Brake actuator unit, strain sensor and electromechanical brake

Abstract

The invention relates to a brake actuator unit, a strain sensor and an electromechanical brake. A brake actuator unit (12) for an electromechanical brake (10), the brake actuator unit having: a main shaft (44); the brake (10) includes a main shaft (44), a main shaft bearing (96) receiving the main shaft (44), and a cup-shaped brake piston bearing section (74) having a circumferential wall (76) and a base (78) on which the main shaft bearing (96) is axially supported during actuation of the brake (10). The brake actuator unit (12) also has a strain sensor (142) having a sensor element which is arranged on an outer periphery (148) of an axial section (144) of the circumferential wall (76) and is configured to detect a strain of the axial section (144) in the circumferential direction (U). Furthermore, a strain sensor (142) and an electromechanical brake (10) are provided.

Description

Technical Field

[0001] The invention relates to a brake actuator unit for an electromechanical brake, comprising: a spindle; a brake piston, which is coupled to the spindle in terms of drive; a spindle bearing, which receives the spindle and absorbs the axial reaction forces of the spindle during actuation of the brake; and a cup-shaped brake piston support section, which has a circumferential wall and a base, on which the spindle bearing is axially supported during actuation of the brake. The invention also relates to a strain sensor for such a brake actuator unit. Furthermore, the invention relates to an electromechanical brake having such a brake actuator unit and / or having such a strain sensor. Background Art

[0002] Brake actuator units of this type and brakes having such brake actuator units are known and are provided for decelerating or stopping a vehicle equipped with said brake.

[0003] Here, the braking force or force with which the brake actuator unit acts on the brake disk when the brake is actuated depends on a number of influencing factors, such as friction pads and spindle drive, and generally varies with age and aging of the brake.

[0004] In order to ensure a constant effect of the brake over time, the brake must therefore be controlled as a function of changing influencing factors. Summary of the invention

[0005] It is an object of the present invention to provide a brake actuator unit by means of which a constant effect of the brake over time can be ensured in a reliable manner.

[0006] The object is achieved by a brake actuator unit for an electromechanical brake, the brake actuator unit having a spindle, a brake piston, which is coupled to the spindle in terms of drive, a spindle bearing, which receives the spindle and absorbs axial reaction forces of the spindle during actuation of the brake, and a cup-shaped brake piston support section, which has a circumferential wall and a base, on which the spindle bearing is axially supported during actuation of the brake. In this case, the brake actuator unit has a strain sensor, which has at least one sensor element, which is arranged on the outer periphery of an axial section of the circumferential wall and is configured to detect a strain of the axial section in the circumferential direction.

[0007] The invention has recognized that when the brake is actuated, the base of the cup-shaped brake piston bearing segment is subjected to an axial reaction force to the action force via the main shaft. In the process, this reaction force generates a proportional strain of the axial segment, which is detected by at least one sensor element. With the help of the strain sensor, it is therefore possible to reliably determine the currently acting action force at any time. Based on this information, the brake actuator unit can be controlled in a suitable manner in order to ensure a constant effect of the brake even when the influencing factors change.

[0008] In one embodiment, the axial section is adjacent to the base, thereby ensuring that the strain in the axial section is particularly large and can therefore be determined very accurately.

[0009] Additionally or alternatively, the outer periphery of the axial segment may be formed by a cylindrical lateral surface at least in a certain portion or portions. This configuration promotes uniform strain of the outer periphery in the circumferential direction, thus enabling reliable determination of the strain of the axial segment.

[0010] In another embodiment, the at least one sensor element is mounted on a flat surface on the outer periphery of the axial section, which flat surface extends in the axial direction and in the tangential direction. In this way, the at least one sensor element is fixed at a defined position on the outer periphery and is arranged to accurately determine the strain of the outer periphery. Furthermore, the brake actuator unit thus has a particularly compact design.

[0011] Furthermore, the strain sensor can have an electrical terminal which is connected to the at least one sensor element in a signal-transmitting manner, thereby simplifying the assembly of the brake actuator unit.

[0012] Furthermore, it can be provided that the strain sensor has a contact band which is annular at least in some part or some part and which extends in the circumferential direction around the axial section. In this case, the contact band has a terminal portion which has the electrical terminal and the contact band has a contact portion with an electrical contact on the inner periphery, the electrical terminal being connected to the at least one sensor element in a signal-transmitting manner via the electrical contact. This enables assembly of the brake actuator unit to be performed effortlessly.

[0013] In this arrangement, the contact collar can be prestressed in the circumferential direction so that the contact collar is pressed radially against the axial section. This ensures a reliable contact between the electrical contacts of the contact part and the at least one sensor element.

[0014] According to one embodiment, the contact ferrule has a gap in the circumferential direction which separates a first circumferential end from an opposite second circumferential end. In this case, the contact ferrule has a connecting element which connects the first circumferential end to the second circumferential end in the circumferential direction. This enables the contact ferrule to be mounted effortlessly and to be prestressed in the circumferential direction in an effective manner.

[0015] According to an alternative embodiment, the strain sensor has a flexible cable portion which extends in the circumferential direction around the axial section at least in a certain section or sections. In this arrangement, the flexible cable portion has electrical leads with electrical contacts, via which the electrical terminals are connected to the at least one sensor element in a signal-transmitting manner. This structure simplifies the assembly of the brake actuator unit.

[0016] In this arrangement, the at least one sensor element can have electrical pin contacts and the flexible cable section can have a complementary flat socket with the electrical contacts. In this case, the pin contacts and the flat socket form a plug-in connection, which allows for easy assembly. In addition, this construction makes the strain sensor particularly compact.

[0017] Furthermore, it can be provided that the brake actuator unit has an electronic module having a circuit board and an electrical connection device having a plurality of electrical connection leads, each having a first connection contact and an opposite second connection contact. In this arrangement, the electrical connection device is connected to the electrical terminal via the first connection contact and to the circuit board via the second connection contact in a signal-transmitting manner. In this way, the circuit board is effectively connected to the strain sensor in a signal-transmitting manner.

[0018] In one embodiment, the electrical terminal is designed as a socket and the first connecting contact is designed as an insertion pin, which forms a plug connector for the socket. Thus, the brake actuator unit can be assembled without difficulty.

[0019] Furthermore, the plug connector and the socket can form a plug-in connection with an axial plug-in direction, which further simplifies assembly.

[0020] In another embodiment, the second connection contacts are plug-in compression connector contact pins extending in the axial direction, thereby enabling the second connection contacts to be effectively connected to the circuit board in a signal transmission manner without difficulty.

[0021] Additionally or alternatively, the electrical connection leads can be formed by a stamped grid, which can be produced at particularly low cost. Furthermore, a stamped grid is dimensionally stable, which simplifies assembly.

[0022] Furthermore, it can be provided that the electrical connection device has a stepped profile with an axial portion and a radial portion. This configuration has the advantage that the electrical connection device extends radially and axially between adjacent components of the brake actuator unit, thereby enabling the brake actuator unit to be constructed in a particularly compact manner.

[0023] According to one embodiment, the brake actuator unit has a transmission module which is drive-coupled to the spindle and is arranged in the axial direction between the strain sensor and the electronics module. The brake actuator unit thus has a particularly space-saving design.

[0024] In this arrangement, the transmission module can have a ring gear and a transmission carrier, which has a receptacle in which the electrical connection device is arranged in a positively engaged manner at least in a certain section or sections. In this case, the ring gear is connected to the transmission carrier by a press fit. Furthermore, the electrical connection device is clamped between the ring gear and the transmission carrier in the axial direction and / or in the radial direction. This configuration enables the brake actuator unit to be manufactured in a particularly compact and effortless manner.

[0025] Additionally or alternatively, the strain sensor can be arranged in the radial direction in the transmission housing of the transmission module, thereby making the brake actuator unit have a particularly space-saving construction. In addition, the strain sensor is protected by the transmission housing in this way, and the brake actuator unit thus has a particularly efficient construction.

[0026] According to another embodiment, the strain sensor has a positioning contour which positively engages with a complementary positioning contour on the outer periphery of the axial section. As a result, an exact arrangement of the strain sensor is ensured and assembly is possible with little effort.

[0027] Furthermore, it can be provided that the cup-shaped brake piston bearing section is an integral part of the brake housing of the brake actuator unit, as a result of which the brake actuator unit is particularly compact. Furthermore, this results in a particularly robust construction of the brake actuator unit, thereby ensuring that forces acting on the brake actuator unit during actuation of the brake as well as vibrations during driving can be absorbed or dissipated in a particularly effective manner. Furthermore, the small number of individual components has advantages in terms of logistics and assembly.

[0028] In one embodiment, the brake housing forms a brake caliper, thereby improving the structural integrity of the brake actuator unit and damping vibrations during operation in a particularly effective manner.

[0029] According to one aspect, the cup-shaped brake piston bearing section at least partially accommodates the brake piston in a cylindrical socket, and the radial inner side of the circumferential wall forms a sliding guide surface for the brake piston. A brake actuator unit arranged in this way advantageously makes it possible to compensate for eccentric force components. The sliding guide surface on the radial inner side of the circumferential wall generates a restoring force in the direction of the axis of rotation of the spindle. In this way, the orientation and mounting of the individual components of the brake actuator unit can be improved, in particular the symmetry with respect to the axis of rotation of the spindle. Overall, this leads to an improved application of force to the brake piston and reduced wear.

[0030] According to the present invention, the above object is also achieved by providing a strain sensor having the above advantages, which is used in a brake actuator unit according to the present invention.

[0031] According to the present invention, the above-mentioned object is also achieved by providing an electromechanical brake, which has an electric motor for actuating the brake, which is connected to the main shaft in a torque-transmitting manner, and the electromechanical brake has a brake actuator unit according to the present invention and / or has a strain sensor according to the present invention with the above-mentioned advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Other advantages and features will become apparent from the following description and the accompanying drawings, in which:

[0033] Figure 1 shows a longitudinal section through an electromechanical brake according to the invention having a brake actuator unit according to the invention;

[0034] Figure 2 Shown from Figure 1 An exploded view of an electromechanical actuation unit of a brake, the electromechanical actuation unit having a transmission module;

[0035] Figure 3 Shown from Figure 1 A perspective view of a brake housing and a sensor element of a brake actuator unit;

[0036] Figure 4 Shown from Figure 3 A perspective view of a sensor element;

[0037] Figure 5 According to an alternative embodiment, Figure 3 A perspective view of a sensor element;

[0038] Figure 6 According to another alternative embodiment, Figure 3 A top view of a sensor element;

[0039] Figure 7 Shown from Figure 6 A bottom view of a sensor element;

[0040] Figure 8 Shown from Figure 1 An exploded view of an annular contact collar of a strain sensor of a brake actuator unit;

[0041] Fig. 9 Shown from Figure 8 A perspective view of the electrical leads of the contact ferrule;

[0042] Fig.10 Shown from Figure 3 The brake housing and sensor element from Figure 8 Exploded view of the contact hoop;

[0043] Fig.11 Shown in assembled state Fig.10 The brake housing and contact collar from Figure 1 An exploded view of the electrical connection device of the brake actuator unit;

[0044] Fig.12 Shown from Figure 8 The contact ferrule and the Fig.10 Detailed view of the sensor element;

[0045] Fig.13 According to an alternative embodiment, Figure 8 Exploded view of the contact hoop;

[0046] Fig.14 Shown from Figure 2 The transmission housing and ring gear of the transmission module and the Fig.11 An exploded view of the electrical connection device;

[0047] Fig.15 Shown in assembled state Fig.14 A three-dimensional view of a transmission housing, a ring gear and an electrical connection device;

[0048] Fig.16 Shown from Fig.11 The electrical connections from the strain sensor to the Figure 2 A longitudinal section of a path of a circuit board of an electromechanical actuation unit;

[0049] Fig.17 An alternative embodiment is shown with Figure 1 The strain sensors of the brake actuator units come from Figure 3 An exploded view of the brake housing;

[0050] Fig.18 Shown from Fig.17 Exploded view of the strain sensor;

[0051] Fig.19 According to an alternative embodiment, Fig.17 An exploded view of the strain sensor; and

[0052] Fig. 20 shows a cross section through a nanolayer, from Figure 3 The brake housing and the sensor element are connected to one another via the nano-multilayer. DETAILED DESCRIPTION

[0053] The following detailed description in conjunction with the accompanying drawings (in which like numbers refer to like elements) is intended as a description of various embodiments of the disclosed subject matter and is not intended to represent the only embodiments. Any embodiment described in this disclosure is purely by way of example or illustration and should not be construed as preferred or advantageous over other embodiments.

[0054] All features disclosed below with respect to the exemplary embodiments and / or drawings may be combined with features of various aspects of the present disclosure (including features of the preferred embodiments) alone or in any subcombination, as long as the resulting feature combination is beneficial to those skilled in the art.

[0055] Figure 1 An electromechanical brake 10 with a brake actuator unit 12 is shown.

[0056] In this case, the electromechanical brake 10 is a disk brake for a vehicle and is assigned to the wheels of the vehicle.

[0057] The brake actuator unit 12 has a brake housing 14 with a brake caliper 16 and a base support 18 by means of which the brake 10 is fastened to the body of the vehicle.

[0058] The brake housing 14 is made of, for example, ductile iron (ie, cast iron containing ductile iron).

[0059] In this case, the brake caliper 16 is mounted via a guide support 20 (see Figure 3 ) is connected to the base support 18 and can be moved in the axial direction A relative to the base support 18 by means of the linear guide and is therefore mounted in a floating manner.

[0060] The brake caliper 16 surrounds a brake disk 22 , in particular a brake disk rotor, which can be clamped in the axial direction by two brake pads 24 , 26 .

[0061] The brake pad 24 located on the inner side in the axial direction A is mounted on the base support 18 so that it can move in the axial direction A.

[0062] The brake pad 26 located on the outside in the axial direction A is mounted on a pad carrying section 28 which is an integral part of the brake caliper 16 .

[0063] When the brake 10 is activated, the brake pad 24 located on the inside along the rotation axis R of the brake actuator unit 12 actively receives the force Fz applied by the brake actuator unit 12 .

[0064] In the present case (in the ideal case of compensation of transverse forces), the rotational axis R of the brake actuator unit 12 also corresponds to the cylinder axis of the brake housing 14 and the brake disk rotational axis of the brake disk 22 .

[0065] The axially movable brake caliper 16 ensures that the brake pad 26 located on the outside in the axial direction A is also acted upon by the force Fz. In this case, the magnitude of the force Fz is distributed substantially evenly between the inner brake pad 24 and the outer brake pad 26. As a result of the contact pressure provided, a frictional engagement of the two brake pads 24, 26 with the brake disk 22 can therefore be ensured, which serves to decelerate or immobilize the vehicle.

[0066] The brake actuator unit 12 also has a positioning device 30 and an electromechanical actuation unit 32 (see Figure 2 ), the electromechanical actuation unit having a transmission module 34 and an electronic module 36.

[0067] In this case, the positioning device 30 and the transmission module 34 are arranged to be connected to the electric motor 38 (see Figure 2 ) together generate a force Fz.

[0068] Together with the electric motor 38 , the electromechanical actuating unit 32 forms a closed subassembly which can be assembled separately.

[0069] The transmission module 34 has a transmission housing 40 and a transmission 42, which connects the electric motor 38 to a main shaft 44 of the positioning device 30 in terms of transmission (see Figure 1 ).

[0070] The transmission case 40 has an integral transmission mount 46 to which the transmission 42 is secured or mounted.

[0071] In the embodiment considered, the transmission housing 40 is of single-piece construction and forms the outer housing of the transmission module 34 .

[0072] Furthermore, the transmission housing 40 may be formed of plastic (particularly fiber-reinforced plastic) or a lightweight metal (eg, aluminum alloy).

[0073] Here, the transmission 42 is a multi-stage reduction gear and includes a planetary transmission 48, which includes a ring gear 50 (see Fig.14 ).

[0074] The ring gear 50 is made of metal (particularly sintered metal).

[0075] In the embodiment under consideration, the ring gear 50 is arranged in a cylindrical socket 52 (see Fig.14 ) and connected by interference fit and knurling on the transmission bracket 46 (see Fig.15 ) to fix it.

[0076] In order to form the knurled connection, the ring gear 50 has a knurled outer peripheral portion 54 .

[0077] In an alternative embodiment, the ring gear 50 is embedded in the transmission carrier 46 by overmolding, the transmission carrier then being manufactured in particular from plastic.

[0078] The clearance-free press fit between the ring gear 50 and the cylindrical socket 52 ensures effective centering and alignment of the ring gear 50 with the transmission carrier 46 .

[0079] Furthermore, the knurled connection ensures that the ring gear 50 is effectively prevented from rotating in the transmission carrier 46 by positive engagement, in particular even at high temperatures.

[0080] In the embodiment under consideration, the transmission 42 is torque-transmitting via a drive shaft extension 56 (see Figure 3 ) is connected to the positioning device 30, and the drive shaft extension is arranged at one axial end of the main shaft 44.

[0081] The spindle 44 also has a shank 58 on the brake pad side (see Figure 1 ) and a transition portion 60 arranged between the drive shaft extension 56 and the shank 58 along the rotation axis R of the main shaft 44. The outer diameter of the drive shaft extension 56 of the brake actuator unit 12 in the radial direction is smaller than the outer diameter of the shank 58 in this direction. The main shaft 44 tapers accordingly with respect to its outer diameter in the region of the transition portion 60.

[0082] The positioning device 30 also has a spindle transmission 64, which in this case is designed as a recirculating ball screw and is not self-locking, and a spindle nut 62 that is fixed to prevent rotation. The spindle transmission 64 includes a thread 66, in which balls 68 are arranged and roll. The spindle 44 and the spindle nut 62 have corresponding race components, which together form the thread 66. The balls 68 can allow the spindle nut 62 to move in translation along the axis of rotation R relative to the spindle 44 along the ball race 70 of the thread 66. For this purpose, the ball race 70 is at least partially formed in the shank 58 of the spindle 44 and the spindle nut 62.

[0083] The diameter of the ball race 70 corresponds to the diameter of the balls 68 taking into account manufacturing tolerances and the required gap dimensions.

[0084] In the embodiment under consideration, the spindle nut 62 forms a brake piston 72 of the brake actuator unit 12 .

[0085] In an alternative embodiment, the brake piston 72 and the spindle nut 62 are separate components that are drivingly connected to each other.

[0086] Due to the translational movement of the spindle nut 62 in the direction of the brake disk 22 , the spindle nut 62 or the brake piston 72 is moved in the direction of the inner brake pad 24 and thus ensures that the force Fz is actively applied to the inner brake pad 24 .

[0087] Here, the rotation of the spindle 44 is ensured by the electric motor 38, which is engaged with the drive shaft extension 56 of the spindle 44 via the transmission 42. The inclination of the spindle transmission 64, in particular the ball race 70, and the blocking of the rotational movement of the spindle nut 62 then have the effect that the rotation of the spindle 44 causes a translational movement of the spindle nut 62. This movement is transmitted to the brake pads 24, 26 via the spindle nut 62 or the brake piston 72.

[0088] The resulting force Fz is proportional to the torque generated by the motor 38 and the transmission 42 at the drive shaft extension 56 .

[0089] In this case, the brake caliper 16 has a cup-shaped brake piston bearing section 74 with a circumferential wall 76 extending along the rotation axis R and a base 78 extending radially from the circumferential wall 76 toward the rotation axis R. The open end of the cup-shaped brake piston bearing section 74 is arranged on the brake pad side along the rotation axis R. This means that the base 78 is arranged at the end of the brake piston bearing section 74 opposite the brake disk 22. The base 78 has a through hole 80 for the drive shaft extension 56 of the spindle 44, which is held in the through hole 80 by a radial bearing 82.

[0090] In the embodiment considered, the brake caliper 16 is of one-piece design.

[0091] In principle, the brake caliper 16 can be formed from a plurality of individual components, but in all embodiments of the brake piston support section 74 the brake piston support section 74 is connected integrally to the pad carrier section 28 .

[0092] The base 78 and the circumferential wall 76 (more precisely the radial inner side 84 of the circumferential wall 76) define a cylindrical socket 86 in which the spindle 44 and the spindle nut 62 or the brake piston 72 are at least partially arranged. Due to the linear mobility of the spindle nut 62 or the brake piston 72, these components can also be arranged at least partially outside the cylindrical socket 86.

[0093] In this arrangement, the inner side 84 forms a sliding guide surface 88 for the spindle nut 62 or the brake piston 72 , against which the spindle nut 62 or the brake piston 72 abuts and is guided at least in a certain portion or portions.

[0094] As already mentioned, the spindle nut 62 is linearly guided and is secured against rotation relative to the brake piston bearing section 74 within the cylindrical socket 86 by means of a rotation lock 90 .

[0095] For this purpose, the spindle nut 62 has an axial groove 92 on the outer periphery which engages with a pin 94 which projects radially from the inner side 84 of the circumferential wall 76 into the cylindrical socket 86 in order to form a rotation lock 90 .

[0096] In the embodiment shown, the pin 94 is formed by a screw which extends through the circumferential wall 76 in the radial direction.

[0097] This rotation lock 90 is necessary in particular when contact between the spindle nut 62 or the brake piston 72 and the carrier of the inner brake pad 24 has not yet been established. As soon as contact has been established between the spindle nut 62 or the brake piston 72 and the carrier of the inner brake pad 24 or its carrier, the force Fz generates a friction torque which fixes the spindle nut 62, in particular against rotation.

[0098] The generated force Fz is proportional to the axial travel of the spindle nut 62. Here, the proportionality factor corresponds to the instantaneous system stiffness. The axial travel of the spindle nut 62 also compensates for the friction pad wear.

[0099] As a result of the generated action force Fz, a reaction force Fr is generated along the rotation axis R, which is opposite to the action force Fz. Due to the elastic expansion of the components of the brake 10, an angular misalignment usually occurs between the rotation axis of the brake disk and the cylinder axis of the brake housing 14, as a result of which the reaction force Fr has eccentric force components. These eccentric force components can lead to radial instabilities of the components of the brake actuator unit 12, in particular if the core diameter of the spindle drive 64 is smaller than the outer diameter of the bearing for absorbing the reaction force Fr.

[0100] In the present case, therefore, the brake actuator unit 12 comprises a rotationally symmetrical spindle bearing 96 (see Figure 1 ), which is embodied as an axial bearing with a bearing ring 98 having a spherical bearing contact surface arranged on the brake pad side. The main shaft bearing 96 is in contact with the conical transition section 60 of the main shaft 44, which has a contact surface complementary to the spherical bearing contact surface.

[0101] The bearing ring 98 also has a flat contact surface which is arranged along the axis of rotation R opposite the spherical bearing contact surface.

[0102] Furthermore, the brake actuator unit 12 has rolling elements 100 which are in contact with the bearing ring 98 via a planar contact surface.

[0103] Furthermore, a bearing disk 102 is arranged between the rolling element 100 and the base 78 of the brake piston bearing section 74, which bearing disk has two planar contact surfaces opposite along the axis of rotation R and is pressed into the base 78 so as to be rotationally fixed by friction and / or positive engagement. One contact surface of the bearing disk 102 is in contact with the base 78. The rolling element 100 rolls on the other of the two contact surfaces of the bearing disk 102.

[0104] The reaction force Fr which thus occurs is transmitted from the spindle 44 via the transition 60 to the spherical bearing contact surface of the spindle bearing 96 and from there is absorbed by the base 78 of the brake piston bearing section 74 via the rolling elements 100 and the bearing disk 102. In other words, during the application of the brake 10, the axial reaction force Fr of the spindle 44 is introduced into the base 78 via the spindle bearing 96.

[0105] In principle, in alternative embodiments, the spindle bearing 96 embodied as an axial bearing may be configured in any desired manner.

[0106] In this case, the base 78 has an axial, annular, protruding seat 104 which protrudes axially into the cylindrical socket 86 while being spaced apart by a gap from the inner side 84 of the circumferential wall 76. This enables the spindle bearing 96 to be arranged in an initial position in the inner bore of the spindle nut 62, thereby ensuring a reduction in the axial length of the positioning device 30.

[0107] In this arrangement, the spindle nut 62 may partially protrude axially into the gap between the axial base 104 and the inner side 84 of the circumferential wall 76 .

[0108] The drive shaft extension 56 of the main shaft 44 is radially supported by radial bearings 82 .

[0109] The radial bearing 82 has a collar which acts on one side as an axial stop or axial bearing and is supported by the outer wall of the base 78 which is arranged opposite the cylindrical socket 86 .

[0110] The radial bearing 82 is advantageously made of plastic, thereby making it possible to provide a stop damping in order to reduce noise.

[0111] The brake actuator unit 12 also has an assembly consisting of a retaining ring 106, which snaps into a groove in the spindle 44, and a washer 108, which transmits unilateral axial forces from the spindle 44 to the collar of the radial bearing 82. This assembly prevents unidirectional translational movements of the spindle 44 in the direction of the spindle nut 62. In addition, the retaining ring 106 positions the transmission 42 on one side in the axial direction A on the spindle 44.

[0112] In order to center the transmission 42 relative to the brake piston bearing section 74 , the transmission housing 40 has a centering through-opening 110 which is positively connected to a centering collar 112 of the brake caliper 16 .

[0113] In this case, the centering through hole 110 and the centering collar 112 extend in the axial direction A and are arranged coaxially to one another and to the axis of rotation R.

[0114] In the exemplary embodiment under consideration, the centering collar 112 is arranged on the outer circumference of the brake piston bearing section 74 .

[0115] In principle, the centering collar 112 can be fastened at any desired location on the brake caliper 16 , in particular at any desired outer circumference.

[0116] The centering collar 112 has a circumferential groove 114 in which a seal 116 is arranged. In this arrangement, the seal 116 statically seals the transmission housing 40 relative to the brake caliper 16 and thus prevents moisture and foreign particles from penetrating from the environment into the brake actuator unit 12 .

[0117] In this case, the brake actuator unit 12 has a bellows 118 which prevents moisture and foreign particles from penetrating from the environment into the spindle drive 64 over the entire stroke of the spindle nut 62. For this purpose, the bellows 118 has two cylindrical sealing beads 120, 122 at its opposite ends. The inner sealing bead 120 is seated under prestress in an outer circumferential groove 124 on the spindle nut 62. The outer sealing bead 122 is seated in an inner circumferential groove in the inner side 84 of the circumferential wall 76 and provides a dynamic seal relative to the outer diameter of the spindle nut 62.

[0118] The transmission housing 40 is fixed directly to the brake caliper 16 in the axial direction A and in the tangential direction by positive and frictional engagement by means of at least two prestressing screws.

[0119] By means of this threaded connection, all reaction forces and reaction torques generated by the electric motor 38 and the transmission 42 during the generation of a drive torque on the main shaft 44 are transmitted directly from the transmission housing 40 to the brake caliper 16 .

[0120] Furthermore, the transmission housing 40 supports all reaction forces and reaction torques occurring during the vibration effects and transmits them to the brake caliper 16 .

[0121] In this condition, the transmission case 40 and the brake caliper 16 are in force and torque balance.

[0122] Furthermore, the threaded connection between the transmission housing 40 and the brake caliper 16 provides a measure to prevent the transmission module 34 from rotating and provides an axial fixation of the transmission module 34 on the brake caliper 16 .

[0123] In order to control the electric motor 38 , the electronic module 36 has a circuit board 130 which is connected to the electric motor 38 in a signal-transmitting manner.

[0124] The circuit board 130 is arranged in an electronics housing 132 of the electronics module 36 , which is sealed in a gas-tight manner by a cover 134 .

[0125] The electronic module 36 is connected by screws 136 (see Figure 2 ) is fixed to the transmission housing 40 via the electronic housing 132 and is connected to the transmission module 34 in an airtight manner via a stuffing rope 138 .

[0126] In this arrangement, electronics housing 132 forms a cover or cap for transmission housing 40 .

[0127] In this case, the brake actuator unit 12 has a strain sensor 142 which is connected in a signal-transmitting manner or via an electrical connection device 140 (see Fig.16) is connected to the circuit board 130 and is arranged to be in contact with the spindle 44 (see Figure 1 ) is introduced into the base 78 via the spindle bearing 96 to detect the axial reaction force Fr of the brake piston support section 74 in the circumferential direction U (see Figure 3 ) on the resulting proportional strain.

[0128] More precisely, the strain sensor 142 is arranged to determine the strain in the circumferential direction U of the axial section 144 of the brake piston bearing section 74, the sensor element 146 of the strain sensor 142 (see Figure 3 ) is arranged on the axial section 144.

[0129] In this arrangement, the axial section 144 is adjacent to the base 78 in the radial direction.

[0130] In addition, the axial section 144 is located in the axial direction A of the transmission 42 (see Figure 1 ) extends between the centering collar 112 and is therefore arranged radially within the transmission housing 40.

[0131] In the illustrated embodiment, the strain sensor 142 is arranged completely radially within the transmission housing 40 and is therefore protected from the outside by the transmission housing 40 .

[0132] Furthermore, the axial section 144 has a cylindrical lateral surface 150 on the outer periphery 148 (see Figure 3 ) and a positioning contour 154, the cylindrical lateral surface being interrupted by a flat surface 152 on which the sensor element 146 is fixed, the positioning contour having a positioning contour 156 (see Figure 8 ) complementary structure.

[0133] In this arrangement, the flat surface 152 extends in the axial direction A and tangentially relative to a virtual cylindrical lateral surface (not shown) having a radius slightly smaller than the radius of the cylindrical lateral surface 150 .

[0134] Here, the positioning contour 154 is partially formed by a planar surface similar to the planar surface 152 .

[0135] In principle, however, the positioning contour 154 can have any desired configuration.

[0136] The sensor element 146 is, for example, a strain sensitive sensor manufactured using thin film technology.

[0137] In the embodiment under consideration, the sensor element 146 (see Figure 4) has a flat carrier plate 158 which consists, in particular, of a 0.2 mm thick steel sheet and which is coated on one side with an approximately 6 μm thick electrically insulating layer, which consists, for example, of aluminum oxide ceramic (Al 2 O 3 ).

[0138] During production, the surface of the carrier plate 158 is polished prior to coating. The coating of aluminum oxide ceramic may be applied by plasma spraying.

[0139] The electrically insulating layer has a 10 μm thick strain-sensitive, electrically conductive meander-shaped metal coating 160 on one side.

[0140] The meander-shaped metal coating 160 is composed of, for example, a nickel-chromium precision resistance alloy and can be formed by physical vapor deposition.

[0141] Furthermore, the meandering metal coating 160 is connected in sections to form a Wheatstone half-bridge or full-bridge and is oriented in such a way that longitudinal and transverse strains or shear strains can be detected while compensating for temperature-related strains.

[0142] The microstructure of the meander-shaped metal coating 160 may be formed by photolithography and subsequent wet chemical etching or by laser machining.

[0143] For the purpose of external contacting, the sensor element 146 has several (for example three or four) contact blocks 162 which are mounted on the carrier plate 158 and are connected to the meander-shaped metal coating 160 in a signal-transmitting manner.

[0144] The carrier plate 158 is connected to the flat surface 152 via its rear side, ie the side arranged opposite to the side on which the contact block 162 is mounted, by so-called “bonding”.

[0145] In bonding, the reactive film 164 (see Fig. 20 ) is placed between the carrier plate 158 and the outer periphery 148 of the axial section 144 and is subjected to a joining pressure.

[0146] Optionally, the surfaces to be joined are pre-soldered or coated with a joining layer 166 .

[0147] The reactive film 164 is composed of a reactive nano-multilayer 168 having a plurality of alternating metal or semi-metal monolayers having a thickness of a few nanometers.

[0148] The reactive film 164 is ignited by an electric spark 170 or a laser, i.e., activation energy acts on the reactive nano-multilayer 168. This leads to an exothermic reaction in the layer, which propagates in the form of a reaction zone 172 in the propagation direction B. Due to the high reaction heat released in the process and limited to a local area, the axial section 144 and the carrier plate 158 and / or the optional bonding layer 166 melt and are thus converted into a bonded state, which is Fig. 20 The left side of the reaction zone 172 is shown.

[0149] The joining method can be automated and have a short processing time of less than one second.

[0150] The strains of the brake piston bearing section 74 that occur when the brake 10 is applied are transmitted to a carrier plate 158 that is fixed to the outer periphery 148 of the axial section 144 (see Figure 4 ). Here, the strain is proportional to the magnitude of the reaction force Fr. As a result, the meandering metal coating 160 on the carrier plate 158 is strained in a corresponding manner, so that the resistance of the meandering metal coating 160 changes. Here, the change in the resistance of the measuring bridge is proportional to the strain.

[0151] In order to be able to detect strain, the meandering metal coating 160 is contacted with a constant supply voltage and a resistance-dependent signal voltage through a contact block 162. Here, the signal voltage is proportional to the strain.

[0152] In one embodiment, the signal voltage may be amplified by a signal amplifier (not shown) additionally mounted on the carrier board 158 .

[0153] In another embodiment (see Figure 5 ), a SENT (Single Edge Nibble Transmission) interface mounted on a carrier board 158 is provided, which provides an output signal in digital form. In this case, the sensor element 146 has an electronic evaluation chip 174 with an application specific integrated circuit (ASIC) mounted on the carrier board 158. In this arrangement, the meander-shaped metal coating 160 is in contact with a constant supply voltage. In addition, the evaluation chip can be in contact with the meander-shaped metal coating 160 by bonding.

[0154] In another embodiment (see Figure 6 ), the sensor element 146 is designed as a strain-sensitive MEMS sensor (MEMS=microelectromechanical system) based on the piezoresistive effect. In this case, the sensor element 146 has a measuring chip 176, which has a silicon chip with a microelectromechanical measuring bridge and an electronic evaluation circuit (ASIC). The microelectromechanical measuring bridge consists of four measuring resistors diffused into the silicon chip. In this case, metal nanoparticles are incorporated into the silicon matrix, wherein the piezoresistive properties of silicon are utilized. The measuring resistors are connected to form a Wheatstone full bridge.

[0155] The measuring chip 176 is on its lower side (see Figure 7 ) is connected to a substrate 178 consisting of stainless steel by bonding. An electrically insulating layer is applied to the substrate 178. In this embodiment, the carrier plate 158 has a cutout 180, through which the substrate 178 is directly connected to the outer periphery 148 of the axial section 144 by bonding. In this arrangement, the carrier plate 158 is also connected to the outer periphery 148 of the axial section 144 by bonding.

[0156] In this embodiment, the strain occurring at the outer periphery 148 of the axial section 144 when the brake 10 is applied is transmitted to the measuring chip 176 via the substrate 178. The resistance of the four resistors of the measuring bridge changes according to the piezoresistive effect. In this case, the output voltage or output signal of the measuring chip 176 is a measure of the strain occurring at the outer periphery 148 of the axial section 144 and therefore a measure of the force generated instantaneously.

[0157] In alternative embodiments, the sensor element 146 may have any desired configuration as long as it is configured to detect strains of the axial section 144 , particularly strains in the circumferential direction U.

[0158] Additionally or alternatively, the sensor element 146 may be fixed at any desired location on the outer periphery 148 of the axial section 144 .

[0159] In alternative embodiments, the sensor element 146 may also be mounted on the outer periphery 148 of the axial section 144 in any desired manner.

[0160] During operation, the signal voltage or output voltage of the sensor element 146 is used as input variable for manipulated variables including forces by a control unit (ECU) which is part of the circuit board 130. In this case, the instantaneous actual value is continuously compared with the setpoint value.

[0161] In order to ensure a stable, trouble-free contact between the sensor element 146 and the circuit board 130, which is required for a continuous signal transmission connection, the strain sensor 142 has an annular contact ring 182 made of plastic (see Figure 8 ), an electrical lead 184 made of metal (see Fig. 9 ) is encapsulated in the annular contact hoop 182.

[0162] In this arrangement, the contact collar 182 and the electrical lead 184 extend in the circumferential direction U.

[0163] At one end, the electrical lead 184 has an electrical contact 186 in the form of a contact cylinder, which has a contact portion 188 (see FIG. Figure 8 ) protrudes radially inwardly from the contact ring 182.

[0164] In this case, the electrical contacts 186 (see Fig.12 ) are arranged in such a way that they are each directly opposite to the contact block 162 of the sensor element 146 in the radial direction and are in contact with the contact block 162 in a signal transmission manner.

[0165] At the other end, the electrical lead 184 is connected to a spring socket contact 192 (see Fig. 9 ), the spring socket contact 192 forms an electrical terminal 194 of the strain sensor 142 (see Figure 8 ).

[0166] In this arrangement, the socket contact 192 is arranged in the terminal portion 196 of the strain sensor 142 to form a socket 198 having an insertion direction in the axial direction A.

[0167] In this case, the positioning contour 156 is arranged in the terminal section 196 .

[0168] In this case, the contact collar 182 is a single piece, but it can also be different.

[0169] In the illustrated embodiment, the contact collar 182 has a gap 200 separating a first circumferential end 202 of the contact collar 182 from a second circumferential end 204 , which is located on the opposite side in the circumferential direction U, and two connecting elements 206 , by which these circumferential ends 202 , 204 are connected to each other.

[0170] In this case, the connecting elements 206 are screws which, together with corresponding threads in the first circumferential end 202 , form a threaded connection, by means of which the contact collar 182 can be prestressed in the circumferential direction U.

[0171] In an alternative embodiment (see Fig.13 ), the contact hoop 182 has a connecting element 206 in the form of a spring clip, which engages with a correspondingly configured cutout 208 in the contact hoop 182 and in this way connects the circumferential ends 202, 204 together and prestresses them in the circumferential direction U.

[0172] During assembly of the brake actuator unit 12 , the contact bracket 182 is mounted in the axial direction A on the brake piston bearing section 74 (see FIG. Fig.10) on which the sensor element 146 is already fastened, with the result that the positioning contour 156 of the contact ferrule 182 engages forcibly in the complementary positioning contour 154 on the outer periphery 148 of the axial section 144. The contact ferrule 182 is thus arranged in a defined manner on the brake piston bearing section 74 in the axial direction A and in the circumferential direction U (see Fig.11 ). In particular, the electrical contact 186 is arranged directly opposite the contact block 162 of the sensor element 146 and is in contact with said block.

[0173] For axial installation, the circumferential ends 202 , 204 are elastically spread apart in the circumferential direction U, so that the diameter of the contact collar 182 is temporarily enlarged in a corresponding manner.

[0174] In a following step, the circumferential ends 202 , 204 are pulled toward each other in the circumferential direction U by means of the connecting element 206 , as a result of which the contact ring 182 is clamped securely in the radial direction on the outer periphery 148 of the axial section 144 and the electrical contact 186 rests on the contact block 162 of the sensor element 146 under prestress.

[0175] In this way, the sensor element 146 is connected to the electrical terminal 194 of the strain sensor 142 in a signal-transmitting manner.

[0176] In this case, the strain sensor 142 is connected to the electrical connection device 140 on the circuit board 130 in a signal transmission manner (see Fig.16 ) has an electrical connection lead 210 (see Fig.14 ), each of these electrical connection leads has a first connection contact 212 designed as a plug-in pin at one end and a second connection contact 214 designed as a plug-in compression connector contact pin at the opposite end.

[0177] In particular, the number of connecting leads 210 corresponds to the number of contact blocks 162 , which in the present case is four.

[0178] Here, the connecting leads 210 are formed by a stamped grid which is encapsulated with plastic in certain sections or certain sections.

[0179] In alternative embodiments, the connecting leads 210 may in principle be configured in any desired manner.

[0180] In the illustrated embodiment, the first connection contact 212 forms a plug connector 216 having a connection to the socket 198 (see FIG. 1 ) of the strain sensor 142. Fig.11 ) are complementary in structure and are connected to the socket 198 via a plug-in connection having an axial insertion direction S in a signal transmitting manner.

[0181] In this case, the contacting of the plug connector 216 with the socket 198 is carried out without visibility during the installation of the electromechanical actuating unit 32 on the brake housing 14 .

[0182] Furthermore, the electrical connection 140 extends from the strain sensor 142 via the transmission mount 46 and through the electronics housing 132 to form a stepped profile having an axial portion 218 and a radial portion 220 (see FIG. Fig.16 ) extends to the circuit board 130.

[0183] For this purpose, the transmission support 46 has a stepped receiving portion 222 (see Fig.14 ), the connecting device 140 is received in the step-shaped receiving portion in a forced engagement manner.

[0184] In this case, the connecting device 140 is firmly clamped in the axial, radial and tangential directions by the toothed ring 50 pressed into the transmission support 46 by positive and non-positive engagement (see Fig.15 ).

[0185] The second connection contact 214 is aligned in the axial direction A via an alignment guide 224 (see Fig.16 ), passes through the electronic housing 132 and extends into the circuit board 130, and the second connection contact is connected to the circuit board 130 in a signal transmission manner through a plug-in contact, and the plug-in contact has a structure complementary to the contact pin of the plug-in compression connector.

[0186] The contact between the second connecting contact 214 and the circuit board 130 is achieved by axial compression. In this case, the reaction force of the compression force is supported on the transmission support 46 via the stepped connection device 140.

[0187] Now refer to Fig.17 and Fig.18 A brake actuator unit 12 with a strain sensor 142 according to an alternative embodiment is described. The same reference numerals are used for the constituent parts known from the above-described embodiments, and to this extent reference is made to the preceding description.

[0188] and Figure 8 In contrast to the strain sensor 142 shown, the strain sensor 142 in the embodiment under consideration does not have a contact collar 182 , but rather has a flexible cable portion 226 which extends along the axial section 144 in the circumferential direction U from the terminal portion 196 to the sensor element 146 .

[0189] In this case, the flexible cable portion 226 comprises an electrical lead 184 , the electrical contact 186 of which is connected in a signal-transmitting manner to the contact block 162 of the sensor element 146 by bonding or welding.

[0190] In the embodiment shown, the flexible cable portion 226 is guided on the outer periphery 148 of the axial section 144. For this purpose, a spacer 228 consisting of an elastomer is molded onto the flexible cable portion 226, which spacer holds the flexible cable portion 226 at a defined distance from the axial section 144 of the brake piston bearing section 74 and from the inner periphery of the transmission housing 40. Fraying of the flexible cable portion 226 is thereby avoided.

[0191] Now refer to Fig.19 A strain sensor 142 according to a further alternative embodiment is described. The same reference numerals are used for the constituent parts known from the above-described embodiments, and to this extent reference is made to the preceding description.

[0192] and Fig.17 and Fig.18 In contrast to the strain sensor 142 shown in , the strain sensor 142 in the embodiment under consideration has a flat socket 230 , wherein the electrical contacts 186 of the electrical leads 184 form spring socket contacts or are connected to them in a signal-transmitting manner.

[0193] The pin contacts 232 in the form of forked contact pins are mounted on the contact block 162 of the sensor element 146 by bonding or welding.

[0194] In this arrangement, the pin contacts 232 form a plug connector which has a configuration complementary to the flat socket 230 and forms a plug-in connection with the flat socket 230. Via this plug-in connection, the sensor element 146 is connected to the electrical terminal 194 in a signal-transmitting manner.

[0195] In all these embodiments, a brake actuator unit 12 and an electromechanical brake 10 having a brake actuator unit 12 are provided in this way, which brake actuator unit has in each case a strain sensor 142, by means of which the strain at the outer periphery 148 of the brake piston bearing section 74 due to the action of the reaction force Fr to the action force Fz can be measured. Thus, the instantaneously occurring action force Fz can be directly detected.

[0196] By means of the momentarily generated force Fz, mechanical changes in the efficiency of the multi-step transmission 42 , the spindle bearing 96 and the spindle drive 64 can be detected, in particular as a function of the power consumption of the electric motor 38 , which is detected, for example, by a power consumption sensor.

[0197] This enables the electric motor 38 to be controlled accordingly in order to ensure a constant effect of the brake 10 over its service life.

[0198] Furthermore, brake actuator unit 12 has a compact design.

Claims

1. A brake actuator unit (12) for an electromechanical brake (10), the brake actuator unit comprising: spindle (44); a brake piston (72) which is drive-coupled to the spindle (44); a spindle bearing (96) receiving the spindle (44) and absorbing an axial reaction force (Fr) of the spindle (44) during actuation of the brake (10); and a cup-shaped brake piston bearing section (74) having a circumferential wall (76) and a base (78) on which the spindle bearing (96) is axially supported during actuation of the brake (10), It is characterized in that The brake actuator unit (12) has a strain sensor (142) having at least one sensor element (146) which is arranged on an outer periphery (148) of an axial section (144) of the circumferential wall (76) and is configured to detect strain of the axial section (144) in a circumferential direction (U).

2. The brake actuator unit (12) according to claim 1, characterized in that The axial section (144) is adjacent to the base (78).

3. The brake actuator unit (12) according to claim 1 or 2, characterized in that The outer periphery (148) of the axial section (144) is formed, at least in a certain section or sections, by a cylindrical lateral surface (150).

4. The brake actuator unit (12) according to any one of the preceding claims, characterized in that The at least one sensor element (146) is mounted on a flat surface (152) on the outer periphery (148) of the axial section (144), the flat surface extending in the axial direction (A) and in the tangential direction.

5. The brake actuator unit (12) according to any one of the preceding claims, characterized in that The strain sensor (142) has an electrical terminal (194) which is connected to the at least one sensor element (146) in a signal-transmitting manner.

6. The brake actuator unit (12) according to any one of the preceding claims, characterized in that The strain sensor (142) has a contact hoop (182) which is annular at least in a certain portion or certain portions and extends in the circumferential direction (U) around the axial section (144), wherein the contact hoop (182) has a terminal portion (196) having the electrical terminal (194), and the contact hoop (182) has a contact portion (188) with an electrical contact (186) on an inner periphery (190), and the electrical terminal (194) is connected to the at least one sensor element (146) via the electrical contact in a signal transmission manner.

7. The brake actuator unit (12) according to claim 6, characterized in that The contact collar (182) is prestressed in the circumferential direction (U) so that the contact collar (182) is pressed radially against the axial section (144).

8. The brake actuator unit (12) according to claim 6 or 7, characterized in that The contact ferrule (182) has a gap (200) in the circumferential direction (U) that separates a first circumferential end (202) from an opposite second circumferential end (204), wherein the contact ferrule (182) has a connecting element (206) that connects the first circumferential end (202) to the second circumferential end (204) in the circumferential direction (U).

9. The brake actuator unit (12) according to any one of claims 1 to 5, characterized in that The strain sensor (142) has a flexible cable portion (226) which extends in the circumferential direction (U) around the axial section (144) at least in a certain portion or certain portions, wherein the flexible cable portion (226) has an electrical lead (184) with an electrical contact (186), and the electrical terminal (194) is connected to the at least one sensor element (146) in a signal-transmitting manner via the electrical contact.

10. The brake actuator unit (12) according to claim 9, characterized in that The at least one sensor element (146) has an electrical pin contact (232), and the flexible cable portion (226) has a complementary flat socket (230) with the electrical contact (186), wherein the electrical pin contact (232) and the flat socket (230) form a plug-in connection.

11. The brake actuator unit (12) according to any one of claims 5 to 10, characterized in that The brake actuator unit (12) has an electronic module (36) having a circuit board (130) and an electrical connection device (140), the electrical connection device having a plurality of electrical connection leads (210), each of the electrical connection leads having a first connection contact (212) and an opposite second connection contact (214), wherein the electrical connection device (140) is connected to the electrical terminal (194) via the first connection contact (212) and is connected to the circuit board (130) via the second connection contact (214) in a signal transmission manner.

12. The brake actuator unit (12) according to claim 11, characterized in that The electrical terminal (194) is designed as a socket (198), and the first connecting contact (212) is designed as an insertion pin, which forms a plug connector (216) for the socket (198).

13. The brake actuator unit (12) according to claim 12, characterized in that The plug connector (216) and the socket (198) form a plug-in connection having an axial plug-in direction (S).

14. The brake actuator unit (12) according to any one of claims 11 to 13, characterized in that The second connection contact (214) is a male compression connector contact pin extending in the axial direction (A).

15. The brake actuator unit (12) according to any one of claims 11 to 14, characterized in that The electrical connection leads (210) are formed from a stamped grid.

16. The brake actuator unit (12) according to any one of claims 11 to 15, characterized in that The electrical connection device (140) has a stepped profile with an axial portion (218) and a radial portion (220).

17. The brake actuator unit (12) according to any one of claims 11 to 16, characterized in that The brake actuator unit (12) has a transmission module (34) which is coupled to the spindle (44) in terms of drive and is arranged in an axial direction (A) between the strain sensor (142) and the electronic module (36).

18. The brake actuator unit (12) according to claim 17, characterized in that The transmission module (34) has a ring gear (50) and a transmission support (46), the transmission support having a receiving portion (222), and the electrical connection device (140) is arranged in the receiving portion in a forced engagement manner, wherein the ring gear (50) is connected to the transmission support (46) by a press fit, wherein the electrical connection device (140) is clamped between the ring gear (50) and the transmission support (46) in an axial direction (A) and / or in a radial direction.

19. The brake actuator unit (12) according to any one of claims 1 to 18, characterized in that The strain sensor (142) has a positioning contour (156) which positively engages with a complementary positioning contour (154) on the outer periphery (148) of the axial section (144).

20. A strain sensor (142) for a brake actuator unit (12), the brake actuator unit having: a spindle (44); a brake piston (72), which is coupled to the spindle (44) in terms of driving; a spindle bearing (96), which receives the spindle (44) and absorbs axial reaction forces (Fr) of the spindle (44) during actuation of the brake (10); and a cup-shaped brake piston support section (74), which has a circumferential wall (76) and a base (78), on which the spindle bearing (96) is axially supported during actuation of the brake (10), It is characterized in that The strain sensor (142) has at least one sensor element (146) which is arranged on an outer periphery (148) of an axial section (144) of the circumferential wall (76) and is configured to detect strain of the axial section (144) in a circumferential direction (U).

21. The strain sensor (142) according to claim 20, characterized in that The strain sensor (142) has an electrical terminal (194) which is connected to the at least one sensor element (146) in a signal-transmitting manner.

22. The strain sensor (142) according to claim 21, characterized in that The strain sensor (142) has a contact hoop (182) which is annular at least in a certain portion or portions and extends in the circumferential direction (U) around the axial section (144), wherein the contact hoop (182) has a terminal portion (196) having the electrical terminal (194), and the contact hoop (182) has a contact portion (188) with an electrical contact (186) on the inner periphery (190), and the electrical terminal (194) is connected to the at least one sensor element (146) via the electrical contact in a signal transmission manner.

23. The strain sensor (142) according to claim 22, characterized in that The contact collar (182) is prestressed in the circumferential direction (U) so that the contact collar (182) is pressed radially against the axial section (144).

24. The strain sensor (142) according to claim 22 or 23, characterized in that The contact ferrule (182) has a gap (200) in the circumferential direction (U) that separates a first circumferential end (202) from an opposite second circumferential end (204), wherein the contact ferrule (182) has a connecting element (206) that connects the first circumferential end (202) to the second circumferential end (204) in the circumferential direction (U).

25. The strain sensor (142) according to any one of claims 21 to 24, characterized in that The strain sensor (142) has a flexible cable portion (226) which extends in the circumferential direction (U) around the axial section (144) at least in a certain portion or certain portions, wherein the flexible cable portion (226) has an electrical lead (184) with an electrical contact (186), and the electrical terminal (194) is connected to the at least one sensor element (146) in a signal-transmitting manner via the electrical contact.

26. The strain sensor (142) according to claim 25, characterized in that The at least one sensor element (146) has an electrical pin contact (232), and the flexible cable portion (226) has a complementary flat socket (230) with the electrical contact (186), wherein the electrical pin contact (232) and the flat socket (230) form a plug-in connection.

27. An electromechanical brake (10) having an electric motor (38) for actuating the electromechanical brake (10), the electric motor being coupled to a main shaft (44) in a torque-transmitting manner, the electromechanical brake having a brake actuator unit (12) according to any one of claims 1 to 19, and / or the electromechanical brake having a strain sensor (142) according to any one of claims 20 to 26.

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