DE102016203735A1 - Method for operating a brake system, pressure regulator for a brake system and brake system - Google Patents

Abstract

Method for operating a brake system (1) comprising wheel brakes (8, 9, 10, 11) into which a pressure supply device (5) shifts pressure medium to build up pressure as required by providing a system pressure (PSys), a desired system pressure (PSys, Soll ) is requested, and wherein due to the target system pressure request from the pressure supply means (5) the system pressure (PSys) in the required level of the desired system pressure (PSYS, Soll) is constructed, the temporal course of the system pressure (PSYS) is monitored for pressure oscillations, and wherein upon detection of a pressure oscillation, the volume flow of the pressure medium provided by the pressure supply device (5) for pressure buildup is reduced.

Description

The invention relates to a method for operating a brake system, comprising wheel brakes, in which a pressure supply device for pressure buildup pressure medium displaces by providing a system pressure, wherein a target system pressure is requested, and wherein due to the target system pressure request from the pressure supply device, the system pressure in the required height of Target system pressure is built. It further relates to a pressure regulator for a brake system. It also relates to a brake system.

"Brake-by-wire" brake systems for motor vehicles 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, which is usually designed as a master brake cylinder, serves to give the driver as familiar and comfortable 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 supply device in the brakes.

The actual braking thus takes place by active pressure build-up in the brake circuits by means 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 or linear units in which a piston is axially displaced into a hydraulic pressure chamber for pressure build-up, which is built in series with a rotational-translation gear. 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 normal operation, the driver is disconnected from the wheel brakes by switching the isolation valves or driver isolation valves, and the linear actuator is hydraulically connected to the wheel brakes by switching the engagement valves. A movement of the piston of the linear actuator from its rest position into the pressure chamber displaces the volume of brake fluid from the linear actuator via the open inlet valves into the wheel brakes and thus causes a build-up of pressure in the wheel brakes. In the opposite case, so when moving back the piston in the direction of its rest position, there is 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.

For pressure control, a pressure sensor is available which detects the hydraulic system pressure applied by the linear actuator, which also prevails in the hydraulic chamber or the pressure chamber of the linear actuator. The position of the piston of the linear actuator is usually measured by a motor angle sensor. From this motor angle signal, an engine speed signal, for example by differentiation, determined.

The dimensioning and parameterization of the pressure regulator is based on the static and dynamic behavior of the process to be controlled, in this case the brake system, e.g. in its nominal state. If the process to be controlled differs greatly from this design state in such a way that the control actions of the pressure control are too great, this leads in part to significant oscillations in the system pressure which have a negative effect on the brake function, noise and comfort and also in the closed pressure control circuit lead to increased wear of the components involved.

Such deviations are caused, for example, by the operation of the brake system at low temperatures, which causes a considerable increase in the viscosity of the brake fluid. You may also be conditional by Aktuatorzuschaltventile that are not open at all or only insufficiently due to a low current to the valve spools.

The invention is therefore an object of the invention to allow trouble-free operation of the brake system. Furthermore, a pressure regulator is to be provided, which enables trouble-free operation of a brake system. In addition, a brake system is to be provided, which can be operated particularly trouble-free.

With regard to the method, this object is achieved in that the temporal course of the system pressure is monitored for pressure oscillations, wherein upon detection of a pressure oscillation of the provided by the pressure supply means for pressure build-up volume flow of the pressure medium is reduced.

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

The invention is based on the consideration that for various reasons, pressure oscillations in the brake system should be prevented. Namely, they prevent a precise setting of a requested brake pressure and cause disturbances during control processes. A pressure request can be effected by a braking request issued by the driver by actuating the brake pedal and / or by a driver assistance and / or driving safety system.

As has now been recognized, pressure oscillations which have occurred can be reduced to a minimum and the occurrence of new pressure oscillations can be prevented by reducing the volume flow. In this case, the required pressure is still set, but this measure can lead to a reduction in the speed of the pressure build-up, so that rapid brake fluid movements that can lead to the occurrence of pressure oscillations are avoided.

The basic idea of the method is thus to detect the vibrations caused thereby on the basis of the measured system pressure curve and to cause a corresponding adaptation of the control inputs of the pressure regulator from this. Upon detection of a pressure oscillation, the speed with which the pressure supply device shifts the brake fluid volume required for the pressure build-up into the wheel brakes is thus preferably reduced.

The reduction in the volume flow means that the time required to reach the required system pressure starting from the instantaneous system pressure is extended by appropriate measures compared to the currently set case.

Advantageously, the volume flow is increased again when no pressure fluctuation was detected for a predetermined period of time. In this way, the dynamics of the active pressure control can be optimized again, if pressure oscillations do not occur.

The pressure-providing device preferably has an electric motor whose motor shaft is operated at an engine speed, wherein a rotational-translation gear converts the rotation of the motor shaft in a translation of a pressure piston, which is moved to build up pressure in a hydraulic pressure chamber of the pressure supply device, and wherein for adjusting the system pressure a desired engine speed is requested, and wherein to reduce the speed of the pressure build-up, a reduction of the required target engine speed is carried out. The higher the engine speed, the faster the axial travel speed of the pressure piston into the hydraulic pressure chamber. A reduction of the engine speed thus results in a reduced travel speed, so that the pressure build-up is slower.

To reduce the target engine speed, it is preferably multiplied by a speed scaling factor that is less than or equal to one (≦ 1) and greater than a predetermined, minimum speed scaling threshold.

In the next brake application, the speed scaling factor is advantageously increased by a speed scaling increase value. In this way, a faster pressure build-up is set again, so that the dynamics of the corresponding pressure regulator is increased again. If pressure oscillations are detected again in this braking process, a reduction of the engine speed takes place again as described above.

In a preferred embodiment, the speed scaling increase value depends on the current value of the speed scaling factor. For example, it can be achieved that with a strong previous reduction of the engine speed, these are only slightly increased in order not to immediately land again in an engine speed range in which pressure vibrations arise.

When detecting pressure oscillations, the energization of already activated connecting valves is preferably changed. The connection valves connect the pressure supply device with the wheel brakes in the open state and separate them from these in the closed state. The change in the energization is preferably carried out essentially in that the already energized valves are energized again with a value for opening the valves, wherein the value for the valve opening current as well as the value for the holding current compared to the setting for normal operation can be increased.

A pressure oscillation is advantageously detected when the time derivative of the system pressure, ie its temporal gradient, and / or the change of sign of the time derivative of the system pressure are each outside one or more predetermined threshold ranges. A detected pressure oscillation is preferably characterized by simultaneously large pressure changes and a high frequency of these changes.

Advantageously, the value of the Istsystemdruckgradienten and sign change of Istsystemdruckgradienten are determined or determined at preferably the same time interval, wherein a first counter is provided with an original value, which is in particular zero, by a first value, preferably one, is increased when the Istsystemdruckgradient is at a detection time outside a predetermined first pressure gradient tolerance band. This means, in particular, that the temporal Istdruckgradient amount exceeds a predetermined positive threshold. Such a counter can be implemented in a controller in a reliable and robust manner, the detection times preferably corresponding to controller loops which follow one another at the same time intervals.

The first counter is additionally preferably increased by the first value if the Istsystemdruckgradient is at a detection time outside a predetermined second pressure gradient tolerance band. This can be used to illustrate that particularly large pressure changes have a greater effect on the detection of a pressure oscillation.

After a predetermined number of acquisition times, the first counter is preferably reduced by a second value, preferably one, if it was greater than its original value. This ensures that the counter is reduced back to its original value when no pressure oscillations occur.

Preferably, a second counter is provided which counts the number of detection times between two sign changes of Istsystemdruckgradienten. The second counter maps the second vibration detection criterion, which relates to the frequency of the respective vibration.

A pressure oscillation is preferably detected when the first counter has exceeded a predetermined counter threshold value and when the value of the second counter is within a predetermined evaluation interval.

With respect to the pressure regulator, the abovementioned object is achieved according to the invention in that a method described above is implemented in it in terms of hardware and / or software.

With respect to the brake system, the above object is achieved according to the invention with such a pressure regulator.

The advantages of the invention are, in particular, that the comfort of the brake system is increased by the method described, since noises or restrictions of the brake functions caused by pressure vibrations can be reduced or avoided altogether. In addition, the service life of the installed components or the brake system is increased by reducing the wear of the components.

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 pressure regulator for the brake system according to 1 ;

3 a detailed view of the pressure regulator according to 2 with a limitation function; and

4 the limitation function according to 3 in more detail.

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 1 shown. The brake system comprises one by means of an actuating or brake pedal 1a actuated master cylinder 2 , one with the master cylinder 2 cooperative simulation device 3 , a master cylinder 2 assigned, under atmospheric pressure medium reservoir 4 , an electrically controllable pressure supply device 5 , which by a cylinder-piston arrangement with a hydraulic pressure chamber 37 is formed, whose pistons 36 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 12 ,

The unspecified pressure modulation device comprises according to the example per hydraulically actuated wheel brakes 8th . 9 . 10 . 11 and each operable wheel brake 8th . 9 . 10 . 11 a motor vehicle, not shown, an inlet valve 6a - 6d and an exhaust valve 7a - 7d , the hydraulically interconnected in pairs via center ports and to the wheel brakes 8th . 9 . 10 . 11 are connected. The inlet connections of the inlet valves 6a - 6d be by means of brake circuit supply lines 13a . 13b supplied with pressures that are derived in a "brake-by-wire" mode from a system pressure in one to the pressure chamber 37 the pressure supply device 5 connected system pressure line 38 is present. The brake 8th . 9 are doing to a first brake circuit 27 , the brake 10 . 11 to a second brake circuit 33 hydraulically connected.

The inlet valves 6a - 6d is one to each of the brake circuit supply lines 13a . 13b opening check valve 50a - 50d connected in parallel. In a fallback mode, the brake circuit supply lines become 13a . 13b via hydraulic lines 22a . 22b with the pressures of the pressure chambers 17 . 18 of the master cylinder 2 applied. The outlet connections of the outlet valves 7a - 7d are via a return line 14b with the pressure medium reservoir 4 connected.

The master cylinder 2 points in a housing 21 two pistons arranged one behind the other 15 . 16 on top of the hydraulic pressure chambers 17 . 18 limit. The pressure chambers 17 . 18 on the one hand over into the piston 15 . 16 formed radial bores and corresponding pressure equalization lines 41a . 41b with the pressure medium reservoir 4 in conjunction, wherein the connections by a relative movement of the pistons 17 . 18 in the case 21 can be shut off. The pressure chambers 17 . 18 On the other hand, by means of the hydraulic lines 22a . 22b with the already mentioned brake circuit supply lines 13a . 13b in connection.

In the pressure compensation line 41a is a normally open valve 28 contain. The pressure chambers 17 . 18 take unspecified return springs on which the pistons 15 . 16 with unoperated master cylinder 2 position in a starting position. A piston rod 24 couples the pivoting movement of the brake pedal 1 due to a pedal operation with the translational movement of the first master cylinder piston 15 , whose actuation path of a, preferably redundantly running, displacement sensor 25 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 17 . 18 connected line sections 22a . 22b is ever a separating valve 23a . 23b arranged, which is designed as an electrically actuated, preferably normally open, 2/2-way valve. Through the isolation valves 23a . 23b can the hydraulic connection between the pressure chambers 17 . 18 the master cylinder and the brake circuit supply lines 13a . 13b be shut off. One to the line section 22b connected pressure sensor 20 detects the in the pressure room 18 by a displacement of the second piston 16 built up pressure.

The simulation device 3 is hydraulic to the master cylinder 2 can be coupled and essentially consists, for example, of a simulator chamber 29 , a simulator spring chamber 30 as well as one the two chambers 29 . 30 mutually separating simulator piston 31 , The simulator piston 31 is supported by a in the simulator spring chamber 30 arranged elastic element (eg., A spring), which is advantageously biased on the housing 21 from. The simulator chamber 29 is by means of an electrically operated simulator valve 32 with the first pressure chamber 17 of the master cylinder 2 connectable. When setting a pedal force and open simulator valve 32 flows pressure medium from the master cylinder pressure chamber 17 into the simulator chamber 29 , A hydraulic anti-parallel to the simulator valve 32 arranged check valve 34 allows independent of the switching state of the simulator valve 32 a largely unhindered backflow of the pressure medium from the simulator chamber 29 to the master cylinder pressure chamber 17 , Other designs and connections of the simulation device to the master cylinder 2 are conceivable.

The electrically controllable pressure supply device 5 is designed as a hydraulic cylinder-piston arrangement or a single-circuit electrohydraulic actuator whose / whose pressure piston 36 which the pressure room 37 limited, by a schematically indicated electric motor 35 can be actuated with the interposition of a rotation-translation gear also shown schematically. One of the detection of the rotor position of the electric motor 35 serving, only schematically indicated rotor position sensor is denoted by the reference numeral 44 designated. In addition, a temperature sensor for sensing the temperature of the motor winding may also be used.

The by the force effect of the piston 36 on the in the pressure room 37 enclosed pressure fluid generated actuator pressure is in the System pressure line 38 fed and with a preferably redundant pressure sensor 19 detected. With open connection valves 26a . 26b the pressure medium enters the wheel brakes 8th . 9 . 10 . 11 for their operation. By pushing back and forth the piston 36 takes place with open connection valves 26a . 26b in a normal braking in the "brake-by-wire" mode a Radbremsdruckaufbau and degradation for all wheel brakes 8th . 9 . 10 . 11 , During pressure reduction, this flows from the pressure chamber before 37 in the wheel brakes 8th . 9 . 10 . 11 shifted pressure medium on the same way back into the pressure chamber 37 back. On the other hand, when braking with different individual wheel flows, with the help of the intake and exhaust valves 6a - 6d . 7a - 7d controlled wheel brake pressures (eg in the case of anti-lock control (ABS control)) via the exhaust valves 7a - 7d drained pressure medium content in the pressure fluid reservoir 4 and thus initially stands the pressure supply device 5 for actuating the wheel brakes 8th . 9 . 10 . 11 no longer available. A suction of pressure medium in the pressure chamber 37 is by a return of the piston 36 with closed connection valves 26a . 26b possible.

In the control unit 12 is a method described above, which in a preferred embodiment in connection with the 2 to 4 is discussed, implemented in software. The control unit 12 is signal input side with the pressure sensor 19 whose signal gives it the currently prevailing system pressure or actual system pressure.

The control unit 12 preferably comprises a pressure regulator 70 (This can also be provided separately), which in 2 is shown in a preferred embodiment. The pressure regulator 70 has a pressure control module 72 on, the target system pressure P _{Sys, Soll} 76 and the example by means of the pressure sensor 19 certain actual system pressure P _sys 78 be supplied. A calculation module 80 is the signal for the target system pressure P _{Sys, Soll} 76 also supplied. The calculation module 80 calculated with the aid of the setpoint system pressure P _Sys, as part of a speed precontrol calculation _, a pilot control engine speed ω _{Akt, Soll, DR, FFW of} the motor axis.

The actual system pressure or system pressure P _Sys is in a subtraction module 86 from the target system pressure P _Sys, subtracted and the result of this subtraction a pressure control module 92 fed, which calculates therefrom a manipulated variable ω _{Akt, Soll, DR, Ctrl} for the engine speed. This manipulated variable is the Vorsteuerungsmotordrehzahl in an adding module 96 adds, whereby a target engine speed ω _{Akt, Soll is} calculated. This becomes a limiting module 100 fed, which limits it to a predetermined range of values, resulting in the resulting limited target engine speed ω _{Alt, Soll, Result} results.

The limited target engine speed ω _{Akt, Soll, Result} becomes a subtraction module 106 fed to the determined actual engine speed ω _act 110 is supplied and is subtracted from the target engine speed ω _{Akt, Soll, Result} . The determined in this way engine speed difference is a speed control module 112 fed, which calculates a target engine torque based on this size, which in a limiting module 116 is limited to a predetermined motor torque value range. The limiting module 116 provides as output a target engine torque M _{Akt, Soll} , with which the electric motor 35 the pressure supply device is driven.

The in 2 illustrated pressure regulator 70 has even more modules that are in 3 are shown and related to 3 be discussed. The pressure regulator 70 according to 2 has an in 2 not shown adaptation module 120 on, which as an input via a signal line 78 the target system pressure P _{Sys, Soll} and 126 receives the system pressure P _Sys . The adaptation module 120 performs a detection of pressure oscillations.

The detection of the pressure oscillations takes place on the basis of the measured values for the system pressure P _Sys , by considering the system pressure change d (P _Sys ) / dt determined by derivation. If the signal P _{Sys shows} a vibrating behavior, then pressure changes result, which are much larger in comparison to the normal, non-oscillating pressure gradient, and additionally increased changes in the pressure change direction. In addition, the setpoint signal P _{Sys, Soll is} also differentiated. To improve the vibration detection, the target pressure signal is preferably passed before the differentiation via a rise limiting function, in which the change of the desired signal is limited to the value that the pressure supply device 5 or the linear actuator can actually set.

The two signals d (P _sys ) / dt and d (P _{sys, setpoint} ) / dt are now a counter module 130 that prefers the adjustment module 120 integrated, supplied. In this counter module 130 The determined gradient of the system pressure P _Sys is now evaluated in each controller loop in comparison to the target pressure gradient. In addition, the sign changes of the actual pressure gradient are considered.

For this purpose, a first counter N _{Cnt, ε is} provided, which is increased by the value 1 if the actual pressure gradient d (P _Sys ) / dt that by (d (P _{Sys, soll} ) / dt - ε) and (d (P _{Sys , soll} ) / dt + ε) violates the defined tolerance band. to Increasing the tripping speed, another, coarser tolerance band [(d (P _{sys, soll} ) / dt -ε ₂ )... (D (P _{sys, soll} ) / dt + ε ₂ )] can be defined with ε <ε ₂ , so that when leaving this band, the counter N _{Cnt, ε is} again increased by the value 1. After every nth controller loop, N _{Cnt, ε is} again reduced by 1, so that with a longer oscillation-free operation, this counter reading again approaches the value 0.

A second counter N _{cnt, T} counts the time or the number of controller loops between two sign changes of the signal Istdruckgradient d (P _Sys ) / dt and thus determines a measure of the period of the system pressure oscillation. For a better evaluation of the calculated counter readings, the last m values for N _{cnt, T} are stored.

If the first counter N _{Cnt, ε exceeds} a predefined limit value N _{Cnt, ε, Limit} and the determined values of the second counter N _{cnt, T are} within an evaluation _interval , then a pressure _oscillation is detected which requires an intervention in the gain of the pressure regulator. In addition, a second evaluation interval can be defined, which is an adaptation of the lighting strategy for the additional valves 26a . 26b required.

If the adjustment requirements required due to the detected pressure _oscillation have been set, the two counters N _{Cnt, ε} and N _{cnt, T are} reset and the recognition process begins again.

Thus, it can be determined in some way during braking, whether the action requested by the vibration detection leads to the desired effect.

In the following, by way of example, the adjustment of the setting attacks of the pressure regulator 70 the further implementation of the requirement represented by the vibration detection. This is achieved by multiplying the engine nominal engine speed ω _Akt determined by the pressure regulator, which is to be weighted by a scaling factor λ _SC , by means of which the control actions of the pressure regulator 70 can be attenuated in the sense of vibration reduction. For the factor λ _SC : 0 <λ _{SC, Min} ≤ λ _SC ≤ 1.0

Here, λ _SC = 1.0 represents the value that is set as the starting value and that is set for the normal state in the controller tuning. Is due to the vibration detection a requirement to reduce the control actions of the pressure regulator 70 and thus to reduce the scaling factor λ _SC , this is, as long as the lower limit λ _{SC, Min} is not yet reached, reduced by one Δλ at each oscillation detection caused by the vibration detection and then the request is reset: λ _{SC, new} = λ _{SC, old} - Δλ

Now that the vibration detection is restarted after resetting the counter, it can now be determined whether this reduction of the scaling factor was already sufficient. In this case, no vibrations are subsequently detected. If the vibration detection reacts again during braking, the setting of a corresponding requirement reduces the scaling factor by a further Δλ.

After the brake operation has ended, a value λ _{SC, 2} for the scaling factor thus results. To avoid that, in view of the greatest possible dynamics of the linear actuator in the operation of the brake, this value is not permanently reduced, is now in the adjustment module 120 the scaling factor λ _SC is recalculated before the next brake application by increasing it by Δλ _{SC, AUF} : λ _{SC, 3} = λ _{SC, 2} + Δλ _{SC, UP}

In the simplest case, Δλ _{SC, AUF can be} a predefined value Δλ _{SC, AUF, Const} .

In a further preferred embodiment, it can additionally be taken into account how much the scaling factor has been reduced during the preceding braking. Λ _{SC, 2} denotes the value of the scaling factor after termination of the braking. The factor λ _{SC, 1,} however, represents the scaling factor before the start of the last braking. If the scaling factor is only slightly reduced, that is to say λ _{SC, 2} ≈ λ _{SC, 1} , ie the difference of the two scaling factors is, in particular, less than a predefined threshold value, the scaling factor before the next braking is increased by the mentioned value Δλ _{SC, UP, Const} increased.

If, on the other hand, a greater reduction of the manipulated variable interventions has been made by means of the factor λ _SC , then the scaling factor is increased again before the next stoppage in smaller steps, which are then represented by Δλ _{SC, AUF} = (λ _{SC, 1} - λ _{SC, 2} ) / N are defined. The choice of N can influence how strongly the change in the scaling factor is corrected again or how stable the scaling factor resulting from the vibration detection remains.

The scaling factor calculated in this way as well as the target engine speed ω _{Akt, Soll} become a limitation module 136 fed in which 2 with the reference number 100 is designated and which receives as additional input variables a minimum engine speed ω _Min and a maximum engine speed ω _Max . The resulting limitation module 136 calculates with the help of these variables the resulting target engine speed ω _{Alt, Soll, Result} .

The in the limitation module 136 implemented functionality is in 4 shown. The target engine speed ω _{Akt, Soll} and the scaling factor λ _SC are in a multiplier module 150 multiplied by each other. Since the scaling factor is equal to or less than the value 1, the target engine speed ω _{Akt, Soll is} reduced in this way, or it remains the same for the case that the scaling factor λ _SC = 1. The calculated in this way intermediate target engine speed ω _{Akt, Soll} * is in a limiting module 156 limited to a predetermined engine speed range, resulting in the resulting target engine speed ω _{Akt, Soll, Result} results. This will, as in 2 represented, the subtraction module 106 fed.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102013204778 A1 [0006]

Claims (15)

Method for operating a brake system ( 1 ), comprising wheel brakes ( 8th . 9 . 10 . 11 ) into which a pressure delivery device ( 5 ) displaces pressure medium to build up pressure as necessary by providing a system pressure (P _Sys ), wherein a desired system pressure (P _{Sys , Soll} ) is requested, and wherein due to the target system pressure request from the pressure supply device ( 5 ) the system pressure (P _Sys ) in the required amount of the target system pressure (P _{Sys , Soll} ) is constructed, characterized in that the time profile of the system pressure (P _Sys ) is monitored for pressure oscillations, wherein upon detection of a pressure oscillation of the pressure supply device ( 5 ) provided for pressure build-up volume flow of the pressure medium is reduced. The method of claim 1, wherein the volume flow is increased again when no pressure oscillation was detected for a predetermined period of time. Method according to claim 1 or 2, wherein the pressure supply device ( 5 ) an electric motor ( 35 ), wherein the motor shaft is operated at an engine speed (ω), and wherein a rotation-translation gear converts the rotation of the motor shaft in a translation of a pressure piston, which is used for pressure build-up in a hydraulic space ( 37 ) of the pressure supply device ( 5 ), wherein for adjusting the system pressure (P _Sys ) a target engine speed (ω _{Akt, Soll} ) is requested, and wherein for reducing the volume flow, a reduction of the required target engine speed (ω _{Akt, Soll} ) takes place. The method of claim 3, wherein the required target engine speed (ω _{Akt, Soll} ) is multiplied by a speed scaling factor (λ _SC ) that is less than one and greater than a predetermined minimum speed scaling threshold (λ _{SC, Min} ). The method of claim 4, wherein at the next brake application the speed scaling factor (λ _SC ) is increased by a speed scaling increase value (Δλ _{SC, AUF} ). The method of claim 5, wherein the speed scaling increase value depends on the current value of the speed scaling factor (λ _SC ). Method according to one of claims 1 to 6, wherein upon detection of a pressure oscillation, the energization of Zuschaltventilen ( 26a . 26b ) is changed. Method according to one of claims 1 to 7, wherein a pressure oscillation is detected when the time derivative (d (P _Sys ) / dt) of the system pressure (P _Sys ) and / or the change of sign of the time derivative of the system pressure (P _Sys ) each outside one or more predetermined threshold ranges are / lie. Method according to claim 8, wherein the value of the system pressure gradient and sign change of the system pressure gradient (d (P _sys ) / dt) are detected at, in particular at the same time interval, recurring detection _times , and wherein a first counter with an initial value, which is in particular zero, is provided, which is increased by a first value, in particular one, when the system pressure gradient (d (P _Sys ) / dt) is outside a predetermined first pressure gradient _{tolerance band} at a detection time. The method of claim 9, wherein the first counter is incremented by the first value when the system pressure gradient (d (P _sys ) / dt) is outside a predetermined second pressure gradient _{tolerance band} at a detection time. The method of claim 9 or 10, wherein after a predetermined number of detection times of the first counter by a second value, in particular one, is reduced, if it was greater than its original value. Method according to one of claims 9 to 11, wherein a second counter is provided, which counts the number of detection times between two sign changes of the actual system pressure gradient (d (P _sys ) / dt). The method of claim 12, wherein a pressure oscillation is detected when the first counter has exceeded a predetermined counter threshold and when the value of the second counter is within a predetermined evaluation interval. Pressure regulator ( 70 ) for a brake system ( 1 ) in which a method according to any one of claims 1 to 13 hardware and / or software implemented. Brake system ( 1 ) with a pressure regulator according to claim 14.

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