^¬ if in addition the values of the first and second Measurement variable which have been stored at or a predetermined Zeitschwel ^¬ lenwert before entry into the third operating mode vorlie ^¬ gene in order to use these values in the third Be ^¬ operating mode.

According to a preferred embodiment of the method according to the invention is switched on, the simulation device upon entry into the third operation mode ^¬, to give the vehicle operator a known brake pedal feel.

The simulation device is preferably activated by opening a simulator release valve when the value of the second measured variable, which is present on admission, or a given before ^¬ time threshold before entry into the third Be ^¬ operating mode is smaller than a predetermined first pressure threshold is because small value of the second Measured variable is only a slight yielding of the brake pedal to he ^¬ wait.

Furthermore, it is preferred to switch in the simulation device by controlled or regulated opening and closing ei ^¬ nes simulator release valve when the value of the second measured variable, which is present on admission, or a given before ^¬ time threshold before entry into the third Be ^¬ operation mode is greater than or equal to a predetermined first pressure threshold is. Through the controlled or regulated opening and closing the simulator cut-off valve and a quick jerk-shaped yielding of Bremspe ^¬ dals under the action of Fahrzeugführerfußkraft when to switch ^¬ the simulation device is reduced. According to another preferred embodiment of the inventive method, the simulation ^¬ device upon entry into the third operational mode and the third mode of operation is switched off when the value of the second measured variables ^¬ SSE, which is present on admission, or a predetermined time threshold value before entry into the third mode of operation, greater is a predetermined second pressure threshold. So a problem caused by energizing the Simulati ^¬ onseinrichtung with brake pedal depressed yielding of the brake pedal is avoided.

According to a preferred embodiment of the invention, the first operating mode of the brake system is ei ^¬ ne fallback mode, in the second operating mode of the brake system to a first "brake-by-wire" mode and the third mode of operation by a second "brake by-wire "mode. In the first operation mode, all valves of the brake system are particular ^¬ DERS preferably energized, that is in its de-energized state. The third operating mode is particularly preferably a transient operating mode (transitional state), ie the brake system only lingers in this mode for a limited period of time.

The simulation device can preferably be switched on and off by means of a simulator release valve.

It is preferably a brake system for ^motor vehicles, which can be ^activated in a so-called "brake-by-wire" mode (second operating mode) both by the driver and independently of the vehicle driver, preferably in the "brake-by-wire Operating mode and in at least one fallback mode (first mode of operation) can be operated in the only operation by the driver is possible.

The master cylinder preferably comprises a housing and two pistons which delimit two pressure chambers in the housing, which line section two braking circuits each with a Bremskreisdrucklei-, to the at least one wheel brake is CONNECTING ^¬ bar or connected, are assigned.

Advantageously, there is a brake system, wherein the brake circuit pressure line section, in particular be ^¬ vorzugt each brake circuit pressure line section, via a hydraulic connecting line with a normally open isolation valve with the main brake cylinder and over a wide ^¬ re hydraulic connecting line with an electroless ge ^¬ closed sequence valve with the pressure generating device connected is.

Preferably, it is a brake system in which the wheel brakes in the "brake-by-wire" mode are pressurized only by the pressure supply device and in the fallback mode operable only by the brake pedal main brake ^¬ cylinder.

Preferably, the brake system comprises a Radbremsdruckmodul tion device with at least one valve per wheel brake.

The first measuring device for detecting a first measuring variable characterizing an actuating travel of the brake pedal is advantageously a travel-detecting device which controls the actuating travel of the brake pedal or of a piston connected to the brake pedal detected .

In the second detection means for detecting a pressure of the master cylinder characterizing the second measured variable is advantageously ei ^¬ NEN pressure sensor.

The invention also relates to a braking system for motor vehicles driving ^¬ in which an inventive method is Runaway ^¬ leads.

Further preferred embodiments of the invention will become apparent from the subclaims and the following description with reference to figures.

It show schematically

1 is an exemplary brake system,

2 shows a diagram for illustrating an embodiment of a method according to the invention for operating a brake system,

3 shows an example of a supply for controlling a simulator release valve, and

Fig. 4 shows exemplary values for a Übergangsskalie ^¬ magnification factor.

In Fig. 1 an exemplary brake system is shown schematically. The brake system comprises a Betätigungsein ^¬ direction 2, which by means of an actuating or Bremspe- dals 1 can be actuated by a driver, an electromechanical actuator unit 3, which is an elekt ^¬ cally controllable pressure supply device 3, a hydraulic Radbremsdruckmodulationseinrich- device 4 (HCU: hydraulic control unit), at whose ^{Ausgangsan ¬} wheel brakes 6 are connected, and an electro ^¬ nische control and regulation unit 5 (ECU: electronic control unit), which serves to control and / or verification of the components of the brake system.

Actuator 2 comprises a dual-circuit master cylinder or tandem master cylinder 22 with two successively arranged piston 33, 34, the hydraulic chambers or pressure chambers 36, 37 limit. The pressure chambers 36, 37 are connected via formed in the piston 33, 34 radial bores with a pressure medium reservoir 35 in connection, which can be shut off by a relative movement of the piston 33, 34 in the housing of the master cylinder 22. In addition, each pressure chamber 36, 37 by means of a hydraulic line 38 a, 38 b with a Bremskreisdruck- line section 12, 13, are connected to the two wheel brakes 6 ^¬ connected. In the hydraulic lines 38a, 38b is ever a separating valve 39a, 39b inserted, which is designed as an electrically actuated, preferably normally open (SO), 2/2-way valve. By Trennven ^¬ valve 39a and 39b, the hydraulic connection between the pressure chamber 36 and 37 and the associated brake circuit pressure line section 12, 13 are shut off.

A coupled to the brake pedal 1 piston rod cooperates with the first master cylinder piston 33, wherein a the actuating travel of the brake pedal 1 characterizing size Xp _{ed is} detected by a, preferably redundantly designed Wegsen ^¬ sor 7.

An example according to the line 38b connected, preferably redundantly executed, pressure sensor 8 detects the built-up in the pressure chamber 37 by a displacement of the second piston 34 pressure P _THZ , which corresponds to the pedal force generated by the driver.

Actuation device 2 further comprises a simulation device 40, which cooperates with the brake master cylinder 22 and the vehicle driver in the "brake-by-wire." - mode gives a pleasant pedal feel Simula ^¬ tion means 40 is hydraulically carried out and supply by means of an electrically operable simulator release valve 41 and According to the example, the simulation device 40 essentially consists of a simulator chamber, a simulator spring chamber with simulator spring 30 and a simulator piston separating these two chambers, whereby the simulator chamber is connected to at least one pressure chamber 36, 37 of the master cylinder 22. By way of example, the simulator spring chamber is interposed with the simulator release valve 41 connectable to the Druckmit ^¬ telvorratsbehälter 35, whereby the simulation device 40 by opening the example according to electromagnetically closed ^¬ executed running Simulatorfreigabeventils 41 ^{¬ is} switchable.

Pressure supply device 3 is designed as a hydraulic cylinder-piston arrangement, the piston 46 of a schematically indicated electric motor 47 with the interposition of a rotation, not shown Translationsgetriebes is actuated. For detecting a characteristic of the position / position of the piston 46 of the Druckbereitstel ^¬ treatment device 3 size is a, preferably redundantly executed, sensor 9 is provided, which is exemplified as a the detection of the rotor position of the electric motor 47 serving rotor position sensor 9. Piston 46 delimits a pressure chamber 48, which can be connected to the brake circuit pressure line sections 12, 13 via a hydraulic line 44, for example by opening electrically actuatable, normally closed connecting valves 45a, 45b. It is the Zuschaltventilen 45a, 45b, for example according to a respective brake circuit to the pressure line section 12, 13 opening towards Rückschlagven ^¬ til 20a, 20b connected in parallel. Alternatively, for example, can, with suitable dimensioning of the cross sections of the sequence valves 45a, 45b, the check valves 20a, 20b are omitted ^¬ ver.

For modulating the pressure at the wheel brakes 6, the hydraulic pressure modulator device 4 each wheel brake 6 comprises, for example in accordance with an intake and an exhaust valve 42, 43. The input terminals of the intake valves 42 are connected to the corresponding brake circuit pressure line section 12, 13 ver ^¬ prevented. The input ports of the intake valves 42 can thus be supplied with the pressure of the master cylinder 22 (via the lines 38a, 38b with the isolation valves 39a, 39b) or with the pressure of the pressure delivery device 3 (via the line 44 with the isolation valves 45a, 45b). The output ports of the exhaust valves 43 are connected via return lines to the pressureless pressure medium reservoir 35. By way of example, a pressure sensor 10, 11 for detecting the pressure prevailing at the inlet ports of the associated intake valves 42 is arranged in each brake circuit pressure line section 12, 13. Alternatively, a pressure sensor may also be arranged in only one of the two brake circuit pressure line sections 12, 13. Instead of one or two pressure sensors in the brake circuit pressure line sections 12, 13, a pressure sensor may also be arranged in the line 44 in order to measure the pressure of the pressure supply device 3.

In a fallback mode of the brake system (first Be ^¬ operating mode Z _P ), for example, when the brake system is not geschal ^¬ tet or in case of failure of the electrical power supply of the brake system, all valves of the brake system are in their de-energized state. Simulation device 40 is closed by the normally closed

Simulator-release ^valve 41 is switched off and Druckbereit ^¬ positioning device 3 is separated by the normally closed Zuschaltventile 45a, 45b of the Bremskreisdruckleitungsab- sections 12, 13. Master brake cylinder 22 is connected via the normally open isolation valves 39a, 39b with the brake circuit pressure line sections 12, 13 and thus the wheel brakes 6, so that the driver can directly build pressure in the wheel brakes 6 by pressing the brake pedal 1.

In a normal brake function of the brake system ("brake-by-wire" mode, second operating mode Z _A ) is the main ^¬ brake cylinder 22, and thus the driver, from the brake circuit pressure line sections 12, 13 by closed isolation valves 39a, 39b decoupled and the brake circuit pressure line sections 12, 13 are connected via 45b open to ^¬ switching valves 45a, with the pressure provisioning ^¬ means. 3 Pressure supply device 3 thus provides the pressure for actuating the wheel brakes 6 ready. Simulation device 40 is switched on by the opened simulator release valve 41, so that the pressure medium volume displaced by the actuation of the brake pedal 1 by the vehicle driver in the master brake cylinder 22 is received by the simulation device 40 and the simulation device 40 gives the vehicle driver a familiar brake pedal feel.

An exemplary embodiment of a method according to the invention for operating a brake system will be explained below with reference to the highly schematic diagram of FIG.

The brake system is initially in a Passivzu ^¬ stand (Block 50), for example, because the brake system is switched off or similar due to malfunction has passed into the passive state. The brake system is thus in the first operating mode Z _P (fallback mode), in wel ^¬ chem all valves, in particular the valves 39a, 39b, 41 and 45a, 45b, are not energized. In case of Actuate the ^¬ supply the brake pedal 1 by the driver would

Pressure fluid from the master cylinder 22 via the open separating valves 39a, 39b and the Bremskreisdruckleitungsab- sections 12, 13 displaced into the wheel brakes 6 and so builds up a pressure in the wheel brakes 6 by the operating force of the driver. The present in this first Betriebsmo ^¬ dus Z _P, noticeable to the vehicle operator brake pedal characteristics ^¬ differs significantly from that which in the second operating mode of the brake system upstream Z _A lies .

If the brake system is started by a start condition S, for example by switching on the engine ignition by the driver, by opening the driver's door or by any other detection eg in a keyless entry (eg by means of appropriate environmental sensors), the brake system is first initialized, which, for example the sensors 7, 8, 9, 10, 11 of the brake system are ready to measure. In the event that kei ^¬ ne brake pedal operation by the driver is present (left branch at block 51 in Fig. 2), the brake system is after initialization in the active, ready for operation second operating mode Z _A (normal "brake-by-wire"; mode). If now an operation of the brake ^¬ pedal 1, so as to be at the beginning of the driver's operation, the separating valves 39a closed 39b, at the same time the simulator release valve 41 and the sequence valves 45a, 45b of the pressure supply device 3 is opened. the driver is no longer directly hydraulically with the brake circuit pressure line sections 12, 13 and the wheel brakes 6 is connected, but operates the simulation device 40 having a suitable brake pedal characteristics, so ^¬ that a sufficiently accurate metering of the requested braking requirement is possible for the vehicle driver. the braking circuit pressure line sections 12, or 13 The wheel brakes 6 are de with a pressure Pressure supply device 3 acted upon whose size P _Br , s _o ii according to a first pre ^¬ given relationship F _A (Bremskraftverstärkungsfunktιοη r _A ) is determined (block 52).

The brake pressure demand of the driver by the brake pedal ^¬ operation is, for example, based on the operating Device 2 associated displacement and pressure sensors 7, 8 detected, which detect a the actuation of the brake pedal 1 characterizing first measured variable X _Pec i and the pressure of the master cylinder 22 and the pedal force generated by the driver second characteristic measure P _THZ . From these two variables X _Pedr P _THZ the brake ^¬ pressure request of the driver in the form of a value Ρ _ΒΓ , _{ΒΟΙΙ calculated} for the target pressure of the pressure supply device 3. Thus available for the driver intention detecting two different physical measures of the driver's braking wish ^¬ representing driver's operation to Solldruckwert- generation of the pressure supply device 3 is available.

The target pressure P _Br, soii is in the second operating mode _A at Z ^¬ example by a weighted superposition of actuation based on the X i _Pec pressure component P CMCI. x and a pressure component Pcmci, p based on the pressure P _TH z in the simulator are determined according to the following equation (1): ΡΒΓ, ΒΟΙΙ ⁼ F _A (Xpeci / PTHZ)

⁼ Pcmcl, X + Pcmcl, P ⁼ λχ * fχ (Xp _e dr V _Pe d) + λ _Ρ * f _P (P _TH z)

Where:

Pcm _d , x: an actuating path-based desired pressure component, Pcmci _,? : A simulator or driver pressure-based target pressure ^¬ share,

f _x: a predetermined brake pressure setpoint function dependent on the actuating path _Χ Ρβ _<ι and optional depending on the pedal ^¬ speed (operating speed) V _Ped,

f _P : a predetermined brake pressure setpoint function depending on the driver pressure P _THZ , and

λ _χ , λ _Ρ : weighting factors (between zero and One) for f _x or f _P.

The special definition and parameter selection for the brake pressure requirement by the driver according to equation (1) is vehicle and manufacturer and thus application ^¬ specific. It also depends on the pedal characteristic implemented in the simulation device 40.

In case of no brake pedal operation

is it?

Brake system thus as described above from the passive state or deactivated state (block 50) (in which the brake system is in the first operating mode Z _P ) in ei ^¬ nen active ready state (block 52) (in which the brake system in the second operating mode Z _A befin about ^¬ det). In the second operating mode Z _A braking ^¬ pressure request of the driver leads to a target pressure _Ρ ΒΓ, _ΒΟΙΙ the pressure supply device 3, which consists of about ^¬ least to the actuating travel X _Pec i and the master brake cylinder ^¬ pressure (or pressure of the simulation device 40) P _THZ according to a predetermined "normal" Bremskraftverstärkungsfunkti ^¬ on F _A. An exemplary Bremskraftverstär ^¬ kungsfunktion F _A is given by equation (1).

If the brake system is in a passive state (block 50) and the brake system is started by a start condition S, the brake system is initially briefly held in the first operating mode Z _P , for example, and in block 51 using the path sensor signal X _Pec i and optionally the pressure sensor signal P _THZ checked if the driver is the

Brake system operated beyond a certain extent in the fallback ^¬ level. As a decision criterion for this is For example, checked whether the actuation _path Χ _{Ρβ <} ι is smaller than a predetermined threshold Χ _{Ρβ <} ι, _εΐ and the measured pressure P _TH z is approximately zero:

Xped <Xped, El And ΡτΗΖ ~ 0

The value of the threshold Χ _{Ρβ <} ι, ε _ΐ is advantageously selected such that in the case of the positive presence of the above decision criterion, the pedal operation is so small that when switching to the second operating mode Z _A on the one hand not irritating to the driver jumps on the brake pedal 1 would be noticeable and, on the other hand, that there would be no significant sudden change in the requested pressure P _br , s _o ii. The value of the threshold value Χρ _β ( _ΐ , _εΐ therefore lies, for example, in the range of a few millimeters.

If the driver does not depress the brake pedal 1 or below the threshold value Χ _{Ρβ <} ι, _εΐ (left branch in block 51), then the transition described below from the first operating mode Z _P to a third operating mode can be dispensed with and the brake system can be used directly. as already ^¬ be written are transferred from the first operation mode _P Z in the second operating mode Z _A (block 52). For this example, the valves 39a, 39b, 41, 45a, 45b are energized and the determination of the desired pressure Ρ _ΒΓ , _ΒΟΙΙ takes place according to the first predetermined brake booster function F _A , for example, according to equation (1).

If the brake pedal is actuated above the threshold X _Pe ci, ei (right branch in block 51), ie X _Fecl ^ Χρβ _< ι, ε _ΐ , then the brake system from the first operating mode Z _{P is} in a third - IS

th mode (transition mode to, second "brake-by-wire" mode) transferred, for which a second brake booster function F _{Ü is} given, which is not based on the determination of the target pressure according to

_{Brake force boosting} function F _A (eg, according to equation (1)) is based, but, for example, substantially as a function based on the pressure value P _{THZ is} executed. The Determined ^¬ development of the desired pressure according to the Bremskraftverstärkungsfunkti ^¬ on F _A, which also depends essentially on the implemented pedal characteristic is not applied in the third operating mode to because the ^¬ level in the hydraulic relapse present pedal characteristics significantly from the pedal characteristic in the active Operating condition of the

Brake system (with connected simulation device 40) is present differs.

For the transfer of the brake system from the first operating mode Z _P in the third operating mode to example, first in block 53, a pressure equalization performed by the pressure _{supply device} 3, since the driver by the brake pedal operation in the first operating mode Z _P already has a certain brake pressure P _Br = P _THZ in the brake circuit pressure line sections 12, 13 and wheel brakes 6 has generated. For this purpose, the pressure P _Br, s _o ii the pressure supply device 3, for example, is linearly increased by suitable control of the pressure supply device 3 to the set by the driver brake pressure P _TH z is reached _(Ρ ΒΓ, _ΒΟΙΙ = P _THZ) · According to this setpoint In ^¬ game according to the actuator of the pressure supply device 3 via the respective check valve 20a, 20b of the still closed Zuschaltventile 45a, 45b comfortably the same pressure, which already by the driver operation present in the wheel brakes 6. In the event that the two check valves 20a, 20b are not present, be ^¬ preferred already during the described

Druckangleichvorgangs the Zuschaltventile 45a, 45b geöff ^¬ net. If the pressure equalization takes place, measures for activating the brake booster function F _{Ü of} the third operating mode Zu are carried out.

In the activation of the brake booster function LON _{t of} the third operating mode to in block 55, the vehicle ^¬ leader is separated from the wheel brakes 6 (switching to a "brake-by-wire" mode) and the pressure ^{supply ¬ device} 3 provides the pressure for the wheel brakes 6 is available. as the driver has already set a brake pressure through the Bremspedalbetä ^¬ actuation in the first mode, it is advantageously according to the example considered in the brake ^¬ force gain function F _O. therefore, initially in block 54, the in the activation or immediately prior to the Activation of the brake booster function F _Ü stored at a time t = tO values X _Ped , o and P _THZ , O for the actuation _travel Χ _{Ρβ <} ι and the pressure P _THZ stored.

When separating the driver from the wheel brakes 6 in block 55, the separating valves 39a, 39b of the master cylinder 22 are closed according to the example, the connection valves 45a, 45b of the pressure supply device 3 are opened or remain open. The method for controlling the simulator release valve 41 for connecting the Simula ^¬ tion means 40 (shown in block 55, not shown in detail in Fig. 2) is preferably carried out depending on the size of the already applied by the driver pressure P _THZ, _O, which is present at the time tO of switching. A game according to at ^¬ method for driving the

Simulator enable valve 41 is described below:

If the pressure P _THZ , _{O is} less than a second threshold PTHZ, E2 (ΡΤΗΖ, Ο <ΡΤΗΖ, ΕΣ), the simulator enable valve 41 is also opened (directly). Thereby, since a zusätzli ^¬ ches pressure fluid volume is opened, the brake pedal under the effect of the applied actuation force of the driver is to slow, causing thus changes the actuation. The pressure threshold P _THZ, _E2 is advantageously chosen so that this yielding of the brake pedal komforta ^¬ bel and non-irritating to the driver.

For larger pressures, ie P _THZ , O - P _THZ , _E2 , the immediate opening of the simulator _{release valve} 41 would lead to a depending on the applied operating force, rapid and jerky yielding of the brake pedal 1. For this case, therefore, for example, the simulator release valve 41 is energized to ^¬ next by means of a pulse train and then kept permanently open.

An exemplary energization is shown in FIG. During the pulse train, the simulator enable valve 41 is opened (OPEN) for a period Tl (e.g., approximately T1 = 2-3ms) and then closed (ZU) for a period T2, with the time T2 substantially greater than the time Tl. By briefly opening and closing the

Simulatorfreigabeventils 41, the effect of a quick and jerky yielding of the brake pedal 1 is reduced under Einwir ^¬ effect of the driver's foot force, since the addi ^¬ che pressure fluid volume of the simulation device 40 to Next only briefly switched on. Thus, even at higher pressures P _THZ , _O, a comfortable transition to the simulator operation of the third operating mode Zu is shown. Is carried out by the pulse sequence transition is complete, is from t = t open _on the simulator release valve 41 dau ^¬ nently for the duration of braking (ON).

The brake booster function F _Ü in the third mode of operation to (block 55) is essentially designed as a Druckver ^¬ tonic based on the master cylinder pressure / simulator pressure P _TH z. The corresponding pressure setpoint Ρ _ΒΓ , _ΒΟΙΙ for the _{Druckbereitstellungsseinrich} ^¬ device 3 is thus determined according to the brake booster function F _Ü from the pressure P _THZ :

As mentioned above, in determining the pressure set point _Ρ ΒΓ, _{_Β} Ο _ΙΙ advantageously also the time ^¬ point tO already ^¬ presented by the driver in the fallback pressure _Ρ ΤΗΖ, Ο and optionally the actuating _Χ Ρθ _<ι, ο considered. _By way of example, the target pressure P _{br is} determined according to the following equation (2):

ΡΒΓ, ΒΟΙΙ ⁼ PTHZ, offset + λϋ * Κρ _(Β οο3ί * PTHZ

The factor K _{P (B} oost represents the pressure ^boosting factor for the transition operating mode Zu, wherein for an amplification of the driver pressure, it must hold that K _{P (B} oost> 1.0.

The factor λο represents a transition scaling factor to avoid jerking values changes in the setpoint _Ρ ΒΓ, _ΒΟΙΙ the transition of the pressure-adjusting and Ak ^¬ tivierung of the brake booster function at the time t = tO. Examples of values for the factor λο are in

Fig. 4 shown. Before and at the time t = t0, λο is

= 0 and increases for a predetermined time period T ^ _Ü ^¬ continu ously (for example, linearly with time t) to the value λο = 1.

The pressure offset value P _TH z, offset takes into account the pressure value which the driver has already applied in the fallback level and is reduced during the further brake actuation (preferably when releasing the brake) eg linearly with the actuation travel to the value 0. At the time t = tO ent ^¬ speaks this value, for example according to the already applied by the driver brake pressure:

PTHZ, offset ⁼ ΡΤΗΖ, Ο ·

As long as the actuating _travel Χ _{Ρβ <} ι greater than or equal to a threshold X _P eci, o (Xped - ed, o), the currently valid Druckoff ^¬ setwert P _THZ , offset is maintained. Falls below the Actuate the ^¬ gungsweg Xpe the threshold _d X _Ped, o, then the offset value is reduced linearly with, for example, the actuation. It then applies fol ^¬ constricting equation (3):

PTHZ, Offset, New ⁼ ΡτΗΖ, Ο * (Xped ^- Xped, s) / (Xped, 0 ^- Xped, s)

If P _THZ , offset, new smaller than the previous offset value

P _THZ , offset is, this is replaced by the newly calculated value. If the actuating travel falls below the lower Threshold Χ _{Ρθ <} ι, ε, so wi d de considered offset value PTHz, offset set to the value 0.

According to another advantageous embodiment of a method for driving the simulator release valve 41 is provided, that in connection with the uncoupling of the vehicle driver a further pressure ^¬ threshold of the wheel brakes 6 P _THZ, _E 3 is provided, which is greater than or equal to the threshold pressure P _T HZ, E2 is (P _T HZ, E2-PTHZ, E3) If the pressure P _T HZ, O exceeds this further threshold P _T HZ, E3, ie P _T HZ, O> P _THZ , _E 3, then the simulator _{release valve} 41 becomes not ge ^¬ opens and remains closed for the duration of this brake application. The driver then does not actuate the simulation ^{¬ device} 40 as in the above-described embodiment, but only compresses the pressure medium volume located in the master cylinder 22, which results in a very stiff pedal characteristic, but this is eliminated by opening the

Simulator-release valve 41 caused by the brake pedal 1 yielding the brake pedal. 1

For the calculation of the brake pressure Ρ _ΒΓ , _Β Ο _ΙΙ is ^¬ example according to a relation to equation (2) modified equation used. In the event that P _THZ - _Ρ ΤΗΖ, Ο is, fol ^¬ constricting equation (4) applies:

ΡβΓ, ΒοΙΙ ⁼ ΡτΗΖ, Ο + Kp _(B oost * (ΡτΗΖ ^_ ΡτΗΖ, θ)

Is the further threshold _T P HZ, E3 chosen so that P HZ _T, E2 = P _THZ, _E3, then in the activation of Bremskraftverstär ^¬ _Ü kung function F for the third operating mode to the Brake system instead of the previously described pulse-like opening the simulator release valve 41 the

Simulator release valve 41 kept closed.

The brake system advantageously remains in the third operating mode (block 55 in FIG. 2) as long as the driver holds the brake pedal 1 pressed (NO in query 56). If the driver releases the brake pedal 1 and thus there is no more brake pedal actuation by the driver (YES in query 56, ie Xp _ed ~ 0), then the third operating mode to the brake system is ended and the brake system changes to the second operating mode Z _A (block 52). All other brake pressure demands of the driver are then, for example, according to the already explained above approach ^¬-worked.

The invention preferably deals with a method for Akti ^¬ vation of an operating mode with a brake boosting an electric-motor-driven power brake system, wherein the activation of the passive state of the brake system (usually the hydraulic fallback mode) is carried out with simultaneous actuation of the brake system by the driver.

The invention offers, for example, the advantage that for the transition from a passive state to an active state of the brake system with simultaneous actuation of the brake pedal 1 and applying a brake pressure by the vehicle ^¬ leader, the brake pedal characteristic comfortable and without significant irritation to the driver of the passive in the active state is transferred, ensuring the fastest possible provision of a brake booster function during this operation becomes. The advantages of the invention are particularly useful when the brake system is activated by restarting (eg by switching on the ignition) while the driver is standing on the brake pedal 1.

An alternative solution is to keep the activated at be ^¬ tätigtem brake pedal 1 the brake system provided in the hydraulic auxiliary level (ie, in the first operation mode Z _P without braking force gain) until the driver does not depresses the brake pedal 1 (ie _Χ Ρθ _< ι = 0) and only then the brake system in the active state (the two ^¬ th operating mode Z _A ) to switch, provides no Bremskraftverstärkungsfunktion ready. Therefore, the method according to Invention ^¬ or the brake system according to the invention is part way before ^¬.

Claims

Claims:

1. A method for operating a brake system for motor vehicles with

A master brake cylinder (22) which can be actuated by means of a brake pedal (1) and which is connectable (39a, 39b) to at least one brake circuit pressure line section (12, 13) to which at least one wheel brake (6) can be connected or connected,

• a to the master brake cylinder (22) cooperating simulation means (40), which is designed switched on and off and which has a pleasant feeling in her pedal to ^¬ connected state to the driver,

• an electrically controllable pressure supply device (3), which line section (12, 13) separable (45a, 45b) with the Bremskreisdrucklei- verbun is ^¬, and which is formed in particular by a Zylin ^¬ the piston arrangement, the piston (46 ) is actuable by an electromechanical actuator (47),

A first detection device (7) for detecting a first _measuring variable (Χ _{Ρθ <} ι) characterizing an actuating _{travel of} the brake pedal (1), and

• a second detecting means (8) for detecting a pressure of the master cylinder (22) characterizing the second measuring quantity (P _THZ), wherein in a first mode of operation (Z _P) of the Bremsanla ^¬ ge the simulation device (40) is switched off and the brake circuit pressure line section (12 , 13) with the Pressure of the master cylinder (22) is acted upon, and wherein in a second operating mode (Z _A ) of the

Brake system, the simulation device (40) is supplied scarf ^¬ tet and the brake circuit pressure line section (12, 13) is subjected to a pressure of the pressure supply device (3), characterized in that in the second operating mode (Z _A) of the brake circuit pressure line section (12, 13) is subjected to a pressure of Druckbe ^¬ riding device (3), which according to a first predetermined relationship (F _a), especially from the first measurement variable (X _{Pe <i)} and / or the second measuring quantity (P _T HZ), is determined, and that in the presence of a predetermined condition (S, 51) during the first operating mode (Z _P ), a transition (53, 54, 55) from the first operating mode (Z _P ) to a third operating mode (Zu) of the brake system is performed, where ^¬ in the third operating mode (To) the Bremskreis- pressure line section (12, 13) with a pressure

(Ρ _ΒΓ , _ΒΟΙΙ ) of the pressure _{supply device} (3) is beauf ^¬ strike, which is determined according to a second predetermined relationship (F _Ü ), which is different from the first predetermined relationship (F _A ).

2. The method according to claim 1, characterized in that the predetermined condition is a start or restart or activation of the brake system (S) during a Betä ^¬ tion (51) of the brake pedal (1).

3. The method according to claim 2, characterized in that an actuation of the brake pedal (1) is detected when at least the first measured variable (X _{Pe <} i) is greater than or equal to a predetermined first actuation threshold value

4. The method according to any one of claims 1 to 3, characterized in that in the third operating mode (to) the pressure (Ρ _ΒΓ , _ΒΟΙΙ ) of the pressure _{supply device} (3) according to the second predetermined relationship (F _Ü ) from the second measured variable (P _THZ ) is determined.

5. The method according to any one of claims 1 to 4, characterized in that in the transition from the first Be ^¬ operating mode (Z _P ) in the third operating mode (Z ü) to the next pressure (Ρ _ΒΓ , _Β Ο _ΙΙ ) in the Pressure ^{supply device} (3) to the current value of the pressure

(P _THZ ) of the master cylinder (22) is adjusted

(53).

6. The method according to any one of claims 1 to 5, characterized in that the value (Ρ _ΤΗΖ , Ο) of the second measurement ^¬ size (P _THZ ), and in particular the value (Xp _ec i, o) of ers ^¬ th measured variable ( _Χ Ρθ _<ι) which is at or a pre give ^¬ NEN time threshold before entry (to) into the third operating mode is present (to), in particular in an electronic control unit (5) is vomit ^¬ chert (54).

7. The method according to claim 6, characterized in that in the third operating mode (to) the pressure (P _Br , soii) of the pressure supply device (3) taking into account the stored value (Ρ _ΤΗΖ , _Ο ) of the second measurement ^¬ size, in particular the stored values (Ρ _ΤΗΖ , Ο,

Xp _ec i, o) of the first and second measurands.

8. The method according to any one of claims 1 to 7, characterized in that for entry into the third Be ^¬ drive mode (to) the master cylinder (22) from the brake circuit pressure line section (12, 13) is separated and the pressure supply means (3) with the brake circuit pressure line section (12, 13) is connected.

9. The method according to claim 8, characterized in that the entry into the third operating mode (to) is performed only after the pressure (Ρ _ΒΓ , _ΒΟΙΙ ) in the pressure _{supply device} (3) to the value of the pressure (P _THZ ) of the master cylinder (22), and in particular the values (X _Peclr0 , P _THZ , _O ) of the first and second _measurands (X _Pe d, P _THZ ) which at or a predetermined time threshold before entry (t0) into the third Operating mode (To) present ge ^{¬ are} stores (54).

10. The method according to any one of claims 1 to 9, characterized in that when entering the third Be ^¬ operating mode (To), the simulation device (40) is supplied ^¬ switched.

11. The method according to claim 10, characterized in that the simulation device (40) is switched on by opening a simulator _{release valve} (41), if the value (Ρ _ΤΗΖ , _Ο ) of the second measured variable, which at or a predetermined time threshold before entry (tO) in the third operating mode (Zu), smaller than a predetermined first pressure _{threshold value} (P _THZ , _ε2 ) lSt.

12. The method according to claim 10, characterized in that the simulation device (40) by controlled or controlled opening and closing of a

Simulator- _{release valve} (41) is switched on, if the value (Ρ _ΤΗΖ , _Ο ) of the second measured variable, which at or a predetermined time threshold before entry (tO) in the third operating mode (To) is greater than or equal to a predetermined first pressure threshold

13. The method according to any one of claims 1 to 9, characterized in that when entering the third Be ^¬ operating mode (To) and in the third operating mode (To), the simulation _device (40) remains switched off when the value (Ρ _ΤΗΖ , _Ο ) the second measured variable, which is in the third operating mode (Zu) at or a predetermined time threshold value before entry (tO), is greater than a predefined second pressure _{threshold value} (P _THZ , _E3 ).

14. Brake system for motor vehicles with

A master brake cylinder (22) which can be actuated by means of a brake pedal (1) and which is separably connected to at least one brake circuit pressure line section (12, 13) to which at least one wheel brake (6) can be connected or connected,

• a to the master brake cylinder (22) cooperating simulation means (40), which is designed switched on and off and which has a pleasant feeling in her pedal to ^¬ connected state to the driver, • an electrically controllable pressure supply device (3), which line section (12, 13) separable (45a, 45b) with the Bremskreisdrucklei- verbun is ^¬, and which is formed in particular by a Zylin ^¬ the piston arrangement, the piston (46 ) is actuable by an electromechanical actuator (47),

A first detection device (7) for detecting a first _measuring variable (Χ _{Ρθ <} ι) characterizing an actuating _{travel of} the brake pedal (1),

A second detection device (8) for detecting a second measured variable (P _THZ ) characterizing a pressure of the master brake cylinder (22), and

• an electronic control unit (5), wherein in a first operating mode (Z _P ) of the Bremsanla ^¬ ge the simulation device (40) is switched off and the brake circuit pressure line section (12, 13) is acted upon by the pressure of the master cylinder (22), and wherein in a second operating mode (Z _A ) the

Brake system, the simulation device (40) is supplied scarf ^¬ tet and the brake circuit pressure line section (12, 13) is subjected to a pressure of the pressure supply device (3),

characterized in that in this a method according to any one of claims 1 to 13 is performed.