DE102019213058A1 - Actuating unit for a hydraulically actuated brake system and associated brake system - Google Patents

Abstract

Actuating unit (2) for a hydraulic brake system (200) comprising a brake pedal arrangement (3), a braking device (5) and a master brake cylinder (10), the braking device (5) comprising an actuating force module (6a) with a body (6) closing it off to the outside ), in which in a main bore (36) inside the body (6) a pedal force transmission element (32), an actuator force transmission element (30), a total force transmission element (40) and an elastic element (44) are linearly movably guided along the main bore axis, wherein the actuation unit (2) further comprises a means for detecting the travel path difference between the pedal force transmission element (32) and the actuator force transmission element (30), the difference path detection means comprising cantilevers (129, 130) which contain the path information from the pedal force transmission element (32) and the actuator force transmission element ( 30) mechanically transferred to a location radially offset with respect to the main bore axis, whereby on ei A position transmitter element (102) is fastened to a boom (110) and a sensor element (112) is fastened to another boom (100), which sensor element detects the position of the position transmitter element (102) relative to the sensor element (112).

Description

The invention relates to an actuation unit for a hydraulic brake system with which the brakes of a motor vehicle can be actuated both with brake pedal and electronically controlled, the actuation unit comprising a brake pedal arrangement, a braking device and a master brake cylinder, the braking device comprising an actuating force module with a body that closes it off to the outside, Via which the braking device can be connected to the body of the motor vehicle and to which the master brake cylinder is attached and in which a pedal force transmission element, an actuator force transmission element, a sum force transmission element and an elastic element along the axis of the main bore, in particular directly or in a main bore inside the body, can be connected indirect, d. H. one component in the other, are linearly movably guided, wherein the pedal force transmission element and the actuator force transmission element are arranged concentrically with respect to the main bore axis, and wherein the brake master cylinder can be acted upon by a sum of pedal force and actuator force by the elastic element on an input side of the pedal force transmission element and the actuator force transmission element and on an output side the total force on the total force transmission element for transmission to a primary piston of the master brake cylinder, the actuating unit further comprising means for detecting the travel path difference of the pedal force transmission element and the actuator force transmission element, the difference path detection means comprising cantilevers that contain the path information from the pedal force transmission element and actuator force transmission element mechanically offset radially to one with respect to the main bore axis nth place. It also concerns a corresponding brake system.

A brake system with a hydraulic drive stage and a path difference mechanically guided into an area next to the master brake cylinder for the purpose of detecting it by means of a sensor device is shown in FIG DE 10 2014 207 219 A1 in connection with 3rd described.

According to the (elastic) deformation properties of the elastic element, this path difference is a function of actuator force and pedal force. If the actuator force is also known in addition to the path difference, the pedal force can be determined.

In the illustrated embodiment with hydraulic transmission of the actuator force, a pressure sensor can be used to generate a corresponding signal representing the actuator force.

A connection of a sensor element for detecting a path difference representing a force difference by means of a flexible electrical connection laid in a loop is from FIG DE 10 2016 111 869 A1 known.

The location described in this publication for the sensor and the cable loop - namely in the vehicle interior - is unfavorable. It is also structurally complex to install these components in the area of the fastening flange of an actuation unit and thus in the area of the corresponding opening in the vehicle bulkhead between the vehicle interior and the engine compartment.

The invention is therefore based on the object of improving a brake actuation unit in such a way that it enables space-saving installation - especially in the area of its flange for its connection to the vehicle body - and at the same time enables precise and robust detection of its actuation state. Furthermore, an advantageous braking system is to be provided.

With regard to the brake actuation unit, the above-mentioned object is achieved in that a position transmitter element is fastened on one arm and a sensor element which detects the position of the position transmitter element relative to the sensor element is fastened on another arm.

Advantageous refinements of the invention are the subject matter of the subclaims.

The invention is based on the consideration that in modern brake systems the requirements for space saving and precision of the currently measured brake system state are very high.

As has now been recognized, these requirements can be met in that two cantilevers are provided, in which a position transmitter element is mounted on one and a sensor element is mounted on the other, which measures the position relative to the position transmitter element. To a certain extent, the cantilevers transport the path information to be detected from the elastic element with its installation location, which is unfavorable for attaching sensors, to a path detection location or installation space at which a sensor device can be arranged in a structurally favorable manner.

Since the relative position is measured between the two cantilevers, the two cantilevers together only require insignificantly more Installation space as a single boom, so that the corresponding boom arrangement can be accommodated even if the installation space available for the actuation unit is limited.

Advantageously, locations or positions outside the braking device body are assigned to the travel paths of the sensor element and position transmitter element with the aid of the boom.

The assigned travel distances of the sensor element and position transmitter element are preferably arranged parallel to the master cylinder and outside the master cylinder bore, in particular in a corresponding recess in a master cylinder body.

The movable sensor element is advantageously electrically connected to non-movable electronic sensor connection components with the aid of a flexible electrical connection in order to both supply the sensor element with the electrical energy it requires and to receive the differential travel signals generated by the sensor element, in particular to receive these signals forward to a control and regulation unit.

The movable sensor element, the flexible electrical connection and the non-movable electronic sensor connection components are advantageously arranged within a common electronics housing, which is in particular dimensioned in such a way that it allows the required free travel path of the sensor element, in particular the space required by a loop of the flexible electrical connection , provides.

A control and regulating unit is advantageously provided which is accommodated in the electronics housing which accommodates the flexible electrical connection and the sensor element.

In a preferred embodiment, the non-movable electronic sensor connection components are electrically connected to the control and regulation unit. or in which the control and regulation unit is structurally integrated.

The actuators for providing the actuator force and the control and regulating unit are preferably arranged adjacent to one another so that the latter can provide the required electrical actuator currents via electrical connections that preferably do not leave the installation space shared by the actuator and the neighboring open and closed-loop control unit. As a result, a configuration can be avoided in which an actuator power cable is required for the electrical connection of a control and regulating unit with an actuator system that is spatially separated therefrom, which would require complex measures for its electrical shielding and for its mechanical sealing. The actuator system preferably comprises an electronically commutated electric motor with a 3-phase power supply.

The two arms preferably run parallel at least in sections.

The two arms are advantageously guided parallel to an edge region of the master brake cylinder.

One of the two cantilevers is preferably arranged radially, in particular with respect to the main cylinder bore axis, inside the other cantilever.

The relative position is preferably determined in a contactless manner, the contactless transmission of the path information using an electrical, magnetic or optical operating principle.

Both the sensor element and the position transmitter element are advantageously arranged in the axial actuation direction behind the braking device body.

In further preferred embodiments, other paths, in particular that of the pedal force transmission element, are recorded, for which purpose appropriate means are provided.

These means preferably include a sensor for detecting the pedal force transmission element path. This further sensor preferably detects the position of the same position transmitter element via which the above-described differential travel detection takes place. Alternatively, an additional position encoder can be used. The detection range of the sensor preferably comprises the entire possible travel path of the pedal force transmission element.

The actuator force transmission element is preferably designed as a hydraulic piston, in particular as an annular piston.

The actuator system can comprise an electrically controllable pressure source. The electrically controllable pressure source can comprise an electric motor, a transmission and a hydraulic cylinder-piston device - or a pump that can be driven by an electric motor.

The total force transmission element is advantageously set up to compensate for possible production-related small misalignments and misalignments between the preferably coinciding axes of the actuating unit and the master cylinder.

The claimed actuation unit preferably offers the operating mode of pedal-controlled braking even when the electronics are not ready for operation.

The claimed actuation unit preferably offers the operating mode of a purely electronically controlled braking, even when the brake pedal is not actuated. In this operating mode, the actuator force, for example in the form of a pressure signal in the case of hydraulic actuator force transmission, is a suitable controlled variable. The path difference on the elastic element can be used in the control algorithm to achieve the best possible control quality, but is not essential in this operating mode.

A pressure sensor for detecting a signal representing the actuator force can be connected to a hydraulic actuator system. Such a pressure sensor is electrically connected to the electronics unit, which supplies the sensor with electrical energy and receives the signals generated by the sensor. The pressure sensor is preferably arranged within the electronics housing. This has the advantage that no cable connection to the sensor that is resistant to environmental influences is required.

The claimed actuation unit preferably offers the operating mode of electronically amplified pedal-controlled braking. For this purpose, the differential travel is recorded and regulated to zero. The resulting equilibrium of forces on the elastic element ("reaction disk") causes an actuator force proportional to the pedal force. In this operating mode, the path difference on the elastic element is a suitable control variable. The actuator force information can be used in the control algorithm to achieve the best possible control quality, but is not essential in this operating mode.

The claimed actuation unit offers easy switching between the above-mentioned operating modes. Mixed forms such as the superposition of an electronically controlled and a pedal-controlled braking can thus be displayed without any problems.

With regard to the brake system, the above-mentioned object is achieved according to the invention with an actuation unit described above in combination with a pressure modulation device hydraulically connected to the main brake cylinder of the actuation unit and wheel brakes hydraulically connected to the pressure modulation device.

The advantages of the invention are, in particular, that by means of an electro-hydraulic actuator force supply (the actuator force can be an external force in the case of a purely electronically controlled braking and a boosting force in the case of a pedal-controlled braking) and the detection of a boosting force requirement via a differential travel detection, a precise master brake cylinder actuation detection is possible and at the same time a brewing space-saving actuation unit can be implemented. By mechanically forwarding the differential travel information to a location next to the master brake cylinder, a particularly slim design is possible.

By electrically connecting a differential travel sensor via a flexible electrical connection, it can be electronically connected to the control and regulating unit in a space-saving manner. In particular, the area of the fastening flange of the actuation unit can be kept structurally very compact because no sensor installation space is required in this area.

A common housing provides protection for sensors (differential travel sensor, pedal force transmission element travel sensor and pressure sensor), flexible electrical connection and electronic unit.

• 1 eine Betätigungseinheit in einer bevorzugten Ausführungsform in einem Axialschnitt; und
• 2 eine Bremsanlage mit einer Betätigungseinheit gemäß 1.

An embodiment of the invention is explained in more detail with reference to a drawing. It shows in a highly schematic representation:

• 1 an actuating unit in a preferred embodiment in an axial section; and
• 2 a brake system with an actuation unit according to 1 .

The same parts are provided with the same reference symbols in both figures.

One in 1 illustrated brake actuation unit 2 includes a brake pedal assembly 3rd , a braking device 5 and a master cylinder 10 . The braking device 5 includes an actuation force module 6a with a body 6th which closes it from the outside and via which the braking device 5 with the body or pointed wall 12a of the motor vehicle can be connected and to which the master cylinder 10 is attached. The master cylinder designed as a tandem master cylinder (THZ) 10 includes a master cylinder body 14th and at least one pressure piston movable therein. In the present embodiment, a primary piston 12th and a secondary piston (not shown) is provided.

The two pressure pistons delimit a primary chamber and a secondary chamber. A reservoir 18th for brake fluid is hydraulically connected to the two chambers in such a way that the respective chamber is in hydraulic balance with the reservoir 18th or brake fluid reservoir in Connection is when the respective pressure piston is in its starting position.

The master cylinder 10 has two hydraulic connections 20th , 22nd which are hydraulically connected to the respective chamber, with connections 20th , 22nd and chambers each have a brake circuit I, II of a brake system 200 are assigned (see 2 ).

The braking device body 6th has a first cavity 26th and a second cavity, seen in the direction of the THZ, adjoining it 28 on that as the main hole 36 are trained. Both cavities 26th , 28 are cylindrical, with the radius of the second cavity 28 is larger than that of the first cavity 26th . An actuator force transmission element is axially movable in the two cavities 30th arranged, which is an elastic element 44 and a pedal force transmission element 32 at least partially absorbs. The pedal force transmission element 32 is via a pedal coupling rod 34 and two joints with a brake pedal 7th mechanically coupled. The brake pedal assembly 3rd includes the brake pedal 7th who have favourited the pedal coupling rod 34 as well as a pedal bracket 7a .

When the brake pedal is pressed 7th becomes the pedal force transmission element 32 axially in the direction of the master cylinder 10 moved, doing one with the leverage of the pedal 7th Increased pedal actuation force on a first surface (inner ring surface) of the elastic element 44 exercises. Over a second surface of the elastic element 44 can the actuator force transmission element 30th an actuator force in the direction of actuation on the elastic element 44 exercise.

The elastic element stands over a third surface opposite the first and second surfaces 44 in mechanical contact with a pedal-side end face of a total force transmission element 40 which in turn is in mechanical, force-transmitting contact with the primary piston at its other end in the direction of actuation 12th of the master cylinder 10 stands. For the purpose of a radial centering that does not influence the force transmission in the axial direction, the total force transmission element is used 40 in sections both in the actuator force transmission element 30th as well as in the primary piston 12th guided. For adjusting the length of the total force transmission element 40 When assembling the actuating unit, the total force transmission element comprises a coupling element 48 , which is selected or adjusted in the appropriate length when it is installed.

The total force transmission element 40 has a recess through which a section of a boom (see below) is guided, the recess being dimensioned such that the boom is relative to the total force transmission element 40 is freely movable.

The elastic element 44 has a function comparable to the so-called reaction disk in the vacuum brake booster. The deformation state of such a reaction disk shows the relationship between the pedal force and the actuator force. The elastic element 44 is designed as an elastically deformable but practically incompressible elastomer disc, so that material stresses in the elastomer can be described by the sum of an internal pressure and additional elastic stresses.

mit

• FP = vom Pedalkraftübertragungselement 32 übertragene Kraft,
• AP = Fläche, mit der das Pedalkraftübertragungselement 32 das elastische Element 44 in axialer Richtung berührt,
• FA = vom Aktuatorkraftübertragungselement 30 übertragene Kraft,
• AA = Fläche, mit der das Aktuatorkraftübertragungselement 30 das elastische Element 44 in axialer Richtung berührt,
• FS = vom Summenkraftübertragungselement 40 übertragene Kraft,
• AS = Fläche, mit der das Summenkraftübertragungselement 40 das elastische Element 44 in axialer Richtung berührt

The restraint of the elastic element 44 between corresponding contact surfaces of the pedal force transmission element 32 , Actuator force transmission element 30th and total force transmission element 40 has the consequence that its state of deformation is essentially due to the difference in the travel paths of the pedal force transmission element and the actuator force transmission element 30th is described. An amount of elastomer material that is displaced by the approach of the elastomer contact surfaces of the pedal force transmission element and the total force transmission element leads to a thickening of the elastomer disk in the area between the elastomer contact surfaces of the actuator force transmission element 30th and total force transmission element 40 and vice versa. If the difference is zero, there is no deformation and the internal pressure in the elastic element is the same at every point. In particular, applies in this equilibrium state $$\text{FP}/\text{AP}=\text{FA}/\text{AA}=\text{FS}/\text{AS}$$

With

• FP = from the pedal force transmission element 32 transmitted force,
• AP = area with which the pedal force transmission element 32 the elastic element 44 touches in the axial direction,
• FA = from the actuator force transmission element 30th transmitted force,
• AA = area with which the actuator force transmission element 30th the elastic element 44 touches in the axial direction,
• FS = from the total force transmission element 40 transmitted force,
• AS = area with which the total force transmission element 40 the elastic element 44 touches in the axial direction

was bedeutet, dass die Summenkraft FS gleich der um einen Faktor 1 + AA/AP verstärkten Pedalkraft ist. Während in einem Vakuumbremskraftverstärker als eine auf den Differenzweg ansprechende und die Aktuatorkraft einstellende Regeleinrichtung eine Pneumatikventileinrichtung verwendet wird, ist hier eine elektronische Regeleinrichtung vorgesehen, die den Differenzweg mit einem Sensor erfasst und die Aktuatorkraft elektronisch gesteuert bereitstellt.By means of a control device that responds to the differential travel, the actuator force is varied in such a way that the equilibrium specified in the equation is maintained. In other words: a control device adjusts the actuator force in such a way that the differential travel is kept at zero. Then applies $$\text{FS}=\left(1+\text{AA}/\text{AP}\right)\cdot \text{FP}\text{,}$$

which means that the total force FS is equal to that by a factor 1 + AA / AP is increased pedal force. While a pneumatic valve device is used in a vacuum brake booster as a control device that responds to the differential travel and adjusts the actuator force, an electronic control device is provided here that detects the differential travel with a sensor and provides the actuator force in an electronically controlled manner.

Such an electronic control device has the advantage that its function can be varied using software. For example, a so-called active braking can be superimposed on the boost function, or a so-called brake assistant function can be implemented via software, which generates an actuation process that is optimized with regard to the vehicle deceleration effect from an actuation of the brake pedal that is recognized as an initiation of emergency braking due to its acceleration dynamics, but is subsequently powerless.

The actuation unit 2 allows brake pressure to be built up both through muscle power and an electronically controlled active pressure build-up. With these technical requirements, by means of the actuation unit 2 signal-controlled braking interventions, pedal-controlled reinforced braking interventions, pedal-controlled non-amplified braking interventions as well as mixed forms of these braking interventions can be carried out. For this purpose there is a pressure supply device 50 provided, which is designed or functions as an electrohydraulic pressure source. It includes a hydraulic pressure chamber 52 into which a plunger 58 is movable.

The rotor of an electric motor 54 is via a rotation-translation gear 56 with the plunger 58 connected, whereby an axial movement of the pressure piston by means of a motor rotation 58 is performed. The rotation-translation gear 56 preferably comprises a ball screw drive (KGT) with a spindle 60 and a mother 62 . The mother 62 is with the help of an anti-twist device 54a rotatably mounted, so that a rotation of the spindle 60 to an axial movement of the nut 62 and the pressure piston coupled therewith at least in the axial direction 58 leads.

The pressure provision facility 50 , the pedal force transmission element 32 , the actuator force transmission element 30th as well as the total force transmission element 40 are components of the actuation force module 6a .

In the illustrated standby state of the pressure supply device 50 is the pressure room 52 connected by hydraulic openings to a reservoir, which prevents the pressure medium in the pressure chamber from heating up due to possible heating 52 - for example as a result of an increase in the ambient temperature - an unintentional pressure build-up occurs as a result of temperature expansion. In the event of an electronically controlled displacement of the pressure piston from its standby position, the pressure equalization connections are first closed, so that a pressure build-up is possible.

The pressure medium reservoir of the pressure supply device can be connected to the pressure medium reservoir 18th of the master cylinder 10 form a structural unit. In this case it is advisable to use a uniform pressure medium. In the case of separate reservoirs, the pressure medium used in the brake device can also be, for example, a hydraulic oil, that is to say chemically different from the brake fluid that usually circulates in the brake circuits.

Through a pressure line 70 is the pressure room 52 hydraulic with a booster pressure chamber 72 connected, which is in an inner area of the body 6th between a surface closing off a main bore section and the actuator force transmission element 30th is arranged.

The pressure provision device 50 is controlled by an electronic control and regulation unit 80 controlled. The pressure piston is used to actively build up pressure 58 in the printing room 52 proceed so that through the pressure line 70 Pressure medium in the booster pressure chamber 72 is promoted, so that the actuator force transmission element 30th axially in the direction of the master cylinder 10 is moved. At the same time, the brake pedal can 7th are actuated, whereby the pedal force transmission element 32 axially in the direction of the master cylinder 10 is moved. The through the two transmission elements 30th , 32 Forces transmitted are through the sum force transmission element 40 and the associated coupling element 48 on the primary piston 12th transfer. The total force transmission element 40 and the coupling element 48 are rigidly connected to one another in the embodiment shown. They can also be designed in one piece.

The actuation unit 2 is designed to receive the path information from the pedal force transmission element 32 and actuator force transmission element 30th to a place next to the master cylinder 10 to be transmitted and at least one differential path measurement value of the two transmission elements 30th , 32 to determine. There is also a first boom 100 provided, which, preferably rigidly with the pedal force transmission element 32 is connected and at the end of a position transmitter element 102 is arranged.

There is also a second boom 110 provided, which, preferably rigidly, with the actuator force transmission element 30th is connected and at the end of a sensor element 112 is arranged. With this arrangement, the differential value of the travel of the sensor element 112 and position sensor element 102 continuously recorded. Alternatively, the position transmitter element 102 on the second boom 110 and the sensor element 112 on the first boom 100 be arranged.

So-called contactless measuring principles are preferably used, which in this context means that measuring principles with possible wear of electrical contacts that generate measuring signals - i. H. the use of potentiometric sensors - because of their mechanically conditioned susceptibility to failure, should not be used. The preferred measuring principles are those based on magnetic, electromagnetic or optical effects and known to allow signal generation that is not affected by mechanical wear.

The two outriggers 100 , 110 are formed in the illustrated preferred embodiment as webs, which in a first area within the body 6th run and in one end area along the master cylinder 10 or master cylinder housing 14th run, with the boom 110 seen radially with respect to the main bore axis within the radius of the boom 100 runs. This arrangement can save installation space.

The sensor element 112 is by means of a flexible electrical connection 148 with the control and regulation unit 80 connected.

The actuation unit 2 furthermore has an electronics housing 150 on, which is preferably right next to the master cylinder housing 14th is arranged and in which the flexible electrical connection 148 are arranged as well as non-movable components 250 , for the mechanical and electrical connection of the flexible electrical connection 148 .

The control and regulation unit is also preferred 80 in which the flexible electrical connection 148 and electronics housing accommodating the sensor 150 with housed, eliminating the need for a separate electronics housing for the control and regulation unit 80 is avoided. In addition, this enables the electrical connection of the aforementioned non-movable components 250 to the control and regulation unit 80 be designed as an electrical connection inside the electronics housing and is thus protected against environmental influences by the electronics housing. If two separate electronics housings were used, a comparatively complex cable connection would be necessary.

An essential component of the control and regulation unit 80 is an electronics board 80a that establishes the electrical connections in the form of conductor tracks between their electronic components (integrated electronic circuits, diodes, transistors, coils, capacitors, connection elements, etc.). Such a control and regulation unit 80 typically comprises a board, the components on the board, electrical connections in the form of cable connections, contact springs, plugs and an electronics housing with electrical and mechanical connections to the outside.

A contact surface is preferred 260 intended for flexible electrical connection.

In another preferred embodiment, the path of the pedal force transmission element can also be detected. A sensor is preferably used for this purpose 100a provided for detecting the pedal force transmission element path. This further sensor preferably detects 100a the position of the same position transmitter element via which the previously described differential travel detection takes place. Alternatively, an additional position encoder can be used. The detection range of the sensor preferably comprises the entire possible travel path of the pedal force transmission element.

A pressure sensor 52a or 52b can be connected to hydraulic actuators to acquire a signal representing the actuator force. Such a pressure sensor is electrical 52a , 52b connected to the electronics unit that controls the sensor 52a , 52b supplied with electrical energy and receives the signals generated by the sensor. The pressure sensor is preferred 52b arranged within the electronics housing. This has the advantage that no cable connection that is resistant to environmental influences is required between the electronics unit and the sensor.

In 2 is a braking system 200 shown which the actuation unit 2 according to 1 includes. The braking system 200 further comprises a pressure modulation device 210 , which in the present case is designed as an ESC module and has wheel-specific inlet and outlet valves for setting wheel-specific wheel brake pressures. The braking system 200 has four hydraulically operated wheel brakes 220 , 222 , 224 , 226 on, with two of the wheel brakes 220 , 222 a first brake circuit I and two of the wheel brakes are assigned to a second brake circuit II. The first brake circuit I comprises a first hydraulic brake circuit line 230 that have the hydraulic connection 20th with the primary chamber of the tandem master cylinder 10 connects. The second brake circuit II comprises a second hydraulic brake circuit line 232 that have the hydraulic connection 22nd with the secondary chamber of the tandem master cylinder 10 connects.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was 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.

Patent literature cited

• DE 102014207219 A1 [0002]
• DE 102016111869 A1 [0005]

Claims (14)

Actuating unit (2) for a hydraulic brake system (200) with which the brakes of a motor vehicle can be actuated both with brake pedal and electronically controlled, the actuation unit (2) comprising a brake pedal arrangement (3), a braking device (5) and a master brake cylinder (10) , the braking device (5) comprising an actuating force module (6a) with a body (6) closing it off to the outside, via which the actuating force module can be connected to the body (12a) of the motor vehicle and to which the master brake cylinder (10) is attached and in which in a main bore (36) inside the body (6) a pedal force transmission element (32), an actuator force transmission element (30), a total force transmission element (40) and an elastic element (44) are linearly movably guided along the main bore axis, the pedal force transmission element ( 32) and the actuator force transmission element (30) are arranged concentrically with respect to the main bore axis , and wherein the brake master cylinder (10) can be acted upon by a sum of pedal force and actuator force, in that the elastic element (44) can be acted upon by force on an input side from the pedal force transmission element (32) and the actuator force transmission element (30) and on an output side the sum force can be applied to the sum force transmission element (40) for forwarding to a primary piston (12) of the master brake cylinder (10), the actuating unit (2) further comprising a means for detecting the travel path difference of the pedal force transmission element (32) and the actuator force transmission element (30), the difference path detection means being an extension arm (129, 130) which mechanically transmit the path information from the pedal force transmission element (32) and the actuator force transmission element (30) to a location radially offset with respect to the main bore axis, characterized in that a position transmitter element (102) is attached to a boom (110) and where when a sensor element (112) is attached to another boom (100), which detects the relative position of the position transmitter element (102) to the sensor element (112). Actuation unit (2) Claim 1 , the travel distances of the sensor element (112) and position transmitter element (102) being assigned to locations outside the body (6) with the aid of the arms (100, 110). Actuation unit (2) Claim 2 , wherein the assigned travel distances of the sensor element (112) and position transmitter element (102) are arranged parallel to the master cylinder (10) and outside the master cylinder bore, in particular in a corresponding recess of a master cylinder housing (14). Actuating unit (2) according to one of the Claims 1 to 3rd , wherein the movable sensor element (112) is electrically connected to non-movable electronic sensor connection components (250) with the aid of a flexible electrical connection (148) in order to supply both the sensor element (112) with the electrical energy it needs and the to receive differential travel signals generated by the sensor element (112), in particular to forward them to a control and regulating unit (80). Actuation unit (2) Claim 4 , wherein the movable sensor element (112), the flexible electrical connection (148) and the non-movable electronic sensor connection components (250) are arranged within a common electronics housing (150), which is in particular dimensioned in such a way that it allows the required free travel of the Sensor element (112), in particular the space required by a loop of the flexible electrical connection (148). Actuation unit (2) Claim 5 , wherein a control and regulating unit (80) is provided, in which the flexible electrical connection (148) and the sensor element (112) receiving electronics housing (150) are received. Actuation unit (2) Claim 6 , wherein the non-movable electronic sensor connection components (250) are electrically connected directly to the control and regulating unit (80) and / or in which the control and regulating unit are structurally integrated. Actuation unit (2) Claim 6 or 7th , wherein the actuator system for providing the actuator force and the control and regulating unit (80) are arranged adjacent to one another, so that the control and regulating unit can provide the actuator with the required electrical actuator currents via short electrical connections. The actuator system preferably comprises an electronically commutated electric motor with a three-phase power supply. Actuating unit (1) according to one of the Claims 1 to 8th , the two arms (100, 110) running parallel at least in sections. Actuation unit (2) Claim 9 , the two arms (100, 110) being guided parallel to an edge region of the master brake cylinder (10). Actuation unit (2) Claim 9 or 10 , wherein one of the two arms (100) is radial, is arranged in particular with respect to the master cylinder bore axis, seen inside the other arm (110). Actuating unit (2) according to one of the Claims 1 to 11 , wherein the determination of the relative position takes place without contact, and wherein the contactless transmission of the path information uses an electrical, magnetic or optical operating principle. Actuating unit (2) according to one of the Claims 1 to 12th wherein both the sensor element (112) and the position transmitter element (102) are arranged in the axial actuation direction behind the braking device body (6). Brake system (200), comprising an actuation unit (2) according to one of the preceding claims, further comprising an electrohydraulic pressure modulation device (210) hydraulically connected to the master brake cylinder (10) of the actuation unit (2) and wheel brakes (220) hydraulically connected to the pressure modulation device (210) , 222, 224, 226).

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