Brake actuator unit, strain sensor for such a brake actuator unit, and electromechanical brake

Abstract

A brake actuator unit (12) for an electromechanical brake (10) has a spindle (44), a spindle bearing (96) that receives the spindle (44), and a cup-shaped brake piston bearing section (74) that has a circumferential wall (76) and a base (78) against which the spindle bearing (96) is axially supported when the brake (10) is actuated. The brake actuator unit (12) also has a strain sensor (142) with a sensor element that is arranged on an outer circumference (148) of an axial section (144) of the circumferential wall (76) and is configured to detect a strain of the axial section (144) in a circumferential direction (U). Furthermore, a strain sensor (142) is provided for such a brake actuator unit (12). Furthermore, an electromechanical brake (10) is provided with such a brake actuator unit (12) and / or with such a strain sensor (142).

Description

[0001] The invention relates to a brake actuator unit for an electromechanical brake, comprising a spindle, a brake piston drivingly coupled to the spindle, a spindle bearing accommodating the spindle and absorbing the axial reaction forces of the spindle when the brake is applied, and a cup-shaped brake piston bearing section having a peripheral wall and a base against which the spindle bearing is axially supported when the brake is applied. Furthermore, the invention 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.

[0002] Such brake actuator units and brakes with such brake actuator units are known and are intended to decelerate or immobilize vehicles equipped with them.

[0003] The braking force or clamping force with which the brake actuator unit acts on a brake disc when the brake is applied depends on several influencing factors, such as the friction lining and the spindle drive, and usually changes over the service life and age of the brake.

[0004] In order to ensure a constant effect of the brake over time, it is therefore necessary to control the brake according to the changing influencing factors.

[0005] The object of the invention is to provide a brake actuator unit by means of which a constant effect of the brake can be reliably ensured over time.

[0006] The problem is solved by a brake actuator unit for an electromechanical brake, comprising a spindle, a brake piston drivingly coupled to the spindle, a spindle bearing that accommodates the spindle and absorbs the axial reaction forces of the spindle when the brake is applied, and a cup-shaped brake piston bearing section that has a peripheral wall and a base against which the spindle bearing is axially supported when the brake is applied. The brake actuator unit has a strain sensor with at least one sensor element that is arranged on an outer circumference of an axial section of the peripheral wall and is configured to detect a strain of the axial section in a circumferential direction.

[0007] According to the invention, the base of the cup-shaped brake piston bearing section is subjected to an axial reaction force of the application force via the spindle when the brake is applied. This reaction force generates a proportional strain in the axial section, which is detected by at least one sensor element. Thus, the strain sensor can reliably determine the currently acting application force at any time based on the detected strain. Based on this information, the brake actuator unit can be controlled accordingly to ensure a constant brake action even under changing influencing factors.

[0008] In one embodiment, the axial section borders on the bottom, whereby the expansion of the axial section is particularly large and can therefore be determined very precisely.

[0009] Additionally or alternatively, the outer circumference of the axial section can be formed, at least in sections, by a circular-cylindrical surface. This design promotes uniform expansion of the outer circumference in the circumferential direction, so that the expansion of the axial section can be reliably determined.

[0010] In a further embodiment, the at least one sensor element is attached to a planar surface on the outer circumference of the axial section, which extends in the axial direction and in the tangential direction. In this way, the at least one sensor element is attached to a defined location on the outer circumference and configured to precisely determine the expansion of the outer circumference. Furthermore, this results in a particularly compact brake actuator unit.

[0011] Furthermore, the strain sensor can have an electrical connection that 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, the strain sensor can be provided with a contact bracket that is at least partially annular and extends circumferentially around the axial section. The contact bracket has a connection section with the electrical connection and, on the inner circumference, a contact section with electrical contacts, via which the electrical connection is connected to the at least one sensor element in a signal-transmitting manner. In this way, the brake actuator unit can be assembled with minimal effort.

[0013] The contacting bracket can be preloaded in the circumferential direction such that the contacting bracket is pressed radially against the axial section. This ensures reliable contact between the electrical contacts of the contact section and the at least one sensor element.

[0014] According to one embodiment, the contacting bracket has a gap in the circumferential direction that separates a first circumferential end from an opposite second circumferential end. The contacting bracket has a connecting element that connects the first circumferential end to the second circumferential end in the circumferential direction. In this way, the contacting bracket can be mounted with minimal effort and effectively preloaded in the circumferential direction.

[0015] According to an alternative embodiment, the strain sensor has a flexible cable section that extends circumferentially around the axial section. The flexible cable section includes electrical lines with electrical contacts, via which the electrical connection is connected to the at least one sensor element in a signal-transmitting manner. This design simplifies the assembly of the brake actuator unit.

[0016] In this case, 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. The pin contacts and the flat socket form a plug-in connection, allowing for particularly low-effort assembly. Furthermore, this design makes the strain sensor particularly compact.

[0017] Furthermore, the brake actuator unit can be provided with an electronic module with a circuit board and an electrical connection device having electrical connection lines, each with a first connection contact and an opposite second connection contact. The connection device is connected to the electrical connection via the first connection contacts and to the circuit board via the second connection contacts in a signal-transmitting manner. In this way, the circuit board is efficiently connected to the strain sensor in a signal-transmitting manner.

[0018] In one embodiment, the electrical connection is designed as a socket, and the first connecting contacts are designed as pins that form a plug for the socket. This allows the brake actuator unit to be installed with minimal effort.

[0019] Furthermore, the plug and socket can form a plug connection with an axial plug-in direction, so that assembly is further simplified.

[0020] In a further embodiment, the second connecting contacts are plug-in compression connector contact pins that extend in the axial direction, whereby the second connecting contacts can be effectively connected to the circuit board in a signal-transmitting manner with little effort.

[0021] Additionally or alternatively, the connecting lines can be formed by a stamped grid, which is particularly cost-effective to manufacture. Furthermore, the stamped grid is dimensionally stable, simplifying assembly.

[0022] Furthermore, the connecting device can be provided with a stepped profile with axial and radial sections. This design has the advantage that the connecting device extends radially and axially between adjacent components of the brake actuator unit, allowing it to be designed particularly compactly.

[0023] According to one embodiment, the brake actuator unit comprises a gear module that is drive-coupled to the spindle and arranged axially between the strain sensor and the electronics module. This makes the brake actuator unit particularly space-saving.

[0024] The transmission module can comprise a ring gear and a transmission web with a receptacle in which the connecting device is arranged in a form-fitting manner in sections. The ring gear is connected to the transmission web by means of a press fit. Furthermore, the connecting device is clamped axially and / or radially between the ring gear and the transmission web. This design makes the brake actuator unit particularly compact and easy to manufacture.

[0025] Additionally or alternatively, the strain sensor can be arranged radially within a gear housing of the transmission module, thereby providing a particularly space-saving design for the brake actuator unit. Furthermore, the strain sensor is protected by the transmission housing, thus making the brake actuator unit particularly efficient.

[0026] According to a further embodiment, the strain sensor has a positioning contour that positively engages a complementary positioning contour on the outer circumference of the axial section. This ensures precise positioning of the strain sensor and allows for minimal installation effort.

[0027] It can further be provided that the cup-shaped brake piston bearing section is an integral part of a brake housing of the brake actuator unit, making the brake actuator unit particularly compact. Furthermore, this makes the brake actuator unit particularly robust, so that forces acting on the brake actuator unit when the brake is applied, as well as vibrations during travel, can be absorbed or dissipated particularly effectively. Furthermore, fewer individual parts offer advantages in logistics and assembly.

[0028] In one embodiment, the brake housing forms a brake caliper, so that the structural integrity of the brake actuator unit is improved and vibrations during operation are particularly effectively suppressed.

[0029] According to one aspect, the cup-shaped brake piston bearing section accommodates the brake piston, at least in part, in a cylindrical receptacle, and the peripheral wall forms a sliding guide surface for the brake piston on its radial inner side. The brake actuator unit configured in this way advantageously enables the compensation of off-center force components. The sliding guide surface on the radial inner side of the peripheral wall creates a restoring force in the direction of the spindle's rotational axis. This can improve the orientation and bearing of the individual components of the brake actuator unit, in particular the symmetry with respect to the spindle's rotational axis. Overall, this leads to improved force application to the brake piston and reduced wear.

[0030] According to the invention, a strain sensor is also provided to achieve the above-mentioned object, which is used with the aforementioned advantages in a brake actuator unit according to the invention.

[0031] According to the invention, in order to achieve the above-mentioned object, an electromechanical brake is further provided with an electric motor for actuating the brake, which is coupled to the spindle in a torque-transmitting manner, with a brake actuator unit according to the invention and / or with a strain sensor according to the invention with the aforementioned advantages.

[0032] Further advantages and features are evident from the following description and the attached drawings. These show: - Fig. 1 shows a longitudinal sectional view of an electromechanical brake according to the invention with a brake actuator unit according to the invention, - Fig. 2 in an exploded view an electromechanical actuation unit of the brake from Fig. 1 with a gear module, - Fig. 3 shows a perspective view of a brake housing and a sensor element of the brake actuator unit from Fig. 1, - Fig. 4 shows a perspective view of the sensor element Fig. 3, - Fig. 5 shows a perspective view of the sensor element Fig. 3 according to an alternative embodiment, - Fig. 6 in a top view the sensor element from Fig. 3 according to a further alternative embodiment, - Fig. 7 in a bottom view the sensor element Fig. 6, - Fig. 8 shows an exploded view of a ring-shaped contact bracket of a strain sensor of the brake actuator unit from Fig. 1, - Fig. 9 in a perspective view electrical lines of the contact bracket made of Fig. 8, - Fig. 10 in an exploded view the brake housing and the sensor element from Fig. 3 and the contact bracket from Fig. 8, - Fig. 11 in an exploded view the brake housing and the contact bracket from Fig. 10 in an assembled state and an electrical connection device of the brake actuator unit from Fig. 1, - Fig. 12 in a detailed view of the contact bracket Fig. 8 and the sensor element from Fig. 10, - Fig. 13 in an exploded view the contact bracket from Fig. 8 according to an alternative embodiment, - Fig. 14 in an exploded view a gear housing and a ring gear of the gear module from Fig. 2 and the electrical connection device from Fig. 11, - Fig. 15 shows in a perspective view the gear housing, the ring gear and the electrical connection device from Fig. 14 in an assembled state, - Fig. 16 shows in a longitudinal section the course of the electrical connection device Fig. 11 from the strain sensor to a circuit board of the electromechanical actuation unit Fig. 2, - Fig. 17 shows an exploded view of the brake housing Fig. 3 with a strain sensor of the brake actuator unit Fig. 1 according to an alternative embodiment, - Fig. 18 shows an exploded view of the strain sensor Fig. 17, - Fig. 19 shows an exploded view of the strain sensor Fig. 17 according to an alternative embodiment, and - Fig. 20 shows a cross-sectional view of a nanomultilayer by means of which the brake housing and the sensor element are made of Fig. 3 are connected to each other.

[0033] The following detailed description, taken in conjunction with the accompanying drawings, in which like numerals refer to like elements, is intended to describe various embodiments of the disclosed subject matter and is not intended to be the only embodiments. Each embodiment described in this disclosure is merely exemplary or illustrative and should not be construed as preferred or advantageous over other embodiments.

[0034] All features disclosed below with respect to the embodiments and / or the accompanying figures may be combined alone or in any sub-combination with features of the aspects of the present disclosure, including features of preferred embodiments, provided that the resulting combination of features is meaningful to a person skilled in the art.

[0035] Fig. 1 shows an electromechanical brake 10 with a brake actuator unit 12.

[0036] The electromechanical brake 10 is here a disc brake for a vehicle and is assigned to a wheel of the vehicle.

[0037] 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 attached to the body of the vehicle.

[0038] The brake housing 14 is made, for example, of spheroidal cast iron, ie cast iron with spheroidal graphite.

[0039] In this context, the brake calliper 16 is mounted on guide supports 20 (see Fig. 3) attached linear guides to the base support 18 and can be moved in the axial direction A relative to the base support 18 and is thus mounted in a floating manner.

[0040] The brake calliper 16 surrounds a brake disc 22, in particular a brake disc rotor, which can be clamped in the axial direction A by two brake pads 24, 26.

[0041] The inner brake pad 24 in the axial direction A is mounted on the base carrier 18 so that it can move in the axial direction A.

[0042] The outer brake pad 26 in the axial direction A is attached to a pad carrier section 28 which is an integral part of the brake calliper 16.

[0043] The inner brake pad 24 along a rotation axis R of the brake actuator unit 12 is actively subjected to an application force Fz by the brake actuator unit 12 when the brake 10 is activated.

[0044] The rotation axis R of the brake actuator unit 12 corresponds in this case (in the ideal case of compensated transverse forces) also to the cylinder axis of the brake housing 14 and the brake disc rotation axis of the brake disc 22.

[0045] The axially movable brake caliper 16 ensures that the outer brake pad 26, located in the axial direction A, is also subjected to the application force Fz. The application force Fz is distributed essentially equally between the inner brake pad 24 and the outer brake pad 26. Thus, as a result of the applied contact force, a frictional engagement with the brake disc 22 can be ensured for both brake pads 24, 26, which is used to decelerate or immobilize the vehicle.

[0046] The brake actuator unit 12 further comprises an actuating device 30 and an electromechanical actuating unit 32 (see Fig. 2) with a gear module 34 and an electronic module 36.

[0047] The actuating device 30 and the gear module 34 are designed to actuate, together with an electric motor 38 (see Fig. 2) to generate the clamping force Fz.

[0048] The electromechanical actuating unit 32 forms a closed, separately mountable subassembly with the electric motor 38.

[0049] The gear module 34 has a gear housing 40 and a gear 42, which drives the electric motor 38 with a spindle 44 (see Fig. 1) of the adjusting device 30.

[0050] The gear housing 40 has an integral gear web 46 to which the gear 42 is attached or mounted.

[0051] In the present embodiment, the gear housing 40 is designed in one piece and forms an outer housing of the gear module 34.

[0052] Furthermore, the gear housing 40 can be formed from plastic, in particular a fiber-reinforced plastic, or a light metal, for example an aluminum alloy.

[0053] The gear 42 is a multi-stage reduction gear and comprises a planetary gear 48 with a ring gear 50 (see Fig. 14).

[0054] The ring gear 50 is made of metal, in particular sintered metal.

[0055] In the present embodiment, the ring gear 50 is in a cylindrical receptacle 52 (see Fig. 14) of the gear web 46 and is secured to the gear web 46 by an interference fit and a knurled connection (see Fig. 15).

[0056] To form the knurled connection, the ring gear 50 has a knurled outer peripheral section 54.

[0057] In an alternative embodiment, the ring gear 50 is overmolded in the gear web 46, which is then made in particular of plastic.

[0058] The play-free press fit between the ring gear 50 and the cylindrical holder 52 ensures effective centering and alignment of the ring gear 50 with the gear web 46.

[0059] Furthermore, the knurled connection ensures effective anti-twist protection of the ring gear 50 in the gear web 46 through positive locking, especially at high temperatures.

[0060] In the present embodiment, the transmission 42 is connected via a drive shaft extension 56 (see Fig. 3) is coupled to the actuating device 30 in a torque-transmitting manner, which is arranged at one axial end of the spindle 44.

[0061] The spindle 44 also has a brake pad side shaft section 58 (see Fig. 1) and a transition section 60, which is arranged along the rotational axis R of the spindle 44 between the drive shaft extension 56 and the shaft section 58. The outer diameter of the drive shaft extension 56 of the brake actuator unit 12 is smaller along the radial direction than the outer diameter of the shaft section 58 along this direction. Accordingly, the spindle 44 tapers with respect to its outer diameter in the region of the transition section 60.

[0062] The adjusting device 30 further comprises a spindle nut 62 secured against rotation and a spindle drive 64, which in this case is designed as a self-locking recirculating ball screw. The spindle drive 64 comprises a thread 66 in which balls 68 are arranged and roll. The spindle 44 and the spindle nut 62 have corresponding raceway parts that together form the thread 66. The balls 68 can enable a translational movement of the spindle nut 62 along the ball raceways 70 of the thread 66 along the rotation axis R relative to the spindle 44. For this purpose, the ball raceways 70 are formed at least partially in the shaft section 58 of the spindle 44 and the spindle nut 62.

[0063] The diameter of the ball raceways 70 corresponds to the diameter of the balls 68, taking into account manufacturing tolerances and required gap dimensions.

[0064] In the present embodiment, the spindle nut 62 forms a brake piston 72 of the brake actuator unit 12.

[0065] In an alternative embodiment, the brake piston 72 and the spindle nut 62 are separate components that are drivingly coupled to one another.

[0066] Due to the translational movement of the spindle nut 62 in the direction of the brake disc 22, the spindle nut 62 or the brake piston 72 is moved in the direction of the inner brake pad 24 and thus ensures the active application of the application force Fz to the inner brake pad 24.

[0067] The rotation of the spindle 44 is ensured by the electric motor 38, which engages the drive shaft extension 56 of the spindle 44 via the gear 42. The pitches of the spindle drive 64, in particular the ball races 70, and the blocking of a rotational movement of the spindle nut 62 then result in the rotation of the spindle 44 causing 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.

[0068] The clamping force Fz generated is proportional to the torque produced on the drive shaft extension 56 by the electric motor 38 and the gear 42.

[0069] In this context, the brake caliper 16 has a cup-shaped brake piston bearing section 74 with a peripheral wall 76 extending along the rotation axis R and a base 78 extending radially from the peripheral wall 76 toward the rotation axis R. The open end of the cup-shaped brake piston bearing section 74 is arranged along the rotation axis R on the brake pad side. This means that the base 78 is arranged at the end of the brake piston bearing section 74 opposite the brake disc 22. The base 78 has a through hole 80 for the drive shaft extension 56 of the spindle 44, which is held therein by means of a radial bearing 82.

[0070] In the present embodiment, the brake caliper 16 is formed in one piece.

[0071] In principle, the brake caliper 16 can be formed from several individual parts, but in all embodiments the brake piston bearing section 74 is integrally connected to the pad carrier section 28.

[0072] The base 78 and the peripheral wall 76, more precisely the radial inner side 84 of the peripheral wall 76, define a cylindrical receptacle 86 in which the spindle 44 and the spindle nut 62 or the brake piston 72 are arranged at least in sections. Due to the linear displaceability of the spindle nut 62 or the brake piston 72, these components can also be arranged at least partially outside the cylindrical receptacle 86.

[0073] 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 rests at least in sections and is guided axially by this.

[0074] The spindle nut 62 is guided linearly within the cylindrical receptacle 86 relative to the brake piston bearing section 74 by means of a rotary lock 90, as already mentioned, and is secured against rotation.

[0075] For this purpose, the spindle nut 62 has an axial groove 92 on the outer circumference, which engages with a pin 94 which projects radially from the inner side 84 of the peripheral wall 76 into the cylindrical receptacle 86 in order to form the rotary lock 90.

[0076] In the illustrated embodiment, the pin 94 is formed by a screw that extends radially through the peripheral wall 76.

[0077] This rotary lock 90 is necessary especially when contact between the spindle nut 62 or the brake piston 72 and a carrier of the inner brake pad 24 is not established. When contact is established between the spindle nut 62 or the brake piston 72 and the carrier of the inner brake pad 24 or its carrier, the clamping force Fz generates a friction torque that secures the spindle nut 62, in particular, against rotation.

[0078] The generated clamping force Fz is proportional to the axial stroke of the spindle nut 62. The proportionality factor corresponds to the instantaneous system stiffness. The axial stroke of the spindle nut 62 also compensates for friction lining wear.

[0079] As a result of the generated application force Fz, a reaction force Fr opposite to the application force Fz occurs along the rotation axis R. Due to the elastic expansion of the components of the brake 10, an angular offset can generally occur between the brake disc rotation axis and the cylinder axis of the brake housing 14, so that the reaction force Fr has off-center force components. These off-center force components can lead to instability of the components of the brake actuator unit 12 along the radial direction, particularly if the core diameter of the spindle drive 64 is smaller than the outer diameter of a bearing intended to absorb the reaction force Fr.

[0080] Therefore, the brake actuator unit 12 comprises a rotationally symmetrical spindle bearing 96 designed as an axial bearing (see Fig. 1) with a bearing ring 98 having a spherical bearing contact surface arranged on the brake pad side. The spindle bearing 96 is in contact with the conical transition section 60 of the spindle 44, which has a contact surface complementary to the spherical bearing contact surface.

[0081] The bearing ring 98 further has a planar contact surface arranged along the rotation axis R opposite to the spherical bearing contact surface.

[0082] Furthermore, the brake actuator unit 12 has rolling elements 100 which are in contact with the bearing ring 98 via the more planar contact surface.

[0083] Additionally arranged between the rolling elements 100 and the base 78 of the brake piston bearing section 74 is a bearing disc 102, which has opposing planar contact surfaces along the rotation axis R and is pressed into the base 78 in a rotationally secure manner by frictional and / or positive engagement. One of the contact surfaces of the bearing disc 102 is in contact with the base 78. The rolling elements 100 roll on the other of the two contact surfaces of the bearing disc 102.

[0084] Thus, the reaction force Fr occurring from the spindle 44 is transmitted via the transition section 60 to the spherical bearing contact surface of the spindle bearing 96, and from there, via the rolling elements 100 and the bearing disc 102, is absorbed by the bottom 78 of the brake piston bearing section 74. In other words, the axial reaction force Fr of the spindle 44 is introduced into the bottom 78 via the spindle bearing 96 when the brake 10 is applied.

[0085] In principle, in an alternative embodiment, the spindle bearing 96 designed as an axial bearing can be designed as desired.

[0086] In this context, the base 78 has an axially protruding, annular pedestal 104, which projects axially into the cylindrical receptacle 86 at a distance from the inner side 84 of the peripheral wall 76. This allows the spindle bearing 96 to be arranged in an inner bore of the spindle nut 62 in the initial position, thereby achieving an axial length reduction of the adjusting device 30.

[0087] In this case, the spindle nut 62 can protrude axially in sections into the space between the axial platform 104 and the inner side 84 of the peripheral wall 76.

[0088] The drive shaft extension 56 of the spindle 44 is radially supported by the radial bearing 82.

[0089] The radial bearing 82 has a collar which acts as an axial stop or as a one-sided axial bearing and is supported by the outer wall of the base 78 arranged opposite the cylindrical receptacle 86.

[0090] The radial bearing 82 is advantageously made of plastic, which can provide stop damping to reduce noise.

[0091] The brake actuator unit 12 further includes a package consisting of a retaining ring 106 snapped into a groove in the spindle 44 and a fitting ring 108, which transmits unilateral axial forces from the spindle 44 to the collar of the radial bearing 82. The package prevents a unilateral translational movement of the spindle 44 in the direction of the spindle nut 62. Furthermore, the retaining ring 106 positions the gear 42 unilaterally in the axial direction A on the spindle 44.

[0092] In order to center the gear 42 relative to the brake piston bearing section 74, the gear housing 40 has a centering through-hole 110 which is positively connected to a centering collar 112 of the brake caliper 16.

[0093] The centering through hole 110 and the centering collar 112 extend in the axial direction A and are aligned coaxially to each other and to the rotation axis R.

[0094] In the present embodiment, the centering collar 112 is arranged on the outer circumference of the brake piston bearing section 74.

[0095] In principle, the centering collar 112 can be attached to any location on the brake caliper 16, in particular to any outer circumference.

[0096] The centering collar 112 has a circumferential groove 114 in which a seal 116 is arranged. The seal 116 statically seals the transmission housing 40 against the brake caliper 16 and thus prevents moisture and foreign particles from the environment from penetrating the brake actuator unit 12.

[0097] In this context, the brake actuator unit 12 has a bellows 118 that prevents moisture and foreign particles from the environment from penetrating 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. An inner sealing bead 120 is preloaded into a circumferential outer groove 124 on the spindle nut 62. The outer sealing bead 122 is preloaded into a circumferential inner groove in the inner side 84 of the peripheral wall 76 and dynamically seals against the outer diameter of the spindle nut 62.

[0098] The gear housing 40 is fixed directly to the brake calliper 16 in the axial direction A and in the tangential direction by means of at least two preloaded threaded screws by means of positive and frictional engagement.

[0099] Via this screw connection, all reaction forces and reaction moments generated by the electric motor 38 and the gearbox 42 during the generation of a drive torque on the spindle 44 are transmitted directly from the gearbox housing 40 to the brake calliper 16.

[0100] Furthermore, the transmission housing 40 supports all reaction forces and reaction moments that arise during the action of vibrations and transmits them to the brake caliper 16.

[0101] The gear housing 40 is in force and moment equilibrium with the brake caliper 16.

[0102] Furthermore, the screw connection between the gear housing 40 and the brake calliper 16 ensures anti-twist protection and axial fixation of the gear module 34 on the brake calliper 16.

[0103] 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.

[0104] The circuit board 130 is arranged in an electronics housing 132 of the electronics module 36, which is tightly closed by a cover 134.

[0105] The electronic module 36 is connected to the electronic housing 132 by means of connecting screws 136 (see Fig. 2) attached to the gear housing 40 and tightly connected to the gear module 34, for example by means of a sealing cord 138.

[0106] The electronics housing 132 forms a kind of cover or cap for the gear housing 40.

[0107] In this context, the brake actuator unit 12 has a circuit board 130 connected to it via an electrical connection device 140 (see Fig. 16) signal-transmittingly connected strain sensor 142, which is designed to measure the resulting proportional strain of the brake piston bearing section 74 in the circumferential direction U (see Fig. 3) when the axial reaction force Fr of the spindle 44 (see Fig. 1) is introduced into the base 78 via the spindle bearing 96 when the brake 10 is applied.

[0108] More precisely, the strain sensor 142 is designed to determine the strain in the circumferential direction U of an axial section 144 of the brake piston bearing section 74, on which a sensor element 146 (see Fig. 3) of the strain sensor 142.

[0109] The axial section 144 borders on the bottom 78 in the radial direction.

[0110] Furthermore, the axial section 144 extends in the axial direction A between the gear 42 (see Fig. 1) and the centering collar 112 and is thereby arranged radially inside the gear housing 40.

[0111] In the illustrated embodiment, the strain sensor 142 is arranged completely radially within the gear housing 40 and is thus protected from the outside by it.

[0112] Furthermore, the axial section 144 has a circular cylindrical surface 150 on the outer circumference 148 (see Fig. 3), which is interrupted by a planar surface 152 to which the sensor element 146 is attached, and a positioning contour 154, which is complementary to a positioning contour 156 (see Fig. 8) of the strain sensor 142.

[0113] The planar surface 152 extends in the axial direction A and tangentially to a virtual circular-cylindrical surface (not shown), the radius of which is slightly smaller than the radius of the circular-cylindrical surface 150.

[0114] The positioning contour 154 is here partly formed from a planar surface analogous to the planar surface 152.

[0115] In principle, however, the positioning contour 154 can be designed as desired.

[0116] The sensor element 146 is, for example, a strain-sensitive sensor manufactured using thin-film technology (also referred to as thin-film technology).

[0117] In the present embodiment, the sensor element 146 (see Fig. 4) a planar carrier board 158, which consists in particular of 0.2 mm thin steel sheet, and is coated on one side with an approximately 6 micrometer thin current insulation layer, which consists for example of aluminum oxide ceramic (Al2O3).

[0118] During manufacturing, the surface of the carrier board 158 is polished prior to coating. The aluminum oxide ceramic coating can be applied by plasma spraying.

[0119] The current insulation layer has a strain-sensitive, electrically conductive, meander-shaped metal coating 160 up to 10 micrometers thin on one side.

[0120] The meander-shaped metal coating 160 consists, for example, of a NiCr precision resistance alloy and can be formed by means of a PVD (Physical Vapor Deposition) treatment.

[0121] Furthermore, the meander-shaped metal coating 160 is segmentally connected and oriented to a Wheatstone half or full measuring bridge, so that either longitudinal and transverse strains or shear strains can be detected while compensating for the temperature strains.

[0122] The microstructure of the meandering metal coating 160 can be worked out by photolithography and subsequent wet chemical etching or by lasering.

[0123] 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 board 158 and are connected to the meander-shaped metal coating 160 in a signal-transmitting manner.

[0124] The carrier board 158 is connected with its rear side, ie the side opposite to the side on which the contact blocks 162 are mounted, to the planar surface 152 by so-called bonding.

[0125] During bonding, a reactive foil 164 (see Fig. 20) is placed between the carrier plate 158 and the outer circumference 148 of the axial section 144 and subjected to a joining pressure.

[0126] The surfaces to be joined are optionally pre-soldered or coated with a joining layer 166.

[0127] The reactive film 164 consists of a reactive nanomultilayer 168 (RNMS), which has a plurality of alternating individual layers of metal or semimetal with a thickness of a few nanometers.

[0128] With the help of an electric spark 170 or a laser, the reactive foil 164 is ignited, i.e. an activation energy acts on the reactive nanomultilayer 168. This results in an exothermic reaction in the layers, which spreads in the form of a reaction zone 172 in the propagation direction B. By means of the high reaction heat released, which is locally limited, the axial section 144 and the carrier plate 158 or the optional joining layer 166 are melted and thus converted into the connected state, which in Fig. 20 is shown to the left of the reaction zone 172.

[0129] This joining process can be automated and has a short process time of less than one second.

[0130] The expansion deformations of the brake piston bearing section 74 occurring when the brake 10 is applied are transferred to the carrier plate 158 attached to the outer circumference 148 of the axial section 144 (see Fig. 4). The strains are proportional to the magnitude of the reaction force Fr. As a result, the meandering metal coating 160 on the carrier board 158 stretches accordingly, and as a result, the electrical resistance of the meandering metal coating 160 changes. The change in resistance of the measuring bridge is proportional to the strain.

[0131] To detect the strain, the meandering metal coating 160 is contacted with a constant supply voltage and a resistance-dependent signal voltage via the contact blocks 162. The signal voltage is proportional to the strain.

[0132] In one embodiment, the signal voltage can be amplified by a signal amplifier (not shown) that is additionally mounted on the carrier board 158.

[0133] In another embodiment (see Fig. 5) A SENT (Single Edge Nibble Transmission) interface is provided on the carrier board 158, which provides the 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), which is mounted on the carrier board 158. The meandering metal coating 160 is contacted with a constant supply voltage. Furthermore, the evaluation chip can be contacted with the meandering metal coating 160 by bonding.

[0134] In another embodiment (see Fig. 6), the sensor element 146 is designed as a strain-sensitive MEMS sensor (MEMS = Micro-Electro-Mechanical-Systems) based on the piezoresistive effect. In this case, the sensor element 146 has a measuring chip 176, which comprises 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. Metallic nanoparticles are embedded in the silicon matrix, utilizing the piezoresistive properties of silicon. The measuring resistors are connected to form a Wheatstone full measuring bridge.

[0135] The measuring chip 176 is on its underside (see Fig. 7) is bonded to a stainless steel substrate 178. A current insulation layer is applied to the substrate 178. In this embodiment, the carrier board 158 has a recess 180 through which the substrate 178 is bonded directly to the outer circumference 148 of the axial section 144. The carrier board 158 is also bonded to the outer circumference 148 of the axial section 144.

[0136] In this embodiment, the strain deformations occurring on the outer circumference 148 of the axial section 144 when the brake 10 is applied are transmitted via the substrate 178 to the measuring chip 176. The four resistors of the measuring bridge change their electrical resistances according to the piezoresistive effect. The output voltage or output signal of the measuring chip 176 is a measure of the strain occurring on the outer circumference 148 of the axial section 144 and thus a measure of the instantaneously generated application force.

[0137] In an alternative embodiment, the sensor element 146 can be designed as desired, as long as it is configured to detect the expansion of the axial section 144, in particular in the circumferential direction U.

[0138] Additionally or alternatively, the sensor element 146 may be attached at any location on the outer circumference 148 of the axial portion 144.

[0139] Furthermore, in an alternative embodiment, the sensor element 146 may be attached to the outer circumference 148 of the axial portion 144 in any manner.

[0140] During operation, the signal voltage or output signal of sensor element 146 is used by a control unit (ECU), which is part of circuit board 130, as an input variable for the clamping force control variable. The current actual value is continuously compared with the setpoint value.

[0141] In order to ensure the stable, interference-free contact between the sensor element 146 and the circuit board 130 required for a permanent signal-transmitting connection, the strain sensor 142 has an annular contacting bracket 182 (see Fig. 8) made of plastic, in which electrical cables 184 (see Fig. 9) are overmolded in metal.

[0142] The contacting bracket 182 and the electrical lines 184 extend in the circumferential direction U.

[0143] The electrical leads 184 have electrical contacts 186 in the form of contact cylinders at one end, which are connected to a contact section 188 (see Fig. 8) protrude radially inwards from the contacting bracket 182 on the inner circumference 190 of the contacting bracket 182.

[0144] The electrical contacts 186 (see Fig. 12) are arranged in such a way that they are each directly opposite a contact block 162 of the sensor element 146 in the radial direction and contact this in a signal-transmitting manner.

[0145] At the other end, the electrical lines 184 are connected to spring-loaded socket contacts 192 (see Fig. 9) which has an electrical connection 194 (see Fig. 8) of the strain sensor 142.

[0146] The socket contacts 192 are arranged in a connection section 196 of the strain sensor 142 to form a socket 198 which has a plug-in direction in the axial direction A.

[0147] In this context, the positioning contour 156 is arranged in the connecting section 196.

[0148] The contact bracket 182 is one piece here, but this can also be different.

[0149] In the illustrated embodiment, the contacting bracket 182 has a gap 200 which separates a first circumferential end 202 from a second circumferential end 204 of the contacting bracket 182 which is opposite in the circumferential direction U, as well as two connecting elements 206 by means of which the circumferential ends 202, 204 are connected to one another.

[0150] The connecting elements 206 here are screws, each of which forms a screw connection with a corresponding thread in the first circumferential end 202, by means of which the contacting bracket 182 can be preloaded in the circumferential direction U.

[0151] In an alternative embodiment (see Fig. 13), the contacting bracket 182 has a connecting element 206 in the form of a spring clip, which engages with correspondingly designed recesses 208 in the contacting bracket 182 and in this way connects and prestresses the circumferential ends 202, 204 in the circumferential direction U.

[0152] When assembling the brake actuator unit 12, the contact bracket 182 is pushed in the axial direction A onto the brake piston bearing section 74 (see Fig. 10) to which the sensor element 146 is already attached, so that the positioning contour 156 of the contacting bracket 182 engages positively with the complementary positioning contour 154 on the outer circumference 148 of the axial section 144. As a result, the contacting bracket 182 is arranged in a defined manner in the axial direction A and in the circumferential direction U on the brake piston bearing section 74 (see Fig. 11). In particular, the electrical contacts 186 are arranged directly opposite the contact blocks 162 of the sensor element 146 or contact them.

[0153] For axial placement, the circumferential ends 202, 204 are elastically spread apart from each other in the circumferential direction U, so that the diameter of the contacting bracket 182 temporarily increases accordingly.

[0154] In a subsequent step, the circumferential ends 202, 204 are pulled towards each other in the circumferential direction U by means of the connecting elements 206, whereby the contacting bracket 182 is clamped in the radial direction to the outer circumference 148 of the axial section 144 and the electrical contacts 186 rest against the contact blocks 162 of the sensor element 146 under prestress.

[0155] In this way, the sensor element 146 is connected to the electrical connection 194 of the strain sensor 142 in a signal-transmitting manner.

[0156] The electrical connection device 140 (see Fig. 16), which connects the strain sensor 142 to the circuit board 130 in a signal-transmitting manner, has in this context electrical connecting lines 210 (see Fig. 14), each having at one end a first connecting contact 212 designed as a plug-in pin and at the opposite end a second connecting contact 214 designed as a plug-in press-connector contact pin.

[0157] The number of connecting lines 210 corresponds in particular to the number of contact blocks 162, which in the present case is four.

[0158] The connecting lines 210 are formed here by a punched grid, which is partially overmolded with a plastic.

[0159] In principle, the connecting lines 210 can be designed in any way in an alternative embodiment.

[0160] In the illustrated embodiment, the first connecting contacts 212 form a plug 216 which is complementary to the socket 198 (see Fig. 11) of the strain sensor 142 and is connected to it via a plug connection with axial plug direction S for signal transmission.

[0161] The contacting of the plug 216 with the socket 198 is carried out blindly during the assembly of the electromechanical actuation unit 32 on the brake housing 12.

[0162] The electrical connection device 140 further extends in a stepped profile (see Fig. 16) with axial sections 218 and radial sections 220 from the strain sensor 142 via the gear web 46 and through the electronics housing 132 to the circuit board 130.

[0163] For this purpose, the gear web 46 has a stepped receptacle 222 (see Fig. 14) in which the connecting device 140 is positively received.

[0164] The connecting device 140 is clamped in a form-fitting and force-fitting manner in the axial, radial and tangential directions by the ring gear 50 pressed into the gear web 46 (see Fig. 15).

[0165] The second connecting contacts 214 extend over an alignment guide 224 (see Fig. 16) in axial direction A through the electronics housing 132 and into the printed circuit board 130, to which they are connected in a signal-transmitting manner via plug-in contacts which are designed to be complementary to the plug-in compression connector contact pins.

[0166] The contact between the second connecting contacts 214 and the circuit board 130 is established by axial pressing. The reaction force of the pressing force is supported by the stepped connecting device 140 on the gear web 46.

[0167] Based on the Fig. 17 and Fig. 18, a brake actuator unit 12 with a strain sensor 142 according to an alternative embodiment will now be described. The same reference numerals are used for the components known from the above embodiment, and reference is made to the previous explanations.

[0168] In contrast to the Fig. 8, the strain sensor 142 in the present embodiment does not have a contacting bracket 182 but rather a flexible cable section 226 which extends from the connection section 196 in the circumferential direction U along the axial section 144 to the sensor element 146.

[0169] The flexible cable section 226 comprises the electrical lines 184, whose electrical contacts 186 are connected to the contact blocks 162 of the sensor element 146 by bonding or soldering in a signal-transmitting manner.

[0170] In the illustrated embodiment, the flexible cable section 226 is guided along the outer circumference 148 of the axial section 144. For this purpose, spacers 228 made of an elastomer are molded onto the flexible cable section 226, which hold the flexible cable section 226 at a defined distance from the axial section 144 of the brake piston bearing section 74 and from the inner circumference of the transmission housing 40. This prevents the flexible cable section 226 from fraying.

[0171] Based on the Fig. 19, a strain sensor 142 according to another alternative embodiment will now be described. The same reference numerals are used for components known from the above embodiment, and reference is made to the previous explanations.

[0172] In contrast to the Fig. 17 and Fig.18, the strain sensor 142 in the present embodiment has a flat socket 230 in which the electrical contacts 186 of the electrical lines 184 form resilient socket contacts or are connected to them in a signal-transmitting manner.

[0173] Pin contacts 232 in the form of fork contact pins are attached to the contact blocks 162 of the sensor element 146 by bonding or soldering.

[0174] The pin contacts 232 form a connector that is designed to complement the flat socket 230 and forms a plug connection with it. The sensor element 146 is connected to the electrical connector 194 via this plug connection for signal transmission.

[0175] In all embodiments, a brake actuator unit 12 and an electromechanical brake 10 with a brake actuator unit 12 are provided in this way, each of which has a strain sensor 142, by means of which the strain deformations on the outer circumference 148 of the brake piston bearing section 74, due to the action of the reaction force Fr of the application force Fz, can be measured at a defined position. Thus, the instantaneously generated application force Fz can be directly detected.

[0176] Based on the instantaneously generated clamping force Fz, mechanical efficiency changes of the multi-stage gear 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 means of a current consumption sensor.

[0177] In this way, the electric motor 38 can be controlled accordingly to ensure a constant effect of the brake 10 over its service life.

[0178] Furthermore, the brake actuator unit 12 is designed to be compact.

Claims

[1] Brake actuator unit (12) for an electromechanical brake (10), with a spindle (44), a brake piston (72) drivingly coupled to the spindle (44), a spindle bearing (96) receiving the spindle (44) and absorbing the axial reaction forces (Fr) of the spindle (44) when the brake (10) is actuated, and a cup-shaped brake piston bearing section (74) having a peripheral wall (76) and a base (78) on which the spindle bearing (96) is axially supported when the brake (10) is actuated, characterized by that the brake actuator unit (12) has a strain sensor (142) with at least one sensor element (146) which is arranged on an outer circumference (148) of an axial section (144) of the circumferential wall (76) and is designed to detect a strain of the axial section (144) in a circumferential direction (U). [2] Brake actuator unit (12) according to claim 1, characterized by that the axial section (144) is adjacent to the bottom (78). [3] Brake actuator unit (12) according to claim 1 or 2, characterized by that the outer circumference (148) of the axial section (144) is formed at least in sections by a circular-cylindrical outer surface (150). [4] Brake actuator unit (12) according to one of the preceding claims, characterized by that the at least one sensor element (146) is attached to a planar surface (152) on the outer circumference (148) of the axial section (144), which extends in the axial direction (A) and in the tangential direction. [5] Brake actuator unit (12) according to one of the preceding claims, characterized by that the strain sensor (142) has an electrical connection (194) which is connected to the at least one sensor element (146) in a signal-transmitting manner. [6] Brake actuator unit (12) according to one of the preceding claims, characterized byin that the strain sensor (142) has a contacting bracket (182) which is at least partially annular and extends in the circumferential direction (U) around the axial section (144), wherein the contacting bracket (182) has a connection section (196) with the electrical connection (194) and, on the inner circumference (190), a contact section (188) with electrical contacts (186), via which the electrical connection (194) is connected to the at least one sensor element (146) in a signal-transmitting manner. [7] Brake actuator unit (12) according to claim 6, characterized by that the contacting bracket (182) is prestressed in the circumferential direction (U) such that the contacting bracket (182) is pressed radially against the axial section (144). [8] Brake actuator unit (12) according to claim 6 or 7, characterized byin that the contacting bracket (182) has a gap (200) in the circumferential direction (U) which separates a first circumferential end (202) from an opposite second circumferential end (204), wherein the contacting bracket (182) has a connecting element (206) which connects the first circumferential end (202) to the second circumferential end (204) in the circumferential direction (U). [9] Brake actuator unit (12) according to one of claims 1 to 5, characterized by in that the strain sensor (142) has a flexible cable section (226) which extends in sections around the axial section (144) in the circumferential direction (U), wherein the flexible cable section (226) has electrical lines (184) with electrical contacts (186) via which the electrical connection (194) is connected to the at least one sensor element (146) in a signal-transmitting manner. [10] Brake actuator unit (12) according to claim 9, characterized bythat the at least one sensor element (146) has electrical pin contacts (232) and the flexible cable section (226) has a complementary flat socket (230) with the electrical contacts (186), wherein the pin contacts (232) and the flat socket (230) form a plug connection. [11] Brake actuator unit (12) according to one of claims 5 to 10, characterized by that the brake actuator unit (12) has an electronic module (36) with a printed circuit board (130) and an electrical connecting device (140) which has electrical connecting lines (210) each with a first connecting contact (212) and an opposite second connecting contact (214), wherein the connecting device (140) is connected to the electrical connection (194) via the first connecting contacts (212) and to the printed circuit board (130) via the second connecting contacts (214) in a signal-transmitting manner. [12] Brake actuator unit (12) according to claim 11, characterized bythat the electrical connection (194) is designed as a socket (198) and the first connecting contacts (212) are designed as plug pins which form a plug (216) for the socket (198). [13] Brake actuator unit (12) according to claim 12, characterized by that the plug (216) and the socket (198) form a plug connection with axial plug-in direction (S). [14] Brake actuator unit (12) according to one of claims 11 to 13, characterized by that the second connecting contacts (214) are plug-in compression connector contact pins extending in the axial direction (A). [15] Brake actuator unit (12) according to one of claims 11 to 14, characterized by that the connecting lines (210) are formed by a punched grid. [16] Brake actuator unit (12) according to one of claims 11 to 15, characterized by that the connecting device (140) has a stepped profile with axial sections (218) and radial sections (220). [17] Brake actuator unit (12) according to one of claims 11 to 16, characterized by that the brake actuator unit (12) has a gear module (34) which is drivingly coupled to the spindle (44) and is arranged in the axial direction (A) between the strain sensor (142) and the electronic module (36). [18] Brake actuator unit (12) according to claim 17, characterized by in that the transmission module (34) has a ring gear (50) and a transmission web (46) with a receptacle (222) in which the connecting device (140) is arranged in a form-fitting manner, wherein the ring gear (50) is connected to the transmission web (46) by means of a press fit, wherein the connecting device (140) is clamped in the axial direction (A) and / or radial direction between the ring gear (50) and the transmission web (46). [19] Brake actuator unit (12) according to one of claims 1 to 18, characterized bythat the strain sensor (142) has a positioning contour (156) which is in positive engagement with a complementary positioning contour (154) on the outer circumference (148) of the axial section (144). [20] Strain sensor (142) for a brake actuator unit (12) with a spindle (44), a brake piston (72) drivingly coupled to the spindle (44), a spindle bearing (96) receiving the spindle (44) and absorbing the axial reaction forces (Fr) of the spindle (44) when the brake (10) is actuated, and a cup-shaped brake piston bearing section (74) having a peripheral wall (76) and a base (78) on which the spindle bearing (96) is axially supported when the brake (10) is actuated, characterized by that the strain sensor (142) has at least one sensor element (146) which is arranged on an outer circumference (148) of an axial section (144) of the circumferential wall (76) and is designed to detect a strain of the axial section (144) in a circumferential direction (U). [21] Strain sensor (142) according to claim 20, characterized by that the strain sensor (142) has an electrical connection (194) which is connected to the at least one sensor element (146) in a signal-transmitting manner. [22] Strain sensor (142) according to claim 21, characterized by in that the strain sensor (142) has a contacting bracket (182) which is at least partially annular and extends in the circumferential direction (U) around the axial section (144), wherein the contacting bracket (182) has a connection section (196) with the electrical connection (194) and, on the inner circumference (190), a contact section (188) with electrical contacts (186), via which the electrical connection (194) is connected to the at least one sensor element (146) in a signal-transmitting manner. [23] Strain sensor (142) according to claim 22, characterized bythat the contacting bracket (182) is prestressed in the circumferential direction (U) such that the contacting bracket (182) is pressed radially against the axial section (144). [24] Strain sensor (142) according to claim 22 or 23, characterized by in that the contacting bracket (182) has a gap (200) in the circumferential direction (U) which separates a first circumferential end (202) from an opposite second circumferential end (204), wherein the contacting bracket (182) has a connecting element (206) which connects the first circumferential end (202) to the second circumferential end (204) in the circumferential direction (U). [25] Strain sensor (142) according to one of claims 21 to 24, characterized byin that the strain sensor (142) has a flexible cable section (226) which extends in sections around the axial section (144) in the circumferential direction (U), wherein the flexible cable section (226) has electrical lines (184) with electrical contacts (186) via which the electrical connection (194) is connected to the at least one sensor element (146) in a signal-transmitting manner. [26] Strain sensor (142) according to claim 25, characterized by that the at least one sensor element (146) has electrical pin contacts (232) and the flexible cable section (226) has a complementary flat socket (230) with the electrical contacts (186), wherein the pin contacts (232) and the flat socket (230) form a plug connection. [27] Electromechanical brake (10) with an electric motor (38) for actuating the brake (10), which is coupled to the spindle (44) in a torque-transmitting manner, with a brake actuator unit (12) according to one of claims 1 to 19 and / or with a strain sensor (142) according to one of claims 20 to 26.

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