EP2534024A1

EP2534024A1 - Brake system having a pressure model and prioritization device

Info

Publication number: EP2534024A1
Application number: EP11704591A
Authority: EP
Inventors: Heinz Leiber; Christian Koeglsperger; Anton Van Zanten
Original assignee: Ipgate AG
Current assignee: Ipgate AG
Priority date: 2010-02-13
Filing date: 2011-02-11
Publication date: 2012-12-19
Also published as: JP2013519564A; DE102010008033A1; CN102753412A; KR20120135508A; WO2011098573A1; US20120306261A1

Abstract

The invention relates to a brake system comprising a brake booster, the piston-cylinder system (14, HZ, THZ) of which is driven mechanically or hydraulically by an electric motor, in particular by means of transmission means, at least one working chamber of the piston-cylinder system (14, HZ, THZ) being connected to at least two wheel brakes via hydraulic lines, each wheel brake being associated with a 2/2 distribution control valve (17a, 17b, 17c, 17d) and the hydraulic connecting lines between the wheels brakes (18a, 18b, 18c, 18d) and the piston-cylinder system (14, HZ) being selectively disconnectable or jointly closable by means of the 2/2 distribution control valves (17a, 17b, 17c, 17d) such that in the wheel brakes (18a, 18b, 18c, 18d) a pressure can be adjusted consecutively in terms of a multiplex method and/or simultaneously, the electric motor and the control valves (17a, 17b, 17c, 17d) being actuated by a regulating device, characterized in that the regulating device calculates the respective pressure ( p_R(t) ) in the wheel brakes by means of a pressure model (103) and transmits the calculated pressure values ( p_R(t) ) to at least one ABS-ESP regulator (104) and to a pressure regulating device (106), wherein the pressure regulating device (106) actuates at least the 2/2 distribution control valves (17a, 17b, 17c, 17d) and the electric motor, and a prioritization device (105) performs a wheel selection on the basis of the data transmitted by the ABS/ESP regulator (104) and transmits it to the pressure regulating device (106).

Description

description

Brake system with pressure model and prioritization device

The present invention relates to a brake system according to the preamble of claim 1.

State of the art

With ABS / ESP, the accuracy and dynamics of the pressure curve determine the control quality and thus the braking distance and the stability of the pressure

Vehicle. Decisive for a good control is a fast and fine pressure control. Except for the electromechanical brake EMB, all hydraulic systems work with 2/2-way agnet valves. For this purpose, the brake manual 2nd edition v. 2004 p.114-119 with bibliographical references the detailed basic information. Without special measures, these valves have a purely digital switching behavior, ie they are either open or closed (open / close). Due to the rapid closing, depending on the pressure gradient, pressure oscillations with a high amplitude occur, which have an effect on the wheel behavior and above all cause noises. The pressure gradient depends on the differential pressure, which fluctuates strongly in the control range between μ = 0.05 (ice) and μ = 1.0 (asphalt dry) and also depends on the strongly fluctuating THz pressure of the brake booster. The dosing of the often clocked pressure increase amplitude in the range of 1-10 bar (setpoint) succeeds only relatively inaccurate. A Improvement can be made by an elaborate PWM control of

2/2 solenoid valves can be achieved. In particular, this makes it possible to influence the transition from the pressure build-up to the pressure hold, so that the pressure oscillations and the noise become smaller. These

PWM control is difficult and relatively inaccurate because it has to consider the pressure gradient, the pressure amplitude and also the temperature. For pressure reduction, this PWM control is not used.

In EP 06724475 a method for pressure control by means of electric motor and piston control is described. This determines the

HZ piston movement of the brake booster the pressure control and thus has considerable advantages in terms of accurate pressure control and variable gradients. EP 06724475 also describes the pressure control of several wheel brakes by the so-called multiplex method (MUX method). So u.a. described that

2/2-way solenoid valves should have a large flow area with negligible throttle effect and the lines from the piston-cylinder system to the brake cylinder should have a negligible flow resistance. It is further stated that the pressure reduction at two wheel brakes can occur simultaneously, if initially approximately the same pressure level prevails.

Despite these measures described in EP 06724475, the multiplex method has the disadvantage that at unequal pressure level in two wheel brakes, a simultaneous pressure reduction is not possible, since here in the dimensioning described in EP 06724475 during pressure reduction, a pressure equalization between two to four wheel brakes can erfoigen, if the flow resistance from the HZ or THZ to the wheel cylinder is too low. In addition, two or more pressure reduction requirements, which occur slightly offset from one another, can likewise not be carried out simultaneously or partly simultaneously due to the above-mentioned problem of the possible pressure compensation between the wheel cylinders. This is particularly problematic because especially the temporal offset of printing requirements of the same sign can quite possibly occur. As mentioned above, pressure relief and pressure buildups can be simultaneous or semi-simultaneous. It is spoken of simultaneously when two or more solenoid valves are opened simultaneously and closed at the same time. Teilimultan the printing position is then designated when two or more solenoid valves either open delayed or closed with a time delay.

Furthermore, no simultaneous pressure build-up is provided in EP 06724475. This has the consequence that a possible increase in pressure can not be performed in the short term, which may result in a longer braking distance.

Object of the invention

The object of the invention is to provide an improved braking system with a control device, to reduce costs and to optimize braking distance and stability.

Solution of the task

The solution is achieved according to the invention with a brake system with the features of claim 1. Further advantageous embodiments of the brake system according to claim 1 result from the features of the subclaims.

The invention is advantageously characterized in that a pressure model for calculating the wheel brake pressures is used, the calculated pressure values of which are transmitted to the ABS / ESP controller and to the pressure control device. As a result, pressure sensors can be saved and the pressure control accuracy can be increased. In addition, by means of a prioritizing device, in particular based on main criteria, such as "optimal braking distance" and / or "stability of the control", the selection of the wheel brake or wheel brakes in which or next to the pressure build-up or pressure reduction should take place. Likewise, the prioritizer makes the decision as to whether a simultaneous, semi-simultaneous or a pressure change in only one wheel brake or should be done simultaneously. This decision can be made, for example, on the basis of the determined slip value and / or on the basis of the instantaneous wheel acceleration or wheel deceleration. Furthermore, no pressure reduction p _{ab is} permitted for a pressure buildup p _{aUf that} is currently _{taking place} . In order to minimize the loss of time for the pressure build-up, a high piston or pressure reduction speed with short switching times of the motor and solenoid valves is necessary. In this case pressure model ABS / ESP controller, prioritization device and pressure control can also be increased during the subsequent pressure build-up p _at the desired pressure via the action chain in order to regulate the pressure level close to the blocking limit.

A simultaneous or partial simultaneous pressure reduction and pressure build-up is possible even at different pressure levels of all wheel brakes. This can be achieved by correspondingly high piston speeds, the dimensioning of the flow resistances RL of the line from the 2/2-way solenoid valve to the working space of the piston-cylinder system (HZ or THZ) and the flow resistance RV of the 2/2 solenoid valve and the hydraulic lines to the wheel cylinder. It is advantageous if the flow resistance RL is smaller than the flow resistance RV. It is particularly advantageous if the flow resistance RL is smaller by a factor of 1.5 to 3 than the flow resistance RV. It is particularly advantageous if, in addition, the flow resistance RVR of the hydraulic line from the solenoid valve to the wheel cylinder is taken into account, this advantageously being chosen to be considerably smaller than the flow resistance RV of the solenoid valve.

In an improved embodiment of the invention, it can be considered that the total flow resistance (RL + RV) is designed such that at maximum HZ piston dynamics, which corresponds to the maximum engine dynamics of the drive of the brake booster and with two or more open solenoid valves the simultaneous volume absorption or volume delivery of Radzylinderbremsen short-term (ie within the valve opening times) no pressure compensation can take place.

In the design of the switching valves is therefore important to ensure that you achieve a very low flow resistance that does not fall below the minimum described above. It is important to ensure that the simultaneous pressure reduction sufficient pressure difference between HZ or THZ and wheel cylinder is present, so that no pressure equalization between the individual wheel cylinders of the wheel brakes can take place in the common pressure ^¬ degradation.

Another way to prevent the pressure equalization in simultaneous pressure reduction or pressure build-up is to reduce the flow area of the valves via a PWM control and thus to increase the flow resistance. For example, if there are different pressure change prompts for the four wheels, the controller can set different PWMs to achieve different flow resistances for each wheel based on instantaneous actual pressures and the calculated individual set pressures. This is preferably done first at the wheels or associated solenoid valves with the largest pressure difference. It is advantageous in this case that the pressure gradients can be selected depending on the situation, even in the case of simultaneous or partially simultaneous pressure build-up and pressure drops, and there is no binding to the pressure profiles predetermined by the design of RL and RV and optionally RVR. Even simultaneous or partially simultaneous Druckab- or pressure structures with extremely different pressure levels in two or more wheels are thereby manageable. Since the maximum possible flow velocity drops to low pressures during pressure reduction and the pressure-volume characteristics of the individual wheels represent a non-linear function, a variable or different piston speed is absolutely necessary for simultaneous or partially simultaneous pressure reduction and pressure build-up. In simultaneous or partially simultaneous pressure reduction must be due to the volume flow from the wheel cylinder in the HZ or THZ whose piston through appropriate control or regulation can be readjusted to maintain the pressure difference. The volume that flows out of the HZ or THZ into the wheel cylinder, would lead to an increase in pressure without adjustment of the HZ-piston and static to a

Pressure compensation. This piston adjustment takes place primarily via the regulator, which calculates the necessary pressure difference, determines the volume intake in the HZ and uses the HZ pressure and advantageously a pressure model. When adjusting the HZ or

It must be ensured that the HZ or THZ pressure is always below the minimum pressure level of all wheel cylinders currently connected to the HZ or THZ via an open solenoid valve or switching valve. The same applies to simultaneous or semi-simultaneous pressure build-up. Here again, the controller indicates the pressure level of the pressure increase. The HZ or THZ pressure is readjusted accordingly via the piston stroke and the piston speed in order to take into account the volume of the wheel cylinders of the wheel brakes for pressure build-up. When readjusting the HZ piston, make sure that the HZ or THZ pressure before decompression in the range of the maximum pressure level of all at the moment with the HZ or THZ connected via an open solenoid valve wheel cylinders and during the pressure reduction p _is below the target pressure of the lowest wheel. Only when the target pressure is reached, the HZ pressure is adjusted to this level.

Knowledge of the pressure-volume characteristic curve of the individual wheels is of great importance both for simultaneous, semi-simultaneous and non-simultaneous pressure build-up, as well as for simultaneous or semi-simultaneous pressure reduction. This is recorded at intervals for vehicle standstill for each wheel by the volume is detected with knowledge of the HZ pressure or THZ pressure on the corresponding piston stroke. The process takes place with a relatively low dynamics, so that the Radzylin- derdruck corresponds to the pressure in HZ or THZ.

As is well known in highly dynamic processes in the pressure control both in pressure build-up and in pressure reduction infoige the flow resistance in the switching valve, which is usually a solenoid valve, and in the hydraulic lines to the wheel cylinder a big pressure difference. The controller determines the pressure change at the wheel brake, which is proportional to the braking torque. Therefore, conventional

ABS / ESP systems, even with pressure sensors at the outlet of the solenoid valve, only measure the wheel pressure statically. For dynamic measurement, a pressure model is used whose accuracy is limited. It is also complicated to install a pressure transducer for each wheel. In the system according to the invention with piston control, however, with knowledge of the pressure-volume characteristic, the wheel cylinder pressure can be set accurately even with different dynamics.

With simultaneous, semi-simultaneous or non-simultaneous pressure build-up and pressure reduction, two or more wheel cylinders are operated simultaneously. The predetermined by the controller pressure difference is over the

Pressure-volume curves of the wheels converted into a corresponding piston travel. With the help of an additional printing model, the wheel cylinder pressure is constantly included. Once the target pressure for a wheel is reached, the respective solenoid valve is closed. The piston of the HZ or THZ then continues to operate the remaining wheel cylinder. With the last wheel cylinder to be controlled, pressure control is carried out via the piston path, which was previously calculated from the pressure-volume characteristic curve. Thereafter, the solenoid valve of the last wheel brake can be closed.

The pressure model for piston control is very important for the brake system according to the invention in connection with the simultaneous and also non-mechanical pressure reduction and pressure build-up, since it serves to calculate or estimate the wheel cylinder pressures. The calculated wheel cylinder pressures are used both for the calculation of closing and opening times of the 2/2-solenoid valves (Schaitventile) as well as the actual value of the controlled variable of the pressure regulator in the multiplex process. In addition, the wheel cylinder pressures from the pressure model find use in higher-level controller structures (eg ABS / ESP, driver assistance functions such as ACC, etc.). Since it is advantageous that the HZ or THZ pressure before the pressure change in the wheel cylinder is first brought into the vicinity of the output pressure of the wheel cylinder to be controlled, it is necessary that the wheel cylinder pressures are continuously calculated and stored. This task is also taken over by the printing model.

For the control dynamics, the resulting noise and the control accuracy especially in connection with the simultaneous or semi-simultaneous pressure reduction and pressure build-up, the pressure model is therefore extremely important. The pressure model uses the HZ or THZ pressure as an input signal. The different wheel cylinder pressures are then calculated from the pressure model. The model parameters, such as Replacement flow resistance, equivalent line inductance and pressure-volume characteristic can be adapted via the temperature (eg ambient temperature or separate temperature sensor on a solenoid valve). If changes in the transition behavior occur, it is also possible via an adaptation to adapt the parameters of the model.

The process of simultaneous or semi-simultaneous pressure change is relatively rare in normal ABS / ESP braking and tends to occur in borderline cases such as asymmetric or inhomogeneous roadway. Therefore, it is very important that the multiplexer can switch from one wheel cylinder to the next as fast as possible. This is possible because the piston speed and thus the pressure change rate is very high and variably adjustable and thus in extreme cases, the piston can be controlled with maximum dynamics. Due to the variability, it is usually possible to reduce the piston speed and resort to maximum dynamics only in extreme cases. Furthermore, the switching time between the beginning of the piston movement and the opening and closing of the solenoid valve in turn depends on the pressure difference to be controlled and the absolute pressure in the wheel cylinder.

When designing the HZ or THZ, make sure that the HZ or THZ with closed solenoid valves or switching valves is as rigid a structure as possible, since the elasticity or rigidity of the HZ or THZ has a significant influence on the switching time. A rigid as possible HZ or THZ with the associated liquid volume and the connection channels, z. B. RL, thus allowing very short switching times.

To check and possibly correct the wheel cylinder pressures calculated by the pressure model during a longer control intervention, a comparison of the wheel cylinder pressure with the HZ or THZ pressure takes place at relatively long intervals. When the piston is stopped and the solenoid valve is open, therefore, a static adjustment is performed after a certain pressure settling time, which automatically takes place due to the construction of the pressure model without additional adaptation rules or extensions in the pressure model. The check can also be made if the slip or wheel acceleration specified by the controller is not achieved. It is also possible, without simultaneous or teilsimultane pressure change only on the basis of the pressure-volume curve and corresponding piston adjustment to work proportionally to the controller request.

In contrast to the conventional ABS / ESP controller, which is for the parallel, i. Independent pressure control requires twelve solenoid valves and some pressure transmitters, according to the MUX controller. the invention an equivalent or even better pressure control with only four solenoid valves and electric motor possible on the chain of action pressure model, ABS / ESP controller, Priori- sierungseinrichtung and highly dynamic and accurate pressure control or pressure control. The individual tasks of the individual modules are described in more detail below.

Similar to the ABS / ESP controller, the entire function must be fail-safe. For this purpose, a second arithmetic unit MCU2 is preferably connected in parallel, which likewise calculates plausibility checks of input, output or intermediate signals or calculation results. If the data does not match, the entire controller is switched off and the normal brake without controller function is switched on. In EP 06724475 a braking system is described in which a travel simulator is used. The brake system according to the invention may comprise a travel simulator. For cost reasons, however, it is also possible to dispense with a travel simulator. In this case, can take place via the electric drive and a mechanical connection between the brake pedal and brake booster retroactivity to the brake pedal. The brake system described can also be used as a full brake-by-wire system without a mechanical connection to the brake pedal. It is also conceivable that a THZ similar to the EHB is used in parallel to the brake system, which supplies corresponding pressure on additional changeover valves in case of failure of the described brake system.

The invention will be explained in more detail with reference to drawings. 1 shows a basic structure of the actuator for pressure control; 2 shows a block diagram of a printing model; Fig. 3: Signal flow chart of a possible software structure.

1 shows the basic structure of the brake system according to the invention consisting of HZ or THZ 14, EC motor 10, spindle 11 for driving the push rod piston, spindle reset 12 and rotary encoder 13 for determining the position of the piston and the detection of the rotor position and the piston travel.

If the piston receives the actuating command to build up a specific pressure, the corresponding piston movement via position transmitter 13 and pressure transmitter 19 in the pressure rod circuit takes place via the previously recorded pressure-volume curve stored in a characteristic diagram. At a subsequent short constant pressure, which is usually the case during braking, the correlation comparison takes place on the basis of new measured data with the stored map data. At a deviation is at later vehicle standstill again individually

Pressure-volume curve was recorded for each wheel brake and the map corrected. Is the deviation significant, z. B. on a wheel cylinder, the note is to visit the workshop. The pressure generated in the HZ or THZ passes via the lines 15, 16 from the push rod piston and floating piston via the 2/2-Mägnetventile 17a-d to the wheel cylinders 18a and 18d. Instead of push rods and floating piston and a different piston assembly or coupling can be used by springs. The push rod piston is advantageously fixedly connected to the spindle so that the push rod piston can be moved back by the drive for rapid pressure reduction.

Here, the dimensioning of the flow resistances RL from the HZ to the solenoid valve 17i (with i = a, b, c, d) in the lines 15 and 16 and then the flow resistance RV in the solenoid valve and hydraulic connection to the wheel cylinder is of great importance. Both resistors RL and RV should be low, where RL should be much smaller than RV and the flow resistance from the solenoid valve to the wheel cylinder RVR is small compared to the solenoid valve, preferably

RL <RV / factor, where the factor should be 1.5 to 5, in particular 1.5 to 3, at room temperature. The 2/2-solenoid valves 17a-d with the lines 15 and 16 and pressure transducer 19 are preferably integrated in a block, this can also be the HZ or THZ included.

If the control command for pressure reduction, so again the pressure setting via the piston stroke and then the adjustment with the pressure measurement. Pressure build-up and breakdown correspond to the usual BKV function. For this purpose, a supplement with the components, eg. As pedal, Pedalweggeber, travel simulator, inter alia, as described in the aforementioned EP 6724475. The braking system of EP 6724475, however, has the pressure control and modulation to the content and does not require all the above components. If a pressure modulation takes place, eg for the ABS / ESP function, then the MUX function is switched on. If, for example, the pressure on the wheel 18a is reduced after the HZ or THZ 14 has previously generated a specific pressure in the lines 15 and 16 and wheel cylinders 18b and 18d via an engine 10, then the solenoid valves 17b to 17d are closed.

If the pressure reduction Pa predetermined by the controller is reached via the corresponding piston travel, the solenoid valve 17a is closed, and the piston of the HZ or THZ moves into the desired position specified by the regulator. Should then z. B. in the wheel cylinder 18d a pressure build-up p _au f done, the solenoid valve opens 17d, and the piston is moved to the new desired position for the setpoint p _on . If a simultaneous or partially simultaneous pressure reduction p _a b is to take place in the wheel cylinders 18 a and 18 d, then the solenoid valves 17 a and 17 d are de-energized and thus switched to the open position and the solenoid valves 17 b and 17 c are closed. Again, the piston moves to the new target position. These operations for the

Pressure modulation is extremely fast with special switching conditions for the motor and solenoid valves. These are described in FIG. 2 and FIG.

FIG. 2 shows a possible pressure model for calculating the individual wheel cylinder pressures. As an input signal 121, the pressure model uses the HZ pressure PHz (t), which only corresponds to the wheel pressure in the wheel brake in the swung-in state (static). The model 122 to 131 is fourfold for a vehicle with four wheel brakes. Alternatively, it is possible for the pressure model to calculate the HZ pressure 121 via a stored pressure-volume characteristic 132 of the HZ. This means that the wheel pressure can also be adjusted dynamically via the corresponding ΉΖ position or piston travel. The task of the pressure model is to obtain a dynamic or high-frequency estimation of the wheel cylinder pressure p _R (t). The function of the individual signals and signal blocks is explained in more detail below. The piston travel or the piston position s _k (t) 135 of the HZ is used as the input signal for the pressure model 103 (see also FIG. 3). About the summation point 134 is from the volume at the wheel 129.1 to 129.3 and the piston stroke s _k (t) 135 calculates the volume in HZ 133. Under wheel volume, the invention, the volume of the wheel brake including the supply lines and the working space of the HZ. The HZ pressure p _H z (t) 121 is calculated via the volume-pressure characteristic curve 132 of the HZ. It is also conceivable to adjust the HZ pressure signal of the pressure sensor with the simulated signal 121. This measure serves to diagnose a pressure sensor failure via the characteristic curve 132, the piston position of the HZ correlates with a specific pressure. For diagnosis, one can also use the phase current of the motor. If only the HZ pressure is used as the input signal of the printing model, the signal path 135 to 121 is not necessary. One then obtains the HZ pressure 121 directly from the pressure sensor.

A summation point gives the differential pressure 122, which leads to the flow Q via the model block "hydraulic equivalent inductance or line inductance" 123, which stands for the mass and / or inertia of the brake fluid, and an integrator 126. The signal block 127 takes into account the flow resistance The model parameter equivalent flow resistance R corresponds to the hydraulic resistance of the path from the piston-cylinder system 14, HZ via the switching valve 17a, 17b, 17c, 17d to the wheel cylinder of the wheel brake In addition, the signal block 127 takes into account a parameter (kappa) which represents a weighting of the flow conditions laminar / turbulent within the hydraulic path from the piston-cylinder system 14, HZ via the switching valve 17a, 17b, 17c, 17d to the wheel cylinder of the wheel brake. About the second Integr Ator 125 is obtained from the pressure flow Q 126, the current volume at the wheel 129 and from there via the volume-pressure characteristic of the wheel cylinder 130, which describes the capacity or the stiffness of the wheel cylinder and the connected brake lines, the pressure at the wheel 131st Furthermore, it is possible in the pressure model 103, (see FIG. 3) to simulate the hysteresis present in reality, inter alia due to seals, etc. This increases the estimation accuracy of the print model. The used The pressure-volume curves are thereby statically adapted or recorded at vehicle start and stored as a function with the associated function parameters or as a table.

FIG. 5 shows a possible signal flow plan of the software structure. Reference numeral 101 represents the actuator pHz (t) = f (s _K (t)), which is shown in detail in FIG. The sensor technology of the actuator supplies the HZ pressure 121 and the HZ piston travel 135 via the evaluation of a rotary encoder. Other sensor signals, such as driver's desired pressure, pedal position, motor phase currents, battery currents, etc., are not listed here, but can be taken into account.

The pressure model 103 calculates the different wheel brake pressures 131 from the signals 121 and 135 as a function of the time pressure curve pHz (t) in the HZ and / or the DK piston travel s _K (t), or as a function of both, where p _R (t ) = f (p _HZ ) or p _R (t) = f (p _HZ , s _K ) or p _R (t) = f (S _K ).

About an adaptation in block 102, the model parameters of the printing model 103, such. B. Replacement flow resistance, Ersatzleitungsinduktivität and pressure-volume curve or pressure-volume curve of the wheel cylinder and the HZ or THZ, on the temperature, eg the vehicle ambient temperature or by means of a temperature sensor to a solenoid valve or the temperature-proportional resistance measurement of Solenoid valve measured temperature, adapted. The Adaptionsvorschift can be determined during the development of the system in temperature tests and deposited. Also, the parameters of the hysteresis simulation mentioned above can be adapted depending on the temperature. Various vehicle-specific parameters, such. B. line lengths or on and off time of the solenoid valve, can be measured at initial commissioning of the vehicle or programmed from a file. Depending on the temperature, either the model parameters are stored in a table or the model parameters are calculated and passed on to the model. If, for example, changes in the transition behavior occur, it is about the adaptation also possible to adjust the parameters of the model. The adjustment of the pressure model and thus the parameters of the pressure model can be done several times in succession or in shorter time intervals, if the

Pressure model deviates from the actual measured values. The pressure model is constantly included in the calculation and is very important for the accuracy of the printing position, especially in connection with the pressure modulation with ESP / ABS 104 or other higher-level controllers. The wheel cylinder pressures p _R (t) from the pressure model become the

ABS / ESP controller supplied. The ESP / ABS controller 104 and especially the pressure control or pressure control 106 are dependent on wheel brake pressures p _R (t) as controlled variables. The ESP / ABS controller calculates a target wheel brake pressure P soii (t) based on ABS / ESP sensor signals such as wheel speeds, lateral acceleration, yaw rate, etc., and wheel brake pressures p _R (t). Alternatively, the wheel brake target pressure p _Rso ii (t) may also be only a differential pressure or be expanded in its information _content by the pressure gradient. The wheel brake target pressure is of course calculated individually for each wheel.

In order to prioritize the operations of the pressure regulator 106, the pressure regulator is preceded by the function block "prioritization device" 105, which is used for determining the priorities 108, eg wheel slip, vehicle transverse dynamics parameters, pressure control deviation, etc., the wheel selection 109. The wheel selection dictates which pressure which wheel brake (s) it will need to adjust next to the pressure regulator 106. For example, a pressure reduction request has a higher priority than a requested pressure reduction on another wheel and will therefore be executed first allows one wheel to perform two pressure buildups in succession without having to operate another wheel in the meantime Prioritization also takes the decision whether a single wheel or simultaneous pressure build-up or decompression must occur and how many wheels are involved in it as a criterion for prioritization apply preferential Wheel speed, wheel acceleration, cornering, μ-jump (positive and negative), μ-split lane and time of the Regulation. If, for example, an excess of the setpoint slip or a wheel acceleration threshold is detected at several wheels on the first control cycle, the number of wheels involved is switched to simultaneously or partially simultaneously. If during a pressure reduction of a wheel an exceeding of the nominal slip with a higher wheel acceleration, eg -5g, occurs with another wheel, then this is regulated in a partially simulated manner. If the control cycle is almost completed, there is no switchover. The respective set values for slip and acceleration for simultaneous or semi-simultaneous are changed in the sense of smaller values when cornering in order to obtain full stability. At higher sliding wheel re-accelerations, eg due to a corresponding change in the coefficient of friction of the road, it is also possible to switch to simultaneous or semi-simultaneous with corresponding slip values. That is, in all cases in which a gain of braking distance or driving stability can be achieved or is present, the switchover to simultaneous or teilsimultan.

The respective time sequences, as shown in FIG. 2 and FIG. 3, are then calculated by the pressure control 106. By stored pressure-volume curves is here, taking into account the hysteresis of the wheel cylinder of the required

HZ piston travel calculated. An ideally subordinate position controller then sets the desired piston travel via control signals 11. For this purpose, the respective switching valves 17a, 17b, 17c, 17d are driven 110 in the correct time sequence. It is quite possible that the pressure mode 103 is used to estimate future wheel pressures. This may be particularly important to the pressure controller 106 to calculate the correct valve timing. The determined values can be temporarily stored in a memory. List of reference numbers:

1-9 phases in the control cycle

p _HZ master cylinder pressure

p _R wheel cylinder pressure

PR _SO II wheel cylinder target pressure

Pauf pressure build-up

p _from pressure reduction

p * _from pressure change rate at pressure reduction

p * _at pressure change rate at pressure build-up

s _k HZ piston stroke

s * _k HZ piston speed

T _E Settling time before valve closing

Tum switchover time from the beginning of piston movement to open the valve

T _MU x Total time to set the desired pressure on one or more wheels

t _v delay time to close the solenoid valve

a Transient course in pressure-time behavior with settling time before

valve closing

b Transient course in the pressure-time behavior with hard valve closing without egg-swinging time

V solenoid valve / switching valve

U _MV voltage curve 2/2 solenoid valve

RL flow resistance in the line from HZ or THZ to

Solenoid valve / switching valve

RV flow resistance in the solenoid valve

RV _R Connection from the solenoid valve to the wheel cylinder

R RV + RV _R + RL

10 EC motor

11 spindle

12 spindle reset -

13 rotary encoder (position transmitter)

14 HZ or THZ

15 pressure line from push rod piston

16 pressure line from the floating piston 17a-17d 2/2 solenoid valves as switching valves

18a-18d wheel cylinder

19 pressure transmitter

101 Actuator Hardware in electronics and sensors

102 Software function block "Calculation specification or adaptation

the print model parameter

103 Software Function Block "Print Model"

104 Software Function Block "ABS / ASR / ESP Controller"

105 Software Function Block "Prioritization"

106 Software Function Block "Pressure Control"

107 Sensor signals of the ESP / ABS sensors

108 signals for determining the priorities

109 Signal for specifying the wheel selection

110 Control of the switching valves

111 Control motor

112 wheel set pressures p _Rs0 ii (t)

121 master cylinder pressure p _H z (t)

122 Differential pressure to determine the pressure flow

123 hydr. lead inductance

124 dQ / dt

125 integrators

126 flow Q

127 Flow resistance of the path from the piston-cylinder system (14, HZ) via the switching valve (17a, 17b, 17c, 17d) to the wheel cylinder 128 Pressure drop at 127

cn ^ uue itis V U I U I I ICI I a Kau

130 Volume-pressure characteristic (capacity) of the wheel cylinder and the

associated connecting cables

131 wheel cylinder pressure p _R (t)

132 Volume-pressure characteristic (capacity) of the master cylinder

with closed switching valves

133 current volume in the master cylinder

134 summation block

135 HZ piston travel s _K (t)

Claims

claims

Braking system with a brake booster, the piston-cylinder system (14, HZ, THZ), in particular by transmission means, mechanically or hydraulically driven by an electric motor, wherein at least one working space of the piston-cylinder system (14, HZ, THZ) via hydraulic lines with at least two wheel brakes is in communication, wherein in each case a wheel brake is assigned a 2/2-way switching valve (17a, 17b, 17c, 17d) and the hydraulic connecting lines between the wheel brakes (18a, 18b, 18c, 18d) and the piston-cylinder system (14, HZ) optionally separated or together by means of

2/2-way switching valves (17a, 17b, 17c, 17d) can be closed or are closed, so that in the wheel brakes (18a, 18b, 18c, 18d) successively in the sense of a multiplex process and / or a pressure is einregelbar, wherein the electric motor and the switching valves (17a, 17b, 17c, 17d) are controlled by a control device, characterized in that the control device by means of a pressure model (103) calculates the respective pressure (p _R (t)) in the wheel brakes and the calculated pressure values (P _R (t)) at least one ABS / ESP controller (104) and a pressure control device (106) transmitted, wherein the pressure control device (106) at least the 2/2-way switching valves (17 a, 17 b, 17 c, 17 d) and drives the electric motor, and that a prioritization device (105) makes a wheel selection at least on the basis of the data transmitted by the ABS / ESP controller (104) and transmits them to the pressure control device (106).

Brake system according to claim 1, characterized in that the ABS / ESP controller (104) based on sensor signals and the pressure model (103) transmitted pressure values (p _R (t)) the target pressure (p _Rso n (t)) and / or determines the pressure change (dp _Rso n (t)) for the wheels or wheel brakes.

3. Brake system according to claim 1 or 2, d a d e r c h e c e n e c e s in that a computer (MCU), in particular by means of software modules, the pressure model, the ABS / ESP controller and the pressure control maps and performs the respective calculations.

4. Brake system according to one of claims 1 to 3, dadurchgekennzehnet that the pressure model (103) the pressure values (p _R (t)) based on the pressure (PHZO) in the working space of the piston-cylinder system (14, HZ, THZ), the piston position (s _H z (t)) or based on the pressure (pHz (t)) and the piston position (s _H z (t)) calculated.

5. Brake system according to claim 4, characterized in that the control device, the pressure model parameters based on the determined temperature in the brake system or at certain points in the brake system, in particular in the wheel brakes, hydraulic lines, 2/2 ege-switching valves and / or the piston-cylinder system determined temperatures, adapted.

6. Braking system according to one of the preceding claims, characterized in that the prioritization device (105) the prioritization of the wheel selection on the basis of

Criterion "optimal braking distance" and / or "stability of the control" makes.

7. A braking system according to one of the preceding claims, wherein the prioritization device (105) does not simultaneously permit a build-up of pressure in one or more wheel brakes and, vice versa, in the case of pressure reduction in one or more wheel brakes.

8. The braking system according to claim 1, wherein the prioritizing device (105) is larger than the wheel slip during a wheel slip

Slip limit value and / or during a wheel acceleration or Delay greater than +/- 10g, preferably 5g or -5g, switches to simultaneous or partially-simultaneous pressure build-up or pressure reduction.

9. Brake system according to one of the preceding claims, characterized in that a second arithmetic unit (MCU2) is a plausibility check of the input, output signals and / or intermediate signals of the entire control loop or the action chain pressure model (103), ABS / ESP controller (104), Prioritizer (105) and pressure control (106) performs.