DE102011078272A1 - Method for operating an electrically actuated brake, electrically actuated brake and brake system - Google Patents

Abstract

A method of operating an electrically operable brake (4) having an electric motor (8) and a power train that transmits the torque of the motor (8) to an actuator that converts a rotary motion into a translational motion of a brake element, wherein for pressure build-up the motor (8) rotates in the direction of pressure buildup and thereby presses the brake element against a brake body, wherein in the power train, a clutch (60) is connected, different requirements for electrically actuated brakes and their operation in terms of strong or rapid pressure build-up and degradation enable at the same time. For this purpose, the clutch (60) is substantially completely engaged for pressure build-up and the motor (8) is rotated in the pressure build-up direction, and the clutch (60) is essentially completely disengaged to reduce the pressure.

Description

The invention relates to a method for operating an electrically actuated brake with an electric motor and a power train, which transmits the torque of the motor to an actuator, which converts a rotary motion into a translational movement of a brake element, wherein the pressure buildup of the motor rotates in the pressure buildup direction and thereby pressing the brake element against a brake body. It further relates to an associated electrically actuated brake and an associated brake system.

In brake-by-wire brake systems, the brakes are controlled electronically ("by wire") by a control and regulation unit. The braking request of the driver is determined in such systems by an operating unit with a brake pedal. In this case, for example, the pedal travel, so the way the brake pedal covers by pressing the driver, measured by a corresponding sensor and the control unit as an input to adjust the corresponding brake pressure or the corresponding application force in the brakes. The braking request of the driver is effectively converted into a desired braking torque, which serves as the control and regulating unit as a target value for adjusting the corresponding brake pressure. In such systems, the driver is thereby decoupled from the actuation of the brakes. This allows z. As the implementation of safety routines such as ABS, ESP, TCS, etc., in which the brake pressure is wheel individually and briefly increased and decreased several times without the driver feels these processes on the foot. The so-called "pumping" of the brake pedal can be avoided in this way.

Electromechanically actuated or electromechanical brakes (EMB) are often used in the abovementioned brake systems. The application of such brakes is carried out by the driving of an electric motor whose rotational movement of the motor shaft is converted by an actuator in a translational movement. By this translational movement then, for example, a brake piston is driven against a brake pad, which then presses against a brake disc. The actuator may for example be designed as a ball screw (KGT), wherein upon rotation of the spindle by the rotor (via an intermediate gear) a rotatably mounted on the spindle spindle nut is placed in a translational movement, whereby then the brake piston is moved. From the DE 10 2004 012 35 A1 is z. B. an actuating unit for an electromechanically actuated disc brake known.

From the WO 2011/029812 A1 is a "brake-by-wire" -Bremsanlage known, in which the hydraulically actuated wheel brakes of the brake system can be electrically actuated by means of an electrically controllable pressure supply device. For this purpose, the pressure supply device is designed as a hydraulic cylinder-piston arrangement whose piston can be actuated by an electric motor with the interposition of a rotation-translation gear. By means of the pressure provided by the pressure supply device, the wheel brakes are actuated.

In the case of electromechanical brakes, strong brake pressures can be generated over short time scales compared to conventional hydraulic brake systems. In known systems, the motor and the actuator are directly coupled via a power train. In other words: The mechanical output variable (compressive force) and the mechanical input variable (motor position or speed) are directly coupled.

Especially as a rule (eg by an antilock braking system (ABS), electronic stability program (ESP), traction control system (TCS), ...) are both extremely large and fast pressure or force strokes and rapid sign changes (pressure build-up / pressure reduction / Pressure build-up / ...) required. The obvious contradiction between a large pressure stroke or pressure build-up, ie | dF / dt | »0, where F denotes the clamping force and t the time and its repeated rapid change of sign, | d ² F / dt ² | »0, is particularly well seen, if one considers the temporal speed curve of the motor shaft: on the one hand, namely, large stroke requires a high engine speed. On the other hand, causes a rapid change of sign, ie a quick change of Druckauf- and pressure reduction low engine speed or steady re-acceleration.

Based on the following requirements for the construction of a corresponding electrically actuated brake with an electric motor, the resulting design conflict becomes obvious: For high pressure or force strokes, large, heavy, torque-strong actuator motors are necessary. For the realization of a fast dynamics (pressure build-up / pressure reduction), on the other hand, small, lightweight motors with low rotational torque are advantageous.

Such a conflict is avoided in today's brake designs or dealt with by a compromise in the design of the corresponding engine, which does not offer optimal performance in both cases.

The invention is therefore based on the object to improve this situation and to meet the different requirements of electrically actuated brakes and their operation in terms of strong or rapid pressure build-up and -down simultaneously, so that common compromises need not be received.

With regard to the method, the above-mentioned object, in particular in the case of rapid control processes, is achieved in a first variant in that the clutch is essentially completely engaged to build up pressure and the engine rotates in the direction of pressure build-up, and that the clutch is essentially completely disengaged to reduce the pressure becomes. By substantially complete engagement or disengagement is meant that disengages completely or almost completely, which means ranges of about 90 to 100%.

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

It is preferably an electrically actuated brake with an electric motor and a power train, which transmits the torque of the motor to an actuator which converts a rotational movement of a spindle rotatably mounted in a spindle spindle in a translational movement of a coupled with the spindle nut brake element.

Alternatively, it is preferably an electrically actuated brake with an electric motor and a power train, which transmits the torque of the motor to an actuator, which converts a rotational movement via a hydraulic pump into a translational movement of a brake element.

The invention is based on the consideration that a significant reason for the above design compromises in the design of the electric motor of an electrically actuated brake in the direct or rigid coupling of motor and actuator. As has now been recognized, this design conflict or compromise can be avoided by resolving this rigid or direct connection and by switching a clutch into the power train which transfers the torque of the electric motor to the actuator, the latter being controlled in this way in that the pressure build-up is almost or completely engaged, so that the full torque of the engine is available, but that it is almost or completely decoupled for pressure reduction.

In this way, a pressure reduction can be achieved without the motor has to change its direction of rotation. That is, in order to enable a short-term pressure reduction, it is sufficient to decouple the actuator from the engine. Once disengaged, the speed and direction of rotation of the motor are arbitrary in some ways, as they are irrelevant due to the non-existing frictional connection. The decoupling can be achieved for example by a controllable coupling in the form of a (mechanical) coupling. In this way, the pressure / force actual value may decrease (pressure build-up) while the engine speed is maintained, increases or only slightly decreases. Thus, the engine can be large, heavy and powerful designed, without compromises must be made in the rapid pressure reduction.

The above-described method for controlling an electrically actuated brake also has advantages over conventional systems in terms of subsequent pressure restoration required after pressure reduction. In this case, instead of the usual and required reversing or restart of the motor armature in Zuspann- or pressure buildup direction of the frictional connection on the engagement of the clutch can be restored. The engine speed drops only briefly below the nominal level, and then rise again. In these cases, therefore, the engine speed does not have to be raised from zero or even the opposite direction against a resistance (the prevailing brake pressure or the clamping force) and the motor armature / rotational torque to the nominal rotational speed.

Particularly in the case of rapid control processes, it is advantageous if the engine rotates (further) in the pressure build-up direction during pressure reduction. That is, the brake pressure is reduced substantially by the decoupling of the engine and actuator. Advantageously, when rebuilding pressure, the engine is rotated in the pressure build-up direction and the clutch is engaged. During a sequence of pressure build-up and pressure reduction, therefore, the direction of rotation of the motor does not have to be reversed. Such control or regulation of the brake is particularly advantageous in fast control processes such as ABS, ESP, TCS, etc.

In a second variant of the method, the above-mentioned object, in particular in normal operation of the brake, is achieved by coupling the clutch substantially completely engaged to reduce the pressure and the motor is rotated opposite to the pressure build-up direction. In contrast to the first variant of the method so here the direction of rotation of the motor between pressure build-up and pressure reduction is reversed. Both the pressure build-up and the pressure reduction, the clutch is substantially fully engaged. In this case, both in the pressure build-up and in the pressure reduction is a direct coupling or almost complete coupling between actuator and motor given.

The above object is further achieved by a method for operating an electrically actuated brake, wherein the pressure buildup of the motor rotates in the pressure buildup direction and thereby the brake member is pressed against a brake body, wherein in the power train a clutch is connected, wherein in normal braking operations for pressure reduction the clutch is substantially fully engaged and the motor rotates in the opposite direction to the direction of pressure build-up, and during braking operations with automatic deceleration braking, the clutch is substantially fully disengaged and the motor rotates in the direction of pressure build-up.

That is, in ordinary braking situations in which the driver brings the vehicle to a halt, and on compared to control operations done comparatively large time scales, a direct connection between the engine and the actuator is created by the substantially complete engagement, by the reversal of the direction of rotation Depressurization via the engine. In such situations, extremely rapid reversal of the direction of rotation of the engine is not required in a pressure reduction. By reversing the direction of rotation of the motor between pressure build-up and -down can be reduced in a pressure reduction after a normal braking operation, the brake piston also back to the stop.

For fast control operations, however, the direction of rotation of the motor is not reversed and the pressure reduction realized exclusively by a complete or almost complete disengagement of the clutch. In this way, pressure can be quickly built up again by engaging the clutch. This can also happen several times in a sequence. Only when the control process is completed and the driver no longer expresses a braking request, the direction of rotation of the motor is set opposite to the pressure build-up direction to reduce the pressure in the brake. Advantageously, in an automatic control operation of the brake, the motor is rotated in the pressure build-up direction until the control process is completed.

The above object is further achieved by an electrically operable brake with an electric motor and a power train, which transmits the torque of the motor to an actuator, which converts a rotational movement into a translational movement of a brake element, wherein the pressure to build up the motor rotates in the pressure build-up direction and thereby the brake element presses against a brake body, wherein in the power train, a clutch is connected.

The brake may be an electromechanically or hydraulically actuated brake. In the case of a hydraulically actuated brake, the actuator comprises an at least partially hydraulic coupling between the spindle nut and the brake element. In the case of an electromechanically actuated brake, the spindle nut is purely mechanically coupled to the brake element.

The electrically actuated brake advantageously has a power train with a transmission, wherein the clutch is arranged in the power train between the engine and transmission. This point in the power path deals with comparatively high speeds and comparatively small torques, which allows a compact design of the clutch.

The coupling is advantageously designed as a rheological coupling with a magnetorheological or electrorheological material. Such a rheological material changes its state of aggregation depending on the strength of an applied magnetic or electric field. When no electromagnetic field is present, at ordinary operating temperatures in the range of -40 to 150 ° C, the rheological material is in a liquid state. By applying an electromagnetic field, the state of matter of this material in analog, d. H. continuous, changing from liquid to solid. Such a clutch has the advantages over other clutches such as friction clutches or multi-plate clutches that it is extremely maintenance-free and reliable. The changes in aggregate states from liquid to solid to liquid again, etc. are absolutely reversible in all practical applications and during the typical lifetime of an EMB of about 15 years. Such a coupling also has no wearing parts.

The above object is further achieved by a braking system having an electrically operable brake as described above and a control unit having means for carrying out a method mentioned above. The control unit can also be integrated in the brake, whereby an advantageous embodiment of an electromechanical brake is realized.

The advantages of the invention are, in particular, that can be achieved in electrohydraulic or mechatronic brake systems by a controllable clutch in the power train which decouples the engine from the actuator, an improvement in the speed of Bremskraftaufbau and degradation. With electro-hydraulic brake systems, the eccentric shaft end can do this of the pump motor are separated from the motor shaft by said coupling. As a result, such brake systems can be cost-effectively designed with space, weight and power consumption advantages. By decoupling the engine and actuator during braking pressure reduction, the clamping force or the brake pressure can be rapidly reduced, regardless of the engine speed or direction. This feature can be used to improve the control performance of the corresponding brakes.

By using the method according to the invention, the elimination of the need for the rapid reversal of the direction of rotation of the motor usually eliminates the current peaks which are thus generated and thus jump-type on-board network loads. Due to the elimination of the need for the rapid reversal of the motor in rapid control operations, d. H. By eliminating the dynamic demands on the engine, this does not have to be designed for corresponding high dynamics.

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

1 an electromechanical brake according to the prior art with an electric motor, a transmission, a ball screw, a brake piston and a brake pad,

2 a typical application or pressure buildup characteristic,

3 an electrically actuated brake in a preferred embodiment with an electric motor, a clutch, a transmission, a ball screw, a brake piston and a brake pad,

4 a pressure build-up characteristic for a brake according to 1 , and

5 a generalized pressure build-up characteristic for a brake according to 3 ,

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

At the in 1 illustrated electromechanical brake 2 According to the prior art gives the electric motor 8th via a motor shaft (not shown) with an associated pinion 10 an engine torque M ₁ from. In this case, φ denotes the angle of rotation of the motor shaft and ω ₁ the corresponding angular velocity. After a transmission 14 are then on the power train, the torque M ₃ and the angular velocity ω ₃ before. Through a ball screw (KGT) 20 this rotational movement is translated into a linear force F ₁ , with which a brake piston 26 against a brake pad 32 is pressed. The force F ₁ or F generated in this way is a function of the angle of rotation φ, ie F = f (φ), where: Ḟ> 0 during pressure build-up and Ḟ <0 during pressure reduction. The force F or F ₁ as a function of the angle of rotation φ is in 2 shown. On the abscissa 46 is the angle of rotation φ and on the ordinate 40 the force F applied. The curve 50 illustrates the force curve as a function of the rotation angle φ.

The mechanical torque M _Mech , which corresponds to the motor torque M ₁ delivered by the engine, is composed of the torque M _Mot originally generated by the engine minus the torques consumed by the speed-dependent friction and the acceleration, ie M _Mech = M _Mot -M _Friction - M _acceleration . It can be further expressed as M _Mech = k _Mot · I _phase (t) - k _friction · ω ₁ - Jω. ₁ . Here, k _Mot and k _friction denote constants, I _phase the current, ω ₁ the angular velocity, ω. ₁ their time derivative and J the rotational moment of armature, pinion and gear, ie the total rotational moment.

From the above equation it can be seen that the mechanical torque M _Mech decreases when ω. ₁ increased. In other words, the bigger ω. ₁ ie the temporal change of ω. ₁ , becomes, the smaller becomes the available torque M _Mech . Since control functions such as ABS, TCS, ESP, etc. naturally require rapid force build-up and force reduction in a very short time, ie | dF / dt | »0, the direction of rotation must be reversed or reversed very often and quickly on the actuator motor and immediately accelerated again, ie | ω. ₁ | »0 , This leads to a low output moment M _Mech and therefore to a low maximum clamping force.

This in 1 shown system is through the direct coupling of engine 8th and ball screw 20 or brake piston 26 and the consequent direct reduction of the mechanical braking torque M _Mech with increasing ω. ₁ systemically limited by principle. From a certain quotient ΔF / Δt or a certain time derivative of the force F, Ḟ, either certain forces are no longer or only very slowly approachable.

In the 3 highly schematically illustrated electrically operated brake according to the invention 4 In a preferred embodiment, it has an electric motor 8th with pinion 10 , a gearbox 14 , a ball screw 20 , a brake piston 26 and a brake pad 32 on. Optional is between ball screw 20 and brake pistons 26 a hydraulic active connection / coupling 22 arranged. Ball Screw 20 and optionally active compound / coupling 22 thus form an actuator which rotational movement of the spindle of the ball screw rotatably mounted in the spindle nut in a translational movement of the operatively connected to the spindle nut brake piston 26 transforms.

Unlike the in 1 illustrated brake 2 is between electric motor 8th and gear 14 a clutch 60 connected. This is the brake 4 according to 3 designed to allow a pressure reduction without the direction of rotation of the electric motor 8th must be reversed.

In the following, the parameter α shall denote the degree of coupling. Here, α = 1 denotes a complete coupling or coupling and α = 0 denotes a complete decoupling, α ε R {0 ... 1}. As a target for a clutch operation, which is suitable for fast control operations, applies -1 / (5 ms) ≈≤ α. ≈≤ + 1 / (10 ms). The torque of the electric motor 8th from now behind the clutch 60 is present, with M ₂ , the corresponding angular velocity is denoted by ω ₂ . The associated angle of rotation is designated here by γ. Behind the transmission 14 Then there are a torque M ₃ and an associated angular velocity ω ₃ . Due to the coupling 60 becomes the direct coupling between electric motor 8th and ball screw 20 or the translational movement of the brake piston 26 solved. A rigid coupling is still present at α = 1, the engine 8th is completely decoupled at α = 0.

The following is the operation of the brake 2 out 1 and the brake 4 out 3 be compared in two different operating situations. First of all, the fastest possible pressure reduction from a strong force build-up should take place with the respective brake. At the brake 2 out 1 applies during heavy pressure build-up: | Ḟ | »0, | ω | »0. At the brake 4 according to 3 applies: | Ḟ | »0, | ω ₁ | = | ω ₂ | »0, α = 1. That is, the strong pressure build-up here is the clutch 60 fully engaged. In both cases, the pressure should now be reduced as quickly as possible, ie the desired state | Ḟ | «0 be reached as soon as possible.

Now applies to the brake 2 according to 1 in that the force F is a direct function of the angle of rotation φ and a direct function of the angular velocity ω ₁ , ie F = f (φ) = g (ω ₁ ). At the brake 4 according to 3 is the force F due to the presence of the clutch 60 and the fact that in this case it is now decoupled for depressurization, ie α is set from the value 1, which it had set to a lower value during the rapid pressure buildup, no longer a direct function of φ, but now a function f ~ (γ), ie a function of the angle of rotation behind the clutch 60 or a function g (ω ₂ ) and thus a function h (α, ω ₁ ), ie F = f ~ (γ) = g (ω ₂ ) = h (α, ω ₁ ).

Since now α for decoupling of motor and actuator or KGT 20 can be used, applies to the amounts of the functions g (ω ₁ ) in the brake according to 1 and h (α, ω ₁ ) in the brake according to 3 | ġ (ω ₁ ) | <| ḣ (α, ω ₁ ) |. That is, the amount of time change of the function h (α, ω ₁ ) is due to the possibility of decoupling by the clutch 60 greater. Since this applies in terms of magnitude and the time derivative of the force F is negative when pressure is reduced, ie Ḟ «0, it now holds true that the time change of the force for the brake in accordance with 3 in terms of amount greater and therefore faster negative than the brake according to 1 , That is, through the use of the clutch 60 , ie the decoupling, in the brake according to the invention 4 according to 3 after a quick pressure build-up, quicker pressure is released than with the brake 2 according to 1 ,

Next, the case is considered that after a pressure reduction as quickly as possible pressure is built up, as happens for example during an ABS control. For the brake 2 according to 1 the following applies: Ḟ «0, ω ₁ « 0, ie the electric motor 8th turns opposite to the application direction or pressure build-up direction to reduce brake pressure. At the brake 4 according to 3 The following applies: Ḟ «0, ω ₁ » 0, ω ₂ «0, α = 0. That is, the reduction of the pressure is realized here by a complete decoupling α = 0. This decoupling ensures that the brake piston 26 from the brake pad 32 releases and the brake piston 26 moves back, ie ω ₂ «0. The rotational speed of the electric motor 8th on the other hand, it is not reversed during pressure reduction, ie, ω ₁ »0 and opposite in sign to ω ₂ .

The desired state for the fastest possible pressure build-up is now Ḟ »0. Since, as shown above, | ġ (ω ₁ ) | <| ḣ (α, ω ₁ ) | can in this case with the brake according to the invention 4 quicker pressure than with the EMB 2 according to 1 , This is because the pressure build-up only has to be engaged with the electric motor 8th , which continues to rotate in the application direction during the pressure reduction phase. In contrast to the brake according to 1 Thus, a reversal of the direction of motor rotation is not necessary, ie ω ₁ must not change its sign.

The processes described above will be illustrated by two diagrams. In 4 is on the abscissa 46 the angle of rotation φ and on the ordinate 40 the corresponding applied by a brake force F applied. The curve 110 illustrates between the points P ₁ , P ₂ , P ₃ and P ₄ = P ₁ the force curve in a preferred version of the method, in which both the pressure build-up and the pressure reduction, the clutch 60 completely or almost completely engaged and to build up the pressure of the engine 8th rotates in the pressure build-up direction and rotates to depressurize opposite to the pressure reduction direction. From P ₁ , the angle of rotation is increased to P ₂ , ie, the motor rotates in the direction of pressure build-up, so that a high clamping force is achieved at P ₂ . In order to come to a state with a lower clamping force, ie to come from P ₂ to P ₃ , the engine speed is reversed so that the rotation angle φ is reduced. The hysteresis behavior results from the setting behavior of the covering material.

A similar diagram for operating a brake according to the invention 4 with a clutch 60 is in 5 shown. On the x-axis 90 is the rotation angle φ, on the y-axis 96 is the degree of coupling α and on the z-axis 102 the force F is applied. Again, P ₂ corresponds to the presence of a high clamping force, for example during the blocking of the wheel. To reduce the pressure or the clamping force starting from P ₂ now the characteristic along the y-axis 96 followed to the point P ₃ * out. As can be seen in this illustration, the engine speed does not have to be reduced in the pressure reduction in this way. The reduction of the pressure happens here so to speak along the y-axis 96 perpendicular to the x-axis 90 solely due to the activation of the clutch 60 ,

P₁:

Ruhezustand (idle)

P₂:

Spannkraft aufgebaut, Rad blockiert

P₃*:

Spannkraft abgebaut, Rad bewegt sich wieder

P₂:

Spannkraft aufgebaut

...During an ABS control process, the points of the in 5 shown diagram correspond to the following states:

P ₁ :

Idle state

P ₂ :

Tension built up, wheel blocked

P ₃ *:

Tension reduced, wheel moves again

P ₂ :

Built up clamping force

...

When using a coupling 60 based on magnetorheological or electrorheological materials / liquids can in case of failure of the parent control unit, for example, due to a defect in the hardware, a loss of supply voltage, a bug in the software or the like as quickly as possible, the mechatronic drive dropped and thus further pressure build-up can be prevented because the Shutdown (de-energized state) eliminates the electromagnetic excitement of the clutch and then opens due to their normally open characteristic.

By the method according to the invention and the electrically actuated brake or the associated brake system according to the invention, an improvement can be achieved for any type of motor-driven application in which repeated reversal of rotation of the actuator motor as well as high speeds and rotational speed gradients occur equally. Application areas are z. B. purely electromechanically actuated brakes with a corresponding electric motor for clamping force, electro-hydraulic brake systems with a pressure supply device with an electric motor or electro-hydraulically / electromechanically combined braking systems. Here fast position changes can be achieved with ABS processes. In electro-hydraulic brake systems with an actuatable by means of an electric motor piston of a piston-cylinder arrangement, the electric motor for recovering delivery volume can be quickly reduced and so a regular, rapid pressure build-up can be achieved. Even with electrohydraulic brake systems with a piston pump, the concepts presented here can find application. So z. B. the piston pump driving the pump motor eccentric are decoupled from the pump motor shaft, so that they can accept variable relative speeds (even with the opposite sign / direction of rotation) by the analog controllable decoupling. So z. B. the pump motor are kept at a predetermined speed, z. B. because a continuous control intervention is expected, while the piston pump is temporarily disconnected, and does not need to run up at a resume only. In these systems can be provided by the introduction of a clutch in the power train for rapid pressure reduction, which is particularly advantageous because the corresponding electric motors must be designed for a high torque for high pumping pressure and correspondingly required speed for the pumping volume.

LIST OF REFERENCE NUMBERS

2

electromechanical brake

4

electrically actuated brake

8th

electric motor

10

pinion

14

transmission

20

Ball Screw

26

brake pistons

32

brake lining

40

ordinate

46

abscissa

50

Curve

60

clutch

66

Curve

72

Curve

90

X axis

96

y-axis

102

z-axis

110

Curve

M ₁

Motor torque rotation angle

φ

angle of rotation

ω ₁

angular velocity

M ₃

torque

ω ₃

angular velocity

F, F ₁

force

M _Mech

mechanical torque

J _Overall

rotational moment

α

degree of coupling

M ₂

torque

ω ₂

angular velocity

γ

angle of rotation

M ₃

torque

ω ₃

angular velocity

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10200401235 A1 [0003]
• WO 2011/029812 A1 [0004]

Claims (12)

Method for operating an electrically actuated brake ( 4 ) with an electric motor ( 8th ) and a power train, the torque of the engine ( 8th ) transmits to an actuator, which converts a rotational movement into a translational movement of a brake element, wherein the pressure buildup of the engine ( 8th ) in the pressure build-up direction and thereby presses the brake element against a brake body, characterized in that in the power train a clutch ( 60 ) is connected, wherein the pressure to build the clutch ( 60 ) is substantially fully engaged and the engine ( 8th ) rotates in pressure build-up direction, and wherein the pressure reduction, the clutch ( 60 ) is substantially completely disengaged. Method according to claim 1, wherein the engine ( 8th ) rotates during pressure reduction in pressure buildup direction. Method according to claim 2, wherein in the reconstruction of pressure the engine ( 8th ) in pressure build-up direction and the clutch ( 60 ) is engaged. Method for operating an electrically actuated brake ( 4 ) with an electric motor ( 8th ) and a power train, the torque (M ₁ ) of the engine ( 8th ) transmits to an actuator, which converts a rotational movement into a translational movement of a brake element, wherein the pressure buildup of the engine ( 8th ) in the pressure build-up direction and thereby presses the brake element against a brake body, characterized in that in the power train a clutch ( 60 ) is connected, wherein the pressure to build the clutch ( 60 ) is substantially fully engaged and the engine ( 8th ) rotates in pressure build-up direction, and wherein the pressure reduction, the clutch ( 60 ) is substantially fully engaged and the engine ( 8th ) opposite to the pressure buildup direction turns. Method for operating an electrically actuated brake ( 4 ) with an electric motor ( 8th ) and a power train, the torque of the engine ( 8th ) transmits to an actuator, which converts a rotational movement into a translational movement of a brake element, wherein in the power train a clutch ( 60 ), wherein the pressure buildup of the engine ( 8th ) rotates in the pressure build-up direction and thereby presses the brake element against a brake body, wherein in the power train a clutch ( 60 ), wherein in normal braking operations, the method steps are carried out according to claim 4, and wherein during braking operations with automatic control of the brake ( 4 ) the method steps according to claims 1 or 2 are performed. Method according to claim 5, wherein in an automatic control operation of the brake ( 4 ) the motor ( 8th ) is turned in the pressure build-up direction until the control process is completed. Electrically actuated brake ( 4 ) with an electric motor ( 8th ) and a power train, the torque of the engine ( 8th ) transmits to an actuator, which converts a rotational movement into a translational movement of a brake element, wherein the pressure buildup of the engine ( 8th ) rotates in the pressure build-up direction and thereby presses the brake element against a brake body, wherein in the power train a clutch ( 60 ) is switched. Electrically actuated brake ( 4 ) according to claim 7, wherein the power train is a transmission ( 14 ) and wherein the coupling ( 60 ) in the power train between engine ( 8th ) and gearboxes ( 14 ) is arranged. Electrically actuated brake ( 4 ) according to claim 7 or 8, wherein the coupling ( 60 ) is designed as a rheological coupling with a magnetorheological or electrorheological material. Electrically actuated brake ( 4 ) according to one of claims 7 to 9, wherein the actuator converts a rotational movement of a rotatably mounted in a spindle nut spindle in a translational movement of a coupled with the spindle nut brake element. Electrically actuated brake ( 4 ) according to one of claims 7 to 9, wherein the actuator converts a rotational movement via a hydraulic pump into a translational movement of a brake element. Braking system with an electrically actuated brake ( 4 ) according to one of claims 7 to 11 and a control and regulation unit with means for carrying out a method according to one of claims 1 to 6.

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