Actuation device for a brake disc and disc brake

Abstract

An actuation device for a disc brake and disc brake, the actuation device comprising: a piston; a first ramp-ball motion converter having a first ramp portion axially constrained and actuatable in rotation about an actuation axis, a second ramp portion coupled to the piston and a plurality of rolling elements placed in contact between the ramp tracks formed by the first ramp portion and the second ramp portion; a second screw and nut motion converter connected between the second ramp portion and the piston; a torque limiter: - which realizes a torsional connection of the first ramp portion and the second ramp portion, so that they rotate together about the actuation axis up to a predetermined limit torque in said torsional connection, - which decouples the rotation of the first ramp portion about the actuation axis with respect to the second ramp portion when the predetermined limit torque is exceeded.

Description

Technical Field

[0001] This technology relates to an actuation device for disc brakes, particularly electromechanical disc brakes, and a disc brake equipped with such an actuation device. Background Technology

[0002] Actuation devices for disc brakes, including geared motors associated with ball screws, are known to convert the torque generated by the geared motors into linear braking forces directed against the disc brake pads.

[0003] In these actuation devices, the ball screw performs two functions. The first is to transmit braking force to the disc brake pad, causing the pad to apply braking torque to the disc brake. The second function is to repair and compensate for wear on the pad.

[0004] Although ball screw actuators are suitable for transferring braking loads to disc brake pads and compensating for wear, they have several drawbacks.

[0005] In reality, these actuators have a high axial dimension, that is, a high dimension in the direction in which braking force is applied, as well as high cost, noise and weight.

[0006] The inability to define a non-linear travel law is another drawback of ball screw actuators. In reality, ball screws have a constant screw pitch, and therefore, they exhibit a linear travel law that is directly proportional to the screw's rotation angle.

[0007] On the other hand, it is ideal to make the actuator have a non-linear travel motion, which is more suitable for the different steps of bringing the piston close until piston-pad-disc contact is achieved and tightening the piston so that the pad is against the brake disc.

[0008] Another known actuation device is the so-called "ball-in-ramp" mechanism. The ball-in-ramp mechanism is also used to convert rotational motion into translational motion, and it comprises two opposing rotating parts and a plurality of balls positioned in contact between the two opposing parts and received in a rolling track (or ramp) formed in the two parts. The rolling track has a helical extension, causing the relative rotation between the two opposing parts to produce a wedge effect and causing the two opposing parts to translate axially away from each other.

[0009] The ball-driven ramp mechanism has a much smaller axial dimension than the ball screw mechanism and can generate very high linear or nonlinear braking force based on the relative rotation angle of the two opposing components (depending on the construction of the ball ramp track).

[0010] However, the known drawback of ball bearings in ramp mechanisms is their very limited axial travel, which makes it difficult to restore wear on disc brake pads. Summary of the Invention

[0011] The object of the present invention is to provide an actuation device for a disc brake that has features that avoid at least some of the disadvantages of the prior art.

[0012] A specific object of the present invention is to provide an actuation device for a disc brake that has a smaller axial dimension, lower cost and weight, and the same or improved braking efficiency.

[0013] Another specific object of the present invention is to provide an actuation device for a disc brake that can be constructed with a nonlinear travel law. Another objective of the present invention is to reconcile the apparent conflict between the need for a smaller axial dimension and the need for additional stroke of the piston for restoring wear on the pad, the need for a smaller axial dimension that is currently incompatible with the use of a screw motion converter, and the need for additional piston stroke that is currently incompatible with the use of a ball ramp system.

[0014] These and other objectives are achieved by the actuation device for disc brakes according to this application. Attached Figure Description

[0015] To better understand the present invention and its advantages, some non-limiting exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which: Figure 1 This is a perspective view of a disc brake according to an embodiment of the present invention; Figure 2 This is a cross-sectional view taken along the radial plane showing details of a disc brake according to an embodiment of the present invention; Figure 3 This is an exploded view of an actuation device for a disc brake according to an embodiment of the present invention; Figure 4A This is a perspective view of a partially assembled actuation device for a disc brake according to an embodiment of the present invention; Figure 4B yes Figure 4A A perspective view of the assembled actuator for a disc brake; Figure 5 yes Figure 4B Radial cross-sectional view of the actuator in the diagram; Figure 5A This is a specific view of an actuation device according to an embodiment of the present invention; Figure 5B It is based on Figure 3 Exploded view of details of the actuator in an alternative embodiment of the implementation method; Figure 6A It is a cross-sectional view orthogonal to the actuation axis under the first operating configuration; Figure 6B It is a cross-sectional view orthogonal to the actuation axis under the second operating configuration; Figure 7 This is a cross-sectional view taken along the radial plane showing details of a disc brake according to another embodiment of the present invention. Figure 8 This is an exploded view of an actuation device for a disc brake according to another embodiment of the present invention; Figure 8A yes Figure 8 Another exploded view of the actuation device for a disc brake shown; Figure 9 This is a perspective view of a partially assembled actuation device for a disc brake according to another embodiment of the present invention. Figure 10 yes Figure 9 A radial cross-sectional view of the assembled actuator; Figure 10A This is a radial cross-sectional view of an actuation device for a disc brake according to an embodiment of the present invention; Figure 11A This is a perspective view of a partially assembled actuation device for a disc brake according to an embodiment of the present invention; Figure 11B yes Figure 11A A perspective view of the assembled actuator for a disc brake; Figure 12 This is a radial cross-sectional view of an actuator for a disc brake according to another embodiment; Figure 13A This is a perspective view of an actuation system according to another embodiment of the present invention; Figure 13B yes Figure 13A Front view of the actuator. Detailed Implementation

[0016] In the following description, unless otherwise stated, the term "front" orientation refers to the orientation of the side, face, surface, etc., in the piston's travel (braking) direction, and the term "rear" orientation refers to the orientation of the side, face, surface, etc., in the piston's retraction direction. Unless otherwise stated, the terms "radial," "circumferential," and "axial" are used relative to the piston's actuation axis.

[0017] Referring to the accompanying drawings, the actuation device 1 for the disc brake 2 includes: - Piston 7, which is slidably supported along the actuation axis 8. A first ramp-ball motion converter 100 comprising: a first ramp portion 101, which is axially fixed and actuable to rotate about an actuation axis 8; a second ramp portion 102, which is connected to a piston and faces the first ramp portion 101; and a plurality of rolling elements (balls) 29, which are positioned in contact between the ramp track 103 formed by the first ramp portion 101 and the second ramp portion 102, such that rotation of the first ramp portion 101 relative to the second ramp portion 102 causes the second ramp portion 102 to perform a braking translational motion relative to the first ramp portion 101 along the actuation axis 8 together with the piston 7. - A second screw and nut motion converter 4 without ball recirculation, which is connected between the second ramp portion 102 and the piston 7, such that rotation of the second ramp portion 102 about the actuation axis 8 relative to the piston 7 causes the piston 7 to perform additional compensating translational motion along the actuation axis 8 relative to the second ramp portion 102. -Torque limiter 10 (or in other words, torsion clutch): The torque limiter 10 forms a torsional connection between the first ramp portion 101 and the second ramp portion 102, causing the first ramp portion 101 and the second ramp portion 102 to rotate together about the actuation axis 8 until a predetermined limiting torque is reached in the torsional connection. When the predetermined limiting torque is exceeded, the torque limiter 10 decouples the rotation of the first ramp portion 101 about the actuation axis 8 relative to the second ramp portion 102.

[0018] Therefore, in the first step (the step of additional stroke required to compensate for the thickness of the worn pad) until the piston 7 approaches the pad and the piston-pad-brake disc engagement is achieved, the two ramp portions 101, 102 of the first ramp-ball motion converter 100 rotate together and the piston 7 is moved by means of the second screw and nut motion converter 4.

[0019] At the end of the first approach step, the pressing engagement of the piston-pad-disc brake increases the mechanical resistance to further travel of the piston 7 until the predetermined limiting torque in the torsional connection between the first ramp portion 101 and the second ramp portion 102 is exceeded, and the relative rotation of the first ramp portion 101 and the second ramp portion 102 causes the piston 7 to perform a braking translational movement (very limited braking stroke) solely by means of the action of the first ramp-ball motion converter 100.

[0020] The first ramp section 101 can be connected to an input shaft or a general input rotary element 3, such as a reduction gear or an input rotary element of an electric motor.

[0021] Typically, piston 7 is configured to transmit axial force along the actuation axis 8 to disc brake pad 9 of disc brake 2.

[0022] Advantageously, the actuator 1 constructed in this way is more compact and lighter than the actuators of the prior art.

[0023] Furthermore, the actuator 1 does not require the use of a ball screw and has a smaller size, lighter weight, and lower cost.

[0024] Furthermore, the actuator 1 constructed in this way reconciles the need for a braking stroke with high force and good motion irreversibility and high efficiency with the need for an irreversible, low force stroke to compensate for wear of the pad 9.

[0025] The actuator 1, constructed in this way, converts the torque from the rotating element 3 into a linear force through two distinct operational steps. In the first step, wear on the pad 9 of the disc brake 2 is restored by bringing the piston 7 close to the pad 9 of the disc brake 2. This movement is achieved by the second screw and nut motion converter 4 using a relatively low force, i.e., less than the braking force. Actual braking, i.e., the braking force generated by the piston 7 on the pad 9 of the disc brake 2, occurs in the second step. The translational movement of the piston 7 that generates the braking force is produced by the second ramp-ball motion converter 100.

[0026] Detailed description of the first ramp-ball motion converter 100 According to an embodiment of the present invention, the first ramp portion 101 itself can form the input rotating element 3 of the device 1, and the second ramp portion 102 can be directly formed at the screw body 5 of the second screw and nut motion converter 4.

[0027] This increases the compactness of the actuator 1, thereby reducing the space requirement of the actuator 1 in the direction of the actuation axis 8.

[0028] According to an advantageous embodiment, the first ramp portion 101 is formed by a rotating body 23 having a generally cylindrical shape, the rotating body 23 having a front wall 26, a rear wall 27, and a circumferential wall 25 extending along the actuation axis 8.

[0029] The front wall 26 of the rotating body faces the direction of travel of the piston 7, and forms one or more, preferably three, first rolling tracks 28 of the ramp track 103, as well as a drive shaft 24 protruding from the front wall 26. The drive shaft 24 is coaxial with the actuation axis 8 and connected to the torque limiter 10. The drive shaft 24 may also form a rotatable, centrally located support for supporting the second ramp section 102.

[0030] The circumferential wall 25 of the rotating body may, for example, form a toothed portion 50 extending around the actuation axis 8 at the rear wall 27 of the rotating body for transmitting actuation torque and / or rotation.

[0031] According to alternative implementation methods ( Figure 12 The rotating body 23 is formed as a radially enlarged shaft 48, which forms the axially extending drive shaft 24 in the actuation device 1 and the input shaft extending on the rear side of the rotating body 23 opposite to the drive shaft 24.

[0032] According to an embodiment, the first motion converter 100 includes a support assembly 105 configured to: position the first ramp portion 101, particularly the rotating body 23, in a fixed position during translational motion and coaxial with respect to the actuation axis 8; and support the axial load generated during operation of the actuation device 1 and the radial load that may be generated due to engagement with the toothed portion 50.

[0033] Advantageously, the support assembly 105 is positioned inside the rotating body 23 and coaxial with the rotating body 23, and the support assembly 105 can be positioned at the location of the toothed portion 50 (to directly provide radial reaction force constraint on the rotating body 23).

[0034] The support assembly 105 may include a four-point contact rolling bearing.

[0035] According to the embodiment, the screw rear wall 21 of the screw body 5 facing the rotating body body 23 forms at least one, preferably three, second rolling tracks 22 of the cam track 103.

[0036] Advantageously, the first rolling track 28 and the second rolling track 22 facing each other respectively accommodate rolling balls 29 between the first rolling track 28 and the second rolling track 22.

[0037] The ramp tracks 103 of ramp sections 101 and 102 extend spirally relative to the actuation axis 8 (or, in other words, extend eccentrically in the circumferential direction). Each ramp section 101 and 102 may form, for example, two or three rolling tracks 103, which are arranged in a circumferential sequence and separated from each other by spacer ribs to accommodate the rolling element (ball) 29 at the designed positions of the rolling tracks 103.

[0038] The ramp track 103 can be constructed as a helical structure with variable pitch along the actuation axis 8, thereby defining a nonlinear rotation-translation conversion law.

[0039] According to an embodiment, the at least one ramp track 103 is configured to radially constrain the movement of the ball 29.

[0040] Advantageously, this avoids the risk of the at least one ball 29 dislodging from the corresponding ramp track 103.

[0041] According to an advantageous embodiment, the rolling ball 29 is also accommodated by a receiving cage 30, which is positioned between the first ramp portion 101 and the second ramp portion 102, i.e. between the rotating body 23 and the screw body 25. Advantageously, the receiving cage 30 is (rotatably) supported on the drive shaft 24.

[0042] According to the embodiment, the cage-like member 30 is formed in the radially open or closed encapsulating blade 104 or ball seat to prevent the rolling ball 29 from disengaging radially.

[0043] According to the embodiment, the first ramp portion 101, the second ramp portion 102 and the rolling element (ball) 29 are elastically pushed into contact with each other in the direction of the actuation axis 8.

[0044] This avoids ball bearing vibration and noise in the ramp track and keeps the individual components in their designed positions.

[0045] According to the implementation method ( Figure 11A , 11B The actuating device 1 includes an axial preload spring 42 configured to axially push the first ramp portion 101 toward the second ramp portion 102, or in other words, the axial preload spring 42 configured to axially push the screw body 5 against the rotating body body 23. The same axial preload spring 42 can be arranged to axially preload the assembly of the first motion converter 100 and the torque limiter 10.

[0046] The axial preload spring 42 can be supported (e.g., by Seeger ring 41) to the drive shaft 24 and fastened between the free (front) end portion of the drive shaft 24 (facing the direction of travel of the piston 7) and the front wall 20 of the screw body 5. The axial preload spring 42 is, for example, a coil spring, one or more Belleville springs in series, or a wave spring.

[0047] According to the implementation method ( Figure 10 , Figure 10A The drive shaft 24 (formed as a single piece or integral with the rotating body 23) has an axial through hole that accommodates a connecting rod 46 having a rear end portion and a mushroom-shaped or plate-shaped front end portion axially resting against the front wall 20 of the screw body 5 (in the direction opposite to the travel direction of the piston 7), and the rear end portion protruding into the internal cavity of the rotating body 23. An axial preload spring 42′ inserted on the connecting rod 46—advantageously a Belleville spring, one or more Belleville springs in series, or one or more coil springs—can be supported (e.g., by means of Seeger coil 41′) on the connecting rod 46, and the axial preload spring 42′ is preferably clamped between the rear end portion of the connecting rod 46 and the bottom surface of the internal cavity of the rotating body 23 by means of an inserted (rolling) axial support 47.

[0048] Advantageously, the first motion converter 100, the second motion converter 4, and the torque limiter 10 are at least partially, preferably completely, housed within the internal cavity of the piston 7, thereby occupying the same axial space.

[0049] Another advantage is that the torque limiter 10 is at least partially, preferably completely, housed in the internal cavity of the second motion converter 4. Preferably, the torque limiter 10 is at least partially, preferably completely, housed in the internal cavity of the screw body 5, thereby occupying the same axial space.

[0050] Detailed description of piston 7 and second screw and nut motion converter 4 According to the embodiment, the piston 7 has a generally hollow cylindrical shape coaxial with the actuation axis 8. The piston 7 has a cylindrical wall 14 that defines an outer piston surface 11 and an inner piston surface 12, and a head wall 13 that is transverse to the side wall 14 and formed at the front end of the piston 7. In the operating mode, the head wall 13 faces the pad 9 of the disc brake 2.

[0051] According to a preferred embodiment, the inner surface 12 of the piston is threaded and screwed onto the screw body 5 to form the nut 6 of the second screw and nut motion converter 4.

[0052] According to an embodiment, the piston 7 is provided with an anti-rotation device, such as one or more radial protrusions 16, which are slidably accommodated in one or more corresponding guides 16', which are formed in the cylinder 16″ and extend along the direction of the actuation axis 8, so as to allow the piston 7 to translate relative to the axis of the cylinder 16″ and prevent the piston 7 from rotating relative to the cylinder 16″.

[0053] According to the embodiment, the protrusion 16 may be formed by a flat-head screw, preferably, the protrusion 16 is made of steel, and the protrusion 16 is inserted or screwed into the (threaded) hole 15 of the cylindrical wall 14 and oriented in a radial direction relative to the actuation axis 8.

[0054] By preventing the piston 7 from rotating around the actuation axis 8 and the screw 5 from translating in the direction of the actuation axis 8, the rotation of the screw body 5 screwed into the internal thread of the piston 7 causes the piston 7 to translate along the actuation axis 8.

[0055] According to an embodiment, the cylindrical wall 14 may have a circumferential groove 17 formed on the side of the head wall 13, which is suitable for accommodating the dustproof seal.

[0056] According to a preferred embodiment, the screw body 5 is formed with: - A cylindrical side wall 18, which is coaxial with respect to the actuation axis 8, has external threads to be screwed together with the internal threads of the piston 7. - A screw front wall 20 and a screw rear wall 21 opposite to the screw front wall 20, the screw front wall 20 facing the direction of travel of the piston 7. - Connecting seat 19, preferably, is positioned internally relative to the external thread in the radial and axial directions, and the connecting seat 19 accommodates the torque limiter 10.

[0057] This configuration helps to further reduce the axial dimension of device 1.

[0058] According to the embodiment, a through hole 43 is formed in the rear wall 21 of the screw, which leads to the connecting seat 19, and the drive shaft 24 extends into the connecting seat 19 through the through hole 43.

[0059] The through hole 43 forms a central rotating element that allows the screw body 5 to be supported so that the screw body 5 is centered and rotatable relative to the rotating body 23.

[0060] The circumferential edge between the threaded side wall 18 and the front wall 20 of the screw is inclined to facilitate the insertion and screwing of the screw body 5 into the nut 6 formed by the piston 7.

[0061] Detailed description of torque limiter 10 According to an embodiment, the torque limiter 10 includes one or more, preferably two, jaws 31, which are connected integrally with the screw body 5 in terms of rotation, and the jaws 31 are elastically biased to engage with the drive shaft 24.

[0062] According to one embodiment, the connecting seat 19 forms two abutment surfaces 44 and two side guide surfaces 44', the two abutment surfaces 44 being radially opposite each other relative to the actuation axis 8. A jaw member 31 (which may include a slider) is accommodated between the side guide surfaces 44' and radially guided to the actuation axis 8. A preloaded elastic element 32, such as a compression spring 33, is arranged between the abutment surfaces 44 and the jaw member 31.

[0063] The torsional engagement portion of the drive shaft 24 and the jaw member 31 are formed by interference fit (through elastic preload) to form a rotating integral assembly.

[0064] Specifically, the torsional engagement portion of the drive shaft 24 may have two flat and parallel opposing faces 38, while the jaw member 31 may form a trapezoidal connecting surface 34 facing the drive shaft 24. Figure 8 , Figure 8A ).

[0065] When the transmitted torque is less than the limiting torsional torque, the drive shaft 24 is engaged between the jaw members 31, and the jaw members 31 are able to rotate integrally with the drive shaft 24.

[0066] When the limiting torsional torque is exceeded, the drive shaft 24 overcomes the elastic force of the compression spring 33 and causes the jaws to open away from each other, thereby allowing the rotating body 23 to rotate relative to the screw body 5.

[0067] The torque limiter 10 constructed in this way has a simple structure that allows for easy maintenance and replacement of the worn jaws 31 when needed.

[0068] Advantageously, the torque limiter 10 includes two jaws 31 positioned opposite each other relative to the drive shaft 24.

[0069] According to the embodiment, each jaw member 31 is formed with a biasing surface 35 and a connecting surface 34 facing the drive shaft 24, and a spring element 32 that biases the jaw member 31 against the drive shaft 24 acts on the biasing surface 35.

[0070] Advantageously, the biasing surface 35 is formed with a seating portion 40 for accommodating the end of the elastic element 32.

[0071] According to another embodiment, the connecting surface 34 includes a generally flat central surface 36 disposed between two walls or receiving surfaces 37 that extend laterally or obliquely relative to the biasing surface 35, such that the connecting surface 34 is shaped into a trapezoidal or polygonal open channel.

[0072] According to an embodiment, the connecting portion of the drive shaft 24 forms two generally flat opposing surfaces 38, which are arranged between the surfaces 39 of two oppositely curved cylindrical or elliptical segments.

[0073] Advantageously, the transition region between the opposing surface 38 of the shaft 24 and the curved surface 39 is connected (without an interior angle) or inclined to reduce local contact pressure and thus reduce wear on the surface. Furthermore, this allows the jaw 31 to be manufactured from a material with a lower hardness than that of the shaft 24.

[0074] In the engagement configuration between the drive shaft 24 and the jaw member 31, the central surface 36 of the jaw member 31 contacts the corresponding opposing surface 38 of the drive shaft 24, and the receiving wall or surface 37 of the jaw member 31 surrounds the drive shaft 24 at the curved surface 39.

[0075] The front end of the mushroom-shaped head of the connecting rod 46 ( Figure 10 ) or spring 42 ( Figure 11A , Figure 11B To prevent the jaws 31 from undesirably disengaging from the connecting seat 19 in the axial direction, the front end of the mushroom-shaped head of the connecting rod 46 or the spring 42 at least partially blocks the outward passage by holding the jaws 31 in the space between the mushroom-shaped head or the spring 42 and the abutment wall 45 formed in the bolt body 5.

[0076] According to the implementation method ( Figure 3 The actuator 1 includes a retaining ring 41 (e.g., a steel Seeger ring) which is fixed to the drive shaft 24 to hold the jaw 31 between the retaining ring 41 and the abutment wall 45 of the screw body, thereby preventing the jaw 31 from being released from the coupling seat 19.

[0077] According to alternative implementation methods ( Figure 13A , Figure 13B The torque limiter 10 includes a torsion spring 51, such as a coil spring, which is connected between the first ramp portion 101 and the second ramp portion 102 of the first motion converter 100.

[0078] The torque-deformation curve of the torsion spring 51 is selected such that: when the torque is below a predetermined limit, the flat coil spring 51 substantially connects the first ramp portion 101 and the second ramp portion 102 in a rotational manner; while when the torque is above the predetermined limit, the torsion spring 51 deforms gradually, thereby allowing the first ramp portion 101 to rotate relative to the second ramp portion 102.

[0079] According to the embodiment, the first end of the torsion spring 51 is integrally connected to the rotating body 23, particularly the drive shaft 24, and the second end of the torsion spring 51 is integrally connected to the screw body 5.

[0080] According to the embodiment, the predetermined limiting torque is between 800 Nmm and 400 Nmm, preferably between 690 Nmm and 490 Nmm, even more preferably between 640 Nmm and 540 Nmm, and even more preferably, the predetermined limiting torque is 590 Nmm.

[0081] Advantageously, the predetermined limiting torque of this value prevents the braking torque generated by the disc brake 2 from becoming unstable or irregular.

[0082] Description of disc brake 2 The disc brake 2 comprises, in a known manner: a caliper including two spaced-apart side walls that define a disc space to accommodate a portion of the brake disc; means for securing the caliper to a vehicle; a connecting structure extending across the disc space and connecting the side walls to each other; at least one seat formed in each of the side walls and adapted to accommodate at least one friction pad; and a thrust device constrained to one or both side walls and adapted to bias the friction pad against the brake disc to clamp the brake disc, wherein, according to the invention, the thrust device includes the actuation device 1 described herein.

Claims

1. An actuation device (1) for a brake disc (2), the actuation device (1) comprising: - Piston (7), which is slidably supported along the actuation axis (8) - A first ramp-ball motion converter (100) having a first ramp portion (101), a second ramp portion (102), and a plurality of rolling elements (29), the first ramp portion (101) being axially constrained and capable of being braked to rotate about the actuation axis (8), the second ramp portion (102) being coupled to the piston (7) and facing the first ramp portion (101), the rolling elements (29) being placed in contact between the ramp track (103) formed by the first ramp portion (101) and the second ramp portion (102), such that rotation of the first ramp portion (101) relative to the second ramp portion (102) causes the second ramp portion (102) to perform a brakeed translational motion relative to the first ramp portion (101) along the actuation axis (8) together with the piston (7). - A second screw and nut motion converter (4), which is connected between the second ramp portion (102) and the piston (7), such that rotation of the second ramp portion (102) about the actuation axis (8) relative to the piston (7) causes the piston (7) to perform a compensating translational motion along the actuation axis (8) relative to the second ramp portion (102). -Torque limiter (10): The torque limiter (10) torsionally connects the first ramp portion (101) and the second ramp portion (102), thereby causing the first ramp portion (101) and the second ramp portion (102) to rotate together about the actuation axis (8) until a predetermined limiting torque is reached in the torsional connection. When the predetermined limiting torque is exceeded, the torque limiter (10) decouples the rotation of the first ramp portion (101) about the actuation axis (8) relative to the second ramp portion (102). The torque limiter (10) includes one or more jaws (31) that are integral with the coupling seat (19) of the second ramp portion (102) in terms of rotation, and the jaws (31) are elastically biased to engage with the drive shaft (24) formed at the first ramp portion (101).

2. The actuation device (1) according to claim 1, wherein, The second ramp portion (102) is formed directly on the screw body (5) of the second screw and nut motion converter (4).

3. The actuation device (1) according to claim 2, wherein, The piston (7) is formed with: - Cylindrical wall (14) having a threaded piston inner surface (12) which is screwed onto the screw body (5) to form the nut (6) of the second screw and nut motion converter (4). -Anti-rotation device, which prevents the piston (7) from rotating about the actuation axis (8).

4. The actuation device (1) according to claim 3, wherein, The screw body (5) is formed of: - A cylindrical side wall (18), which is coaxial with respect to the actuation axis (8), has an external thread for screwing into the internal thread of the piston (7). - A front wall (20) and a rear wall (21) of the screw, the front wall (20) facing the direction of travel of the piston (7), and the rear wall (21) opposite to the front wall (20), the rear wall (21) forming one or more second rolling tracks (22) of the ramp track (103). - The connecting seat (19) extends radially and axially inside relative to the external thread, and the connecting seat (19) accommodates the torque limiter (10).

5. The actuation device (1) according to claim 4, wherein, The first ramp portion (101) is formed by a rotating body (23), which has: - The front wall (26) of the rotating body faces the direction of travel of the piston (7) and forms one or more first rolling tracks (28) of the ramp track (103). - The drive shaft (24) protrudes from the front wall (26) of the rotating body, the drive shaft (24) is coaxial with the actuation axis (8), and the drive shaft (24) is connected to the torque limiter (10), wherein the second ramp portion (102) is rotatably supported on the drive shaft (24) and centered on the drive shaft (24).

6. The actuation device (1) according to claim 5, wherein, The rear wall (21) of the screw has a through hole (43) leading to the connecting seat (19). The drive shaft (24) extends into the connecting seat (19) through the through hole (43). The through hole (43) forms a central rotating member that allows the screw body (5) to be supported so that the screw body (5) rotates centrally relative to the rotating body (23).

7. The actuation device (1) according to claim 5, wherein, The support assembly (105) supports the rotating body (23) in an axially abutting manner, and the support assembly (105) is coaxial with respect to the actuation axis (8), and the support assembly (105) is positioned inside the rotating body (23).

8. The actuation device (1) according to claim 5, wherein, The rolling element (29) is also housed by a receiving cage (30) which is positioned between the first ramp portion (101) and the second ramp portion (102) and is supported on the drive shaft (24).

9. The actuation device (1) according to claim 1, wherein, The first ramp portion (101), the second ramp portion (102), and the rolling element (29) are elastically pushed into contact with each other in the direction of the actuation axis (8).

10. The actuation device (1) according to claim 9, the actuation device (1) comprising an axial preload spring (42) configured to axially push the assembly of the first ramp-ball motion converter (100) and the torque limiter (10).

11. The actuation device (1) according to claim 4, wherein, The actuation device (1) includes an axial preload spring (42) supported on the drive shaft (24) and sandwiched between the free end portion of the drive shaft (24) and the screw front wall (20) of the screw body (5).

12. The actuation device (1) according to claim 5, wherein, The drive shaft (24) has an axial through hole, which accommodates a connecting rod (46), the connecting rod (46) having: - An enlarged front end portion, which is axially positioned to abut against the screw front wall (20) of the screw body (5), and - The rear end portion protrudes into the internal cavity of the rotating body (23). The axial preload spring (42′) is sandwiched between the rear end portion of the connecting rod (46) and the bottom surface of the internal cavity of the rotating body (23). The axial preload spring (42′) can be sandwiched between the rear end portion of the connecting rod (46) and the bottom surface of the internal cavity of the rotating body (23) by inserting a rolling axial support (47).

13. The actuation device (1) according to claim 1, wherein, The first ramp-ball motion converter (100), the second screw and nut motion converter (4) and the torque limiter (10) are at least partially or completely housed in the internal cavity of the piston (7).

14. The actuation device (1) according to claim 1, wherein, The torque limiter (10) is at least partially or completely housed in the internal cavity of the screw body (5) of the second screw and nut motion converter (4).

15. The actuation device (1) according to any one of claims 1 to 5, wherein, - The connecting seat (19) has two abutting surfaces (44) and two side guide surfaces (44'), the abutting surfaces (44) being opposite each other in the diametrical direction relative to the actuation axis (8). - The jaw (31) is accommodated between the side guide surfaces (44') and the jaw (31) is radially guided to the actuation axis (8). - A preloaded elastic element (32) is arranged between the abutting surface (44) and the jaw member (31).

16. The actuation device (1) according to any one of claims 1 to 5, wherein, The torque limiter (10) includes two jaws (31) positioned opposite each other relative to the drive shaft (24).

17. The actuation device (1) according to claim 15, wherein, The torque limiter (10) includes two jaws (31) positioned opposite each other relative to the drive shaft (24).

18. A disc brake (2), said disc brake (2) comprising: The caliper has two spaced-apart side walls that define a disc space to accommodate a portion of the brake disc. Device for securing the caliper to the vehicle; A connecting structure that extends across the disk space and connects the side walls to each other; At least one cushion placement portion is formed in each of the side walls and is adapted to accommodate at least one friction pad; A thrust device, constrained to one or two side walls and adapted to push the friction pad against the brake disc to clamp the brake disc, wherein the thrust device includes the actuation device (1) of claim 1.

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